JP2015152116A - power transmission shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power transmission shaft which can change torsional rigidity according to input torque.SOLUTION: A power transmission shaft has a first shaft 10, a second shaft 20 and a third shaft 30, connects the first shaft 10 and the second shaft 20 so as to be capable of transmitting torque, and connects the first shaft 10 and the second shaft 20 via the third shaft 30 so as to be capable of transmitting torque, and a clearance in a circumferential direction is formed at a connecting part between the first shaft 10 and the second shaft 20. Until the circumferential clearance of the connecting part between the first shaft 10 and the second shaft 20 is eliminated, torque is transmitted to the second shaft 20 from the first shaft 10 via the third shaft 30, and when the circumferential clearance is eliminated, the connecting part between the first shaft 10 and the second shaft 20 contributes to torque transmission. In such a way, torsional rigidity is changed according to input torque (torsion amount). Concretely, the torsional rigidity in a constant region straddling a torsional angle zero can be set to be lower than torsional rigidity in a region other than the constant region.

Description

  The present invention relates to a power transmission shaft. More specifically, the torsional rigidity is changed in accordance with the torsional amount, and is not intended to be limited. It can be changed to improve the ride comfort of the vehicle.

  FIG. 4 shows a typical automobile drive shaft. This drive shaft is composed of a shaft S, a fixed type constant velocity universal joint J1 and a sliding type constant velocity universal joint J2 attached to both ends thereof, and plays a role of transmitting power from an engine, that is, torque, to driving wheels. .

When torque is applied, the drive shaft is twisted in the circumferential direction due to elastic deformation of components. The twist amount (twist angle) ω (rad) of the end portion of the fixed type constant velocity universal joint J1 and the end portion of the sliding type constant velocity universal joint J2 is expressed by the following equation.
ω = (1 / K1 + 1 / K2 + 1 / K3) · T
here,
K1: Torsional rigidity (Nm / rad) of fixed type constant velocity universal joint J1,
K2: Torsional rigidity (Nm / rad) of sliding type constant velocity universal joint J2,
K3: Torsional rigidity of shaft S (Nm / rad),
T: Input torque (Nm).

  In general, K1, K2, and K3 are constants within the elastic range, and are constant even when the input torque changes. The drive shaft generally has a relationship of K3 << K1, K2, and therefore the torsional characteristics of the driveshaft are greatly influenced by the characteristics of the shaft S.

  Patent Document 1 (Japanese Patent No. 5182419) describes that an intermediate shaft (center shaft) of a drive shaft is provided with a vibration damping mechanism that attenuates vibration by frictional contact (see FIG. 1 of Patent Document 1). . In this vibration damping mechanism, a fixed portion fixed to the shaft and a friction contact portion that is in frictional contact with the shaft are arranged apart from each other in the axial direction, and damping performance is exhibited by applying friction contact pressure to the friction contact portion. I am doing so.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2012-255555) describes a flexible shaft joint in which a driving end piece and a driven end piece are connected by a flexible annular sleeve. Torsional vibration damping function by transmitting torque.

  In Patent Document 3 (Japanese Utility Model Publication No. 62-179421), there is a drive shaft that has an inner shaft and a cylindrical body, and the cylindrical body is connected to the inner shaft by a connecting member having higher torsional rigidity than the inner shaft. (See FIG. 1 of Patent Document 3). The inner shaft is provided with outward projections, while the cylindrical body is provided with inward projections. These projections are alternately and relatively rotatable, and are fluid-tight fluid chambers between them. To form an incompressible fluid (see FIG. 3 of Patent Document 3). According to this drive shaft, the static torque is reliably transmitted by the inner shaft with sufficient strength, and the fluctuating torque causes the inner shaft to torsionally deform to cause a volume fluctuation in the fluid chamber, so that the fluid is It is attenuated by the resistance that flows around.

  Patent Document 4 (Japanese Patent Application Laid-Open No. 2010-265929) includes an inner shaft and an outer shaft that are relatively movable in the axial direction. The inner shaft has spline external teeth, and the outer shaft has variable rigidity having spline internal teeth. An axis is described (see FIG. 3 of Patent Document 4). When the engagement between the spline outer teeth and the spline inner teeth is disengaged, the power is transmitted only by the inner shaft, and when the spline outer teeth and the spline inner teeth are engaged, the power is generated by both the inner shaft and the outer shaft. Is in a highly rigid state.

  The variable rigidity shaft is provided between the torque converter that transmits power from the internal combustion engine and the drive wheel, and changes the relative axial position of the inner shaft and outer shaft to engage the spline outer teeth and spline inner teeth. Change torsional stiffness by changing state. For example, when the lockup state detection unit detects that the lockup mechanism of the torque converter is in the lockup state and the detected torque detected by the torque detection unit is smaller than a preset set torque, the It is controlled to be in a rigid state. When the torque converter is in the lock-up state, that is, when the engine power is transmitted directly, the variable rigidity shaft becomes in the low rigidity state. Noise is reliably suppressed. Further, when the torque converter is not in the lock-up state, the variable rigidity shaft is in the high rigidity state. Therefore, even if the engine power is amplified by the torque converter and a high load torque is input to the variable rigid shaft, the variable rigid shaft is not significantly twisted, and the fatigue strength of the variable rigid shaft is not reduced. The durability is remarkably improved.

Japanese Patent No. 5182419 JP 2012-255555 A Japanese Utility Model Publication No. 62-179421 JP 2010-265929 A

  In the case of a drive shaft for an automobile, high torsional rigidity tends to be required particularly in an M / T (manual transmission) vehicle or a sports type vehicle so that a direct feeling during acceleration can be obtained. For this reason, among the components of the drive shaft, there are some components that use a hollow shaft having a high rigidity and a light weight for a portion of the shaft having a relatively low rigidity.

  In recent years, EV (electric vehicle) / HEV (hybrid vehicle) has attracted attention and is widely used as an environmentally friendly vehicle. These vehicles have a deceleration energy regeneration mechanism (hereinafter simply referred to as a regeneration mechanism) that changes energy during deceleration to electricity. Some internal combustion engine vehicles also have a mechanism for regenerating energy during deceleration. In the case of a car with a regenerative mechanism, while driving, the drive shaft rotates in the forward direction of the vehicle while positive torque from the engine works during acceleration, and negative torque from the tire works during regenerative mechanism operation, that is, during deceleration. . Even in a car without a regenerative mechanism, negative torque works when the engine brake works, but the negative torque due to regeneration in a car with a regenerative mechanism is larger.

  When a car with a regenerative mechanism performs strong acceleration, naturally, the rigidity of the drive shaft is high and a solid sense of acceleration is required. On the other hand, if you repeat slow acceleration and deceleration due to regeneration during steady running after acceleration, there is a situation that crosses zero torque (0), such as plus torque → torque zero → minus torque, minus torque → torque zero → plus torque. Occur. In this case, if the rigidity of the drive shaft is high, a change in torque is transmitted sensitively and gives a jerky feeling, which impairs the riding comfort of the vehicle.

  For this reason, from the viewpoint of ride comfort, it is considered that the drive shaft is low in rigidity, the drive shaft rotation change is delayed with respect to the torque change, and the behavior is slow. That is, as shown in FIG. 5B, a characteristic is required such that the rigidity is low in a certain region across the torsion angle zero and the rigidity is high in other regions.

  Here, FIG. 5 schematically shows the rigidity characteristics with the torque (T) on the vertical axis and the torsion angle (ω) on the horizontal axis. Whereas the diagram of FIG. 5A changes linearly, the diagram of FIG. 5B shows that the torsional stiffness in a certain region across the torsion angle (ω) is a region other than the region described above. This is smaller than the torsional rigidity.

  Accordingly, an object of the present invention is to provide a power transmission shaft capable of changing torsional rigidity in accordance with input torque.

  The prior art described in Patent Documents 1 and 2 is a vibration damping technique for the purpose of damping torsional vibration, and changes the torsional rigidity itself of the drive shaft to change the ride comfort of the vehicle. It does not improve.

  In the drive shaft described in Patent Document 3, when static torque and variable torque are transmitted by the inner shaft, the static torque is reliably transmitted by the inner shaft without fear of strength, and the variable torque twists and deforms the inner shaft. Since the volume fluctuation occurs on both sides in the circumferential direction of the outward protrusion, the fluid is attenuated by the resistance that flows around the protrusions, particularly in the gap outside the outward protrusion. In short, torque is transmitted exclusively by the inner shaft, and for the purpose of damping torsional vibration, an outer shaft is provided to form a fluid chamber, and the torsional rigidity of the drive shaft is not changed.

  The variable rigidity shaft described in Patent Document 4 switches between a low rigidity state and a high rigidity state by moving the inner shaft and the outer shaft relative to each other in the axial direction and changing the meshing state between the spline outer teeth and the spline inner teeth. . Moreover, this switching is performed by the control device in response to signals from the lock-up state detection means and the torque detection means, and the rigidity of the rotating shaft does not automatically change. In addition, the entire apparatus becomes large, and control becomes necessary, so that the apparatus becomes complicated.

  The present invention realizes rigidity characteristics as shown in FIG. 5B by a simple structure of the power transmission shaft. That is, the power transmission shaft of the present invention is characterized in that the torsional rigidity in the region where the torsion angle is zero is lower than the torsional rigidity in the region outside the region.

  The torsional rigidity of the power transmission shaft of the present invention changes according to the magnitude of the input torque. Therefore, the ride comfort of a vehicle can be improved by applying to the drive shaft of a motor vehicle. That is, a firm acceleration feeling is obtained in the region where the torsional rigidity is high, and the torque reversal (plus torque → torque zero → minus torque, minus torque → torque zero → plus torque) is slowed down in the region where the torsional angle is low. As a result, the jerky feeling is eliminated and the ride comfort is improved.

It is a longitudinal cross-sectional view of the power transmission shaft which shows embodiment of this invention. It is a longitudinal cross-sectional view of the drive shaft using the power transmission shaft shown in FIG. (A) is a cross-sectional view taken along the line III-III in FIG. 1, (B) is a partially enlarged view of the connecting portion between the first shaft and the second shaft, and (C) is a portion of the connecting portion between the second shaft and the third shaft. It is an enlarged view. It is a longitudinal cross-sectional view of the conventional drive shaft. (A) is a schematic diagram which shows the rigidity characteristic of the conventional drive shaft, (B) is a schematic diagram which shows the rigidity characteristic of the drive shaft of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, taking as an example a case where the present invention is applied to an automobile drive shaft.

An embodiment of a power transmission shaft is shown in FIG. 1, and an embodiment of an automobile drive shaft using the power transmission shaft is shown in FIG.

As described above, in the conventional drive shaft shown in FIG. 4, the fixed type constant velocity universal joint J1 is attached to one end portion of the intermediate shaft S, and the sliding type constant velocity universal joint J2 is attached to the other end portion. It is attached. While the intermediate shaft S is a single shaft, the power transmission shaft shown in FIG. 1 includes three axes, that is, a first axis 10, a second axis 20, and a third axis 30. Yes.

The first shaft 10 has a spline shaft 12 for connecting to the inner ring of the fixed type constant velocity universal joint J1 so that torque can be transmitted.

The second shaft 20 has a spline shaft 22 for connecting to the inner joint member of the sliding constant velocity universal joint J2 so as to be able to transmit torque.

The third shaft 30 is interposed between the first shaft 10 and the second shaft 20, is connected to the first shaft 10 so that torque can be transmitted at one end, and transmits torque to the second shaft 20 at the other end. Connect as possible.

As for the 1st axis | shaft 10, the axial part 10a and the cylindrical part 10b are integrally formed. In addition, although it has taken out the lead line as if the bottom of the cylindrical part 10b is a boundary of the axial part 10a and the cylindrical part 10b, it is for the sake of convenience.

The shaft portion 10a of the first shaft 10 has a spline shaft 12 formed at the shaft end, and on the cylindrical portion 10b side, the inner peripheral surface shape of the small diameter side mounting portion of the boot B1 (see FIG. 2) A boot fixing portion 14 having a corresponding shape is provided.

The cylindrical portion 10b of the first shaft 10 has a spline hole 16 formed on the inner peripheral surface on the end surface side, and the spline hole 16 is connected to the spline shaft 26 of the second shaft 20 so as to be able to transmit torque. Yes. A bottom hole 18 for connecting to the third shaft 30 is provided at the bottom of the cylindrical portion 10b.

The first shaft 10 is strengthened by selecting medium carbon steel of about S40C as the material and subjecting the outer peripheral surface to surface hardening treatment by induction hardening.

The second shaft 20 is formed integrally with a shaft portion 20a and a head portion 20b. The shaft portion 20a of the second shaft 20 is formed with a spline shaft 22 at the shaft end portion, and on the head portion 20b side, the inner peripheral surface shape of the small-diameter side mounting portion of the boot B2 (see FIG. 2) A boot fixing portion 24 having a corresponding shape is provided.

The head portion 20b of the second shaft 20 is formed with a spline shaft 26. As described above, the spline shaft 26 is connected to the spline hole 16 of the first shaft 10 so that torque can be transmitted. In addition, a pilot hole 28 for connecting to the third shaft 30 is provided on the end surface of the head portion 20b.

For the second shaft 20, medium carbon steel of about S40C is selected as the material, and the outer peripheral surface is reinforced by performing a surface hardening process by induction hardening.

The third shaft 30 is strengthened by selecting medium carbon steel of about S40C as the material and subjecting the outer peripheral surface to surface hardening treatment by high frequency heat treatment.

Spline shafts 32 and 34 are formed at both ends of the third shaft 30. By press-fitting the spline shaft 32 into the lower hole 18 of the first shaft 10, the first shaft 10 and the third shaft 30 are connected so that torque can be transmitted. Similarly, the second shaft 20 and the third shaft 30 are connected so that torque can be transmitted by press-fitting the spline shaft 34 into the lower hole 28 of the second shaft 20.

As shown in FIG. 3B, the connecting portion formed by the spline shaft 16 of the first shaft 10 and the spline hole 26 of the second shaft 20 has a circumferential clearance δ. 3 (A) and 3 (B), the radial clearance is exaggerated, but the spline shaft 16 and spline hole 26 of this connecting portion are adjusted to have a large diameter or a small diameter so that there is no backlash in the bending direction. It is desirable to do.

As shown in FIG. 1, a flexible cap 29 formed of rubber or synthetic resin is attached to the joint portion of the first shaft 10 and the second shaft 20 in order to prevent intrusion of foreign matter. preferable.

  In the embodiment, the first shaft 10 and the third shaft 30 and the second shaft 20 and the third shaft 30 are connected by plastic coupling. That is, the pilot hole 18 of the first shaft 10 and the pilot hole 28 of the second shaft 20 are processed so as not to be affected by the heat treatment and left unquenched. And the spline shafts 32 and 34 of the 3rd axis | shaft 30 which gave the surface hardening process layer are press-fit in these prepared holes 18 and 28, respectively. As a result, the teeth of the spline shafts 32 and 34 bite into the lower holes 18 and 28, and no play is generated between the first shaft 10 and the third shaft 30 and between the second shaft 20 and the third shaft 30. (See FIG. 3C).

  The concave / convex fitting portions between the teeth of the spline shaft 32 and the lower hole 18 are in close contact with each other in the circumferential direction and the entire axial direction. Similarly, the concave and convex fitting portions between the teeth of the spline shaft 34 and the lower hole 28 are in close contact with each other in the circumferential direction and the entire axial direction. Each connection is not limited to plastic coupling, and the concave and convex fitting structures are formed by cutting the inner walls of the pilot holes 18 and 28 with the teeth of the spline shafts 32 and 34, and the concave and convex fitting portions are arranged in the circumferential direction and the axial direction. You may make it closely_contact | adhere in the whole area.

In the above-described structure, the torsion characteristic when torque is applied will be described.
There is no contact of the spline teeth at the connecting portion of the first shaft 10 and the second shaft 20 until the input torque is small and the relative twist amount of the connecting portions 16 and 26 of the first shaft 10 and the second shaft 20 becomes δ, The cylindrical portion 10b of the first shaft 10 is not involved in torque transmission. Therefore, torque is transmitted through a path such as the shaft portion 10 a of the first shaft 10, the third shaft 30, and the second shaft 20.

  When the input torque increases and the relative torsion of the connecting portions 16 and 26 between the first shaft 10 and the second shaft 20 reaches δ, the spline teeth come into contact with the connecting portions 16 and 26 between the first shaft 10 and the second shaft 20. The cylindrical portion 10b of the first shaft 10 is also involved in torque transmission. Therefore, torque transmission is performed through paths such as the shaft portion 10 a of the first shaft 10, the cylindrical portion 10 b of the first shaft 10, the third shaft 30, and the second shaft 20. In this case, the rigidity of the cylindrical portion 10b of the first shaft 10 and the third shaft 30 appears as a sum.

Simply, torsional rigidity of each part,
Shaft portion 10a of first shaft 10: Kaa
Cylindrical portion 10b of the first shaft 10: Kab
Third axis 30: Kc
Second axis 20: Kb
Then, the torsional rigidity of the shaft is expressed as follows.
If 0 <the relative twist amount of the connecting portions 16 and 26 of the first shaft 10 and the second shaft 20 <δ,
Shaft torsional rigidity = 1 / (1 / Kaa + 1 / Kc + 1 / Kb),
When the relative twist amount of the connecting portions 16 and 26 of the first shaft 10 and the second shaft 20 is δ,
Shaft torsional rigidity = 1 / (1 / Kaa + 1 / (Kab + Kc) + 1 / Kb).

  If the third shaft 30 is designed so that Kc is smaller than Kaa, Kab, and Kb, rigidity characteristics as shown in FIG. 5B can be obtained.

  By attaching the constant velocity universal joints J1 and J2 to both ends of the power transmission shaft described above, the automobile drive shaft shown in FIG. 2 is obtained. The details of the constant velocity universal joints J1 and J2 are well known, but briefly described as follows.

The fixed type constant velocity universal joint J1 includes an inner ring 42, an outer ring 44, a cage 46, and a ball 48 as main components, and connects the spline hole of the inner ring 42 to the spline shaft 12 of the first shaft 10. Since the spherical outer peripheral surface of the inner ring 42 and the spherical inner peripheral surface of the outer ring 44 are in spherical contact via the cage 46, the fixed type constant velocity universal joint J1 can only be angularly displaced.

The inner ring 42 is formed with ball grooves extending in the axial direction on the spherical outer peripheral surface at equal intervals in the circumferential direction. The outer ring 44 has ball grooves extending in the axial direction on the spherical inner peripheral surface formed at equal intervals in the circumferential direction. A ball 48 is incorporated between the ball groove of the inner ring 42 and the ball groove of the outer ring 44 that form a pair. The cross-sectional shape of the ball track formed by the ball groove of the inner ring 42 and the ball groove of the outer ring 44 is an arc shape in which the center of curvature is offset in the opposite direction across the joint center. It has a wedge shape that expands toward the end face. The cage 46 has pockets for accommodating the balls 48 formed at predetermined intervals in the circumferential direction, and all the balls 48 are held on the same plane by the cage 46.

The outer ring 44 is filled with lubricating grease. In order to prevent leakage of the lubricating grease and to prevent foreign matter from entering from the outside, a boot B1 is attached. In the illustrated example, the boot B1 is a bellows type molded into a substantially conical shape with a synthetic resin. It is attached to.

The sliding type constant velocity universal joint J2 is a tripod type constant velocity universal joint. The main components are an inner joint member (52, 54), a spherical roller 56 as a torque transmission member, and a housing 58 as an outer joint member. Yes.

The inner joint member includes a boss 52 and a trunnion journal 54, and a spline hole formed in the boss 52 is connected to the spline shaft 22 of the second shaft 20. The trunnion journals 54 are arranged at equal intervals in the circumferential direction of the boss 52 and project in the radial direction of the boss 52. A spherical roller 56 is supported on each trunnion journal 54 so as to be rotatable via a needle roller.

A track groove running in the axial direction of the housing 58 is formed on the inner periphery of the housing 58, and the spherical roller 56 is accommodated in the track groove. When the joint rotates at an angle, the spherical roller 56 moves in the axial direction of the housing 58 while rolling along the track groove.

The housing 58 is filled with lubricating grease. In order to prevent leakage of the lubricating grease and to prevent foreign matter from entering from the outside, a boot B2 is attached. The illustrated boot B2 is a bellows type molded into a substantially conical shape with rubber, and has a large-diameter end attached to the opening end of the housing 58 and a small-diameter end attached to the seal attaching portion 24 of the second shaft 20. .

  The effects of the above-described embodiment can be summarized as follows.

As shown in FIG. 5 (B), the power transmission shaft is applied to an automobile drive shaft, in particular, by making the torsional rigidity in a certain region across the zero torsion angle lower than the torsional rigidity outside the certain region. Can contribute to improving the ride comfort. In the case of a drive shaft for automobiles, the input torque can be reversed, such as from plus torque to minus torque across the torsion angle, and from minus torque to plus torque. This improves riding comfort. On the other hand, by increasing the torsional rigidity outside a certain region across the torsion angle of zero, a firm acceleration feeling can be obtained when performing strong acceleration.

The first shaft 10, the second shaft 20, and the third shaft 30 are connected, the first shaft 10 and the second shaft 20 are connected so as to be able to transmit torque, and the first shaft 10 and the second shaft 20 are connected to the third shaft. 30 is connected to be able to transmit torque, and a clearance in the circumferential direction is provided at the connecting portions 16 and 26 of the first shaft 10 and the second shaft 20. By adopting such a configuration, torque is transmitted from the first shaft 10 to the second shaft 20 through the third shaft 30 until there is no circumferential clearance, and when there is no circumferential clearance, The connecting portion between the single shaft 10 and the second shaft 20 is also involved in torque transmission. In this way, the torsional rigidity changes according to the amount of torsion.

In the fixed region, the first shaft 10, the third shaft 30, and the second shaft 20 are connected in a state where there is a circumferential clearance δ at the connection portion of the first shaft 10 and the second shaft 20, and the fixed shaft Outside the region, the first shaft 10, the third shaft 30, and the second shaft 20 are connected, and the first shaft 10 and the second shaft 20 are directly coupled with each other with no circumferential clearance δ. By adopting such a configuration, the torque is reliably transmitted from the first shaft 10 to the second shaft 20 via the third shaft 30 until the circumferential clearance δ is eliminated, and the circumferential clearance is eliminated. When δ is eliminated, the connection between the first shaft 10 and the second shaft 20 is also involved in torque transmission.

Concave and convex connection by plastic bonding or cutting based on the press-fitting of teeth of the spline shafts 32 and 34 of the third shaft 30 to the connection portion of the first shaft 10 and the third shaft 30 and the connection portion of the second shaft 20 and the third shaft 30 By forming the structure, the concave-convex fitting portion is in close contact with the entire area in the circumferential direction and the axial direction. Therefore, torque is more reliably transmitted from the first shaft 10 to the second shaft 20 through the third shaft 30 until the circumferential clearance δ disappears, and when the circumferential clearance δ disappears, the first shaft The connecting portion between the second shaft 20 and the second shaft 20 is also involved in torque transmission.

The first shaft 10, the second shaft 20, and the third shaft 30 are made of carbon steel for mechanical structure, and the outer peripheral surface is subjected to surface hardening treatment by induction hardening, thereby ensuring the strength of each shaft, and The plastic coupling of the one axis 10 and the second axis 20 and the second axis 20 and the third axis 30 is enabled.

The automobile drive shaft having the fixed type constant velocity universal joint J ₁ attached to one end of the power transmission shaft and the slidable type constant velocity universal joint J ₂ attached to the other end, as described above, is particularly suitable for an automobile drive shaft. When applied, it can contribute to improving ride comfort.

  The embodiment of the present invention has been described above by taking the case of application to an automobile drive shaft as an example. However, the present invention is not limited to the embodiment shown and described herein, and departs from the scope of the claims. It goes without saying that various modifications can be made and implemented.

For example, the power transmission shaft has no direction on the input side and the output side, and therefore the fixed type constant velocity universal joint J ₁ and the sliding type constant velocity universal joint J ₂ in FIG. 1 may be interchanged. Although the Rzeppa type constant velocity universal joint is illustrated as the fixed type constant velocity universal joint, other fixed type constant velocity universal joints may be adopted. Similarly, although the tripod type constant velocity universal joint is illustrated as an example of the sliding type constant velocity universal joint, other sliding type constant velocity universal joints may be adopted.

  In addition, the spline is illustrated as a structure for connecting the first shaft 10 and the second shaft 20 so as to be able to transmit torque. However, there is a clearance δ in the circumferential direction, and a connection similar to a spline that can transmit torque by meshing. Any structure is acceptable. In FIG. 3 (B), the clearance on both sides of the spline teeth is represented by the symbol δ, but the clearance values of both are not necessarily equal.

  Furthermore, although the case where the both ends of the 3rd axis | shaft 30 were made into the spline shafts 32 and 34 was illustrated, the shape similar to the spline with a peak and a trough which can transmit torque may be sufficient. An example is serration.

10 first shaft 10a shaft portion 10b cylindrical portion 12 spline shaft 14 boot mounting portion 16 spline hole 18 lower hole 20 second shaft 22 spline shaft 24 boot mounting portion 26 spline shaft 28 lower hole 29 cap 30 third shaft 32 spline shaft 34 Spline shaft B1 Boot B2 Boot J1 Fixed type constant velocity universal joint J2 Sliding type constant velocity universal joint

Claims (6)

A power transmission shaft in which a torsional rigidity in a certain region across a torsional angle is lower than a torsional rigidity in a region outside the region. Has a first axis, a second axis, and a third axis, connects the first axis and the second axis so that torque can be transmitted, and allows the first axis and the second axis to transmit torque via the third axis The power transmission shaft according to claim 1, wherein a clearance in the circumferential direction is provided at a connection portion between the first shaft and the second shaft. In the fixed region, the first shaft, the third shaft, and the second shaft are connected with the clearance between the first shaft and the second shaft, and outside the fixed region, the first shaft and the second shaft are connected. The power transmission shaft according to claim 2, wherein the three shafts and the second shaft are connected, and the first shaft and the second shaft are directly coupled without the clearance. 3. A concave / convex fitting structure is formed by plastic bonding or cutting based on press-fitting of teeth of the spline shaft of the third shaft at the connection portion of the first shaft and the third shaft and the connection portion of the second shaft and the third shaft. Or 3 power transmission shafts. The power transmission shaft according to any one of claims 2 to 4, wherein the first shaft, the second shaft, and the third shaft are made of carbon steel for mechanical structure and are subjected to surface hardening treatment by induction hardening. A drive shaft for an automobile, wherein a fixed type constant velocity universal joint is attached to one end of the power transmission shaft according to any one of claims 1 to 5 and a sliding type constant velocity universal joint is attached to the other end.

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