JP4712304B2 - Fixed constant velocity universal joint - Google Patents

Description

  The present invention relates to a fixed type constant velocity universal joint, and can be used for a power transmission system in a drive shaft, a propeller shaft, other automobiles, and various industrial machines, in addition to various steering devices including an electric power steering.

  In general, a plurality of cardan joints (cross shaft joints) have been used in automobile steering devices. Cardan joints are inconstant universal joints whose rotational fluctuation increases between the input shaft and output shaft when the operating angle increases, and it is necessary to ensure constant speed by combining multiple cardan joints. There is a problem that the degree of freedom is impaired.

  Therefore, if a fixed type constant velocity universal joint is used as the shaft coupling for the steering device, it is possible to ensure constant velocity at an arbitrary operating angle, and there is an advantage that the degree of freedom in designing the vehicle is increased. The fixed type constant velocity universal joint is composed of an outer ring having a plurality of curved track grooves on the spherical inner surface, an inner ring having a plurality of curved track grooves on the spherical outer surface, and a torque incorporated between the track grooves of the outer ring and the inner ring. It consists of a transmission ball and a cage that holds the torque transmission ball.

  The center of curvature of the outer ring track groove (outer ring track center) is with respect to the spherical center of the spherical inner surface of the outer ring, and the center of curvature of the track groove of the inner ring (inner ring track center) is with respect to the spherical center of the spherical outer surface of the inner ring. Each is offset to the opposite side by an equal distance in the axial direction, so that the ball track composed of the outer ring track groove and the inner ring track groove has a wedge shape that expands toward the opening side of the outer ring. .

  By the way, in this type of fixed type constant velocity universal joint, there is a gap between the outer ring track groove and the inner ring track groove due to functional and processing requirements. When either the inner ring or the outer ring is fixed in the neutral state and the other is moved, it appears as an axial clearance, radial clearance, or circumferential clearance depending on the direction.

  The track clearance greatly affects the circumferential play (rotational backlash) between the inner ring and the outer ring. With fixed constant velocity universal joints, track clearance is indispensable from the viewpoint of machining tolerances and assemblability, and as a result, rotational backlash is large, which may cause a deterioration in steering operation feeling in the vicinity of the vehicle and noise. Concerned.

In order to solve this problem, Japanese Patent Application Laid-Open No. 2003-130082 proposes a fixed type constant velocity universal joint that can eliminate or suppress the rotation backlash by reducing the track clearance by preloading means provided inside the joint. ing.
Japanese Patent Laid-Open No. 2003-130082

The fixed constant velocity universal joint for steering described in Japanese Patent Application Laid-Open No. 2003-130082 eliminates the track clearance that causes play in the rotational direction by providing a preload means inside the constant velocity universal joint, and the steering The operability deterioration and abnormal noise generation are improved. However, referring to FIG. 2, when no torque is applied in the rotational direction of the shaft, the inner ring 2 and the cage 4 are pushed out to the opening side of the outer ring 1 (outer ring track center O ₁ side) due to its structure. . The cage 4 is displaced in the axial direction to a position where the inner spherical surface 1b of the outer ring 1 and the outer spherical surface 4b of the cage 4 come into contact with each other, and the inner ring 2 is displaced in the axial direction until the track clearance is eliminated. At this time, if the axial clearance between the inner ring 2 and the cage 4 is not larger than the amount by which the inner ring 2 is displaced in the axial direction due to the track clearance, backlash cannot be achieved. On the other hand, when a large torque in the rotation direction of the shaft 5 is loaded, like a normal BJ, and the outer ring in the spherical 1b and the cage outer spherical surface 4b of the opening side of the outer ring 1 (outer track center O ₁ side) This The inner ring 2 is displaced in the axial direction to the position where the cage inner spherical surface 4c and the inner ring outer spherical surface 2b on the inner side of the outer ring come into contact with each other. As described above, the positional relationship between the components is stabilized during the rotational operation regardless of the presence or absence of the torque load. Therefore, even if the operating angle θdeg is taken, the torque transmission ball 3 controls the cage 4 to the position of θdeg / 2. Stable rotational operability can be obtained.

On the other hand, as shown in FIG. 18, the cross operation in the no-load state (the shaft 5 is bent in the operating angle direction with the outer ring 1 fixed) differs from the rotation operation in that the shaft 5 is bent by θdeg. The torque transmission ball 3 cannot stably control the cage 4 to the position of θdeg / 2, and as a result, the inner ring 2 is pushed into the inner side of the outer ring 1 (inner ring track center O ₂ side). As a result, as shown in FIG. 20, the outer spherical surface 2b of the inner ring 2 and the inner spherical surface 4c of the cage 4 interfere with each other and appear as a hook when the cross is actuated. In the case of a fixed type constant velocity universal joint for a steering device, tilt-up and tilt-down operations in tilt steering cannot be performed smoothly, and in some cases, the operation may become impossible.

  The main object of the present invention is to improve the cross operation of the fixed type constant velocity universal joint.

Fixed type constant velocity universal joint of the present invention, an outer ring 1 having a spherical surface 1b among which a plurality of track grooves formed 1a, an inner ring 2 having an outer spherical surface 2b forming a plurality of track grooves 2a, track grooves of the outer ring 1 1a and a track groove 2a of the inner ring 2, a wedge-shaped ball track that is reduced from one to the other in the axial direction of the joint, a torque transmission ball 3 incorporated in each ball track, and a torque A cage 4 having a pocket 4a for holding the transmission ball 3 and interposed between the inner spherical surface 1b of the outer ring 1 and the outer spherical surface 2b of the inner ring 2 is provided. The center of curvature O ₁ of the track groove 1a of the outer ring ₁ and the inner ring In the fixed type constant velocity universal joint in which the center of curvature O ₂ of the two track grooves 2 a is offset from the joint center O in the axial direction by an equal distance from each other in the axial direction, The center position is shifted from the joint center O to the curvature center O ₁ side of the track groove 1a of the outer ring 1 (Δc), and a preload mechanism is provided between the inner ring 2 and the cage 4 so that the track clearance is reduced. In this state, a gap (ΔIC-i) is formed between the inner spherical surface 4c of the cage 4 and the outer spherical surface 2b of the inner ring 2 (see FIG. 1).

  The shift amount of the center position in the axial direction of the pocket 4a has a dimensional relationship that can secure a clearance between the inner ring 2 and the cage 4 that is necessary for reducing the track clearance by preload. Specifically, the axial center position shift amount of the pocket 4a is preferably set to 1.0% to 3.0% of the track groove offset amount. With the above dimensional relationship, a large clearance can be secured between the inner ring 2 and the cage 4 on the inner side of the outer ring, and the inner side interference between the inner ring 2 and the cage 4 during the operation of the cross is surely avoided. Smooth and stable operability can be obtained. If the shift amount is too small, the inner ring 2 and the cage 4 interfere with each other on the inner side of the outer ring during the cross operation. On the other hand, if it is too large, the inner ring 2 and the cage 4 interfere before the track groove and the torque transmission ball 3 come into contact with each other when there is no load. Also, if the spherical clearance is too large in advance, the amount of twist when a torque is applied increases, which is not preferable.

  The difference between the axial dimension of the pocket 4a of the cage 4 and the diameter of the torque transmitting ball 3 is preferably in the range of 0 to 30 μm. The positive clearance is set to reduce the resistance value. However, if the clearance is too large, the behavior of the torque transmission ball 3 cannot be suppressed and the smooth operation is not possible. If it is said range, the stable rotation action of the torque transmission ball | bowl 3 will be obtained.

According to the present invention, by shifting the axial center position of the pocket 4a of the cage 4 outer opening side with respect to the center of the inner and outer spherical surface of the cage 4 in (outer track center O ₁ side), the outer ring inner side of the inner ring 2 and the cage 4 is added to the radial clearance by shifting the axial center position of the cage pocket. This added clearance is generated by the displacement of the inner ring 2 on the outer ring side (inner ring track center O ₂ side) caused by the cage 4 not being positioned at ½ of the operating angle θ due to the cross operation in the no-load state due to this added clearance. Interference between the inner ring outer spherical surface 2b and the cage inner spherical surface 4c can be avoided. Therefore, it is possible to provide a fixed type constant velocity universal joint that operates smoothly without being caught even when the cross is operated.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, a Zepper type (BJ), which is a type of fixed type constant velocity universal joint, will be described as an example. However, the present invention is not limited to this and can be applied to an undercut free type (UJ). .

  As shown in FIG. 2, the fixed type constant velocity universal joint includes an outer ring 1, an inner ring 2, a plurality of torque transmission balls 3, and a cage 4 as main components. The outer ring 1 has an inner spherical surface 1b, and a track groove 1a extending in the axial direction is formed on the inner spherical surface 1b. The inner ring 2 has an outer spherical surface 2b, and a track groove 2a extending in the axial direction is formed on the outer spherical surface 2b. The inner ring 2 and the shaft 5 constitute an inner member 6 by coupling the inner ring 2 to the shaft 5 via torque transmission means such as serrations and splines. The track groove 1a of the outer ring 1 and the track groove 2a of the inner ring 2 are paired to form a ball track, and one torque transmission ball 3 is incorporated in each ball track. The cage 4 is interposed between the inner spherical surface 1b of the outer ring 1 and the outer spherical surface 2b of the inner ring 2, and has pockets 4a for accommodating the torque transmitting balls 3 at equal intervals in the circumferential direction.

The number of track grooves 1a, 2a is six, for example, but there are cases where there are three or eight, and there is no particular limitation. The track grooves 1a and 2a are arc-shaped when viewed in a longitudinal section (FIG. 2), and the center of curvature (outer ring track center) O ₁ of the track groove 1a of the outer ring 1 is relative to the spherical center O of the inner spherical surface of the outer ring 1. center of curvature (inner track center) O ₂ of the track groove 2a of the inner ring 2 with respect to the spherical center O of the inner ring 2 outer spherical surface 2b, are then offset to the opposite side in the axial direction by equal distances. Therefore, the ball track formed by the pair of track grooves 1a and 2a has a wedge shape that decreases from the opening side of the outer ring 1 toward the back side.

The spherical center of the inner spherical surface 1 b of the outer ring 1 and the spherical center of the outer spherical surface 4 b of the cage 4 are both coincident with the joint center O. Further, the spherical center of the outer spherical surface 2 b of the inner ring 2 and the spherical center of the inner spherical surface 4 c of the cage 4 also coincide with the joint center O. Therefore, the offset amount of the outer ring track center O ₁ becomes a distance from the joint center O to outer race track center O _1, the offset amount of the inner race track center O ₂ becomes a distance from the joint center O to inner race track center O _2, both Are equal. In FIG. 2, the spherical centers of the outer spherical surface 4b and the inner spherical surface 4c of the cage 4 are made to coincide with the joint center O, but these spherical centers are sandwiched with the joint center O in the same manner as the track centers O ₁ and O _2. It can also be offset by an equal distance to the opposite side in the axial direction.

  In this constant velocity universal joint, when the outer ring 1 and the inner ring 2 take an operating angle, the torque transmitting ball 3 guided by the cage 4 is always maintained within the bisector of the operating angle at any operating angle, The constant velocity of the joint is ensured.

  A pressing member 10 is provided at the shaft end of the shaft 5. The pressing member 10 in the illustrated example includes a ball as the pressing portion 11, a compression coil spring as the elastic member 12, and a case 13 for using the pressing portion 11 and the elastic member 12 as an assembly. The elastic member 12 acts as an elastic force through the pressing portion 11. The pressing part 11 may have any other shape as long as the contact point with the receiving part 15 is spherical. The case 13 is fixed to the front end portion of the shaft 5 integrated with the inner joint member 2 by serration coupling by an appropriate means such as press fitting or an adhesive.

  A receiving member 14 is attached to an end of the cage 4 on the outer ring back side. The receiving member 14 has a lid shape that covers the end opening of the cage 4 on the back side of the outer ring, and includes a spherical portion 14a having a partially spherical shape and a mounting portion 14b that is formed annularly on the outer periphery thereof. The inner surface (surface facing the shaft 5) of the spherical portion 14 a is a concave spherical surface, and this concave spherical portion functions as a receiving portion 15 that receives a pressing force from the pressing portion 11. The attachment portion 14b is fixed to the end portion of the cage 4 by appropriate means such as press fitting or welding.

  In this embodiment, the pressing portion 11 is provided on the inner ring side and the receiving portion 15 is provided on the cage side. Conversely, the pressing portion is provided on the cage side and the receiving portion is provided on the inner ring side. A structure is also possible.

  In the above configuration, when the inner ring 2 is fitted to the shaft 5 and both are positioned by the retaining ring 16 or the like, the pressing portion 11 of the pressing member 10 and the receiving portion 15 of the receiving member 14 come into contact with each other, and the elastic member 12 is Compressed. As a result, the inner member 6 (the shaft 5 and the inner ring 2) is pressed toward the opening side of the outer ring 1, and relative movement in the axial direction occurs therebetween. This means that when viewed from the torque transmitting ball 3, it is pushed into the reduction side of the ball track. Accordingly, this relative movement closes the track clearance and eliminates rotational backlash.

As shown in FIG. 19, the position of the pocket 4a of the cage 4 is basically the inner and outer spherical surfaces 4b and 4c of the cage 4 except when the contact portion between the pocket 4a and the torque transmitting ball 3 is not secured at a high angle. Therefore, the center of the inner and outer spherical surfaces 4b, 4c of the cage 4 and the position of the pocket 4a are half the diameter d of the torque transmitting ball 3 (d / 2). I was trying. For this reason, the radial clearance between the inner ring 2 and the cage 4 is (spherical clearance) / 2. On the other hand, as indicated by reference sign Δc in FIG. 1, the position of the pocket 4a of the cage 4 is shifted to the outer ring opening side (outer ring track center O ₁ side) with respect to the center (position of the distance Co from the end face) of the inner and outer spherical surfaces 4b and 4c. Thus, the clearance between the inner ring 2 on the inner side of the outer ring and the cage 4 is increased by the amount of shifting of the pocket position of the cage 4 to the radial clearance. The difference between the clearance ΔIC-i in FIG. 1 and the clearance ΔIC in FIG. 18 represents this. FIG. 3 is a view corresponding to FIG. 20 showing the prior art. As is clear from the comparison of both figures, in the case of FIG. 20, the inner ring outer spherical surface 2b and the cage inner spherical surface 4c contact each other on the inner side of the outer ring. In contrast, in FIG. 3, there is a gap between the two 2b and 4c. Therefore, problems such as catching at the time of cross operation and eventually locking are eliminated.

  By the way, in the fixed type constant velocity universal joint, for the convenience of processing and function, apart from the above-mentioned track clearance, between the outer spherical surface 4b of the cage 4 and the inner spherical surface 1b of the outer ring 1, and the inner spherical surface of the cage 4. A minute spherical clearance exists between 4c and the outer spherical surface 2b of the inner ring 2. Of these axial clearances due to the spherical clearance, if the axial clearance between the inner spherical surface 4c of the cage 4 and the outer spherical surface 2b of the inner ring 2 is smaller than the axial clearance due to the track clearance, the track clearance is The inner ring 2 and the cage 4 come into contact with each other before the resulting axial clearance is completely reduced, and the axial movable range of the cage 4 with respect to the inner ring 2 is narrowed. Therefore, the axial clearance caused by the track clearance should be sufficiently reduced. It is not possible to limit. Therefore, it is necessary to set the axial clearance between the cage 4 and the inner ring 2 to be larger than the axial clearance caused by the track clearance, including the state where the joint takes an operating angle.

Therefore, in order to clarify the axial backlash between the inner ring 2 and the cage 4, the axial clearance between the inner ring 2 and the cage 4 is set to 2.5 to 6 of the radial clearance caused by the track clearance. Set to 5 times. This magnification, that is, a range of 2.5 to 6.5 times is obtained from the axial distance (track offset amount) from the joint center O to the outer ring track center O ₁ and the inner ring track center O ₂ and the track PCD. Here, the track PCD means the track groove center diameter of the outer ring 1 and the inner ring 1.

  When the magnification of the axial clearance between the inner ring 2 and the cage 4 with respect to the radial clearance caused by the track clearance is less than 2.5 times, torque is applied to the track grooves 1a and 2a of the outer ring 1 and the inner ring 2. It becomes difficult to secure the necessary depth for transmission, and conversely, when it is larger than 6.5 times, the bending operability of the constant velocity universal joint is reduced when the operating angle is taken between the input and output shafts. Invite worse. Therefore, it is desirable to set the axial clearance between the inner ring and the cage to 2.5 to 6.5 times the radial clearance caused by the track clearance.

  Further, a chamfered portion is formed on the outer spherical surface 2 b of the inner ring 2 to be an interference escape with the inner spherical surface 4 c of the cage 4. In addition, the inner spherical surface 4 c of the cage 4 is formed into an aspheric shape that suppresses interference with the outer spherical surface of the inner ring 2. As a result, the inner ring 2 moves smoothly with respect to the cage 4, and the amount of movement of the inner ring 2 due to the preload can be secured and the track clearance can be more reliably reduced.

Various forms shown in FIGS. 4 to 9 are conceivable as the form of forming the chamfered portion on the outer spherical surface 2 b of the inner ring 2. 4 shows a case where a tapered chamfered portion m ₁ (the broken line portion in the figure shows a conventional shape) is formed on the outer ring opening side edge of the outer spherical surface 2 b of the inner ring 2, and FIGS. Chamfered portions m _{2 to} m _{6 made of} curved surfaces having spherical centers O _{3 to} O ₇ that are offset from the joint center O in the axial direction or radial direction at the outer ring opening side edge of the outer spherical surface 2b (the broken line portion shown in the figure is conventional) The case where the shape is formed is shown. The tapered chamfered portion m _{1 in} FIG. 4 has a predetermined inclination angle α from the end surface of the inner ring 2. The chamfered portions m _{2 to} m _{6 in} FIGS. 5 to 9 are spherical centers O _{3 to} O ₇ that are offset from the joint center O in the axial direction and the radial direction (in FIG. 8, including the inclination angle β direction from the joint center O). To form a convex spherical surface having radii R _{2 to} R ₆ .

4 to 9 show the chamfered portions m _{1 to} m ₆ formed at the outer ring opening side edge of the outer spherical surface 2b of the inner ring 2, whereas the outer ring of the inner ring 2 is shown in FIGS. Chamfered portions m ₁ ′ to m ₆ ′ can also be formed at the outer ring back side edge of the spherical surface 2 b. FIG. 10 shows a case where a tapered chamfered portion m ₁ ′ is formed at the outer ring inner side edge of the outer spherical surface 2 b of the inner ring 2. 11 to 15 show a chamfered portion formed of a curved surface having spherical centers O ₃ ′ to O ₇ ′ offset from the joint center O in the axial direction or the radial direction at the outer ring inner side edge of the outer spherical surface 2 b of the inner ring 2. The cases where m ₂ ′ to m ₆ ′ are formed are shown respectively. The tapered chamfered portion m ₁ ′ in FIG. 10 has a predetermined inclination angle α from the end surface of the inner ring 2. The chamfered portions m ₂ ′ to m ₆ ′ in FIGS. 11 to 15 are each spherical center O ₃ ′ that is offset from the joint center O in the axial direction or radial direction (in FIG. 14, including the inclination angle β direction from the joint center O). A convex spherical surface having radii R ₂ ′ to R ₆ ′ from ˜O ₇ ′.

Moreover, as an aspect which makes the inner spherical surface 4c of the cage 4 an aspherical shape that suppresses interference with the outer spherical surface of the inner ring 2, those shown in FIGS. 16 and 17 are conceivable. FIG. 16 shows a spherical center O ₈ , O in which a flat portion p is formed at the joint center O portion of the inner spherical surface 4c ′ of the cage 4 and both sides of the flat portion p are offset from the joint center O in the axial direction and the radial direction. 'when formed by the concave spherical surface of Figure 17, the inner spherical surface 4c of the cage 4' radius R with ₉ 'with the concave spherical surface of radius R''having a spherical surface center O ₁₀ which is offset from the joint center O in the radial direction Each case is shown.

In the shape of the outer spherical surface 2 b of the inner ring 2, the inner ring 2 is moved to the outer ring by the elastic contact between the pressing portion 11 and the receiving portion 15 by combining the embodiments of FIGS. 4 to 9 and the embodiments of FIGS. 1 is pushed toward the opening side of the shaft 1, and relative movement in the axial direction occurs between the two. Even when the joint takes an operating angle, the cage 4 does not interfere with the inner ring 2, and the inner ring 2 is pivoted until the track clearance is reduced. Since it is movable in the direction, the clearance of the track is surely filled, and the structure of the torque transmission ball 3 cannot stably control the cage 4 to the position of θdeg / 2 at the time of cross operation. As a result, the inner ring 2 There interference of the inner spherical surface 4c of the inner side of the inner ring 2 is pushed in (inner track center O ₂ side) outer spherical surface 2b and the cage 4 of the outer ring 1 can be reliably avoided.

  In order to ensure the product performance of the constant velocity universal joint, the radial clearance of the truck is 0 to 1.5% with respect to the truck PCD, and the radial clearance between the outer ring 1 and the cage 4 is 0 to 0 with respect to the truck PCD. It is desirable to make it 1.7%. When the ratio of these clearances increases, the radial clearance of the truck increases, and it is necessary to increase the axial clearance between the inner ring 2 and the cage 4 in order to reduce backlash. When the joint is rotated at a high torque, the inner ring 2 moves toward the inner side of the outer ring 1 from the shape of the ball track. If the axial clearance between the inner ring 2 and the cage 4 is large, before the outer spherical surface 2b of the inner ring 2 and the inner spherical surface 4c of the cage come into contact with each other, the outer spherical surface 2b of the inner ring 2 and the partial spherical surface 14a of the receiving member 14 The inner concave sphere will interfere. In order to avoid this, the receiving member 14 and the cage 4 are fixed at the rear side of the outer ring 1 or the mounting portion 14b of the receiving member 14 is enlarged in diameter, and the inner concave spherical portion of the partial spherical surface 14a of the receiving member 14 is formed. There is a need to expand. As a result, the cage outer spherical surface 4b and the outer ring inner spherical surface for compensating for the decrease in the strength due to the reduction in the thickness of the cage 4 or the aforementioned reduction in the thickness of the cage in the fixing portion between the mounting portion 14b of the receiving member 14 and the cage 4. It is possible to avoid problems such as a reduction in the service life due to a decrease in the groove depth of the outer ring track groove 1a due to the diameter increase of 1b.

  Furthermore, in order to ensure the shape, the ratio of the track PCD to the torque transmission ball diameter is desirably 1.5 to 4.0 times. If this ratio is less than 1.5, the strength of the inner ring 2 is reduced. Conversely, if the ratio is greater than 4.0, not only the strength of the cage 4 is lowered but also the outer diameter of the outer ring 1 is increased.

  FIG. 21 shows an example of a steering device. In this steering device, the rotational movement of the steering wheel 21 is transmitted to the steering gear 23 through a steering column composed of one or a plurality of steering shafts 22 to be converted into a reciprocating movement of the tie rod 24. . If the steering shaft 22 cannot be arranged in a straight line in consideration of the vehicle-mounted space or the like, the one or more universal joints 25 are arranged between the steering shafts 22 so that the steering gear 23 can be rotated accurately even when the steering shaft 22 is bent. It is possible to transmit exercise. A fixed type constant velocity universal joint can be used for the universal joint 25. Reference sign α in FIG. 21B represents the bending angle of the joint, and a large angle at which the bending angle α exceeds 30 ° can be set. The steering device may be an electric power steering device (EPS) that applies auxiliary force by a motor or a hydraulic power steering device.

It is a principal part enlarged view of FIG. 2, and shows embodiment of this invention. It is a longitudinal cross-sectional view of a fixed type constant velocity universal joint. It is an enlarged view of FIG. 1 which shows embodiment of this invention. FIG. 3 is an enlarged view of a main part of FIG. 2. It is a longitudinal cross-sectional view of an inner ring. It is a longitudinal cross-sectional view of an inner ring. It is a longitudinal cross-sectional view of an inner ring. It is a longitudinal cross-sectional view of an inner ring. It is a longitudinal cross-sectional view of an inner ring. It is a longitudinal cross-sectional view of an inner ring. It is a longitudinal cross-sectional view of an inner ring. It is a longitudinal cross-sectional view of an inner ring. It is a longitudinal cross-sectional view of an inner ring. It is a longitudinal cross-sectional view of an inner ring. It is a longitudinal cross-sectional view of an inner ring. It is a longitudinal cross-sectional view of a cage. It is a longitudinal cross-sectional view of a cage. It is a principal part longitudinal cross-sectional view of the fixed type constant velocity universal joint which shows the prior art. It is a longitudinal cross-sectional view which shows the state at the time of the cross action | operation of the coupling of FIG. It is an enlarged view of the part enclosed with the dashed-two dotted line of FIG. A is a plan view of the steering device, and B is a side view of the steering device.

Explanation of symbols

1 Outer member (outer ring)
1a track groove O ₁ outer ring track center 1b inner spherical surface 2 inner member (inner ring)
2a Track groove O ₂ Inner ring track center 2b Outer spherical surface m _{1 to} m ₆ Chamfered part (outer ring opening side)
m ₁ 'to m ₆ ' chamfered part (outer ring back side)
3 Torque transmission ball 4 Cage 4a Pocket 4b Outer spherical surface 4c Inner spherical surface

Claims (4)

An outer ring having an inner spherical surface formed with a plurality of track grooves, an inner ring having an outer spherical surface formed with a plurality of track grooves, and a joint formed by a pair of an outer ring track groove and an inner ring track groove from one to the other in the axial direction. A wedge-shaped ball track that is reduced in size, a torque transmission ball incorporated in each ball track, and a pocket that holds the torque transmission ball, and is interposed between the inner spherical surface of the outer ring and the outer spherical surface of the inner ring. A fixed type constant velocity universal joint, wherein the center of curvature of the track groove of the outer ring and the center of curvature of the track groove of the inner ring are offset from the joint center by an equal distance in the opposite direction from each other in the axial direction. shifting the axial center position in the center of curvature side of the track grooves of the outer ring from the joint center, and the track gap is provided a preload mechanism between the inner ring and the cage The structure packing, in unloaded condition, the fixed type constant velocity universal joint being characterized in that a gap is formed between the inner spherical surface and the inner ring of the outer spherical surface of the cage.   2. The fixed type constant velocity universal joint according to claim 1, wherein the shift amount of the center position of the cage pocket in the axial direction is 1.0% to 3.0% of the offset amount of the track groove. 3. The fixed type constant velocity universal joint according to claim 1 , wherein a difference between an axial dimension of the cage pocket and a diameter of the torque transmitting ball is in a range of 0 to 30 [mu] m . The fixed type constant velocity universal joint according to any one of claims 1 to 3 , wherein the fixed type constant velocity universal joint is used for a steering device of an automobile .