JP2011102639A - Reduction gear for electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reduction gear for an electric motor enabling reduction in the size and weight while having a structure capable of providing a high reduction ratio, and capable of effectively reducing loss of a driving system. <P>SOLUTION: The reduction gear 1 for an electric motor includes a motor M having a hollow cylindrical rotor shaft L1, a speed reduction mechanism T input with driving force from the rotor shaft L1, and a differential mechanism D distributing and transmitting driving force reduced by the speed reduction mechanism T to right and left axles L2, L3. The speed reduction mechanism T is constituted of two sets of planetary gear mechanisms PG1, PG2, and the axle L2 transmitted with output of the differential mechanism D is installed piercing an inner side of the rotor shaft L1. By adopting the planetary gear mechanisms PG1, PG2 in the speed reduction mechanism T, disposing the motor M, the speed reduction mechanism T, and the differential mechanism D on the same axis, and piercing the axle L2 through the inner side of the rotor shaft L1, an outer diameter size of the reduction gear 1 can be compactified, and miniaturization and weight reduction can be carried out. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a reduction gear for an electric motor for decelerating and transmitting an output of an electric motor mounted on a vehicle to an axle.

  In recent years, an electric vehicle (hereinafter referred to as “EV”) using an electric motor as a drive source has been developed. In the EV, a drive transmission device is provided that includes a reduction gear that decelerates the output of the motor and transmits it to the axle. As this type of drive transmission device mounted on a conventional vehicle, for example, devices described in Patent Documents 1 and 2 have been proposed. A drive device for an electric vehicle described in Patent Document 1 includes a motor, a parallel shaft type reduction mechanism that reduces the rotation of the motor, and a differential gear that distributes and transmits the reduced rotation to left and right drive shafts. (Differential mechanism). The motor and the differential gear are arranged coaxially, and the drive shaft connected to the differential gear is passed through the rotor of the motor. In addition, the electric vehicle power train described in Patent Document 2 includes a motor and a speed reducer for reducing the output of the motor, and the output shaft of the motor and the input shaft of the speed reducer are on the same axis. The motor case and the speed reducer case are combined so as to be coupled with each other.

  By the way, in the EV, it is important to reduce the size and weight of the vehicle from the viewpoint of improving the running performance and energy efficiency of the vehicle. Therefore, it is required to reduce the size and weight as much as possible even for the drive transmission device including the reduction gear as described above, while having a structure capable of obtaining a high reduction ratio. Further, in order to increase the degree of freedom in the appearance design of the vehicle, it is desirable to make the speed reducer and the drive transmission device as compact as possible.

  In this respect, since the drive device described in Patent Document 1 includes a parallel shaft type reduction mechanism, the outer dimensions of the counter gear and the case covering the same are increased. For this reason, when the driving device described in Patent Document 1 is employed in an FF vehicle, the bonnet height of the vehicle increases or the overall length increases. Therefore, it is difficult to take a design with a low bonnet line unique to an electric vehicle (EV) or a design with a small front overhang. Further, in the power train described in Patent Document 2, since the differential gear (not shown in Patent Document 2) and the motor are arranged on different axes, the outer dimensions of the reduction gear, particularly high The size becomes large.

  Further, the reduction gear described in Patent Document 1 employs a parallel shaft gear. However, in the parallel shaft gear, a thrust component in the thrust direction is generated at the meshing point of the helical gear when the driving force is transmitted. . However, if the thrust component force acting on each helical gear is not balanced, this thrust component force acts as a moment load in the direction in which the gear is to be tilted. Therefore, there is a concern that the gear meshing point may be shifted due to the moment load, thereby reducing the durability of the gear, the deterioration of the gear noise, and the interference with another part. In addition, the differential case and the case of the speed reduction mechanism need to have sufficient rigidity against the moment load, which causes an increase in size, weight, and cost of the speed reducer.

  In addition, since the moment load due to the thrust component described above also acts on the differential gear, a taper roller bearing having high rigidity is often used as the bearing that supports the side of the differential gear (the support bearing of the differential case). Yes. This tapered roller bearing is installed with a preload (axial load) that eliminates the gap in advance when assembling to the vehicle body in order to ensure bearing capacity and rigidity. In order to ensure sufficient rigidity even when the temperature changes, a corresponding preload is required. For this reason, there is a problem in that a preload setting part (shim) is required separately, or the assembly man-hours are increased.

  Further, since the tapered roller bearing rotates in principle with sliding, the friction loss is larger than that of a ball bearing or roller bearing that rotates only by rolling. Furthermore, friction loss tends to increase due to the preload or thrust force acting on the sliding surface, which is one of the causes of drive system loss.

JP-A-50-106320 JP-A-9-48250

  The present invention has been made in view of the above points, and its object is to achieve a reduction in size and weight while having a structure capable of easily obtaining a high reduction ratio, and to achieve an effect of driving system loss. An object of the present invention is to provide a reduction gear for an electric motor that can be reduced.

  In order to solve the above problems, a reduction gear for an electric motor according to the present invention receives an electric motor (M) having a hollow cylindrical output shaft (L1) and a driving force from the output shaft (L1) of the electric motor (M). And a differential mechanism (D) for distributing and transmitting the driving force decelerated by the deceleration mechanism (T) to the left and right axles (L2, L3), and an electric motor (M) The speed reduction mechanism (T) and the differential mechanism (D) are arranged coaxially with each other, and the speed reduction mechanism (T) is composed of planetary gear mechanisms (PG1, PG2), and the differential mechanism (D ) Is transmitted through the inside of the output shaft (L1), and is characterized in that it is installed.

  According to the speed reducer for an electric motor according to the present invention, the electric motor, the speed reduction mechanism, and the differential mechanism are arranged coaxially with each other, and the axle to which the output of the differential mechanism is transmitted is penetrated inside the output shaft of the electric motor. Therefore, the outer diameter of the speed reducer can be made compact, and it becomes possible to reduce the size and weight. In particular, by arranging the electric motor, the speed reduction mechanism, and the differential mechanism on the same axis as described above, the height dimension or width dimension (width dimension with respect to the axial direction) of the speed reducer can be kept small. It is possible to easily take a design specific to EV vehicles such as lowering the bonnet line or shortening the front overhang. In addition, in the present invention, since the planetary gear mechanism is used as the speed reduction mechanism, the structure of the high speed reduction ratio can be obtained, but compared with the case where the speed reduction mechanism including the parallel shaft gear is provided, the reduction gear has a higher height. The size or width dimension can be reduced.

In the planetary gear mechanism, since the radial load and moment load generated in the gear during power transmission are balanced inside, these loads hardly act on the outside of the planetary gear mechanism. Therefore, the bearing supporting the speed reduction mechanism can be reduced in size and simplified, and the weight of the speed reducer can be reduced. In addition, since the load acting on the bearing can be suppressed to a low level, friction loss generated in the bearing is reduced. Thereby, improvement of the power consumption of a motor can be expected. In addition, since radial load and moment load do not act on the differential mechanism, the bearing that supports the side of the differential mechanism is changed from a conventional large capacity, high price taper roller bearing to a small capacity, low price ball bearing. Can be substituted. Therefore, by adopting a tapered roller bearing in the past, it is possible to greatly reduce the friction loss of the bearing that supports the side portion of the differential mechanism that has a high energy loss rate in the drive system. .
In addition, replacing the tapered roller bearing with a ball bearing eliminates the need for preload management when assembling the bearing, thereby reducing the number of preload setting parts and assembly management man-hours, and reducing the cost of the product. .
In addition, since the radial load and moment load do not act on the differential case, the rigidity of the differential case and the speed reduction mechanism can be kept low, making it thinner and lighter. Can be made lighter and lighter.

  In the motor speed reducer, the planetary gear mechanism (PG1, PG2) constituting the speed reduction mechanism (T) is a first planetary gear to which driving force from the output shaft (L1) of the motor (M) is input. It is good to comprise with two sets of planetary gear mechanisms, the mechanism (PG1) and the second planetary gear mechanism (PG2) that outputs the driving force input from the first planetary gear mechanism (PG1) to the differential mechanism (D). . According to this, since effective deceleration using two sets of planetary gear mechanisms is possible, a large reduction ratio can be established. Therefore, it becomes easy to adapt the output characteristics of the electric motor to the vehicle characteristics. Further, since the use of an electric motor having a low output torque is allowed, the electric motor can be reduced in size.

  In the above-described electric motor speed reducer, the planetary gear mechanism (PG1, PG2) may be a single pinion type planetary gear mechanism. As described above, by adopting the single pinion type planetary gear mechanism, it is possible to increase the transmission efficiency of the gear by improving the meshing efficiency as compared with the case of using the double pinion type planetary gear mechanism. . Further, the number of parts of the planetary gear mechanism can be reduced to simplify the connection configuration.

  As one embodiment of the above-described reduction gear for an electric motor, the output shaft (L1) of the electric motor (M) is connected to the sun gear (S1) of the first planetary gear mechanism (PG1), and the first planetary gear mechanism. The carrier (C1) of (PG1) is connected to the sun gear (S2) of the second planetary gear mechanism (PG2), and the carrier (C2) of the second planetary gear mechanism (PG2) is the differential mechanism (D). The ring gear (R1) of the first planetary gear mechanism (PG1) and the ring gear (R2) of the second planetary gear mechanism (PG2) are fixed to the member (10) on the fixed side. It is good to be.

  According to said connection structure, a larger reduction ratio can be obtained compared with the case where other connection structures are adopted for the two sets of planetary gear mechanisms. Further, since the output shaft of the motor and the planetary gear mechanism can be connected by integrating the output shaft of the motor and the sun gear of the first planetary gear mechanism, the connection configuration between the motor and the planetary gear mechanism can be simplified. Can do. Furthermore, since the ring gear provided on the outer peripheral side of the first and second planetary gear mechanisms is always used as a fixing element, the planetary gear mechanism can be easily and reliably fixed to the casing that houses the planetary gear mechanism. It becomes.

  In the above-described electric motor speed reducer, the carrier (C2) of the second planetary gear mechanism (PG2) may be configured integrally with the input member (20) of the differential mechanism (D). According to this, the number of parts of a reduction gear can be restrained small, and size reduction, weight reduction, and cost reduction are attained. Further, it is possible to improve the power transmission efficiency from the second planetary gear mechanism to the differential mechanism.

  As another embodiment of the motor speed reducer, the pinion gear (P1) of the first planetary gear mechanism (PG1) and the pinion gear (P2) of the second planetary gear mechanism (PG2) are the same carrier (C). The output shaft (L1) of the electric motor (M) is connected to the carrier (C), and the sun gear (S2) of the second planetary gear mechanism (PG2) is connected to the fixed-side member (10 The sun gear (S1) of the first planetary gear mechanism (PG1) is preferably connected to the input member (20) of the differential mechanism (D).

  In the above configuration, the engagement of the first and second planetary gear mechanisms is only the engagement of the sun gear and the pinion gear. Therefore, the transmission efficiency (meshing efficiency) of the gear in the reduction gear can be improved. Further, since it is not necessary to provide ring gears in the first and second planetary gear mechanisms, it is possible to reduce the diameter of the speed reducer, reduce the number of parts, and reduce the weight accordingly.

  As another embodiment of the motor speed reducer, the pinion gear (P1) of the first planetary gear mechanism (PG1) and the pinion gear (P2) of the second planetary gear mechanism (PG2) are the same carrier (C). The output shaft (L1) of the electric motor (M) is connected to the carrier (C), and the ring gear (R1) of the first planetary gear mechanism (PG1) is connected to the fixed member (10 The ring gear (R2) of the second planetary gear mechanism (PG2) is preferably connected to the input member (20) of the differential mechanism (D).

  In the above configuration, the meshing in the first and second planetary gear mechanisms is only the meshing of the pinion gear and the ring gear. Therefore, the transmission efficiency (meshing efficiency) of the gear in the reduction gear can be improved. Further, since the centrifugal force acting on the pinion gear and the radial reaction force due to the meshing of the ring gear cancel each other, the pinion bearing provided in the pinion gear so as to be relatively rotatable with respect to the carrier can be reduced in size. Further, it is not necessary to increase the rigidity of the carrier with respect to the centrifugal force acting on the pinion gear. Therefore, the thickness of the carrier can be reduced, so that the configuration of the speed reduction mechanism can be simplified and reduced in weight.

  As another embodiment of the motor speed reducer, the output shaft (L1) of the motor (M) is connected to the sun gear (S2) of the second planetary gear mechanism (PG2), and the second planetary gear. The pinion gear (P2) meshing with the sun gear (S2) of the mechanism (PG2) is integrally formed with the pinion gear (P1) of the first planetary gear mechanism (PG1) and supported by the same carrier (C). The ring gear (R1) that meshes with the pinion gear (P1) of the first planetary gear mechanism (PG1) is fixed to the member (10) on the stationary side, and meshes with the pinion gear (P2) of the second planetary gear mechanism (PG2). The ring gear (R2) is preferably connected to the input member (20) of the differential mechanism (D).

In this configuration, since the rotation speed of the carrier is lower than in the other embodiments, the centrifugal force generated in the pinion gear is reduced. Further, since the gear reaction force of the pinion gear acts in the opposite direction between the sun gear and the ring gear of the second planetary gear mechanism, they cancel each other. Further, in the pinion gear, since the centrifugal force and the gear reaction force of the ring gear cancel each other, the load on the bearing (pinion bearing) that supports the pinion gear can be reduced. In addition, since the pinion gear meshes with the sun gear of the second planetary gear mechanism connected to the output shaft of the motor, it is possible to set the rotation speed of the pinion gear to be equal to or less than the rotation speed of the motor (the rotation speed of the output shaft). It becomes. Further, in the above configuration, since the first planetary gear mechanism is not provided with the sun gear, the pinion gear of the first planetary gear mechanism can be expanded to the inner diameter side. Thereby, the freedom degree of ratio setting becomes high. In addition, the outer diameter of the speed reduction mechanism can be laid out in a compact manner.
In addition, the code | symbol in said parenthesis has shown the code | symbol of the corresponding component of embodiment mentioned later as an example of this invention.

  According to the speed reducer for an electric motor according to the present invention, it is possible to achieve a reduction in size and weight while effectively reducing a drive system loss, while having a structure capable of easily obtaining a high reduction ratio.

(A) is a skeleton figure which shows the structure of the reduction gear for electric motors concerning 1st Embodiment of this invention, (b) is a speed diagram of the reduction gear for electric motors shown to (a). (A) is a skeleton figure which shows the structure of the reduction gear for electric motors concerning 2nd Embodiment of this invention, (b) is a speed diagram of the reduction gear for electric motors shown to (a). (A) is a skeleton figure which shows the structure of the reduction gear for electric motors concerning 3rd Embodiment of this invention, (b) is a speed diagram of the reduction gear for electric motors shown to (a). (A) is a skeleton figure which shows the structure of the reduction gear for electric motors concerning 4th Embodiment of this invention, (b) is a speed diagram of the reduction gear for electric motors shown to (a). (A) is a skeleton figure which shows the structure of the reduction gear for electric motors concerning 5th Embodiment of this invention, (b) is a speed diagram of the reduction gear for electric motors shown to (a). (A) is a skeleton figure which shows the structure of the reduction gear for electric motors concerning 6th Embodiment of this invention, (b) is a speed diagram of the reduction gear for electric motors shown to (a).

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[First Embodiment]
FIG. 1A is a skeleton diagram showing the configuration of a reduction gear for an electric motor (hereinafter simply referred to as “reduction gear”) 1 according to a first embodiment of the present invention, and FIG. FIG. A reduction gear 1 shown in FIG. 1A includes a motor (electric motor) M having a hollow cylindrical rotor shaft (output shaft) L1, and first and second planetary gear mechanisms PG1 for reducing the rotation of the motor M. , PG2 and a differential mechanism (differential mechanism) D for distributing and transmitting the output from the speed reduction mechanism T to the left and right axles L2, L3. The motor M, the speed reduction mechanism T, and the differential mechanism D are arranged on the same axis, and one axle L2 connected to the differential mechanism D penetrates the inside of the hollow cylindrical rotor shaft L1, and the tip thereof is illustrated. Not connected to the wheel.

  The speed reduction mechanism T includes two planetary gear mechanisms (planetary gear sets), which are a first planetary gear mechanism PG1 and a second planetary gear mechanism PG2 that are arranged coaxially with each other. The first planetary gear mechanism PG1 disposed on the motor M side includes a sun gear S1, a carrier C1, and a ring gear R1, and the second planetary gear mechanism PG2 disposed on the differential mechanism D side includes the sun gear S2, the carrier C2, and the like. A ring gear R2 is provided. The sun gear S1 of the first planetary gear mechanism PG1 is connected to the rotor shaft L1 of the motor M, and the carrier C1 is connected to the sun gear S2 of the second planetary gear mechanism PG2. The carrier C2 of the second planetary gear mechanism PG2 is configured integrally with the gear case (input member) 20 of the differential mechanism D. The ring gear R1 of the first planetary gear mechanism PG1 and the ring gear R2 of the second planetary gear mechanism PG2 are both fixed to a reduction gear case (fixed side member) 10 that houses the reduction mechanism T. The first planetary gear mechanism PG1 and the second planetary gear mechanism PG2 are both single-pinion type planetary gear mechanisms. Reference numerals B1 and B2 shown in FIG. 1A are bearings for supporting the rotor shaft L1, reference numeral B3 is a bearing for supporting one end of the axle L2, and reference numeral B4 is a side portion of the differential mechanism D. Is a bearing (supporting bearing of the gear case 20).

  In the speed reducer 1, as shown in the velocity diagram of FIG. 1B, the ring gear R1 of the first planetary gear mechanism PG1 is fixed to the speed reducer case 10 from the rotor shaft L1 of the motor M. Is input to the sun gear S1. The driving force decelerated by the first planetary gear mechanism PG1 is output from the carrier C1, and the output from the carrier C1 is input to the sun gear S2 of the second planetary gear mechanism PG2. Since the ring gear R2 of the second planetary gear mechanism PG2 is fixed to the reduction gear case 10, the driving force decelerated by the second planetary gear mechanism PG2 is output from the carrier C2 to the differential mechanism D. It has become.

  In the speed reducer 1 of the present embodiment, as described above, the motor M, the speed reduction mechanism T, and the differential mechanism D are coaxially arranged, and one axle L2 to which the output of the differential mechanism D is transmitted is connected to the rotor shaft L1. By penetrating inward, the outer diameter of the speed reducer 1 can be made compact, and it becomes possible to reduce the size and weight. In particular, since the motor M, the speed reduction mechanism T, and the differential mechanism D are arranged on the same axis, the height dimension or width dimension (width dimension with respect to the axial direction) of the speed reducer 1 can be kept small. It is possible to easily take a design specific to EV vehicles, such as lowering the line or shortening the front overhang.

  Further, in the first and second planetary gear mechanisms PG1 and PG2, the radial load generated in each gear during power transmission and the moment load generated by the thrust force are canceled out internally, so that these loads are first and second. It hardly acts outside the two planetary gear mechanisms PG1, PG2. Therefore, the reduction mechanism T and bearings (such as bearings B1 to B4) that support the members connected thereto can be reduced in size and simplified, and the reduction gear 1 can be reduced in size and weight. In addition, since the load acting on the bearing can be suppressed to a small amount, the friction loss generated in the bearing is reduced. Thereby, the improvement of the power consumption of the motor M can be expected. Also, since radial load and moment load do not act on the differential mechanism D, the bearing B4 that supports the side of the differential mechanism D is replaced with a small-capacity / low-cost ball from the conventional large-capacity / high-cost tapered roller bearing. It can be replaced with a bearing. Therefore, by adopting a tapered roller bearing conventionally, it is possible to significantly reduce the friction loss of the bearing B4, which has a high energy loss ratio in the drive system. Also, by replacing the bearing B4 from a tapered roller bearing to a ball bearing, it is not necessary to perform preload management when assembling the bearing B4, so the number of preload setting parts (shims) and assembly management man-hours can be reduced. Cost reduction is possible.

  Further, since the radial load and the moment load hardly act on the gear case 20 of the differential mechanism D, the rigidity of the gear case 20 and the speed reducer case 10 can be reduced accordingly. Therefore, the gear case 20 and the reduction gear case 10 can be reduced in thickness and weight, and the reduction gear 1 can be further reduced in size and weight.

  Moreover, in this reduction gear 1, since effective deceleration using two sets of planetary gear mechanisms PG1 and PG2 is possible, a large reduction ratio can be established. Therefore, it becomes easy to adapt the output characteristics of the electric motor M to the vehicle characteristics. Further, since the electric motor having a low output torque can be used, the electric motor M can be reduced in size and weight.

  Further, the planetary gear mechanisms PG1 and PG2 are single pinion type planetary gear mechanisms, thereby improving the gear transmission efficiency by improving the meshing efficiency as compared with the case of using the double pinion type planetary gear mechanism. Is possible. In addition, the number of parts of the planetary gear mechanisms PG1 and PG2 can be reduced to simplify the configuration.

  Further, in the reduction gear 1, as a specific coupling configuration of the two sets of planetary gear mechanisms PG1 and PG2, the rotor shaft L1 of the motor M is coupled to the sun gear S1 of the first planetary gear mechanism PG1, The carrier C1 of the planetary gear mechanism PG1 is connected to the sun gear S2 of the second planetary gear mechanism PG2, and the carrier C2 of the second planetary gear mechanism PG2 is connected to the gear case 20 of the differential mechanism D. The ring gear R1 of the gear mechanism PG1 and the ring gear R2 of the second planetary gear mechanism PG2 are fixed to the speed reducer case 10.

  According to this connection configuration, a larger reduction ratio can be obtained as compared with the case where another connection configuration is adopted. The motor M and the first planetary gear mechanism PG1 are connected by integrating the rotor shaft L1 of the motor M and the sun gear S1 of the first planetary gear mechanism PG1. Therefore, the connection configuration between the motor M and the planetary gear mechanism PG1 can be simplified. Furthermore, the ring gears R1 and R2 installed on the outer peripheral side of the two sets of planetary gear mechanisms PG1 and PG2 are always used as fixed elements, so that the reduction gear case 10 that accommodates the planetary gear mechanisms PG1 and PG2 can be used. Thus, the planetary gear mechanisms PG1 and PG2 can be easily and reliably fixed.

  Moreover, in this reduction gear 1, the gear case 20 of the differential mechanism D and the carrier C2 of the second planetary gear mechanism PG2 are integrally formed of the same parts. Thereby, the number of parts of the reduction gear 1 can be suppressed to a small size, and downsizing, weight reduction, and cost reduction are possible. Further, it is possible to improve the power transmission efficiency from the second planetary gear mechanism PG2 to the differential mechanism D.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the description of the second embodiment and the corresponding drawings, the same or corresponding components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted below. In addition, matters other than those described below are the same as those in the first embodiment. These points are the same for the other embodiments.

  Fig.2 (a) is a skeleton figure which shows the structure of the reduction gear 1-2 concerning 2nd Embodiment of this invention, The same figure (b) is a velocity diagram of the reduction gear 1-2. The speed reduction mechanism T provided in the speed reducer 1-2 of the second embodiment is configured by only one set of planetary gear mechanisms PG2. The planetary gear mechanism PG2 includes a sun gear S2 connected to the rotor shaft L1 of the motor M, a ring gear R2 fixed to the speed reducer case 10, and a carrier C2 configured integrally with the gear case 20 of the differential mechanism D. ing. As a result, as shown in the velocity diagram of FIG. 2B, the driving force from the motor M is input to the sun gear S2 of the planetary gear mechanism PG2 while the ring gear R2 is fixed, and the planetary gear mechanism PG2 decelerates. The rotated rotation is output from the carrier C2 to the differential mechanism D.

  Since the reduction gear 1-2 of this embodiment is provided with the reduction gear mechanism T which consists of 1 set of planetary gear mechanisms PG2, size reduction and weight reduction of the reduction gear 1-2 can be achieved. Further, since the planetary gear mechanism is one set, the driving force of the motor M can be transmitted with higher efficiency. However, on the other hand, the reduction ratio obtained is smaller than that of the reduction gear 1 of the first embodiment. Therefore, at present, it is suitable for mounting on a vehicle having a relatively low low-speed driving force requirement. For example, it is preferably mounted on a small vehicle such as a commuter vehicle or a minicar. In addition, when a motor with a large torque can be used (such as when a long motor can be used with a sufficient axial dimension, or when a new small motor with high torque is developed in the future), the shortage of torque can be compensated. It can also be installed in normal size vehicles.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. Fig.3 (a) is a skeleton figure which shows the structure of the reduction gear 1-3 concerning 3rd Embodiment of this invention, The same figure (b) is a velocity diagram of the reduction gear 1-3. The speed reducer 1-3 of the present embodiment replaces the differential mechanism D formed by combining the bevel gears included in the speed reducer 1 of the first embodiment, and a differential mechanism (hereinafter referred to as “planetary differential”) formed of a planetary gear mechanism. D) is adopted. The planetary differential D ′ includes a sun gear Sd connected to one axle L2, a carrier Cd connected to the other axle L3, and a ring gear Rd connected to a ring gear R2 included in the second planetary gear mechanism PG2 of the speed reduction mechanism T. It consists of and. On the other hand, the second planetary gear mechanism PG2 of the speed reduction mechanism T includes a sun gear S2 to which the carrier C1 of the first planetary gear mechanism PG1 is coupled, a carrier C2 fixed to the speed reducer case 10, and a planetary differential D ′. A ring gear R2 connected to the ring gear Rd is provided.

  In the speed reducer 1-3 of the present embodiment, by adopting the planetary differential D ′ as the differential mechanism, the axial dimension of the differential mechanism can be reduced, so the length dimension in the axial direction of the speed reducer 1-3 can be reduced. It can be kept small.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. Fig.4 (a) is a skeleton figure which shows the structure of the reduction gear 1-4 concerning 4th Embodiment of this invention, The same figure (b) is a velocity diagram of the reduction gear 1-4. The first planetary gear mechanism PG1 provided in the speed reducer 1-4 of the present embodiment includes a sun gear S1 connected to the gear case 20 of the differential mechanism D and a pinion gear P1 connected to the rotor shaft L1 of the motor M via the carrier C. And. The second planetary gear mechanism PG2 includes a sun gear S2 fixed to the speed reducer case 10 and a pinion gear P2 configured integrally with the pinion gear P1 of the first planetary gear mechanism PG1. The pinion gear P <b> 1 and the pinion gear P <b> 2 are connected coaxially at a predetermined interval, and the diameter dimension and the number of teeth are different from each other. Both the pinion gear P1 and the pinion gear P2 are supported by the carrier C.

In the speed reducer 1-4, as shown in the velocity diagram of FIG. 4B, the output from the rotor shaft L1 of the motor M is transmitted through the carrier C to the pinion gear P1 of the first planetary gear mechanism PG1 and the second planetary gear P1. It is transmitted to the pinion gear P2 of the gear mechanism PG2. Since the sun gear S2 of the second planetary gear mechanism PG2 is fixed to the speed reducer case 10, the reduced driving force is applied from the sun gear S1 of the first planetary gear mechanism PG1 to the gear case 20 of the differential mechanism D. Is output. In this case, the following relationship holds for ρ1 and ρ2 in the velocity diagram shown in FIG.
ρ1 = Zp1 / Zs1
ρ2 = Zp2 / Zs2
ρ2> ρ1
here,
Zs1: Number of teeth of sun gear S1 Zs2: Number of teeth of sun gear S2 Zp1: Number of teeth of pinion gear P1 Zp2: Number of teeth of pinion gear P2

  In the speed reducer 1-4 of the present embodiment, the meshing at the first planetary gear mechanism PG1 is only the meshing of the sun gear S1 and the pinion gear P1, and the meshing at the second planetary gear mechanism PG2 is the meshing of the sun gear S2 and the pinion gear P2. Only meshing. Therefore, there is an advantage that gear transmission efficiency (meshing efficiency) is good. Further, since the first and second planetary gear mechanisms PG1 and PG2 do not have the ring gear, it is possible to reduce the diameter of the speed reducer 1-4, reduce the number of parts, and reduce the weight accordingly. it can. Further, there is an advantage that the rotational speeds of the pinion gears P1 and P2 are not so high as compared with the fifth embodiment described later.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. Fig.5 (a) is a skeleton figure which shows the structure of the reduction gear 1-5 concerning 5th Embodiment of this invention, The same figure (b) is a velocity diagram of the reduction gear 1-5. The first planetary gear mechanism PG1 provided in the speed reducer 1-5 of this embodiment includes a ring gear R1 fixed to the speed reducer case 10 and a pinion gear P1 connected to the rotor shaft L1 of the motor M via the carrier C. And. The second planetary gear mechanism PG2 includes a ring gear R2 configured integrally with the gear case 20 of the differential mechanism D and a pinion gear P2 configured integrally with the pinion gear P1 of the first planetary gear mechanism PG1. The pinion gear P <b> 1 and the pinion gear P <b> 2 are connected coaxially at a predetermined interval, and the diameter dimension and the number of teeth are different from each other. Both the pinion gear P1 and the pinion gear P2 are supported by the carrier C.

In the speed reducer 1-5, as shown in the velocity diagram of FIG. 5B, the output from the rotor shaft L1 of the motor M is transmitted through the carrier C to the pinion gear P1 of the first planetary gear mechanism PG1 and the second planetary gear P1. It is input to the pinion gear P2 of the gear mechanism PG2. Since the ring gear R2 of the second planetary gear mechanism PG2 is fixed to the reduction gear case 10, the reduced driving force is applied from the ring gear R2 of the second planetary gear mechanism PG2 to the gear case 20 of the differential mechanism D. Is output. In this case, the following relationship holds for ρ3 and ρ4 in the velocity diagram shown in FIG.
ρ3 = Zp2 / Zr2
ρ4 = Zp1 / Zr1
ρ4> ρ3
However,
Zr1: Number of teeth of ring gear R1 Zr2: Number of teeth of ring gear R2 Zp1: Number of teeth of pinion gear P1 Zp2: Number of teeth of pinion gear P2

  In the speed reducer 1-5 of the present embodiment, the meshing at the first planetary gear mechanism PG1 is only the meshing of the pinion gear P1 and the ring gear R1, and the meshing at the second planetary gear mechanism PG2 is the meshing of the pinion gear P2 and the ring gear R2. Only meshing. Therefore, as in the fourth embodiment, there is an advantage that the transmission efficiency (meshing efficiency) of the gear is good. Further, since the centrifugal force acting on the pinion gears P1 and P2 and the radial reaction force due to the meshing of the ring gears R1 and R2 cancel each other, a pinion bearing provided in the pinion gears P1 and P2 so as to be rotatable relative to the carrier C. It is possible to reduce the size (not shown). Further, it is not necessary to make the rigidity of the carrier C so high as to the centrifugal force acting on the pinion gears P1 and P2. Therefore, the structure of the speed reduction mechanism T can be simplified and reduced in weight by reducing the thickness of the carrier C.

[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described. Fig.6 (a) is a skeleton figure which shows the structure of the reduction gear 1-6 concerning 6th Embodiment of this invention, The same figure (b) is a velocity diagram of the reduction gear 1-6. The first planetary gear mechanism PG1 included in the speed reducer 1-6 of the present embodiment includes a ring gear R1 fixed to the speed reducer case 10 and a pinion gear P1 meshing with the ring gear R1. The second planetary gear mechanism PG2 includes a ring gear R2 configured integrally with the gear case 20 of the differential mechanism D, a pinion gear P2 configured integrally with the pinion gear P1 of the first planetary gear mechanism PG1, and a rotor shaft of the motor M. And a sun gear S2 connected to L1. The pinion gear P <b> 1 and the pinion gear P <b> 2 are connected coaxially at a predetermined interval, and the diameter dimension and the number of teeth are different from each other. Both the pinion gear P1 and the pinion gear P2 are supported by the carrier C.

In the speed reducer 1-6, as shown in the velocity diagram of FIG. 6B, the output from the rotor shaft L1 of the motor M is input to the sun gear S2. The pinion gear P1 of the first planetary gear mechanism PG1 and the pinion gear P2 of the second planetary gear mechanism PG2 are integrally configured, and the ring gear R1 of the first planetary gear mechanism PG1 is fixed to the speed reducer case 10. Therefore, the decelerated driving force is output from the ring gear R2 of the second planetary gear mechanism PG2 to the gear case 20 of the differential mechanism D. In this case, the following relationship holds for ρ2, ρ3, and ρ4 in the velocity diagram shown in FIG.
ρ2 = Zp2 / Zs2
ρ3 = Zp2 / Zr2
ρ4 = Zp1 / Zr1
ρ4> ρ3
However,
Zs2: Number of teeth of sun gear S2 Zr1: Number of teeth of ring gear R1 Zr2: Number of teeth of ring gear R2 Zp1: Number of teeth of pinion gear P1 Zp2: Number of teeth of pinion gear P2

  In the speed reducer 1-6 of this embodiment, a larger speed reduction is possible than the speed reducers 1-4 and 1-5 of the fourth and fifth embodiments. The speed reducer 1-4 of the fourth embodiment has a high rotational speed of the carrier C, and the centrifugal force generated in the pinion gears P1, P2 increases. Further, since the gear reaction force and the centrifugal force of the pinion gears P1 and P2 act in the same direction, an excessive load may be applied to the bearing (pinion bearing) that supports the pinion gears P1 and P2. On the other hand, in the speed reducer 1-6 of the present embodiment, the rotational speed of the carrier C is low, and the centrifugal force generated in the pinion gears P1, P2 is small. Further, since the gear reaction force of the pinion gear P2 acts in the opposite direction between the sun gear S2 and the ring gear R2, they cancel each other. Further, in the pinion gears P1 and P2, since the centrifugal force and the gear reaction force of the ring gears R1 and R2 cancel each other, the load on the bearing (pinion bearing) that supports the pinion gears P1 and P2 can be reduced.

  Further, in the speed reducer 1-5 of the fifth embodiment, the rotation speed of the pinion gears P1, P2 increases from the rotation speed of the motor M (rotation speed of the rotor shaft L1). On the other hand, in the reduction gear 1-6 of the present embodiment, it is possible to set the rotation speed of the pinion gears P1 and P2 to be equal to or lower than the rotation speed of the rotor shaft L1. Further, in the speed reducer 1-6 of the present embodiment, since the first planetary gear mechanism PG1 is not provided with a sun gear, the diameter of the pinion gear P1 can be increased to the position of the outer diameter of the rotor shaft L. Accordingly, the degree of freedom in setting the ratio is increased. In addition, the outer diameter of the speed reducer 1-6 can be laid out in a compact manner.

  The calculation example of the ratio of the reduction gear 1-6 of this embodiment and the rotation speed ratio of the pinion gears P1 and P2 with respect to the output shaft L1 of the motor M is shown. Here, the ratio NL = (ρ2 + ρ4) / (ρ4-ρ3). Therefore, large deceleration is possible with ρ4≈ρ3. Further, the rotational speed ratio NP = 1 / (ρ2 + ρ4) of the pinion gears P1, P2 with respect to the output shaft L1 of the motor M. Therefore, if (ρ2 + ρ4)> 1 is set, the rotation speed of the pinion gears P1 and P2 can be made smaller than the rotation speed of the output shaft L1 of the motor M.

  The above relationship is illustrated by specific numerical values. If Zs2 = 35, Zr2 = 97, Zr1 = 111, Zp2 = 31, Zp1 = 45, then ρ2 = 0.886, ρ3 = 0.320, and ρ4 = 0.405. Therefore, since the ratio NL = 15.045, a large reduction ratio can be obtained. Further, the rotational speed ratio NP = 0.775 (<1). Therefore, the rotational speed of the pinion gears P1 and P2 can be kept lower than the rotational speed of the output shaft L1 of the motor.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea described in the claims and the specification and drawings. Is possible. For example, the vehicle on which the motor speed reducers 1 to 1-5 according to the present invention shown in the above embodiments is mounted is not limited to an EV including only a motor as a drive source. The present invention can also be applied to a vehicle equipped with an assist-type four-wheel drive system (four-wheel drive system in which front wheels are driven by an engine and rear wheels are auxiliary driven by a motor).

1-1-6 Reducer (Speed reducer for electric motor)
10 Reducer case (member on the fixed side)
20 Gear case (input member)
B1-B4 Bearing C1, C2 Carrier D Differential mechanism (differential mechanism)
D 'differential mechanism (planetary diff)
L1 Rotor shaft (output shaft)
L2, L3 Axle M Motor (electric motor)
P1, P2 Pinion gear PG1 First planetary gear mechanism PG2 Second planetary gear mechanism R1, R2 Ring gears S1, S2 Sun gear T Reduction mechanism

Claims (8)

An electric motor having a hollow cylindrical output shaft;
A speed reduction mechanism to which driving force from the output shaft of the electric motor is input;
A differential mechanism that distributes and transmits the driving force decelerated by the deceleration mechanism to the left and right axles,
The electric motor, the speed reduction mechanism, and the differential mechanism are arranged coaxially with each other,
The reduction mechanism is composed of a planetary gear mechanism,
One of the axles to which the output from the differential mechanism is transmitted is installed so as to penetrate the inside of the output shaft. The planetary gear mechanism constituting the speed reduction mechanism is:
Two sets of planets: a first planetary gear mechanism to which the driving force from the output shaft is input, and a second planetary gear mechanism that outputs the driving force input from the first planetary gear mechanism to the differential mechanism. 2. The reduction gear for an electric motor according to claim 1, wherein the reduction gear is constituted by a gear mechanism. The reduction gear for an electric motor according to claim 1 or 2, wherein the planetary gear mechanism is a single pinion type planetary gear mechanism. The output shaft of the electric motor is connected to a sun gear of the first planetary gear mechanism,
The carrier of the first planetary gear mechanism is connected to the sun gear of the second planetary gear mechanism;
A carrier of the second planetary gear mechanism is connected to an input member of the differential mechanism;
The reduction gear for an electric motor according to claim 2 or 3, wherein the ring gear of the first planetary gear mechanism and the ring gear of the second planetary gear mechanism are fixed to a fixed member. The speed reducer for an electric motor according to claim 4, wherein the carrier of the second planetary gear mechanism is configured integrally with an input member of the differential mechanism. The pinion gear of the first planetary gear mechanism and the pinion gear of the second planetary gear mechanism are supported by the same carrier,
The output shaft of the electric motor is connected to the carrier;
The sun gear of the second planetary gear mechanism is fixed to a member on the fixed side,
The reduction gear for an electric motor according to claim 2, wherein a sun gear of the first planetary gear mechanism is connected to an input member of the differential mechanism. The pinion gear of the first planetary gear mechanism and the pinion gear of the second planetary gear mechanism are supported by the same carrier,
The output shaft of the electric motor is connected to the carrier;
The ring gear of the first planetary gear mechanism is fixed to a fixed member,
The reduction gear for an electric motor according to claim 2, wherein the ring gear of the second planetary gear mechanism is connected to an input member of the differential mechanism. The output shaft of the electric motor is connected to a sun gear of the second planetary gear mechanism;
The pinion gear that meshes with the sun gear of the second planetary gear mechanism is configured integrally with the pinion gear of the first planetary gear mechanism and supported by the same carrier,
A ring gear meshing with the pinion gear of the first planetary gear mechanism is fixed to a member on the fixed side;
The reduction gear for an electric motor according to claim 2 or 3, wherein a ring gear meshing with a pinion gear of the second planetary gear mechanism is connected to an input member of the differential mechanism.

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