JPH08177425A - Valve system of internal combustion engine - Google Patents

Abstract

PURPOSE: To prevent enlargement of a cylinder head and increase of its weight by restraining increase of height of a valve lifter and to prevent generation of large sliding resistance and partial abrasion. CONSTITUTION: A cam 6 for high speed to move suction valves 3, 3 to open and a pair of cams 4, 5 for low speed are provided on an outer periphery of a camshaft 1, and a valve lifter 9 to transmit cam lift to the suction valves 3, 3 by way of sliding on each of the cams 4-6 is furnished. Motion of a first lifter part 12 and a second lifter part 13 against each of the cams 4, 5, 6 of the valve lifter 9 is switched over. A pin hole of a switchover means, a plunger hole, a pin and a plunger are formed on each of lower end parts of a cylindrical part 11 and the second lifter part 13 at a position below the first lifter part 12 and is formed in the axis rectangular direction of the cam lift 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating system for variably controlling the opening / closing timing and the opening amount of an intake valve or an exhaust valve according to the engine operating condition.

[0002]

2. Description of the Related Art Conventionally, an internal combustion engine for an automobile has a lift of an intake valve or an exhaust valve depending on an operating state for the purpose of achieving both improvement of fuel consumption at low and medium speeds and improvement of output torque at high speeds. It is known that a valve operating device is used which variably controls the opening / closing timing and the opening amount of the intake / exhaust valve with different characteristics (see Japanese Patent Laid-Open No. 4-276107).

This is between a pair of left and right low speed cams having different profiles for opening and operating a pair of intake valves against the spring force of a valve spring on the outer periphery of a cam shaft which is rotationally driven by a crankshaft. Is integrally provided with a high speed cam, and a valve lifter is interposed between the both cams and the intake valve. This valve lifter has two first lifter parts slidably provided in an elliptical bore of a cam carrier formed in an elongated elliptical shape in the axial direction of the camshaft, and between the first lifter parts. An elliptical second lifter portion that slides in the elliptical sliding hole is provided. In both the first lifter parts, the slippers at the upper end are in sliding contact with the low speed cams, and in the second lifter parts, the slippers at the upper end are in sliding contact with the high speed cams. Further, switching means is provided between the lower portions of the first lifter section and the second lifter section.
The switching means has a pair of pin holes continuously formed in the camshaft axial direction between the first lifter portion and the second lifter portion, and two connecting pins slide in the both pin holes. It is movably installed.

Then, hydraulic pressure is supplied to and discharged from each pressure receiving chamber provided on the rear end side of each connecting pin according to the operating state of the engine, and the first lifter portion and the second lifter portion are connected to each other as the connecting pin slides in the axial direction. The lifter section is connected or disconnected to selectively operate, and the intake valve lift and valve timing are variably controlled by the low speed cam when the engine is running at low and medium speeds and by the high speed cam when the engine is running at high speeds. ing.

[0005]

However, in the above-mentioned conventional valve operating device, the pin holes and the connecting pins of the switching means are formed inside the lower ends of the first lifter portion and the second lifter portion as described above. Since it is formed along the axial direction of the camshaft, the height of the entire valve lifter in the vertical direction is necessarily increased. That is, the first lifter section and the second
Since the pin holes are formed in each of the lifter parts along the axial direction of the camshaft, the thickness of both lifter parts must be sufficiently increased. For this reason, the camshaft has to be placed upwards by the amount that the upper end portion of the valve lifter is enlarged upwards.As a result, the cylinder head must be upsized and remodeled, which increases the weight and size of the entire engine. Not only is it leading to higher manufacturing costs.

Moreover, since the bore of the cam carrier, the entire first lifter portion, the sliding hole, and the second lifter portion are formed in an elliptical shape, the cutting and polishing of the respective portions become extremely complicated, and the working efficiency decreases. And soaring processing costs are inevitable.

Further, since the second lifter portion is formed into an elliptical shape which is long in the direction perpendicular to the camshaft axis, the outer end surface on the long axis side is inclined to the sliding hole so that the second end portion tilts in the long axis direction especially at high engine speed. There is a possibility that a large sliding resistance is generated on the inner peripheral surface due to shouldering, a smooth sliding cannot be obtained, and uneven wear occurs between the two.

[0008]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above problems of the prior art. The invention of claim 1 includes a camshaft which is rotationally driven by a crankshaft of an engine,
A high-speed cam and a low-speed cam that are provided on the outer periphery of the cam shaft to open and close the intake and exhaust valves, a valve lifter that slidably contacts the cams and transmits the lift of each cam to the intake and exhaust valves, and an engine. In a valve operating system for an internal combustion engine, comprising a switching means for switching the operation of the valve lifter with respect to each of the cams according to an operating state, the valve lifter includes a tubular portion that slides in a guide hole of a cylinder head, A first lifter portion integrally provided on the outer side of the upper end of the tubular portion and slidingly contacting the cam on the one side, and a first lifter portion slidably provided inside the tubular portion and slidingly contacting the cam on the other side. While having a second lifter part, the switching means is formed between the tubular part and the second lifter along a direction perpendicular to the axis of the camshaft, and is arranged below the first lifter part. Characterized by That.

According to a second aspect of the present invention, each guide hole of the cylinder head on which the tubular portion and the first lifter portion slide is formed in a substantially circular shape, and is formed in a wall portion inside the tubular portion. The present invention is characterized in that the circular hole and the columnar portion of the second lifter that slides in the circular hole are formed in a substantially circular cross section.

[0010]

According to the first aspect of the invention, the switching means is formed in the direction perpendicular to the camshaft axis, and is not directly formed on the first lifter portion but is formed on the lower end portion of the tubular portion and the second lifter portion. Therefore, the wall thickness of the first lifter portion can be set as small as possible. Therefore, the height of the entire valve lifter can be set small, and the cylinder head can be prevented from increasing in size.

According to the second aspect of the present invention, the guide hole, the tubular portion of the valve lifter, and the first lifter portion are each formed in a perfect circular shape, and the cylindrical portion of the second lifter portion in the tubular portion is also traversed. Since the surface is formed in a circular shape, cutting and polishing of the respective parts are facilitated.

[0012]

1 to 5 show an embodiment in which the valve operating system according to the present invention is applied to the intake side of a multi-cylinder internal combustion engine.
Is a cam shaft whose journal is supported by the upper end of the cylinder head 2, which is the upper wall of the engine, via a cam bracket, and is rotationally driven by a crankshaft. 3, 3 are open ends of a pair of intake ports in the cylinder head 2. There are two intake valves per cylinder that opens and closes.

The camshaft 1 is provided with a pair of low speed cams 4, 5 arranged at positions corresponding to substantially the center of the valve stems 3b, 3b of the intake valves 3, 3, and the low speed cams 4, 5 respectively. A high speed cam 6 disposed between the two is integrally provided. The low speed cams 4 and 5 are set to have the same profile, the outer peripheral surfaces 4a and 5a are set to have a small valve lift characteristic as shown by X in FIG. 6, and each has a uniform width. The dimensions are set relatively small. On the other hand, the high-speed cam 6 is set to have a profile such that the outer peripheral surface 6a has a large valve lift characteristic as indicated by Y in FIG. The width of the low-speed cams 4 and 5 is set smaller than that of each high-speed cam 6.

The both intake valves 3 and 3 have respective stem ends 3
a, 3a, a spring retainer 7 fixed to the outer periphery of the cotter, a valve spring 8 elastically contacted with the cotter,
8 is urged in the closing direction by the spring force of 8, and at high and low speeds via direct-acting valve lifters 9 provided between the upper end surfaces of the stem ends 3a, 3a and the low speed cams 4, 5. The valve springs 8, 5 are lifted by the lift of the cams 4, 5, 6
It is designed to be opened against the spring force of No. 8.

The valve lifter 9 is vertically movable in three guide holes 10a, 10b, 10c formed at the upper end of the cylinder head as shown in FIGS. 1 to 3, and has a large diameter at the center. A cylindrical portion 11 slidably disposed in the perfect circular guide hole 10a, and an upper end portion of the cylindrical portion 11 are integrally provided on both sides in the axial direction of the cam shaft, and the left and right guide holes 10b and 10c are provided. It is provided with two first lifter parts 12 and 12 provided so as to be vertically movable, and a perfect circular second lifter part 13 slidably provided inside the tubular part 11.

As shown in FIGS. 1 and 2, the cylindrical portion 11 has a rectangular hole 14 formed at the upper end thereof, and a central wall 15 is formed in the lower portion of the rectangular hole 14 in a direction perpendicular to the camshaft axis.
Are integrally formed.

Each of the first lifter portions 12 and 12 has a substantially rectangular shape, and the outer surfaces thereof are arranged with the inner peripheral surfaces of the respective guide holes 10b10c with a certain gap therebetween, and the low speed is provided at the center of each upper surface. Square-shaped wear-resistant pads 16, 16 that are in sliding contact with the cams 4, 5 are fixed. Further, the stem ends 3a, 3a of the intake valves 3, 3 abut on the lower surfaces of the respective first lifter portions 12, 12 and are biased by the spring force of the valve springs 8, 8 in the low speed cams 4, 5 directions. There is.

The second lifter portion 13 is integrally fixed to a rectangular head portion 13a that slides in the rectangular hole 14 of the tubular portion 11 and the center of the lower surface of the head portion 13a.
And a columnar portion 13b that slides in a circular hole 15a that is formed by penetrating in the vertical direction. The head 13a
Is fixed to a rectangular wear-resistant pad 17 with which the high-speed cam 6 is in sliding contact with the upper surface. The upper surface of the pad 17 is formed in an arc shape along the direction perpendicular to the camshaft axis. The second lifter portion 13 has a coil spring 19 elastically mounted between the bottom surface of the bottom groove of the cylindrical portion 13b and a disc-shaped retainer 18 fixed to the lower end portion of the tubular portion 11.
Is urged in the direction of the high speed cam 6 by the spring force.

A part of the switching means 20 is provided between the tubular portion 11 and the lower end of the column portion 13b. As shown in FIGS. 2 and 4, this switching means 20 has a first
A first pin that is arranged sufficiently lower than the contact position between the lifter parts 12, 12 and the stem ends 3a, 3a and is formed along the inner longitudinal direction of the central wall 15 (the direction perpendicular to the camshaft axis). A hole 21 and a plunger hole 22, a second pin hole 23 penetratingly formed in the diametrical direction of the cylindrical portion 15b,
A first pin 24 slidably provided in the first pin hole 21.
And the first pin 24 is slidably provided in the second pin hole 23, and when the first pin hole 21 and the second pin hole 23 are aligned with each other.
A second pin 25 that is engaged in the second pin hole 23 by
A plunger 27 provided in the plunger hole 22 for pushing the second pin 25 toward the first pin 24 via the compression spring 26, and a pressure receiving chamber 28 formed at the rear end side of the first pin 24.
And a hydraulic circuit 29 for supplying and discharging hydraulic pressure.

The pin holes 21 and 23 and the plunger hole 22 are set to have the same diameter and linearly match each other in the base circle areas of the low speed cams 4 and 5 and the high speed cam 6. The position is set to. Further, the first pin 24 has a rear end portion formed in a stepped shape in order to secure a sufficient pressure receiving area of the hydraulic pressure in the pressure receiving chamber 28, while the second pin 25 is slightly smaller than the first pin 24. It is formed in a long shape, and is formed in a spherical shape so that the front and rear ends make point contact with the first pin 24 and the plunger 27. Further, the plunger 27 has a substantially T-shaped vertical cross section, and is biased toward the second pin hole 23 by the compression spring 26 that elastically contacts the rear surface of the flange portion at the front end.

The hydraulic circuit 29 has an oil pan 3 at one end through the cylinder block and the inside of the cylinder head 2.
0, an oil passage 31 communicating with 0, an oil pump 32 provided at an upstream end of the oil passage 31, and an electromagnetic switching valve provided at a downstream side of the oil pump 32 and switching between the oil passage 31 and the drain passage 33. And 34.

The oil passage 31 has a side end portion 31a formed in the cylinder head 2 communicating with the pressure receiving chamber 28.

The electromagnetic switching valve 34 is a controller 35.
The controller 35 is operated to change over by an ON-OFF signal from the engine. The controller 35 outputs information signals such as the engine speed from the crank angle sensor, the air flow meter, the intake air amount, and the engine cooling water temperature from the water temperature sensor. The current engine operating state is detected based on the.

The operation of this embodiment will be described below.
First, in the engine low / medium speed range, an OFF signal is output from the controller 35 to the electromagnetic switching valve 34 to connect the oil passage 31 and the drain passage 33, so that no hydraulic pressure is supplied to the pressure receiving chamber 28 and a low pressure state is set. Become. Therefore, the first pin 24
4 is held in each first pin hole 21 by the plunger 27 by the spring force of the compression spring 26 without pressing the second pin 25 as shown in FIG. 4, and the second pin 25 is also held in the second pin hole 23. Held in. Therefore, the second lifter portion 13
Means that the cylindrical portion 13b freely slides in the circular hole 15a,
That is, the connection with the first lifter parts 12, 12 is released.

As a result, the first lifter parts 12, 12
1 slides up and down according to the profile of the low speed cams 4 and 5 as shown in FIGS.
As indicated by X, the opening / closing operation is performed according to the small valve lift characteristic.

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

On the other hand, when the engine shifts from the low / medium speed range to the high speed range, an ON signal is output from the controller 35 to the electromagnetic switching valve 34 to cut off the communication between the oil passage 31 and the drain passage 33. The hydraulic pressure pumped from the oil pump 32 is supplied into the hydraulic chamber 28 through the oil passage 31. Therefore, the pressure in the pressure receiving chamber 28 becomes high, the first pin 24 is pushed out, and each pin hole 2 is pushed during the cam base circle.
When the Nos. 1 and 23 and the plunger hole 22 are aligned, the second
The pin 25 and the plunger 27 are pushed out to the maximum against the spring force of the compression spring 26 as shown by the one-dot chain line in FIG. As a result, the first pin 24 moves to a position straddling between the first pin hole 21 and the second pin 25, and the second pin 25 is
The first lifter portions 12, 12 and the second lifter portion 13 are connected to each other by moving to a position straddling between the plunger hole 22 and the second pin hole 23.

Therefore, the first lifter parts 12, 12
Moves up and down according to the profile of the high speed cam 6 through the second lifter portion 13 as shown in FIG. 8, and the intake valves 3 and 3 open and close according to the large valve lift characteristic as shown in Y of FIG. Operate. As a result, the intake charging efficiency is improved and high output torque is obtained.

At this time, the low speed cams 4 and 5 are shown in FIG.
As shown in, the outer peripheral surface of the base circle only slides on the upper surfaces of the pads 16 and 16 of the first lifter portions 12 and 12 only when the high speed cam 6 is in the base circle, and when the high speed cam 6 is lifted, it is separated from the upper surface. . Therefore, sliding friction resistance is reduced.

Further, in this embodiment, the pin holes and the plunger holes 21 to 23 of the switching means 20, the pins 24 and 25, etc. are formed in the direction perpendicular to the axis of the camshaft 1, and the first lifter portions 12 and 12 are provided. It is not directly formed, but is formed between the lower end portions of the tubular portion 11 and the second lifter portion 13, that is, is formed at a position lower than the contact position between the first lifter portions 12 and 12 and the valve stems 3a and 3a. Therefore, the first lifter section 1
The wall thicknesses of 2 and 12 can be set sufficiently small. Therefore, the height of the entire valve lifter 9 can be set small, and the height of the cylinder head 2 can be suppressed.

As a result, it is possible to prevent the cylinder head 2 from being increased in weight and size and to eliminate the need for modification. Therefore, it is possible to prevent an increase in the size of the engine, and it is possible to suppress a decrease in manufacturing work efficiency and a cost increase.

Moreover, since the guide holes 10a to 10c and the tubular portion 11 are formed into a perfect circular shape, the circular hole 15a in the tubular portion 11 and the cylindrical portion 13b of the second lifter portion 11 are also formed into a perfect circular shape. Also, the cutting and polishing of the respective parts are facilitated, and also in this respect, the manufacturing work efficiency can be improved and the cost can be reduced. Further, in particular, by making the cylindrical portion 13b of the second lifter portion 13 and the circular hole 15a have a perfect circular shape, shoulder contact between the both 13b and 15a is prevented,
Occurrence of uneven wear can also be prevented.

[0033]

As is apparent from the above description, according to the present invention, the pin holes or the like of the switching means are formed along the camshaft axial direction as in the prior art, or formed in the first lifter portion. Instead, the valve lifter overall height can be set as low as possible because it is formed in the direction perpendicular to the axis of the camshaft and at the lower end portions of the tubular portion and the second lifter portion other than the first lifter portion. Therefore, the overall height of the cylinder head can be set sufficiently low, and no modification is required.
As a result, an increase in the size of the engine can be prevented and a rise in manufacturing cost can be suppressed.

Moreover, since the guide holes, the cylindrical portion, etc. are formed in a perfect circular shape, cutting and polishing of each portion are extremely easy as compared with the conventional elliptical shape, and the manufacturing work efficiency is improved. And the cost can be reduced. In particular, by making the circular hole of the second lifter portion and the circular hole of the tubular portion into a perfect circle shape, shoulder contact between the two is prevented during sliding, and an increase in sliding friction resistance and uneven wear are prevented. It can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view taken along line AA of FIG. 2 showing an embodiment of the present invention.

FIG. 2 is a view taken along the line BB of FIG.

FIG. 3 is a perspective view showing a valve lifter of this embodiment.

4 is a cross-sectional view taken along the line CC of FIG.

5 is a cross-sectional view taken along line DD of FIG.

FIG. 6 is a valve lift characteristic diagram of a low speed cam and a high speed cam.

7 is a cross-sectional view taken along the line AA of FIG. 2 when the low speed cam is lifted.

8 is a cross-sectional view taken along the line AA of FIG. 2 when the high speed cam is lifted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cam shaft 2 ... Cylinder head 3 ... Intake valve 4, 5 ... Low speed cam 6 ... High speed cam 8 ... Valve spring 9 ... Valve lifter 10a-10c ... Guide hole 11 ... Cylindrical part 12 ... 1st lifter part 13 ... 2nd lifter part 13b ... Cylindrical part 15 ... Central wall 15a ... Circular hole 20 ... Switching means

Claims (2)

[Claims] 1. A cam shaft rotatably driven by a crank shaft of an engine, and a cam shaft provided on an outer periphery of the cam shaft,
A high speed cam and a low speed cam for opening and closing the intake and exhaust valves;
A valve lifter for an internal combustion engine provided with a valve lifter which is in sliding contact with each cam and transmits the lift of each cam to an intake / exhaust valve, and a switching means for switching the operation of the valve lifter with respect to each cam according to the engine operating state. In the apparatus, the valve lifter includes a tubular portion that slides in a guide hole of a cylinder head, and a first lifter portion that is integrally provided outside the upper end of the tubular portion and that is in sliding contact with the cam on the one side. ,
A second lifter portion slidably provided inside the tubular portion and in sliding contact with the cam on the other side;
A valve operating device for an internal combustion engine, wherein the switching means is formed between the tubular portion and the second lifter along a direction perpendicular to the axis of the camshaft, and is arranged below the first lifter portion. .. 2. The guide hole of the cylinder head on which the tubular portion and the first lifter portion slide is formed in a substantially circular shape, and a circular hole formed in a wall portion in the tubular portion and the circular shape. 2. The valve operating system for an internal combustion engine according to claim 1, wherein each of the columnar portions of the second lifter that slides in the hole is formed to have a substantially circular cross section.