JPH07259519A - Variable valve system of internal combustion engine - Google Patents

Abstract

PURPOSE:To smooth a resultant torque in offsetting both positive and negative signs of torque as well as to reduce the extent of torque variations by forming a cam profile so as to make the lift decreasing period of a cam on one side precedingly operating and the increasing period of a cam on the other succeedingly operating accord with each other in an interval between these cams themselves of different cylinders operating before and after. CONSTITUTION:A hydraulic fluid collected in a hydraulic chamber 20 is put back to another hydraulic chamber 13 by an accumulator spring 21 at the time of lift decrease in a cam 1, making it act on such a force as driving this cam 1 via a cam side piston 7. A rotary sleeve 10 is rotated by a rack pinion mechanism 17, then height in the reciprocating direction of the end of a window 12 is varied to some extent and timing for opening an oil hole 11 is changed, whereby a lift value in a suction-exhaust valve 24 is adjusted. In succession, a lift increasing period in a certain cam and a cam lift decreasing period of another cam of a cylinder opening precedingly to the former are almost accorded with each other, through which both positive and negative signs of cam shaft driving torque are nearly negated with each other and smoothened, and thus any torque variation in the cam shaft is reducible in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a variable valve operating system for an internal combustion engine, which controls lift and timing of intake valves or exhaust valves (hereinafter referred to as "intake / exhaust valves") via hydraulic pressure. .

[0002]

2. Description of the Related Art As a variable valve actuating device of this kind, as disclosed in, for example, Japanese Patent Laid-Open No. 1-134013, a cam driven to rotate in synchronization with an engine and a reciprocating motion following the cam. There is a cam side piston and a valve side piston that interlocks with the cam side piston via hydraulic pressure, and an intake / exhaust valve is opened / closed via the valve side piston.

This is the timing and valve for closing the intake / exhaust valve by opening the hydraulic pressure release valve during the opening / closing operation of the intake / exhaust valve to change the timing at which the hydraulic pressure acting on the valve side piston is released from the cam side piston. The amount of lift can be adjusted.

As the hydraulic pressure release valve, for example, a rotary sleeve valve as shown in FIGS. 9 and 10 is used. A window 12 is provided in a rotary sleeve 10 covering the outside of the cam side piston 7, and a window 12 is provided in the window 12 through a check valve 22 to a hydraulic pump (not shown), and a check valve 18 so as to prevent the cam side piston 7 from moving. Oil passages 16 connected to the inner hydraulic chambers 13, respectively
Are in communication.

When the cam side piston 7 is pushed down via the rocker arm 3 by the operation of the cam 1, the hydraulic pressure in the hydraulic chamber 13 is transmitted to the valve side piston (not shown) while rising, and the intake / exhaust valve is opened. During operation of the cam side piston 7, an oil hole 11 provided in the cam side piston 7
Is communicated with the window 12 of the rotary sleeve 10, whereby the hydraulic pressure from the hydraulic chamber 13 to the valve side piston is released and the intake / exhaust valve is closed.

The window 12 of the rotary sleeve 10 is formed in a triangular shape. By rotating the rotary sleeve 10 by driving the rack-pinion mechanism 17, the oil hole 11 of the cam side piston 7 and the window of the rotary sleeve 10 are rotated. The amount of lift of the intake / exhaust valve is increased or decreased by changing the timing of communication with 12 and the communication section.

Reference numeral 19 in FIG. 10 indicates an accumulator for temporarily storing the working hydraulic pressure released from the hydraulic chamber 13 when the intake and exhaust valves are closed.

[0008]

By the way, the shape of the cam 1 in such a variable valve operating device is generally determined so as to satisfy the required maximum lift of the intake and exhaust valves (see FIG. 11), and within that range. As described above, the lift of the intake / exhaust valve is terminated by releasing the hydraulic pressure. On the other hand, since a strong reaction force from the valve spring acts on the cam 1 from the start to the end of the lift, in the conventional device, a large torque fluctuation occurs in the cam shaft as shown in FIG. There is.

FIG. 11 shows the shape of a conventional cam, and FIG. 12 shows the drive torque fluctuation and valve lift characteristic of a cam shaft for an in-line 4-cylinder engine when the cam is used. In the graph of the cam profile in FIG. 12, the solid line shows the cam profile (cam lift), and the broken line shows the valve lift. In the graph of camshaft drive torque in the figure, the broken line shows the drive torque per cam, and the solid line shows the total torque of each cam, that is, the drive torque of the entire camshaft. Further, reference signs a to c in FIG. 11 correspond to reference signs a to c in FIG.

As shown in the drawing, the cam pushes the cam side piston from a to b, the cam shaft drive torque increases and decreases according to the shape of the cam, and from b to c, the cam hydraulically moves the cam side piston. The camshaft drive torque decreases and increases again according to the shape of the cam. By the reaction force acting on the cam in this way,
For four cylinders, a large camshaft drive torque fluctuation as shown by the solid line in FIG. 12 occurs.

Such a large torque fluctuation causes noise and vibration of the valve operating system or the valve operating system, which causes the durability of the valve operating system to be impaired.

The present invention has been made by paying attention to such a conventional problem, and the fluctuation of the driving torque of the camshaft is small,
Moreover, it is an object of the present invention to provide a variable valve operating device capable of accurately opening and closing the intake and exhaust valves.

[0013]

In order to achieve the above object, as a first invention, a cam driven to rotate in synchronization with an engine, a cam side piston that reciprocates following the cam, and a cam side. A valve-side piston that interlocks with the piston via hydraulic pressure, an intake valve or an exhaust valve that opens and closes following the valve-side piston, and a hydraulic release valve that reduces the hydraulic pressure that acts on the valve-side piston during valve opening and closing operation. ,
In a variable valve operating device for an internal combustion engine, which stores an oil pressure released through an oil pressure release valve, and which has an accumulator that causes the stored oil pressure to act on a cam side piston when a cam lift is reduced, a common valve drive system is used. Between the cams of different cylinders that are driven by each other and operate in chronological order, the lift decrease period of one cam that operates first and the lift increase period of the other cam that operates subsequently substantially match. To form a cam profile.

As a second invention, a cam which is rotationally driven in synchronism with the engine, a cam side piston which reciprocates following the cam, and a valve side piston which is hydraulically linked to the cam side piston. , An intake valve or an exhaust valve that opens and closes following the valve-side piston, a hydraulic release valve that reduces the hydraulic pressure that acts on the valve-side piston during valve opening and closing, and a hydraulic pressure that is released via the hydraulic release valve. In a variable valve operating system for an internal combustion engine, which is provided with an accumulator that stores and stores the stored hydraulic pressure on a cam side piston when a cam lift is reduced, the variable valve operating system is driven through a common valve drive system and operates backward and forward in time. Between the cams of different cylinders, the inflection point of the lift curve when the lift of one of the preceding cams decreases, and the lift of the other cam that follows subsequently increases And the inflection point of the lift curve in the form of cam profile to time to substantially coincide.

Further, as a third invention, in the structure of any one of the above inventions, an area where the cam lift is substantially constant is provided in the cam profile between the end point of the lift increase and the start point of the lift decrease. To propose.

[0016]

When the cam starts to lift, the lift is transmitted from the piston on the cam side to the piston on the valve side across the hydraulic chamber via the hydraulic chamber to lift the intake / exhaust valve.
During this period of increase in cam lift, the torque required to drive the cam shaft (positive torque) due to the reaction force of the valve spring.
Will increase.

When the valve closing timing arrives during the cam lift, the hydraulic release valve opens to release the hydraulic oil in the hydraulic chamber, so the intake / exhaust valve starts closing and the operation released from the hydraulic chamber at this time. Oil pressure is stored in the accumulator.

The hydraulic pressure thus accumulated in the accumulator continues to act on the cam from the hydraulic chamber via the cam side piston, and when the cam starts to decrease in lift, the hydraulic pressure is increased during the lift decreasing period. As a result, torque (negative torque) in the direction for driving the cam shaft is added to the cam shaft.

Therefore, between the cams of the different cylinders which are driven by the common valve drive system and are operated in chronological order, the lift reduction period of one of the cams that precedes and the trailing end of the lift period of one cam follow. If the lift increase period of the other cam that is activated is substantially the same, or the lift curve inflection point when the lift of one of the preceding cams decreases, the inflection point of the other cam When the inflection point of the lift curve is made to substantially coincide with the lift curve when the lift is increased, the positive torque during the increase of the cam lift described above and the decrease of the cam lift of the cams of other cylinders preceding the positive torque. , And the negative torque of is canceled out, and these combined torques are smoothed to reduce the torque fluctuation.

Further, when a region where the cam lift is substantially constant is provided in the cam profile between the end point of the lift increase and the start point of the lift decrease, in the vicinity of the maximum cam lift where it is difficult to cancel the positive and negative torques. Since the cam driving torque is smoothed, the torque fluctuation is further reduced.

[0021]

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

FIG. 1 shows a schematic structure of a variable valve mechanism using a rotary sleeve valve similar to that shown in FIG. 9 as a hydraulic pressure release valve. In FIG. 1, the same parts as those in FIG. 9 or 10 are designated by the same reference numerals.

In FIG. 1, a cam 1 driven to rotate in synchronism with an engine is in contact with a roller follower 2, and one of them is connected to a cam follower 7 via a rocker arm 3 having a roller follower 2 supported by a pivot end 4. Reciprocate up and down. The cam side piston 7 has a protrusion 6 formed on the upper end thereof, and by engaging this with the groove 5 of the rocker arm 3, the cam side piston 7 is prevented from rotating to position the oil hole 11 in the circumferential direction. .

FIG. 1 shows a fully opened state of the rotary sleeve valve. When the cam side piston 7 is pushed down by the rotation of the cam 1 from this state, the valve side piston 15 is moved through the hydraulic pressure generated in the hydraulic chamber 13. It is pushed down and the intake / exhaust valve 24 opens.

The oil hole 11 of the piston 7 on the cam side communicates with the window 12 of the rotary sleeve 10 to release the hydraulic pressure, and the hydraulic oil in the hydraulic chamber 13 opened at this time is supplied to the accumulator 19.

When the intake / exhaust valve 24 is opened, the oil hole 11
And the window 12 communicate with each other, and the hydraulic oil in the hydraulic chamber 13 is transferred to the oil passage 16
The valve opening force acting on the valve-side piston 15 is lost by being released to the oil reservoir chamber 20 of the accumulator 19 through the valve spring 23.
The valve is closed by the urging force of.

The hydraulic oil stored in the oil storage chamber 20 is stored in the cam 1
When the lift is reduced, it is returned to the hydraulic chamber 13 by the accumulator spring 21, and a force for driving the cam 1 is applied via the cam side piston 7.

The rotary sleeve 10 is rotated by a rack-pinion mechanism 17, and the height of the end of the window 12 in the reciprocating direction is changed to change the opening timing of the oil hole 11, thereby changing the height of the intake / exhaust valve 24. Adjusting the lift amount.

The hydraulic chamber 13, the oil passage 16, and the oil reservoir chamber 20 communicate with a hydraulic source such as a hydraulic pump (not shown) via one-way valves 22 and 18, and the cam side piston 7 and the valve side piston 1 are connected.
The hydraulic oil leaking from the sliding portion of No. 5 is replenished.

As shown in FIG. 2, an annular chamber 25 is provided above the valve-side piston 15 so as to be defined in the small lift region. The annular chamber 25 and the hydraulic chamber 13 are separated from each other. A check valve 26 is provided on the way to communicate with each other through a passage 27 and an orifice 28. When the cam 1 lifts and the pressure in the hydraulic chamber 13 increases, at this time, the check valve 26 is opened in the annular chamber 25 to introduce the hydraulic oil from the hydraulic chamber 13, so that the valve side piston 15 moves quickly. The intake / exhaust valve 24 is opened. On the other hand, when the valve is closed, the check valve 26 closes the passage 27, and the annular chamber 25 is in communication with the hydraulic chamber 13 via only the orifice 28. Therefore, the damping action of the orifice 28 closes the annular chamber 25. The valve closing speeds of the valve-side piston 15 and the intake / exhaust valve 24 immediately before the valve are reduced, and a cushioning action when the valve is seated is obtained.

In the present invention, for example, in such a variable valve operating device, the cams of different cylinders which are driven via a common valve operating system and are operated back and forth in time,
The profile of each cam 1 is formed so that the cam shaft drive torque when the cam lift increases and the cam drive torque due to the hydraulic pressure from the accumulator 19 when the cam lift of the cam of the other cylinder preceding the cam lift decreases.

FIG. 3 shows the operating characteristics of the cam 1 according to the first embodiment for realizing such an action. This shows the torque fluctuation of the cam shaft of the in-line 4-cylinder engine having the cam 1, and the period from the symbol d to e or h to i in the figure is the cam lift increasing period, during which the cam 1 moves to the position shown in FIG. Valve spring 23 shown in
Since the cam side piston 7 is pushed against the above, the cam shaft drive torque increases in the positive direction. Next, the period from e to f or i to j is the cam lift reduction period, and the cam 1 is pushed by the hydraulic pressure from the accumulator 19 acting via the cam side piston 7, so the cam shaft drive torque is in the negative direction. Increase to.

At this time, since the cam lift increasing period of a certain cam and the cam lift decreasing period of the cam of the cylinder that is opened prior to this cam are made to substantially coincide with each other, as shown in the torque curve in the figure, the cam lift is increased. The positive and negative camshaft drive torques in the increasing and decreasing sections cancel each other out and are smoothed, and the camshaft drive torque fluctuations decrease.

As shown by the dotted line in FIG. 3, since the valve lift is controlled by the hydraulic pressure release valve, the valve lift amount and opening / closing timing are restricted by adopting the cam shape of this embodiment. There is no.

Further, in FIG. 3, a slight positive driving torque is generated also in the base circle area of the cam, but this is due to the friction of the cam surface, and when the roller follower 2 is used as in the embodiment. This friction torque is actually smaller.

Next, FIGS. 4 and 5 show the second embodiment of the cam shape according to the present invention and the operating characteristics when the second embodiment is applied to the cam shaft of an in-line four-cylinder engine. However, reference numeral n in FIG.
q corresponds to the symbols n to q in FIG.

In this embodiment, the inflection point of the lift curve when the cam lift of the cam of an arbitrary cylinder increases and the inflection curve of the lift curve of the cam of the other cylinder that is opened prior to this when the cam lift decreases. The cam profile is set so that the points coincide with each other. In this case as well, the torque when the cam lift increases and the torque when the lift of the cam that operates prior to this increases are almost canceled at the same timing. Therefore, the same torque fluctuation reducing action as in the first embodiment can be obtained.

However, when the inflection points are made to coincide with each other in this way, the positive and negative camshaft drive torques rise with symmetrical characteristics, so that the combined torque becomes smoother.

FIGS. 6 and 7 show the third embodiment of the cam shape according to the present invention and the operating characteristics when it is applied to an in-line four-cylinder engine. However, the symbols j to m in FIG. 6 correspond to the symbols j to m in FIG. 7.

The cam of this embodiment has the above first or second cam.
In the cam having the characteristics as in the above embodiment, the cam profile is formed so as to have a region where the cam lift is substantially constant between the end point of the lift increase and the start point of the lift decrease.

It is difficult to cancel the positive and negative camshaft drive torques in terms of timing during the period when the cam lift is maximum, but by providing the region where the cam lift is substantially constant in this way, the maximum lift region can be increased. Since the camshaft drive torque can be made small and constant, fluctuations in the camshaft drive torque can be further reduced.

In each of the above-described embodiments, an example of application to an in-line 4-cylinder engine is shown, but the present invention is an in-line 6-cylinder, V-type engine.
It goes without saying that the invention can also be applied to other types of engines such as a 6-cylinder engine.

Further, in order to cancel the driving torque fluctuation of the cam shaft, if the cams are driven by the common valve drive system, it is not always necessary to use the cams immediately before and after the position.

On the other hand, FIG. 8 shows a cam profile (solid line), a valve lift (broken line), a target valve lift (dotted line), and an accumulator displacement (one point) at the time of high lift when a rotary sleeve valve is used as the hydraulic pressure release valve. As shown in the figure, when the cam shape of the present invention is applied, the opening timing of the hydraulic release valve can be set longer than in the conventional case, so that the intake and exhaust valves are closed. Will be done smoothly.

That is, the opening period of the rotary sleeve valve depends on the shape of the cam 1, and generally, the period in which the oil hole 11 is opened in the window 12 becomes shorter as the lift increases, so that the conventional cam profile is as shown in FIG. As shown, when the lift is high, the hydraulic oil in the hydraulic chamber 13 cannot be fully opened, and the closing timing of the intake / exhaust valve is delayed from the target. On the other hand, according to the configuration of the present invention, the time when the cam lift starts to decrease is later than in the conventional case, and the hydraulic pressure release time can be taken longer, so even when the rotary sleeve valve is used as the hydraulic pressure release valve, The valve closing delay of the intake / exhaust valve in the valve lift region can be prevented and the valve closing operation can be reliably performed.

[0046]

As described above, according to the present invention, the cam lift is transmitted to the intake and exhaust valves via hydraulic pressure,
In a variable valve operating system that adjusts the lift amount of intake and exhaust valves by releasing hydraulic pressure to the accumulator side during the cam lift, it is driven through a common valve drive system and operates backward and forward in time. Between the cams of different cylinders, the lift decreasing period of one of the cams that operates earlier and the lift increasing period of the other cam that operates subsequently substantially match, or The cam profile so that the inflection point of the lift curve when the lift of one cam decreases and the inflection point of the lift curve when the lift of the other cam that operates subsequently increases substantially in time. As a result, the cam shaft drive torque when the cam lift increases and the cam drive torque due to the hydraulic pressure from the accumulator when the cam lift of the cam of the other cylinder preceding this increases. Are canceled out, the fluctuation in the drive torque of the camshaft is reduced, and the noise and vibration from the valve train or the valve drive system caused by this can be reduced, and at the same time, the valve drive system, etc. The effect that the durability of can be improved can be obtained.

Further, in the present invention, the cam profile is provided with a region where the cam lift is substantially constant between the end point of the lift increase and the start point of the lift decrease. The effect that the drive torque of the camshaft can be smoothed and the fluctuation of the drive torque of the camshaft can be further reduced is obtained.

Further, according to the present invention, since the hydraulic pressure release time can be extended, even when the rotary sleeve valve is used as the hydraulic pressure release valve, the valve closing delay of the intake and exhaust valves in the high valve lift range can be prevented. Reliable operability is obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a variable valve operating device.

FIG. 2 is a detailed view of a valve side piston of the variable valve mechanism of FIG.

FIG. 3 is a characteristic diagram according to the first embodiment of the present invention.

FIG. 4 is a front view of a cam according to a second embodiment of the present invention.

FIG. 5 is a characteristic diagram according to the second embodiment.

FIG. 6 is a front view of a cam according to a third embodiment of the present invention.

FIG. 7 is a characteristic diagram according to the third embodiment.

FIG. 8 is a characteristic diagram showing a hydraulic pressure releasing action according to the present invention in comparison with a conventional example.

FIG. 9 is a perspective view of a rotary sleeve valve.

FIG. 10 is a vertical sectional view of a rotary sleeve valve.

FIG. 11 is a front view of a conventional cam.

FIG. 12 is a characteristic diagram of a conventional variable valve operating device using a cam.

[Explanation of symbols]

 1 cam 2 roller follower 3 rocker arm 4 pivot end 5 cam side piston positioning groove 6 cam side piston positioning protrusion 7 cam side piston 10 rotating sleeve 11 cam side piston hole (for releasing hydraulic pressure) 12 rotating sleeve window 13 hydraulic chamber 15 Valve-side piston 16 Oil passage 17 Rack-pinion mechanism 18 Check valve 19 Accumulator 20 Oil reservoir 21 Accumulator spring 22 Check valve 23 Valve spring 24 Intake / exhaust valve 25 Annular chamber 26 Check valve 27 Passage 28 Orifice

Claims (3)

[Claims] 1. A cam which is rotationally driven in synchronization with an engine,
A cam side piston that reciprocates following the cam, and a valve side piston that interlocks with the cam side piston via hydraulic pressure,
The intake valve or exhaust valve that opens and closes following the valve-side piston, the hydraulic release valve that reduces the hydraulic pressure that acts on the valve-side piston during valve opening and closing, and the hydraulic pressure that is released via the hydraulic release valve are stored. In a variable valve operating system for an internal combustion engine having an accumulator that causes the accumulated hydraulic pressure to act on a cam side piston when the cam lift is reduced, different valve operating systems are driven via common valve operating systems Between the cams of the cylinders, the cam profile is formed such that the lift decreasing period of one of the cams that operates first and the lift increasing period of the other cam that operates subsequently substantially coincide with each other. Variable valve device for internal combustion engine. 2. A cam which is rotationally driven in synchronization with an engine,
A cam side piston that reciprocates following the cam, and a valve side piston that interlocks with the cam side piston via hydraulic pressure,
The intake valve or exhaust valve that opens and closes following the valve side piston, the hydraulic release valve that reduces the hydraulic pressure that acts on the valve side piston during valve opening and closing, and the hydraulic pressure that is released via the hydraulic release valve are stored. In a variable valve operating system for an internal combustion engine having an accumulator that causes the accumulated hydraulic pressure to act on a cam side piston when the cam lift is reduced, different valve operating systems are driven via common valve operating systems Between the cams of the cylinders, the inflection point of the lift curve when the lift of one of the preceding cams decreases and the inflection point of the lift curve when the lift of the other cam that follows operates increase A variable valve operating device for an internal combustion engine, wherein a cam profile is formed so as to substantially match each other. 3. The cam profile according to claim 1, wherein a region where the cam lift is substantially constant is provided in the cam profile between the end point of the lift increase and the start point of the lift decrease. A variable valve operating device for an internal combustion engine as described above.