Wheel drive device and wheel drive unit

Abstract

The present invention provides a technique for driving a wheel using another motor different from a first motor. A wheel drive device for driving a wheel that causes a device installed in a natural environment to travel, the wheel drive device being provided with: a first motor (30); a first speed reducer (32) for reducing the speed of the output of the first motor (30) and outputting the output to a wheel (20) from a first output shaft; and a second motor (38) provided on a second power transmission path (36) that merges with a first power transmission path (34) from the first motor (30) to the first output shaft.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2023-203754 filed on December 1, 2023. The entire content of the Japanese application is incorporated herein by reference. Technical Field

[0002] The present invention relates to a wheel drive device for a device to be installed in a natural environment. Background Art

[0003] Patent Document 1 discloses a wheel drive device for driving wheels of a device installed in a natural environment. The wheel drive device includes a first motor and a first speed reducer that decelerates the output of the first motor and outputs it to the wheels.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2015-140225

[0005] In a wheel drive device for driving wheels of a device installed in a natural environment, there may be a case where it is advantageous to be able to drive the wheels using another motor different from the first motor. Summary of the Invention

[0006] Therefore, one object of the present invention is to provide a technique that can also drive wheels using another motor different from the first motor.

[0007] A wheel drive device according to an embodiment of the present invention is a wheel drive device for driving wheels of a device installed in a natural environment, and includes: a first motor; a first speed reducer that decelerates the output of the first motor and outputs it from a first output shaft to the wheels; and a second motor disposed on a second power transmission path that merges with a first power transmission path from the first motor to the first output shaft.

[0008] According to the present invention, in a wheel drive device for driving wheels of a device installed in a natural environment, it is possible to drive the wheels using a motor different from the first motor. Brief Description of the Drawings

[0009] Figure 1 It is a perspective view schematically showing the device of the first embodiment.

[0010] Figure 2 It is a schematic view showing the wheel drive device of the first embodiment.

[0011] Figure 3 It is a schematic view showing the wheel drive device of the second embodiment.

[0012] Figure 4 It is a schematic view showing the wheel drive device of the third embodiment.

[0013] Figure 5 This is a schematic diagram showing the wheel drive device of the fourth embodiment.

[0014] Figure 6 This is a schematic diagram showing the wheel drive unit of the fifth embodiment.

[0015] In the figure: 10 - wheel drive device, 10A - first wheel drive device, 10B - second wheel drive device, 12 - equipment, 20 - wheel, 30 - first motor, 32 - first speed reducer, 32c - first output shaft, 34 - first power transmission path, 36 - second power transmission path, 38 - second motor, 40 - second speed reducer, 40c - second output shaft, 48a - first bevel pinion, 48b - first bevel gear, 60 - wheel drive unit, 62 - control device, 70 - clutch. Specific Embodiments

[0016] Hereinafter, embodiments of the wheel drive device of the present invention will be described. Hereinafter, the same or equivalent components are denoted by the same reference numerals, and repeated descriptions are omitted. In each drawing, for the sake of convenience of explanation, the components are appropriately omitted, enlarged, or reduced. The drawings are viewed according to the orientation of the reference numerals.

[0017] (First Embodiment)

[0018] Reference Figure 1 . The wheel drive device 10 is used to be provided on the equipment 12 in a natural environment. Here, the natural environment means: an environment directly exposed to the naturally generated wind. Places satisfying such conditions include, for example, watersides such as harbors, coasts, lake shores, and river banks, as well as land. When installed on land, places satisfying the conditions of the natural environment include, for example, freight terminals such as cargo stations, as well as construction sites. As the equipment 12 installed in such a natural environment, a harbor crane installed in a harbor is illustrated here. The specific example of this equipment 12 is not particularly limited. For example, it can be various handling machines such as cranes and unloaders, or other equipment.

[0019] Here, as the harbor crane that is the equipment 12, a gantry crane is shown, but its specific example is not particularly limited, and it can also be a jib crane or the like. The equipment 12 includes an equipment main body 14 and a spreader device 16 mounted on the equipment main body 14 and used for loading and unloading. The equipment main body 14 includes a lower structure part 14a on which a plurality of wheels 20 are installed and an upper structure part 14b supported by the lower structure part 14a and on which the spreader device 16 is mounted. The equipment 12 travels along a guide rail 18 laid on the ground through the plurality of wheels 20.

[0020] The device 12 travels via a plurality of wheels 20, and thus can move between a working position for working with the device 12 and an avoidance position to be avoided from the working position. Figure 1 Indicates the state where the device 12 is located at the working position. When located at the working position, for example, the device 12 can be used for loading and unloading work. The standby position is a position for reducing the wind pressure load borne by the device 12 more than when it is at the working position, and is set at a location far from the working position. Around the avoidance position, for example, a windbreak wall can be provided for reducing the wind pressure load on the device 12 disposed at the avoidance position.

[0021] The plurality of wheels 20 are used for the device 12 to travel. The wheel drive device 10 is used to drive at least a part of the plurality of wheels 20. The wheels 20 driven by the wheel drive device 10 function as drive wheels. Here, an example is shown where all the wheels 20 function as drive wheels driven by the wheel drive device 10, but a part of them can also function as driven wheels not driven by the wheel drive device 10. And here, for the sake of convenience of explanation, a case where the wheel drive device 10 is located at a position far from the device 12 is illustrated, but in fact, each wheel drive device 10 is fixed to the device main body 14 of the device 12.

[0022] Reference Figure 2 The wheel drive device 10 includes a first motor 30, a first speed reducer 32 that decelerates the output of the first motor 30 and outputs it from the first output shaft 32c to the wheel 20, a second motor 38 provided on a second power transmission path 36 that joins a first power transmission path 34 from the first motor shaft 30a of the first motor 30 to the first output shaft 32c, and a second speed reducer 40 that decelerates the output of the second motor 38. And the wheel drive device 10 includes a first brake 42 provided on the first power transmission path 34 and a second brake 44 provided on the second power transmission path 36.

[0023] The wheel drive device 10 includes the above-mentioned first power transmission path 34 and second power transmission path 36. The first power transmission path 34 is used to transmit rotation from the first motor 30 to the wheel 20 via the first output shaft 32c. The first power transmission path 34 includes a confluence portion rotating shaft 46, which is provided at a portion where it joins the second power transmission path 36 and receives power from the second power transmission path 36. The second power transmission path 36 is used to transmit rotation from the second motor 38 to the portion where it joins the first power transmission path 34. The rotation output from the second power transmission path 36 is output to the wheel 20 via the first power transmission path 34.

[0024] The first motor 30 illustrates a three-phase induction motor, but its specific example is not particularly limited, and it may also be a single-phase induction motor, a synchronous motor, etc. The first motor 30 includes a first motor shaft 30a that rotates through a first stator and a first rotor (not shown), and a first motor housing 30b that houses the first stator, the first rotor, and the first motor shaft 30a. The first motor housing 30b is supported on a first reduction gear housing 32d described later. To achieve this, in the present embodiment, the first motor housing 30b is fixed to the first reduction gear housing 32d, but the first motor housing 30b may also be fixed to other components supported on the first reduction gear housing 32d.

[0025] The first reduction gear 32 includes a first input shaft 32a to which the output of the first motor 30 is input, a first reduction mechanism 32b that reduces the output of the first motor 30, a first output shaft 32c that outputs the rotation reduced by the first reduction mechanism 32b to the wheel 20, and a first reduction gear housing 32d that houses them. In addition, the first reduction gear 32 of the present embodiment includes at least one first intermediate shaft 32e that forms a part of a first power transmission path 34 from the first input shaft 32a to the first output shaft 32c.

[0026] In the present embodiment, an example in which the first input shaft 32a also serves as the first motor shaft 30a is illustrated, but they may also be separate. When they are separate, the first input shaft 32a and the first motor shaft 30a are directly or indirectly connected via other components so as to be able to rotate integrally with each other. The first output shaft 32c outputs rotation to the wheel 20 directly or indirectly from the first output shaft 32c. In the present embodiment, there are a total of two first intermediate shafts 32e. In the present embodiment, the above-mentioned confluence portion rotation shaft 46 is constituted by the first intermediate shaft 32e on the front stage side.

[0027] Although not shown, the first reduction gear housing 32d is fixed to the equipment main body 14 of the equipment 12 via a torque arm 32f fixed to the first reduction gear housing 32d. The first reduction gear housing 32d supports each rotating shaft such as the first input shaft 32a as rotatable via a bearing (not shown).

[0028] The first speed reduction mechanism 32b of the present embodiment includes a front-stage speed reduction unit 32ba provided on the front-stage side of the first power transmission path 34 closer to the first input shaft 32a than the confluence unit rotation shaft 46, and a rear-stage speed reduction unit 32bb provided on the rear-stage side of the first power transmission path 34 closer to the confluence unit rotation shaft 46. In the present embodiment, the front-stage speed reduction unit 32ba is constituted by a first orthogonal gear set 48, and the rear-stage speed reduction unit 32bb is constituted by a two-stage parallel gear set 50. The orthogonal gear set means a gear set in which their rotation center lines are orthogonal to each other when observed from a direction orthogonal to both the axial direction of the front-stage orthogonal pinion and the axial direction of the rear-stage orthogonal gear. The parallel gear set 50 means a gear set in which the axial direction of the front-stage pinion and the axial direction of the rear-stage gear are parallel.

[0029] The first orthogonal gear set 48 is constituted by a front-stage first orthogonal pinion 48a and a rear-stage first orthogonal gear 48b that meshes with the first orthogonal pinion 48a. Here, the first orthogonal pinion 48a and the first orthogonal gear 48b illustrate a set of a bevel pinion and a bevel gear, but may also be a set of a hypoid pinion and a hypoid gear, or may also be a set of a worm pinion and a worm wheel. The first orthogonal pinion 48a is connected to the first input shaft 32a, and the first orthogonal gear 48b is connected to the confluence unit rotation shaft 46. The pinion of the front-stage parallel gear set 50 in the two-stage parallel gear set 50 is connected to the confluence unit rotation shaft 46, and the gear that meshes with the pinion is connected to the first intermediate shaft 32e on the rear stage. The pinion of the rear-stage parallel gear set 50 is connected to the first intermediate shaft 32e on the rear stage, and the gear that meshes with the pinion is connected to the first output shaft 32c.

[0030] The second motor 38 illustrates a three-phase induction motor, but its specific example is not particularly limited, and it may also be a single-phase induction motor, a synchronous motor, etc. The second motor 38 includes a second motor shaft 38a that rotates through a second stator and a second rotor (not shown), and a second motor housing 38b that houses the second stator, the second rotor, and the second motor shaft 38a. The second motor housing 38b is supported on the first speed reducer housing 32d. To achieve this, in the present embodiment, the second motor cover 38b is fixed to the second speed reducer housing 40d, which is another component supported on the first speed reducer housing 32d, but it may also be fixed to the first speed reducer housing 32d.

[0031] The second speed reducer 40 is provided on the second power transmission path 36. The second speed reducer 40 decelerates the output of the second motor 38 and outputs it to the confluence part rotating shaft 46 on the first power transmission path 34. The second speed reducer 40 includes a second input shaft 40a into which the output of the second motor 38 is input, a second speed reduction mechanism 40b that decelerates the output of the second motor 38, a second output shaft 40c that rotationally outputs the decelerated output from the second speed reduction mechanism 40b to the confluence part rotating shaft 46, and a second speed reducer housing 40d that houses them. Here, an example is shown in which the second input shaft 40a also serves as the second motor shaft 38a, but they may also be separate. When they are separate, the second input shaft 40a and the second motor shaft 38a are directly or via other components connected so as to be able to rotate integrally with each other.

[0032] In the present embodiment, the second output shaft 40c of the present embodiment also serves as the confluence part rotating shaft 46. To achieve this, the confluence part rotating shaft 46 has an extension part 46a that extends outward from the first speed reducer housing 32d, and this extension part 46a constitutes the second output shaft 40c. The confluence part rotating shaft 46 and the second output shaft 40c are constituted by the same component. In addition, the second output shaft 40c and the confluence part rotating shaft 46 may also be separate. When they are separate, the second output shaft 40c and the confluence part rotating shaft 46 are directly or via other components connected so as to be able to rotate integrally with each other. In either case, the second output shaft 40c is provided on the axial extension line of the confluence part rotating shaft 46 and can rotate integrally with the confluence part rotating shaft 46.

[0033] In the present embodiment, the first power transmission path 34 is constituted by the first motor shaft 30a, the first input shaft 32a, the first speed reduction mechanism 32b, and the first output shaft 32c. When the first speed reducer 32 has a first intermediate shaft 32e, the first power transmission path 34 is constituted by the first motor shaft 30a, the first input shaft 32a, the first speed reduction mechanism 32b, the first output shaft 32c, and the first intermediate shaft 32e. The first power transmission path 34 includes the above-mentioned confluence part rotating shaft 46. In the present embodiment, the second power transmission path 36 is constituted by the second motor shaft 38a, the second input shaft 40a, the second speed reduction mechanism 40b, and the second output shaft 40c.

[0034] Here, the rated output (kW), rated torque (N·m), and rated speed (min -1 ) of the first motor 30 are referred to as the first rated output Or1, the first rated torque Tr1, and the first rated speed Nr1. The rated output (kW), rated torque (N·m), and rated speed (min -1)They are called the second rated output Or2, the second rated torque Tr2, and the second rated speed Nr2. The rated output means the rated value of the output that can be continuously output at the rated voltage and the rated frequency. The rated torque and the rated speed mean the rated values of the torque and the speed when the rated output is continuously output. The meaning of the rated torque for the rated output and the rated speed is the same. The rated output becomes the product of the rated torque and the rated speed. The rated outputs of the first motor 30 and the second motor 38 respectively become the outputs that can be output by the motors 30, 38 at the same rated voltage and the same rated frequency.

[0035] The reduction ratio of the part on the first power transmission path 34 that is more on the upstream side than the part where it merges with the second power transmission path 36 is called the upstream first reduction ratio R1a. The reduction ratio of the part on the first power transmission path 34 that is more on the downstream side than the part where it merges with the second power transmission path 36 is called the downstream first reduction ratio R1b. The reduction ratio of the second speed reducer 40 is called the second reduction ratio R2. When a part of the first reduction mechanism 32b does not exist on the upstream side part of the first power transmission path 34, the upstream first reduction ratio R1a becomes 1. When, as in the present embodiment, there is an upstream reduction part 32ba that is part of the first reduction mechanism 32b on the upstream side part of the first power transmission path 34, the upstream first reduction ratio R1a becomes the reduction ratio of this upstream reduction part 32ba. When the entire first reduction mechanism 32b exists on the downstream side part of the first power transmission path 34, the downstream first reduction ratio R1b becomes the total reduction ratio of the first reduction mechanism 32. When, as in the present embodiment, only a part of the first reduction mechanism 32b exists on the downstream side part of the first power transmission path 34, the downstream first reduction ratio R1b becomes the reduction ratio of the downstream reduction part 32bb. The second reduction ratio R2 means the total reduction ratio of the second speed reducer 40.

[0036] The torque and speed acting on the confluence part rotating shaft 46 when the first rated output Or1 is output from the first motor 30 are called the first confluence part torque Tt1 and the first confluence part speed Nc1. The torque and speed acting on the confluence part rotating shaft 46 when the second rated output Or2 is output from the second motor 38 are called the second confluence part torque Tt2 and the second confluence part speed Nc2.

[0037] The torque and its speed output from the first output shaft 32c when the first rated output Or1 is output from the first motor 30 are called the first output torque To1 and the first output speed No1. The torque and its speed output from the first output shaft 32c when the second rated output Or2 is output from the second motor 38 are called the second output torque To2 and the second output speed No2. Each output torque is used to drive the wheels 20.

[0038] At this time, in the present embodiment, the first rated torque Tr1 of the first motor 30 is greater than the second rated torque Tr2 of the second motor 38. Also, the first rated speed Nr1 of the first motor 30 is greater than the rated speed Nr2 of the second motor 38. That is, Tr1 > Tr2 and Nr1 > Nr2. And in the present embodiment, by satisfying the conditions regarding the reduction ratio described below, the second output torque To2 becomes greater than the first output torque To1. That is, To1 < To2. And in the present embodiment, by satisfying the conditions regarding the reduction ratio described below, the first output speed No1 becomes greater than the second output speed No2. That is, No1 > No2. Further, the first rated output Or1 of the first motor 30 is greater than the second rated output Or2 of the second motor 38. That is, Or1 > Or2.

[0039] An idea of how to satisfy the condition of To1 < To2 regarding the output torque under the condition of Tr1 > Tr2 regarding the rated torque will be described. When the first rated torque Tr1 is output from the first motor 30, the first confluence torque Tt1 acting on the confluence portion rotating shaft 46 is the product of the first rated torque Tr1 and the front-stage first reduction ratio R1a (= Tr1 × R1a). And when the second rated torque Tr2 is output from the second motor 38, the second confluence torque Tt2 acting on the confluence portion rotating shaft 46 is the product of the second rated torque Tr2 and the second reduction ratio R2 (= Tr2 × R2). Both the first confluence torque Tt1 and the second confluence torque Tt2 are amplified by the same amount by the post-stage reduction unit 32bb and then output as the first output torque To1 and the second output torque To2. Therefore, the magnitude relationship between the first output torque To1 and the second output torque To2 is the same as the magnitude relationship between the first confluence torque Tt1 and the second confluence torque Tt2. When the second confluence torque Tt2 is greater than the first confluence torque Tt1, the second output torque To2 is greater than the first output torque To1. In other words, when the condition regarding the confluence torque of Tt1 < Tt2 is satisfied, that is, when the following formula (1) is satisfied, the second output torque To2 becomes greater than the first output torque To1.

[0040] Tr1 × R1a < Tr2 × R2... Formula (1)

[0041] In this embodiment, the first reduction ratio R1a and the second reduction ratio R2 of the previous stage are adjusted so that, under the condition of Tr1 > Tr2 regarding the rated torque, the condition of To1 < To2 regarding the output torque is satisfied, that is, the formula (1) is satisfied. To achieve this, the second reduction ratio R2 is increased relative to the first reduction ratio R1a of the previous stage. That is, it is set as R1a < R2. For example, the first reduction ratio R1a of the previous stage is set to 50, and the second reduction ratio R2 is set to 100. At this time, it can be seen from the formula (1) that the larger the second reduction ratio R2 is relative to the first reduction ratio R1a of the previous stage, the easier it is to satisfy the above-mentioned condition regarding the output torque. That is, by increasing the second reduction ratio R2 relative to the first reduction ratio R1a of the previous stage, the higher the second reduction ratio R2 is set, the easier it is to satisfy the condition of To1 < To2 regarding the output torque under the condition of Tr1 > Tr2 regarding the rated torque. In addition, if the condition of To1 < To2 regarding the output torque is satisfied under the condition of Tr1 > Tr2 regarding the rated torque, the condition of R1a < R2 regarding the reduction ratio will necessarily be satisfied.

[0042] Next, the idea of how to satisfy the condition of No1 > No2 regarding the output speed will be described. When the first rated speed Nr1 is output from the first motor 30, the first confluence part speed Nc1 of the confluence part rotating shaft 46 is the product of the first rated speed Nr1 and the reciprocal of the first reduction ratio R1a of the previous stage (= Nr1 × (1 / R1a)). And when the second rated speed Nr2 is output from the second motor 38, the second confluence part speed Nc2 of the confluence part rotating shaft 46 is the product of the second rated speed Nr2 and the reciprocal of the second reduction ratio R2 (= Nr2 × (1 / R2)). Both the first confluence part speed Nc1 and the second confluence part speed Nc2 are decelerated by the same amount by the subsequent stage reduction part 32bb and then output as the first output speed No1 and the second output speed No2. Therefore, the magnitude relationship between the first output speed No1 and the second output speed No2 is the same as the magnitude relationship between the first confluence part speed Nc1 and the second confluence part speed Nc2. When the first confluence part speed Nc1 is greater than the second confluence part speed Nc2, the first output speed No1 is greater than the second output speed No2. In other words, when the condition of Nc1 > Nc2 regarding the confluence part speed is satisfied, that is, when the following formula (2) is satisfied, the first output speed No1 is greater than the second output speed No2.

[0043] Nr1×(1 / R1a)>Nr2×(1 / R2)……Formula (2)

[0044] In this embodiment, as described above, under the condition of Nr1 > Nr2 regarding the rated speed, the condition of R1a < R2 regarding the reduction ratio is satisfied. Therefore, the relationship of formula (2) will necessarily be satisfied, thereby satisfying the condition of No1 > No2 regarding the output speed.

[0045] As described above, when the first rated output Or1 is output from the first motor 30, the first output torque To1 smaller than the second output torque To2 is output at the first output speed No1 greater than the second output speed No2. Further, when the second rated output Or2 is output from the second motor 38, the second output torque To2 greater than the first output torque To1 is output at the second output speed No2 smaller than the first output speed No1.

[0046] The effects of the above-described wheel drive device 10 will be described.

[0047] (A) The wheel drive device 10 includes a second motor 38 provided on a second power transmission path 36 that merges with the first power transmission path 34. Thus, in the wheel drive device 10 that drives the wheel 20 of a device traveling in a natural environment, the wheel 20 can be driven using the second motor 38 different from the first motor 30.

[0048] (B) The wheel drive device 10 includes a second speed reducer 40 provided on the second power transmission path 36. Thus, by adjusting the second reduction ratio R2 of the second speed reducer 40, without adjusting the first output torque To1 output from the first output shaft 32c by the output of the first motor 30, the second output torque To2 output from the first output shaft 32c by the output of the second motor 38 can be easily adjusted.

[0049] (C) The second output torque To2 output from the first output shaft 32c when the second rated output Or2 is output from the second motor 38 is greater than the first output torque To1 output from the first output shaft 32c when the first rated output Or1 is output from the first motor 30. Thus, compared with the case of driving the wheel 20 using only the first motor 30, the output torque output from the first output shaft 32c when driving the wheel 20 using only the second motor 38 can be increased. Further, it is not necessary to increase the capacity of the first motor 30 to increase the output torque output from the first output shaft 32c.

[0050] (D) The second rated torque Tr2 of the second motor 38 is smaller than the first rated torque Tr1 of the first motor 30. Thus, when the condition of the first output torque To1 < the second output torque To2 is satisfied, miniaturization of the capacity of the second motor 38 smaller than the capacity of the first motor 30 can be achieved. Therefore, compared with the case of using the second motor 38 having a larger capacity than the first motor 30, cost reduction of the wheel drive device 10 is facilitated.

[0051] Generally, when increasing the output torque, compared with simply increasing the capacity of the motor, the method of combining a small-capacity motor and a speed reducer with a high reduction ratio is more conducive to cost reduction. According to this embodiment, by using the second motor 38 with a smaller capacity than the first motor 30 and the second speed reducer 40 with a high reduction ratio, compared with the case where the first motor 30 is increased in capacity to be able to output the second output torque To2, it is more conducive to cost reduction of the wheel drive device 10.

[0052] In particular, since the device 12 is set in a natural environment, when the device 12 travels in a typhoon environment with a large maximum wind speed, a very large wind pressure load acts on the device 12. In order to make the device 12 travel while overcoming the large wind pressure load acting on the device 12, an increase in the output torque output from the first output shaft 32c is required. According to this embodiment, it is effective in the following aspects: without increasing the capacity of the first motor 30, a small-capacity second motor 38 can be used to achieve cost reduction while achieving such an increase in output torque.

[0053] (E) The first output speed No1 of the first output torque To1 output from the first output shaft 32c when the first motor 30 outputs the rated output Or1 is greater than the second output speed No2 of the second output torque To2 output from the first output shaft 32c when the second motor 38 outputs the second rated output Or2. That is, when the first motor 30 outputs the rated output Or1, an output torque with a high speed and low torque is output from the first output shaft 32c, and when the second motor 38 outputs the rated output Or2, an output torque with a low speed and high torque is output from the first output shaft 32c. Thus, when a large output torque is not required, the first motor 30 is used to output an output torque with a high speed from the first output shaft 32c to drive the wheel 20, so that the device 12 can travel at a high speed. In contrast, when a large output torque is required, the second motor 38 can be used to output an output torque with a high torque from the first output shaft 32c to drive the wheel 20.

[0054] The "case of requiring a large torque" here refers to, for example, the situation where the device 12 is driven to the avoidance position under the condition that the wind pressure load acting on the device 12 is very large. The "case of not requiring a large output torque" here refers to, for example, the situation where the wind pressure load acting on the device is not large and the device 12 is driven at the working position. In particular, when the device 12 is driven to the avoidance position under the condition that the wind pressure load acting on the device 12 is very large, it is only necessary to drive the device 12 to the avoidance position. Therefore, different from the case where the device 12 is driven at the working position in order to use the device 12 for work, high speed is not required when the device 12 is driven. That is, in this situation, a high-torque output torque is required, but a rotational speed as high as when using the device 12 for work is not required. Therefore, if in this situation, when the second motor 38 outputs a high-torque output torque, there is no problem in outputting a low-rotational-speed output torque. Therefore, when set in a natural environment and used in this situation, this structure is particularly effective.

[0055] Next, other features of the wheel drive device 10 will be described. The traveling direction of the wheel 20 is set as the wheel traveling direction X ( Figure 2 the depth direction of the paper surface), the axial direction of the first output shaft 32c is set as the output shaft direction Y, and the direction orthogonal to the traveling direction X and the output shaft direction Y is set as the height direction Z. In the present embodiment, the wheel traveling direction X and the output shaft direction Y are horizontal directions, and the height direction Z is a vertical direction. In this specification, "parallel" and "orthogonal" include approximately parallel and approximately orthogonal in addition to the strictly geometrically parallel and orthogonal.

[0056] The wheel 20 is provided at a portion of the first output shaft 32c that protrudes toward the side in the output shaft direction Y ( Figure 2 the right side of the paper surface) from the first reduction gear housing 32d. The second reduction gear 40 is arranged on the side in the output shaft direction Y with respect to the first reduction gear 32. That is, the second reduction gear 40 is not arranged with respect to the first reduction gear 32 in the wheel traveling direction X, nor is it arranged on the other side in the output shaft direction Y with respect to the first reduction gear 32.

[0057] (F) Thus, compared with the case where the second reduction gear 40 is arranged with respect to the first reduction gear 32 in the wheel traveling direction X, it is easy to avoid interference with other wheel drive devices 10 adjacent in the wheel traveling direction X. And compared with the case where the second reduction gear 40 is arranged on the other side ( Figure 2 the left side of the paper surface) in the output shaft direction Y with respect to the first reduction gear 32, it is beneficial to miniaturize the wheel drive device 10 in the output shaft direction Y.

[0058] The first motor 30 is disposed above the first speed reducer 32 in the height direction Z (here, the upper side in the vertical direction). That is, the first motor 30 is not disposed in the wheel traveling direction X with respect to the first speed reducer 32, nor is it disposed in the output shaft direction Y with respect to the first speed reducer 32.

[0059] (G) Thus, compared with the case where the first motor 30 is disposed in the wheel traveling direction X with respect to the first speed reducer 32, it is easier to avoid interference with other wheel drive devices 10 adjacent in the wheel traveling direction X. Also, compared with the case where the first motor 30 is disposed on the other side in the output shaft direction Y with respect to the first speed reducer 32, it is beneficial for miniaturization in the output shaft direction Y of the wheel drive device 10.

[0060] The first motor shaft 30a of the first motor 30 is parallel to the height direction Z, and the second output shaft 40c of the second speed reducer 40 is parallel to the output shaft direction Y. Thus, the first motor shaft 30a and the second output shaft 40c are arranged such that their axial directions are orthogonal to each other. Rotation is input from the first motor shaft 30a and the second output shaft 40c, whose axial directions are orthogonal to each other, to the first speed reducer 32. To achieve this, the first speed reducer 32 includes a first orthogonal gear set 48 provided on the first power transmission path 34 and a confluence portion rotating shaft 46 that is parallel to the output shaft direction Y and is arranged to be rotatable integrally with the second output shaft 40c. The first orthogonal gear set 48 includes a first orthogonal pinion 48a parallel to the height direction Z and a first orthogonal gear 48b parallel to the output shaft direction Y. The confluence portion rotating shaft 46 can be arranged to be rotatable integrally with the first orthogonal gear 48b, or can be disposed at a position on a more downstream side than the rotating shaft that can be rotatable integrally with the first orthogonal gear 48b. For example, the confluence portion rotating shaft 46 can be constituted by the downstream-side first intermediate shaft 32e among a total of two first intermediate shafts 32e. The second output shaft 40c is disposed on the axial extension line of the confluence portion rotating shaft 46.

[0061] The second motor 38 is disposed above the second speed reducer 40 in the height direction Z. The orientation of the position of the first motor 30 with respect to the first speed reducer 32 in the height direction Z is upward in the vertical direction, and the orientation of the position of the second motor 38 with respect to the second speed reducer 40 in the height direction Z is also upward in the vertical direction. That is, the orientation of the position of the first motor 30 with respect to the first speed reducer 32 in the height direction Z is the same as the orientation of the position of the second motor 38 with respect to the second speed reducer 40 in the height direction Z.

[0062] (H) Thus, by arranging the second motor 38 relative to the second speed reducer 40 in the height direction Z, it is easier to avoid interference with other wheel drive devices 10 adjacent in the wheel traveling direction X compared to the case of arranging the second motor 38 relative to the second speed reducer 40 in the wheel traveling direction X. Also, compared to the case of arranging the second motor 38 relative to the second speed reducer 40 in the output shaft direction Y, it is beneficial for miniaturization in the output shaft direction Y of the wheel drive device 10. Moreover, by making the orientation of the position of the first motor 30 relative to the first speed reducer 32 the same as the orientation of the position of the second motor 38 relative to the second speed reducer 40, it is beneficial for miniaturization in the height direction Z of the wheel drive device 10.

[0063] When arranging the second motor 38 and the second speed reducer 40 in this layout, it is necessary to make the axial direction of the second input shaft 40a of the second speed reducer 40 orthogonal to the axial direction of the second output shaft 40c of the second speed reducer 40. To achieve this, the second speed reducer 40 includes the above-described second orthogonal gear set 52 provided on the second power transmission path 36. The second orthogonal gear set 52 of the present embodiment is composed of a second orthogonal pinion 52a connected to the front stage side of the second input shaft 40a and a second orthogonal gear 52b connected to the rear stage side of the second output shaft 40c.

[0064] Next, a wheel drive unit 60 using the wheel drive device 10 will be described. Refer to Figure 1 machine Figure 2 . The wheel drive unit 60 includes a control device 62 that controls the operation of the wheel drive device 10. The control device 62 is implemented by a combination of hardware and software or only by hardware. As the hardware, a processor, a ROM (Read Only Memory), and a RAM (Random Access Memory) can be used. As the software, programs such as an operating system and an application program can be used.

[0065] A first motor drive circuit for driving the first motor 30 and a second motor drive circuit for driving the second motor 38 are assembled in the control device 62. The motor drive circuit is, for example, an inverter, but it can also be a servo amplifier or the like. The motor drive circuit converts the power supplied from an external power source into drive power and supplies the drive power to the motors 30, 38 to drive the motors 30, 38. The motors 30, 38 are driven according to the drive power supplied from the motor drive circuit of the control device 62, thereby controlling the operation of the wheel drive device 10. At this time, the control device 62 supplies, for example, drive power for making the motors 30, 38 reach the target rotational speed to the motors 30, 38, whereby the motors 30, 38 are driven to the target rotational speed.

[0066] The control device 62 can execute a normal mode as a first mode in which the wheels 20 are driven by the first motor 30 and an avoidance mode as a second mode in which the wheels 20 are driven at least by the second motor 38. The normal mode is used for the case where the device 12 travels at the working position. The avoidance mode is used for the case where the device 12 avoids from the working position to the avoidance position. The control device 62 can execute either the normal mode or the avoidance mode according to an instruction sent from an instruction device (not shown). The instruction device can send an instruction for determining the mode executed by the control device 62 to the control device 62 according to a user's input operation. The instruction device can be constituted by, for example, not only a console provided in the device 12 but also an information processing terminal such as a smart phone or a tablet computer.

[0067] When executing the normal mode, the control device 62 drives the first motor 30 through the first motor drive circuit and does not drive the second motor 38 through the second motor drive circuit. At this time, the control device 62 can drive the first motor 30 in such a manner that the first motor 30 becomes the first rated rotational speed Nr1, for example. When executing the standby mode, the control device 62 drives the second motor 38 at least through the second motor drive circuit. At this time, the control device 62 can drive the second motor 38 in such a manner that the second motor 38 becomes the second rated rotational speed Nr2, for example. In the present embodiment, when executing the avoidance mode, the control device 62 drives the wheels 20 by using both the first motor 30 and the second motor 38. Therefore, at this time, the control device 62 drives the first motor 30 through the first motor drive circuit and drives the second motor 38 through the second motor drive circuit.

[0068] When driving both the first motor 30 and the second motor 38, the control device 62 rotates the first motor 30 at a rotational speed corresponding to the rotational speed of the second motor 38. Specifically, the rotational speed of the second motor 38 is set as the motor rotational speed Ni2, and the rotational speed of the confluence portion rotating shaft 46 when the second motor 38 rotates at this motor rotational speed Ni2 is set as the confluence portion rotational speed Nc2'. The confluence portion rotational speed Nc2' becomes the value obtained by multiplying the reciprocal of the second reduction ratio R2 by the motor rotational speed Ni2 (=Ni2×(1 / R2)). When the rotational speed of the first motor 30 is set as the motor rotational speed Ni1, the rotational speed of the confluence portion rotating shaft 46 when the first motor 30 rotates at this motor rotational speed Ni1 is set as the confluence portion rotational speed Nc1'. The confluence portion rotational speed Nc1' becomes the value obtained by multiplying the reciprocal of the first reduction ratio R1a of the previous stage by the motor rotational speed Ni1 (=Ni1×(1 / R1a)). At this time, the first motor 30 is rotated at the motor rotational speed Ni1 such that the confluence portion rotational speed Nc1' in the confluence portion rotating shaft 46 based on the output of the first motor 30 is made to coincide with the confluence portion rotational speed Nc2' in the confluence portion rotating shaft 46 based on the output of the second motor 38. Actually, the first motor 30 is rotated at the motor rotational speed Ni1 corresponding to the motor rotational speed Ni2 of the second motor 38 in a manner that satisfies the following formula (3).

[0069] Ni1=Ni2×(R1a / R2)……Formula (3)

[0070] At this time, the control device 62 reads, for example, the first reduction ratio R1a of the previous stage and the second reduction ratio R2 stored in advance in the storage unit, and sets the motor rotational speed Ni2 of the second motor 38 for driving the wheels 20. The motor rotational speed Ni2 set for the second motor 38 is, for example, the above-described second rated rotational speed Nr2. Then, the control device 62 can derive the motor rotational speed Ni1 of the first motor 30 using Formula (3) based on the read reduction ratios R1a, R2 and the set motor rotational speed Ni2, and drive the first motor 30 at this motor rotational speed Ni1.

[0071] (I) In this way, the control device 62 can execute the avoidance mode in which the wheels 20 are driven by both the first motor 30 and the second motor 38. As a result, in the confluence portion rotating shaft 46, the torque transmitted through the output of the second motor 38 and the torque transmitted through the output of the first motor 30 are added together, and the added torque is amplified in the subsequent-stage reduction unit 32bb and then output from the wheels 20. Further, in the avoidance mode, by driving the wheels 20 with the first motor 30 and the second motor 38, the output torque output from the first output shaft 32c to the wheels 20 can be increased compared to the case where the wheels 20 are driven only by the second motor 38.

[0072] In addition, when executing the avoidance mode, the control device 62 can also drive the wheels 20 only with the second motor 38.

[0073] Reference Figure 2 Figure 2 Next, the first brake 42 and the second brake 44 will be described. The first brake 42 of the present embodiment is a friction brake, but is not limited thereto, and may be constituted by various brakes represented by an electric brake such as a regenerative brake. The first brake 42 of the present embodiment is used as a part of the brake motor attached to the first motor 30. The first brake 42 can apply a first braking torque to the first power transmission path 34. The first brake 42 of the present embodiment applies a first braking torque to the first motor shaft 30a on the first power transmission path 34.

[0074]

[0074] The second brake 44 of the present embodiment is a friction brake, but is not limited thereto, and may be constituted by various brakes represented by an electric brake such as a regenerative brake. The second brake 44 of the present embodiment is used as a part of the brake motor attached to the second motor 38. The second brake 44 can apply a second braking torque to the second power transmission path 36. The second brake 44 of the present embodiment applies a second braking torque to the second motor shaft 38a on the second power transmission path 36.

[0075]

[0075] The first brake 42 can be switched between a braking state in which the first braking torque is applied to the first motor shaft 30a and a braking release state in which the application of the first braking torque is released. The second brake 44 can be switched between a braking state in which the second braking torque is applied to the second motor shaft 38a and a braking release state in which the application of the second braking torque is released. Each of the brakes 42 and 44 of the present embodiment is a non-excitation operation type brake, which becomes a braking state when not energized and becomes a braking release state when energized. In addition, the brakes 42 and 44 may be excitation operation type brakes that become a braking state when energized.

[0076]

[0076] The control device 62 of the present embodiment can control the energization of the first brake 42 and the second brake 44 to control the operation of each of the brakes 42 and 44. The control device 62 can control the energization of the first brake 42 to switch the first brake 42 between a braking state and a braking release state. Further, the control device 62 can control the energization of the second brake 44 to switch the second brake 44 between a braking state and a braking release state.

[0077] During the period when the control device 62 drives the wheels 20 using the first motor 30 or the second motor 38 in the normal mode or the avoidance mode, the first brake 42 and the second brake 44 are switched to the brake release state so that each brake 42, 44 does not apply a braking torque. After the control device 62 finishes driving the first motor 30 or the second motor in the normal mode or the avoidance mode, at least one of the first brake 42 and the second brake 44 is switched from the brake release state to the brake state. In the present embodiment, both the first brake 42 and the second brake 44 are switched from the brake release state to the brake state. Thereby, compared with the case where only one of the first brake 42 and the second brake 44 is switched to the brake state, the braking torque output from the first output shaft 32c to the wheels 20 can be increased.

[0078] When the device 12 is maintained in the stopped state against a large wind pressure load, it is necessary to output a large braking torque. Since the first brake 42 and the second brake 44 can be used together to output a large braking torque, it is not necessary to increase the size of the first brake 42 in order to output a large braking torque, which is advantageous. In particular, when the first brake 42 forms part of a belt brake motor, if the size of the first brake 42 is increased, the first motor 30 has to be increased in capacity accordingly. This is advantageous in terms of avoiding the need to increase the capacity of the first motor 30 by avoiding an increase in the size of the first brake 42.

[0079] In the present embodiment, when both the first brake 42 and the second brake 44 are switched to the brake state, one of the brakes is first switched to the brake state and then the other brake is switched to the brake state. Thereby, compared with the case where the two brakes 42, 44 are switched to the brake state simultaneously, the braking torque output from the first output shaft 32c to the wheels 20 during the running of the device 12 can be gradually increased, so that the device 12 can be easily and stably stopped during the running of the device 12. In addition, both the first brake 42 and the second brake 44 can be simultaneously switched from the brake release state to the brake state.

[0080] (Second Embodiment)

[0081] Reference Figure 3 In the following embodiments, the components not described below among the components described in the first embodiment apply the same content as in the first embodiment.

[0082] The wheel drive device 10 of the present embodiment includes a clutch 70 provided on the second power transmission path 36. The clutch 70 is provided at a position on the second power transmission path 36 that is more downstream than the second stator and the second rotor (not shown) of the second motor 38. The clutch 70 of the present embodiment is provided at a position on the second power transmission path 36 that is more downstream than the second reduction mechanism 40b of the second speed reducer 40 and is provided on the second output shaft 40c. Here, the downstream side refers to the side of the confluence portion rotation shaft 46 on the second power transmission path 36.

[0083] The clutch 70 can be switched between a power transmission state that allows power to be transmitted through itself on the second power transmission path 36 and a power cut-off state that cuts off the power that is to be transmitted through itself. The clutch 70 can be switched between the power transmission state and the power cut-off state under the control of the control device 62. The control device 62 sets the clutch 70 in the power cut-off state in the normal mode. Thereby, it is possible to avoid a situation where rotation is transmitted from the first power transmission path 34 to the second motor shaft 38a side of the second power transmission path 36 during the driving of the wheels 20 by the output of the first motor 30. And, the control device 62 sets the clutch 70 in the power transmission state in the avoidance mode. Thereby, the output of the second motor 38 can be transmitted to the first power transmission path 34 to drive the wheels 20 by this output.

[0084] As described above, by providing the clutch 70 on the second power transmission path 36, when driving the wheels by the output of the first motor 30, the clutch 70 is switched to the power cut-off state, whereby it is not necessary to rotate the second motor shaft 38a of the second motor 38. Furthermore, it is possible to avoid a situation where unnecessary operating sounds and heat are generated in the second motor 38 due to the rotation of the second motor shaft 38a of the second motor 38 without driving the second motor 38. In particular, when the second speed reducer 40 is provided on the second power transmission path 36, when driving the wheels 20 by the output of the first motor 30, the rotation of the confluence portion rotation shaft 46 on the first power transmission path 34 is increased in speed by the second speed reducer 40. As a result, the second motor shaft 38a rotates at a high speed, and the above-mentioned problems of the influence of unnecessary operating sounds and heat becoming larger occur. According to the present embodiment, there is an advantage that this problem can be advantageously solved.

[0085] In addition, with the wheel drive device 10 of the present embodiment, it is also possible to obtain the same effects as (A) to (I) described in the first embodiment.

[0086] (Third Embodiment)

[0087] Reference Figure 4。In the first embodiment, an example was described in which the first motor shaft 30a of the first motor 30 also serves as the first input shaft 32a of the first speed reducer 32 and a separate confluence section rotating shaft 46 separate from the first input shaft 32a is provided. In addition, the confluence section rotating shaft 46 may be constituted by the first input shaft 32a on the basis that the first motor shaft 30a of the first motor 30 also serves as the first input shaft 32a of the first speed reducer 32. At this time, the first motor 30 is not arranged in a direction (vertical direction on the paper surface) orthogonal to the output shaft direction Y with respect to the first speed reducer 32, but is arranged in the output shaft direction Y with respect to the first speed reducer 32. The first speed reduction mechanism 32b of the present embodiment does not have a pre-stage reduction section 32ba provided at a position more upstream than the confluence section rotating shaft 46, but has a post-stage reduction section 32bb. At this time, the above-mentioned pre-stage first reduction ratio R1a becomes 1. With the wheel drive device 10 of the present embodiment, the same effects as those described in (A) to (E) and (I) in the first embodiment can also be obtained.

[0088] (Fourth Embodiment)

[0089] Reference Figure 5 。In the first embodiment, an example in which the second speed reducer 40 is not provided on the first power transmission path 34 was described. Instead, the second speed reducer 40 may also be provided on the first power transmission path 34. In the present embodiment, the second output shaft 40c of the second speed reducer 40 is arranged to be rotatable integrally with the first motor shaft 30a of the first motor 30 and is arranged to be rotatable integrally with the first input shaft 32a of the first speed reducer 32. The first power transmission path 34 of the present embodiment is constituted by the first motor shaft 30a, the second output shaft 40c, the first input shaft 32a, the first speed reduction mechanism 32b, and the first output shaft 32c. And the second power transmission path 36 of the present embodiment is constituted by the second motor shaft 38a, the second input shaft 40a, and the second speed reduction mechanism 40b. At this time, the confluence section rotating shaft 46 is constituted by the second output shaft 40c.

[0090] The second speed reducer 40 is arranged between the first motor 30 and the first speed reducer 32, and the second motor 38 is arranged in the output shaft direction Y with respect to the second speed reducer 40. The first speed reduction mechanism 32b of the present embodiment also, like the third embodiment, does not have a pre-stage reduction section 32ba provided at a position more upstream than the confluence section rotating shaft 46, and only has a post-stage reduction section 32bb. The first orthogonal gear set 48 that constitutes the pre-stage reduction section 32ba in the first embodiment becomes a part of the post-stage reduction section 32bb. With the wheel drive device 10 of the present embodiment, the same effects as those described in (A) to (E) and (I) in the first embodiment can also be obtained.

[0091] (Fifth Embodiment)

[0092] Reference Figure 6 . Figure 6 FIG. is a diagram schematically showing wheels 20 and wheel drive devices 10A and 10B used in device 12. Here, an example is shown in which there are a total of eight wheels 20 and a total of eight wheel drive devices 10A and 10B. In addition, the total number of wheels 20 and wheel drive devices 10A and 10B used in device 12 is not particularly limited.

[0093] The wheel drive unit 60 includes a plurality of wheel drive devices 10A and 10B. The plurality of wheel drive devices 10A and 10B are respectively used to drive the respective wheels 20 used in device 12. The plurality of wheel drive devices 10A and 10B include a first wheel drive device 10A and a second wheel drive device 10B.

[0094] The first wheel drive device 10A is the wheel drive device described in the first embodiment and the like. In addition to including a first motor 30 and a first speed reducer 32, it also includes a second motor 38 and a second speed reducer 40. Further, the first wheel drive device 10A also includes a first brake 42 and a second brake 44 having an arbitrary structure.

[0095] The second wheel drive device 10B includes a third motor 80 that drives the wheel 20. As an arbitrary structure, in addition to including the third motor 80, the second wheel drive device 10B further includes a third speed reducer 82 that decelerates the output of the third motor 80 and outputs it to the wheel 20. Further, as an arbitrary structure, the second wheel drive device 10B includes a third brake 84 that is provided on the power transmission path from the motor shaft (not shown) of the third motor 80 to the wheel 20 and applies a braking torque to the power transmission path. In the present embodiment, the third motor 80, the third speed reducer 82, and the third brake 84 are the above-described first motor 30, first speed reducer 32, and first brake 42, but they may also be different motors, speed reducers, and brakes. The second wheel drive device 10B drives the wheel 20 only by one third motor 80 and does not include other motors for driving the wheel 20.

[0096] The wheel drive unit 60 can use at least one of all the wheel drive devices 10A and 10B as the first wheel drive device 10A and the rest as the second wheel drive device 10B. In the present embodiment, half of all the wheel drive devices 10 are the first wheel drive devices 10A. Specifically, out of a total of eight wheel drive devices 10A and 10B, four, which is half of them, are the first wheel drive devices 10A, and the remaining four are the second wheel drive devices 10B. In addition, only one of all the wheel drive devices 10A and 10B can be used as the first wheel drive device 10A and the rest as the second wheel drive device 10B. In either case, the number of the first wheel drive devices 10A among all the wheel drive devices 10A and 10B is not particularly limited.

[0097] Compared with the second wheel drive device 10B, the first wheel drive device 10A has more motors, and accordingly, the cost is higher. In the present embodiment, a part of all the wheel drive devices 10 is used as the first wheel drive device 10A, so that an increase in cost can be suppressed as compared with the case where all are used as the first wheel drive device 10A.

[0098] In addition, in the wheel drive unit 60, all the wheel drive devices 10A and 10B can also be used as the first wheel drive device 10A.

[0099] Next, modified examples of the respective components described above will be described.

[0100] The first power transmission path 34 is a path from the first motor 30 to the first output shaft 32c of the first speed reducer 32, and specific examples of the components constituting the intermediate part thereof are not particularly limited. The second power transmission path 36 is a path from the second motor 38 to the confluence part rotating shaft 46, and specific examples of the components constituting the intermediate part thereof are not particularly limited.

[0101] The number of gear sets included in the first speed reduction mechanism 32b and the second speed reduction mechanism 40b is not particularly limited, and the types of gear sets are also not limited. An orthogonal gear set may not be included. The types of gear sets for the respective speed reduction mechanisms 32b and 40b are not particularly limited, and various gear sets such as an orthogonal gear set, a parallel gear set, and a coaxial gear set (gear sets of a simple planetary speed reducer, a gear set of an eccentric swing type speed reducer, and a gear set of a flexure engagement type speed reducer) can be used.

[0102] The wheel drive device 10 only needs to be provided with the second motor 38 on the second power transmission path 36, and the second speed reducer 40 and the second brake 44 are not necessary. A clutch 70 may not be provided on the second power transmission path 36.

[0103] The arrangement position of the second speed reducer 40 relative to the first speed reducer 32 is not particularly limited. For example, the second speed reducer 40 can be arranged on the other side of the first speed reducer 32 in the wheel traveling direction X or the output shaft direction Y. When the second speed reducer 40 is arranged relative to the first speed reducer 32 in the output shaft direction Y, the second speed reducer 40 may include a coaxial gear set instead of a bevel gear set. Also, the arrangement position of the first motor 30 relative to the first speed reducer 32 is not particularly limited. For example, the first motor 30 can be arranged relative to the first speed reducer 32 in the wheel traveling direction X or the output shaft direction Y. When the first motor 30 is arranged relative to the first speed reducer 32 in the output shaft direction Y, the first speed reducer 32 may include only a parallel gear set instead of a bevel gear set.

[0104] The second motor 38 can also be arranged relative to the second speed reducer 40 in either the wheel traveling direction X or the output shaft direction Y. Also, the orientation in the height direction Z of the position of the first motor 30 relative to the first speed reducer 32 can be different from the orientation in the height direction Z of the position of the second motor 38 relative to the second speed reducer 40.

[0105] In order to satisfy the condition that the first output torque To1 < the second output torque To2, it can also be set that the first rated torque Tr1 of the first motor 30 < the second rated torque Tr2 of the second motor 38.

[0106] As described above, compared with the case where only the first motor 30 drives the wheel 20, from the viewpoint of increasing the output torque output from the first output shaft 32c to the wheel 20, after the second speed reducer 40 is provided on the second power transmission path 36, the second output torque To2 is set to be greater than the first output torque To1. From the same viewpoint, the control device 62 can also execute only the mode in which the wheel 20 is driven by the first motor 30 and the second motor 38 (the avoidance mode described in the embodiment).

[0107] The above embodiments and modification examples are for illustration. These abstract technical ideas should not be construed restrictively as the content of the embodiments and modification examples. The content of the embodiments and modification examples can be subjected to various design changes such as changes, additions, and deletions of constituent elements. In the above embodiments, the content that can be subjected to such design changes is marked with the label "Embodiment" to emphasize. Also, the manner of mutually replacing any one of the constituent elements and expressions of the present invention among methods, devices, systems, etc. is also effective as an embodiment of the present invention.

Claims

1. A wheel drive device that drives a wheel of a device installed in a natural environment to move, the wheel drive device comprising: No. 1 motor; a first speed reducer that reduces the speed of the output of the first motor and outputs it from a first output shaft to wheels; and The second motor is provided on a second power transmission path that merges with a first power transmission path extending from the first motor to the first output shaft.

2. The wheel drive device according to claim 1, characterized in that: A second speed reducer is provided on the second power transmission path and reduces the speed of the output of the second motor.

3. The wheel drive device according to claim 2, characterized in that: When the rated output of the first motor is output from the first motor, a first output torque is output from the first output shaft, When the rated output of the second motor is output from the second motor, a second output torque is output from the first output shaft, The second output torque is greater than the first output torque.

4. The wheel drive device according to claim 3, characterized in that: A rated torque of the second motor is smaller than a rated torque of the first motor.

5. The wheel drive device according to claim 3, characterized in that: When the rated output of the first motor is output from the first motor, a first output torque having a first output speed is output from the first output shaft, When the rated output of the second motor is output from the second motor, a second output torque having a second output speed is output from the first output shaft, The first output speed is greater than the second output speed.

6. The wheel drive device according to claim 2, characterized in that: The wheel is provided on a portion of the first output shaft that protrudes from a reducer housing of the first reducer toward one side in the axial direction of the first output shaft. The second reduction gear is arranged on one side in the axial direction with respect to the first reduction gear.

7. The wheel drive device according to claim 6, characterized in that: The first motor is arranged in a height direction perpendicular to the traveling direction and the axial direction of the wheel relative to the first reduction gear.

8. The wheel drive device according to claim 7, characterized in that: The second motor is arranged in the height direction with respect to the second reduction gear.

9. The wheel drive device according to claim 1, characterized in that: A clutch is provided on the second power transmission path.

10. A wheel drive unit, characterized in that: have: The wheel drive device according to any one of claims 1 to 8; and a control device for controlling the movement of the wheel drive device, The control device is capable of executing a first mode in which the wheel is driven by the first motor and a second mode in which the wheel is driven by the first motor and the second motor.

11. A wheel drive unit, characterized in that: A plurality of wheel drive devices are provided, wherein the plurality of wheel drive devices drive a plurality of wheels for driving a device installed in a natural environment. The plurality of wheel drive devices include a first wheel drive device and a second wheel drive device, The first wheel drive device is the wheel drive device according to any one of claims 1 to 9, The second wheel drive device is a wheel drive device that drives a wheel using only one motor.

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