JP7356374B2 - differential - Google Patents

Description

The present invention relates to a differential, and particularly to a differential disposed inside a transmission, a speed reducer, or the like, which is a vehicle power unit.

Generally, driving force generated by an engine or electric motor is converted by a transmission or a reduction gear (motor reduction gear), and then transmitted to the drive wheels of a vehicle via a final reduction gear and a differential. The final reduction gear reduces the rotation speed of the drive shaft and transmits power to the differential.The differential reduces the speed difference (rotation difference) between the inside wheel (inner turning wheel) and the outer wheel (outer turning wheel) when the vehicle turns. ), while distributing driving force between the inner and outer wheels, improving vehicle maneuverability.

In transmissions, speed reducers, and the like, transmission cases and speed reducer cases are mainly made of, for example, aluminum (or aluminum-based alloy) from the viewpoints of mass (light weight), cost, and the like. On the other hand, the differential case of the differential is mainly made of cast iron, for example, from the viewpoint of strength and the like.

Incidentally, as a bearing disposed between a transmission case, a reduction gear case, etc. and supporting a differential case, a tapered bearing is mainly used because the load applied thereto is large (see, for example, Patent Document 1). Further, from the viewpoint of reliability, the tapered bearing is used by being sandwiched between aluminum cases and preloaded so that no gaps are formed inside.

Japanese Patent Application Publication No. 2011-153640

However, when the temperature of the transmission or reducer increases, for example while the vehicle is running, the taper bearing The preload may decrease. Therefore, in order to prevent gaps from forming inside the taper bearing even at high temperatures, it is necessary to increase the preload at low temperatures, leading to a problem in which the friction of the taper bearing increases (which in turn leads to deterioration of fuel efficiency).

On the other hand, if an iron-based material is used for the transmission case or reduction gear case in order to prevent the preload of the tapered bearing from decreasing at high temperatures, the mass, cost, etc. will increase significantly. Therefore, in a differential placed inside a transmission or reduction gear, even if the differential is made of a material with a different (lower) coefficient of thermal expansion than the transmission case or reduction gear case, the mass and It is desirable to have a technology that can suppress changes in preload of tapered bearings due to temperature changes (decrease in preload on tapered bearings at high temperatures) while suppressing increases in costs (that is, without significant increases in mass or costs). It was rare.

The present invention has been made in order to solve the above problems, and in a differential disposed inside a transmission or a reduction gear, the differential has a coefficient of thermal expansion smaller than that of the transmission case or the reduction gear case. Even if the tapered bearing is made of a material, it is possible to suppress the increase in mass, cost, etc. (in other words, without a significant increase in mass, cost, etc.) The purpose of the present invention is to provide a differential capable of suppressing a decrease in preload of a tapered bearing during operation.

The differential according to the present invention includes a differential case formed from a metal material having a coefficient of thermal expansion smaller than that of the transmission case or the reduction gear case, and a differential case that rotates the differential case. A bearing retainer is formed from a metal material having the same or substantially the same coefficient of thermal expansion as the differential case and is attached to cover the differential case and the taper bearing.

According to the differential according to the present invention, the differential case includes a bearing retainer that is formed from a metal material having the same or substantially the same coefficient of thermal expansion as the differential case and is attached to cover the differential case and the tapered bearing. Therefore, for example, even if the temperature of the transmission or speed reducer increases while the vehicle is running, the difference in thermal expansion coefficient between the bearing retainer and the differential case is small, so a decrease in preload of the tapered bearing is suppressed. Therefore, for example, the minimum required preload at room temperature can be reduced, and the friction of the tapered bearing can be reduced. Furthermore, the mass and cost can be significantly reduced compared to suppressing changes in preload of the tapered bearing by making the transmission case or the reduction gear case made of iron-based material. As a result, for differentials placed inside transmissions and reduction gears, even if the differential is made of a material with a lower coefficient of thermal expansion than the transmission case or reduction gear case, the weight and cost increase. It is possible to suppress changes in preload of a tapered bearing due to temperature changes (decrease in preload of a tapered bearing at high temperatures) while suppressing increases in the Become.

In the differential according to the present invention, the bearing retainer is composed of a plurality of parts around which a flange is formed, and the plurality of parts are arranged so as to sandwich the differential case, and are fastened with bolts at the flange. It is preferable. In this way, the bearing retainer can be easily assembled.

In the differential according to the present invention, the tapered bearing is disposed at one end and the other end of the differential case, and the inside of one end is the outer periphery of the outer ring of the one tapered bearing. It is preferable that the bearing retainer is attached so that the bearing retainer extends from the surface to the side surface and comes into contact with the bearing retainer, and the other end is fixed to the transmission case or the reduction gear case. In this way, even if the transmission case or reducer case undergoes thermal expansion (especially thermal expansion in the vehicle width direction/axle shaft thrust direction), the bearing retainer can be fixed so as to suppress a decrease in preload of the tapered bearing. can do.

The differential according to the present invention is formed using a metal material having the same or substantially the same coefficient of thermal expansion as a transmission case or a reduction gear case, and has one end of a bearing retainer that comes into contact with a tapered bearing on one side. It is preferable to have a second bearing retainer that supports the bearing retainer in the radial direction at the outer peripheral portion. In this way, one end of the bearing retainer (that is, the end that is not directly fixed to the transmission case or the reduction gear case) can be supported in the radial direction.

Further, in the differential according to the present invention, it is preferable that the bearing retainer is attached such that one end has a clearance with the second bearing retainer in the thrust direction. In this way, the difference in thermal expansion in the thrust direction between the bearing retainer and the second bearing retainer can be absorbed by the clearance provided in the thrust direction.

In the differential according to the present invention, it is preferable that the bearing retainer has an opening formed at a portion where the final gear meshes with the bearing retainer. In this way, the bearing retainer can be prevented from coming into contact with the meshing portion of the final gear.

In the differential according to the present invention, it is preferable that the bearing retainer has a plurality of oil discharge holes formed at a position higher than the oil level in the transmission or reduction gear when the vehicle is running. In this way, the bearing retainer can have a baffle function. Therefore, due to the baffle effect of the bearing retainer, oil can be discharged from the oil discharge hole and the oil level in the final gear part during running can be lowered than the oil level in the transmission or reducer, reducing oil agitation loss. can do.

In the differential according to the present invention, it is preferable that a rib is provided on the outer surface of the bearing retainer to suppress deformation of the bearing retainer. In this way, the rigidity of the bearing retainer can be increased, and even if a large load is applied to the differential while the vehicle is running, deformation of the bearing retainer can be suppressed.

According to the present invention, in a differential disposed inside a transmission or a reduction gear, even if the differential is made of a material having a smaller coefficient of thermal expansion than the transmission case or the reduction gear case, To suppress changes in preload of a tapered bearing due to temperature changes (decrease in preload of a tapered bearing at high temperatures) while suppressing increases in mass, cost, etc. (that is, without significant increases in mass, cost, etc.) becomes possible.

FIG. 1 is a cross-sectional view along the vehicle width direction (left-right direction) showing the configuration of a vehicle power plant including a differential according to an embodiment. 2 is a sectional view taken along line II-II in FIG. 1. FIG. 2 is an enlarged view of a portion surrounded by a broken line in FIG. 1. FIG. It is a figure showing the relationship between temperature and preload of a taper bearing.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in the figures, the same reference numerals are used for the same or corresponding parts. Further, in each figure, the same elements are given the same reference numerals and redundant explanations will be omitted.

First, the configuration of a vehicle power plant equipped with a differential according to an embodiment will be described using FIGS. 1 to 3 together. FIG. 1 is a cross-sectional view along the vehicle width direction (left-right direction) showing the configuration of a vehicle power plant including a differential. FIG. 2 is a cross-sectional view taken along line II-II in FIG. Further, FIG. 3 is an enlarged view of a portion surrounded by a broken line in FIG. 1. As shown in FIG. In this embodiment, a case where the present invention is applied to a motor reduction gear mounted on a vehicle as a differential will be described as an example.

The motor speed reducer 10 is installed, for example, in an electric vehicle (EV) that drives drive wheels by an electric motor, or a hybrid vehicle (HEV) that drives drive wheels by an engine and an electric motor, and is configured to reduce the rotational speed of the electric motor, etc. is output after decelerating (that is, increasing the driving torque).

The motor speed reducer 10 has a speed reducer case 11 . A differential (differential mechanism) 12 is rotatably incorporated within the reducer case 11 . The differential 12 has a differential case 14 in which a final reduction large gear 13 is provided. The differential case 14 is rotatably supported by a taper bearing (tapered roller bearing) 15 and a taper bearing (tapered roller bearing) 16, which are assembled between the differential case 14 and the reducer case 11.

The differential case 14 has a side gear 18a fixed to an axle shaft 17a that is connected to one of the left and right drive wheels via a drive shaft (not shown), and a side gear 18a that is connected to the other drive wheel via a drive shaft (not shown). A side gear 18b fixed to the axle shaft 17b is rotatably incorporated. These side gears 18a, 18b are arranged opposite to each other.

A pinion shaft 19 is attached to the differential case 14 in a direction perpendicular to the rotation center axis of each axle shaft 17a, 17b. Pinion gears 20a and 20b, which face each other and mesh with both side gears 18a and 18b, are rotatably mounted on the pinion shaft 19.

A rotor shaft 21 is rotatably installed coaxially on the outside of one axle shaft 17b. Ball bearings 23 and 24 that support the rotor shaft 21 are assembled into the reducer case 11.

An electric motor 25 is arranged outside the rotor shaft 21. The electric motor 25 includes a rotor 26 provided with a plurality of permanent magnets corresponding to the number of poles and attached to the rotor shaft 21, and a stator 27 in which a coil portion is assembled in a slot of a core surrounding the outer periphery of the rotor 26. It is a permanent magnet type synchronous motor. The stator 27 is fixed to the reducer case 11.

A reduction shaft 31 is rotatably provided within the reduction gear case 11. One end of the reduction shaft 31 is supported by the reduction gear case 11 by a ball bearing 32, and the other end is supported by the reduction gear case 11 by a ball bearing 33. The deceleration shaft 31 is provided with a driven gear 35 that meshes with a driving gear 34 provided on the rotor shaft 21 . The diameter of the driven gear 35 is set larger than the diameter of the drive gear 34, and these gears 34 and 35 form a first stage reduction gear train.

Further, the reduction shaft 31 is provided with a small final reduction gear 36 that meshes with the large final reduction gear 13 of the differential 12, and these final reduction gears 13 and 36 form a second stage reduction gear train. There is. Note that oil (lubricating oil) is stored in the reducer case 11 so that the lower part of the final reduction large gear 13 is submerged below the stationary oil level.

Here, the reducer case 11 described above is made of, for example, aluminum (or aluminum-based alloy) from the viewpoints of mass (light weight), cost, and the like. On the other hand, the differential 12 (differential case 14) is made of cast iron, for example, from the viewpoint of strength and the like. That is, the differential 12 (differential case 14) is formed from a metal material having a smaller coefficient of thermal expansion than the reducer case 11.

Even if the differential 12 is made of a material with a different (lower) coefficient of thermal expansion than the reducer case 11, it is possible to suppress increases in mass, cost, etc. (i.e., prevent significant increases in mass, cost, etc.) It has a function of suppressing changes in the preload of the tapered bearings 15 and 16 due to temperature changes (reduction in the preload of the tapered bearings 15 and 16 at high temperatures).

Therefore, the differential 12 is made of a plate-shaped metal material (e.g., iron) that has the same or substantially the same coefficient of thermal expansion as the differential case 14 and is attached to a bearing retainer ( It is equipped with a differential side bearing retainer) 121. Note that it is preferable that the plate thickness (thickness) of the iron sheet metal material forming the bearing retainer 121 be about 1/3 of the thickness of the reducer case 11.

The bearing retainer 121 is composed of a plurality of parts (two in this embodiment), namely an upper bearing retainer 1211 and a lower bearing retainer 1212, around which flanges 1211a and 1212a are formed. The upper bearing retainer 1211 and the lower bearing retainer 1212 are arranged so as to sandwich the differential 12 (differential case 14), and are fastened by bolts 1251 at flanges 1211a and 1212a.

One taper bearing 16 is disposed at one end of the differential case 14 , and the other taper bearing 15 is disposed at the other end of the differential case 14 . As shown enlarged in FIG. 3, the inner side of one end of the bearing retainer 121 wraps around from the outer peripheral surface of the outer ring of the tapered bearing 16 on one side (right side in FIG. 1) and abuts on the side surface, and the other side is attached to the reducer case 11 so that the end thereof is fixed by a bolt 1252.

Here, the differential 12 is formed using a metal (i.e., aluminum) material having the same or substantially the same coefficient of thermal expansion as the reducer case 11, and is one of the bearing retainers 121 that abuts the tapered bearing 16 on one side. A second bearing retainer 129 that supports the bearing retainer 121 in the radial direction is provided at the outer peripheral portion of the end portion.

As shown in FIG. 3, the bearing retainer 121 is attached such that one end (end surface) has a clearance with the second bearing retainer 129 in the thrust direction.

As shown in FIGS. 1 and 2, an opening 122 is formed in the bearing retainer 121 (upper bearing retainer 1211) at the meshing portion of the final reduction small gear 36 and the final reduction large gear 13.

In addition, the bearing retainer 121 (upper bearing retainer 1211 and lower bearing retainer 1212) has a plurality of oil discharge holes 123 (two in this embodiment) at a position higher than the oil level in the reducer when the vehicle is running. is formed.

Note that it is preferable that ribs are provided on the outer surface of the bearing retainer 121 to suppress deformation of the bearing retainer 121. However, the flanges 1211a and 1212a can also function as ribs.

With the configuration described above, for example, even if the temperature of the motor reduction gear 10 increases while the vehicle is running, the difference in thermal expansion coefficient between the bearing retainer 121 and the differential 12 (differential case 14) is small. Therefore, a decrease in preload of the tapered bearings 15 and 16 is suppressed. Therefore, the minimum required preload at lower temperatures can be reduced, and the friction of the tapered bearings 15 and 16 can be reduced.

Here, the relationship between temperature and preload of the tapered bearings 15 and 16 is shown in FIG. The horizontal axis in FIG. 4 is temperature, and the vertical axis is preload. Further, in FIG. 4, a graph of the differential 12 according to the present embodiment is shown as a solid line, and a graph of a conventional differential (comparative example) that does not have the bearing retainer 121 is shown as a broken line.

Since aluminum (reducer case 11) has a larger thermal expansion than iron (differential 12), the preload on the tapered bearings 15, 16 decreases as the temperature increases, as shown in FIG. However, in the differential 12 according to the present embodiment, since the difference in the coefficient of thermal expansion between the bearing retainer 121 and the differential 12 is small, the decrease in preload of the tapered bearings 15 and 16 due to temperature rise is suppressed, and the slope of the graph is It is gentler than a conventional differential (comparative example) that does not have the bearing retainer 121. As a result, for example, assuming that 80°C is the maximum in the range of normal use, the differential 12 according to this embodiment maintains the preload to satisfy the requirements up to 80°C, while maintaining the minimum The required preload can be lowered (that is, the preload at room temperature can be set smaller). Therefore, the friction of the tapered bearings 15 and 16 can be reduced.

As described above in detail, according to the present embodiment, the differential case 14 and the taper bearing 16 are made of a plate-shaped metal material (for example, iron) that has the same or substantially the same coefficient of thermal expansion as the differential case 14. Since the configuration includes the bearing retainer 121 that is attached to cover the bearing retainer 121, for example, even if the temperature of the motor reduction gear 10 rises while the vehicle is running, a decrease in the preload of the tapered bearings 15 and 16 is suppressed. Therefore, for example, the minimum required preload at room temperature can be reduced, and the friction of the tapered bearings 15 and 16 can be reduced. In addition, by making the reducer case 11 of iron-based material, mass and cost can be significantly reduced compared to suppressing changes in preload of the tapered bearings 15 and 16. As a result, in the differential 12 disposed inside the motor reducer 10, even if the differential 12 is made of a material with a smaller coefficient of thermal expansion than the reducer case 11, the weight, cost, etc. Preload change in the tapered bearings 15, 16 due to temperature change (preload drop in the tapered bearings 15, 16 at high temperatures) is suppressed while suppressing the increase (in other words, without a significant increase in mass, cost, etc.) becomes possible.

According to this embodiment, the bearing retainer 121 is composed of a plurality of parts (an upper bearing retainer 1211 and a lower bearing retainer 1212) each having flanges 1211a and 1212a formed around the upper bearing retainer 1211 and a lower bearing retainer 1212. Since the bearing retainer 1212 is arranged to sandwich the differential case 14 and is fastened with bolts 1251 at the flanges 1211a and 1212a, the bearing retainer 121 can be easily assembled.

According to this embodiment, the taper bearings 15 and 16 are disposed at one end and the other end of the differential case 14, and the inside of the one end is connected to the taper bearing 16 on the one side. The bearing retainer 121 is attached so that the bearing retainer 121 wraps around from the outer peripheral surface of the outer ring to the side surface and comes into contact with the side surface, and the other end is fixed to the reducer case 11. Even if thermal expansion occurs in the width direction/thrust direction of the axle shafts 17a, 17b), the bearing retainer 121 can be fixed so as to suppress a decrease in preload of the tapered bearings 15, 16.

According to this embodiment, one of the bearing retainers 121 is formed using a metal material (for example, aluminum) having the same or substantially the same coefficient of thermal expansion as the reducer case 11, and is in contact with the tapered bearing 16 on one side. One end of the bearing retainer 121 (that is, the end that is not directly fixed to the reducer case 11) has a second bearing retainer 129 that supports the bearing retainer 121 in the radial direction on the outer circumference of the end. can be supported in the radial direction.

Further, according to the present embodiment, since the bearing retainer 121 is attached such that one end has a clearance with the second bearing retainer 129 in the thrust direction, the clearance provided in the thrust direction is Accordingly, the difference in thermal expansion in the thrust direction between the bearing retainer 121 and the second bearing retainer 129 can be absorbed.

According to this embodiment, since the opening 122 is formed in the bearing retainer 121 at the meshing location between the final reduction small gear 36 and the final reduction large gear 13, the bearing retainer 121 It is possible to avoid contact with the meshing portion of the large reduction gear 13.

According to this embodiment, a plurality of oil discharge holes 123 (two in this embodiment) are formed in the bearing retainer 121 at a position higher than the oil level in the motor reducer 10 while the vehicle is running. , the bearing retainer 121 can have a baffle function. Therefore, due to the baffle effect of the bearing retainer 121, oil is discharged from the oil discharge hole 123, and the oil level in the final gear part during running (see the oil level in the baffle during running in Figures 1 and 2 (solid line)) is reduced by the motor deceleration. It is possible to lower the oil level in the machine 10 (see the oil level in the reducer during traveling (broken line) in FIG. 1), and it is possible to reduce oil agitation loss.

According to this embodiment, since the outer surface of the bearing retainer 121 is provided with a rib that suppresses deformation of the bearing retainer 121, the rigidity of the bearing retainer 121 can be increased, and when the vehicle is running, the differential 12 Even when a large load is applied, deformation of the bearing retainer 121 can be suppressed.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be modified in various ways. For example, in the embodiment described above, the present invention is applied to the motor reduction gear 10, but the present invention can also be applied to a transmission, etc.

Furthermore, the method of dividing the bearing retainer 121 is not limited to the above embodiment. Furthermore, in addition to the tapered bearing 16, the outer peripheral surface of the tapered bearing 15 may be covered with a bearing retainer 121.

Further, the number, size, arrangement, etc. of the oil discharge holes 123 can be arbitrarily set according to requirements and the like.

10 Motor reducer 11 Reducer case 12 Differential 13 Final reduction large gear 14 Differential case 15, 16 Taper bearing (differential side bearing)
17a, 17b Axle shaft 18a, 18b Side gear 19 Pinion shaft 20a, 20b Pinion gear 36 Final reduction small gear 121 Bearing retainer (differential side bearing retainer)
1211 Upper bearing retainer 1212 Lower bearing retainer 1211a, 1212a Flange 122 Opening 123 Oil discharge hole 1251, 1252 Bolt 129 Second bearing retainer

Claims (8)

In a differential placed inside a transmission or reduction gear,
a differential case formed from a metal material having a lower coefficient of thermal expansion than the transmission case or the reduction gear case;
a taper bearing that rotatably supports the differential case;
A differential comprising: a bearing retainer formed from a metal material having the same or substantially the same coefficient of thermal expansion as the differential case and attached to cover the differential case and the tapered bearing. The bearing retainer is composed of a plurality of parts each having a flange formed therearound,
The differential according to claim 1, wherein the plurality of parts are arranged so as to sandwich the differential case, and are fastened with bolts at the flange. The tapered bearing is disposed at one end and the other end of the differential case,
The inner side of one end of the bearing retainer wraps around and comes into contact with the side surface of the outer ring of the tapered bearing on one side, and the other end is fixed to the transmission case or the reduction gear case. 3. The differential according to claim 1 or 2, wherein the differential is installed as follows. In the outer periphery of one end of the bearing retainer, which is formed using a metal material having the same or substantially the same coefficient of thermal expansion as the transmission case or the reduction gear case, and comes into contact with the tapered bearing on one side, The differential according to claim 3, further comprising a second bearing retainer that supports the bearing retainer in the radial direction. 5. The differential according to claim 4, wherein the bearing retainer is attached such that one end thereof has a clearance with the second bearing retainer in the thrust direction. The differential according to any one of claims 1 to 5, wherein the bearing retainer has an opening formed at a meshing location of the final gear. 7. The differential according to claim 6, wherein a plurality of oil discharge holes are formed in the bearing retainer at positions higher than an oil level level in the transmission or reduction gear while the vehicle is running. The differential according to any one of claims 1 to 5, wherein the outer surface of the bearing retainer is provided with a rib that suppresses deformation of the bearing retainer.

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