JPH08109812A - Intake and exhaust valve control device for four-cycle engine - Google Patents

Abstract

PURPOSE: To obtain a variable intake and exhaust valve device which enables intake and exhaust according to an engine speed with a simple structure. CONSTITUTION: An intake and exhaust valve control device for a four-cycle engine has a cam 1 which determines an operation timing of at least one of an intake valve and an exhaust valve of the engine, and a valve operation member 5 which is operated while being pressurized according to the rotation of the cam, and presses down at least one of the valve bodies of the intake valve and the exhaust valve. In such a device, operation of the cam is transmitted to the valve operation member. A cam follower 2 and a rocker arm 5 are inserted between the cam and the valve operation means, which are varied in stances according to external force and in contact positions in respect to the cam, for varying a timing of transmission of the cam operation to the valve operation means and a valve lifting amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for changing the operation timing of a supply / exhaust valve of a four-cycle engine, and more particularly to a device for changing the timing of transmitting cam operation to the valve and the valve lift amount.

[0002]

2. Description of the Related Art Supply and exhaust of an engine are performed by operating at least one of an intake valve and an exhaust valve in accordance with the rotational movement of a cam. The charging efficiency and the combustion efficiency of the supply / exhaust cannot be optimized unless the timing of supply / exhaust with respect to the piston operation of the engine is changed depending on whether the engine speed is low or high. In other words, it is necessary to advance the timing of supply and exhaust as the engine speed becomes higher. Therefore, conventionally, there has been provided a technique for adjusting the timing of air supply to the engine combustion chamber and further the timing of exhaust according to the engine rotation speed by using two types of cams called VTEC and MIVEC.

Further, a helical gear called VANOS is used so that the degree of transmission of the acting force to at least one of the air supply valve and the exhaust valve of the cam operation can be changed, and the helical gear is separately detected according to the engine speed. Rotate
There are also those that change the degree of transmission of the acting force.

[0004]

Since these devices use two types of cams or helical gears, the advance angle of the cam and the valve lift amount cannot be controlled simultaneously and continuously, and the filling operation is not performed. Not only can efficiency and combustion efficiency not always be kept at the best level, but also the overall mechanism is complicated.

The present invention has been made in view of the above points, and an object of the present invention is to provide a supply / exhaust valve control device for a four-cycle engine capable of performing variable supply / exhaust according to the engine speed with a simple mechanism. .

[0006]

In order to achieve the above object, according to the present invention, a cam for determining the operation timing of at least one of an intake valve and an exhaust valve of an engine according to claim 1, and a cam depending on the rotation of the cam. In a supply / exhaust valve control device for a four-cycle engine, which is operated by being pressed and which has a valve actuating member that pushes down at least one valve element of the air supply valve and the exhaust valve, between the cam and the valve operating member. A timing and a valve for transmitting the cam operation of the cam to the valve actuating member, and changing the contact position with respect to the cam by changing the posture according to an external force to transmit the cam operation of the cam to the valve actuating member 3. A supply / exhaust valve control device for a four-cycle engine, wherein a cam follower and a rocker arm for varying the lift amount are inserted. In the device described in the above, it has a cylindrical hole that connects the cam and the valve actuating member, and has a rotating body that rotates about a rotation center line parallel to the rotation axis of the cam. A supply / exhaust valve control device for a four-cycle engine in which the cam follower is supported so as to be movable in the axial direction; and the engine in the device according to claim 3, wherein the engine has one or more cylinders, 5. The intake / exhaust valve control device for a 4-cycle engine, wherein the rotating body is provided in common for each cylinder, and claim 1.
The cam follower in the device described above provides a supply / exhaust valve control device for a four-cycle engine, which is offset in the advance direction from the rotation center of the cam.

[0007]

According to the first aspect of the present invention, the operation timing of at least one of the air supply valve and the exhaust valve of the engine determined by the cam is transmitted to the valve operating member via the cam follower. The posture of the cam follower can be changed by applying an external force, and the phase angle position in contact with the cam is changed by changing the posture, so that the timing of receiving the operation from the cam is changed. As a result, the operation timing of the valve operating member changes and the timing relationship between the cam operation and the operation of the valve operating member changes, and the engine charging efficiency and combustion efficiency corresponding to the engine speed can be optimized. Further, by changing the posture of the cam follower, the contact position with the valve actuating member changes, so that the valve lift amount also changes.

According to a second aspect of the present invention, the cam follower is axially movably supported by a rotating body which rotates about a rotation center line parallel to the cam shaft, and the rotating body is rotated to change the posture of the cam follower. . As a result, the timing of transmitting the operation of the cam to the valve actuating member changes according to the change of the rotation angle of the rotating body.

According to the third aspect of the present invention, the cam follower is supported by a single cylinder or a rotating body provided commonly to a plurality of cylinders, so that the supply and exhaust of the entire engine are performed synchronously.

According to the fourth aspect of the present invention, the cam follower responds to the cam operation at a position offset from the rotation center of the cam in the advance direction.

[0011]

According to the first aspect of the present invention, the operation of the cam is transmitted to the valve actuating member via the cam follower whose contact position with the cam changes when the posture changes due to an external force. By changing the attitude of the cam follower, the operation can be transmitted to the valve actuating member at a timing that changes according to the engine speed. As a result, the operation of at least one of the intake valve and the exhaust valve can be changed according to the engine speed. Further, the lift amount of the valve can be changed by changing the contact position between the cam follower and the valve operating member. Moreover, since the present invention has the structure of the upper portion of the cylinder head of the engine, it can be similarly applied to the addition and modification to the existing engine.

According to the second aspect of the present invention, the cam follower is supported by the rotating body which rotates about the rotation center line parallel to the cam shaft. Therefore, if the rotating body is rotated in accordance with the engine speed, the engine speed is increased. According to the above, at least one of the air supply valve and the exhaust valve can be operated.

According to the third aspect of the present invention, since the rotating body is provided in a single cylinder or in a plurality of cylinders in common, the supply and exhaust of the entire engine can be performed synchronously even in the case of a plurality of cylinders. . Therefore, it is possible to provide a device that is harmonious for the entire engine and that has an air supply / exhaust performance according to the engine speed.

Since the cam follower is offset in the advance direction from the rotation center of the cam, the relative position between the cam and the follower can be appropriately selected, and the degree of freedom in design is increased. .

[0015]

1 (a) and 1 (b) show, as an embodiment of the present invention, a vertical cross-section around a supply / exhaust valve of a 4-cycle engine. As shown in the figure, the air-fuel mixture or air-fuel mixture for the engine is introduced into the cylinder from the air-intake hole 10, is discharged from the exhaust hole 20 after being compressed and burned.

In FIG. 1, only the mechanism for operating the air supply valve provided in the air supply hole 10 is shown in detail and the others are omitted, but the exhaust valve provided in the exhaust hole 20 has the same structure. It is possible to take

The operation of the air supply valve is controlled by the operation of the cam 1. The cam 1 rotates in the clockwise direction in the figure in synchronization with the rotation of the engine, and pushes down the valve element through another member against the extension force of the spring incorporated in the air supply valve at a predetermined rotational position, and the air supply hole is opened. Air is supplied to the cylinder from 10.

The cam follower 2 and the rocker arm 5 as a valve actuating member are the main elements for transmitting the cam operation of the cam 1 to the air supply valve at this time. Cam Follower 2
As shown in FIG. 1A, it is formed in a cylindrical shape, and is housed in a through hole provided in the cylindrical rotating body 3 so as to be movable in the axial direction. The cam follower 2 is shown in FIG.
As shown in (b), the contact portion with the cam may have a large diameter, and the guide portion may have a smaller diameter than that of the guide portion.

The pushing force of the valve body by the cam follower 2 is transmitted to the rocker arm 5 via the hemispherical body 4. The hemispherical body 4 is in sliding contact with the upper surface of the rocker arm 5 in the figure, and applies a pressing force from the cam follower 2 to the rocker arm 5 downward in the figure. For this reason, the rocker arm 5 rotates counterclockwise in the figure, and exerts a force that pushes down the valve body 8 against the extension force of the spring 7 to the upper end of the valve body 8 in the figure via the spherical body 6.

The rocker arm 5 receives a acting force in the clockwise direction due to the extension force of the spring 7, and rotates to a preset operating position around the rotation center near the right end in the figure. Then, the acting force is received from the cam follower 2, and the acting force is given to the valve body 8.

Among the elements provided in the transmission path of the acting force, the rocker arm 5 particularly transmits the acting force received from the cam follower 2 to the valve body 8. When the point where the acting force is received from the cam follower 2 and the point where the valve force is given to the valve body 8 are only slightly apart from each other in position, the strength of the rocker arm 5 does not have to be so large.

When the valve body 8 is pushed down, the end of the air supply hole closed by the valve body 8 opens, and the air supply hole 10 and the cylinder communicate with each other to supply air.

Although not shown and described in detail, a similar valve operation is performed between the exhaust hole 20 and the cylinder for exhaust.

2A and 2B are views for explaining the changing operation of the supply / exhaust timing according to the present invention. FIG. 2A shows the case of normal timing, and FIG. 2B shows the case of early timing. ing.

First, in FIG. 1A, the cam 1 rotates in the clockwise direction in the figure and comes into contact with the upper surface of the cam follower 2 shown in the figure. As a result, the cam follower 2 is pushed down in the axial direction along the through hole of the rotating body 3, and pushes down the hemispherical body 4.

Next, in FIG. 2B, the rotating body 3 is rotated counterclockwise by an angle θ, and the cam follower 2 is inclined with respect to the cam 1 as compared with the state of FIG. It is in. Therefore, the right end of the upper surface of the cam follower 2 shown in the figure first comes into contact with the cam 1. Since the right end of the upper surface of the cam follower 2 is displaced to the right side in the drawing when viewed from the central axis of the cam follower 2, it is the first contact portion of the upper surface of the cam follower 2 with the cam 1. Therefore, in the case of FIG. 4A, the cam follower 2 responds to the movement of the cam 1 earlier than in the case of FIG. If the tilt angle of the cam follower 2 is reversed clockwise, the cam 1
The cam follower 2 responds to the movement of.

Therefore, if the rotation angle of the rotating body 3 is changed according to the engine speed, the cam follower 2 changes its posture with respect to the cam 1 according to the engine speed. If the cam follower 2 comes into contact with the cam 1 in the posture shown in FIG. 7A when the engine speed is low, then when the engine speed is high, FIG.
By rotating the rotating body 3 via a link mechanism operated by an actuator such as a control motor or hydraulic pressure (not shown) so that the cam follower 2 comes into contact with the cam 1 in the posture shown in FIG. It will be done earlier for engine rotation.

Therefore, the air supply / exhaust according to the engine speed is performed.

FIG. 3 shows the shape of the rotating body 3. The rotating body 3 has a substantially cylindrical overall shape as shown in the drawing, is arranged side by side along the longitudinal direction thereof, and has two through holes 3a, 3a that are drawn out from one of the peripheral surfaces of the rotating body 3 to the other. . The cam follower 2 is housed in the through hole 3a so as to be axially movable in the through holes 3a and 3b. In this case, only two valves in the DOHC engine are shown, but a longer rotating body 3 common to a plurality of cylinders may be formed. Thereby, the postures of the cam followers 2 of the plurality of cylinders can be changed by a single control motor or an actuator such as hydraulic pressure.

A connecting portion 3b is provided on at least one end face of the rotating body 3, and the rotating body is driven by an actuator such as a control motor or hydraulic pressure connected to a link mechanism (not shown). Change the rotation angle of 3 to change the posture of the cam follower 2.

FIGS. 4 and 5 show how the lift change rate of the valve changes by the rotation of the cam follower 2 in the embodiment of FIG. 1 due to the rotation of the rotating body 3, and the cam follower 2 and the rocker arm. 5 is a schematic diagram for explaining how the clearance between the upper limit position of 5, that is, the rotation limit position taken by the rocker arm 5 pushed up by the spring of the valve changes, with reference to FIGS. is there. The cam follower 2 has a total length St of 50 mm, and rotates to the position of the angle θ with the point of the distance S from the contact surface with the cam 1 as the fulcrum. The lower end of the cam follower 2 is in contact with the rocker arm 5 via the hemispherical body 4.

In this schematic diagram, the cam follower 2 that contacts the cam 1 is in the upright state, which is the reference state, and when the cam follower 2 rotates about the rotation center Cf and rotates to the position of the angle θ shown by the imaginary line. Shows.

In particular, in FIG. 5, the cam follower drawn in a rectangular shape in FIG. 4 is drawn in a T-shape to clearly show its function.

FIG. 6 is a characteristic diagram obtained by applying the conditions of FIG. 4 and performing simulation. The inclination angle θ of the cam follower 2 is plotted on the horizontal axis, and the lift amount of the valve (not shown) is plotted on the vertical axis. It was taken. In this case, the fulcrum position of the cam follower 2 is the distance S from the upper end of the cam follower 2 is S =
In the range of 10 mm to 40 mm, 7 steps are changed in steps of 5 mm. As a result, the valve lift amount is such that the inclination angle θ is + 8 °.
At 130 to 148%, and at -8 ° to 80 to 75%, and by arbitrarily changing the tilt angle in the range of + 8 ° to -8 °, the valve lift change rate within the above range. Is obtained. The change in the valve lift amount can be roughly calculated by the following equation (1). L ′ = {A / (AX)} × L> L (1) As described above, it is understood that the valve lift amount can be significantly changed by selecting the fulcrum position of the cam follower 2.

Similar to FIG. 6, FIG. 7 is a characteristic diagram obtained by applying the conditions of FIG. 4 and performing simulation. The inclination angle θ of the cam follower 2 is the horizontal axis, and the clearance change amount Δl of the cam follower 2 is the vertical axis. This is taken on the shaft, and the clearance between the cam and the cam follower must be within a range that can absorb this change. The clearance change amount Δl is calculated by the following equation (2). Δl = (r + 1)-{(r + 1) cos θ + (r + S) sin2 θ} (2) The position S of the fulcrum S is the distance S from the upper end of the cam follower 2 is S
= 18.7 mm to 19.1 mm, the inclination angle θ is 8 °
The variation amount Δl of the clearance changes in the range of −4 μm to +3 μm. If the amount of change in clearance is in this range, there is no practical problem. Since the clearance change amount Δl is required to be more precise than the valve lift amount described in FIG. 6, it is necessary to consider the clearance change amount when selecting the fulcrum position of the cam follower 2. If the fulcrum position is selected as S = 18.8 mm, it can be said that the change amount of the clearance is almost zero until the inclination angle θ is about 5 °, and the fulcrum position is S = 18.9.
If it is selected to be mm, the variation of the clearance can be kept within 1 μm up to the inclination angle of 8 °. Further, the valve opening angle can be narrowed by arranging the clearance in the direction of increasing the clearance.

8 (a) and 8 (b) show another embodiment of the present invention, in which the cam follower 12 is formed into a mushroom shape and is supported by a ring 13. Ring 13
Are supported by the cylinder head by a known structure (not shown). Further, the ring 13 is a cam follower 12
Not only a cylinder but a notched shape may be used as long as it can support. In this case, the upper surface of the rocker arm shown in the figure is an arcuate surface having a radius R centered on the cam shaft.

As a modification of the above embodiment, the cam 1
The position of the cam follower 2 with respect to the center position of
That is, the configuration may be offset to the right in the figure.

By applying such a modification, various timings for transmitting the operation of the cam 1 to the cam follower can be selected. Further, the shape can be determined in consideration of the strength of the cam follower 2.

[Brief description of drawings]

FIG. 1 (a) is a vertical cross-sectional view around a supply / exhaust valve of a four-cycle engine to which the present invention is applied, and FIG. 1 (b) is FIG.
Partial detailed view of (a).

2A and 2B are diagrams for explaining the changing operation of the supply / exhaust timing according to the present invention, in which FIG. 2A shows the case of normal timing and FIG. 2B shows the case of early timing.

FIG. 3 is a view showing the shape of a rotating body 3 in the embodiment of FIG.

FIG. 4 is a schematic diagram illustrating the operation of the cam follower in the embodiment of FIG.

5 is a schematic view for explaining the operation of the cam follower in the embodiment of FIG. 1 more simply than in FIG.

6 is a characteristic diagram showing the relationship between the inclination angle of the cam follower and the rate of change of the valve lift amount due to the inclination angle of the cam follower in the embodiment of FIG.

7 is a characteristic diagram showing the relationship between the inclination angle of the cam follower and the amount of change in the clearance of the rocker arm that abuts on the cam follower in the embodiment of FIG.

8A and 8B are views showing another embodiment of the present invention, in which FIG. 8A shows a state viewed from the same angle as FIG. 1, and FIG. 8B shows XX of FIG. The state seen along the direction is shown.

[Explanation of symbols]

 1, 11 Cam 2, 12 Cam follower 3, 13 Rotating body 3a Through hole 3b Connecting part 4 Hemispherical body 5, 15 Rocker arm 6 Lift guide 7 Spring 8 Valve body

Claims (4)

[Claims] 1. A cam that determines the operation timing of at least one of an air supply valve and an exhaust valve of an engine, and a cam that is actuated by being pressed according to the rotation of the cam, and that has at least one of the air supply valve and the exhaust valve. A supply / exhaust valve control device for a four-cycle engine, comprising a valve actuating member for pushing down, transmitting a cam operation of the cam to the valve actuating member between the cam and the valve actuating member, and depending on an external force. A cam follower and a rocker arm for changing a contact phase angle with respect to the cam to change a timing and a valve lift amount of transmitting the cam operation of the cam to the valve actuating member by changing a posture are inserted. Supply / exhaust valve controller for 4-cycle engine. 2. The rotating body according to claim 1, further comprising a cylindrical hole connecting the cam and the valve actuating member, and rotating about a rotation center line parallel to a rotation axis of the cam. A supply / exhaust valve control device for a 4-cycle engine, wherein the cam follower is axially movably supported in a hole of the rotating body. 3. The supply / exhaust valve control device for a four-cycle engine according to claim 1, wherein the engine has one or more cylinders, and the rotating body is provided in common to each cylinder. 4. The supply / exhaust valve control device for a four-cycle engine according to claim 1, wherein the cam follower is offset in an advance direction from a rotation center of the cam.