JP2007239876A - Sliding type constant velocity universal joint and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sliding type constant velocity universal joint capable of reducing vibration of a vehicle, by reducing sliding resistance at operation initial time, by improving initial conformability, by restraining generation of a scale after high frequency heat treatment. <P>SOLUTION: This sliding type constant velocity universal joint has an outside joint member of forming a guide groove 2 on a cylindrical inner peripheral surface 1, an inside joint member of forming a guide groove 5 on a spherical surface-shaped outer peripheral surface 4, a torque transmission ball 7 interposing between the guide groove 2 of the outside joint member and the guide groove 5 of the inside joint member, and a holder for holding the torque transmission ball. A hardened layer 11 is formed by forming a carburized quenched layer by induction hardening in oil, in a surface hardened layer of a sliding part without performing finishing processing after the induction hardening of at least any one of the outside joint member and the inside joint member. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sliding type constant velocity universal joint and a method for manufacturing the same.

  Sliding type constant velocity universal joints transmit rotational power by allowing axial displacement and angular displacement between the drive and driven shafts, and are incorporated in the power transmission mechanisms of automobiles and various industrial machines. Have been used.

  As the sliding type constant velocity universal joint, for example, a double offset type constant velocity universal joint and a tripod type constant velocity universal joint are known. Among them, a tripod type constant velocity universal joint uses a roller as a torque transmission member, and other constant velocity universal joints use a ball as a torque transmission member.

  The double offset type constant velocity universal joint has an outer ring in which a plurality of linear guide grooves are formed in an axial direction on a cylindrical inner peripheral surface, and a plurality of linear guide grooves in a spherical outer peripheral surface in the axial direction. The inner ring formed on the outer ring, the torque transmission ball interposed between the guide groove of the outer ring and the guide groove of the inner ring, and the holding which holds the torque transmission ball interposed between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring. With a bowl. Since the center of the spherical outer peripheral surface and the center of the spherical inner peripheral surface of the cage are offset from the joint center to the opposite side in the axial direction, they are called double offset types. When this type of joint transmits rotational torque while taking an operating angle, the cage rotates to the position of the torque transmitting ball that moves on the guide groove according to the inclination of the inner ring, and the torque transmitting ball is rotated to the angle of the operating angle. Hold in bisector. Furthermore, when the outer ring and the inner ring move relative to each other in the axial direction, slippage occurs between the outer peripheral surface of the cage and the inner peripheral surface of the outer ring, thereby enabling smooth axial movement (plunging) and driving shaft. Absorbs axial displacement between the shaft and the driven shaft.

  Conventionally, there is one in which a vibration absorbing member having greater elasticity than the inner ring is disposed on the outer peripheral surface of the inner ring (Patent Document 1). In other words, when the inner ring interferes with the cage due to axial displacement, the one described in Patent Document 1 is such that the vibration absorbing member disposed on the inner ring comes into contact with the inner peripheral surface of the cage, thereby causing a collision force between the two. This is intended to reduce vibrations by this relaxation.

  However, in the sliding type constant velocity universal joint, when the outer ring and the inner ring are relatively moved in the axial direction, slip occurs between the outer peripheral surface of the cage and the inner peripheral surface of the outer ring. For this reason, a sliding resistance (sliding resistance) is generated by the frictional resistance of the sliding part. And when this slide resistance increases, there exists a problem which worsens NVH of a vehicle. For this reason, it is desired to reduce this slide resistance as much as possible.

  Further, the sliding surface of the outer ring is subjected to heat treatment in order to improve the strength. As the heat treatment, induction hardening is performed. A scale is generated by oxidation on the induction-quenched surface. When scale is generated in this way, the surface properties are extremely deteriorated and the conformability of the surface is deteriorated. In addition, the scale bites or gets mixed into the grease, increasing the coefficient of friction. This increased the slide resistance.

  For this reason, conventionally, various methods for removing scales generated by induction hardening have been proposed (Patent Documents 2 to 4). Patent Document 2 describes performing buffing to remove scale after induction hardening, Patent Document 3 describes performing electropolishing after induction hardening, and Patent Document 4 describes high-frequency hardening. The thing which raises the pressure of the cooling water at the time of quenching and removes a scale is described. In Patent Documents 1 to 4, not a constant velocity universal joint but a ball screw or the like.

JP-A-9-88996 JP 2003-119518 A JP 2003-25152 A JP 2002-129231 A

  As described in Patent Document 2, when a scale generated after induction hardening is processed by buffing, it may not be completely removed, and there is a problem that processing time is long. In addition, as described in Patent Document 3, when the scale is removed by electropolishing, it is possible to completely remove the scale, but the processing time is greatly increased, the surface becomes rough, and due to the heat of chemical reaction. There are problems such as softening of the surface. Furthermore, as described in Patent Document 4, the cooling water pressure at the time of induction hardening cannot be removed uniformly, and a black scale remains minutely in the form of spots, requiring a separate descaling process. .

  By the way, as for the material of the conventional outer ring, in consideration of the hardness after induction hardening, carbon steel or low alloy steel equivalent to 0.55C is adopted, but the cold forgeability is lowered as compared with a carburized material or the like. . Accordingly, if a hard material is processed in a cold state, a large amount of strain remains after the processing, and if the hardness is increased even in the subsequent turning, a large amount of strain remains on the surface. If a large amount of strain remains before the heat treatment, the strain is released by the heat treatment and a large dimensional change occurs. Therefore, it is preferable to use a material having low hardness (carbon content). However, a material having a low carbon content also has a problem that sufficient hardness cannot be obtained after quenching.

  In view of the above problems, the present invention suppresses the generation of scale after high-frequency heat treatment, improves initial conformability, reduces slide resistance at the initial stage of driving, and can reduce vehicle vibration. Provide type constant velocity universal joint.

  The sliding type constant velocity universal joint of the present invention includes an outer joint member in which a plurality of linear guide grooves are formed in an axial direction on a cylindrical inner peripheral surface, and a plurality of linear guide grooves on a spherical outer peripheral surface. An inner joint member formed in the axial direction, a torque transmission ball interposed between the guide groove of the outer joint member and the guide groove of the inner joint member, and a cage for holding the torque transmission ball, In a sliding type constant velocity universal joint in which sliding occurs between the outer peripheral surface of the cage and the inner peripheral surface of the outer joint member when the outer joint member and the inner joint member move relative to each other in the axial direction. A carburized and quenched layer is formed on the surface hardened layer of the sliding portion where the finishing process after the induction heat treatment of at least one of the joint members is not performed.

  In the sliding type constant velocity universal joint of the present invention, the carburized and hardened layer of the surface hardened layer has a carbon concentration higher than that of the base material (a part other than the hardened layer). This is because carbon diffused (carburized) from the oil in the induction hardening atmosphere to the surface of the sliding portion. Oxidation reaction is suppressed by this carburization and generation of scale is suppressed.

  In addition, this carburization causes the hardened layer to have a higher surface hardness than usual induction hardening. This hardness is due to an increase in the carbon content, increasing the softening resistance in a high-temperature atmosphere, maintaining the initial hardness, improving the wear resistance and peeling resistance, and the life (rolling life). To increase.

  Residual austenite is generated on the surface of the surface hardened layer. Thereby, the life is further improved by the improvement of the conformability and the relaxation hardening of the surface pressure.

  The manufacturing method of the sliding type constant velocity universal joint of the present invention includes an outer joint member in which a plurality of linear guide grooves are formed in an axial direction on a cylindrical inner peripheral surface, and a plurality of linear shapes on a spherical outer peripheral surface. An inner joint member formed in the axial direction, a torque transmission ball interposed between the guide groove of the outer joint member and the guide groove of the inner joint member, and a cage for holding the torque transmission ball; In the manufacturing method of the sliding type constant velocity universal joint that slips between the outer peripheral surface of the cage and the inner peripheral surface of the outer joint member when the outer joint member and the inner joint member relatively move in the axial direction. In addition, induction hardening is performed in oil on at least one of the sliding portions of the outer joint member and the inner joint member to form an induction carburized and hardened layer.

  In the manufacturing method of the sliding type constant velocity universal joint of the present invention, the hardened layer formed by induction hardening in oil diffuses (carburizes) the carbon of the oil from the base material (part other than the hardened layer). Carbon concentration increases. For this reason, in the hardened layer, the oxidation reaction is suppressed and the generation of scale is suppressed.

  Moreover, the hardened layer becomes higher than the normal induction-hardened surface hardness due to the increase in the carbon amount due to the carburization. For this reason, the softening resistance in a high-temperature atmosphere is increased, the initial hardness is maintained even after a long period of use, the wear resistance and peel resistance are improved, and the life (rolling life) is increased.

In the present invention, generation of scale is suppressed, slide resistance can be reduced, and vehicle vibration can be reduced. Moreover, by induction hardening in oil, it is carburized from the surface and becomes high hardness, and the seizure resistance is improved. Furthermore, even if the material is low carbon steel, the required surface hardness can be obtained. For this reason, the carbon of the material can be reduced, the deformability is improved, and the mold life is improved (extended). Further, since retained austenite is generated by short-time treatment of induction hardening, the initial conformability is improved, and the slide resistance at the initial operation can be stably reduced.

  An embodiment of a sliding type constant velocity universal joint according to the present invention will be described with reference to FIGS. As the sliding type constant velocity universal joint according to this embodiment, a double offset type constant velocity universal joint is shown.

  The constant velocity universal joint includes an outer ring 3 as an outer joint member in which a plurality of (for example, eight) linear guide grooves 2 are formed in an axial direction on a cylindrical inner peripheral surface 1, and a spherical outer peripheral surface 4. Further, an inner ring 6 as an inner joint member in which the same number of linear guide grooves 5 as the guide grooves 2 of the outer ring 3 are formed in the axial direction is interposed between the guide groove 2 of the outer ring 3 and the guide groove 5 of the inner ring 6. A torque transmission ball 7 for holding the torque transmission ball 7 and a cage 8 for holding the torque transmission ball 7. A serration (or spline) 9 for connecting a shaft (not shown) to the inner peripheral surface of the inner ring 6 is formed.

  The cage 8 is a ring body including a plurality of (in this case, eight) pockets 10 for accommodating the torque transmission balls 7, and the spherical outer peripheral surface 8 a is contacted and guided to the inner peripheral surface 1 of the outer ring 3. The spherical inner peripheral surface 8 b is contact-guided with the outer peripheral surface 4 of the inner ring 6. The spherical center O1 of the outer peripheral surface 8a and the spherical center O2 of the inner peripheral surface 8b are offset to the opposite side by an equal distance in the axial direction with respect to the center O of the pocket 10, respectively.

  In the constant velocity universal joint configured as described above, the side of the outer ring 3 and the inner ring 6 connected to the drive shaft (for example, the outer ring 3) rotates with the rotation of the drive shaft, and the driven side via the torque transmission ball 7 ( For example, rotational torque is transmitted to the inner ring 6). Further, when an operating angle is given between the outer ring 3 and the inner ring 6, the torque transmission ball 7 guided by the cage 8 is always maintained in the bisection plane of the operating angle at any operating angle, The constant velocity of the joint is ensured. Furthermore, when the outer ring 3 and the inner ring 2 move relative to each other in the axial direction, slippage occurs between the outer peripheral surface 8a of the cage 8 and the inner peripheral surface 1 of the outer ring 3, thereby enabling smooth axial movement. Absorbs axial displacement between the drive shaft and the driven shaft.

  In this constant velocity universal joint, the inner peripheral surface 1 of the outer ring 3 is a hardened layer 11. This hardened layer 11 is formed by induction hardening in oil. For example, it is formed by induction hardening with the outer ring 3 immersed in oil. Here, induction hardening means that an induction current is generated in the surface portion of the derivative (workpiece) by passing a high-frequency current through the quenching coil to generate heat, and this heat rapidly heats the surface of the workpiece. And quenching. In this case, the high-frequency heating temperature is preferably 900 ° C. or higher and 1350 ° C. or lower. In this embodiment, the hardened layer 11 includes a sliding portion with the outer peripheral surface 8a of the cage 8 and an inner surface of the guide groove 2 on which the ball 7 rolls.

  As a result of induction hardening in oil, the carburized and hardened layer of the surface hardened layer 11 has a carbon concentration higher than that of the base material (a part other than the hardened layer). This is because carbon diffused (carburized) from the ambient oil to the surface of the sliding part. Oxidation reaction is suppressed by this carburization and generation of scale is suppressed.

  Further, the hardness of the hardened layer 11 is as shown in FIG. 2 and is higher than the surface hardness subjected to normal induction hardening. This is because the carburizing treatment was performed as described above, and this hardness is due to an increase in the amount of carbon as shown in FIG. For this reason, the softening resistance in a high temperature atmosphere increases, the initial hardness is maintained, the wear resistance and the peel resistance are improved, and the life (rolling life) is increased.

  In addition, as shown in FIG. 3, residual austenite (γ) is formed on the surface portion of the hardened layer 11 (the carburized layer in FIG. 3). Here, retained austenite means that when a steel is quenched and the martensitic transformation end temperature (Mf point) of the steel is below room temperature, the austenite that has not yet undergone transformation remains as it is after quenching. This is what remains. This retained austenite improves toughness and rolling fatigue strength. For this reason, the lifetime of the hardened layer 11 is further improved by improving the conformability and reducing and hardening the surface pressure.

As described above, in the present invention, scale generation is suppressed, slide resistance can be reduced, and vehicle vibration can be reduced. Moreover, by induction hardening in oil, it is carburized from the surface and becomes high hardness, and the seizure resistance is improved. Furthermore, even if the material is low carbon steel, the required surface hardness can be obtained. For this reason, the carbon of the material can be reduced, the deformability is improved, and the mold life is improved (extended). Further, since retained austenite is generated by short-time treatment of induction hardening, initial conformability is improved, and slide resistance at the initial operation can be stably reduced.
In particular, by setting the high-frequency heating temperature to 900 ° C. or more and 1350 ° C. or less, the oxidation reaction due to carburization can be stably suppressed, and the generation of scale can be reliably suppressed. In addition, if the temperature of the high frequency heating is less than 900 ° C., sufficient hardness cannot be obtained, the oxidation reaction is promoted, the generation of scale increases, the carburization amount decreases, and the temperature of the high frequency heating exceeds 1350 ° C. Although the number of layers increases, the crystal grains become coarse and become brittle.

  By the way, in the said embodiment, although the hardened layer 11 was formed in the inner peripheral surface 1 of the outer ring | wheel 3, in the sliding site | part of the outer peripheral surface 8a of the holder | retainer 8 which slides with respect to the inner peripheral surface 1 of the outer ring | wheel 3. The hardened layer 11 may be formed. Thus, if the hardened layer 11 is formed on the inner peripheral surface 1 of the outer ring 3 and the outer peripheral surface 8a of the cage 8, the generation of scale on the inner peripheral surface 1 of the outer ring 3 and the outer peripheral surface 8a of the cage 8 is suppressed. In addition, the dimensional accuracy is stabilized, and the durability life is remarkably improved by increasing the hardness. Alternatively, the hardened layer 11 may be formed only on the sliding portion of the cage 8 without forming the hardened layer 11 on the sliding portion of the outer ring 3. Further, the hardened layer 11 may be formed on the outer peripheral surface 4 of the inner ring 6 that is an inner joint member, particularly on the inner surface of the guide groove 6.

  With respect to the outer ring of the sliding type constant velocity universal joint having the structure shown in FIG. 1, a conventional product that has been subjected to conventional normal induction hardening and an invention product that has been induction-quenched in oil are manufactured. The results are shown in Table 1 below. Conventional products used medium carbon steel with a carbon content of 0.53 wt%, and invention products used medium carbon steel with a carbon content of 0.46 wt%. The conventional product and the invention product were subjected to cutting after cold forging and outer diameter grinding. In addition, the conventional product was induction-quenched in the atmosphere, and water-cooled after the quenching. On the other hand, in the invention, cooling was started and quenched at the same time as the heating power was turned off after high-frequency heating in the atmosphere of quenching oil.

  A slide resistance test was performed for 5 seconds with a vibration speed of 600 r / min, a surface pressure of 0.9 GPa, an operating angle of 8 degrees, a frequency of 1 kHz, and an amplitude of 0.1 mm. In Table 1, the Δ of the conventional product of the mold life indicates a short life, and the ◎ of the invention product indicates a long life.

  As can be seen from Table 1, the generation of the scale of the inventive product was minimal, and the color was the same as that of the base material of the generated scale. On the other hand, the generation of the scale of the conventional product was large, and the generated scale was black. In terms of surface hardness, the conventional product is almost the same as the invention product at a depth of 0.1 mm, whereas the conventional product is Hv700 at a depth of 0.05 mm. The invention is Hv785. This is because the retained austenite layer was formed in the range of 5 μm from the surface in the invention. Further, the thrust resistance (induced thrust resistance) was large in the conventional product and small in the invention product.

  Thus, it can be seen that in the invention product, the generation of scale is suppressed and the durable life is increased. In addition, because the material is carburized from the surface by induction quenching in oil, the required surface hardness can be obtained even if the material is low carbon steel. Is also possible.

It is principal part sectional drawing of the sliding type constant velocity universal joint which shows embodiment of this invention. It is a graph which shows the hardness of the hardened layer of the said sliding type constant velocity universal joint. It is a simplified diagram showing the range of the carburized layer of the sliding type constant velocity universal joint. It is a graph which shows the carbon content of the hardened layer of the said sliding type constant velocity universal joint.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner peripheral surface 2 Guide groove 4 Outer peripheral surface 5 Guide groove 7 Torque transmission ball 8 Cage 8a Outer peripheral surface 11 Hardened layer

Claims (3)

An outer joint member in which a plurality of linear guide grooves are formed in an axial direction on a cylindrical inner peripheral surface; an inner joint member in which a plurality of linear guide grooves are formed in an axial direction on a spherical outer peripheral surface; A torque transmission ball interposed between the guide groove of the outer joint member and the guide groove of the inner joint member; and a cage for holding the torque transmission ball, wherein the outer joint member and the inner joint member are arranged in the axial direction. In the sliding type constant velocity universal joint that slips between the outer peripheral surface of the cage and the inner peripheral surface of the outer joint member when the relative movement is performed,
A sliding type constant velocity universal joint, characterized in that a carburized and quenched layer is formed on a surface hardened layer of a sliding portion where a finishing process after high frequency heat treatment of at least one of an outer joint member and an inner joint member is not performed.   2. The sliding constant velocity universal joint according to claim 1, wherein retained austenite is generated in the surface hardened layer. An outer joint member in which a plurality of linear guide grooves are formed in an axial direction on a cylindrical inner peripheral surface; an inner joint member in which a plurality of linear guide grooves are formed in an axial direction on a spherical outer peripheral surface; A torque transmission ball interposed between the guide groove of the outer joint member and the guide groove of the inner joint member; and a cage for holding the torque transmission ball, wherein the outer joint member and the inner joint member are arranged in the axial direction. In the manufacturing method of the sliding type constant velocity universal joint in which sliding occurs between the outer peripheral surface of the cage and the inner peripheral surface of the outer joint member when relatively moved.
A method for manufacturing a sliding type constant velocity universal joint, characterized in that at least one of an outer joint member and an inner joint member is subjected to induction hardening in oil to form a carburized and quenched layer.

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