JP6537164B2 - Rack bar electric heating device - Google Patents

Description

  The present invention relates to a rack bar electrical heating apparatus used, for example, when quenching and tempering a tooth surface of a vehicle rack bar by electrical heating.

  Conventionally, this type of electric heating apparatus includes a pair of electric conduction electrodes disposed opposite to each other in the heating range along the longitudinal direction of the rack bar, and a power supply apparatus for supplying a current of a predetermined frequency to the electric conduction electrodes. There is. Then, when heat treating the tooth surface of the rack bar, the rack bar is first set to the heating apparatus for quenching, and the high frequency power source of the apparatus supplies high frequency current of the quenching frequency to the energizing electrode for a predetermined time, A predetermined range of the tooth surface is quenched by cooling.

  Then, the hardened rack bar is taken out from the heating apparatus for hardening and set in the heating apparatus for tempering, and the high frequency power supply of the apparatus supplies a high frequency current for the tempering frequency to the conducting electrode for a predetermined time. It tries to temper the tooth surface. In addition, as a gazette regarding the energization heating device of a rack bar, it is indicated by patent documents 1, for example.

Patent No. 4232973

  However, such an electric heating apparatus includes two electric heating apparatuses, one for hardening and one for tempering, and the rack bar hardened by the electric heating apparatus for hardening is taken out from the electric heating apparatus and is used for tempering. It is necessary to set in an electric heating device and to perform tempering. Therefore, it is difficult to perform quality control simply and with high accuracy, for example, the heat treatment process becomes two processes with separate devices, and tempering work may be forgotten. In addition, high-frequency power sources and current-carrying electrodes are required for each current-flowing heating device, and equipment investment costs increase. As a result, the cost of heat treatment is high and the cost tends to be disadvantageous.

The present invention has been made in view of such circumstances, and an object thereof is to perform hardening and tempering continuously by one set of rack bars and to perform quality control easily and accurately. It is an object of the present invention to provide a rack bar electric heating apparatus which is cost-effective by simplifying the equipment. Another object of the present invention is to provide a rack bar electrical heating apparatus which can alternatively use a current-carrying electrode according to the form of the tooth surface of the rack bar and can be applied to heat treatment of various rack bars.

In order to achieve the above object, the invention according to claim 1 of the present invention is a pair of current-carrying electrodes which can contact from both sides in the axial direction both ends of the tooth surface of the rack bar with a predetermined interval, Clamping means that can contact the back of the bar from above and press the tooth surface downward with a predetermined pressure, cooling means disposed between the pair of current-carrying electrodes and capable of injecting cooling water to the tooth surface, and a power supply means having a quenching power supply unit and the tempering power supply unit capable of supplying a high-frequency current to the pair of current electrodes, a resistance heating apparatus of the rack bar which Ru and a control means for controlling these, wherein the pair of current supply electrodes The contact surface which contacts the axial both ends of the tooth surface of the rack bar has the same shape, and the electric heating device has a semicircular arc shape in which the contact surface conforms to the outer shape outside both ends of the tooth surface Circles formed on both sides of the tooth surface A first form contacting the surface, a second form wherein the contact surface is formed flat and contacts the bottom of the groove at both axial ends of the tooth surface, and the contact surface is formed flat and the tooth According to the form of the rack bar, any one pair of electrification is provided according to the form of the rack bar. An electrode is selected as the pair of current-carrying electrodes , and these are fixed on the conductive plate so as to be attachable / detachable and / or position adjustable, and the control means is predetermined to the pair of current-carrying electrodes from the quenching power supply portion of the power source means The tooth surface is quenched by supplying a high frequency current, heating to a predetermined temperature, and rapidly cooling by injection of the cooling water, and after the quenching, the rack bar remains as it is in the state of the rack bar and the power supply means Specified from the tempering power supply section of Characterized by tempering the tooth surface by slowly cooling supplying high-frequency current is heated to a predetermined temperature.

The invention as set forth in claim 2 is characterized in that the tempering power supply unit can supply a high frequency current tempered from the hardening range of the tooth surface by the hardening power supply unit to the inner side of the tooth surface. Do. Further, according to Claim 3 invention, provided with the rack bar detectable radiation thermometer temperature during electrical heating of the tooth surfaces of the said control means energized on the basis of the detected temperature of the radiation thermometer It is characterized by controlling. The present invention as described in claim 4, wherein said control means includes detection means for detecting the state of contact between the said pair of energizing electrodes rack bar teeth surface, a predetermined contact by said detecting means detects In this case, a high frequency current is supplied from the hardening power supply unit to the pair of current-carrying electrodes.

According to the invention described in claim 1 of the present invention, the control means quenches the tooth surface by supplying a predetermined high frequency current to the pair of current-carrying electrodes from the hardening power supply portion of the power supply means and rapidly cooling it. After tempering , the rack surface is cooled by supplying a predetermined high frequency current from the tempering power supply section of the power supply means to the conduction electrode while cooling the rack bar as it is, thereby tempering the tooth surface. Quenching and tempering can be performed continuously in one set, quality control can be performed easily and with high accuracy, equipment can be simplified, and cost-effective rack bars can be easily obtained. .

Further, the contact surface of the pair of conducting electrodes has the same shape, and a plurality of types of first to third forms are set according to the configuration of the tooth surface of the rack bar, and any pair of the conducting electrodes Because it is detachably and / or positionally fixed on the conductive plate, it is possible to use alternatively the electrification electrode according to the form of the tooth surface of the rack bar, and can be applied to heat treatment of various rack bars Can be obtained.

Further, according to the invention of claim 2, in addition to the effect of the invention according to claim 1, high-frequency tempering power unit is tempered to the interior side of the tooth surface than the hardened range of tooth surfaces by quenching power unit Since the current can be supplied, the internal stress of the hardened portion can be removed by tempering , and it is possible to easily obtain a rack bar of a tooth surface excellent in quality such as impact resistance and wear resistance.

  Further, according to the invention of claim 3, in addition to the effect of the invention of claim 1 or 2, the radiation thermometer capable of detecting the temperature at the time of electric current heating of the tooth surface of the rack bar is provided. Since the control means controls the energization state based on the temperature detected by the thermometer, the quenching temperature and the tempering temperature during energization heating can be accurately maintained at a predetermined temperature, and heat treatment on the tooth surface of the rack bar is more highly accurate. It can be carried out.

  According to the fourth aspect of the invention, in addition to the effects of the first to third aspects of the invention, the detection means detects a predetermined contact state between the pair of current-carrying electrodes and the tooth surface of the rack bar. Since the high frequency current is supplied from the hardening power supply to the pair of conducting electrodes, a predetermined high frequency current can be supplied only when the conducting electrodes are in contact with the tooth surface reliably, and sparks etc. The occurrence can be prevented, and the heat treatment with higher accuracy can be easily performed by the tooth surface of the rack bar.

The schematic block diagram of the electricity supply heating apparatus of the rack bar concerning this invention Sectional drawing which shows an example of the heat processing state of the tooth surface of the same. Schematic block diagram of the power supply unit Top view of the same conducting electrode The figure which shows the various forms of the tooth surface of the same electricity supply electrode and a rack bar Process chart showing the same heat treatment Process chart showing other heat treatment

Hereinafter, the best mode for carrying out the present invention will be described in detail based on the drawings.
1 to 6 show an embodiment of the rack bar electrical heating apparatus according to the present invention. As shown in FIG. 1, the rack bar W has a tooth surface Wa and a back surface Wb of a predetermined length formed at one end in the longitudinal direction (axial direction).

  Then, the electric heating device 1 is a power source in which the pair of electric conduction electrodes 2 that can contact from below with the both end portions of the tooth surface Wa (or the rear surface Wb) of the rack bar W and the electric conduction electrodes 2 are electrically connected. The apparatus 3, a cooling cylinder 4 disposed between the pair of current-carrying electrodes 2, and a cooling apparatus 5 for supplying cooling water into the cooling cylinder 4 are provided. In addition, a pair of clamp devices 6 are provided at positions substantially facing the respective conducting electrodes 2 in the diameter direction (vertical direction in FIG. 1) on the back surface Wb of the rack bar W.

  The power supply device 3, the cooling device 5 and the clamp device 6 are connected to the output side of a control device 7 having a microcomputer, sequencer or the like (not shown). A radiation thermometer 8 or the like for detecting (measuring) the temperature at a predetermined position of the tooth surface Wa (or the back surface Wb) is connected.

  Further, as shown in FIG. 3, the power supply 3 includes a hardening power supply 3a, a tempering power supply 3b, and a switch (not shown), and the control signal of the control device 7 indicates whether the switch is on the hardening power supply 3a side. By selectively switching to the tempering power supply unit 3b side, a high frequency current of a predetermined frequency is supplied (energized) to each conducting electrode 2. The hardening power supply 3a and the tempering power supply 3b each have a semiconductor inverter circuit, the hardening power supply 3a can output high frequency current of 40 to 250 KHz, and the tempering power supply 3b has high frequency current of 5 to 10 KHz. Is configured to be able to output.

  As shown in FIGS. 1 and 4, the pair of current-carrying electrodes 2 are formed of, for example, a copper plate in an L-shape in a side view, and each have an electrode portion 2b perpendicular to the horizontal fixing portion 2a. The fixing portion 2a is detachably fixed to each conductive plate 10 made of a copper plate formed larger than the fixing portion 2a by a plurality of bolts 9, and the contact surface 2c which is the upper surface of the electrode portion 2b. Recesses 11 having a substantially semicircular arc shape that matches the outer shape of both ends outside of the tooth surface Wa of the rack bar W are respectively formed.

  As shown in FIG. 5A, each concave portion 11 of the pair of current-carrying electrodes 2 is in surface contact with a circumferential surface of both ends outside (only one is shown in the drawing) of the tooth surface Wa of the rack bar W with a predetermined width from below. The high frequency current is caused to flow to the tooth surface Wa of the rack bar W through the pair of current-carrying electrodes 2. In the case of the electric heating device 1 of the present invention, in addition to the electric conduction electrode 2 having the recess 12 in the contact surface 2c, the electric conduction electrode 2 having flat contact surface 2c shown in FIG. It has become.

  That is, in the current-carrying electrode 2 shown in FIG. 5B, the contact surface 2c of the electrode portion 2b is formed as a flat flat surface of a predetermined width, and this contact surface 2c is at both longitudinal ends of the tooth surface Wa of the rack bar W. Contact the bottom of the groove 12. At this time, since the bottom surface of the groove 12 of the tooth surface Wa is formed as a flat surface having a predetermined width, the flat contact surfaces 2c of the current-carrying electrodes 2 come into contact with the bottom surface of the groove 12 in a surface contact state. . The fixed position of the pair of current-carrying electrodes 2 to the conductive plate 10 is, for example, a long hole for fixing the current-carrying electrodes provided in the current-carrying plate 10, depending on the form of the tooth surface Wa of the rack bar W, etc. It can be fixed while adjusting its position.

  Further, in the current-carrying electrode 2 shown in FIG. 5C, the contact surface 2c of the electrode portion 2b is formed flat with a predetermined width, and the flat contact surface 2c is outside both ends of the tooth surface Wa of the rack bar W in the longitudinal direction. It contacts the bottom of the groove 12 as a non-tooth surface being formed. Also at this time, since the bottom surface of the groove 12 is formed flat with a predetermined width, the flat contact surface 2c of each conducting electrode 2 comes into contact with the bottom surface of each groove 12 in a surface contact state. Then, these three types of current-carrying electrodes 2 are prepared as accessories of the current-carrying heating device 1, and the predetermined current-carrying electrodes 2 are selected according to the form of the tooth surface Wa and back surface Wb of the rack bar W to be heat treated. The respective conductive plates 10 are fixed by bolts 9.

  The cooling cylinder 4 is formed in a rectangular box shape having substantially the same length as the distance between the pair of current-carrying electrodes 2, and a large number of injection holes are formed on the upper surface thereof and provided on a predetermined side surface or the like. The other end of the hose whose proximal end is connected to the cooling device 5 is connected to a hose connector (not shown). The cooling device 5 has a pump (not shown), a cooling water tank (or a cooling water supply source such as a water pipe or the like), an open / close valve, etc., and the pump operates and the open / close valve opens Thus, the cooling water is supplied into the cooling cylinder 4 and is jetted from the injection holes to the tooth surface Wa (or the back surface Wb) of the rack bar W at a predetermined pressure.

  The clamp device 6 is formed of a hydraulic cylinder or an air cylinder, and operates according to a control signal of the control device 7 so that the pressing portion 6a at the tip of the cylinder shaft makes the back surface Wb of the rack bar W downward, that is, in the direction of the energizing electrode 2. The rack bar W is pressed and held on the energizing electrode 2 by pressing with a predetermined pressure. At this time, the pair of clamp devices 6 are provided at positions opposed to the pair of current-carrying electrodes 2 in the vertical direction, and both end portions of the tooth surface Wa of the rack bar W and the current-carrying electrodes 2 are pressed downward by the back surface Wb. The contact surface 2c is set to be in surface contact.

  The radiation thermometer 8 is, for example, a non-contact thermometer such as an infrared radiation thermometer, and detects infrared radiation emitted from the tooth surface Wa (or back surface Wb) of the rack bar W by electric heating. A temperature signal is output to the control device 7.

  Next, an example of the heat treatment operation of the rack bar W using the electric heating device 1 will be described based on the process chart of FIG. First, in accordance with the shape of the tooth surface Wa and the rear surface Wb of the rack bar W to be heat-treated, the predetermined conducting electrodes 2 shown in FIGS. 5A to 5C are fixed at predetermined positions on the conductive plate 10 with bolts 9. Set (K01). In this state, the rack bar W is placed on the contact surface 2c of the pair of current-carrying electrodes 2 and set (K02), and the clamp device 6 is operated to clamp the rack bar W (K03).

Both ends of the tooth surface Wa of the rack bar W come into surface contact with the contact surface 2c of each conducting electrode 2 by this clamp, and in this state, the switch of the power supply 3 is used as the hardening power supply 3a side. For example, a high frequency current having a frequency of 40 to 250 KHz is supplied to each of the current-carrying electrodes 2 through the conductive plate 10 to conduct quenching (K04). At the time of this quenching current, the heating temperature of the tooth surface Wa to be current-heated is measured by the radiation thermometer 8, the signal thereof is inputted to the control device 7, and compared with the preset quenching temperature. At the time when it is reached, the quenching current is terminated.

  When this hardening energization is finished, the cooling device 5 is operated by the control signal of the control device 7 to supply the cooling water into the cooling cylinder 4 and the tooth surface is energized and heated to the predetermined temperature of the rack bar W from the injection hole. The tooth surface Wa is cooled (K05) by injecting it to the Wa from below. As shown in FIG. 2, the rack bar W is heated and rapidly cooled by a predetermined range in the center direction from the surface side of the tooth surface Wa, for example, as shown in FIG. The face Wa is hardened.

When the hardening is completed, the set positions of the rack bar W and the energizing electrode 2 are kept as they are, and the switch of the power supply 3 is switched to the tempering power supply 3b side by the control signal of the controller 7. Then, a high frequency current of 5 to 10 KHz, which is a frequency for tempering, is supplied from the tempering power supply unit 3b of the power supply 3 to the conducting electrode 2 via the conductive plate 10 to energize the tempering (K06). At the time of the tempering energization, the heating temperature of the tooth surface Wa is measured (monitored) by the radiation thermometer 8 similarly to the case of the quenching energization, and tempering is performed when the heating temperature reaches a predetermined tempering temperature set in advance. Turn off the power.

By tempering, the rack bar W is tempered by a predetermined range b wider in the center direction of the rack bar W than the range b shown by the two-dot chain line in FIG. 2, that is, the hardened range a of the tooth surface Wa. As described above, by cooling slowly after heating, tempering is performed, and internal stress and the like generated at the quenched portion are removed by heating and rapid cooling, and the impact resistance and wear resistance of the tooth surface Wa are improved. That is, the internal stress generated or remaining inside is removed by tempering the high frequency current having a relatively low frequency while securing a predetermined hardness to the tooth surface Wa by temporarily quenching with a high frequency current having a relatively high frequency. It is possible to easily secure the desired quality, such as the hardness of the surface side of the tooth surface Wa, which is likely to be so fragile by quenching.

Then, the rack bar W thus tempered after quenching is operated in the same manner as in the case of the quenching according to the control signal from the control device 7 in the tempered state, and the cooling water is supplied to the cooling cylinder 4 The coolant is supplied from the injection holes to the tooth surface Wa to cool the tooth surface Wa heated at the tempering temperature (K07). This cooling does not need to rapidly cool the tooth surface Wa electrically heated to the quenching temperature as in the case of the quenching, and takes a predetermined time, for example, slowly cools and tempers to take out the rack bar W described later It may be cooled to a temperature that does not disturb the work. Therefore, as shown by the two-dot chain line c in FIG. 6, this process K07 is omitted if there is a margin for the process time, or if the rack bar W is taken out by a robot etc. in process K08 described later. It may be allowed to cool naturally.

When tempering is completed by cooling after tempering energization in step K07, the clamp device 6 is operated by the control signal of the control device 7 to retract (raise) the pressing portion 6a, and clamp the rack bar W by the clamp device 6 Unclamp the state (K08). Then, the unclamped rack bar W is taken out from above the current-carrying electrode 2 (K09), whereby the heat treatment of the tooth surface Wa of the rack bar W is completed. As a result, as described above, a rack bar W having a tooth surface Wa with excellent impact resistance and wear resistance can be obtained by removing internal stress and the like generated at the quenched portion, in that case, Quenching and tempering of the tooth surface Wa can be performed in a substantially continuous process while being set on the energizing electrode 2.

  In the above description, as indicated by the two-dot chain line d in FIG. 6, for example, the contact surfaces 2c of the pair of current-carrying electrodes 2 are in surface contact with the tooth surface Wa both ends of the rack bar W before hardening energization. It is also possible to detect whether or not there is, and to carry out the quenching energization only in the case of surface contact. At this time, detection of the contact state between the current-carrying electrode 2 and both ends of the tooth surface Wa is performed, for example, by supplying a predetermined detection current from the quenching power supply 3a and detecting that a predetermined amount of current flows. The detection may be performed by bringing a pair of detection electrodes for contact into contact with predetermined positions of the conductive plate 10 (or the conduction electrode 2) and the rack bar W.

Furthermore, although the case where the tooth surface Wa of the rack bar W is heat-treated (quenched and tempered ) has been described in the above description, for example, heat treatment (quenching) is performed on the back surface Wb opposite to the tooth surface Wa of the lamber W in the diameter direction. In the case of performing this operation, it may be performed as shown in FIG.

  That is, a pair of current-carrying electrodes 2 corresponding to the shape of the back surface Wb to be heat-treated is fixed on the conductive plate 10 and set (K10), and the back surface Wb of the rack bar W is mounted on the current-carrying electrode 2 and set K11) Do. Then, the clamp device 6 is operated by the control signal of the control device 7 to clamp the rack bar (K12), and in this state, the switch of the power supply device 3 is set to the hardening power supply portion 3a side by the control signal of the control device 7 The high-frequency current is supplied to the current-carrying electrode 2 and the back surface Wb is quenched (K13).

Then, while the heating temperature is monitored by the radiation thermometer 8, the quenching current is stopped when reaching a predetermined heating temperature, and the control signal of the control device 7 is kept in the state where the rack bar W is set to the energizing electrode 2 The cooling device 5 is operated to cool the heated rear surface Wb (K14). By this hardening energization and rapid cooling, for example, the range e shown in FIG. 2 of the back surface Wb of the rack bar W is hardened to a predetermined hardness, and the clamping device 6 is operated in this state to unclamp the rack bar W (K15). Then, the hardened rack bar W is rotated 180 degrees around the axis on the current-carrying electrode 2, and the process proceeds to step K01 in FIG. 6 to perform hardening and tempering of the tooth surface Wa. As a result, predetermined heat treatment is performed on both the back surface Wb and the tooth surface Wa of the rack bar W.

As described above, according to the conductive heating device 1, the control device 7 supplies a predetermined high frequency current to the pair of conductive electrodes 2 from the quenching power supply unit 3 a of the power supply device 3 to quench the tooth surface Wa of the rack bar W After the quenching, the rack bar W is supplied with a predetermined high frequency current from the tempering power supply 3b of the power supply 3 to the pair of conducting electrodes 2 with the rack bar W as it is to temper the tooth surface Wa. Quenching and tempering can be performed continuously by one set on the electrode 2, quality control can be performed easily and with high precision, equipment can be simplified and the rack bar W advantageous in cost can be easily made Can be obtained.

In addition, since a plurality of types of contact surfaces 2c of the pair of current-carrying electrodes 2 are set in accordance with the shape of the tooth surface of the rack bar W and these are detachably fixed on the conductive plate 10 and position adjustable. The current-carrying electrode 2 according to the form of the tooth surface of the bar W can be alternatively used, and the current-carrying heating device 1 excellent in versatility applicable to the heat treatment of various rack bars W can be obtained. In addition, since the tempering power supply portion 3b is a conduction condition under which tempering is performed from the quenching range a of the tooth surface Wa by the quenching power source portion 3a to the inner side, internal stress etc. can be eliminated by tempering . It is possible to easily obtain a rack bar W of a tooth surface excellent in quality such as wear resistance and the like.

  Furthermore, a radiation thermometer 8 capable of detecting the temperature of the tooth surface Wa of the rack bar W during energization heating is provided, and the control device 7 controls the energization state based on the detection temperature of the radiation thermometer 8. Since the quenching temperature and the tempering temperature at that time can be accurately maintained at a predetermined temperature, the tooth surface Wa of the rack bar W can be subjected to heat treatment with higher accuracy. In addition, when the contact state between the pair of current-carrying electrodes 2 and the tooth surface Wa of the rack bar W is detected by the detecting means, high-frequency current is supplied from the hardening power source 3a to the pair of current-carrying electrodes 2; A predetermined high frequency current can be supplied only when the electrode 2 is in contact with the tooth surface Wa reliably, and generation of sparks and the like due to energization at the time of contact failure can be prevented. Accurate heat treatment can be easily performed.

  Furthermore, since the contact surface 2c of the pair of current-carrying electrodes 2 and the tooth surface Wa of the rack bar W and the back surface Wb can be brought into surface contact with a predetermined area, the current-carrying state is stabilized, sparks etc. It is possible to easily obtain higher-precision quenching and tempering quality on the tooth surface Wa and the rear surface Wb of the rack bar W while suppressing the occurrence of the above. In addition, if the contact surfaces 2c of the pair of current-carrying electrodes 2 have a semicircular arc shape, surface contact over a wider area becomes possible, and heat treatment quality with higher accuracy can be obtained.

  If the contact surface 2c of the current-carrying electrode 2 is brought into contact with the groove 12 of the tooth-surface Wa of the rack bar W as shown in FIGS. 5 (b) and 5 (c), the current-carrying electrode 2 and the tooth-surface The positioning with Wa becomes reliable, the change of the positional relationship at the time of energization, etc. is surely regulated, the energized state is further stabilized, and the more accurate quenching and tempering quality is facilitated by the tooth surface Wa of the rack bar W. Can be obtained.

  In addition, the form of the contact surface 2c of each electricity supply electrode 2 in the said embodiment is not limited to three forms shown in figure, The electricity supply electrode of the appropriate form which can be surface-contacted by a predetermined area can be used The form of the cylinder 4 and the frequency of the high frequency current output from the power supply device 3 are also an example, for example, using a frequency substantially the same as or close to the frequency at the time of quenching during tempering, etc. It can change suitably in the range which does not deviate.

  The present invention is not limited to the application to a rack bar of a vehicle such as a car, but can be applied to various rack bars having tooth surfaces of a predetermined form.

DESCRIPTION OF SYMBOLS 1 ... Electric conduction heating apparatus 2 ... Electric conduction electrode, 2a ... Fixed part, 2b ... Electrode part, 2c ... Contact surface, 3 ... Power supply device, 3a ... Quenched power supply part , 3b ... tempering power supply unit, 4 ... cooling cylinder, 5 ... cooling device, 6 ... clamping device, 6a ... pressing unit, 7 ... control device, 8 ... radiation temperature Total, 10: conductive plate, 11: recess, 12: groove, W: rack bar, Wa: tooth surface, Wb: rear surface.

Claims (4)

A pair of current-carrying electrodes which can contact from below the axial end of the tooth surface of the rack bar with a predetermined interval, and can come in contact with the rear surface of the rack bar from above and press the tooth surface downward with a predetermined pressure Clamping means, cooling means disposed between the pair of current-carrying electrodes and capable of injecting cooling water onto the tooth surface, and a hardening power supply portion and a tempering power-supply portion capable of supplying high frequency current to the pair of current-carrying electrodes and power supply means, a resistance heating apparatus of the rack bar and control means for Ru provided with a controlling these,
In the pair of current-carrying electrodes, the contact surfaces contacting the axial direction both ends of the tooth surface of the rack bar have the same shape,
In the electric heating device, the contact surface is formed in a semicircular arc shape conforming to the outer shape of both ends outside of the tooth surface, and the first form in which the contact surface contacts the circumferential surface outside both ends of the tooth surface The second form in which the surface is formed flat and contacts the bottom surface of the groove at both axial ends of the tooth surface, and the contact surface is formed flat and the groove as the non-tooth surface at both axial ends of the tooth surface And three pairs of current-carrying electrodes set in different forms of the third form which can be contacted, and any one pair of current- carrying electrodes is selected as the pair of current- carrying electrodes according to the form of the rack bar These are detachably and / or positionably fixed on the conductive plate, and
The control means quenches the tooth surface by supplying a predetermined high frequency current from the quenching power supply of the power source to the pair of current-carrying electrodes, heating to a predetermined temperature, and rapidly cooling by spraying the cooling water. After the quenching, the rack surface is tempered as it is by supplying a predetermined high frequency current from the tempering power supply section of the power supply means to the pair of current-carrying electrodes as it is and heating to a predetermined temperature and slowly cooling it. Rack bar electrical heating device characterized by   The energization of the rack bar according to claim 1, wherein the tempering power supply unit can supply a high frequency current tempered to an inner side of the tooth surface from a quenching range of the tooth surface by the quenching power supply unit. Heating device.   The radiation thermometer according to claim 1, further comprising: a radiation thermometer capable of detecting a temperature at the time of energization heating of a tooth surface of the rack bar, wherein the control means controls an energization state based on a temperature detected by the radiation thermometer. The rack bar electrical heating apparatus according to 2.   The control means includes detection means for detecting the contact state between the pair of current-carrying electrodes and the tooth surface of the rack bar, and when the predetermined contact state is detected by the detection means, the pair of quenching power sources 4. The rack bar conduction heating apparatus according to claim 1, wherein a high frequency current is supplied to the conduction electrode.

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