JPH06307217A - Valve device of internal combustion engine - Google Patents

Abstract

PURPOSE:To make low fuel consumption compatible with high output by simplifying the structure, and also restraining the increase of costs, extending the degree of freedom of the layout, in a valve device of an internal combustion engine. CONSTITUTION:A cam contact part 14 is attached to a rocker arm 12 so as to be oscillated, and a cylinder part 24 is formed inside the rocker arm 12, and a piston 22 wherein the lower part of the cam contact part 14 comes in contact with the cylinder part 24, and is provided with a stepped part 25 is arranged. A return spring 26 is arranged between the tip of the piston 22 and the bottom wall of the cylinder part 24. And an oil pressure passage 27 is connected to the cylinder part 24 in which the rear end side of the piston 22 is positioned. Moreover, the other end of an oil pressure passage 27 whose one end is connected to the cylinder part 24 of the rocker arm 12 is connected to an oil pump, and also a controller is connected to the oil pressure passage 27 through an oil pressure control valve. By this structure, the cam contact part 14 is inclined by oil pressure, and the valve lift amount of an intake valve 11 connected to the rocker arm 12 is changed depending upon high speed rotation or low speed rotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve device for an internal combustion engine mounted on a vehicle such as an automobile.
The valve lift amount and the valve timing are made variable by switching the contact portion of the rocker arm with the cam shaft by hydraulic pressure.

[0002]

2. Description of the Related Art Generally, a contact portion of a rocker arm for an internal combustion engine with a camshaft is switched by a hydraulic pressure to change a valve lift amount and a valve timing.
For example, there is an invention described in Japanese Patent Publication No. 2-58445.

In the above invention, as shown in FIGS. 18 and 19, the camshaft 1 is provided with a pair of intake valves 2 and 3, which corresponds to one intake valve 2 of the pair of intake valves 4 and the engine. A low-speed cam 5 having a shape corresponding to low-speed operation and a high-speed cam 6 having a shape corresponding to high-speed operation of the engine are integrally provided, and also slidably contact the low-speed cam 5 and abut one intake valve 2. A first rocker arm 7, a second rocker arm 8 that abuts the other intake valve 3, and a third rocker arm 9 that abuts on the high-speed cam 6 are arranged adjacent to each other so as to be relatively displaceable. 3rd rocker arm 7,8,
9 is provided with a connecting means (not shown) for integrally connecting the rocker arms 7, 8, 9 or for relative displacement. In the figure, reference numeral 10 is a rocker shaft, and reference numeral 10 a is a perfect circular protrusion provided on the camshaft 1.

When the engine is operating at a low speed, if the first, second and third rocker arms 7, 8 and 9 are disconnected from each other, only one intake valve 2 is rotated and the low speed cam 5 is rotated. By swinging the first rocker arm 7 in accordance with the above, the opening / closing operation can be performed in accordance with the low speed operation.

When the engine is operating at high speed, the first and second
If the third rocker arm 7, 8 and 9 are integrally connected to each other, the first rocker arm 7 and the second rocker arm 8 are swung together with the third rocker arm 9 which is in sliding contact with the high speed cam 6 so that one intake air The valve 2 and the other intake valve 3 can be simultaneously opened and closed in accordance with high speed operation.

As a result, the fuel consumption is reduced and the idle characteristic is improved, and the engine output can be improved in a wide range from the low speed range to the high speed range.

There is a device disclosed in Japanese Utility Model Publication No. 63-18725 as an intake / exhaust valve drive device for an internal combustion engine which variably controls the valve lift of the intake / exhaust valve according to operating conditions. According to this invention, one end contacts a valve drive cam that rotates in synchronization with engine rotation, the other end contacts a valve stem, and
A rocker arm having two recesses on the back surface and one end rotatably supported on the back surface of the rocker arm,
The lever is composed of a lever having a convex portion, the other end of which is fitted in the concave portion, and a control cam which contacts the back surface of the lever and regulates the inclination of the lever.

As a result, the thrust force applied to the rocker arm from the valve drive cam is received by the fitting portion, and the rocker arm is given a swinging force during the valve lift to reduce the bending moment of the valve stem, thereby reducing the valve stem's bending moment. It is designed to prevent breakage and improve the followability when the valve lift is small.

[0009]

[Problems to be Solved by the Invention]
The invention of Japanese Patent No. 58445 discloses that a cam shaft is provided with two types of cams, a low speed cam and a high speed cam, and three types of rocker arms that swing according to the low rotation cam and the high rotation cam, and the rocker arm. Since the rocker arms are integrally connected to each other and the connecting means for relatively displacing the rocker arms are provided, the valve mechanism becomes complicated and the cost increases. Further, with the above-mentioned configuration, there is a problem that space is taken due to this and the degree of freedom in layout is reduced.

Since the intake / exhaust valve drive device for an internal combustion engine described in Japanese Utility Model Publication No. 63-18725 has a lever and a control cam in addition to the rocker arm, the degree of freedom in layout is reduced in terms of space. There is a problem that is difficult to secure.

The present invention has been made to solve the above-mentioned conventional problems. The cam contact portion of the rocker arm is hydraulically changed to make sliding contact with the cam, thereby avoiding the complexity of the structure. An object of the present invention is to provide a valve device for an internal combustion engine, which suppresses an increase in cost, expands the degree of freedom of layout, and achieves both low fuel consumption and high output.

[0012]

As a means for solving the above problems, the present invention provides a rocker arm that comes into contact with an engine valve of an internal combustion engine on a camshaft that is rotated in synchronization with the rotation of the engine. In a valve device for an internal combustion engine, which is configured to open and close the engine valve by interlocking with a cam, a cam contact portion that contacts the cam is attached to the rocker arm so as to be swingable along the rotation direction of the cam. ,
A cylinder portion is formed inside the rocker arm, and a piston having a step portion that abuts a lower portion of the cam contact portion is arranged in the cylinder portion, and a return spring is arranged in the cylinder portion where one end side of the piston is located. It is characterized in that a hydraulic passage is connected to the cylinder portion on which the other end of the piston is located.

Further, the present invention is characterized in that the oil source side of the hydraulic passage connected to the cylinder portion of the rocker arm is connected to an oil pump and the controller is connected to the hydraulic passage via a hydraulic control valve.

[0014]

Since the present invention is constructed as described above,
When the engine is running at low speed, the hydraulic pressure from the hydraulic passage connected to the cylinder is not applied to the piston, so the piston is pushed back by the force of the return spring. This causes the step of the piston to contact the piston,
The cam contact portion of the rocker arm will be inclined. When the cam slides in contact with the inclined cam contact portion, the lift amount of the engine valve decreases due to the contact range of the cam, and the engine valve can be opened / closed in accordance with the low speed operation.

Further, when the engine is rotating at high speed, hydraulic pressure is applied to the piston through the hydraulic passage connected to the cylinder portion, and the piston is pressed against the bottom wall of the cylinder portion against the return spring. As a result, the cam contact portion of the rocker arm, which comes into contact with the piston, is lifted and held horizontally by the step portion of the piston. When the cam provided on the cam shaft slides on the horizontal cam contact portion, the lift amount of the engine valve increases due to the contact range of the cam, and the engine valve can be opened and closed in accordance with high speed operation.

Further, since the oil pump and the controller are connected to the hydraulic passage connected to the cylinder portion via the hydraulic control valve, the cam contact portion connected to the piston of the cylinder portion is connected to the piston depending on the engine speed and engine load. It can be changed accurately.

[0017]

An embodiment of the present invention will be described below with reference to the drawings. First, a diagram of an internal combustion engine for carrying out this embodiment is shown.
Explain by 17. The figure shows an internal combustion engine (hereinafter referred to as an engine) in which a rocker arm 12 in contact with an intake valve 11, which is an engine valve, is of a swing arm type.

In the figure, the reference numeral 13 is an exhaust valve which is an engine valve like the intake valve 11. Exhaust valve 13 and intake valve 11
Are provided in pairs for one cylinder (not shown) adjacent to each other.

The rocker arm 12 connected to the upper part of the intake valve 11 is provided with a cam contact portion 14, and the cam contact portion 14 is in sliding contact with a cam 16 provided on a cam shaft 15.

Further, one end of a rocker arm 18, which is swingably supported by a rocker arm shaft 17, is in contact with the upper portion of the exhaust valve 13, and the other end of the rocker arm 18 is in sliding contact with a cam 16 provided on a cam shaft 15. It is like this. Further, the rocker arm 12 of the intake valve 11 is connected to the rocker arm shaft 17.

When the camshaft 15 is rotationally driven in synchronization with the rotation of the engine with the above-described structure, the cam 16 of the camshaft 15 causes the rocker arm 12 and the rocker arm 18 to swing, and the intake valve 11 and the exhaust valve 13 are oscillated.
Is designed to open and close.

Next, the cam contact portion 14 of the rocker arm 12 will be described in detail with reference to FIG. The cam contact portion 14 has a substantially arcuate shape in a sectional view, and its arcuate surface portion is directed toward the cam 16,
It is attached to the rocker arm 12 along the rotation direction of the cam 16.

A protruding portion 19 is formed at the lower portion of the cam contact portion 14, and the cam contact portion 14 is rotatable with respect to the rocker arm 12 by a pin 20 passing through the protruding portion 19.

A protrusion 19 is provided at the bottom of the cam contact portion 14.
Besides, a protrusion 21 is formed, and the protrusion 21 is in contact with a piston 22 described later. That is, the protrusion 21 is constantly rotated and urged toward the piston 22 (arrow) by the fixed spring 23 attached to the protrusion 19 (see FIGS. 2 and 3).

A cylinder portion 24 is formed inside the rocker arm 12 along the rotation direction of the cam 16, and a piston 22 is arranged inside the cylinder portion 24. The piston 22 has a small diameter portion on the front side (the mounting side of the intake valve 11) and a large diameter portion on the rear side. An inclined step portion 25 is provided between the large diameter portion and the small diameter portion.

The bottom wall of the cylinder portion 22 and the piston
A return spring 26 for urging the piston 22 is interposed between the front end portion of 22 and the front end portion of 22. Further, one end of a hydraulic passage 27 is connected to the cylinder portion 24 where the rear end portion of the piston 22 is located (see FIG. 4).

The other end of the hydraulic passage 27 is, as shown in FIG.
It is connected to an oil pump 30 provided inside an oil pan 29 via a hydraulic control valve 28. Also,
A controller 31 is connected to the hydraulic control valve 28.

The controller 31 checks the temperature of the engine cooling water, the intake air temperature, the engine speed and the engine load. Therefore, the hydraulic pressure for driving the piston 22 is switched on and off by switching the hydraulic passage 27 by the hydraulic control valve 28.

In FIG. 1, reference numeral 32 is a clip provided on the rocker arm shaft 17, reference numeral 33 is a lock nut, and reference numeral 34 is a valve adjusting screw.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. First, when the engine is started, the piston 22 of the cylinder portion 24 is set so that hydraulic pressure is not applied, so the engine has a low rotation cam timing (step S1).

That is, if no hydraulic pressure is applied to the piston 22, the piston 22 is returned to the hydraulic pressure source side by the pressing force of the return spring 26, as shown in FIG. This allows
The protruding portion 21 of the cam contact portion 14 is a stepped portion rather than the large diameter portion of the piston 22.
After coming into contact with the small diameter portion via 25, the cam contact portion 14 is held in an inclined state.

When the cam contact portion 14 is inclined in this way,
The contact point between the cam contact portion 14 and the cam 16 is a2. Also,
The cam contact area is indicated by arrow A2.

When the engine speed increases, the controller 31 determines whether the engine cooling water temperature and the intake air temperature are above the set values (step S2).

If the temperature is equal to or higher than the set temperature (step S3), the switching timing set by the engine speed and the engine load is determined (step S4).
This switching timing is shown in FIG. 12 described later.

The switching timing is equal to or greater than the setting (step S
If it is 5), the hydraulic passage 27 is turned on, and hydraulic pressure is applied to the piston 22 (arrow P is hydraulic pressure) as shown in FIG. 1 to set the valve timing during high rotation (step S6).

When hydraulic pressure is applied to the piston 22, as shown in FIG.
As shown in, the piston 22 moves forward against the return spring 26, and the protruding portion 21 of the cam contact portion 14 moves from the small diameter portion to the step portion.
After coming into contact with the large diameter portion via 25, the cam contact portion 14 is held in a horizontal state, that is, parallel to the upper surface of the rocker arm 13.

When the cam contact portion 14 is held horizontally as described above, the contact point between the cam contact portion 14 and the cam 16 is a1. Further, the cam contact area is indicated by the arrow A1.

In the above, the clearance B1 between the cam contact portion 14 and the cam 16 when the cam contact portion 14 is in the horizontal state.
And the cam contact portion 14 when the cam contact portion 14 is in the inclined state.
The clearance B2 between the cam 16 and the cam 16 is the same so that it does not change during high rotation and low rotation. That is, B
Let 1 = B2.

FIG. 9 shows the cam contact portion 14 and the cam shown in FIG.
16 is an enlarged view of the contact state of 16, where c is the contact start point (see FIG. 10), d is the lift amount by the cam 16, and e is the maximum lift point of the intake valve 11.

The relationship between the valve lift amount and the crank angle when the cam contact portion 14 is switched between high rotation and low rotation in this way is shown in FIG. Looking at the intake valve 11 side in the figure, when the crank angle is between 0 degrees at TDC (top dead center) and 180 degrees at BDC (bottom dead center), the valve lift amount is higher at high speed and at lower speed. You can see that it is larger. Further, the valve lift amount and the valve timing can be known from this figure.

FIG. 12 shows the engine speed (rpm) and shaft torque.
It shows the full open performance of the valve from the relationship with (Nm).
The shaft torque when fully opened is as shown in the figure. Also, FIG. 13 shows the switching timing at the time of low rotation and high rotation,
FIG. 13 shows only the high axial torque portion of the characteristic curve at low speed and high speed in FIG.

If the temperature is not above the set value in step 3 of the flowchart of FIG. 6 and if the switching timing is not OK in step 5, the process returns when the engine is started.

In this embodiment, the rocker arm 12 of the swing arm type is used on the intake valve 11 side, but it may be used on the intake side of the rocker arm type. In this case as well, it is possible to obtain the same effect as described above.

In this embodiment, the intake valve 11 is used to switch the valve lift amount during low rotation and high rotation.
However, the valve lift amount may be switched by both the intake valve 11 and the exhaust valve 13 without being limited to this.

FIG. 13 shows the exhaust valve 13
The cam contact portion 14 of the rocker arm 35 connected to is movable so that the valve lift amount can be switched.

Also in this case, the piston 22 with which the protruding portion 21 of the cam contact portion 14 abuts is operated by the hydraulic pressure P, whereby the cam contact portion 14 is tilted. In this figure,
Reference numeral 17 indicates a rocker arm shaft, reference numeral 26 indicates a return spring, and reference numeral 16 indicates a cam. Further, reference numeral f1 indicates a cam contact point during high speed rotation, and reference numeral f2 indicates a cam contact point during low speed rotation.

FIG. 15 shows the relationship between the valve lift and the crank angle when the cam contact portion 14 on the side of the exhaust valve 13 shown in FIG. 14 is made movable. On the valve 13 side, when the crank angle is between 0 degrees at TDC (top dead center) and -180 degrees at BDC (bottom dead center), the valve lift amount is higher at high speed than at low speed. Recognize. Further, the valve lift amount and the valve timing can be known from this figure.

Although the cam contact portion 14 described above has a substantially arcuate shape in cross section, not only this shape, but also the cam contact portion 14 is rotated at a high rotation contact portion 14a and a low rotation portion as shown in FIG. It may be formed from the contact portion 14b.

[0049]

Since the present invention is configured as described above, the cam contact portion of the rocker arm inclines when the engine rotates at low speed, and the valve lift amount of the engine valve varies depending on the contact range of the cam. The engine valve can be reduced and the engine valve can be opened and closed in accordance with the low speed operation.

Further, the cam contact portion of the rocker arm is held horizontally when the engine is rotating at a high speed, and the cam contact range resulting from this increases the valve lift amount of the engine valve, which allows the engine valve to operate in accordance with high-speed operation. Can be opened and closed.

As described above, it is possible to achieve both low rotation and low load performance and high rotation and high load performance. That is, it is possible to achieve both low fuel consumption and high output.

Further, with the above construction, it is not necessary to manufacture two types of cams for low rotation and high rotation as in the conventional case, the structure of the valve device is simplified, and high cost can be avoided. Further, since the structure is simplified, the space is increased and the degree of freedom of layout can be increased.

[Brief description of drawings]

FIG. 1 is a partially sectional front view showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a cam contact portion shown in FIG.

FIG. 3 is a left sectional side view of what is shown in FIG.

FIG. 4 is a perspective view of a rocker arm on the intake valve side of FIG. 1.

5 is a diagram showing the hydraulic path of FIG. 1. FIG.

FIG. 6 is a flowchart for explaining the operation of the cam contact portion.

FIG. 7 is a cross-sectional view showing an aspect of a cam contact portion shown in FIG.

8 is a cross-sectional view showing another aspect of the cam contact portion shown in FIG.

9 is a schematic diagram showing a relationship between a contact start point and a valve lift amount and the like between the cam and the cam contact portion of FIG.

10 is a front view showing the entire cam that is in sliding contact with the cam contact portion of FIG.

FIG. 11 is a diagram showing a relationship between a valve lift amount and a crank angle.

FIG. 12 is a diagram showing a relationship between engine speed and shaft torque.

FIG. 13 is a diagram showing a switching timing based on the relationship between the engine speed and the shaft torque.

FIG. 14 is a cross-sectional view of a rocker arm having a movable cam contact portion on the exhaust valve side.

FIG. 15 is a diagram showing characteristics of the one shown in FIG.

FIG. 16 is a front view showing another shape of the cam contact portion.

FIG. 17 is a cross-sectional view for explaining the engine.

FIG. 18 is a plan view showing a conventional valve gear.

19 is a cross-sectional view taken along the line GG of FIG.

[Explanation of symbols]

 11 Intake valve 12 Rocker arm 14 Cam contact part 15 Cam shaft 16 Cam 22 Piston 24 Cylinder part 25 Step part 26 Return spring 27 Hydraulic path 28 Hydraulic control valve 30 Oil pump 31 Controller

Claims (2)

[Claims] 1. An internal combustion engine in which a rocker arm that contacts an engine valve of an internal combustion engine is interlocked by a cam provided on a cam shaft that rotates in synchronization with the rotation of the engine to open and close the engine valve. In the valve device described above, a cam contact portion that comes into contact with the cam is attached to the rocker arm so as to be swingable along the rotation direction of the cam, a cylinder portion is formed inside the rocker arm, and the cam portion is provided on the cylinder portion. A piston having a step portion, which is in contact with the lower portion of the contact portion, is provided, a return spring is provided in the cylinder portion where one end side of the piston is located, and a hydraulic passage is provided in the cylinder portion where the other end side of the piston is located. A valve device for an internal combustion engine, wherein: 2. A hydraulic circuit having one end connected to a cylinder portion of a rocker arm, the other end being connected to an oil pump, and a controller being connected to the hydraulic line via a hydraulic control valve. Valve device for internal combustion engine.