Power transmission and vehicle

Abstract

To provide a power transmission which can reduce a repair cost when a torque cut-off section breaks and enables a vehicle to remain self-propelled after breakage without increasing complexity or size of a configuration.SOLUTION: A vehicle comprises a first power transmission at the front of the vehicle and a second power transmission at the rear of the vehicle. The first power transmission has an electric motor, a power transmission mechanism, a differential device, a first drive shaft, and a second drive shaft. Torque cut-off sections (torque fuses) are installed at ends of the first and the second drive shafts. Each torque cut-off section is covered by a boot. When excessive torque is input and a torque cut-off section breaks, control means controls drive of the electric motor so that relative rotation speeds between a first drive wheel and the first drive shaft and between a second drive wheel and the second drive shaft are matched, thereby enabling a vehicle to remain self-propelled using rear wheel drive while avoiding frictional damage to the boot.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a power transmission device and a vehicle having the same.

Background Art

[0002] Generally, in designing the drive system in a vehicle, it is common to adopt a specification that ensures reliability against the maximum impact torque of the assumed driving conditions. Therefore, in a drive shaft with a large rated torque (hereinafter also referred to as the "main drive shaft"), even if there is a considerably excessive input, the risk of breakage is extremely low. However, in a drive shaft with a rated torque smaller than that of the main drive shaft (hereinafter also referred to as the "sub-drive shaft"), although it has a specification that ensures reliability against the use cases assumed in normal use, it often has a lower design strength than the specification of the main drive shaft, and its specification may be smaller than the limit torque transmitted by the tire. Then, when excessive torque is input to the sub-drive shaft due to unexpected usage situations or external force inputs, there is a risk that the components constituting the sub-drive shaft may be damaged.

[0003] On the other hand, although there is also a design concept of making the specification of the sub-drive shaft as strong as that of the main drive shaft, doing so would result in excessive strength compared to the usage situations assumed in normal driving, and problems such as an increase in the size of the structure, an increase in weight, a decrease in acceleration and deceleration responsiveness, a decrease in fuel efficiency (electricity cost), and an increase in price would occur. Therefore, the specification of the sub-drive shaft is made to have a lower strength than the main drive shaft in accordance with the rated torque and the maximum input torque that can be assumed.

[0004] The drive system is connected to drive wheels, a drive shaft, and a gearbox (including the concepts of a gear case and a casing). The gearbox may contain a differential, a speed reducer, a motor, or other prime movers. When an external force exceeding the assumption is input from the drive wheels during driving and excessive torque is input to the shaft, a configuration may be adopted to cut off the torque in order to prevent unexpected damage. In order to control the breaking location with respect to the torque applied to the entire drive shaft, the weakest part (the vulnerable part) is created. Such a vulnerable part is called a torque fuse.

[0005] Patent Document 1 discloses a fail-safe device in which an output shaft connected to a motor via a transmission mechanism and a shaft portion of a wheel hub of a wheel are connected by a connecting member having a vulnerable part. When the connecting part breaks, the broken connecting member is pressed by an elastic mechanism from both axial sides to bring the fracture surfaces into contact with each other. Based on the signal input of a sensor or a switch, it is determined whether the connecting member has broken. If it is determined that it has broken, the control of the motor is stopped. After stopping, the fracture surfaces are brought into contact with each other by elastic force, that is, in a state of light connection, the rotational speed and torque of the motor are limited so that it can run by itself without requiring traction. The transmission mechanism, the motor, the connecting member having a vulnerable part, etc. are housed in a casing.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] As described above, it is common practice to provide a torque fuse inside the gearbox. However, broken pieces generated from the fuse part at the time of breakage may have an adverse effect on other components, and repairs may involve various aspects. In such cases, it is necessary to replace the unit (gearbox) as a whole, resulting in an increase in repair costs.

[0008] When there are circumstances such that a torque fuse cannot be provided inside the gearbox due to design considerations or other reasons, it is conceivable to provide the torque fuse on the drive shaft side located outside the gearbox. In that case, the torque fuse is provided inside the boot to prevent the drive shaft from falling off. Here, when the torque fuse breaks, the broken shaft will be supported by its own weight by the boot. However, when attempting to drive, the rotational speed of the wheel driven by the main drive wheel will not match the rotational speed of the broken drive shaft on the gearbox side. If driving is continued in such a state, excessive friction will occur on the surface where the boot and the shaft come into contact, causing the boot to be damaged and making driving impossible. Therefore, a problem occurs where it is impossible to self-drive even for a short distance, such as to a maintenance factory, where repair after breakage is possible.

[0009] In the configuration described in Patent Document 1, it is possible to self-drive for a short distance to a location where repair after breakage is possible. However, the problem caused by broken pieces of the vulnerable part inside the casing that houses a plurality of components still cannot be solved, and an elastic mechanism for abutting the broken surfaces against each other is required, leading to a complication and enlargement of the configuration. Installation inside the boot, which is a narrow space, is not practical in terms of design.

[0010] The present invention has been made in view of the above points, and its main object is to provide a power transmission device that can reduce the repair cost when the torque cutoff part breaks and can self-drive after breakage without causing complication and enlargement of the configuration.

Means for Solving the Problem

[0011] In order to achieve the above object, the power transmission device (4) of the present invention includes a first drive source (8), a power transmission mechanism (10) connected to the first drive source (8) and transmitting the power of the first drive source (8), a differential device (12) connected to the power transmission mechanism (10) and having two output shafts (12a, 12b) for transmitting the power transmitted by the power transmission mechanism (10) in two directions, a first drive shaft (14) connected to one output shaft (12a) of the differential device (12), and a second drive shaft (16) connected to the other output shaft (12b) of the differential device (12). The power transmission device in a vehicle (2) includes a first drive shaft (18), and a torque cut-off portion (60) for cutting off torque transmission is provided at an end portion (14a) of the first drive shaft (14) or / and an end portion (16a) of the second drive shaft (16) when a load of a predetermined torque or more is applied to each drive shaft (14, 16).

[0012] According to the power transmission device of the present invention, since the torque cut-off portion is provided on the drive shaft located outside the gearbox, even if the torque cut-off portion breaks due to an excessive torque input, the influence on other components is extremely small, and the repair and replacement costs can be significantly reduced.

[0013] Further, in the above power transmission device (4), the first drive shaft (18) is provided with a first drive wheel (34R) connecting one end portion (14a) on the first drive shaft (14) side and a second drive wheel (34L) connecting the other end portion on the second drive shaft (16) side. The torque cut-off portion (60) may be provided at the end portion (14a) of the first drive shaft (14) on the first drive wheel (34R) side or / and the end portion (16a) of the second drive shaft (16) on the second drive wheel (34L) side. According to this, even if the torque cut-off portion breaks due to an excessive torque input, the influence on other components is extremely small, and the repair and replacement costs can be significantly reduced.

[0014] Also, in the above power transmission device (4), the torque cut-off portion (60) may be provided at the differential device (12) side end of the first drive shaft (14) or / and the differential device (12) side end of the second drive shaft (16). According to this, even if the torque cut-off portion breaks due to excessive torque input, the influence on other components is extremely small, and the repair and replacement costs can be significantly reduced.

[0015] Also, in the above power transmission device (4), boots (36a, 36c) may be provided at the end (14a) of the first drive shaft (14) or / and the end (16a) of the second drive shaft (16), and the torque cut-off portion (60) may be provided inside the boots (36a, 36c). According to this, the sagging of the drive shaft when the torque cut-off portion breaks can be supported by the boots, and the vehicle can continue to run until the boots are damaged.

[0016] Also, in the above power transmission device (4), it may have a first rotational information acquisition means (38a) for acquiring the rotational speed of the first drive wheel (34R), a second rotational information acquisition means (38b) for acquiring the rotational speed of the second drive wheel (34L), a first drive source rotational information acquisition means (40) for acquiring the rotational speed of the first drive source (8), and a torque cut-off portion break detection means (42) for detecting the break of the torque cut-off portion (60) based on the relationship between the rotational speed of the first drive source (8), the rotational speed of the first drive wheel (34R), and the rotational speed of the second drive wheel (34L). According to this, it is possible to reliably detect that the torque cut-off portion has broken, and it is possible to quickly shift to subsequent countermeasures.

[0017] Also, in the above power transmission device (4), the vehicle (2) includes a second drive source and a second drive shaft (48) including other drive wheels (46R, 46L), and when torque cut-off breakage is detected, when the vehicle (2) travels by the second drive shaft (48), it may be configured to have control means (42) for controlling the first drive source (8) to be driven at a predetermined speed. According to this, the rotation of the broken drive shaft can be synchronized with the rotation of the drive wheels (34R, 34L), damage to the boot due to friction between the drive shaft and the boot can be suppressed, and the self-running distance can be extended.

[0018] Also, in the above power transmission device (4), the first drive shaft (18) may be arranged in front of the second drive shaft (48) with respect to the forward direction (F) of the vehicle (2).

[0019] Also, in the above power transmission device (4), the first drive shaft (18) may be arranged behind the second drive shaft (48) with respect to the forward direction (F) of the vehicle (2).

[0020] Also, in the above power transmission device (4), the vehicle (2) further includes a third drive source and a third drive shaft including other drive wheels, and when torque cut-off breakage is detected, when the vehicle (2) travels by the second drive shaft (48) and / or the third drive shaft, it may be configured to have control means (42) for controlling the first drive source (8) to be driven at a predetermined speed. According to this, the rotation of the broken drive shaft can be synchronized with the rotation of the drive wheels, damage to the boot due to friction between the drive shaft and the boot can be suppressed, and the self-running distance can be extended.

[0021] Also, in the above power transmission device (4), the first drive shaft (18) may be arranged in front of the second drive shaft (48) and the third drive shaft with respect to the forward direction (F) of the vehicle (2).

[0022] Further, in the above-described power transmission device (4), the first drive shaft (18) may be arranged behind the second drive shaft (48) and the third drive shaft with respect to the forward direction (F) of the vehicle (2).

[0023] Further, in the above-described power transmission device (4), the first drive shaft (18) may be arranged between the second drive shaft (18) and the third drive shaft with respect to the forward direction (F) of the vehicle (2).

[0024] Further, in the above-described power transmission device (4), the output of the first drive source (8) may be the same as or lower than the output of the second drive source.

[0025] Further, in the above-described power transmission device (4), the output of the first drive source (8) may be higher than the output of the second drive source.

[0026] Further, in the above-described power transmission device (4), the output of the first drive source (8) may be the same as or lower than the outputs of the second drive source and the third drive source.

[0027] Further, in the above-described power transmission device (4), the output of the first drive source (8) may be higher than the outputs of the second drive source and the third drive source.

[0028] Further, in the above-described power transmission device (4), the predetermined speed of the first drive source (8) may be a value obtained by multiplying the value obtained by dividing the sum of the rotational speeds of the first drive wheels (34R) and the second drive wheels (34L) by 2 by the reduction ratios of the differential device (12) and the power transmission mechanism (10). According to this, damage to the boots can be suppressed with high precision.

[0029] Further, in the above-described power transmission device (4), the first drive source (8) may be an electric motor. According to this, simplification of the vehicle configuration, weight reduction, and ease of control can be achieved.

[0030] Further, in the above-described power transmission device (4), the second drive source may be configured as an electric motor. According to this, simplification of the vehicle configuration, weight reduction, and ease of control can be achieved.

[0031] Further, in the above-described power transmission device (4), the second drive source may be configured as an internal combustion engine. According to this, improvement of the driving force of the vehicle can be achieved.

[0032] Further, in the above-described power transmission device (4), the second drive source may be configured as a hybrid prime mover combining an electric motor and an internal combustion engine. According to this, improvement of the driving force of the vehicle can be achieved, and improvement of fuel efficiency (electricity cost) can be achieved according to the driving situation.

[0033] Further, in the above-described power transmission device (4), the torque cut-off portions (60A, 60B) may be configured by a structure in which the shaft diameters of the first drive shaft (14) or / and the second drive shaft (16) are reduced. According to this, breakage of the torque cut-off portion can be surely caused with a simple configuration, and the breakage position can be controlled.

[0034] Further, in the above-described power transmission device (4), the torque cut-off portion (60C) may be configured by one or a plurality of holes that penetrate or do not penetrate a part of the shaft of the first drive shaft (14) or / and the second drive shaft (16). According to this, breakage of the torque cut-off portion can be surely caused with a simple configuration, and the breakage position can be controlled.

[0035] Further, in the above-described power transmission device (4), the torque cut-off portion (60D) may be configured by a material having a low strength in a part of the shaft of the first drive shaft (14) or / and the second drive shaft (16). According to this, breakage of the torque cut-off portion can be surely caused without causing a shape change, and the breakage position can be controlled.

[0036] Further, in the above-described power transmission device (4), the torque interruption portion (60D) may be configured such that the strength of a part of the material of the shaft of the first drive shaft (14) or / and the second drive shaft (16) is reduced by metal heat treatment. According to this, it is possible to surely cause the torque interruption portion to break without causing a shape change, and the break position can be controlled.

[0037] Further, in the above-described power transmission device (4), the torque interruption portion (60E) may be configured such that a part of the shaft of the first drive shaft (14) or / and the second drive shaft (16) is divided and connected by a connecting member having a lower strength than the shaft. According to this, it is possible to surely cause the torque interruption portion to break, and the break position can be controlled.

[0038] Further, in the above-described power transmission device (4), the torque interruption portion (60F) may be configured such that a part of the shaft of the first drive shaft (14) or / and the second drive shaft (16) is divided and spline-connected, and the bottom of the groove of the spline shaft (14a-6) of the spline connection has the lowest strength. According to this, it is possible to surely cause the torque interruption portion to break, and the break position can be controlled.

[0039] Further, in the above-described power transmission device (4), the torque interruption portion (60G) may be configured such that a part of the shaft of the first drive shaft (14) or / and the second drive shaft (16) is divided and connected by one or a plurality of key members (68) having a lower strength than the shaft. According to this, it is possible to surely cause the torque interruption portion to break, and the break position can be controlled.

[0040] Further, in the above-described power transmission device (4), the torque interruption portion (60H) may be configured such that a part of the shaft of the first drive shaft (14) or / and the second drive shaft (16) is divided and connected by a gear shape (14f) having a lower strength than the shaft. According to this, it is possible to surely cause the torque interruption portion to break, and the break position can be controlled.

Advantages of the Invention

[0041] According to the present invention, it is possible to reduce the repair cost when the torque cut-off portion breaks, and it is possible to self-run after the break without causing complication and enlargement of the configuration.

Brief Description of the Drawings

[0042]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Modes for Carrying Out the Invention

[0043] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0044] [First Embodiment] The first embodiment will be described with reference to FIGS. 1 to 7. As shown in FIG. 1, a vehicle 2 according to this embodiment is a four-wheel drive vehicle having a first power transmission device 4 including a sub-drive shaft provided with a torque cut-off portion (synonymous with a torque fuse) described later on the front-wheel side in the forward direction (arrow F direction), and a second power transmission device 6 including a main drive shaft on the rear-wheel side.

[0045] As shown in FIG. 2(a), the first power transmission device 4 includes an electric motor 8 as a first drive source, a power transmission mechanism 10 connected to the electric motor 8 and transmitting the power of the electric motor 8, a differential device 12 connected to the power transmission mechanism 10 and having two output shafts 12a and 12b for transmitting the power transmitted by the power transmission mechanism 10 in two directions, a first drive shaft 14 connected to one output shaft 12a of the differential device 12, and a second drive shaft 16 connected to the other output shaft 12b of the differential device 12. The first drive shaft 18 is a sub-drive shaft having a torque cut-off portion 60 (see FIG. 4) for cutting off torque transmission when a load of a predetermined torque or more is applied to each of the drive shafts 14 and 16 at the end portion 14a of the first drive shaft 14 and the end portion 16a of the second drive shaft 16. The combination of the first drive shaft 14 and the second drive shaft 16 is the first drive shaft 18. The electric motor 8, the power transmission mechanism 10, and the differential device 12 are housed in a gearbox 20 and unitized.

[0046] The electric motor 8 includes a stator 22, a rotor 24 rotatably disposed on the inner peripheral side of the stator 22, and a rotor shaft 26 coupled to the inner peripheral portion of the rotor 24 and through which one output shaft 12a is inserted. The power transmission mechanism (speed reduction mechanism) 10 includes a first gear 28 integrally formed on one end side of the rotor shaft 26, a second gear 30 having the same rotation axis as the first gear 28 and connected to a differential case (not shown) of the differential device 12, and a counter gear 32 meshing with the first gear 28 and the second gear 30. The counter gear 32 includes a large-diameter gear 32a meshing with the first gear 28, a small-diameter gear 32b meshing with the second gear 30, and a counter shaft 32c for integrally and rotatably supporting the large-diameter gear 32a and the small-diameter gear 32b.

[0047] The first drive shaft 18 is provided with a first drive wheel (right wheel) 34R connecting to one end 14a (the side opposite to the differential device 12 side) of the first drive shaft 14 on the first drive shaft 14 side, and a second drive wheel (left wheel) 34L connecting to the other end 16a (the side opposite to the differential device 12 side) of the second drive shaft 16 on the second drive shaft 16 side. The torque interruption portion 60 is provided at the end 14a of the first drive shaft 14 on the first drive wheel 34R side and at the end 16a of the second drive shaft 16 on the second drive wheel 34L side. The end 14a of the first drive shaft 14 is one end when viewed as the entire first drive shaft 18, and is the end on the first drive wheel 34R side with respect to the first drive shaft 14 itself. Similarly, the end 16a of the second drive shaft 16 is the other end when viewed as the entire first drive shaft 18, and is the end on the second drive wheel 34L side with respect to the second drive shaft 16 itself. Rubber boots 36a, 36b, 36c, and 36d are respectively provided at both ends 14a, 14b of the first drive shaft 14 and both ends 16a, 16b of the second drive shaft 16, and the torque interruption portion 60 is provided in the boots 36a, 36c located axially outward.

[0048] The first power transmission device 4 includes a wheel speed sensor 38a as first rotation information acquisition means for acquiring the rotational speed of the first drive wheel 34R, a wheel speed sensor 38b as second rotation information acquisition means for acquiring the rotational speed of the second drive wheel 34L, a resolver 40 as first drive source rotation information acquisition means for acquiring the rotational speed of the electric motor 8, and control means 42 (see FIG. 3) that also serves as torque cut-off section break detection means for detecting a break in the torque cut-off section 60 based on the relationship between the rotational speed of the electric motor 8, the rotational speed of the first drive wheel 34R, and the rotational speed of the second drive wheel 34L.

[0049] As shown in FIG. 2(b), the second power transmission device 6 includes a gearbox 44 that houses the second drive source and others, and a second drive shaft 48 as a main drive shaft that includes other drive wheels, namely, a third drive wheel 46R and a fourth drive wheel 46L that are different from the first drive wheel 34R and the second drive wheel 34L in the first power transmission device 4. When it is detected that the torque cut-off section 60 has broken and the vehicle 2 travels by means of the second drive shaft 48, the control means 42 controls the electric motor 8 to be driven at a predetermined speed (described later). The first drive shaft 18 is disposed in front of the second drive shaft 48 with respect to the forward direction (arrow F direction) of the vehicle 2. The output of the electric motor 8 is set to be the same as or lower than the output of the second drive source. The second drive source may be any of an electric motor, an engine, and a hybrid prime mover.

[0050] In this specification, main drive means driving by the main drive unit during traveling (the second power transmission device 6 in this embodiment), and the main drive shaft means the drive shaft of the main drive unit (the second drive shaft 48 in this embodiment). Also, sub-drive means driving by a drive unit different from the main drive unit (the first power transmission device 4 in this embodiment), and the sub-drive shaft means the drive shaft in the different drive unit (the first drive shaft 18 in this embodiment). However, these are distinctions for convenience, and there may be cases where the main and sub cannot be clearly distinguished from the viewpoints of driving force and torque resistance.

[0051] FIG. 4(a) is an enlarged cross-sectional view of the end portion 14a of the first drive shaft 14, i.e., the connecting portion with the first drive wheel 34R. The end portion 14a is connected to the first drive wheel 34R via a constant velocity joint 50. The constant velocity joint 50 includes an outer joint member 52, an inner joint member 54 spline-fitted to the end portion 14a, a cage 58 that holds balls 56, and the like. The boot 36a is provided to cover the connecting portion between the end portion 14a and the inner joint member 54. The small-diameter side end portion 36a-1 is fitted and fixed to the outer peripheral surface of the end portion 14a, and the large-diameter side end portion 36a-2 is fitted and fixed to the outer peripheral surface of the outer joint member 52. The end portion 16a of the second drive shaft 16 in the first power transmission device 4 has the same configuration. Hereinafter, the portion of the end portion 14a of the first drive shaft 14 will be described as a representative, and the illustration and description of the second drive shaft 16 side will be omitted as appropriate.

[0052] A torque cut-off portion 60 is provided at the end portion 14a of the first drive shaft 14 within the boot 36a. The torque cut-off portion 60 is configured by a structure in which the shaft diameter of the first drive shaft 14 is decreased. Specifically, as shown in FIG. 4(b), a groove 60a having a V-shaped cross section is formed annularly over the entire circumference of the end portion 14a. In other words, the torque cut-off portion 60 is a weak portion whose strength is intentionally lowered by locally decreasing the shaft diameter of the first drive shaft 14.

[0053] When the vehicle 2 is running and an excessive load such as an impact is applied to the drive wheels, and when such excessive torque is applied to the first drive shaft 18 which is a sub-drive shaft, the end portion 14a of the first drive shaft 14 breaks at the torque cut-off portion 60 as shown in FIG. 4(c). When the torque cut-off portion 60 breaks, the broken first drive shaft 14, that is, the portion of the first drive shaft 14 on the differential device 12 side, is supported by its own weight without hanging down by the boot 36a. Even in this state, running is possible by the second drive shaft 48 which is the main drive shaft, and the first drive wheel 34R and the second drive wheel 34L on the first drive shaft 18 which is the sub-drive shaft rotate accordingly, but the broken first drive shaft 14 generates under-rotation to over-rotation according to the rotational speed of the electric motor 8, and a difference occurs in the correlation between the rotational speeds of the left and right wheels (the first drive wheel 34R and the second drive wheel 34L) of the first drive shaft 18 and the rotational speed of the rotor shaft 26 detected by the resolver 40.

[0054] In other words, when attempting to run after the torque cut-off portion 60 breaks, the rotational speeds of the first drive wheel 34R and the second drive wheel 34L driven by the rotation of the third drive shaft 46R and the fourth drive shaft 46L of the second drive shaft 48 and the rotational speed of the broken first drive shaft 14 will not match. If attempting to continue running in that state, the broken first drive shaft 14 will spin freely, and the friction between the boot 36a and the first drive shaft 14 will become too large, causing the boot 36a to break. In this case, there is a risk that the boot 36a will fall off without being able to hold the first drive shaft 14. Running is possible until the boot 36a breaks, but once it breaks, running becomes impossible at that point. Therefore, a problem occurs where it is impossible to self-run even for a short distance, for example, to a place where repairs can be made (such as a maintenance factory).

[0055] Therefore, in the present embodiment, the breakage of the torque interruption portion 60 is automatically determined (detected). When the breakage is detected, the electric motor 8 is driven to match (synchronize) the rotational speed of the first drive shaft 14 that has broken with the rotational speed of the first drive wheel 34R, thereby reducing the load applied to the boot 36a and enabling the vehicle to travel on its own while suppressing damage to the boot 36a even when the first drive shaft 14 breaks. In other words, control is performed to extend the life of the boot 36a and gain a travelable distance.

[0056] Next, a method for detecting the breakage of the torque interruption portion 60 by the control means 42 that also serves as the torque interruption portion breakage detection means will be described.

[0057] FIG. 5 is a collinear diagram showing the relationship between the rotations of the right wheel (R wheel), the left wheel (L wheel), and the motor (MOT). The R wheel corresponds to the first drive wheel 34R, the L wheel corresponds to the second drive wheel 34L, and the motor corresponds to the electric motor 8. The black circles indicate the rotational speeds after the breakage of the drive shaft. When there is no drive instruction for the motor, the motor stops due to its own friction, so the broken end of the drive shaft rotates in the reverse direction because the load disappears, as shown by line 62 in the collinear diagram, and slip occurs between the drive shaft and the boot (see FIG. 6). In FIG. 6, reference numeral 64a indicates the rotational direction of the first drive wheel 34R, and 64b indicates the rotational direction of the first drive shaft 14 after breakage, and the rotational directions are reversed.

[0058] Assuming the rotational speed of the motor is Mn, the rotational speed of the L wheel is Ln, the rotational speed of the R wheel is Rn, and the gear ratio is Z, then Normal: Mn / Z = (Ln + Rn) / 2 Abnormal (torque interruption portion breakage): Mn / Z ≠ (Ln + Rn) / 2 The relationship is as follows.

[0059] When there is a drive instruction for the motor, the motor cannot receive the driving force due to the breakage of the drive shaft and over - rotates excessively. The broken end of the drive shaft over - rotates with respect to the drive wheel, and slip occurs between the drive shaft and the boot. In either state, Motor rotational speed / reduction ratio = (right drive wheel rotational speed + left drive wheel rotational speed) / 2 From the relationship of the formula, the rotational speed of the motor will necessarily deviate from the normal value range, so breakage detection (detection) becomes possible.

[0060] When the torque cut-off part 60 of the first drive shaft 14 breaks, in order to prevent wear with the boot 36a and damage to the boot 36a, it is necessary to make the rotational speed of the first drive shaft 14 coincide (synchronize) with the rotational speed of the first drive wheel 34R. Therefore, after breakage detection, the control means 42 does not perform normal driving force control, and for the electric motor 8, it always Motor rotational speed = reduction ratio * (rotational speed of the first drive wheel 34R + rotational speed of the second drive wheel 34L) / 2 performs rotational control (synchronization control) to rotate at this rotational speed. When the rotational synchronization control by the control means 42 is performed, as shown in FIG. 7, the rotational direction 64a of the first drive wheel 34R and the rotational direction 64b of the first drive shaft 14 after breakage are in the same direction. The "predetermined speed" of the electric motor 8 controlled by the control means 42 is the value obtained by multiplying the value obtained by dividing the sum of the rotational speeds of the first drive wheel 34R and the second drive wheel 34L by 2 by the reduction ratio of the differential device 12 and the power transmission mechanism 10. As a result, no matter what kind of turning occurs, since the relative speed of the rotational speeds of the first drive wheel 34R and the first drive shaft 14 coincides, the boot 36a and the broken first drive shaft 14 do not rub against each other, and damage to the boot 36a is suppressed. For this reason, it becomes possible to run for a while, and it is possible to reach, for example, a maintenance factory by self-running without stopping due to a failure on the spot.

[0061] That is, it is possible to prevent secondary damage that leads to the vehicle being unable to run by preventing damage to unexpected parts (by providing the torque cut-off part 60). Since the torque cut-off part 60 is provided on the drive shaft outside the gearbox 20, it is easy to identify the breakage position and the repair is also easy. In addition, the influence of breakage on expensive parts inside the gearbox 20 can be avoided.

[0062] As described above, in the present embodiment, since the torque cutoff portion 60 is provided on the first drive shaft 14 and the second drive shaft 16 located outside the gearbox 20, when the torque cutoff portion 60 breaks and needs to be repaired, mainly only the first drive shaft 14 and / or the second drive shaft 16 need to be replaced. Compared with the prior art where there is a risk of replacing the entire gearbox 20 as a unit, cost reduction can be achieved. Also, since it is possible to drive to the repair location only by controlling the electric motor 8 without adding a new mechanism as in Patent Document 1, further cost reduction can be achieved without increasing the size and complexity of the configuration.

[0063] In the present embodiment, the differential device 12 does not have a limited slip differential (LSD) function that restricts the left - right rotation difference, nor does it have a mechanism such as a clutch that cuts off the torque transmission between the differential device 12 and the drive wheels. These may be present, but are not made to function when implementing the functions of the present invention. In the case of an LSD, torque fuses are set on each of the first drive shaft 14 and the second drive shaft 16. When excessive torque occurs, if both break, they function as torque fuses. However, in some cases, it is possible that only one of them does not break. If the LSD functions at that time, there is a possibility that the break detection will be delayed or impossible.

[0064] [Second Embodiment] The second embodiment (a modified example of the arrangement pattern of the torque cutoff portion) will be described with reference to FIGS. 8 and 9. Here, the torque cutoff portion is described as a torque fuse.

[0065] In FIG. 8, the front wheels of the vehicle 2 are denoted as FW and the rear wheels as RW. The pattern P1 in FIG. 8(b) is the pattern described in the first embodiment, and the first drive shaft 18 (sub-drive shaft) having the front wheels FW provided with torque fuses is disposed in front of the second drive shaft 48 having the rear wheels RW with respect to the forward direction (arrow F direction) of the vehicle 2. In the pattern P2, the first drive shaft 18 having the rear wheels RW provided with torque fuses is disposed behind the second drive shaft 48 having the front wheels FW with respect to the forward direction (arrow F direction) of the vehicle 2. That is, this is an example in which the rear wheels RW are driven by the first power transmission device 4 and the front wheels FW are driven by the second power transmission device 6.

[0066] FIG. 9(a) shows an example in which the vehicle 2A is provided with middle wheels CW between the front wheels FW and the rear wheels RW. The vehicle 2A further includes a third drive source and a third drive shaft including other drive wheels (for example, middle wheels CW) compared to the configuration of the vehicle 2, and has control means 42 for controlling the first drive source to be driven at a predetermined speed when the vehicle 2A travels by the second drive shaft and / or the third drive shaft when torque interruption is detected. Note that the drive shaft of the middle wheels CW is not necessarily the third drive shaft. That is, the correspondence between the front wheels FW, the rear wheels RW, and the middle wheels CW and the first drive shaft, the second drive shaft, and the third drive shaft is arbitrary.

[0067] As shown in FIG. 9(b), in pattern P3 of the vehicle configuration in FIG. 9(a), a torque fuse is provided on the drive shaft of the front wheels FW, and either one or both of the rear wheels RW and the middle wheels CW serve as the driving force. That is, the first drive shaft of the front wheels FW is arranged in front of the second drive shaft of the rear wheels RW and the third drive shaft of the middle wheels CW with respect to the forward direction (arrow F direction) of the vehicle 2A. In pattern P4, a torque fuse is provided on the drive shaft of the rear wheels RW, and either one or both of the front wheels FW and the middle wheels CW serve as the driving force. That is, the first drive shaft of the rear wheels RW is arranged behind the second drive shaft of the front wheels FW and the third drive shaft of the middle wheels CW with respect to the forward direction (arrow F direction) of the vehicle 2A. In pattern P5, a torque fuse is provided on the drive shaft of the middle wheels CW, and either one or both of the front wheels FW and the rear wheels RW serve as the driving force. In this case, the drive shaft of the middle wheels CW becomes the first drive shaft, and either one of the front wheels FW and the rear wheels RW becomes the second drive shaft and the other becomes the third drive shaft. That is, the first drive shaft is arranged between the second drive shaft and the third drive shaft with respect to the forward direction (arrow F direction) of the vehicle 2A.

[0068] As shown in FIG. 9(c), there may be a plurality of drive shafts provided with torque fuses. In pattern P6, torque fuses are provided on the drive shafts of the front wheels FW and the middle wheels CW, and the drive shaft of the rear wheels RW becomes the main drive shaft. In pattern P7, torque fuses are respectively provided on the drive shafts of the front wheels FW and the rear wheels RW, and this is an example where the drive shaft of the middle wheels CW becomes the main drive shaft. In pattern P8, torque fuses are provided on the drive shafts of the middle wheels CW and the rear wheels RW, and this is an example where the drive shaft of the front wheels FW becomes the main drive shaft. Note that torque fuses may be provided on all three drive shafts of the front wheels FW, the middle wheels CW, and the rear wheels RW.

[0069] [Third Embodiment] Referring to FIGS. 10 and 11, the third embodiment (output relationship pattern between the drive shaft provided with the torque fuse and other drive shafts) will be described.

[0070] In FIG. 10(b), “first” indicates a first drive source that drives a drive shaft provided with a torque fuse, and “second” indicates a second drive source that drives another drive shaft not provided with a torque fuse. Pattern P9 is an example in which the output of the first drive source is the same as or lower than the output of the second drive source. Pattern P10 is an example in which the output of the first drive source is higher than the output of the second drive source. Note that the correspondence between the first drive source and the second drive source and the front wheels FW and the rear wheels RW is arbitrary. In FIG. 11(b), “third” indicates a third drive source that drives a third drive shaft. Pattern P11 is an example in which the output of the first drive source is the same as or lower than the outputs of the second drive source and the third drive source. Pattern P12 is an example in which the output of the first drive source is higher than the outputs of the second drive source and the third drive source. Note that the correspondence between the first drive source, the second drive source, and the third drive source and the front wheels FW, the middle wheels CW, and the rear wheels RW is arbitrary.

[0071] [Fourth Embodiment] The fourth embodiment (relationship pattern between drive shafts and drive sources) will be described with reference to FIGS. 12 and 13.

[0072] In FIG. 12, “first” indicates a first drive source that drives a first drive shaft provided with a torque fuse, and “second” indicates a second drive source that drives a second drive shaft, and the correspondence with the front wheels and the rear wheels is arbitrary. Pattern P13 shows an example of the first embodiment, in which the first drive source is the motor M and the second drive source can be anything. Pattern P14 is an example in which the second drive source is the motor M and the first drive source can be anything as long as the torque cut-off portion functions. Pattern P15 is an example in which the second drive source is the engine E and the first drive source can be anything as long as the torque cut-off portion functions. Pattern P16 is an example in which the second drive source is a hybrid prime mover HB having the motor M and the engine E, and the first drive source can be anything as long as the torque cut-off portion functions.

[0073] FIG. 13(a) is an example in which the first drive source is the motor M in pattern P14. FIG. 13(b) is an example in which the first drive source is the motor M in pattern P15. FIG. 13(c) is an example in which the first drive source is the motor M in pattern P16.

[0074] [Fifth Embodiment] The fifth embodiment (a modification example of the torque cut-off portion 60) will be described with reference to FIGS. 14 to 20.

[0075] FIG. 14 shows an example in which the torque cut-off portion 60 is configured by a structure in which the shaft diameters of the first drive shaft 14 and / or the second drive shaft 16 are reduced. The torque cut-off portion 60A shown in FIG. 14(a) has an annular groove 60b with a smoothly curved cross-section formed in a U-shape over the entire circumference. When excessive torque is input to the first drive shaft 14, stress concentrates on the small-diameter portion of the torque cut-off portion 60A and it breaks. The torque cut-off portion 60B shown in FIG. 14(b) is an example in which the diameter of a portion 14a-1 on the first drive wheel 34R side of the end portion 14a of the first drive shaft 14 is made thinner. When excessive torque is input, the torque cut-off portion 60B, which is the boundary portion with different shaft diameters, breaks.

[0076] FIG. 15 shows an example in which the torque cut-off portion 60C is configured by one or a plurality of holes that penetrate or do not penetrate a part of the shaft of the first drive shaft 14 and / or the second drive shaft 16. Here, a hole 60c that penetrates in the radial direction is formed at the end portion 14a of the first drive shaft 14. Since the cross-sectional area of the portion where the hole 60c exists (torque cut-off portion 60C) is smaller than the others, when excessive torque is input, it breaks at the torque cut-off portion 60C. FIG. 16 shows an example in which the torque cut-off portion 60D is configured by a material with low strength in a part of the shaft of the first drive shaft 14 and / or the second drive shaft 16. Here, the strength of a part 14a-2 of the end portion 14a of the first drive shaft 14 is lowered by metal heat treatment. When excessive torque is input, it breaks at the torque cut-off portion 60D, which is brittle in terms of material.

[0077] FIG. 17 shows an example in which the torque cutoff portion 60E is configured by a structure in which a part of the shaft of the first drive shaft 14 or / and the second drive shaft 16 is divided and connected by a connecting member having a lower strength than the shaft. Here, the end portion 14a of the first drive shaft 14 is divided into an end portion 14a-3 and an end portion 14a-4, and is integrally joined by a cylindrical connecting member 66 having a lower strength than the first drive shaft 14. When excessive torque is input, the low-strength connecting member 66 breaks, the integral rotation of the end portion 14a-3 and the end portion 14a-4 fails, and the first drive shaft 14 idles. FIG. 18 shows an example in which the torque cutoff portion 60F is configured such that a part of the shaft of the first drive shaft 14 or / and the second drive shaft 16 is divided and spline-connected, and the bottom of the groove of the spline shaft of the spline connection has the lowest strength. Here, the end portion 14a of the first drive shaft 14 is divided into an end portion 14a-5 and an end portion 14a-6. A plurality of external teeth 14c are formed in the circumferential direction on the end portion 14a-6 as a spline shaft, and internal teeth 14d into which the external teeth 14c are fitted are formed on the end portion 14a-5. Both circumferential sides (boundaries with the external teeth 14c) of the bottom of the groove between the external teeth 14c are acute-angle portions formed by cutting. When excessive torque is input, the external teeth 14c break starting from the acute-angle portion at the bottom, the integral rotation of the end portion 14a-5 and the end portion 14a-6 fails, and the first drive shaft 14 idles.

[0078] FIG. 19 shows an example in which the torque cutoff portion 60G is configured by a structure in which a part of the shaft of the first drive shaft 14 or / and the second drive shaft 16 is divided and connected by one or a plurality of key members having a lower strength than the shaft. Here, the end portion 14a of the first drive shaft 14 is divided into an end portion 14a-7 and an end portion 14a-8, and is connected by a key member 68 having a lower strength than the first drive shaft 14. The connection portion is covered with a collar 70 that prevents the key member 68 from coming off. When excessive torque is input, the key member 68 breaks, the integral rotation of the end portion 14a-7 and the end portion 14a-8 fails, and the first drive shaft 14 idles. FIG. 20 shows an example in which the torque cutoff portion 60H is configured by a structure in which a part of the shaft of the first drive shaft 14 or / and the second drive shaft 16 is divided and connected by a gear shape having a lower strength than the shaft. Here, the end portion 14a of the first drive shaft 14 is divided into an end portion 14a-9 and an end portion 14a-10, a boss portion 14e is formed on the end portion 14a-9, and a gear shape 14f that fits into the boss portion 14e is formed on the end portion 14a-10. The connection portion is covered with a collar 72. The connection strength between the boss portion 14e and the gear shape 14f is set to be lower than the strength of the first drive shaft 14. When excessive torque is input, the teeth of the gear shape 14f break, the integral rotation of the end portion 14a-9 and the end portion 14a-10 fails, and the first drive shaft 14 idles.

[0079] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments, and various modifications are possible within the scope of the claims and the technical idea described in the specification and the drawings. For example, in the first embodiment, the torque cutoff portion 60 is provided at the end portion 14a on the first drive wheel 34L side of the first drive shaft 14 and the end portion 16a of the second drive wheel 34R of the second drive shaft 16, but it may be provided on either one. Further, the torque cutoff portion 60 may be provided at the end portion 14b on the differential device 12 side of the first drive shaft 14 or / and the end portion 16b on the differential device 12 side of the second drive shaft 16. Further, the boot 36 may not be provided at the end portion where the torque cutoff portion 60 is not provided.

Description of Reference Numerals

[0080] 2 vehicles 4 First power transmission device 6 Second power transmission device 8 Electric motor (first drive source) 10 Power transmission mechanism 12 Differential device 12a One output shaft 12b The other output shaft 14 First drive shaft 14a End on the first drive wheel side 14a-6 Spline shaft 14b End on the differential device side 14f Gear shape 16 Second drive shaft 16a End on the second drive wheel side 16b End on the differential device side 18 First drive shaft 34R First drive wheel 34L Second drive wheel 36a~36d Boots 38a Wheel speed sensor (first rotation information acquisition means) 38b Wheel speed sensor (second rotation information acquisition means) 40 Resolver (first drive source rotation information acquisition means) 42 Control means (torque cut-off part breakage detection means) 46R Third drive wheel 46L Fourth drive wheel 48 Second drive shaft 60, 60A~60H Torque cut-off parts 60c Hole 66 Connecting member 68 Key member CW Middle wheel E Engine (internal combustion engine) FW Front wheel HB Hybrid prime mover RW Rear wheel

Claims

1. a first drive source, a power transmission mechanism connected to the first drive source for transmitting the power of the first drive source, a differential device connected to the power transmission mechanism and having two output shafts for transmitting the power transmitted by the power transmission mechanism in two directions, a first drive shaft having a first drive shaft connected to one output shaft of the differential device and a second drive shaft connected to the other output shaft of the differential device, a power transmission device in a vehicle comprising: a torque interruption portion provided at an end of the first drive shaft or / and an end of the second drive shaft for interrupting torque transmission when a load of a predetermined torque or more is applied to each drive shaft.

2. the first drive shaft is provided with a first drive wheel connected to one end on the first drive shaft side and a second drive wheel connected to the other end on the second drive shaft side, the power transmission device according to claim 1, wherein the torque interruption portion is provided at an end of the first drive shaft on the first drive wheel side or / and an end of the second drive shaft on the second drive wheel side.

3. the power transmission device according to claim 1, wherein the torque interruption portion is provided at an end of the first drive shaft on the differential device side or / and an end of the second drive shaft on the differential device side.

4. a boot is provided at an end of the first drive shaft or / and an end of the second drive shaft, and the torque interruption portion is provided in the boot, the power transmission device according to claim 1.

5. first rotation information acquisition means for acquiring the rotation speed of the first drive wheel, second rotation information acquisition means for acquiring the rotation speed of the second drive wheel, first drive source rotation information acquisition means for acquiring the rotation speed of the first drive source, the power transmission device according to claim 1, further comprising torque interruption portion break detection means for detecting breakage of the torque interruption portion based on the relationship between the rotation speed of the first drive source, the rotation speed of the first drive wheel, and the rotation speed of the second drive wheel.

6. the vehicle further comprises a second drive source and a second drive shaft including other drive wheels. The power transmission device according to claim 5, further comprising control means for controlling the first drive source to be driven at a predetermined speed when the vehicle travels by the second drive shaft when the breakage of the torque interruption portion is detected.

7. The power transmission device according to claim 6, wherein the first drive shaft is disposed in front of the second drive shaft with respect to the forward direction of the vehicle.

8. The power transmission device according to claim 6, wherein the first drive shaft is disposed behind the second drive shaft with respect to the forward direction of the vehicle.

9. The vehicle further includes a third drive source and a third drive shaft including other drive wheels, The power transmission device according to claim 6, further comprising control means for controlling the first drive source to be driven at a predetermined speed when the vehicle travels by the second drive shaft and / or the third drive shaft when the breakage of the torque interruption portion is detected.

10. The power transmission device according to claim 9, wherein the first drive shaft is disposed in front of the second drive shaft and the third drive shaft with respect to the forward direction of the vehicle.

11. The power transmission device according to claim 9, wherein the first drive shaft is disposed behind the second drive shaft and the third drive shaft with respect to the forward direction of the vehicle.

12. The power transmission device according to claim 9, wherein the first drive shaft is disposed between the second drive shaft and the third drive shaft with respect to the forward direction of the vehicle.

13. The power transmission device according to claim 6, wherein the output of the first drive source is the same as or lower than the output of the second drive source.

14. The power transmission device according to claim 6, wherein the output of the first drive source is higher than the output of the second drive source.

15. The power transmission device according to claim 9, wherein the output of the first drive source is the same as or lower than the outputs of the second drive source and the third drive source.

16. The power transmission device according to claim 9, wherein the output of the first drive source is higher than the outputs of the second drive source and the third drive source.

17. The predetermined speed of the first drive source is a value obtained by multiplying the sum of the rotational speeds of the first drive wheel and the second drive wheel by the reduction ratio of the differential device and the power transmission mechanism and dividing the result by 2. The power transmission device according to claim 6 or 9, characterized in that.

18. The power transmission device according to claim 1, characterized in that the first drive source is an electric motor.

19. The power transmission device according to claim 6 or 9, characterized in that the second drive source is an electric motor.

20. The power transmission device according to claim 6 or 9, characterized in that the second drive source is an internal combustion engine.

21. The power transmission device according to claim 6 or 9, characterized in that the second drive source is a hybrid prime mover combining an electric motor and an internal combustion engine.

22. The power transmission device according to claim 1, characterized in that the torque interruption portion is configured by a structure in which the shaft diameter of the first drive shaft and / or the second drive shaft is reduced.

23. The power transmission device according to claim 1, characterized in that the torque interruption portion is configured by one or a plurality of holes that penetrate or do not penetrate a part of the shaft of the first drive shaft and / or the second drive shaft.

24. The power transmission device according to claim 1, characterized in that the torque interruption portion is configured by a part of the shaft of the first drive shaft and / or the second drive shaft having low material strength.

25. The power transmission device according to claim 1, characterized in that the torque interruption portion is configured by reducing the strength of a part of the material of the shaft of the first drive shaft and / or the second drive shaft by metal heat treatment.

26. The power transmission device according to claim 1, characterized in that the torque interruption portion is configured by a structure in which a part of the shaft of the first drive shaft and / or the second drive shaft is divided and connected by a connecting member having lower strength than the shaft.

27. The power transmission device according to claim 1, characterized in that a part of the shaft of the first drive shaft and / or the second drive shaft is divided and spline-connected, and the bottom of the groove of the spline shaft of the spline connection is configured to have the lowest strength.

28. The torque interruption part is configured by a structure in which a part of the shaft of the first drive shaft and / or the second drive shaft is divided and connected by one or a plurality of key members having a lower strength than the shaft. The power transmission device according to claim 1.

29. The torque interruption part is configured by a structure in which a part of the shaft of the first drive shaft and / or the second drive shaft is divided and connected by a gear shape having a lower strength than the shaft. The power transmission device according to claim 1.

30. A vehicle having the power transmission device according to any one of claims 1 to 29.

Images