JP2003194193A - Bearing structure of transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce gear noises by reducing the transmission of vibration to gears even if bending vibrations occur in a relatively long rotating shaft. <P>SOLUTION: This bearing structure has a reduction driven gear 2 formed with an inner spline while constituting one of gear trains to which power is transmitted; a pair of ball bearings 5 supporting the reduction driven gear 2 at each end and capable of being exerted with thrust loads; and a drive pinion shaft 1 formed with an outer spline at an end, with the outer spline being coupled to the inner spline of the reduction driven gear 2 by a loose spline having a backlash. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing structure for a transmission such as an automobile, and more particularly to a bearing structure suitable for supporting a relatively long rotating shaft.

[0002]

2. Description of the Related Art Generally, a transmission employs a gear train in which a power input portion and an output portion are separated from each other, so that a drive pinion shaft or the like tends to be elongated. For example, in the case of a vertical transmission, the optimum position of the front differential device is the vehicle center coaxial with the wheels. Therefore, the drive pinion shaft for driving the differential device arranged at the optimum position tends to be necessarily long. The same applies to the horizontal transmission, and a drive pinion shaft that substantially corresponds to the entire length of the main transmission is often used.

As described above, in the structure using the drive pinion shaft having a relatively long axis, the drive pinion shaft may cause bending vibration (that is, periodic axial displacement in the radial direction). Radial axial displacement due to bending vibration of the shaft is transmitted to a gear attached to the end of the shaft. As a result, tooth contact changes occur in the gear train including this gear. Here, the "tooth contact change" refers to a phenomenon in which the tooth contact deviates from an ideal position due to the tilt of the shaft, and the tooth contact locally and eccentrically occurs. When this tooth contact change occurs,
Not only does the power transmission efficiency decrease and the gears wear faster, but gear noises occur in synchronization with bending vibrations, which causes a driver to feel uncomfortable.

As a method for eliminating such inconvenience, it is considered that the bending vibration itself of the shaft is regulated by adding a bearing in the middle of the long shaft. In addition, JP-A-6-2
Japanese Patent No. 41288 discloses a bearing structure that uses a support having a first bearing opening and a second bearing opening and in which a main shaft and a sub shaft of a transmission extend through the respective bearing openings. Since the main shaft and the sub shaft are axially supported by the support in the middle of both ends, the center distance between the main shaft and the sub shaft is irrespective of the fact that the separating force of the gear teeth acts laterally with respect to the shaft. It is kept the same as the center distance of the meshing gear train.

[0005]

However, in the above-mentioned conventional technique, the displacement itself of the shaft is regulated by utilizing the fact that the meshing reaction force of the gear is generated in the action / reaction relationship. A sufficient effect cannot be expected for gear noise due to bending vibration.

The present invention has been made in view of such circumstances, and an object thereof is to reduce vibration transmission to the gear side even when bending vibration occurs in a relatively long rotating shaft,
It is to effectively reduce gear noise.

Another object of the present invention is to improve the workability and the assemblability while suppressing the expansion of the bearing arrangement space.

[0008]

In order to solve such a problem, the present invention provides a rotating shaft and one end of the rotating shaft,
Inside of the gear and the connecting means that allows the bending displacement of the rotary shaft while restricting the displacement of the gear while rotationally coupling the gear that constitutes one of the gear trains that transmits power to the rotary shaft and the gear (EN) Provided is a bearing structure for a transmission, which has a ball bearing mounted on the gear and bearing a gear load, and a thrust bearing mounted on the outside of the gear and bearing the gear load.

Here, in the above structure, the connecting means is
It is preferably composed of an inner spline formed on the gear and an outer spline formed on the end of the rotary shaft, and the outer spline is preferably connected to the inner spline by a loose spline having backlash. in this case,
It is desirable that the outer spline has a spline outer diameter curved in an arcuate shape toward the outside, and the tooth trace is provided with crowning.

The ball bearing may be a deep groove ball bearing, a four-point contact ball bearing or a double row angular contact ball bearing. Further, an intermediate bearing, which is provided at a substantially intermediate position of the rotary shaft and supports the rotary shaft, may be added.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a configuration diagram of a main part of a vertical transmission. Drive pinion shaft 1
Is provided on the output side of the automatic transmission. A reduction driven gear 2 which is a helical gear is integrally attached to one end of the drive pinion shaft 1, and a hypoid pinion gear 3 meshing with a hypoid ring gear is attached to the other end thereof. A relatively large driving force changed by the speed change mechanism of the transmission is transmitted to the drive pinion shaft 1 via a gear train (not shown) including a reduction drive gear and a reduction driven gear 2. Then, the driving force of the drive pinion shaft 1 is transmitted to the wheels via a hypoid ring gear that meshes with the hypoid pinion gear 3.

As described above, the drive pinion shaft 1 that drives the differential device 7 tends to be elongated because of the relationship with the optimal arrangement position of the front differential device 7. In this transmission, the shaft length of the drive pinion shaft 1 is determined by a main transmission unit (not shown) located above the drive pinion shaft 1 (that is, a transmission mechanism mainly composed of a multi-disc clutch, a multi-disc brake, a planetary gear, etc.). It is longer than the total length of the existing part).

One end of the drive pinion shaft 1 is supported by a double row tapered roller bearing 4. The double row tapered roller bearing 4 is arranged inside the hypoid pinion gear 3. The inner ring of the bearing 4 is fixed to the drive pinion shaft 1, and the outer ring of the bearing 4 is fixed to the transmission case by bolts. A plurality of tapered rollers (taper rollers) are provided in the space between the inner and outer rings. On the other hand, the other end of the drive pinion shaft 1 is spline-fitted with a rotatably supported reduction driven gear 2, and the pinion shaft 1 is rotatably supported via a gear 2.

That is, the drive pinion shaft 1 and the reduction driven gear 2 are connected by a spline portion 6 which is one form of a connecting mechanism. The reduction driven gear 2 has a gear portion 2a and a tubular portion 2b projecting inward from the gear portion 2a in the axial direction of the drive pinion shaft 1. An inner spline is formed on the inner peripheral surface of the tubular portion 2b. Are formed. The inner spline is spline-fitted with the outer spline formed at the end of the drive pinion shaft 1. Here, the end portion of the drive pinion shaft 1 stays at an intermediate position of the reduction driven gear 2 and does not completely penetrate the reduction driven gear 2. The reason for connecting in such a non-penetrating state is that the backlash management described later becomes easier than the case of penetrating because of the relationship with the tooth trace accuracy of the spline. Another reason is that the drive pinion shaft 1 can be shortened by making it non-penetrating, and the shaft 1 can be reduced in weight accordingly. However, if it is not necessary to consider these points, the drive pinion shaft 1 may be passed through the reduction driven gear 2.

The outer spline provided at the end of the drive pinion shaft 1 has a backlash. This backlash is provided to restrict the transmission of the shaft vibration of the drive pinion shaft 1 to the reduction driven gear 2. Generally, "backlash"
As shown in FIG. 2, in a pair of gears meshing with each other, a gap is formed between a tooth surface on the opposite side of a tooth surface on which a load is applied and a tooth surface of a mating gear opposite to the tooth surface. Such a gap can be similarly defined as backlash for spline fitting. Since the reduction driven gear 2 and the drive pinion shaft 1 are loosely connected by backlash, bending displacement of the drive pinion shaft 1 is allowed, but displacement of the reduction driven gear 2 due to this is restricted.

The reduction driven gear 2 includes a ball bearing 5
And a thrust needle bearing 8 provided on the outer side of the bearing and the needle is rotatably fixed. Ball bearing 5 is gear 2
The inner ring is fixed to the stepped fixing portion 2c formed on the outer periphery of the cylindrical portion 2b of the, and the outer ring is fixed to the transmission case, and the load of the gear 2 is applied from the inner side (extending direction of the drive pinion shaft 1). To do. In addition, this ball bearing 5
It is preferable to use a bearing capable of bearing both a thrust load and a radial load acting on the reduction driven gear 2, for example, a deep groove ball bearing, a three-point contact ball bearing, a four-point contact ball bearing, a double-row angular ball bearing or the like.

On the other hand, the thrust needle bearing 8 is composed of the gear 2
Is interposed between an end surface of the transmission cover and a transmission cover 9 attached to a side portion of the transmission case. FIG. 3 is a diagram showing a mounting structure of the thrust needle bearing 8. By forming a step on the end surface of the reduction driven gear 2, a ring-shaped fixed portion 2d is formed. A washer 8a is interposed in the fixed portion 2d, and the thrust needle bearing 8 is sandwiched between the washer 8a and the step portion 9a on the transmission cover 9 side.
The thrust needle bearing 8 applies the thrust load acting on the reduction driven gear 2 from the outside of the gear 2. The washer 8a may be omitted and the thrust needle bearing 8 may be directly provided on the fixed portion 2d of the reduction driven gear 2.

The backlash in the spline section 6 is
It is necessary to set an appropriate value in consideration of both transmission regulation of shaft vibration and prevention of rattling noise due to torque fluctuation. If the backlash is too large (for example, 0.2 mm or more), rattling noise or fretting wear due to torque fluctuation may occur. On the contrary, if the backlash is too small (for example, 0.02 mm or less), rattling noise can be prevented, but the shaft vibration may be transmitted to the gear. From this point of view, it is important to set the backlash value of the spline, and care must be taken when setting the specifications and assembling. As a result of the inventor's examination through experiments and simulations, as a specific setting value of backlash, a range of 0.03 mm or more and 0.15 mm or less is preferable, and particularly 0.05 mm or more.
It has been found that it is preferable to set the range within 0.08 mm.

As described above, in this embodiment, a loose spline having an appropriate backlash is used as a connecting mechanism for rotationally coupling the drive pinion shaft 1 and the reduction driven gear 2. Since the drive pinion shaft 1 has a relatively long axial length, the pinion shaft 1 may cause bending vibration during rotation. Since the spline portion 6 is a loose spline, it restricts the displacement of the reduction driven gear 2 and allows only the bending displacement of the drive pinion shaft 1. Therefore, the vibration transmission from the drive pinion shaft 1 side to the reduction driven gear 2 side is restricted by the spline portion 6. As a result, even in a vibration mode in which the drive pinion shaft 1 causes bending vibration, tooth surface vibration of the reduction driven gear 2 can be reduced and tooth contact change can be prevented, so that gear noise caused by shaft vibration can be effectively suppressed. Is possible.

Since gear noise countermeasures can be taken without increasing the shaft diameter of the drive pinion shaft 1, it is possible to suppress an increase in weight of the transmission. Furthermore, the drive pinion shaft 1 can be shortened by the amount that the drive pinion shaft 1 does not penetrate the reduction driven gear 2.
This is advantageous not only in reducing the axial load described above but also in productivity.

Furthermore, Japanese Patent Application No. 200, which is the prior application of the present applicant,
The axial length of the transmission can be shortened as compared with the transmission bearing structure disclosed in No. 1-107613. This prior application describes that the drive pinion shaft and the reduction driven gear are connected by a loose spline, and the inside and the outside of the reduction driven gear are supported by a pair of ball bearings at both ends. In such a configuration, a space for the width of the ball bearing provided outside the reduction driven gear is required, which increases the axial length of the transmission. On the other hand, in the present embodiment, since the thrust needle bearing 8 is used instead of the outer ball bearing, there is an effect that such an increase in axial length can be suppressed.

Further, there is an effect that workability and assemblability can be improved as compared with the above-mentioned prior application. In the structure in which the reduction driven gear is supported on both sides by ball bearings as in the prior application, high precision is required for machining the bearing housing holes in order to match the shaft centers of the pair of ball bearings. Therefore, before assembling the gear, the rotary shaft, and the like in the transmission, a method is adopted in which the transmission case and the main cover are joined and the housing hole is simultaneously machined in this joined state. In this case, it is necessary to disassemble the transmission case body that has been joined at one end and to assemble the internal members. On the other hand, if the thrust needle bearing 8 is used as in the present embodiment, such simultaneous machining becomes unnecessary, and the machining accuracy required by the ball bearing is not required, and the clearance adjustment by the shim or the like is not required. Will also be possible. Therefore, the workability and the assemblability can be remarkably improved.

In this embodiment, an intermediate bearing may be provided at a substantially intermediate position of the drive pinion shaft 1, and the drive pinion shaft 1 may be supported at both ends and the intermediate position. By providing this intermediate bearing, bending vibration itself of the drive pinion shaft 1 can be suppressed, so that the occurrence of gear noise can be further effectively reduced. From the viewpoint of suppressing such bending vibration itself, a similar intermediate bearing may be provided in each of the embodiments described below.

(Second Embodiment) In the present embodiment, the spline portion 6 is used as a gear joint as a connecting mechanism to allow bending displacement of the drive pinion shaft 1. FIG. 4 is an enlarged view of a main part of the drive pinion shaft 1 according to this embodiment. As shown in (a) of the figure, the outer spline 1a provided at the end of the drive pinion shaft 1 has a spline outer diameter curved in an arcuate shape toward the outside, and is finished in a convex barrel shape. is there. FIG. 2B shows the tooth trace shape of the outer spline 1a. A normal spline is manufactured so that the tooth trace is true as shown by the chain double-dashed line A, but in the present embodiment, the tooth trace is provided with crowning. When manufacturing the outer spline 1a having such a shape, first, the arcuate shape of the outer diameter is given as a blank shape before gear cutting or by grinding after heat treatment. The crowning of the tooth trace can be performed by shaving after forming the straight tooth surface. When the spline portion 6 is a gear joint having the above shape, the center portion of the tooth width of the spline tooth surface comes into contact with the surface, so that the relative movement of the spline portion 6 can be easily performed.

In this embodiment, the drive pinion shaft 1 and the reduction driven gear 2 are rotationally coupled by a gear joint having a crowning which is one form of a connecting mechanism. As a result, only the bending displacement of the drive pinion shaft 1 is allowed while the displacement of the reduction driven gear 2 is restricted. Therefore, it is possible to prevent the tooth contact change due to the bending vibration of the drive pinion shaft 1, and it is possible to effectively suppress the occurrence of gear noise. Further, by modifying the shape of the spline portion 6 as described above, the contact position of the spline tooth surface and the inner and outer diameters of the spline is limited, so that the backlash management in the spline portion 6 becomes easy. Further, since the spline tooth surface is close to the point contact, even if the backlash is further reduced, the tolerance for bending deformation of the drive pinion shaft 1 is not impaired, which is advantageous for rattling sound.

(Third Embodiment) In the present embodiment, a double offset type constant velocity joint 10 is used as a connecting mechanism for rotationally coupling the drive pinion shaft 1 and the reduction driven gear 2 in place of the spline portion 6 described above. , Allows bending displacement of the drive pinion shaft 1. As shown in FIG. 5, the constant velocity joint 10 itself has a known structure.
The inner ring 11 of the constant velocity joint 10 is spline-fitted with the drive pinion shaft 1, and a plurality of ball grooves 11a capable of accommodating the balls 12 are formed on the outer wall surface thereof. On the other hand, the reduction driven gear 2 functions as an outer ring of a constant velocity joint, and a plurality of ball grooves 12a capable of accommodating the balls 12 are formed on the inner wall surface thereof. Ball 12
Is held by the ball groove 11a on the inner ring 11 side and the ball groove 12a on the reduction driven gear 2 side, which is the outer ring, and rolls by the circlip 13 without falling off. The diameter of the ball 12 in the constant velocity joint 10 is such that there is no play in the twisting direction, and
The drive pinion shaft 1 is set to an appropriate value so that bending vibration of the shaft 1 can be effectively permitted.

According to the present embodiment, by using the double offset type constant velocity joint 10 as the connecting mechanism,
While restricting the displacement of the reduction driven gear 2, only the bending displacement of the drive pinion shaft 1 is allowed. Therefore, generation of gear noise due to bending vibration of the drive pinion shaft 1 can be effectively suppressed. In particular, since the constant velocity joint 10 has no rattling, rattling noise is not generated due to torque fluctuation, and fretting wear does not occur.
Moreover, since the friction of the balls 12 is small due to the effect of the balls 12, it is possible to effectively isolate the vibration during the torque transmission.

Since the axial displacement due to bending vibration of the drive pinion shaft 1 is extremely small, the same effect can be obtained even if a constant velocity joint made of a commercially available flexible body is used as the connecting mechanism.

(Fourth Embodiment) In each of the above-described embodiments, an example of application to a driven gear provided on the drive pinion shaft side has been described. However, the present invention
It can be widely applied to rotary shafts other than the drive pinion shaft (particularly, rotary shafts having a long shaft length). Further, as described in the fourth embodiment below, it is also applicable to the drive gear side.

FIG. 6 is a skeleton diagram of a transmission in which the present invention is applied to the drive gear side. Input shaft 2 of this transmission
The power input to 0 is transmitted to the front drive shaft 22 after being appropriately changed in speed by a speed change mechanism 21 mainly composed of a synchronizing mechanism and a speed change gear train. The power transmitted to the front drive shaft 22 is transmitted to the differential device 23 that drives the front wheels, and is also transmitted to the rear drive shaft 25 via the gear trains 24a and 24b. With such a configuration, the front drive shaft 22 that is rotationally coupled to the drive gear 24a tends to be elongated, and bending vibration may occur. Therefore, the drive gear 24
Gear noise countermeasures on the a side are required.

Therefore, the loose spline described in the first embodiment is replaced with the front drive shaft 22 and the drive gear 2.
It is applied to the spline portion 26 which is a binding site with 4a.
As a result, transmission of bending vibration from the front drive shaft 22 side to the drive gear 24a side is reduced, so that the occurrence of gear noise can be effectively suppressed. Also,
As described in the second embodiment, the spline portion 26 may be a gear joint. Furthermore, as described in the third embodiment, a constant velocity joint may be used instead of the spline portion 26.

[0032]

As described above, according to the present invention, the rotary coupling between the rotary shaft and the gear uses the connecting mechanism which restricts the displacement of the gear and allows only the bending displacement of the rotary shaft. This allows
Even in the vibration mode in which the rotating shaft causes bending vibration, the tooth surface vibration of the gear mounted on the rotating shaft can be reduced. As a result, it is possible to effectively suppress the generation of gear noise due to the shaft vibration, and it is possible to improve quietness.
In particular, when it is applied to a rotary shaft having a long shaft length, that is, a rotary shaft longer than the entire length of the main transmission unit in the transmission, a remarkable effect regarding quietness can be obtained. Further, it is possible to improve the workability and the assemblability while suppressing the expansion of the bearing arrangement space.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a main part of a vertical transmission.

FIG. 2 is an explanatory diagram of backlash.

FIG. 3 is a diagram showing a mounting structure of a thrust needle bearing.

FIG. 4 is an enlarged view of a main part of a drive pinion shaft according to a second embodiment.

FIG. 5 is a sectional view of a constant velocity joint according to a third embodiment.

FIG. 6 is a skeleton diagram of the transmission according to the fourth embodiment.

[Explanation of symbols]

1 drive pinion shaft 2 Reduction driven gear 3 Hypoid pinion gear 4 Double row tapered roller bearing 5 ball bearings 6 Spline part 7 Differential device 8 Thrust needle bearing 9 Transmission cover 10 constant velocity joints 11 inner ring 11a ball groove 12 balls 12a ball groove 13 Circlip 20 input axis 21 speed change mechanism 22 Front drive shaft 23 Differential device 24a drive gear 24b driven gear 25 Rear drive shaft

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Claims (5)

[Claims] 1. A bearing structure for a transmission, comprising: a rotary shaft; a gear that is provided at one end of the rotary shaft and constitutes one of a gear train that transmits power to the rotary shaft; the rotary shaft and the gear; And a ball bearing mounted on the inner side of the gear for allowing the bending displacement of the rotary shaft and a load bearing the load of the gear while restricting the displacement of the gear, and the outer side of the gear. And a thrust bearing to which the load of the gear is applied, the bearing structure of the transmission. 2. The connecting means comprises an inner spline formed on the gear and an outer spline formed on an end portion of the rotating shaft, the outer spline being a loose spline having a backlash. The bearing structure for a transmission according to claim 1, wherein the bearing structure is coupled to the inner spline. 3. The speed change according to claim 2, wherein the outer spline has an outer diameter of the spline curved in an arcuate shape toward the outside, and the tooth trace is provided with crowning. Bearing structure of machine. 4. The transmission according to claim 1, wherein the ball bearing is any one of a deep groove ball bearing, a four-point contact ball bearing and a double row angular contact ball bearing. Bearing structure. 5. The transmission according to claim 1, further comprising an intermediate bearing that is provided at a substantially intermediate position of the rotating shaft and that supports the rotating shaft. Bearing structure.