JPH03151508A - Variable valve timing-type valve device - Google Patents

Abstract

PURPOSE:To simplify structure and make change-over smooth in a device pro vided with two pairs of low-speed and high-speed cams and locker arms by forming at least the high-speed locker arm into an end-pivot type, and performing change-over by oil supply/discharge to/from a pivot. CONSTITUTION:At the low-speed time of a vehicular engine, a solenoid valve 9 is opened by a control unit 30 to drain a hydraulic chamber 17, and a movable pivot 18 is thereby lowered to dissolve the support of a high-speed locker arm 11. Then the high-speed locker arm 11 is separated from a low-speed locker arm 12 by the stroke of the lift valve 3 of a high-speed cam 14. At this time, the low-speed locker arm 12 is oscillated around a fixed pivot 20 as a fulcrum by the rotation of a low-speed cam 15, and the valve 3 is driven to be switched by the stroke of a pin 19. At the high speed time, the movable pivot 18 is ele vated with oil pressure so as to support the high-speed locker ara 11, and the valve 3 is driven to be switched by the high-speed locker arm 11.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a variable valve timing type valve train that variably controls the opening/closing timing of intake and exhaust valves, that is, the valve timing, in a vehicle engine depending on various operating conditions. Specifically, the present invention relates to a method of selectively operating two types of cams, one for low speeds and one for high speeds.

[Conventional technology]

In naturally aspirated vehicle engines, the valve timing of the intake and exhaust valves is important for volumetric efficiency and low-speed stability.

This greatly affects high-speed performance, etc. That is, if the overlap between the periods during which both the intake and exhaust valves are open near top dead center is large, intake air will be promoted using exhaust inertia at high speeds, and performance will improve as well as volumetric efficiency. On the other hand, when idling, this will lead to blowback and reduce stability, so it is better to reduce the overlap when idling. Therefore, in order to consistently demonstrate stability and high performance over a wide range of engine operating ranges, variable control of valve timing is required at low and high speeds.

Therefore, various methods have already been proposed as means for controlling such variable valve timing. One of them is that it has two sets of cams and rocker arms, one for low speeds and one for high speeds, and the two sets of rocker arms can be separated or combined at low speeds and high speeds, or the valves can be opened and closed by changing the position of the end pivot of each rocker arm. There are valve timings that are controlled by a low-speed cam for a narrow opening angle and a high-speed cam for a wide opening angle.

Therefore, conventionally, regarding the above-mentioned mechanical separation/coupling variable valve timing type valve train, for example, Japanese Patent Application Laid-Open No. 62-322
There is a prior art in Publication No. 06. Here, one of the two rocker arms supported by the rocker shaft is connected to the valve side, and low-speed and high-speed cams are brought into sliding contact with the intermediate slipper of the double-ended lock arm. Further, a connection switching means is built in between the two rocker arms in a direction perpendicular to the two rocker arms, and this switching means is a hydraulic piston.

A spring-loaded stopper is arranged coaxially,
have been shown to separate or combine.

[Problem to be solved by the invention]

However, in the prior art described above, the rocker arms are engaged and disengaged by the piston of the connection switching means, which complicates the structure of the rocker arms and increases the weight. Further, there are problems such as the durability of the piston is likely to deteriorate due to abrasion of the piston, and it is difficult to always smoothly insert and remove the piston when transitioning between low speed and high speed.

The present invention has been made in view of the above, and its purpose is to simplify the rocker arm side in a system that selects two sets of cams and rocker arms, one for low speed and one for high speed, and to ensure constant and reliable switching. An object of the present invention is to provide a variable valve timing type valve operating device that can be operated smoothly and has improved durability.

[Means to solve the problem]

In order to achieve the above object, the variable valve timing type valve operating device of the present invention connects the tip of a low-speed rocker arm that is swingably supported on the stem end side of the valve and has a U-shape in plan view. high-speed rocker arm,
Inside the low-speed rocker arm, one end is connected to the tip of the low-speed rocker arm, and the other end is supported by a movable pivot. and a high-speed cam are in sliding contact with each other, and the hydraulic chamber of the movable pivot is configured to supply and drain oil according to each operating condition.

[For production]

Based on the above structure, a low-speed rocker arm is connected to the valve, and an end-pivot type high-speed rocker arm is connected thereon. Therefore, when the hydraulic chamber of the movable pivot is drained at low speeds, the high speed rocker arm becomes unable to operate the valve, and the low speed cam and rocker arm lift the valve to open and close at a narrow opening angle. Also, when the hydraulic chamber is refueled at high speed, the movable pivot moves to a raised position and swingably supports the high speed rocker arm.
In this case, the high lift of the high-speed cam lifts the valve via two sets of rocker arms, allowing it to open and close at a wide angle.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

1 to 3, reference numeral 1 is a cylinder head, 2 is an intake (exhaust) port (hereinafter referred to as a port), and a valve 3 is provided on this boat 2. In FIG. Valve 3 is
It is movably supported by the valve guide 4, and the umbrella part 3a is seated on the valve seat 5 to close it, and the valve spring 7 is biased in the direction of closing the valve 3 by the retainer 6 on the stem end 3b side. There is. The valve 3 is provided with a double overhead camshaft (DOHC) type valve operating device 1o with variable valve timing.

In the DOHC type valve train 10, an end-pivot type high-speed rocker arm 11 is arranged at a position corresponding to the valve 3, and a similar end-pivot-type low-speed rocker arm 12 is arranged in parallel next to the high-speed rocker arm 11. A camshaft 13 is mounted orthogonally above the high-speed and low-speed rocker arms 11 and 12. The camshaft 13 rotates synchronously at 1/2 of the engine speed, and a high-speed cam 14 and two
Two low-speed cams 15.degree. 15' are formed in a comb shape with the same base circle.

The high-speed cam 14 is formed with a wide opening angle and high lift, and adjacent to the left and right sides of this high-speed cam 4 are low-speed cams 15 with a narrow opening angle and low lift.
．． 15' is provided.

The high-speed rocker arm 11 is rod-shaped and slightly curved, and has a valve drive portion ILa at its tip. In addition, a pivot receiver llb is provided at the bottom of the other end of the high-speed rocker arm 11.
However, a slipper lie is formed in the middle upper part. On the other hand, a movable pivot [
A high-speed rocker arm 11 is swingably supported with a pivot receiver Ilb in spherical contact with a movable pivot 18.

And the valve drive part 1 at the tip of the high-speed rocker arm 11
1a is connected to the stem end 3b of the valve 3 via the pin 19 of the low speed rocker arm 12, and the slipper li
The high-speed cam 14 is installed substantially horizontally with the high-speed cam 14 in sliding contact with the high-speed rocker arm 11, and as the movable pivot 18 moves up and down, the high-speed rocker arm 11 is supported in a valve-operable manner or loses its function.

The low-speed rocker arm 12 is longer than the high-speed rocker arm 11 and has a slightly curved U-shape in plan view, and has a valve drive pin 1 at the end of the two arm parts 12a and 12'a.
9 is fixed. Also in the case of the low-speed rocker arm 12, the pivot receiver 12b is provided at the other end, and the arm portions 12a, 1
Slippers 12c, 12'c are formed at the upper part of the middle of the cylinder head 1, and are installed approximately horizontally on the left and right sides of the high-speed rocker arm 11, with the pivot receiver 12b supported in spherical contact with the fixed pivot 20 of the cylinder head l. Ru. The pin 19 comes into direct contact with the valve stem end 3b, and each of the low speed cams 15° and 15' comes into sliding contact with the slippers 12c and 12'c, making it possible to operate the valve with the pin 19 or the drive section 11a. .

Regarding the high/low speed switching control system, oil pump 2
A lubricating oil passage 26 from 5 communicates with the fixed pivot 20, and an oil passage 27 communicates with the hydraulic chamber 17 of the movable pivot 18 and a relief solenoid valve 29 via a check valve 28. Then, the control unit 30 judges each operating condition and, for example, at low speeds below a predetermined engine speed, the solenoid valve 2
9 is opened to drain the hydraulic chamber 17, and at high speed, the solenoid valve 29 is closed to supply oil to the hydraulic chamber 17.

In the hydraulic chamber 17, the lost motion spring 21 is biased against the movable pivot 18, and the high-speed rocker arm 1
1, the pin 19 of the low-speed rocker arm 12, and the valve stem end 3b are always in elastic contact.

Next, the operation of the valve train having such a configuration will be described.

First, at low speeds, the control unit 30 opens the solenoid valve 29 to drain the hydraulic chamber 17, allowing the movable pivot 18 to descend, thereby losing its support function for the high speed rocker arm 11. Therefore, the high-speed rocker arm If is separated from the low-speed rocker arm 12 by the lift of the high-speed cam 14 and the stroke of the valve 3, and moves independently of the valve operation with the valve driving portion 11a in contact with the pin 19.

Therefore, in this case, only the fixed low-speed rocker arm 12 can operate the valve, and the rotation of the low-speed cam 15° 15' causes the low-speed rocker arm 12 to swing about the fixed pivot 20, and the pin 19 moves toward the valve 3. Stroke to open and close. Therefore, the characteristics of the low-speed cams 15 and 15' result in a low lift, resulting in a narrow opening angle valve timing as shown by the 1° curve in FIG. 5, providing low-speed idle stability and full-open high torque.

Next, at high speeds, the control unit 30 closes the solenoid valve 29 to supply oil to the hydraulic chamber 17, so that the movable pivot 18 is held in the raised position by hydraulic pressure, making it possible to support the high speed rocker arm 11. Thus, in this case, two sets of high-speed and low-speed rocker arms 11.1
However, due to the high lift of the high-speed cam 14, the high-speed rocker arm 11 swings around the movable pivot 18, taking priority over the low-speed cam 15. The valve 3 is opened and closed while being pushed down and stroked. Therefore, the characteristics of the high-speed cam 14 result in a high lift, and high-speed performance is achieved with a wide angle valve timing as shown by curve LH in FIG.

Here, high speed cam 14. If the movable pivot 18 is switched in the base circle of the low-speed cam 15.15' with lubricant I-, it will be switched continuously during the next lift of the high-speed cam 14 or the low-speed cam 15.15'. Also, low speed cam 1
When the movable pivot 18 rises during the lift of 5.15', a smooth switch is made to the lift by the high speed cam I4 from this point on. When the movable pivot 18 descends while the high-speed cam 14 is lifted, the low-speed cam 15°15' smoothly contacts the slippers 12c, 12'c due to the resistance when oil drains, the viscosity of the oil, etc., and the low-speed cam 15 .15'
Switch to lift by

Referring to FIG. 4, another embodiment of the present invention will be described.

In the one shown in FIG. 4(a), the low speed rocker arm 12 is of a swing arm type and the end portion is supported by a rocker shaft 31, and the operation is similar in this case as well.

The one shown in FIG. 4(b) is applied to two valves 3 and 3', and the tips of the two arm parts 12a and 12'a of the low-speed rocker arm 12 are attached to adjustment screws 32 and 32'.
It is connected to valves 3 and 3' via , and is otherwise constructed in the same manner. Therefore, in this embodiment, the two valves 3.3' are operated simultaneously by the low-speed rocker arm 12 or the high-speed rocker arm U.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto.

〔Effect of the invention〕

As described above, according to the present invention, in a valve train that uses two sets of cams and rocker arms, one for low speeds and one for high speeds, and selectively operates valves to variably control valve timing, at least The rocker arm is an end-pivot type, and is switched by oil supply/drainage of the pivot, making the rocker arm simpler, lighter, smaller, and more operable.

Fuel efficiency can be improved.

Furthermore, the pivot can always be smoothly switched by supplying and discharging oil, the switching operation is reliable, and there is no problem of reduced durability.

In addition, the two sets of rocker arms are compactly combined,
It is preferable that the spring on the pivot side allows the connection to be made without play.

Furthermore, the U-shaped low-speed rocker arm can be easily applied to a two-valve system.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view showing an embodiment of the variable valve timing type valve train of the present invention, Fig. 2 is a plan view thereof, Fig. 3 is a side view thereof, and Figs. 4(a) and (b) are A side view and a plan view of main parts showing another embodiment, and FIG. 5 is a characteristic diagram of a valve lift curve. 3...Valve, 10...Valve train, 11...High speed rocker arm, I2...Low speed rocker arm, 12
c, 12' c...Slipper, 14...High speed cam,
15. 15'...Low speed cam, 18...Movable pivot, 19...Pin, 20...Fixed pivot Figure 2 Figure 3 Figure 0

Claims (4)

[Claims] (1) Connect the tip of a low-speed rocker arm that is swingably supported on the stem end side of the valve and has a U-shape in plan view, and connect the end-pivot type high-speed rocker arm with one end inside the low-speed rocker arm. The low-speed cam and the high-speed cam are connected to the tip of the low-speed rocker arm and installed with the other end supported by a movable pivot, and the low-speed cam and the high-speed cam are respectively slidably contacted with the upper middle slippers of the low-speed and high-speed rocker arms. A variable valve timing type valve train characterized in that a hydraulic chamber of a movable pivot is configured to supply and drain oil according to each operating condition. (2) Claim (1) characterized in that the low-speed rocker arm is an end pivot type or a swing arm type.
The variable valve timing type valve train described above. (3) The variable valve timing type actuator according to claim (1), characterized in that a lost motion spring is biased against the movable pivot in the hydraulic chamber so that the tip of the high-speed and low-speed rocker arms and the valve are always in elastic contact with each other. Valve device. (4) Attach the tips of the two arm parts of the low-speed rocker arm to
The variable valve timing type valve operating device according to claim 1, wherein the variable valve timing type valve operating device is connected to stem ends of one or two valves.