JPH07293216A - Valve system of internal combustion engine - Google Patents

Abstract

PURPOSE:To achieve high engine performance by providing an engine valve system with a valve lifting amount adjusting mechanism and a variable valve timing mechanism for achieving at least two kinds of valve timing by the same lifting amount in an uncomplicated but compact form. CONSTITUTION:A cam follower 33 actuated by being slid and brought into contact with a driving cam 41 driven, by following the rotation of an engine is relatively rotatably supported on an eccentric shaft 31 normally/reversely rotatably supported on an engine main body.

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 an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine used in an automobile or the like, in order to sufficiently exert the performance of the engine such as high-speed running performance and fuel consumption characteristics, the opening / closing valve timing and the valve timing are adjusted according to the engine operating condition, for example, the engine speed. A valve operating device capable of changing the lift amount (valve opening degree) is known from, for example, Japanese Utility Model Laid-Open No. 2-39505.

In the valve operating system disclosed in the above publication, a rocker arm is interposed between a drive cam driven by engine rotation and a driven cam that abuts an intake valve or an exhaust valve. Depending on the number, the lift amount of the intake valve or the exhaust valve and the opening / closing valve timing are adjusted.

[0004]

However, in the conventional valve train, since the displacement direction of the rocker arm support is only uniaxial, when the displacement position of the rocker arm support is determined, the valve lift curve is as shown in FIG. As shown in, it will be decided uniquely. In such a valve lift curve shown in FIG. 7, when the valve lift amount is changed to the maximum lift point a ′ side of the maximum valve lift curve, the valve opening start timing is advanced, but conversely the valve closing completion timing is delayed. Further, when the valve lift amount is changed to the minimum lift point b ′ side of the minimum valve lift curve, the valve opening start timing is delayed, but the valve closing completion timing is advanced, so that only one type of adjustment can be performed. Therefore,
Shift the valve opening start timing and the valve closing completion timing simultaneously in the same direction while keeping the valve lift amount constant,
It is difficult to deal with both cases of making it earlier or later.

The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to make both functions of a valve lift amount adjusting mechanism and a variable valve timing mechanism having a high degree of freedom, uncomplicated and compact. In view of the above, it is an object of the present invention to provide a valve train for an internal combustion engine that can obtain higher engine performance.

[0006]

In order to achieve the above-mentioned object, in a valve operating system for an engine of the present invention, a drive cam driven by an internal combustion engine and between the drive cam and the intake valve or the exhaust valve are provided. In a valve operating system of an internal combustion engine, which is provided with a cam follower that opens and closes the intake valve or the exhaust valve by the driving force of the drive cam, the cam follower is configured to rotate relative to an eccentric shaft axially supported by the engine body. It is characterized by being movably supported.

At this time, it is desirable that the eccentric shaft is axially supported by the engine body so as to be capable of normal rotation and reverse rotation. The cam follower includes a rocker arm rotatably supported by an eccentric shaft, and a driven cam rotatably supported by the engine body and rotationally driven by the rocker arm to open and close an intake valve or an exhaust valve. May be configured.

Further, it is desirable to interpose a roller on the sliding contact surface of the rocker arm which is in sliding contact with the drive cam. Further, the cam follower may include a second rocker arm that is driven by a driven cam and has one end supported by the hydrolash adjuster and the other end that abuts the intake valve or the exhaust valve. It is desirable to interpose a roller on the surface.

[0009]

The cam follower, which is slidably contacted with the drive cam driven by the rotation of the engine, is supported by the eccentric shaft rotatably supported by the engine body so as to be relatively rotatable.
By rotating the eccentric shaft, the cam follower swings, and the contact portion between the cam follower and the drive cam and the contact between the cam follower and the intake valve or the exhaust valve moves. As a result, the intake valve or the exhaust valve changes the valve lift amount, and at the same valve lift amount,
Two kinds of opening / closing valve timing modes are obtained, in which both the valve opening timing and the valve closing timing are advanced and the valve opening timing is both delayed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view of an intake valve side of a valve operating system for a double overhead cam four-valve engine to which an embodiment of the present invention is applied. The exhaust valve side is arranged so as to be line-symmetric with respect to the alternate long and short dash line 60, but since the configuration is substantially the same as the intake valve side, it is not shown here.

The valve operating device includes two intake valves (intake valves).
5, a swing arm (second rocker arm) 10, a swing cam (following cam) 20, a rocker arm 33, a drive cam 41, etc., and is located above the combustion chamber 8 of the engine. The cylinder head lower 2 and the cylinder head upper 3 It is arranged inside a cylinder head portion (engine body) 1 including the cam cap 4. Here, the swing arm (second rocker arm) 10, the swing cam (driven cam) 20, the rocker arm 33, etc. are connected to the drive cam 4
The cam follower is driven by 1 to open and close the intake valve 5.

Each intake valve 5 that connects or disconnects the intake passage 9 for intake of the mixed gas and the combustion chamber 8 is attached to the cylinder head lower 2 via a valve spring 6 and a retainer 7, and each intake valve 5 is connected. The swing arm 10 is in contact with each of the above at the swing arm tip portion 11. The base end of each swing arm 10 is
The hydro-lash adjuster (HLA) 15 is pivotally supported by a pivot portion 16, and the swing arms 10 and the cam portions 23 and 24 of the swing cam 20 are in sliding contact with approximately the center of each swing arm 10 to reduce frictional resistance during sliding. A roller 12 for reducing the pressure is interposed. Hydro Rush Adjuster (HLA) 1
5 is that when a gap is created between the swing arm 10 and the intake valve 5, or between the roller 12 and the swing cam 20,
The adjusting device operates so as to eliminate the gap, and prevents noise from being generated when the swing arm 10 is operated.

Left and right cam portions 23, which are in sliding contact with the rollers 12,
As shown in FIG. 2, 24 is integrally formed via a sliding contact portion 21, and the cam shafts 20a, 20a extending horizontally outward from the side surfaces of the cam portions 23, 24 are the cylinder head lower 2 The center point 22 is pivotally supported on the contact surface between the cylinder head upper 3 and the cylinder head upper 3. Each cam portion 23,
The sliding contact portion 21 provided between the 24 is in sliding contact with the rocker arm 33.

The rocker arm 33 has a base end portion 33a rotatably supported by the rocker shaft 30, and a tip end portion 33b is in sliding contact with the sliding contact portion 21 of the swing cam 20 as described above. At the center of the rocker arm 33,
A hole having a quadrangular shape in a top view is formed so as to penetrate therethrough, and the roller 35 that is in sliding contact with the drive cam 40 to reduce frictional resistance.
Is installed.

A disk-shaped eccentric portion (eccentric shaft) 31 is integrally formed on the rocker shaft 30 with its center point 34 deviated from the center point 32 of the center axis. The eccentric portion 31 of the rocker shaft 30 is fitted into a hole 33c formed in the base end portion 33a of the rocker arm 33, and both ends of the rocker shaft 30 are centered on the contact surface between the cylinder head upper 3 and the cam cap 4. The point 32 is pivotally supported about the center of rotation.

Due to the deviation between the center points 32 and 34,
When the rocker shaft 30 rotates, the center point 34 moves around the center point 32. Along with this, the rocker arm 33 that rotates about the center point 34 is
It swings according to the rotation of 0. Further, the swing cam 20 is attached to the rocker arm 33 on the rocker shaft 30.
A torsion coil spring 37 for constantly pressing against the side is mounted, and one end of the torsion coil spring 37 abuts on a stopper portion 38 provided on the cylinder head upper 3. The torsion coil spring 37 is provided on the drive cam 41 and the roller 35.
Also, when a gap is formed between and, it acts so as to eliminate the gap.

The drive cam 41 is used for the cylinder head upper 3
Is formed integrally with a cam shaft 40 which is axially supported on a contact surface between the cam cap 4 and the cam cap 4 about a center point 42 as a rotation center. It is rotatably connected via a chain (not shown) and a belt (not shown). As a result, the drive cam 41 rotates in synchronization with the rotation (crank angle) of the crankshaft, and the rocker arm 33 can be swung. And
The swing cam 20, which is operated via the rocker arm 33, simultaneously opens and closes the two intake valves 5 via the swing arm 10.

The swing cam 20 as described above is effective when a plurality of intake valves 5 are arranged side by side in one combustion chamber 8, and the drive cam 41 is provided for each intake valve.
Also, since it is not necessary to provide the swing cam 20, the number of parts is reduced, and the valve train can be made compact without complicating it. FIG. 3 shows the camshaft 4.
FIG. 3 is a schematic diagram showing how the rocker shaft 30, the rocker shaft 30, and the swing cam 20 are attached to the cylinder head portion (engine body) 1. As described above, the cam shaft 40 and the rocker shaft 30 are pivotally supported so that the respective center points 42 and 32 thereof coincide with the contact surface position between the cylinder head upper 3 and the cam cap 4, and the swing cam 20 has its center. Point 22 is cylinder head lower 2 and cylinder head upper 3
It is rotatably supported so as to coincide with the position of the contact surface with.

As described above, since the shaft supporting portion is provided on the contact surfaces of the cylinder head lower 2, the cylinder head upper 3 and the cam cap 4, the structure of the valve operating device is simple and the maintenance is easy. Become. Further, by arranging the cam shaft 40 and the rocker shaft 30 in parallel on the contact surface of the cylinder head upper 3, the engine height can be kept low so that the cylinder head lower 2 can be applied to various vehicle types. And bolts 62 and 61 for connecting the cylinder head upper 3 and the cylinder head upper 3 and the cam cap 4, respectively.
It can be easily arranged at a position where it does not interfere with the camshaft 40 and the like, and it is possible to obtain sufficient strength of the cylinder head portion that can withstand high speed rotation of the engine.

FIG. 4 is a three-dimensional exploded perspective view of the valve operating device described above. As a result, a rocker shaft 30 drive device, a valve lift adjusting mechanism and a variable valve timing mechanism of the valve operating device are shown. The operation of will be described in more detail. The rocker shaft 30 is rotationally driven by, for example, a drive motor 50 provided inside or outside the engine. One end of the rocker shaft 30 is connected to the shaft 53 through a pair of spur gears 54 and 55 having a predetermined reduction ratio, and the shaft 53 is connected through a pair of worm gears 51 and 52 having a predetermined high reduction ratio. Connected to the drive motor 50. The position of the rocker shaft 30 is detected by a position sensor 55 attached to the shaft 53, and an electronic control unit (not shown) that performs various controls is provided with the rocker shaft 30 at a predetermined position or When it is detected that the drive motor 50 has rotated to a predetermined angle, the operation of the drive motor 50 is stopped.

As described above, when the rocker shaft 30 rotates and the rocker arm 33 fitted with the eccentric portion 31 swings, the sliding contact position of the rocker arm 33 with the drive cam 41 and the swing cam 20 moves, and the drive cam. The operation start timing and the operation amount of the rocker arm 33 by 41 or the swing cam 20 by the rocker arm 33 change.
As a result, Hydro Rush Adjuster (HLA) 1
The opening / closing valve timing and the valve lift amount of the intake valve 5 operated via the swing arm 10 supported by the valve 5 are changed, and the intake timing and the intake amount of the mixed gas can be adjusted.

FIG. 5 shows the set positions of the eccentric portion 31 set in accordance with the rotation of the rocker shaft 30 at every 90 ° rotation angle.
It is the figure which showed (1)-(4), and has shown that the rocker shaft 30 can be normally rotated or reversely rotated in any setting position. Further, FIG. 6 shows the valve lift amount and opening / closing valve timing (crank angle) of the intake valve 5 that change according to the set positions (1) to (4) of the eccentric portion 31 shown in FIG.
It is a graph showing the relationship of.

The curves (1) to (4) shown in FIG. 6 are shown in FIG.
When the eccentric portion 31 of the rocker shaft 30 is in the set position (1) shown by the solid line in FIG. 5, the intake valve 5 starts to open. Then, the valve lift amount changes so as to draw the maximum valve lift curve (1) also shown by the solid line. Therefore, when the engine is rotating at a high speed such that the intake air becomes difficult to follow the movement of the intake valve 5, the set position of the eccentric part 31 is changed.
By achieving the maximum valve lift as (1), a sufficient intake amount can be realized.

On the other hand, when the eccentric portion 31 is at the set position (4) indicated by the alternate long and short dash line, the valve lift amount changes so as to draw the minimum valve lift curve (4) also indicated by the alternate long and short dash line. This minimum valve lift curve (4) has a smaller overall valve lift amount than the maximum valve lift curve (1), and at the same time has a short valve opening period. Therefore, when the intake can follow the movement of the intake valve 5 with a good response to some extent and the engine is rotating at a low speed, the setting position of the eccentric part 31 is set to (4),
It is possible to reduce the intake loss by reducing the overlap with the valve closing timing on the exhaust side.

Here, since the maximum lift point a indicated by the maximum valve lift curve (1) and the maximum lift point b indicated by the minimum valve lift curve (4) are reached at approximately the same time, While the valve opening start timing of the valve lift curve (4) is delayed compared to the maximum valve lift curve (1), the valve closing timing is set earlier than the maximum valve lift curve (1). The start timing side and the valve closing timing side are almost equal.

The eccentric portion 31 of the rocker shaft 30 has a setting position (2) indicated by a broken line or a setting position (3) indicated by a chain double-dashed line.
In the case of, the valve lift amount at the maximum lift point (point c or point d) is the same as in the intermediate valve lift curve (2) indicated by the broken line or the intermediate valve lift curve (3) indicated by the chain double-dashed line. However, there are two types of curves with different achievement times.

When the eccentric portion 31 is at the set position (2), the time when the maximum lift point c is reached is later than the time when the set position is reached (1) or (4) when the maximum lift points a and b are reached. ,
On the other hand, in the case of the set position (3), the time when the maximum lift point d is reached is earlier than the time when the maximum lift points a and b are reached. In this case, since the cam shape of the drive cam 41 does not change, the shapes of the curve (2) and the curve (3) and the valve opening period can be regarded as almost the same, and therefore the curve (2)
The difference between the maximum lift point c of the curve (3) and the maximum lift point d of the curve (3) becomes the valve opening start timing difference or the valve closing timing difference between the set positions (2) and (3).

Therefore, as shown in FIG. 7, the timing of achieving the maximum lift point c'is almost the same as the timing of the maximum lift point a'of the maximum valve lift curve or the maximum lift point b'of the minimum valve lift curve. Compared with the intermediate valve lift curve of the conventional valve operating system like this, in curve (2), the difference between the maximum lift points c and c'achievement time, the curve
In the case of (3), the opening / closing valve timing is shifted forward or backward by the difference between the achievement times of the maximum lift points d and c '.

As described above, in the intermediate valve lift state, the eccentric portion 31 of the rocker shaft 30 is set to the set position (2).
Alternatively, by setting to (3), the opening / closing valve timing of the intake valve 5 can be set to two types. For example,
In the medium speed range where the engine speed is relatively high, the eccentric part 3
By setting 1 to the set position (2) and slightly delaying the intake timing, the intake of the mixed gas is further executed even after the piston (not shown) reaches bottom dead center without increasing the overlap amount with the exhaust timing. However, the filling efficiency can be improved. On the other hand, in the medium speed range where the engine speed is relatively low and a high load is required, the eccentric part 31 is set to the set position (3) and the intake timing is slightly advanced to reduce the intake amount of the mixed gas, It is possible to reduce the backflow of the mixed gas into the intake passage 9 in the compression stroke and to realize sufficient compression of the mixed gas.

By the way, the eccentric portion 3 of the rocker shaft 30
1 has a rotation angle of 90 as shown in FIG.
Not only in the case of the setting positions (1) to (4) for each °, it can be freely set based on the parameters such as the engine speed.By monitoring the engine output etc. by the electronic control unit, the engine As described above, the intake side valve operating device has been mainly described so that it is possible to perform the optimum control adapted to the characteristics. However, since the exhaust side has the same configuration, the combustion gas exhaust amount and the exhaust timing are the same. Therefore, the description thereof is omitted here.

In the present embodiment, the swing cam 2
Although 0 is configured to be axially supported by the cylinder head portion 1, it is not limited to this, and it may be formed integrally with the rocker arm 33. Further, all constituent elements of the cam follower such as the swing arm 10, the swing cam 20 and the swing cam 20 may be combined to form an integrated cam follower having the same function, or the swing cam 20 may be formed integrally with the swing arm 10. You may do it.

[0032]

As described above, according to the present invention, the drive cam driven by the internal combustion engine, and the drive cam interposed between the drive cam and the intake valve or the exhaust valve, the intake force is generated by the drive force of the drive cam. In a valve operating system of an internal combustion engine having a cam follower for opening and closing a valve or an exhaust valve, the cam follower is supported so as to be rotatable relative to an eccentric shaft rotatably supported by the engine body. By rotating the cam follower, it is possible to displace the cam follower and the drive cam or the part where the cam follower and the intake valve or the exhaust valve come into contact with each other, whereby the valve lift amount adjusting mechanism and the degree of freedom can be increased. It is possible to obtain higher engine performance by combining both the functions of the high variable valve timing mechanism with a compact and uncomplicated one.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a cylinder head portion of an engine and a valve train according to the present invention.

FIG. 2 is a view showing an arrow A in FIG.

FIG. 3 is a diagram showing the axial support positions of a cam shaft, a rocker shaft, and a swing cam in a cylinder head portion of an engine.

FIG. 4 is an exploded perspective view showing the valve operating device of FIG. 1.

FIG. 5 is a diagram showing a setting position of an eccentric portion according to rotation of a rocker shaft.

FIG. 6 is a graph showing changes in the valve lift amount and the opening / closing valve timing depending on the set position of the eccentric portion of the rocker shaft.

FIG. 7 is a graph showing changes in valve lift amount and opening / closing valve timing of a conventional valve operating device.

[Explanation of symbols]

 1 Cylinder Head Part (Engine Body) 2 Cylinder Head Lower 3 Cylinder Head Upper 4 Cam Cap 5 Intake Valve (Intake Valve) 10 Swing Arm (Second Rocker Arm) 12 Roller 20 Swing Cam (Following Cam) 30 Rocker Shaft 31 Eccentric Part ( Eccentric shaft) 33 Rocker arm 35 Roller 40 Cam shaft 41 Drive cam 50 Drive motor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takaaki Hirano 1 Uzumasa-cho, Ukyo-ku, Kyoto City, Kyoto Prefecture Mitsubishi Motors Engineering Co., Ltd. Kyoto office (72) Inventor Hideaki Okamoto 1-Uzumasa-cho, Ukyo-ku, Kyoto City, Kyoto Mitsubishi Automotive Engineering Co., Ltd. Kyoto Office

Claims (10)

[Claims] 1. A drive cam driven by an internal combustion engine, and a cam follower which is interposed between the drive cam and an intake valve or an exhaust valve, and which opens and closes the intake valve or the exhaust valve by the driving force of the drive cam. In the valve operating system for an internal combustion engine, the cam follower is rotatably supported by an eccentric shaft rotatably supported by the engine body. 2. The cam follower is rotatably supported by a rocker arm, which is rotatably supported by the eccentric shaft, and rotatably supported by the engine body, and is rotatably driven by the rocker arm to drive the intake valve or the exhaust valve. 2. The valve operating system for an internal combustion engine according to claim 1, further comprising a driven cam for opening and closing the valve. 3. The valve operating system for an internal combustion engine according to claim 2, wherein a roller is provided on a sliding contact surface of the rocker arm that is in sliding contact with the drive cam. 4. The cam follower further comprises a second rocker arm that is driven by the driven cam, has one end supported by a hydrolash adjuster, and the other end abutting the intake valve or the exhaust valve. A valve operating system for an internal combustion engine according to claim 2 or 3. 5. The valve operating system for an internal combustion engine according to claim 4, wherein a roller is provided on a sliding contact surface of the second rocker arm that is in sliding contact with the driven cam. 6. The present invention is applied to an internal combustion engine having a plurality of intake valves or exhaust valves, and the driven cam is provided in each of the plurality of intake valves or exhaust valves and a sliding portion that makes sliding contact with the rocker arm. The valve operating system for an internal combustion engine according to claim 4 or 5, further comprising a plurality of cam portions that abut the second rocker arm. 7. The valve operating system for an internal combustion engine according to claim 6, wherein the sliding portion is arranged between the plurality of cam portions. 8. The valve operating system for an internal combustion engine according to claim 1, wherein the eccentric shaft is pivotally supported by the engine body so as to be capable of forward rotation and reverse rotation. 9. The valve operating system for an internal combustion engine according to claim 2, further comprising a spring member for urging the driven cam toward the rocker arm. 10. The engine body includes a cylinder head lower, a cylinder head upper mounted and fixed on an upper surface of the cylinder head lower, and a cam cap mounted and fixed on an upper surface of the cylinder head upper, The drive cam and the eccentric shaft are pivotally supported by the contact surface between the cylinder head upper and the cam cap, and the driven cam is pivotally supported by the contact surface between the cylinder head upper and the cylinder head lower. A valve operating system for an internal combustion engine according to claim 2.