JPH04143410A - Valve driver for internal combustion engine - Google Patents

Abstract

PURPOSE:To control the output torque of an internal combustion engine so effectively in keeping a throttle valve intact in a state of being opened by constituting a valve opening angle at the time of partial load driving so as to make it smaller than the said opening angle. CONSTITUTION:At the time of partial load driving of an internal combustion engine E, a worm gear shaft 31 is rotated by a servomotor 30, and a camshaft support member 22 rocks via a worm gear 311 and a sector gear 191. Accordingly, two cams 29a, 29b come into contact with each tip side of slipper arms 16a, 16b of rocker arms 13a, 13b. In this state, each rocking angle of these rocker arms 13a, 13b decreases and each valve lift of an inlet valve 7a and an exhaust valve 7b become lessened. Thus, a variable range of valve timing is increased, through which a yet more improvement in volumetric efficiency is thus promoted.

Description

Detailed Description of the Invention A9 Object of the Invention (1) Industrial Application Field The present invention provides a method for swinging a camshaft support member that supports a camshaft about a swing axis in accordance with the operating state of an internal combustion engine. The present invention relates to a valve drive device for an internal combustion engine in which the valve timing and valve lift of a valve driven by the rocker arm are made variable by changing the position at which the cam provided on the camshaft contacts the rocker arm.

(2) Prior Art Such a valve drive device for internal combustion engines has already been proposed by the present applicant in Japanese Patent Application No. 2-137889. According to the above valve drive device for an internal combustion engine, by advancing the valve timing during partial load operation, the intake valve can be closed before the piston reaches bottom dead center during the intake stroke to control the intake amount of fresh air. can. As a result, it is possible to control the output torque of the internal combustion engine while keeping the throttle valve open during partial load operation, and the flow resistance of fresh air passing through the throttle valve during the intake stroke is reduced. Gross decreases.

(3) Problems to be Solved by the Invention By the way, in the conventional valve driving device described above, the closing timing of the intake valve is advanced by advancing the valve timing mainly during partial load operation. In order to control over a wider range, it is desirable to increase the range of change in the opening angle of the valve during full load operation and during partial load operation.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to further improve the conventional valve control device described above, increase the variable range of valve timing, and further improve volumetric efficiency.

B0 Structure of the Invention (1) Means for Solving the Problems In order to achieve the above-mentioned object, the present invention provides a structure in which a camshaft support member that supports a camshaft is swung around an axis in accordance with the operating state of an internal combustion engine. In a valve drive device for an internal combustion engine in which the valve timing and valve lift of a valve driven by the rocker arm are varied by swinging and changing the position where the cam provided on the camshaft abuts the rocker arm, partial load can be achieved. The opening angle of the valve during operation is
The first feature is that the opening angle is smaller than the opening angle during full load operation.

In addition to the first feature described above, the present invention also provides a method for changing the substantial clearance between the cam and the rocker arm along the rocker arm, such that the clearance during partial load operation is greater than the clearance during full load operation. The second feature is that it is configured so that

Furthermore, in addition to the above-mentioned second feature, the present invention has a third feature of including a member that absorbs the clearance between the cam and the rocker arm.

(2) Operation According to the first feature of the present invention described above, when the camshaft support member that supports the camshaft is swung around the oscillation axis, the cam provided on the camshaft comes into contact with the rocker arm. Since the contact position moves, the valve timing and valve lift of the valve driven by the rocker arm change. At this time, the opening angle of the valve is reduced during partial load operation of the internal combustion engine, so the intake valve closes. It becomes possible to control the timing over a wide range. Therefore, by controlling the intake amount of fresh air by closing the intake valve earlier than the bottom dead center, the output torque of the internal combustion engine is controlled with the throttle valve open, and the flow path of the throttle valve is controlled. Resistance by Pombingroska Castle can be reduced.

According to the second feature of the present invention, when the camshaft support member is rocked, the substantial clearance between the cam provided on the camshaft and the rocker arm changes, so that the clearance increases during partial load operation. With this setting, the play of the rocker arm increases and the opening angle of the valve can be reduced. As a result, the minute lift region of the valve during partial load operation is reduced, reducing throttling loss at the valve seat, and the time area of valve overlap during partial load operation is reduced, reducing the amount of harmful components in the exhaust gas. decreases.

Furthermore, according to the third feature of the present invention, the clearance between the cam and the rocker arm is absorbed, thereby preventing the rocker arm from swinging.

(3) Examples Hereinafter, the present invention will be explained in detail based on the drawings.

Figures 1 to 7 show one embodiment of the present invention.
The figure is a vertical cross-sectional view of an internal combustion engine equipped with the valve drive device.
The figure is a sectional view taken along the line ■-■ in Figure 1, and Figure 3 is a cross-sectional view taken along the line ■-■ in Figure 1.
FIG. 4 is a large cross-sectional view taken along line IV--IV in FIG. 1; FIG. 5 and FIG. 6 are explanatory diagrams of the operation; and FIG. 7 is a graph showing valve characteristics.

As shown in FIGS. 1 and 2, a double-over-rad camshaft type four-stroke internal combustion engine E has a cylinder head 3 connected to the top of a cylinder block 2 on which a piston 1 slides, and a cylinder head 3 connected to the top of the cylinder block 2. Hend cover to be used
4.

A combustion chamber 5 is formed in the cylinder head 3 so as to face the top surface of the piston l, and a pair of intake ports 6a and an exhaust port 6b opening into the combustion chamber 5 each have an intake valve 7.
a and exhaust valve 7b are installed. Intake valve 7a and exhaust valve 7b
is slidably supported by the valve guides 8a and 8b, and its umbrella portion is the valve seat 9a.

9b, upper and lower retainers 10a.

10b; Valve springs 12a and 1 contracted between lla and llb
It is urged upward by 2b. And both the valves 7a, 7b
The upper end of the shaft portion is driven by contacting the intake side rocker arm 13a and the exhaust side rocker arm 13b.

As is clear from FIG. 3 and FIG. 4, the intake side rocker arm 13a is swingable around an intake side rocker arm shaft 15a, which is an eccentric shaft installed on a pair of brackets 14a provided on the cylinder rod 3. Supported by

The intake-side rocker arm 13a includes a slipper arm 16a and a sub-rocker arm 17, each having boss portions 16a+ and 17a fitted to the outer periphery of the intake-side rocker arm shaft 15a.
A spring 18a, which is weaker than the valve spring 12a, is compressed between the lower surface of the slipper arm 16a and the upper surface of the sub-rocker arm 17a. This spring 18a not only buffers the driving force received from a cam 29a (described later) and transmits it to the intake valve 7a, but also acts as a buffer for the slipper arm 1.
By constantly bringing the slipper arm 6a into contact with the cam 29a, it is possible to prevent the slipper arm 16a from swinging, thereby preventing the occurrence of tappet noise.

As is clear from FIG. 6, the upper surface of the slipper arm 16a is formed with a slipper surface 16a2 that the cam 29a contacts, and the lower surface of the slipper surface 16a2 is formed with a sub-rocker arm 17a.
An upper stopper member 16a is provided that can come into contact with a lower stopper member 17a2 provided on the upper surface. Both stopper members 16a, 1? 'at' is used to restrict the moving end of the slipper arm 16a when it is pressed by the cam 29a and descends towards the sub-rocker arm 17a while compressing the spring 18a. Made of high quality synthetic resin or hard rubber. When the slipper surface 16a2 is at the solid line position in contact with the base circle of the cam 29a, the center of the arc constituting the slipper surface 16at is located at the camshaft support member 2, which will be described later.
It is formed to coincide with the swing axis 0 of No. 2. Therefore,
When the slipper arm 16a is lowered to the position indicated by the chain line and the stopper member 16a is in contact with the stopper member 17a2 of the sub-rocker arm 17a, the slipper surface 1
6a2 is located on a circular arc centered on 0', which is off from the pivot axis 0.

Note that the structure of the exhaust valve 7b and the exhaust side rocker arm 13b is the same as that of the intake valve 7a and the intake side rocker arm 13 described above.
Since the structure is the same as that of a, redundant explanation will be omitted by assigning the same reference numerals with suffixes.

As shown in FIGS. 1 and 2, a pair of fan-shaped side plates 1
A camshaft support member 22 formed by interconnecting 9.20 with two connecting members 21 is swingably attached to a pair of bosses 23 and 24 provided on the cylinder head 3 concentrically with the swing axis O. Supported. An intake side camshaft 25a and an exhaust side camshaft 25b are rotatably installed between the pair of side plates 19 and 20 of the camshaft support member 22, and are supported by the pair of bosses 23 via pawl bearings 26 to support the crankshaft. An idler gear 27 that rotates in conjunction with this meshes with an intake cam gear 28a provided on the intake camshaft 25a and an exhaust cam gear 28b provided on the exhaust camshaft 25b. Then, the intake cam 29a provided on the intake camshaft 25a comes into contact with the slipper arm 16a of the intake rocker arm 13a, and the exhaust cam 29a provided on the exhaust camshaft 25a comes into contact with the slipper arm 16a of the intake rocker arm 13a.
b is the slipper arm 1 of the exhaust side rocker arm 13b.
6b. As is clear from FIG. 1, both camshafts 25a, 25b are
camshafts 25a, 25b are both driven counterclockwise via idler gear 27 and cam gears 28a, 28b.

A worm gear shaft 31 that is connected to a servo motor 30 and rotates is provided at the top of the head cover 4, and the worm gear 31 formed on the outer periphery of the worm gear shaft 31 is connected to the sector gear 19 formed on one side plate 19 of the camshaft support member 22.
meshes with 1. Thereby, when the servo motor 30 is driven to rotate the worm gear shaft 31, the camshaft support member 22 supporting the two camshafts 25a and 25b can be swung around the bosses 23 and 24.

Next, the operation of the embodiment of the present invention having the above-described configuration will be explained.

The rotation of the idler gear 27, which is interlocked with the crankshaft as the internal combustion engine E operates, is controlled by a pair of cam gears 28a, 28.
camshaft 25a via b.

25b, and drives the camshafts 25a, 25b at 1/2 the rotational speed of the crankshaft. Cams 29a, 2 rotating together with camshafts 25a, 25b
The rocker arms 13a, 13b in contact with the rocker arms 13a, 13b swing around the rocker arm shafts 15a, 15b, and the intake valve 7a and the exhaust valve 7 pressed by the rocker arms 13a, 13b
The valve b opens once every two revolutions of the crankshaft.

At this time, both the intake side cam 29a and the exhaust side cam 29b rotate counterclockwise in FIG.
As a result, the opening period of the exhaust valve 7b occurs first, followed by the opening period of the intake valve 7a.Then, the opening period of the exhaust valve 7b and the opening period of the intake valve 7a occur. overlap slightly, and a valve overlap period between the exhaust valve 7b and the intake valve 7a is formed there.

Now, during partial load operation of the internal combustion engine E, the servo motor 3
0 causes the worm gear shaft 31 to rotate, and the worm gear 31. Then, the camshaft support member 22 swings to the position shown in FIG. 5(a) via the sector gear 191. As a result, both cams 29a and 29b are connected to the rocker arm 13a.
, 13b, and in this state, the lever ratio from the rocker arm shafts 15a, 15b to the point of contact between the cams 29a, 29b and the slipper arms 16a, 16b becomes large, so that the rocker arms 13a, 13b As a result, the valve lifts of both the intake valve 7a and the exhaust valve 7b become smaller as shown in FIG.

During full load operation of the internal combustion engine E, the camshaft support member 2
2 swings clockwise to the position shown in Fig. 5(b), and both cams 2
9a and 29b abut on the base end sides of the slipper arms 16a and 16b of the rocker arms 13a and 13b. In this state, the cams 29a, 2 are connected to the rocker arm shafts 15a, 15b.
Since the lever ratio up to the contact point between the rocker arm 9b and the slipper arms 16a and 16b becomes smaller, the rocker arm 13a1
As the swing angle of valve 3b increases, the valve lifts of intake valve 7a and exhaust valve 7b both increase as shown in FIG. 7, and the time area of valve over-ramp also increases compared to during partial load operation. At the same time, due to the clockwise rocking of the camshaft support member 22, the intake cam gear 29a and the exhaust cam gear 29b, which mesh with the idler gear 27, rotate slightly clockwise, that is, in the opposite direction to the rotational direction of the camshafts 25a and 25b. Therefore, the phase angle between the intake cam 29a and the exhaust cam 29b moves to the lag side, causing a delay in valve timing. In other words, during full load operation, the valve lift increases and the valve timing is delayed compared to during partial load operation.

By controlling the closed position of the intake valve 7a in a range past the bottom dead center during full-load operation, it is possible not only to maximize the intake inertia effect and improve volumetric efficiency. By controlling the closing position of the exhaust valve 7b, the time area of the valve overlap can be changed and the pulsation effect of the exhaust system can be effectively utilized, thereby increasing the output and torque of the internal combustion engine E. Flattening can be achieved at the same time.

Furthermore, during partial load operation, the reduction in valve lift makes it possible to reduce mechanical noise associated with valve drive, and also to reduce friction associated with valve drive.

Furthermore, as the valve lift decreases, the time area of valve overlap decreases, which not only reduces the amount of fresh air passing through and makes the exhaust cleaner, but also reduces the amount of exhaust pressure that flows into the intake system. This reduces intake noise.

Now, in the present invention, during partial load operation, the intake valve 7a
Since the opening angle of the exhaust valve 7b is automatically reduced, further effects can be achieved in addition to the above-mentioned effects. That is, both the cams 29a and 29b move the slipper surfaces 16az,
Although it is in constant contact with 16bz, the slipper arm 16a
, 16b are pushed down by the cams 29a, 29b, and the stopper members 16aa, 16b:+ is the sub-rocker arm 1.
The driving force of the cams 29a, 29b is not transmitted to the intake valve 7a and the exhaust valve 7b, and both valves 7a, 7b are held in the closed position until they come into contact with the stopper members 17az, 17b2 of the cams 7a, 1'7b. It will remain. The stopper members 16as and 16bs of the slipper arms 16a and 16b are the stopper members 17az of the sub-rocker arms 17a and 17b.
, 17b2, both valves 7a, 7b are pushed down and separated from the valve seats 9a, 9b. And slipper arms 16a, 16b and sub rocker arm 17a,
Slipper surface 16az until the moment when 17b is integrated,
The air movement distance of cam 29a is as shown in FIG.
, 29b is relatively small during full load operation when the cams 29a, 29b abut against the proximal ends of the slipper arms 16a, 16b;
δ becomes relatively large during partial load operation when it comes into contact with the tip side of b. As a result, as shown in FIG. 7, the zero lift line LH1 during full load operation, that is, both valves 7a
, 7b are set at a normal position close to the horizontal axis, whereas the zero lift line LL during partial load operation is largely deviated upward from the horizontal axis. As a result, during partial load operation, both valves 7a, 7b
The opening angles (Aa and Ab) of the intake valve 7a are significantly reduced, and together with the above-mentioned change in valve timing, the effective closing timing 1c of the intake valve 7a is significantly moved to a position just before the bottom dead center. This makes it possible to control the intake amount of fresh air with the throttle valve open and control the output torque of the internal combustion engine E, reducing pumping loss due to a decrease in flow path resistance of the throttle valve. . Furthermore, the minute valve lift region during partial load operation is reduced, which not only makes it possible to reduce intake and exhaust throttling resistance at the valve seats 9a and 9b, but also eliminates most of the valve overlap period and reduces the exhaust gas flow. It becomes possible to more effectively reduce harmful components inside.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various small design changes may be made without departing from the scope of the present invention as set forth in the claims. It is possible to do so.

For example, instead of interposing the springs 18a, 18b between the slipper arms 16a, 16b and the sub-rocker arms 17a, 17b, a material with a high self-damping function may be embedded in the tappet portion, or a hydraulic tappet having a hydraulic damper effect may be used. .

C9 Effects of the Invention As described above, according to the first feature of the present invention, the opening angle of the valve becomes small during partial load operation of the internal combustion engine, so the closing timing of the intake valve can be adjusted even under various layout constraints. It becomes possible to perform control over a wide range. As a result, it is possible to control the intake valve closing timing before bottom dead center to control the intake amount of fresh air, and to effectively control the output torque of the internal combustion engine with the throttle valve open.

Furthermore, according to the second feature of the present invention, not only the slight lift region of the valve is reduced during partial load operation to reduce throttling loss at the valve seat, but also pulp overlap during partial load operation is reduced. Since the time area becomes smaller, the amount of fresh air passing through is reduced and the amount of harmful components in the exhaust gas is reduced.

Furthermore, according to the third feature of the present invention, the clearance between the cam and the rocker arm is absorbed, thereby preventing the rocker arm from swinging and reducing pulp noise.

[Brief explanation of the drawing]

Figures 1 to 7 show one embodiment of the present invention.
The figure is a vertical cross-sectional view of an internal combustion engine equipped with the valve drive device.
The figure is a sectional view taken along the line ■-■ in Figure 1, and Figure 3 is a cross-sectional view taken along the line ■-■ in Figure 1.
Figure 4 is an enlarged section taken along the line IV-IV in Figure 1.
The top view, FIGS. 5 and 6 are explanatory diagrams of the action, and FIG. 7 is a graph showing the valve characteristics. 7a, 7b...Valve, 13a, 13b...Rocker arm, 18a, 18b...Spring, 22...Camshaft support member, 25a, 25...Camshaft,
29a, 29b-cam, E... internal combustion engine

Claims (1)

[Scope of Claims] [1] The camshaft support member (22) that supports the camshafts (25a, 25b) is oscillated about the oscillation axis according to the operating state of the internal combustion engine (E), and the camshaft shaft(
By changing the position where the cams (29a, 29b) provided on the rocker arms (13a, 13b) contact the rocker arms (13a, 13b), the valve timing of the valves (7a, 7b) driven by the rocker arms (13a, 13b) can be adjusted. In a valve drive system for an internal combustion engine with variable valve lift,
A valve drive device for an internal combustion engine, characterized in that the opening angle of the valves (7a, 7b) during partial load operation is smaller than the opening angle during full load operation. [2] The cams (29a, 29b) and the rocker arm (1
3a, 13b) is varied along the rocker arms (13a, 13b) so that the clearance during partial load operation is larger than the clearance during full load operation. The valve drive device for an internal combustion engine according to claim 1. [3] The cams (29a, 29b) and the rocker arm (1
A member (18) that absorbs the clearance between
Claim [2] characterized by comprising: a, 18b)
The valve drive device for the internal combustion engine described above.