WO1999040350A1

WO1999040350A1 - Flow control valve

Info

Publication number: WO1999040350A1
Application number: PCT/DK1999/000055
Authority: WO
Inventors: Anders Valbjørn; Erik Haugaard
Original assignee: Danfoss A/S
Priority date: 1998-02-06
Filing date: 1999-02-03
Publication date: 1999-08-12
Also published as: DE19804692C2; AU2265799A; DE19804692A1

Abstract

The invention concerns a flow control valve (1) with an inlet connection (26), an outlet connection (12) having between them a throttling arrangement (2, 3) comprising a first throttle and a second throttle, the second throttle (5, 9) being adjustable in dependence of the pressure difference between the inlet connection (26) and the outlet connection. For a flow control valve of this kind the opportunity of remote controlling is desired. For this purpose, the first throttle (21, 22) is made as an auxiliary force operable throttle valve (2) and that a bypass line (29) is provided from the inlet connection (26) to the second throttle (5, 9).

Description

- 1 - Flow control valve

The invention concerns a flow control valve with an inlet connection, an outlet connection having between them a throttling arrangement comprising a first throttle and a second throttle, the second throttle being adjustable in dependence of the pressure difference between the inlet connection and the outlet connection.

A flow control valve of this kind is known from DE 4341848 C2. By means of the first throttle a desired value for the flow quantity is specified. In this connection the first throttle is made as a slide, a housing part of which sets a throttle opening more or less free. The position of this slide can be adjusted by means of a manually operable knob. The second throttle has an adjusting element acted upon by the pressure in the inlet connection on the one side and from the pressure in the outlet connection on the other side, that is by the pressure difference between these two connections. This adjusting element adjusts so that the second throttle enables the desired constant flow.

In many applications it is desired not only to be able to operate such a control valve manually, but also by using an auxiliary force, for example electric power, to be able to perform remote control.

The task of the invention is to make a flow control valve remotely controllable.

In a flow control valve as described in the introduction, this task is solved in that the first throttle is made as an auxiliary force operable throttle valve and that a - 2 - bypass line is provided from the inlet connection to the second throttle.

The throttle valve is a simple auxiliary force operable valve, by means of which the desired value can now be defined in the way that was previously possible with the manually adjustable first throttle. However, such auxiliary force operable valves often have the disadvantage that, at least in an inexpensive embodiment, they only have a limited compressive strength. Thus, it must be ensured that the differential pressure over this auxiliary force operable valve gets no higher than is permissible for the valve. However, this differential pressure is in many cases smaller than required for the application in which the flow control valve is to be used. For this reason a bypass line is provided from the inlet connection to the second throttle, the bypass line being connected so that the second throttle can still be acted upon by pressure. This bypass line makes the throttle valve "leaky", that is, it is provided that fluid can bypass the valve, so that the differential pressure over the throttle valve remains within the preset limits. This combination enables a relatively inexpensive valve to replace the first throttle, which valve permits remote control. In addition, the control properties of the flow control valve remain as good as is the case with embodiments known from DE 43 41 848 C2.

Preferably, a third throttle is arranged in the bypass line. This throttle ensures that the fluid flow passing by the first throttle remains in limits. Indeed, a pressure balancing occurs. However, this pressure balancing does not influence the function of the auxiliary force operable valve during operation. - 3 - Advantageously, the throttle valve is a solenoid valve.

Thus, the throttle valve can be controlled by means of an electric current supplied to a magnet. This gives many opportunities of triggering. For example, the triggering can be performed via a process calculator or some other electrical control arrangement, involving the advantage that returned measuring values can be processed relatively easily.

Advantageously, the solenoid valve is time operated. Thus, a fixed setting of the closure element of the solenoid valve is not required, a procedure which is relatively difficult with a solenoid valve anyway. Rather, the opening degree of the valve results from the duty cycle, that is, the relation of the opening times of the solenoid valve to the sum of the opening and closing times. This enables a relatively accurate adjustment of the first throttle.

Advantageously, the second throttle has an adjusting element, and the bypass line penetrates the adjusting element. Thus, a relatively compact construction can be realised. As a line from the input connection to the adjusting element must be available anyway, which line acts upon the adjusting element, the extension of this line through the adjusting element only involves little effort. Only slight modifications of known adjusting elements are required.

Advantageously, the pressure drop over the second throttle is larger than over the throttle valve. While the bypass ensures that in the closed state of the throttle valve the pressure difference over the throttle valve does not exceed a predetermined value and accordingly the renewed opening of the throttle valve is possible without prob- - 4 - lems, this embodiment ensures that also during operation the pressure drop over the throttle valve remains small enough. The main pressure drop, which is required for the control of the flow quantity, then takes place over the second throttle.

Advantageously, a shut-off device is arranged in the bypass line. In many cases the small fluid flow through the bypass line is not disturbing, as it is too small to provoke significant reactions. However, in many cases it is also desired to stop this flow, for example when a working machine, e.g. a motor, connected to the flow control valve must be stopped completely. Due to the leaks at the throttle valve, a connected motor might turn very slowly. To prevent this, the shut-off device is provided, which stops any fluid flow through the bypass line, if desired.

In this connection, it is particularly preferred that a control arrangement is connected with the throttle valve and the shut-off device, which opens the shut-off device for a predetermined period before operating the throttle valve. This ensures that the pressure balancing over the bypass line can take place on both sides of the throttle valve before the throttle valve opens. Thus, the throttle valve is only operated when the permissible differential pressure is not exceeded. This also applies in the opposite situation. The throttle valve is closed before the shut-off device is closed.

Preferably, the shut-off device is a solenoid valve. As explained above, a solenoid valve can be remotely controlled by electricity, and is therefore easy to integrate in a control arrangement. - 5 - Advantageously, the throttle valve, the second throttle and the shut-off device are arranged in a common housing on a common axis. This gives a relatively compact design. The movement directions of the shut-off device, the throt- tie valve and the adjusting element of the second throttle are approximately the same. Thus, it is possible to prescribe a preferred direction for the mounting of the flow control valve.

In the following the invention is described on the basis of preferred embodiments in connection with the drawings, showing:

Fig. 1 a first embodiment of a flow control valve

Fig. 2 a second embodiment of a compact design of a flow control valve

Fig. 3 a third embodiment of a flow control valve with shut-off device

A flow control valve 1 shown in Fig. 1 has a throttle valve 2, forming a first throttle, and a throttling unit 3 comprising a second throttle. The throttling unit 3 sub- stantially corresponds to the control valve shown in DE 43 41 848 C2. However, here the opportunity of manual adjustment of one of the slides has been dispensed.

In a housing 4 the throttle unit 3 has a slide 5 arranged slideably in a bore 6. The slide 5 has the shape of a hollow cylinder. By means of a compression spring 7 the slide is loaded in the opening direction, meaning that its control edge 8 has the largest possible distance from a valve seat 9. In this connection the valve seat 9 is made as a bore, whose inside diameter corresponds to the out- - 6 - side diameter of the slide 5. On the side of the valve seat 9, on which also the slide 5 is arranged, a chamber 10 is arranged, which is connected with an outlet connection 12 via an outlet throttle 11.

The compression spring 7 presses a second slide 13 against a cover 14, which closes the housing 4. The slide 13, in the known embodiment according to DE 43 41 848 C2 serving the purpose of specifying the desired value, is in this case considered to be stationary in the housing 4. On the side of the valve seat 9 facing the second slide 12, a second chamber 15 is arranged, which is connected with a connection line 17 via an inlet throttle 16. The connection line 17 provides a connection to the outlet 18 of the throttle valve 2.

In a connecting channel 19 between the connection line 17 and the front side of the slide 5 turning away from the valve seat 9, a plug 20 is arranged, which closes the connection channel 19.

The throttle valve 2 is a solenoid valve. In this connection, a closure element 21 co-operates with a valve seat 22. The closure element 21 is moved via a magnet armature 23, that is, lifted from the valve seat 22. The return movement is effected by the return spring 24.

The throttle valve 2 has an inlet 25, which is connected with an inlet connection 26 of the flow control valve 1.

The connection between the inlet 25 and the outlet 18 of the throttle valve 2 can also be interrupted or released by means of the closure element 21 and the valve seat 22. Additionally, a bypass opening 28 is provided in a wall 27 of the valve seat 22, which opening is made as a throttle, - 7 - as shown in the enlarged section. For example, the bypass opening 28 can have a diameter in the range from 0.5 to 1 mm. Also when the throttle valve 2 is closed, a pressure balancing between the inlet 25 and the outlet 18 of the throttle valve 2 can take place through the bypass opening

28, so that the two pressures P₀, Pi can approach each other and the permissible differential pressure over the throttle valve 2 is not exceeded. The throttle valve 2 can open without risking to get damaged.

From the inlet 25 of the throttle valve 2 a line 29 leads to the front side 30 of the slide 5, the front side 30 being arranged on that side of the slide 5 turning away from the valve seat 9. The line 29 also comprises a throt- tie 31. The throttling resistance of the line 29 can also result from the construction of the line itself. Thus, the pressure P₀ from the inlet connection 26 of the flow control valve 1 reaches the slide 5. The slide 5 is born in the housing 4 with a small play or slot. Through this slot hydraulic fluid from the line 29 can get into the chamber 10. The slot between the slide 5 and the housing 4 forms an auxiliary throttle, whose opening depends on the position of the slide 5 in the housing 4. The more the slide 5 is pushed in the direction of the valve seat 9, the lower is the throttle resistance by the auxiliary throttle. The pressure on the front side 30 of the slide 5 is also determined by the pressure on the middle pick-off of a pressure divider between the inlet connection 26 and the chamber 10 (that is, in practice the outlet connection 12) , which is formed by the throttle 31 and the auxiliary throttle.

The throttle valve 2 is time operated, that is, it is opened and closed periodically. The relation of the open- ing times to the sum of the opening and closing times, the - 8 - so-called duty cycle, determines the opening degree of the throttling valve 2, and thus also the pressure Pi in the connection line 17, that is, in the chamber 15.

The pressure P₂ at the outlet connection 12 acts upon the slide 5 in the opening direction, when disregarding the pressure drop at the outlet throttle 11. The pressure acting upon the front side 30 of the slide 5, however, is a closing pressure. When the pressure P₂ at the outlet connection 12 drops, the slide 5 is pushed further in the direction of the valve seat 9, causing a reduction of the fluid flow through the slot between the valve seat 9 and the slide 5. If, however, the pressure P₂ in the outlet connection 12 increases, for example caused by an in- creased load from a connected consumer, the slot between the slide 5 and the valve seat 9 opens further, thus releasing an increased fluid quantity. Thus, the flow quantity can be kept practically constant, meaning that its size is predetermined by the pressure Pi in the con- nection line 17.

The embodiment according to Fig. 1 is assembled from two standard parts, which only have to be slightly amended. Thus, the throttle unit 3 can be formed by the control valve from DE 43 41 848 C2, in which only on slide 1 must be fixed and the line 19 must be closed. The throttle valve 2 could for example be a solenoid valve of the type EVSIM 6-20 of the applicant, which only requires a bypass opening 28 to be made in the wall 27. Finally, the parts 2, 3 must be connected to each other by means of the connection line 17 and the line 29.

Fig. 2 shows a more compact embodiment, the same parts having the same reference numbers. A valve of this kind could, for example, be built into a motor. Here the throt- - 9 - tie valve 2 and the throttle unit 3 are made as one unit, that is, the solenoid valve forming the throttle valve 2 is flanged onto the housing 4. The valve seat 22 of the throttle valve 2 is arranged in an insert 32 supporting the spring 7 pressing the slide 5 into its opening position. Accordingly, the line 29 is formed in the insert 32. The line 29 is arranged in the housing 4. The throttle 31 is formed by a restriction arranged close to the spot where the line 29 transforms to a pressure chamber 33 on the front side 30 of the slide 5. Of course the slide 5 can also be replaced by another adjusting device, for example a diaphragm. If required, such a diaphragm can be made leaky" by a small opening or a bypass line, to permit a pressure balancing.

The bypass line is made as a bore 34 in the slide 5, which bore has a throttling section 35. Also when the valve 21, 22 is closed, fluid can reach the second throttle 5, 9. Otherwise, the function of the flow control valve shown in Fig. 2 corresponds to that of Fig. 1.

Fig. 3 shows a further embodiment of a flow control valve, substantially corresponding to the one in Fig. 2.

Additionally, another solenoid valve 36 has been inserted, which can close the bypass line between the inlet connection 26 and the second throttle 5, 9. For this purpose the solenoid valve interrupts a connection between the line 29 and the pressure chamber 33 by means of a closure element 37, which can be brought to bear on a valve seat 38. In this case the penetration of hydraulic fluid from the inlet connection 26 to the outlet connection 12 is prevented. - 10 - With this embodiment, an unpermissibly high differential pressure may occur over the throttle valve 2, which would prevent an opening of the valve 21, 22 or cause damages.

For this reason a control arrangement 39 is provided, which opens the solenoid valve 36 before the opening of the throttle valve 2 for so long that a pressure balancing over the throttle valve 2 can take place.

A flow control valve of this kind is preferably applied when water is used as hydraulic fluid.

Claims

- 11 -Patent Claims

1. Flow control valve with an inlet connection, an outlet connection having between them a throttling arrangement comprising a first throttle and a second throttle, the second throttle being adjustable in dependence of the pressure difference between the inlet connection and the outlet connection, characterised in that the first throttle (21, 22) is made as an auxiliary force operable throttle valve (2) and that a bypass line (29) is provided from the inlet connection (26) to the second throttle (5, 9) .

2. Valve according to claim 1, characterised in that a third throttle (35) is arranged in the bypass line (29) .

3. Valve according to claim 1 or 2, characterised in that the throttle valve (2) is a solenoid valve.

4. Valve according to claim 3, characterised in that the solenoid valve is time operated.

5. Valve according to one of the claims 1 to 4, characterised in that the second throttle (5, 9) has an adjusting element (5), and the bypass line (34, 35) penetrates the adjusting element.

6. Valve according to one of the claims 1 to 5, characterised in that the pressure drop over the second throttle (5, 9) is larger than over the throttle valve (2) .

- 12 - 7. Valve according to one of the claims 1 to 6, characterised in that a shut-off device (36 to 38) is arranged in the bypass line (29) .

8. Valve according to claim 7, characterised in that a control arrangement (39) is connected with the throttle valve (2) and the shut-off device (36 to 38), which opens the shut-off device for a predetermined period before operating the throttle valve (2) .

9. Valve according to claim 7 or 8, characterised in that the shut-off device (36 to 38) is a solenoid valve.

10. Valve according to one of the claims 7 to 9, charac- terised in that the throttle valve (2) , the second throttle (5, 9) and the shut-off device (36 to 38) are arranged in a common housing (4) on a common axis.