GB2040585A - Yoke structure for solenoid device - Google Patents

Abstract

A yoke structure for a solenoid device comprises a laminated hollow cylindrical body portion 20, a pair of end portions 21 of annular form and a plurality of retaining elements 23 located between the body portion and the end portions, the retaining elements having an interference fit with the body portion and the end portions. In one method of making the yoke, the body 20 is forced over the retaining members which are placed about the edge of the end portions 21. <IMAGE>

Description

SPECIFICATION Solenoid devices This invention relates to a yoke structure for a solenoid device and to a method of making the same, the yoke structure comprising an intermediate body portion and end portions at the opposite ends respectively of the body portion.

A solenoid device incorporating such a yoke structure comprises a tubular member in which is slidably located an armature and a core member disposed within the tubular member at one end thereof. An electrical winding surrounds the tubular member and the yoke structure extends around the winding and between the core member and a portion of the tubular member adjacent the armature. The core member, armature and yoke structure are formed from magnetisable material and the portion of the tubular member in the region of the armature is also formed from magnetisable material. When the winding is energised the core member and armature assume opposite magnetic polarity and an attraction force is developed resulting in relative movement of the .armature and core member.

For the best performance any air gaps apart from the air gap between the armature and core member should be as small as possible. The air gap between the armature and the tubular member is kept as small as possible and the yoke structure must be accurately constructed to ensure a minimum or zero air gap between the core member and the wall of the tubular member.

It is also desirable that the yoke structure should completely surround the winding and that it should be constructed of material having a low hysteresis loss. Moreover, the eddy current loss should also be as small as possible. High quality materials are therefore desirable but these are generally only available in strip form. When using such materials it is desirable to subject them to the minimum of working stress otherwise their magnetic performance is impaired and can only be restored by careful annealing.

The object of the present invention is to provide a yoke structure and a method of constructing same in a simple and convenient form.

According to the invention a yoke structure for a solenoid device comprises a hollow cylindrical laminated body portion, a pair of annular end portions, the end portions being disposed within the ends respectively of the body portion and a plurality of retaining elements disposed between the outer peripheral surface of each end portion and the internal peripheral surface of the body portion, said retaining elements being located about the respective end portions, being formed from magnetisable material and having an interference fit with the body portion and respective end portions.

According to another aspect of the invention a method of making a yoke structure for a solenoid device comprises forming a hollow cylindrical laminated body portion and an annular end portion, engaging about said end portion a plurality of retaining elements and forcing said body portion over said retaining elements thereby to secure the end portion within the end of said body portion.

According to a further feature the body portion is formed by winding a strip of material in spiral form and securing the outer end of the strip relative to the wound assembly.

An example of a yoke structure in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a sectional side elevation of a known form of solenoid device to which a yoke structure constructed in accordance with the invention may be applied.

Figure 2 shows in sectional side elevation, a yoke structure in accordance with the invention, Figure 3 shows an end view of an end portion of the yoke structure, Figure 4 shows a cross section of a retaining element, Figure 5 shows a stage in the construction of the yoke assembly of Figure 2, Figure 6 is a view similar to Figure 2 showing a modification and Figure 7 is a viewsimilarto Figure 3.

With reference to Figure 1 of the drawings, the solenoid device comprises a cylindrical core member 10 formed from magnetizable material and in which is formed an axially extending borel 1.

The peripheral surface of the core member defines a step and located about the narrower portion of the step is a tubular member which is formed in two parts 12, 13. The part 12 of the tubular member is formed from non-magnetic material whiie the part 13 is formed from magnetisable material. The two parts are secured together in fluid tight engagement as also is the part 12 to the core member 10. The open end of the part 13 of the tubular member is closed by a closure 14 but before such closure occurs an armature 1 5 is located within the tubular member. The armature 1 5 has a rod 1 6 connected thereto and which extends through the bore 11 to contact the operating member of a fluid control valve (not shown) with which the solenoid is associated.As will be seen in Figure 1, in the upper half of the drawing the core member is provided with a threaded peripheral portion of reduced diameter whereby the core member can be screwed into the housing of the valve whilst in the lower half of the drawing, a different form of connection is provided which includes a clamping ring 1 6.

Surrounding the core member and tubular member is a winding 17 and this is located within a yoke structure which comprises a hollow cylindrical body portion 1 8 and a pair of end portions 19 which are located within the body portion and secured thereto conveniently as shown in the drawing, by rolling reduced end portions of the body portion against flanges formed on the end portions 19. The end portions 1 9 are of one piece construction as also in the body portion 18. As will be seen from the drawing one end portion is in engagement with the core member 10 whilst the other end portion engages the part 13 of the tubular member.The arrangement is such that when the winding is energised, the end portions 19 assume opposite magnetic polarity as also do the core member 10 and the armature 1 5. As a result an attraction force is generated between the core member and the armature and the armature moves within the tubular member towards the core member thereby actuating the aforesaid valve member.

Turning now to Figur 2 of the drawings, there is shown the yoke structure of the invention together with the associated winding 17. The yoke structure comprises a hollow cylindrical laminated body portion 20 and this is conveniently formed by winding in spiral fashion, a strip of suitable material. The winding of the material can be effected about a mandrel and when the appropriate length of material has been wound, the free end is secured conveniently by spot welding, to the portion of the strip lying beneath the free end.

The end portions 21 of the yoke structure are also formed in a laminated fashion and each end portion comprises a stack of laminations 22 having the form shown in Figure 3. It will be observed that each lamination is of annular form and that is has a radial slit for the purpose of reducing eddy current loss. Each laminiation is formed by a punching operation.

As will be observed from Figure 2, the end portions 21 are located within the ends of the body portion 20 and they are secured therein by means of retaining elements 23. The section of the retaining elements before assembly of the yoke structure takes place is seen in Figure 4 and as will be seen from Figure 5, the retaining elements are of arcuate form and are constructed from magnetisable material such for example as EN1 or soft iron. As seen in Figure 4 each element comprises a central limb 25 having an upper flange 26 which extends generally at right angles to the limb 25. There is also a lower flange 27 and as will be observed from Figure 4 this inclines upwardly rather than extending at right angles to the limb 25.Moreover, at the lower end of the limb 25 there is provided a base portion 28 which defines a face 29 extending at right angles to the limb 25 and on the opposite side of the limb to the flanges 26 and 27.

As seen in Figure 2 the limb 25 of each element in the assembled condition of the yoke structure, is interposed between the internal peripheral surface of the body portion 20 and the external peripheral surface formed by the stacks of iaminations 22 forming the end portions 21. An interference fit exists so that the end portions are locked within the body portion. Moreover, it will be observed that the limbs 26 and 27 lie on opposite sides of the stack of laminations forming the end members and that following assembly the lower flange 27 is deformed so as to urge the laminations into firm facial engagement with other.

In order to avoid eddy current loss, the elements 23 are spaced from each other in the circumferential direction. Moreover, the elements are so disposed that they do not bridge the radial slit in the individual laminations 22.

The yoke structure is assembled as shown in Figure 5. The actual assembly involves a press operation and for this purpose a boister 30 is provided which has a central spigot portion 31 about which are located the laminations 22. The correct orientation of the lamination is assured by means of a guide member extending radially from the spigot portion 31. When so positioned the outer portions of the laminations lie over an annular recess 32 formed in the bolster and which has an outwardly inclined outer peripheral wall.

The recess 32 enables the retaining elements to be positioned about the stack of laminations so that they assume the position shown in Figure 5.

In this position the body portion 20 is forced over the limbs 25 of the retaining elements by means of the application in the axial direction, of pressure. During such movement the limbs of the retaining elements move into engagement with the external peripheral surface of the stack of laminations and the tilting movement which takes place is facilitated by the outwardly inclined face of the recess 32, and the curved surface of the bulbous portion 28 of the retaining elements.

During this movement the flange 27 is deformed as aforesaid and the pressure is removed when the end face of the body portion 20 engages the aforesaid faces 29 of the retaining elements.

Following assembly of one of the end portions 21 into the body portion 20, the winding 17 is inserted within the body portion 20 and the process is repeated so as to secure the other end portion 21 in position. The result is a yoke structure together with a winding, as seen in Figure 2. The limbs of the aforesaid elements provide a low reluctance path between the end portions and the body portion of the yoke structure. During the assembly as described the laminations 22 close inwardly a small extent, this being permitted by the radial slots formed therein.

When the yoke assembly is removed from the press the only machining operation which is required is to ream the apertures defined in the end portions. Since the laminations are securely held, the reaming operation results in substantially no distortion of the laminations and the reaming operation is carried out at the same time on the two apertures.

It is necessary to provide an electrical connector for the winding and the connector may be secured to the body portion 20 by drilling a small hole for the reception of a rivet or the like to retain the connector in position.

An alternative construction is shown in Figure 6 in which where possible, the same reference numerals are used. In this case the arcuate elements 23 are replaced by a series of flat elements generally indicated at 32. The flat elements are formed from sheet material having the desired magnetic properties and have a main limb 33 and a base portion 34 which defines on one side of the limb 33, a face 35 for engagement by the end face of the body portion 20. The outer edge of the limb 33 is urged into engagement with the inner surface of the body 20, whilst the inner edge of the limb 33 is engaged by the laminations 36 forming the end portion 21 of the yoke. As will be seen from Figure 7 the laminations 36 are of annular form with a radial slit but they are also provided with apertures 37 disposed adjacent but on opposite sides of the slot.

The flat elements 32 are pressed from sheet material and are assembled in a stack and conveniently secured together by flexible strips 38. For the purpose of assembly an appropriate length of stack is prepared and is deformed to annular form to allow it to be inserted in the end of the body portion 20. The flexible strips allow the stack to be deformed. A stack of laminations 36 is then assembled and using a suitable tool in the apertures 37, the laminations are compressed in the manner of a circlip to reduce their external diameter by an amount sufficient to enable the stack to be assembled into the annular stack of flat elements 33. The tool is then relaxed and the laminations expand so that their edges press into firm engagement with the inner edges of the flat elements. As shown the inner edges of the flat elements define flange portions 39, 40 against which the end laminations bear in the assembled condition. However, the projecting portions are not essential providing the stack of laminations 36 is carefully located prior to relaxing the tool. The expansion of the laminations 36 also results in the outer edges of the limbs 33 being pressed into firm engagement with the body 20.

As an alternative method of assembly the stack of flat elements may be assembled about the stack of laminations 36 which is then contracted, the body placed over the flat elements and the stack allowed to expand.

Claims (17)

1. A yoke structure for a solenoid device comprising a hollow cylindrical laminated body portion, a pair of annular end portions, the end portions being disposed within the ends respectively of the body portion and a plurality of retaining elements disposed between the outer peripheral surface of each end portion and the internal peripheral surface of the body portion, said retaining elements being located about the respective end portions, being formed from magnetisable material and having an interference fit with the body portion and respective end portions.

2. A yoke structure according to Claim 1 in which said retaining elements are of arcuate form.

3. A yoke structure according to Claim 1 in which said retaining elements are of flat form, an annular stack of said retaining elements being disposed about each end portion.

4. A yoke structure according to Claims 2 or 3, in which each retaining element defines a central limb which is disposed between the body portion and the end portion, and a base portion integral with the central limb and defining an outwardly extending face in engagement with end face of the body portion,

5. A yoke structure according to Claim 4 in which the retaining element includes inwardly extending flanges engaging with the opposite end faces of the end portion.

6. A yoke structure according to any one of the preceding Claims in which said end portions are formed from a stack of annular laminations each having a radial slot.

7. A method of making a yoke structure for a solenoid device comprising forming a hollow cylindrical laminated body portion and an annular end portion, engaging about said end portion a plurality of retaining elements and forcing said body portion over said retaining elements thereby to secure the end portion within the end of said body portion.

8. A method according to Claim 7 including the step of winding a strip of material in spiral form and securing the outer end of the strip relative to the wound assembly to form the body portion.

9. A method according to claim 8, including the step of assembling a stack of annular laminations to form said annular end portion.

10. A method according to Claim 9 in which said annular laminations are formed with a slot.

11. A method of making a yoke structure for a solenoid device comprising forming a hollow cylindrical laminated body portion, forming an end portion from a stack of annular laminations each lamination having a slot and means whereby the laminations can be deformed to reduce its external diameter, locating a plurality of retaining elements within the end of the body portion, deforming said annular laminations and inserting said laminations against said retaining elements and relaxing said laminations.

12. A method according to Claim 11, including the step of winding a strip of material in spiral form and securing the outer end of the strip relative to the wound assembly to form the body portion.

1 3. A method according to Claim 11 in which said retaining elements are formed from strip material and are assembled into a stack and held relative to each other by a flexible strip.

14. A yoke structure for a solenoid device comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figures 2, 3 and 4 of the accompanying drawings.

1 5. A yoke structure for a solenoid device comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figures 6 and. 7~of.theaccompa nying drawings.

16. A method of making a yoke structure for a solenoid device substantially as hereinbefore described with reference to Figure 5 of the accompanying drawings.

17. A method of making the yoke structure shown in Figures 6 and 7 substantially as herein before described.