Vehicle suspension system

Abstract

To provide a vehicle suspension device which can prevent change in pitching behavior of the entire vehicle when a regenerative brake and a friction brake are used in the vehicle including an electric motor.SOLUTION: The invention relates to a suspension device of a vehicle including electric motors 30, 32 and includes: a front suspension arm 66 that may swing in a vehicle vertical direction with reference to a front wheel swinging axis A; a front damper 68 extending substantially perpendicularly to the front wheel swinging axis A in a side view; a rear suspension arm 46 that may swing in the vehicle vertical direction with reference to a rear wheel swinging axis A; and a rear damper 48 extending substantially perpendicularly to the rear wheel swinging axis A in the side view. In the side view, the front wheel swinging axis A and a first imaginary line C perpendicular to a direction of extension of the front damper are substantially parallel to each other. Further, the rear wheel swinging axis A and a second imaginary line C perpendicular to a direction of extension of the rear damper are substantially parallel to each other.SELECTED DRAWING: Figure 10

Description

Technical Field

[0003]

[0001] The present invention relates to a suspension device for a vehicle, and particularly to a suspension device for a vehicle equipped with an electric motor.

Background Art

[0002] Conventionally, a suspension control device for setting suspension geometries of anti-dive and anti-lift for front and rear wheels has been known (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, in recent years, during the research and development of electric vehicles, the inventors have intensively studied the suspension structure optimal for electric vehicles. Normally, the suspension geometry of a vehicle is set in consideration of the attitude change of the vehicle during braking and driving. And in an electric vehicle, during braking, in addition to a friction brake that applies a braking force to the wheels using a conventional hydraulic system, a regenerative brake that drives an electric motor as a generator to charge the battery is used.

[0005] Here, the difference between friction brakes and regenerative brakes is that the point of application of the braking force is different, resulting in different anti-lift angles and anti-dive angles during braking. Specifically, with friction brakes, the point of application of the braking force is the center of the tire contact patch, so the angle that the line connecting the center of the tire contact patch and the instantaneous center of rotation of the wheel makes with respect to the ground is the anti-lift angle (rear wheels) / anti-dive angle (front wheels). On the other hand, with regenerative brakes, the point of application of the braking force is the wheel center, so the angle that the line connecting the wheel center and the instantaneous center of rotation of the wheel makes with respect to the ground is the anti-lift angle / anti-dive angle. Therefore, for example, when coordinating the control of friction brakes and regenerative brakes, changing the braking force of the friction brakes and the braking force of the regenerative brakes could cause unstable pitching behavior throughout the vehicle, raising concerns that it might cause discomfort to the occupants.

[0006] Therefore, the present invention has been made to solve the above-mentioned problems, and aims to provide a vehicle suspension system that can suppress changes in the pitching behavior of the entire vehicle when using regenerative braking and friction braking in a vehicle equipped with an electric motor. [Means for solving the problem]

[0007] To solve the above-mentioned problems, the present invention provides a vehicle suspension system equipped with an electric motor that transmits driving force to at least one of the front or rear wheels via an output transmission shaft, comprising: a front suspension arm that can swing in the vertical direction of the vehicle with respect to the front wheel oscillation axis at a vehicle body mounting portion at the front of the vehicle; a front damper that extends in a direction perpendicular to the front wheel oscillation axis in a side view; a rear suspension arm that can swing in the vertical direction of the vehicle with respect to the rear wheel oscillation axis at a vehicle body mounting portion at the rear of the vehicle; and a rear damper that extends in a direction perpendicular to the rear wheel oscillation axis in a side view, wherein in a side view, the front wheel oscillation axis and a first imaginary line perpendicular to the direction in which the front damper extends extend in directions parallel to each other, and the rear wheel oscillation axis and a second imaginary line perpendicular to the direction in which the rear damper extends extend in directions parallel to each other. Furthermore, the front wheel pivot axis and the rear wheel pivot axis each extend diagonally upward toward the front of the vehicle in a side view, and the electric motor comprises a front motor mounted on the front of the vehicle body and a rear motor mounted on the rear of the vehicle body, with the rear motor located at the rear of the vehicle being the primary drive. It is characterized by the following.

[0008] According to the present invention configured in this manner, in a vehicle suspension system equipped with an electric motor that transmits driving force to at least one of the front or rear wheels via an output transmission shaft, the front wheel oscillation axis and a first imaginary line perpendicular to the direction in which the front damper extends extend in directions parallel to each other, and the rear wheel oscillation axis and a second imaginary line perpendicular to the direction in which the rear damper extends extend in directions parallel to each other. As a result, when braking the front and rear wheels, including the wheel on which regenerative braking acts (at least one of the front or rear wheels), differences in the behavior of the front and rear of the vehicle are suppressed. This suppresses changes in the pitching behavior of the entire vehicle when using regenerative braking and friction braking, for example when coordinating control of friction braking and regenerative braking, thereby reducing discomfort for the occupants. Furthermore, with the present invention configured in this way, there is no difference in the anti-lift angle (anti-dive angle) between the regenerative brake and the friction brake at both the front and rear wheels, or the difference can be made very small. Therefore, changes in the behavior of the entire vehicle when using the regenerative brake and the friction brake can be suppressed more reliably. In particular, since the rear electric motor is the main drive, the anti-lift angle of the rear suspension can suppress the lift of the rear of the vehicle when using the regenerative brake and the friction brake.

[0009] Furthermore, in the present invention, preferably, the front wheel pivot axis and the rear wheel pivot axis extend in directions that coincide with the longitudinal direction of the vehicle when viewed from below. With the present invention configured in this way, the front wheel oscillation axis and the rear wheel oscillation axis each extend in directions that coincide with the longitudinal direction of the vehicle when viewed from below. This makes it possible to more reliably suppress differences in the behavioral changes of the front and rear of the vehicle when braking the front and rear wheels, including the wheel on which regenerative braking acts (at least one of the front or rear wheels). This suppresses changes in the pitching behavior of the entire vehicle, for example, when coordinating control of friction brakes and regenerative brakes, thereby reducing discomfort for the occupants. Furthermore, since the front wheel oscillation axis and the rear wheel oscillation axis each extend in directions that coincide with the longitudinal direction of the vehicle when viewed from below, the front wheels and rear wheels (each wheel center) can each oscillate linearly in the same direction as the damper extends. This makes it possible to more effectively suppress changes in the behavior of the entire vehicle when using regenerative brakes and friction brakes.

[0010] Furthermore, in the present invention, preferably, the front wheel pivot axis and the rear wheel pivot axis each extend diagonally upward toward the front of the vehicle when viewed from the side. With the present invention configured in this way, an anti-lift angle is formed in particular on the rear suspension, thereby suppressing lift of the rear of the vehicle when using regenerative braking and friction braking. Furthermore, with the present invention, the front wheel oscillation axis and the rear wheel oscillation axis extend diagonally upward toward the front of the vehicle in a side view, a first imaginary line perpendicular to the direction in which the front wheel oscillation axis and the front damper extend in directions parallel to each other, and a second imaginary line perpendicular to the direction in which the rear wheel oscillation axis and the rear damper extend in directions parallel to each other. As a result, the difference between the behavior of the front and rear of the vehicle can be reduced when braking the front and rear wheels, thereby suppressing changes in the pitching behavior of the entire vehicle when using regenerative braking and friction braking.

[0011] Furthermore, in the present invention, preferably, the electric motor includes a rear electric motor that is mounted on the vehicle body at the rear of the vehicle and drives the rear wheels, with the rear electric motor provided at the rear of the vehicle serving as the main drive source. With the present invention configured in this way, the braking force of the regenerative brake acting on the rear wheels is increased, but since the rear wheel oscillation axis and the second imaginary line extend in directions parallel to each other, it is possible to more effectively suppress changes in the pitching behavior of the rear of the vehicle when using the regenerative brake and friction brake of the rear wheels. Furthermore, since the rear motor drives the rear wheels as the main drive source, and the first imaginary line perpendicular to the direction in which the front wheel oscillation axis and the front damper extend in directions parallel to each other, and the second imaginary line perpendicular to the direction in which the rear wheel oscillation axis and the rear damper extend in directions parallel to each other, it is possible to prevent the front of the vehicle from lifting when the vehicle starts up by using the rear wheels as the main drive wheels.

[0013] Furthermore, in the present invention, preferably, the front suspension arm and the rear suspension arm are attached to a vehicle frame that extends in the longitudinal direction of the vehicle from a battery case located in the lower center of the vehicle. According to the present invention configured in this manner, the support rigidity of the front and rear wheels can be increased, thereby reducing the response delay of the vehicle's behavior (for example, the response delay of cornering force).

[0014] Furthermore, in the present invention, preferably, the suspension device is a strut-type suspension device in which the wheel-side ends of the front suspension arm and the rear suspension arm are connected, the front and rear wheel hub carriers supporting the front and rear wheels respectively, the lower part of the front damper and the lower part of the rear damper are attached to the hub carriers, and the upper parts of the front damper and the rear damper are attached to the vehicle body, respectively. According to the present invention configured in this manner, it is possible to suppress changes in the overall behavior of the vehicle when using regenerative braking and friction braking with a strut-type suspension. [Effects of the Invention]

[0015] According to the vehicle suspension system of the present invention, in a vehicle equipped with an electric motor, it is possible to suppress changes in the pitching behavior of the entire vehicle when using regenerative braking and friction braking. [Brief explanation of the drawing]

[0016] [Figure 1] This is a side view showing a schematic configuration of a vehicle to which a vehicle suspension system according to an embodiment of the present invention is applied. [Figure 2] Figure 1 is a perspective view of the vehicle, seen from the side and obliquely above, showing the vehicle body at the top and the battery assembly, vehicle frame, front suspension system, and rear suspension system at the bottom of the vehicle separated vertically. [Figure 3] Figure 2 is a perspective view of the vehicle from the rear and diagonally above, showing the battery assembly, body frame, and rear suspension system at the bottom of the vehicle. [Figure 4] Figure 3 is a side view of the left rear suspension unit of the vehicle, as seen from the left side of the vehicle. [Figure 5] Figure 3 is a bottom view of the left rear suspension unit of the vehicle, as seen from below. [Figure 6]FIG. 2 is a perspective view of a vehicle from the rear and obliquely above, showing a battery assembly, a vehicle body frame, and a front suspension device below the vehicle. [Figure 7] FIG. 6 is a side view of the front suspension device on the left side of the vehicle in the front suspension device shown in FIG. 6, viewed from the left side of the vehicle. [Figure 8] FIG. 6 is a bottom view of the front suspension device on the left side of the vehicle in the front suspension device shown in FIG. 6, viewed from below. [Figure 9] FIG. 9 is a conceptual diagram for explaining the relationship between the anti-tail lift angle during frictional braking and the anti-tail lift angle during regenerative braking according to Comparative Example (A) and Embodiment (B) of the present invention. [Figure 10] FIG. 12 is a conceptual diagram showing the relationship between the swing axis of the lower arm, the direction in which the damper extends, and a virtual line orthogonal to the direction in which the damper extends in the front suspension device and the rear suspension device according to the embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0017] Hereinafter, a suspension device for a vehicle according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0018] First, the schematic configuration of a vehicle to which a suspension device for a vehicle according to an embodiment of the present invention is applied will be described with reference to FIGS. 1 and 2. FIG. 1 is a side view showing the schematic configuration of a vehicle to which a suspension device for a vehicle according to an embodiment of the present invention is applied, and FIG. 2 is a perspective view of the vehicle from the side and obliquely above, showing the vehicle body above the vehicle shown in FIG. 1 and the battery assembly, the vehicle body frame, the front suspension device, and the rear suspension device below the vehicle, separated vertically. First, as shown in Figures 1 and 2, the vehicle 1 comprises a body 2 made of a monocoque body above it, a battery assembly 4 located below the body 2 in the center of the vehicle in the longitudinal direction, a rear body frame 6 extending from the battery assembly 4 to the rear of the vehicle, a front body frame 8 extending from the battery assembly 4 to the front of the vehicle, a rear suspension device 10 attached to the rear body frame 6, and a front suspension device 12 attached to the front body frame 8.

[0019] The battery assembly 4 comprises a battery case 14 and a battery body (not shown). Although not shown in Figures 1 and 2, in this embodiment the battery case 14 comprises four frame members made of extruded material or the like, the battery body is housed within these four frame members, and further comprises cover members 14a that cover the top and bottom of the battery body.

[0020] Next, the general configuration of each part of the vehicle will be explained with reference to Figures 1 to 8. Figure 3 is a perspective view from the rear and diagonally above of the vehicle showing the battery assembly, body frame, and rear suspension system at the bottom of the vehicle as shown in Figure 2. Figure 4 is a side view of the left rear suspension system of the vehicle shown in Figure 3, viewed from the left side of the vehicle. Figure 5 is a bottom view of the left rear suspension system of the vehicle shown in Figure 3, viewed from below. Figure 6 is a perspective view from the rear and diagonally above of the vehicle showing the battery assembly, body frame, and front suspension system at the bottom of the vehicle as shown in Figure 2. Figure 7 is a side view of the left front suspension system of the vehicle shown in Figure 6, viewed from the left side of the vehicle. Figure 8 is a bottom view of the left front suspension system of the vehicle shown in Figure 6, viewed from below.

[0021] First, as shown in Figures 1 to 5, the rear vehicle frame 6 comprises a base member 16 fixed to the rear edge of the battery case 14, two rear side frames 18 integrally formed with the base member 16 by welding or the like and extending in the longitudinal direction of the vehicle, and two rear cross members 20 attached to these rear side frames 18 by bolting and welding or the like. The base member 16 of the rear body frame 6 is directly connected to the frame member 14b at the rear edge of the battery case 14 by bolting and welding, and the rigidity of the lower part of the vehicle body is increased by the frame members on all four sides of the battery case 14 and the rear body frame 6.

[0022] Next, as shown in Figures 3 to 5, the rear cross member 20 functions as rear suspension support members 20a and 20b for supporting the rear suspension device 10. In this way, the rear suspension device 10 is attached to the rear side frame 18, which is directly connected to the battery case 14, via the rear suspension support members 20a and 20b.

[0023] Next, as shown in Figures 1, 2, 6 to 8, the front vehicle frame 8 comprises a base member 22 fixed to the front edge of the battery case 14, two front side frames 24 integrally formed with the base member 22 by welding or the like, extending in the longitudinal direction of the vehicle and diagonally in the width direction of the vehicle, a front cross member 26 attached to these front side frames 24, and a front suspension support member 28 integrally formed with the base member 22 and extending forward along each front side frame 24, for supporting the front suspension device 12.

[0024] The base member 22 / front suspension support member 28 of the front body frame 8 is directly connected to the frame member 14c at the front edge of the battery case 14 by bolting and welding, and the rigidity of the lower part of the vehicle body is increased by the frame members on all four sides of the battery case 14 and the front body frame 8.

[0025] Next, the monocoque body 2 of the vehicle 1 shown in Figures 1 and 2 is attached to the frame members on all four sides of the battery case 14 at the bottom of the vehicle body, the rear cross member 20, the front cross member 26, etc., by bolting and welding, thereby forming an integral part of the vehicle 1.

[0026] Next, as shown in Figures 2, 3 to 5, a rear electric motor 30, which has a large output and serves as the main drive source, is provided at the rear of the vehicle. This rear electric motor 30 is connected to the rear wheels 34 (shown by dashed lines in Figures 4 and 5) via two output transmission shafts 32 extending from the rear electric motor 30 to the left and right, and drives the rear wheels 34. In other words, in this embodiment of vehicle 1, the rear wheels are the main drive wheels. On the other hand, as shown in Figures 2, 6 to 8, a front motor 36 is provided at the front of the vehicle, which has a lower output than the rear motor 30 and serves as a secondary drive source. This front motor 36 is connected to the front wheels 40 (shown by dashed lines in Figures 7 and 8) via two output transmission shafts 38 extending from the front motor 36 to the left and right, and drives the front wheels 40. As a result, in this embodiment of the vehicle 1, the front wheels become secondary drive wheels.

[0027] Next, the configuration of the rear suspension system 10 and its mounting structure to the vehicle body will be explained with reference to Figures 3 to 5. Figures 4 and 5 show the rear suspension system 10 on the left side of the vehicle. Note that the rear suspension system 10 on the right side of the vehicle has the same configuration as the rear suspension system 10 on the left side of the vehicle, so its explanation will be omitted below. First, as shown in Figures 3 to 5, the rear suspension device 10 is equipped with a hub carrier 42 for supporting the rear wheel 34. The hub carrier 42 has an opening in its center that holds the hub 44 and through which the output transmission shaft (axle) 32 passes. Furthermore, the rear suspension system 10 includes a rear lower arm 46, a rear damper 48, and a toe control link 50, which are respectively connected to the hub carrier 42. The rear damper 48, together with the coil spring 49, constitutes a shock absorber. As shown in Figure 4, the rear suspension device 10 is located above the lower end of the battery case 14.

[0028] These suspension configurations will be explained in more detail. First, the rear lower arm 46 is an A-type lower arm, and its tip on the wheel 34 side is connected via a pivot shaft 52 to a portion of the hub carrier 42 that protrudes downward from the center. In this embodiment, the pivot shaft 52 is made of a pillow ball joint. On the other hand, the A-type rear lower arm 46 is connected to the rear suspension support members 20a and 20b at two points on the vehicle body side via pivot shafts 54 and 56, respectively. In this embodiment, each pivot shaft 54 ​​and 56 is composed of a bush housing, an elastic bush, and a bolt shaft attached to the vehicle body side.

[0029] In this embodiment, as shown in Figure 5, the positions of each pivot axis 54 and 56 are set such that the pivot axis A formed by each pivot axis 54 and 56 extends in a direction that coincides with the longitudinal direction of the vehicle when viewed from below (in a plan view). Furthermore, in this embodiment, as shown in Figure 4, the position and inclination of each pivot axis 54, 56 are set such that the pivot axis A formed by each pivot axis 54, 56 extends inclined upward at a predetermined angle toward the front of the vehicle when viewed from the side.

[0030] Next, as is clear from Figure 3, the lower end of the rear damper 48 is attached in the vertical direction of the vehicle to the tip of the portion that extends inward in the vehicle width direction above the center of the hub carrier 42. On the other hand, the upper end of the rear damper 48 is attached to the vehicle body 2. In this embodiment, as shown in Figure 4, the rear damper 48 is attached to the hub carrier 42 and the vehicle body 2 such that its longitudinal axis B (the direction in which the rear damper 48 extends) extends perpendicularly to the direction in which the pivot axis A extends when viewed from the side.

[0031] Next, the toe control link 50 is connected to the portion of the hub carrier 42 that protrudes rearward from the center.

[0032] Next, the configuration of the front suspension system 12 and its mounting structure to the vehicle body will be explained with reference to Figures 6 to 8. Figures 7 and 8 show the front suspension system 12 on the left side of the vehicle. Note that the front suspension system 12 on the right side of the vehicle has the same configuration as the front suspension system 12 on the left side, so its explanation will be omitted below. First, as shown in Figures 6 to 8, the front suspension device 12 is equipped with a hub carrier 60 for supporting the front wheel 40. The hub carrier 60 has an opening in its center that holds the hub 62 and through which the output transmission shaft (axle) 38 passes. The front suspension system 12 also includes a front lower arm 66, a front damper 68, and a tie rod (not shown) which controls the toe direction of the front wheels 40 by a steering mechanism (not shown), each connected to the hub carrier 60. The front damper 68, together with the coil spring 69, constitutes a shock absorber.

[0033] These suspension configurations will be explained in more detail. First, the front lower arm 66 is an L-shaped lower arm, and its tip on the wheel 40 side is connected via a pivot shaft 72 to a portion of the hub carrier 60 that protrudes downward from the center. In this embodiment, the pivot shaft 72 is made of a pillow ball joint. On the other hand, the L-shaped front lower arm 66 is connected to the aforementioned front suspension support member 28 at two points on the vehicle body side via pivot shafts 74 and 76, respectively. In this embodiment, each pivot shaft 74 and 76 is composed of a bush housing, an elastic bush, and a bolt shaft attached to the vehicle body side.

[0034] In this embodiment, as shown in Figure 8, the positions of each pivot axis 74 and 76 are set such that the pivot axis A formed by each pivot axis 74 and 76 extends in a direction that coincides with the longitudinal direction of the vehicle when viewed from below (in a plan view). Furthermore, in this embodiment, as shown in Figure 7, the position and inclination of each pivot axis 74, 76 are set such that the pivot axis A formed by each pivot axis 74, 76 extends diagonally upward at a predetermined angle toward the front of the vehicle when viewed from the side.

[0035] Next, as is clear from Figure 6, the lower end of the front damper 68 is attached in the vertical direction of the vehicle to the tip of the portion that extends inward in the vehicle width direction above the center of the hub carrier 60. On the other hand, the upper end of the front damper 68 is attached to the vehicle body 2. In this embodiment, as shown in Figure 7, the front damper 68 is attached to the hub carrier 60 and the vehicle body 2 such that its longitudinal axis B (the direction in which the front damper 68 extends) extends perpendicularly to the direction in which the pivot axis A extends when viewed from the side.

[0036] Next, a tie rod (not shown) is connected to a portion of the hub carrier 60 that protrudes forward from its central part.

[0037] Next, the main geometric configuration of the suspension device according to an embodiment of the present invention will be described with reference to Figure 9. Figure 9 is a conceptual diagram illustrating the relationship between the anti-tail lift angle during friction braking and the anti-tail lift angle during regenerative braking, according to comparative example (A) and embodiment (B) of the present invention. Figure 9 shows the rear suspension device 10 (100). In this embodiment, the front suspension device 12 also has the same geometric configuration as the rear suspension device 10, so its description will be omitted below. Figure 9 shows the state of each part when the vehicle is stationary (1G state). Similarly, Figures 3 to 8 mentioned above also show the state of each part when the vehicle is stationary.

[0038] First, as shown in Figure 9(A), in the conventional vehicle used as a comparative example, the instantaneous rotation center Ic of the rear suspension device 100 is typically set to be located above the rear suspension device 100 and inside the vehicle when viewed from the side, so that a predetermined anti-tail lift force is obtained during braking. The instantaneous rotation center Ic is the intersection point of the imaginary line C1, which is perpendicular to the longitudinal axis of the rear damper, and the oscillation axis A1 of the lower arm.

[0039] Here, when regenerative braking is used in a motorized vehicle (a so-called electric vehicle), the point of operation of the braking force is the wheel center Wc, so the anti-tail lift angle is the angle of the line connecting the instantaneous rotation center Ic and the wheel center Wc (shown as a dashed line in Figure 9(A)) with respect to the ground G. On the other hand, when friction brakes (such as disc brakes inside the wheels) are used, the point of operation of the braking force is the tire contact center Gc, so the anti-tail lift angle is the angle of the line connecting the instantaneous rotation center Ic and the tire contact center Gc (shown as a dashed line in Figure 9(A)) with respect to the ground G. Therefore, in comparative examples such as those shown in Figure 9(A), when the braking force of the friction brake and regenerative brake is changed, for example, when the friction brake and regenerative brake are controlled in coordination, or when switching between the friction brake and regenerative brake, the pitching behavior of the rear of the vehicle changes due to the difference in the anti-tail lift angle, which in turn makes the behavior of the entire vehicle unstable. In Figure 9(A), the symbol T1 indicates the motion trajectory of the rear wheel, and this oscillation trajectory T1 is an arc-shaped trajectory that extends perpendicular to the line connecting the instantaneous rotation center Ic and the wheel center Wc.

[0040] On the other hand, in this embodiment, as shown in Figures 9(B) and 4, the longitudinal axis B of the rear damper 48 is made to extend perpendicular to the oscillation axis A in a side view, so that the imaginary line C perpendicular to the longitudinal axis B of the rear damper 48 extends parallel to the oscillation axis A. Furthermore, in this embodiment, as shown in Figure 5, the pivot axis A extends in a direction that coincides with the longitudinal direction of the vehicle when viewed from below (plan view). Furthermore, in this embodiment, by ensuring that the oscillation axis A extends in a direction that coincides with the vehicle's longitudinal direction when viewed from below, the ball joint 52 of the rear lower arm 46 and the rear wheel 34 swing linearly in the vertical direction that coincides with the direction in which the longitudinal axis B of the rear damper 48 extends (the oscillation trajectory is indicated by the symbol T), as shown in Figure 9(B). Note that since the rear lower arm 46 swings around the oscillation axis A that extends in the vehicle's longitudinal direction, the oscillation trajectory T of the ball joint 52 on the wheel side is linear when viewed from the side. Furthermore, in this embodiment, as shown in Figures 9(B) and 4, the pivot axis A of the rear lower arm 46 is made to extend diagonally upward toward the front of the vehicle in a side view, thereby forming an anti-lift angle in the rear suspension device 10.

[0041] In this embodiment, by setting the suspension geometry as described above, the anti-tail lift angle when using regenerative braking and the anti-tail lift angle when using friction braking are made to be the same angle in the electric vehicle 1, as shown in Figure 9(B). As a result, in this embodiment, changes in the pitching behavior of the rear of the vehicle are suppressed, for example, when the friction brake and regenerative brake are controlled in coordination, and the behavior of the vehicle is stabilized. Furthermore, as shown in Figure 9(B), the rear damper 48 is set to extend perpendicularly to the oscillation axis A in a side view, so that the linear oscillation direction (motion trajectory) T of the rear wheel 34 coincides with the longitudinal axis B of the rear damper. In this embodiment, the load transmitted from the rear wheel 34 is efficiently input to the rear damper 48 via the hub carrier 42, thereby enabling the rear damper 48 to operate efficiently. Furthermore, in this embodiment, the rear electric motor 30 is used as the main drive source with a high output, and the rear wheels 34 are driven primarily. As shown in Figure 9(B), the anti-lift angle formed in the rear suspension device 10 can suppress lift of the rear of the vehicle body, especially when using regenerative braking and friction braking.

[0042] As explained above, the technical concept of the present invention is, firstly, to create a state in which there is no instantaneous center of rotation, or a position at infinity (particularly with respect to the position of the instantaneous center of rotation Ic as shown in Figure 9(A)), by having the damper 48 extend in a direction perpendicular to the oscillation axis A in a side view, and having a virtual line C perpendicular to the longitudinal axis B of the damper 48 extend in a direction parallel to the oscillation axis A, thereby suppressing changes in the pitching behavior of the vehicle even when the braking force of the regenerative brake and the friction brake is changed. Furthermore, the technical concept of the present invention is, secondly, to create a state in which there is no instantaneous center of rotation, or a position that is infinitely far away (particularly with respect to the position of the instantaneous center of rotation Ic as shown in Figure 9(A)), by making the oscillation axis A extend in a direction that coincides with the longitudinal direction of the vehicle in a bottom view (plan view), thereby suppressing changes in the pitching behavior of the vehicle even when the braking force of the regenerative brake and the friction brake is changed. Furthermore, the technical concept of the present invention is, thirdly, to form an anti-lift angle in which, in a side view, the oscillation axis A extends diagonally upward toward the front of the vehicle, thereby suppressing changes in the pitching behavior of the vehicle (especially changes in the pitching behavior of the rear of the vehicle) when coordinating control of regenerative braking and friction braking. Furthermore, the technical concept of the present invention is, fourthly, to ensure that in a bottom view (plan view), the oscillation axis A extends in a direction that coincides with the longitudinal direction of the vehicle, and in a side view, the damper 48 extends in a direction perpendicular to the oscillation axis A, thereby aligning the linear oscillation direction (motion trajectory) T of the rear wheel 34 (ball joint 52) ​​with the longitudinal axis B of the rear damper, thereby efficiently inputting the load transmitted from the rear wheel 34 to the rear damper 48.

[0043] The technical concept of the present invention described above is also applicable to the front suspension device 12.

[0044] As described above, in the present invention, the angle of the longitudinal axis B of the damper with respect to the oscillation axis A in a side view, the parallelism between the oscillation axis A and the imaginary line C in a side view, and the direction in which the oscillation axis A extends in a bottom view are important. On the other hand, these values ​​are not limited to those of the embodiments described above, and may be adjusted to a range (angle, parallelism, direction) that can substantially suppress changes in the pitching behavior of the vehicle during coordinated control of friction brakes and regenerative brakes, for example, when designing a vehicle or when testing a test vehicle, taking into consideration the length of the vehicle's wheelbase, the position of the center of gravity, and the movement of each part during suspension oscillation, which affect the pitching behavior of the vehicle. For example, the angle between the oscillation axis A and the longitudinal axis B of the rear damper 48 is preferably set to a range of 90° ± 2.5°.

[0045] As a modified example of the vehicle 1 of this embodiment, it may be a front-wheel drive vehicle that uses only a front motor 36 to drive the front wheels 40, or a rear-wheel drive vehicle that uses only a rear motor 30 to drive the rear wheels 34, or a single motor that drives both the front wheels 40 and the rear wheels 34.

[0046] Furthermore, the present invention is not limited to the strut-type suspension system described above, but is also applicable to other types of suspension systems. For example, in the case of a double wishbone suspension system, if the pivot axis of the lower arm and the pivot axis of the upper arm are made to extend in directions parallel to each other in a side view, and if these pivot axes are made to extend in a direction that coincides with the longitudinal direction of the vehicle in a bottom view (plan view), a similar effect can be obtained in which changes in the pitching behavior of the vehicle can be suppressed even when the braking force of the regenerative brake and the friction brake is changed. The same effect can be obtained by making each pivot axis extend diagonally upward toward the front of the vehicle in a side view.

[0047] Next, Figure 10 will further illustrate the main geometry of the suspension device according to an embodiment of the present invention and its effects. Figure 10 is a conceptual diagram showing the relationship between the pivot axis of the lower arm, the direction in which the damper extends, and a virtual line perpendicular to the direction in which the damper extends, in the front suspension device and rear suspension device according to an embodiment of the present invention. As shown in Figure 10, in this embodiment, in the rear suspension device 10 and the front suspension device 12, the direction in which the longitudinal axis B of the dampers 48 and 68 extends is perpendicular to the oscillation axis A of the lower arms 46 and 66, so that a virtual line C perpendicular to the longitudinal axis B of the dampers 48 and 68 extends in a direction parallel to the oscillation axis A, and the oscillation axis A formed by the lower arms 46 and 66 extends diagonally upward toward the front of the vehicle in a side view. In this embodiment, with this configuration, no difference in the anti-lift angle (anti-dive angle) between the regenerative brake and the friction brake occurs between the front wheels 40 and the rear wheels 40, thereby suppressing the difference in behavioral changes between the front and rear of the vehicle, and thereby suppressing changes in the pitching behavior of the entire vehicle when using regenerative brakes and friction brakes.

[0048] In this embodiment of vehicle 1, the output of the front motor 36 is set to be smaller than the output of the rear motor 30, so that a large driving force is not applied to the front wheels 40. As a result, the effect of the anti-nose lift angle of the front of the vehicle during driving can be ignored due to the smaller output. On the other hand, as described above, for both regenerative braking and friction braking applied to the front wheels 40 during braking, the virtual line C perpendicular to the longitudinal axis B of the front damper 68 extends in a direction parallel to the oscillation axis A, thereby suppressing changes in the pitching behavior of the entire vehicle when using regenerative braking and friction braking. Furthermore, in both the rear suspension system 10 and the front suspension system 12, if the oscillation axis A and the virtual line C are parallel, the change in the vehicle's attitude during coordinated control of the friction brake and regenerative brake can be suppressed, regardless of the difference in their anti-lift angle and anti-dive angle.

[0049] Next, the effects and advantages of this embodiment will be explained. This embodiment provides suspension devices 10, 12 for a vehicle 1, which include electric motors 30, 36 that transmit driving force to the front wheels 40 and rear wheels 34 (in a modified example, at least one of the front wheels 40 or rear wheels 34) via output transmission shafts 32, 38, and further includes a front lower arm 66 that can swing in the vertical direction of the vehicle with respect to the front wheel oscillation axis A at the vehicle body mounting portion at the front of the vehicle, and a front damper 68 that extends in a direction perpendicular to the front wheel oscillation axis A in a side view, The vehicle comprises a rear lower arm 46 that can swing vertically with respect to the rear wheel pivot axis A at the vehicle body mounting portion at the rear of the vehicle, and a rear damper 48 that extends perpendicular to the rear wheel pivot axis A in a side view, wherein in a side view, the front wheel pivot axis A and a first imaginary line C perpendicular to the direction in which the front damper 68 extends extend in directions parallel to each other, and the rear wheel pivot axis A and a second imaginary line C perpendicular to the direction in which the rear damper 48 extends extend in directions parallel to each other. According to this embodiment, in a side view, the front wheel oscillation axis A and a first imaginary line C perpendicular to the direction in which the front damper 68 extends extend in directions parallel to each other, and the rear wheel oscillation axis A and a second imaginary line C perpendicular to the direction in which the rear damper 48 extends extend in directions parallel to each other. As a result, when braking the front and rear wheels 40 and 34 under the effect of regenerative braking (in a modified example, when braking the front and rear wheels 40 and 34 under the effect of regenerative braking on at least one of the front wheel 40 or the rear wheel 34), differences in the behavior of the front and rear of the vehicle are suppressed. This suppresses changes in the pitching behavior of the entire vehicle when using regenerative braking and friction braking, for example, when coordinating control of friction braking and regenerative braking, thereby reducing discomfort for the occupants.

[0050] Furthermore, according to this embodiment, the front wheel oscillation axis A and the rear wheel oscillation axis A each extend in directions that coincide with the longitudinal direction of the vehicle when viewed from below, thus more reliably suppressing differences in the behavior of the front and rear of the vehicle. This suppresses changes in the pitching behavior of the entire vehicle, for example, when coordinating the control of friction brakes and regenerative brakes, thereby reducing discomfort for the occupants. In addition, since the front wheels 40 and the rear wheels 34 (each wheel center Wc) oscillate linearly in the same direction as the dampers 68 and 48, respectively, changes in the behavior of the entire vehicle when using regenerative brakes and friction brakes can be suppressed more effectively.

[0051] Furthermore, according to this embodiment, the front wheel oscillation axis A and the rear wheel oscillation axis A each extend diagonally upward toward the front of the vehicle in a side view, so an anti-lift angle is formed in particular on the rear suspension device 10, suppressing lift of the rear of the vehicle when regenerative braking and friction braking are used. Moreover, according to this embodiment, the first imaginary line C, which is perpendicular to the direction in which the front wheel oscillation axis A and the front damper 68 extend, extend in directions parallel to each other, and the second imaginary line C, which is perpendicular to the direction in which the rear wheel oscillation axis A and the rear damper extend, extend in directions parallel to each other. As a result, the difference between the behavior of the front and rear of the vehicle can be reduced when braking the front and rear wheels, thereby suppressing changes in the pitching behavior of the entire vehicle when regenerative braking and friction braking are used.

[0052] Furthermore, according to this embodiment, the vehicle includes a rear electric motor 30 that is attached to the rear of the vehicle body and drives the rear wheels 34. Since the rear electric motor 30, located at the rear of the vehicle, is the main drive source for driving the rear wheels 34, the braking force of the regenerative brake acting on the rear wheels 34 is increased by making the rear wheels 34 the main drive wheels. However, since the rear wheel pivot axis A and the second imaginary line C extend in directions parallel to each other, it is possible to more effectively suppress changes in the pitching behavior of the rear of the vehicle when using the regenerative brake and friction brake of the rear wheels 34. In addition, by making the rear wheels 34 the main drive wheels, it is possible to suppress the lift of the front of the vehicle when the vehicle starts moving.

[0053] Furthermore, according to this embodiment, the front wheel oscillation axis A and the rear wheel oscillation axis A extend diagonally upward toward the front of the vehicle in a side view, and are equipped with a front motor 36 attached to the front of the vehicle body and a rear motor 30 attached to the rear of the vehicle body, respectively. Since the rear motor 30 located at the rear of the vehicle is the main drive, there is no difference in the anti-lift angle (anti-dive angle) between regenerative braking and friction braking for both the front wheels 40 and the rear wheels 34, or the difference can be made very small. Therefore, changes in the behavior of the entire vehicle when using regenerative braking and friction braking can be suppressed more reliably. In particular, since the rear motor 30 is the main drive, the anti-lift angle of the rear suspension device 10 can suppress the lift of the rear of the vehicle body when using regenerative braking and friction braking.

[0054] Furthermore, according to this embodiment, the front lower arm 66 and the rear lower arm 46 are attached to the vehicle body frames 6 and 8 that extend in the longitudinal direction of the vehicle from the battery case 14 located in the lower center of the vehicle. This increases the support rigidity of the front wheel 40 and the rear wheel 34, respectively, thereby reducing the response delay of the vehicle's behavior (for example, the response delay of cornering force).

[0055] Furthermore, according to this embodiment, the front suspension device 12 and the rear suspension device 10 are strut-type suspension devices in which an opening is formed in the center through which the output transmission shafts 32 and 38 pass and are held, and which are equipped with hub carriers 60 and 42 that support the wheels 40 and 34, and the lower parts of the front damper 68 and the rear damper 48 are attached to the hub carriers 60 and 42, and the upper parts of the front damper 68 and the rear damper 48 are attached to the vehicle body 2. As such, it is possible to suppress changes in the overall behavior of the vehicle when using regenerative braking and friction braking with a relatively simple strut-type suspension. [Explanation of symbols]

[0056] 1 vehicle 2 car bodies 4. Battery Assembly 6. Rear body frame 8. Front body frame 10 Rear suspension system 12 Front suspension system 14 Battery Case 18 Rear side frame 20a, 20b Rear cross member, rear suspension support member 24 Front side frame 28 Front suspension support member 30 Rear electric motor 32 Output transmission shaft 34 Rear wheel 36 Front electric motor 38 Output transmission shaft 40 Front Wheel 42 Hub Carrier 46 Rear lower arm 48 Rear damper 52. Wheel-side pivot axis (pillow ball joint) of the rear lower arm 54, 56 Rear lower arm's pivot axis on the vehicle body side 60 Hub Carrier 66 Front Lower Arm 68 Front damper 72 Front lower arm wheel-side pivot axis (pillow ball joint) 74, 76 Front lower arm's pivot axis on the vehicle body side A pivot axis of the rear lower arm / front lower arm B. Longitudinal axis of the rear damper / front damper (direction in which the damper extends) C Imaginary line perpendicular to the longitudinal axis of the rear damper / front damper G ground Ic Instantaneous center of rotation Wc Wheel Center Gc tire ground contact center T, T1 Wheel oscillation trajectory

Claims

1. A vehicle suspension system comprising an electric motor that transmits driving force to at least one of the front or rear wheels via an output transmission shaft, A front suspension arm that can swing vertically in the vehicle direction with respect to the front wheel pivot axis at the vehicle body mounting point at the front of the vehicle, In a side view, the front damper extends in a direction perpendicular to the front wheel pivot axis, A rear suspension arm that can swing vertically in the vehicle direction with respect to the rear wheel pivot axis at the vehicle body mounting point at the rear of the vehicle, In a side view, it comprises a rear damper extending in a direction perpendicular to the rear wheel pivot axis, In a side view, the front wheel pivot axis and a first imaginary line perpendicular to the direction in which the front damper extends extend in directions parallel to each other, and the rear wheel pivot axis and a second imaginary line perpendicular to the direction in which the rear damper extends extend in directions parallel to each other. The front wheel pivot axis and the rear wheel pivot axis mentioned above each extend diagonally upward toward the front of the vehicle when viewed from the side. The above-mentioned motor comprises a front motor mounted on the front of the vehicle body and a rear motor mounted on the rear of the vehicle body, and the rear motor provided at the rear of the vehicle is the main drive, characterized in that the vehicle suspension system is a vehicle suspension system.

2. The suspension structure for a vehicle according to claim 1, wherein the front wheel pivot axis and the rear wheel pivot axis each extend in directions that coincide with the longitudinal direction of the vehicle when viewed from below.

3. The vehicle suspension device according to claim 1 or claim 2, wherein the front wheel pivot axis and the rear wheel pivot axis each extend diagonally upward toward the front of the vehicle in a side view.

4. The vehicle suspension system according to claim 1, wherein the above-mentioned electric motor is mounted on the vehicle body at the rear of the vehicle and includes a rear electric motor that drives the rear wheels, and the rear electric motor provided at the rear of the vehicle is the main drive source.

5. The vehicle suspension device according to claim 1, wherein the front suspension arm and the rear suspension arm are attached to a vehicle frame that extends in the longitudinal direction of the vehicle from a battery case located in the lower center of the vehicle.

6. The suspension device for a vehicle according to claim 1, wherein the wheel-side ends of the front suspension arm and the rear suspension arm are connected, and the device comprises front and rear wheel hub carriers that support the front and rear wheels, respectively, the lower part of the front damper and the lower part of the rear damper are attached to the hub carriers, respectively, and the upper parts of the front damper and the rear damper are attached to the vehicle body, respectively, and the device is of the strut type.

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