NO311188B1 - Hydraulic valve control - Google Patents

Description

The present invention relates to a hydraulic control unit and a hydraulic piston pump according to the claims.

Such valve controls replace the mechanical controls with lever systems, e.g. push rods for intake and/or exhaust valves from engines. Mechanical controls undergo wear and tear on the mechanical parts of the control and must be replaced relatively often. In addition, hydraulic controls allow a change in the steering times with relatively simple means. This setting is particularly critical and complicated on engines with more than one intake and/or exhaust valve.

It is important that they e.g. two intake and exhaust valves of a cylinder open and close synchronously. With a hydraulic valve control, a so-called valve piston usually hits the valve stem, which is pressed against the valve piston by spring force.

Especially on large diesel engines, small deviations can occur during the manufacture of the valve seats in the cylinder cover and especially when grinding the valve and valve seat, which can lead to different lengths of the valve stems. The differences can be in the range of -1/+3 mm. This deviation is of the order of magnitude of the damper's immersion depth, which could lead to large deviations and differences when closing the valves. The increase in manufacturing accuracy and the reduction of manufacturing tolerances could certainly provide some improvement, but due to the costs, cannot be defended. Even then, certain differences had to be expected which would be disruptive when closing the valves.

The task of the invention is to create a hydraulic valve control unit which, under the given conditions, ensures the safe synchronous opening and closing of intake or exhaust valves.

As far as the invention is concerned, such a hydraulic valve control is described with the characteristics in claim 1. The sub-claims concern advantageous further developments of the invention. The valve control can advantageously be operated with a hydraulic piston pump and with the hydraulic line system in claim 6-7. Claims 8-9 relate to advantageous designs of the piston pump with the line system.

With the hydraulic control unit relating to the invention, two or more valves can be operated synchronously. The controls for each of the valves are in this way independent of each other, in that differences in the frictional resistance of each individual valve have no influence on the synchronisation. The difference in the length of the valve stems is equalized and changes in the lengths of the valve stems during operation are continuously compensated. The damper devices ensure that the synchronizing pistons of the hydraulic control unit and thus also the valves are set damped in the valve seats. The high alternating load with undamped impacts is avoided. This increases the service life of valve seats and valves. Furthermore, with the damped closing, the so-called irritation, i.e. the formation of indentations in the sealing surface of the valves, is also prevented. But the hydraulic control also allows extending the closing sequence of the valve in time within certain limits.

It should be noted that hydraulic pressure sources other than the hydraulic piston pump according to requirements 6-9 can also be used as control for the hydraulic valve control. For example, known hydraulic high-pressure systems under the name "Common rail system" can also fit, where high-pressure fluid from a high-pressure fluid system via electromagnetically controlled valves is supplied to the hydraulic steering and the hydraulic fluid from the hydraulic steering that flows back to the reservoir of the high-pressure fluid system is returned. When using "Common rail" systems, it is an advantage to provide a damper frame also on the front side, i.e. on the side of the steps of the synchronizing piston to dampen the impact on the cylinder cover. In another design for the "Common rail" system, damper devices can be provided for the valve pistons in the opening direction of the valves.

In the following, the invention is explained in more detail with the help of the schematic figures which show design examples for the invention. Figure 1 shows a hydraulic control unit according to the invention for operating two valves in a schematic section, Figure 2 a diagram showing the position of the valves depending on the crankshaft angle for a four-stroke engine, Figure 3 a hydraulic piston pump with a hydraulic line system for operating the hydraulic the control according to the invention, Figure 4 is a diagram, which shows the course of the valve position (upper curve) and the course of the piston position of the piston in the piston pump (lower curve) depending on the drive shaft angle or the cam angle and which illustrates the possibility of the delay of the closing course of the valve in relation to the operation of the steering pump .

Figure 1 shows a hydraulic control which relates to the invention for, for example, both intake valves 11 and 1F in a diesel engine where the valve seats 111 and 111' are incorporated into the cylinder cover 10 (only partially shown). The two stems 112, 112' each have a collar 113, respectively 113' where a valve spring 115, respectively 115' rests on each of them. The other end of the valve springs 115, 115' rests on the cylinder cover 10.

The hydraulic control for the valves 11, 11' further has a synchronizing piston 12 which is here shaped as a flow piston. Each of the steps 121 and 122 moves in a chamber 1210 and 1220, respectively. The synchronization piston 12 is shaped so that in case of displacement, there will be the same volume change in each of the chambers 1210 and 1220. As soon as the hydraulic fluid can flow back from the cylinder space 120 through the line 1200 to the hydraulic piston pump 31, the synchronizing piston 121 is pushed by the valve springs 115, 115' over the valve pistons 13, 13' and their hydraulic connecting line in the direction towards the starting position. As a result of fluid loss (gap) this may not be reached completely, so that the spring 1211 located in the chamber 1210 pushes the synchronizing piston all the way back to the starting position.

In order to prevent the synchronizing piston 12 from striking too strongly against the cylinder base 123, the end of the cylinder of the synchronizing piston 12 is shaped so that together they form a damper 124. The damper 124 inhibits the return flow of hydraulic oil to the line 1200 and thus reduces the amount of return per unit time.

The dampening of the impact of the synchronizing piston 12 against the cylinder base 123 causes the valves 11, 11' to also hit the valve seats 111, 111' dampened.

When both valve pistons 13 and 13' are the same size and the corresponding active surfaces 125, 125' on the synchronizing piston 12 are the same size, then both valve pistons 13, 13' move the same distance when moving over a certain path length. The valve stems 112, 112' are thus moved synchronously. Synchronous in the present context shall mean at the same time and with the same movement over the same length of road.

It is of course possible with other configurations of synchronizing pistons and valve pistons where the active surfaces 125, 125' of the synchronizing piston are not the same size. The essential thing is only that the displacement volumes in each chamber 1210 and 1220 for the synchronizing piston 12 are thus matched to the cylinder 130 and 130' for the valve pistons 13 h.h.b. 13' and thus also the valves 11, 11' perform the same stroke.

Through both supply lines 114, 114', the hydraulic circuit is supplied with hydraulic fluid to compensate for any losses due to leakage currents. With the one-way valves 1141 and 1141', the backflow of hydraulic oil is prevented. But the supply of hydraulic oil to the system also results in the valve pistons being in contact with the ends of the valve stems 112, 112 at all times, regardless of any different lengths (the distance from the end of the valve stem to the cylinder cover) H, respectively H' for the valve stems 112, 112' .

Other possibilities for offsetting losses in the event of an oil leak include, for example, in passing the amount of loss over a bore in the synchronizing piston 12 which connects pressure chamber 120 with chambers 1210, 1220. In order to keep the influence between the chambers sufficiently small, throttles are placed in the channels between them. In another arrangement, the boreholes, for the supply of hydraulic oil to compensate for losses due to leakage, could run in the housing and be led to each of the chambers.

Figure 2 shows an example of the sequence of opening and closing of a valve in a four-stroke diesel engine depending on the drive shaft angle. The valve is open over an angle of the main axis that lies between approx. 180° and 250°. After closing the valve, the valve 11,11' rests in the rest position, ie in the closed position R until it is opened again. The duration of the closure is then between 470° and 540° for the main axis angle. The replenishment of hydraulic oil in the system takes place through the supply lines when the valves 11,11' are in the rest position R.

The hydraulic piston pumps shown schematically in figure 3 serve to control the synchronization piston of the hydraulic control in e.g. figure 1. The device essentially consists of a piston pump 31 for transporting hydraulic oil. From this piston pump, the main line 32 with the one-way valve 321 leads to a control such as e.g. is shown in Figure 1.

The bypass line 33 overrides the one-way valve 321 and opens into the cylinder chamber 310 of the piston 31. The bypass line 34 similarly overrides the one-way valve 321 but opens into the main line 32 at both ends. In the bypass 34, the controllable valve 341 is built in, which is, for example, connected via the compressed air connection 342.

The controllable valve 341 could also be a hydraulic, electromagnetic or other controllable valve. The bypass line 34 can be omitted when, for example, the one-way valve 321 in the main line can be blocked in the open state.

The supply line 35 serves for the supply of hydraulic fluid which is missing in the hydraulic system due to leaks. It has a one-way valve 351. Excess hydraulic oil can again be returned through bypass 352 to the supply line. The piston of the piston pump 31 becomes e.g. operated with a comb (not shown).

In what follows, the function and operation of the hydraulic piston pump with the line system 3 is explained.

The control pressure in the control line 342 is switched on. During the transport stroke of the pump piston 311, the following takes place: After completion of 3512 with the piston 311, the hydraulic fluid is transported over the road 33, 32 34 to the hydraulic control for the valve operation. Later, the connection 332 to the bypass 33 is closed, the flow of hydraulic oil continues over 32 and 34.

During the downward stroke of the pump piston 311, the following takes place: Through the non-return valve, the main line 32 is closed. Bypass 33 is still closed by piston 311 above bore 332. But bypass 34 is open and the closing movement of the controlled synchronizing piston follows piston 311. The process is shown in the upper part of Figure 4 with the solid curve 41.

The control pressure in the control line 342 is switched off, i.e. the bypass 34 is closed. During the transport stroke of the pump piston 311, the following takes place: After the completion of 3512 with the piston 311, the hydraulic fluid is transported over the path 33, 32 to the hydraulic control of the valve operation. Later, the connection 332 to bypass 33 is closed, the flow of hydraulic oil continues over 32.

During the downward stroke of the pump piston 311, the following takes place: Through the non-return valve, the main line 32 is closed. Bypass 33 is closed by the piston 311 above the bore 332. Bypass 34 is likewise closed. The controlled hydraulic synchronization piston 121 does not follow the piston 311 as long as the connection 332 to the bypass 33 from the piston 311 is closed. The piston 311 thus moves downwards, initially without the valves opened by the synchronizing piston 12 (figure 1) moving. The course of the closing curve is shown in the upper part of figure 4 with the dashed line 42.

The increase in the system volume is compensated by the supply of hydraulic fluid through the supply line 35. As a rule, a pressure of e.g. to 8 bar in the supply line is sufficient. As soon as the piston 311 begins to open the bore 33! there is a return flow through bypass 33. Valve closing movement now begins and is controlled by the downward movement of piston 311. Near the downward turning point of piston 311, bore 3512 is opened. The closing movement takes place n "uncontrolled". To prevent a hard closing of the valves, the damper 124 on the synchronizing piston now comes into action (figure 1).

The closing course 42 of the valve is drawn dotted in Figure 4. The curve 40 in the lower diagram in Figure 4 shows the course of the stroke of the piston 311 in a device according to Figure 3. The point 44 on the lower curve 40 which shows the course of the movement of the pistons 311 above the main shaft angle, corresponds to the position of the piston 311, where on return to the piston 311 releases the bore 332, so that hydraulic oil can flow back. Now the closing sequence of the valves 11, 11' must begin, before this position 44 of the stem point is reached, then this can be achieved with the opening of the valve 341.

The hydraulic control 1 is suitable for two or more valves 11, 11' in an engine cylinder, especially the intake valves 11, 11' or the exhaust valves of a diesel engine. A hydraulic synchronizing piston 12, 121 has for each valve to be controlled a control chamber 1210, 1220, which controls a valve piston 13, 13' for each valve 11, 11' to be controlled, so that the valve pistons 13, 13' move synchronously o with the same stroke. A damping device 124 damps the return of the synchronizing piston 12 to its initial position. With a hydraulic device 1, the differences in the length H, H' of the stems 112, 112' of the valves 11, 11' were equalised.

Claims (10)

1. Hydraulic control unit (1) for two or more valves (11, 11') in an engine cylinder, in particular the intake valves of a large diesel engine, characterized in that a hydraulic synchronizing piston (12, 121) for each driven valve (11, 11') has an operating chamber (1210, 1220) with a separate valve piston (13, 13') for each driven valve (11, 11') so that the valve pistons (13, 13') move synchronously, that a damping device (124) is arranged to to dampen the return movement of the synchronizing piston (12) and the valves (11, 11') to the initial position, and that a hydraulic device (1) is arranged to compensate for the differences in length (H, H') of the stems (112,112') which are controlled with the hydraulic control unit (1) with two or more valves (11, 11'). 2. Hydraulic control unit (1) according to claim 1, characterized in that the damping device for damping the return movement of the synchronizing piston (12) has a device for reducing (124) the flow cross-section of the back-flowing hydraulic control means. 3. Hydraulic control unit (1) according to claim 2, characterized in that the device (124) for reducing the flow cross-section is formed by the shape on the control side of the synchronization piston (121) and the wall of the piston cylinder. 4. Hydraulic control unit (1) according to the preceding claim, characterized in that the hydraulic device for compensating the difference in the lengths (H, H') has a feeding device (114, 114') for hydraulic fluid. 5. Hydraulic control unit (1) with a control piston for the forward and return stroke of the synchronization piston in a hydraulic control unit according to the preceding claim, characterized in that with a hydraulic coupling device (3) for delaying the return movement of the synchronization piston (12) to the starting position, compared to the return movement to the steering piston (311) to its initial position and thereby the return flow of the hydraulic fluid to the cylinder space (310) in the cylinder of the steering piston (311). 6. Hydraulic piston pump (31) for the control of a hydraulic control unit according to the preceding claim, characterized in that it comprises a hydraulic piston pump for operating the synchronization piston (12, 121), a hydraulic line system (32, 33, 34, 35, 352) for the forward and backward movement of hydraulic fluid with the piston pump (31) for forward and backward control, with a main line (32) with a one-way valve (321) that prevents the backflow of fluid to the pump cylinder (310) and with a bypass line (34) with a switchable valve (341) that overrides the one-way valve (321) in the main line (32), and also with a side forward and reverse line (33) that similarly overrides the one-way valve (321) in the main line (32) and which through the cylinder wall (332) to the hydraulic piston pump (31) opens into the cylinder chamber (310) of the piston pump (31). 7. Hydraulic piston pump (31) for the control of a hydraulic control unit according to claims 1-5, characterized in that it comprises a hydraulic piston pump for operating the synchronization piston (12, 121), a hydraulic line system (32, 33, 34, 35, 352 ) for the reciprocation of hydraulic fluid with the piston pump (31) for reciprocating control, with a main line (32) with a one-way valve (321) which can optionally be held in the open position, and which prevents the return flow of liquid to the pump cylinder (310 ) in the unblocked state, and a side-forward and return line (33) which overrides the one-way valve (321) in the main line (32) and which through the cylinder wall (332) of the hydraulic piston pump (31) empties into the cylinder chamber (310) to the piston pump (31). 8. Hydraulic piston pump (31) according to claims 6-7, characterized in that the supply device (35, 352) for hydraulic fluid from and to a reservoir with a supply line (35) with a one-way valve (351) which prevents backflow of hydraulic fluid to the reservoir and with a forward and backward line (352) which overrides the supply line (35) and which opens in the area of the lower turning point in the cylinder chamber (310, 3512) of the piston pump (311). 9. Hydraulic piston pump (311) according to claim 8, characterized in that the supply line (35) opens out in the area at the upper turning point in the cylinder space (310), that the forward and return line (352,3512) opens out in the area at the lower turning point in the cylinder space (310), and the side-forward and return line (33) from the hydraulic control unit opens at a height located in between (332) in the cylinder space (310). 10. Large diesel engines with a hydraulic control unit (1) for cylinder intake (11, 11') or exhaust valves according to the preceding claim.