JP7101092B2 - Quenching equipment and quenching method for rack bars - Google Patents

Description

The present invention relates to a quenching device and a quenching method for a rack bar used in an automobile steering device or the like.

The rack bar has a rack formed in a part of the length of the shaft member, and a rack bar made of a hollow shaft member is also known for weight reduction. When the rack bar is quenched after machining, the cross-sectional shape of a part of the section where the rack is formed is asymmetric and the residual stress during rack machining is high, so bending is likely to occur due to quenching. The tendency is remarkable for those made of hollow shaft material. Therefore, a quenching device and a quenching method for quenching with the rack bar restrained are known (see, for example, Patent Document 1 and Patent Document 2).

The quenching device described in Patent Document 1 includes four restraining jigs for restraining the rack bar from the vertical direction and the horizontal direction. Each restraint jig is provided with a plurality of convex portions in contact with the rack bar, and a small hole cooling liquid injection port is formed in the concave portion between these convex portions. The coolant injection ports are lined up in the length direction of the rack bar. In a state where the heated rack bar is restrained from the vertical direction and the horizontal direction by four restraining jigs, the cooling liquid is ejected from these coolant injection ports and the rack bar is hardened.

The quenching device described in Patent Document 2 also includes four restraint jigs for restraining the rack bar from the vertical direction and the horizontal direction. Among the four restraint jigs, the restraint jig that comes into contact with the rack includes the restraint jig. Instead of the small hole coolant injection port, a coolant injection slit extending over the entire length of the rack is formed.

Japanese Unexamined Patent Publication No. 2000-119739 Japanese Unexamined Patent Publication No. 2001-11536

In the quenching device described in Patent Document 1, the cooling rate may differ depending on the teeth, and the pitch of the teeth of the rack may become irregular. Irregular tooth pitches interfere with the smooth meshing of the rack and pinion and can reduce the performance of mechanical devices that use rack bars. In the quenching device described in Patent Document 2, in the restraint jig that contacts the rack among the four restraint jigs, the nozzle for injecting the coolant is replaced with a slit extending from the small hole to the entire length of the rack. As a result, the cooling rate of each tooth is made uniform and the irregularity of the tooth pitch is suppressed. However, with the improvement of the performance of the mechanical device using the rack bar, the rack bar is required to have more uniform tooth accuracy, and additional measures are required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress irregularity of tooth pitch due to quenching strain and to provide a more accurate rack bar.

The rack bar quenching device according to one aspect of the present invention is a rack bar quenching device in which a rack is formed in a partial section of the length of the hollow shaft member, and the heated partial section is described as described above. A plurality of restraint jigs for restraining from a plurality of radial directions over the entire length of a part of the section are provided, and the plurality of restraint jigs are injection units for injecting coolant to a portion facing the restraint jig in the part of the section. The injection unit uniformly injects the coolant onto a plurality of annular regions that circulate around the outer periphery of the partial section through at least each tooth bottom of the rack.

Further, in the method for quenching a rack bar according to one aspect of the present invention, at least a part of the rack bar in which a rack is formed in a part of the length of the hollow shaft member is heated and heated. The section is constrained from a plurality of radial directions over the entire length of the section, and the section is constrained to a plurality of annular regions that orbit the outer periphery of the section at least through each tooth bottom of the rack. The coolant is uniformly sprayed from a plurality of restraint jigs.

According to the present invention, it is possible to suppress irregularity of tooth pitch due to quenching strain and provide a rack bar with higher accuracy.

It is a perspective view of an example of a rack bar for demonstrating an embodiment of this invention. It is a schematic diagram which shows the molding method of the rack of the rack bar of FIG. It is a schematic diagram which shows the molding method of the rack of the rack bar of FIG. It is sectional drawing of an example of the quenching apparatus of a rack bar for demonstrating the embodiment of this invention. It is a vertical sectional view of the quenching apparatus of FIG. It is a top view of the rack restraint jig of the quenching apparatus of FIG. It is a top view of the restraint jig other than the rack restraint jig of the quenching apparatus of FIG. It is a top view of the modification of the rack restraint jig of FIG. It is a schematic diagram which shows the evaluation method of the tooth pitch of a rack. It is a graph which shows the evaluation result of the tooth pitch of the rack of the rack bar hardened by the quenching apparatus of FIG. It is sectional drawing of another modification of the rack restraint jig of FIG. It is a graph which shows the evaluation result of the tooth pitch of the rack of the rack bar hardened by the quenching apparatus including the rack restraining jig of FIG. It is a schematic diagram of a steering device. It is a schematic diagram which shows the meshing of a rack and a pinion in a steering apparatus. It is a schematic diagram which shows the meshing of a rack and a pinion in a steering apparatus. It is sectional drawing of another example of the quenching apparatus for demonstrating embodiment of this invention. It is a vertical sectional view of the quenching apparatus of FIG. It is a schematic diagram of an example of pressurization by the pressurization mechanism of FIG. It is a schematic diagram of another example of pressurization by the pressurization mechanism of FIG.

FIG. 1 shows an example of a rack bar for explaining an embodiment of the present invention.

The rack bar 10 is a rack bar made of a hollow shaft member 11 having a circular cross section, and the rack 12 is formed in a part of the length of the shaft member 11. The rack bar 10 is manufactured, for example, as follows.

The shaft member 11 is a hollow shaft member made of steel such as JIS-S45C. As shown in FIG. 2, a part of the length of the shaft member 11 is flatly crushed to the vicinity of the tooth bottom height by press working to form a flat crushed portion 13 extending in the axial direction of the shaft member 11. ..

Next, as shown in FIG. 3, a part of the shaft member 11 including the flattening portion 13 is held by the die 20. The mold 20 includes an upper mold 21 and a lower mold 22. The upper mold 21 and the lower mold 22 are opened and closed by a mold clamping mechanism (not shown), sandwich the shaft member 11 in the vertical direction, and hold the outer periphery of the shaft member 11. A rack tooth mold 23 is detachably attached to the upper mold 21, and the rack tooth mold 23 is fixed in contact with a substantially flat outer surface of the flattened portion 13. A plurality of tooth grooves for forming the rack 12 are provided on the forming surface 24 of the rack tooth mold 23 in contact with the outer surface of the flattening portion 13.

The core metal 25 is inserted into the shaft member 11 through the opening on one end side of the shaft member 11 in a state where the rack tooth mold 23 is in contact with the flattened portion 13, and is inserted into the flattened portion 13 by the push rod 26. It is press-fitted. Then, the press-fitted core metal 25 is pushed back by the push rod 27 inserted from the opening on the other end side of the shaft member 11, and is discharged from the shaft member 11. In the process of reciprocating the core metal 25 over the entire length of the flattening portion 13, the material of the flattening portion 13 is squeezed by the core metal 25 and plastically flows toward the rack tooth mold 23. The core metal 25 is gradually replaced with a larger one, and by repeatedly press-fitting the core metal 25, the material of the flattening portion 13 gradually bites into the tooth groove of the forming surface 24 of the rack tooth mold 23, and the shape of the forming surface 24 is changed. It is transferred to the flat crushing portion 13, and the rack 12 is formed on the flat crushing portion 13.

The shaft member 11 on which the rack 12 is formed is subjected to bending correction accompanying tooth formation, grinding of the outer peripheral surface, and quenching to increase the hardness of the rack 12. as necessary. The heating at the time of quenching of the shaft member 11 can be performed by, for example, high frequency induction heating, but is not limited to high frequency induction heating. Further, the heating range of the shaft member 11 is not particularly limited as long as it includes a partial section in which the rack 12 is formed (hereinafter referred to as a rack forming section), and may be only the rack forming section or the entire length of the shaft member 11. good.

Here, as a factor that the pitch of the teeth of the rack becomes irregular due to quenching, it is mentioned that the cooling rate at the time of quenching becomes non-uniform at each tooth bottom of the rack. That is, when each tooth bottom is cooled from the heating temperature of quenching, shrinkage due to thermal expansion occurs, but the quickly cooled portion shrinks ahead of the other portions. On the other hand, the slow-cooled portion is limited in shrinkage by the previously cooled and strengthened portion. As a result, the tooth pitch is narrow in the portion of each tooth bottom where cooling is fast, and the tooth pitch is wide in the portion where cooling is slow. Further, quenching of the rack bar is usually performed by heating not only the rack but also the entire circumference of the rack forming section. Therefore, the non-uniform cooling rate of the annular region Ai ( _i = 1 to n) (see FIG. 1) that orbits the outer periphery of the rack forming section through each tooth bottom also affects the irregularity of the rack tooth pitch. do.

In the conventional rack bar quenching device, the coolant is sprayed from a plurality of small holes arranged in the length direction of the rack bar, but the correspondence between the small holes and the teeth of the rack, in other words, the small holes and the tooth bottom pass through. The correspondence with the annular region Ai ( _i = 1 to n) is not constant. The coolant will eventually flow through all the annular regions Ai ( _i = 1 to n), but when viewed in detail, the way the coolant hits each annular region Ai ( _i = 1 to n) is not uniform. For example, in some annular regions, the coolant directly hits, and in some annular regions, the coolant that hits other annular regions wraps around. It is considered that such non-uniformity of the contact of the coolant causes non-uniformity of the cooling rate at the time of quenching, and the pitch of the teeth of the rack becomes non-uniform. Therefore, the rack bar quenching device described below uniformly injects the coolant into each annular region Ai ( _i = 1 to n) to suppress the irregularity of the rack tooth pitch. be.

Further, since the cross-sectional shape of the rack forming section is asymmetric, the rack bar is liable to bend due to quenching. In particular, a rack bar made of a hollow shaft material has a weak binding force inside the material against a bending force unlike a rack bar made of a solid shaft material, so that bending is likely to occur. Therefore, it is preferable to restrain the rack bar during cooling. The rack bar quenching device described below also has such a restraining means and suppresses bending of the rack bar.

4 and 5 show a quenching device for the rack bar 10.

The quenching device 100 includes a plurality of restraining jigs for restraining the rack forming section from a plurality of radial directions over the entire length of the rack forming section of the rack bar 10. In the example shown in FIG. 4, four restraint jigs 101 to 104 arranged around the central axis of the rack bar 10 at intervals of 90 ° are provided, but the number of restraint jigs is not particularly limited, and for example, three restraints are provided. Jigs may be arranged around the central axis of the rack bar 10 at 120 ° intervals.

The restraint jig 101 is arranged below the rack bar 10 in which the rack 12 is arranged downward, and comes into contact with the rack 12. Hereinafter, the restraint jig 101 is particularly referred to as a rack restraint jig. The restraint jig 102 is arranged above the rack bar 10, and the restraint jigs 103 and 104 are arranged on the left and right sides of the rack bar 10. At least one of the rack restraint jig 101 and the restraint jig 102 paired in the vertical direction is attached to a pressurizing device such as a hydraulic cylinder (not shown). Further, at least one of the restraint jigs 103 and 104 paired in the horizontal direction is also attached to a pressurizing device such as a hydraulic cylinder (not shown). The rack forming section of the rack bar 10 is restrained in a state of being pressurized in the vertical direction and the horizontal direction by the rack restraint jig 101 and the restraint jigs 102 to 104.

The rack restraint jig 101 has a coolant supply chamber 111 inside, and has an injection unit 112 that injects the coolant supplied to the coolant supply chamber 111 into the rack 12. The other restraint jigs 102 to 104 also have a coolant supply chamber 113 inside, and each has an injection unit 114 for injecting coolant to a portion facing each restraint jig in the rack forming section of the rack bar 10. Have. In the example shown in FIG. 4, four jackets 105 for injecting coolant are further provided in the rack forming section, and the jackets 105 are two adjacent restraint jigs 101 to 104 among the four restraint jigs 101 to 104. Each is placed between. As described above, it is free to separately add a jacket 105 that assists in cooling the rack forming section.

FIG. 6 shows the rack restraint jig 101, and FIG. 7 shows the restraint jig 102.

As shown in FIGS. 5 and 6, the rack restraint jig 101 has a tip surface 120 in contact with the rack 12, and the tip surface 120 is formed to have a length equal to or longer than the rack forming section of the rack bar 10. .. The tip surface 120 is formed in a flat shape over the entire length thereof, and comes into contact with the tooth tips of all the teeth of the rack 12. The injection portion 112 of the rack restraint jig 101 has a coolant injection slit 121 that opens to the tip surface 120. The coolant injection slit 121 extends in the widthwise central portion of the tip surface 120 in the length direction of the rack bar 10, and is formed to have a length equal to or longer than the rack forming section. The coolant supply chamber 111 inside the rack restraint jig 101 is also formed to have a length longer than the rack forming section of the rack bar 10, and the coolant injection slit 121 is provided in the coolant supply chamber 111 over substantially the entire length. Communicating.

The cooling liquid sprayed from the cooling liquid injection slit 121 has a curtain shape and hits the rack forming section of the rack bar 10 while intersecting with all the teeth of the rack 12. That is, the coolant injected from the coolant injection slit 121 directly hits all the tooth bottoms of the rack 12, and all the tooth bottoms are cooled under the same conditions. The coolant flows on both sides along each tooth bottom, and each tooth bottom is evenly cooled over the entire width. Therefore, it suffices if one coolant injection slit 121 is provided so as to face the central portion in the width direction of the tooth bottom, but two or more coolant injection slits 121 may be provided in parallel with each other.

As shown in FIGS. 5 and 7, the restraint jig 102 has a tip surface 130 in contact with the outer peripheral surface of the rack forming section excluding the rack 12 of the rack bar 10, and the tip surface 130 is the rack of the rack bar 10. It is formed to a length longer than the formation section. The injection portion 114 of the restraint jig 102 has a coolant injection slit 131 that opens to the tip surface 130, and a plurality of concave grooves 132. The coolant injection slit 131 extends in the widthwise central portion of the tip surface 130 in the length direction of the rack bar 10, and is formed to have a length equal to or longer than the rack forming section. The coolant supply chamber 113 inside the restraint jig 102 is also formed to have a length longer than the rack forming section of the rack bar 10, and the coolant injection slit 131 communicates with the coolant supply chamber 113 over its entire length. is doing. The plurality of concave grooves 132 are provided at intervals in the length direction of the tip surface 130, and extend in the width direction of the tip surface 130 so as to intersect the coolant injection slit 131.

The cooling liquid sprayed from the cooling liquid injection slit 131 has a curtain shape and hits the rack forming section of the rack bar 10 while intersecting with all the annular regions Ai ( _i = 1 to n). That is, the coolant injected from the coolant injection slit 131 directly hits all the annular regions A _i (i = 1 to n), and all the annular regions A _i (i = 1 to n) are cooled under the same conditions. To. The coolant flows on both sides along each groove 132 and is discharged. Preferably, the pitch of the plurality of grooves 132 is the same as the pitch of the annular region Ai ( _i = 1 to n), that is, the pitch of the teeth of the rack 12, and each groove 132 has each annular region Ai ( _i ). It is arranged along i = 1 to n). Thereby, the cooling conditions of each annular region Ai ( _i = 1 to n) can be further made uniform.

The coolant supply chamber 113 and the injection unit 114 of the restraint jig 103 and the restraint jig 104, respectively, are configured in the same manner as the coolant supply chamber 113 and the injection unit 114 of the restraint jig 102. The coolant sprayed from the coolant injection slits 131 of the restraint jig 103 and the restraint jig 104 also intersects with all the annular regions Ai ( _i = 1 to n) and extends over the entire length of the rack forming section. In the rack bar 10, all the annular regions A _i (i = 1 to n) are cooled under the same conditions. The number of coolant injection slits 131 for each of the restraint jigs 102 to 104 may be one or two or more.

In this way, the coolant is uniformly sprayed from the rack restraint jig 101 and other restraint jigs 102 to 104 onto the annular region Ai ( _i = 1 to n) passing through each tooth bottom of the rack 12. By doing so, the cooling rate of the annular region Ai ( _i = 1 to n) is made uniform, and the irregularity of the tooth pitch of the rack 12 is suppressed. Further, since the rack bar 10 is quenched in a state where the rack forming section is restrained from a plurality of radial directions by the rack restraint jig 101 and other restraint jigs 102 to 104, bending due to quenching is also suppressed. ..

Here, in order to make the cooling rate of the annular region Ai ( _i = 1 to n) uniform, the injection amount of the coolant injected from the coolant injection slits 121 and 131 is made uniform over the entire length of the slit. That is essential. In the example shown in FIG. 5, a plurality of coolant introduction ports 115 are provided in the coolant supply chambers 111 and 113 in order to make the injection amount of the coolant uniform over the entire length of the slit. The rectifying plate 116 is provided inside the coolant supply chambers 111 and 113.

For example, in the rack restraint jig 101, the inside of the coolant supply chamber 111 is divided into two spaces by a straightening vane 116. The coolant injection slit 121 communicates with one of the two spaces partitioned by the straightening vane 116, and the plurality of coolant inlets 115 communicate with the other space. For example, the straightening vane 116 is provided with a large number of small holes evenly distributed over the entire surface, and the fluid resistance is cooled when the coolant introduced from the coolant inlet 115 passes through the straightening vane 116. It acts on the liquid. As a result, the flow velocity inside the coolant supply chamber 111 is reduced and the pressure is made uniform, and the injection amount of the coolant injected from the coolant injection slit 121 is made uniform over the entire length of the slit.

The means for equalizing the injection amount of the coolant over the entire length of the slit is not limited to the installation of the plurality of coolant introduction ports 115 and the installation of the straightening vane 116. For example, the internal volumes of the coolant supply chambers 111 and 113 may be made as large as possible, whereby the flow velocity and the pressure inside the coolant supply chambers 111 and 113 can be reduced and the pressure can be made uniform.

Further, in order for the injection amount of the coolant to be uniform over the entire length of the slit, the slit widths w of the coolant injection slits 121 and 131 are important. If the slit width w is excessive, the shunting of the coolant becomes insufficient, and the injection amount of the coolant may become non-uniform. The slit width w is preferably 0.2 mm or more and 0.5 mm or less, although it is related to the pressure of the coolant in the coolant supply chambers 111 and 113.

FIG. 8 shows a modified example of the rack restraint jig 101 described above.

The rack restraint jig 201 shown in FIG. 8 and the rack restraint jig 101 described above are different in the configuration of the injection portion for injecting the coolant to the rack 12. The injection portion 212 of the rack restraint jig 201 has a plurality of coolant injection ports 221 that open to the tip surface 220 in contact with the rack 12. The tip surface 220 is formed to have a length equal to or longer than the rack forming section of the rack bar 10, and the plurality of coolant injection ports 221 are spaced apart from each other in the length direction of the tip surface 220 to cover the entire length of the tip surface 220. It is provided over. The pitch of the plurality of coolant injection ports 221 is the same as the pitch of the teeth of the rack 12, and each coolant injection port 221 is arranged so as to overlap each tooth bottom of the rack 12. The coolant injected from each coolant injection port 221 directly hits each tooth bottom of the rack 12, and each tooth bottom is cooled under the same conditions. The plurality of coolant injection ports 221 may be arranged in a single row or may be arranged in a plurality of rows.

Although not shown, in the injection unit 114 of each of the restraint jigs 102 to 104 described above, the nozzle for injecting the coolant may be composed of a plurality of injection ports instead of the slits. In this case, the pitches of the plurality of injection ports are the same as the pitches of the teeth of the rack 12. The coolant injected from each injection port directly hits each annular region A _i (i = 1 to n), and each annular region A _i (i = 1 to n) is cooled under the same conditions.

Also in this example, the coolant is uniformly sprayed onto the annular region Ai ( _i = 1 to n) passing through each tooth bottom of the rack 12. As a result, the cooling rate of the annular region Ai ( _i = 1 to n) is made uniform, and the irregularity of the tooth pitch of the rack 12 is suppressed.

FIG. 9 shows a method of evaluating the overpin size of the teeth of the rack 12, and FIG. 10 shows an example of the evaluation result of the overpin size of the teeth of the rack 12. In FIG. 10, the alternate long and short dash line shows the evaluation result before quenching, the solid line shows the evaluation result after quenching when quenching by the quenching apparatus 100 shown in FIGS. 4 and 5, and the broken line shows the evaluation result after quenching. The evaluation result after quenching when quenching by the conventional quenching apparatus is shown.

The outer diameter of the rack-forming section of the hardened rack bar 10 is 26 mm, the inner diameter is 17 mm, and the length is 180 mm. This rack forming section was heated to about 950 ° C. by high frequency induction heating, and the heated rack bar 10 was quenched by the quenching device 100 and the conventional quenching device. In the conventional quenching device, in the quenching device 100 shown in FIGS. 4 and 5, the cooling liquid is injected to the four restraint jigs 101 to 104 in which the nozzle for injecting the cooling liquid is composed of slits. The nozzle is replaced with four restraining jigs composed of a plurality of small holes, and the pitch of the small holes is different from the pitch of the teeth of the rack 12.

To evaluate the tooth pitch of the rack 12, the rod (pin) 30 is placed so as to be fitted in the groove between the teeth as shown in FIG. 9, and the height position h of the top of the outer peripheral surface of the rod 30 is measured. , So-called overpin measurement. When the distance between the teeth becomes large, the rod 30 is deeply fitted into the groove, and the height position h of the rod 30, that is, the overpin dimension becomes low.

As shown in FIG. 10, the overpin size of the teeth of the rack 12 is uniform before quenching. It can be seen that in the rack bar 10 hardened by the quenching device 100, irregularity in the tooth pitch of the rack 12 is suppressed as compared with the rack bar 10 hardened by the conventional quenching device.

FIG. 11 shows a modified example of the rack restraint jig 101 described above.

The rack restraint jig 301 shown in FIG. 11 and the rack restraint jig 101 described above are different in the configuration of the tip surface in contact with the rack 12. The tip surface 320 of the rack restraining jig 301 is formed to have a length longer than the rack forming section of the rack bar 10. A recess 322 is provided in the central portion of the tip surface 320 in the length direction, and the tip surface 320 is formed in a flat shape except for the recess 322. The injection portion 312 of the rack restraint jig 301 has a coolant injection slit 321 similar to the injection portion 112 of the rack restraint jig 101 shown in FIG. 6, but the rack restraint jig 201 shown in FIG. Similar to the injection unit 212 of the above, there may be a plurality of coolant injection ports arranged at the same pitch as the tooth pitch of the rack 12.

The rack restraint jig 301 is in non-contact with the tooth tips of the teeth in the central portion of the rack 12 in the recess 322. In this case, the rack bar 10 is quenched in a state where the teeth at the center of the rack 12 are not pressed in the vertical direction between the rack restraint jig 301 and the restraint jig 102. As a result, as shown by the alternate long and short dash line in FIG. 12, the rack 12 is formed in a so-called crown shape in which the overpin size at the central portion is relatively large. Note that FIG. 12 shows the evaluation result of the tooth pitch of the rack 12 similar to that of FIG. 10, in FIG. 12, the alternate long and short dash line shows the evaluation result before quenching, and the solid line is shown in FIGS. 4 and 5. The evaluation result after quenching in the case of quenching by the quenching apparatus 100 is shown.

Here, the function of the crown-shaped rack will be described. 13 shows a schematic configuration of a vehicle steering device, and FIGS. 14 and 15 show the operation of a pinion that meshes with a rack.

As shown in FIG. 13, in a vehicle steering device, the pinion 1 is rotatably supported by a pair of bearings 2 and 3 and is connected to a vehicle steering shaft (not shown). Normally, the rack bar 10 is incorporated in the steering device so that the pinion 1 meshes with the teeth in the center of the rack 12 when the steering angle of the vehicle is 0 °, that is, in a straight running state. The pinion 1 is rotated according to the operation of the steering wheel, and the rack bar 10 meshing with the pinion 1 in the rack 12 is moved in the axial direction as the pinion 1 rotates.

When the central axis of the pinion 1 and the rotation axis of the pair of bearings 2 and 3 match, the distance between the central axis of the pinion 1 and the central axis of the rack bar 10 is constant regardless of the rotation of the pinion 1. Is. However, due to a molding error of the pinion 1 or the like, the central axis of the pinion 1 and the rotation axes of the pair of bearings 2 and 3 are misaligned, and as shown in FIG. 14, the pinion 1 is rotated with the rotation of the pinion 1. The distance D between the central axis of the rack 12 and the central axis of the rack 12 changes. The distance D between the axes of the pinion 1 and the rack 12 affects the force required for operating the steering wheel. Generally, as the distance between the axes increases, the force required for operating the steering wheel increases and the responsiveness decreases. By forming the rack 12 in a crown shape, as shown in FIG. 15, the inter-axis distance D is reduced at the steering angle of 0 ° and its vicinity. As a result, the responsiveness of steering from a straight-ahead state is enhanced.

In this example, the coolant is uniformly sprayed from the rack restraint jig 301 and other restraint jigs 102 to 104 onto the annular region Ai ( _i = 1 to n) passing through each tooth bottom of the rack 12. As a result, irregularity in the tooth pitch of the rack 12 is suppressed. Then, by forming the rack 12 in a crown shape with the rack restraining jig 301 and the tooth tips of the teeth in the center of the rack 12 in non-contact manner, the rack 12 can be accurately formed into a desired shape. ..

The shape of the rack 12 can be changed according to the specifications of the steering device into which the rack bar 10 is incorporated, and is not limited to the crown shape. The rack 12 may be formed in an inverted crown shape having relatively large overpin dimensions at both ends, for example. When the rack 12 is formed in an inverted crown shape, the recesses 322 are provided at both ends of the tip surface 320 of the rack restraining jig 301 in the length direction.

16 and 17 show other examples of quenching equipment for explaining embodiments of the present invention.

According to the quenching device 100 described above, since the rack bar 10 is quenched in a state of being restrained by four restraining jigs, bending due to quenching is suppressed, but the quenching shown in FIGS. 16 and 17 is suppressed. The quenching device 400 further suppresses bending due to quenching. Similar to the quenching device 100 described above, the quenching device 400 includes four restraint jigs 401 to 404 arranged at intervals of 90 ° around the central axis of the rack bar 10, and these four restraint jigs 401. By 404, the rack forming section is constrained from a plurality of radial directions over the entire length of the rack forming section.

The rack restraint jig 401 has an injection unit 412 for injecting a coolant to the rack 12. The injection unit 412 has a coolant injection slit 421 formed to a length equal to or longer than the rack formation section of the rack bar 10, but has a plurality of coolant injection ports arranged at the same pitch as the tooth pitch of the rack 12. You may have. The restraint jig 402 has an injection unit 414 that injects a coolant to a portion facing the restraint jig 402 in the rack forming section of the rack bar 10. The injection unit 414 has a coolant injection slit 431 formed to a length equal to or longer than the rack formation section of the rack bar 10, but has a plurality of coolant injection ports arranged at the same pitch as the tooth pitch of the rack 12. You may have. Since the remaining two restraint jigs 403 and 404 are the same as the restraint jig 402, the description thereof will be omitted.

The quenching device 400 further includes a pressurizing mechanism 440, in which the pressurizing mechanism 440 has a portion adjacent to both sides or one side of the rack forming section of the rack bar 10 in a direction perpendicular to the length direction of the rack bar 10. Press on. In this example, the rack bar 10 is arranged with the rack 12 facing downward, and the quenching strain caused by the asymmetry of the cross-sectional shape of the rack forming section appears mainly as a vertical bending of the rack bar 10. Therefore, the pressurizing mechanism 440 has a rack restraining jig 401 that is paired in the vertical direction and a pressing member 441 provided at both ends of the restraining jig 402 in the length direction. When the rack restraint jig 101 and the restraint jig 102 are driven by a pressurizing device such as a hydraulic cylinder to restrain the rack forming section in the vertical direction, the rack restraint jig 401 and the pressing member 441 of the restraint jig 402 are used. , Interlocking with the rack restraint jig 401 and the restraint jig 402, presses the pressed portion B in the vertical direction.

The pressing force of the pressurizing mechanism 440 can be adjusted separately from the pressing force of the rack restraint jig 101 and the restraint jig 102. The pressing member 441 of the rack restraining jig 401 has a position adjusting portion 442 that adjusts the position of the pressing member 441 along the contact direction (vertical direction) between the rack restraining jig 401 and the rack 12, and the restraining jig 402. The pressing member 441 also has a position adjusting portion 442 that adjusts the position of the pressing member 441 along the contact direction (vertical direction) between the restraining jig 402 and the rack forming section of the rack bar 10. The position adjusting portion 442 is composed of a screw portion 443 formed on the pressing member 441 and a locknut 444. The pressing member 441 of the rack restraint jig 401 is rotated to move forward and backward with respect to the rack restraint jig 401, and appropriately protrudes or retracts from the tip surface (contact surface with the rack 12) 420 of the rack restraint jig 401. Is placed. Similarly, the pressing member 441 of the restraint jig 402 is moved back and forth with respect to the restraint jig 402 by being rotated, and appropriately protrudes or retracts from the tip surface (contact surface with the rack forming section) 430 of the restraint jig 402. And are placed. By changing the amount of protrusion of the pressing member 441, the pressing force of the pressurizing mechanism 440 is adjusted separately from the pressing force of the rack restraint jig 101 and the restraint jig 102.

The pressurizing mechanism 440 applies a pressing force to the rack bar 10 so as to cancel the quenching strain generated in the rack bar 10, thereby suppressing bending of the rack bar 10 due to quenching. For example, when the tip of the pressing member 441 is arranged at a position where it just contacts the perfectly straight rack bar 10, and the rack bar 10 bends in the direction of contacting the pressing member 441, the pressurizing mechanism 440 racks the pressing force. It acts on the bar 10.

18 and 19 show an example of pressurizing the rack bar 10 using the pressurizing mechanism 440.

FIG. 18 shows a case where an upward pressing force is applied to the pressed portions B on both sides of the rack bar 10 by the pressing members 441 on both sides of the rack restraining jig 401. In this case, the rack bar 10 is subjected to an upward pressing force. Will act as a bending force as indicated by the arrow in the figure. Of course, if the pressing members 441 on both sides of the restraining jig 402 are used to reverse the acting direction of the pressing force, the bending direction is reversed. Since the rack bar 10 tends to be deformed so as to be curved in one direction, the pressurization of the embodiment shown in FIG. 18 is effective.

As shown in FIG. 19, an upward pressing force is applied to one of the pressed portions B by the pressing member 441 on one side of the rack restraining jig 401, and downward by the pressing member 441 on one side of the restraining jig 402. It is also possible to apply the pressing force of the above to the other pressed portion B. In this case, a bending force as shown by an arrow in the figure acts on the rack bar 10. Further, the pressing member 441 on one side of the rack restraining jig 401 or the restraining jig 402 can apply a pressing force only to one of the pressed portions B.

As described above, the pressurizing mechanism 440 can adjust the mode of pressurization and the pressing force according to the tendency of quenching strain of the rack bar 10 to occur. In actual quenching, for example, quenching is repeated by changing the mode of pressurization and the setting of pressurization, and it is possible to find the condition that the bending of the product is minimized by trial and error. Further, without using the pressurizing mechanism 440, the rack bar 10 is restrained by the rack restraint jig 401 and other restraint jigs 402 to 404 for test quenching, and then the bending generated in the test quenching is corrected. The main quenching may be performed by setting the pressurizing mode and the pressing force of the pressurizing mechanism 440 so as to perform the main quenching.

The pressing member 441 is replaced with the rack restraint jig 401 and the restraint jig 402 paired in the vertical direction, or in addition to the rack restraint jig 401 and the restraint jig 402, the restraint jigs paired in the horizontal direction. The pressing member 441 may be provided on the 403 and the restraining jig 404. Further, the pressing member 441 may be provided separately from the rack restraining jig 401 and the restraining jig 402, and may be driven by an independent pressurizing device.

As described above, the rack bar quenching device disclosed in the present specification is a rack bar quenching device in which a rack is formed in a part of the length of the hollow shaft member, and is heated. A plurality of restraint jigs for restraining the partial section from a plurality of radial directions over the entire length of the partial section are provided, and the plurality of restraint jigs are placed on a portion facing the restraint jig in the partial section. Each has an injection unit for injecting the coolant, and the injection unit uniformly injects the coolant into a plurality of annular regions that circulate around the outer periphery of the partial section at least through each tooth bottom of the rack. Inject.

Further, the quenching device disclosed in the present specification has an injection slit in which the injection portion extends in the length direction of the rack bar and is formed to have a length equal to or longer than a part of the section.

Further, the quenching device disclosed in the present specification has a plurality of injection ports in which the injection portions are arranged in the length direction of the rack bar at intervals equal to the tooth pitch of the rack.

Further, in the quenching device disclosed in the present specification, the plurality of restraining jigs include a rack restraining jig in contact with the rack, and the contact surface of the rack restraining jig with the rack is one. There are one or more recesses.

Further, in the quenching apparatus disclosed in the present specification, the recess is provided in the central portion in the length direction of the contact surface.

Further, the quenching apparatus disclosed in the present specification includes a pressurizing mechanism for pressing a portion of the shaft material adjacent to both sides or one side of the partial section in a direction perpendicular to the length direction. ..

Further, in the quenching device disclosed in the present specification, the pressurizing mechanism has one or more pressing members provided in at least one of the plurality of restraining jigs, and the above-mentioned The pressing member has a position adjusting portion that adjusts the position of the pressing member along the contact direction between the restraining jig provided with the pressing member and the partial section.

Further, in the method of quenching the rack bar disclosed in the present specification, at least the partial section of the rack bar in which the rack is formed in a partial section of the length of the hollow shaft member is heated and heated. The partial section is constrained from a plurality of radial directions over the entire length of the partial section, and the partial section is applied to a plurality of annular regions that orbit the outer periphery of the partial section at least through each tooth bottom of the rack. Coolant is uniformly sprayed from a plurality of restraining jigs.

Further, in the quenching method of the rack bar disclosed in the present specification, the portions adjacent to both sides or one side of the partial section restrained by the plurality of restraining jigs are arranged with respect to the length direction of the rack bar. Quench while pressing in the vertical direction.

1 Pinion 2 Bearing 3 Bearing 10 Rack bar 11 Shaft 12 Rack 13 Part 20 Mold 21 Upper mold 22 Lower mold 23 Rack tooth mold 24 Molding surface 25 Core metal 26 Push rod 27 Push rod 30 Rod 100 Hardening device 101 Rack restraint jig 102 Restraint jig 103 Restraint jig 104 Restraint jig 105 Jacket 111 Coolant supply chamber 112 Injection unit 113 Coolant supply chamber 114 Injection unit 115 Coolant inlet 116 Coolant inlet 116 Cooling plate 120 Tip surface 121 Coolant injection slit 130 Tip surface 131 Coolant injection slit 132 Concave groove 201 Rack restraint jig 212 Injection part 220 Tip surface 221 Coolant injection port 301 Rack restraint jig 312 Injection part 320 Tip surface 321 Coolant injection slit 322 Recession 400 Hardening device 401 Restraint jig 401 Rack restraint jig 402 Restraint jig 403 Restraint jig 404 Restraint jig 412 Injection part 414 Injection part 420 Tip surface 421 Cooling liquid injection slit 430 Tip surface 431 Cooling liquid injection slit 440 Pressurizing mechanism 441 Pressing member 442 Position adjusting part 443 Threaded part 444 Lock nut Ai Circular region B Pressed part D Distance between axes h Overpin size w Slit width

Claims (7)

A rack bar quenching device in which a rack is formed in a part of the length of the hollow shaft material.
A plurality of restraining jigs for restraining the heated partial section from a plurality of radial directions over the entire length of the partial section are provided.
The plurality of restraint jigs each have an injection unit for injecting a coolant to a portion facing the restraint jig in the partial section.
The injection unit uniformly injects the coolant onto a plurality of annular regions that circulate around the outer periphery of the partial section through at least each tooth bottom of the rack.
The plurality of restraint jigs include a rack restraint jig that comes into contact with the rack.
The contact surface of the rack restraining jig with the rack is provided with one or more recesses.
The recess is provided in the center of the contact surface in the longitudinal direction of the rack bar .
The rack restraining jig is in non-contact with the tooth tips of the teeth in the central portion of the rack in the recess, and the teeth in the central portion of the rack are among the rack restraining jig and the plurality of restraining jigs. A quenching device for quenching the rack bar without being pressurized in the vertical direction between the rack restraint jig and the restraint jig paired in the vertical direction . The quenching device according to claim 1.
The quenching device having an injection slit extending in the length direction of the rack bar and having a length equal to or longer than a part of the section. The quenching device according to claim 1.
The injection unit is a quenching device having a plurality of injection ports arranged in the length direction of the rack bar at intervals equal to the tooth pitch of the rack. The quenching apparatus according to any one of claims 1 to 3.
A quenching device provided with a pressurizing mechanism for pressing a portion of the shaft material adjacent to both sides or one side of the partial section in a direction perpendicular to the length direction. The quenching apparatus according to claim 4, wherein the quenching device is used.
The pressurizing mechanism has one or more pressing members provided on at least one of the plurality of restraining jigs.
The pressing member is a quenching device having a position adjusting portion for adjusting the position of the pressing member along the contact direction between the restraining jig provided with the pressing member and the partial section. At least a part of the rack bar in which the rack is formed in a part of the length of the hollow shaft member is heated.
The heated partial section is constrained from a plurality of radial directions over the entire length of the partial section.
Coolant is uniformly sprayed from a plurality of restraining jigs that constrain the partial section to a plurality of annular regions that circulate around the outer periphery of the partial section at least through each tooth bottom of the rack.
The plurality of restraint jigs include a rack restraint jig that comes into contact with the rack.
The contact surface of the rack restraining jig with the rack is provided with one or more recesses.
The recess is provided in the center of the contact surface in the longitudinal direction of the rack bar .
The rack restraining jig is in non-contact with the tooth tips of the teeth in the central portion of the rack in the recess, and the teeth in the central portion of the rack are among the rack restraining jig and the plurality of restraining jigs. A method for quenching a rack bar by quenching the rack bar in a state where the rack bar is not pressurized in the vertical direction between the rack restraint jig and the restraint jig paired in the vertical direction . The quenching method according to claim 6, wherein the quenching method is used.
A quenching method in which portions adjacent to both sides or one side of a partial section constrained by the plurality of restraining jigs are hardened while being pressed in a direction perpendicular to the length direction of the rack bar.

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