WO2004113734A1

WO2004113734A1 - Electromagnetic valve drive

Info

Publication number: WO2004113734A1
Application number: PCT/DK2004/000430
Authority: WO
Inventors: Helge Søe PLOUGSGAARD
Original assignee: Sauer-Danfoss Aps
Priority date: 2003-06-24
Filing date: 2004-06-19
Publication date: 2004-12-29
Also published as: DE10328221A1; DE10328221B4

Abstract

The invention concerns an electromagnetic valve drive with at least two solenoid coils, at least one sensor coil and an electronic unit, which is electrically connected with the solenoid coils and the sensor coil. It is endeavoured to facilitate the handling. For this purpose, it is provided that the solenoid coils (17 to 20), the sensor coil (37), the electronic unit (11) and the electrical connections (41) between them are cast into a block of plastic (44).

Description

Electromagnetic valve drive

The invention concerns an electromagnetic valve drive with at least two solenoid coils, at least one sensor coil and an electronic unit, which is electrically connected with the solenoid coils and the sensor coil.

Hydraulic valves are often controlled by means of solenoid valves, either directly or via pilot pressures. The position of a valve element of the hydraulic valve is then reported via a sensor. For this reason, at least two solenoid valves and one sensor are used in such an electromagnetic valve drive. The coils of the solenoid valves, the solenoid coils, and the coil of the sensor, the sensor coil, are usually located on a side of the valve to be controlled.

The mounting of the individual components on the valve to be controlled is relatively expensive, as many individual parts have to be handled, and only a limited space is available. The components mentioned can be premounted in a housing. However, this procedure is expensive, and in many cases does not create the desired, stable conditions.

The invention is based on the task of facilitating the handling.

With an electromagnetic valve drive as mentioned in the introduction, this task is solved in that the solenoid coils, the sensor coil, the electronic unit and the electric connections between them are cast into a block of plastic . This embodiment gives a substantially improved and more stable valve drive, which can, in principle, also be manufactured at low cost . The components of the valve drive are completely protected against humidity, which is in many other cases a problem in connection with hydraulics and its application fields. The relative positions of the individual components remain unchanged, also when heavy loads or load changes occur. The electrical connections are protected in the plastic block, so that the risk of a failure due to damaged electrical connections remains small .

Preferably, the solenoid coils, the sensor coil, the elec- tronic unit and the electrical connections are inserted in a plastic housing, which is then filled with plastic. This simplifies the mounting. The plastic housing forms a mould for the plastic. However, the plastic no longer has to be removed from the housing during manufacturing of the block, but, together with the plastic filled in, the housing forms the block of plastic. In the housing, the individual components can be premounted, that is, located in their desired positions. It is merely required to secure the individual components in their positions for as long as it takes for the plastic to harden. Usually, the fixing of the components in the housing does not have to be extremely stable.

Preferably, each of the solenoid coils and the sensor coil are mechanically connected with the electronic unit. Thus, there is not only an electrical connection, but also a mechanical connection between the coils and the electronic unit. Of course, the mechanical connection can at the same time be the electrical connection. The individual components are thus mutually stabilised, that is, an assembled group of the solenoid coils, the sensor coil and the electronic unit can be inserted in the housing. An additional 5 fixing can then be realised with relatively little effort.

Preferably, each solenoid coil and/or the sensor coil are located in a coil carrier, which is supported on the bottom of the plastic housing. The coil carrier has several

D tasks. Firstly, during the casting process, it holds each coil in its place. Secondly, it keeps the inside of the coils free of the cast plastic, so that later an armature for the solenoid coils or a transmitter for the sensor coils can be inserted here. The fact that the coil carrier

5 is supported on the bottom of the plastic housing provides a defined height for each coil in the plastic housing and thus in the plastic block.

Preferably, the bottom of the plastic housing has, for D each coil carrier, a through opening, through which a projection of the coil carrier projects. By means of this projection, a local fixing of the coil carrier and thus of the coils in the housing can be achieved. This local fixing is sufficient to keep the individual components suffi- 5 ciently stable during the filling of the housing with plastic. Therefore, additional fixing measures are not required. The manufacturing gets extremely simple.

It is preferred that the projection of the coil carrier 0 for the solenoid coils ends outside with the bottom of the housing. It is also possible that the projection has a somewhat smaller height than the thickness of the bottom of the plastic housing. In this way it is avoided that the projection projects outwards, thus causing disturbances on the outside of the plastic housing.

Preferably, a yoke surrounds the block on at least three sides. Thus, this yoke has two tasks. Firstly, it serves the purpose of conduction the magnetic flow, which is generated by the coils. Secondly, the yoke contributes to an improvement of the mechanical stability of the block. In other words, the yoke is used as cover for the block. The fact that the yoke surrounds the block on the outside makes it possible to fix the yoke on the block after manufacturing the block of plastic. Thus, the casting process can be made without the yoke, that is, the yoke does not disturb the filling of the plastic. The plastic (or an- other casting material) can, for example, be inserted under vacuum. In an additional step, the yoke is then fixed.

It is preferred that in a section the yoke has a U-shape with a base and two legs, and is pushed onto the block. This is a relatively simple way of fixing the yoke.

It is particularly preferred that the legs are prestressed in relation to each other. Thus, the yoke will be held on the block by its own force .

Preferably, the electronic unit is located on the side of the solenoid coils facing away from the base. Thus, it is achieved that the distance between the solenoid coils and the yoke can be kept small, so that good magnetic condi- tions are obtained.

Preferably, at least one leg engages in a slot on a section of the sensor coil carrier projecting from the block. Thus, the yoke secures the sensor coil carrier against an axial movement. Movements in other directions are not possible, as then the sensor coil carrier would have to displace plastic, which is no longer possible after the hard- ening. Thus, in a simple manner, the yoke forms a protection against an axial pulling or pressing out of the sensor coil carrier.

Preferably, the yoke has fixing holes. Thus, the yoke gets a third task. It is used for fixing the drive on a related valve unit .

Preferably, in the area of the fixing holes the block has recesses. Thus, screws or bolts can be led through the complete block, without having to consider the block.

Preferably, the recesses are formed by a course of the housing wall. From the beginning, the housing is made so that around the areas, through which screws and bolts are guided, the housing wall makes a curve. Thus, after filling the housing with plastic, it is no longer required to bore holes or to cut out recesses. Thus, the material consumption for the filling of plastic can be kept small.

Preferably, the solenoid coils and the sensor coil are arranged next to each other in a row, the electronic unit being arranged next to the row. This makes it simpler to integrate and fix the parts on the same printed circuit board. Thus, the electronic unit serves the stabilising of the coils in relation to each other.

Preferably, a connector is cast into the block. The connector serves the creation of electrical connections to the environment, for example for receiving signals for the solenoid valves or for sending signals from the sensor.

When the connector is cast directly into the block, loose electrical connections between the connector and the coils or the electronic unit, respectively, are not required. On the contrary, these electrical connections are protected inside the plastic.

It is preferred that the connector is located on one of the front sides of the block. Here, it causes least interference .

It is also preferred that the housing has an opening in a sidewall, whose size corresponds to the size of the con- nector. Before filling the housing with plastic, the opening is closed by the connector, or rather, a housing belonging to the connector. Thus, on the one hand, it is achieved that the connector is retained in the plastic, when the casting process is finished. On the other hand, it is possible to use different connectors, whose outer dimensions must in principle merely correspond to each other. The sealing between the connector and the housing can, for example, be made in that the housing engages in a circumferential groove on the connector housing.

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

Fig. 1 a schematic view for explaining a valve drive

Fig. 2 a valve drive in a sectional view II-II according to Fig. 3 Fig. 3 a sectional view III-III according to Fig. 2

Fig. 4 a sectional view IV-IV according to Fig. 2

Fig. 1 is a schematic view of a hydraulic circuit diagram for a drive of a merely schematically shown valve 1, for example a proportional valve, which controls a consumer (not shown in detail) . The valve 1 has a slide 2, whose two front sides acted upon by hydraulic pressures in pressure chambers 3, 4. The pressure in the pressure chambers 3, 4 is controlled by four solenoid valves 5 to 8 , which are arranged in the form of a bridge . In a diagonal of this bridge the valve 1 is located. In the remaining cor- ner points of the bridge are a pressure source 9 and a tank 10.

The solenoid valves 5 to 8 are controlled by an electronic unit 11, which comprises several schematically shown com- ponents 12, 13, 14. The position of the slide 2 is transmitted by a transmission link 15 to a sensor 16, which reports the position of the slide 2 back to the electronic unit 11.

The Figs. 2 to 4 show the mechanical design of the valve drive, or part of it, respectively, namely a total of four solenoid coils 17 to 20 of the four solenoid valves 5 to 8. Each solenoid coil 17 to 20 comprises an armature 21 to 24, which, when the related solenoid coil 17 to 20 is sup- plied with current, changes its position, thus displacing a valve element (not shown in detail) of the related solenoid valve. Each solenoid coil 17 to 20 is adopted in a coil carrier 25 to 28. The four coil carriers 25 to 28 with the coils 17 to 20 are arranged in a housing 29, which has a bottom 30 and sidewalls 31 to 34. For each coil carrier 26 to 28, the bottom 30 has an opening 35, through which a projection 36 of the coil carrier 25 pro- jects. The length of the projection 36 maximum corresponds to the thickness of the bottom 30, that is, it does not project from the lower side of the bottom 30.

The sensor 16 has a sensor coil 37, which is located in a sensor coil carrier 38. Also the sensor coil carrier 38 is supported on the bottom 30 of the housing 29. It projects through the bottom with a projection 39 and projects downwards from the bottom.

In the present embodiment, the electronic unit 11 is realised by means of a circuit board 40, on which the corresponding components 12 to 14 are located. Via connections 41, the coils 17 to 20 are mechanically and electrically connected with the circuit board 40. The connections can, for example, be made by thicker wires, so that not only an electrical connection between the coils 17 to 20 and the electronic unit 11 is provided, but also a mechanical connection.

Also the sensor coil 37 is connected with the circuit board 40. Here, the coil carrier 38 can even bear flat on the circuit board 40.

The solenoid coils 17 to 20 and the sensor coil 37 are ar- ranged next to each other in a row. The electronic unit 11 is, as appears from Fig. 4, located on the side of the row. In the sidewall 33 is provided an opening, into which a connector housing 42 is inserted. On three sides, the connector housing has a circumferential groove 43, so that the connector housing 42 can be pushed into the sidewall 33, filling and sealing the opening. Then, the housing 29 can be filled with plastic material 44. The plastic material 44 can, for example, be inserted under vacuum. It fixes the solenoid coils 17 to 20, the sensor coil 37 and the connector housing 42 as well as the wires 45 between the connector housing 42 and the electronic unit 11. The plastic material 44 ends upwards with the housing 29, thus forming together with the housing 29 a block of plastic. The housing 29 and the plastic material 44 can consist of the same material. However, this is not necessarily re- quired.

In the edges between the sidewall 31 and the front side- walls 33, 34, the housing has a recess, which prevents recesses 46, 47 in the block from being filled with plastic material 44. Also in the sidewall 32 a corresponding recess is provided, which forms a recess 48.

A yoke 49 with a base 50 and two legs 51, 52 surrounds the block of housing 29 and plastic material 44 in a U-shape. The two legs 51, 52 may be prestressed in relation to each other. The block 29, 44 is then clamped between the legs 51, 52.

The lower leg 51 engages in a slot 53 on the projection 39 of the sensor coil carrier 38 and thus secures the sensor coil carrier 38 against an axial movement in the plastic 44. Of course, further measures can be taken to prevent a movement of the sensor coil carrier 38 in relation to the yoke 49. For example, a spring washer can be inserted between the sensor coil carrier 38 and the yoke 49 or between the yoke 49 and one or more of the solenoid valves. Also, a unit for fixing the sensor coil carrier 38 can be cast into the plastic material 44 or project from it.

Thus, the yoke 49 has several tasks. Firstly, it serves as auxiliary means for a magnetic circuit in the environment of the solenoid coils 17 to 20. Secondly, it provides a mechanical stabilisation of the unit of housing 29 and plastic material 44. Finally, it retains the sensor coil carrier 38.

In order to provide favourable magnetic conditions, the circuit board 40 is located on the side of the solenoid coils 17 to 20 facing the base 50.

Casting the connector housing 42 into the block of plastic 29, 44 also makes it possible to offer the drive with dif- ferent connectors, which is an advantage in many fields, as some users demand special connectors. The only condition is that the connector housing 42 has the same size as the opening of the sidewall 33 of the housing 29.

With the design shown, all parts are electrically and mechanically connected with each other before the filling process, thus forming a mechanically prestabilised unit. When inserting this unit in the housing 29, all parts are connected stably with each other, so that a filling of the housing 29 with the plastic material 44 is possible. Subsequently, the individual components are stably connected, both mechanically and electrically. After the filling, the yoke is mounted. This gives a mechanically extremely sta- ble arrangement, which has good magnetical properties and is sufficiently stable, both mechanically and electrically. Due to the filling, all electrical components are protected against humidity.

The yoke 50 has an additional task. In the yoke 50, fixing holes 54 to 56 are provided, through which screws or bolts can be inserted to fix the shown unit on a valve. The fixing holes 54 to 56 are provided in the area of the re- cesses 46 to 48.

Claims

Patent Claims

1. Electromagnetic valve drive with at least two solenoid coils, at least one sensor coil and an electronic unit, which is electrically connected with the solenoid coils and the sensor coil, characterised in that the solenoid coils (17 to 20) , the sensor coil (37) , the electronic unit (11) and the electrical connec- tions (41) between them are cast into a block of plastic (44) .

2. Drive according to claim 1, characterised in that the solenoid coils (17 to 20) , the sensor coil (37) , the electronic unit (11) and the electrical connections

(41) are inserted in a plastic housing (29) , which is then filled with plastic (44) .

3. Drive according to claim 2, characterised in that each of the solenoid coils (17 to 20) and the sensor coil

(37) are mechanically connected with the electronic unit (11) .

4. Drive according to claim 2 or 3 , characterised in that each solenoid coil (17 to 20) and/or the sensor coil

(37) is located in a coil carrier (25 to 28, 38), which is supported on the bottom (30) of the plastic housing (29) .

5. Drive according to claim 4, characterised in that the bottom (30) of the plastic housing (29) has, for each coil carrier (25 to 28, 38), a through opening (35), through which a projection (36, 39) of the coil carrier (25 to 28, 38) projects.

6. Drive according to claim 5, characterised in that the projection (36) of the coil carrier (25 to 28, 38) for the solenoid coils (17 to 20) ends on the outside with the bottom (30) of the housing (29) .

7. Drive according to one of the claims 1 to 6 , charac- terised in that a yoke (49) surrounds the block on at least three sides.

8. Drive according to claim 7, characterised in that in a section the yoke (49) has a U-shape with a base (50) and two legs (51, 52) , and is pushed onto the block.

9. Drive according to claim 8, characterised in that the legs (51, 52) are prestressed in relation to each other.

10. Drive according to claim 8 or 9, characterised in that the electronic unit (11) is located on the side of the solenoid coils (17 to 20) facing away from the base (50) .

11. Drive according to one of the claims 8 to 10, characterised in that at least one leg (51) engages in a slot (53) on a section (39) of the sensor coil carrier (38) projecting from the block.

12. Drive according to one of the claims 7 to 11, characterised in that the yoke (49) has fixing holes 54 to 56) .

13. Drive according to claim 12, characterised in that in the area of the fixing holes (54 to 56) the block has recesses (46 to 48) .

14. Drive according to claim 13, characterised in that the recesses (46 to 48) are formed by a course of the housing wall (31 to 34) .

15. Drive according to one of the claims 1 to 14, characterised in that the solenoid coils (17 to 20) and the sensor coil (37) are arranged next to each other in a row, the electronic unit (11) being arranged next to the row.

16. Drive according to one of the claims 1 to 15, characterised in that a connector (42) is cast into the block.

17. Drive according to claim 16, characterised in that the connector (42) is located on one of the front sides of the block.

18. Drive according to claim 16 or 17, characterised in that the housing has an opening in a sidewall (33) , whose size corresponds to the size of the connector (42) .