JP2800557B2 - 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.

[0002]

2. Description of the Related Art As a valve train for operating an intake valve or an exhaust valve (hereinafter referred to as an intake and exhaust valve) of an internal combustion engine at an arbitrary valve timing and valve lift, for example, a valve train as shown in FIG. Known (Japanese Unexamined Patent Publication No. 1-134013)
Reference).

[0003] To explain this, reference numeral 101 denotes a camshaft which rotates in synchronization with a crankshaft (not shown), and 102 denotes a crankshaft and a camshaft 1.
01 and a phase converter that changes the phase (relative angle) of the camshaft 101 with respect to the crankshaft. Reference numeral 103 denotes a control valve for controlling the valve lift amount of the intake / exhaust valve 104. First, when the control valve 103 is in the closed state, the cam 10 formed on the camshaft 101 is controlled.
The cam plunger 106 reciprocates following this.
Is driven, the hydraulic piston 107 moves the cam plunger 1
The intake / exhaust valve 104 is pushed down in conjunction with the hydraulic pressure at which 06 occurs. When the valve lift reaches a predetermined value, the control valve 10 is controlled to further restrict the lift of the intake / exhaust valve 104.
3 is controlled to the open state. At this time, the hydraulic piston 10
7, the valve spring 108 pushes up the hydraulic piston 107, and the hydraulic oil pushed out from the hydraulic piston 107 is stored in the accumulator 109 via the control valve 103.

Accordingly, an arbitrary valve timing can be obtained by controlling the phase conversion device 102, and an arbitrary valve lift can be obtained by controlling the control valve 103.

[0005] A damper chamber 110 is formed in the hydraulic piston 107 for the purpose of cushioning the shock when the intake / exhaust valve 104 is seated. That is, when the control valve 103 is in the open state, the intake / exhaust valve 104 starts the closing operation, but immediately before the valve closing, the damper chamber 110 and the accumulator 109 communicate with each other via the throttle unit 111. , The pressure in the damper chamber 110 rises and the check valve 1
12 is in the closed state. As a result, the hydraulic oil pushed out from the damper chamber 110 to the accumulator 109 has to pass through the narrow throttle portion 111, and the seating speed of the intake / exhaust valve 104 is limited due to the passage resistance by the throttle portion 111. The impact caused by closing the intake / exhaust valve 104 can be reduced.

The hydraulic oil stored in the accumulator 109 is returned to the cam plunger 106 via the control valve 103 and the check valve 113 in the return stroke of the cam plunger 106, and the hydraulic oil in such a hydraulic circuit Check valve 11
4 supplies hydraulic oil.

[0007]

However, in such a conventional valve train, the intake / exhaust valve 104 is used in order to reduce the impact when the intake / exhaust valve 104 is closed.
Since the kinetic energy of closing the valve is absorbed by the damping action of the hydraulic oil as described above, the optimum valve closing conditions are always set in response to changes in various conditions such as the viscosity of the hydraulic oil and the engine speed. Difficult to maintain. In other words, the optimum valve closing speed cannot be maintained due to the change in the viscosity of the hydraulic oil, and particularly at high rotation speed, the kinetic energy of the intake / exhaust valve 104 cannot be completely absorbed, causing abnormal noise or causing the intake / exhaust valve 104 to jump. There was a problem that

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and is intended to provide a valve train of an internal combustion engine which can appropriately obtain the closing characteristics of an intake valve or an exhaust valve regardless of the operating state of the engine. It is intended to provide a device.

[0009]

In order to solve the above-mentioned problems, the present invention provides a first cam and a second cam which rotate in different phases, and a first cam which reciprocates following the first cam. A plunger, a second cam plunger that reciprocates following the second cam, and reciprocates in conjunction with a hydraulic pressure generated by the second cam plunger when in the first mode; A hydraulic piston that reciprocates in conjunction with a hydraulic pressure generated by the cam plunger, and a hydraulic pressure generated by the first cam plunger when in the first mode;
An accumulator for accumulating the hydraulic pressure generated by the second cam plunger when in the first mode; and a hydraulic switching valve for switching between the first mode and the second mode when the cam lifts of the first cam and the second cam match. , An intake valve or an exhaust valve that opens and closes following the hydraulic piston.

[0010]

The hydraulic switching valve has two switching modes, one for guiding the first hydraulic pressure generated by the first cam plunger to the accumulator and the second for generating the second hydraulic pressure by the second cam plunger. 2 The first mode for guiding the hydraulic pressure to the hydraulic piston, one for the first mode generated by the first cam plunger
This is a second mode in which the hydraulic pressure is guided to the hydraulic piston while the second hydraulic pressure generated by the second cam plunger is guided to the accumulator. Switching between these modes is performed when the cam lift amounts of the first cam and the second cam match, that is, when the hydraulic pressures generated by the first cam plunger and the second cam plunger match.

On the other hand, the first cam and the second cam rotate with different phases. Therefore, first, the hydraulic piston operates the intake valve or the exhaust valve by interlocking with one of the hydraulic pressures generated by one of the first cam plunger and the second cam plunger, and the accumulator operates the first cam plunger and the second cam plunger.
The hydraulic oil is stored in conjunction with the other hydraulic pressure generated by one of the cam plungers. Next, when the hydraulic pressures generated by the first cam plunger and the second cam plunger match, one hydraulic pressure that has been guided to the hydraulic piston is guided to the accumulator, and the other hydraulic pressure that has been guided to the accumulator is It will be guided to the hydraulic piston.

In short, when the cam lift amounts of the first cam and the second cam coincide, the valve characteristics of the intake valve or the exhaust valve become:
That is, the characteristics change from the first cam to the characteristics of the second cam, or the characteristics change from the second cam to the characteristics of the first cam.

When the intake valve or the exhaust valve is closed,
Since the hydraulic oil pushed out from the hydraulic piston returns to either the first cam plunger or the second cam plunger, the valve closing characteristics of the intake valve or the exhaust valve are restricted by the cam profile of the first cam or the second cam. Will be. Therefore, since the valve closing characteristics of the intake valve or the exhaust valve do not depend on the damping action of the hydraulic oil as in the conventional example, the seating condition greatly changes with the change of the viscosity of the hydraulic oil and the engine speed. Therefore, stable valve closing characteristics can be obtained regardless of the operation state.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment according to the present invention will be described below with reference to FIGS.

Referring to FIG. 1, reference numeral 1 denotes a first camshaft which rotates in synchronization with a crankshaft (not shown).
2 is interposed between the crankshaft and the first camshaft 1 so that the first camshaft 1
Is a first phase converter that changes the phase (relative angle) of the first phase. The first cam 3 formed on the first camshaft 1 drives a first cam plunger 4 that reciprocates following the first cam shaft 1, and the first oil pressure P ₁ generated by the first cam plunger 4 is sent to the oil pressure switching valve 5. Be guided. The first cam plunger 4
A piston 4a reciprocating according to the first cam 3,
And a cylinder 4b for movably storing the cylinder. A hydraulic chamber 4c is provided between the piston 4a and the cylinder 4b.
Is formed.

Similarly, reference numeral 6 denotes a second camshaft which rotates in synchronization with a crankshaft (not shown), and reference numeral 7 denotes a second camshaft interposed between the crankshaft and the second camshaft 6.
It is a phase converter. The second cam 8 formed on the second camshaft 6 drives a second cam plunger 9 that reciprocates following the second cam 8, and the second hydraulic pressure P 2 generated by the second cam plunger 9 is transmitted to the hydraulic switching valve 5. I will 9a is a piston, 9b is a cylinder, and 9c is a hydraulic chamber.

The hydraulic switching valve 5 has two switching modes, one of which guides the first hydraulic pressure P ₁ generated by the first cam plunger 4 to the accumulator 10 and generates the first hydraulic pressure P ₁ by the second cam plunger 9. The second hydraulic pressure P _{2 is applied} to the hydraulic piston 11
In the first mode 5a, the first hydraulic pressure P ₁ generated by the first cam plunger 4 is guided to the hydraulic piston 11, while the second hydraulic pressure P ₂ generated by the second cam plunger 9.
Is a second mode 5b for guiding the flow to the accumulator 10.

The intake valve or an exhaust valve hydraulic piston 11 for driving (hereinafter referred to as intake and exhaust valves 12) reciprocates in conjunction with the hydraulic pressure P _V selected by the hydraulic switching valve 5, intake and exhaust valves 12 and the hydraulic valve spring 13 against the pressure P _V is arranged between the piston 11. Reference numeral 11a denotes a cylinder that accommodates the hydraulic piston 11 in a reciprocating manner.

The accumulator 10, the piston 14 that reciprocates in conjunction with the hydraulic pressure P _A that is selected by the hydraulic selector valve 5
When, is generally composed of a coil spring 15 which acts against the hydraulic pressure P _A, play a temporary effect of accumulating the hydraulic oil introduced to the accumulator 10.

Here, the hydraulic piston 11 and the piston 14
Is set to the same pressure receiving area, and the valve spring 13 and the coil spring 15 are set to the same set load and spring constant.

The hydraulic switching valve 5 is activated when the first hydraulic pressure P ₁ generated by the first cam plunger 4 matches the second hydraulic pressure P ₂ generated by the second cam plunger 9,
When the cam lift amounts of the first cam 3 and the second cam 8 coincide with each other, the second mode 5b is switched from the first mode 5a to the second mode 5b.
The mode is switched from the mode 5b to the first mode 5a, and the specific configuration is as shown in FIG.

That is, referring to FIG.
A cylindrical insertion hole 22 is formed along the longitudinal direction of the body 21 forming an outer shell with both ends closed, and a spool 23 can slide in the insertion hole 22 in the axial direction. ing.

A first input port 24 and a second input port 25 having a diameter larger than that of the insertion hole 22 are formed in the body 21 at predetermined positions of the insertion hole 22, respectively.
Communicates with the first cam plunger 4 via the first oil passage 26, and the second input port 25 communicates with the second cam plunger 9 via the second oil passage 27. Similarly, in the insertion hole 22,
Valve-side output port 28 communicating with hydraulic piston 11
And accumulator-side output ports 29, 29 communicating with the accumulator 10, respectively, and the valve-side output port 28 has a first input port 24 and a second input port 2.
5 and an output port 2 on the accumulator side.
Reference numerals 9 and 29 are respectively formed on the left side of the first input port 24 in the drawing and on the right side of the second input port 25 in the drawing.

The spool 23 has lands 30, 3 at both ends.
1 has lands 32 in the center, and these lands 30
The lands 31 and 32 are in sliding contact with the insertion holes 22, and the lands 30 and the lands 32 and the lands 32 and the lands 31 are connected by shafts 33 and 33 having a smaller diameter than the insertion holes 22. At one end (left side in the drawing) of the insertion hole 22, a second hydraulic chamber 34 formed with the land 30 is formed, and the second hydraulic passage 2 branched from the second hydraulic passage 27.
7 '. Similarly, a first hydraulic chamber 35 forming the land 31 is formed at the other end (right side in the drawing) of the insertion hole 22 and communicates with a first oil passage 26 ′ branched from the first oil passage 26. In the first hydraulic chamber 35, a spring 36 for urging the spool 23 toward the second hydraulic chamber 34 is housed.
It may be very weak enough to operate to the hydraulic chamber 34 side.

Based on such a configuration, although shown in the figure in a neutral state, when the hydraulic pressure in the first hydraulic chamber 35 becomes larger than that in the second hydraulic chamber 34, ie, the first cam plunger 4 When There is larger than the second hydraulic P ₂ of first hydraulic P ₁ and the second cam plunger 9 is generated to occur, the spool 23 is moved to the left in the drawing, has, the second hydraulic second cam plunger 9 occurs P ₂ is guided to the hydraulic piston 11 as the hydraulic pressure P _v, the first hydraulic P ₁ of the first cam plunger 4 is generated accumulator 10 as a hydraulic P _a
It is led to. When the hydraulic pressure in the second hydraulic chamber 34 becomes larger than that in the first hydraulic chamber 35,
When the first hydraulic pressure P ₁ in which the cam plunger 4 is generated is smaller than the second hydraulic P ₂ of the second cam plunger 9 occurs, conversely, the spool 23 moves to the right side in the drawing, the first cam plunger 4 is generated first hydraulic P ₁ to is guided to the hydraulic piston 11 as the hydraulic pressure P _v, the second hydraulic P ₂ of the second cam plunger 9 occurs is directed to the accumulator 10 as the hydraulic pressure P _a. It has been, when the first hydraulic pressure P ₁ of the first cam plunger 4 is generated and the second hydraulic P ₂ of the second cam plunger 9 occurs match, switches the first mode 5a and a second mode 5b It is.

In FIG. 1, reference numeral 37 designates a check valve disposed between the accumulator 10 and a hydraulic source (not shown). Hydraulic oil is supplied from a hydraulic source via a check valve 37.

Next, the operation based on such a configuration will be described. FIG. 3A shows the cam lift characteristic (curve) of the first cam 3, the cam lift characteristic (curve) of the second cam 8, and the valve characteristic of the intake / exhaust valve 12 (curved line). FIG. 3B shows a first hydraulic pressure P ₁ characteristic (curve) generated by the first cam plunger 4 and a second hydraulic pressure P ₂ characteristic (curve) generated by the second cam plunger 9.
It is.

The first phase converter 2 and the second phase converter 7 determine the cam lift characteristics of the first cam 3 and the second cam 8,
As shown in FIG. 3, the phase difference is set so that the second cam 8 follows the preceding first cam 3 and the second cam 8 starts operating before the first cam 3 ends operating. give.

[0029] Now, when the first cam 3 starts to operate, first hydraulic P ₁ generated from the first cam plunger 4 to follow this is introduced into the hydraulic switching valve 5, the second cam 8 at this time is still acting Since it has not been performed, the hydraulic pressure switching valve 5 is in the state of the first mode 5a. Thus, in until the second cam 8 starts to act (section A), the first hydraulic P ₁ of the first cam plunger 4 is generated it is stored in the accumulator 10 as the hydraulic pressure P _A, has been intake and exhaust valves 12 Has not yet started the lift.

When the crankshaft rotates further, the first
Until the first hydraulic pressure P ₁ generated by the cam plunger 4 and the second hydraulic pressure P ₂ generated by the second cam plunger 9 match (section B), the first hydraulic pressure P ₁ is still at the second hydraulic pressure P ₁ . Hydraulic pressure P
_Since it is larger than ₂ , the hydraulic switching valve 5 is maintained in the first mode 5a. Accordingly, the hydraulic piston 11 when the second cam 8 starts to operate, the second hydraulic P ₂ is pressure P _V of the second cam plunger 9 to follow this occurs
It is led to. Then, the hydraulic piston 11 is pushed down against the valve spring 13 guided to the hydraulic piston 11, and the opening operation of the intake / exhaust valve 12 starts. On the other hand, when the operation of the first cam 3 exceeds the peak, the hydraulic oil stored in the accumulator 10 is urged by the coil spring 15 and starts to return to the first cam plunger 4, and the first cam plunger 4 is moved to the first cam plunger. Enter the return journey according to the cam profile of 3.

When the first hydraulic pressure P ₁ from the first cam plunger 4 which is decreasing is equal to the second hydraulic pressure P ₂ which is increasing from the second cam plunger 9 (point C), the hydraulic pressure switching valve 5 switches the mode from the first mode 5a to the second mode 5b. That is, when the first oil pressure P ₁ generated by the first cam plunger 4 matches the second oil pressure P ₂ generated by the second cam plunger 9, the hydraulic pressure switching valve 5 is switched to the first oil pressure P 1.
Mode 5a returns to the neutral state. At the point C, the first cam plunger 4 and the second cam plunger 9 have the same displacement, and the hydraulic piston 11 and the piston 14 have the same displacement.

When the section shifts to the section D at the point C, the second hydraulic pressure P ₂ from the second cam plunger 9 continues to increase, so that the hydraulic switching valve 5 changes from the neutral state to the second mode 5.
switched to b, the second hydraulic P ₂ which has been guided to the hydraulic piston 11 initially is guided to the accumulator 10 as the hydraulic pressure P _A, the first hydraulic P ₁ hydraulic piston 11 as the hydraulic pressure P _V which has been guided to the accumulator 10 It is led to. Therefore, the operation of the intake / exhaust valve 12 is changed from the second cam 8 to the first cam 3.
Will take over. Accordingly, the first cam plunger 4 is in the return stroke, and the hydraulic piston 11 associated therewith also shifts to the return stroke, so that the intake / exhaust valve 12 starts the valve closing operation. The closing operation of the intake / exhaust valve 12 is performed by the urging force of the valve spring 13 that has been compressed, and the valve is closed when the intake / exhaust valve 12 is seated on a valve seat (not shown). On the other hand, the accumulator 10
In the section B, the hydraulic oil is discharged in accordance with the first cam plunger 4 which tends to return after the operation of the first cam 3 has passed the peak, but the operation of the second cam 8 is initially Since the peak has not yet been reached, the hydraulic oil is again stored in accordance with the second cam plunger 9 which is rising.

When the crankshaft further rotates and shifts to the section E, the operation of the second cam 8 has passed its peak, and the operating oil stored in the accumulator 10 is released by the urging force of the coil spring 15 to the second cam plunger 9. Is returned to. When the hydraulic oil stored in the accumulator 10 returns to the inside of the second cam plunger 9, the first oil
When the pressures of the cam plunger 4 and the second cam plunger 9 are balanced, the hydraulic switching valve 5 returns to the neutral state.

Eventually, the intake / exhaust valve 12 starts lift in the section B depending on the second cam 8, peaks at the point C, and closes in the section D depending on the first cam 3. Enter the operation.

When the intake / exhaust valve 12 is closed, the hydraulic oil pushed out from the hydraulic piston 11 is supplied to the first cam plunger 4 which operates according to the cam profile of the first cam 3.
Therefore, the valve closing characteristics of the intake and exhaust valves 12 are governed by the cam profile of the first cam 3. Thus, the valve closing characteristics of the intake and exhaust valves 12 do not depend on the damping action of the hydraulic oil as in the conventional example, so that the seating conditions greatly change with changes in the viscosity of the hydraulic oil and the engine speed. As a result, stable valve closing characteristics can be obtained regardless of the operating state of the engine.

On the other hand, by arbitrarily changing the phase of the second cam 8 with respect to the first cam 3, the maximum lift of the intake / exhaust valve 12 can be made variable. FIGS. 4A to 4C show how the valve characteristics of the intake / exhaust valve 12 are changed by arbitrarily changing the phase of the second cam 8 with respect to the first cam 3. Therefore, the valve characteristics of the intake / exhaust valve 12 are indicated by thick lines in the figure. That is, FIG.
4A shows a case where the phase difference between the first cam 3 and the second cam 8 is reduced, and FIGS. 4B and 4C show cases where the phase difference between the first cam 3 and the second cam 8 is smaller. This is a case where a large phase difference is taken. That is, it can be understood that as the phase difference between the first cam 3 and the second cam 8 increases, the valve opening period of the intake / exhaust valve 12 becomes shorter and the lift amount also becomes smaller. FIG. 5 shows the phase difference of the first cam 3 (diagram) and the second cam 8 (diagram) with respect to the crankshaft with respect to the engine speed, and shows the engine speeds N ₁ and N ₁ . ₂ and N ₃ correspond to FIGS. 4 (c), 4 (b) and 4 (a), respectively. From this figure, it can be seen that a larger phase difference is provided between the first cam 3 and the second cam 8 as the engine speed decreases, so that the intake / exhaust valve 1
2, the valve opening period and the lift amount are kept small.
It can be clearly understood that the valve characteristics of the above are matched to the operating state of the engine.

Therefore, if the phase of the second cam 8 with respect to the first cam 3 is changed by the first phase converter 2 and the second phase converter 7, an arbitrary valve lift can be obtained. If the phase difference between the first camshaft 1 and the second camshaft 6 is fixed and the phase of the first camshaft 1 and the second camshaft 6 is changed with respect to the crankshaft, any valve timing can be obtained, and Arbitrary valve timing and valve lift can be obtained accordingly.

In addition, the hydraulic switching valve 5 according to the present embodiment
The first hydraulic pressure P ₁ generated by the first cam plunger 4 and the second hydraulic pressure P ₁
Because using the second hydraulic P ₂ cam plunger 9 is produced as a pilot pressure, means for operating such hydraulic switching valve 5, for example not the dare require electromagnetic means control circuit, or the like, simplification of the hydraulic circuit It is being made.

In this embodiment, the hydraulic pistons 11 and 14, the valve springs 13 and the coil springs 15 have the same specifications. However, the present invention is not limited to these specifications. However, as long as the combination generates the same pressure, different specifications may be used. That is, if the volume of the piston is increased, the set load and the spring constant of the spring may be increased in proportion thereto.

Next, a second embodiment according to the present invention will be described with reference to FIGS.
It will be described based on. Hydraulic switching valve 5 in previous embodiment
Is the first hydraulic pressure P ₁ generated by the first cam plunger 4,
Of the second hydraulic pressure P ₂ generated by the second cam plunger 9,
Although the intake / exhaust valve 12 is operated with the lower oil pressure, the present embodiment aims at obtaining a wider variable width, and specifically, as shown in FIG. It is also possible to operate the intake / exhaust valve 12 with the higher one of the first oil pressure P ₁ generated by the first cam plunger 4 and the second oil pressure P ₂ generated by the second cam plunger 9. They are trying to squeeze.

The hydraulic switching valve 51 according to this embodiment is as shown in FIG. 6, and the other configuration except for the hydraulic switching valve 51 is the same as that of the first embodiment as shown in FIG. The description is omitted here.

The hydraulic switching valve 51 generally comprises a first spool valve 52 and a second spool valve 53 attached thereto.

When the first hydraulic pressure P ₁ generated by the first cam plunger 4 and the second hydraulic pressure P ₂ generated by the second cam plunger 9 match, the first spool valve 52 switches from the first mode 5a. The mode is switched between the second mode 5b and the second mode 5b to the first mode 5a, and the associated second spool valve 53 reverses the operation of the first spool valve 52. It is a hurry.

A cylindrical insertion hole 54 is formed in a body 86 forming an outer shell of the hydraulic switching valve 51 along a longitudinal direction of the body 86 in a state where both ends are closed.
Can slide in the axial direction.

A first input port 56 and a second input port 57 having a diameter larger than that of the insertion hole 54 are formed in the body 86 at predetermined positions of the insertion hole 54, respectively.
Communicates with the first cam plunger 4 via the first oil passage 58, and the second input port 57 communicates with the second cam plunger 9 via the second oil passage 59. Similarly, in the insertion hole 54,
Valve side output port 60 communicating with hydraulic piston 11
And accumulator-side output ports 61, 61 communicating with the accumulator 10, respectively, and the valve-side output port 60 is provided with a first input port 56 and a second input port 57.
And an accumulator-side output port 6
Reference numerals 1 and 61 are respectively formed on the left side of the first input port 56 in the drawing and on the right side of the second input port 57 in the drawing.

The spool 55 has lands 62, 6 at both ends.
4 has lands 63 in the center,
The lands 63 and 64 are in sliding contact with the insertion holes 54, and the lands 62 and the lands 63 and the lands 63 and the lands 64 are connected by shafts 65 and 66 smaller in diameter than the insertion holes 54, respectively.

At one end (left side in the figure) of the insertion hole 54, a second hydraulic chamber 67 which is formed as a land 62 is formed.
A first hydraulic chamber 68 that forms a land 64 is formed at the other end (the right side in the figure) of the 4. In the first hydraulic chamber 68, a spring 69 for urging the spool 55 toward the second hydraulic chamber 67 is housed. The spring constant is such that the spring 55 can overcome the friction and operate toward the second hydraulic chamber 67. However, it may be very weak.

In the hydraulic switching valve 5 according to the first embodiment, the first hydraulic pressure P ₁ from the first cam plunger 4 is always guided to the first hydraulic chamber 68 and the second hydraulic pressure P ₁ from the second cam plunger 9. Although the second hydraulic pressure P ₂ is always guided to the second hydraulic chamber 67, the hydraulic switching valve 51 in the second embodiment is
By providing the second spool valve 53 together, the first hydraulic chamber 6
8. The pilot hydraulic pressure guided to the second hydraulic chamber 67 is arbitrarily reversed.

That is, the second spool valve 53 is provided in the body 86 which forms the outer shell of the hydraulic switching valve 51, and the cylindrical insertion hole 70 is closed in the body 86 along its longitudinal direction at both ends. The spool 71 is pierced and can slide in the insertion hole 70 in the axial direction.

A first input port 72 and a second input port 73 having a diameter larger than that of the insertion hole 70 are formed in the body 86 at predetermined positions of the insertion hole 70, respectively.
Communicates with the first oil passage 58 (the first cam plunger 4) via the oil passage 74, and the second input port 73 communicates with the second oil passage 59 (the second cam plunger 9) via the oil passage 75. . Similarly, the second hydraulic chamber side output ports 76, 76 communicating with the second hydraulic chamber 67 of the first spool valve 52 are provided in the insertion holes 70.
And a first hydraulic chamber side output port 77 communicating with the first hydraulic chamber 68 is formed, and the first hydraulic chamber side output port 77 is formed between the first input port 72 and the second input port 73. The second hydraulic chamber side output ports 76 are formed on the left side of the second input port 73 in the drawing and on the right side of the first input port 72 in the drawing.

The spool 71 has lands 78 and 8 at both ends.
0, a land 79 in the center, and these lands 78,
The lands 79 and 80 are in sliding contact with the insertion holes 70, and the lands 78 and the lands 79 are connected to each other by shafts 81 and 81 having a smaller diameter than the insertion holes 70.

A spring 82 is housed at one end (left side in the figure) of the insertion hole 70 and urges the spool 71 toward the proportional solenoid 83. On the other hand, a proportional solenoid 83 is provided at the other end (right side in the figure) of the insertion hole 54,
The plunger 85 housed in the electromagnetic coil 84 moves the spool 76 against the urging force of the spring 82.

Therefore, by controlling the proportional solenoid 83, the first hydraulic pressure P ₁ and the second hydraulic pressure P ₂ to be guided to the first hydraulic chamber 68 and the second hydraulic chamber 67 of the first spool valve 52 are arbitrarily switched. It becomes possible.

Now, regarding the control of the proportional solenoid 83, the spool 71 is urged to the left (L range) in the drawing in the low speed region where the engine speed is lower than N, and in the high speed region where the engine speed is N or higher. Stops the energization of the electromagnetic coil 84 and moves the spool 71 to the right side in the figure (H range).
Move to Thus, in a low-speed region where the engine speed is low, the hydraulic circuit in the hydraulic switching valve 51 is substantially the same as in the first embodiment, but in a high-speed region where the engine speed is high, the operation of the hydraulic switching valve 51 This is reversed from the case of the first embodiment.

That is, in the low-speed region where the engine speed is low, as in the first embodiment, the operation of the intake / exhaust valve 12 is controlled by the first cam plunger 4 as shown in FIGS. 7 (b) and 7 (c). The first hydraulic pressure P ₁ generated and the second cam plunger 9
There out of the second hydraulic P ₂ that occurs, will be operating the intake and exhaust valves 12 pressure with a lower pressure of, whereas, in the high high-speed range the engine speed, the second spool valve 53 is switched As a result, the operation of the hydraulic switching valve 51 is reversed, and the first hydraulic pressure P ₁ generated by the first cam plunger 4 is:
The second of the hydraulic P ₂ of the second cam plunger 9 occurs, the higher the any pressure, supposed to do the operation of the intake and exhaust valves 12, the valve characteristics of the intake and exhaust valves 12 FIG. 7 (a )
It becomes as shown in. FIG. 8 shows the first cam 3 (diagram) and the second cam 8 with respect to the engine speed.
(Diagram) represents the phase difference with respect to the crankshaft, and the engine speeds N ₁ , N ₂ and N ₃ correspond to FIGS. 7 (c), 7 (b) and 7 (a), respectively. . From this figure, it can be seen from the figure that both the valve opening period and the lift amount of the intake / exhaust valve 12 are reduced as the engine speed becomes lower in the low speed region, while the valve opening period and the lift amount both increase in the high speed region. That is, it can be clearly understood that the valve characteristics of the intake / exhaust valve 12 are set in accordance with the operating state of the engine. Thus, the valve timing and the valve lift of the intake / exhaust valve 12 can be obtained with a wider variable width, and optimal valve characteristics according to the operating state can be obtained.

Here, the valve closing characteristics of the intake / exhaust valve 12 according to the present embodiment do not depend on the damping action of the hydraulic oil as in the conventional example. The seating condition does not greatly change with the change of the engine speed, and stable valve closing characteristics can be obtained regardless of the operating state of the engine.

[0057]

As described above, according to the present invention, the valve closing characteristics of the intake valve or the exhaust valve depend on the cam profile of the first cam or the second cam regardless of the damping action of the hydraulic oil. Therefore, even if the operating state of the engine such as the viscosity of the hydraulic oil or the engine speed changes greatly, appropriate valve closing characteristics of the intake valve or the exhaust valve can be stably obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a hydraulic circuit according to a first embodiment.

FIG. 2 is a diagram illustrating a hydraulic switching valve according to a first embodiment.

FIG. 3 is a diagram for explaining the operation characteristics of the intake / exhaust valve according to the first embodiment.

FIG. 4 is a diagram for explaining the operation characteristics of the intake / exhaust valve according to the first embodiment.

FIG. 5 is a diagram illustrating the phases of a first cam and a second cam with respect to the engine speed.

FIG. 6 is a diagram illustrating a hydraulic switching valve according to a second embodiment.

FIG. 7 is a diagram for explaining the operation characteristics of the intake / exhaust valve according to the second embodiment.

FIG. 8 is a view for explaining the phases of the first cam and the second cam with respect to the engine speed.

FIG. 9 illustrates a conventional variable valve timing / valve lift mechanism.

[Explanation of symbols]

 3 First cam 4 First cam plunger 5 Hydraulic switching valve 8 Second cam 9 Second cam plunger 10 Accumulator 11 Hydraulic piston 12 Intake / exhaust valve (intake or exhaust valve)

Claims (1)

(57) [Claims] A first cam and a second cam rotating in different phases.
A cam, a first cam plunger reciprocating following the first cam, a second cam plunger reciprocating following the second cam, and a hydraulic pressure generated by the second cam plunger when in the first mode. And a hydraulic piston that reciprocates in conjunction with the hydraulic pressure generated by the first cam plunger when in the second mode, and stores hydraulic pressure generated by the first cam plunger in the first mode. The accumulator for accumulating the hydraulic pressure generated by the second cam plunger when in the second mode, and the first mode and the second mode when the cam lifts of the first cam and the second cam match. A valve train for an internal combustion engine, comprising: a hydraulic switching valve for switching, and an intake valve or an exhaust valve that opens and closes following a hydraulic piston.