JP2511335Y2 - Induction hardening coil for steering rack shaft - Google Patents

Description

[Detailed Description of the Invention] Industrial field of application The present invention relates to an induction hardening coil used for hardening a rack tooth portion formed on a steering rack shaft of a 4WS (four-wheel steering mechanism). is there.

2. Description of the Related Art Induction hardening is one of the methods for hardening a steering rack shaft. This induction hardening method makes use of the fact that the steering rack shaft is a conductor, and causes a high frequency current to flow in the section where the rack teeth are formed, and forms a closed loop of the high frequency current together with the section where the rack teeth are formed. By disposing the conducting conductor close to the section, heat is generated by the electric resistance of the high-frequency current flowing in the section, and eddy current is generated in the section to perform induction heating, whereby efficient heating can be achieved. Furthermore, it is more suitable than other quenching methods in that it can uniformly heat and quench the predetermined area where the rack teeth are formed from the surface to a certain depth due to the skin effect due to the high frequency current. Many are used (eg
(See JP-A-57-158325).

Further, in the steering rack shaft 1 for 4WS as shown in FIGS. 6 and 7, two tooth flanks 2 and 3 are formed in a substantially V shape, and the two tooth flanks 2 adjacent to each other are formed. , 3 need to be quenched at the same time. Therefore, this quenching coil 5 that induction-heats the steering rack shaft 1
Has a base plate 6 serving as a base and an induction coil / water jacket 7 mounted on the base plate 6 and having a cavity serving as a quenching liquid supply path therein. The upper surface of the induction coil / water jacket 7 is A V-shaped concave portion 7a having an angle substantially equal to the angle formed by the two tooth flanks 2 and 3 of the steering rack shaft 1 is formed therein. Further, in the recess 7a of the induction coil / water jacket 7, a large number of ejection holes 7b for ejecting the quenching liquid introduced therein are formed.

Further, on one end side (left side in FIG. 8) of the induction coil / water jacket 7, an electrode 8 is placed on the substrate 6 via an insulating plate 9 and is not in contact with the induction coil / water jacket 7. An electrode 10 is provided on the other end side and is placed in a conductive state on the substrate 6, and the section where the rack teeth 2a and 3a of the steering rack shaft 1 are formed is between the electrodes 8 and 10. Will be handed over to.

When the steering rack shaft 1 is hardened, the high frequency current passes from the end (the left end in FIG. 8) on the side where the electrode 8 of the substrate 6 is insulated and passes through the induction coil / water jacket 7 to reach the end. Of the steering rack shaft 1 through the electrode 10 of the steering rack shaft 1 to the electrode 8 on the opposite side.
The section where a is formed is indirectly heated by induction (see FIG. 9) by the eddy current generated by the high-frequency current flowing through the induction coil / water jacket 7 and flows through this section of the steering rack shaft 1. The electric resistance of the high frequency current directly induces the induction heating to efficiently heat.

Then, when a predetermined quenching depth is obtained, quenching liquid such as water is jetted from the jet holes 7b of the induction coil / water jacket 7 toward both tooth surfaces 2 and 3, and quenching is performed.

However, in the case of the conventional induction hardening coil of the steering rack shaft 1 described above, the two tooth surfaces 2 and 3 on which the rack teeth 2a and 3a are formed are close to each other in the center. There is a problem in that the portion 4 is overheated and is likely to cause quality defects such as quench cracking and quenching depth becoming too deep.

This is because the central portion 4 is a V-shaped pointed portion, so the heat capacity is small, and as a result of being heated from both sides by both induction coils 2 and 3, the V-shaped outer ends having a large heat capacity are located ahead of both ends. This is because the temperature rises and becomes overheated.

Then, when the surface hardness and the quenching depth of the work when such quenching is performed are examined, the results are as shown in FIGS. 10 and 11. That is, the surface hardness, as shown in FIG. 10, near the fully heated central portion is within the standard Vickers hardness Hv: 600 ~ 800,
At the outer edge, the Hv is below the standard, about 200 to 300, which is below the standard.

The quenching depth is 0.5 mm to 1.5 mm in standard and the hardness is Hv: 450 or more, but in the surface hardness, as shown in FIG. 11, the central portion 4 (the portion C in FIG. 11). However, there is a problem in that the hardened portion becomes too deep, the hardened portion becomes brittle, and the rack teeth are easily chipped.

Furthermore, the outer edges of the two tooth flanks 2, 3 (A in FIG. 11)
However, there was a problem that the quenching depth was insufficient and the surface hardness was below the standard.

Therefore, the present applicants have proposed that the V of the steering rack shaft 1 is
An induction hardening coil capable of preventing overheating of the central portion 4 of the tooth-shaped tooth flanks 2 and 3 has already been proposed (Japanese Patent Application No. 1-88947).

This is because a magnetic flux blocking member is provided between the inner edges of a pair of induction hardening coils that are arranged to face each other in a substantially V shape, and the cross-sectional shape of the current-carrying tip that serves as a path for the high-frequency current of both induction hardening coils is It is formed so that the inner edge side is thinner than the outer edge, reducing the magnetic flux generated on the inner edge side of the induction hardening coil and at the same time overheating the inner edge part that is induction-heated by the magnetic flux blocking member. It is designed to prevent it.

This invention reduces the magnetic flux on the inner edge side of the induction hardening coil provided in a substantially V-shape similar to the above-mentioned technique. As a means for this, a pair of induction coils in which the high-frequency current flows in the same direction is used. It is an object of the present invention to provide an induction hardening coil capable of preventing overheating due to induction heating by providing an induction coil in which a high-frequency current flows in the opposite direction, by canceling out magnetic lines of force acting on a portion that easily overheats. I am trying.

Means for Solving the Problems As a means for solving the above problems, the present invention has rack teeth formed on two surfaces of a substantially V-shaped cross section of a steering rack shaft by means of an eddy current generated in an induction coil. In an induction hardening coil for induction heating and quenching, the induction coil includes side coil portions facing the rack teeth and central coil portions facing the central portions of the rack teeth. It is characterized in that the direction of the high-frequency current flowing through the coil is opposite to that of the central part and the central coil part.

The induction hardening coil of the steering rack shaft according to the present invention has a pair of side coil portions facing the rack teeth on the two sides, and a space between the side coil portions on both sides of the pair of side coil portions so as to face the center portion of both rack teeth. It is divided into a central coil provided, and these three coil portions are connected, for example, in an S shape. When a high-frequency current is passed from one end of the S-shape to the other end, the direction in which the side coil portions on both sides flow is opposite to the direction in which the central coil portion flows. Therefore, when the induction hardening coil is used to quench the sections of the rack teeth formed on the two surfaces of the V-shaped cross section of the steering rack shaft, the central portion of the V-shape is
Since a part of the magnetic field generated from each of the side coil portions on both sides interferes with the magnetic field generated from the central coil portion and cancels each other, overheating of the central portion formed in the V shape can be prevented.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

The induction hardening coil 11 for steering rack shaft is
An induction coil 13 also serving as a water cooling jacket and electrodes 14 and 15 fixed to the base 12 via an insulating plate 12a are provided.

Further, the steering rack shaft 1 which is hardened by the induction hardening coil 11 is provided with two surfaces 2 and 3 having a substantially V shape at a certain portion on one end side thereof, and rack teeth 2a and 3a are formed on the two surfaces, respectively. Then, the section in which these rack teeth 2a and 3a are formed is heated by the induction hardening coil 11 to quench it.

Then, the induction portion coil 13 of the induction hardening coil 11 is
Is a first induction coil 13a, a second induction coil 13b, and a third induction coil 13a.
It is composed of three parts of the induction coil 13c, and a second induction coil 13b having a low height is provided substantially in the center of the base 12 in the width direction, and both sides of the first induction coil 13b are provided with an inner inclined surface. The coil 13a and the third induction coil 13c are spaced apart from each other and arranged in parallel with each other.
Steering rack shaft 1 for quenching between 13c
A V-shaped space having substantially the same angle as the V-shape in the section where the rack teeth 2a and 3a are formed is formed. Also, the first
Each of the induction coil 13a and the third induction coil 13c also serves as a water cooling jacket, and a passage for introducing cooling water for quenching is provided inside thereof, and the steering rack shaft 1 is heated on the inner inclined surface thereof. A large number of ejection holes 16 for ejecting the cooling water toward the portion are formed.

On the other hand, electrodes 14 and 15 are provided at both ends of the induction coil 13 so that one side of the L-shaped section is fixed on the insulating plate 12a and are separated from the ends of the induction coil 13. V-shaped recesses 14a and 15a are provided at the upper ends of the electrodes 14 and 15 for supporting the steering rack shaft 1 for quenching at substantially the center.

Then, the first to third three induction coils of the induction coil unit 13
13a, 13b, 13c are connected to each other by connecting tools 17, 17 at their ends to connect them to each other in an S-shape, and high-frequency waves are directed from one end of the S-shape to the other end. When an electric current is passed, the first induction coil 13a and the third induction coil 13c on both sides
And the direction of flow in the central second induction coil 13b are opposite. A first induction coil that is one end of the induction coil 13 that is continuously connected in an S shape.
The end of 13a is electrically connected to the base 12 connected to the output side wiring of the high frequency transformer (not shown) by the connecting tool 18, and is also connected to the other end of the S-shaped induction coil 13 Become the third
The end portion of the induction coil 13c is connected to one side (first
It is electrically connected to the electrode 15 on the right side in the figure.

Therefore, as shown by the arrow in FIG. 1, the high-frequency current first flows from the base 12 through the first induction coil 13a, the second induction coil 13b, and the third induction coil 13c to the electrode 15, and both electrodes 1
It flows to the electrode 14 via the steering rack shaft 1 that is bridged between the five and fourteen.

Although not shown, the first and third induction coils 13a, 13
A cooling water supply pipe for quenching is connected to a passage formed inside each of c through a valve.

Next, the induction hardening coil 11 configured as described above.
The operation of quenching the steering rack shaft 1 will be described with reference to FIG.

First, the steering rack shaft 1 is attached to its rack teeth 2a, 3
The induction hardening coil is formed so that the two V-shaped surfaces 2 and 3 on which a is formed face the inclined surfaces of the first induction coil 13a and the third induction coil 13c on both sides of the induction hardening coil 11, respectively. When the high-frequency current is passed between the base 1 and the electrode 14 after supporting both outer portions of the quenching section between the 11 electrodes 14 and 15 and energizing them, the induction coil A magnetic field is generated around each of the first to third induction coils 13a, 13b, and 13c by the high-frequency current flowing through 13, and the quenching section of the steering rack shaft 1 arranged in proximity is induction-heated (see FIG. 3). ). At this time, since the directions of the currents flowing between the first induction coil 13a and the third induction coil 13c on both sides and the second induction coil 13b in the center are opposite, the polarities of the magnetic fields generated are also opposite.

Therefore, of the magnetic fields generated in the first induction coil 13a and the third induction coil 13c arranged on both sides,
In the vicinity of the center near the second induction coil 13b provided between the coils 13a and 13c, the magnetic fields of opposite polarities generated by the second induction coil 13b interfere with each other and cancel each other out. As a result, the V of the heated steering rack shaft 1 is increased.
The effect of induction heating on the inner end edges (central portion 4) of the character-shaped two surfaces 2 and 3 is suppressed, and overheating of the central portion 4 is prevented, and the entire section where the rack teeth 2a and 3a are formed. Are heated almost evenly.

Then, when the section of the steering rack shaft 1 where the rack teeth 2a, 3a are formed is heated to a predetermined depth, the valve of the cooling water supply pipe is opened to serve also as the cooling jacket. Cooling water is introduced into the respective passages inside the induction coil 13a and the third induction coil 13c, and is sprayed onto the surface of the steering rack shaft 1 which is jetted from the jetting light 16 and heated to perform quenching.

Next, with respect to the rack teeth 2a and 3a of the steering rack shaft 1 that has been quenched as described above, a quality inspection is performed on the surface hardness, the hardening depth, and the presence or absence of hardening cracks, and the results are shown in FIG. This is shown in FIG. 5 and will be described based on this.

As a result, no quench cracks occur, and the surface hardness of the quenched portion is, as shown in FIG. 4, Vickers hardness Hv in all portions where the rack teeth 2a, 3a are formed. : Approximately 800, which is within the Hv: 600-800 standard. Regarding the quenching depth, as shown in Fig. 5, the surface hardness is Hv: 450 or more in most parts and the quenching depth is within the range of 0.5 to 1.5 mm, or It is a close value.

Thus, by using the induction hardening coil 11 of the present embodiment, it is possible to prevent the occurrence of quench cracks due to partial overheating,
The surface hardness and the quenching depth of the quenched portion are appropriate, and ideal induction hardening of the steering rack shaft can be performed.

As described above, in the induction hardening coil of the steering rack shaft according to the present invention, the induction coil has a pair of side coil portions respectively facing rack teeth formed on two V-shaped faces, It is composed of the central portion of both rack teeth and the central coil portion facing each other.The side coil portion on both sides and the central coil portion make the direction of the high-frequency current flowing through the coil to be the opposite direction, and to surround the side coil on both sides. The polarity of the magnetic field generated,
Since the polarity of the magnetic field generated around the central coil is set to be opposite, the magnetic fields interfere and cancel each other out at the central portions of the rack teeth, resulting in the action of the magnetic field on the central portions of the rack teeth. It is suppressed, and it is possible to prevent overheating of this portion and prevent occurrence of quality defects such as quench cracking due to overheating and excessive quenching depth.

[Brief description of drawings]

1 to 5 show an embodiment of the present invention. FIG. 1 is an explanatory view showing a current flow in an induction hardening coil, FIG. 2 is a plan view of the induction hardening coil, and FIG. Fig. 2 is a sectional view taken along the line III-III, Fig. 4 is a diagram showing the surface hardness of the quenched portion, Fig. 5 is a diagram showing the quenching depth, and Fig. 6 is a main part of the steering rack shaft. FIG. 7 is a side view, FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 6, FIGS. 8 to 11 show a conventional example, and FIG. 8 is an explanatory view showing a current flow in a conventional induction hardening coil. 9 is a sectional view taken along the line IX-IX in FIG. 8, FIG. 10 is a diagram showing the surface hardness of a portion quenched by a conventional coil, and FIG. 11 is a diagram showing the quenching depth. . 1 ... Steering rack shaft, 2a, 3a ... Rack teeth, 4
…… Center part, 11 …… Induction hardening coil, 12 …… Base, 12a …… Insulating plate, 13 …… Induction part coil, 13a …… First
Induction coil, 13b …… Second induction coil, 13c …… Third induction coil, 14,15 …… Electrode, 16 …… Spout hole, 17,18,19 ……
Connection.

Claims (1)

(57) [Scope of utility model registration request] 1. An induction hardening coil in which rack teeth formed on two surfaces of a substantially V-shaped cross section of a steering rack shaft are induction-heated and hardened by an eddy current generated in an induction coil. A side coil portion facing each of the rack teeth, and a central coil portion facing the central portion of the rack teeth, and the direction of the high-frequency current flowing through the coil in the side coil portion and the central coil portion. The induction hardening coil for the steering rack shaft is characterized in that