DE8529255U1 - Switching valve - Google Patents

Description

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G 4197 J.M. Voith GmbH

Password: "Topfkolben" Heidenheim

Switching valve

The invention relates to a switching valve for controlling the pressure medium supply to a pressure medium consumer, in detail with the features specified in the preamble of claim 1:

Switching valves of this type are used, for example, to control the pressure medium supply to the switching elements (e.g. clutches or brakes ) of a multi-step transmission. Each switching element (= "pressure medium consumer ¹¹ ") is assigned a switching valve. If a gear change is to take place in the multi-step transmission, then the actuation of the relevant control valves is usually triggered by a command center; ie "the valve bodies of the relevant valves are moved. Normally, during such a gear change, the pressure medium supply to one of the previously loaded switching elements is interrupted and at the same time opened to a previously unloaded switching element.

The invention is based on the known switching valve according to DE-PS 27 20 877. This has, in addition to the features specified in the preamble of claim 1, the following features:

The consumer channel arranged in the housing has a central ring channel that surrounds the valve body and is bordered on both sides by an annular web. In addition to these two annular webs, an outer ring channel is arranged in the housing, one of which belongs to the supply channel and the other to the relief channel. Finally, an outer ring-shaped web is arranged (at both ends of the housing) next to the two outer ring channels to guide the valve body.

In accordance with this design of the housing, the valve body is designed as follows: The pressure medium control channel is formed by an annular groove; the width of this is approximately equal to the sum of the widths of the aforementioned webs and the annular channel belonging to the consumer channel. The annular groove is permanently connected to the middle annular channel of the housing. In the middle position of the valve body, the connections from the annular groove to the outer annular channels of the housing are completely or almost completely blocked. By moving the valve body, either one or the other of these connections is fully opened. At both ends, the valve body has cylindrical outer surfaces that slide in the outer annular webs of the housing.

(~) The control of the pressure medium flow is thus carried out by control edges running around the cylindrical surface of the valve body and by corresponding control edges of the housing. A disadvantage of this design is that in unfavorable cases (e.g. if the manufacturing is not precise) there is a risk of increased resistance to the displacement of the valve body at these control edges. In certain circumstances, jamming can occur between the valve body and the housing. To avoid these disadvantages, the valve body of the known valve is relatively long, with the valve body being guided in the housing mainly at its two ends. This means that the construction volume and space requirements are relatively high.

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Another known switching valve according to DE-AS 25 X2 778 has the following features:

a) The pressure medium control channel of the piston-like valve body is again designed as a channel between two collars 4,

5 arranged annular groove is formed, into which the consumer channel 8 opens.

b) Each end face of the valve body 3 is assigned a compression spring 9 or 25. As long as both compression springs act on the valve body, the latter is in its rest position in which it connects the consumer channel 8 with the relief channel 7.

·- c) A two-stage piston 22 can reduce the effect of one Compression spring 25 is released so that the other compression spring can move the valve body 3 axially. d) In order to achieve a controlled pressure build-up in the consumer, the following is provided: One end face 13 of the valve body 3 is subjected to the pressure in the consumer via a throttle point 11. The preload of the opposing compression spring 9 is gradually increased with the aid of a damping piston 15, with the valve body initially assuming a middle position. Finally, the valve body is moved to the end position opposite the rest position (into the so-called "full pressure position ¹¹ ").

Disadvantages of this known design: The space required and the effort for the two compression springs, for the two-stage piston, for the separately arranged pilot solenoid valve required to control it and for the damping piston are considerable. The large number of components requires tight manufacturing tolerances and increases the number of places where friction occurs (therefore sensitivity to dirt).

It is the object of the present invention to provide a switching valve

according to the preamble of claim 1, which - compared with the known switching valves mentioned - at

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has smaller dimensions for the same flow cross-sections. Nevertheless, resistance-free movement of the valve body and thus high reliability should be guaranteed. If necessary, similar to the known valve, the pressure in the consumer should be able to be regulated at least temporarily to a value below the maximum pressure.

This problem is solved by the characterizing features of claim 1.

A. Advantages of the switching valve according to OE-PS 27 20 877 and thus also of the switching valve according to the invention compared to the subject matter of OE-AS 25 12 778.

Because the pressure in the consumer is constantly acting unthrottled on one end of the valve body, when the actuating force (which the actuator exerts on the valve body when the consumer is under pressure) is switched off, the pressure prevailing in the consumer channel is generally sufficient to move the valve body quickly and safely into the rest position in which the consumer channel is connected to the relief channel. This means that a compression spring that acts on the valve body in the same direction as the aforementioned pressure can generally be dispensed with. If a compression spring is provided in exceptional cases (according to claim 2), then a very weak spring force is sufficient. In addition, the spring can be accommodated largely in the interior of the preferably pot-shaped valve body, so that no additional installation space is required for the compression spring.

During the reverse movement of the valve body from the rest position towards the "full ^- pressure position" (ie when the actuating force is switched on), only a very small displacement force is required at the beginning, partly because the opposing pressure spring, as already mentioned, is very weak or completely absent, and partly thanks to the fact that the valve body is the only moving element apart from the actuator.

Despite this simple design, the valve can also be designed and used as a combined switching and pressure control valve without any structural changes if required. For example, when the consumer is connected to the pressure medium source (similar to OE-AS 2 512 778), the pressure build-up in the consumer can be regulated by creating a balance between the actuating force, which in this case must be adjustable to a setpoint, and the counterforce resulting from the pressure in the consumer channel.

The switching valve according to the invention can also be used to solve other control tasks, whereby the truck in the consumer is regulated to the desired setpoint for any period of time.

Another important advantage of the switching valve according to DE-PS 27 20 877 and the switching valve according to the invention is the following if the actuating force according to claim 7 is generated directly by an electromagnet: When the valve body is adjusted from the rest position, the counterforce (which results from the pressure in the consumer channel) counteracting the actuating force (a magnetic force) only begins to build up when the connection from the supply channel to the consumer channel opens and thus only when the air gap between the armature and the armature counterpole has already been overcome by about half and the (initially relatively weak) magnetic force has therefore already reached a high value. In other words: Compared to other known valves operated directly by the armature of an electromagnet, the actuating force surplus over the hydraulic counterforce is higher (assuming the same electrical excitation power). This means that greater switching reliability is achieved, or a smaller and cheaper electromagnet can be used. Finally, this advantage can also be used as follows: The armature can be designed as a so-called flat armature, in contrast to the design according to DE-OS 19 08 659 (= US-PS 3,665,963), where the armature and armature counterpole are conically shaped in order to achieve a higher initial magnetic force.

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This known construction form has the disadvantage that the highest dimensional accuracy is required, otherwise a transverse force is created, which can result in increased frictional resistance and/or the risk of jamming. These disadvantages are avoided by the invention.

For all these reasons, the design according to DE-PS 27 20 (and thus also the design according to the invention) is particularly suitable for the valve body to be driven directly by the armature of an electromagnet.

In special cases, however, the switching valve according to the invention can also be combined with actuators of a different type, e.g. with the piston of a pilot valve.

B. Advantages of the switching valve according to the invention compared to the known valves according to DE-PS 27 20 877 and DE-AS 25 12 778.

The pressure medium control channel of the valve body is not designed as an annular groove, but as a connecting channel from the so-called consumer face to the cylindrical surface of the valve body. This means that the pressure medium control channel in the valve body has at least one radial channel that radially penetrates the cylinder wall. Preferably, several radial channels are provided that are evenly distributed around the circumference in order to avoid a transverse force. It is important that each radial channel opens directly into the cylindrical surface. This design avoids the control edges that were previously required and ran around the cylindrical outer surface. The disadvantage of these edges is, as already mentioned, that in unfavorable cases they can lead to the valve body jamming at the corresponding edges of the housing bore or at least prevent the valve body from being moved with little resistance. In other words: With the design according to the invention, the valve body is already guided in the area of these openings in the housing bore thanks to the longitudinal webs that remain between the openings of the radial channels. This eliminates the need for the guide surface arranged in the area of the relief channel as required in DE-PS 27 20 877.

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Pair. The two ring-shaped housing webs that serve to guide the valve body can often be arranged directly on both sides of the ring channel belonging to the supply channel. This significantly shortens the overall length of the entire valve.

A pot-shaped valve body is particularly advantageous. In this case, the thickness of the cylindrical wall of the valve body can be chosen to be very small, so that the radial channels are very short and their throttling losses are extremely low; this is in contrast to the throttling channel (11) in the valve body of the OE-AS 25 12 778.

Regarding the feature of claim 6, reference is made to OE-AS 20 19 345 (= US-PS 3,671,814).

Embodiments of the invention are described below with reference to the drawing.

Figure 1 shows a longitudinal section through a switching and pressure control valve, with the valve body in the rest position (i.e. consumer relieved).

Figure 2 shows a section of Figure 1, with the valve body in the middle position (consumer subjected to low, regulated pressure).

Figure 3 shows a section of Figure 1, valve body in the so-called full pressure position (consumer subjected to full pressure without pressure regulation).

Figure 4 shows a variant of Figure 1.

The main parts of the switching and pressure control valve shown are a pot-shaped valve body 10 (with thin-walled cylinder jacket 10a and base 10b) ₁ a housing 12, 12a shown only in a cabinet, preferably in two parts and a preferably bolt-shaped, coaxially arranged to the valve body

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Actuator 22. The valve body has an outer cylindrical surface 101 and two end faces 102 and 103. A recess 104 extends from one end face (102) into the interior of the valve body 10. The actuator 22 rests against the other end face 103. The latter is rigidly connected to the plunger 32 of an only partially visible electromagnet 30. The housing bore 13 serving to guide the valve body 10 is formed by two annular webs 23 and 25. The web 23 located near the bottom 10b is relatively narrow. Between the webs 23 and 25, the housing encloses a relatively large interior space 26, preferably designed as an annular channel, into which a supply channel 16 coming from a pressure medium source 15 opens. A similar interior space 24 is enclosed by the housing 12 in the area of the so-called consumer front side 102 of the valve body. A consumer channel 14 is connected to this interior space 24 and leads to a consumer 9 (shown only schematically) (e.g. actuating cylinder for a gearshift brake or clutch). In the area of the other front side 103 of the valve body (where the valve body 10 has the base 10b), a further interior space 28 is provided, from which a relief line 18 leads to the outside, for example into a sump 17.

The housing part 12 can be part of a transmission housing. As a rule, several consumers 9 and, corresponding to the C, several switching and pressure control valves of the type shown are arranged in it. It is therefore important that these valves take up little space while being highly reliable. In the drawing, the valve is shown approximately twice as large as the reality. The valve body 10 is actually only about the size of a thimble.

Near the bottom 10b, the valve body has at least two, preferably about six radial bores 11, which - in order to avoid radial forces - are evenly distributed over the circumference of the valve body. The axes of these bores are preferably all in the same plane. The bores all have the same diameter, which is approximately equal to the width of the annular web 23 or slightly larger than this width. Thus, the radial bores can be arranged in a multi-

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In the open position of the valve body 10, the valve body 10 can be completely or almost completely covered by the web 23. Instead of the circular holes 11, milled slots can also be provided.

The electromagnet 30 has a housing 31 (onto which the valve housing part 12a can be formed) with an armature counterpole 33 (in which the actuator 22 with the plunger 32 is guided in a sliding manner) and a housing 32 with a plunger 33. The housing 31 can be formed with a plunger 32.

Excitation current fed from a current source 35 and by means of lines 36, 37 and 38 as well as by means of an electrically controllable switching element jz*B* switching transistor 39* The mutually facing end faces 32' and 33' of the armature 32 and the armature counterpole 33 are flat, ie they lie in planes normal to the axis.

A control device 40 compares an actual value for the armature attraction force (measuring device 41, measuring line 42) with a setpoint value provided by a setpoint generator 43. If the valve is designed as a pure switching valve - without the possibility of pressure control, the control device 40 is not required.

In Figure 1 it is assumed that the electromagnet 30 which actuates the bolt 22 is switched off. The valve body 10 is therefore in its rest position, which is determined by the fact that a collar or adjusting ring 22a arranged on the bolt 22 rests on the housing 12a, 31. The valve body 10 generally reaches this rest position due to the residual pressure in the consumer 9. This is largely reduced because the consumer channel 14 is connected to the relief channel 18 via the interior 20 of the valve body and via the radial bores 11. As a rule, no compression spring is required to hold the valve body 10 in this rest position. In exceptional cases,

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In certain cases, however, as indicated by dashed lines, a weak compression spring 21 can be clamped in the interior 20 between the valve body base 10b and the housing 12.

When the electromagnet 30 is fully excited, the open end of the valve body 10 rests against the housing 12, with the radial bores according to Figure 3 connecting the feed channel 16 with the consumer channel 14. If the electromagnet is only opened by means of the control device α, i.e. the manifold force is applied to the valve body 10.

If the valve body 10 is in the middle position (Figure 2, the radial bores 11 are at least largely covered) , a state of equilibrium can be established between the displacement forces acting on the valve body. In other words: the displacement force exerted by the bolt 22 in this state is equal to the pressure force acting on the valve body 10 from the pressure in the consumer 9.

The design according to Fig. 4 enables an even further reduction in the length of the valve body 10' and the housing part 12* compared to Fig. 1. Instead of the ring web 25 an inner guide sleeve 25· is provided. In this case, a higher machining effort must be accepted, e.g. for the additional sliding surface 8 on the inside of the valve body.

11.10.1985 Sh/Py
0277k

Claims (1)

G 4197 J.M. V-oith GmbH Password: "Topfkolben ¹¹ Heidenheim fo sayings Switching valve for controlling the pressure medium supply to a pressure medium consumer (9) _f with the following features: a) a piston-like valve body (IQ) which has a cylindrical outer surface (101), two end faces (102, 103) and at least one pressure medium control channel (11) is axially displaceable in a bore (13) of a housing (12) by means of an actuator (22) between two end positions; b) the housing (12) has a consumer channel (14) leading to the consumer (S), a supply channel (16) connectable to a pressure medium source (15) and a relief channel (18) (leading, for example, to a sump (17)); c) the pressure medium control channel (11) of the valve body (10) connects the consumer channel (14) el) in one end position ("rest position") with the relief channel (18), whereby the supply channel (16) is blocked, c2) and in the other end position ("full pressure position") with the supply channel (16), whereby the relief channel (18) is blocked; d) the pressure prevailing in the consumer channel (14) exerts pressure on &igr; one end face (“consumer end face” 102) of the Valve body (10) exerts a pressure force; this is counteracted by an actuating force exerted by the actuator (22) on the valve body (10); characterized by the following additional features: e) the consumer channel (14) is directly connected to the area of said consumer front side (102) of the valve body (10); &bull; I· · Il Il Il <· ··· Il · I IM f) the pressure medium control channel (11) arranged in the valve body (10) comprises a recess (104) open towards the consumer end face (102) and at least one radial channel (11) leading from this recess to the cylindrical surface (101), wherein the radial channel opens directly into the cylindrical surface; g) to guide the valve body (10) in the housing bore (13), only two annular housing webs (23 and 25) arranged on both sides of the supply channel (16) are provided, one of which (23) is arranged in such a way that it can at least largely cover the mouth of the radial channel (11), or the mouths of the radial channels (11), in a middle position of the valve body (10). 2. Switching valve according to claim 1, characterized in that between the inside of the base (10b) and the housing (13) a weak compression spring (21) is clamped. 3. Switching valve according to claim 1 or 2, characterized in that the pressure medium control channel of the valve body (10) comprises at least two radial channels (11) which are evenly distributed over the circumference of the valve body. 4. Switching valve according to one of claims 1 to 3, characterized in that the radial channel or the radial channels (11) is or are arranged near the bottom (10b) of the pot-shaped valve body. 5. Switching valve according to one of claims 1 to 4, characterized by the following known features: a) Between the end positions, the valve body (10) serves to regulate the pressure in the consumer by closing the consumer channel. (14) temporarily with the supply channel (.16) and temporarily with the relief channel (18) or simultaneously throttled with both channels (16 and 18), whereby the element (22) and adjustable to a setpoint value and the counterforce acting on the valve body from the pressure in the consumer channel are in equilibrium; b) the radial bore(s) of the valve body (10) can be completely or almost completely covered by the housing bore (13) (e.g. ring web 23). 6. Switching valve according to claim 5, characterized in that the electromagnet is equipped in a known manner with a control device for adjusting the magnetic force (= armature attraction force = the actuating force exerted by the actuator 22 on the valve body 10) to a desired value. 11.10.1985 Sh/Py
0277k