JP2010181016A - Universal coupling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure effectively preventing intrusion of foreign matters in an external space into an internal space 25. <P>SOLUTION: The end of the radial seal lip 18a of a seal ring 15a is formed into a forked shape, and includes a pair of axially separated seal edges 27a, 27b. The volume of a sealed space 29 existing between both the seal edges 27a, 27b and having an inside diameter side closed by the peripheral surface of a shaft portion 12 is set equal to or larger than a variation with the volume of the internal space 25 cut off from the external space by the seal ring 15a changed with the fact that the shaft portion 12 and a bearing cup 11 are axially relatively displaced. With this structure, the foreign matters sucked from the external space into the sealed space 29 when the internal space 25 is enlarged are kept within the sealed space 29. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an improvement in a universal joint used in a state where it is incorporated in a steering device of an automobile, for example, to transmit the movement of a steering shaft to a steering gear. Specifically, with respect to the structure in which the surface is coated for corrosion prevention or the like, the sealing performance is prevented from being deteriorated due to a minute step existing at the end of the coating film.

  The steering apparatus for an automobile is configured as shown in FIG. 8 as described in, for example, Patent Documents 1 and 2. The movement of the steering wheel 1 operated by the driver is transmitted to the input shaft 6 of the steering gear unit 5 through the steering shaft 2, the universal joint 3, the intermediate shaft 4, and another universal joint 3. A pair of left and right tie rods 7 and 7 are pushed and pulled by a rack and pinion mechanism built in the steering gear unit 5, and the operation amount of the steering wheel 1 is applied to a pair of left and right steering wheels (generally, front wheels). Depending on the situation, an appropriate rudder angle is provided.

  In general, a cross joint called a cardan joint is widely used as a universal joint incorporated in such a steering apparatus. 9 to 10 show an example of a universal joint that has been widely known so far, as described in Patent Documents 1 and 2 above. The structure shown in FIGS. 9 to 10 is a so-called vibration-proof joint that prevents transmission of vibration, but the universal joint that is the subject of the present invention does not necessarily have to have a vibration-proof structure. Therefore, in the following description, the structure of the main body portion of the universal joint 3 will be described with the vibration-proof structure omitted.

  The universal joint 3 includes a pair of yokes 8a and 8b each formed in a bifurcated shape by a metal material having sufficient rigidity, and a cross shaft 9 made of a hard metal such as an alloy steel such as bearing steel. Consists of Concentric holes 10 and 10 are formed at both ends of each of the yokes 8a and 8b. And in these circular holes 10 and 10, bearing cups 11 and 11 made of a hard metal plate material such as bearing steel and case-hardened steel are formed in a state where the openings face each other. It is fitted and fixed. The cross shaft 9 has a shape such that the middle portions of the pair of column portions are orthogonal to each other, and has four shaft portions 12 and 12 each having a cylindrical shape. In other words, the base end portions of the shaft portions 12 and 12 are fixedly coupled to four positions at equal intervals in the circumferential direction of the coupling base portion 13 provided in the center portion. The central axes of these shaft portions 12 and 12 exist on the same plane.

  The axial direction intermediate part thru | or the front-end | tip part of each such shaft part 12 and 12 are inserted in each said bearing cup 11 and 11. FIG. Further, radial bearings 14, 14 such as needle bearings are provided between the inner peripheral surfaces of the bearing cups 11, 11 and the front half outer peripheral surfaces of the shaft portions 12, 12. The yokes 8a and 8b are oscillated and displaced with a light force. Due to such a configuration, even when the central axes of the yokes 8a and 8b do not coincide with each other, the rotational force can be transmitted between the yokes 8a and 8b with little transmission loss.

  Of the universal joints 3 and 3 as described above, in the case of the universal joint 3 installed on the outside of the passenger compartment (lower side in FIG. 8), the base ends of the shaft portions 12 and 12 constituting the cross shaft 9. Seal rings 15 and 15 are provided between the portion (the end portion on the coupling base 13 side) and the opening of each of the bearing cups 11 and 11, respectively. The seal rings 15 and 15 prevent muddy water and the like from entering the installed portions of the radial bearings 14 and 14, thereby ensuring the durability of the universal joint 3. Each of the seal rings 15, 15 is formed by reinforcing an elastic material 17 with a cored bar 16. Of these, the metal core 16 is formed in an annular shape with an L-shaped cross section by a metal plate such as a mild steel plate. The elastic member 17 is made of an elastomer such as rubber, covers the core 16 over the entire circumference, and has a pair of seal lips 18 and 19 including a radial seal lip 18 and a thrust seal lip 19. .

  Each of the seal rings 15 and 15 having such a structure is formed by tightening a base portion embedded with the core metal 16 on a base end portion of each of the shaft portions 12 and 12 (part of the elastic material 17). By being externally fitted (in a state of being elastically deformed), the base end portions of the shaft portions 12 and 12 are supported in a state in which the sealing performance of the fitting portions is ensured. In this manner, the seal rings 15 and 15 are supported on the base end portions of the shaft portions 12 and 12, and the seal lips 18 are combined with the cross shaft 9 and the bearing cups 11 and 11. 19, the seal edge of the radial seal lip 18 is elastically abutted over the entire periphery of the outer peripheral surface of each of the bearing cups 11 and 11 toward the end near the opening. Further, the seal edge of the thrust seal lip 19 is elastic over the entire circumference on the outer surface of the inward flange portion 20 formed in the opening of each of the bearing cups 11 and 11 (the surface facing the coupling base portion 13). Abut.

  Furthermore, the axial direction of each said shaft part 12 and 12 in the state which opened the bottomed insertion hole 21 and 21 in the center part of each said shaft part 12 and 12 at the front end surface of these each shaft part 12 and 12, respectively. Is formed. Then, synthetic resin pins 22 and 22 are inserted inside these insertion holes 21 and 21, respectively. The pins 22 and 22 are stretched between the bearing cups 11 and 11 and the shafts 12 and 12, so that the distance between the opening end of the bearing cups 11 and 11 and the base 13 is increased. Preventing it from shrinking too much. Then, the thrust seal lip 19 of each of the seals 15 and 15 is prevented from being excessively compressed, and conversely, the amount of compression is not excessively reduced. That is, when the universal joint 3 is used, the thrust load acting side (anchor side) seal ring 15 is excessively compressed on the basis of the thrust load applied between the cross shaft 9 and the bearing cups 11, 11. Is prevented, and the amount of compression of the seal ring 15 on the opposite side (anti-anchor side) is excessively reduced, thereby preventing the sealing performance of the seal ring 15 from being impaired. Each of the pins 22 and 22 supports the thrust load as described above while elastically deforming in the axial direction. The above-described seal rings 15 and 15 can be obtained without particularly increasing the dimensional accuracy and assembly accuracy of the constituent members 8a, 8b, 9, 11, and 15 of the universal joint 3 due to the change in the axial dimension due to the elastic deformation. The amount of compression can be kept within the proper range.

  However, a cross shaft type universal joint that does not have the pins 22 and 22 as described above has been widely known, for example, as described in Patent Documents 3 to 4. FIG. 11 shows the structure of a universal joint described in Patent Document 4 among them. In the case of this second example of the conventional structure, the ridges 24, 24 are formed on the portion near the center of the inner surface of the bottom 23 of the bearing cup 11a, and the tip edges of these ridges 24, 24 are the shaft portions constituting the cross shaft. It is made to contact | abut to the 12 front end surface. Even with such a structure, the compression amount of the seal ring 15 (see FIG. 10) provided between the bearing cup 11a and the shaft portion 12 can be reduced as long as the dimensional accuracy and assembly accuracy of the components of the universal joint are ensured. It can be kept in the aptitude range.

  In any structure, the amount of insertion of the shaft portion 12 into the bearing cups 11 and 11a changes during operation of the universal joint. As the amount of insertion changes, the radial bearing 14 is installed between the inner surfaces of the bearing cups 11 and 11 and the outer surface of the shaft portion 12, and is cut off from the external space by the seal ring 15. The atmospheric pressure in the internal space 25 is changed. That is, as described above, a thrust load is applied between the cross shaft 9 and each bearing cup 11 when the universal joint 3 is used. Then, the amount of elastic deformation of each constituent member based on this thrust load and the amount of insertion of the shaft portion 12 into the bearing cups 11 and 11a change. Such a change in the amount of insertion becomes remarkable in the case of the structure provided with the pins 22 and 22 as shown in FIG. 10, but also in the case of the structure as shown in FIG. 11, the bottom 23 of the bearing cup 11a and the like. Occurs with elastic deformation. In any case, the atmospheric pressure in the internal space 25 that is blocked from the external space by the seal ring 15 changes. At the same time as the atmospheric pressure changes, the leading edge of the radial seal lip 18 displaces the outer peripheral surfaces of the bearing cups 11 and 11a in the axial direction.

  For example, when the amount of insertion of the shaft portion 12 into the bearing cups 11 and 11a is reduced (changes in the extraction direction), the atmospheric pressure in the internal space 25 is reduced and the radial seal lip 18 is The bearing cups 11 and 11a are displaced in the direction of arrow A in FIG. At this time, depending on the attitude of the bearing cups 11 and 11a, foreign matter such as muddy water adhering to the outer peripheral surface of the bearing cups 11 and 11a may be the leading edge of the radial seal lip 18 as indicated by the arrow b. And the bearing cup 11, 11 a through the rubbing portion of the outer peripheral surface, and is sucked into the space 26 existing between the radial seal lip 18 and the thrust seal lip 19 and collected in the space 26. there is a possibility. Thus, the foreign matter accumulated in the space 26 during this time, when the atmospheric pressure in the internal space 25 is lowered next, as shown by the arrow C, the leading edge of the thrust seal lip 19 and the inward flange 20 There is a possibility of passing through the rubbing portion with the outer surface and entering the internal space 25. If foreign matter enters the internal space 25, the rolling contact portion of the radial bearing 14 is damaged, and the durability of the universal joint is reduced.

  Patent Document 5 describes a structure that improves the contact state between the seal edge of the thrust seal lip and the inward flange of the bearing cup by forming an annular groove at the tip of the thrust seal lip. By adopting such a structure, it is possible to prevent foreign matter accumulated in the space 26 from further entering the internal space 25. However, in the state in which foreign matter has accumulated in the space 26 during this period, even if the sealing performance of the thrust seal lip is improved, it is sufficient that the foreign matter enters the internal space 25 with use over a long period of time. It is difficult to prevent.

Japanese Patent Application Laid-Open No. 8-135684 Japanese Patent Laid-Open No. 9-60650 JP-A-6-280890 JP 7-208492 A JP 2006-29551 A

  The present invention has been invented to realize a structure capable of effectively preventing foreign matters existing in the external space from entering the internal space in view of the circumstances as described above.

The universal joint of the present invention is a pair of yokes, four circular holes, four bearing cups, a cross shaft, and four sets of radial bearings, similar to the previously known universal joints. And four seal rings.
Each of the pair of yokes is formed in a bifurcated shape.
The circular holes are concentrically formed at both ends of the yokes.
Each of the bearing cups has a bottomed cylindrical shape, and is fitted and fixed inside the circular holes with the openings facing each other.
Further, the cross shaft is formed by radially fixing four shaft portions on the outer peripheral surface of the coupling base portion, and these shaft portions are inserted into the bearing cups and combined with the yokes. Yes.
Each radial bearing is provided between the inner peripheral surface of each bearing cup and the outer peripheral surface of each shaft portion.
The seal rings are provided between the base end portions of the shaft portions and the opening portions of the bearing cups, with the base portions fitted and supported on the base end portions of the shaft portions. It has been.
Each of the seal rings includes a radial seal lip that is in contact with the entire end of the outer peripheral surface of each of the bearing cups over the entire periphery, and an outer surface of an inward flange provided at the open end of the bearing cup. And a thrust seal lip that contacts the entire circumference.

  In particular, in the universal joint of the present invention, each of the radial seal lips has a pair of seal edges that are bifurcated at the tip and spaced apart in the axial direction. And the volume of the sealed space that exists between these seal edges and the inner diameter side is closed by the outer peripheral surface of the bearing cup, the volume of the internal space that is blocked from the external space by the seal rings, The amount of change (decrease amount, increase amount) or more that changes as the shaft portion and the bearing cup are relatively displaced from the neutral state is set.

  When implementing such a universal joint of the present invention, preferably, as in the invention described in claim 2, the amount of change in the volume of the internal space due to the relative displacement between the shaft portion and the bearing cup is determined geometrically. The amount of change in the volume of the internal space is less than or equal to that obtained from a scientific viewpoint. The amount of reduction in the volume of the internal space that is geometrically required is that the shaft portion is equal to the minimum thickness of the gap existing between the tip end surface of the shaft portion and the bottom inner surface of the bearing cup in the neutral state. This is a volume determined as the product of the minimum thickness and the cross-sectional area of the shaft when it is assumed that it has entered the bearing cup.

  However, the volume of the sealed space can be secured more than the maximum change amount of the volume of the internal space. That is, the change in volume of the internal space based on the total stroke in which the shaft portion is displaced in the axial direction with respect to the bearing cup {total amount of displacement (decrease amount, increase amount) displaced in both directions around the neutral position} The volume of the sealed space can be secured more than the amount. However, it is useless to increase the volume of the sealed space so as to greatly exceed the volume change amount of the internal space based on the entire stroke. In other words, the maximum value of the volume of the sealed space can be regulated by the volume change amount based on the entire stroke.

  According to the universal joint of the present invention configured as described above, foreign matter existing in the external space enters the space existing between the radial seal lip and the thrust seal lip beyond the radial seal lip. Can be prevented. That is, when the atmospheric pressure in the internal space is reduced due to the relative displacement in the axial direction between the bearing cup and the shaft portion, foreign matter such as muddy water existing in the external space is caused by the leading edge of the radial seal lip and the outer periphery of the bearing cup. There is a possibility of being sucked through a contact portion (sliding contact portion) with the surface. In the case of the present invention, the foreign matter sucked in this way stops in the sealed space existing between the pair of seal edges constituting the radial seal lip, and does not enter the space. . For this reason, the foreign matter does not enter the inner space which is further in the interior of the space, preventing the radial bearing installed in the inner space from being damaged and improving the durability of the universal joint.

[First example of embodiment]
1 to 3 show a first example of an embodiment of the present invention. The feature of the present invention including this example is related to the axial displacement between the shaft portion 12 of the cross shaft 9 and the bearing cup 11 fitted in the circular hole 10 of the yoke, which occurs during the operation of the universal joint. In this structure, foreign matter existing in the external space is prevented from entering the interspace 26, and this foreign matter is effectively prevented from reaching the internal space 25. The structure and operation of other parts are the same as those of the first example of the conventional structure shown in FIGS. 9 to 10 or the second example of the conventional structure shown in FIG. In addition, the description will be omitted or simplified, and the following description will focus on the features of the present invention.

Between the base end portion (the lower end portion in FIGS. 1 and 2) of the shaft portion 12 and the opening side end portion (the lower end portion in FIGS. 1 and 2) of the bearing cup 11, from the core metal 16 and the elastic material 17a. A seal ring 15a is provided. The elastic member 17 a has a pair of seal lips 18 a and 19 including a radial seal lip 18 a and a thrust seal lip 19. Of these, the radial seal lip 18a is formed with a bifurcated tip, and has a pair of seal edges 27a, 27b spaced apart in the axial direction. That is, the thickness of the tip of the radial seal lip 18a is made larger than the thickness of the tip of the radial seal lip 18 having the conventional structure shown in FIG. The concave groove 28 opened to the inner peripheral surface side is formed over the entire circumference. The both sides of the concave groove 28 are the seal edges 27a and 27b, respectively. Both the seal edges 27a and 27b are separated by L _{27 in} the axial direction. Therefore, in the state where the seal ring 15a is assembled between the shaft portion 12 and the bearing cup 11, an inner diameter side opening is formed at the outer peripheral surface of the bearing cup 11 between the seal edges 27a and 27b. A sealed space 29 having a volume commensurate with the cross-sectional area of the concave groove 28, which is closed by the above, is defined. On the other hand, the thrust seal lip 19 is the same as the conventional structure described above, and its seal edge is in contact with the outer surface of the inward flange portion 20 formed on the bearing cup 11 over the entire circumference.

  The volume of the sealed space 29 is regulated by the relationship with the amount of change in the volume of the internal space 25 based on the thrust load applied between the shaft portion 12 and the bearing cup 11 as the universal joint is used. That is, when the universal joint is used, the shaft portion 12 and the bearing cup 11 reciprocate in the axial direction centered on the neutral position as assembled, based on the thrust load applied in both directions during one rotation. Moving. And the volume of the said internal space 25 expands / contracts with this reciprocation. That is, when the shaft portion 12 is displaced in the direction in which it is pushed into the bearing cup 11, the volume of the internal space 25 decreases and the pressure in the internal space 25 increases. Conversely, when the shaft portion 12 is displaced in the direction in which it is pulled out from the bearing cup 11, the volume of the internal space 25 increases and the pressure in the internal space 25 decreases.

When the pressure in the internal space 25 increases, the air in the internal space 25 tends to be discharged to the external space. Conversely, when the pressure in the internal space 25 decreases. The air tends to be sucked into the internal space 25 from the external space. In the state where air tends to be sucked into the internal space 25 in this way, if foreign matter adheres to the outer peripheral surface of the bearing cup 11 and the tip edge of the radial seal lip 18a abuts, There is a possibility that the foreign matter is sucked toward the internal space 25. When foreign matter is sucked in this way, the foreign matter first passes through a contact portion between the seal edge 27a on the distal end side and the outer peripheral surface of the bearing cup 11, and is defined by the concave groove 28. It enters the sealed space 29. In the case of this example, the volume V ₂₉ of the sealed space 29 is set to a change amount ΔV ₂₅ or more (V ₂₉ ≧ Δ) of the volume of the internal space 25 due to the relative displacement between the shaft portion 12 and the bearing cup 11. V ₂₅ ).

Incidentally, as this variation △ V ₂₅ of the volume of the internal space 25, it can be considered four types shown in the following (1) to (4). Which one is adopted is selected by design in consideration of the required foreign matter intrusion prevention performance. The obtained foreign matter intrusion prevention performance is generally excellent in the order of (1) → (2) → (3) → (4). However, the order of (1) (3) and (2) (4) will not be reversed, but the order of (1) (2), the order of (2) (3), (3) (4 ) May be reversed depending on the size and rigidity of each part. Therefore, it is necessary to secure at least the following (1) or (2) or more for the change amount ΔV ₂₅ . On the other hand, it is useless to secure this amount of change ΔV ₂₅ beyond (4) or (3). The maximum value of the volume V ₂₉ of the sealed space 29 is limited to a range where the tip of the radial seal lip 18a does not interfere with the arm portion of the yoke.

(1) With respect to the structure shown in FIGS. 1 and 2, the bearing cup 11 and the shaft portion 12 are relative to each other in the axial direction from the neutral state based on elastic deformation of the pin 22, the bearing cup 11, and the seal ring 15a. The amount of change ΔV ₂₅ that changes with the displacement.
(2) With respect to the structure shown in FIG. 2, in the neutral state, the bearing cup 11 has a minimum thickness T ₃₀ of the gap 30 existing between the tip end surface of the shaft portion 12 and the inner surface of the bottom portion 23a of the bearing cup 11. And a change amount ΔV ₂₅ 2 that changes as the shaft portion 12 is relatively displaced in the axial direction from the neutral state.
(3) The shaft portion 12 is axially moved with respect to the bearing cup 11 based on twice the amount of change ΔV ₂₅ 1 defined in (1) above, that is, based on the elastic deformation of the members 22, 11, 15 a. The amount of change ΔV ₂₅ 3 based on the entire stroke displaced to (= ΔV ₂₅ 1 × 2).
(4) Change based on the full stroke in which the shaft portion 12 is displaced in the axial direction with respect to the bearing cup 11 based on twice the amount of change ΔV ₂₅ 2 defined in (2) above, that is, on the gap 30. Amount ΔV ₂₅ 4 (= ΔV ₂₅ 2 × 2).

Among the above (1) to (4), the reason for setting the variation ΔV ₂₅ 1 defined in (1) is as follows. The amount of change ΔV ₂₅ 1 is ½ (half amplitude) of the relative displacement amount in the axial direction between the bearing cup 11 and the shaft portion 12 based on the elastic deformation of the members 22, 11, 15 a, It is obtained as the product of the cross-sectional areas of the shaft portion 12. When the universal joint is used, the shaft portion 12 and the bearing cup 11 are relatively displaced in the axial direction based on a thrust load applied between the members 12 and 11. This relative displacement is caused by the rigidity in the thrust direction of the synthetic resin pin 22 provided between the shaft portion 12 and the bearing cup 11, the rigidity in the thrust direction (of the bottom 23a) of the bearing cup 11, and the seal ring. This is done against the rigidity in the thrust direction of 15a. Then, the amount of elastic deformation of each member 11, 15a, 22 existing on the front side in the displacement direction of the cross shaft 9 is increased, and the amount of elastic deformation of each member 11, 15a, 22 also present on the rear side is decreased. The rigidity of each of the members 11, 15a, and 22 and the thrust load can be obtained by calculation or experiment. Therefore, the relative displacement amount (maximum value) in the axial direction between the bearing cup 11 and the shaft portion 12 that occurs when the universal joint is used can also be obtained by calculation or experiment. Then, if the relative displacement amount is known, the change amount ΔV ₂₅ 1 is calculated by the product of the relative displacement amount and the cross-sectional area of the shaft portion 12 (of which the portion exists on the inner diameter side of the seal ring 15a). Desired.
Then, if the volume V ₂₉ of the sealed space 29 is ensured by this change amount ΔV ₂₅ 1 or more (V ₂₉ ≧ ΔV ₂₅ 1), the bearing cup 11 and the shaft portion 12 are relatively moved in the axial direction from the neutral state. Even if the foreign matter passes through a contact portion between the seal edge 27 a on the distal end side and the outer peripheral surface of the bearing cup 11, the foreign matter is completely contained in the sealed space 29.

Among the (1) to (4), the reason for setting the change amount ΔV ₂₅ 2 defined in (2) is as follows. The amount of change ΔV ₂₅ 2 is obtained as the product of the minimum thickness T ₃₀ of the gap ₃₀ and the cross-sectional area of the shaft portion 12.
When the universal joint is used, the shaft portion 12 and the bearing cup 11 are relatively displaced in the axial direction. The displacement in the direction in which the shaft portion 12 enters the bearing cup 11 is theoretically the shaft portion 12. This is possible until the front end surface of the bearing abuts against the inner surface of the bottom 23a of the bearing cup 11. The actual case, before the front end surface of the above by the minimum thickness T ₃₀ of the gap 30 (if the minimum thickness T ₃₀ is large) the shaft portion 12 abuts the inner surface of the bottom portion 23a, the pin In some cases, the tension force of 22 becomes larger than the thrust load generated with the use of the universal joint, and the tip surface of the shaft portion 12 does not contact the inner surface of the bottom portion 23a.
Conversely, if the minimum thickness T ₃₀ is small, between bracing force of the pin 22 is smaller than the thrust load, even if the inner surface of the front end surface and the bottom 23a of the shaft portion 12 is in contact Conceivable. In such a case, there is room for the shaft portion 12 to be displaced in the direction of entering the bearing cup 11 based on the elastic deformation of the bottom portion 23a. However, the contact portion between the tip end surface of the shaft portion 12 and the inner surface of the bottom portion 23a is a portion of the bottom portion 23a near the outer diameter having high rigidity. For this reason, the amount of displacement based on the elastic deformation as described above is negligible and almost negligible.
Considering the above, the volume V ₂₉ of the sealed space 29 existing between the seal edges 27 a and 27 b is set between the tip surface of the shaft portion 12 and the inner surface of the bottom portion 23 a of the bearing cup 11. if the amount of change is the product of the cross-sectional area of the existence minimum clearance 30 thickness T ₃₀ and the shaft portion 12 for △ V ₂₅ 2 or more _{(V 29 ≧ △ V 25 2} ) secured, the bearing cup 11 and the shaft Even if the portion 12 is relatively displaced in the axial direction from the neutral state and the foreign matter passes through the contact portion between the seal edge 27a on the distal end side and the outer peripheral surface of the bearing cup 11, the foreign matter is not sealed. Fits in the space 29. Further, even when the pin 22 is bent, the entry of the foreign matter can be prevented.

Among the (1) to (4), the reason for setting the change amount ΔV ₂₅ 3 defined in (3) is as follows. When the universal joint is used, the shaft portion 12 and the bearing cup 11 are relatively displaced by the same amount on both sides in the axial direction with the neutral position as the center. At the moment when the volume of one of the internal spaces 25 related to the pair of shaft portions 12 arranged coaxially with each other decreases, the volume of the other increases. That is, the internal space 25 repeats expansion and contraction while the universal joint rotates once. And the pressure in this internal space 25 falls at the time of expansion, and also rises at the time of contraction. When a long time has passed with the universal joint stopped while the volume of a certain internal space 25 is most contracted, the air in the internal space 25 is discharged to the outside space, and the volume of the internal space 25 is contracted the most. The possibility that the pressure of the internal space 25 is reduced to atmospheric pressure cannot be denied. In this way, a certain internal space 25 is in a state where the volume is most contracted and the universal joint is restarted from a state where the pressure is atmospheric pressure, and the volume of the internal space 25 is maximized. Then, the pressure in the internal space 25 decreases by an amount corresponding to the entire stroke. Therefore, in order to allow the foreign matter to be contained in the sealed space 29 even if the foreign matter passes through the contact portion between the seal edge 27a on the distal end side and the outer peripheral surface of the bearing cup 11 in such a state. , the volume V ₂₉ of the enclosed space 29, the (3) defines the amount of change in △ V ₂₅ 3 or more (V ₂₉ ≧ △ V ₂₅ 3) to secure. In other words, if it is not considered that the pressure in the internal space 25 escapes to the outside in a stopped state, the volume V _{29 of the} sealed space should be ensured by the change amount ΔV ₂₅ 1 or ΔV ₂₅ 2 or more. It is enough.

Wherein (1) of the - (4), (4) The reason for setting the amount of change △ V ₂₅ 4 as defined, in accordance with the reason for adopting the (2) defines the amount of change in △ V ₂₅ 2, This is because the change amount ΔV ₂₅ 3 defined in (3) above is adopted. That is, the pressure in the internal space 25 is changed by the total amount of the pair of gaps 30 existing on both sides of the pair of shaft portions 12 arranged coaxially with each other and the amount of displacement of the shaft portion 12 in the axial direction. This is because the foreign matter that has passed through the contact portion between the front end seal edge 27 a and the outer peripheral surface of the bearing cup 11 is accommodated in the sealed space 29 along with the change.

As described above, the change amount ΔV ₂₅ 1, ΔV ₂₅ 2, ΔV ₂₅ 3, ΔV in which the minimum value of the volume V ₂₉ of the sealed space 29 is regulated by the above (1) to (4). _The choice of 4 is determined by design in consideration of the required sealing performance. If the volume V ₂₉ of the sealed space 29 is too small, foreign matter that does not fit in the sealed space 29 can easily enter the space 26. On the other hand, if the volume V ₂₉ of the sealed space 29 is excessively large, the radial seal lip 18a becomes large, making it difficult to design for securing the installation space, or the radial seal lip 18a and the arm portion of the yoke. Interferes with each other and causes inconveniences such as deterioration in sealing performance by the radial seal lip 18a. Therefore, the volume V ₂₉ of the sealed space 29 has the smallest value of the change amounts ΔV ₂₅ 1 and ΔV ₂₅ 2 as the minimum value, and the volume V ₂₉ of the change amounts ΔV ₂₅ 3 and ΔV ₂₅ 4 The larger value is defined as the maximum value during this period, or to the extent that it is slightly larger than the larger value of the change amounts ΔV ₂₅ 3 and ΔV ₂₅ 4.

If the volume V ₂₉ of the sealed space 29 is set in the above range, the contact portion between the seal edge 27a on the distal end side and the outer peripheral surface of the bearing cup 11 while preventing the radial seal lip 18a from becoming large. The foreign matter that has passed through can be completely stored in the sealed space 29, and the foreign matter can be prevented from entering the space 26. For this reason, it is possible to effectively prevent the foreign matter from reaching the inner space 25 that exists deeper than the space 26 during this time, and to prevent damage to the radial bearing 14 installed in the inner space 25. The durability of the universal joint can be secured.

[Second Example of Embodiment]
FIG. 4 shows a second example of the embodiment of the present invention. In the case of this example, the shape of the synthetic resin pin 22a assembled between the bearing cup 11 and the shaft portion 12 is different from that of the first example of the above-described embodiment. The pin 22a incorporated in the structure of the present example includes a flange portion 31 having an outward flange shape at the distal end portion, and the flange portion 31 is abutted against the opening peripheral portion of the insertion hole 21 at the distal end surface of the shaft portion 12. ing. A protrusion 32 is formed at the center of the tip surface of the pin 22a. Further, the base end portion (the lower end portion in FIG. 4) of the pin 22 a has a small diameter and abuts against the center portion of the bottom surface of the insertion hole 21. In a neutral state in which a universal joint is assembled and no external force is applied, the protrusion 32 abuts against the center of the inner surface of the bottom portion 23a of the bearing cup 11, and the flange portion 31 and the inner surface of the bottom portion 23a pass through a minute gap. Separated from each other. On the other hand, when a thrust load is applied in the direction in which the shaft portion 12 is pushed into the bearing cup 11 along with the use of the universal joint, the amount of elastic deformation (compression amount) of the protrusion 32 increases. The flange 31 contacts the inner surface of the bottom 23a. In this state, the rigidity of the pin 22a in the thrust direction is improved.

  In short, in the structure of this example, the rigidity related to the force in the direction in which the shaft portion 12 is pushed into the bearing cup 11 changes in two stages. For this reason, in the structure of this example, the amount of the shaft portion 12 pushed into the bearing cup 11 based on the thrust load can be reduced while securing the buffering action by the pin 22a. Therefore, even if the volume of the sealed space 29 defined between the pair of seal edges 27a and 27b provided at the tip of the radial seal lip 18a is reduced, the volume is taken into the sealed space 29 from the external space. It is possible to prevent the foreign matter overflowing from the sealed space 29 and entering the interspace 26 side.

[Third example of embodiment]
5 to 6 show a third example of the embodiment of the present invention. This example relates to a structure that does not have a pin made of synthetic resin, and shows a case where the present invention is applied. The bearing cup 11b incorporated in the structure of this example forms a partially spherical convex portion 33 at the center of the inner surface of the bottom 23b by causing the center of the bottom 23b to bulge inward. And the center part of this convex part 33 is made to contact | abut to the center part of the front end surface of the axial part 12. FIG.

  In the case of such a structure of this example, when a thrust load is applied between the bearing cup 11b and the shaft portion 12 in accordance with the use of a universal joint, the bearing cup 11b and the bearing cup 11b The shaft portion 12 is relatively displaced in the axial direction. Since the relative displacement amount based on the elastic deformation is small, if only the relative displacement amount based on the elastic deformation is taken into consideration, the portion between the pair of seal edges 27a and 27b provided at the distal end portion of the radial seal lip 18a. The volume of the sealed space 29 defined in the above can be reduced. However, in the case of the structure of this example, the convex portion 33 is gradually worn with use over a long period of time, and the bearing cup 11b and the shaft portion 12 are relative to each other in the axial direction. The amount of displacement may increase. Therefore, in the case of the present example, the volume of the sealed space 29 is set to the axial length (the displacement amplitude or the displacement amplitude or the sum of the relative displacement based on the elastic deformation of the bottom 23b and the relative displacement based on the wear. The volume is commensurate with the product of the amplitude) and the cross-sectional area of the shaft portion 12. As a result, even after use for a long period of time, foreign matter taken into the sealed space 29 from the external space can be prevented from overflowing from the sealed space 29 and entering the interspace 26 side.

[Fourth Example of Embodiment]
FIG. 7 shows a fourth example of the embodiment of the present invention. In this example, there is no pin made of synthetic resin, and no member such as a pin is provided between the tip surface of the shaft portion 12 and the inner surface of the bottom portion 23a of the bearing cup 11, and a simple space is provided between these two surfaces. The case where the present invention is applied to the structure is shown. In such a structure, in a neutral state where no external force is applied to the universal joint, the positional relationship between the shaft portion 12 and the bearing cup 11 is neutral only by the elastic force of the thrust seal lip 19 constituting the seal ring 15a. Become.

In the case of the present example in order to apply the present invention to such a structure, a pair of seal edges 27a provided at the tip of the radial seal lip 18a, as in the embodiment shown in FIG. The minimum thickness T of the gap 30 existing between the front end surface of the shaft portion 12 and the inner surface of the bottom portion 23a of the bearing cup 11 in the neutral state is defined as the volume of the sealed space 29 defined in the portion between the portions 27b. _The volume corresponds to the product of ₃₀ and the cross-sectional area of the shaft portion 12. For this reason, it is possible to prevent foreign matter taken into the sealed space 29 from the external space from overflowing from the sealed space 29 and entering the interspace 26 side.

  The present invention is not limited to a universal joint for a steering device, but can be applied to a cross-shaft type universal joint that is incorporated in a non-linear connection portion of various conductive force transmission devices.

The figure equivalent to the AA cross section of FIG. 10 which shows the 1st example of embodiment of this invention. The right part enlarged view of FIG. The lower half enlarged view of FIG. The figure similar to FIG. 1 which shows the 2nd example of embodiment of this invention. The figure similar to FIG. 1 which shows the 3rd example. The right part enlarged view of FIG. The figure similar to FIG. 1 which shows the 4th example of embodiment of this invention. The perspective view which shows an example of the steering device incorporating a universal joint. The partial cut side view which shows the 1st example of the universal joint known conventionally. FIG. 10 is an enlarged CC cross-sectional view of FIG. The figure equivalent to the lower end part of FIG. 10 which shows the 2nd example of the universal joint known conventionally. The same figure as FIG. 3 for demonstrating the problem of a conventional structure.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Universal joint 4 Intermediate shaft 5 Steering gear unit 6 Input shaft 7 Tie rod 8a, 8b Yoke 9 Cross shaft 10 Circular hole 11, 11a, 11b Bearing cup 12 Shaft part 13 Coupling base part 14 Radial bearing 15, 15a Seal ring 16 Core 17, 17 a Elastic material 18, 18 a Radial seal lip 19 Thrust seal lip 20 Inward flange 21 Insertion hole 22, 22 a Pin 23, 23 a, 23 b Bottom 24 Projection 25 Internal space 26 Space 27 a, 27 b Seal Edge 28 Concave groove 29 Sealed space 30 Clearance 31 Gutter part 32 Protrusion part 33 Convex part

Claims (2)

  A pair of yokes each formed in a bifurcated shape, four circular holes formed concentrically with each other at both ends of both yokes, and inside each of these circular holes with the openings facing each other Four bearing cups, each fitted with an inner fitting and each having a bottomed cylindrical shape, and four shafts radially fixed on the outer peripheral surface of the coupling base, each of these shafts being A cross shaft combined with both the yokes in a state of being inserted into each bearing cup, and four sets of radial bearings provided between the outer peripheral surface of each shaft portion and the inner peripheral surface of each bearing cup; Four seal rings provided between the base end portions of the shaft portions and the opening portions of the bearing cups in a state in which the base portions are externally supported by the base end portions of the shaft portions. These seal rings are provided at the end closer to the opening of the outer peripheral surfaces of the bearing cups. In a universal joint comprising a radial seal lip that makes contact over the circumference and a thrust seal lip that makes contact over the entire circumference on the outer surface of the inward flange provided at the opening end of the bearing cup, Each radial seal lip has a pair of seal edges that are bifurcated at the tip and are axially spaced from each other, and the inner diameter side between the seal edges is the outer circumference of the bearing cup. The volume of the sealed space closed by the surface is present in the bearing cup as the bearing cup and the shaft portion are relatively displaced from the neutral state, and is blocked from the external space by the seal rings. A universal joint characterized in that it is more than the amount of change in the volume of the internal space.   The amount of change in the volume of the internal space due to the relative displacement between the bearing cup and the shaft portion is such that the minimum thickness of the gap existing between the tip end surface of the shaft portion and the bottom inner surface of the bearing cup in the neutral state and the shaft portion The universal joint according to claim 1, wherein the universal joint is equal to or less than a change amount of the volume of the internal space, which is obtained as a product with a cross-sectional area.

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