JPH03271511A - Variable timing valve system - Google Patents

Abstract

PURPOSE:To reduce a shock at the time of changeover by arranging a hydraulic piston provided with a lost motion function which is oscillated vertically or stopped with supply or discharge of lubricating oil at an intermediate part of a stay of a rocker arm, and abutting the hydraulic piston against an upper surface of the rocker arm end. CONSTITUTION:A solenoid valve 26 is set ON based on a signal from a control unit 25 and a relief valve 24 is opened at the time of low speed operation. A hydraulic piston 18 is then set free by draining a hydraulic chamber 19, and a rocker arm 12 for low speed alone is under an operable condition. To the contrary, the solenoid valve 26 is set OFF, the relief valve 14 is closed and oil is supplied to the hydraulic chamber 19 at the time of high speed opera tion. The hydraulic piston 18 then descends, being abuttingly supported by the end of the rocker arm 12 for low speed. Two pairs of rocker arms 13, 13' and 12 respectively for high speed and low speed are oscillated with a rocker shaft 11 being a fulcrum. A valve 3 is then under an operable condition, lifted highly by the characteristic of cams 15, 15' for high speed. The valve 3 shows high speed ability with valve timing of a wide opening angle.

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, mouths and hook arms for low speed and high speed, and the two sets of rocker arms can be separated or combined at low speed and high speed, or the end pivot position of each rocker arm can be changed to control the valve. There are valve timings that open and close, with a narrow opening angle using a low-speed cam and a wide opening angle using a high-speed cam.

Conventionally, regarding the above-mentioned variable valve timing type valve operating system, prior art is known, for example, as shown in Japanese Patent Application Laid-Open No. 61-250318.

[Problem to be solved by the invention]

By the way, in the prior art mentioned above, the low-speed rocker arm and the high-speed rocker arm are switched on and off using a locking piece such as a pin, so the impact at the time of switching is large and the locking is difficult. Durability is likely to deteriorate due to wear of the pieces, resulting in problems with operational reliability.

Furthermore, since the low-speed cam and the rocker arm are also driven by sliding contact of the slipper, it is difficult to form an oil film through fluid lubrication, resulting in problems such as a significant increase in friction torque.

The present invention has been made in view of the above-mentioned problems, and in a system that selects two sets of cams and rocker arms for low speed and high speed, the present invention simplifies the rocker arm side and reduces friction at low speeds. Ensures reliable and smooth operation at all times, improves durability, and improves idling stability and low
Medium speed torque.

The present invention provides a variable valve timing type valve train that aims to achieve high output and reduce practical fuel consumption.

[Means to solve the problem]

To achieve this object, the present invention provides a valve train having a rocker arm on the stem end side of the valve that is swung by a low-speed cam and a high-speed cam, one end of which is attached to the rocker shaft on the stem end side of the valve. The rocker arm is arranged so that the tips of the supported rocker arms are in contact with each other, and is connected to the rocker shaft in a U-shape in plan view by stays on both sides of the rocker arm, the tips of which are located above the rocker arm. A roller follower is arranged in a groove formed in the middle part of the rocker arm, and a part of the roller follower on which the cam slides is exposed upward, and the tip part is connected to the middle part of the stay of the rocker arm. A hydraulic piston with a lost motion function that slides up and down or stops by supplying and discharging lubricating oil from an oil pump is disposed in the section, and the hydraulic piston is brought into contact with the top surface of the tip of the rocker arm. The present invention is characterized in that lubricating oil is supplied to and discharged from the hydraulic chamber according to signals from a control unit according to each operating condition.

[For production]

In the variable valve timing type valve train of the present invention, first, when driving a low-speed rocker arm, the low-speed rocker arm is driven by a low-speed cam, the high-speed rocker arm is driven by a high-speed cam, and the solenoid valve is turned on. Since the hydraulic piston of the lost motion function installed in the high-speed rocker arm is in a free state, the rocking motion of the high-speed rocker arm by the high-speed cam is not transmitted to the low-speed rocker arm, so the low-speed rocker arm is moved by the low-speed cam with small friction. It swings and opens and closes the valve at a narrow opening angle.

Next, when driving the high-speed rocker arm, by turning off the solenoid valve, the operation of the hydraulic piston with the lost motion function installed on the high-speed rocker arm is stopped and fixed, so that the driving force from the high-speed cam is transferred to the high-speed Since the low-speed rocker arm is swung from the low-speed rocker arm via a hydraulic piston with a lost motion function, the valve can be opened and closed over a wide range of angles.

〔Example〕

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

In Figures 1 to 4, 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 movably supported by a valve guide 4, the valve head portion 3a is seated on the valve seat 5 and closed, and the stem end 3
A valve spring 7 is biased in the retainer 6 on the b side in a direction to close the valve 3. And to the valve 3,
A valve train 10 with variable valve timing is provided.

The valve train 10 is provided with a low-speed rocker arm 12 whose end is supported by a rocker shaft 11 at a position corresponding to the valve 3 . A high-speed rocker arm 13.13° connected by a stay 13a positioned above is coaxially and parallelly supported on the rocker shaft II.

Low-speed rocker arm 12 A camshaft 14 is mounted perpendicularly above the middle of the high-speed rocker arm 13°13°. The camshaft 4 rotates synchronously at 1/2 the engine speed, and the camshaft 14 is provided with two high-speed cams 15, 15° and one low-speed cam 16 between them. It will be done.

High speed cam 15.15° has small diameter base circle 15a
.

The cam ridges 15b and 15[deg.]b are formed at 15'a with a wide opening angle and high lift, and the low speed cam 16 has a cam ridge 16b formed at a large diameter base circle 16a with a narrow opening angle and low lift.

Groove 12a formed in the middle part of the low speed rocker arm 12
A portion of the roller follower 17 on which the low-speed cam 16 slides is exposed upward.

In addition, the high-speed rocker arm L3.13° is formed in a U-shape in plan view and is appropriately curved, and the high-speed cam 1 is located in the middle of the upper part.
Slippers 13b and 13°b, which are in sliding contact at 5° and 15°, are formed separately.

On the other hand, a hydraulic piston 18 with a lost motion function that comes into contact with the top surface of the tip of the low-speed rocker arm 12 is installed in the middle of the stay 13a that connects the tips of the high-speed rocker arms 13 and 13 degrees. .

The hydraulic piston 18 is disposed within a hydraulic chamber 19 formed in the stay 13a of the high-speed rocker arm 13 via a spring 20 so as to be vertically movable. Inside the hydraulic chamber 19,
A lubricating oil passage 22a from the oil pump 21 is connected to the oil passage 11a of the rocker shaft 11, the oil hole Llb, and the check valve 23 that prevents oil from returning. The lubricating oil passages 22'b communicate with each other via the lubricating oil passages 22'b, and a relief valve 24 is disposed in the lubricating oil passages 22b. The relief valve 24 is turned on and off by a signal from the control unit 25.
It is opened and closed by a solenoid valve 26 that is turned off.

The control unit 25 judges each operating condition and, for example, at low speeds below a predetermined engine speed, the solenoid valve 2
6 is turned on, the relief valve 24 is opened to drain the hydraulic chamber 19, and the hydraulic piston 18 is placed in a free state. In addition, at high speeds exceeding a predetermined engine speed, the solenoid valve 26 is turned off, the relief valve 24 is closed, and the hydraulic chamber 9 is supplied with oil, and the hydraulic piston 1
8 is prevented from moving up and down.

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

First, when the engine starts, the low speed rocker arm 12 is driven by the low speed cam 16, and the high speed rocker arm 13,1 is driven by the low speed cam 16.
3° is driven by a high-speed cam 15.15', and at low speed, a signal from the control unit 25 turns on the solenoid valve 26 to open the relief valve 24 and open the hydraulic chamber 19.
By draining the hydraulic piston I8, the hydraulic piston I8 only moves up and down, and the high-speed rocker arms 13, 13° only swing in response to the rotation of the high-speed cams 15, 15°, resulting in a lost motion, resulting in a free state. .

Therefore, in this case, only the low-speed rocker arm 12 enables the valve 3 to operate, and the low-speed rocker arm 12 swings about the rocker shaft 11 via the roller follower 17 due to the rotation of the low-speed cam 16. Stroke the valve 3 to open and close it. So low speed cam 16
This characteristic results in low lift, narrow opening angle valve timing as shown by curve flL in Fig. 6, and low-speed stability and output performance. Further, due to the transfer of the roller follower 17, the low speed rocker arm 12 swings smoothly with small friction relative to the low speed cam 16, and the valve 3 operates.

Next, at high speed, the solenoid valve 26 is turned off by a signal from the control unit 25, and the relief valve 24 is turned off.
is closed and oil is supplied to the hydraulic chamber 19, so the hydraulic piston 1
8 is lowered by hydraulic pressure and is held in contact with the tip of the low speed rocker arm 12. In this case, the two sets of high-speed and low-speed rocker arms 13°, 13°, and 12 swing around the rocker shaft 11, and the valve 3 becomes operable, but the cam ridges 15b of the high-speed cams 15, 15° , 15°b
As a result, the hydraulic piston 18 of the high-speed rocker arm 13.13 pushes down the valve 3 via the low-speed rocker arm 12 and opens and closes it while stroking. For this reason,
The characteristics of the high-speed cam 15.15' provide high lift, and the valve timing with a wide opening angle, as shown by curve LH in Figure 6, provides high-speed performance.

Here, at the positions of the high-speed cam 15, 15° and the base circle 15a, 15'a, 18a of the low-speed cam 1B, oil is supplied and drained to the hydraulic chamber I9 of the high-speed rocker arm 13, 13'' for low-speed and high-speed operation. When switched, high speed cam 15,15°
Alternatively, it is continuously switched during the next lift of the low-speed cam 1B.

Furthermore, when the relief valve 24 is opened by a signal from the control unit 25 while the valve 3 is being lifted by the low-speed cam 16, and the lock of the hydraulic piston (8) is released, the oil in the hydraulic chamber 19 is resisted when draining. Due to the viscosity of the oil, the low speed cam 16 smoothly contacts the roller follower 17 and the lift is switched to the low speed cam 16.

Although the embodiments of the present invention have been described above, the present invention can also be applied to two valves by configuring the tip of the low speed rocker arm 12 to come into contact with two valves.

〔Effect of the invention〕

As explained 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, the tip of the high speed rocker arm A hydraulic piston is installed in the middle of the stay, and the hydraulic piston is brought into contact with the upper surface of the tip of the low-speed rocker arm, and the hydraulic chamber is lubricated by signals from the control unit according to each operating condition. Since the structure is configured to supply and drain oil, valve operation by the high-speed rocker arm and lost motion of the high-speed rocker arm can be achieved by supplying and draining lubricating oil, resulting in low
High-speed cam switching is performed smoothly without shock, and the switching operation is reliable and durability can be improved.

Furthermore, since a roller follower is used for the low-speed rocker arm, friction between the cam and the rocker arm can be reduced.

[Brief explanation of drawings]

11 is a diagram showing an embodiment of the variable valve timing type valve operating system of the present invention, FIG. 2 is an exploded perspective view of the same, FIG. 3 is a view taken along the line X-X in FIG. IV-IV sectional view of the figure,
FIG. 5 is a partially enlarged view of FIG. 4, and FIG. 6 is a characteristic diagram of a valve lift curve. 8... Valve, lO... Valve train, 12... Low speed rocker arm, 12a... Groove, IS, IGO...
High-speed rocker arm, 13a--stay, 13b, 1
3'b-7, ripper, 15, 15'--high speed cam,
16...Low speed cam, IV...Roller follower, 18
...Hydraulic piston, 19...Hydraulic chamber, 21...Oil pump, 22a, 22b...Lubricating oil path, 23...
・Check valve, 24 ・Relief valve, 25...
Control unit, 26... solenoid valve.

Claims (1)

[Claims] In a valve train having a rocker arm that is swung by a low-speed cam and a high-speed cam, the tip of the rocker arm, one end of which is supported by a rocker shaft, is arranged so as to abut the stem end side of the valve. and a rocker arm connected to the rocker shaft in a U-shape in plan view by a stay whose tip end is located above the rocker arm is disposed on both sides of the rocker arm, and is formed in the middle part of the rocker arm. A part of the roller follower on which the cam slides is exposed upward in the groove formed by the roller, and lubricating oil from an oil pump is supplied and discharged to the middle part of the stay of the rocker arm, which is formed by connecting the tips of the roller follower. A hydraulic piston with a lost motion function that slides up and down or stops by applying oil is installed, and the hydraulic piston is brought into contact with the upper surface of the tip of the rocker arm, and the hydraulic chamber is controlled according to each operating condition. A variable valve timing type valve train characterized in that it is configured to supply and drain lubricating oil according to a signal from the unit.