KR100538679B1 - A hydraulically actuated valve - Google Patents

Abstract

The present invention relates to a hydraulically actuated valve for an internal combustion engine. The valve according to the invention comprises a hydraulic actuator for operating the valve between a closed position and an open position. The valve has a stem 24 connected with a piston 32 arranged in a fixed housing 31 of the actuator. The primary flow path connects the inlet / outlet port 11 to the primary pressure chamber 35 in which pressurized fluid acts on the surface of the piston 32 to open the valve. The actuator includes a device that changes the flow resistance of the primary flow path according to the position of the piston.

Description

Hydraulically Actuated Valves {A HYDRAULICALLY ACTUATED VALVE}

The present invention relates to hydraulically actuated valves for internal combustion engines such as two or four stroke diesel or gas engines. The valve can be used as an intake valve or a discharge valve. More specifically, the present invention provides a hydraulic actuator for operating a valve between a closed position and an unseated position, the valve having a stem connected with a first piston disposed in a fixed housing of the actuator. The first piston is in a retracted position when the valve is closed and in an extended position when the valve is open, and pressurized fluid acts on the surface of the first piston to advance the piston. For internal combustion engines characterized by a primary pressure chamber sending to a position, a port that can alternately connect to a high pressure source or return line of hydraulic fluid, and a primary flow path between the port and the primary pressurized pressure chamber. It relates to a hydraulically actuated valve.

 This type of valve actuator is operated by supplying high pressure hydraulic fluid from a dedicated common rail system to the hydraulic actuator via an on / off valve. It is necessary to supply a relatively high pressure to overcome the opposing pressure in the combustion chamber acting on the valve at the first stage of the opening movement and to accelerate the valve quickly. However, the opposing pressure of the combustion chamber drops considerably even if the valve is slightly opened. Since the hydraulic pressure must be supplied over most of the stroke, the actuators and valves reach significant speeds towards the end of the stroke. Without the end of the stroke damper, the piston strikes the stroke limiter at an inappropriate high speed, causing damage and noise.

US 3, 209, 737 discloses a hydraulically actuated exhaust valve with an actuator piston in two parts, according to which a large diameter first piston part surrounds a second piston part which is made integral with the valve stem. The second piston part has a vertical pin, which enters into the buffer chamber forming a hydraulic buffer at the end of the hydraulically actuated closing movement, slowing the closing movement of the valve. Similar means may be provided at the end of the open stroke.

The hydraulic shock absorber operates on the following principle: the hydraulic fluid is retained in the chamber and can only flow out through a suitable gap between the chamber bore and a portion of the piston entering the shock absorbing chamber. The impact that occurs when the piston strikes its stroke limiter can be reduced by appropriately selecting the dimensions of the gap. The hydraulic shock absorber therefore works well only for a given speed, at which the piston approaches the shock absorber, ie for this purpose the hydraulic shock absorber is corrected by selecting the appropriate clearance. If the speed at which the piston reaches the shock absorber changes due to pressure changes in the common rail system, the shock absorber does not function properly.

However, the pressure of the high pressure fluid generated by the combustion engine can vary considerably. If the pressure is too low, the valve will not open completely because there is not enough kinetic energy to fully push the piston into the buffer chamber, and if the pressure is too high, the piston will be improper because the kinetic energy of the piston to be absorbed by the hydraulic shock absorber is too high. Strongly hitting the administrative limiter. Changes in the viscosity of the hydraulic liquid can exacerbate this problem.

The object of the present invention against the background of this prior art situation is to overcome the above problems and to operate at a wide range of supply pressures, such as the usual pressure of a common rail for fuel injection. It is an object of the present invention to provide a hydraulically actuated valve. This object may be achieved by providing a hydraulically actuated valve of the kind according to claim 1 comprising means for varying the flow resistance of the primary flow path according to the position of the first piston.

Thus, the pressure of the fluid in the primary pressure chamber can be at a desired value depending on the stroke of the valve. Therefore, the piston can be operated at a relatively high pressure at the start of the open stroke to overcome the pressure in the combustion chamber and to accelerate the valve, and the open stroke of the open stroke to prevent the valve from reaching excessive speeds so that it can come into close contact with the stroke limiter. In the remaining periods it can be operated at a relatively low pressure. Therefore, the pressure change of the hydraulic fluid supplied to the actuator has less influence on the dynamic behavior of the valve actuator. Thus, as a high pressure hydraulic fluid source for the valve actuator, for example, the fuel injection can use high pressure fluid (fuel) from the common rail system for fuel injection, which must be changed according to the operating state of the engine. Therefore, the engine can be manufactured without a dedicated high pressure common rail system for valve actuators.

Preferably, means are provided for varying the flow resistance of the primary flow path such that the flow resistance changes according to a predetermined profile for the position of the first piston. Depending on the valve design and the desired open contour, the flow resistance can increase linearly, stepwise, gradually, or with any other desired contour.

The first piston includes a tapered portion that defines a flow restriction, with a flange projecting inwardly from the bore in the actuator housing, the flow restriction having the first piston moved from the retracted position to the forward position. Increases as you move.

The tapered portion can be formed into a truncated cone to obtain a linearly decreasing flow through the region. Deform this truncated cone to have a slightly outwardly curved surface to quickly reduce the flow through the area as the first piston moves to the forward position, or to have a slightly inwardly curved surface to shape the truncated cone into a funnel shape. Thereby slowly decreasing the flow through the region as the first piston moves to the forward position.

In another preferred embodiment, the primary flow path comprises a plurality of relatively small tubes, which are open in the retracted position and are in turn closed by the piston as the piston moves from the retracted position to the forward position. Thus, when the first piston moves from the retracted position to the forward position, the flow restriction of the primary flow path increases. The tube may have the same flow resistance or different flow resistance, depending on the desired appearance.

Optionally, the actuator housing is provided with a sloped port leading to the chamber of the housing, the port interacting with the first piston to form a flow resistance that varies with the position of the first piston. Thus, the flow restriction can vary continuously.

The valve actuator is also

A second piston disposed coaxially with the first piston and acting on the first piston at the first stage of the stroke of the first piston in the forward direction,

A secondary pressure chamber in which the compression fluid acts on the surface area of the second piston, actuating the piston in the open direction,

A secondary flow path between the port and the secondary pressure chamber, and means for closing the secondary flow path before the second piston reaches the end of its working stroke. The second piston assists the first piston to overcome the opposing pressure in the combustion chamber. By closing the secondary flow path in a timely manner, it is possible to avoid the second piston from improperly hitting its stroke restrictor.

The speed at which the valve closes and the speed at which the first piston contacts the stroke restrictor can be further reduced by providing an end of the stroke shock absorber for the first piston in the form of a blind buffer chamber into which part of the first piston enters at the end of each stroke. Can be.

Moreover, the objects, features, advantages and characteristics of the hydraulically actuated valve according to the present invention will become apparent from the detailed description.

1 shows a uniflow cylinder 1 having a scavenging air port 2 located in an air box 3, which is pressurized by a turbocharger, for example, from a scavenging air reservoir (not shown). It is supplied with scavenging air.

The exhaust valve 4 is mounted in the upper center of the cylinder in the cylinder cover 24 '. At the end of the expansion stroke, the exhaust valve is opened before the engine piston 5 goes down past the scavenging air port 2 so that the combustion gases in the combustion chamber 6 above the piston enter the exhaust receiving section 8. It is discharged through the subsequent discharge path (7). That is, during the upward movement of the piston at an adjustable moment in accordance with the desired effective compression ratio for continuous combustion, the exhaust valve is closed again. During the closing movement, the exhaust valve is driven upward by the pneumatic spring 23.

Taking into account the durability of the valve and the precise control of the combustion chamber conditions and the engine efficiency, the exhaust valve can be effectively controlled very accurately.

The exhaust valve is opened by the hydraulically actuated actuator 9. The hydraulic fluid is connected to a control port on the upper surface of the distribution block 12 supported by the console 13 and a pressure tube 10 connecting the port 11 of the actuator (shown only in FIGS. 3, 4 and 6, 7). Supplied through. The console is connected to a high pressure tube 14 for hydraulic fluid supplied from a common rail (not shown), for example at a pressure in the range of 16 to 500 bar. The common rail also preferably serves as a high pressure fluid source for the fuel injection system.

In the common rail, hydraulic fluid (in this case fuel) can be used to drive the valve actuator directly or indirectly via a pressure amplifier / separator separating the fuel and hydraulic fluid for the valve actuator from the common rail. In a common rail fuel system, the pressure varies with the engine's operating conditions such as travel speed and load conditions. In general, for large two-stroke diesel engines, the pressure in the common rail fuel system varies between 800 bar and 2000 bar.

When a dedicated common rail for the valve actuator is used, the hydraulic fluid can be supplied from the storage tank through the pump station, the hydraulic fluid can be for example standard hydraulic oil, but preferably the lubricating oil of the engine is hydraulic fluid And the system is supplied from the engine's tank.

The internal combustion engine may be a medium speed four stroke diesel or gas engine, which is a propulsion engine of a ship or a fixed mover of a power plant, or a low speed two stroke crosshead diesel engine.

The cylinder of each engine is coupled with an electronic control device 15, which receives a general synchronization / control signal via wire 16, and an electronic control signal to control valve 17 via wire 18. Send it. One control device 15 may be provided per cylinder, or several cylinders may be connected to the same control device. The control device can also receive signals from the entire control device common to all cylinders.

At the console, a channel 19 branching out of the high pressure tube directs pressurized hydraulic fluid to the high pressure port of the control valve 17.

The channel 19 is provided with a plurality of fluid accumulators 20 which deliver the majority of the fluid volume when the control valve is opened, which is supplied from the high pressure tube when the control valve is closed.

The control port of the control valve 17 is connected to the discharge port on the upper surface of the block 12 via the channel 21 of the distribution block. The control valve is also equipped with a tank port connected to the return tube for the hydraulic fluid used via the channeled return line 22. Optionally, the return line can be connected to an outlet pipe connected to the oil sump of the engine, for example at atmospheric pressure. The pressure in the return line can range between atmospheric pressure and overpressure several bars higher than atmospheric pressure. In order to prevent the ingress of air in the actuator, the return line 22 preferably has an overpressure of at least 1 bar, so that the overpressure is maintained in the pressure tube 10 while the hydraulic fluid is discharged from the actuator.

When the exhaust valve 4 should be opened, the control signal from the control device 15 adjusts the control valve 17 to a position where the high pressure port 19 is connected to the control port, so that the high pressure fluid is connected to the pressure pipe 10. And free access to the fluid supply (11). When the exhaust valve 4 is closed, the control valve 12 is adjusted to the position where the tank port connected to the return line 22 is connected to the control port, so that the high pressure of the pipe 10 is discharged.

The control valve 17 can be any conventional form such as a single electronically actuated on / off valve having three ports and two positions. However, for quick and accurate valve setting, the control valve 17 is preferably composed of two valves, namely the solenoid valve 17a and the main valve 17b, for the valve actuator. The actuation valve 17a can have three ports and two positions. For example, a magnetic lock is made in the distal position, in which the valve is operated by magnetization of one of two coils located at each end of the valve slider made of ferromagnetic material. In case the two coils are not magnetized, the valve slider can be pre-pressurized with a spring so that the tank port to return line 22 is in an inactive position, which becomes the active supply port. Alternatively, the actuation valve may be a conventional solenoid valve. The outlet port of the actuating valve is connected to an intermediate channel that delivers pressure to the piston face at one end of the slider of the main valve 17b. The other end of the slider has a small area piston surface permanently connected to the high pressure tube. In one position of the actuating valve, the high pressure acting on the small piston region causes the main slider to go to the position where the return tube is connected to the outlet port of the main valve via return line 22. The discharge port leads to a pressure tube 10. When the actuating valve 17a is in the second position where the intermediate channel is connected to the high pressure pipe 14, the slider of the main valve is transferred to the high pressure pipe 10 by the high pressure of the large piston surface so that the actuator opens the exhaust valve. Goed to the 2nd position opened.

2 to 4, a first embodiment of the actuator 9 and the pneumatic spring will be described in more detail.

The exhaust valve has a stem 24 perpendicular to the valve disc, the top of the stem supporting a spring piston 25 mounted to the stem in a longitudinally displaceable manner within the pneumatic cylinder 26 with a pressure seal. Below the spring piston is a spring chamber 27 connected to a compressed air supply (not shown). The compressed air supply is adapted to maintain a spring chamber filled with compressed air at a predetermined minimum pressure (eg overpressure of 4.5 bar). In addition, other air pressures such as 3 to 10 may also be used. The minimum pressure is selected according to the desired spring characteristics of the pneumatic spring. It is possible to connect the spring chambers of several different cylinders, but preferably each spring chamber is individually separated by a non-return valve 56 in the compressed air supply. Compressed air in the spring chamber 27 generates a constant upward force on the spring piston 25. When the spring piston 25 moves downward and pressurizes the air in the spring chamber 27 which is prevented from leaking by the non-return valve, the upward force increases.

The housing 28 restricts the cavity 29 at and around the pneumatic spring. The cavity is connected to the outlet 57 and has atmospheric pressure.

The hydraulic actuator 9 consists of a cylinder 31 which is supported by the upper part of the housing 28. The first piston 32 is contained in the central bore of the cylinder 31. The central bore closes at the top of the cylinder and is open at the bottom of the cylinder 31. The central bore is disposed coaxially with the bore 34 of the housing 28.

The primary pressure chamber 35 is limited between the cylinder 31 and the top of the first piston. Hydraulic fluid is supplied to and discharged from the valve actuator via the port 11. The port 11 is connected via a pipe 30 to a port 36 which is connected to the central bore of the cylinder 31. The ports 11 are alternately connected to the high voltage source and the return line. The port 36 is connected with the intermediate pressure chamber 37 which is restricted between the cylinder 31 and the small diameter portion 38 of the first piston. The tube 39 branches off from the tube 30 and is connected to the central bore via the port 43 and encounters the recess 41 of the first piston at the first stage of the opening stroke. Through the recess 41, the hydraulic fluid reaches the secondary pressure chamber 40. The secondary pressure chamber is constrained between the large diameter of the central bore and the second piston 42 coaxially arranged with the first piston. The second piston contacts the flange 45 of the first piston, thereby assisting the first piston in the first stage of the open stroke. The stroke of the second piston 42 is significantly shorter than the stroke of the first piston 32. At the end of the stroke of the second piston, the second piston is in contact with the stroke limiter 46. Thus, in the first stage of the open stroke, the first and second pistons move together. Since the flow path between the secondary pressure chamber 40 and the port 43 is past the position where the recess 41 of the first piston connects the port 43 with the central bore, the second piston is a stroke restrictor. Blocked before contacting 46. Thus, the supply of the compressed hydraulic fluid is ended shortly before the second piston is in contact with the stroke limiter, and as a result, the second piston slowly touches its stroke limiter 46.

In order to allow the secondary pressure chamber to be emptied for the closing movement, a return tube 47 provided with a check valve 44 connects the secondary pressure chamber to the tube 10.

When opening the exhaust valve, the control valve 17 supplies the high pressure fluid to the port 11, and the primary, intermediate and secondary pressure chambers are pressurized. The first and second pistons are simultaneously pressed downward by high pressure hydraulic fluid in the primary and secondary pressure chambers.

The upper portion of the first piston includes a tapered portion 48 that increases in diameter toward the upper portion of the first piston. 1 to 3, the tapered portion is intended to have a slightly outwardly curved contour, but other contours such as a truncated cone, slightly inwardly curved combination, a combination of these shapes, or any desired desired contour are possible. Do. Such appearance can be determined through test, computer simulation, or analytical methods, which indicate how wide the flow restriction should be at each position along the stroke for optimal dynamic behavior of the valve actuator. This results in a tapered portion.

The inner protruding annular flange 49 extends from the central bore just above the position where the port 36 communicates with the central bore. The tapered portion 48 together with the annular flange 49 form a narrow annular gap having a size that varies with the position of the first piston. Hydraulic fluid must be pressurized through the annular gap to flow from the intermediate pressure chamber to the primary pressure chamber. This causes a pressure drop between the intermediate pressure chamber and the primary pressure chamber. As the size of the annular gap decreases, the pressure drop increases, and the pressure drop increases gradually with the flow rate increase, thus effectively preventing the first piston from becoming high speed. The dimension of the tapered portion is such that the gap becomes smaller as it goes to the end of the open stroke. Thus, even if the supply pressure of the hydraulic liquid is relatively high, the speed of the first piston is effectively limited as it goes to the end of the stroke. The first piston is also provided with one end of the stroke shock absorber in the form of a buffer chamber 50. The flange 45 is dimensioned to fit a small gap connected to the blind buffer chamber, and when the flange enters the buffer chamber, most residual kinetic energy is absorbed by the hydraulic liquid exiting the buffer chamber through the small gap, And the lower surface of the first piston gradually contacts the stroke restrictor 51.

The first piston returns to the retracted position under the influence of the pneumatic spring. The actuator is also provided with one end of the closing movement stroke buffer in the form of a buffer chamber 52. The upper part of the piston is dimensioned to fit a small gap connected with the blind buffer chamber 52. When the top of the first piston enters the buffer chamber, most of the residual kinetic energy is absorbed and the valve slowly contacts the valve seat.

The flow resistance of the flow path between the port 36 and the primary pressure chamber 35 is adjusted by the design change of the tapered portion according to the pressure required for the primary pressure chamber 35 at each position of the first piston. . Thus, the valve actuator can be properly operated with a high pressure source having a variable pressure. If the supply pressure is relatively low, the acceleration of the valve will be slow. Thus, the electronic control device 15 keeps the valve open for a slightly longer time. As shown in FIG. 5, the electronic control device 15 adapts the timing and length to the valve opening to compensate for the pressure change in the high pressure hydraulic fluid supply. Typical valve timing for standard hydraulic fluid pressure is indicated by continuous solid lines in FIG. 5. If the supply pressure is relatively low, the electronic control device will open the valve relatively quickly and leave it open for a relatively long time to ensure that the valve is open long enough for proper evacuation of the gas in the combustion chamber (in dashed line in FIG. 5). And opposite when the supply pressure is relatively high (indicated by the broken line in FIG. 5).

The cylinder comprises an exhaust / recirculation tube 53 which connects the primary pressure chamber 35 to the bore 34. The lukewarm hydraulic fluid may be circulated through the actuator when the first piston is in an intermediate position. This is beneficial to keep the valve at operating temperature when the engine is not running, and furthermore provides effective degassing.

6 is a second embodiment of a valve actuator. This valve actuator has the same configuration in principle as the valve actuator according to the first embodiment, except that the means for changing the flow restriction of the primary fluid path between the port 11 and the primary pressure chamber 35 Is that there is. Port 36 in this embodiment is replaced with inclined port 36 '. The inclined port, together with the top, forms a flow restriction that increases when the first piston moves from the retracted position to the forward position, and before the opening stroke the primary flow path is completely blocked and no hydraulic fluid can flow into the primary pressure chamber anymore. , So the first piston and valve decelerate during the last part of the opening stroke. Hydraulic fluid flows from the port 36 'into the intermediate pressure chamber and then goes to the primary pressure chamber through a pipe 54 connecting the intermediate pressure chamber and the primary pressure chamber 35.

7 is a third embodiment of a valve actuator. This valve actuator has the same configuration in principle as the valve actuator according to the first embodiment, except that the means for changing the flow restriction of the primary fluid path between the port 11 and the primary pressure chamber 35. Is that there is. The pipe 30 is connected to a plurality of relatively narrow pipes 55 which are arranged up and down to be introduced into the intermediate pressure chamber through the port 36 ". A pressure drop occurs. During the opening stroke, the top of the first piston closes the ports 36 "one by one. Therefore, during the open stroke, the fluid resistance of the primary flow path gradually increases. The cross section of the narrow tubes 55 shown in FIG. 7 is narrowed in the direction of the open stroke. Thus, when the first piston moves to the forward position, the flow restriction in the primary fluid path gradually increases. Optionally, the tubes 55 may have the same cross section (not shown), or may have a relatively wide cross section and a flow restrictor (not shown) arranged in the tube 55.

The pneumatic spring of the embodiment described above can be replaced by a return stroke pressure chamber and a piston surface that presses the first piston into the retracted position.

In this embodiment, a slightly modified control valve will be required (not shown) capable of supplying compressed hydraulic fluid to the return stroke pressure chamber to pressurize the piston to the retracted position. The same theory as above can be used to control the pressure in the return stroke pressure chamber according to the position of the first piston.

While the invention has been described in detail for purposes of illustration, it should be understood that it is for that purpose only, and modifications may be made by those skilled in the art without departing from the scope of the following claims.

As described above, according to the present invention, there is provided a hydraulically actuated valve capable of overcoming the above problem and operable at a wide range of supply pressures generally present in a common rail for fuel injection.

1 is a cross sectional view schematically showing a cylinder of a cylinder cover and a two-stroke crosshead engine;

Figure 2 is a longitudinal sectional view of the first embodiment of the hydraulically actuated exhaust valve of the cylinder of Figure 1 with the valve closed and the first piston in the retracted position;

3 is an enlarged cross sectional view of the actuator, in which the first piston is in a partial forward position;

4 is a view like FIG. 3 showing a state in which the first piston approaches the stroke restrictor.

5 is an opening diagram for an exhaust valve at another hydraulic supply pressure.

6 is a sectional view of an actuator according to a second embodiment;

7 is a sectional view of an actuator according to a third embodiment;

Explanation of symbols on the main parts of the drawings

1. cylinder 2. air port

3. Air box 4. Exhaust valve

9. Actuator 10. Pressure tube

12. Distribution Block 13. Console

15. Control unit 19. High pressure port

Claims (9)

A hydraulic actuator for operating the valve between a closed position and an open position, the valve having a stem 24 connected with a first piston 32 disposed in a fixed housing 31 of the actuator, the valve being closed Said hydraulic actuator being in the retracted position when in the retracted position and in the forward position when the valve is open, A primary pressure chamber 35 in which pressurized fluid acts on the surface of the first piston and directs the piston to the forward position, A port 11 which can be alternately connected to a high pressure source or return line of hydraulic fluid, and A hydraulically operated valve for an internal combustion engine comprising a primary flow path between a port and a primary pressure chamber, And hydraulic means (48, 49, 36, 36 ', 36 ", 55) for varying the flow resistance of said primary flow path in accordance with the position of said first piston. 2. The hydraulically actuated valve according to claim 1, wherein the flow resistance of the primary flow path increases when the first piston (32) moves from the retracted position to the advanced position. 3. The first piston (32) according to claim 2, wherein the first piston (32) includes a tapered portion (48) forming a flow restriction with a flange (49) projecting inwardly from the housing, wherein the flow restriction is formed of a first 1 Hydraulically actuated valve, characterized in that increases when the piston moves from the retracted position to the advanced position. 4. The hydraulically actuated valve according to claim 3, wherein the tapered portion (48) is formed in a substantially truncated conical, tapered barrel, funnel or a combination thereof. 4. The tapered portion (48) according to claim 3, wherein the tapered portion (48) is shaped into an outline that provides a narrow gap between the tapered portion (48) and the flange (49) that varies in size depending on the position of the first piston. Hydraulically actuated valve. 3. The primary flow path according to claim 2, wherein the primary flow path comprises a plurality of tubes (55), which tubes open in the retracted position and, when the first piston (32) moves from the retracted position to the forward position, Hydraulically actuated valve, characterized in that the closing in turn. 3. The actuator housing 31 is provided with an inclined port 36 'which leads to the intermediate pressure chamber 37, which port 36' interacts with the first piston 32 in a first manner. A hydraulically actuated valve, characterized by forming a flow resistance that varies with the position of the piston. The method according to any one of claims 1 to 6, A second piston 42 disposed coaxially with the first piston 32 and acting on the first piston at the first stage of the stroke of the first piston in the open direction, A secondary pressure chamber 40 in which the pressurized fluid acts on the surface area of the second piston, actuating the piston in the open direction, A secondary flow path between the port 11 and the secondary pressure chamber, and And means (41) for closing said secondary flow path before said second piston reaches the end of its working stroke. 8. A stroke according to claim 1 or 7, comprising an end of a stroke shock absorber for the first piston 32 in the form of a blind buffer chamber 50, 52 into which part of the first piston enters at the end of each stroke. Hydraulically actuated valve.