JP2792307B2 - Valve train for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve train for an internal combustion engine for controlling the operation of an intake valve and an exhaust valve provided in an automobile engine or the like.

[0002]

2. Description of the Related Art Generally, in opening and closing control of an intake valve and an exhaust valve in an automobile engine, an opening and closing timing is set according to an operating state obtained from an engine speed, an accelerator pedal depression amount, and the like. In such a valve train, there has been proposed a valve train in which fuel consumption is reduced at low speeds and the profile of a cam is changed at high speeds so that intake and exhaust can be performed efficiently at high speeds. . This is performed by changing the opening / closing timing of the intake valve and the exhaust valve, the lift amount, the opening period, and the like at a low speed or a high speed.

That is, in an automobile engine, a high-speed cam and a low-speed cam are provided on a cam shaft, and the high-speed cam has a cam profile capable of obtaining a valve opening / closing timing corresponding to a high-speed operation. The cam has a cam profile capable of obtaining a valve opening / closing timing corresponding to a low-speed operation. By selectively using the high-speed cam or the low-speed cam according to the operating state during the operation of the engine, it is possible to obtain the optimal opening / closing timing of the intake valve and the exhaust valve. I have.

[0004] In such an automobile engine, during idle operation or low-load operation, for example, in the case of a four-cylinder engine, a cylinder stop mechanism for stopping two cylinders to reduce fuel consumption has been conventionally used. Proposed. That is,
In the valve operating device, the piston is operated at the time of idling operation or low-load operation, but the operation of the intake valve and the exhaust valve is stopped so as not to supply fuel.

The cylinder closing mechanism for stopping the operation of the intake valve and the exhaust valve is generally operated by providing a rocker arm with a switching mechanism and controlling the switching mechanism by hydraulic pressure. In this case, hydraulic pressure is supplied from the main oil pump of the engine to the switching mechanism via an oil passage. However, in order to operate the switching mechanism, only the operating oil pressure from the main oil pump of the engine is insufficient because a high oil pressure cannot be obtained. That is, as shown in FIG. 12, there is a minimum required switching oil pressure for operating the switching mechanism, and the operating oil pressure from the main oil pump of the engine is lower than the required switching oil pressure.
Therefore, by providing an assist oil pump separately from the main oil pump of the engine, the operating oil pressure of the switching mechanism is set to be higher than the operation required oil pressure.

FIG. 13 is a plan view of a cylinder head showing a conventional valve train of an engine having a cylinder rest mechanism, and FIG. 14 is a hydraulic path of the valve train.

As shown in FIGS. 13 and 14, a camshaft 202 is rotatably mounted at the center of the cylinder head 201, and a cam (not shown) is integrally formed at a predetermined position. A pair of rocker shafts 203 are mounted on the cylinder head 201 so as to be rotatable in parallel with the camshaft 202. A base end of a rocker arm 206 having a rocker arm 204 and a switching mechanism 205 is mounted on each rocker shaft 203, and a swinging end of each rocker arm 204, 206 faces an upper end of an intake or exhaust valve 207. ing. Further, an oil pump 208, an accumulator 209, and an oil control valve 210 are mounted at an end of the cylinder head 201. The oil pump 208 can be driven by a drive cam 211 attached to one end of the cam shaft 202, and the oil control valve 210 can be operated by a control signal of a control unit 212.

[0008] When the camshaft 202 rotates, the rocker arm 204 and the rocker arm 206 swing by the cam to drive the intake and exhaust valves 207. Then, at the time of idling operation or low load operation of the engine, the operation is performed with two of the four cylinders stopped. That is, the oil pump 208 is driven by the drive cam 211 of the camshaft 202, and the hydraulic pressure is stored in the accumulator 209. On the other hand, the control unit 212 determines the operating state of the engine based on signals from various sensors, sends a control signal to the oil control valve 210, and switches the control signal. Then, the hydraulic pressure is sent to the switching mechanism 205 of the rocker arm 206, and the driving of the corresponding intake and exhaust valves 207 is stopped. Accordingly, the engine operates only by driving the intake and exhaust valves 207 corresponding to the rocker arm 204.

[0009]

In the above-described conventional valve train of an engine, during rocking operation or low load operation, some rocker arms 206 are switched to stop two of the four cylinders. The mechanism 205 is mounted. Therefore, the oil pump 208 or the accumulator 20
9 and the like are required, and these must be mounted on the cylinder head 201. Conventionally, as described above, the cylinder head 201 is provided above one end, but this causes a part of the engine to protrude upward. In addition, the cylinder head cover that covers the upper part of the cylinder head 201 must also have a shape that protrudes upward in accordance with that, and the height of the engine increases.
This not only causes an increase in size, but also makes the layout when mounted on a vehicle difficult.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide a valve train for an internal combustion engine in which the size of the internal combustion engine is reduced.

[0011]

According to the present invention, there is provided a valve train for an internal combustion engine, comprising: a pair of parallel intake valves;
And exhaust camshafts and engine operating conditions.
Operating tie for at least one of the intake or exhaust valves
Variable valve timing mechanism for changing the
In a valve train for an internal combustion engine having an oil pump for supplying oil pressure to a valve timing mechanism, the oil pump is disposed between the intake camshaft and the exhaust camshaft, and the intake camshaft and the exhaust An oil pump cam for driving the oil pump is provided on one of the camshafts.

[0012] In addition, the valve operating system for an internal combustion engine of the present invention, before
The accumulator is located above or below the oil pump.
It is characterized by having been done. Further, the internal combustion engine of the present invention
The valve gear of the engine is composed of the oil pump and accumulator.
It is characterized in that the diameters of the cylinders are formed to be the same .

[0013]

The oil pump is disposed between the intake camshaft and the exhaust camshaft so that the oil pump is driven by the oil pump provided on the camshaft. The oil pump and the accumulator are disposed vertically. With this arrangement, the space can be saved, the device can be made compact, and the layout when mounted on the vehicle is facilitated.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a main part of a cylinder head representing a valve train of an internal combustion engine according to an embodiment of the present invention (AA in FIG. 2).
Cross section, center of cylinder head in FIG. 2 (BB in FIG. 10)
3 is a plan view of a valve train with a cylinder rest mechanism, FIG.
5 is a sectional view showing a switching mechanism of the valve gear, FIG. 6 is an exploded perspective view of the valve gear, and FIG. 8 is a hydraulic path of the valve gear. , FIG. 9 illustrates the operation of the switching mechanism, FIG. 10 illustrates a cross section of the valve train without the cylinder rest mechanism, FIG.
Shows the plane of the cylinder head.

The internal combustion engine of this embodiment is a double over head camshaft type engine (DOHC) having two camshafts in a cylinder head.
It is a four-cylinder engine with two valves and two valves.

As shown in FIGS. 3 to 5 and 11, the cylinder head 11 is provided with a pair of intake camshafts 12 and exhaust camshafts 13 which are parallel to each other along the longitudinal direction. Low speed cam 14 with a small lift for each cylinder and high speed cam 1 with a large lift for each cylinder
5 are integrally formed. The pair of camshafts 12 and 13 are fixed to the upper portion of the cylinder head 11 by bolts 18 and 19 while being held between the upper portion of the camshaft housing 16 and the plurality of cam caps 17. It is rotatably supported.

The cylinder head 11 has a pair of intake rocker shafts 21 and a pair of exhaust rocker shafts 22 that are parallel to each other along the longitudinal direction thereof and are parallel to the pair of camshafts 12 and 13, respectively. It is arranged for each. The pair of rocker shafts 21 and 22 are held between the lower portion of the camshaft housing 16 and the plurality of rocker shaft caps 23 by bolts 19 and 24 and the cylinder head 11.
Is rotatably supported by the cylinder head 11 by being fixed to the lower part of the cylinder head. Note that a cylinder head cover 25 is fixed to an upper portion of the cylinder head 11.

Each of the rocker shafts 21 and 22 has a valve operating device that can be switched between a valve opening / closing timing for high-speed operation and a valve opening / closing timing for low-speed operation. And a valve train that can be closed during low load operation. That is, as shown in FIG. 11, the valve trains 31 of the upper and lower two cylinders among the four cylinders have a cylinder closing mechanism, and the valve train 32 of the central two cylinders does not have the cylinder rest mechanism.

Here, the valve train 31 with a cylinder rest mechanism will be described. As shown in FIG. 6, a main rocker arm 33 having a T-shape in plan view is mounted on the exhaust rocker shaft 22, and low-speed rocker arms 34 and high-speed rocker arms 35 are mounted on both sides thereof as sub rocker arms. . The main rocker arm 33 has a base end whose rocker shaft 2
2, and an adjusting screw 36 is attached to an oscillating end thereof by an adjusting nut 37.
The lower end of the adjusting screw 36 is in contact with the upper end of an exhaust valve 80 described later.

On the other hand, the low-speed rocker arm 34 has its base end pivotally mounted on the rocker shaft 22 and is rotatably supported. A roller bearing 38 is attached to its swinging end. Cam 14 can be engaged. Similarly, the base end of the high-speed rocker arm 35 is pivotally connected to the rocker shaft 22 and is rotatably supported. A roller bearing 39 is attached to the swinging end of the rocker arm 35. Cam 15 can be engaged.

Further, as shown in FIG. 5, the low-speed rocker arm 34 and the high-speed rocker arm 35 are integrally provided with arm portions 40 and 41, respectively, on the side opposite to the swinging end where the roller bearings 38 and 39 are mounted. The lost motions 42 and 43 act on the arm portions 40 and 41. The lost motions 42 and 43 include a cylinder 44 and a plunger 45 fixed to the cam cap 17,
The plunger 45 is constituted by a compression spring 46.
5 presses the arm portions 40 and 41 to urge the rocker arms 34 and 35 shown on the left side in FIG. 5 in the clockwise direction and the rocker arms 34 and 35 shown on the right side in the counterclockwise direction. ing.

Accordingly, the rocker arm 34 for low speed is normally used.
And the high-speed rocker arm 35 has lost motion 4
The roller bearings 38 and 39 are in contact with the outer peripheral surfaces of the low speed cam 14 and the high speed cam 15 of the camshaft 13 by the camshafts 2 and 43. When the camshaft 13 rotates, the cams 14 and 15 act. Thus, the low-speed rocker arm 34 and the high-speed rocker arm 35 can be swung.

As shown in FIG. 7, the low-speed rocker arm 34 and the high-speed rocker arm 35 can be rotated integrally with the rocker shaft 22 by the switching mechanism 50. A through-hole 51 is formed in the rocker shaft 22 at a position corresponding to the low-speed rocker arm 34 along the radial direction. A lock pin 52 is movably mounted in the through-hole 51, and a spring seat 53 is provided. It is urged in one direction by a supported compression spring 54. On the other hand, an engagement hole 55 is formed in the low-speed rocker arm 34 at a position corresponding to the through hole 51 of the rocker shaft 22, and a lock pin 52 urged by a compression spring 54 is engaged with the engagement hole 55. ing. A hydraulic passage 56 communicating with the through hole 51 is formed in the rocker shaft 22 along the axial direction, and the lock pin 52 communicates with the hydraulic passage 56 and has an opening on the side engaged with the engaging hole 55. An oil passage 57 is formed.

A through-hole 58 is formed in the rocker shaft 22 at a position corresponding to the high-speed rocker arm 35 along the radial direction. A lock pin 59 is movably mounted in the through-hole 58. , Compression spring 6
It is biased in one direction by 0. On the other hand, the high-speed rocker arm 35 has a through hole 5 of the rocker shaft 22.
An engagement hole 61 is formed at a position corresponding to 8, and the lock pin 59 is pulled out of the engagement hole 59 by the compression spring 60. A hydraulic passage 62 communicating with the through hole 58 is formed in the rocker shaft 22 along the axial direction, and an oil passage 63 communicating with the end of the through hole 58 on the opposite side to the engaging hole 59 is formed. Have been.

Usually, as shown in FIG.
The low-speed rocker arm 34 is integrated with the rocker shaft 22 by engaging the lock pin 52 urged by the compression spring 54 with the engagement hole 55, and can rotate together with the main rocker arm 33 via the rocker shaft 22. It has become. On the other hand, in the high-speed rocker arm 35, the lock pin 59 urged by the compression spring 60 comes out of the engagement hole 61, and the engagement with the rocker shaft 22 is released, so that the locker arm 35 does not rotate integrally with the rocker shaft 22. It has become. Therefore, the low-speed cam 14 and the high-speed cam 15 swing the low-speed rocker arm 34 and the high-speed rocker arm 35,
Only the transmitted driving force of the low-speed rocker arm 34 is transmitted through the rocker shaft 22 to the main rocker arm 33.
And the main rocker arm 33 can be swung.

When hydraulic pressure is supplied to the hydraulic passages 56 and 62 of the rocker shaft 22, in the low-speed rocker arm 34, the pressure oil flows through the oil passage 57 as shown in FIG. It flows toward the engagement hole 55 of the through hole 51, and pulls out the lock pin 52 from the engagement hole 55 against the urging force of the compression spring 54. Then, rocker arm 3 for low speed
The engagement between the rocker shaft 4 and the rocker shaft 22 is released so that the rocker shaft 22 does not rotate integrally. On the other hand, high-speed rocker arm 3
5, the pressure oil flows through the oil passage 63 to the opposite side of the through hole 58 from the engagement hole 61, and the lock pin 59 is engaged with the engagement hole 61 against the urging force of the compression spring 54. Combine.
Then, the high-speed rocker arm 35 and the rocker shaft 22 are engaged, and both can rotate integrally. Accordingly, the low-speed cam 14 and the high-speed cam 15 swing the low-speed rocker arm 34 and the high-speed rocker arm 35, but only the transmitted driving force of the high-speed rocker arm 35 is transmitted to the main rocker via the rocker shaft 22. The main rocker arm 33 is transmitted to the arm 33 and can swing.

The hydraulic passage 5 of the rocker shaft 22
When the hydraulic pressure is supplied to only 6, as shown in FIG.
In the low-speed rocker arm 34, the pressure oil
1 to the side of the engagement hole 55, and
And the locker arm 34 for low speed and the rocker shaft 22 are disengaged from each other so that they do not rotate together. On the other hand, in the high-speed rocker arm 35,
The lock pin 59 is engaged with the engagement hole 6 by the compression spring 60.
1, the engagement with the rocker shaft 22 is released, and the two do not rotate integrally. Therefore, the low speed cam 14 and the high speed cam 15 are
And the rocker arm 35 for high speed swings, but the driving force is not transmitted to the rocker shaft 22, and the cylinder can be brought into the cylinder-stop state without operating the main rocker arm 33.

Further, in the valve train 32 without the cylinder rest mechanism, as shown in FIG.
Has a T-shaped rocker arm 64 for low speed.
And a high-speed rocker arm 65 is mounted. The base end of the low-speed rocker arm 64 is the rocker shaft 2.
2 are integrally consolidated. A roller bearing 66 is attached to the swinging end of the low-speed rocker arm 64 so that the low-speed cam 14 can be engaged.
The lower end of the adjustment screw 67 is in contact with the upper end of an exhaust valve 80 described later.

On the other hand, the base end of the high-speed rocker arm 65 is rotatably supported by being pivotally mounted on the rocker shaft 22, and a roller bearing 69 is attached to the swing end thereof. High-speed cam 15
Can be engaged. An arm 70 is integrally formed on the high-speed rocker arm 65 on the side opposite to the swinging end on which the roller bearing 69 is mounted, and a lost motion 71 acts on this arm 70, and the high-speed rocker arm 65 65 is urged in one direction. Further, the high-speed rocker arm 65 can be rotated integrally with the rocker shaft 22 by the switching mechanism 72. That is, a through-hole 73 is formed in the rocker shaft 22 at a position corresponding to the high-speed rocker arm 65, a lock pin 74 is movably mounted, and is urged and supported by a compression spring 75. On the other hand, an engagement hole 76 is formed in the high-speed rocker arm 65, and the lock pin 74 is pulled out of the engagement hole 76 by a compression spring 75. And rocker shaft 2
2, a hydraulic passage 77 communicating with the through hole 73 is formed along the axial direction, and an oil passage 78 communicating with an end of the through hole 73 opposite to the engaging hole 76 is formed.

Usually, the high-speed rocker arm 65
The lock pin 74 comes out of the engagement hole 76 by the compression spring 75, and the engagement with the rocker shaft 22 is released, so that the lock pin 74 does not rotate integrally with the rocker shaft 22. Therefore, the low-speed cam 14 and the high-speed cam 15 swing the low-speed rocker arm 64 and the high-speed rocker arm 65, but the driving force of the low-speed cam 14 is transmitted to an exhaust valve 80 described later, and the exhaust valve 80 Can be rocked. When hydraulic pressure is supplied to the hydraulic passage 77 of the rocker shaft 22, in the high-speed rocker arm 65, the pressurized oil flows through the oil passage 78 to the opposite side of the through-hole 73 from the engagement hole 76 and locks. The pin 59 is engaged with the engagement hole 76. Then, the rocker arm 65 for high speed and the rocker shaft 2
2 are engaged, and can be rotated integrally with the rocker shaft 22. Therefore, the high-speed cam 15 swings the high-speed rocker arm 35, and the driving force is transmitted to the exhaust valve 80 via the rocker shaft 22 and the low-speed rocker arm 64 to swing the exhaust valve 80. I can do it.

In the above description of the valve trains 31 and 32, only the exhaust side has been described. However, the intake side has the same structure, and each camshaft is adjusted in accordance with the opening and closing timing of the intake and exhaust valves. Only the formation positions of the cams 12 and 13 in the circumferential direction are different.

As shown in FIG. 5, the intake valve 79 and the exhaust valve 80 are movably mounted on the cylinder head 11, and the intake port 83 and the exhaust port 84 are closed by valve springs 81 and 82. Accordingly, by driving the upper ends of the intake valve 79 and the exhaust valve 80 by driving the above-mentioned main rocker arm 33 (low-speed rocker arm 64), the intake port 83 is formed.
The exhaust port 84 can be opened and closed to communicate with the combustion chamber 85.

As shown in FIG. 1, FIG. 2 and FIG. 11, a hydraulic control device 86 for operating the switching mechanisms 50 and 72 of the valve operating device 31 is provided at a rear portion (an upper portion in FIG. 11) of the cylinder head. Is provided. The hydraulic control device 86 includes an oil pump 87, an accumulator 88, an oil control valve 89 for high-speed switching, and an oil control valve 90 for cylinder switching.

The oil pump 87 and the accumulator 88 are located between the intake camshaft 12 and the exhaust camshaft 13, and are arranged vertically one above the other, and their axial centers are horizontal. ing. That is, the oil pump 87 is provided on the side of the cam cap housing 16 and the cam cap 17 at the rearmost part of the cylinder head 11.
The cylinder 91 is horizontally movable and urged and supported by a compression spring 92, and is fixed by a bolt 94 via a cover 93. A plunger 96 acts on a cylinder 91 of the oil pump 87 via a compression spring 95, and the plunger 96 can be driven by an oil pump cam 97 formed integrally with one end of the intake camshaft 12. It has become.

A cylinder 98 of an accumulator 88 is horizontally movable at the lower side of the cam cap housing 16 and the cam cap 17 and is urged and supported by a compression spring 99. And is fixed by bolts 94. The diameter of the cylinder 91 of the oil pump 87 and the diameter of the cylinder 98 of the accumulator 88 are the same and can be shared.
The high-speed switching oil control valve 89 and the cylinder-stop switching oil control valve 90 are mounted on the cylinder head 11.

As shown in FIGS. 1, 2 and 8, the high-speed switching oil control valve 89 is directly connected to a main oil pump (not shown) of the engine via an oil passage 100, and the oil pressure is controlled via an oil passage 101. It is connected to a passage 62. Further, the cylinder-stop switching oil control valve 90 is connected to the accumulator 88, the oil pump 87, and the main oil pump via an oil passage 102, and to the hydraulic passage 56 via an oil passage 103. Further, each of the oil control valves 89, 90 can be operated by a control signal of the engine control unit 104.

The switching mechanism 72 of the valve train 32 can be operated by a hydraulic control device 86 in the same manner as the valve train 31. An oil passage (not shown) is provided in the hydraulic passage 77 of the rocker shaft 22. The oil control valve 89 is connected via the. As shown in FIG. 2, a hollow plug tube 105 is provided upright for each cylinder in the cylinder head 11, and an ignition plug 106 is provided in each plug tube 105.
Is mounted, and the front end faces each combustion chamber 85.

The operation of the four-cylinder engine of this embodiment will be described below. Engine control unit 104
Detects the operating state of the engine based on the detection results of various sensors, and if the engine is running at a low speed, selects a cam profile suitable for the running state. In this case, the engine control unit 104 outputs a control signal to each of the oil control valves 89, 90, and
Close 0. Then, no pressure oil is supplied to each of the hydraulic passages 56, 62, and 77, and the valve operating device 31 causes the lock pin 52 to lock the low-speed rocker arm 3 as shown in FIG.
4 and the rocker shaft 22 are integrated, and the engagement between the high-speed rocker arm 35 and the rocker shaft 22 is released. Therefore, when the camshafts 12 and 13 rotate, the low-speed cam 14 causes the low-speed rocker arm 34 to rotate.
Swings, and its driving force is transmitted to the main rocker arm 33 via the rocker shaft 22, and the main rocker arm 33 swings. Drive. On the other hand, as shown in FIG.
When the engagement between the high-speed rocker arm 65 and the rocker shaft 22 is released, and the camshafts 12 and 13 rotate, the low-speed cam 14 causes the low-speed rocker arm 64 to rotate.
Swings, and a pair of adjusting screws 67 at the swinging end drive the intake valve 79 and the exhaust valve 80. Thus, the intake valve 79 and the exhaust valve 80 are driven at the valve opening / closing timing corresponding to the low-speed operation, and the engine is operated at a low speed.

When the engine control unit 104 detects the high-speed running state of the engine, the engine control unit 104
A control signal is output to 9, 90, and each valve 89, 90 is opened. Then, pressure oil is supplied to each of the hydraulic passages 56, 62, and 77, and when the engine is running at a high speed, the valve train 31 is operated.
As shown in FIG. 9B, the lock pin 52 is pulled out from the engagement hole 55 by the pressure oil, and the engagement between the low-speed rocker arm 34 and the rocker shaft 22 is released.
Further, the lock pin 59 is engaged with the engagement hole 61 so that the high-speed rocker arm 35 and the rocker shaft 22 are integrated. Accordingly, the high-speed rocker arm 35 swings by the high-speed cam 15, and further, the main rocker arm 33 swings to drive the intake valve 79 and the exhaust valve 80.
On the other hand, in the valve gear 32, the lock pin 59 is engaged with the engagement hole 76 by the supply pressure oil, and the high-speed rocker arm 65 and the rocker shaft 22 are integrated. Therefore, the high-speed rocker arm 35 is moved by the high-speed cam 15.
Swings to drive the intake valve 79 and the exhaust valve 80. Thus, the intake valve 79 and the exhaust valve 80
Drives at the valve opening / closing timing corresponding to high-speed operation,
The engine runs at high speed.

Then, the engine control unit 1
When the engine 04 detects an idling operation state or a low-load running state of the engine, two of the four cylinders are stopped to reduce fuel consumption. That is, the engine control unit 104
Outputs a control signal to each of the oil control valves 89 and 90, and opens only the valve 90. Then, the hydraulic passage 5
As shown in FIG. 9C, the valve gear 31 is disengaged from the low-speed rocker arm 34 and the rocker shaft 22. Therefore, the low speed cam 14
And the driving force of the high-speed cam 15 is the main rocker arm 3.
3, the valve train 31 does not operate and is brought into the cylinder-stop state. On the other hand, in the valve operating device 32, the low-speed rocker arm 64 swings by the low-speed cam 14 to drive the intake valve 79 and the exhaust valve 80. In this way, the engine is operated by driving only the intake valve 79 and the exhaust valve 80 of the valve train 32.

As described above, the engine valve operating system of the present embodiment comprises the oil pump 87 and the accumulator 88 for operating the switching mechanism 50 of the valve operating system 31, the oil control valves 89 and 90, etc. 8
6 is an intake camshaft 12 and an exhaust camshaft 13
Between the oil pump 87 and the accumulator 8
The oil pump 87 and the accumulator 88 can be arranged efficiently because the oil pump 87 and the accumulator 88 are arranged vertically, so that the layout of the cylinder head 11 is compact, and a part of the engine projects upward or the height of the engine increases. No more.

Since the diameters of the cylinders 91 and 98 of the oil pump 87 and the accumulator 88 are the same, not only can the cylinders 91 and 98 be shared,
The peripheral members can be shared, and the cost can be reduced.

[0044]

As described above in detail with reference to the embodiments, according to the valve train of an internal combustion engine of the present invention, a pair of parallel
Intake and exhaust camshafts and engine operating conditions
At least one of the intake and exhaust valves
A variable valve timing mechanism for changing the operation timing,
Oil that supplies oil pressure to this variable valve timing mechanism
A pump and an oil camshaft
And the intake camshaft.
Either the camshaft or the exhaust camshaft
Since the oil pump cam for driving the oil pump is provided, it is possible to prevent a part of the internal combustion engine from projecting upward and the height of the engine from being increased. Also, the oil po
Place an accumulator above or below the pump, or
Pump and accumulator with the same cylinder diameter.
Since, it is possible to arrange the oil pump and the accumulator efficiently, it is possible to reduce the size of the internal combustion engine is the layout of the cylinder head is compact.

[Brief description of the drawings]

FIG. 1 is a sectional view of an essential part (AA in FIG. 2) of a cylinder head representing a valve gear of an internal combustion engine according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view of the center (BB in FIG. 11) of the cylinder head.

FIG. 3 is a plan view of a valve train with a cylinder rest mechanism.

FIG. 4 is a sectional view taken along the line CC of FIG. 3;

FIG. 5 is a sectional view taken along line DD of FIG. 3;

FIG. 6 is an exploded perspective view of the valve train.

FIG. 7 is a sectional view illustrating a switching mechanism of the valve train.

FIG. 8 is a hydraulic path diagram of the valve train.

FIG. 9 is a diagram illustrating the operation of the switching mechanism.

FIG. 10 is a cross-sectional view of a valve train without a cylinder rest mechanism.

FIG. 11 is a plan view of a cylinder head.

FIG. 12 is a graph showing the operating oil pressure when the internal combustion engine is closed.

FIG. 13 is a plan view of a cylinder head showing a valve train of an engine having a conventional cylinder rest mechanism.

FIG. 14 is a hydraulic path diagram of a conventional valve train.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Cylinder head 12, 13 Cam shaft 14 Low speed cam 15 High speed cam 21, 22 Rocker shaft 31, 32 Valve train 33 Main rocker arm 34, 64 Low speed rocker arm (sub rocker arm) 35, 65 High speed rocker arm (Sub rocker arm) 42, 43, 71 Lost motion 50, 72 Switching mechanism 51, 58, 73 Through hole 52, 59, 74 Lock pin 55, 61, 76 Engagement hole 56, 62, 77 Hydraulic passage 79 Intake valve 80 Exhaust valve 85 Combustion chamber 86 Hydraulic control device 87 Oil pump 88 Accumulator 89 High speed switching oil control valve 90 Cylinder closing switching oil control valve 91,98 Cylinder 97 Oil pump cam 104 Engine control unit

────────────────────────────────────────────────── ─── Continued on the front page (56) References JP-A-3-229906 (JP, A) JP-A-2-78712 (JP, A) JP-A-3-127006 (JP, U) (58) Field (Int.Cl. ⁶ , DB name) F01L 13/00 301 F01L 13/00 302 F01L 13/00 303 F01L 1/34

Claims (3)

(57) [Claims] 1. A pair of parallel intake and exhaust camshafts.
Shaft and the intake or exhaust
Variable to change the operation timing of at least one of the lubes
Valve timing mechanism and variable valve timing mechanism
A valve train for an internal combustion engine having an oil pump for supplying oil pressure to the intake camshaft and the exhaust camshaft, wherein the oil pump is disposed between the intake camshaft and the exhaust camshaft. Wherein an oil pump cam for driving the oil pump is provided in any one of the above. 2. A valve train for an internal combustion engine according to claim 1.
And an accumulator above or below the oil pump
A valve gear of an internal combustion engine, characterized in that disposed. 3. The valve train for an internal combustion engine according to claim 2, wherein the cylinder diameters of the oil pump and the accumulator are the same.