FR2559301A1 - SOLENOID WITH NOISE REDUCED CHARACTERISTICS - Google Patents

Abstract

THIS SOLENOID 10 INCLUDES A MOBILE ARMATURE 11 WHICH CAN MOVE OVER A CERTAIN LENGTH 13 OF STROKE RELATIVE TO A MAGNET 15. THE FRAME INCLUDES A CORE 17 CONSTITUTES OF A MAGNETIC MATERIAL AND HAVING A FIRST LENGTH. THE MAGNET MAY BE ELECTRICALLY POWERED TO PROVIDE A MAGNETIC FLOW AND IT SHOWS A FLOW PATH HAVING A SECOND LENGTH WHICH IS GREATER THAN THE FIRST LENGTH OR LENGTH OF THE CORE. THEREFORE, THE MAGNET EXERCISES ON THE CORE A PULLING FORCE THE INTENSITY OF WHICH INCREASES LINEARLY THROUGHOUT THE LENGTH OF THE STROKE. APPLICATIONS: ESPECIALLY TO GAS TAPS USED TO ADJUST THE FLOW OF FUEL IN HEATING APPLIANCES LOCATED IN LIVING ROOMS.

Description

Solenoid with reduced noise characteristics.

  The present invention relates generally to solenoids.

  electromagnetic and it relates more precisely to a solenoid whose length of the core is chosen to be shorter than the path of the useful flux of the magnet, which results in a solenoid with characteristics of

significantly reduced noise.

  One of the disadvantages of solenoids of conventional design and construction, whether of the AC or DC type, is that they frequently exhibit undesirable noise levels when put into operation. work and during operation. This noise comes mainly from two sources, one of which is notably the strong shock of the metal parts against each other, resulting from the high force of attraction exerted by the electromagnet on the movable armature. Typically, this attractive force has

  tendency to increase exponentially to the point where the reinforcement is placed

  fully created in its position of attraction or operation. In AC solenoids, another source of noise from the solenoid is the mechanical vibrations produced when the applied AC signal crosses the zero voltage axis at a rate that

  is twice the frequency of the AC line. This pheno-

  leads is generally known as AC snoring and it can be quite unpleasant, depending on the dimensions of the solenoid,

  details of its construction and its proximity to the human ear.

  One way of approaching the design of a solenoid with reduced noise characteristics is shown and described in US Pat. No. 3,860,894, in which conical arcuate elements made up

  of magnetic material are placed in the passage through which the arma-

  ture, at a location near the end of the passage through which the arma-

  ture seeks to reach when the coil is supplied with current.

  Another method of reducing noise in solenoids is shown

  felt and described in US Patent No. 4,177,440. In the solenoid described in this patent, the core of the armature and its magnetic seat have

  both conical shapes that match and a ring of material

  anti-friction and anti-magnetic line is arranged around the seat cavity

  conical in order to absorb the shock of the frame.

  Another method of reducing noise in alternating current solenoids is to provide a coil for adjusting the noise level in

  the electromagnetic structure. This coil acts as a secondary coil.

  pair of a short-circuited single turn transformer in which

  could be induced a magnetic field which is out of phase by about 90 compared to

  port at the line voltage applied to the coil of the AC solenoid. This results in a reduction in snoring in alternating current. We can combine these noise level adjustment coils with

  fixed supports of elastic material arranged in the structure of the soil

  notde to absorb shocks and reduce noise. An example of this type of

  design is shown and described in U.S. Patent No. 2,888,233.

  Although these solenoid designs have been successful so far, they tend to have certain drawbacks. In particular, these solenoids are constructed in such a way that the attraction force exerted by the magnet on the armature increases exponentially from the moment when the solenoid begins to operate, to reach

  a maximum value when the armature is placed fully in its posi-

  tion of attraction. Typically, the maximum force of attraction

  is several times greater than the initial force of attraction and, consequently

  quence, it is much greater than the force necessary to overcome the effect of gravity and any spring. This therefore results in the production of undesirable noise and excessive wear of the mechanical parts.

  solenoid. Another disadvantage is that the elastic materials

  ques and shock absorbers, placed in the solenoid, tend to disintegrate during prolonged cycles of the solenoid and fragments of these materials can be housed between the movable armature and the passage which guides it, thereby causing operation defective. A solenoid which

  would be built and mounted to provide a pull which increases

  tation is generally linear over the entire stroke length of the arma-

  which could optionally provide elastic and cushioning elements

  shock absorbers at a location outside the solenoid, would constitute a pro-

undeniable technical sandstone.

  In general, a solenoid with reduced noise characteristics comprises a movable armature which can move over a certain length of travel relative to a magnet. The frame includes a core made of magnetic material and having a first length. The magnet can be electrically powered to provide magnetic flux and has a flux path having a second length which is greater than the first length of the core. The magnet therefore exerts on the core an attractive force whose size generally increases linearly over the entire stroke length. In a second embodiment, the solenoid comprises a stop plate and a stop disc mounted on the outside. An elastic bearing element is provided on the stop disc, intended to abut against the stop plate when the armature is in its position of attraction

  due to the power of the magnet coil. In a third example

  full of realization, the magnet and the core each include pro-

  spun so as to increase the magnetic force of attraction which is exerted between them at the moment when the coil is supplied. The solenoid which is the subject of the present invention has proved to be particularly useful in

  gas valves used to regulate the flow of fuel.

  The object of the present invention is to provide a solenoid with a charac-

reduced noise.

  Another object of the present invention is to provide a solenoid armature whose core has a length less than that of the path of the

magnetic flux of the magnet.

  Another object of the present invention is to provide a solenoid in which the force of attraction exerted by the magnet on the core has an intensity which generally increases linearly over the entire length of the

frame stroke.

  Yet another object of the present invention is to provide a

  solenoid in which an elastic damping structure can be pre-

  view outside the electromagnetic organs of the solenoid.

  The present invention will be clearly understood on reading the following description made in relation to the attached drawings, in which: formula 1 is a view in longitudinal section of the solenoid which is the subject of the present invention, certain parts being shown in cutaway and others in solid lines;

  FIG. 2 is a graphic representation of certain characteristics

  force statistics as a function of the stroke, relating to the solenoids described; and FIG. 3 is a view in longitudinal section of the solenoid according to the present invention, certain parts being shown in cutaway and

  others in solid lines, and showing how the solenoid can be incorporated

  has a gas valve used to regulate the flow of a fuel.

  Reference will now be made to FIG. 1. The solenoid 10 shown comprises a movable armature 11 which can move over a length 13 of travel, this displacement being made relative to a magnet 15. The armature 11

  comprises a core 17 made of a magnetic material and having a pre-

  first length. The magnet 15 can be electrically powered to provide

  a magnetic flux which determines a flux path having a second length

  which is greater than the first length of the core 17. The magnet 15 therefore exerts on the core 17 a force of attraction whose intensity generally increases linearly over the entire length 13 of stroke. In a second embodiment, a return structure 19 in the form of a spring is provided in the case where it is desired to effect the withdrawal of the armature 11 by means other than gravity, at the moment when the solenoid ceases to be powered. In a third embodiment, the magnet 15 and the core 17 each comprise respective parts 21, 23 which are shaped so as to increase the magnetic force of attraction which is exerted between them

  when the coil is energized.

  More specifically, the magnet 15 comprises a solenoid coil 25, preferably of the direct current type, which is formed of an annular cylinder.

  and which can be electrically powered to produce a magnetic flux.

  The coil 25 can be easily wound on a body 27 to form a

  coil assembly having a first end 29, a second end

  mite 31 and a longitudinal and cylindrical passage 33 through the coil. In the vicinity of the second end 31, the magnet 15 also comprises an upper stop 35 which has a cylindrical shape as a whole, is made of a magnetic material and the diameter of which is chosen so that this upper stop can be concentrically housed in the longitudinal passage 33 of the coil body, forming a narrow but sliding fit. The upper stop 35 includes an externally threaded part 21 onto which a cylindrical guide tube 37 mounted concentrically in the passage 33 of the body of the coil can be screwed, forming a narrow sliding adjustment. This tube 37 can consist of a

  any rigid antimagnetic material such as brass and it has

  te a smooth interior surface. At its lower end, the tube presents

  te an enlarged shoulder 39 which comes into contact with the underside 41 of the shield 43 of sheet steel and which facilitates the maintenance of the solenoid 10 in operating connection with the device to be controlled. A threaded extension 45 is provided on the upper stop to receive a Grower washer 47 and a nut 49 which make it possible to fix the upper stop 35 and the tube 37 on the shield 43. A washer 51, made of a magnetic material, is placed between the body 27 of the coil and the shield 43

  concentrically with the tube 37 in order to improve the quality of the flow path.

  The frame 11 comprises a cylindrical core 17 as a whole, made of a magnetic material and the diameter of which is chosen so that this core can be housed inside the guide tube 37 by forming an adjustment therewith. narrow but sliding freely. To his

  outer end, the core 17 comprises a concentric hole 53 for drilling

  notched, tapped to receive a rod 55 fixed to the core by a device 71

  of fixing such as a screw which is passed longitudinally in the rod 55.

  The latter is preferably made of a rigid and anti-material

  magnetic such as brass or aluminum, and it is designed to fix the solenoid 10 to the device to be controlled. The upper stop 35 and the core

  17 are preferably made of stainless steel having qua-

  magnetic parts and core 17 can be covered with a thin film

  polytetrafluoroethylene to reduce friction.

  If, when the coil 25 is no longer supplied, it is desired that the movement of the armature 11 to its first position of withdrawal takes place

  by means other than gravity, one can also include in the soil-

  noTde 10 a spring return structure 19. This structure 19 comprises a stop plate 57 comprising an edge 59, a projecting support surface 61 and a hole 63 drilled in the face 61 to allow the fixing of this stop plate 57 on the guide tube 37. The stop plate 57 is held in position on the shoulder 39 of the guide tube 37 by a locking nut disposed on the underside of this tube, while two O-rings 67 are housed in annular grooves of dimensions

  suitable, formed in the shoulder 39 of the tube and in the lock nut 65

  cage, to constitute a gas-tight seal in the case where the solenoid is used in connection with a gas valve 97 as shown in the

figure 3.

  A stop disc 69 is received at the outer end of the rod 55 and held thereon by a fixing device 71. It is preferable

  that this stop disc 69 comprises an annular projection 73 which serves as a guide

  from a helical compression spring 75 placed between the stop plate 57 and the stop disc 69. The length of the spring 75 is chosen as a function of the space between the plate 57 and the disc 69, so as to impose on the spring a low preliminary compression load when

  the frame 11 is in the withdrawal position shown.

  Those skilled in the art will appreciate that when the solenoid coil 25

  noTde 10 of figure 1 will be supplied, the armature 11 may be requested

  by several forces, some of which act in opposite directions to the others.

  One of these forces will be the magnetic force resulting from the creation of a magnetic flux path and it will act in a direction such that the armature 11 will be attracted towards the upper stop 35, upwards when we consider

  Figure 1. A second force, which results from the action of a spring which

  conch such as the spring 75, will be exerted down on the frame 11, as well as gravity. In addition, it will be appreciated that the resulting force acting on the armature 11 when the coil 25 is energized, must be directed upwards and have a sufficient intensity to overcome the combined effects of any forces directed downwards, including those resulting from the action of the spring 75 and gravity, so as to cause the movement of the frame 11 upwards. Depending on the presence or absence of the spring-shaped return structure 19, the length 13 of the stroke determined by the proximity of the core 17 and the upper stop 35, the density of magnetic flux and the characteristics of the device actuated by the solenoid 10, it may be desirable to provide means for increasing the component

  magnetic force attraction.

  Consequently, in a third embodiment, the upper stop 35 can be given a configuration such that this stop has a concentric cavity 77 which is formed according to a first profile and which has a flange 79. In addition, the core 17 of the frame 11 can

  receive a configuration such that this core comprises an element 23 consisting of

  killing a nose which is formed in a second profile and which projects upwards from the core 17. In order to facilitate their manufacture, it is preferable to give the cavity 77 and the element 23 constituting a nose profiles substantially identical to each other and in the shape of a truncated cone. Because the rim 79 of the cavity and the element 23 constituting a nose are, in the first position or withdrawal position, closer to each other than are the upper stop 35 and the cylindrical part of the core 17, the magnetic force of attraction will be increased when the coil is supplied. The element 23 constituting a nose and the core 17 form between them a shoulder 81 intended to come into contact with the flange 79 when the frame 11 is in the second position or position of attraction. We must realize that we would obtain an equivalent attraction effect as a whole if the protruding element 23 formed part of the upper stop 35 and if the cavity 77 was formed in the core 17. In a configuration which it is preferable to adopt, the profiles of the element 23 constituting a nose, and of the cavity 77, are given dimensions which correspond so that, when the shoulder 81 is in contact with the flange 79, there remains a slight gap between

  the element 23 constituting a nose and the surface of the cavity 77.

  The path of the magnetic flux resulting from the supply of the coil will include a first, internal path, formed in the region delimited as a whole by the longitudinal dimension comprised between the flange 70 and the lower external face 41 of the shield 43. It will also include a second, external path, which is formed in the spatial zone located below the face 41 and which will mainly be the path of the leakage flow. It is better to empirically choose the length of the core 17 as a function of the length of the flux. When the coil 25 is energized, the inductive coupling between the magnet 15 and the core 17 will result in an attractive force having a first intensity. When the armature 11 begins its stroke 13 to approach the upper stop 35, this

  moving upwards as shown in Figure 1, the par-

  tie of the core 17 which is contiguous to the element 23 constituting a nose is found

  will increasingly be coupled to the first interior path of the flow, this path

  jet of greater density of flux predominant closer to and at the longitudinal center of the coil 25. At the same time, the part of the core 17 which is contiguous with the rod 55 will be drawn upwards, causing a progressive reduction in the coupling of the core 17 with the second path, outside, of the flow. Consequently, when the armature 11 moves upward, the magnetic force of attraction will increase moderately, gradually and in generally linear relation with the length of the traveled part of the race 13. When the armature 11 is in its second position or

  position of attraction, the force will have a second intensity which is higher

  lower than the first intensity and, in a preferred embodiment, the ratio of the force of the second intensity to the force of the first intensity will be of the order of approximately 3/1 when the solenoid according to the present invention will be used in a gas tap for example. We have to

  be aware that this ratio may vary somewhat in a soil-

  of the type according to the present invention, depending on the application

  made of it. However, it is estimated that for a particular application

  liere, the mentioned ratio of forces resulting from the use of a sol-

  number of the type according to the present invention, will be substantially less than

  report which would result from the use of a classic type solenoid.

  This characteristic is illustrated graphically in Figure 2 on

  which the ordinate 83 represents the force increasing upwards tan-

  say that the abscissa 85 represents the race 13. The vertical axis 87 represents the first position or withdrawal position of the frame 11, while the ordinate 83 represents the second position or position of attraction of this same frame 11 , the shoulder 81 being in contact with the flange 79. The curve 89 as a whole represents the force exponentially

  growing which is exerted on a frame of known conventional construction.

  Curve 91 represents as a whole the force, directed downwards, which is applied to the reinforcement 11 as a result of the compression of spring75, while curve 93 represents as a whole the force of attraction exerted between the armature 11 and the magnet 15. The difference between the curve 91 and the curve 93, measured on any vertical axis, represents the resulting force acting on the armature 11, the weak action of gravity being neglected. We can see, by considering the curves of Figure 2, that when the armature 1 of a conventional solenoid moves to be fully in its position of attraction, the force exerted on this armature can be equal to five or six times what is needed to defeat the action

  of gravity and that of any spring. This usually results-

  lies an unpleasant hammering noise. On the contrary, the force resulting from the construction of the solenoid 10 according to the present invention is only slightly greater than that which is necessary to overcome the action of gravity and that of any spring, in particular at the point of the race. of the frame 11 o the shoulder 81 arrives in the vicinity of the rim 79 and finally comes into contact with the latter. The resulting metal-to-metal shock is significantly reduced and the level decreases

noise emitted.

  Reference will also be made to FIG. 1. It may be desirable to provide additional arrangements for reducing noise and, consequently, the stop disc 69 may include an elastic element 95

  of range, arranged on the face of the disc contiguous to the stop plate 57.

  When the armature 11 moves upwards and is close to the bottom of its position of attraction, the element 95 of bearing will come into contact

  with the stop plate 57 to absorb the shock.

  We will then refer to Figure 3. The solenoid 10 according to the

  present invention is shown in connection with a gas valve 97 used

  used to regulate the flow of a fuel. The tap 97 comprises a body 99 in which are formed conduits 101 which trap the fuel. The body 99 includes an interior seat 1Q3 which delimits a

  circular orifice as a whole and allowing the flow of fuel

  ble when open. A cover 105 is provided for receiving the sol-

  noTde 10 and can be given a shape such that it constitutes the stop plate 57 of the embodiment shown in FIG. 1. On the stop disc 69, it is also possible to place an elastic element 107 d the seal intended to come into contact with the seat 103 when the coil 25 is not supplied and the armature 11 is in its first position or position of withdrawal, as shown in the figure. When the coil 25 is supplied, the armature 11 and the sealing element 107 move upwards away from the seat 103, so that the fuel can flow through the body 99 of the valve. It is preferable to produce the bearing element 95 and the sealing element 107 in the form of a circular sheath as a whole and which has an outer rim 109 intended to engage by overlapping on the disc 69 of stop in order to retain the sheath. When using the solenoid 10 in connection with the gas valve 97, it is preferable to leave a slight clearance between the head of the fixing device 71 and the rod 55 to allow a slight tilting of the disc 69 and its element 107 d and their alignment with the surface

seat seal 103.

  The solenoid 10 according to the present invention and the gas valve 97 associated therewith have proved to be particularly advantageous in

  domestic installations where a fuel-burning appliance is placed

  cé in residential premises. The reduced noise characteristics of the solenoid 10 result in providing a structure which, in terms of audible noise, is significantly less annoying for people

occupying the premises.

  The present invention is not limited to the embodiments which have just been described, it is on the contrary susceptible of variants

  and modifications which will appear to those skilled in the art.

Claims (15)

  1. Solenoid with reduced noise characteristics, characterized in that it comprises a movable armature which can move over a certain length of travel relative to a magnet;   this frame comprising a core made of a magnetic material   tick and having a first length; a magnet which can be electrically powered to provide a   magnetic flux and which has a flux path having a second length   which is greater than the first length; this magnet thereby exerting on the core an attractive force whose intensity increases substantially linearly over the entire length of the stroke. 2. Solenoid according to claim 1, characterized in that the core can move from a first position and continue its race to a second position; the flow path includes a first, interior, flow path and a second, exterior, flow path; the core being more and more coupled to the internal path of the flow and less and less coupled to the external path of the flow, when this core is   moves from the first position to the second position.   3. Solenoid according to claim 2, characterized in that the armature and the magnet each comprise an element, these elements cooperating   magnetically with each other to increase the force of attraction when   that the armature is in the first position.   4. Solenoid according to claim 3, characterized in that the element   ment belonging to the magnet comprises a cavity formed in a first profile and which has a flange; and the frame comprises an element constituting a nose which is formed   according to a second profile and which projects from the core.   5. SolénoTde according to claim 4, characterized in that   the magnet is cylindrical as a whole and in that the armature is dis-   generally placed coaxially with respect to the magnet.   6. Solenoid with reduced noise characteristics, characterized in that it comprises: a solenoid coil which can be electrically supplied to produce a magnetic flux and which has a first end, a second end and a longitudinal passage which passes through it; an armature which is inserted so as to be able to slide in this passage in the vicinity of the first end and which is movable between a first position or position of withdrawal, and a second position or position of attraction; an upper stop disposed in the passage in the vicinity of the second end, this upper stop and the coil constituting together a path of the flow; the coil and the upper stop exerting together a force of attraction on the armature when the coil is supplied; this force having a first intensity when the armature is   is in the first position, and a second intensity when the arma-   ture is in the second position; the ratio of the strength of the second intensity to the strength of the   first intensity being about 3/1.   7. SolénoTde according to claim 6, characterized in that the upper stop has a cavity formed according to a first profile and having a flange; the frame comprises a core comprising a projecting element constituting a nose formed in a second profile; the rim and the element constituting a nose acting together to increase the force of attraction when the frame is in the first position.   8. SolénoTde according to claim 7, characterized in that the element constituting a nose and the core form between them a shoulder intended to come into contact with the edge of the cavity when the frame   is in the second position.   9. Solenoid according to claim 8, characterized in that it further comprises a stop plate mounted on the outside and in that the armature further comprises a stop disc mounted on the latter and   movable with it, this stop disc comprising an elastic carrying element   tee which abuts against the stop plate when the armature is   in the second position, thereby absorbing the shock of the armature. 2559301.   10. Gza tap intended to regulate the flow of a fuel, characterized in that it comprises:   a body in which are formed conduits allowing the flow-   fuel through this body; a solenoid mounted thereon and adapted to regulate the flow of fuel in response to an electrical signal; this solenoid comprising a movable armature which can move over a certain length of travel relative to a magnet;   this frame comprising a core made of a magnetic material   tick and having a first length; a magnet which can be electrically powered to provide a   magnetic flux and which has a flux path having a second length   which is greater than the first length; this magnet thereby exerting on the core an attractive force whose intensity increases substantially linearly over the entire length of the stroke. 11. Gas valve according to claim 10, characterized in that the core can move from a first position and continue its course to a second position and in that the force of attraction has a first intensity when the nucleus is in the first position   and a second intensity when the nucleus is in the second posi-   tion; the ratio of the strength of the second intensity to the strength of the   first intensity being about 3/1.   12. Gas tap according to claim 10, characterized in that the core can move from a first position and continue its stroke to a second position; the flow path includes a first, interior, flow path and a second, exterior, flow path; the core being more and more coupled to the internal path of the flow and less and less coupled to the external path of the flow when this core   moves from the first position to the second position.   13. Gas tap according to claim 12, characterized in that the armature and the magnet each comprise an element, these elements cooperating   magnetically with each other to increase the force of attraction when   that the armature is in the first position.   14. Solenoid-operated gas valve designed to adjust the flow   Lement of a fuel, characterized in that it comprises:   a valve body in which conduits are formed   both the flow of fuel through this body; a solenoid mounted on this body and intended to regulate the flow   fuel in response to a direct current electrical signal, this sol-   a noTde comprising: a solenoid coil which can be electrically supplied to produce a magnetic flux and which has a first end, a second end and a longitudinal passage which passes through it; an armature which is inserted so as to be able to slide in this passage in the vicinity of the first end and which is movable between a first position or position of withdrawal, and a second position or position of attraction; an upper stop disposed in the passage in the vicinity of the second end, this upper stop and the coil constituting together a path of the flow; the coil and the upper stop exerting together a force of attraction on the armature when the coil is supplied; this force having a first intensity when the armature is   is in the first position, and a second intensity when the arma-   ture is in the second position; the ratio of the strength of the second intensity to the strength of the   first intensity being about 3/1.   15. Gas tap according to claim 14, characterized in that   the valve body includes an interior seat which delimits a circular orifice   ring to allow the flow of fuel through the body, and a cover provided to receive the solenoid and constituting a stop plate; the armature further comprises a stop disc mounted on this   last and mobile with it, this stop disc comprising an elastic element   carrying tick intended to abut against the stop plate when the armature is in the second position;   the stop disc also comprises an elastic sealing element 255930 1   frame intended to come into contact with the seat, thereby preventing the flow of fuel through the orifice when the armature is in the first position.