JP2521331Y2 - Variable valve operating system of engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a variable valve operating device for an engine that switches a cam according to an operating condition of the engine.

(Prior Art) As a variable valve operating device of this type, the applicant of the present application, in Japanese Patent Application No. 2-115409, has three cams for one valve, and the cams are provided according to operating conditions. A device has been proposed in which the switching is performed.

Explaining this, two sub-rocker arms, which have no contact portion with the valve, are swingably supported via a sub-rocker shaft, with respect to a main rocker arm whose swing tip contacts the valve. In the swinging part that is separated from the sub-rocker shaft by a predetermined distance, in the direction parallel to the sub-rocker shaft, the coupling pin that responds to the hydraulic pressure fits into the fitting hole or comes out from the fitting hole. The two sub-rocker arms are selectively coupled or uncoupled, and the three cams are switched according to operating conditions.

(Problems to be solved by the invention) However, in the conventional device in which the cams are switched from the low rotation range by including the three cams as described above, when the hydraulic pressure for driving the coupling pin is supplied from the oil pump of the engine. However, in the low rotational speed region where the discharge pressure of the oil pump is low, there is a problem that the hydraulic pressure required to slide the coupling pin cannot be obtained sufficiently, and the cam switching responsiveness deteriorates.

It is an object of the present invention to provide a variable valve operating device that pays attention to such a conventional problem and can sufficiently obtain a cam switching response from a low rotational speed range.

(Means for Solving the Problem) The present invention is directed to a main rocker arm that follows a cam having a relatively small profile to open and close an intake valve or an exhaust valve, and a sub rocker arm that follows a cam having a relatively large profile. A variable valve operating device for an engine, comprising: a coupling pin slidably fitted over the main rocker arm and the sub rocker arm; and a hydraulic chamber into which a hydraulic pressure for sliding the coupling pin against a return spring is introduced. A piston made of a lightweight material is fixed to the connecting pin or another pin that slides while contacting the connecting pin, the diameter of the piston is formed larger than the connecting pin, and the piston is housed in the hydraulic chamber. The pressure receiving area has been expanded.

(Operation) Based on the above configuration, the cam is switched by sliding or uncoupling the main rocker arm and the sub-rocker arm with the sliding of the coupling pin that responds to the hydraulic pressure via the piston.

A piston with a diameter larger than that of the connecting pin is housed in the hydraulic chamber to increase the pressure receiving area, which increases the oil pressure acting on the connecting pin in proportion to the pressure receiving area, resulting in a low discharge speed of the oil pump. A sufficient driving force can be secured from the area.

Further, during operation in which the main rocker arm and the sub-rocker arm swing independently, the end surface of the pin to which the piston is fixed is in sliding contact with the rocker arm or the like, so it is necessary to make the material of the pin highly wear resistant. By forming the piston separately from the pin, the piston can be made of a relatively lightweight material, and the movable mass when sliding the coupling pin can be reduced. As a result, the sliding speed of the coupling pin or the like can be increased, and the responsiveness of switching the cam from the low rotational speed range can be sufficiently ensured, in addition to the effect of increasing the piston pressure receiving area.

(Embodiment) FIGS. 1 and 2 show an engine equipped with two valves (either an intake valve or an exhaust valve, and the illustrated one is an intake valve) having the same function for one cylinder. On the other hand, an embodiment when the present invention is applied is shown.

Explaining this, each cylinder has two intake valves 9
A single main rocker arm 1 is provided corresponding to.
The main rocker arm 1 is formed in a substantially rectangular shape in a plan view,
A base end of the intake valve 9 is swingably supported by a cylinder head via a rocker shaft 12 common to each cylinder, and a pair of valve followers 10 connected to the tops of the stems of the intake valves 9 are provided at the ends thereof.

A sliding cam follower is located in the center of the main rocker arm 1.
1A is formed. The cam follower 1A is opposed to the first cam 21 and protrudes in an arc shape in cross section, and slidably contacts the first cam 21 to swing the main rocker arm 1. Main rocker arm 1
The two intake valves 9 are pushed down while compressing the valve springs 18 by the swinging of, and each intake port is opened.

The main rocker arm 1 is provided with two sub rocker arms 2 and 3 side by side so as to sandwich the cam follower 1A. The base ends of the sub rocker arms 2 and 3 are swingably connected to the main rocker arm 1 via a sub rocker shaft 16.

The second and third cams 22, 22 are attached to the tips of the sub rocker arms 2, 3.
Cam followers 2A and 3A that are slidably contacted with 23 are formed to project in an arc shape in cross section.

The sub-rocker arms 2 and 3 do not have a portion that comes into contact with the intake valve 9, and the lost motion spring 7 that presses the cam followers 2A and 3A against the cams 21 and 23 is provided on the lower side of each of them.
Is interposed and swings independently of the main rocker arm 1. A cylindrical lifter 8 slidably fitted to the main rocker arm 1 is interposed between each lost motion spring 7 and each sub rocker arm 2, 3.

Since one of the sub-rocker arms 2 is connected to the main rocker arm 1, a columnar pin 32 is provided at the swinging portion of the sub-rocker arm 2, and the main rocker arm 1 is also pinched between the pin 32 and the pin 31 coaxially therewith. And the pin 33 are slidably arranged in the direction of the sub-rocker shaft 16, respectively. In the main rocker arm 1, hydraulic pressure for sliding the pins 31, 32, 33 against the return spring 37 is guided to the hydraulic chamber 39 via the passage 40.

Since the other sub-rocker arm 3 is connected to the main rocker arm 1, a columnar pin 35 is provided at the swinging portion of the sub-rocker arm 3, and the main rocker arm 1 is also pinched between the pin 35 and the pin 34 coaxially therewith. And the pin 36 are slidably arranged. In the main rocker arm 1, hydraulic pressure for sliding the pins 34, 35, 36 against the return spring 38 is introduced into the hydraulic chamber 41 via the passage 42.

The discharge hydraulic pressure of an oil pump (not shown) is guided to the passages 40 and 42 via a control valve. The control unit that electronically controls the operation of this hydraulic control valve is the engine rotation signal,
By inputting a throttle valve opening signal or the like, the respective cams 21, 22, 23 are switched according to operating conditions.

As shown in FIG. 3, a fitting hole 45 into which the pins 31 and 32 are slidably fitted is formed in the main rocker arm 1, and a hydraulic chamber 39 is formed coaxially with the fitting hole 45. The formed cylinder portion 46 is formed by expanding its diameter.

The piston 30 is slidably accommodated in the cylinder portion 46,
The piston 30 is formed separately from the pin 31. The piston 30 is formed in a disk shape having a large diameter with respect to the pin 31, and is concentrically fixed to the base end of the pin 31. This piston
As will be described later, the diameter of 30 is set in the hydraulic chamber 39 so that sufficient driving force can be obtained to slide the pins 31, 32, 33 against the return spring 37 even in the low engine speed range. It is set based on the magnitude of the hydraulic pressure guided.

The pin 31 is formed of chrome molybdenum steel like the other pins 32 to 36, but other than that, a steel-based material or an iron-based material may be used as it ensures sufficient wear resistance and rigidity. On the other hand, the piston 30 is formed of an aluminum material, but titanium or synthetic resin or the like may be used as a relatively lightweight material.

One end of the cylinder portion 46 is closed by a plug 47,
A hydraulic chamber 39, which is defined between the piston 30 and the inside of the piston 30, is sealed. The plug 47 is formed with a projection 48 that comes into contact with the end surface of the piston 30, and regulates the sliding of the piston 30 at a predetermined position.

A groove 49 is formed in the fitting hole 45 into which the pins 31 and 32 are fitted,
A space defined between the rear of the piston 30 and the cylinder portion 46 communicates with the rocker chamber.

 Next, the operation will be described.

When the sub-rocker arms 2 and 3 swing independently of the main rocker arm 1, the main rocker arm 1 is driven by the first cam 21 to minimize fuel consumption in the low rotation range where both lift and lift sections are minimized. The important valve timing can be obtained.

At this time, the passage 40 is provided in the hydraulic chamber 39 in which the piston 30 is housed.
The pressure oil is guided through the pin 30, the pins 31, 32, 33 are pushed back against the return spring 37 by a predetermined amount via the piston 30, and the piston 30 causes the piston 30 to fit into the fitting hole 45 and the cylinder portion. The pins 32 and 33 are held at predetermined positions via the pins 31 in a state of being in contact with the stepped portion 50 between the 46, and the coupling between the sub-rocker arm 2 and the main rocker arm 1 is released.

At this time, the end surface 31A of the pin 31 is in sliding contact with the side surface of the sub-rocker arm 2 and the end surface 32A of the pin 32, but since the pin 31 is made of chrome molybdenum steel, sufficient wear resistance and rigidity are secured.

At the time of switching from the first cam 21 to the second cam 22, when the hydraulic pressure introduced into the hydraulic chamber 39 is lowered, the pins 32 and 33 slide due to the urging force of the return spring 37, and as shown in FIG. As shown in FIG. 2, the main rocker arm 1 and the sub rocker arm 2 are fitted together. This allows the sub-rocker arm 2
Are connected to the main rocker arm 1 and swing together. Sub rocker arm 2 is main rocker arm 1
When it is in the base circle of each cam 21, 22, 23, it will be integrated with, and after the integration, the valve timing will be switched according to the second cam 22 with a large lift, and output emphasis in the low and medium speed range will be emphasized. The characteristics are obtained.

In this way, since the pins 31, 32, 33 are driven by the biasing force of the return spring 37, the output from the first cam 21 that emphasizes fuel economy can be promptly emphasized without being affected by the decrease in the discharge hydraulic pressure of the oil pump. The second cam 22 is switched to.

On the contrary, when the second cam 22 is switched to the first cam 21, pressure oil is introduced into the hydraulic chamber 39 in which the piston 30 is housed through the passage 40, and this oil pressure causes the pin 31 to travel through the piston 30. , 32,33
Is pushed back against the return spring 37 by a predetermined amount.

Although the discharge oil pressure of the oil pump is relatively low in the low engine speed range, the oil pressure acting in the axial direction of the pin 31 can be increased in proportion to the pressure receiving area by setting the diameter of the piston 30 large. Return spring to pins 31, 32 and 33
It is possible to secure sufficient driving force to slide against 37.

When the first cam 21 is used, the piston 30 abuts on the step portion 50 between the fitting hole 45 and the cylinder portion 46, and each pin
In the state where the sub-rocker arms 2 and 33 are held at the predetermined positions that do not restrain the sub-rocker arm 2, the end surface 31A of the pin 31 makes a reciprocating motion while slidingly contacting the side surface of the sub-rocker arm 2 and the end surface 32A of the pin 32. By being made of chrome molybdenum steel, sufficient wear resistance and rigidity are secured.

In this way, it is necessary to make the material of the pin 31 highly wear resistant, but by forming the piston 30 separately from this pin 31, the piston 30 is made of a relatively lightweight aluminum material. It is possible to use the material, and each pin 31, 32, 33
The movable mass when sliding can be reduced. As a result, the effect of expanding the pressure receiving area of the piston 30 is
The sliding speed of 32, 33 can be increased, and the cams 21, 22
It is possible to sufficiently secure the switching responsiveness of the engine to promptly bring out the fuel consumption performance and the acceleration performance of the engine, and at the time of switching, it is possible to prevent each coupling pin 32, 33 from being repelled by the main rocker arm 1 or the sub rocker arm 2. Wear of the connecting pins 32, 33 can be suppressed.

Further, when switching to the third cam 23, the pressure oil is guided through the passage 42 to the hydraulic chamber 41 in which the pin 34 is housed, and the pins 34, 35
Is pushed out by a predetermined amount, and the sub rocker arm 3 is connected to the main rocker arm 1. As a result, the valve timing is switched according to the third cam 23 in which both the lift and the lift section are large, and output-oriented characteristics in the high rotation range are obtained.

Since the switching to the third cam 23 is performed in a state where the discharge pressure of the oil pump is sufficiently increased in the high engine speed range, a sufficient driving force can be obtained even with a small pressure receiving area of the pin 34.

A piston made of a lightweight material is fixed to the pin 34 that connects the sub-rocker arm 3, and the piston is fixed to the hydraulic chamber 41.
If the pressure receiving area is increased by mounting the third cam 23, the response of switching to the third cam 23 can be further improved.

(Effect of the Invention) This invention is provided with a sub-rocker arm that is coupled to the main rocker arm according to engine operating conditions.
In a variable valve operating device in which a plurality of cams are switched, a coupling pin slidably fitted between a main rocker arm and a sub-rocker arm, or a pin abutting the coupling pin is housed in a hydraulic chamber. Since the pressure receiving area is expanded by fixing the piston made of a lightweight material, while increasing the hydraulic pressure to move the switching pin, this movable mass is reduced and the cam switching response is reduced in the low rotation range where the discharge pressure of the oil pump is low. Therefore, sufficient control can be secured, and fine control can be performed with emphasis on engine fuel consumption and output.

[Brief description of drawings]

FIG. 1 is a plan view of a valve train showing an embodiment of the present invention, and FIG.
The figure is a cross-sectional view taken along the line AA in the figure, and FIG. 3 is a cross-sectional view of the main part. 1 ... Main rocker arm, 2,3 ... Sub rocker arm, 7
… Lost motion spring, 9… Intake valve, 12… Rocker shaft, 16… Sub rocker shaft, 21,22,23… Cam, 30… Piston, 31-36… Pin, 37,38… Return spring, 39,41… Hydraulic chamber.

Claims (1)

(57) [Scope of utility model registration request] 1. A main rocker arm that drives an intake valve or an exhaust valve to open and close by following a cam with a relatively small profile, a sub-rocker arm that follows a cam with a relatively large profile, and a main rocker arm and a sub-rocker arm. In a variable valve operating system for an engine, comprising: a coupling pin that slides so as to be fittable; and a hydraulic chamber that guides a hydraulic pressure that slides the coupling pin against a return spring. Stick a piston made of lightweight material to another pin that slides while making contact,
A variable valve operating system for an engine, wherein a diameter of the piston is formed larger than that of the connecting pin, and the piston is housed in the hydraulic chamber to expand a pressure receiving area.