Patent Application
20100101662
The invention relates to a control block provided with a plurality of control block elements in each of which a valve arrangement for controlling an associated hydraulic consumer is provided.
In the document DE 100 35 575 A1 an LS control block is described in which a variable displacement pump is adjusted in response to the maximum load pressure of the actuated hydraulic consumers such that the pump pressure is above the maximum load pressure by a predetermined pressure difference Δp. The pressure medium flows to the hydraulic consumers via adjustable metering orifices at directional valves disposed between a feed line outgoing from the variable displacement pump and the hydraulic consumers. Individual pressure-maintaining valves by which a constant pressure difference is given via the metering orifices irrespective of the load pressures of the hydraulic consumers in the case in which a sufficient amount of pressure medium is supplied by the variable displacement pump are allocated to the directional valves. Thus, the amount of pressure medium flowing to the hydraulic consumer is merely dependent on the orifice cross-section of the respective metering orifice. The pressure-maintaining valves are pressurized in the opening direction by a spring and by the pressure downstream of the respective metering orifice and in the closing direction by the pressure upstream of the respective metering orifice.
When a respective control block according to the state of the art is employed in a truck-mounted concrete pump, the case may arise that in a hydraulically controlled concrete pump the concrete spreader boom is not actuated for a rather long period of time and consequently no pressure medium flows to the control disks for the hydraulic consumers of the spreader boom. The control disks for the spreader boom cool down to the ambient temperature, while the pressure medium flowing in the control block and used for driving the concrete pump has an increased temperature. If a valve provided in a control disk for a segment of the spreader boom is actuated, the hot pressure medium flows into the control disk for the respective spreader boom segment. The slide valve in the control disk is heated, while the housing of the control disk initially has an ambient temperature which may be very low in winter. For instance, the temperature of the pressure medium flowing in the control block is 100° C., while the ambient temperature and consequently the temperature of the portion of the control block housing through which no hot pressure medium is flowing amounts to approximately 10° C. By virtue of such difference in temperature, the slide valve may stick in the housing of the control block.
There is provided a control block comprising a plurality of control block elements each of which includes a valve arrangement for the control of a respective hydraulic consumer, the control block having an oil channel through which oil flows for controlling the temperature of at least one control block element independently of the control of the valve arrangement. Thus, even if a valve disk of the control block has not been actuated for a long time, heating of said valve disk can be ensured so that upon actuation of a valve sticking of the slide valve is prevented.
It is preferred that the oil flow is substantially constant, as in this way uniform heating of the valve housing can be ensured.
It is further preferred that a nozzle is disposed in the oil channel, wherein the nozzle may also be formed by the narrow passage itself or by a constriction of the passage.
It is moreover preferred that a constant pressure difference is provided above the nozzle. This is realized especially by providing a pressure relief valve between the feed line and the control oil supply passage. By the constant pressure difference formed a constant volume flow of hot oil through the valve housing can be ensured.
In a further development the nozzle is provided in a terminal element of the control block so that a flow through the valve disks located between the input element and the terminal element can be ensured.
The nozzle is preferably disposed in a terminal member of the control block having components for the control oil supply so that a compact design can be imparted to the control block.
In a preferred embodiment the nozzle is provided between a passage pressurized by pump pressure and a low-pressure passage. Passages pressurized by pump pressure frequently have a large cross-section so that a large heat-exchange area is provided.
Furthermore, it is preferred that the nozzle is disposed between a control oil supply passage and a low-pressure passage. In this way, a pressure loss due to the oil flow for heating can be kept at a low value.
The nozzle may also be provided between a control oil supply passage and a tank passage for the working pressure medium. By virtue of the large diameter of the tank passage a uniform heating can take place.
In a further development, the nozzle is formed between a control oil supply passage and a passage for outgoing control oil which is substantially under atmospheric pressure so that no additional passage is required for heating the valve housing.
In an embodiment the nozzle is disposed between an auxiliary passage connected to a pump connection of the control block when the main pump passage is blocked and a low-pressure passage so as to ensure heating of the valve housing even when the main pump passage is blocked.
Hereinafter the invention is illustrated by way of schematic drawings, in which:
A pump port P, a tank port T and a load-sensing port LS by which the maximum load pressure of the hydraulic consumers controlled by the control block can be tapped off are disposed at the input disk 2. Pressure medium is supplied to the control block from a hydraulic pump not shown in
Further, in the input disk 2 a pressure limiting valve 82 is arranged between the pump port P and the tank port T so that the pressure prevailing in a feed line 42 connected to the pump port P cannot exceed the pressure adjusted at the pressure relief valve 82. A shuttle valve 40 disposed in the input disk 2 is in pressure fluid communication with shuttle valves 36, 38, 39 of the directional valve disks 8, 10, 12 so that the maximum load pressure is applied to the load-sensing port LS of the input disk. For the pressure fluid communication between the shuttle valve 40 in the input disk and the shuttle valve 38 in the directional valve disk 8, a connecting passage 41 is disposed in the terminal disk 6 arranged at the side of the directional valve disk 8 opposed to the input disk 2.
The directional valve disks 8 and 12 include respective directional valves 14, 18, the control pistons of which are adjustable by associated pressure limiting valves, and an associated pressure-maintaining valve 21, 22. The pressure-maintaining valves 21, 22 are pressurized in the opening direction by a pressure spring 32, 34 and the pressure downstream of the respective metering orifice formed at the directional valve 14, 18 and in the closing direction by a control pressure upstream of the respective metering orifice. The maximum load pressure of all simultaneously actuated hydraulic consumers is tapped by the shuttle valves 36, 38 and 39 of the directional valve disks 8, 10 and 12 and the shuttle valve 40 and is transmitted to the pump. The variable displacement pump, not shown in
The feed line 42 hydraulically connected to the pump port P of the input disk 2 passes pressure fluid to the input of the pressure-maintaining valve 22 which can use the pressure fluid through the directional valve 14 to control a hydraulic consumer via working ports A1 and B1.
The directional valve disk 10 includes a directional valve 54 through which the pressure fluid communication can be switched from the feed line 42 to a working port A3 or a working port B3 and a feed line 44 which is in fluid communication with the working port B3. No pressure-maintaining valve is arranged upstream of the directional valve 54.
The feed line 44 adapted to be hydraulically connected to the pump port P of the input disk 2 via the directional valve disk 10 passes pressure medium to the input of the pressure-maintaining valve 21 which can use the pressure fluid via the directional valve 18 to control a hydraulic consumer via working ports A9 and B9.
Moreover, a discharge passage 46 connected to the tank port T at the input disk 2 passes through the directional valve disks 8, 10, 12, extends into the control oil supply disk 4 and is part of a discharge path through which pressure fluid can flow back from the discharge ports T of the directional valves 14, 18, 54 to the tank port T in the input disk 2.
In the idle position of the directional valve 54 of the directional valve disk 10 shown in
In the control oil supply disk 4 connected to the directional valve disk 12 a filter 68, a pressure relief valve 70, a pressure relief valve 70, a pressure limiting valve 72 and a nozzle 78 are formed. The pressure fluid communication between the feed line 44 extending in portions in the control oil supply disk 4 and the filter 68 the discharge port of which is connected via a pressure relief valve 70 to the control oil supply passage 66 extending in the input disk 2 and the directional valve disks 8, 10, 12 is blocked by a plug 67. A pressure limiting valve 72 is provided between the control oil supply passage 66 and a control oil tank passage 64 extending in the input disk 2 and the directional valve disks 8, 10, 12. In the spring-biased pressure chambers of the pressure relief valve 70 and the pressure limiting valve 72 the pressure is prevailing in the control oil tank passage 64, whereas in the control chambers of the pressure relief valve 70 and the pressure limiting valve 72 acting in opposite direction the pressure is applied to the control oil supply passage 66. The pressure relief valve 70 controls a fixed control oil supply pressure in the passage 66. The pressure limiting valve 72 has a safety function. The fixed pressure is 30 bars, for instance.
A load-sensing line 74 connected to the shuttle valve 36 of the shuttle valve cascade in the control oil supply disk 4 is connected to the discharge passage 46. Thus, the tank pressure is applied to the load-sensing line 74 and, consequently, to an input of the shuttle valve 36 of the directional valve disk 12.
In the first embodiment of the present invention an oil channel 76 including the nozzle 78 is disposed between the control oil supply passage 66 and the discharge passage 46 in which substantially tank pressure is prevailing. Furthermore, in the input disk 2 and in the directional valve disks 10 and 12 as well as in the control oil supply disk 4 an auxiliary passage 80 is formed which, on the one hand, is in pressure fluid communication with the feed line 42 and, on the other hand, is connected to the input port of the filter 68. Oil flows through said auxiliary passage 80, independently of whether the directional valve 54 is actuated in the directional valve disk 10, from the feed line 42 via the filter 68 and the pressure relief valve 70 to the control oil supply passage 66 and from there via the oil channel 76 including the nozzle 78 to the discharge passage 46. Thus, independently of whether the feed lines 42 and 44 are interconnected via the directional valve disk 10, pressure medium flows in the directional valve disks 10 and 12 and heats the latter. The directional valve disks are also heated due to the pressure medium flow in the discharge passage 46. This has the advantage that, by virtue of the large diameter of the discharge passages 46 in the control block 1, good heat transfer can take place from the oil to the housing of the control block. As a result, the control piston of the directional valve 18 can be prevented from sticking.
The auxiliary passage 80 is not provided in the directional valve disks solely for an oil flow passing through the same to heat the directional valve disks. A corresponding passage is also recognized in the directional valve disk 8. There it serves for applying the load pressure from the terminal disk 6 to the one input of the shuttle valve 40 of the input disk 2. In general, the passage 80 in the directional valve disks serves for applying, even in the case of plural directional valve disks arranged between the one side of the input disk 2 and a terminal disk 6, the maximum load pressure of hydraulic consumers simultaneously actuated by said directional valve disks which is selected via shuttle valves of said directional valve disks to the one input of the shuttle valve 40.
Oil flows from the auxiliary passage 80 in the directional valve disks 10 and 12 via the filter 68, the pressure relief valve 70 and the nozzle 78 into the discharge passages 46 in which tank pressure is prevailing. Since the pressure relief valve adjusts a particular pressure in the control oil supply passage 66 located upstream of the nozzle 78, the pressures upstream and downstream of the nozzle 78 and thus the pressure difference across the nozzle are constant. That is to say, the oil flow for heating the directional valve disks 10 and 12 is constant and does not depend on the pump pressure. The oil flow can be adjusted by appropriately selecting a nozzle 78 having a particular flow cross-section. However, a precondition for a constant oil flow for heating is the plug 67 that prevents the oil from flowing from the auxiliary passage 80 through the feed line 44 and the non-actuated directional valve 54 to the tank port T of the input disk 2. Without the plug 67 the oil flow provided for heating the directional valve disks 10 and 12 would be dependent on the pump pressure.
Through the auxiliary passage 80 not only the oil flowing off through the discharge passages 46 and heating the directional valve disks 10 and 12 but also the oil removed from the control oil supply passage by the pilot valves for controlling the directional valves flows to the control oil supply disk 4. The supply of the pressure input of the pressure relief valve 70 with pressurized oil would not be ensured without the plug 67.
In
One can take from
The individual pressure-maintaining valve 21 the inlet of which is in pressure fluid communication with the feed line 44 is arranged upstream of the directional valve 18. The pilot valves 62a, 62b cause, as described in the foregoing, an adjustment of the control piston 20 into the working positions a, b and into the idle position 0. The control oil is supplied to the pilot valves 62a, 62b through the control oil supply passage 66 having the cross-section shown in
As can be taken from
The
The control oil supply disk 104 in accordance with the second embodiment shown in
In the third embodiment shown in
The first to third embodiments have in common that there may be provided a constant pressure difference above the nozzles 78, 278 and a defined oil flow through the passage 76, 276. This is ensured especially by the constant control oil supply pressure prevailing in the control oil supply passage 66.
The present invention relates to a control block comprising a plurality of control block elements in each of which a respective valve arrangement is provided for controlling an associated hydraulic consumer. In the control block furthermore an oil channel is provided which runs through at least one control block element for controlling the temperature thereof independently of the control of the valve arrangement.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 008 294.2 | Feb 2007 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE2008/000242 | 2/8/2008 | WO | 00 | 12/17/2009 |
