DE69009097T2 - Valve device for an internal combustion engine. - Google Patents

Description

TITLE OF THE INVENTION 1. FIELD OF APPLICATION OF THE INVENTION AND CHARACTERISTICS OF THE PRIOR ART

The present invention relates to a storage type valve for controlling the opening and closing of an exhaust valve or an intake valve for a diesel engine.

Fig. 8 shows a prior art accumulator type valve system. The system comprises a 5-way valve 01 which supplies hydraulic fluid pressurized by a pump 010 and stored in an accumulator 011 until a predetermined pressure is reached, a cam 02, a tappet roller and a camshaft 04 which drives the control valve, an actuator which controls an intake or exhaust valve 06 attached to a cylinder head by means of the hydraulic fluid, and the piping 08 and 09. Fig. 8 shows the state in which the tappet roller 03 is located on the base circle (ie, the lowest point) of the cam 02, the control valve 01 supplies the hydraulic fluid to the lower chamber 07a of the actuator 07 through the piping 09, and the intake or exhaust valve 06 is closed by being moved upward by the force of the hydraulic fluid. The hydraulic fluid in an upper chamber 07b of the actuating device 07 is drained through the pipe 08 and the control valve 01 into a container 010a of the pump 010. When the tappet roller 03 is raised by rotating the cam 02, the hydraulic fluid in the lower chamber 07a is drained via the pipe 09 and the control valve 01 into the container 010a, and the hydraulic fluid in the accumulator 011, which is subjected to high pressure, acts on the upper chamber 07b via the control valve 01 and the pipe 08. The force of the hydraulic fluid moves the intake or outlet valve 06 downwards against the pressure in the cylinder acting on the intake or outlet valve 06, thereby opening the intake or outlet valve. When the stroke of the tappet roller 03 is reduced and reaches the base circle of the cam by a further rotation of the cam 02, the control valve 01 takes the position shown in the figure shown state, and the intake or exhaust valve 06 is closed by the upward movement described above.

As described, the prior art device requires five slots for the control valve 01, so that it is complicated and large; in addition, two high-pressure hoses 08 and 09 are required, and the actuator 07 is complicated and therefore large. Furthermore, the known device uses a high-pressure hydraulic fluid to open and close the intake and exhaust valve 06, and the high-pressure hydraulic fluid is supplied to the tank 010a and discharged after the actuator 07 is operated, so that the consumption of hydraulic fluid and the energy loss are high. Another disadvantage of the known device is that the control of the control of the opening and closing and the seat of the intake and exhaust valve is complicated.

2. PURPOSE AND SUMMARY OF THE INVENTION

The purpose of the invention is to provide a valve system for an internal combustion engine, which overcomes the problems encountered in the prior art system, simplifies the structures of the control valve and the actuating device, optimally controls the valve closing speed, reduces the consumption of hydraulic fluid to the minimum required amount and largely reduces the energy loss by closing the valve by means of spring force.

The invention aims to produce a valve actuation system of an internal combustion engine, which is equipped with a hydraulic unit with a reservoir in which a hydraulic fluid that pressurizes the fluid is stored, an actuating device with a main body that includes a cylinder in which a piston activated by the hydraulic fluid actuates an intake or outlet valve, and a control valve that supplies the hydraulic fluid in the reservoir to the actuating device in a controlled manner, characterized in that

a) the cylinder is formed by an upper part receiving a main piston with a small diameter, and a part with a large diameter receiving a lower piston with a large diameter, the small and large diameter cylinder parts being connected to one another, the main piston and the lower piston being connected by a rod, and the diameter of the rod is smaller than the small diameter cylinder part;

b) an upper chamber and a main connecting channel or a sub-connecting channel are formed in the upper part of the cylinder, one side of each of these channels opening into the outer wall of the small diameter cylinder part, and the other side of these channels is connected to an inlet or outlet slot of the main body and the cylinder upper part, and furthermore the slot is connected to the hydraulic unit via the three-way control valve;

c) an intermediate chamber and a lower chamber are formed in the lower part of the cylinder, and an intermediate slot which establishes the connection between the return flow slot and the intermediate chamber, the lower chamber which establishes a connection between the return flow slot and the lower chamber, and a lower slot which establishes the connection between the return flow slot and the lower chamber, while the return flow slot is connected to the leakage oil tank of the hydraulic unit, are formed on the outer wall of the cylinder;

d) the small-diameter piston separates the upper chamber from the intermediate chamber, the large-diameter lower piston separates the intermediate chamber from the lower chamber;

e) the distance between the slots is greater than the distance between the pistons, so that in the stroke position of the main piston the main connecting channel is blocked by the latter and the sub-connecting channel is connected to the intermediate chamber via the piston rod, the channel according to the invention is blocked by the sub-piston in the stroke position and the inlet or outlet slot and the chamber are connected to one another via the check valve.

In the present invention, the actuating device is designed so that the high-pressure hydraulic fluid is used exclusively for opening the intake or exhaust valve, and the valve spring energy generated during the stroke of the intake or exhaust valve is stored and used to open the valve.

With the described arrangement, the parts of the control valve, the pressure lines and the actuating device are simplified and reduced in size, so that the consumption of high-pressure hydraulic fluid when opening the valve can be reduced and drive energy can be saved.

3. BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1 to 7 show embodiments of the valve system according to the invention; Figure 1 is an overall section through the system, Figures 2 to 7 are sectional views of the important parts to explain the operation of the actuating device of the system, and Figure 8 is a sectional view of the parts shown in Figure 1 of a system corresponding to the prior art.

4. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

An embodiment of the present invention will be described below with reference to Figs. 1 to 7.

In Fig. 1, which shows the main parts of the valve system of the exhaust valve of a diesel engine, 1 is a three-way valve and a piston 1a is moved in a vertical direction via a tappet roller 3 by a cam 2 fixed to a camshaft 4. While ensuring oil tightness, the piston 1a slides freely in a cylinder 1b provided with an inlet slot 1c, an outlet or inlet slot and an outlet slot 1e for hydraulic fluid. The reference numeral 8 is a pressure pipe connecting the control valve 1 to the actuator 7. The actuator 7 is comprised of a main body 20, a cylinder 21, a piston 22, a cover 23, and a check valve assembly 30. An upper chamber 7b, an intermediate chamber 7c, and a lower chamber 7a are formed in the cylinder 21, and a main communication passage 21a, a sub-communication passage 21b, an intermediate slot 21c, a lower slot 21d, and an oil path 21e are formed in the outer wall of the cylinder. The main communication passage 21a connects an inlet or outlet slot 20a of the main body 20 to the upper chamber 7b of the cylinder 21. The sub-communication passage 21b connects the inlet or outlet slot 20a of the main body 20 and the intermediate chamber 7c. The intermediate slot 21c connects a return flow slot 20b of the main body 20 and the intermediate chamber 7c. The lower slot 21d connects the return flow slot 20b of the main body 20 with the lower chamber 7a. The oil path 21e connects the main communication passage 21a and the check valve assembly 30. The piston 22 comprises a small diameter main piston 22a which separates the upper chamber 7b from the intermediate chamber 7c and a large diameter sub-piston 22b which separates the intermediate chamber 7c from the lower chamber 7a. The main piston 22a and the sub-piston 22b slide in the cylinder 21 while ensuring oil tightness. The check valve assembly 30 comprises a valve body closure 30b which slides oil-tightly on the inside of a guide 30f and is activated by a plug 30c and a spring 30a. The valve housing closure 30b, which has its tip adjacent to a valve seat 30d, separates the oil path 21e and the upper chamber 7b. The valve housing closure 30b blocks the flow of hydraulic fluid from the upper chamber 7b to the oil path 21e, but allows the flow of hydraulic fluid from the oil path 21e to the upper chamber 7b. In addition, the Check valve 30 has a slot 30e at one end of the oil path 21e. The slot 30e serves to discharge the air mixed with the hydraulic fluid together with hydraulic fluid to the outside of the actuating device 7.

The exhaust valve 6 slides within a guide 15 fixed to a cylinder head 5, and its upward movement is activated by a pneumatic valve spring 40. The upper end of a valve tappet 6a of the exhaust valve 6 abuts against the piston 22. A piston 41 is arranged above a taper bushing 43 of the exhaust valve 6 surrounding the valve tappet 6a, and the piston 41 is pressed against the taper bushing 43 by means of a pressure device 44. The piston 41 slides in an airtight manner in the piston 41. Compressed air is supplied to the interior of the cylinder 42 from a compressed air tank 45 via an air hole 42a, whereby a pneumatic valve spring 40 is formed in the cylinder 42. The actuating device 7 is attached to the upper part of the cylinder 42.

A hydraulic unit 10 consists of a tank 10a, a filter 10b, a high-pressure pump 10c, an accumulator 10d, etc., where a high-pressure hydraulic fluid is supplied from the pump 10c to the accumulator 10d and the accumulator stores the high-pressure hydraulic fluid.

Next, the opening of the exhaust valve 6 is described.

Referring to Fig. 2, the tappet roller 3 is raised by rotation of the camshaft 4, the piston 1a is raised so that the outlet port 1e is separated from the inlet port 1d and the outlet port 1d is communicated with the inlet port 1c. As the piston 1a is subsequently further raised, the hydraulic fluid in the reservoir 10d is fed to the inlet port 20a of the actuator 7 via the control valve 1, whereby a portion of the fluid is fed from the inlet port 20a to the upper chamber 7b via the main communication passage 21a, the oil path 21e and the check valve assembly 30, while the remaining portion is fed from the inlet port 20a to the intermediate chamber 7c via the sub-communication passage 21b. Under the influence of this high-pressure hydraulic fluid, the piston 22 is moved downwards in the direction of arrow T and brought into the position shown in Fig. 3. Fig. 3 shows the state of the system just before the connection of the main connecting channel 21a with the upper chamber 7b. The valve body closure 30b of the check valve assembly 30, which was separated from the seat 30d up to this point, is brought into contact with the seat 30d due to the direct inflow of the hydraulic fluid into the upper chamber 7b, and the connection of the oil path 21e with the upper chamber 7b is interrupted. As the piston 22 continues to move downward, the state shown in Fig. 4 occurs. Fig. 4 shows the moment just before the communication between the sub-connecting channel 21b and the intermediate chamber 7c is interrupted. As the piston moves further downward from this state in the direction of the arrow, the hydraulic fluid acts only on the surface of the main piston 22a, but not on the surface of the sub-piston 22b. The piston 22 is then lowered and the state shown in Fig. 5 occurs. Fig. 5 shows the state just before the intermediate chamber 7c is connected to the intermediate slot 21c. It should be noted that the system is designed so that the fluid in the intermediate chamber 7c can expand during the displacement 81 (see Fig. 4) of the piston 22 from the position shown in Fig. 4 to the position shown in Fig. 5; After the position shown in Fig. 5, the liquid in the intermediate chamber 7c is emptied by the main piston 22a under excess pressure into the intermediate slot 21c. The leakage oil in the intermediate slot 21c is emptied into the tank 10a of the hydraulic unit 10 via the return flow slot 20b. The hydraulic fluid entering the upper chamber from the inlet or outlet slot 20a via the main connecting channel 21a acts on the surface of the main piston 22a, so that the piston 22 is moved downwards in the direction of the arrow and reaches the state shown in Fig. 6. Fig. 6 shows the time shortly before the separation of the lower chamber 7a and the lower opening 21d. As the piston 22 continues to move downwards, the pressure of the liquid in the lower chamber 7a increases due to the seal, and the downward movement of the piston 22 is gently braked by the pressure of the hydraulic fluid. This is achieved by the lower chamber 7a forming a damping space and the valve opening movement being terminated when the maximum stroke position (lmax in Fig. 7) of the exhaust valve 6 is reached. It should be noted that the exhaust valve is not moved although the hydraulic fluid continues to act on the surface of the main piston 22a via the inlet and outlet slots 20a, the main and sub-connecting channels 21a and 21b and the upper chamber 7b. During the above-mentioned time, however, the pneumatic valve spring pressure prevailing within the cylinder 42 increased.

Next, the closing of the exhaust valve 6 is described.

While the piston 22 is working, it moves in the direction of the arrow T shown in Fig. 2 to 6. When the cam 2 rotates from the state shown in Fig. 6, the tappet roller 3 reaches the base circle and the piston 1a of the control valve 1 reaches the state shown in Fig. 1, the hydraulic fluid under high pressure in the upper chamber 7b is discharged through the control valve 1 via the main and the Distance between sub-connecting channels 21a and 21b, the inlet and outlet slots 20a and the pressure hose 8 into the tank 10a of the hydraulic unit 10. The outlet valve 6 is moved upwards by the air pressure of the pneumatic valve spring acting on a piston 41 via the tapered bushing 43 and the pressure device 44. The valve closing movement is achieved by the pneumatic valve spring 40. When the state shown in Fig. 6 changes to that of Fig. 5, the intermediate chamber 7c is closed by the lower piston 22b. The pressure prevailing in the intermediate chamber 7c then increases with the stroke of the piston 22, forms a damping effect during the displacement δ 1 shown in Fig. 4 due to the fluid pressure and gently slows down the stroke speed of the piston 22. When the piston 22 reaches the state shown in Fig. 3 by further movement in the direction of arrow T, the connection between the upper chamber 7b and the main connecting channel 21a is interrupted. However, since the seat 30d of the check valve assembly 30 is closed, the pressure of the liquid in the upper chamber 7b then increases and the upper chamber 7b forms a damping space due to the hydraulic pressure. The speed of the stroke movement of the piston 22 is further slowed down by the accompanying secondary damping effect of the upper chamber 7b shown in Fig. 2. During the displacement 82 to the seat of the outlet valve 6, the speed of the outlet valve 6 is regulated so that it is optimal for the stroke movement which completes the seating and thus the valve is closed. The above-described motion is shown in drawings in which Fig. 7(a) shows the relationship between the stroke l of the piston 22 and the crank rotation angle θk, and Fig. 7(b) shows the relationship between the resistance Fv of the exhaust valve, the forces F₁ and F₂ acting on the piston 22, and the crank rotation angle θk. In Fig. 7(a), l₁ represents the distance (of piston movement) during which the hydraulic fluid acts on the main and sub-pistons as shown in Fig. 2. The pressure P of the hydraulic fluid, the diameter ds of the sub-piston, and the stroke l₁ form the following relationship with the force F₁ pushing the exhaust valve downward and the consumption of hydraulic fluid:

where the force F₁ and the resistance Fv of the exhaust valve satisfy the inequality F₁ > Fv.

The stroke interval from l₁ to lmax corresponds to the time during which the hydraulic fluid acts only on the main piston 22a. The following relationship exists between the diameter dm of the main piston and the force F₂ with which the outlet valve is pressed downwards and the consumption Q₂ of hydraulic fluid:

where the force F₂ and the resistance Fv of the exhaust valve give the inequality F₂ > Fv.

Since the consumption Q of hydraulic oil in the case of the state-of-the-art system, which is not a two-stage system, is

is specified,

It follows that

Q₁ + Q₂ < Q

and it can be seen that the consumption of hydraulic fluid can be reduced significantly.

In the course of the valve closing movement over a distance l₂, a primary damping effect braking the upward movement of the piston 22 during the duration of the displacement δ₁ and a secondary damping corresponding to the duration of the displacement δ₂ are also effective, so that it is possible to optimally regulate the seating speed of the exhaust valve and thereby extend the service life of the exhaust valve.

It should be noted that in the above description the control valve 1 is actuated by mechanically driving the piston 1a with the cam 2. However, the piston 1a can also be electrically driven or a solenoid valve can be used as a control valve.

With the above-described inventive construction, the control valve is simplified so that only three slots are required, the number of pressure pipes is reduced to one and the construction of the actuating device is simplified accordingly. Due to the hydraulic pressure, damping effects are generated, whereby the mechanical collision of parts is avoided and it is possible to optimally control the seating of the exhaust valve and thus gently end the valve opening cycle.

In addition, the hydraulic fluid acts on the piston in two stages depending on the resistance of the exhaust valve, the consumption of hydraulic fluid is reduced to the necessary minimum and the drive energy of the hydraulic fluid is reduced, thus contributing to a noticeable reduction in energy loss.

Although the above-mentioned embodiments have been described in connection with the valve system of an exhaust valve, the valve system according to the invention can of course also be used for an intake valve.

Claims (1)

A valve actuation system of an internal combustion engine with hydraulic unit 10, which comprises a reservoir (10d) which stores a hydraulic fluid which pressurizes the fluid, an actuating device (7) with a main body (20) which comprises a cylinder (21) in which a piston (22) actuated by the hydraulic fluid actuates an intake valve or an outlet valve (6), and a control valve (1) which conveys the hydraulic fluid in the reservoir (10d) in a controlled manner to the actuating device (7), characterized in that a) the cylinder (21) is designed as an upper part with a small diameter, which accommodates a main piston (22a) with a small diameter, and a part with a large diameter, which accommodates a lower piston (22b) with a large diameter, the parts of the cylinder (21) with the small and large diameters being connected to one another, the main piston (22a) and the lower piston (22b) being connected by a rod, and the diameter of the rod is smaller than the part of the cylinder (21) with a small diameter; b) an upper chamber (7b) and a main connecting channel (21a) or a sub-connecting channel (21b) are formed in the upper part of the cylinder (21), and one side of each of these channels (21a and 21b) opens into the outer wall of the small-diameter cylinder part (21), the other side of each of these channels (21a, 21b) is connected to an inlet or outlet slot (20a) of the main body (20) and the upper chamber (7b) of the cylinder (21), and furthermore the slot (20a) is connected to the hydraulic unit (10) via the three-way valve (1); c) an intermediate chamber (7c) and a lower chamber (7a) are formed in the lower cylinder part, and an intermediate slot (21c) is formed on the outer wall of the cylinder (21), which establishes the connection between the return flow slot (20b) and the lower chamber (7a), while the return flow slot (20b) is connected to the leakage oil tank (10a) of the hydraulic unit (10): d) the small diameter piston (22a) separates the upper chamber (7b) from the intermediate chamber (7c) when the large diameter lower piston (22b) separates the intermediate chamber (7c) from the lower chamber (7a): e) the distance between the slots (21b) and (21c) is greater than the distance between the pistons (22a) and (22b), so that the main connecting channel (21a) is of the main piston (22a) and the sub-connecting channel (21b) is connected to the intermediate chamber (7c) along the piston rod, the intermediate slot (21c) is blocked by the sub-piston (22b) near its maximum stroke position and the connection between the inlet and outlet slots (20a) and the chamber (7b) is established via the check valve (30).