GB2118499A

GB2118499A - An hydraulic installation

Info

Publication number: GB2118499A
Application number: GB08307926A
Authority: GB
Inventors: Hugo Preun
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1982-04-20
Filing date: 1983-03-23
Publication date: 1983-11-02
Also published as: IT8320648A0; IT1170128B; GB8307926D0; FR2525293B1; FR2525293A1; DE3214468A1; GB2118499B

Abstract

The hydraulic installation consists of a pressure medium source (10), a flow regulating valve (12) connected beyond the source and two load circuits (46,47) connected in parallel from the valve, the first of which is a steering device, the second can be an optional load. The steering device has a steering control valve (50) and a pump (52) driven by a steering shaft (51). The flow regulating valve can occupy two definite positions, namely a rest position (A), in which practically the entire pressure medium is conveyed without loss to the second working circuit and through the steering control valve then located in its neutral position, to the reservoir, and a working position (B) in which a constant pressure medium flow is branched to the steering device, when the steering control valve (50) is located in one of its two working positions. A residual flow then flows from the flow regulating valve to the second load circuit. In that way, a loss-free conveying of the pressure medium flow delivered by the pump (10) to the reservoir or to the second load, is achieved when the loads are in the rest position. <IMAGE>

Description

SPECIFICATION An hydraulic installation State of the Art The invention originates from an installation according to the preamble to the main claim. With one known installation of that kind the control line of the flow regulating valve is connected to one of the two steering cylinder connections in the working positions of the slide control valve. Thus, it is a question of a so-called load sensing installation. It has the disadvantage that the pressure medium flow to the other load or loads is strongly throttled in the flow regulating valve in the neutral position of the slide control valve which means loss of power.

Advantages of the Invention As opposed to this, the installation in accordance with the invention comprising the characterising features of the main claim has the advantage that the expenditure of energy is substantially reduced in such a manner that a high flow of pressure medium with low through flow resistance flows to the reservoir or to the other loads just when it is not used. The installation in accordance with the invention also provides the possibility of a parallel operation of steering and parallel connected working circuits.

Further developments and improvements of the features set forth in the main claim are made possible by the measures set forth in the sub claims.

Drawing An embodiment ofthe invention is illustrated in the drawing and is explained in detail in the following description.

Figure 1 shows an hydraulic installation in diagrammatic representation, Figure 2 shows a flow regulating valve in longitudinal section.

Description ofthe Embodiment In Figure 1 a pump is referenced 10 which withdraws pressure medium from a reservoir 11 and delivers it to a flow regulating valve 12. This is illustrated diagrammatically in Figure 1, but is illustrated in Figure 2 in all its details. The flow regulating valve 12 has a housing 13 provided with a longitudinal bore 14 passing through it in which a control slide 15 is sealingly slidingly guided. The delivery line 16 from the pump is connected to the inlet 17 to the longitudinal bore. Beyond the inlet 17 a chamber 18 is formed in the longitudinal bore 14 which is followed at a short distance by an annular groove 19. A bore 21 extending perpendicular to the longitudinal bore 14 enters the annular groove 19 and a line 23 is connected to its outlet 22.Moreover, an annular groove 24 in the longitudinal bore 14 follows at a short distance from the annular groove 19 and a bore 24' likewise extending perpendicular to the longitudinal bore 14 and to the outlet 25 from which is connected a line 26, enters the annular groove 24. A third annular groove 28 in the slide bore 14 and into which issues a transverse bore 29 the outlet 30 from which is connected to a line 31, follows at a greater distance from the annular groove 24.

At its rear portion, the longitudinal bore 14 is closed by a closure screw 32. There one end of a control spring 33 is supported the other end of which acts on the control slide 15 and attempts to move the latter towards the inlet 17. Two triangular notches 34 are formed at the inlet end 15' of the control slide 15.

The control slide 15 is made hollow cylindrical and has a first longitudinal bore 35 in which is arranged an orifice 36 so that two bore chambers 37,38 are formed. Beyond the orifice 36, a transverse bore 39 passes through the two walls of the slide, that is to say those bounding the chamber 38. Beyond the transverse bore 39 a transversely extending wall 41 is formed in the control slide through which passes a longitudinally extending throttle bore 42. This issues into a second longitudinal bore 43 which is formed in the rear portion of the control slide 15. A transverse bore 44 passing through the wall of the control slide also passes through the longitudinal bore 43.

The line 26 connected to the outlet 25 leads to a first working circuit 46 which forms an hydraulic steering device. The line 23 connected to the outlet 22 leads to a second working circuit 47, for example a hoist on the vehicle. From there, the line 23 leads to the reservoir 11.

A control line 31 leads from the outlet 30 likewise to the steering device 46 where it issues at a steering control valve 50 which has three definite switching positions I, II and Ill with flowing transitions. Apart from the steering valve 50, the steering device 46 is of known construction and has an engine pump 52 actuated by a steering shaft 51 and from which two lines 53, 54 lead to the steering valve 50. From there, two lines 55,56 lead to a double acting steering cylinder 57.

The steering valve 50 has five ports on one side and two ports on the opposite side. In the neutral position II of the control valve 50, the line 26 is connected to a line 59 which issues into a line 60 leading to the reservoir 11. The line 60 is in communication with the line 26 through a nonreturn valve 61. In the neutral position II of the steering valve 50, the line 31 is connected to the line 26 through a duct 62 formed in the steering valve.

The line 59 is also connected to the said duct. The steering valve 50 is coupled to the steering shaft 51 by a linkage 63,64. A pressure limiting valve 65 is connected to the line 26.

In the following, the flow regulating valve 12 is discussed essentially since, together with its arrangement in the installation, it forms the essential inventive portion of the installation. The valve can occupy two definite basic positions A and B. The position A forms the rest position, the position B the working position. If the pump 10 delivers pressure medium through the line 16 to the flow regulating valve 12 and the steering valve 50 is located in its neutral position II, then pressure medium delivered by the pump arrives at the inlet 17 to the flow regulating valve 12. Its control slide 15 is displaced into its right-hand end position against the force of the spring 33 by the operating pressure in the chamber 18 and by the pressure drop at the orifice 36 and at the throttle bore 42.It then fully opens the communication from the inlet 17 through the triangular notches 34 to the annular groove 19 and to the outlet 22. The greater part of the delivered pressure medium flows through the line 23 to the second working circuit 47 and from there to the reservoir 11 when the load connected thereto is not actuated. A smaller control pressure medium flow arrives through the orifice 36 and the throttle bore 42 in the longitudinal bore 43 of the control slide and from there through the transverse bore 44 into the transverse bore 29. From there it flows through the line 31 to the steering valve 50. Since, in its neutral position, the line 31 is connected to the line 59, the said control pressure medium flow can discharge through the line 60 to the reservoir 11.The communication from the bore chamber 38 of the control slide to the outlet 25 and thus to the line 26 is interrupted. The through flow resistance to the pressure medium from the inlet 17 to the outlet 22 is reduced to a minimum whereby a lower power loss is achieved especially at high pressure medium flows. The load arranged in the second working circuit 47 can be actuated at any time.

As can be appreciated from the above, the control valve 50 has an open centre function in its neutral position.

If the steering valve 50 is brought into one of its working positions I or Ill by actuating the steering shaft 51, then the communication from the pump 10 to the control line 31 is interrupted. The flow regulating valve or its control slide 15 then arrives in its second definite working position B. Then, a constant regulated pressure medium flow dependent on the pressure drop at the orifice 36 flows through the bore chamber 38, the transverse bore 39 and the annular groove 24 to the outlet 25 and from there through the line 26 to the steering valve 50. A residual flow flows from the chamber 18 through the triangular notches 34 once again to the outlet 22 and through the line 23 to the second working circuit. A parallel operation of the steering device and the second load is provided thereby.

According to the working position I or Ill of the steering valve 50, the constant pressure medium flow flowing in the line 26 arrives at one or the other end of the steering cylinder 57. The respective pressure medium located in the non-influenced cylinder chamber is discharged through the steering valve 50 to the reservoir 11 through the line 60.

These operations are known and are therefore not described further. The engine pump 52 contributes to maintaining the steering force applied to the steering shaft 51 in that it transmits a torque thereto.

Preferably, a gear pump is provided as a pump as is generally usual with such steering devices.

Claims

1. An hydraulic installation comprising two working circuits supplied from a pressure medium source, one of which is a steering device (46), a flow regulating valve (12) connected in front of the said working circuits having a control slide which is so designed that the steering device is provided pre ferentiallywith pressure medium and consists of an engine pump (52) actuated by a steering shaft, a steering control valve (50) and a steering cylinder controlled thereby and in which a control line (31) leads from the flow regulating valve to the steering device, characterised in that, the control slide (15) has two throttles (36,42) lying one behind the other in its hollow interior and two definite basic positions, namely a rest position (A) which is effective in a neutral position of the steering control valve and in which the greater part of the pressure medium delivered by the pump (10) flows to the second working circuit (47) and a smaller unthrottled pressure medium control flow flows through the steering control valve to the reservoir, and a working position (B) in which a constant pressure medium flow flows to the steering device (42) and a residual flow flows to the other load.

2. An installation according to claim 1, characterised in that, in the working positions of the steering control valve (50), the communication from the control line (31) to the reservoir is blocked.

3. An installation according to claim 1 and/or 2, characterised in that, the main communication (25, 26) from the flow regulating valve (12) to the steering control valve (50) in its neutral position, is blocked by the control slide (15).

4. An installation according to one of claims 1 to 3, characterised in that, the end of the control slide (15) is always fully influenced by the pressure medium flow and that the control slide has at least one notch (34) at the end through which communication from the pressure medium source to the second working circuit (47) can be established.

5. An installation according to one of claims 1 to 4, characterised in that, the control slide is formed as a cylindrical hollow member with a constant outer diameter and is displaceable in the slide bore (14) against a control spring (33) by the pressure medium flow.

6. An installation according to one of claims 1 to 5, characterised in that, the first throttle (36) formed in the interior of the control slide (15) represents an orifice which sub-divides the forward portion of the control slide into two chambers (37, 38) wherein a communication to the second circuit can be established from the chamber (37) lying in front of the orifice (36), a communication (26) can be established from the chamber (38) lying beyond the orifice to the steering device and that the second throttle bore (42) lying downstream forms a third bore portion (43) in the control slide (15) from which a communication (31) to the steering device can also be established.

7. An hydraulic installation comprising a pressure medium source, a flow regulating valve connected beyond the source and two load circuits connected in parallel with the valve, the first of which is a steering device, and the second of which can be an optional load, the steering device having a steering control valve and an engine pump driven by a steering shaft, the flow regulating valve being capable of occupying two definite positions, namely a rest position in which practically the entire pressure medium is conveyed without loss to the second load circuit and through the steering control valve then located in its neutral position, to reservoir, and a working position in which a constant pressure medium flow is branched to the steering device and a residual flow then flows from the flow regulating valve to the second load circuit, when the steering control valve is located in one of its two working positions.

8. An hydraulic installation substantially as herein described with reference to the accompanying drawings.