WO1999017003A1

WO1999017003A1 - Control device for poppet valves for engines

Info

Publication number: WO1999017003A1
Application number: PCT/NO1998/000285
Authority: WO
Inventors: Hans Petter Hildre
Original assignee: Kvaerner Asa
Priority date: 1997-09-30
Filing date: 1998-09-29
Publication date: 1999-04-08
Also published as: AU9368198A; NO974530L; NO974530D0

Abstract

A control device for disc valves of engines, wherein the valve (14) may be held in a neutral position at a distance from its seat by means of a spring device (4). By first moving the valve (14) away from the neutral position by means of a force exerting device and then reasing it, the valve (14) may be set in an oscillating motion between a closed and an open position. According to the invention the stem (12) of the valve (14) is formed as a piston of a double acting pressure fluid actuator (2) forming the force exerting device. Cylinder spaces (24, 25) of the actuator (2) are interconnected by means of a bypass channel (18). The actuator (2) may be controlled by means of valves (34, 36) arranged in respective fluid lines which are connected with the cylinder spaces, and a shut-off valve (22) which is arranged in the bypass channel (18).

Description

CONTROL DEVICE FOR POPPET VALVES FOR ENGINES.

The invention concerns a control device for valves of engines as indicated in the introduction to claim 1.

Exhaust valves, e.g., and other mechanically controlled valves of, e.g., piston engines are usually driven directly or indirectly by means of a cam with a suitable profile. Hence a movement of the exhaust valve away from its seat is performed by the cam, while a closing of the valve is performed by means of a spring. The cam's profile is adapted to the engine concerned with regard to the valve's opening interval, time, size, etc. In other words the valve's displacement is determined by the cam profile and is independent of the engine's load, speed of rotation, etc., which is disadvantageous. There are, however, known devices where the valve activation can be variable. The valve setting or timing (opening time, opening interval, etc.) are hence dependent on the speed of rotation, the load and other factors, which can give the following advantages:

- 10 - 30% reduction in fuel consumption

- 20 - 25% reduction in NO_x emission

- 10 - 15% increase in output and torque

- Redundancy of cam shafts and other mechanical parts which are subject to wear and major stresses.

The following two types of devices are known for variable exhaust valve activation.

In the first device the exhaust valve is clamped between two springs 102, 104 as illustrated in fig. 1. The valve and the springs thus form a spring/mass oscillation device which has a fixed natural frequency during oscillation, the oscillation distance s being a sine function of the time t, as illustrated by the broken line in fig. 2. It is further illustrated by a solid line how the function is altered if a device is provided which during a certain interval secures the exhaust valve in its extreme positions. The exhaust valve's opening and closing movement within a range of movement 108 corresponds in other words to the device's natural movement which is determined by the spring stiffness and the mass. An electromagnetic device 106 is arranged to grip and secure the exhaust valve in a closed and an open position, thus enabling a variable timing to be achieved. The second device is based on the fact that a hydraulic cylinder pushes the exhaust valve away from its seat 1 10, and that a spring effects a return movement. The movement is controlled by hydraulic valves.

The device which is based on electromagnetism has clear technical limitations if the valve displacement distances and forces are large. This device, however, requires little energy, since the amount of energy which is necessary for acceleration of the exhaust valve is stored or retained in the spring system.

The device which is based on hydraulics on the other hand requires a great deal of energy, since there is provided only one spring whose spring force must be overcome by the hydraulic cylinder, and the energy which is used for acceleration of the exhaust valve is lost.

The object of the invention is to provide a device of the type mentioned in the introduction which is not encumbered by the above-mentioned disadvantages.

The characteristics of the device according to the invention are presented by the characteristic features indicated in the claims.

The invention will now be described in more detail with reference to the drawing which schematically illustrates an embodiment of a device according to the invention.

Fig. 3 is a longitudinal section through a plate valve and a control device for this.

Fig. 4 is a longitudinal view through an activator for an exhaust valve according to the invention, and components of a hydraulic system connected to the activator, with sections cut away.

In the following it should be understood that the direction towards the edge of the drawings which faces away from the reader will be designated as up.

The principle of the device is illustrated in fig. 3. Here there is shown a hydraulic actuator 2 in the form of a hydraulic cylinder which is arranged in series with a double-acting spring device 4 comprising two springs 6,8. This means that the force exerted by the spring device 4 is acting in the same directions as the force exerted by the hydraulic actuator 2. One end of the springs 6,8 is mounted in stationary sections of the engine, and the other end of the springs 6,8 influences opposite sides of a flange plate 10 which is securely connected to a stem 12 of a disc valve 14, such as an exhaust valve. This exhaust valve 14 has a valve disc 15 which is arranged to abut against a stationary seat 17 of the engine. The hydraulic cylinder's piston 16 is thereby similarly securely connected to the exhaust valve stem 12, while its cylinder part 20 is stationary relative to the engine.

The principle of the invention is that a hydraulic fluid, such as hydraulic oil, during operation of the device and in a bypass channel 18 which is provided in the hydraulic actuator's cylinder part 20, periodically flows in a short- circuited manner (bypass) between a first cylinder space 24 and a second cylinder space 25, which are located on each side of the piston 16, i.e. that the movement of the valve 14, the piston 16 and the springs 6,8, hereby corresponds to the natural movement of the spring/mass system which comprises these components. The bypass channel 18 is closed, e.g. by means of a third shut-off valve 22 when the engine is started, i.e. during an initial movement of the piston 16. Pressure oil is then brought into one of the cylinder spaces 24,25, whereby the piston 16 is moved to an extreme position and held there. The means whereby the valve is moved retardedly towards its seat 17 is hence important. Furthermore, the design of the device for gripping, securing and releasing of the exhaust valve, i.e. its control device, is important.

An embodiment of such a device is illustrated in more detail in fig. 4 where the same reference numerals as those employed in fig. 3 are used for corresponding components.

The device comprises a hydraulic pump 30 which is arranged to suck a hydraulic fluid, e.g. hydraulic oil from a reservoir 32. Hydraulic oil with increased pressure, i.e. pressure oil can flow from the pump 30 to an accumulator 33 and to a first and a second, two-position, three-port valve 36 and 34 respectively via a pipe 38. From the second valve 34 there extends a pipe 40 to the second cylinder space 25 of the cylinder 20 which faces away from the exhaust valve plate 15 (see fig. 3), there being provided in the cylinder 20 a passage 42 which is connected to the pipe 40. The pipe 40 is branched by means of a pipe 44, wherein there is provided a check valve 46 which is connected in parallel to a choke device 48, these being connected to the second cylinder space 25 via a second channel 50. The second channel 50 similarly leads into the second cylinder space 25 at a first end wall 62 thereof, while the passage 42 leads into a first cut-out 52 in the cylindrical cylinder surface, near the end surface. The bypass channel 18 leads into a second cut-out 54 which is located on the side of the first cut-out 52 which faces away from the cylinder end wall 62. The bypass channel 18 and the passage 42 have respective outlets 66 and 68 near the first end wall 62. At the upper side of the outlets 66, 68 in the upper cylinder space there are formed a first and a second circumferential edge 70 and 72 respectively.

The check valve 46 permits free flow from the first valve 34 to the cylinder space 25.

From the first valve 36 a pipe 58 extends to a first channel 60 provided in the cylinder part 20. At 69 this channel 60 leads into the first cylinder space 24 and into a second end wall 64 defining it. In the first cylinder space 24 at the lower side of the first outlet 67 of the bypass channel there is provided a third, circumferential edge 74.

The shut-off valve 22 may be a two-way, two-port magnetic valve as indicated by the ringed- in section A which is illustrated in more detail in B.

The function of the device is as follows. First of all it should be assumed that the device is in operation and that the shut-off valve 22 is open. It should further be assumed that the position of the valves 34,36 is as shown in fig. 4.

When the piston 16 is moved up during an oscillation phase, hydraulic fluid first flows freely in the bypass channel 18 through the shut-off valve 22. The pump 30 can hereby charge the accumulator 33.

When the upper section of the piston 16 reaches the second circumferential edge 70, the bypass channel is closed by the piston 16.

When the piston 16 reaches the second circumferential edge 72, the passage 42 is closed and hydraulic oil is forced through the choke device 48 before being able to flow to the reservoir 32, thus causing a retardation of the piston and the exhaust valve. The position of the circumferential edges relative to the piston's position when the valve is closed is a parameter which helps to determine the exhaust valve movement. Thus the abutment of the exhaust valve against its seat 17 occurs almost without a jolt, and the piston and thereby the exhaust valve can be secured in this position.

When the exhaust valve has to be opened, the valves 34,36 are reversed, thus enabling oil to flow from the accumulator 32 to the second cylinder space 25 via the one-way valve 46, and to press the piston 16 down. When the upper section of the piston is brought past the first circumferential edge 70, the bypass channel 18 is opened, thus enabling the movable components of the above-mentioned oscillating system to oscillate freely in a harmonic movement until the piston's lower edge passes the third circumferential edge 74. The energy from the hydraulic oil supplied from the oil pump 32 and the accumulator 33 hence compensate for frictional loss and resistance against the exhaust valve in the exhaust channel. The piston 16 may then be moved a short distance further, whereupon it is secured due to the downwardly directed force against the piston 16 which is exerted by the hydraulic oil. The valves 34,36 can then be reversed once again in order once more to move the exhaust valve to the closed position.

It will be understood that the first cylinder space 24 can be designed with circumferential edges like the edges in the second cylinder space, and that the first cylinder space 24 can also be connected to a one-way valve and a choke device (not shown).

The device according to the invention requires little energy, is extremely fast and permits the valve to abut gently against its seat. The exhaust valve's opening intervals and forces can be adapted as required. It will be understood that for this purpose the above-described control device's electrically operated valves are suited for control by a known per se electrical device, e.g. a computer which is programmed with regard to opening times etc. as a function of the engine's speed of rotation, etc.

Claims

PATENT CLAIMS

1. A control device for disc valves of engines, wherein the valve (14) comprises a stem (12) and a disc (15) which is securely connected thereto and which is arranged to abut against a seat (17), and the valve (14) is influenced by a spring device (4) which attempts to hold it in a neutral position, wherein the spring device (4) does not attempt to move the valve (14) and the valve disc (15) is located at a distance from its seat (17), and after having been moved away from the neutral position by means of a force exerting device (2), and thereafter only being influenced by the forces exerted by the spring device (4), the valve (14) is set in a periodic motion about the neutral position between a closed position and an open position, characterized in that

- the force exerting device (2) is a double-acting pressure fluid cylinder, whose piston (16) is located in an intermediate position approximately halfway between the cylinder's ends when the valve (14) is in its neutral position, and which divides the cylinder into a first and a second cylinder space (24 and 25 respectively), where supply of a pressure fluid to the first cylinder space (24) causes a movement of the valve (14) towards its closed position, which cylinder comprises - a bypass channel (18), whose first and second ends (67 and 66 respectively) lead into the first (24) and the second (25) cylinder space respectively near the respective ends of the cylinder spaces (24,25) and can be closed by the piston (16), and the bypass channel (18) can also be closed by means of a shut-off valve (22) provided therein, and - a first inlet channel (60) which by means of a reversible valve (36) alternately provides connection between the first cylinder space (24) and a pressure fluid source (32) and a fluid reservoir (32) respectively, and a second inlet channel (50) which by means of a reversible valve (34) simultaneously alternately provides connection between the second cylinder space (25) and the fluid reservoir (32) and the pressure fluid source (30) respectively, which inlet channels (60,50) lead into the respective cylinder spaces (24,25) between the ends of the cylinder spaces and the outlets (67,69) of the bypass channel (18).

2. A control device according to claim 1, characterized in that - at least the second inlet channel (50) has a check valve (48) and a choke device (46) connected in parallel thereto, where the check valve (48) permits flow towards the related, second cylinder space (25),

- the cylinder space (25) which is connected to an inlet channel (50) with check valve (48) and choke device (46) is connected to a passage (42) which is arranged to be connected to the pressure fluid source and the fluid reservoir respectively in the same way as this inlet channel (50), which passage (42) leads into the cylinder wall between the outlet of the inlet channel (50) and the outlet (68) of the bypass channel (66).

3. A control device according to claim 1 or 2, characterized in that the shut-off valves (22,34,36) are electrically operable.

4. A control device according to one of the preceding claims, characterized in that a hydraulic accumulator (33) is connected to the hydraulic pump's (30) outlet pipe (38).

5. A control device according to one of the preceding claims, characterized in that the valve stem (12) extends sealingly and axially through the pressure fluid cylinder's cylinder part and has an extended section which forms the piston (16).