Electric axle device

Abstract

To provide an electric axle device in which the weight of an electric drive unit including an electric motor is not added to a so-called unsprung weight, and an existing axle case can be used as a De-Dion tube.SOLUTION: An electric axle device includes: an electric drive unit 2 fixed to a vehicle body frame; and an axle case 3 attached to the vehicle body frame via a suspension so as to freely move in a predetermined stroke range in a vertical direction. The axle case 3 has an opening 5 formed in a banjo portion 4. The electric drive unit 2 includes: a motor case portion 7 housing a right motor 6a for driving a right wheel and a left motor 6b for driving a left wheel; and a gear case portion 9 housing a right gear train 8a for transmitting rotation of the right motor 6a to the right wheel and a left gear train 8b for transmitting rotation of the left motor 6b to the left wheel. The gear case portion 9 is inserted into the opening 5, and a vertical dimension A of the gear case portion 9 is smaller than a dimension obtained by subtracting a predetermined stroke from a vertical dimension B of the opening 5.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an electric axle device that reduces the so-called unsprung weight and allows for easy use of existing axle scales. [Background technology]

[0002] Fig. 1(a1) shows a plan view of an axle structure X1 of a general engine-driven vehicle used in vehicles such as trucks, buses, RVs, and SUVs, and Fig. 1(b1) shows a side view of the axle structure X1. The axle case a is attached to a vehicle frame via leaf springs, airbags, control arms, etc., and a differential mechanism b is housed inside. The differential mechanism b includes a drive gear d provided on a propeller shaft c rotated by the engine, side gears f provided on left and right drive shafts e, respectively, a ring gear g rotatably inserted into one of the drive shafts e, and a pinion gear h rotatably supported on the ring gear g via a carrier (not shown), and the drive gear d and the ring gear g are meshed, and the side gear f and the pinion gear h are meshed, absorbing the rotation difference between the inner and outer wheels when the vehicle is traveling around a curve.

[0003] In recent years, with the shift to electric vehicles, various electric axle devices X2, X3 have been developed in which electric motors i, j are incorporated into the axle case a instead of the propeller shaft, as shown in Figures 1(a2), 1(b2), 1(a3), and 1(b3). However, when the motors i, j are assembled into the axle case a, the weight of the motors i, j is added to the so-called unsprung weight, so that the unsprung weight increases by the weight of the motors i, j compared to the conventional axle structure X1, and there is a concern that road tracking performance may deteriorate. In addition, the motors i, j are constantly exposed to impact forces from the road surface, increasing the possibility of failure. In addition, there are the following concerns.

[0004] (Motor-integrated axle 1: vertical) As shown in Figure 1(a2), when motor i is mounted vertically on axle case a, the center of gravity of motor i and the center of rotation of tire T are offset by L1. Therefore, as shown in Figure 1(b2), when viewed from the side of the vehicle, a downward rotational moment M is generated around the tire rotation center on axle case a due to the weight of motor i.

[0005] As shown in Figure 1(a1), in the axle case a of the axle structure X1 of a conventional engine vehicle, the center of gravity of the differential mechanism b (hereinafter also referred to as the diff) and the center of rotation of the tires are offset, so that, as shown in Figure 1(b1), the weight of the diff b similarly generates a downward rotational moment M around the center of rotation of the tires, but the rotation is suppressed by the propeller shaft c.

[0006] On the other hand, as shown in FIG. 1(a2), the axle case a of the electric axle device X2 incorporating the motor i is not supported by the propeller shaft c, so the rotational moment M is supported by the leaf springs and control arms that secure the axle case a to the vehicle frame. This causes twisting in the fixing parts between the leaf springs and control arms and the axle case a, resulting in stress concentration.

[0007] (Motor-integrated axle 2: horizontal) As shown in Figure 1(a3), even in an electric axle device X3 in which motor j is mounted laterally on axle case a, there is still an offset L2 between the center of gravity of motor j and the center of rotation of tire t, so as shown in Figure 1(b3), when viewed from the side of the vehicle, a downward rotational moment M is generated around the tire rotational center due to the weight of motor j in axle case a when viewed from the side of the vehicle, as shown in Figure 1(b3). In addition, as shown in Figure 1(a3), there is an offset L3 between the center of gravity of motor j and the central axis Z of tread W when viewed from above, so a counterclockwise rotational moment is generated around the tread central axis Z due to the weight of motor j in axle case a when viewed from the front of the vehicle (right side in the figure), and stress is concentrated on the right side of the vehicle.

[0008] (2 motor type) Also, as shown in Figures 2(a), 2(b), and 2(c), axle structures Y1, Y2, and Y3 are known in which two motors k1 and k2 are incorporated into an axle case a and the left and right axle shafts m are driven separately, thereby eliminating the need for a differential mechanism b (see Figure 1(a1)). In the case of these axle structures Y1, Y2, and Y3, if the weight of the two motors k1 and k2 exceeds the weight of the conventional differential mechanism b (see Figure 1(a1)), the unsprung weight increases compared to the conventional axle device X1, and road tracking performance deteriorates. In addition, there are the following concerns:

[0009] (Motor-integrated axle 3: wheel arrangement) As shown in Figure 2(a), in the case of axle structure Y1 in which a pair of left and right motors k1, k2 are arranged coaxially near the left and right tires T (wheels), respectively, and the wheels T are driven to rotate via a short motor shaft m, the impact force from the road surface is transmitted to the motor via the short motor shaft m, so there is a concern that the motor shaft m may be deformed or damaged.

[0010] (Motor-integrated axle 4: central location) As shown in FIG. 2(b), in the case of a type in which a pair of motors k1, k2 are positioned toward the center in the vehicle width direction and the wheels T are driven to rotate via a relatively long shaft m, the impact force from the road surface is transmitted to the motors k1, k2 via the relatively long motor shaft m, so the impact force from the road surface to the motors k1, k2 is mitigated. However, the weight of the long motor shaft m becomes unsprung weight, resulting in poor road surface following performance.

[0011] (Motor-embedded axle 5: front and rear placement) As shown in Figure 2(c), in the case of a type in which a pair of motors k1, k2 are arranged in front of and behind the left and right axle shafts m and the left and right axle shafts m are independently rotated and driven via gear n, the impact force from the road surface is transmitted to the motors k1, k2 via the axle shaft m and gear n, so the impact force from the road surface to the motors k1, k2 is significantly mitigated. However, the weight of the axle shaft m and gear n becomes unsprung weight, so road tracking performance is degraded.

[0012] Incidentally, a vehicle drive device that drives wheels with an electric motor is described in Patent Document 1, but unlike the present invention, which uses an existing axle case as a De Dion tube, it uses a dedicated De Dion tube that is curved in a U-shape in plan view to avoid the electric drive unit that houses the motor, which causes stress to concentrate at the curved part of the De Dion tube. Also, since one end of the electric drive unit is supported by the vehicle frame and the other end by the dedicated De Dion tube, part of the weight of the electric drive unit is added to the De Dion tube, which leads to an increase in unsprung weight. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] JP 2020-132101 A Summary of the Invention [Problem to be solved by the invention]

[0014] The object of the present invention, which was devised in consideration of the above circumstances, is to provide an electric axle device in which the weight of the electric drive unit including the electric motor is not added to the so-called unsprung weight and in which the existing axle case can be reused as a De Dion tube. [Means for solving the problem]

[0015] According to the present invention, which has been devised to achieve the above-mentioned object, there is provided an electric axle device comprising: an electric drive unit fixed to a vehicle body frame; and an axle case attached to the vehicle body frame via a suspension so as to be freely movable in the vertical direction within a predetermined stroke range, the axle case having a banjo portion that bulges out in the vertical direction in the center of the vehicle width direction, and an opening formed in front of or behind the banjo portion, the electric drive unit having a motor case portion that accommodates a right motor that drives the right wheel and a left motor that drives the left wheel, and a gear case portion that accommodates a right gear train for transmitting rotation of the right motor to the right wheel and a left gear train for transmitting rotation of the left motor to the left wheel, the gear case portion of the electric drive unit is inserted into the opening of the banjo portion of the axle case, and the vertical dimension of the gear case portion is smaller than the vertical dimension of the opening of the banjo portion minus the above-mentioned predetermined stroke.

[0016] In the electric axle device of the present invention, a right axle shaft is rotatably supported on the right side within the axle case, a left axle shaft is rotatably supported on the left side within the axle case, a final output gear of the right gear train of the gear case portion of the electric drive unit and the right axle shaft are connected via a right drive shaft, a final output gear of the left gear train of the gear case portion of the electric drive unit and the left axle shaft are connected via a left drive shaft, a spline is provided on at least one of the connection portion between the right drive shaft and the right axle shaft and the connection portion between the right drive shaft and the final output gear of the right gear train, and a spline may be provided on at least one of the connection portion between the left drive shaft and the left axle shaft and the connection portion between the left drive shaft and the final output gear of the left gear train.

[0017] In the electric axle device of the present invention, a boot may be interposed between the opening of the banjo portion of the axle case and the gear case portion of the electric drive unit inserted into the opening, blocking outside air while allowing the opening to move vertically relative to the gear case portion. Effect of the Invention

[0018] The electric axle device according to the present invention can achieve the following effects. (1) The gear case of the electric drive unit fixed to the vehicle frame is inserted into the opening of the banjo of the axle case attached to the vehicle frame via a suspension so as to be movable in the vertical direction within a predetermined stroke range, and the vertical dimension of the gear case is smaller than the vertical dimension of the opening of the banjo minus the predetermined stroke. Therefore, even if the axle case moves up and down within the predetermined stroke range during the vehicle's travel, the opening of the banjo does not interfere with the gear case of the electric drive unit. In addition, since the weight of the electric drive unit is not added to the so-called unsprung weight, the weight of the electric drive unit does not deteriorate the road surface following ability. In addition, even if the axle case moves up and down due to an impact force from the road surface, it is not transmitted to the electric drive unit, so the risk of motor failure can be reduced. (2) The electric drive unit houses a right motor and right gear train that drive the right wheels, and a left motor and left gear train that drive the left wheels, so by controlling the right motor and left motor separately, a differential mechanism that absorbs the rotation difference between the inner and outer wheels when driving around a curve is not required. Since a differential mechanism with a complex structure and a large outer diameter is not required, the axle case for existing engine vehicles, which currently houses the differential mechanism in the banjo section, can be reused as a de Dion tube by making the vertical dimension of the gear case section smaller than the vertical dimension of the opening of the banjo section minus the above-mentioned specified stroke. (3) In summary, with the electric axle device according to the present invention, the weight of the electric drive unit is not added to the unsprung weight, and the existing highly reliable axle case can be used as the De Dion tube. An axle case formed in a substantially straight shape in the vehicle width direction is used as the De Dion tube, and a typical De Dion tube that is curved in a U-shape to avoid the electric drive unit as in the past is not used, so it is possible to avoid the concentration of stress in the curved part. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is an explanatory diagram of a conventional electric axle device using one motor, where (a1) is a plan view of an axle device for an engine vehicle as a comparison example, (b1) is a side view thereof, (a2) is a plan view of an electric axle device in which (a1) has been motorized with one vertically mounted motor, (b2) is a side view thereof, (a3) ​​is a plan view of an electric axle device in which (a1) has been motorized with one horizontally mounted motor, and (b3) is a side view thereof. [Diagram 2] FIG. 1 is an explanatory diagram of an electric axle device using two conventional motors, where (a) is a plan view of a wheel-mounted type electric axle device, (b) is a plan view of a centrally mounted type electric axle device, and (c) is a plan view of a front-rear mounted type electric axle device. [Diagram 3] 1A and 1B are explanatory diagrams of an electric axle device showing one embodiment of the present invention, in which (a) is a plan cross-sectional view of the electric axle device, and (b) is a side cross-sectional view of (a) as seen from the direction of arrow b. [Figure 4] 1A to 1D are explanatory diagrams showing the assembly process of the electric axle device according to the above embodiment, in which (a) is a cross-sectional plan view of the drive shaft case assembled to the axle case as the first step, (b) is a front view of the drive shaft case, (c) is a side view of the drive shaft case, and (d) is a front view of a plate attached to the drive shaft case. [Diagram 5] 10(a) is a cross-sectional plan view of the holder attached to the drive shaft case as the second step, (b) is a plan view of the holder, (c) is a front view of the holder, and (d) is a side view of the holder. [Figure 6] (a) is a plan cross-sectional view of the axle shaft assembled to the holder as the third step, (b) is a plan cross-sectional view of the drive shaft assembled to the holder as the fourth step, and (c) is a plan cross-sectional view of the gear case part of the electric drive unit inserted into the opening of the banjo part of the axle case and the final output gear of the gear case part connected to the drive shaft as the fifth step. [Figure 7]13(a) is a cross-sectional plan view showing the sixth step (final step) of attaching the boot provided on the gear case section so as to cover the opening of the banjo section, and FIG. 13(b) is a front view of the same (the boot is omitted). [Figure 8] 1A and 1B are explanatory diagrams showing the positional relationship between the opening and the gear case portion when the axle case of the electric axle device according to this embodiment moves up and down, where (a1) is a front cross-sectional view of the electric axle device showing, in solid lines, the bounding state when the axle case is at its maximum rise and in dashed lines, the rebounding state when the axle case is at its maximum fall, (b1) is a side cross-sectional view thereof, (a2) is a front cross-sectional view of the electric axle device when bouncing with the axle case at its maximum rise, (b2) is a side cross-sectional view thereof, (a3) ​​is a front cross-sectional view of the electric axle case when rebounding with the axle case at its maximum fall, and (b3) is a side cross-sectional view thereof. [Figure 9] FIG. 11 is an explanatory diagram showing a first modified example of the present invention, in which (a) is a plan cross-sectional view of an electric axle device in which the drive shaft case is omitted and a holder is attached to a triangular plate, (b) is a front view of the axle case showing the triangular plate, and (c) is a front view showing the holder of the first embodiment in the upper part and the holder of the first modified example, which is smaller than that in the lower part. [Figure 10] FIG. 11 is a cross-sectional plan view of an electric axle device according to a second modified example of the present invention, in which the bulging portion of the cover is flattened. [Figure 11] FIG. 11 is an explanatory diagram of an electric axle device in which the bulge of the drive shaft case is flattened as a third modified example of the present invention, where (a1) and (b1) are a front view and a side view of a drive shaft case having a bulge as a comparison example, and (a2) and (b2) are a front view and a side view of a drive shaft case in which the bulge is flattened as the third modified example. [Figure 12] 11A and 11B are explanatory diagrams of an electric axle device according to a fourth modified example of the present invention, in which the holder has a cylindrical shape, (a) is a front cross-sectional view of the electric axle device to which a cylindrical holder is attached during bounding, (b) is a side view of the same, (c) is a plan view of the cylindrical holder, (d) is a front view of the holder, and (e) is a side view of the holder. [Figure 13]11 is an explanatory diagram showing a fifth modified example of the present invention, in which (a) is a cross-sectional plan view of the holder in an assembled state with a drive shaft attached in advance, and (b) is a cross-sectional plan view of the holder and drive shaft in the assembled state attached to a drive shaft case. [Figure 14] FIG. 13 is an explanatory diagram of a sixth modified example of the present invention, in which a spline hole is provided in the tire side joint portion of the drive shaft and the spline of the axle shaft is inserted into the spline hole, (a1) and (b1) are front and side views of a comparative example in which a spline is provided in the tire side joint portion of the drive shaft, (a2) and (b2) are front and side views of a fifth modified example in which a spline hole is provided in the tire side joint portion of the drive shaft, and (c) is a partial cross-sectional view of an electric axle device in which the spline of the axle shaft is inserted into the spline hole shown in (a2) and (b2). [Figure 15] FIG. 13 is a cross-sectional plan view of an electric axle device that combines the second and sixth modifications as a seventh modification of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values ​​shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present invention are not shown.

[0021] (Outline of electric axle device) As shown in Fig. 3(a) and Fig. 3(b), an electric axle device 1 according to an embodiment of the present invention includes an electric drive unit 2 fixed to a vehicle body frame (not shown), and an axle case 3 attached to the vehicle body frame via a suspension (leaf spring, airbag, control arm, etc.) so as to be movable in a predetermined stroke range in the vertical direction. The axle case 3 has a banjo part 4 that is bulged in the vertical direction in the center of the vehicle width direction, and openings 5 ​​are formed in front and behind the banjo part 4. The electric drive unit 2 has a motor case part 7 that houses a right motor 6a that drives a right wheel (the wheel on the left in Fig. 3(a)) and a left motor 6b that drives a left wheel (the wheel on the right in Fig. 3(a)), and a gear case part 9 that houses a right gear train 8a for transmitting the rotation of the right motor 6a to the right wheel and a left gear train 8b for transmitting the rotation of the left motor 6b to the left wheel. The gear case portion 9 of the electric drive unit 2 is inserted into the front opening 5 of the banjo portion 4 of the axle case 3, and the vertical dimension A of the gear case portion 9 is set to be smaller than the vertical dimension B of the front opening 5 of the banjo portion 4 minus the above-mentioned specified stroke.

[0022] 3(a) and 3(b), a right axle shaft 10a is rotatably supported on the right side in the vehicle width direction (the wheel on the left in FIG. 3(a)) in the axle case 3, and a left axle shaft 10b is rotatably supported on the left side in the vehicle width direction (the wheel on the right in FIG. 3(a)) in the axle case 3. A final output gear 11a of a right gear train 8a in a gear case portion 9 of the electric drive unit 2 and the right axle shaft 10a are connected via a right drive shaft 12a, and a final output gear 11b of a left gear train 8b in a gear case portion 9 of the electric drive unit 2 and the left axle shaft 10b are connected via a left drive shaft 12b. Splines are provided on at least one of the connection between the right drive shaft 12a and the right axle shaft 10a and the connection between the right drive shaft 12a and the final output gear 11a of the right gear train 8a, and splines are provided on at least one of the connection between the left drive shaft 12b and the left axle shaft 10b and the connection between the left drive shaft 12b and the final output gear 11b of the left gear train 8b.

[0023] 3(a) and 3(b), a boot 13 is interposed between an opening 5 in front of the banjo portion 4 of the axle case 3 and the gear case portion 9 of the electric drive unit 2 inserted into the opening 5, to block outside air while allowing the opening 5 to move up and down relative to the gear case portion 9. Each component will be described below.

[0024] (Axle case 3) The axle case 3 shown in Figures 3(a) and 3(b) is attached to a vehicle body frame (ladder frame, etc.) (not shown) via a suspension (leaf spring, airbag, control arm, etc.) so as to be movable in the vertical direction within a predetermined stroke range, and has a banjo part 4 that bulges out in the vertical direction at the center in the vehicle width direction, and tube parts 14 arranged on the left and right of the banjo part 4. A gear case part 9 of the electric drive unit 2 fixed to the vehicle body frame is inserted into an opening 5 in front of the banjo part 4, so that the axle case 3 is movable in the vertical direction at least within the above-mentioned predetermined stroke range. Therefore, the weight of the electric drive unit 2 is not applied to the axle case 3, and the axle case 3 of the present invention functions as a so-called De Dion tube.

[0025] In this way, the axle case 3 that functions as a De Dion tube can be a banjo-type axle case 3 for existing engine vehicles that are compatible with various vehicle widths and sizes, ensuring high reliability. In addition, the axle case 3 does not have the curved portion of a typical De Dion tube that is curved to avoid the electric drive unit 2, so it can function as a De Dion tube while avoiding the stress concentration at the curved portion that was a problem in the past. Also, the front opening 5 of the banjo part 4 is used as an entrance for attaching the differential mechanism b (see FIG. 1(a1)) inside the banjo part 4 in the existing axle device for engine vehicles, but in the electric axle device 1 of the present invention, it is used as an entrance for inserting the gear case part 9 of the electric drive unit 2.

[0026] (Electric drive unit 2) The electric drive unit 2 shown in Figures 3(a) and 3(b) is fixed to a vehicle body frame (not shown) and has a casing in which a motor case section 7 and a gear case section 9 are integrated. A right motor 6a for driving a right wheel (the wheel on the left side in Figure 3(a)) and a left motor 6b for driving a left wheel (the wheel on the right side in Figure 3(a)) are housed in the motor case section 7 of the casing at a distance from each other on the left and right sides, and input gears 15a and 15b are attached to the right motor 6a and the left motor 6b, respectively. An intermediate gear 16a (16b) meshing with the input gear 15a (15b) and a final output gear 11a (11b) meshing with the intermediate gear 16a (16b) are housed in the gear case section 9 so as to be rotatable via bearings 17, respectively.

[0027] As shown in FIG. 3(a) and FIG. 3(b), the outer diameter of the intermediate gear 16a (16b) and the final output gear 11a (11b) is smaller than the outer diameter of the right motor 6a and the left motor 6b, and the vertical dimension A of the gear case portion 9 is smaller than the vertical dimension C of the motor case portion 7. This allows the vertical dimension A of the gear case portion 9 to be made as small as possible compared to the vertical dimension B of the opening 5 in front of the banjo portion 4, and the suspension stroke (the above-mentioned predetermined stroke) that allows the axle case 3 to move vertically when the vehicle is traveling can be obtained. In FIG. 3(b) which is a view of FIG. 3(a) from the direction of the arrow b, BO is the bound stroke of the suspension, RE is the rebound stroke, and BO+RE is the predetermined stroke. Note that the bound stroke BO and the rebound stroke RE do not have to be equal to each other.

[0028] (assembly) Next, the assembly process of the electric axle device 1 according to this embodiment will be described with reference to Figs. 4 to 7, while describing each of the components used in the assembly.

[0029] FIG. 4(a) shows the axle case 3 before being attached to the vehicle frame via the suspension. The banjo portion 4 of the axle case 3 has openings 5 ​​at the front and rear, and an axle ring 18 is welded to the front opening 5, and a cover 19 is welded to the rear opening 5. The axle ring 18 has a plurality of holes spaced apart in the circumferential direction, and a drive shaft case 20 shown in FIG. 4(b) and FIG. 4(c) is fastened to the holes with bolts 22. The drive shaft case 20 has a ring portion 20a that is overlapped with the axle ring 18, and a case portion 20c having rectangular windows 20b on both the left and right sides through which the holder 21 shown in FIG. 5 is inserted. The ring portion 20a has a plurality of holes 20d spaced apart in the circumferential direction, and the holes 20d of the ring portion 20a and the holes of the axle ring 18 are fastened to each other with bolts 22. Incidentally, a pair of left and right plates 23 shown in FIG. 4(d) are welded in advance to the drive shaft case 20 as shown in FIG. 4(a).

[0030] As shown in FIG. 5(a), the holder 21 shown in FIG. 5(b), FIG. 5(c), and FIG. 5(d) is fixed to the plate 23 welded to the drive shaft case 20 with the bolt 24. The holder 21 has a front plate 21a and a rear plate 21b extending from the inside of the banjo portion 4 to the inside of the tube portion 14 (tire side), and a side plate 21c attached to the ends of the front plate 21a and the rear plate 21b on the outer side (tire side) in the vehicle width direction, and is inserted into the window 20b of the drive shaft case 20 shown in FIG. 4(c). An insertion hole 25 for the bolt 24 is formed in the ends of the front plate 21a and the rear plate 21b on the inner side (banjo portion side) in the vehicle width direction, and the bolt 24 inserted into the insertion hole 25 is fastened to the screw hole 23a of the plate 23. A circular hole 21d is formed in the side plate 21c, and a socket 27 is rotatably attached to the circular hole 21d in advance via a bearing 26.

[0031] In a later process, the drive shaft 12a (12b) and the axle shaft 10a (10b) are assembled to the socket 27 shown in Fig. 5(a) as shown in Fig. 3(a). The holder 21 that supports the socket 27 via the bearing 26 is separated from the drive shaft case 20 in order to make the length of the drive shaft 12a (12b) that correlates with the length from the insertion hole 25 to the circular hole 21d shown in Fig. 5(c) as long as possible and to ensure the ease of assembly into the axle case 3. By lengthening the length from the insertion hole 25 to the circular hole 21d of the holder 21 shown in Fig. 5(c) to make the drive shaft 12a (12b) longer, the inclination angle (operation angle) of the drive shaft 12a (12b) during the suspension operation shown in Fig. 8 can be reduced, and the load on the constant velocity joints 28, 29 provided at both ends of the drive shaft 12a (12b) can be reduced. 5(a), if the holder 21 and the drive shaft case 20 were an integrated part, the integrated part could not be assembled into the axle case 3 through the opening 5 of the banjo portion 4. Therefore, by separating the holder 21 from the drive shaft case 20, the length of the drive shaft 12a (12b) is increased while ensuring ease of assembly.

[0032] As shown in Figure 6(a), the axle shaft 10a (10b) is inserted into a socket 27 supported by holder 21 via a bearing 26, and fastened with a socket bolt 30. A screw hole is formed in the end face of the axle shaft 10a (10b), and a partition is formed inside the socket 27. A fastening hole is formed in the partition, and the axle shaft is fastened to the socket 27 by screwing the socket bolt 30 inserted into the fastening hole into the screw hole in the end face of the axle shaft. A spline is formed in the axle shaft 10a (10b), and a spline hole is formed in the socket 27, so that the two rotate together.

[0033] As shown in FIG. 6(b), the tire-side constant velocity joint 28 of the drive shaft 12a (12b) is inserted into the socket 27 supported by the holder 21 via a bearing 26. The tire-side constant velocity joint 28 has a spline on its outer circumferential surface, and the socket 27 has a spline hole, so that the two rotate together. The tire-side constant velocity joint 28 and the socket 27 are not fastened to each other, and are slidable within a predetermined range in the vehicle width direction. Therefore, if the drive shaft 12a (12b) is released after being inserted, it will fall out, but the spline increases the surface area and increases the frictional resistance, so it is difficult to fall out. It is also possible to use an attachment jig to prevent the drive shaft from falling out.

[0034] As shown in FIG. 6(c), the opening 5 of the banjo portion 4 of the axle case 3 is inserted into the gear case portion 9 of the electric drive unit 2 fixed to the vehicle body frame, and the constant velocity joint 29 on the gear case side of the drive shaft 12a (12b) is inserted into the final output gear 11a (11b) of the gear case portion 9. The constant velocity joint 29 on the gear case side has a spline on its outer circumferential surface, and the final output gear 11a (11b) has a spline hole, so that the two rotate together. The constant velocity joint 29 on the gear case side and the final output gear 11a (11b) are not fastened to each other, and both are slidable within a predetermined range in the vehicle width direction, so that the constant velocity joint 29 can be properly assembled by appropriately moving the drive shaft 12a (12b) in the vehicle width direction and inserting the constant velocity joint 29 into the final output gear 11a (11b).

[0035] As shown in FIG. 7(a), the boot 13 attached to the gear case portion 9 is fastened to the axle ring 18 of the banjo portion 4 of the axle case 3 with the bolt 22 so as to cover the opening 5. When the drive shaft case 20 shown in FIG. 4(b) and FIG. 4(c) is fastened to the axle ring 18 of the banjo portion 4 with the bolt 22, not all of the holes formed in the axle ring 18 are used, and the remaining holes are used to fasten the boot 13 with the bolt 22. The boot 13 allows the opening 5 of the banjo portion 4 to move vertically relative to the gear case portion 9, while isolating the inside of the axle case 3, the drive shaft case 20, the holder 21, the drive shaft 12a (12b), and the socket 27 from the outside air. FIG. 7(b) is a front view of FIG. 7(a) seen from the front with the boot 13 omitted. After that, the axle case 3 is attached to the vehicle frame via the suspension.

[0036] (Activation) FIG. 8 shows the positional relationship between the opening 5 of the banjo part 4 of the axle case 3 and the gear case part 9 of the electric drive unit 2 fixed to the vehicle body frame when the axle case 3, which is attached to the vehicle body frame via a suspension so as to be movable in the vertical direction within a predetermined stroke range, moves up and down within a predetermined stroke range during the vehicle's travel. In FIG. 8(a1) and FIG. 8(b1), the maximum bound of the suspension is shown by a solid line and the maximum rebound is shown by a broken line, FIG. 8(a2) and FIG. 8(b2) show the maximum bound, and FIG. 8(a3) and FIG. 8(b3) show the maximum rebound. Here, when the drive shaft 12a (12b) tilts in response to the suspension stroke, the distance between the final output gear 11a (11b) of the gear case part 9 and the socket 27 becomes longer than when it is horizontal, but this is absorbed by the splines of the constant velocity joints 28, 29 at both ends of the drive shaft 12a (12b).

[0037] The predetermined stroke corresponding to the suspension stroke is regulated by the operating angle limit of the drive shaft 12a (12b), the inner diameter of the opening 5 of the banjo portion 4, and the vertical dimension of the gear case portion 9 of the electric drive unit 2. The operating angle limit of the drive shaft 12a (12b) can be reduced in comparison with the short drive shaft 12a (12b) by lengthening the drive shaft 12a (12b) by making the holder 21 shown in Fig. 5(b), Fig. 5(c), and Fig. 5(d) as long as possible in the vehicle width direction. This reduces the load on the constant velocity joints 28, 29 provided at both ends of the drive shaft 12a (12b), and allows the operating angle limit to be increased.

[0038] As for the vertical dimension of the gear case section 9, as shown in Figures 3(a) and 3(b), the diameters of the intermediate gear 16a (16b) and the final output gear 11a (11b) are made smaller than the diameters of the right motor 6a and the left motor 6b, and the vertical dimension A of the gear case section 9 is made smaller than the vertical dimension C of the motor case section 7. As a result, the vertical dimension A of the gear case section 9 can be made as small as possible compared to the vertical dimension B of the opening 5 of the banjo section 4, and the axle case 3 is provided with a suspension stroke (predetermined stroke) that allows it to move vertically. Note that the inner diameter of the opening 5 of the banjo section 4 is determined by the axle case, since an existing axle case for an engine vehicle is used.

[0039] (Action and effect) As shown in FIG. 3(a) and FIG. 3(b), the gear case part 9 of the electric drive unit 2 fixed to the vehicle body frame is inserted into the opening 5 of the banjo part 4 of the axle case 3 attached to the vehicle body frame via a suspension so as to be movable in a predetermined stroke range in the vertical direction, and the vertical dimension of the gear case part 9 is smaller than the vertical dimension of the opening 5 of the banjo part 4 minus the predetermined stroke. Therefore, even if the axle case 3 moves up and down in the vertical direction within the range of the predetermined stroke while the vehicle is running, the opening 5 of the banjo part 4 does not interfere with the gear case part 9 of the electric drive unit 2. In addition, since the weight of the electric drive unit 2 is not added to the so-called unsprung weight, the weight of the electric drive unit 2 does not deteriorate the road surface following ability. In addition, even if the axle case 3 moves up and down due to the impact force from the road surface, it is not transmitted to the electric drive unit 2, so the risk of failure of the motor 6a (6b) can be reduced.

[0040] As shown in FIG. 3(a), the electric drive unit 2 houses a right motor 6a and a right gear train 8a for driving the right wheels, and a left motor 6b and a left gear train 8b for driving the left wheels. By separately controlling the right motor 6a and the left motor 6b, the differential mechanism b (see FIG. 1(a1)) for absorbing the rotation difference between the inner and outer wheels during curve driving is not required. Since the differential mechanism b, which has a complex structure and a large outer diameter, is not required, as shown in FIG. 3(b), the outer diameters of the final output gear 11a (11b) and the intermediate gear 16a (16b) of the gear case part 9 are made smaller than the outer diameters of the right motor 6a and the left motor 6b, and the vertical dimension A of the gear case part 9 is made smaller than the vertical dimension B of the opening 5 of the banjo part 4 minus the above-mentioned predetermined stroke, so that the axle case 3 for an existing engine vehicle in which the differential mechanism b is housed in the banjo part 4 can be used as a de Dion tube.

[0041] In this way, the axle case 3 that functions as a De Dion tube can use an existing banjo-type axle case 3 for engine vehicles that is compatible with various vehicle widths and sizes, reducing development time and investment while ensuring high reliability. In addition, the axle case 3 does not have the curved portion of a typical De Dion tube that is curved to avoid the electric drive unit 2, so while functioning as a De Dion tube, it can avoid the problem of stress concentration at the curved portion that was an issue with conventional De Dion tubes.

[0042] The electric vehicle incorporating the electric axle device 1 according to this embodiment shown in FIG. 3(a) has an increased weight by the weight of the drive shaft 12a (12b) compared to a conventional engine vehicle. However, since one end (constant velocity joint 29 on the gear case side) of the drive shaft 12a (12b) is supported by the electric drive unit 2, roughly half of the weight of the drive shaft 12a (12b) is the unsprung weight. Therefore, road tracking performance is improved compared to when the entire weight of the drive shaft 12a (12b) is the unsprung weight. In addition, the current engine vehicle can be easily converted to an electric vehicle by removing the differential mechanism b (see FIG. 1(a1)) from the axle case 3 of the current engine vehicle and inserting the gear case part 9 of the electric drive unit 2, which has been retrofitted to the vehicle body frame, into the opening 5 of the banjo part 4 as shown in FIG. 3(a) and FIG. 3(b).

[0043] (First Modification) FIG. 9 shows a first modified example of the present invention. FIG. 9(a) is a plan sectional view of an electric axle device 1a in which the drive shaft case 20 of the previous embodiment shown in FIG. 3(a) is omitted and the holder 21 is attached to a triangular plate 31, and FIG. 9(b) is a front view of an axle case 3a showing the triangular plate 31. The axle case 3a is configured by butting together an upper plate 3x having a U-shaped cross section with an open lower side and a lower plate 3y having a U-shaped cross section with an open upper side and welding them together, and welding the triangular plate 31 to a notch 3z formed in the upper plate 3x and the lower plate 3y near the opening 5. By providing a screw hole 32 in the triangular plate 31 and fastening the holder 21 to the screw hole 32 with a bolt 24, the drive shaft case 20 and the plate 23 (see FIG. 4(a)) that supported the holder 21 in the previous embodiment shown in FIG. 3(a) are no longer necessary, and weight can be reduced. Furthermore, since plate 23 is no longer necessary, as shown in FIG. 9(c), the length of holder 21 (bolted to triangular plate 31) of the first modified example shown in the lower part can be shortened by the length L of plate 23 compared to holder 21 (bolted to plate 23) of the previous embodiment shown in the upper part, thereby making it even lighter.

[0044] (Second Modification) FIG. 10 shows a second modified example of the present invention. FIG. 10 shows a first modified example in which the bulge 19x of the cover 19 shown in FIG. 9(a) is flattened. The axle case 3 basically moves only in the vertical direction relative to the body frame as the suspension strokes, and does not move in the front-rear direction of the body. That is, inside the cover 19 of the banjo part 4, there is a cavity in the front-rear direction that does not interfere with the gear case part 9 of the electric drive unit 2 fixed to the body frame, and the bulge 19x of the cover 19 is eliminated. By flattening the bulge 19x of the cover 19, the center of gravity G1 of the cover 19 is closer to the axial center of the axle shaft 10a (10b) than the center of gravity G2 when the bulge 19x is present. As a result, the rotational force due to the rotational moment around the axis of the axle shaft 10a (10b), which is considered to be one of the causes of stress concentration at the curved part, which is a problem of a general U-shaped De Dion tube, can also be reduced.

[0045] (Third Modification) Fig. 11 shows a third modified example of the present invention. Fig. 11(a1) and Fig. 11(b1) show the drive shaft case 20 according to the first embodiment shown in Fig. 4(b) and Fig. 4(c), and Fig. 11(a2) and Fig. 11(b2) show the drive shaft case 20w according to the third modified example, which is flattened by removing the bulge 20x housed inside the cover 19 shown in Fig. 4(a). By removing the bulge 20x and making it flat, the center of gravity G3 of the drive shaft case 20w is closer to the axial center of the axle shaft 10a (10b) than the center of gravity G4 when the bulge 20x is present, and the same effect as the second modified example can be achieved.

[0046] (Fourth Modification) A fourth modified example of the present invention is shown in Figure 12. As shown in Figures 12(a) and 12(b), in the fourth modified example, instead of the plate-shaped holder 21 shown in Figures 5(b), 5(c), and 5(d) of the first embodiment, a cylindrical holder 21x shown in Figures 12(c), 12(d), and 12(e) is fastened to the side of the drive shaft case 20 with a bolt 33. Making the holder 21x cylindrical increases the rigidity with a simple structure and improves the ease of assembly.

[0047] (Fifth Modification) FIG. 13 shows a fifth modified example of the present invention. In the fifth modified example, the assembly procedure is slightly changed from that of the first embodiment. As shown in FIG. 13(a), the drive shaft 12a (12b) is assembled in advance with a bolt 34 to a socket 27 attached to a holder 21 via a bearing 26 to form an assembly, and the assembly is fastened to a plate 23 of a drive shaft case 20 with a bolt 24 as shown in FIG. 13(b). Since the drive shaft 12a (12b) is assembled in advance with a socket 27, one assembly process can be reduced compared to the first embodiment. Also, since the axle shaft 10a (10b) can be inserted into the socket 27 later, it can be used with a so-called fully floating axle. The slide of the drive shaft 12a (12b), which is required when the suspension is activated by raising and lowering the axle case 3 shown in FIG. 8, is ensured by a spline provided on a constant velocity joint 29 on the gear case side.

[0048] (Sixth Modification) Fig. 14 shows a sixth modified example of the present invention. Fig. 14(a1) and Fig. 14(b1) show the drive shaft 12b (12a is also the same) according to the first embodiment shown in Fig. 3(a), and Fig. 14(a2) and Fig. 14(b2) show the drive shaft 12bx (12a is also the same) according to the sixth modified example. As shown in Fig. 14(a1) and Fig. 14(b1), the drive shaft 12b according to the first embodiment has a spline Sp on the outer circumferential surface of the tire-side constant velocity joint 28, and the spline Sp is slidably inserted into a spline hole of a socket 27 rotatably supported by the holder 21 via a bearing 26 as shown in Fig. 3(a).

[0049] On the other hand, as shown in Fig. 14(a2) and Fig. 14(b2), the drive shaft 12bx according to the sixth modified example has a spline hole Spx in the tire side constant velocity joint 28x, into which the spline formed in the axle shaft 10b (10a as well) is slidably inserted as shown in Fig. 14(c). The tire side constant velocity joint 28x of the drive shaft 12bx is rotatably supported by the holder 21 via the bearing 26. This configuration eliminates the need for the socket 27, thereby reducing the number of parts. Also, since the axle shaft 10b can be inserted into the spline hole sx of the constant velocity joint 28x later, it is compatible with a so-called fully floating axle. 35 is a fully floating wheel hub.

[0050] (Seventh Modification) A seventh modified example of the present invention is shown in Fig. 15. The seventh modified example is a combination of the second modified example shown in Fig. 10 and the sixth modified example shown in Fig. 14 in a superimposed manner. That is, the bulge 19x of the cover 19 is made flat, the holder 21 is fastened to the triangular plate 31 with the bolt 24, and a spline hole sx is provided in the constant velocity joint 28x on the tire side of the drive shaft 12ax (12bx), into which the spline of the axle shaft 10a (10b) is inserted. The same parts are given the same reference numerals and detailed explanations are omitted, but the number of parts can be reduced, which promotes weight reduction.

[0051] The above describes a preferred embodiment of the present invention with reference to the attached drawings. However, it goes without saying that the present invention is not limited to the above-described embodiment, and various modified or altered examples within the scope of the claims also fall within the technical scope of the present invention. [Industrial Applicability]

[0052] The present invention can be used in an electric axle device in which the weight of the electric drive unit including the electric motor is not added to the so-called unsprung weight and an existing axle case can be used as a de Dion tube. [Explanation of symbols]

[0053] 1 Electric axle device 2 Electric drive unit 3 Axle Case 4. Banjo Club 5 aperture 6a Right motor 6b Left motor 7 Motor case 8a Right Gear Train 8b Left gear train 9 Gear case part 10a Right axle shaft 10b Left axle shaft 11a Final output gear of right gear train 11b Final output gear of left gear train 13. Boots 28 Constant velocity joints as connecting parts 29 Constant velocity joints as connecting parts A Gear case vertical dimension B Vertical dimension of the banjo opening

Claims

1. an electric drive unit fixed to a vehicle body frame; and an axle case attached to the vehicle body frame via a suspension so as to be movable in a vertical direction within a predetermined stroke range; The axle case has a banjo portion that is bulged in the vertical direction in the center of the vehicle width direction, and an opening is formed in front or rear of the banjo portion, the electric drive unit has a motor case portion accommodating a right motor for driving a right wheel and a left motor for driving a left wheel, and a gear case portion accommodating a right gear train for transmitting rotation of the right motor to the right wheel and a left gear train for transmitting rotation of the left motor to the left wheel, An electric axle device characterized in that the gear case portion of the electric drive unit is inserted into the opening of the banjo portion of the axle case, and the vertical dimension of the gear case portion is smaller than the vertical dimension of the opening of the banjo portion minus the specified stroke.

2. a right axle shaft is rotatably supported on the right side of the axle case, and a left axle shaft is rotatably supported on the left side of the axle case, a final output gear of the right gear train of the gear case portion of the electric drive unit and the right axle shaft are connected via a right drive shaft, a final output gear of the left gear train of the gear case portion of the electric drive unit and the left axle shaft are connected via a left drive shaft, a spline is provided on at least one of a connection portion between the right drive shaft and the right axle shaft and a connection portion between the right drive shaft and the final output gear of the right gear train; 2. The electric axle device according to claim 1, wherein a spline is provided on at least one of a connection portion between the left drive shaft and the left axle shaft and a connection portion between the left drive shaft and the final output gear of the left gear train.

3. The electric axle device according to claim 1 or 2, characterized in that a boot is interposed between the opening of the banjo portion of the axle case and the gear case portion of the electric drive unit inserted into the opening, the boot blocking outside air while allowing the opening to move vertically relative to the gear case portion.

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