FR2533793A1 - INDUCTION HEATING DEVICE PROVIDED WITH AN ELECTRONIC POSITIONING CONTROL - Google Patents

Abstract

THE INVENTION RELATES TO AN INDUCTION HEATING APPARATUS AGENCY SO AS TO POSITION THE INDUCER PRECISELY IN RELATION TO THE ROOM TO BE HEATED 12, SUCH AS AN ENGINE VALVE SEAT, BEFORE BEGINNING THE HEATING PROCESS. INDUCER 40 IS MOUNTED AT THE FRONT END OF A SHAFT 34 CARRIED BY A TROLLEY 14. THE SHAFT IS MOVED FORWARD BY SPRINGS 78A, 78B AND IS ASSEMBLED AT ITS REAR END TO A TENON COUPLING 65 MOUNTED ON THE SHAFT OF A STEP MOTOR. THE TROLLEY MOVES THE INDUCER IN CONTACT WITH THE PART SO THAT THE SHAFT MOVES REVERSE OF THE TROLLEY AGAINST THE ACTION OF THE SPRINGS AND MOVES AWAY FROM THE COUPLING BY A DISTANCE X WHICH IS MEASURED BY A TRANSDUCER 80. A CONTROL UNIT 82 THEN OPERATES THE MOTOR TO MOVE THE COUPLING BY THE MEASURED DISTANCE, SO AS TO RE-COUPLER THE SHAFT, THEN AN ADDITIONAL DISTANCE TO MOVE THE INDUCER FROM THE MEASURED DISTANCE. ROOM OF A DESIRED DISTANCE.

Description

The present invention relates generally

  to an induction heater and it relates

  more particularly to an induction heater

  tion which includes a positioning control for assu-

  rer optimum spacing between the inductor and the workpiece

during the heating cycle.

  To achieve longer operation and

  more economical internal combustion engines and, in part

  Particularly, of those which work with a fuel having a reduced lead content, the engine valve seats are hardened In the absence of hardening of the valve seats, the very high temperature exhaust gases expelled at

  through the cylinder valves cause ex- wear

  discontinued valve seats, reducing engine service life The most commonly used method for

  increase the hardness of the valve seats of combustion engines

  internal bustion consists of heating the valve seat to a very high temperature and then quenching it with a cooling fluid. To carry out such high-temperature heating of the valve seats of internal combustion engines, heaters are commonly used.

by induction.

  A characteristic induction heater

  tick used to heat induction seats

  Pape of internal combustion engines includes an inductor having a configuration complementary to that of the valve seat When the inductor has been placed in an operating relationship with the valve seat, a high frequency alternating current is applied to the inductor which causes the generation by the inductor of a magnetic field varying as a function of time which is induced in the part of the block

  motor which surrounds the valve seat

  circulating cault which are generated by the magnetic field

  tick induced in the engine block are subjected to high resistance losses which cause the heating of the valve seat In practice, the optimal magnetic coupling between the inductor and the valve seat is obtained when the inductor is separated by a small air gap but the valve seat is finished The spacing of this air gap is critical

  given that a very large air gap results in a

  poor magnetic coupling and, therefore, by a poor

  will heat while too small air gap distance between inductor and valve seat results in

  uneven valve seat heating In practice, a valve

  iron between 0.02 and 0.06 mm is usually satis-

doing.

  In the past, the air gap distance was obtained

  straight between the inductor and the valve seat of the engine block by resiliently mounting the inductor on a frame which is

  sliding mounted on a platform so that it can be effectively

  kill a back-and-forth movement in coming and going

  the motor unit along the axis of the inductor The chas-

  sis and the inductor are biased towards the workpiece so as to bring the inductor into contact with the seat

  engine block valve and, at this time, the induc-

  chassis and the chassis and the inductor are moved away from the motor over a preset air gap distance so that the inductor is separated from the valve seat of the engine block by the desired air gap distance Although such devices induction heating technology

  satisfactory to produce the hardening

  valve seats of internal combustion engines, they nevertheless have this drawback that all

  of the chassis must be moved away from the workpiece to produce the

  desired spacing between the inductor and the valve seat of the

  engine block which increases the risk of improper separation

  between the inductor and the part.

  Therefore, one of the objects of the present invention

  is to make a per-

  designed to harden the valve seat

  internal bust in which the spacing between the inductor and the valve seat of the engine block can be controlled

precisely.

  Another object of the present invention is to provide 3, an improved induction heater for hardening the valve seats of internal combustion engines

  which performs precise positioning of the inductor relative to

  port to the valve seat of the engine block by precisely controlling the movement of the inductor relative to the

port of the inductor.

  In accordance with the invention, there is provided an apparatus for

  induction heating particularly suitable for posi-

  precisely actuate the induction element with respect to the

  valve seat of an engine block before starting the pro-

  heating stops The appliance has a base carrying

  a carriage which can move along a linear path.

  An inductor support shaft is carried by the carriage so that it can perform a limited axial movement and it carries the inductor at one end A spring biases the shaft

  inductor holder towards the workpiece The opposite end

  the shaft is assembled with a coupling which couples the shaft to an actuator The carriage moves the inductor in abutment against the part and makes a slight overshoot

  stroke to cause the displacement of the support shaft

  inductor with respect to the carriage against spring pressure This uncouples the coupling shaft creating

  an interval between the inductor shaft and the coupling.

  This interval is measured by a measuring instrument and data representing the dimension of this interval are transmitted to a control unit which causes the excitation of a stepping motor so that it moves

  coupling a sufficient distance to close the inter-

  valle and re-couple the inductor shaft with the coupling

  The stepper motor continues to run.

  to move the coupling and, therefore, the shaft

  inductor and the associated induction element by the distance required to obtain the desired spacing between

  the induction element and the surface of the valve seat.

  The features of the invention considered to be

  news are specified in the appended claims

  However, the invention will be better understood both with regard to

2533793 '

  relates to its organization as its mode of operation as well as other goals and advantages that shine own

  with reference to the detailed description given below

  seen in light of the accompanying drawings in which: Fig 1 is a sectional view of the improved induction heating machine of the present invention;

  Fig 2 is an end view of the heating machine

  fage by induction of Fig 1; and FIG. 3 is a detail view in section on a larger scale of a part of the machine for heating by

induction of Fig 2.

  Fig 1, to which we will now refer, represents

  feels the improved induction heating machine or apparatus 10 of the present invention designed to induction heat a workpiece 12, such as a valve seat

  internal combustion engine, to cause it to harden

  The apparatus 10 for induction heating comprises a carriage 14 which is slidably mounted on a base 15 so that it can be moved along the base along a path.

  straight towards and away from a part 12.

  A hydraulic cylinder 16 is mounted between the carriage 14 and the base 15 to move the carriage back and forth relative to the workpiece A stop stop 17 is fixed to the base on the movement path of the carriage to limit movement

  from the carriage on the base towards the room.

  On the top of the carriage 14 is fixed a sole 18-

  which carries a chassis 20 which has been more particularly re-

  shown in Fig 2 The chassis 20 carries a series of

  electrode leads 22 axially movable back and forth, the rear end of one of these assemblies being shown

  in the cut-away part of Fig 2 Each set of

  electrode is parallel to an adjacent electrode assembly

  which it is spaced Although the present hardening machine

  induction induction has four sets of electrodes, those skilled in the art will recognize that the number

  of the electrode assemblies carried by the chassis depends

  the configuration of the room The sets of

  electrode 22 all have the same construction and therefore

  only one will be described in detail.

  Referring again to Fig 1, each electrode assembly 22 is composed of a sheath 26 which is slidably mounted so as to be able to move axially in the

  chassis 20 by means of a pair of bearings 28 which are separated

  adorned with each other by a spacer 30

  bearings are pushed back against the ends of the -

  spacer 30 by bearing caps 32 fixed

  at each end of the chassis 20.

  The sleeve 26 is traversed by a bore 33 s'4 tens-

  axially receiving a shaft 34 The bore 33 has a diameter sufficient to allow a limited pivoting movement of the shaft 34 To this end, the shaft 34 is brought to

  its front end in the sheath 26 by a spherical bearing

  rique or patella 36 fixed to the shaft 34 and disposed in a part of larger diameter 37 formed in the end

  front of the sleeve 26 in the vicinity of the part 12.

  The bearing surface 36 is formed by two coupled hemispherical parts which are fixed to the shaft 34 so as to form a sphere or ball which can rotate inside the part 37 of larger diameter of the sheath 26 Thanks to this arrangement, the shaft 34 can pivot around the center of the

  sphere in any direction to make an adjustment

  radially of the inductor 40 and the tip 44 which is associated therewith in order to adapt them to the position of the valve seat. Such a radial adjustment is carried out by moving the tip 44 in abutment against the valve seat while

the shaft 34 is free to pivot.

  However, once the radial adjustment has been made

  killed, the spherical seat 36 is pressed against the furnace

  reau 26 by a hollow piston 38 to lock the shaft 34 in its pivoting position and thereby fix the tip 44 of the inductor 40 in the radial position adjusted in exact alignment with the valve seat on which it

must operate.

  The piston 38 is retained in the front part of the sleeve 26 by a retaining member 39 which is fixed to the end of the sleeve The shaft 34 extends through an axial bore formed in the piston 38, a bore which has a diameter sufficient not to hinder the pivoting movement of the shaft 34 The outer periphery of the piston 38 bears against the internal bore of the retaining member 39 in which the

piston can slide.

  The piston 38 has a radial flange 43 which

  forms an annular surface at which a hydraulic pressure

  applied to tighten the spherical seat in position

  rique or patella 36 The hydraulic pressure is admitted through an orifice 42 in the space between the annular face of

  the collar 43 and the inner end of the retaining member

  held 39 The pressure pushes the piston 38 to the right, considering Fig 1, so that it acts against the

  spherical bearing 36 in order to clamp it against the sheath 26.

  Such an action serves to lock the shaft 34 in its posi-

  pivoting to maintain the tip 44 of the induc-

  in its adjusted radial position.

  The configuration of the tip 44 of the inductor 40 cor-

  responds to the configuration of the valve seats which are hardened Consequently, the magnetic field which varies as a function of time, produced by the inductor 40 when it is excited by a high frequency alternating current transported to the inductor by conductors 47 a and 47 b from the high frequency alternating current source 48, is

  thus concentrated in the valve seat causing the induc-

  tion in the seat of a magnetic field varying as a function of the time of opposite polarity The magnetic field varying as a function of the time induced in the valve seat causes eddy currents to circulate in the valve seat which causes heating due to Joule losses

  high undergone by the eddy currents.

  To obtain the optimal magnetic coupling between the

  tip 44 of the inductor and part 12, it is usual-

  It is desirable that the tip 44 of the inductor 40 be se-

  adorned with part 12 from a distance or small air gap but

  finished, typically in the range of 0.02 to 0.06 mm To obtain

  set the desired spacing between tip 44 of the inductor

  and the part 12 so as to ensure optimal magnetic coupling, the machine 10 is provided with a new positioning control device which comprises a pair of vertically oriented plates a and 50 b which are separated from one another by a series of rods 52 (as shown in Fig 2) Each rod has a threaded end which

  extends through plate 50 a to screw into a bore

  wise complementary thread formed in the right end of a corresponding rod 54 These latter rods 54 are screwed into the frame 20 so that each is co-axial with the corresponding rod 52 Each of the rods 52

  is fixed at its right end to the plate 50 b by a plug

  lon 55 respectively corresponding (one of which was shown

  felt) which extends through the plate 50 b to come

  screw into the bore of the corresponding rod 52.

  A stepping motor 56 is fixed on the right face of the plate 50b so that its shaft 58 extends through a bore formed in the plate, coaxially with the shaft 34 and the sleeve 26 As more particularly shown in Fig 3, the shaft 58 of the stepping motor is coupled to a mother screw 60 The latter meshes with a nut 62 which has one end 63 provided with a flange disposed in an opening 64 formed in the right end of a C-shaped tenon coupling 65 which is screwed to the rear (right) end of the shaft 34 A pin 66 (Fig 1 and 3) extends through a hole formed in the wall of the coupling 65 with tenon and in a hole

  formed radially in the end of the shaft 34 to prevent

  expensive tenon coupling to unscrew from the shaft 34.

  The diameter of the opening -65 formed in the tenon coupling is larger than the diameter of the end 63 provided with a flange of the mother screw nut A plate 68

  is attached to the right end of coupling 65 to te-

  not by bolts 70 and it is crossed by a bore large enough to receive the body 62 of the nut but smaller than the outside diameter of the flange 63 of

  so that there is only a limited degree of freedom between the

nut and tenon coupling.

  In Fig 1 to which we will refer again, we can see that the coupling 65 with tenon is biased backwards by a spring 76 bearing against a flange 74 which surrounds the shaft 34 so as to bias the shaft 34 inductor carrier to the rear relative to the sleeve 26

  so that the spherical part 36 of the shaft 30 supports

  inductor is held in abutment against its fixed seat so that there is no longitudinal movement of the shaft 34 inductor carrier relative to the sleeve 26 when the piston

  38 is loose The collar 74 is biased towards the

  Vant away from the plate 50 by a pair of springs

  78 a and 78 b each of which has its respective opposite ends-

  in support in a recess formed in the flange and in a recess formed in the plate The springs 78 a and 78 b serve to urge the sheath 26 and, consequently, the shaft 34 carrying the inductor forward but allows them to move backwards against the pressure of the springs when the inductor 40 bears against the

Exhibit 12.

  When the sheath 26 is pushed backwards, as happens when the tip 44 of the inductor is moved in contact with the part 12, the coupling 65

  moves backward by the same distance When the

  coupling 65 moves backwards, the plate 68 which is associated with it moves away from the collar 63 of the nut 62

  to create: an interval "X" between the right face, in

  flaring Fig 1, the flange 63 and the left side of the plate 68 However, when the stepping motor 56 is excited to screw the mother screw 60 into the nut 62,

  the latter moves backwards to move the glue

  rette 63 towards plate 68 so as to reduce

  the size of the interval which closes when the col-

  lerette 63 comes into contact with the plate 68 The pursuit

  of the excitation of the motor causes the displacement of the ac-

25337: 93

  coupling 65 and, consequently, of the inductor 40 towards the rear as a result of the movement of the nut

  the excitation of the motor 56 so that the nut 62 is displaced

  backward from the distance "Xl 'from the interval, plus an additional distance, the inductor is also displaced

  backward a distance equal to the additional distance

  beyond the distance "X" '.

  The measurement of the distance of the interval "'X" between the

  plate 68 and the flange 63 of the mother screw nut is ef-

  carried out by a transducer 80 which, in the embodiment

  tion currently preferred, is a differential transformer linear variation fixed to the plate 68 The differential transformer 80 linear variation is coupled, as the stepper motor 56, to a control device 82 which is typically a programmable control unit d a type well known in the art A limit switch 83 mounted at the front end of the sole 18 is

  actuated by the backward movement of the oven-

  reau 26 following the contact of the tip of the inductor with the part The actuation of the switch 83 is a signal which indicates that the inductor is in contact with the part and the programmable control unit 82 then excites the stepping motor 56 as a function of the output signal of the linear transformer differential transformer 80 Thus, the lead screw 60 is screwed into the nut 62 to move the nut backwards by an interval distance "X "plus a predetermined distance equal to the desired spacing between

  the tip 44 of the inductor and the part.

  The induction heater 10 of the present invention operates to induction heat the seats

  valve of an engine block as follows In pre-

  mier lieu, the carriage 14 is moved forward on the base 15 to position the tip 44 of the inductor

  each electrode assembly 22 in a correct valve seat

  correspondent of the engine block 12 As a result of the

  the front of the carriage, the inductor 40, the shaft 34 inductor holder

  tor and, consequently, the sheath 26 of each electrode assembly 22 are moved rearward relative to the chassis so as to create the gap "X" between the plate 68 and the flange 63 of the nut 62 Ce backward movement of the sleeve actuates the limit switch 83 to signal that the tip 44 of the inductor is in contact with the part In response to actuation

  of the limit switch 83, of the hydraulic fluid

  lique is admitted by the orifice 42 to fluid to push the piston 38 in abutment against the spherical bearing 36 in two pieces so as to tighten the shaft 34 inductor carrier against the sheath 26 Following the securing of the shaft 34 inductor holder and sleeve 26, the motor 56 is energized by the programmable control unit 82 to tighten the screw

  mother 60 in the nut 62 in order to move the nut Move it

  ment is equal to the dimension of the interval as detected by the transformer 80, plus a predetermined distance which

  is equal to the desired separation between the tip of the induct-

  part and the workpiece, so that the inductor shaft is

  placed towards the rear of this predetermined distance The

  backward placement of the carrier shaft

  distance from the predetermined distance has the effect that the tip

  of the inductor is spaced from the workpiece by the preset distance

  Once the tip of the inductor is spaced

  of the part of the predetermined air gap distance, the induc-

  is energized to heat the valve seat.

  We have described above an improved induction heating machine provided with a control device

  improved positioning to ensure optimum spacing

  wrong between the inductor and the part during the process of

heater.

  Although the illustrative embodiment of the invention has been described in great detail for the purpose

  to fully disclose a structure work in pra-

  tick incorporating the invention, it is understood that the ap-

  such particular described and represented was it only for the purposes of illustration and that the various new characteristics 1-1 of the invention can be incorporated into other forms of structures without leaving the framework nor deviating from

  the spirit of the invention as defined in the claims

annexed.

Claims (4)

  1 apparatus (10) for induction heating, characterized in that it comprises: a base (15), a carriage (14) mounted on the base so as to be able to move along a path of movement in approach and away from the   part (12) to be heated, an inductor (40) carried by the cha-   riot so that you can move relative to it,   biasing means (78 a, 78 b) biasing the induc-   teur forward on the carriage, an actuator (56), a coupling (65) arranged so as to couple the inductor to the actuator, so that the excitation of the actuator causes an axial displacement of the inductor, means (16) for moving the carriage in a suitable direction for moving the inductor in abutment against the workpiece and for moving the inductor with respect to the carriage against the action of the biasing means so thus disconnecting the coupling from the inductor so as to create an interval (X) between the inductor and the coupling, measuring means (80) arranged to measure the dimension of this interval and   control means (82) connected to receive the data   born of measurement means representing the dimension of the   tervalle and to excite the actuator (56) so as to displace   cer the coupling so as to eliminate the interval then to move the coupling by an additional distance so as to move the inductor by a predetermined distance   so as to space it from the desired distance from the workpiece.   2 Induction heater according to the claim   tion 1, characterized in that the inductor (40) is carried by the end of a shaft (-34) which is pivotally mounted on the   carriage (14) so that the inductor can be adjusted   dialing when it comes into contact with the part so as to be exactly in abutment against the region to be heated and in that it comprises clamping means (38) for immobilizing the shaft in the position adjusted in pivoting during the heating process.   3 Induction heater according to claim-   tion 1, characterized in that it comprises a sheath (26) carrying   ted by the carriage (14) so as to be able to carry out a   axially limited relative to the carriage, the sleeve comprises   bearing an axial bore (33) in which a shaft is mounted so as to be able to move in unison with the sheath, the inductor (40) being mounted on one end of the shaft outside the sheath to be able to support   against the workpiece, the opposite end of the shaft being coupled folded to the coupling- (65).   4 Induction heater according to claim-   tion 3, characterized in that the inductor has a configuration   conical to heat the conical surface of a support seat   pope and in that it comprises a universal joint (36, 37) carrying the shaft (34) in the sleeve (26) to allow the radial adjustment of the inductor when it enters the conical opening of the valve seat and means of   clamping (38) to immobilize the shaft in the radiating position   slightly adjusted during the heating process.