CN1160120A - Hydraulic valve drive - Google Patents

Abstract

The hydraulic drive device (1) is suitable for the situation that there is a valve on an engine cylinder, especially suitable for the situation of the intake valve (11, 11') or the exhaust valve of a large diesel engine. The hydraulic synchronous piston (121, 122) has a corresponding drive chamber (1210, 1220) for each valve to be driven, and this synchronous piston drives the valve of a corresponding valve (11, 11') to be driven in such a way. The pistons (13, 13'), ie the valve pistons (13, 13') move synchronously and have the same stroke. A damping device (124) dampens the return movement of the synchronization piston (12) to the initial position. The hydraulic device (1) enables the compensation of differences in the projecting lengths (H, H') of the shafts (112, 112') of the valves (11, 11').

Description

Hydraulic valve actuator

The invention relates to a hydraulic valve drive according to the preamble of independent claim 1 .

Such a valve drive can be used instead of a mechanical drive with a lever system, for example with pushrods on the intake and/or exhaust valves of the engine. Mechanical drives tend to cause wear to the mechanical parts of the device necessitating rather frequent readjustments. And hydraulics can change the control time in a fairly simple way. This adjustment is particularly critical and delicate for engines having more than one intake and/or exhaust valve.

For example, for a cylinder with two intake and/or exhaust valves, it is important that both valves open and close synchronously. In hydraulic valve actuators, the so-called valve piston (Valve piston) generally collides with the valve shaft (shaft of the valve), because the valve shaft is pressed against the valve piston by spring force.

Especially for large diesel engines, there may be slight discrepancies when manufacturing the valve seats on the cylinder cover, especially during the grinding of the valves and valve seats. This difference can result in a difference in valve shaft extension. These differences may be in the range of plus or minus a few millimeters. Usually these differences are almost always between -1/+3mm. These deviations are of the order of the immersion depth of the damper, which can lead to large deviations and differences in valve closing. Improved machining accuracy and reduced machining tolerances might improve this, but cannot be considered cost-effective due to the manufacturing costs involved. Even so, some annoying discrepancies have to be expected in the valve closure process.

The object of the present invention is to create a hydraulic valve actuating device which can ensure reliable and synchronous opening and closing of either the intake valve or the exhaust valve under given conditions.

According to the present invention, such a hydraulic valve driving device has the following characteristics: it has a synchronous piston, and for each valve to be driven, there is a driving chamber and a valve piston hydraulically driven by the driving chamber, so that the valve The pistons move synchronously, and in order to buffer the movement of the synchronous piston and the valve back to the initial position, a buffer device is also provided. In addition, there is a hydraulic device to compensate the difference in the extension length of the shaft rods of two or more valves. The above The valves are actuated by hydraulic drives. All dependent claims relate to some further advantageous developments of the invention. The valve drive is conveniently driven by a hydraulic piston pump with hydraulic piping system.

The hydraulic driving device according to the present invention can push two or more valves synchronously. The actuation of the individual valves is independent of each other in the sense that differences in the frictional resistance of the individual valves have no effect on synchronization. Differences in the stem extension lengths of the individual valves can be compensated, and changes in the stem extension lengths of the individual valves during operation can also be continuously corrected. The damping device ensures that the synchronous pistons of the hydraulic drives, and thus the valves, come into contact with the valve seat in a damped manner. Unbuffered large pulsating shock stresses can be avoided. This increases the service life of the valve and valve seat. In addition, so-called pitting, ie pitting that forms on the sealing surface of the valve, can also be prevented with a cushioning device. However, the hydraulic drive device can also temporarily delay the sealing process of the valve within a certain limit.

It should be noted that in addition to the hydraulic piston pumps mentioned, other sources of hydraulic pressure are suitable for the hydraulic valve actuators. For example, a hydraulic high-pressure system known as a "common rail system" is also suitable, in which high-pressure fluid is fed from the high-pressure fluid system to the hydraulic drive unit through a solenoid control valve, and the hydraulic fluid is fed from the hydraulic drive unit. Return to the reservoir of the high pressure fluid system. The use of the "common oil pipe system" also facilitates the installation of the buffer device at the front end, that is, the end where the diameter of the synchronizing piston changes, so as to reduce the impact on the cylinder head. In the different configurations of the "common oil supply system", a damping device can be provided for the valve piston in the direction of the opening of the valve.

In the following the invention will be described in more detail with reference to the schematic diagrams showing some exemplary embodiments of the invention. They are briefly introduced as follows.

Fig. 1 is a schematic cross-sectional view of a hydraulic drive device for driving two valves according to the present invention.

Figure 2 is a graph showing the relationship between valve position and crankshaft angle for a four-stroke engine.

Fig. 3 is a hydraulic piston pump with a hydraulic pipeline system for operating a hydraulic driving device according to the present invention.

Figure 4 graphically shows the valve position (upper curve) and piston pump piston position (lower curve) as a function of crankshaft angle and eccentric angle as a function of the valve closing process delay relative to the driving pump operation process possibility.

FIG. 1 shows a hydraulic drive according to the invention, for example, of two intake valves 11, 11' of a diesel engine. The valve seats 111 and 111' are machined on the cylinder head 10 (only a part is shown). Both shafts 112 and 112' each have a corresponding collar 113 and 113' against which a corresponding spring 115 and 115' bears. The other ends of the valve springs 115 and 115 ′ are supported on the cylinder head 10 .

The hydraulic drive of the valves 11 and 11' also has a synchronizing piston 12, which here is designed as a stepped piston. Piston segments 121 and 122 of different diameters move in corresponding bores 1210 and 1220, respectively. The purpose of making the synchronizing pistons in a stepped form is to make the volume changes in each chamber 1210 and 1220 always equal when the pistons move. As long as the hydraulic fluid can flow from the cylinder space 120 back to the hydraulic piston pump 31 through the line 1200, the synchronizing piston 121 will be pushed to the initial position by the valve springs 115, 115 through the valve pistons 13, 13' and their hydraulic connection lines. It is likely that the original position cannot be reached again due to liquid loss (clearance), but the spring 1211 installed in the chamber 1210 can still fully push the synchronizing piston 12 back to its initial position.

In order to prevent the synchronizing piston 12 from striking the cylinder bottom 123 too hard, the cylinder bottom of the synchronizing piston 12 and the end of the synchronizing piston 12 are shaped such that they together form a buffer 124 . The buffer 124 hinders the return flow of hydraulic oil into the pipeline 1200, thus reducing the return flow per unit time.

The damping of the impact of the cylinder bottom 123 by the synchronization piston 12 also results in a damping of the impact of the valve seats 111 and 111' by the valves 11 and 11'.

If the two valve pistons 13, 13' are of equal size and the corresponding active areas 125, 125' of the synchronizing piston 12 are also of equal size, when the synchronizing piston moves over a given path, the two valve pistons 13, 13' also move the same distance. Valve shafts 112 and 112' also move synchronously in this way. In the sense of this text, "synchronous" is used to mean "moving the same distance simultaneously and in the same way".

Of course, other synchronizing piston and valve piston configurations are possible in which the active areas 125, 125' of the synchronizing piston are different in size. It is only important that the displacement volume of one chamber 1210 or 1220 of the synchronizing piston 12 should match the displacement volume of the corresponding valve piston 13, 13' in the corresponding cylinder 130, 130', so that the corresponding valve piston 13, 13', The corresponding valves 11, 11' thus also have the same stroke.

In order to compensate possible losses due to leaks, the hydraulic line can be supplied with hydraulic fluid via two supply lines 114 and 114'. The one-way valves 1141 and 1141' are used to prevent the hydraulic oil from flowing back. In any event, feeding hydraulic oil into the system also has the following consequence: The valve piston is always in contact with the end of the valve shaft 112, 112' and extends the length of the valve shaft 112, 112' (from the valve shaft end The distance from the top to the cylinder head) H, H' is irrelevant for any differences that may exist.

Another possibility for compensating the loss of oil caused by leakage is to introduce a lost amount of oil, for example, through a small hole in the synchronizing piston 12 , which connects the pressure chamber 120 with the chamber bores 1210 , 1220 . In order to make the influence between the chambers sufficiently small, some choke apertures are provided in the passage between them. In a different arrangement, the bores for the supply of hydraulic oil for compensating leakage may open through the housing to the chambers.

Figure 2 shows the relationship between valve opening and closing and crankshaft angle in a four-stroke diesel engine. The valve is open when the crank angle is approximately between 180° and 250°. After the valve is closed, the valve 11, 11' remains in the rest state, or closed state R, until it is opened again. Its closing period is thus between 470° and 540° of crank angle. If the valves 11, 11' are in the rest state R, the hydraulic oil is replenished into the system via the supply line.

A hydraulic piston pump with a piping system 3 is schematically drawn in FIG. 3 . It can be used to drive, for example, the synchronized pistons of the hydraulic drives shown in Figure 1. The device is essentially composed of a piston pump 31 for delivering hydraulic oil. A main line 32 with a non-return valve 321 leads from this piston pump to the drive, as shown in FIG. 1 .

The bypass line 33 is connected across both sides of the one-way valve 321 to discharge the hydraulic oil into the cylinder space 310 of the piston pump 31 . The bypass line 34 is also connected across both sides of the one-way valve 321 , and the hydraulic oil is discharged into the main line 32 from both ends. A switchable valve is provided in the bypass 34, which can be switched, for example, by a compressed air line 342.

The reversing valve 341 may also be a hydraulic, electromagnetic or other reversing valve. The bypass line 34 can be activated if the one-way valve 321 in the main line is likely to be blocked in the open state.

Supply line 35 is used to supply hydraulic fluid lost due to leakage losses in the hydraulic system. The pipeline includes a one-way valve 351 . Excess hydraulic oil can be returned to the supply line through bypass 352 . The pistons of the piston pump 31 can be driven, for example, by an eccentric (not shown).

The effect and mode of operation of the piston pump with the piping system 3 is explained below.

Assume that the control pressure in the control line 342 is opened. During the delivery stroke of the pump piston 311 the following will happen: After 3512 is closed by the piston 311, the hydraulic fluid will then be delivered via the paths 33, 32, 34 to the hydraulic drive to drive the valve. Afterwards, the connection port 332 of the bypass 33 is closed and the hydraulic fluid continues to flow through 32 , 34 .

During the downward stroke of the pump piston 311 the following happens: The main line 32 is closed by the non-return valve. The bypass 33 is still closed by the piston 311 blocking the hole 332 . However, the bypass 34 is open and the closing movement of the driven synchronous piston follows the closing movement of the piston 311 . This movement is indicated by the solid line 41 in the upper part of FIG. 4 .

Assuming that the control pressure in the control line 342 is shut off, this means that the bypass 34 is closed. On the exhaust stroke of the pump piston 311 the following will occur: After the piston 311 closes 3512, hydraulic fluid is delivered via paths 33, 32 to the hydraulic drive to drive the valve. Afterwards, the connection port 332 of the bypass 33 is closed, and the hydraulic oil can continue to flow through the path 32 .

During the downward stroke of the pump piston 311 the following situation will occur: the main circuit 32 is closed by the check valve. The bypass 33 is also closed by the piston 311 blocking the hole 332 . Bypass 34 is also closed. As long as the connection port 332 of the bypass 33 is closed by the piston 311 , the driven hydraulic synchronization piston 121 does not follow the movement of the piston 311 . Thus, when the piston 311 moves downwards, initially the valve ( FIG. 1 ) is not opened by the movement of the synchronized piston 12 . The curve of the closing process is shown by dashed line 42 in the upper part of FIG. 4 .

The increase in system volume is equalized by the hydraulic fluid supplied by supply line 35 . Usually, a small low pressure, eg 3-10 bar, in the supply line is sufficient. Once the piston 311 begins to open the hole 332, a reverse flow (revese flow) begins via 33. The valve closing movement is now also initiated and is controlled by the downward movement of the piston 311. Near the lower turning point of the piston 311, the hole 3512 is opened. The closure motion will now still continue "without control". In order to avoid a violent impact on the valve, the damper 124 on the synchronizing piston works at this moment (FIG. 1).

The closing movement of the valve is indicated by dashed line 42 in FIG. 4 . In the lower figure of Fig. 4, curve 40 has shown the course of stroke (the course of the stroke) by the piston 311 of device shown in Fig. 3. The point 44 on the lower curve 40 corresponds to the position of the piston 311 in which, during the reverse movement, the piston 311 releases the bore 332 so that hydraulic oil can flow back. This curve 40 plots the course of motion of the piston 311 as a function of the crankshaft angle. If the closing process of the valves 11, 11' starts before the piston reaches this position 44, the return flow of hydraulic oil can be realized by opening the valve 341.

The hydraulic drive device 1 is suitable for the situation where there are two or more valves 11, 11' on one engine cylinder, especially for the situation of intake valves 11, 11' or exhaust valves of a large diesel engine. The hydraulic synchronous pistons 12, 122 have a drive chamber 1210, 1220 for each valve to be driven, and they respectively drive the piston 13, 13' of a corresponding valve 11, 11' to be driven, so that the valve pistons 13, 13' are synchronized Earth moves and has the same stroke. The buffer device 124 buffers the return movement of the synchronization piston 12 to the initial position. The use of the hydraulic device 1 makes it possible to compensate for differences in the extension lengths H, H' of the shafts 112, 112' of the valves 11, 11'.

Claims (10)

1. be used for plural cylinder valve, the fluid pressure drive device of the air intake valve of especially big diesel engine (1), it is characterized in that: it has synchronous piston (12,122), for each valve to be driven 11,11 ' all have an actuator chamber (1210,1220) and are driven the hydraulically powered valve piston in chamber (13,13 '), can make valve piston (13 like this, 13 ') be synchronized with the movement, and for the motion that makes synchronous piston (12) and valve (11,11 ') return initial position obtain the buffering, also be provided with a damping device (124), in addition, also have a hydraulic pressure installation (1) to compensate the axostylus axostyle (112 of two or more valves (11,11 '), 112 ') extrusion (H, H) difference, above-mentioned valve (11,11 ') is driven by fluid pressure drive device (1).

2. according to the described fluid pressure drive device of claim 1 (1), it is characterized in that: the damping mechanism that is used to cushion the return movement of synchronous piston (12) has the device (124) of the liquid stream cross section of a hydraulic driving fluid that reduces to return.

3. according to the described fluid pressure drive device of claim 2 (1), it is characterized in that: the device (124) that reduces liquid stream cross section is to be made of the driving side (drive side) of synchronous piston (121) and the shape of piston-cylinder wall.

4. according to each described fluid pressure drive device (1) among the claim 1-3, it is characterized in that: compensation extrusion (H, the hydraulic pressure installation of difference H ') (hydraulic device) has the feeding means (114,114 ') (feeding device) of a hydraulic fluid.

5. according to each described fluid pressure drive device (1) of claim 1-4, it is characterized in that: it has one makes the reciprocating driven plunger of synchronous piston, also has a hydraulic switch device (3), it can be used to postpone the motion that synchronous piston (12) returns initial position, this delay is the motion of returning its initial position with driven plunger (311), thereby is back to hydraulic fluid just that the motion of the cylinder space (310) of driven plunger (311) compares.

6. according to the described hydraulic piston pump (31) that is used for the primer fluid hydraulic driver of one of claim 1-5, it is characterized in that: it has

A pipe-line system of being made up of hydraulic pipe line (32,33,34,35,352), these pipelines are used between reciprocating pump (31) and drive unit delivering hydraulic fluid back and forth,

Main line (32), this one-way valve with one-way valve (321) can prevent fluid flow back to the cylinder of pump (310) and

Bypass (34) with change-over valve (341) of one-way valve (321) both sides that are connected across main line (32) in addition, also has

Supply and return pipeline (33) for one second, it also is connected across one-way valve (321) both sides of main line (32), and by the connection mouth on the cylinder wall of hydraulic piston pump (31) (332) hydraulic oil is entered cylinder space (310).

7. according to the hydraulic piston pump (31) of the described promotion fluid pressure drive device of one of claim 1-5, it is characterized in that: it has:

One is used between reciprocating pump (31) and drive unit the hydraulic plumbing system of delivering hydraulic fluid (32,33,35,352) back and forth,

Main line (32) with an one-way valve (321), one-way valve can remain on open mode selectively, simultaneously it can prevent fluid reflux to the pump cylinder (310) that is in open state (in unblocked state) and

Second supply and a return pipeline (33) that is connected across one-way valve (321) both sides on the main line (32), it enters fluid by the connection mouth on the cylinder wall of hydraulic piston pump (31) (332) cylinder space (310) of reciprocating pump (31).

8. according to claim 6 or 7 described hydraulic piston pumps (31), it is characterized in that: it has:

A feeding means (35,352), it is used for a hydraulic fluid with taking-up in the liquid receiver with to wherein entering.

A feed line (feeding line) (35), be equipped with on it one prevent hydraulic fluid be back to the one-way valve of liquid receiver (reservoir) (351) and

Supply and return pipeline (352), it is in parallel with the one-way valve (351) on the feed line (35), and near rollback point down, it drains into fluid by interface (3512) cylinder (310,3512) of reciprocating pump (311).

9. according to the described hydraulic piston pump of claim 8 (311), it is characterized in that: feed line (35) is discharged hydraulic fluid inlet casing space (310) near last rollback point, supply and return pipeline (352,3512) they are near the rollback point fluid to be entered cylinder space (310) down, and

Second of fluid pressure drive device is supplied with and return pipeline (33) is last, on the height between the following rollback point hydraulic fluid is entered cylinder space (310).

10. according to the described big diesel engine of one of claim 1-9, it is characterized in that: the drive unit (1) that all has a cylinder intake valve (11,11 ') or drain tap.

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