JP3373644B2 - 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 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 having different characteristics and capable of controlling the opening / closing timing and the opening amount of the intake / exhaust valve is provided (see Japanese Patent Laid-Open No. 63-117109, etc.).

In this structure, a low speed cam and a high speed cam having different profiles for integrally opening a pair of intake valves against the spring force of a valve spring are provided on the outer periphery of a cam shaft which is rotationally driven by a crankshaft. In addition, a pair of direct-acting first and second valve lifters for transmitting the lift of the low-speed cam to the intake valve are provided at the upper end of the valve shaft of the intake valve. A third valve lifter that slides according to the lift of the high-speed cam is provided between the valve lifters. Further, the first to third
At each upper end portion of the valve lifter, there is provided a connecting means constituted by a guide hole formed in the cam shaft axial direction, a guide recess, and a pair of hydraulic pistons slidably provided in the guide hole.

When the engine is running at low speed, the supply of 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 is opened / closed according to the small valve lift characteristic of the low speed cam via the first and second valve lifters.

On the other hand, when shifting from the low speed range to the high speed range, the hydraulic pressure is supplied to the pressure receiving chambers so that the hydraulic pistons are inserted into the pair of guide recesses of the third valve lifter and the third valve lifter and the third valve lifter. 1. Connect the second valve lifter. Therefore, 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, the fuel consumption can be improved and the output torque can be improved according to the engine speed.

[0007]

However, in the above-mentioned conventional valve operating device, since the connecting means is constituted by the guide hole or piston formed at the upper end of each valve lifter, the inner and outer diameters are relatively large. The shape of the upper end of each valve lifter that forms and holds the guide hole and the piston is inevitably large. For this reason, the camshaft has to be arranged upward by the amount that the upper end portion is expanded upward, and as a result, the cylinder head and the like must be increased in size.

In addition, since the weight of each valve lifter increases as the size increases, the inertial force during vertical sliding increases,
Smooth operation cannot be obtained at high speed rotation. Therefore, if the spring set load of the valve spring is increased in order to cope with such high-speed rotation, there is a fear that the sliding friction resistance between the intake valve and the cam will increase via the valve lifter this time. .

[0009]

[0010]

[0011]

A camshaft rotatably driven by a crankshaft of an engine, a pair of high and low speed cams provided on the outer periphery of the camshaft for opening and operating valves provided in intake and exhaust ports, and an engine. A valve operating device provided with a transmission member that is slidably provided in a pair of guide holes formed in an upper wall and that transmits the lift of each cam to the valve, wherein the transmission member and each cam are provided. Between the two, a flat plate slider having a follower portion on the upper surface that relatively abuts the outer peripheral surface of each cam and having a pair of main bodies corresponding to the pair of valves is slidable in the axial direction of the camshaft. The slider body on the other side is interlocked by sliding the slider body on the one side in accordance with the engine operating state by linking both bodies of the slider so as to be interlocked with each other.
It is characterized in that switching means is provided for switching the contact position of each follower portion with respect to each outer peripheral surface of the high / low speed cam.

The invention of claim 2 is characterized in that the pair of slider bodies are formed separately from the end portions which are in contact with each other, and are vertically movable independently of each other.

[0013]

[0014]

[0015]

According to the first aspect of the present invention, the flat slider is slid on the upper surface of each transmission member in the axial direction of the camshaft, so that the follower portion can relatively contact the low speed cam and the high speed cam. The contact position can be selectively switched, and the lift of either the high speed cam or the low speed cam can be selectively transmitted to the valve.

Further, since the slider is formed in a flat shape and the switching means for sliding the slider is formed outside each transmission member, it is not necessary to enlarge the upper end portion of the transmission member upward, and the transmission member is large. Is prevented. It
In addition, the pair of slider bodies are linked.
Therefore, switching means is not required for each valve lifter, but for each cylinder.
One for each is better.

According to the second aspect of the present invention, since both slider bodies are formed separately from the end portions which are in contact with each other and can be vertically moved independently of each other, for example, two low speed cams are arranged on both sides of the high speed cam. It is also possible to operate the valves separately by making the profiles of the low speed cams different from each other.

According to the third aspect of the invention, since the guide plate guides the slider, the transmission member can be formed of a material different from the guide plate.

According to the fourth aspect of the present invention, since the area of the upper surface of the follower portion can be increased, a reliable and stable contact state with each cam can be obtained.

[0020]

1 to 3 show a first embodiment in which a valve operating system according to the present invention is applied to the intake side of a multi-cylinder internal combustion engine.
Is journaled at the upper end of the cylinder head, which is an upper wall of the engine (not shown), via a cam bracket 2,
A camshaft that is driven to rotate by a crankshaft (not shown),
Reference numerals 3 and 3 denote two intake valves per cylinder that open and close each open end of a pair of intake ports in the cylinder head.

The camshafts 1 are arranged at the respective positions corresponding to the center of the valve stems of the intake valves 3 and 3, respectively, and the low speed cams 4 are arranged on both sides of the low speed cams 4. A pair of high speed cams 5 and 6 are integrally provided. The outer peripheral surface 4a of the low speed cam 4 is set to have a profile having a small valve lift characteristic as indicated by X in FIG. 4, and the uniform width dimension is set to be relatively small. On the other hand, the high speed cams 5 and 6 are formed such that the outer peripheral surfaces 5a and 6a are formed to have the same profile and the valve lift characteristics are large as shown by Y in FIG. The width W of the low speed cam 4 is set to be larger than that of the high speed cams 5 and 6.

The intake valves 3 and 3 are biased in the closing direction by the spring force of valve springs 8 and 8 elastically contacted with the cotters 7 and 7 fixed to the stem end portions. Through the direct-acting first and second valve lifters 9 and 9 which are transmission members abutting on the ends, the spring force of the valve springs 8 and 8 is resisted by the low speed and high speed cams 4, 5 and 6, respectively. It can be opened.

The first and second valve lifters 9 and 9 are
In the pair of guide holes 11 formed in a guide block 10 integrally formed at the upper end of the cylinder head, which is formed in a substantially cylindrical shape with a lid, the guide holes are slidably guided in the vertical straight line direction independently of each other. Disc-shaped guide plates 12, 12 as guide plates are fitted and fixed in circular grooves formed on the upper surfaces of the upper walls 9a, 9a. Further, as shown in FIG. 2, guide grooves 14, 14 for guiding a slider 13, which will be described later, in the camshaft axial direction are formed in parallel with the camshaft 1 on the upper surfaces of the guide plates 12, 12. That is, the guide grooves 14, 14 are formed with a constant width along the diameter direction of the guide plates 12, 12.

As shown in FIG. 2, the guide block 10 has a spark plug hole 10a formed in the outer center on the inner end side, and the guide holes 11 on both sides on the outer end side.
11 is formed. In addition, the guide grooves 14, 11 are formed in the upper end portions of the partition walls and the upper end portions of both side walls of the both guide holes 11, 11.
Sliding grooves 15, 15 and 15 that are connected to 14 are formed, and each sliding groove 15 is set to a depth larger than the vertical stroke amount of each valve lifter 9, 9.

The slider 13 has a flat plate shape as shown in FIGS. 1 and 2, and has rectangular main bodies 16 and 16 held in the guide grooves 14 and 14, and both ends of the main bodies 16 and 16. Long arm arms 17, 18 which are integrally provided and are held in the respective sliding grooves 15 are composed of long arm portions 17, 17 on one end side and short arm arms 18, 18 on the other end side, which are in contact with each other. It is separated from the end of and can be moved up and down independently of each other. A first follower portion 19 and a second follower portion 20 that appropriately abut on the outer peripheral surfaces 4a, 5a, 6a of the low speed cams 4, 5, 6 are provided on both sides of the upper surfaces of the main bodies 16, 16. They are integrally provided via a constant gap 21.

The first follower parts 19 and 19 are arranged with the same span as the low speed cams 4 and 4 corresponding to the intake valves 3 and 3, while the second follower parts 2 are arranged.
0 and 20 are arranged with the same span as the span between the high speed cams 5 and 5 on one side corresponding to the intake valves 3 and 3, and in the high rotation range, the second follower portions 20 and 20 are While contacting the high speed cams 5, 5 on the one side,
The spans are set so that the follower portions 19, 19 come into contact with the high speed cams 6, 6 on the other side. The slider 13 is slidably in contact with the upper surfaces of the guide plates 12 and 12 and is slidable in the camshaft axial direction by the switching means 22.

The switching means 22 is a guide block 10.
A pressing mechanism 23 provided on both sides of the spark plug hole 10a for pressing the slider 13 to the right in FIG. 2, and a return mechanism 24 that returns the slider 13 to the left in the drawing against the pressing mechanism 23. Is equipped with.

In the pressing mechanism 23, as shown in FIG. 2, a cylinder 27 is formed inside the base portion 26 fixed to one side portion of the guide block 10 by a screw 25 along the cam shaft axial direction. A piston 28 is slidably housed inside the cylinder 27. Further, a first lever 28 bent in a substantially V shape is rotatably provided on a top portion of the base portion 26 by a pivot pin 29. In this first lever 28, one end 28a is in contact with the front end surface of the piston 28, and the other end 28b is in the one side sliding groove 1
5 is arranged in contact with the tip of the long arm 17 on the one side protruding from the slider 5, and the slider 13 moves with the advancing movement of the piston 28.
The whole is pressed rightward in the figure. Further, the maximum rotation of the first lever 28 in the counterclockwise direction is restricted at the position where the outer surface of the one end 28a abuts the stopper pin 30.

Further, hydraulic pressure is supplied to and discharged from a pressure receiving chamber 27a provided at one end of the cylinder 27 through a hydraulic circuit. This hydraulic circuit is provided with a three-way electromagnetic switching valve 33 for switching between the hydraulic passage 31 and the drain passage 32 on the upstream side of the hydraulic passage 31 branched from the oil main gallery, and an oil pan 34 at the upstream end. An oil pump 36 for pumping the lubricating oil therein via a strainer 35 is provided. Further, the electromagnetic switching valve 33 is
Switching operation is performed by a control signal from a controller 37 with a built-in microcomputer.
The current engine operating state is detected based on information signals from sensors such as a crank angle sensor, an air flow meter, a throttle opening sensor, and a water temperature sensor (not shown).

The return mechanism 24 is rotatably provided on the other side of the guide block 10 with an elliptical base 39 fixed by a screw 38 and one end of the base 39 via a pin 41 so as to be rotatable. The portion 40a includes a second lever 40 that is bent into a substantially L shape. This second lever 4
0 indicates that the tip end portion 40a is disposed in contact with the tip end portion of the short arm 18 on the other side through the sliding groove 18, and
As also shown, the torsion spring 42 wound around the pin 41 pushes the short arm 18 on the other side, that is, the slider 13 to the left. The torsion spring 42 has one end 42a elastically contacting the outer surface of the base 39 and the other end 42b elastically contacting the outer surface of the second lever 40.

The operation of this embodiment will be described below.
First, since the OFF signal is output from the controller 37 to the electromagnetic switching valve 33 when the engine is running at low and medium speeds, the drain passage 32 is opened and the upstream and downstream communication of the hydraulic passage 31 is cut off. Therefore, the hydraulic oil in the pressure receiving chamber 27a is discharged from the drain passage 32 to be in a low pressure state. Therefore, as shown in FIG. 2, the second lever 40 presses the short arm 18 on the other side by the spring force of the torsion spring 42 to slide the slider 13 as a whole in the guide grooves 14, 14 to the left, and as shown in FIG. Hold in the position shown in FIG. Therefore, as shown in FIG. 3, the upper surfaces of the first follower portions 19 and 19 come into contact with the outer peripheral surfaces 4a and 4a of the low speed cams 4 and 4 to cam the valve lifters 9 and 9 together with the slider 13. By lifting according to the profile, the intake valves 3 and 3 also open and close according to the small valve lift characteristic shown by X in FIG.

As a result, the overlap with the exhaust valve becomes small, and the residual gas in the combustion chamber can be reduced, so that the combustion is improved and the fuel consumption is improved. Moreover, since the closing timing of the intake valves 3 and 3 can be brought close to the bottom dead center, the intake charging efficiency is improved and the torque can be increased.

On the other hand, at the time of high engine speed, the controller 3
An ON signal is output from 7 to the electromagnetic switching valve 33, and the hydraulic pressure is supplied into the pressure receiving chamber 27 a via the hydraulic passage 31. Therefore, as shown in FIG. 7, the piston 28 moves forward in the cylinder 27 and rotates the first lever 28 until it abuts on the stopper pin 30, and the other end 28b moves the long arm 17 on one side. Press. Therefore, the slider 13 slides to the right against the spring force of the torsion spring 42, which causes the first and second follower portions 19, 20, 19, 2 to slide.
The upper surface of 0 is the outer peripheral surface 5 of both high speed cams 5, 6, 5 and 6.
It contacts a, 6a, 5a, 6a. Therefore, the intake valves 3 and 3 are opened and closed according to the large valve lift characteristic shown by Y in FIG. As a result, the intake filling efficiency is improved,
High torque can be obtained.

Needless to say, the slider bodies 16 and 16 are interlocked by the relative pressing of the first lever 28 and the second lever 40.

As described above, in the present embodiment, the flat slider 13 is moved in the cam groove axial direction within the guide grooves 14 and 14 to switch the high and low speed cams 4, 5 and 6. It is not necessary to enlarge the upper structure of the valve lifters 9, 9 and can be made sufficiently small. Therefore, it is not necessary to displace the camshaft 1 largely upward, and the cylinder head can be downsized. Therefore, it becomes easy to apply this device to an engine that does not have the valve lifters 9 and 9. For example, in an internal combustion engine in which a cam drives an intake / exhaust valve via a rocker arm, the device described above can be applied to the surface where the cam abuts the rocker arm.

Further, by making the valve lifters 9 and 9 compact, it is possible to reduce the weight and sufficiently cope with high speed rotation.

Further, as the weight of the valve lifters 9, 9 is reduced, the spring force of the valve springs 8, 8 can be reduced, so that the friction between the high and low speed cams 4, 5, 6, and the slider 13 is increased. Also, the friction with the intake valves 3 and 3 can be reduced.

Further, the low speed cams 4, 4 are located at the centers of the valve lifters 9, 9 during the low and medium speed cam lifts, and the high speeds are symmetrically located with respect to the center of the valve lifters 9, 9 during the high speed cam lift. Since the loads of the working cams 5, 6, 5, 6 act, the valve lifters 9, 9 do not tilt toward the cam shaft side, and the outer peripheral surfaces of the valve lifters 9, 9 are the inner peripheral surfaces of the guide holes 11, 11. On the other hand, one-sided contact is prevented, and uneven wear and large friction are prevented from occurring. In addition, the slider 13 is prevented from freely rotating because the main bodies 16 and 16 are prevented from rotating by the long arms 17 and 17 protruding on one side.

Moreover, since the slider 13 can move in the axial direction of the camshaft by utilizing the valve clearance between the cam base circles between the follower portions 19 and 20 and the cams 4, 5 and 6, It is not necessary to have a high-precision machining accuracy such as a piston or a guide hole for connecting lifters as in the conventional case. Therefore, the processing cost can be reduced.

Further, the low speed cam 4 is provided at the center of the entire cam mountain.
Since the high-speed cams 5 and 6 are arranged on both sides thereof, the slider 13 can be switched to the high-speed cams 5 and 6 without moving a stroke corresponding to the width W of the central low-speed cam 4. . This case is effective when the width of the low speed cam 4 is set to be large, with emphasis placed on the wear resistance of the low speed cam 4 in the practical range. This is because, as shown in FIG. 4, the low speed cam 4 is generally included in the valve lift of the high speed cams 5 and 6, and thus the first outer surface 4a of the low speed cam 4 and the first outer cam surface 4a.
Even if the upper surface of the follower portion 19 is superposed, it does not interfere. As a result, the operation stroke amount of the slider 13 can be made as small as possible, and the slider 13 can be correspondingly reduced.
Can be made compact, and its operation response can be improved.

Further, since the guide plates 12, 12 are interposed between the upper surfaces of the valve lifters 9, 9 and the slider 13, the valve lifters 9, 9 themselves can freely rotate in the guide holes 11, 11. Therefore, local abrasion can be prevented from occurring. In addition, the valve lifters 9 and 9 include the slider 13 and the guide plates 12 and 12.
Since wear resistance is not required as compared with (1), it is possible to form it with a light material such as an aluminum alloy.

Furthermore, the valve clearance can be easily adjusted at a low cost by appropriately changing the wall thickness of the guide plates 12 having a relatively simple shape. Further, if the guide plates 12 and 12 are formed of bottom friction members, the slider 13 can be slid smoothly, thereby improving the switching response of the device.

Further, each arm 17, 1 of the slider 13 is
Sliding grooves 15,15 for guiding 7,18 vertically
15 is formed in the camshaft direction in which the side force by the cams 4, 5, 6 of the valve lifter 9, 9 does not act. Therefore, since the sliding grooves 15, 15, 15 are not located on the inner peripheral surface of the guide holes 11, 11 on which the side force acts, the side surfaces of the valve lifters 9, 9 and the guide holes 11, 1.
The contact area due to the side force with 1 does not decrease, and the contact surface pressure due to the side force on the valve lifters 9 and 9 does not increase. Therefore, it is possible to prevent wear between the side surfaces of the valve lifters 9 and 9 and the inner peripheral surfaces of the guide holes 11 and 11 and increase of friction when the valve lifters 9 and 9 slide.

Further, since the switching means 22 is provided outside the valve lifters 9 and 9, the valve lifters 9 and 9 can be made more compact.

Further, since the main bodies 16 and 16 of the slider 13 corresponding to the pair of intake valves 3 and 3 are interlocked with each other, the switching means 22 is not necessary for each valve lifter, but only one for each cylinder. .

FIG. 8 shows a second embodiment of the present invention, in which the outer end portions 14 of both guide grooves 14, 14 on the side of the first lever 28 are formed.
a and 14a are extended to the edge portion of the guide hole 11 of the guide block 10 to form a rectangular shape. As a result, the end portions 20a, 20a of the respective second follower portions 20, 20 are
Can be enlarged to form a rectangular shape as a whole.

As a result, the contact area between the second follower portions 20, 20 and the outer peripheral surfaces 5a, 5a of the one-sided high-speed cams 5, 5 is increased, and the wear resistance therebetween is improved.

9 to 11 show a third embodiment of the present invention, in which the guide plate is eliminated and the valve lifters 9 and
Guide groove 44 for guiding the slider 13 on the upper surface of 9,
44 is directly formed.

As a result, the height difference between the follower portions 19 and 20 and the guide grooves 44 and 44 can be increased, and at the same time,
Since the lift difference between the low speed cam 4 and the high speed cams 5 and 6 can be increased, the variable amount of the valve lift can be increased. The valve clearance can be adjusted freely by selecting the slider 13 whose thickness is appropriately changed. In addition, one end portion 44 of the guide groove 44
a and 44a are formed in a rectangular shape as in the second embodiment, and one end portion 19 of the second follower portions 19 and 19 is formed.
a and 19a are also formed in a rectangular shape.

The present invention is not limited to the configuration of the above-described embodiment, and for example, the high speed cams 5 and 6 inside each other may be eliminated and only one outside may be provided. As a result, the width of the journal 1a of the camshaft 1 can be widened, the contact area becomes large, the surface pressure becomes small, the abrasion of the cam bracket 2 can be prevented, and the supporting rigidity by the cam bracket 2 is improved.

It is also possible to use the central cam as a high speed cam and two low speed cams on both sides. In this case, if the cam profiles of both low speed cams are made different, the swirl in the cylinder will be different. The flow becomes high and combustion can be improved. Further, in this case, if a valve stop mechanism that stops one of the low speed cams when the engine is running at low speed is used, it is possible to increase the swirl flow in the cylinder by intake from only the other intake valve. In the case where the both sides are the high speed cams as described above, the same effect as described above can be obtained by making the cam profiles of the two different.

Further, in this way, when the central cam is used as the high speed cam and both sides thereof are used as the low speed cams, the head of the valve stem is passed from the outer peripheral surface of the high speed cam through the first follower portion during the high speed cam lift. Since the load is directly applied to the engine, the rigidity from the cam to the valve stem is increased and it is easy to speed up the engine.

Further, the present invention can be applied to an engine having a single intake valve or exhaust valve per cylinder, and the transmission member is constituted by a so-called zero-lash adjuster valve lifter utilizing hydraulic pressure. Is also possible.
Also, the first lever 28 of the switching means 22 can be rotated by an electromagnetic actuator.

[0054]

As is apparent from the above description, according to the present invention, it is of course possible to selectively transmit the lift of either the high speed cam or the low speed cam to the valve according to the engine operating condition. Since the flat slider is used, the upper structure of the transmission member can be made compact.

Therefore, the cylinder head is prevented from becoming large, and the degree of freedom of layout in the engine room is improved due to the size reduction of the entire engine. In addition, each of the slider
Since the main body is interlocked, the switching means is not required for each valve lifter, but only one switching means is required for each cylinder.

Further, due to the miniaturization of the transmission member, the inertial force becomes small, and it is possible to sufficiently cope with high speed rotation.
Furthermore, since the spring force of the valve spring can be reduced, the sliding frictional resistance between the valve and the cam can be reduced.

Moreover, since the load of each high-speed or low-speed cam acts on the transmission member in the vertical direction, the inclination of the transmission member is prevented, and uneven wear with the guide hole and large friction are prevented. it can.

Further, since the high-speed cam and the low-speed cam can be switched simply by moving the slider, high-precision machining is not required as compared with the conventional case, and the machining work efficiency can be improved and the cost can be reduced.

[Brief description of drawings]

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

FIG. 2 is a plan view of an essential part of this embodiment.

FIG. 3 is a sectional view showing a side portion of this embodiment.

FIG. 4 is a valve lift characteristic diagram of a high speed cam and a low speed cam of the present embodiment.

FIG. 5 is a cross-sectional view of a main part of a return mechanism used in this embodiment.

FIG. 6 is an explanatory diagram showing the operation of the present embodiment.

FIG. 7 is an explanatory diagram showing the operation of the present embodiment.

FIG. 8 is a plan view of an essential part showing a second embodiment of the present invention.

FIG. 9 is a sectional view taken along line BB of FIG. 10 showing a third embodiment of the present invention.

FIG. 10 is a plan view of an essential part of this embodiment.

FIG. 11 is a sectional view showing a side portion of the present embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cam shaft 3 ... Intake valve 4 ... Low speed cam 5, 6 ... High speed cam 9 ... Valve lifter (transmission member) 12 ... Guide plate 13 ... Slider 14 ... Guide groove 14a ... One end part 16, 16 ... Slider main body 19, 20 ... Follower portion 20a ... One end portion 22 ... Switching means

Claims (2)

(57) [Claims] 1. A camshaft rotatably driven by a crankshaft of an engine, a pair of high and low speed cams provided on the outer periphery of the camshaft for opening and operating valves provided in intake and exhaust ports, and formed on an engine upper wall. In a pair of guide holes that are slidably provided, and a transmission member that transmits the lift of each cam to the valve, between the transmission member and each cam, The pair of valves each have a follower portion on the upper surface that is in relative contact with the outer peripheral surface of each cam.
Corresponding to the above, a flat plate-shaped slider provided with a pair of main bodies is provided slidably in the axial direction of the camshaft, and the main bodies of the sliders are linked so as to be interlocked with each other so that one slider can be moved depending on the engine operating state. An internal combustion engine is provided, which is provided with a switching means for switching the contact position of each of the follower portions with respect to each outer peripheral surface of the high-speed cam by interlocking the slider body on the other side by sliding the main body. Valve device. 2. The pair of slider bodies are in contact with each other
The valve operating device for an internal combustion engine according to claim 1, wherein the valve operating device is formed separately from the end portion and is vertically movable independently of each other.