JP3310513B2 - 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 operating apparatus that changes a valve lift and a valve timing of an intake valve or an exhaust valve according to an operating state of an engine.

[0002]

2. Description of the Related Art In an internal combustion engine for a vehicle, a lift of an intake valve or an exhaust valve according to an operation state has been conventionally used for the purpose of achieving both improvement in fuel consumption at low and medium speeds and improvement in output torque at high speeds. There has been known a device provided with a valve operating device capable of controlling the opening / closing timing and opening amount of an intake / exhaust valve by using different characteristics (see Japanese Patent Application Laid-Open No. 63-117109).

[0003] A low-speed cam and a high-speed cam having different profiles for opening two intake valves per cylinder against the spring force of a valve spring are integrally formed on the outer periphery of a camshaft driven to rotate by a crankshaft. And a pair of direct-acting first and second valve lifters for transmitting the lift of the low-speed cam to the intake valve at the upper end of the valve stem of each intake valve. Also,
A third valve lifter that slides in accordance with the lift of the high-speed cam is provided between the two valve lifters.
Furthermore, at each upper end of the first to third valve lifters,
There is provided a connecting means including a guide hole, a guide recess formed in the axial direction of the camshaft, and a pair of hydraulic pistons slidably provided in the guide hole.

When the engine is running at a low speed, the supply of the hydraulic pressure to the pressure receiving chamber at one end of each guide hole of the connecting means is cut off, and the connection of each valve lifter by each hydraulic piston is released. Therefore, each intake valve opens and closes via the first and second valve lifters according to the small valve lift characteristics of the low-speed cam.

On the other hand, when shifting from the low rotation range to the high rotation range, hydraulic pressure is supplied to each pressure receiving chamber, and each hydraulic piston is inserted into a pair of guide recesses of the third valve lifter. 1. Connect the second valve lifter. For this reason, each intake valve opens and closes according to the large valve lift characteristic of the high-speed cam transmitted to the first and second valve lifters via the third valve lifter.

As a result, it is possible to improve the fuel efficiency and output torque according to the engine speed.

[0007]

However, the conventional valve train has a third valve lifter on the high-speed cam side in addition to the first and second valve lifters on the low-speed cam side. As a result, the overall size and weight of the valve lifter must be increased. For this reason, the inertia force at the time of vertical sliding increases, and smooth operation cannot be obtained at high speed rotation. Therefore, if the spring set load of the valve spring is increased to cope with such high-speed rotation, there is a concern that the sliding friction resistance between the intake valve and the cam via the valve lifter will increase.

In addition, when the engine is running at a low speed, the outer peripheral surface of the low-speed cam is in sliding contact with the upper surfaces of the first and second valve lifters. The third valve lifter is always slid in contact with the upper surface of the lifter to push down the third valve lifter against the spring force of the coil spring. Therefore, the sliding friction resistance of each cam as a whole increases, and the mechanical loss of the valve train increases in conjunction with the increase in the sliding friction resistance associated with the increase in the weight of the valve lifter described above.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional valve gear, and a first aspect of the present invention provides a camshaft which is driven to rotate by a crankshaft of an engine. A high-speed cam and a low-speed cam provided on the outer periphery of the camshaft to open and close the intake / exhaust valve; and a high-low speed cam slidably provided in a guide hole formed in a cylinder head. And a slider provided in a sliding hole defined in the upper end of the valve lifter so as to be slidable in the camshaft axial direction. Formed on the upper wall of the valve lifter where the low speed cam slides
An opening window that allows the outer peripheral portion of the high-speed cam to face the inside of the sliding hole, and the slider is slid according to the engine operating state, and the upper surface of the slider is moved relative to the outer peripheral surface of the high-speed cam.
A valve mechanism for an internal combustion engine, comprising: a drive mechanism for separating and contacting in a contact or non-contact state , wherein the drive mechanism moves in a piston hole formed in a valve lifter along a radial direction, and A piston for pushing out a slider, a hydraulic circuit for supplying and discharging hydraulic pressure to a pressure receiving chamber on the rear end side of the piston to move the piston, and a low-speed cam and a high-speed cam by sliding the slider. A timing control means for controlling the movement timing of the piston at the time of switching.

According to a second aspect of the present invention, the timing control means slides through the holding hole formed vertically in the outer peripheral portion of the upper end of the valve lifter, and the upper end portion slides in the holding hole. A control pin that protrudes and disappears from the upper surface of the cam and has a lower end engaged and disengaged from a locking groove formed on the outer peripheral surface of the piston.
While the upper end of the control pin is pressed against the outer peripheral surface of the cam shaft and the lower end is locked in the locking groove,
The control pin is characterized in that the upper end of the control pin is released so that the lower end is separated from the locking groove.

The invention according to claim 3 is characterized in that the lower end of the control pin is formed so as to be able to expand and contract at least vertically.

According to a fourth aspect of the present invention, the front and rear ends of the locking groove formed on the outer peripheral surface of the piston in the axial direction of the piston are tapered.

The invention according to claim 5 is characterized in that a pressing plate member is interposed between the upper end of the control pin and the outer peripheral surface of the camshaft.

Therefore, according to the present invention, when the engine is running at a low speed, the drive mechanism slides, for example, the pair of sliders in a direction away from each other, so that the upper surfaces of the sliders and the outer peripheral surface of the high-speed cam are in contact with each other. Is released. Therefore, the valve lifter slides according to the cam profile of the low speed cam abutting on the upper surface, whereby the intake / exhaust valve opens and closes according to the small valve lift characteristic.

At this point, the high-speed cam is completely free from contact with the sliders, that is, idle, without any sliding contact with other members. No resistance occurs.

On the other hand, when shifting from the low to middle rotation range to the high rotation range, both sliders are slid in a direction approaching each other by the drive mechanism, and at the time when they approach the maximum, each upper surface is brought into contact with the outer peripheral surface of the high speed cam. Abut Therefore, the valve lifter is switched from the low speed cam to the high speed cam, and slides according to the profile of the high speed cam, whereby the intake / exhaust valve opens and closes according to the large valve lift characteristic. At this time, the upper surface of the valve lifter is, of course, in a non-contact state with the outer peripheral surface in the lift region of the low-speed cam.

In addition, when switching between the low-speed cam and the high-speed cam by sliding the two sliders, the timing of the movement of the piston is appropriately performed by the timing control means, regardless of the change in the viscosity of the hydraulic pressure of the hydraulic circuit. It is possible to always and reliably slide the slider.

[0018]

1 to 3 show a first embodiment of a valve train according to the present invention applied to the intake side of a multi-cylinder internal combustion engine.
In the figure, reference numeral 1 denotes a camshaft which is supported on the upper end of a cylinder head 2 via a cam bracket, and which is rotationally driven by a crankshaft (not shown). One intake valve.

The camshaft 1 has a pair of low speed cams 5 and 5 arranged on both sides of the axis of the valve stem 3a of the intake valve 3, and a center between the two low speed cams 5 and 5. Are provided integrally with one another. The low-speed cams 5, 5 are provided with a base circle surface 5a.
And the entire outer peripheral surface of the cam lift surface 5b is set to the same profile so as to have a small valve lift characteristic as indicated by X in FIG. On the other hand, in the high-speed cam 6, the outer peripheral surfaces of the base circle surface 6a and the cam lift surface 6b as a whole are shown in FIG.
The profile is set to have a large valve lift characteristic as indicated by Y in FIG. On the side of the one low-speed cam 5, annular pressing portions 7 having the same outer diameter as the base circle diameter of the low-speed cam 5 are integrally provided.

The intake valve 3 is urged in the closing direction by the spring force of a valve spring 4 resiliently contacted with a spring retainer provided on the outer periphery of a cotter fixed to the stem end. The cams 5, 5, 6 are opened by a lift of the cams 5, 5, 6 via a direct-acting valve lifter 8 provided between the cams 5, 5, 6 against the spring force of the valve spring 4. Has become.

As shown in FIG. 2, the valve lifter 8 is made of a metal material and is formed in a substantially circular cylindrical shape with a substantially circular cross section, and is provided in a substantially circular guide hole 9 formed at the upper end of the cylinder head 2. Is slidably provided. More specifically, as shown in FIGS. 1 to 3, the valve lifter 8 has a substantially circular upper wall portion 10 and a cylindrical skirt formed vertically from an outer peripheral edge of the upper wall portion 10. A base plate 12 horizontally fixed at a predetermined position inside the skirt portion 11, a sliding hole 13 formed between the base plate 12 and the upper wall portion 10, and a sliding hole 13 inside. It mainly comprises a pair of left and right sliders 14 and 14 that slide.

The upper wall portion 10 is formed integrally with the skirt portion 11. The outer peripheral surfaces of the low-speed cams 5 and 5 are in sliding contact with both sides of the upper surface 10a in the axial direction of the camshaft. The outer periphery of the high-speed cam 6 is
The rectangular opening window 15 facing the inside of the camshaft 1
Are formed in a direction perpendicular to the axis.

As shown in FIG. 2, the skirt portion 11 has an inner peripheral surface formed in a circular shape, and has piston holes 16, 16 communicating with an oil passage 25 to be described later on an opposing wall in the axial direction of the camshaft. Are formed, and a step portion 11b is formed in the lower portion of the inner periphery.

The base plate 12 is formed in the shape of a perfect circle having substantially the same shape as the upper wall portion 10 and defines a sliding hole 13 in cooperation with the skirt portion 11 and the upper wall portion 10. 1
2a is fitted into the step portion 11b of the skirt portion 11 from below, and the outer peripheral edge is welded to the skirt portion 11b.
Is fixed to the inner peripheral surface of the. As shown in FIG. 1, the base plate 12 is provided with a circular projection-shaped stopper 17 in the center of the upper surface, and has a U-shaped cross section in which the upper end of the stem end of the intake valve 3 is fitted in the center of the lower surface. Is fixed. Also, at a predetermined position on the outer peripheral portion,
Discharge holes 12b, 12c for discharging oil leaked from the piston holes 16, 16 are formed to penetrate vertically.

As shown in FIGS. 1 and 2, each of the two sliders 14, 14 has an elongated block shape extending in the radial direction of the skirt portion 11, and the sliders 14, 14 move in the sliding hole 13 toward or away from each other. The base plate 12 is relatively slidable on the upper surface. The width L1 of each of the sliders 14, 14 in the camshaft axial direction is determined by a gap C formed when the two members 14, 14 are separated from each other to the maximum.
Is smaller than the width L2, and the front end surfaces 14a, 14a at the time of the maximum separation are located behind the facing surfaces 15a, 15a of the opening window 15 by a dimension of α. Further, support holes 14c, 14c for slidably supporting spring receiving portions 20, 20 described later in the front-rear direction are provided in the center of the bottom of the concave grooves 14b, 14b formed on the front end surfaces of the sliders 14, 14 in the radial direction. It is formed through. Also, at the center of the lower end on the front end side of the sliders 14, 14,
Each of the semicircular arc-shaped engagement grooves is formed to be engaged with the stopper 17.

A driving mechanism for sliding the two sliders 14, 14 toward or away from each other is shown in FIG.
A coil spring 21 for operating both sliders 14, 14 in a direction away from each other via the opposed spring receiving portions 20, 20, as shown in FIG.
The pistons 22, 22, which are supported inside and push the sliders 14, 14 in the direction approaching each other, supply and discharge hydraulic pressure to pressure receiving chambers 29, 29 provided at the rear ends of the pistons 22, 22, respectively. And a hydraulic circuit 23.

The spring receiving portions 20, 20 support both ends of the coil spring 21 at respective U-shaped front ends, and have a rear end formed at the front end of each of the pistons 22, 22, for fixing. It is press-fitted and fixed in the groove, and can be moved back and forth with respect to the slider 14 within a predetermined clearance S range.

As shown in FIG. 5, each of the pistons 22 comes into contact with the substantially cylindrical body 22a and the front end of the body 22a at the time of retreating to the edge of the piston hole 16 for further movement. When controlling and moving forward, the slider 14
Has a flange portion 22b for pressing the rear end surface thereof, and a locking groove 31 is formed on the outer peripheral surface of the main body 22a. The locking groove 31 has an annular shape, and the inner surface on the side of the pressure receiving chamber 29 is formed as a tapered surface 31a inclined outward, while the outer peripheral edge of the rear end surface of the main body 22a also has a tapered surface 22c.
Is formed.

The hydraulic circuit 23, as shown in FIG.
An oil passage 25 having one end communicating with the oil pan 24 through the cylinder block and the inside of the cylinder head 2, an oil pump 26 provided downstream of the oil pan 24,
The oil passage 25 is provided downstream of the oil pump 26.
And a solenoid switching valve 28 for switching between the drain passage 27 and the drain passage 27. The oil passage 25 is branched in the middle, and the other end portions 25 a formed in the cylinder head 2 communicate with the pressure receiving chambers 29, 29.

The electromagnetic switching valve 28 includes a controller 30
The controller 30 is operated by an ON-OFF signal from the controller 30. The controller 30 outputs information signals such as an engine speed from a crank angle sensor, an air flow meter, an intake air amount, and an engine cooling water temperature from a water temperature sensor. , The current engine operating state is detected.

A pair of timing control means 32, 3 for controlling the movement timing of each piston 22 is provided between the camshaft 1 and the outer periphery of the upper end of the valve lifter 8.
2 are provided. That is, as shown in FIG. 1 and FIGS. 5 to 9, the timing control means 32 vertically moves the annular pressing portion 7 of the camshaft 1, the upper wall portion 10 of the valve lifter 8 and the skirt portion 11. It is mainly composed of a holding hole 33 formed along, a control pin 34 slidably provided in the holding hole 33 in a vertical direction, and a coil spring 35 for urging the control pin 34 upward. ing.

The holding hole 33 is formed in a stepped shape having a large diameter on the upper side and a small diameter on the lower side, and an upper end opening 33 a is arranged to face the annular pressing portion 7 of the camshaft 1.
The lower end opening faces the piston hole 16.

As shown in FIGS. 5 to 9, the control pin 34 is arranged so that a cylindrical upper end portion 34a having a flange portion 34c at the lower end protrudes and retracts from the upper end opening 33a. The flange portion 34c abuts on a stopper ring 36 provided at the edge of the hole to restrict the maximum upward projecting position, while the lower end portion 34b is formed by an extendable coil spring. That is, the lower end portion 34b is arranged as shown in FIG.
The upper portion 34d is press-fitted and fixed in the fitting groove 34e on the lower surface of the flange portion 34c, and the lower portion 34f protrudes and retracts from the lower end opening so as to be detachably provided in the locking groove 31 of the piston 22 as shown in FIG. I have. The lower portion 34f is made rigid by increasing the number of coil turns. At the upper end of the skirt portion 11, a breathing hole 37 communicating the holding hole 33 and the outside is formed so as to penetrate in the radial direction.

The operation of this embodiment will be described below. First,
In the low engine speed range, the controller 30 outputs an OFF signal to the electromagnetic switching valve 28 to communicate the oil passage 25 with the drain passage 27. Therefore, no oil pressure is supplied to the pressure receiving chambers 29, 29, and the low pressure state is established. Become. Therefore, both sliders 1
As shown in FIG. 1, the rollers 4 and 14 are held in a direction in which they are separated from each other by the spring force of the coil spring 21, that is, in positions where both rear end surfaces abut against the inner surface of the skirt portion 11.

Therefore, the high-speed cam 6 rotates in a non-contact state in the gap C between the two sliders 14 without the outer peripheral surface abutting on the upper surfaces 14d of the sliders 14, that is, idle. Rotate.

Thus, the outer peripheral surface of the low-speed cams 5, 5 abuts on the upper surface 10a of the upper wall portion 10 of the valve lifter 8,
The valve lifter 8 is slid up and down according to the cam profile. Therefore, the intake valve 3 opens and closes in accordance with the small valve lift characteristic indicated by X in FIG.

As a result, the overlap with the exhaust valve is reduced and the residual gas in the combustion chamber can be reduced, so that the combustion is improved and the fuel efficiency can be improved.

On the other hand, when the engine shifts from the low to medium engine speed range to the high engine speed range, the controller 30 sends an O
Since the N signal is output and the communication between the oil passage 25 and the drain passage 27 is cut off, the oil pressure fed from the oil pump 26 is supplied into the pressure receiving chambers 29 through the oil passage 25. Therefore, the pressure in both the pressure receiving chambers 29, 29 becomes high, and the pistons 22, 22 are pressed in directions approaching each other.

Here, when the low-speed cam 5 is in sliding contact with the upper surface 10a of the valve lifter 8 on the base circle surface 5a (base circle area), the valve lifter 8 is inserted into the guide hole 9 as shown in FIG. , The annular pressing portion 7 of the camshaft 1 pushes down the upper end of the control pin 34. Therefore, the control pin 34 descends against the spring force of the coil spring 35, and the lower end portion 34b
Is locked in the locking groove 31 of the piston 22. For this reason, the piston 22 is prevented from moving forward despite the high pressure of the pressure receiving chamber 29.

Subsequently, the low speed cam 5 is moved to the cam lift surface 5b.
7, the valve lifter 8 is pushed down as shown in FIG. 7, and the pressing of the control pin 34 by the annular pressing portion 7 is released, so that the upper end of the control pin 34 is released. The portion 34a is connected to the stopper ring 36 from the upper end opening 33a of the holding hole 33 by the flange 3
4c rises until it hits. Therefore, control pin 3
Since the lower portion 34f of the lower end portion 34b of the fourth member 4 rides on the outer surface of the main body 22a from the locking groove 31 of the piston 22 via the tapered surface 31a and separates, the movement restriction of the piston 22 is released. Therefore, both pistons 22 press both sliders 14 and 14 in the approaching direction by the clearance S. However, since the cam is being lifted and the cam lift surface 6b of the high-speed cam 6 faces the sliding hole 13, each The front end faces 14a, 14a abut against both side faces of the high-speed cam 6 and cannot move further in the approaching direction.

Next, in the base circle area, at that moment, the sliders 14 and 14 approach each other via the pistons 22 by the high oil pressure in the pressure receiving chamber 29 as shown in FIG. , 14a abut. As a result, the gap C disappears, and the high-speed cam 6 comes into contact with the outer peripheral surface straddling the upper surfaces 14d, 14d of the sliders 14, 14.

Accordingly, the valve lifter 8 slides up and down in accordance with the profile of the high-speed cam 6 through the sliders 14 and 14 and the base plate 12 as the high-speed cam 6 rotates. For this reason, the intake valve 3 is connected to Y in FIG.
Open / close operation according to the large valve lift characteristic shown in FIG.
As a result, the intake charging efficiency is improved, and a high torque is obtained.

At this time, the low-speed cams 5, 5 are connected to the upper surface 10a of the valve lifter 8 only when the high-speed cam 6 is in the base circle (see FIG. 8).
When the high-speed cam 6 is lifted, it is separated from the upper surface 10a only by sliding on the upper surface 10a (see FIG. 9).

On the other hand, when the engine shifts from the high engine speed range to the low / medium speed range, the OF from the controller 30 is transmitted as described above.
The hydraulic oil in each pressure receiving chamber 29 is returned from the oil passage 25 into the oil pan 24 via the electromagnetic switching valve 28 based on the F signal,
The pressure in both pressure receiving chambers 29 becomes low. Therefore, the two pistons 22 try to retreat by the spring force of the coil spring 21. However, as shown in FIG. 8, in the base circle region of the high-speed cam 6, the annular pressing portion 7 pushes down the control pin 34 to lower the lower end portion. The lower portion 34f of the piston 34b radially abuts the rear end face 22d of the piston 22, thereby restricting the piston 22 from retreating.

Subsequently, in the cam lift region, the upper end portion 3 of the control pin 34 is moved from the annular pressing portion 7 as shown in FIG.
4a is separated and rises by the spring force of the coil spring 35, so that the regulation of the piston 22 by the lower end portion 34b is released. However, at this point, each slider 14,
Since 14 is pressed by the cam lift surface 6b of the high-speed cam 6, it cannot move backward, only the pistons 22 move backward by the clearance S, and the lower portion 34f is located on the tapered surface 22c of the rear end surface.

At the moment when the high-speed cam 6 enters the base circle area, the pressing force of the cam 6 is released, and the sliders 14 and 14 are quickly moved away from each other by the spring force of the coil spring 21. Move (see FIG. 6).
At this time, the control pin 34 is pushed down by the annular pressing portion 7, but the lower portion 34f of the lower end portion 34b slides on the rear end tapered surface 22c of the piston 22 and is compressed and deformed while elastically contacting the outer peripheral surface ( Further, the sliders 14 are extended and deformed in the retaining grooves 31 to retain the sliders 14, 14 at the maximum rearward positions via the pistons 22, as shown in FIG. As a result, the high-speed cam 6 is switched to the low-speed cam 5, and the intake valve 3 has the small valve lift characteristic as described above.

As described above, in the present embodiment, the valve lifters 8 for raising and lowering the pair of low-speed cams 5 and 5 and the one high-speed cam 6 can be shared and unified, so that the entire system can be integrated. Can be reduced in size and weight. Therefore, the inertial force at the time of vertical sliding can be reduced as much as possible, and it is possible to sufficiently cope with high rotation.

Further, in the low engine speed rotation region, the outer peripheral surface of the high speed cam 6 is in a non-contact state with each of the sliders 14 and so-called idle rotation, so that the sliding friction resistance can be greatly reduced.

When the low-speed cam 5 and the high-speed cam 6 are switched, the slider 1 is moved during the cam lift of each of the cams 5 and 6 irrespective of the switching timing of the electromagnetic switching valve 28.
4 and 14 become movable (standby state) and become switching points, and switching is completed in the base circle area. Therefore, even when the oil temperature is low and the viscosity is high, for example, when starting the engine at a low temperature, the optimum switching timing (movement timing) of each slider 14 can be obtained. 14d, 1
It is possible to smoothly and reliably ride the optimum position of 4d on the outer peripheral surface of the high-speed cam 6. As a result, generation of abnormal noise due to incomplete riding and sliders 14, 14
And the cams 5 and 6 can be prevented from being worn.

Further, since the lower end portion 34b of the control pin 34 is formed by a coil spring and engages and disengages with the locking groove 31 and the like while being compressed and expanded, a smooth engagement / disengagement action can be obtained. In addition, since the tapered surfaces 22c and 31a provide a smooth sliding contact of the lower portion 34f, the switching operation is improved.

FIGS. 11 and 12 show a second embodiment of the present invention. In this embodiment, the annular pressing portion 7 of the camshaft 1 is eliminated, and the position between the camshaft and the control pin 34 is reduced.
The pressing plate member 38 is interposed. The pressing plate member 38 has a flat U-shape, and has a long plate-like base piece 38a.
Are fixed to the peripheral edge of the guide hole 9 of the cylinder head 2 by screws 39, and the distal ends of the pressing pieces 38b, 38b extending from both ends of the base piece 38a are connected to the control pins 34, 38, respectively.
34 and the outer peripheral surface of the camshaft 1.

Therefore, the control pin 34 is
4a does not come into direct contact with the camshaft 1, so that the upper end portion 34a is prevented from being worn. Other functions and effects are the same as those of the first embodiment.

As another embodiment, a wear-resistant cap is fitted and fixed to the lower portion 34f of the lower end portion 34b of the control pin 34, and is engaged with the engaging groove 31 of the piston 22 via the cap. It is also possible to form as follows. This prevents the lower portion 34f from being worn by the cap. Further, the lower end portion 34b may be configured such that the upper portion is formed of an extendable coil spring and the lower portion is formed of a bar-shaped member.

The present invention is not limited to the configuration of the above-described embodiment, but may be configured with one slider, and may be applied to the exhaust side in addition to the intake side. It is possible.

[0055]

As is apparent from the above description, according to the present invention, by switching between the low-speed cam and the high-speed cam in accordance with the engine operating state, the cam lift characteristic is changed.
Not only can the engine performance be improved, but also both high and low speed cams can be handled with one valve lifter instead of with each valve lifter as in the past. The size and weight of the entire lifter can be reduced.

Therefore, the inertia force when the valve lifter slides up and down is reduced, and the valve lifter can sufficiently cope with high-speed rotation, so that the spring force of the valve spring can be reduced. For this reason, sliding friction resistance between the intake and exhaust valves and both cams is reduced.

In addition, when the engine is running at low and medium speeds, the high-speed cam is brought into non-contact with the valve lifter and idles, so that the sliding friction resistance as a whole is sufficiently reduced also at this point.

As a result, the mechanical loss of the valve train is greatly reduced, and the engine output performance can be improved.

In addition, the slider at the time of switching between the low-speed cam and the high-speed cam is moved in the front-rear direction by releasing the lock between the control pin of the timing control means and the locking groove during the cam lift of each high-low speed cam. Since the movement is completed at the time of the base circle, the slider can be smoothly and reliably switched to each cam regardless of the viscosity of the hydraulic oil of the drive mechanism. Therefore, generation of abnormal noise due to incomplete switching between the respective cams by the slider and generation of wear between the slider and the respective cams can be prevented, thereby improving quietness and reliability.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a plan view of a main part of the embodiment.

FIG. 3 is a partial cross-sectional view of the present embodiment.

FIG. 4 is a valve lift characteristic diagram of the present embodiment.

FIG. 5 is an enlarged sectional view of a main part of the embodiment.

FIG. 6 is a sectional view showing the operation of the present embodiment.

FIG. 7 is a sectional view showing the operation of the present embodiment.

FIG. 8 is a sectional view showing the operation of the present embodiment.

FIG. 9 is a sectional view showing the operation of the present embodiment.

FIG. 10 is a sectional view showing the operation of the present embodiment.

FIG. 11 is a plan view of a main part showing a second embodiment of the present invention.

FIG. 12 is a side view of a main part of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Camshaft 2 ... Cylinder head 3 ... Intake valve 5 ... Low speed cam 6 ... High speed cam 8 ... Valve lifter 9 ... Guide hole 10 ... Top wall 13 ... Sliding hole 14 ... Slider 14d ... Top surface 15 ... Opening window DESCRIPTION OF SYMBOLS 16 ... Piston hole 22 ... Piston 22c ... Tapered surface 23 ... Hydraulic circuit 31 ... Locking groove 31a ... Tapered surface 32 ... Timing control means 33 ... Holding hole 34 ... Control pin 34a ... Upper part 34b ... Lower part 34f ... Lower part 38 ... Pressing plate member

Claims (5)

(57) [Claims] A camshaft rotatably driven by a crankshaft of an engine; and a camshaft provided on an outer periphery of the camshaft,
A high speed cam and a low speed cam for opening and closing the intake and exhaust valves,
A closed cylindrical valve lifter slidably provided in a guide hole formed in the cylinder head for transmitting a lift of the high / low speed cam to the intake / exhaust valve; and a valve lifter formed inside an upper end of the valve lifter. A slider provided slidably in the camshaft axial direction in the sliding hole formed above, and an upper wall portion of the valve lifter on which the low-speed cam is slidably contacted on the upper surface to slide the outer peripheral portion of the high-speed cam. An opening window that faces the moving hole, and a drive mechanism that slides the slider according to the operating state of the engine, and separates the upper surface of the slider into or out of contact with the outer peripheral surface of the high-speed cam. A drive mechanism for the internal combustion engine, comprising: a piston that moves in a piston hole formed in a valve lifter along a radial direction to push out the slider; and a rear end side of the piston. of A hydraulic circuit for supplying and discharging hydraulic pressure to the pressure receiving chamber to move the piston, and for controlling the movement timing of the piston when switching between the low speed cam and the high speed cam by sliding the slider. A valve train for an internal combustion engine, comprising a control unit. 2. The timing control means includes: a holding hole formed in an outer peripheral portion of an upper end of a valve lifter along a vertical direction; and a slide in the holding hole so that the upper end protrudes and retracts from an upper surface of the valve lifter. And a control pin having a lower end engaged and disengaged from a locking groove formed on the outer peripheral surface of the piston, and the upper end of the control pin is pressed against the outer peripheral surface of the camshaft during the base circle of the high / low speed cam. The lower end portion is formed so that the lower end portion is locked in the locking groove while the upper end portion of the control pin is released from the locking groove during cam lift. Of the internal combustion engine. 3. A valve train for an internal combustion engine according to claim 2, wherein a lower end portion of said control pin is formed so as to be able to expand and contract at least in a vertical direction. 4. The valve train for an internal combustion engine according to claim 2, wherein the front and rear edges of the locking groove formed on the outer peripheral surface of the piston in the axial direction of the piston are tapered. 5. The valve train for an internal combustion engine according to claim 2, wherein a pressing plate member is interposed between an upper end portion of the control pin and an outer peripheral surface of the camshaft.