JPH04248061A - Shift control device of automatic transmission - Google Patents

Abstract

PURPOSE:To prevent engine stop accompanying hard braking by constituting a lockup valve out of a movable valve body and an energized spring, and making an arrangement that the movable valve body may be set in the open position of a lockup clutch by application of a pilot pressure and may be set in the closed position of the lockup clutch by release of the pilot pressure. CONSTITUTION:A torque converter line 202 from a regulator valve is connected to a lockup valve 201, and a control line 203 of the main line is connected to one side of a control port 201b. When a lockup solenoid valve 204 is set on by the signal (+) of a control circuit 200, a spool 201a is shifted to the right by means of a spring (not shown in figure), and communication is made between the torque converter line 202 and the line 205, closing a lockup clutch. When the solenoid valve 204 is set on, the control pressure is introduced into the control port 201b, and the spool 201a shifts to the left, opening the lockup clutch.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a speed change control device for an automatic transmission.

0002

[Prior Art] Recently, in vehicles equipped with automatic transmissions, lock-up clutches have been installed in the torque converters to directly connect the engine output shaft and the input shaft of the automatic transmission. are increasing.

[0003] Japanese Patent Publication No. 63-4061 discloses a technique in which a lock-up clutch is released in the event of sudden braking to prevent engine stop. In other words, when sudden braking is applied, the input from the vehicle side acts directly on the engine due to lock-up, causing the engine's rotation speed to drop rapidly and increasing the risk of engine stoppage. This is intended to prevent engine stoppage by releasing the lockup during sudden braking.

0004

[Problems to be Solved by the Invention] By the way, the lock-up control valve provided in the hydraulic circuit of an automatic transmission is
It usually has a movable valve body that is biased by a spring. When pilot pressure is applied to the lock-up valve, this movable valve element takes the first position against the spring force, drains the hydraulic pressure in the lock-up clutch, and turns the lock-up clutch OFF ( emancipation). Furthermore, when the pilot pressure for the lock-up valve is drained, the movable valve body assumes the second position due to spring force, hydraulic pressure is supplied to the lock-up clutch, and the lock-up clutch is turned on (
(concluded).

Therefore, when the technique disclosed in the above publication is adopted, pilot pressure is applied to the lock-up valve during sudden braking, and the movable valve element takes the first position against the spring force. Become.

However, when the engine speed decreases due to sudden braking, the following problem occurs. That is, when the engine speed decreases and the discharge pressure of the oil pump driven by the engine decreases, this causes a decrease in line pressure in the hydraulic circuit of the automatic transmission. Due to this decrease in line pressure, the pilot pressure acting on the lock-up valve described above becomes insufficient, and the movable valve body is succumbed to the spring force and moves to the second position, that is, in the direction of engaging the lock-up clutch. This causes a problem in that it becomes impossible to prevent the engine from stopping.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to prevent the occurrence of engine stop due to the difficulty in maintaining the released state of the lock-up clutch due to the drop in engine speed caused by sudden braking. An object of the present invention is to provide a speed change control device for a transmission.

[0008]

[Means for Solving the Problems] In order to achieve the above technical problem, in the present invention, an oil pump that supplies line pressure to a hydraulic circuit of an automatic transmission is mechanically driven by an engine, and the hydraulic The circuit is provided with a lock-up valve for controlling a lock-up clutch, the lock-up valve having a movable valve body biased by a spring, and when pilot pressure is applied to the lock-up valve. the movable valve body takes a first position against the biasing force of the spring, the hydraulic pressure in the lockup clutch is drained, and the lockup clutch is released;
When the pilot pressure to the lock-up valve is released, the movable valve body assumes the second position due to the biasing force of the spring, hydraulic pressure is supplied to the lock-up clutch, and the lock-up clutch is engaged. Assuming a transmission, as shown in FIG. 6, an engine brake switching means for switching a gear position where engine braking is applied to a gear position where engine braking is not applied;
An engine gear shift detecting means for detecting that a gear gear to which the engine brake is applied is set, a sudden braking detecting means for detecting a sudden braking state of the vehicle, the sudden braking detecting means and the engine gear shift receiving a signal from the stage detection means;
gear position control means for switching the gear position on which the engine operates to a gear position on which the engine brake does not apply when the vehicle is in a sudden braking state while the gear position on which the engine brake is applied is set; The configuration includes the following.

[0009]

[Effect] In other words, engine stop is likely to occur during sudden braking when the gear is in a gear position where engine braking is applied, and when the gear is in a gear where engine braking is not applied. Even if the lock-up clutch is engaged due to lack of pilot pressure, the problem of engine stop will not occur because no input from the wheels will act on the engine.

0010

[Examples] Examples of the present invention will be described below. First, the mechanical configuration of the automatic transmission according to this embodiment will be explained with reference to FIG. 1. The automatic transmission 10 includes a torque converter 20 and a
It has a speed change gear mechanism 30 driven by a zero output, a plurality of frictional engagement elements 41 to 46 such as clutches and brakes, and one-way clutches 51 and 52 that change the power transmission path of the mechanism 30. Driving ranges D, 2, 1, and R are now available, as well as 1st to 4th speeds in the D range, 1st to 3rd speeds in the 2nd range, and 1st to 2nd speeds in the 1st range. There is.

The torque converter 20 includes a pump 2 fixedly installed in a case 21 connected to the engine output shaft 1.
2, and the pump 22 is arranged opposite to the pump 22.
The pump is interposed between the pump 22 and the turbine 23 and supported by the transmission case 11 via a one-way clutch 24 to increase torque. a lock-up clutch 26 provided between the case 21 and the turbine 23 and directly connecting the engine output shaft 1 and the turbine 23 via the case 21; It consists of The rotation of the turbine 23 is outputted to the transmission gear mechanism 30 via the turbine shaft 27. Here, a pump shaft 12 passing through a turbine shaft 27 is connected to the engine output shaft 1, and the shaft 12 drives an oil pump 13 provided at the rear end of the transmission. There is.

On the other hand, the speed change gear mechanism 30 is composed of a Ravigneau type planetary gear device, and includes a small sun gear 31 having a small diameter and loosely fitted onto the turbine shaft 27;
Behind the sun gear 31, there is a large diameter sun gear 32 loosely fitted onto the turbine shaft 27, a plurality of short pinion gears 33 meshed with the small sun gear 31, and a front half of the sun gear 32. A long pinion gear 34 that is meshed with the short pinion gear 33 and whose rear half is meshed with the large sun gear 32, a carrier 35 that rotatably supports the long pinion gear 34 and the short pinion gear 33, and a long pinion gear. 34
The ring gear 36 is meshed with the front half of the ring gear 36.

A forward clutch 41 and a first one-way clutch 51 are interposed in series between the turbine shaft 27 and the small sun gear 31. strike clutch 4
2 is interposed between the turbine shaft 27 and the carrier 35, and a 3-4 clutch 43 is interposed between the turbine shaft 27 and the carrier 35.
Furthermore, a reverse clutch 44 is interposed between the turbine shaft 27 and the large sun gear 32. Further, a 2-4 brake 45 made of a band brake for fixing the large sun gear 32 is provided between the large sun gear 32 and the reverse clutch 44, and a 2-4 brake 45 is provided between the carrier 35 and the transmission case. - the carrier 3
a second one-way clutch 52 that receives the reaction force of 5;
A low reverse brake 46 for fixing the carrier 35 is provided in parallel. The ring gear 36 is connected to the output gear 14, and rotation is transmitted from the output gear 14 to left and right wheels (not shown) via a differential device.

Next, the frictional engagement elements 41 to 46 such as the above-mentioned clutches and brakes, and the one-way clutches 51 and 52
To explain the relationship between the operating state and the gear stage, first, in the first gear, the forward clutch 41 is engaged and the first and second one-way clutches 51 and 52 are in a locked state. Therefore, the output rotation of the torque converter 20 is input from the turbine shaft 27 to the small sun gear 31 of the planetary gear device 30 via the forward clutch 41 and the first one-way clutch 51. In this case, by the action of the second one-way clutch 52, the carrier 35
is fixed, the planetary gear device 30 operates as a fixed gear train that does not perform a differential operation that transmits rotation from the small sun gear 31 to the ring gear 36 via the short pinion gear 33 and the long pinion gear 34. . As a result, a first speed state with a large reduction ratio corresponding to the ratio of the diameters of the small sun gear 31 and ring gear 36 is obtained.

Next, in second speed, in addition to the first speed state described above, the 2-4 brake 45 is activated, the large sun gear 32 in the planetary gear device 30 is fixed, and the second one-way clutch 52 is activated. becomes idle. Therefore, the rotation transmitted from the turbine shaft 27 to the small sun gear 31 is transmitted to the long pinion gear 34 via the short pinion gear 33, and the long pinion gear 34 is connected to the large sun gear 32 that meshes with the long pinion gear 34. Since it is fixed, it revolves on the large sun gear 32, and the carrier 35 rotates accordingly. As a result, the rotation of the ring gear 36 is increased by the rotation amount of the carrier 35 (revolution of the long pinion gear 34) compared to the first speed state, and a second speed state is obtained in which the reduction ratio is smaller than that in the first speed state.

Furthermore, in the third speed, the 2-4 brake 45 is released from the second speed state, and the 3-4 clutch 43 is engaged. Therefore, the rotation of the turbine shaft 27 is input to the small sun gear 31 via the forward clutch 41 and the first one-way clutch 51, and at the same time is input to the carrier 35 via the 3-4 clutch 43. That will happen. As a result, the entire planetary gear device 30 rotates integrally, and the ring gear 36
A third speed state is obtained in which the turbine shaft 27 rotates at the same speed as the turbine shaft 27.

Furthermore, in the fourth gear, the 2-4 brake 45, which was once released in the third gear, is re-engaged. Therefore, the rotation of the turbine shaft 27 is controlled by the 3-4 clutch 4.
3 to the carrier 35 of the planetary gear device 30, causing the long pinion gear 34 to revolve, but the large sun gear 32 with which the long pinion gear 34 meshes is fixed by the 2-4 brake 45. Therefore, the long pinion gear 34 rotates while revolving together with the carrier 35.

As a result, the ring gear 36 meshing with the long pinion gear 34 is rotated by being accelerated by the rotation of the long pinion gear 34 due to the rotation of the carrier 35 (rotation of the turbine shaft 27). −
A 4-speed bar drive state is obtained. In this case, the forward clutch 41 is in the engaged state, but the first one-way clutch 51 in series with it is idling, so
The rotation of the turbine shaft 27 is not input to the small sun gear 31.

Furthermore, at reverse speed, the reverse clutch 44 and the low reverse brake 46 are engaged, and the turbine
The rotation of the bin shaft 27 is input to the large sun gear 32 of the flat gear device 30, and the gear device 30
A carrier 35 is fixed. Therefore, rotation is transmitted through a fixed gear train from the large sun gear 32 to the ring gear 36 via the long pinion gear 34, and the rotation is transmitted through a fixed gear train that corresponds to the ratio of the diameters of the large sun gear 32 and ring gear 36. A reduction ratio is obtained, but in this case the direction of rotation of the ring gear 36 is opposite to the direction of rotation of the turbine shaft 27 or large sun gear 32.

The first one-way clutch 51 transmits rotation in 1st to 3rd gears, and the second one-way clutch 51 receives reaction force in 1st gear.
Since the one-way clutch 52 idles during coasting, the engine brake will not operate in these gears, but the engine brake will not operate in these gears. At D speed, the coast clutch 42 parallel to the first one-way clutch 51 is engaged, and at the first gear of the first range, the low reverse brake 46 parallel to the second one-way clutch 52 is engaged. Engine braking is obtained in the 3rd gear of the range, the 2nd and 3rd gears of the 2nd range, and the 1st and 2nd gears of the 1st range. Each of the above hydraulic fastening elements 41 to 46 and one-way clutches 51 and 5
Table 1 summarizes the relationship between the operation of No. 2 and the gear position.

[Table 1]

Next, as shown in FIGS. 2 and 3, a hydraulic actuator 41a that operates each of the frictional engagement elements 41-46,
The hydraulic circuit 60 that supplies and discharges hydraulic oil to and from 46a will be described. In addition, the circled number 1 attached to each line in Figure 2
~15 and the circled numbers 1 to 15 attached to each line in FIG. 3 correspond to each number, respectively. Here, among the respective hydraulic actuators 41a to 46a, 2-4
The hydraulic actuator 45 of the brake 45 is connected to the apply port.
It is composed of a servo piston having a port 45a' and a release port 45a'', and when hydraulic oil is supplied only to the apply port 45a', the 2-4 brake 45 is engaged, and both ports are engaged. - The 2-4 brake 45 is released when hydraulic oil is not supplied to both ports 45a' and 45a'' and when hydraulic oil is supplied to both ports 45a' and 45a''. The other actuators 41a to 44a and 46a are constituted by ordinary hydraulic pistons, and are adapted to engage the frictional engagement elements when hydraulic oil is supplied.

This hydraulic circuit 60 has an oil pump 13 shown in FIG. 1, which is mechanically driven by an engine (not shown), and oil is discharged from the pump 13 to the main line 100. It looks like this. The hydraulic circuit 60 also includes a regulator valve 61 that adjusts the pressure of hydraulic fluid discharged into the main line 100 to a predetermined line pressure, and a throttle valve 62 that generates a throttle pressure depending on the accelerator opening of the engine. It is provided. After this throttle pressure is further adjusted by the throttle modulator valve 63,
By being supplied to the regulator valve 61,
The line pressure is set to a value corresponding to the accelerator opening of the engine. The hydraulic circuit 60 also includes a manual valve 64 that selectively sends the line pressure to each hydraulic line according to the selected range;
1-2, 2- which operates according to the gear position and selectively supplies line pressure to each of the hydraulic actuators 41a to 46a.
3, 3-4 shift valves 71, 72, and 73 are provided.

The manual valve 64 has an input port f into which line pressure is introduced from the main line 100, and first to fifth output ports a to e, and is controlled by the movement of the spool 64a. , the input port f is the first in the D range,
to the second output ports a, b, to the first, second, third output ports a, b, c in the second range; to the first, third,
It is connected to fourth output ports a, c, and d, and in the R range, to a fifth output port e. First to fifth output lines 101 to 105 are connected to each output port a to e, respectively.

The 1-2, 2-3, 3-4 shift valves 71, 72, 73 are connected to the spools 71a, 72, respectively.
A, 73a are biased to the right side in the drawing by a spring, and control ports 71b, 73a are located on the right side of these spools.
This is a configuration in which 72b and 73b are provided. A first control line 106 branched from the main line 100 is connected to the control port 71b of the 1-2 shift valve 71.
Control port 72b of 3, 3-4 shift valves 72, 73
, 73b are connected to second and third control lines 107, 108 branched from the first output line 101, respectively, and these control lines 106, 107, 10
8, first, second, and third solenoid valves 76, respectively.
, 77, 78 are provided. These solenoid valves 76 to 78 introduce control pressure into the control ports 71b to 73b of the shift valves when they are OFF, respectively.
The spools 71a to 73a are located on the left side in the drawing, and the control pressure in the control ports 71b to 73b is drained when the control port is turned on, so that the spools 71a to 73a are located on the right side. ing.

[0025] Here, these solenoid valves 76~
78 is turned on or off according to the gear position to be set by signals A, B, and C from the control circuit 200 to which the vehicle speed and throttle valve opening are input. This shift stage change, that is, the shift command, is performed based on the shift map by comparing the shift-up shift line and the shift-down shift line of this shift map. Incidentally, the shift map for the two ranges is as shown in FIG.

Further, the ON/OFF combination patterns of the solenoid valves 76 to 78 at each gear stage of the travel range are set as shown in Table 2. Furthermore, D range 2
When shifting from 1st to 3rd speed, the gear passes through the intermediate pattern shown in the table.

[Table 2]

On the other hand, among the first to fifth output lines 101 to 105 connected to the respective output ports a to e of the manual valve 64, the lines communicate with the main line 100 in each of the forward ranges D, 2, and 1. The first output line 101 is led to the actuator 41a of the forward clutch 41 via the one-way orifice 80. Therefore, the forward clutch 41 is always engaged in the D, 2, and 1 ranges. Incidentally, the first output line 101 is provided with an N-D accumulator 81 for buffering when the forward clutch is engaged.

Further, a line 111 is branched from the first output line 101 and led to the 1-2 shift valve 71, and this branch line 111 is connected when the first solenoid valve 76 is turned on. Spool 71a
When it moves to the right, it is communicated with the servo apply line 112 through the one-way orifice 82 to the apply port 45a' of the servo piston 45a. Therefore, the first solenoid valve 76 is turned on in the D, 2, and 1 ranges.
In other words, servo apply pressure is introduced into the apply port 45a' at 2nd, 3rd, and 4th speeds in the D range, 2nd and 3rd speeds in the 2nd range, and 2nd speed in the 1st range. . Incidentally, the servo ply line 112 is also provided with a 1-2 accumulator 83 for buffering when the servo piston (2-4 brake) is fastened.

[0029] Also, main line 100 in D, 2 range.
The second output line 102 is led to a 2-3 shift valve 72. When the second solenoid valve 77 is OFF, the line 102 is connected to the spool 72a.
3 is connected to the actuator 43a of the 3-4 clutch 43 via the one-way orifice 84 when the
-4 clutch line 113. therefore,
When the second solenoid valve 77 is OFF in the D and 2 ranges, that is, in the 3rd and 4th gears of the D range, and in the 3rd gear of the 2nd range, the 3-
4 clutch 43 will be engaged. In addition, above 3-
4 Clutch line 113 has one-way orifice 8
A bypass valve 85 and a 2-3 timing valve 86 are provided in parallel with the 3-4 clutch line 113 to adjust the engagement timing of the 3-4 clutch 43. A 2-3 accumulator 87 is provided for buffering during fastening.

Furthermore, a line 114 branched from the 3-4 clutch line 113 and the first output line 10
A line 115 branched from 1 is led to a 3-4 shift valve 73. And the third solenoid valve 7
When 8 is off and the spool 73a is located on the left side, 3
-Line 114 branched from 4 clutch line 113
However, a line 115 branched from the first output line 101 is connected via a one-way orifice 89 to a servo release line 116 that reaches the release port 45a'' of the servo piston 45a. , are connected to a coast clutch line 117 leading to an actuator 42a of a coast clutch 42, respectively.

Therefore, when the second and third solenoid valves 77 and 78 are both OFF in the D and 2 ranges, that is, the D
At 3rd speed of range and 3rd speed of 2nd range, servo piston 4
A servo release pressure is introduced into the release port 45a'' of 5a, and the 2-4 brake 45 is released.

Furthermore, when the third solenoid valve 78 is OFF in the D, 2, and 1 ranges, that is, the coast clutch is activated in the 3rd gear of the D range, the 2nd and 3rd gears of the 2nd range, and the 1st and 2nd gears of the 1st range. 42 is engaged, and the engine brake is applied.

[0033] Here, the above 3-4 clutch line 113
and the line 114 branched from the line 113, there are three lines via branch lines 118 and 119, respectively.
A 3-2 timing valve 90 and a 3-2 capacity valve 91 are provided to adjust the discharge timing of the -4 clutch pressure and the servo release pressure.

[0034] Also, the coast clutch line 117
A bypass line 120 is provided to bypass the one-way orifice 89, and a 3-4 capacity valve 92 is provided to open and close the line 120. This valve 92 is operated by the bypass when the 3-4 clutch pressure is generated and when the manual valve 64 is selected to the 2nd or 1st range and the third output line 103 is connected to the main line 100. The line 120 is opened to adjust the discharge timing of the coast clutch pressure. Note that a line 121 branched from the third output line 103 is connected to the regulator valve 6 via the throttle backup valve 93.
The line pressure is guided to the pressure increasing side of No. 1, and the line pressure is increased in the No. 2 range and the No. 1 range.

Furthermore, a fourth output line 1 is connected to the main line 100 in one range by a manual valve 64.
04 is led to the 1-2 shift valve 71 via the low-reduction valve 94 and line 122. and,
The line 122 is connected when the first solenoid valve 76 is OFF.
When the spool 71a is located on the left side, it is communicated with the low reverse brake line 123 through the one-way orifice 95 and shuttle valve 96 to the actuator 46a of the low reverse brake 46. Therefore, 1
When the first solenoid valve 76 is OFF in the range, that is, at the 1st speed of the 1st range, the low reverse brake 46 is engaged.

Furthermore, a fifth output line 105 communicating with the main line 100 in the R range communicates with the low-reverse brake line 123 via the one-way orifice 97 and the shuttle valve 96, and also communicates with the fifth output line 123 through the one-way orifice 97 and the shuttle valve 96. A reverse scratch line 124 is branched from the line 105 and extends through a one-way orifice 98 to an actuator 44a of the reverse scratch 44. Therefore, in the R range, the low reverse brake 46 is always
and leaver scratch 44 are engaged. The reverse clutch 124 is also provided with an N-R accumulator 99 for buffering when the reverse clutch is engaged. Also, line 1 branched from the fifth output line 105
25 is led to the pressure increasing side of the regulator valve 61, and the line pressure is increased in the R range.

In addition to the above configuration, this hydraulic circuit 6
0 is provided with a lock-up valve 201 for operating a lock-up clutch 26 in the torque converter 20 shown in FIG.

A torque converter line 202 is led from the regulator valve 61 to this valve 201, and the main line 100 is connected as a control line 203 to a control port 201b at one end. When the lock-up solenoid valve 204 provided in the control line 203 is turned ON by the signal D from the control circuit 200, the control pressure in the control port 201b is drained and the spool 201a is positioned on the right side (second position) by the biasing force of a spring (not shown), so that the torque converter line 202 is communicated with the line 205 leading into the torque converter 20, whereby the torque converter 20 The internal pressure of the lock-up clutch 26 increases and the lock-up clutch 26 is engaged.

[0039] Also, the solenoid valve 204 is turned off.
When the spool 201a moves to the left (first position) against the biasing force of the spring as a result of the control pressure being introduced into the control port 201b, the torque converter
The clutch line 202 communicates with a lockup release line 206, and lockup release pressure is introduced into the torque converter 20, so that the lockup clutch 26 is released.

Next, control when sudden braking is applied when the 2nd range or 1st range is selected will be explained. Here, when a sudden brake is applied, the aforementioned lock-up clutch 26 is forcibly released as in the conventional case.

Based on the above, in this embodiment, when sudden braking is applied, when the vehicle speed is below a predetermined value and the engine speed is below a predetermined value,
The coast clutch 42 is released and the gear position is changed to one in which engine braking is not applied. Therefore, the control circuit 200 includes the sensor group 30.
A signal from 0 is input. The sensor group 300 includes a vehicle speed sensor, a brake switch attached to a brake pedal (not shown), a sensor for detecting the rotation speed of the turbine shaft 27, and the like.

A specific example of the above control is shown in FIG. In the flowchart shown in the figure, step S
1 (hereinafter, the step number is indicated by the symbol "S"), it is determined whether the 2nd range or 1st range is currently selected, and if YES, the process proceeds to S2 where the vehicle suddenly decelerates. A determination is made as to whether the state is present or not.

This determination is made based on whether the rate of change in the rotational speed of the turbine shaft 27 is greater than or equal to a predetermined value. If YES, the process proceeds to S3 where it is determined whether the current vehicle speed is less than or equal to a predetermined value. This determination is made, and if YES, it is determined that the vehicle is in a running state in which the need for engine braking has decreased, and the process proceeds to S4, where it is determined whether or not the engine speed is below a predetermined value.

When a YES determination is made in S4, the engine speed is lower than the idle speed, the discharge pressure of the oil pump 13 is reduced, and the line pressure of the hydraulic circuit 100 is in a state of insufficient pressure. If so, the process proceeds to S5, where it is determined whether the brake switch is ON (brake pedal depressed).
If YES, it is assumed that the spool 201a of the lock-up valve 201 may be displaced to the second position (lock-up) by the spring force due to insufficient line pressure, and the process advances to S6 to disengage the coast clutch 42. It will be done.

That is, the third solenoid valve 78 is
N, and the gear position is changed to one in which the engine brake is not applied. The control contents of S6 are shown in parentheses in Table 2 above.

On the other hand, if any one of the above S1 to S5 is determined to be NO, the process moves to S7 and normal control is performed. For example, even if a sudden deceleration occurs when the 2nd range is selected, if the vehicle speed is high, the shift will proceed to S7 and the gear position will be changed to apply engine braking.

[0047]

As is clear from the above explanation, according to the present invention, even if the lock-up clutch is turned on due to insufficient line pressure due to a drop in engine speed due to sudden braking, the engine Since the brake is changed to a mode in which it does not work, it is possible to prevent the engine from stopping.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing an automatic transmission.

FIG. 2 is a diagram showing a hydraulic circuit of an automatic transmission.

FIG. 3 is a diagram showing a hydraulic circuit of an automatic transmission.

FIG. 4 is a diagram showing a map used when two ranges are selected as an example of a shift map.

[Fig. 5] Flowchart showing an example of control according to the embodiment.
to.

FIG. 6 is an overall configuration diagram of the present invention.

[Explanation of symbols]

10 Automatic transmission 13 Oil pump 20 Torque converter 26 Lock-up clutch 42 Coast clutch 78 Solenoid valve 200 Control circuit 201 Lock-up valve 201a Spool (movable valve body) 204 Lock-up solenoid valve 300
sensor group

Claims (2)

[Claims] 1. An oil pump that supplies line pressure to a hydraulic circuit of an automatic transmission is mechanically driven by an engine, and the hydraulic circuit is provided with a lock-up valve that controls a lock-up clutch. The lock-up valve has a movable valve body biased by a spring, and when pilot pressure is applied to the lock-up valve, the movable valve body resists the biasing force of the spring and assumes a first position; When the hydraulic pressure in the lock-up clutch is drained to release the lock-up clutch and the pilot pressure to the lock-up valve is released, the movable valve body assumes the second position due to the biasing force of the spring, and In an automatic transmission in which oil pressure is supplied to a lock-up clutch and the lock-up clutch is engaged, an engine brake switching means for switching a gear position where the engine brake is applied to a gear position where the engine brake is not applied. , an engine gear position detection means for detecting that a gear position at which the engine brake is applied is set, and a sudden braking detection means for detecting a sudden braking state of the vehicle;
In response to signals from the sudden braking detection means and the engine gear shift detecting means, when the vehicle enters a sudden braking state while a gear shift at which engine braking is applied is set, the engine brake is activated. 1. A speed change control device for an automatic transmission, comprising: a speed control means for switching a speed to a speed in which engine braking is not applied. 2. According to claim 1, further comprising vehicle speed detection means for detecting vehicle speed, and said gear stage control means receiving a signal from said vehicle speed detection means, when said vehicle speed is lower than a predetermined vehicle speed and the engine is When the vehicle is suddenly braked while a gear position where the brakes are applied is set, the gear position where the engine is applied is switched to a gear position where the engine brake is not applied. .