JPH03213607A - Variable timing valve system - Google Patents

Abstract

PURPOSE:To simplify a variable timing valve system by disposing a hydraulic piston provided with a lost motion function, against which a high speed cam abuts, in the center of the upper face of a lifter body, the upper face of which the high and low speed cams abut against, and controlling a vertical stroke of the hydraulic piston according to an operational condition. CONSTITUTION:In a DOHC type valve system 10 provided with a lifter body 11 in contact with a stem end 3b of a valve 3, and a cam shaft 14 having a pair of right and left low speed cams 12 and a high speed cam 13 above the lifter body 11, a hydraulic piston 16 abutting against the high speed cam 13 is disposed in the center of the upper face of the lifter body 11. The hydraulic piston 15 is disposed for a free vertical stroke in a hydraulic chamber 11a formed inside the lifter body 11 via a spring 16, and supplies a lubricant from an oil pump 17 to the hydraulic chamber 11a through a lubricant passage 18. An electromagnetic relief valve 24 disposed in the lubricant passage 18 is opened or closed according to an operational condition so that the vertical stroke of the hydraulic piston 15 is unlocked or locked, thus allowing a valve timing to be varied.

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 a naturally aspirated vehicle engine, the valve timing of the intake and exhaust valves, volumetric efficiency, and low-speed stability are important.

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 is promoted using exhaust inertia etc. at high speeds, improving performance 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.

Conventionally, variable valve timing type valve train has a hydraulic chamber provided between a cam and a valve driven by the cam, and the hydraulic pressure is Prior art is known in which the flow of oil from the chamber is controlled to obtain optimal valve timing and lift characteristics for the operating conditions of the engine.

[Problem to be solved by the invention]

By the way, in the prior art mentioned above, low speed,
If the oil in the hydraulic chamber is drained during high-speed switching, the clearance between the cam and the valve will increase, causing impact and knocking noise, which may increase the clearance due to wear and damage the valve train, reducing durability. There is a problem.

Additionally, due to insufficient clearance management, there are problems with operational reliability, etc.

The present invention has been made in view of the above-mentioned problems, and includes:
One valve has two sets of cams for low speed and high speed with different base circles, and a hydraulic piston with a lost motion function using a high speed cam is installed in the valve body disposed between the cam and the valve. Therefore, the present invention provides a variable valve timing type valve train which aims to improve operational reliability, durability, and output by ensuring reliable and smooth switching operations at all times.

[Means to solve the problem]

To achieve this object, the present invention provides a valve train in which a lifter body is interposed between a cam and a valve, in which a high-speed cam and a low-speed cam having different base circles are brought into contact with the upper surface of the lifter body, and the lifter body A hydraulic piston with a lost motion function that is in contact with the high-speed cam is installed in the center of the top surface, and lubricating oil is supplied to the hydraulic chamber that moves the hydraulic piston up and down according to signals from the control unit according to each operating condition. It is characterized by being configured to supply and drain oil.

[For production]

First, in the variable valve timing type valve train of the present invention, when the valve is driven by the low-speed cam via the lifter body at low speed, the solenoid valve is turned on by a signal from the control unit, and the oil in the hydraulic chamber is drained. Since the piston is in a free state, the movement of the high-speed cam is not transmitted to the lifter body, and the low-speed cam opens and closes the valve at a narrow opening angle.

Next, at high speeds, the solenoid valve is turned off by a signal from the control unit to supply oil into the hydraulic chamber and lock the vertical movement of the hydraulic piston, so the high lift of the high-speed cam gives priority to the low-speed cam and allows oil to flow through the hydraulic piston. Push down on the lifter body and move the knob up and down to open and close at a wide opening angle.

〔Example〕

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

1 and 2, reference numeral 1 is a cylinder head, 2 is an intake (exhaust) port (hereinafter referred to as a port), and this port 2 has an intake (exhaust) valve (hereinafter referred to as a valve) 3. provided. The valve 3 is supported by a valve guide 4 so as to be movable up and down, the valve head portion 3a is seated on the valve seat 5 and closed, and a valve spring 7 is mounted on a retainer 6 on the stem end 3b side to close the valve 3. biased in the direction. The valve 3 is provided with a double overhead camshaft (DOHC) type valve operating device IO with variable valve timing.

The DOHC type valve train 10 has a stem end 3 of a valve 3.
Lifter body 11 that slides the valve 3 up and down in contact with b
and a pair of left and right low-speed cams 1 that drive the lifter body 11.
The low speed cam 12.12 and the high speed cam 13 are arranged in the middle of the low speed cam 12.12, and the low speed cam 12. It is located in

The camshaft 14 rotates synchronously at 1/2 the engine speed, and the low speed cam 12.12
cam ridge 12b for the large diameter base circle 12a
is formed with a narrow angle and low lift, and the high-speed cam 13 is
A cam crest 13b is formed in a small diameter base circle 13a with a wide opening angle and a high lift.

On the other hand, a hydraulic piston 15 with a lost motion function that comes into contact with the high-speed cam 13 is interposed between the low-speed cam 12, 12 and the high-speed cam 13 and the stem end 3b of the valve 3, and in the center of the upper surface of the lid body 11. It is arranged.

The hydraulic piston I5 is disposed in a hydraulic chamber 11a formed in the lifter body [1 so as to be vertically movable via a spring 16, and an oil pump 17 is disposed in the hydraulic chamber 11a.
A lubricating oil passage 18 is connected to the lubricating oil passage 18 through check valves 19a and 19b that prevent oil from returning, and a relief valve 2° and a hydraulic regulator 22 are installed in the lubricating oil passage 18.

The relief valve 20 is controlled to open and close by a solenoid valve 24 that receives a signal from an operating condition detection sensor 22 and turns on and off in response to a signal from a control unit 23 that determines each operating condition based on engine speed and the like.

The control unit 23 judges each operating condition and, for example, at low speeds below a predetermined engine speed, the solenoid valve 2
4, the relief valve 20 is opened to drain the hydraulic chamber], 1a, and the vertical movement of the hydraulic piston 15 is made free. Also, at high speed, the solenoid valve 24
By turning off the valve, the relief valve 20 is closed, oil is supplied from the oil pump 17 into the hydraulic chamber 11a, and the vertical movement of the hydraulic piston 15 is locked.

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

First, when the engine starts, the camshaft 14 rotates, and the low speed cam 12.12 and high speed cam 13 move the lifter body 11 up and down to open and close the valve 3. At low speeds, the solenoid valve is opened and closed by a signal from the control unit 23. 24 turns on, opens the relief valve 20, and the hydraulic chamber 1
By draining 1a, the hydraulic piston 15 becomes free and loses the function of operating the lifter body 11 by the high-speed cam [3, so the high-speed cam 13 rotates independently of the operation of the valve 3 without acting on the lifter body 11. .

Therefore, in this case, only the low speed cam 12.1.2 allows the operation of the valve 3, and the low speed cam 12. The rotation of the valve 12 moves the valve 3 up and down through the lifter body 11 to open and close it. Therefore, due to the characteristics of the low speed cam 12.12, the lift is low and the valve timing becomes narrow opening angle as shown by the curve IL in Fig. 3, thereby demonstrating low speed stability and output function.

Next, at high speed, the solenoid valve 24 is turned off by a signal from the control unit 23, the relief valve 20 is closed, and oil is supplied from the oil pump 17 to the hydraulic chamber 11a, so that the hydraulic piston 15 is moved to a raised position by the hydraulic pressure. It is held and comes into contact with high speed cam 3. Thus, in this case, the high speed cam 13 and the low speed cam 12. 12 is rotated by the camshaft 14 to enable the operation of the valve 3, but due to the high lift of the high speed cam 13, the low speed cam 12 is rotated by the camshaft 14.
．． Hydraulic piston 15, which comes into contact with high-speed cam 13 in priority over 12, pushes down valve 3 via lifter body 11 and opens and closes it while moving up and down. For this reason, high-speed cam 1
High-speed cam 13 provides high lift with the characteristics of 3, and exhibits high-speed performance with wide opening angle valve timing as shown by curve 1H in Figure 3.2 Here, high-speed cam 13. At the base circles 13a and 12a of the low speed cam 1.2.12, lifter body 1
When the low-speed and high-speed operation is switched by supplying and discharging oil to the first hydraulic chamber 11a, the switching occurs continuously when the high-speed cam 13 or the low-speed cam 12, 12 is next lifted. Also, low speed cam 12
When the relief valve 20 is closed by a signal from the control unit 23 and the vertical movement of the hydraulic piston 15 is locked while the valve 3 is being lifted by the high-speed cam 13, from this point on, the lift is smoothly switched to the high-speed cam 13. When the relief valve 20 is opened by a signal from the control unit 23 while the valve 3 is being lifted by the high-speed cam 13, and the lock of the hydraulic piston 15 is released, the resistance when the oil in the hydraulic chamber 11a drains and the viscosity of the oil etc., the low speed cam 12.12 smoothly contacts the cam ridge 12b, and the low speed cam 12.12 smoothly contacts the cam crest 12b. Switch to lift by 12.

Although the embodiments of the present invention have been described above, the present invention can also be applied to a two-valve type by configuring the shape of the lifter body 11 so as to come into contact with two valves.

〔Effect of the invention〕

As explained above, according to the present invention, a high-speed cam and a low-speed cam with different base circles are brought into contact with the top surface of the lifter body, and a hydraulic piston with a lost motion function, which is brought into contact with the high-speed cam, is provided in the center of the top surface of the lifter body. The system is configured so that lubricating oil is supplied and drained from the hydraulic chamber that moves the hydraulic piston up and down according to signals from the control unit according to each operating condition, simplifying the valve train and making it lighter and smaller. , operability and practical fuel efficiency can be improved.

Furthermore, smooth switching is possible at all times by supplying and discharging oil to the hydraulic chamber that operates the hydraulic piston, so the switching operation is reliable and durability can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the variable valve timing type valve operating system of the present invention, FIG. 2 is a perspective view of a cam, and FIG. 3 is a characteristic diagram of a valve lift curve. 3...Valve, ■0...Valve train, 11...Lifter body, 11a...Hydraulic chamber, 12...Low speed cam,
13...High speed cam, 14...Camshaft, 15.
...Hydraulic piston, 20...Relief valve, 23.
...Control unit, 24...Solenoid valve. Figure 3

Claims (1)

[Claims] In a valve train in which a lifter body is interposed between a cam and a valve, a high-speed cam and a low-speed cam having different base circles are brought into contact with the upper surface of the lifter body, and in the center of the upper surface of the lifter body, A hydraulic piston with a lost motion function that the high-speed cam comes into contact with is installed, and lubricating oil is supplied and drained into the hydraulic chamber that moves the hydraulic piston up and down according to signals from the control unit according to each operating condition. A variable valve timing type valve train characterized by having the following configuration.