JP2017057442A - Electrification heating device for steering rack bar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrification heating device capable of easily forming a hardened lay with a prescribed form in a state continuous to the whole region in the circumferential direction of the outer circumferential face of a rack bar, further capable of efficiently performing electrification operation while simplifying the constitution of the device, and capable of obtaining a cost-effective steering rack bar.SOLUTION: Under a condition that a first electrification electrode and a second electrification electrode are contacted with the tooth face and the back face of a rack bar, electric current is fed from power source means, the whole region in the circumferential direction of the rack bar is subjected to electrification heating, and the heated part is cooled by cooling means to form a hardened layer continuous to the whole region in the circumferential direction of the rack bar. The hardened layer is obtained by tempering, with a prescribed tempering electrification condition, the hardened layer subjected to hardening under a prescribed hardening electrification condition, and the depth of the hardened layer is set as the tooth face part>the back face part>both the side face parts.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an electric heating apparatus for a rack bar used when a back surface and a tooth surface of a steering rack bar (hereinafter simply referred to as a rack bar) are quenched and tempered by electric heating.

  Conventionally, as this kind of electric heating apparatus, it is indicated by patent documents 1, for example. This energization heating device has a tooth surface quenching device and a back surface quenching device each having a pair of contact electrodes disposed in the heating range along the longitudinal direction of the tooth surface and back surface of the rack bar, The pair of contact electrodes of each quenching apparatus is set so that the shape of the contact surface to the rack bar is different. Then, the tooth surface of the rack bar is quenched by supplying a predetermined high-frequency current to the tooth surface of the rack bar supported on the contact electrode of the tooth surface quenching device (energization heating), and then the tooth surface is quenched. The rack bar is supported on the contact electrode of the back quenching apparatus, and the back surface of the rack bar is quenched by supplying a predetermined high-frequency current (energized heating).

Japanese Patent Laid-Open No. 10-25156

  However, in such an electric heating apparatus, as shown in FIG. 7, the hardened hardened layer K on the tooth surface Wa and the back surface Wb of the rack bar W has both sides in the circumferential direction of the rack bar W having a circular cross section. It becomes a state where it is divided by the surface Wc, and it is not possible to obtain a hardened and hardened layer K continuous over the entire circumferential direction of the outer peripheral surface of the rack bar W, and performances such as unprecedented durability and weight reduction are required. Application to the rack bar W is difficult. Moreover, in order to quench the tooth surface Wa and the back surface Wb, dedicated quenching devices for the tooth surface and the back surface are required, and the configuration of the current heating device itself becomes complicated, and the rack bar W is set in each device. It is difficult to obtain a rack bar W that is inferior in work efficiency and low in cost, such as troublesome setup work such as work.

  The present invention has been made in view of such circumstances, and the object thereof is to easily form a hardened layer of a predetermined form in a state of being continuous over the entire circumferential direction of the outer peripheral surface of the rack bar, It is an object of the present invention to provide a steering rack bar energization heating apparatus capable of efficiently performing energization work while simplifying the configuration of the apparatus and obtaining a cost-effective rack bar.

  In order to achieve this object, the invention according to claim 1 of the present invention is characterized in that a first energizing electrode comprising a pair of contact electrodes capable of contacting both ends of the heating range of the tooth surface of the rack bar, A second energizing electrode comprising a pair of contact electrodes capable of contacting both ends of the heating range on the back surface, power supply means capable of supplying a current of a predetermined frequency to the first energizing electrode and the second energizing electrode, and the rack bar A cooling means disposed at a predetermined interval substantially in the entire outer peripheral side of the heating range; and a control means for controlling the cooling means, wherein the control means places the first energizing electrode and the second energizing electrode on the outer circumferential surface of the rack bar. A current is supplied from the power supply means in contact with the power supply, and the entire circumferential direction of the rack bar is energized and heated, and the heated portion is cooled by the cooling means, and is continuously applied to the entire circumferential direction of the rack bar. Shape hardened layer Characterized in that it.

  The invention according to claim 2 is characterized in that the hardened layer is obtained by tempering a quenching layer quenched under a predetermined quenching energization condition under a predetermined tempering energization condition. The invention according to claim 3 is characterized in that the depth of the hardened layer is set to tooth surface portion> back surface portion> both side surface portions. Furthermore, the invention according to claim 4 is characterized in that the power supply means supplies different currents to the first energizing electrode and the second energizing electrode by a current adjusting means. The invention according to claim 5 is characterized in that the cooling means has a plurality of cooling jackets that can be disposed opposite to each other in the entire circumferential direction of the rack bar. The invention according to claim 6 is characterized in that the rack bar is formed in a circular cross section or an irregular cross section.

  According to the first aspect of the present invention, current is supplied from the power supply means in a state where the contact electrodes of the first energizing electrode and the second energizing electrode are in contact with the tooth surface and the back surface of the rack bar. In order to energize and heat the entire area of the rack bar in the circumferential direction and cool the heated portion with a cooling means to form a continuous hardened layer in the entire area of the rack bar in the circumferential direction. By simultaneously energizing and simultaneously cooling the heated part, it is possible to easily obtain a hardened layer with a predetermined form in a continuous state throughout the circumferential direction of the rack bar, and there is no need for a heating device dedicated to the tooth surface or the back surface. It is possible to easily obtain a rack bar that is advantageous in terms of cost, for example, heating operation can be efficiently performed by simultaneous energization or the like while simplifying the configuration.

  According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, the hardened layer is tempered under a predetermined tempering energization condition by tempering the hardened layer under a predetermined tempering energization condition. Therefore, predetermined quenching and tempering can be continuously performed on the tooth surface, the back surface, and both side surfaces serving as the connecting portions, and a desired hardened layer can be efficiently formed.

  Further, according to the invention described in claim 3, in addition to the effect of the invention described in claim 1 or 2, since the depth of the hardened layer is set to tooth surface portion> back portion> both side portions, durability Therefore, it is possible to easily obtain a rack bar having a desired hardened layer that matches the characteristics required of the rack bar.

  Further, according to the invention described in claim 4, in addition to the effects of the invention described in claims 1 to 3, the power supply means supplies different currents to the first energizing electrode and the second energizing electrode by the current adjusting means. The depth of the hardened layer such as the tooth surface and the back surface can be adjusted as desired, and a rack bar having an effective hardened layer in the entire circumferential direction of the outer peripheral surface can be easily obtained.

  According to the invention described in claim 5, in addition to the effects of the invention described in claims 1 to 4, the cooling means has a plurality of cooling jackets that can be opposed to each other in the entire circumferential direction of the rack bar. The cooling medium can be effectively jetted and cooled over the entire area of the outer peripheral surface that is electrically heated, so that the quenching quality can be stabilized and a highly accurate rack bar can be obtained.

  Further, according to the invention described in claim 6, in addition to the effects of the invention described in claims 1 to 5, since the rack bar is formed in a cross-sectional circle or a cross-sectional irregular shape, a conventionally used cross-sectional circle is used. The desired hardened layer can be formed on the entire outer peripheral surface of the rack bar, and the desired hardened layer can be easily formed on the entire outer peripheral surface while reducing the weight of the rack bar by applying it to the rack bar having a deformed cross section. Can be formed.

Schematic configuration diagram of an electric heating device for a steering rack bar according to the present invention. The figure which shows the structure of the current adjustment means Diagram showing the configuration of the cooling means Process drawing showing an example of the same heating method Sectional drawing which shows the hardened layer of the same rack bar Sectional view similar to FIG. 5 showing a modification of the same rack bar Sectional drawing which shows the hardened layer of the conventional rack bar

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
1 to 6 show an embodiment of an electric heating apparatus according to the present invention. As shown in FIG. 1, a steering rack bar W (rack bar W) to which the energization heating device 1 of the present invention is applied is formed in a columnar shape having a circular cross section as a whole, and has an oblique angle with respect to an axis. A tooth surface Wa having teeth, a back surface Wb composed of a substantially semicircular arc surface opposite to the tooth surface Wa, and a side surface Wc serving as a connecting portion (connecting portion) between the tooth surface Wa and the back surface Wb are formed.

  Then, the energization heating device 1 is provided with a first energization electrode 2 that can contact the tooth surface Wa, a second energization electrode 3 that can contact the back surface Wb, and the first energization electrode 2 and the second energization electrode 3. A transistor inverter 4 as power supply means for supplying a current (alternating current), a cooling means 5 having a plurality of cooling jackets 5a capable of injecting cooling water, and a cooling water supply section 5b for supplying cooling water to the cooling jacket 5a; And a control device 6 and the like.

  The first energizing electrode 2 has a pair of first contact electrodes 2a and 2b that can be contacted from below at both ends of the heating range of the tooth surface Wa of the rack bar W, and the second energizing electrode 3 is formed on the rack bar W. A pair of contact electrodes 3a and 3b that can be contacted from above are provided at both ends of the heating range of the back surface Wb. The contact electrodes 2a and 2b and the contact electrodes 3a and 3b are each formed of, for example, an L-shaped copper plate having a predetermined thickness, and the contact surface thereof has, for example, a substantially semicircular arc shape corresponding to the outer peripheral surface shape of the rack bar W. (Not shown) and the like are appropriately formed.

  The pair of contact electrodes 2a, 2b, 3a, 3b of the first energizing electrode 2 and the second energizing electrode 3 are electrically connected in parallel to the output terminal of the transistor inverter 4, and the first energization from the transistor inverter 4 is performed. A current having a predetermined frequency is supplied to the pair of contact electrodes 2 a and 2 b of the electrode 2 and the pair of contact electrodes 3 a and 3 b of the second energizing electrode 3. At this time, a regulator 7 as a current regulating means is connected between one contact electrode 3 a of the second energizing electrode 3 that is in contact with the back surface Wb and one output terminal of the transistor inverter 4.

  As shown in FIG. 2, the adjuster 7 has a U-shaped copper plate 7 (including a copper column), and one end of the copper plate 7 serves as one output terminal of the transistor inverter 4. A copper plate and a conductor such as a cable are connected, and the other end is connected to one contact electrode 3a of the second energizing electrode 3 via a conductor such as a copper plate and a cable. The pair of vertical portions of the copper plate 7 of the adjuster 7 are formed with a plurality of screw holes 7b facing each other, and both ends of the connecting conductor 7c made of a copper plate or the like are formed in the pair of opposed screw holes 7b. It is fixed by a bolt 7d or the like.

  The circuit impedance of the second conducting electrode 3 is adjusted (changed) by changing the fixing position of the adjuster 7 with respect to each screw hole 7b of the connecting conductor 7c as shown by two-dot chain lines a and b in FIG. . As a result, the current value supplied to the second energizing electrode 3 is, for example, a predetermined value lower than the current value supplied to the first energizing electrode 2 directly connected to the output terminal of the transistor inverter 4 by a conductor. Is set. The first energizing electrode 2 and the second energizing electrode 3 are connected to an energizing electrode moving unit (not shown), and the energizing electrode moving unit is actuated by a control signal from the control device 6 as will be described later. It is comprised so that contact / separation is possible with respect to the tooth surface Wa and back surface Wb.

  As shown in FIG. 3A, the cooling jacket 5a constituting the cooling means 5 is composed of four cooling jackets 5a1 to 5a4 arranged at predetermined intervals on the outer peripheral surface of the rack bar W having a circular cross section. Is formed. That is, the rack bar W includes cooling jackets 5a1 and 5a2 arranged to face the tooth surface Wa side and the back surface Wb side, and cooling jackets 5a3 and 5a4 arranged to face the side surface Wc. Are arranged in an opposing state at a cross position on the outer peripheral surface side.

  Each cooling jacket 5a has an internal cooling water flow path (not shown), and a large number of injection holes (not shown) provided on the side wall on the opposite surface side of the rack bar W, and the like. Cooling water (or a cooling medium such as cooling gas) supplied into the cooling water flow path via a hose or the like is jetted toward the outer peripheral surface of the rack bar W from the jet hole at a predetermined pressure. At this time, the direction of the injection hole of each cooling jacket 5a is set so that the cooling water is injected substantially uniformly over the entire circumferential direction (referred to as the entire outer peripheral surface) of the outer peripheral surface of the rack bar W having a circular cross section. . Further, each cooling jacket 5a is set at an injection position with respect to the outer peripheral surface of the rack bar by an operation of a jacket moving unit (not shown), and in order to allow the rack bar W that has been quenched and tempered to be taken out, It is possible to move from to the exit position.

  The configuration of the cooling means 5 is not limited to the use of the four substantially flat cooling jackets 5a1 to 5a4 shown in FIG. 3A, but as shown in FIG. Two cooling jackets 5a1 and 5a2 may be used. In this case, the injection holes of the two cooling jackets 5a1 and 5a2 can be arranged on the outer peripheral surface of the rack bar W with a substantially uniform interval. The cooling jacket 5a is also connected to the jacket moving unit, and the jacket moving unit is operated by a control signal from the control device 6, so that the tooth surface Wa, the back surface Wb, and both side surfaces Wc of the rack bar W are operated. It is configured to be able to contact and separate.

  The cooling water supply unit 5b of the cooling means 5 has a tank as a cooling water supply source, a pump for pumping up the cooling water in the tank, and the like, and each cooling jacket 5a has a predetermined pressure for cooling water pumped up by the pump. To supply. In addition, the structure of each cooling jacket 5a which comprises the cooling means 5 is not limited to two examples, Each cooling jacket 5a1-5a4 shown to Fig.3 (a) is made into circular arc shape as shown in FIG.3 (b). Of course, the number of the cooling jackets 5a1, 5a2 may be three or five.

  The transistor inverter 4 has two inverter circuits using a semiconductor switching element, for example, for quenching and tempering, and a current of a predetermined output at two predetermined frequencies suitable for quenching and annealing is output from its output terminal. Output to the contact electrodes 2a, 2b of the first energizing electrode 2 and the contact electrodes 3a, 3b of the second energizing electrode 3 is possible.

  The control device 6 includes a microcomputer, a sequencer, or the like having a CPU, ROM, RAM, timer, etc., and the transistor inverter 4, the regulator 7, the cooling water supply unit 5 b, and none are shown on the output side. The energizing electrode moving part, the jacket moving part, a support part for supporting (chucking) both ends of the rack bar W are connected, and a radiation thermometer for measuring the heating temperature of the rack bar is connected to the input side thereof. Various sensors are connected.

  Next, an example of a method of heating the rack bar W using the energization heating device 1 will be described based on the process diagram of FIG. First, the position of the connecting conductor 7b of the regulator 7 connected to the output terminal of the transistor inverter 4 is adjusted, and the circuit impedance of the second conducting electrode 3 is directly connected to the output terminal of the transistor inverter 4. It is set to be different from the circuit impedance of one energizing electrode 2. At this time, the position of the connecting conductor 7b of the adjuster 7 is set in advance according to the depth of each part of the hardened layer 9 described later formed on the rack bar W.

  Also, the rack bar W is formed in a cylindrical shape (circular cross section) at both ends in the longitudinal direction, and the left and right sides arranged at both ends of the rack bar W by the control signal of the control device 6 prior to the start of energization work. The rack bar W is set to the support part (K01) by the operation of the support part. In this set state, the energizing electrode moving unit is operated by the control signal of the control device 6, and the contact electrodes 2 a and 2 b of the first energizing electrode 2 and the contact electrodes 3 a and 3 b of the second energizing electrode 3 are moved to the teeth of the rack bar W. Contact (K02) is made to both ends of the heating range of the surface Wa and the back surface Wb.

  Further, at the same time as or before or after the contact of each contact electrode 2a, 2b, 3a, 3b, the jacket moving part is operated by the control signal of the control device 6 to set each cooling jacket 5a to the injection position (K03). The transistor inverter 4 is operated by the control signal of the control device 6 in the set state of the current-carrying electrodes 2 and 3 and the cooling jackets 5a, so that the first current-carrying electrode 2 and the second current-carrying electrode 3 have a predetermined output at a predetermined frequency. The current is supplied to start the first energization (quenching energization) (K04).

  This first energization is performed by supplying a quenching current to the first energizing electrode 2 and the second energizing electrode 3, and energizing the outer peripheral surface of the rack bar W with a first current. By setting the frequency and current value (output) of 1 energization or the form of the contact surface of each energizing electrode 2 and 3 to a predetermined value, the tooth surface Wa and the back surface Wb of the rack bar W are energized and heated, and their connecting portions The both side surfaces Wc are heated by energization, and the entire outer peripheral surface of the rack bar W is energized and heated.

  At the time of the first energization, a constant output current for quenching set in advance from the inverter circuit for quenching of the transistor inverter 4 is simultaneously supplied to the first energizing electrode 2 and the second energizing electrode 3. A regulator 7 is connected to the electrode 3, and its circuit impedance is different from the circuit impedance of the first current-carrying electrode 2, so that the rack bar W is energized and heated by the first current-carrying electrode 2 and the second current-carrying electrode 3. The conditions are set differently. By changing the current heating conditions, for example, predetermined depths H1 to H3 different from each other are formed in the hardened layer 9 as described later.

  When this first energization is performed for a predetermined time set in advance or when the temperature of the heated portion of the rack bar W detected by the radiation thermometer reaches a predetermined value, the control signal of the control device 6 controls the transistor inverter 4. The current supplied to the first energizing electrode 2 and the second energizing electrode 3 from the inverter circuit for quenching is stopped to stop the first energization (quenching energization) (K05). Then, substantially simultaneously with the stop of the first energization, the cooling water supply unit 5b is operated by the control signal of the control device 6 to supply the cooling water into each cooling jacket 5a, and from the injection hole of each cooling jacket 5a, the first Cooling water is jetted (K06) toward the outer peripheral surface of the rack bar W heated to a predetermined temperature by one energization.

  The heated portion of the rack bar W is rapidly cooled by jetting the cooling water for a predetermined time. As a result, each cooling jacket 5a is disposed at a predetermined interval over the entire outer peripheral surface of the tooth surface Wa, the back surface Wb, and the both side surfaces Wc of the rack bar W, so that the cooling water is supplied to the outer periphery of the rack bar W. The entire surface is sprayed almost evenly and the entire heated portion is quenched to form a hardened layer having a predetermined hardness (for example, 62 to 65 HRC).

  Then, when the outer peripheral surface of the rack bar W is quenched by the first energization heating and the cooling water injection, the first energization electrode 2 and the first energization electrode 2 and the first energization electrode 2 are transmitted from the transistor inverter 4 by the control signal of the control device 6 in the quenched state. A predetermined current is supplied to the second energizing electrode 3 to start the second energization (tempering energization) (K07). In this second energization, the tempering current is supplied to the first energizing electrode 2 and the second energizing electrode 3 from the tempering inverter circuit of the transistor inverter 4 and the tempering current is energized to the quenching layer of the rack bar W. The hardened layer in the entire outer peripheral surface of the wack bar W is tempered to a predetermined hardness (for example, 56HRC). Also at the time of tempering, the current value supplied to the first energizing electrode 2 and the second energizing electrode 3 by the regulator 7 is different from that at the time of quenching.

  When the second energization is performed for a predetermined time, the current supply from the transistor inverter 4 to the energization electrodes 2 and 3 is stopped by the control signal of the control device 6 to stop the second energization (tempering energization) (K08). The rack bar W is forcibly cooled (K09) to form the hardened layer 9 over the entire outer peripheral surface of the rack bar W. Thereafter, the jacket moving unit is operated by the control signal of the control device 6 to retract each cooling jacket 5a to the retracted position, and the support unit is operated to release the support state of the rack bar W, and the rack bar W is taken out. (K10). Thereby, a series of quenching and tempering operations (heat treatment operations) of the rack bar W is completed. Note that the forced cooling of the rack bar W in the process K09 is performed by spraying cooling water from the cooling jacket 5a, for example, similarly to the case of quenching because the tempering temperature is about 200 to 250 ° C.

  That is, the heat treatment (quenching and tempering treatment) of the rack bar W is performed by quenching the entire outer peripheral surface of the rack bar W by heating by the first energization and rapid cooling by the cooling jacket 5a while supporting both ends of the rack bar W. Then, a quenching layer is formed, and after this quenching, the rack bar W, the first energizing electrode 2 and the second energizing electrode 3 are left as they are, and the heating by the second energization is continuously performed to temper the quenching layer. Thus, a hardened layer 9 having a predetermined hardness is obtained over the entire outer peripheral surface of the rack bar W.

  And this hardened layer 9 is comprised as shown in FIG. That is, the depth (width) from the outer peripheral surface (bottom surface of the inclined tooth) of the rack bar W toward the center is H1, the depth of the back surface Wb is H2, and the depth of both side surfaces Wc is H3. Differently, the relationship is set as H1> H2> H3. That is, the depth H1 of the hardened layer 9 of the tooth surface Wa to which the load is applied most among the outer peripheral surfaces is made deepest to sufficiently enhance the durability of the rack bar W.

  As described above, according to the energization heating device 1, current is supplied from a predetermined inverter circuit of the transistor inverter 4 in a state where the first energization electrode 2 and the second energization electrode 3 are in contact with the outer peripheral surface of the rack bar W. The entire outer peripheral surface of the rack bar W is energized and heated, and the heated portion is rapidly cooled by the cooling jacket 5a to form a continuous hardened layer 9 over the entire outer peripheral surface of the rack bar W. By simultaneously energizing the second energizing electrode 3 and simultaneously cooling the heated portion, the hardened layer 9 having a predetermined shape can be easily formed in a state of being continuous over the entire circumferential direction of the rack bar W.

  In addition, the conventional heating device dedicated to the tooth surface Wa and the back surface Wb is not required, and the heating operation can be efficiently performed by simultaneously energizing the tooth surface Wa and the back surface Wb while simplifying the configuration of the energization heating device 1. In addition, since the hardened layer 9 is formed by tempering a hardened layer that has been quenched under a predetermined quenching energization condition under a predetermined tempering energization condition, a predetermined amount is provided on the tooth surface Wa, the back surface Wb, and both side surfaces Wc that serve as a connecting portion thereof. Quenching and tempering can be performed continuously, the setup time of the rack bar W can be shortened, etc., and the desired hardened layer 9 can be efficiently formed on the entire outer peripheral portion to obtain a low-cost rack bar W. Can do.

  Further, since the depths H1, H2, and H3 of the hardened layer 9 are set such that the tooth surface Wa (H1)> the back surface Wb (H2)> the both side surfaces Wc (H3), particularly the hardened layer 9 of the tooth surface Wa. While the depth H1 can be deepened, the durability of the rack bar W itself can be sufficiently increased, and while the depths H2 and H3 of other portions are kept to the minimum necessary to prevent the formation of a useless hardened layer 9, The depth of the hardened layer 9 can be adjusted according to the position in the circumferential direction, and the rack bar W having the desired form of the hardened layer 9 that is not brittle and can provide sufficient durability can be easily manufactured. it can.

  Further, since the regulator 7 is connected to the second energizing electrode 3, different currents can be supplied from the transistor inverter 4 to the first energizing electrode 2 and the second energizing electrode 3, and the tooth surface Wa and the back surface Wb are cured. The depth H1, H2, etc. of the layer 9 can be adjusted as desired, and the rack bar W having the desired hardened layer 9 over the entire outer peripheral surface can be easily obtained. At the same time, by providing two types of inverter circuits with different frequencies and outputs in the transistor inverter 4, it is possible to cope with quenching and tempering, so that it is possible to obtain a power supply means that is simple in configuration and excellent in terms of energy saving.

  Further, since the cooling means 5 includes four cooling jackets 5a1 to 5a4 and two semicircular arc shaped cooling jackets 5a1 and 5a2 that can be arranged to face each other on the entire outer peripheral surface of the rack bar W, the rack bar W that is energized and heated. The cooling water can be uniformly and effectively sprayed and cooled on the entire outer peripheral surface of the steel plate, the quenching quality of the hardened layer can be stabilized, and as a result, the rack bar W having the highly accurate hardened layer 9 can be easily obtained.

  By the way, in the said embodiment, although the case where the rack bar W was circular in cross section in the longitudinal direction whole region (except for the tooth surface Wa part) was demonstrated, this invention is not limited to this structure, For example, FIG. The present invention can also be applied to a rack bar W having a deformed cross section as shown. That is, the rack bar W shown in FIG. 6 (a) has a rear surface Wb and both side surfaces Wc formed in a cross-sectional straight line (flat surface) instead of an arc-shaped cross-section, and have an irregular shape. Further, the rack bar W shown in FIG. 6 (b) has an irregular shape in which only the back surface Wb is formed with a straight cross section (flat surface).

  The rack bar W in this example is formed by drawing, for example, but it goes without saying that both end portions in the longitudinal direction are formed in a circular cross section. Also in this example, the hardened layer 9 is formed over the entire outer peripheral surface of the rack bar W in the same manner as in the above embodiment, and in addition to the same effects as the above embodiment, the cross sectional area of the rack bar W is circular in cross section. In this case, the weight of the rack bar W itself can be reduced, and for example, the effect of contributing to weight reduction of the vehicle can be obtained.

  In the embodiment, the transistor inverter 4 has two inverter circuits for quenching and tempering. However, for example, the transistor inverter 4 has a single inverter circuit whose frequency and output can be adjusted. May be switched or adjusted by a control signal of the control device 6. The power supply means of the present invention uses an appropriate power supply circuit capable of outputting an alternating current as well as using an inverter circuit, and the circuit configuration is not limited to the use of an inverter circuit, while the frequency of the alternating current is set from a low frequency to a high frequency. can do.

  Furthermore, the form of each energizing electrode 2, 3 in the above embodiment, the contact position to the rack bar W, the form of the adjuster 7, the depth of the hardened layer 9, etc. are examples, and for example, the tooth surface of the rack bar W Depending on the shape of the rack bar W, the contact electrodes 2a, 2b, 3a, 3b on the Wa side and the back surface Wb side are made different, or the depths of the hardened layers 9 on the back surface Wb and the both side surfaces Wc are made substantially the same. Can be changed as appropriate.

  INDUSTRIAL APPLICABILITY The present invention can be used for all steering rack bars that require a hardened layer over the entire outer peripheral surface including the tooth surface and the back surface by using electric heating.

  DESCRIPTION OF SYMBOLS 1 ... Current heating apparatus, 2 ... 1st electricity supply electrode, 2a, 2b ... contact electrode, 3 ... 2nd electricity supply electrode, 3a, 3b ... contact electrode, 4 * transistor inverter, 5 ... Cooling means, 5a, 5a1 to 5a4 ... Cooling jacket, 5b ... Cooling water supply part, 7 ... Adjuster, 7a ... Copper plate, 7b ... Screw hole, 7c ... Connecting conductor, 9 ... hardened layer, W ... rack bar, Wa ... tooth surface, Wb ... back surface, Wc ... side surface.

Claims (6)

A first energizing electrode comprising a pair of contact electrodes capable of contacting both ends of the heating range of the tooth surface of the rack bar, and a second energizing electrode comprising a pair of contact electrodes capable of contacting both ends of the heating range of the back surface of the rack bar. A power supply means capable of supplying a current of a predetermined frequency to the first energization electrode and the second energization electrode, a cooling means disposed at a predetermined interval substantially all over the outer peripheral side of the heating range of the rack bar, and Control means for controlling,
The control means supplies electric current from the power supply means in a state where the first energizing electrode and the second energizing electrode are in contact with the outer peripheral surface of the rack bar, and energizes and heats the entire circumferential direction of the rack bar. An electric heating apparatus for a steering rack bar, wherein a heating layer is cooled by the cooling means to form a continuous hardened layer in the entire circumferential direction of the rack bar.   2. The steering rack bar electric heating device according to claim 1, wherein the hardened layer is obtained by tempering a hardened layer quenched under a predetermined quenching energization condition under a predetermined tempering energization condition.   3. The electric heating apparatus for a steering rack bar according to claim 1, wherein the depth of the hardened layer is set to tooth surface portion> back surface portion> both side surface portions.   4. The energization heating apparatus for a steering rack bar according to claim 1, wherein the power supply means supplies different currents to the first energization electrode and the second energization electrode by current adjustment means.   5. The steering rack bar electrification heating apparatus according to claim 1, wherein the cooling means includes a plurality of cooling jackets that can be arranged to face each other in the entire circumferential direction of the rack bar.   6. The electric heating apparatus for a steering rack bar according to claim 1, wherein the rack bar has a circular cross section or an irregular cross section.

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