JPS61112709A - Device for controlling intake and exhaust valve lift of internal combustion engine - Google Patents

Abstract

PURPOSE:To enable timing and lift of valves to be controlled by curving a contact surface of either a swing lever driven by a cam or a control arm bearing against the head of a valve shaft and adjusting the slant angle of the control arm to vary the contact position. CONSTITUTION:A drive cam 16 is provided above an intake valve 11, and a swing lever 21 swung by thic cam 16 is supported on one end by a pivot 23 and contacts on the central portion the upper surface of a control arm 22 which bears against a valve shaft head 11a on one end and bears against a control cam 30 on the other end so that the slant angle can be adjusted. The contact surface of either the swing lever 21 or the control arm 22 is curved so that the contact position of the lever 21 and the arm 22 is displaced with the change in said slant angle and the timing and lift amount of the valve 11 driven by a cam 16 to be opened and closed are varied. A predetermined timing and lift amount can be achieved by adjusting the control cam 20.

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) As a conventional intake/exhaust valve drive of this type, for example, the first
The ones shown in Fig.
-90711).

As shown in Figures 10 and 11, this device
The exhaust valve is driven by a three-dimensional cam 1, and by displacing the three-dimensional cam 1 in two directions of the camshaft according to operating conditions, the amount of lift of the intake and exhaust valves is made variable. Note 2
3 is a cap that is fitted onto the valve shaft head, 4 is a sliding block having a protrusion 4A on the lower surface, and 5 is a seating groove 5A 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 via the block 4, saddle 5, and cap 3.

FIG. 12 shows changes in valve lift characteristics due to 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, in such conventional devices, suction and
It is impossible to arbitrarily change the opening/closing timing of the exhaust valve (see Figure 12), and the problem is that, for example, it is not possible to sufficiently increase intake air filling efficiency during high loads or improve thermal efficiency during low loads. It had

(Means for Solving the Problems) The present invention provides an intake/exhaust valve lift control device for an internal combustion engine in which an intake/exhaust valve drive cam is disposed above the valve shaft head of the intake/exhaust valve.・On the bottom surface of the swing lever that swings by the exhaust valve drive cam.

One end of the arm is provided in contact with the valve shaft head so that it can swing freely, and at least one of the upper and lower surfaces of the arm is curved along its longitudinal direction. This contact position can be displaced in the longitudinal direction depending on the operating conditions.

(Function) With the above configuration, the intake/exhaust valve drive cam rotates to swing the swinging lever, and along with this swinging, the arm swings to drive the intake/exhaust valves to open and close. In this case, by displacing the contact position between the arm and the lever in the longitudinal direction according to the operating conditions of the engine, the lift amount of the intake/exhaust valve is changed, and the opening/closing timing thereof is also changed.

(Example) An embodiment of the present invention will be described below 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, 11 indicates an intake valve, which opens and closes an intake boat 13 formed in the cylinder head 12.
Ru. A valve spring 14 is fixed to the valve shaft head 11A or interposed between the retainer 15 and the cylinder head 12. The intake valve drive cam 16 is disposed above the valve shaft head 11A of the intake valve 11 and is rotationally driven in synchronization with the output shaft of the engine.

Note that 18 is a bracket that rotatably supports the camshaft 19.

Here, the side of the valve shaft head 11A of this intake valve 11 (the first
A lift control cam 20 consisting of a multifaceted cam is disposed on the left side in the figure. Further, this lift control cam 20 is arranged below the drive cam 6. 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, one end (the right end in the figure) of the swing lever 21 is fitted and supported by the hydraulic pivot 23, and the drive cam 16 abuts the tip 24 on the top surface of the other end. Lower surface 21A of swing lever 21
is curved downward at a predetermined curvature with respect to the longitudinal direction within the plane of illustration. On the other hand, this curved lower surface 21A
The upper surface 22A of the swing arm 22 that comes into contact with the swing arm 22 is formed substantially flat in the longitudinal direction.

The hydraulic pivot 23 serves as a swinging fulcrum for the swinging lever 21, and the contact position between the two surfaces 21A and 22A is displaced in the longitudinal direction as the swinging lever 21 swings. The control arm 22 has one end in contact with the valve shaft 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 provided so as to be able to swing around the other end of the lift control cam 20 as a fulcrum. Configure points. 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 2I 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 is
Fork portion 2 protruding from the lower surface of the other end of the control arm 22
The cam control shaft 30 consists of a cylindrical portion 20A that engages with the cylindrical portion 2B, and a pair of cam portions 20B, 20B that are provided to sandwich the cylindrical portion 20A and come into contact with the lower surface of the other end of the control arm 22.
is inserted into. Cam control shaft 30 and lift control cam 2
0 is connected by a coil spring 31, 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 to, for example, 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 is rotated. . 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 portion that rotatably supports the lift control cam 20 and is, for example, a part of the cylinder head 12 .

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 a spherical part 40 that fits into the concave part 21B at one end of the swing lever 21 is attached to the lower end of the case 41. have. 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 with oil. Further, a spring 46 is compressed in the oil chamber 45 and urges the case 41 downward.

Therefore, the hydraulic pivot 23 is moved upwardly in the figure by the swinging lever 21.
When biased at one end, the fulcrum of the swing lever 21 is held at a predetermined position by the spring force and the oil pressure in the oil chamber 45 sealed by the check valve 44.

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

Figure 4 shows a case in which, for example, the lift amount of the intake valve 11 is increased under high load and high rotation to improve intake air filling efficiency and obtain high output. The control unit 33 determines the operating conditions 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. In addition,
At this time, the rotation of the cam control shaft 30 is controlled by the lift control cam 20.
In order to transmit the rotational force to the lift control cam 20, the rotational force is temporarily stored in the coil spring 31, and the lift control cam 20 is operated while the intake valve 11 is closed, when the load of the valve spring 14 is not applied to the lift control cam 20 via the control arm 22. Rotate. When the intake valve drive cam 16 rotates in the state shown in FIG. 4, 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, the overlap between the intake and exhaust valves should be reduced, and the closing timing of the intake valve 11 or the opening timing of the exhaust valve should be brought closer to the bottom dead center (BDC) to improve combustion and increase the thermal efficiency of the engine. The purpose is to

That is, the control unit 33 determines the state of this engine, drives the stepping motor 32, and supports the control arm 22 on the smallest cam surface of the lift control cam 20. Therefore, the control arm 22 maintains its inclination, as shown in FIGS. 5 and 6, and the swing lever 21 and the control arm 22
The contact position shifts to the right in the figure (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 , it is small and the valve opening timing is delayed.

Valve closing time will be earlier.

As described above, according to this embodiment, the opening/closing timing of the intake valve (or exhaust valve) can be suitably and variably controlled in accordance with the operating conditions of the engine.

In addition, as shown in FIGS. 1 and 3, the swing lever 21 and the control arm 22, the control arm 22 and the lift control cam 20
, are partially engaged with the grooves of the other, so that no deviation in the camshaft direction occurs during operation.

8 and 9 show other embodiments of the invention.

This embodiment uses a three-dimensional cam 50 whose profile also changes in the camshaft direction as an intake valve drive cam in place of the shaft control cam in the previously described embodiment.

Therefore, the camshaft 51 is provided so as to be able to be displaced in the axial direction by an actuator at the same time as it rotates, and the tip 53 at the other end of the swing lever 52 is also inclined in the same direction in accordance with the profile of the cam 50. Further, the other end of the control arm 54 is supported by a fixed pivot 55.

In this case, if the camshaft 51 is axially displaced in accordance with the operating conditions of the engine using an actuator provided at the end of the camshaft 51, the same effects as in the embodiment described above can be achieved.

Other configurations and functions will be omitted.

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

(effect) As explained above, according to the present invention.

Even with an intake/exhaust valve lift control device in which an intake/exhaust valve drive cam is arranged above the valve shaft head of the intake/exhaust valve, not only the amount of lift of the intake/exhaust valve but also the opening/closing timing can be controlled arbitrarily. As a result, it is possible to obtain an opening/closing timing suitable for one engine operating condition, and it is possible to improve intake air filling efficiency and engine thermal efficiency.

[Brief explanation of the drawing]

1 to 7 show an embodiment of the present invention,
Fig. 1 is a sectional view showing the entire structure, Fig. 2 is a sectional view of the hydraulic pivot, Fig. 3 is an exploded perspective view showing the lift control cam and actuator, and Figs. 4 to 6 are for explaining its operation. Main part sectional view. FIG. 7 is a graph showing lift characteristics. FIGS. 8 and 9 show other embodiments, with FIG. 8 being a front sectional view showing the main parts, and FIG. 9 being a side view. 10 to 12 show a conventional device, FIG. 10 is an exploded perspective view thereof, FIG. 11 is a front sectional view thereof, and FIG. 12 is a graph showing its lift characteristics. 11... Intake valve, 11A... Valve shaft head of intake valve, 16, 50...
... Intake valve drive cam, 21.52 ... Swing lever. 21A...Bottom surface of the swing lever. 22, 54...Brake arm, 22A...Top surface of the brake arm.

Claims (1)

[Claims] In an intake/exhaust valve lift control device for an internal combustion engine in which an intake/exhaust valve driving cam is disposed above the valve shaft head of the intake/exhaust valve, a swinging lever that is swung by the intake/exhaust valve driving cam is By bringing into contact with the lower surface the upper surface of an arm provided swingably with one end abutting the valve stem head, and by forming at least either the upper surface or the lower surface to be curved along its longitudinal direction. An intake/exhaust valve lift control device for an internal combustion engine, characterized in that the contact position can be displaced in the longitudinal direction according to engine operating conditions.