JP7438082B2 - hydraulic drive system - Google Patents

Description

The present invention relates to a hydraulic drive system comprising two hydraulic pumps.

Hydraulic vehicles such as industrial vehicles and construction vehicles are configured to be driven by a pair of left and right travel motors and to be operated by various actuators. Hydraulic vehicles having such functions are equipped with a hydraulic drive system to supply hydraulic fluid to the travel motor and various actuators. As an example of a hydraulic drive system, for example, a hydraulic control device disclosed in Patent Document 1 is known.

Japanese Patent Application Publication No. 2015-78748

The hydraulic pressure control device of Patent Document 1 includes a straight travel control valve. The straight-ahead travel control valve has a normal position, a straight-ahead travel position, and a merging position. At the merging position, the working fluid of the first pump is merged with the working fluid of the second pump to form a circuit including the second traveling control valve, the bucket control valve, the boom 1 control valve, and the arm 2 control valve. can lead to lineage. On the other hand, the hydraulic fluid cannot be combined and guided into the circuit system including the first travel control valve, the swing control valve, the boom 2 control valve, and the arm 1 control valve. However, in order to size each hydraulic pump, it is desired to introduce the combined hydraulic fluid into both circuit systems.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a hydraulic drive system capable of merging the working fluids of two hydraulic pumps and guiding the combined working fluid to each circuit system.

The hydraulic drive system of the present invention includes a first hydraulic pump that discharges hydraulic fluid, a second hydraulic pump that discharges hydraulic fluid, and a first hydraulic pump that is connected to the first hydraulic pump and the first travel motor, a normally open type first travel control valve that controls the flow of hydraulic fluid from the first hydraulic pump to the first travel motor and opens and closes the first bypass passage; and a first travel control valve that is connected to at least one first work actuator. , a first circuit system that controls the flow of hydraulic fluid to the at least one first working actuator; and a first circuit system that is connected to the second travel motor and controls the flow of hydraulic fluid to the second travel motor; a normally open second traveling control valve that opens and closes the second bypass passage; and a normally open second traveling control valve that opens and closes the second bypass passage; connected to a second circuit system that controls the flow of hydraulic fluid to the working actuator, the first hydraulic pump, the second hydraulic pump, the first circuit system, and the second travel control valve, a switching valve that switches connection destinations of the first hydraulic pump and the second hydraulic pump to the first circuit system and the second travel control valve, respectively; interposed in a first merging passage connecting a downstream portion of the control valve and a first supply passage connecting the switching valve and the first circuit system, and connecting the first supply passage from the first bypass passage to the first supply passage; a second supply connecting a first check valve that allows the flow of hydraulic fluid, a downstream portion of the second travel control valve in the second bypass passage, the second hydraulic pump and the second circuit system; and a second check valve that is interposed in a second merging passageway that connects the second bypass passageway to the second supply passageway, and that allows the hydraulic fluid to flow from the second bypass passageway to the second supply passageway.

According to the invention, the first hydraulic pump is connected to the second traveling control valve and the second hydraulic pump is connected to the first circuit system by the switching valve. In such a merging state, when the hydraulic fluid is introduced into the first circuit system and the second circuit system, the hydraulic fluids of the two hydraulic pumps merge as follows. That is, when the hydraulic fluid is guided to the first circuit system, the hydraulic fluid is guided from the first bypass passage to the first supply passage through the first check valve. As a result, the working fluids of the two hydraulic pumps are combined and guided to the first circuit system. On the other hand, when the hydraulic fluid is guided to the second circuit system, the hydraulic fluid is guided from the second bypass passage to the second supply passage through the second check valve. As a result, the working fluids of the two hydraulic pumps are combined and guided to the second circuit system. In this way, in the hydraulic drive system, the working fluids of the two hydraulic pumps can be combined, and the combined working fluid can be guided to each circuit system.

According to the present invention, the working fluids of two hydraulic pumps can be combined, and the combined working fluid can be guided to each circuit system.

FIG. 1 is a hydraulic circuit diagram showing a hydraulic drive system according to an embodiment of the present invention. FIG. 2 is a hydraulic circuit diagram showing a state in which working fluids from two hydraulic pumps are combined and flowed into a first circuit system in the hydraulic drive system of FIG. 1. FIG. In the hydraulic drive system of FIG. 1, it is a hydraulic circuit diagram which shows the state where the hydraulic fluid from two hydraulic pumps is combined and it flows into a 2nd circuit system. In the hydraulic drive system of FIG. 1, this is a hydraulic circuit showing a state in which each traveling control valve is operating and hydraulic fluid is flowing through each circuit system, and (a) shows a state in which the first traveling control valve is operating and the hydraulic fluid is flowing through each circuit system. In addition, it is a hydraulic circuit diagram showing a state in which hydraulic fluid is flowing in the first circuit system, and (b) shows a state in which the second travel control valve is activated and hydraulic fluid is flowing in the second circuit system. It is a hydraulic circuit diagram.

Hereinafter, a hydraulic drive system 1 according to an embodiment of the present invention will be described with reference to the above-mentioned drawings. Note that the concept of direction used in the following explanation is used for convenience in explanation, and does not limit the orientation of the structure of the invention to that direction. Moreover, the hydraulic drive system 1 described below is only one embodiment of the present invention. Therefore, the present invention is not limited to the embodiments, and additions, deletions, and changes can be made without departing from the spirit of the invention.

<Hydraulic vehicle>
Hydraulic vehicles, such as construction vehicles and industrial vehicles, can travel and perform various tasks. In this embodiment, the hydraulic vehicle is a hydraulic excavator (not shown). A hydraulic excavator can be driven by a traveling device. Further, the hydraulic excavator can perform works such as excavation and leveling by operating the revolving body, boom, arm, and bucket. To explain in more detail, the traveling device has two traveling motors 2 and 3. The two travel motors 2 and 3 run the hydraulic excavator by being supplied with hydraulic fluid (for example, oil, but not necessarily oil). Further, the traveling device is provided with a swinging body thereon so as to be able to turn. Further, the revolving body is provided with a bucket via a boom and an arm. Therefore, the hydraulic excavator can direct the bucket in various directions by rotating the revolving body. In addition, the hydraulic excavator can perform excavation and leveling using the bucket by vertically swinging the boom, arm, and bucket.

The hydraulic excavator configured in this manner includes a plurality of hydraulic actuators 4 to 7 and a hydraulic drive system 1 in addition to the two travel motors 2 and 3. The plurality of hydraulic actuators 4 to 7 are operated by hydraulic fluid supplied from the hydraulic drive system 1. In this embodiment, the plurality of hydraulic actuators 4 to 7 are a swing motor 4, an arm cylinder 5, a bucket cylinder 6, and a boom cylinder 7. The turning motor 4 turns the turning body. Further, the arm cylinder 5, bucket cylinder 6, and boom cylinder 7 can move the arm, boom, and bucket, respectively. In this embodiment, the swing motor 4 and the arm cylinder 5 are the first working actuators, and the bucket cylinder 6 and the boom cylinder 7 are the second working actuators. However, the swing motor 4 and the arm cylinder 5 do not necessarily need to be the first work actuators, and the bucket cylinder 6 and the boom cylinder 7 also do not necessarily need to be the second work actuators.

<Hydraulic drive system>
The hydraulic drive system 1 controls the flow of hydraulic fluid to the left and right travel motors 2, 3 and a plurality of hydraulic actuators 4-7. Thereby, the hydraulic drive system 1 controls the movements of the left and right travel motors 2 and 3 and the plurality of hydraulic actuators 4 to 7. To explain in more detail, the hydraulic drive system 1 includes two hydraulic pumps 11L and 11R, a first travel control valve 12, a merging valve 13, a second travel control valve 14, and a first circuit system. 15, a second circuit system 16, a first check valve 17, a second check valve 18, a third check valve 19, an operating device 20, and a control device 21.

Each of the two hydraulic pumps 11L and 11R discharges hydraulic fluid. More specifically, the two hydraulic pumps 11L and 11R are connected to a drive source (for example, an engine or an electric motor) not shown. The two hydraulic pumps 11L and 11R discharge hydraulic fluid by being rotationally driven by a drive source. The two hydraulic pumps 11L and 11R are variable displacement swash plate pumps in this embodiment. However, the two hydraulic pumps 11L and 11R are not limited to swash plate pumps, but may be slant shaft pumps. Further, the hydraulic pumps 11L and 11R are connected to the first and second pump passages 31L and 31R, respectively. A first bypass passage 32L branches off in the middle of the first pump passage 31L. Further, a second supply passage 33R, which will be described later, branches off in the middle of the second pump passage 31R, and is connected to the second circuit system 16 via the second supply passage 33R.

The first travel control valve 12 is connected to one of the travel motors 2, the first travel motor 2, and the first hydraulic pump 11L. The first travel control valve 12 controls the flow of hydraulic fluid to the first travel motor 2. Further, the first travel control valve 12 is a normally open type control valve, and opens and closes the first bypass passage 32L. More specifically, the first travel control valve 12 is interposed in the first bypass passage 32L and is connected to a branch passage 32La that branches from the first bypass passage 32L. Further, the first travel control valve 12 is connected to a tank 25 and two supply/discharge ports 2a and 2b of the first travel motor 2.

The first travel control valve 12 arranged in this manner is an electronically controlled spool valve. That is, the first travel control valve 12 moves the spool 12a according to the input signal. The first traveling control valve 12 switches the connection state of the branch passage 32La, the tank 25, and the two supply/discharge ports 2a and 2b by moving the spool 12a. Thereby, the first travel control valve 12 can control the flow of hydraulic fluid to the first travel motor 2. Further, the first travel control valve 12 is a normally open type control valve as described above, and when the spool 12a is moved from the neutral position to flow the working fluid to the first travel motor 2, the first bypass passage 32L is closed. .

The merging valve 13, which is an example of a switching valve, is connected to two hydraulic pumps 11L and 11R, a second travel control valve 14, and a first circuit system 15. The merging valve 13 switches the connection destinations of the two hydraulic pumps 11L and 11R to the second travel control valve 14 and the first circuit system 15, respectively. More specifically, the merging valve 13 is connected to the first hydraulic pump 11L via the first pump passage 31L, and is also connected to the second hydraulic pump 11R via the second pump passage 31R. Furthermore, the merging valve 13 is connected to the first circuit system 15 via the first supply passage 33L. That is, the first supply passage 33L connects the merging valve 13 and the first circuit system 15. It is also connected to the second travel control valve 14 via the second bypass passage 32R.

The merging valve 13 arranged in this manner is an electronically controlled spool valve, and moves the spool 13a from the neutral position M to the offset position A1 in response to an input signal. At the neutral position M, the first pump passage 31L and the first supply passage 33L are connected, and the second pump passage 31R and the second bypass passage 32R are connected. On the other hand, at the offset position A1, the first pump passage 31L and the second bypass passage 32R are connected, and the second pump passage 31R and the first supply passage 33L are connected.

The second travel control valve 14 is connected to the second travel motor 3, which is the other travel motor 3. The second travel control valve 14 controls the flow of hydraulic fluid to the second travel motor 3. Further, the second travel control valve 14 is a normally open type control valve, and opens and closes the second bypass passage 32R. More specifically, the second travel control valve 14 is interposed in the second bypass passage 32R, and is connected to the merging valve 13 via the second bypass passage 32R. That is, hydraulic fluid is guided to the second traveling control valve 14 from one of the two hydraulic pumps 11L and 11R depending on the position of the spool 13a of the merging valve 13. Further, the second travel control valve 14 is connected to a branch passage 32Ra that branches from the second bypass passage 32R. Further, the second travel control valve 14 is connected to a tank 25 and two supply/discharge ports 3a and 3b of the second travel motor 3.

The first travel control valve 12 arranged in this manner is an electronically controlled spool valve. That is, the second traveling control valve 14 moves the spool 14a according to the input signal. The second traveling control valve 14 switches the connection state of the branch passage 32Ra, the tank 25, and the two supply/discharge ports 3a and 3b by moving the spool 14a. Thereby, the second travel control valve 14 can control the flow of hydraulic fluid to the second travel motor 3. Further, the second travel control valve 14 is a normally open type control valve as described above, and closes the second bypass passage 32R when the spool 14a is moved from the neutral position to flow the working fluid to the second travel motor 3. .

The first circuit system 15 is connected to the swing motor 4 and the arm cylinder 5. The first circuit system 15 controls the flow of hydraulic fluid to the swing motor 4 and the arm cylinder 5. More specifically, the first circuit system 15 is connected to the merging valve 13 via the first supply passage 33L. That is, hydraulic fluid is introduced into the first circuit system 15 from one of the two hydraulic pumps 11L and 11R depending on the position of the spool 13a of the merging valve 13. The first circuit system 15 supplies the guided hydraulic fluid to the swing motor 4 and arm cylinder 5, and returns the hydraulic fluid discharged from the swing motor 4 and arm cylinder 5 to the tank 25. Further, the first circuit system 15 includes a first bypass passage 32L. The first circuit system 15 then blocks the first bypass passage 32L when operating at least one of the swing motor 4 and the arm cylinder 5 or in response to an input command. The first circuit system 15 having such a function includes a swing control valve 41, an arm control valve 42, and a first bypass cut valve 43.

The swing control valve 41, which is an example of a first work control valve, controls the flow of hydraulic fluid to the swing motor 4. Further, the swing control valve 41 is a normally open type control valve, and opens and closes the first bypass passage 32L. More specifically, the swing control valve 41 is connected to the first supply passage 33L, the tank 25, and the two suction and exhaust ports 4a and 4b of the swing motor 4. Further, the swing control valve 41 is, for example, an electronically controlled spool valve. That is, the swing control valve 41 moves the spool 41a according to the input signal. Then, the swing control valve 41 switches the connection state of the first supply passage 33L, the tank 25, and the two suction and discharge ports 4a and 4b by moving the spool 41a. Thereby, the swing control valve 41 can control the flow of hydraulic fluid to the swing motor 4. Further, the swing control valve 41 is a normally open type control valve interposed in the first bypass passage 32L. The swing control valve 41 can close the first bypass passage 32L when the spool 41a is moved from the neutral position to flow the working fluid to the swing motor 4.

The arm control valve 42, which is another example of the first work control valve, controls the flow of hydraulic fluid to the arm cylinder 5. Further, the arm control valve 42 is a normally open type control valve, and opens and closes the first bypass passage 32L. More specifically, the arm control valve 42 is connected to the first supply passage 33L in parallel to the swing control valve 41. Further, the arm control valve 42 is connected to the tank 25 and two ports 5a and 5b of the arm cylinder 5. Further, the arm control valve 42 is, for example, an electronically controlled spool valve. That is, the arm control valve 42 moves the spool 42a according to the input signal. The arm control valve 42 switches the connection state of the first supply passage 33L, the tank 25, and the two ports 5a and 5b by moving the spool 42a. Thereby, the arm control valve 42 can control the flow of hydraulic fluid to the arm cylinder 5. Further, the arm control valve 42 is a normally open type control valve, and is interposed in the first bypass passage 32L so as to be in series with the swing control valve 41 and on the downstream side thereof. Then, when the arm control valve 42 moves the spool 42a from the neutral position to flow the working fluid into the arm cylinder 5, the first bypass passage 32L is closed.

The first bypass cut valve 43 is interposed in the first bypass passage 32L and can block the flow of the hydraulic fluid from the first bypass passage 32L to the tank 25. More specifically, the first bypass cut valve 43 is an electromagnetic switching valve. The first bypass cut valve 43 is disposed on the most downstream side with respect to the control valves 41 and 42 in the first bypass passage 32L. Then, the first bypass cut valve 43 closes the first bypass passage 32L according to the input signal. This blocks the flow of the working fluid from the first bypass passage 32L to the tank 25.

The second circuit system 16 is connected to the bucket cylinder 6 and the boom cylinder 7. The second circuit system 16 then controls the flow of hydraulic fluid to the bucket cylinder 6 and boom cylinder 7. More specifically, the second circuit system 16 is connected to the second hydraulic pump 11R via the second supply passage 33R. That is, the second supply passage 33R connects the second hydraulic pump 11R and the second circuit system 16. The second circuit system 16 then supplies the guided hydraulic fluid to the bucket cylinder 6 and boom cylinder 7 , and returns the hydraulic fluid discharged from the bucket cylinder 6 and boom cylinder 7 to the tank 25 . Further, a second bypass passage 32R passes through the second circuit system 16. The second circuit system 16 then blocks the second bypass passage 32R when operating at least one of the bucket cylinder 6 and the boom cylinder 7 or in response to an input command. The second circuit system 16 having such a function includes a bucket control valve 44, a boom control valve 45, and a second bypass cut valve 46.

The bucket control valve 44, which is an example of a second work control valve, controls the flow of hydraulic fluid to the bucket cylinder 6. Further, the bucket control valve 44 is a normally open type control valve, and opens and closes the second bypass passage 32R. More specifically, the bucket control valve 44 is connected to the second supply passage 33R in parallel to the boom control valve 45. Further, the bucket control valve 44 is connected to the tank 25 and two ports 6a and 6b of the bucket cylinder 6. Furthermore, the bucket control valve 44 is, for example, an electronically controlled spool valve. That is, the bucket control valve 44 moves the spool 44a according to the input signal. Then, the bucket control valve 44 switches the connection state between the second supply passage 33R, the tank 25, and the two ports 7a and 7b by moving the spool 44a. Thereby, the bucket control valve 44 can control the flow of hydraulic fluid to the bucket cylinder 6. Moreover, the bucket control valve 44 is a normally open type control valve interposed in the second bypass passage 32R. Then, the bucket control valve 44 closes the second bypass passage 32R when the spool 42a is moved from the neutral position to allow the hydraulic fluid to flow into the bucket cylinder 6.

A boom control valve 45, which is another example of the second work control valve, controls the flow of hydraulic fluid in the boom cylinder 7. Moreover, the boom control valve 45 is a normally open type control valve, and opens and closes the second bypass passage 32R. More specifically, the boom control valve 45 is connected to the second supply passage 33R, the tank 25, and the two ports 7a and 7b of the boom cylinder 7. Further, the boom control valve 45 is, for example, an electronically controlled spool valve. That is, the boom control valve 45 moves the spool 45a according to the input signal. Then, the boom control valve 45 switches the connection state of the second supply passage 33R, the tank 25, and the two ports 4a and 4b by moving the spool 45a. Thereby, the boom control valve 45 can control the flow of hydraulic fluid in the boom cylinder 7. The boom control valve 45 is a normally open type control valve, and is interposed in the second bypass passage 32R in series with the bucket control valve 44 and downstream thereof. Then, when the boom control valve 45 moves the spool 45a from the neutral position to flow the hydraulic fluid to the boom cylinder 7, the second bypass passage 32R is closed.

The second bypass cut valve 46 is interposed in the second bypass passage 32R and blocks the flow of the hydraulic fluid from the second bypass passage 32R to the tank 25. More specifically, the second bypass cut valve 46 is an electromagnetic switching valve. The second bypass cut valve 46 is disposed most downstream with respect to the control valves 44 and 45 in the second bypass passage 32R. The second bypass cut valve 46 then cuts off the connection between the second bypass passage 32R and the tank 25 in accordance with the input signal. Thereby, the hydraulic fluid flowing through the second bypass passage 32R can be prevented from being discharged into the tank 25.

The first check valve 17 is interposed in the first merging passage 22 that connects the downstream portion of the first travel control valve 12 in the first bypass passage 32L and the first supply passage 33L. The first check valve 17 allows the hydraulic fluid to flow from the first bypass passage 32L to the first supply passage 33L, and prevents the hydraulic fluid from flowing in the opposite direction. To explain in more detail, the first merging passage 22 is connected between the first traveling control valve 12 and the turning control valve 41 in the first bypass passage 32L. That is, when the first bypass passage 32L is closed by the control valves 41, 42 or the first bypass cut valve 43, the first check valve 17 causes the hydraulic fluid flowing through the first bypass passage 32L to flow through the first supply passage 33L. Combine with liquid. On the other hand, when the first bypass passage 32L is open, the first check valve 17 closes the first merging passage 22 to prevent the flow of the hydraulic fluid.

The second check valve 18 is interposed in the second merging passage 23 that connects the downstream portion of the second travel control valve 14 in the second bypass passage 32R and the second supply passage 33R. The second check valve 18 allows the hydraulic fluid to flow from the second bypass passage 32R to the second supply passage 33R, and prevents the hydraulic fluid from flowing in the opposite direction. More specifically, the second merging passage 23 is connected between the second travel control valve 14 and the boom control valve 45 in the second bypass passage 32R. That is, when the second bypass passage 32R is closed by the control valves 44, 45 or the second bypass cut valve 46, the second check valve 18 causes the hydraulic fluid flowing through the second bypass passage 32R to flow through the first supply passage 33L. Combine with liquid. On the other hand, when the first bypass passage 32L is open, the first check valve 17 closes the second merging passage 23 to prevent the flow of the hydraulic fluid.

The third check valve 19 is interposed in the third merging passage 24 that connects the first pump passage 31L and the first supply passage 33L. Further, the third check valve 19 allows the hydraulic fluid to flow from the first pump passage 31L to the first supply passage 33L, and prevents the hydraulic fluid from flowing in the opposite direction. More specifically, when the hydraulic fluid supplied to the second travel motor 3 is insufficient in a state where the spool 13a of the merging valve 13 is located at the offset position A1, the third check valve 19 closes the third merging passage 24. open. This allows the working fluid from the second hydraulic pump 11R to join the working fluid flowing through the first pump passage 31L, thereby supplementing the flow rate necessary to operate the second travel motor 3.

The operating device 20 outputs operating commands for operating the travel motors 2 and 3 and the hydraulic actuators 4 to 7 to the control device 21. In this embodiment, the operating device 20 is, for example, an operating valve or an electric joystick. That is, the operating device 20 has a plurality of operating tools. In this embodiment, the operating device 20 has four operating levers 20a to 20d as a plurality of operating tools. The operating device 20 outputs operating commands to the travel motors 2 and 3 and the hydraulic actuators 4 to 7 in accordance with the operations of the four operating levers 20a to 20d (in this embodiment, the operating direction and amount). Note that the operation command is a command that instructs the operating amount (displacement amount, speed, etc.) of each of the travel motors 2 and 3 and the hydraulic actuators 4 to 7. For example, each of the travel levers 20a and 20b, which are two of the four operation levers 20a to 20d, can swing in the front and rear directions. Further, each of the working levers 20c and 20d, which are the remaining two operating levers 20c and 20d, can swing in all directions by 360 degrees when viewed from above. Then, the operating device 20 outputs operation commands for the corresponding travel motors 2 and 3 (i.e., a first travel operation command and a second travel operation command) in response to the operation of the travel levers 20a and 20b. The operating device 20 also issues operating commands for the corresponding hydraulic actuators 4 to 7 (i.e., a swing operating command, an arm operating command, a boom operating command, and a bucket operating command) in accordance with the operating levers 20c and 20d. Output.

The control device 21 controls the operations of the first travel control valve 12 , the merging valve 13 , the second travel control valve 14 , the first circuit system 15 , and the second circuit system 16 in response to operation commands from the operating device 20 . Control. To explain in more detail, the control device 21 is electrically connected to the operating device 20. Each operation command from the operating device 20 is input to the control device 21 . Then, the control device 21 sets the flow rate of the hydraulic fluid flowing to the first travel motor 2, the second travel motor 3, and the four hydraulic actuators 4 to 7 in accordance with each operation command. Further, the control device 21 is connected to each of the control valves 12 , 14 , 41 , 42 , 44 , 45 , the merging valve 13 , the first bypass cut valve 43 , and the second bypass cut valve 46 . Then, the control device 21 outputs each signal according to the set flow rate to each control valve 12, 14, 41, 42, 44, 45. Thereby, the control device 21 supplies each control valve 12, 14, 41, 42, The operations of 44 and 45 can be controlled. Further, the control device 21 outputs signals corresponding to each operation command from the operating device 20 to the merging valve 13, the first bypass cut valve 43, and the second bypass cut valve 46. Thereby, the control device 21 controls the movements of the merging valve 13, the first bypass cut valve 43, and the second bypass cut valve 46.

<About the operation of the hydraulic system>
The hydraulic drive system 1 can run the hydraulic vehicle or perform various tasks by operating the operating levers 20a to 20d. Below, the operation of the hydraulic drive system 1 when each of the operating levers 20a to 20d is operated will be explained in more detail.

[Straight driving operation]
The hydraulic drive system 1 causes the hydraulic vehicle to travel straight when the travel levers 20a and 20b are operated simultaneously. To explain in more detail, when the travel levers 20a and 20b are operated simultaneously, the first travel operation command and the second travel operation command are input to the control device 21. . The merging valve 13 has a function as a straight travel valve. Therefore, when the first travel operation command and the second travel operation command are input, the control device 21 moves the spool 13a of the merging valve 13 to the offset position A1 (merging state). Then, the first hydraulic pump 11L is connected to the two travel motors 2 and 3 via the first travel control valve 12 and the second travel control valve 14, respectively. The hydraulic fluid from the first hydraulic pump 11L is then supplied to both of the two travel motors 2 and 3. This causes the hydraulic vehicle to travel straight.

In addition, in the hydraulic drive system 1, in a merging state such as when traveling straight, the hydraulic fluid guided from the first hydraulic pump 11L to the two travel motors 2 and 3 may be insufficient. In that case, in the hydraulic drive system 1, the working fluid of the second hydraulic pump 11R can be supplemented via the third check valve 19. Thereby, the vehicle can be driven at a speed corresponding to the amount of operation of the travel levers 20a, 20b. That is, it is possible to improve the operability of the hydraulic vehicle. Further, by providing the third check valve 19, which can supplement the working fluid of the second hydraulic pump 11R, separately from the merging valve 13, the pressure loss of the working fluid passing through the merging valve 13 can be reduced.

[Hydraulic actuator operation]
Next, a case where the working levers 20c and 20d are operated alone will be described. For example, if the amount of operation of the operating levers 20c and 20d is less than a predetermined amount, that is, the flow rate flowing to the corresponding hydraulic actuator 4 to 7 in response to an operation command from the operating device 20 is less than a predetermined flow rate, the control The device 21 maintains the spool 13a of the merging valve 13 at the neutral position M. The control device 21 then operates the control valves 41, 42, 44, and 45 according to the output operation command. As a result, the hydraulic actuators 4 to 7 corresponding to the operation command operate at a speed corresponding to the operation amount.

On the other hand, when the amount of operation of the working levers 20c and 20d is a predetermined amount or more, that is, when the flow rate flowing to the corresponding hydraulic actuator 4 to 7 in response to an operation command from the operating device 20 is a predetermined flow rate or more, the control device 21 , it works as follows. That is, when the first circuit system operation command or the second circuit system operation command is input, the control device 21 moves the spool 13a of the merging valve 13 to the offset position A1 (see FIGS. 2 and 3). Note that the first circuit system operation command is an operation command for operating the control valves 41 and 42 provided in the first circuit system 15, and is at least one of a swing operation command and an arm operation command in this embodiment. The second circuit system operation command is an operation command for operating the control valves 44 and 45 provided in the second circuit system 16, and is at least one of a boom operation command and a bucket operation command in this embodiment. When the spool 13a moves to the offset position A1, the first hydraulic pump 11L is connected to the second travel control valve 14, and the second hydraulic pump 11R is connected to the first circuit system 15. The hydraulic drive system 1 guides the hydraulic fluid to the first circuit system 15 and the second circuit system 16, respectively, but the hydraulic fluids of the two hydraulic pumps 11L and 11R are merged as follows to each circuit system. Lead to 15 and 16.

That is, when the hydraulic fluid is introduced into the first circuit system 15 as shown in FIG. 2, the hydraulic fluid is introduced from the first bypass passage 32L through the first check valve 17 to the first supply passage 33L. As a result, the working fluids of the two hydraulic pumps 11L and 11R are combined and guided to the first circuit system 15. On the other hand, when the hydraulic fluid is introduced into the second circuit system 16 as shown in FIG. The working fluids of the two hydraulic pumps 11L and 11R are combined and guided to the second circuit system 16. In this manner, in the hydraulic drive system 1, the hydraulic fluids of the two hydraulic pumps 11L and 11R can be combined, and the combined hydraulic fluids can be guided to the respective circuit systems 15 and 16. This will be explained in more detail below.

For example, when the first circuit system operation command is input, the control device 21 operates the first circuit system 15 to flow the hydraulic fluid to the hydraulic actuators 4 and 5, and operates the second circuit system 15 by the second bypass cut valve 46. The bypass passage 32R is blocked. When the second bypass passage 32R is shut off, the hydraulic pressure in the first bypass passage 32L increases and the first check valve 17 opens. As a result, the working fluid from the first hydraulic pump 11L flows into the first supply passage 33L via the first merging passage 22. The hydraulic fluid from the first hydraulic pump 11L then joins the hydraulic fluid from the second hydraulic pump 11R in the first supply passage 33L. The combined hydraulic fluid is then supplied to the hydraulic actuators 4 and 5 via the first circuit system 15.

More specifically, when a swing operation command is input, the control device 21 moves the spool 41a of the swing control valve 41 from the neutral position, and shuts off the second bypass passage 32R with the second bypass cut valve 46. do. Then, the first check valve 17 opens. Then, in the first supply passage 33L, the hydraulic fluid from the first hydraulic pump 11L joins with the hydraulic fluid from the second hydraulic pump 11R, and the joined hydraulic fluid flows through the swing control valve 41 to the swing motor 4. (See Figure 2). Similarly, when an arm operation command is input, the hydraulic fluid from the first hydraulic pump 11L can be merged with the hydraulic fluid flowing through the first supply passage 33L via the first merging passage 22. The combined working fluid is then supplied to the arm cylinder 5 via the arm control valve 42.

Further, when the second circuit system operation command is input, the control device 21 operates the second circuit system 16 to flow the hydraulic fluid to the hydraulic actuators 6 and 7, and operates the first bypass cut valve 43 to operate the second circuit system 16. The bypass passage 32L is shut off. When the first bypass passage 32L is shut off, the hydraulic pressure in the second bypass passage 32R increases and the second check valve 18 opens. Thereby, the working fluid from the second hydraulic pump 11R flows into the second supply passage 33R via the second merging passage 23. Then, the hydraulic fluid from the second hydraulic pump 11R joins the hydraulic fluid from the first hydraulic pump 11L in the second supply passage 33R. The combined hydraulic fluid is then supplied to the hydraulic actuators 6 and 7 via the second circuit system 16.

To explain in more detail, when the bucket operation command is input, the control device 21 moves the spool 44a of the bucket control valve 44 from the neutral position, and shuts off the first bypass passage 32L with the first bypass cut valve 43. do. Then, the second check valve 18 opens. Then, in the second supply passage 33R, the hydraulic fluid from the second hydraulic pump 11R merges with the hydraulic fluid from the first hydraulic pump 11L, and the merged hydraulic fluid flows through the bucket control valve 44 to the bucket cylinder 6. (See Figure 3). Similarly, when a boom operation command is input, the hydraulic fluid from the second hydraulic pump 11R can be merged with the hydraulic fluid flowing through the second supply passage 33R via the second merging passage 23. The combined hydraulic fluid is then supplied to the boom cylinder 7 via the boom control valve 45.

In this way, in the hydraulic drive system 1, when the flow rate according to the circuit system operation command exceeds a predetermined flow rate, the working fluids of the two hydraulic pumps 11L and 11R can be combined and guided to the respective circuit systems 15 and 16. . Therefore, it is possible to prevent the flow rate of the hydraulic fluid from being insufficient in each of the circuit systems 15 and 16.

Similarly, when a plurality of hydraulic actuators 4 to 7 are operated by operating at least one of the working levers 20c and 20d, the merging valve 13 The position of the spool 13a is switched. If the sum of the flow rates described above exceeds the set amount, the control device 21 moves the spool 13a of the merging valve 13 to the offset position A1. As a result, as in the case of independent operation, the hydraulic fluid from the two hydraulic pumps 11L and 11R is combined by either the first check valve 17 or the second check valve 18, and is not allowed to flow to each hydraulic actuator 4 to 7. It will be done.

<Simultaneous operation of travel motor and work motor>
When the traveling levers 20a and 20b are operated and the working levers 20c and 20d are operated, the control device 21 operates as follows. That is, when the operation command is input, the control device 21 moves the spool 13a of the merging valve 13 to the offset position A1. The control device 21 then operates the control valves 12, 14, 41, 42, 44, and 45 according to the operation command.

For example, when the first travel operation command and the first circuit system operation command are input, the control device 21 moves the spool 12a of the first travel control valve 12 from the neutral position as shown in FIG. 4(a). , and activates the first circuit system 15. Then, the working fluid from the first hydraulic pump 11L is supplied to the first travel motor 2 via the first travel control valve 12 (see the thick line in FIG. 4(a)). This causes the first travel motor 2 to operate. Further, the control device 21 shuts off the second bypass passage 32R using the second bypass cut valve 46. Then, the working fluid from the second hydraulic pump 11R is guided to the first circuit system 15 via the first supply passage 33L. That is, when a swing operation command, which is a first circuit system operation command, is input, the hydraulic fluid from the second hydraulic pump 11R is guided to the swing control valve 41 via the first supply passage 33L, and further the swing operation command is inputted. It is supplied to the swing motor 4 via the control valve 41 (see the one-dot thick line in FIG. 4(a)). This causes the swing motor 4 to operate. On the other hand, when an arm operation command, which is a first circuit system operation command, is input, the hydraulic fluid from the second hydraulic pump 11R is guided to the arm control valve 42 via the first supply passage 33L, and further the arm operation command is inputted. It is supplied to the arm cylinder 5 via the control valve 42. This causes the arm cylinder 5 to operate.

Further, when the second travel operation command and the second circuit system operation command are input, the control device 21 moves the spool 14a of the second travel control valve 14 from the neutral position as shown in FIG. 4(b). , and activates the second circuit system 16. Then, the working fluid from the second hydraulic pump 11R is supplied to the second travel motor 3 via the second travel control valve 14 (see the thick line in FIG. 4(b)). This causes the second travel motor 3 to operate. Further, the control device 21 uses the first bypass cut valve 43 to cut off the first bypass passage 32L. Then, the working fluid from the second hydraulic pump 11R is guided to the second circuit system 16 via the second supply passage 33R. That is, when a bucket operation command, which is a second circuit system operation command, is input, the hydraulic fluid from the second hydraulic pump 11R is guided to the bucket control valve 44 via the second supply passage 33R, and further the bucket operation command is inputted. It is supplied to the bucket cylinder 6 via the control valve 44 (see the dotted thick line in FIG. 4(b)). This causes the bucket cylinder 6 to operate. On the other hand, when the boom operation command, which is the second circuit system operation command, is operated, the hydraulic fluid from the second hydraulic pump 11R is guided to the boom control valve 45 via the second supply passage 33R, and It is supplied to the boom cylinder 7 via the control valve 45. This causes the boom cylinder 7 to operate.

In this way, in the hydraulic drive system 1, even if the travel control valves 12 and 14 are activated, the hydraulic fluid is supplied to each circuit system 15 and 16 by moving the spool 13a of the merging valve 13 to the offset position A1. can lead to. Thereby, the traveling motors 2 and 3 and the hydraulic actuators 4 to 7 can be operated simultaneously. Further, in a similar manner, when the travel motors 2 and 3 are simultaneously operated to cause the vehicle to travel straight, the hydraulic actuators 4 to 7 can also be operated simultaneously.

<Other embodiments>
In the hydraulic drive system 1 of this embodiment, when each control valve 41, 42, 44, 45 of the work equipment actuator moves each spool 41a, 42a, 44a, 45a from the neutral position, the corresponding bypass passage Close 32L and 32R. However, each control valve 41, 42, 44, 45 does not necessarily need to be configured in this way. That is, each control valve 41, 42, 44, 45 may maintain the corresponding bypass passage 32L, 32R open when the spool 41a, 42a, 44a, 45a is moved from the neutral position. In this case, when each control valve 41, 42, 44, 45 is operated, the control device 21 operates the bypass cut valves 43, 46. This closes the bypass passages 32L and 32R.

Furthermore, in the hydraulic drive system 1 of this embodiment, when the operation amount of the working levers 20c and 20d, that is, the flow rate of the hydraulic fluid to the hydraulic actuators 4 to 7 is equal to or higher than a predetermined flow rate, the two hydraulic pumps 11L, The hydraulic fluid from 11R is combined. However, when the flow rate of the hydraulic fluid to the hydraulic actuators 4 to 7 is less than a predetermined flow rate, the hydraulic fluid from the two hydraulic pumps 11L and 11R may be combined.

Furthermore, in the hydraulic drive system 1 of this embodiment, there is one control valve 42, 44, 45 corresponding to the arm cylinder 5, bucket cylinder 6, and boom cylinder 7, but one control valve is provided corresponding to each cylinder 5 to 7. Two control valves may also be provided. That is, each circuit system 15, 16 is provided with a control valve corresponding to each cylinder 5 to 7, respectively. Then, the control device 21 operates one or two corresponding control valves depending on the amount of operation of the working levers 20c and 20d. Thereby, the hydraulic fluid can be merged by the control valve.

Further, although the vehicle equipped with the hydraulic drive system 1 includes the arm cylinder 5, the bucket cylinder 6, and the boom cylinder 7, it may include other actuators. The hydraulic drive system 1 may be configured to supply hydraulic fluid to actuators other than the arm cylinder 5, bucket cylinder 6, and boom cylinder 7. Furthermore, the number of actuators that each circuit system 15, 16 has is not limited to two. That is, the number of actuators that each circuit system 15, 16 has may be one, or may be three or more.

Furthermore, the operating device 20 of the hydraulic drive system 1 does not necessarily need to have an operating tool, and may be configured to create and output an operating command based on a program or the like. In this case, the hydraulic drive system 1 can automatically drive the hydraulic vehicle.

1 Hydraulic drive system 2 First travel motor 3 Second travel motor 4 Swing motor 5 Arm cylinder 6 Bucket cylinder 7 Boom cylinder 11L First hydraulic pump 11R Second hydraulic pump 12 First travel control valve 13 Merging valve ( switching valve)
14 Second traveling control valve 15 First circuit system 16 Second circuit system 17 First check valve 18 Second check valve 19 Third check valve 20 Operating device 21 Control device 22 First merging passage 23 Second merging passage 24 3 Merging passage 25 Tank 32L First bypass passage 32R Second bypass passage 33L First supply passage 33R Second supply passage 41 Swing control valve (first work machine control valve)
42 Arm control valve (first work machine control valve)
43 First bypass cut valve 44 Bucket control valve (second work machine control valve)
45 Boom control valve (second work equipment control valve)
46 Second bypass cut valve

Claims (5)

a first hydraulic pump that discharges hydraulic fluid;
a second hydraulic pump that discharges working fluid;
a normally open type first which is connected to the first hydraulic pump and the first travel motor, controls the flow of the working fluid from the first hydraulic pump to the first travel motor, and opens and closes the first bypass passage; A travel control valve,
a first circuit system connected to at least one first working actuator and controlling the flow of hydraulic fluid to the at least one first working actuator;
a normally open second travel control valve that is connected to a second travel motor and controls the flow of hydraulic fluid to the second travel motor and opens and closes a second bypass passage;
a second circuit system connected to the second hydraulic pump and at least one second working actuator to control the flow of hydraulic fluid from the second hydraulic pump to the at least one second working actuator;
connected to the first hydraulic pump, the second hydraulic pump, the first circuit system, and the second travel control valve, and to which each of the first hydraulic pump and the second hydraulic pump is connected; a switching valve that switches the control valve to the first circuit system and the second travel control valve, respectively;
interposed in a first merging passage connecting a downstream portion of the first travel control valve in the first bypass passage and a first supply passage connecting the switching valve and the first circuit system; a first check valve that allows hydraulic fluid to flow from the first bypass passage to the first supply passage;
interposed in a second merging passage connecting a downstream portion of the second traveling control valve in the second bypass passage and a second supply passage connecting the second hydraulic pump and the second circuit system; and a second check valve that allows hydraulic fluid to flow from the second bypass passage to the second supply passage. an operating device that outputs an operation command instructing the amount of operation of the first working actuator and the second working actuator; controlling the operations of the first circuit system and the second circuit system to supply the first working actuator and the second working actuator, respectively, via two circuit systems, and controlling the operation of the switching valve; further comprising a control device;
The control device connects the first hydraulic pump to the second traveling control valve by the switching valve and connects the second hydraulic pump to the first circuit system in response to an operation command from the operating device. 2. The hydraulic drive system of claim 1, wherein the hydraulic drive system is connected to a hydraulic drive system. The control device connects the first hydraulic pump to the second travel control valve by the switching valve when the flow rate according to the operation command from the operation device exceeds a predetermined flow rate, and connects the first hydraulic pump to the second travel control valve and controls the second hydraulic pressure. 3. The hydraulic drive system of claim 2, wherein a pump is connected to the first circuit system. The first circuit system includes a normally open type first work control valve that controls the flow of hydraulic fluid to the first work actuator and opens and closes the first bypass passage, and a normally open first work control valve that is interposed in the first bypass passage. and a first bypass cut valve capable of blocking the flow of the working fluid from the first bypass passage to the tank,
The second circuit system includes a normally open second work control valve that controls the flow of hydraulic fluid to the second work actuator and opens and closes the second bypass passage, and a normally open second work control valve that is interposed in the second bypass passage. and a second bypass cut valve capable of blocking the flow of the working fluid from the second bypass passage to the tank,
When the hydraulic fluid flows to the second working actuator via the second working control valve, the control device controls the flow of the working fluid from the first bypass cut valve to the tank using the first bypass cut valve. When shutting off and flowing the hydraulic fluid to the first working actuator via the first working control valve, the second bypass cut valve shuts off the flow of the working fluid from the second bypass cut valve to the tank. , A hydraulic drive system according to claim 2 or 3. interposed in a third confluence passage connecting a pump passage connecting the first hydraulic pump and the switching valve and the first supply passage connecting the switching valve and the first circuit system, and from the pump passage. The hydraulic drive system according to any one of claims 1 to 4, further comprising a third check valve that allows hydraulic fluid to flow into the first supply passage.

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