JPH0213125B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake/exhaust valve lift control device for an internal combustion engine. The present invention relates to an exhaust valve lift control device.

(Prior Art) This type of conventional intake/exhaust valve drive is known, for example, as shown in FIGS.

As shown in Figs. 10 and 11, this device drives the intake and exhaust valves by a three-dimensional cam 1, and the three-dimensional cam 1 can be displaced in two directions of the camshaft depending on the operating conditions. The lift amount of the intake and exhaust valves is variable. In addition, 3 is a cap fitted to the valve shaft head, 4 is a sliding block having a protrusion 4A on the lower surface, and 5 is a seating groove that holds the protrusion 4A rotatably around an axis orthogonal to the camshaft 2. The rotation of the cam 1 causes the intake and exhaust valves to reciprocate through the block 4, the saddle 5, and the cap 3.

FIG. 12 shows the change in the variable lift characteristics caused by this device. In the figure, the solid line shows the actual lift characteristic, and the broken line shows it according to the profile of the three-dimensional cam 1.

(Problems to be Solved by the Invention) However, with such conventional devices, it is impossible to arbitrarily change the opening/closing timing of the intake and exhaust valves (see Figure 12). However, the problem has been that it is not possible to sufficiently increase the intake air filling efficiency at low loads or to improve the thermal efficiency at low loads.

(Means for Solving the Problems) The present invention provides an intake/exhaust valve drive cam disposed above the valve shaft head of the intake/exhaust valve, and is swung by the intake/exhaust valve drive cam. The upper surface of the control arm, which is freely swingable with one end in contact with the valve stem head and the other end in contact with the lift control cam, is brought into contact with the lower surface of the swing lever, and at least In an intake/exhaust valve lift control device for an internal combustion engine, the lift control cam is configured to have either one curved along its longitudinal direction so that the contact position can be longitudinally displaced depending on the operating conditions of the engine. is composed of a cylindrical portion that engages with a fork portion protruding from the lower surface of the other end of the control arm, and a pair of cam portions that are provided across the cylindrical portion and abut against the lower surface of the other end of the control arm. In addition, the fork portion is located approximately on the longitudinal center line of the control arm.
This is a section set up.

(Function) With the above configuration, the intake/exhaust valve drive cam rotates to swing the swing lever, and along with this swing, the control arm swings to drive the intake/exhaust valves to open and close.
In this case, by displacing the contact position between the control arm and the lever in the longitudinal direction according to the operating conditions of the engine, the lift amount of the intake/exhaust valves is changed, and the opening/closing timing thereof is also changed. Moreover, the control arm can be formed compactly without increasing the width of the control arm, and the weight of the control arm, which is a moving part, can be reduced, and inertia force can be reduced. Therefore, reliable operation is possible up to a higher rotation range.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

1 to 6 show an embodiment of the present invention.

First, the configuration will be explained. Note that this embodiment is an example of application to an intake valve. In FIG. 1, reference numeral 11 indicates an intake valve, which opens and closes an intake port 13 formed in the cylinder head 12. 14 is a valve spring, which is fixed to the valve shaft head 11A or attached to the retainer 15.
and the cylinder head 12.
The intake valve drive cam 16 is connected to the valve shaft head 1 of the intake valve 11.
It is arranged above 1A and is rotationally driven in synchronization with the engine output shaft. Note that 18 is a bracket that rotatably supports the camshaft 19.

Here, a lift control cam 20 consisting of a multifaceted cam is disposed on the side of the valve shaft head 11A of the intake valve 11 (left side in FIG. 1). Further, this lift control cam 20 is arranged below the drive cam 16. The mechanism for transmitting the rotation of the drive cam 16 to the intake valve 11 is composed of a swing lever 21 located above and a control arm 22 located below, which have their backs in contact with each other. When the swing lever 21 swings, the control arm 22 reciprocates the intake valve 11 in conjunction with the swing.

That is, the swing lever 21 has one end (the right end in the figure)
is fitted and supported by the hydraulic pivot 23, and the drive cam 16 comes into contact with the tip 24 on the upper surface of the other end. The lower surface 21A of the swinging lever 21 is curved downwardly at a predetermined curvature with respect to the longitudinal direction within the plane of illustration. On the other hand, an upper surface 22A of the swing arm 22 that contacts the curved lower surface 21A is formed substantially flat in the longitudinal direction. Note that the hydraulic pivot 23 serves as a swinging fulcrum for the swinging lever 21, and the above-mentioned both sides 21
The contact positions of A and 22A are displaced in the longitudinal direction with the rocking. The control arm 22 has one end in contact with the valve stem head 11A below the pivot 23, and the other end in contact with the lift control cam 20. That is, the control arm 22 is swingably provided with the other end abutting part with the lift control cam 20 as a fulcrum, and the point of contact with the swing lever 21 is the point of force, and the point of contact with the swing lever 21 is the point of contact with the valve shaft head 11A.
The contact position with the contact point constitutes the point of action. Note that the swing lever 21 and the control arm 22 are locked by a coil spring 24 to prevent separation during swing.

The lift control cam 20 displaces the contact position with the lever 21 in the longitudinal direction by changing the inclination of the control arm 22 in the illustrated plane.

Here, as shown in FIG. 3, the lift control cam 20 includes a cylindrical portion 20A that engages with a fork portion 22B protruding from the lower surface of the other end of the control arm 22;
The control arm 2 is provided across the cylindrical portion 20A.
A pair of cam portions 20B, 2 that come into contact with the lower surface of the other end of 2
0B, and is inserted into the cam control shaft 30. Further, the fork portion 22B is provided at one location substantially on the center line of the control arm 22 in the longitudinal direction (direction perpendicular to the axis of the cam 16). Cam control axis 3
0 and lift control cam 20 are coil springs 3
1, and when the cam control shaft 30 rotates by a predetermined angle, the lift control cam 20 also rotates via the coil spring 31, and the cam surface that contacts the arm 22 is changed. The cam control shaft 30 is connected, for example, to a rotating shaft 32A of a stepping motor 32 via a joint, and when the stepping motor 32 is driven in response to a signal from a control unit 33, the cam control shaft 30 rotates. be done. The control unit 33 outputs an appropriate drive signal to the stepping motor 32 based on, for example, an engine rotational speed signal, a load signal, etc. (that is, depending on the operating conditions of the engine). In addition, in Figure 3, 34
is a concave support part, for example, a part of the cylinder head 12, which rotatably supports the lift control cam 20.

FIG. 2 also shows the hydraulic pivot 23. As shown in FIG. As shown in the figure, the hydraulic pivot 23 is fitted into and fixed to a part of the support bracket 18 of the camshaft 19, and is attached to the concave portion 21B at one end of the swing lever 21.
The lower end of the case 41 has a spherical portion 40 that fits into the case 41. A fixed cylindrical member 42 is provided in the case 41 to support the case 41 so as to be movable up and down, and pressure oil introduced through the oil passage 43 and the internal space of the cylindrical member 42 passes through the check valve 44 and is transferred to the case 41.
The oil chamber 45 inside is filled. In addition, the oil chamber 45
A spring 46 is compressed to urge the case 41 downward. Therefore, when the hydraulic pivot 23 is urged upward in the figure by one end of the swinging lever 21, the swinging lever 21 is moved to a predetermined position by the spring force and the oil pressure in the oil chamber 45 sealed in the check valve 44. Hold the fulcrum.

Next, the operation of this embodiment will be explained with reference to FIGS. 4 to 7.

FIG. 4 shows a case where, for example, the lift amount of the intake valve 11 is increased under high load and high rotation, thereby increasing the intake air filling efficiency and obtaining high output.

In this case, the control unit 33 determines the operating conditions based on signals such as engine speed and throttle valve opening and drives the stepping motor 32. As a result, the cam control shaft 30 rotates by a predetermined angle, and the maximum cam surface of the lift control cam 20 pushes the other end of the control arm 22 upward in the figure. Furthermore, at this time,
In order to transmit the rotation of the cam control shaft 30 to the lift control cam 20, the rotation force is temporarily stored in the coil spring 31, and the load of the valve spring 14 is not applied to the lift control cam 20 via the control arm 22. lift control cam 2 while valve 11 is closed.
0 rotates. In the state shown in Figure 4, the intake valve drive cam 1
6 rotates, the swing lever 21 swings, causing the control arm 22 to swing about the point of contact with the lift control cam 20 as a fulcrum, thereby driving the intake valve 11 to open and close. Curve X in FIG. 7 shows the lift characteristic at this time. In this case, the point of force of the control arm 22, that is, the point of contact with the swing lever 21, has shifted to the lift control cam 20 side as the lever 21 is raised.

5 and 6 show the operation of the engine at low load and low rotation speed. In this case, it is possible to improve combustion by reducing the overlap between the intake and exhaust valves, and by closing the intake valve 11 or opening the exhaust valve closer to the bottom dead center (BDC), thereby increasing the thermal efficiency of the engine. With the goal.

That is, the control unit 33 determines the state of this engine and controls the stepping motor 32.
The control arm 22 is supported by the minimum cam surface of the lift control cam 20. Therefore, the control arm 22
As shown in FIGS. 5 and 6, the inclination is maintained, and the contact position between the swing lever 21 and the control arm 22 shifts to the right in the drawings (toward the intake valve 11 side). As a result, when the drive cam 16 pushes down the swing lever 21 at its maximum lift surface (Fig. 6), the force point of the control arm 22 approaches the point of action, so the lift amount is equal to the curve Y in Fig. 7. As shown in
Moreover, the valve opening timing is delayed and the valve closing timing is advanced. Furthermore, due to the rotation of the drive cam 16, the swing lever 21
The thrust force acting on the tip 24 (in the left-right direction in FIG. 1) acts on the pivot 23. The direction of the force acting on the control arm 22 changes depending on the lift amount of the intake valve 11 and the swing angle of the control arm 22. direction component) acts on the cylindrical portion 20A of the lift control cam 20 via the fork portion 22B of the control arm 22.
is the direction perpendicular to the cam 16 axis direction (left and right direction in Figure 1)
This prevents the control arm 22 from shifting and also prevents the control arm 22 from coming off the lift control cam 20. Then, the fork portion 22B of the control arm 22 is positioned approximately on the longitudinal center line of the control arm.
Since the control arm 22 can be made compact without increasing the width of the control arm 22, it is possible to reduce the weight of the control arm 22, which is the moving part, and reduce the inertia, so it can be used even in a higher rotation range. Reliable driving becomes possible.

As described above, according to this embodiment, the opening and closing timing of the intake valve (or exhaust valve) can be suitably controlled variably according to the operating conditions of the engine, and the control arm can be formed compactly without increasing the width of the control arm. do,
The weight of the control arm, which is a moving part, can be reduced, and the inertia force can be reduced. As a result, reliable operation is possible up to a higher rotation range.

As shown in FIGS. 1 and 3, the swing lever 21 and the control arm 22, and the control arm 22 and the lift control cam 20, each have a part engaged with the groove of the other, so that the camshaft No deviations in direction occur during operation.

In each of the above embodiments, only the lower surface of the swing lever is curved, but in the present invention, the upper surface of the control arm or both may be curved.

(Effects) As explained above, according to the present invention,
An intake/exhaust valve driving cam is disposed above the valve shaft head of the intake/exhaust valve, and the lift control cam is provided with a cylindrical part that engages with a fork part protruding from the lower surface of the other end of the control arm, and the cylindrical part. and a pair of cam parts which are provided on both sides of the control arm and come into contact with the lower surface of the other end of the control arm.The fork part is provided at one location approximately on the longitudinal center line of the control arm, so that the intake/exhaust valve As a result, not only the lift amount but also the opening/closing timing can be arbitrarily varied, resulting in opening/closing timing suitable for the engine operating conditions, increasing the width of the control arm while improving intake air filling efficiency and engine thermal efficiency. The control arm can be formed compactly without any problems, and the weight of the control arm, which is a moving part, can be reduced, and the inertia force can be reduced. As a result,
Reliable operation is possible up to a higher rotation range.

[Brief explanation of drawings]

Figures 1 to 7 show one embodiment of the present invention, with Figure 1 being a cross-sectional view showing the whole, Figure 2 being a cross-sectional view of the hydraulic pivot, and Figure 3 showing the lift control cam and actuator. FIGS. 4 to 6 are sectional views of essential parts for explaining its operation, and FIG. 7 is a graph showing lift characteristics. Figure 8~
FIG. 10 shows a conventional device, FIG. 8 is an exploded perspective view thereof, FIG. 9 is a front sectional view thereof, and FIG. 10 is a graph showing its lift characteristics. DESCRIPTION OF SYMBOLS 11... Intake valve, 11A... Valve shaft head of intake valve, 16... Intake valve drive cam, 20... Lift control cam, 20A... Cylindrical part, 20B... Cam part,
21... Swinging lever, 21A... Lower surface of swinging lever, 22... Control arm, 22A... Upper surface of control arm, 22B... Fork portion.

Claims (1)

[Claims] 1. An intake/exhaust valve drive cam is disposed above the valve shaft head of the intake/exhaust valve, and one end is attached to the lower surface of the swinging lever that is swung by the intake/exhaust valve drive cam. The upper surface of the control arm, which is provided in contact with the head and which is freely swingable with the other end abutting on the lift control cam, is brought into contact with the control arm, and at least one of the upper surface and the lower surface is formed to be curved along the longitudinal direction. In this internal combustion engine intake/exhaust valve lift control device in which the contact position can be longitudinally displaced according to engine operating conditions, the lift control cam is provided protruding from the lower surface of the other end of the control arm. It consists of a cylindrical part that engages with the fork part, and a pair of cam parts that are provided on both sides of the cylindrical part and come into contact with the lower surface of the other end of the control arm, and the fork part is located approximately at the longitudinal center of the control arm. An intake/exhaust valve lift control device for an internal combustion engine, characterized in that it is provided at one location on a line.