JP3011016B2 - Hydraulic valve device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic valve system for an internal combustion engine.

[0002]

2. Description of the Related Art For example, by controlling the intake air amount by changing the opening period of an intake valve of an internal combustion engine, it becomes possible to omit a throttle valve and prevent pumping loss. As a variable valve timing mechanism that satisfies this requirement, there has been proposed a hydraulic valve operating device that drives an intake valve and / or an exhaust valve (engine valve) of an internal combustion engine with hydraulic pressure.

[0003] In a general hydraulic valve operating apparatus, a hydraulic cylinder is interposed between an engine valve and a cam, and the operation of the cam is transmitted to the engine valve via a pressure chamber in the hydraulic cylinder. It has a shape that gives the engine valve the maximum valve opening period.Generally, the pressure chamber is opened and the hydraulic oil in the pressure chamber is discharged to the accumulator during opening of the engine valve after the lift exceeds the maximum value. By doing so, the engine valve is closed by a spring that urges the engine valve in the valve closing direction, and it is possible to achieve a desired valve opening period of the engine valve by accelerating the valve closing timing in this way. In such a hydraulic valve operating device, if the engine valve is suddenly closed simultaneously with the opening of the pressure chamber, a large impact force is generated between the engine valve and its valve seat. Is provided with a throttle that acts at least immediately before the closing of the engine valve, and the hydraulic oil is gradually discharged by the throttle to exert a damper effect at this time.

As a result, there is a certain time difference between when the pressure chamber is opened and when the engine valve is actually closed, and this time difference may vary among the hydraulic cylinders due to a change with time of the throttle or the like. For this reason, it is necessary to determine the opening timing of the pressure chamber by detecting the actual closing timing of each engine valve, grasping the degree of change with time of the throttle, and determining the opening timing of the pressure chamber. for that reason,
Japanese Patent Laying-Open No. 4-301104 describes a hydraulic valve operating device that measures the pressure in the pressure chamber of each hydraulic cylinder with a pressure sensor and detects the actual closing timing of each engine valve based on this pressure. I have.

[0005]

The above-described hydraulic valve operating apparatus requires a pressure sensor for each hydraulic cylinder corresponding to each engine valve, which considerably increases the cost.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a hydraulic valve operating apparatus for an internal combustion engine that can detect the closing timing of each engine valve without increasing the cost.

[0007]

A hydraulic valve operating apparatus for an internal combustion engine according to the present invention is a hydraulic cylinder for driving a valve, and when a corresponding engine valve is closed, at least a part of the valve is opened from its pressure chamber. A hydraulic cylinder for discharging hydraulic oil, and an accumulator common to each hydraulic cylinder for temporarily storing hydraulic oil discharged from the pressure chamber of each hydraulic cylinder;
Detecting means for detecting the behavior of the piston in the accumulator, and closing timing determining means for determining the closing timing of each engine valve based on the behavior of the piston detected by the detecting means. And

[0008]

In the above-described hydraulic valve operating apparatus, the detecting means stores the operating oil discharged from the pressure chamber of the hydraulic cylinder when the corresponding engine valve is closed. The behavior is detected, and the valve closing timing determining means determines the closing timing of each engine valve based on the behavior of the piston detected by the detecting means.

[0009]

FIG. 1 is a schematic diagram showing the structure of a hydraulic valve train according to the present invention. This hydraulic valve train is for an intake valve of a multi-cylinder internal combustion engine, and if necessary, a similar hydraulic valve train is provided for an exhaust valve. An intake valve 1 is urged by a spring 2 in a valve closing direction. Reference numeral 3 denotes a cam which rotates once every two rotations of the crankshaft.

Reference numeral 4 denotes a hydraulic cylinder, which has first and second sliding members 4a and 4b which can be slid while being sealed in an oil-tight manner in the internal space thereof.
c is formed. The outer surface of the first sliding member 4a is in contact with the intake valve 1, and the second sliding member 4b is
And the outer surface thereof is in contact with the cam 3, whereby the operation of the cam 3 is transmitted to the intake valve 1 via the hydraulic chamber 4c. The cam 3 has a shape that provides the intake valve 1 with a maximum valve opening period.

The hydraulic chamber 4c of the hydraulic cylinder 4 is connected to a circulation passage 6 by a first connection passage 5, and the circulation passage 6 allows the flow of hydraulic oil only in the same direction (arrow direction) on both sides of the connection. Allowable first and second check valves 6a, 6b are provided. The first connection passage 5 branches into two branches on the hydraulic chamber side, and one of the first connection paths 5 communicates with the hydraulic chamber 4c via a throttle hole provided in the first sliding member 4a from immediately before closing the intake valve to completion of closing the valve. Connected to the hydraulic cylinder 4 so that
The other has a check valve 5a that allows the flow of hydraulic oil in the direction of the hydraulic chamber 4c, and always has a check valve 5a regardless of the above-described throttle hole.
It is connected to the hydraulic cylinder 4 so as to communicate with c.
A spill valve 7 that allows or shuts off the flow of hydraulic oil is disposed in a portion of the circulation passage 6 downstream of the first check valve 6a and upstream of the second check valve 6b.

Although not shown in FIG. 1, hydraulic cylinders 4 including such circulation passages 6 are provided corresponding to the intake valves of the respective cylinders, and a second reverse valve is provided downstream of the spill valve 7 of each circulation passage 6. A common accumulator 9 is connected to a portion upstream of the stop valve 6b by each of the second connection passages 8, and a common hydraulic oil replenishing means 10 is configured to allow only the flow of hydraulic oil in the direction of the circulation passage. It is connected via a stop valve 11.

The hydraulic oil supply means 10 includes a hydraulic oil tank 10
a to supply hydraulic fluid of a relatively low constant pressure to each of the circulation passages 6 as needed.
A supply passage 10b, a continuously driven pump 10c provided in the supply passage 10b, and a return passage 10e having a normally closed pressure valve 10d that bypasses the pump 10c and opens at the above-described constant pressure. Therefore, it is possible to make the hydraulic valve operating device for exhaust valves more common.

In the hydraulic valve apparatus configured as described above, the volume of the pressure chamber of the hydraulic cylinder 4 is maintained by keeping the spill valve 7 closed, and the operation of the cam 3 and the opening / closing operation of the intake valve 1 are performed one at a time. Thus, the maximum valve opening period from the predetermined valve opening timing of the intake valve 1 is realized. On the other hand, when the spill valve 7 is opened during the opening of the intake valve 1, the pressure chamber 4a is opened to the circulation passage 6 via the first connection passage 5, and the spring 2 discharges the hydraulic oil in the pressure chamber 4a. While the intake valve 1 is closed, the opening period of the intake valve 1 can be controlled by appropriately selecting the opening timing of the spill valve 7. Generally, the opening period of the intake valve 1 is at least about half of the maximum opening period.
The opening control of the spill valve 7 is performed during opening of the engine valve after the lift amount of the intake valve 1 exceeds the maximum value. When the intake valve 1 is closed, the throttle hole provided in the first sliding member 4a acts immediately before the intake valve 1 closes, so that the intake valve 1 is gradually closed and a large impact is applied to the valve seat. No force is generated.

The hydraulic oil discharged from the pressure chamber 4a when the intake valve 1 is closed is temporarily stored in the accumulator 9, and immediately after the intake valve 1 is closed, the hydraulic oil is released along with the operation of the cam 3. When the volume of 4a is restored, it is returned into the pressure chamber 4a, so that the hydraulic oil replenishing means 10 described above needs only to be small enough to replenish a small amount of leakage,
Thus, the accumulator 9 is provided with the hydraulic oil replenishing means 1.
0 is required to reduce the size.

There is a time lag between the opening of the spill valve 7 and the actual closing of the intake valve 1 due to the above-mentioned throttle, and this time difference is initially reduced due to the difference in processing accuracy of the throttle. Since it differs between the cylinders 4 and changes with time even in the same hydraulic cylinder 4,
It is necessary to detect the actual closing timing of each engine valve and to grasp the degree of change with time of the throttle to determine the opening timing of the pressure chamber for each hydraulic cylinder, and the control device 20 is in charge of this.

The accumulator 9 is, as described above,
The operation of temporarily storing the hydraulic oil from the hydraulic chamber 4a of the hydraulic cylinder 4 with the closing of the intake valve 1 and then returning the hydraulic oil to the hydraulic chamber 4a is repeated for each closing of the intake valve 1. The timing of the maximum value in the time chart of the change in the oil storage amount coincides with the actual closing timing of each intake valve 1. Even in the case where the number of cylinders of the internal combustion engine is large, the opening periods of the two intake valves that are continuously closed are greatly different, so that the other intake valve is closed before the other intake valve is closed. Unless the corresponding spill valve is opened, the above-described timing is the closing timing of each intake valve 1.

The amount of hydraulic oil stored in the accumulator 9 is
In order to correspond to the displacement of the piston 9a therein, it is possible to detect the closing timing of each intake valve 1 by detecting the behavior of the piston 9a. For example, in the embodiment shown in FIG. 1, an electromagnetic speed sensor 9b is provided as a sensor for this purpose.
This is to generate an induced current of a magnitude corresponding to the moving speed of a.

FIG. 2 is a time chart showing the relationship between the lift amount of the intake valve 1, the displacement amount of the piston 9a of the accumulator 9, and the speed thereof. As described above, when the displacement of the piston 9a is maximum, it is the valve closing timing of the intake valve 1. On the other hand, when the displacement of the piston 9a is maximum, the moving speed of the piston 9a is smaller than the hydraulic oil storage amount. This is the time when zero is inverted from the increasing direction to the decreasing direction. Therefore, by detecting the moving speed of the piston 9a with the speed sensor 9b, the closing timing of each intake valve 1 can be grasped. Based on this closing timing, the intake valve is closed at a desired closing timing. Can accurately determine the opening timing of the corresponding spill valve 7.

As another embodiment, an optical or acoustic position sensor is provided instead of the electromagnetic speed sensor 9b, and the intake valve 1 is closed based on the displacement of the piston 9a detected by the position sensor. It is also possible to know the time. Since the maximum value of the displacement amount of the piston 9a is a variable value that increases when the closing timing of the intake valve 1 is advanced, it is generally difficult to determine the maximum value in the control device 20, and therefore, the displacement amount curve of the piston 9a Is differentiated by time and piston 9b
It is also possible to calculate the speed and determine the closing timing of the intake valve 1 as described above.

In the embodiment shown in FIG. 1, the provision of another similar hydraulic valve train for each exhaust valve is intended to close the exhaust valves of the other cylinders before closing the intake valves. This is because there is a possibility that the spill valve corresponding to is opened.
Thus, when hydraulic oil is being discharged from one hydraulic cylinder to close the engine valve, the hydraulic cylinder corresponding to the other engine valve must not discharge the hydraulic oil, For example, in the case of a four-valve multi-cylinder internal combustion engine having two intake valves and two exhaust valves opened and closed simultaneously per cylinder, if all intake and exhaust valves are driven by separate hydraulic cylinders, In order to detect the closing timing of each engine valve, two hydraulic valve operating devices, two for the intake valve and two for the exhaust valve, are required.

[0022]

As described above, according to the hydraulic valve operating apparatus for an internal combustion engine according to the present invention, the detection for detecting the behavior of the piston is performed by the accumulator common to the hydraulic cylinders corresponding to each of the plurality of engine valves. Means is provided, and it is possible to determine the closing timing of each engine valve based on the behavior of the piston detected by this detection means, which significantly reduces the cost as compared with the related art having a detection means for each hydraulic cylinder. It is possible to lower it.

[Brief description of the drawings]

FIG. 1 is a schematic view of a hydraulic valve device for an internal combustion engine according to the present invention.

FIG. 2 is a time chart showing a relationship between a lift amount of an intake valve, a displacement amount of a piston of an accumulator, and a speed thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Intake valve 2 ... Spring 3 ... Cam 4 ... Hydraulic cylinder 4c ... Hydraulic chamber 5 ... 1st connection passage 6 ... Circulation passage 7 ... Spill valve 8 ... 2nd connection passage 9 ... Accumulator 9a ... Piston 9b ... Speed sensor 20 ... Control device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-301104 (JP, A) JP-A-2-221610 (JP, A) JP-A-4-30459 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) F01L 9/02 F01L 1/46

Claims (1)

(57) [Claims] A hydraulic cylinder for driving a valve, wherein when closing a corresponding engine valve, a hydraulic cylinder for discharging at least a part of hydraulic oil from a pressure chamber thereof, and a pressure chamber of each hydraulic cylinder An accumulator common to each hydraulic cylinder for temporarily storing the hydraulic oil discharged from the accumulator, detection means for detecting the behavior of the piston in the accumulator, and a behavior of the piston detected by the detection means. A valve closing timing determining means for determining a valve closing timing of each engine valve.