GB2072806A

GB2072806A - A flow regulating valve

Info

Publication number: GB2072806A
Application number: GB8109558A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1980-03-29
Filing date: 1981-03-26
Publication date: 1981-10-07
Also published as: IT8120759A0; FR2479504A1; DE3012348C2; DE20321123U1; FR2479504B3; IT1136866B; GB2072806B; DE3012348A1

Abstract

The flow regulating valve has a control slide (15) made substantially cup-like, sliding in a housing bore (11) and engaging by way of an end edge (16) of its opening a supporting member (13) under the force of a control spring (18). In this position, its inner chamber and the spring chamber are unloaded. Pressure medium delivered by a pressure medium source first of all influences only an annular area (24) at the open end of the control slide. As soon as the control slide is displaced by the pressure medium flow becoming greater, its inner chamber is also influenced and then the control slide regulates the flow of pressure medium to the load ports 31, 35. In this manner, the so-called initial jump, that is an excessively large flow of pressure medium at the start of the control operation, is prevented. In a modification the control slide 15 slides within a main spool valve closure member. <IMAGE>

Description

SPECIFICATION A flow regulating valve State of the Art The invention originates from a flow regulating valve according to the preamble to the main claim, To this end, one known flow regulating valve of that kind requires two control pistons and two regulating springs whereby its construction becomes very expensive.

Advantages of the Invention As opposed to this, the flow regulating valve according to the invention comprising the characterising features of the main claim has the advantage that it is of very simple construction in that it requires only one control slide -- like normal flow regulating valves without the possibility of preventing the starting response.

Thus, it is of very simple construction whilst completely retaining the known advantage.

Advantageous further developments and improvements of the flow regulating valves set forth in the main claim are made possible by the measures set forth in the sub-c.laims.

Drawing An embodiment of the invention is illustrated in the drawing and is described in detail in the following specification. Figure 1 shows a longitudinal section through a flow regulating valve, Figure 2 is a longitudinal section through a second embodiment, Figures 3 and 4 are modifications of a detail, Figures 5 and 6 are modifications of the embodiment according to Figure 2 and Figure 7 is a diagram.

Description of the Embodiments The embodiment according to Figure 1 shows a so-called 3-way flow regulator. This has a valve housing 10 provided with a longitudinal bore 11 passing through it which is closed at one end by a threaded plug 12. An inlet union 1 3 which has an inlet bore 14 and which extends coaxially with respect to the longitudinal bore 11, is screwed into the longitudinal bore at the opposite end. A substantially cup-like control slide 1 5 is slidingly guided in the longitudinal bore 11.At its open end, it has a slightly inclined annular edge 16 by means of which it is forced against a frusto-conical surface 19 at the inner end of the inlet union 13 by the force of a control spring 1 8. Near to the inner end of the inlet bore 14, a plurality of radially extending through bores 20 are formed in the inlet union and which issue into a chamber 21 which is formed between the longitudinal bore 11 and the frusto-conical surface 1 9. The cup-like form of the control slide 1 5 is produced by a central blind bore 23 whereby an annular surface 24 is formed at its end facing the supply union 1 3. A throttle diaphragm 25, which is retained by a snap ring 26, is arranged in the blind bore 23 near to the said annular surface.A plurality of radial bores 28 passing through the wall of the control slide are formed in the vicinity of the closed end of the slide. These issue into a chamber 29 which is formed by an annular groove 30. An outlet bore 31, which is in communication with a load, not shown (a constant flow load), issues into the said annular groove.

Another annular groove 34 into which a second outlet bore 35 issues and which is also in communication with a load, not shown (residual flow load), is formed in the longitudinal bore 11 in the vicinity of the supply union 13.

When pressure medium from a pressure medium source (not shown) is supplied to the inlet bore 14, then it arrives through the radial bores 20 in the chamber 21 and there influences the annular area 24 on the control slide 1 5. If a particular delivery flow or delivery pressure is reached, then the control slide 1 5 is displaced against the force of the regulating spring 18. At this instant, the pressure medium arrives through the throttle diaphragm 25 into the blind bore 23 of the control slide and from there through the radial bores 28 into the outlet bore 31. With a further increase in delivery flow, such a pressure difference is generated at the throttle diaphragm 25 that the control slide is so adjusted that a constant delivery of pressure medium flows to the outlet bore 31.With a further increase in the pressure medium rate of flow and with it an increasing pressure difference at the throttle diaphragm 25, the control slide is displaced until communication is established with the annular groove 34. Then, a residual flow flows through the outlet bore 34 to the second load.

With the control slide in accordance with the invention, it is essential that at the start of a control operation, only the end surface 24 influenced and indeed so that it engages the frusto-conical surface 1 9 on the supply union 13.

If that were not the case - as with known flow regulating valves in which the complete slide is influenced in cross section - a so-called initial jump would take place as is illustrated in the diagram according to Figure 7 by the dotted line.

In the diagram, the time t is plotted on the abscissa and the fluid flow q is plotted on the ordinate. Q signifies the desired flow value. By initial jump, is to be understood a flow of pressure medium at the start of a control operation increasing momentarily considerably beyond the desired value as is shown by the dotted line in the diagram according to Figure 7. This leads to a hefty initial movement at the load which is, of course, undesirable. With the valve in accordance with the invention, only a very slight excess beyond the desired flow value takes place during starting as is illustrated in the full line in Figure 7.

This is achieved by the fact that the control slide 1 5 engages the surface 1 9 by means of its annular edge. Thereby, the inner chamber of the control slide and also the chamber 29 are initially unloaded. They are only influenced by pressure medium when the control slide has moved away from the surface 1 9.

The embodiment according to Figure 2 shows the arrangement of a similar flow regulating valve, formed as a 2-way flow regulator, arranged in the longitudinal slide 40 of a multi-way valve 41. A blind bore 42, which is closed by a threaded plug 43, is arranged in the end of the longitudinal slide.

At that end, a double-acting centering device 44 is located which will not be described further since it is not essential to the invention. A control slide 46 is slidingly guided in the blind bore 42. The end edge 48 of the slide is forced by the force of a control spring 47 against a frusto-conical surface 49 of a screw 50 which is screwed into the base of the blind bore 42. Moreover, the control slide has an annular area 52 which bounds a chamber 53 which is formed between the screw 50 and the longitudinal bore 42. A radial bore 55 penetrates into the said chamber. At its spring end, the control slide 46 also has a plurality of radial bores 56 passing through it which can be brought into communication with the radial bores 57 in the control slide 40. The radial bores 56 are in communication through an axially extending measuring orifice 58 with the interior of the control slide 46.A plurality of annular grooves are formed in the longitudinal bore receiving the control slide 40, of which only the annular grooves 61,62 and 63 are specifically referenced. The annular groove 63 is in communication with a pump, the annular groove 62 is in communication with a load port and the annular groove 61 is in communication with a pressureless discharge.

If the longitudinal slide 40 is located in a position in which the annular grooves 61, 62 are in communication with the radial bores 53 and 57, then the cyamber within the control slide 46 and the chamber 47 receiving the spring are relieved to the discharge, that is to say they are pressureless. However, the pressure from the load side 62 acts on the annular surface 52 of the control slide 46. If, due to a corresponding setting of the control slide, this has reached a predetermined value, the control slide 46 is displaced against the force of the control spring 47. Then, its inner chamber is also influenced and communication is established through the measuring orifice 58 and the radial bores 56 to the radial bores 57 and thus to the discharge 61.

A pressure drop is generated at the measuring orifice through which the control slide is displaced into a balanced position in cooperation with the control spring. However, the cross section of the passage to the bore 57 is also reduced by the bore 56, that is to say, these two bores form a variable outlet cross section (control orifice).

In this manner, a constant through flow from the load side 62 to the discharge side 61 is provided. The operation of the control slide is once again exactly like that according to the embodiment of Figure 1.

Figures 3 and 4 show that the control slide need not necessarily engage a conical surface with its annular edge but can also engage a flat surface. With these two embodiments, this is formed by a screw 70 which has a plane surface 71 which has a cylindrical shoulder 72. The edge 73 of the control slide 46 engages the plane surface. A narrow slot 74 provides for a free residual cross section 75. In this case, a very slight residual flow can flow when the control slide engages the supporting member and which provides no other essential function.

In the embodiment according to Figures 5 and 6, which correspond completely according to that of Figure 2, two opposite pocket like flats 77,78 are formed at the outer periphery of the longitudinal slide 40' and which lie in the neighbourhood of the bore 55, extend parallel thereto and extend towards the bore 57 but do not reach it. However, the flats do not contact the openings in the bore 55.

In this way, the flow limiting function is effective both from 62 towards 61 and from 63 towards 62. Morevoer, by means of the frustoconical areas, the control slide also acts as a nonreturn valve from 63 towards 64. However, when the longitudinal side 40 has been moved far enough, the flow control valve is by-passed by the flats 77, 78.

When annular edges on the control slide are discussed in the specification, these edges can, of course, also have a small area as in the embodiment according to Figure 1 or the embodiments according to Figures 3 and 4.

However, this annular edge area is relatively small in comparison to the annular area 24 or 52.

Claims

1. A flow regulating valve comprising a control slide guided in a bore, formed substantially cuplike and loaded by a control spring, the control slide comprising a measuring throttle through which pressure medium flows from the inlet to at least one load port, the flow regulating valve completely suppressing the so-called initial jump when the load is switched in, characterised in that, in the rest position, the control slide substantially engages a supporting member arranged in the inlet by way of an annular edge on its end surface, whereby, in this position, substantially only an annular area on the control slide is influenced.

2. A valve according to claim 1 characterised in that at least one transverse bore which is in communication with an outlet leads outwards from the hollow interior of the control slide.

3. A valve according to claim 1 or 2 characterised in that at least one supply duct is formed in the supporting member for the supply of pressure medium to the control slide.

4. A valve according to one of claims 1 to 3 characterised in that the supporting memberis a threaded plug which is arranged at or near the inlet and has a frusto-conical or cylindrical area, against which engages the annular edge on the control slide.

5. A valve according to one of claims 1 to 4 characterised in that the control slide is arranged in a blind longitudinal bore in the longitudinal slide of a multi-way valve, wherein a screw with a frusto-conical point is arranged at the base of the longitudinal bore and against which the control slide engages under the force of the control spring and that the pressure medium supply and discharge for the control slide is formed by two bores arranged spaced from one another and passing through the wall of the longitudinal slide.

6. A valve according to claim 5 characterised in that at least one through passage is formed at the closed end of the control slide and together with at least one transverse bore in the longitudinal slide forms the control orifice and that the said control orifice is connected in front of a measuring diaphragm.

7. A valve according to one of claims 1 to 6 characterised in that a narrow slot is formed at the supporting member where the control slide engages.

8. A valve according to claim 5 characterised in that at least one pocket like recess is formed at the outer periphery of the longitudinal slide and which extends in the vicinity of the bore forming the pressure medium supply to the control slide and parallel thereto and extends towards the bore.

9. A flow regulating valve substantially as herein described with reference to Figure 1, Figures 1 and 3, Figures 1 and 4, Figure 2, Figures 2 and 3, Figures 2 and 4, Figures 2 and 5, Figures 2 and 6 or Figure 7 of the accompanying drawings.