Cross shaft joint

A cross shaft joint tiltably coupling two shaft members each other includes: a cross shaft which includes four shaft portions and is arranged between the two shaft members; outer ring cups rotatably provided to the four shaft portions, respectively, the outer ring cups being adapted to be coupled to corresponding shaft members; and an attachment portion to which a balance weight for balancing the outer ring cups can be attached is formed on at least one of the outer ring cups.

BACKGROUND OF THE INVENTION

The present invention relates to a cross shaft joint.

In a power transmitting portion of a vehicle, a cross shaft joint is used to tiltably couple two shaft members to each other. The cross shaft joint includes a cross shaft and four rolling bearings provided in four shaft portions of the cross shaft respectively. The rolling bearing is usually a roller bearing and includes a plurality of needle-shaped rollers and an outer ring cup.

In a conventional cross shaft joint, the outer ring cup is directly fixed to the end of a corresponding shaft member without using a yoke (see Patent Document 1). More specifically, two of the four outer ring cups which are opposed to each other by 180 degrees are integrated in a rotating direction through a key and a key groove at the ends of one of the shaft members, and furthermore, are fixed with a bolt. Two other outer ring cups are also fixed to the ends of the other shaft members in the same way.

Patent Document 1

In the cross shaft joint described in the Patent Document 1, generally, the schematic shape of the outer ring cup is obtained by die forging in order to enhance the strength of the outer ring cup and to simplify a processing process. In the outer ring cup, an outer ring raceway surface in an inner part is finished with high precision by abrasion after the forging. A side surface and an outer surface such as an outer peripheral surface are left as forged surfaces without finishing. For this reason, a difference in a weight is made for each outer ring cup.

On the manufacturer side of the cross shaft joint, conventionally, the cross shaft joint is assembled into the shaft member. The assembled member of the cross shaft joint and the shaft member is applied to a balancing machine to detect a whole balance. According to a result, a balance piece is attached to the shaft member to carry out a balance adjustment and shipping to customers is then performed.

In the case in which only the cross shaft joint is exchanged in the customer such as a user, however, it is necessary to newly detect and adjust a balance for the whole assembled member including the cross shaft joint. However, the customers usually retain no balancing machine. For this reason, the whole balance adjustment cannot be carried out. Therefore, the customers have to send the assembled member having the cross shaft joint exchanged back to the manufacturer side in order to adjust the balance. Consequently, a great deal of time and labor and an excessive cost are required.

SUMMARY OF THE INVENTION

In order to solve the conventional problems, it is an object of the invention to easily adjust a balance.

In order to solve the aforesaid object, the invention is characterized by having the following arrangement.(1) A cross shaft joint tiltably coupling two shaft members each other, the cross shaft joint comprising:

a cross shaft which includes four shaft portions and is arranged between the two shaft members;

outer ring cups rotatably provided to the four shaft portions, respectively, the outer ring cups being adapted to be coupled to corresponding shaft members; and

an attachment portion to which a balance weight for balancing the outer ring cups can be attached is formed on at least one of the outer ring cups.(2) The cross shaft joint according to (1), wherein the attachment portion includes an attachment hole having a substantially constant inside diameter, into which a bar-shaped balance weight can be inserted.(3) The cross shaft joint according to (1), wherein

a key groove is formed on an end of one of the shaft members,

the outer ring cup is provided with a key portion protruded in a radial direction corresponding to the key groove, and

a screw hole concaved in a longitudinal direction of the key portion from an inner end of the key portion in the radial direction is formed,

the balance weight having bar shape is adapted to be inserted into the screw hole and fixed with a plug screwed into the screw hole.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will be described below in detail with reference to the drawings.FIGS. 1 to 3show an embodiment of the invention, andFIG. 1is a perspective view showing a cross shaft joint according to the embodiment, a part of which is exploded.FIG. 2is a front view showing the cross shaft joint inFIG. 1, illustrating, in a section, one of outer ring cups provided in each shaft portion of a cross shaft and the other outer ring cups in only outer shapes in a chain line.FIG. 3is a sectional view taken along a line (3)—(3) ofFIG. 2.

In these drawings, the reference numeral1denotes a whole cross shaft joint, and the reference numerals2and3denote shaft members coupled tiltably by the cross shaft joint1. The reference numeral2denotes a first shaft member and the reference numeral3denotes a second shaft member. The cross shaft joint1includes a cross shaft4, and four roller bearings5A,5B,5C and5D (which will be generally indicated as5) provided in four shaft portions41A,41B,41C and41D (which will be generally indicated as41) of the cross shaft4. All of these roller bearings5employ the four shaft portions41of the cross shaft4as inner rings respectively, and include a plurality of needle-shaped rollers6, a plurality of thrust bushes7, and outer ring cups8A,8B,8C and8D (which will be generally indicated as8). The four roller bearings5have identical structures to each other. Referring to the roller bearings5A and5D, therefore, internal members are shown in the drawings.

The outer ring cup8is a fan-shaped block seen from a front and is formed by die forging. An insertion hole9for a bolt is formed on the fan-shaped bulged portion of the outer ring cup8, and furthermore, a key portion10protruded in a radial direction is formed in surface portions opposed to the corresponding shaft members2and3.

On the other hand, the ends of the shaft members2and3are provided with fan-shaped attachment seats11and12protruded toward the outer ring cup8side corresponding to the outer ring cup8. The end of the first shaft member2is provided with the attachment seats11which are opposed to each other by 180 degrees. These two attachment seats11and11correspond to the two outer ring cups8A and8B opposed to each other by 180 degrees. The other attachment seats12are provided on the end face of the second shaft member3and correspond to two other outer ring cups8C and8D.

Each of the attachment seats11and12is provided with a screw hole13in a fan-shaped bulged region thereof, and furthermore, a key groove14in a radial direction is formed in a central portion thereof. In a state in which the corresponding outer ring cups8are bonded to the attachment seats11and12, the key portion10of the outer ring cup8is fitted in the key groove14, and the insertion hole9of the outer ring cup8corresponds to the screw hole13. The reference numeral15denotes a bolt to be screwed into the screw holes13of the attachment seats11and12of the shaft members2and3through the insertion holes9of the outer ring cups8. The outer ring cup8is fixed to the attachment seats11and12of the corresponding shaft members2and3with the bolt15so as to be rotated integrally.

Each of the outer ring cups8is provided with a balance weight16for a balance adjustment with the other outer ring cups8. More specifically, the outer ring cup8D is shown inFIG. 1and the outer ring cups8A and8B are shown inFIG. 3respectively. Thus, a screw hole17concaved in the longitudinal direction of the key portion10from the inner end of the key portion10in a radial direction is formed as the attachment portion for the balance weight16in the key portion10of each of the outer ring cups8. Herein, the balance weight16is bar-shaped and is inserted in the screw hole17. An embedded plug18is screwed and inserted into the screw hole17so that the balance weight16is fixed into the screw hole17. As is clearly illustrated byFIG. 3, the screw hole17has a substantially constant inside diameter.

The same screw hole17is formed on the key portions10of the other outer ring cups8which are not shown inFIGS. 1 and 3, and the bar-shaped balance weight16is inserted into the screw hole17and is fixed with the embedded plug18. InFIGS. 2 and 3, the reference numeral19denotes a seal on the opening side of the roller bearing5and the reference numeral20denotes an oil feeding path formed in the shaft portion41of the cross shaft4.

In the cross shaft joint1having the structure described above, if the outer ring cups8are formed by the die forging and outer surfaces are maintained to be forged surfaces which are not subjected to finishing, a difference in a weight is made for each of the outer ring cups8and the balance adjustment can be carried out by the balance weight16.

In order to carry out the balance adjustment by using the balance weight16, first of all, the weights of two outer ring cups8opposed to each other by 180 degrees, for example, the outer ring cups8A and8B are measured excluding the balance weight16respectively, and furthermore, the weight of the balance weight16is regulated based on the result of the measurement. In order to regulate the weight, it is preferable that the balance weight16should be cut to have a proper length because it is bar-shaped. The balance weights16having the weights regulated are inserted into the screw holes17provided on the key portions10of the corresponding outer ring cups8respectively, and are fixed into the screw holes17with the plugs18. Consequently, the weights of the two outer ring cups8A and8B opposed to each other by 180 degrees are equal to each other and a static balance can be taken between the two outer ring cups8A and8B. Referring to two other outer ring cups8C and8D opposed to each other by 180 degrees, it is preferable that the balance adjustment should be carried out in the same procedure.

As described above, the cross shaft joint1having the structure described above can take the static balance by itself. Even if the cross shaft joint1is not assembled into the shaft members2and3to apply the whole assembled member to a balancing machine, accordingly, the balance adjustment can be carried out. The user can exchange and utilize the cross shaft joint without a hindrance.

In addition, since the outer ring cup8is a block having a great weight and is provided on each of the shaft ends of the cross shaft4, a moment of rotations thereof is great. If the static balance is taken for such an outer ring cup8, it can be supposed that the whole assembled member obtained by assembling the cross shaft joint1into the shaft members2and3is almost balanced. For this reason, it is sufficient that the balance of the whole assembled member obtained by assembling the cross shaft joint1into the shaft members2and3is adjusted finely.

In addition, the screw hole17to be the attachment portion for the balance weight16can easily be formed and the processing step can be executed without a burden. Since the balance weight16is bar-shaped, moreover, it is possible to easily regulate the weight by cutting the balance weight16to have a proper length.

In the transmission of a power, furthermore, a centrifugal force acts to press the balance weight16into the inner part of the screw hole17. Consequently, there is no possibility that the balance weight16might be jumped out by the centrifugal force. Thus, the balance weight16can reliably be held in the screw hole17.

Moreover, the screw hole17to be the attachment portion for the balance weight16is provided on the key portion10protruded from the body portion of the outer ring cup8. Therefore, the strength of the outer ring cup8can be prevented from being reduced by the screw hole17.

The attachment portion for the balance weight is not restricted to the screw hole17according to the embodiment but may be a square concave portion, and furthermore, the shape of the balance weight may be bar-shaped or plate-shaped. In brief, it is sufficient that the balance weight16can be attached to any portion of the outer ring cup8. For example, the screw hole17to be the attachment portion for the balance weight according to the embodiment is not restricted to the above-mentioned shapes but may be formed on the key portion10of the outer ring cup8so as to be concaved in the longitudinal direction of the key portion10from an outer end in a radial direction thereof.

Moreover, it is also possible to form a screw hole which is parallel with the insertion hole9for the bolt15or a circular hole having no female screw as the attachment portion for the balance weight in the fan-shaped bulged portion of the outer ring cup8, thereby inserting the bar-shaped balance weight16into the same hole. In the case in which the attachment hole for the balance weight is a screw hole, the balance weight may be fixed into the screw hole with a male screw such as a bolt to be screwed into the screw hole or the balance weight itself may be screwed, as a male screw member, into the screw hole. In the case in which the attachment hole is a circular hole having no female screw, the balance weight may be pressed into the hole so as to be fixed into the hole.

As described above, in the case in which the fan-shaped bulged portion of the outer ring cup8is utilized for attaching the balance weight, it is desirable that holes such as screw holes should be provided on the respective bulged portions formed on both sides of the key portion10to distribute and hold the balance weight16into these holes. If the balance weight is provided in a thick portion by utilizing the bulged portion of the outer ring cup8, the balance weight provided on each of the outer ring cups8is almost aligned with a position surrounding the central portion of the cross shaft4so that a whole balance can easily be taken.

In addition, the invention is not restricted to the cross shaft joint1of such a type as to directly attach the outer ring cup8to the shaft members2and3but can also be executed for a cross shaft joint of such a type as to attach the outer ring cup to the shaft member through a yoke or a yoke-shaped portion formed integrally with the end of the shaft member. Moreover, each shaft portion41of the cross shaft4may be provided with a rolling bearing other than a roller bearing having a needle-shaped roller.

According to the invention, balance weights having predetermined weights are attached to two outer ring cups opposed to each other by 180 degrees, respectively. Consequently, the weights of the two outer ring cups opposed to each other are caused to be equal so that the static balance of a whole joint can be taken. Accordingly, it is not necessary to assemble a cross shaft joint into a shaft member and to apply the whole assembled member to a balancing machine. Even a user having no balancing machine can easily carry out a balance adjustment.