JP2014031804A - Drive shaft for vehicle - Google Patents

Abstract

Provided is a vehicle drive shaft capable of preventing the internal pressure of a boot from becoming a negative pressure even if the internal temperature of the boot suddenly drops after the temperature has risen to a high temperature.
The vehicle drive shaft 1 has a hollow drive shaft 7 having an opening 7b at one end 7a and a pressure adjusting chamber 7c communicating with the opening 7b, and one end 7a of the hollow drive shaft 7. A constant velocity universal joint 9 connected to the hollow drive shaft 7 and the constant velocity universal joint 9, and a boot 13 that is filled with grease 19 inside, and an opening 7 b. 7a is provided with a breathable filter 17 that permits passage of air while restricting passage of grease 19, and between the volume V1 of the boot 13 and the volume V2 of the pressure adjusting chamber 7c, A relationship is established.
[Selection] Figure 1

Description

  The present invention relates to a vehicle drive shaft in which a connecting portion between a hollow drive shaft and a constant velocity universal joint is covered with a boot.

  In a vehicle such as an automobile, a drive shaft that transmits the driving force of the differential gear to the drive wheel is connected between the differential gear and the drive wheel (for example, Patent Document 1).

  The vehicle drive shaft of Patent Document 1 includes a hollow drive shaft, a constant velocity universal joint connected to both ends of the hollow drive shaft, and a boot that covers a connection portion between the hollow drive shaft and the constant velocity universal joint. I have. A lubricant is sealed inside the constant velocity universal joint. In addition, an air permeable filter that allows gas to pass but prevents lubricant from passing is disposed on the inner surface of the boot. In this vehicle propeller shaft, the breathable filter can keep the internal pressure of the boot constant (atmospheric thickness) while preventing the lubricant from seeping out from the boot.

JP 2008-232302 A

  However, in the vehicle drive shaft of Patent Document 1, when the internal temperature of the boot continues to be high, the air inside the boot gradually escapes to the outside of the boot. And then, when the internal temperature of the boot suddenly drops, the internal pressure of the boot suddenly drops, but at that time, the inflow of air from the outside of the boot does not catch up with the sudden fall and escapes to the outside The internal pressure of the boot becomes negative by the amount of air. This negative pressure may cause wear at the bellows portion of the boot and irreversible deformation of the boot.

  Therefore, the present invention has been made in view of the above problems, and for a vehicle capable of preventing the internal pressure of the boot from becoming negative even if the internal temperature of the boot suddenly decreases after rising to a high temperature. An object is to provide a drive shaft.

  In order to solve the above problems, a drive shaft of the present invention has a hollow drive shaft having an opening at one end and a pressure adjusting chamber communicating with the opening inside, and at one end of the hollow drive shaft. A connected constant velocity universal joint; a boot that covers a connecting portion between the hollow drive shaft and the constant velocity universal joint; and a grease-filled boot; and an opening that covers the opening. In the vehicle drive shaft provided with a breathable filter that allows passage of air while restricting passage of grease, an expression is provided between the volume V1 of the boot and the volume V2 of the pressure adjustment chamber. The relationship 2 is established.

  According to the above configuration, since the relationship of Formula 2 is established between the volume V1 of the boot and the volume V2 of the pressure adjustment chamber, even if the boot internal temperature rises to a high temperature, It is possible to prevent the pressure from becoming negative.

  According to the vehicle drive shaft of the present invention, it is possible to prevent the internal pressure of the boot from becoming a negative pressure even if the internal temperature of the boot suddenly decreases after rising to a high temperature.

1 is a schematic cross-sectional view of a vehicle drive shaft according to a first embodiment of the present invention. It is the figure which showed an example of the time change of the internal temperature of the boot of the drive shaft for vehicles, and an example of the time change of the internal pressure difference of the said boot. It is a figure which shows an example of each internal pressure, volume, and internal temperature of the boot at the normal temperature and a saturation temperature, and a pressure regulation chamber. It is the cross-sectional schematic of the drive shaft for vehicles which concerns on the modification 1 of this invention. It is the cross-sectional schematic of the drive shaft for vehicles which concerns on the modification 2 of this invention. It is the cross-sectional schematic of the drive shaft for vehicles which concerns on the modification 3 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<< First Embodiment >>
<Description of configuration>
FIG. 1 is a schematic cross-sectional view of a vehicle drive shaft according to this embodiment.

  As shown in FIG. 1, the vehicle drive shaft 1 according to this embodiment is connected between a drive wheel 3 and a differential gear 5, and transmits the driving force of the differential gear 5 to the drive wheel 3. More specifically, the boot 13 and the pressure adjusting chamber 7c that can be ventilated are provided inside the hollow drive shaft 7 to prevent the air from leaking from the inside of the boot 13 to the outside when the internal temperature of the boot 13 is high. This prevents the internal pressure of the boot 13 from becoming a negative pressure (that is, a pressure lower than the external atmospheric pressure) at the normal temperature of the boot 13 thereafter.

  The vehicle drive shaft 1 includes a hollow drive shaft 7, constant velocity universal joints 9 and 11 connected to both ends of the hollow drive shaft 7, and a connection between the hollow drive shaft 7 and the constant velocity universal joints 9 and 11. And elastic boots 13 and 15 covering the portion.

  The hollow drive shaft 7 is formed in, for example, a cylindrical shape, and an opening 7b is formed at one end 7a thereof, and a hollow pressure adjusting chamber 7c communicating with the opening 7b is formed therein. A breathable filter 17 is disposed at one end 7a of the hollow drive shaft 7 so as to cover the opening 7b. The air-permeable filter 17 is a filter that allows passage of air while restricting (prohibiting) passage of later-described grease filled in the constant velocity universal joint 13. The volume of the pressure adjusting chamber 7c is set so that air does not escape from the inside of the boot 13 to the outside when the internal temperature of the boot 13 is high, as will be described later.

  The constant velocity universal joint 9 is configured as, for example, a fixed type constant velocity universal joint, and is arranged between an outer ring 9a as an outer joint member, an inner ring 9b as an inner joint member, and an outer ring 9a and an inner ring 9b. A plurality of balls 9c and a cage 9d for holding each ball 9c are provided.

  The outer ring 9a is formed, for example, in a hollow hemispherical shape having an opening 9m, and on the opposite side of the outer peripheral surface of the opening 9m, a rotating shaft 9n to which the drive wheel 3 is connected is a central axis Q1 of the outer ring 9a. It is formed to protrude outward along the direction. A plurality of track grooves 9f are formed in the inner peripheral surface 9e of the outer ring 9a along the direction of the central axis Q1.

  The inner ring 9b is formed in a cylindrical shape, for example, and is disposed inside the outer ring 9a. A plurality of track grooves 9h that are paired with the track grooves 9f of the outer ring 9a are formed on the outer peripheral surface 9g of the inner ring 9b along the direction of the central axis Q2 of the inner ring 9b. The end 7a side of the hollow drive shaft 7 is fitted and fixed concentrically in the center hole 9j of the inner ring 9b.

  Each ball 9c is disposed between the track groove 9f of the outer ring 9a and the track groove 9h of the inner ring 9b.

  The gauge 9d is formed in a cylindrical shape, for example, and a plurality of pockets 9i for holding the balls 9c are formed on the peripheral wall thereof. The gauge 9d is disposed between the inner peripheral surface 9e of the outer ring 9a and the outer peripheral surface 9g of the inner ring 9b, and each ball 9c is disposed in each pocket 9i, thereby holding the ball 9c.

  With this configuration, in this constant velocity universal joint 9, the inner ring 9 b and the outer ring 9 a can be displaced so that the oblique angle between the central axis Q 1 of the outer ring 9 a and the central axis Q 2 of the inner ring 9 b is within a predetermined angular range. Is attached. As a result, the constant velocity universal joint 9 is driven with the hollow drive shaft 7 so that the oblique angle between the rotation axis of the hollow drive shaft 7 and the rotation axis of the drive wheel 3 is freely displaceable within a predetermined angle range. The wheel 3 is connected.

  The constant velocity universal joint 11 is configured as, for example, a sliding type constant velocity universal joint, and includes an outer ring 11a as an outer joint member, an inner ring 11b as an inner joint member, and a plurality of rollers disposed on the inner ring 11b. 11c.

  The outer ring 11a is formed, for example, in a bottomed cylindrical shape, and a rotating shaft part 11e to which the differential gear 5 is coupled is formed on the bottom part so as to protrude outward along the direction of the central axis Q3 of the outer ring 11a. A plurality of track grooves 11g are formed in the inner peripheral surface 11f of the outer ring 11a along the direction of the central axis Q3.

  The inner ring 11b is formed in a cylindrical shape, for example, and is disposed inside the outer ring 11a. A plurality of rotating shaft portions 11i that are paired with the track grooves 11f of the outer ring 11a are formed on the outer peripheral surface 11h of the inner ring 11b in the radial direction of the inner ring 11b (that is, the direction orthogonal to the central axis Q4 of the inner ring 11b). Yes. The end 7d side of the hollow drive shaft 7 is fitted and fixed concentrically in the center hole 11j of the inner ring 11b.

  Each roller 11c is rotatably disposed on each rotation shaft portion 11i of the inner ring 11b, and is disposed in a track groove 11g of the outer ring 11a.

  With this configuration, in this constant velocity universal joint 11, the oblique angle between the central axis Q3 of the outer ring 11a and the central axis Q4 of the inner ring 11b is freely displaceable within a predetermined angle range, and the central axis Q3 of the outer ring 11a The inner ring 11b is attached to the outer ring 11a so that the central axis Q4 of the inner ring 11b can move in parallel with each other within a predetermined range in the direction of the central axis Q3. As a result, the constant velocity universal joint 11 can freely displace the oblique angle between the rotation shaft of the hollow drive shaft 7 and the rotation shaft of the differential gear 5 within a predetermined angle range, and the hollow drive shaft 7 and the differential gear 5. The hollow drive shaft 7 and the differential gear 5 are coupled so that the two can move in parallel with each other within a predetermined range in the direction of the central axis Q3.

  Each boot 13 and 15 is formed in a cylindrical shape by an elastic member (for example, rubber or a flexible member). The boot 13 (15) is fixed to the outer ring 9a (11a) of the constant velocity automatic joint 9 (11) in an outer fitting manner and to the hollow drive shaft 7 in an outer fitting manner. The small-diameter mounting portion 13b (15b) and the cylindrical bellows portion 13c (15c) integrally connecting the mounting portions 13a and 13b (15a and 15b). In the following description, the boot 13 on the drive wheel 3 side may be referred to as the outer boot 13, and the boot 15 on the differential gear 5 side may be referred to as the inner boot 15.

  Grease 19 is filled in each constant velocity automatic joint 9, 11 and each boot 13, 15.

  In the vehicle drive shaft 1, since the inside of the pressure adjusting chamber 7 c can be ventilated with the inside of the boot 13 through the gap inside the constant velocity universal joint 9, the internal pressure of the pressure adjusting chamber 7 c is always the boot 13. It becomes the same as the internal pressure.

<Method for setting the volume of the pressure adjusting chamber 7c>
First, before explaining the method of setting the volume of the pressure adjusting chamber 7c, a phenomenon in which the internal pressure of the conventional boot of the vehicle drive shaft becomes negative will be explained.

  FIG. 2A is a graph showing an example of a temporal change of the internal temperature t1 of the boot of the vehicle drive shaft, and is a graph common to the vehicle drive shaft 1 of this embodiment and the conventional vehicle drive shaft. It is. FIG. 2B is a graph showing an example of the time change of the internal pressure difference ps of the vehicle drive shaft boot. The solid line 20 shows the time change of the internal pressure difference ps of the conventional vehicle drive shaft boot. The dotted line 21 indicates the time change of the internal pressure difference ps of the boot 13 of the vehicle drive shaft 1 of this embodiment.

  The internal pressure difference ps is a pressure difference obtained by subtracting the external air pressure P (P = 100 [kPa (kilopascal)]) from the internal pressure p1 of the boot (ie, ps = p1−P), and ps> 0. At times, the internal pressure p1 of the boot is a positive pressure (that is, a pressure larger than the external atmospheric pressure), and when ps <0, the internal pressure p1 of the boot is a negative pressure.

  In the conventional vehicle drive shaft, the internal pressure difference ps of the boot changes with time as the internal temperature t1 of the boot changes with time, as indicated by the solid line 20 in FIG. For example, in the section A, the internal temperature t1 of the boot is initially normal temperature T (that is, the same temperature as the external air temperature, for example, 27 ° C.), and the internal pressure difference ps of the boot at this normal temperature T becomes 0. The internal temperature t1 of the boot rapidly rises due to frictional heat generated from the driving parts of the vehicle when the vehicle is traveling at high speed or when the steering angle is large. The internal pressure difference ps of the boot increases as the internal temperature t1 of the boot increases due to the sealing inside the boot. When the internal pressure difference ps of the boot becomes greater than or equal to the threshold pressure difference Pm (= 35 kPa, for example), the air inside the boot escapes to the outside.

  In the section B, when the internal temperature t1 of the boot reaches the saturation temperature T1 (that is, the maximum temperature that the internal temperature t1 of the boot can take due to heat generation of the driving parts of the vehicle, for example, 150 ° C.) and is saturated, the internal pressure of the boot The difference ps reaches the saturation pressure difference Pn (= 47 [kPa], for example), and the thermal expansion of the air inside the boot stops, but as long as the internal pressure difference ps of the boot is greater than or equal to the threshold pressure difference Pm, Since air continues to escape to the outside, the internal pressure difference ps of the boot decreases.

  In section C, when the internal pressure difference ps of the boot decreases to the threshold pressure difference Pm, the air inside the boot stops to escape to the outside.

  In section D, when the heat generation of the driving component suddenly decreases and converges to a value of 0 due to a vehicle stop or the like, the internal temperature t1 of the boot rapidly decreases and converges to room temperature T. Along with this, the internal pressure difference ps of the boot also rapidly decreases. At that time, due to a sudden decrease in the internal temperature t1 of the boot, the inhalation of air from the outside of the boot is not in time, and the internal pressure difference ps of the boot is the pressure difference (= Pn− Pm) converges to a negative value (that is, the internal pressure p1 of the boot becomes negative). In this way, the internal pressure p1 of the conventional vehicle drive shaft boot becomes negative.

  Next, a method for setting the volume of the pressure adjusting chamber 7c of this embodiment will be described.

  As described above, in the conventional vehicle drive shaft, when the internal temperature t1 of the boot is high (that is, any temperature exceeding the threshold temperature Tm corresponding to the threshold pressure difference Pm), the internal pressure difference ps of the boot is the threshold pressure. When the difference Pm is exceeded (that is, the internal pressure p1 of the boot exceeds the threshold pressure P ′ (= Pm + P)), the internal temperature t1 of the boot is changed to room temperature T. When the pressure falls, the internal pressure difference ps of the boot becomes negative (that is, the internal pressure p1 of the boot becomes negative).

  In view of this, in this embodiment, in order to prevent the internal pressure p1 of the boot 13 from becoming a negative pressure, the internal pressure p1 of the boot 13 is the threshold pressure P ′ when the internal temperature t1 of the boot 13 is high. (That is, the internal pressure p1 of the boot 13 does not exceed the threshold pressure P ′ when the internal temperature t1 of the boot 13 is the saturation temperature T1), the volume of the pressure adjusting chamber 7c is set.

  Here, for convenience of calculation, first, consider a case where the volume of the pressure adjusting chamber 7c is set so that the internal pressure p1 of the boot 13 becomes the threshold pressure P ′ when the internal temperature t1 of the boot 13 is the saturation temperature T1. .

  In this case, as shown in FIG. 3, when the volume of the boot 13 is V1 and the volume of the pressure adjusting chamber 7c is V2, when the internal temperature t1 of the boot 13 is normal temperature T, the internal temperature of the pressure adjusting chamber 7c. t2 is also normal temperature T, and the internal pressure p1 of the boot 13 and the internal pressure p2 of the pressure adjusting chamber 7c are both equal to the atmospheric pressure P. When the internal temperature t1 of the boot 13 is the saturation temperature T1, the internal temperature t2 of the pressure adjusting chamber 7c becomes the temperature T2, and both the internal pressure p1 of the boot 13 and the internal pressure p2 of the pressure adjusting chamber 7c are the threshold pressure P. 'become. FIG. 3 is a diagram illustrating an example of the internal pressure, volume, and internal temperature of the boot 13 and the pressure regulation chamber 7c when the internal temperature t1 of the boot 13 is normal temperature T and the saturation temperature T1.

  When the Boyle's law is applied to the air inside each of the boot 13 and the pressure adjusting chamber 7c between the normal temperature and the saturation temperature, the relationship of Equation 1 is established.

  That is, in order for the internal pressure p1 of the boot 13 to become the threshold pressure P ′ when the internal temperature t1 of the boot 13 is the saturation temperature T1, the volume V2 of the pressure adjusting chamber 7c is related to the volume V1 of the boot 13 by the equation (1). It may be set so as to hold.

  Therefore, in order for the internal pressure p1 of the boot 13 not to exceed the threshold pressure P ′ when the internal temperature t1 of the boot 13 is the saturation temperature T1, the volume V2 of the pressure adjustment chamber 7c is between the volume V1 of the boot 13 and What is necessary is just to set so that the relationship of Formula 2 may be materialized.

  In Formula 2, for example, T1 = 150 + 273 [K] = 423 [K], T = T2 = 27 + 273 [K] = 300 [K], P = 100 [kPa] (Note that the atmospheric pressure P is exactly 101. 3 [kPa], but simply set to 100 [kPa]) and P ′ = 135 [kPa], V2 / V1 ≧ 0.121. That is, when the internal temperature t2 of the pressure adjusting chamber 7c is t2 = T2 = 300 [K] (= 27 [° C.]), the volume V2 of the pressure adjusting chamber 7c is 12.1% or more of the volume V1 of the boot 13. If the size is set, the internal pressure p1 of the boot 13 is prevented from becoming a negative pressure even if the internal temperature t1 of the boot 13 suddenly decreases after rising to a high temperature.

  As can be seen from the above description, the threshold pressure P ′ is a threshold pressure inside the boot 13 at which air escape from the inside of the boot 13 occurs. The normal temperature T is the internal temperature of the boot 13 when the internal pressure p1 of the boot 13 becomes equal to the atmospheric pressure P. The normal temperature T is, for example, 27 ° C., but is not limited to this value. Any value can be used as long as the internal temperature t1 of the boot 13 when the internal pressure p1 of the boot 13 becomes equal to the atmospheric pressure P. Good. The saturation temperature T1 is the saturation temperature inside the boot 13. The saturation temperature T1 varies depending on the usage environment of the vehicle drive shaft 1. The temperature T2 is the internal temperature t2 of the pressure adjusting chamber 7c when the internal temperature t1 of the boot 13 is the saturation temperature T1.

<Main effects>
According to the vehicle drive shaft 1 configured as described above, since the relationship of Equation 2 is established between the volume V1 of the boot 13 and the volume V2 of the pressure adjusting chamber 7c, the internal temperature t1 of the boot 13 is high. Even if it suddenly decreases after rising up to, the internal pressure p1 of the boot 13 can be prevented from becoming negative. Thereby, it is possible to prevent wear at the bellows portion of the boot 13 and irreversible deformation of the boot 13 due to the negative internal pressure p1 of the boot 13.

<< Modification 1 >>
This modification is obtained by changing the shape of the pressure adjustment chamber 7c in the first embodiment. Hereinafter, based on FIG. 4, this modified example will be described with a focus on differences from the first embodiment, and the same components as those of the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  FIG. 4 is a schematic cross-sectional view of a vehicle drive shaft according to this modification.

  As shown in FIG. 4, the shape of the pressure adjustment chamber 7e of this modification is such that the diameter D2 of a portion (hereinafter referred to as a small diameter portion) 7g overlapping the constant velocity universal joint 9 and the boot 13 in the pressure adjustment chamber 7e. The constant velocity universal joint 9 and the portion that does not overlap the boot 13 (hereinafter referred to as a large diameter portion) 7f are formed to be smaller than the diameter D1. That is, the pressure adjusting chamber 7e is composed of a large diameter portion 7f and a small diameter portion 7g having a diameter D2 smaller than the diameter D1 of the large diameter portion 7f and communicating the large diameter portion 7f and the opening 7b. . In addition, the other component part of this modification is comprised similarly to 1st Embodiment.

  Note that, in this modification as well, Expressions 1 and 2 of the first embodiment are valid.

  According to the vehicle drive shaft 1B configured as described above, the diameter D2 of the small-diameter portion 7g overlapping the constant velocity universal joint 9 and the boot 13 in the pressure adjustment chamber 7e is equal to that of the constant velocity universal joint 9 and the boot 13. Since it is formed smaller than the diameter D1 of the large-diameter portion 7f that does not overlap, (a) the internal temperature of the pressure adjusting chamber 7e can be hardly affected by the heat from the constant velocity universal joint 9 and the boot 13. Thereby, even when the internal temperature of the boot 13 is high, the internal temperature of the pressure adjusting chamber 7e can be easily maintained at room temperature. (B) Further, the end 7a side of the hollow drive shaft 7 may be slightly reduced in diameter due to the provision of the constant velocity universal joint 9 and the boot 13, but even in such a case, the hollow drive shaft 7 The pressure adjusting chamber 7e can be formed while securing a sufficient wall thickness around the small diameter portion 7g.

<< Modification 2 >>
In the first embodiment, the case where the internal pressure of the boot 13 (that is, the outer boot 13) is prevented from being negative is described. However, in this modification, the inside of the boot 15 (that is, the inner boot 15) is described. The case where the pressure is prevented from becoming negative will be described. Hereinafter, based on FIG. 5, this modified example will be described with a focus on differences from the first embodiment, and the same components as those of the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  FIG. 5 is a schematic cross-sectional view of a vehicle drive shaft according to this modification.

  In the first embodiment, as shown in FIG. 1, an opening 7b is formed at the end 7a of the hollow drive shaft 7 on the drive wheel 3 side, and the pressure adjusting chamber 7c communicates with the opening 7b so as to communicate with the hollow drive. In this modification, as shown in FIG. 5, an opening 7h is formed in the end 7d of the hollow drive shaft 7 on the differential gear 5 side, and the pressure adjusting chamber 7i is formed in the opening 7h. 7 h is formed in the hollow drive shaft 7.

  In this modification as well, a breathable filter 18 similar to the breathable filter 17 of the first embodiment is disposed at the end 7d of the hollow drive shaft 7 so as to cover the opening 7h. In addition, the other component part of this modification is comprised similarly to 1st Embodiment.

  Also in this modified example, when the volume of the boot 15 is V1 ', the relationship of Expression 3 is established as in Expression 2. That is, if the volume V2 of the pressure adjusting chamber 7i is set so as to satisfy the expression 3 with respect to the volume V1 ′ of the boot 15, even if the internal temperature of the boot 15 suddenly decreases after rising to a high temperature, the boot 15 Is prevented from becoming negative pressure.

  According to the vehicle drive shaft 1C configured as described above, the opening 7h is formed at the end 7d of the hollow drive shaft 7, and the air permeable filter 18 is formed covering the opening 7h. Since the pressure adjusting chamber 7i is formed in the hollow drive shaft 7 in communication with the opening 7h, it is possible to prevent the internal pressure of the inner boot 15 from becoming a negative pressure.

<< Modification 3 >>
In this modification, in the first embodiment, the pressure adjustment chamber 7c prevents the internal temperatures of both the boots 13 and 15 from becoming negative pressure. Hereinafter, based on FIG. 6, this modified example will be described with a focus on differences from the first embodiment, and the same components as those of the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  FIG. 6 is a schematic cross-sectional view of a vehicle drive shaft according to this modification.

  In this modified example, as shown in FIG. 6, the end portion 7a of the hollow drive shaft 7 is formed with an opening 7b and covers the opening 7b in the same manner as in the first embodiment. 17 is disposed. In addition, an opening 7h is formed at the end 7d of the hollow drive shaft 7, and a breathable filter 18 is disposed so as to cover the opening 7h. The hollow drive shaft 7 is formed with a pressure adjusting chamber 7j so as to communicate with the openings 7b and 7h. In addition, the other component part of this modification is comprised similarly to 1st Embodiment.

  In this modification, for example, the volumes of the boots 13 and 15 are set to the same volume V1, and the changes in the internal temperature of the boots 13 and 15 change in the same way (therefore, accordingly) When the internal temperature of the boot 13 is the saturation temperature T1, the internal temperature of the boot 15 is also the saturation temperature T1). In this case, Formula 4 which is a formula in which V1 is replaced with 2 · V1 in Formula 2 of the first embodiment is established.

  That is, in this case, if the volume V2 of the pressure adjusting chamber 7j is set so as to satisfy Equation 4 with respect to the volume V1 of the boots 13 and 15, the internal temperature of the boots 13 and 15 rises to a high temperature. Even if it suddenly drops, the internal pressure of each boot 13, 15 is prevented from becoming negative.

  According to the vehicle drive shaft 1D configured as described above, it is possible to prevent the internal pressure of each of the boots 13 and 15 from becoming a negative pressure by one pressure adjusting chamber 7j.

≪Attached matters≫
As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to such an example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

  Further, it is understood that the invention combining any of the first embodiment and the first to third modifications belongs to the technical scope of the present invention.

  The present invention is most suitable for application to a vehicle drive shaft in which a connecting portion between a hollow drive shaft and a constant velocity universal joint is covered with a boot.

DESCRIPTION OF SYMBOLS 1 Vehicle drive shaft 7 Hollow drive shaft 7a One end part 7b Opening part 7c Pressure adjustment chamber 9 Constant velocity universal joint 13 Boot 17 Breathable filter 19 Grease P External pressure P 'Threshold pressure T Room temperature T1 Saturation temperature T2 Internal temperature of boot 13 Temperature inside the pressure adjustment chamber when is at the saturation temperature T

Claims (1)

A hollow drive shaft having an opening at one end and a pressure adjusting chamber communicating with the opening inside;
A constant velocity universal joint connected to the one end of the hollow drive shaft;
A boot that covers a connecting portion between the hollow drive shaft and the constant velocity universal joint and is filled with grease;
An air-permeable filter that covers the opening and is disposed at the one end and allows passage of air while restricting passage of the grease;
In a vehicle drive shaft with
2. The vehicle drive shaft according to claim 1, wherein a relationship of Formula 2 is established between a volume V1 of the boot and a volume V2 of the pressure adjusting chamber.

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