JPH0543206Y2 - - Google Patents

Description

[Detailed description of the invention] <<Industrial application field>> This invention relates to engine valve drive devices.
In particular, the present invention relates to a valve driving device for an engine that uses cams that open and close valves as appropriate depending on the operating state of the engine, or that stops valve operation.

<<Prior Art>> Conventionally, as this type of valve driving device, there is one disclosed in, for example, Japanese Utility Model Application Publication No. 61-58605. This valve drive device is used in an engine in which two intake valves are arranged for each cylinder, and the camshaft has a low-speed cam with a low-speed cam profile and a high-speed cam profile that includes the low-speed cam. A first rocker arm for low speeds (hereinafter referred to as a low speed rocker arm) that transmits the movement of the low speed cam to both intake valves is brought into sliding contact with the low speed cam, and
A second high-speed rocker arm (hereinafter referred to as the high-speed rocker arm) is disposed on the side of the low-speed rocker arm, and is in sliding contact with the high-speed cam and transmits its movement to the low-speed rocker arm.
The low-speed rocker arm is provided with actuating means for engaging and disengaging the low-speed rocker arm and the high-speed rocker arm in accordance with the engine speed to bring them into an interlocked state or a non-interlocked state, thereby switching the opening/closing operation characteristics of the valve.

This operation switching means is a hydraulic type, and includes a hydraulic chamber formed in the high-speed rocker arm, and is slidably provided within this hydraulic chamber. The protruding plunger and the plunger fitting hole formed in the low-speed rocker arm corresponding to the position of the plunger when both the high-speed and low-speed rocker arms are in contact with the base circles of the respective cams. , a receiver, etc., which is provided in the fitting hole and pushes the plunger back toward the hydraulic chamber side with a return spring when the pressure in the hydraulic chamber is low.

The high-speed Rockscar arm and the Rockscar shaft are formed with an oil supply passage that connects the hydraulic chamber and an oil passage in the Rockscar shaft and supplies lubricating oil flowing through the oil passage into the hydraulic chamber as hydraulic oil. The oil supply passage is constantly communicated with the oil passage in the rocker shaft via an annular groove formed on the inner circumferential surface of the boss portion.

In addition, the pressure of the lubricating oil supplied to the oil passage of the Rocker shaft is regulated by a pressure regulator according to the engine speed, and in the low engine speed range, the lubricating oil supply oil pressure decreases. is set to a low pressure, the operation switching means is switched to a non-interlocked state, and the intake valve is driven by a low-speed cam, while in the high rotation range of the engine, the lubricating oil supply oil pressure is set to a high pressure and the above-mentioned operation switching means is switched to an interlocked state. The intake valve is driven by a high-speed cam, which opens and closes the intake valve at timings that correspond to the engine speed.

Furthermore, Japanese Utility Model Application Publication No. 194511/1983 exists as a mechanism in which a similar mechanism is applied to stop a valve.

[Problems to be solved by the invention] By the way, when the plunger is moved in and out using hydraulic pressure and the biasing force of the return spring to engage and disengage the low-speed rocker arm and the high-speed rocker arm, as in the former case, If the movement of the plunger is completed while both the low-speed Rotsuker arm and the high-speed Rotsuker arm are in sliding contact with the base circle of each cam, there will be no problem in switching between the interlocking state and non-interlocking state. If the movement of the plunger becomes stiff immediately after the start of the cam lift, there is a problem that problems such as the generation of hammering noise and a decrease in durability occur.

In other words, when switching from a non-interlocking state to an interlocking state, the plunger is not fully inserted into the fitting hole, and when switching from an interlocking state to a non-interlocking state, the plunger is not fully twisted into the hydraulic chamber. However, once the cam lift starts, the movement resistance of the plunger increases, so the movement of the plunger slows down or stops.
The low-speed rocker arm is lifted by the high-speed cam while being incompletely engaged with the high-speed rocker arm.

At this time, if the plunger is lifted with a small amount of insertion and is slightly caught, the plunger will be pushed back into the hydraulic chamber during the lift and the engagement between the low-speed rocker arm and the high-speed rocker arm will be disengaged, causing the low-speed rocker arm to be lifted. falls onto the low-speed cam and generates a hitting sound, which reduces durability.

Also, since the contact area between the plunger and the fitting hole becomes smaller, the stress acting on them increases.
There is also a possibility that this may cause a decrease in durability.

Furthermore, due to errors in the machining accuracy of the plunger, hydraulic chamber, fitting hole, return spring, etc., the movement resistance when the plunger is inserted or removed inevitably varies depending on the valve drive mechanism of each cylinder. There will be a difference in the actual actuation start pressure and differential start timing of each plunger, that is, the responsiveness. For this reason, even if the hydraulic pressure in the hydraulic chamber is switched from low pressure to high pressure or from high pressure to low pressure immediately after the end of the cam lift in which both the low-speed rocker arm and the high-speed rocker arm are in sliding contact with the cam base circle, the response will be slow. The plunger's travel period may extend immediately after the start of the next cam lift.

Therefore, in order to prevent such problems from occurring as much as possible, it is desirable to increase the responsiveness of the plunger movement so that the plunger movement does not occur immediately after the cam lift starts. Therefore, if the spring constant of the return spring is reduced to improve the responsiveness during fitting, there is a problem in that the responsiveness during fitting and disengaging is impaired.

Also, in the latter case where the valve is stopped using a similar configuration, if the first rocker arm and the second rocker arm disengage during lift, the valve will be seated on the valve seat with an impact. There are similar problems.

The present invention was developed in view of the above circumstances, and its purpose is to engage and disengage adjacent rocker arms using a hydraulic plunger so that the operating characteristics of the valve can be appropriately switched and used depending on the operating state of the engine. It is an object of the present invention to provide an engine valve drive device that can prevent as much as possible the generation of tapping noise and deterioration of durability due to defective switching operations.

<Means for Solving the Problems> In order to solve the above-mentioned problems, the present invention provides a first rocker arm that is slidably supported on the rocker shaft and abuts at least the valve. A second rocker arm is provided adjacent to the rocker arm and swingably supported on the rocker shaft with one end in contact with the cam of the camshaft, and the second rocker arm and the first rocker arm on the side thereof are provided.
A hydraulic chamber is formed in one of the Rocker arms to which high hydraulic pressure is supplied depending on the operating state of the engine, and a plunger is provided in the hydraulic chamber that can freely extend and retract from this chamber toward the other Rocker arm on the side. , a fitting hole into which the plunger is fitted is formed in the other rocker arm, and the fitting hole has a nonlinear characteristic that pushes the plunger back into the hydraulic chamber when the pressure in the hydraulic chamber becomes low. A return spring is provided.

<Operation> According to the present invention having the above configuration, when the low-speed cam and the high-speed cam are used separately, the pressure in the hydraulic chamber is reduced to low pressure when the engine is running at low speeds, and the plunger is fitted with a return spring. Pushed back into the hydraulic chamber by the force for low speed (first)
The rocker arm and the high-speed (second) rocker arm are in a non-interlocked state, and the valve is driven to open and close by the low-speed cam.

On the other hand, when the engine speed becomes high,
The pressure in the hydraulic chamber is made high, the plunger is fitted into the fitting hole, the low-speed (first) rocker arm and the high-speed (second) rocker arm are interlocked, and the valve is driven to open and close by the high-speed cam. Ru.
At this time, when the pressure in the hydraulic chamber is switched from the set pressure on the low pressure side to the set pressure on the high pressure side, the spring constant of the return spring has nonlinearity, and the spring constant at the initial stage of compression is small, and the spring constant at the end of compression is small. Since the constant is set large, the plunger starts moving at an early stage as the pressure in the hydraulic chamber increases, and quickly reaches a predetermined position where there is no risk of it becoming disengaged from the fitting hole. It is inserted quickly and then slowly moved through its entire travel stroke.

Furthermore, the same operation occurs when the valve stop mechanism is employed.

<<Example>> A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

Figures 1 to 4 show an embodiment in which the engine valve drive device of the present invention is applied to the intake valve side of a three-valve type engine, and Figure 1 is a side sectional view showing the overall configuration. FIG. 2 is a side sectional view of the main part thereof, FIG. 3 is a plan view of the intake valve side, and FIG. 4 is a sectional view taken along the - line in FIG. 2.

In the figure, reference numeral 1 indicates an intake valve, and two intake valves 1 are provided per cylinder.
Also, 2 is an exhaust valve, and this exhaust valve 2 is 1
One is provided per cylinder. Reference numeral 3 denotes a camshaft, and the camshaft 3 is provided with three cams 4a, 4b, 5 for driving intake valves and one cam 6 for driving exhaust valves per cylinder.

Cams 4a, 4b, 5 for driving three intake valves
Two of them are low speed cams 4a and 4b that have a low speed cam profile, and the remaining one is a high speed cam 5 that has a high speed cam profile that has a larger lift amount than the low speed cam. The cams 4a and 4b are arranged at both ends of each cylinder, and a high-speed cam 5 and a cam 6 for driving exhaust valves are arranged between them.

Rocker shafts 7 and 8 are provided above the camshaft 3 and on both sides thereof, and the rocker shaft 7 on the exhaust valve 2 side has a cam 6 for driving the exhaust valve of the camshaft 3 and a valve of the exhaust valve 2. A rocker arm 24 for driving an exhaust valve is swingably provided so as to span between the stem 2a and the exhaust valve. Further, three rocker arms 9, 10, and 11 for driving the intake valves are swingably disposed on the rocker shaft 8 on the side of the intake valve 1.

The two rocker arms provided on both sides are low-speed (first) rocker arms 9 and 10, and the arm portions 9a and 10a at one swinging end are connected to the low-speed cams 4a and 4b of the camshaft 3 via rollers 12. At the same time, the arm portions 9b and 10b at the other swing end are connected to the valve stems 1 of the intake valves 1 and 1 via a hydraulic lash adjuster 13.
a, 1a, and these low speed cams 4a,
4b and the intake valves 1, 1 in a substantially linear manner. Further, each of the low-speed rocker arms 9 and 10 is formed symmetrically.

On the other hand, these two low-speed Rotsuker arms 9,
The rocker arm provided in sliding contact with the side surfaces of 10 and between them is the high speed (second) rocker arm 1.
1, this high-speed rocker arm 11 has an arm portion 11a at the swinging end on one side of the camshaft 3 in sliding contact with the high-speed cam 5 of the camshaft 3 by a slipper 14.

In addition, as shown in FIGS. 3 and 4, this high-speed rocker arm 11 and the low-speed rocker arms 9, 10 include a low-speed rocker arm 9,
Hydraulic operation switching means 1 for switching the opening/closing operation characteristics of the intake valves 1, 1 by engaging and disengaging 10 and a high-speed rocker arm 11 according to the engine speed.
5 is provided.

The operation switching means 15 is provided with a hydraulic chamber 16 integrally formed in the valve-side arm portion 11b of the high-speed rocker arm 11, and is slidably provided in the hydraulic chamber 16 so that the pressure in the hydraulic chamber 16 is high. When this happens, the plunger 17 protrudes laterally toward the low-speed rocker arms 9 and 10, and the high-speed rocker arms 11 and low-speed rocker arms 9 and 1.
The plungers 17 are formed in the respective low-speed rocker arms 9, 10 in correspondence with the positions of the plungers 17 when the cams 4a, 4b, 5 are in contact with the base circles of the respective cams 4a, 4b, 5. A receiver 20 is provided in the hole 18 and in the fitting hole 18 and pushes the plunger 17 back toward the hydraulic chamber 16 by the biasing force of the return spring 19 when the pressure in the hydraulic chamber 16 is low.
etc.

The hydraulic chamber 16 is connected to an oil supply passage 2 formed in the rocker shaft 8 and the high-speed rocker arm 11.
1 is connected to an oil passage 8a in the rocker shaft 8, and the lubricating oil in the oil passage 8a is supplied as hydraulic oil into the hydraulic chamber 16 through the oil supply passage 21.

Oil supply passage 21a on the high-speed Rotsuker arm 11 side
and the oil supply passage 21b on the Rocker shaft 8 side,
Communication is established only when the high-speed rocker arm 11 is in sliding contact with the cam base circle of the high-speed cam 5, and the rocker shaft 8
The oil supply passage 21b on the side communicates with the oil passage 8a in the rocker shaft 8 by being inclined at a predetermined angle α toward the upstream side of the oil passage 8a in order to smoothly introduce lubricating oil.

In addition, in the oil passage 8a in the rocker shaft 8,
Although not shown, a pressure regulator is used to pump and supply lubricating oil that is regulated to a high pressure according to the engine rotation speed when the engine rotates at high speeds, and lubricating oil that is regulated to a low pressure when the engine speeds are low. It's becoming like that.

By the way, the above-mentioned return spring 19 has a spring constant having a non-linear characteristic. That is, as shown in FIG. 5, for example, the return spring 19 is
The spring constant k1 is small until a certain set value l (the amount of insertion of the plunger 17) is reached, and when the set value l is exceeded, the spring constant k2 is increased. The above set value l is determined by the low-speed rocker arms 9 and 10 engaging the high-speed rocker arm 11 and the high-speed cam 5.
When the plunger 17 and the fitting hole 18 are lifted, the stress that acts on the plunger 17 and the fitting hole 18 at that time is minimized to the extent that there is no risk of the plunger 17 and the fitting hole 18 coming out of engagement during the lift. are set to the minimum value within a range that does not impair their durability.

Therefore, in the engine valve drive device constructed as described above, the pressure in the hydraulic chamber 16 is set to a high pressure in the high speed rotation range of the engine, and the plunger 17 is fitted into the fitting hole 18 of the rocker arms 9 and 10 for low speed. The high-speed rocker arm 11 and the low-speed rocker arm are integrated and interlocked, and the intake valves 1, 1 are driven to open and close by the high-speed cam 5.

On the other hand, when the engine is running at low speed, the hydraulic chamber 1
The pressure inside 6 is reduced to a low pressure, and the plunger 17 is pushed back into the hydraulic chamber 16 by the return spring 19 via the receiver 20. As a result, the high-speed rocker arm 11 is separated from the low-speed rocker arms 9 and 10, and they are separated. The two intake valves 1, 1 are in a non-interlocking state, and the low speed cam 4a,
It is driven to open and close by 4b. At this time, the low-speed rocker arms 9, 10 and the high-speed rocker arm 11 slide on the low-speed cams 4a, 4b and the high-speed cam 5, respectively, and swing independently, and there is no relative movement between them. will occur.

By the way, when the engine speed shifts from a low-speed rotation range to a high-speed rotation range, the low-speed rocker arms 9 and 10 and the high-speed rocker arms 11 are switched from the non-interlocked state to the interlocked state. The pressure in the hydraulic chamber 16 that is switched from low to high pressure increases from the low pressure set pressure p1 to the high pressure set pressure p2, as shown in the graph of FIG. 6, for example.

At this time, the return spring 19 is compressed until its displacement (the amount of insertion of the plunger 17) reaches the set value l, and the initial spring constant k1 is reduced.
Since the spring constant k2 in the latter stage of compression exceeding the set value l is increased, when the pressure in the hydraulic chamber 16 increases higher than the set pressure p1 on the low pressure side, the plunger 17 immediately After the movement is started, it is quickly inserted to the set value l within a short period of time, and thereafter it is inserted slowly and moved by the full amount L of the movement stroke.

Therefore, even if the latter half of the movement period of the plunger 17 is immediately after the start of the cam lift, the plunger 17 can be quickly fitted into the position at the beginning of the movement to a position where it will not be pushed back into the hydraulic chamber 16 by the cam lift. Since it is fitted into the hole 18, the low-speed rocker arms 9, 10 and the high-speed rocker arm 11 are separated from each other during the lift, and the low-speed rocker arms 9, 10 are attached to the low-speed cam 4.
There is no possibility of the ball falling onto surfaces a and 4b, and this will not cause any knocking noise or deterioration of durability.

On the other hand, due to processing accuracy, the oil supply passage 21 formed in the high-speed rocker arm 11 and the rocker shaft 8 has a slight difference in flow resistance depending on the valve drive mechanism of each cylinder.
There is a time lag in the pressure rise within 6. Similarly, a difference occurs in the movement resistance of the plunger 17. For this reason, there will be some variation in the pressure and timing at which each plunger 17 starts moving, that is, in its responsiveness.

For this reason, if the return spring is given a single spring constant as in the past, the volume of the hydraulic chamber will expand after the responsive plunger begins to move. Until the movement is completed, the pressure in the hydraulic chamber does not rise to the movement start pressure of other plungers with poor responsiveness, and therefore, plungers with poor responsiveness tend to have their movement period immediately after the start of cam lift.

However, in this embodiment in which the return spring 19 is given non-linear characteristics, the movement start pressure of each plunger 17 in response to a pressure change in the hydraulic chamber 16 is lower than in the conventional one in which a single spring constant is given. In addition, the amount of displacement with respect to the pressure change until the insertion amount of the plunger 17 reaches the set value l is large, and the responsiveness at the initial stage of the movement is excellent, and the plunger 17 has particularly excellent responsiveness and starts moving quickly. When the plunger 17 moves to the position of the set value l, the movement of this plunger 17 slows down or stops, and during this time all the other plungers 17 are moved to the position of the set value l, so each plunger 17 can be moved. It becomes possible to fit the parts to the position of the set value 1 at an early stage, and the movement start timings can be approximately aligned.

In this embodiment, the return spring 19 has a discontinuous point in its nonlinear spring constant, but a return spring whose spring constant changes continuously with respect to displacement is used. You can do it like this.

Furthermore, FIG. 7 shows a modification of the oil supply passage 21 formed in the rocker shaft 8 and the high-speed rocker arm 11. As shown in this figure, the oil supply passage 21a on the high-speed rocker arm 11 side is also connected to the oil supply passage 21a in the rocker shaft 8. The supply passage 2 on the rocker shaft 8 side is inclined toward the upstream side with respect to the passage 8a.
It may be formed coaxially with 1b.

In addition, in the embodiment, the low speed (first) rocker arms 9 and 10 and the high speed (second) rocker arm 1
1 and disengaged depending on the operating condition of the engine,
An example is shown in which the present invention is applied to a so-called select valve timing mechanism, in which cams for opening and closing the valve are used appropriately. However, the first rocker arm only contacts the valve side, and does not contact the low-speed cam, etc. In a predetermined operating state, the second rocker arm on the driving side and the first rocker arm on the driven side are disengaged to stop the valve operation, so-called valve stop. The present invention may be adopted in the mechanism.

<<Effects>> In summary, according to the present invention, the return spring that pushes the plunger back into the hydraulic chamber is given non-linear characteristics to improve the responsiveness of each plunger at the initial stage of movement to pressure changes within the hydraulic chamber. When the pressure is switched from low to high, the plunger can be quickly fitted into the fitting hole, and the plunger can be quickly moved to a position where it does not disengage from the fitting hole even when a cam lift is started. Therefore, even if the latter half of the moving mechanism of each plunger is moved immediately after the start of the cam lift, it is possible to prevent the first rocker arm from detaching from the second rocker arm and falling onto the low-speed cam as much as possible. This makes it possible to prevent the occurrence of tapping noise from the valve drive unit and a decrease in durability. Further, it is possible to equalize as much as possible the variations in response of each plunger due to processing accuracy errors and the deviations in the movement start timing of each plunger caused by this.

[Brief explanation of the drawing]

Figures 1 to 4 show an embodiment in which the engine valve drive device of the present invention is applied to the intake valve side of a three-valve type engine, and Figure 1 is a side sectional view showing the overall configuration of the present invention. , FIG. 2 is a side cross-sectional view of the main part in FIG. 1, FIG. 3 is a plan view of the intake valve side, and FIG. 4 is a cross-sectional view taken along the - line in FIG. 2. In addition, Fig. 5 is a graph showing an example of the nonlinear characteristics of the return spring, Fig. 6 is a graph showing an example of the increase characteristic of the oil pressure in the hydraulic chamber when switching to the interlocking state, and Fig. 7 is the deformation of the oil supply passage. It is a figure which shows an example. 1... (intake) valve, 3... camshaft, 5...
(For high speed) Cam, 8...Rotsuka shaft, 9,
10...1st (low speed) Rotsuker arm, 11...
...Second (high speed) rocker arm, 16...Hydraulic chamber, 17...Plunger, 18...Fitting hole, 1
9...Return spring.

Claims (1)

[Scope of utility model registration request] A first rocker arm is provided on the rocker shaft so as to be swingably supported and abuts at least the valve, and the first rocker arm is adjacent to the first rocker arm and has one end abutting a cam of a camshaft, so that the rocker shaft can be rocked. A second rocker arm is rotatably supported, and a hydraulic chamber is formed in either one of the second rocker arm and the first rocker arm on the side thereof, to which high hydraulic pressure is supplied depending on the operating state of the engine. , a plunger is provided in the hydraulic chamber so as to be freely retractable toward the other rocker arm on the side, and a fitting hole into which the plunger is inserted is formed in the other rocker arm;
A valve drive device for an engine, characterized in that a return spring having a nonlinear characteristic that pushes the plunger back into the hydraulic chamber when the pressure in the hydraulic chamber becomes low is provided in the fitting hole.