EP1339988A1

EP1339988A1 - Locking block

Info

Publication number: EP1339988A1
Application number: EP01969276A
Authority: EP
Inventors: Burkhard KNÖLL
Original assignee: Bosch Rexroth AG
Current assignee: Bosch Rexroth AG
Priority date: 2000-12-08
Filing date: 2001-09-07
Publication date: 2003-09-03
Also published as: US6904938B2; WO2002046622A1; US20030167915A1; CA2427290A1; DE10061208A1

Abstract

The invention relates to a locking block (1) for controlling a hydraulic consumer. A main piston (16) which is configured with an advanced opening can be lifted from a valve seat (26) in a return function, by means of an opening piston (68). A pressure chamber (76) which is delimited by the main piston on one side and by the opening piston on the other side is connected to a tank channel or low-pressure channel (8) for both the return function and the non-return function of the locking block, so that the changeover from the return function to the non-return function and vice-versa can take place very quickly.

Description

description

locking block

The invention relates to a locking block according to the preamble of patent claim 1.

Lock blocks of this type are used, for example, in mobile hydraulics to control double-acting hydraulic cylinders, which are provided, for example, for actuating front linkages, rear linkages or other peripheral devices such as mowers, packers, etc. The hydraulic cylinders are actuated, for example, via a valve arrangement, as is known from DE 197 34 479 A1. This valve arrangement is disc-shaped and has a proportional valve with a directional and a speed section, via which a pressure connection can optionally be connected to two working connections. The two working connections are connected to a cylinder space or an annular space of the hydraulic cylinder to be controlled. A generic blocking block is assigned to each of the working connections and is designed as an unlockable check valve arrangement. In its non-return function, the blocking block allows pressure medium to be supplied from the proportional valve to the associated work connection, while the blocking block connected in parallel and assigned to the other work connection controls the return flow of the pressure medium from the hydraulic cylinder to a tank or low-pressure connection in its return function.

Each locking block has a main piston biased against a valve seat, which in the check function opens a connection between the pressure connection and the associated work connection. To open the main piston in the return function, an opening piston which can be acted upon by a control pressure is assigned to it, via which the main piston can be brought into its open position in order to open the connection between the working connection and the tank connection. The opening piston opens a pre-opening of the main piston, so that the end face which is effective in the closing direction is relieved and the opening piston can lift the main piston from the valve seat due to the effect of the control pressure. The push piston is supported by a spring on the adjacent end face of the main piston. The pressure at the pressure connection, ie the pump pressure, is present in the non-return function (extension of the hydraulic cylinder) in this pressure chamber receiving the spring. Conversely, in the return function (retraction of the hydraulic cylinder), the load pressure is applied to the consumer in this pressure chamber. When switching from the check function to the return function or vice versa, the respective pressure in the pressure chamber must first be reduced before the respective other function can take effect. In the known solution, for example when switching from the check function to the return function during the axial displacement of the pushing piston caused by the application of the control pressure, a tank channel is opened via a control edge, so that the pressure chamber towards the tank is relieved. In the initial phase, however, the pump pressure still acts in said pressure chamber, so that the response behavior of the valve arrangement, in particular when switching quickly, does not meet the requirements under certain operating conditions.

In contrast, the invention is based on the object

To create a blocking block that enables a quick switch between the reverse function and the return function and vice versa.

This object is achieved by a locking block with the features of claim 1.

According to the invention, the pressure space between a main piston and a push-up piston is always relieved of pressure to a tank or a low-pressure connection, so that the delayed response behavior disadvantageous in the prior art due to the required pressure reduction in said

Pressure chamber cannot occur.

In a particularly preferred exemplary embodiment, an end section of the push-up piston is sealingly guided in an end recess of the main piston, so that the pressure space is limited only by the push-up piston and the main piston designed with a pre-opening. The latter is preferably designed as a stepped piston, the area difference being effective in the closing direction, so that the pushing piston can be moved back into its closed position as quickly as possible.

In the valve according to the invention, the pre-opening of the main cone is opened in the return function via the push-open piston, so that a rear space of the main piston towards the tank or low-pressure connection is relieved.

The annular space delimited by the radial shoulder of the main piston is hydraulically connected to a pilot channel downstream of the pilot valve seat on the one hand and to the working connection on the other. A nozzle is provided in the pressure medium flow path from the annular space to the working connection, the effective diameter of which is substantially smaller than that of the pre-opening, so that an effective relief of the pressure in the annular space and in the pilot channel is possible. In a particularly simple embodiment, this nozzle is formed by an axial groove on the outer circumference of the main piston.

The smaller diameter of the main piston preferably has the same diameter as the push-up piston.

The production of the locking block according to the invention is particularly simple if a channel is formed in the push-up piston, via which the pressure chamber is connected to the tank or low-pressure connection.

In a particularly preferred embodiment, the hydraulic connection between the pilot channel and the annular space is controlled when the main piston is lifted from its valve seat and a larger opening cross-section is opened between the annular space and the associated working connection, so that pressure differences as a result of a leakage via the activated pre-opening and thus displacements of the Return characteristic can be prevented. With a further displacement of the push piston, a connection between the working connection and the tank connection is opened, so that the pressure medium can flow out from the hydraulic cylinder to the tank.

A non-return spring arrangement which prestresses the main piston in the closing direction acts on the one hand as a non-return valve spring which enables the supply to the consumer in the non-return function and on the other hand as a control spring to control the return from the consumer to the tank.

As a check valve spring, this spring should be designed to be relatively weak so that there are no major pressure losses across the check valve. On the other hand, as a control spring, the spring should have a steeper characteristic curve in order to enable a good response behavior in the return control.

In order to ensure these contradicting requirements for the check spring arrangement, the check valve arrangement is implemented by combining a weak check spring and a control spring with a steep characteristic curve, the comparatively weakly designed check spring determining the check function, while the control spring with a steep spring characteristic curve only after a predetermined axial movement of the main piston engages to control the return function.

The construction of the locking block is particularly simple if the main piston is guided in a sleeve inserted into a valve housing (valve disk), on the outer circumference of which a flange is provided for sealing. A mechanical seal is preferably formed on the outer circumference of the main piston so that the leakage of the check valve is minimal even at high load pressures.

Other advantageous developments of the invention are the subject of the further subclaims.

Two preferred exemplary embodiments of the invention are explained in more detail below with the aid of schematic drawings. Show it: 1 shows a section through a locking block according to the invention and FIG. 2 shows a variant of the locking block from FIG. 1.

1 shows a longitudinal section through a locking block 1, which is inserted into a receiving bore 4 of a plate-shaped valve housing 2.

A control channel 6, a tank channel 8, a working channel 10 and a pressure channel 12, which are connected to a control port S, a tank port T, a working port A and a pressure port P of the valve arrangement, open into this receiving bore 4 via annular spaces.

In the receiving bore 4, a sleeve 14 is inserted, in which a main piston 16 is guided axially. In the exemplary embodiment shown in FIG. 1, the sleeve 14 extends from the end face of the valve housing on the right in FIG. 1 to the working channel A. In this area, a flange 18 is formed on the outer circumference in the sleeve 14, which seals when the sleeve 14 is inserted abuts the peripheral wall of the receiving bore 4.

The main piston 16 is designed as a stepped piston, a portion 22 with a larger diameter D3 being guided in sections in a radially expanded area of an inner bore 20 of the sleeve 14. This radially widened part 22 of the main piston protrudes axially from the sleeve 14 and, in the basic position shown, is biased against a valve seat 26 via a non-return spring arrangement 24 which is formed in the area between the pressure channel 12 and the working channel 10 on the receiving bore 4. In the area of the valve seat 26, the main piston 16 is provided with a radially projecting annular collar 28 which is immersed in a correspondingly designed gradation of the receiving bore 4. The annular collar 28 controls a further flow cross-section lying in series with a flow cross-section at the valve seat 26 between its one 360-degree edge and a 360-degree edge in the receiving bore 4 of the valve housing 2. This additional flow cross-section begins to open when the flow area at the valve seat is already wide open. By such a design the forces due to the pressure medium flow and acting in the closing direction are kept low. The annular collar 28 also increases the area on the main piston 16 on which a pressure acting in the open direction can be present. Overall, the pressure drop is kept low in this way when the pressure medium flows from the pressure channel 12 via the main piston 16 to the working channel 10.

The part 22 of the main piston 16 with the diameter D3 is stepped down to the diameter D1 via a radial shoulder 32, this stepped end section 30 being guided in a corresponding radially recessed area of the inner bore 20. The end section 30 has a mechanical seal 34 on its outer circumference, so that an annular space delimited by the radial shoulder 32 of the main piston 16 and the opposite shoulder of the inner bore 20 of the sleeve 14 is hydraulically sealed against a spring space 36 for the non-return spring arrangement 24. This spring chamber (36) is closed in the axial direction by a screw plug 38 screwed into the sleeve 14.

The main piston 16 is designed with a pre-opening and has an end recess 40, in the bottom of which a pilot channel 42 which penetrates into the end section 30 of the main piston 16 opens. In the mouth area of the pilot channel 42, a pilot valve seat 44 is formed, against which a pilot valve body 46 is biased by means of a weak pilot spring 48. This is supported on a bolt 50 which is screwed into the pilot channel 42 and whose right end section in FIG. 1 protrudes axially from the main piston 16. At this end section of the bolt 50, a non-return spring 52 of the non-return spring arrangement 24, which is supported on the locking screw 38, engages, so that the main piston 16 in the basic position shown in FIG. 1 is biased against its valve seat 26 via this comparatively weak return spring 52.

The non-return spring arrangement 24 also has a control spring 54 with a steeper spring characteristic than the aforementioned weak return spring 52. This control spring 54 is supported on a spring plate 56 which is axially spaced from the right end face of the end section 30 in FIG. 1. This spring plate 56 is on a radial shoulder in the NEN bore 20 of the sleeve 14 supported. The other end portion of the control spring 54 abuts the screw plug 38. The control spring 54 is only effective when the end portion 30 of the main piston 16 runs onto the spring plate 56. A plurality of radial bores 58, which are connected to the annular space 34 in the closed position of the main piston 16, open into the pilot control channel 42. The main piston 16 has a control edge 60 in the area of the radial bores 58, through which the connection between the annular space 34 and the radial bores 58 can be controlled when the main piston 16 is lifted off the valve seat 26.

The spring chamber 36 is connected to the space of the main piston 16 delimited by the end recess 40 via a bore 62, which is indicated by dashed lines and penetrates the end section 30.

In the area between the annular space 34 and the working channel 10, 14 axial grooves 64 are formed on the outer circumference of the part 22 of the main piston, these being narrowed towards the annular space 34 toward a nozzle 66. The effective cross section of this nozzle 66 is significantly smaller than the diameter of the pilot valve seat 44. When the main piston 16 is axially displaced, the narrowed part of the axial grooves 64 forming the nozzle 66 is displaced into the annular space 34, so that a larger opening cross section for the connection of the Annulus 34 is opened with the working channel 10.

In addition, an impact piston 68 is guided in the receiving bore 4, the right end section in FIG. 1 sealingly immersed in the end recess 40 of the main piston 16. A spring 70 is supported on the bottom of the front recess 40, by means of which the pushing piston 68 is biased against an end surface 72 of the receiving bore 4 in the region of the control channel 6. At its right end section, the push-up piston 68 has an axial projection 74 which, when the push-up piston 68 is axially displaced, runs onto the pilot valve body 46 and lifts it off its pilot valve seat 44. The pressure chamber 76 formed between the pushing piston 68 and the main piston 16 is connected to the tank channel 8 via at least one angular bore 78 passing through the pushing piston 68 and extending from the right end face in FIG. 1 to the outside. The outer circumference of the push piston 68 extends in the region of the tank channel 8. The mouth area of the angle bore 78 in the area of the tank channel 8 is selected so that the pressure chamber 76 is always connected to the tank channel 8.

In the area of this tank channel 8, a control recess 80 is provided on the outer circumference of the pushing piston 68, which forms a further control edge 82, via which the connection between the tank channel 8 and the space 84 which extends from the mouth area of the pressure channel 12 to the valve seat 26 extends extends so that when the main piston 16 is lifted off, a hydraulic connection between the working channel 10 and the tank channel 8 is opened. The axial position of the control edge 82 is selected such that the connection between the working channel 10 and the tank channel 8 is only opened when the larger opening cross section of the axial grooves 64 is open.

The outer diameter of the butt piston 68 has the same diameter D1 as the end portion 30 of the main piston 16.

As mentioned at the beginning, the blocking block 1 is preceded by a proportional valve, via which the pressure channel 12 can be connected or blocked to the pump. In the non-return function, the pump pressure is present in the pressure channel 12, so that a resultant compressive force acting in the opening direction acts on the ring end face delimited by the diameters D3 and D1. The main piston 16 then lifts off its valve seat 26 when the resultant compressive force in the opening direction is greater than the resultant compressive force in the annular space 34 in the closing direction and the force of the return spring 52 and the frictional force generated by the mechanical seal 35. Since the check spring 52 is designed to be relatively weak, the pressure loss in the check function is minimal. The pressure chamber 76 is always connected to the tank channel 8 via the angular bore 78.

When changing over to the return function, the connection of the pressure channel 12 to the pump is shut off via the proportional valve and the control channel 6 is acted upon by a control pressure which acts on the rear end face. Before the pushing piston 68 acts, so that it is acted upon to the right in the illustration according to FIG. Since the pressure chamber 76 is relieved of pressure due to its connection to the tank channel 8, the pushing piston 68 can be displaced to the right by the action of the control pressure against the force of the spring 70, so that the axial projection 74 runs onto the pilot valve body 46 and this against the Force of the pilot spring 48 lifts from its valve seat 44 - the pre-opening of the main piston 16 is opened. As a result, the control oil located in the annular space 34 and in the pilot channel 42 can flow out through the pre-opening into the pressure chamber 76 and from there via the angular bore 78 to the tank channel 8, so that the pressure forces acting in the main piston 16 in the closing direction are reduced. The push piston 68 then runs onto the main piston 16 so that it is lifted off its valve seat 26 due to the control pressure effective in the opening direction. The effective nozzle 66 when lifting the main piston 16 and the diameter of the pilot valve seat 44 are designed so that the effective pressure in the annular space 34 can be reduced to the tank channel 8 even at a high pressure in the working channel 10.

As soon as the main piston 16 is lifted off the valve seat 28, the

Connection between the radial bores 58 and the annular space 34 is controlled by the control edge 60 and, as a result, the larger opening cross section of the axial grooves 64 is opened, so that pressure differences due to leakages via the pilot valve arrangement and thus displacements of the return characteristic can be prevented. With a further axial displacement of the main piston 16, the connection between the tank channel 8 and the working channel 10 is then opened via the further control edge 82, so that the pressure medium can flow out of the hydraulic cylinder to the tank channel 8. Before the further control edge 82 opens the connection between the tank channel 8 and the working channel 10, the main piston 16 runs on the spring plate 56, so that the further opening in the return function takes place essentially against the force of the stronger control spring 54, which starts in an optimal manner this rule task is adapted. The tank or low pressure prevailing in the pressure chamber 76 is always present in the spring chamber 36 of the control spring 54 and the return spring 52, since this spring chamber 36 is connected to the pressure chamber 76 via the bore 62. FIG. 2 shows a simplified exemplary embodiment of the blocking block 1 from FIG. 1. In this exemplary embodiment, the nozzle 66 is not formed by one or more axial grooves 64 but by a jacket bore 86 which defines the sleeve 14 in the region between the flange 18 and the other side Working channel 10 passes through the adjacent end section. The casing bore 86 opens on the one hand in the annular space 34 and on the other hand in an axial channel 88 which is formed between the outer circumference of the sleeve 14 and the inner circumferential wall of the receiving bore 4. The main piston 16 has a control edge 90 in the region of the radial shoulder 32, via which the casing bore 86 is closed after the main piston 16 has been lifted off. An additional control edge 92 then opens a larger opening cross section when the main piston 16 is axially displaced, which is realized by a radially recessed peripheral section 94 of the main piston 16.

In the exemplary embodiment shown in FIG. 2, the annular collar 28 of the main piston 16 in the region of the valve seat 26 was also dispensed with, so that the basic structure of the main piston 16 is simplified compared to the solution described at the beginning. Otherwise, the solution shown in FIG. 2 corresponds to the exemplary embodiment described at the beginning, so that further explanations can be dispensed with.

Disclosed is a blocking block for actuating a hydraulic consumer, in which a main piston designed with a pre-opening can be lifted off a valve seat in a return function by means of an impact piston. A pressure chamber delimited by the main piston on the one hand and by the control piston on the other is connected to a tank or low-pressure channel both in the return function and in the return function of the locking block, so that the changeover from the return function to the return function and vice versa can take place very quickly. LIST OF REFERENCE NUMBERS

1 blocking block 66 nozzle

2 valve housings 68 push-up pistons

4 location hole 70 spring

6 control channel 72 end face

8 tank channel 74 axial projection

10 working channel 76 pressure chamber

12 pressure channel 78 angle bore

14 sleeve 80 control recess

16 main pistons 82 additional control edge

18 flaring 84 room

20 inner bore 86 jacket bore

22 part of the main piston 88 axial channel

24 Non-return spring arrangement 90 control edge

26 valve seat 92 control edge

28 ring collar 94 circumferential section

30 end section

32 radial shoulder

34 annulus

35 Mechanical seal

36 spring chamber

38 screw plug

40 forehead recess

42 pilot channel

44 pilot valve seat

46 pilot valve body

48 pilot spring

50 bolts

52 non-return spring

54 control spring

56 spring washers

58 radial bores

60 control edge

61 hole

64 axial grooves

Claims

claims

1. blocking block for connecting a working connection (A) with a pressure connection (P) and a tank or low pressure connection (T), with a main piston (16) biased against a valve seat (26), in which a against a on the pilot valve seat (44) Preloaded valve body (46) is received, which can be brought into its open position by means of an opening piston (68), characterized in that the opening piston (68) and the main piston (16) delimit a pressure chamber (76) which is always connected to the Tank or low pressure connection (T) is connected.

2. Locking block according to claim 1, wherein the push piston (68) with an end portion 5 sealingly in an end recess (40) of the main piston

(16) is guided, in the bottom of which the pilot valve seat (44) opens.

3. Locking block according to claim 1 or 2, wherein the main piston (16) is designed as a stepped piston, whose area difference acts in the closing direction o.

4. locking block according to claim 3, wherein one of a radial shoulder (32) of the main piston (16) delimited annular space (34) via a nozzle (66, 86) is connected to the working connection (A). 5

5. blocking block according to claim 4, wherein the nozzle (66) is formed by an axial groove (64) in the main piston (16).

6. locking block according to one of claims 3 to 5, wherein the smaller 0 diameter (D1) of the main piston (16) the outer diameter of the

Corresponds to push piston (68).

7. blocking block according to one of the preceding claims, wherein the push piston (68) has one or more angle bores (78) through which 5 the pressure chamber (76) is connected to the tank or low-pressure connection (T).

8. blocking block according to one of claims 4 to 7, wherein a pilot channel (42) downstream of the pilot valve seat (44) via radial bores (58) of the main piston (16) is connected to the annular space (34) and this connection by a control edge (60) the main piston (16) can be controlled.

9. blocking block according to claim 8, wherein the connection to the tank connection (T) via a control edge (82) of the push piston (68) can be opened.

10. Locking block according to claim 8 or 9, wherein before opening the tank connection (T) on the push piston (68) has a larger opening cross-section than the cross-section of the nozzle (66, 86) between the annular space (34) and the working connection (A ) is taxable.

11. Locking block according to one of the preceding claims, wherein a seal (35) is arranged on the outer circumference of the main piston (16).

12. Locking block according to one of the preceding claims, wherein a spring chamber (36) for a the main piston (16) acting in the closing direction check spring arrangement (24) via a bore (62) of the main piston (16) is connected to the pressure chamber (76).

13. Locking block according to claim 12, wherein the non-return spring arrangement (24) has a non-return spring (52) and a control spring (54) which is effective only after an axial displacement of the main piston (16) and which has a higher spring rate than the non-return spring (52).

14. Locking block according to one of the preceding claims, wherein the main piston (16) is guided in a sleeve (14) which is inserted into a valve housing (2) and sealed on the end face by means of an embossing (18).