Patent Description:
Conventionally, a suspension control device for setting an anti-dive, anti-lift suspension geometry to front wheels and rear wheels is known (<CIT>).

Further suspension systems are known from <CIT>, <CIT>, and <CIT>. An electric vehicle with electric motors configured for transmitting a drive force to wheels of the vehicle via output transmission shafts is known from <CIT>.

On the other hand, amidst research and development related to electric cars conducted in recent years, the present inventors carried out diligent studies with respect to an optimum suspension structure for electric cars.

Normally, a suspension geometry of a vehicle is set in consideration of a change in an attitude of the vehicle during braking and when being driven. Furthermore, with electric cars, in addition to conventional friction brakes which apply a braking force to wheels using a hydraulic system, regenerative brakes which cause an electric motor to be driven as a generator to charge a battery are used during braking.

In this case, between friction brakes and regenerative brakes, a phenomenon occurs in which, due to a difference in points of application of a braking force, anti-lift angles/anti-dive angles during braking differ. In other words, with friction brakes, since a point of application of the braking force thereof is at a center of tire-ground contact, an angle formed by a straight line connecting the center of tire-ground contact and an instantaneous center of rotation of a wheel relative to the ground is the anti-lift angle (rear wheel)/anti-dive angle (front wheel) but, on the other hand, with regenerative brakes, since a point of application of the braking force thereof is a wheel center, an angle formed by a straight line connecting the wheel center and an instantaneous center of rotation of a wheel relative to the ground is the anti-lift angle/anti-dive angle. Therefore, for example, when subjecting friction brakes and regenerative brakes to coordinated control or the like, there is a risk that changing the braking force of the friction brakes and the braking force of the regenerative brakes may cause an unstable pitching behavior to be created in a vehicle as a whole and may impart a sense of discomfort to an occupant. <CIT> and <CIT> disclose, respectively, a front suspension system and a rear suspension system that would not have this problem.

In consideration thereof, the present invention has been made in order to solve the problem described above and an object of the present invention is to provide a vehicle equipped with an electric motor, comprising a suspension device for a vehicle capable of suppressing a change in a pitching behavior of the entire vehicle during use of regenerative brakes and friction brakes.

In order to solve the problem described above, the present invention relates to a vehicle according to claim <NUM>, which is equipped with an electric motor for transmitting a drive force to at least one of a front wheel or a rear wheel via an output transmission shaft, and with a suspension device, the suspension device characterized by including: a front suspension arm capable of swinging in a vehicle up-down direction with reference to a front wheel swinging axis in a vehicle body-side mounting portion in a front portion of the vehicle; a front damper which extends in a direction perpendicular to the front wheel swinging axis in a side view; a rear suspension arm capable of swinging in the vehicle up-down direction with reference to a rear wheel swinging axis in a vehicle body-side mounting portion in a rear portion of the vehicle; and a rear damper which extends in a direction perpendicular to the rear wheel swinging axis in a side view, wherein the front wheel swinging axis and a first imaginary line perpendicular to a direction of extension of the front damper extend in a direction parallel to each other and the rear wheel swinging axis and a second imaginary line perpendicular to a direction of extension of the rear damper extend in a direction parallel to each other in a side view.

According to the present invention configured as described above, in a suspension device for a vehicle equipped with an electric motor for transmitting a drive force to at least one of a front wheel or a rear wheel via an output transmission shaft, since a front wheel swinging axis and a first imaginary line perpendicular to a direction of extension of a front damper extend in a direction parallel to each other and a rear wheel swinging axis and a second imaginary line perpendicular to a direction of extension of a rear damper extend in a direction parallel to each other, an occurrence of a difference in behavior changes of a front portion of the vehicle and a rear portion of the vehicle can be suppressed during braking of the front and rear wheels including a wheel (at least one of the front wheel or the rear wheel) on which a regenerative brake acts and, accordingly, a change in a pitching behavior of the entire vehicle can be suppressed during use of the regenerative brakes and a friction brake, for example, when the friction brake and the regenerative brake are subjected to coordinated control, and a sense of discomfort imparted to an occupant can be reduced.

In addition, in the present invention, preferably, the front wheel swinging axis and the rear wheel swinging axis respectively extend in a direction coinciding with a vehicle front-rear direction in a bottom view.

According to the present invention configured as described above, since the front wheel swinging axis and the rear wheel swinging axis respectively extend in a direction coinciding with the vehicle front-rear direction in a bottom view, an occurrence of a difference in behavior changes of the front portion of the vehicle and the rear portion of the vehicle can be more reliably suppressed during braking of the front and rear wheels including a wheel (at least one of the front wheel or the rear wheel) on which a regenerative brake acts and, accordingly, a change in a pitching behavior of the entire vehicle can be suppressed, for example, when the friction brake and the regenerative brake are subjected to coordinated control, and a sense of discomfort imparted to an occupant can be reduced. In addition, since the front wheel swinging axis and the rear wheel swinging axis respectively extend in a direction coinciding with the vehicle front-rear direction in a bottom view, (respective wheel centers of) the front wheel and the rear wheel can each be made to linearly swing in a same direction as the direction of extension of the dampers and, accordingly, a change in the behavior of the entire vehicle during use of the regenerative brake and the friction brake can be suppressed more effectively.

Furthermore, in the present invention, preferably, the front wheel swinging axis and the rear wheel swinging axis each extend obliquely upward toward a front of the vehicle in a side view.

According to the present invention configured as described above, since an anti-lift angle is particularly formed in a rear suspension, a lift of the rear portion of the vehicle body during use of the regenerative brake and the friction brake is suppressed. In addition, according to the present invention, since the front wheel swinging axis and the rear wheel swinging axis extend obliquely upward toward the front of the vehicle in a side view, the front wheel swinging axis and a first imaginary line perpendicular to a direction of extension of the front damper extend in a direction parallel to each other, and the rear wheel swinging axis and a second imaginary line perpendicular to a direction of extension of the rear damper extend in a direction parallel to each other, a difference between the behavior of the front portion of the vehicle and the behavior of the rear portion of the vehicle during braking of the front and rear wheels can be reduced and, accordingly, a change in a pitching behavior of the entire vehicle during use of the regenerative brake and the friction brake can be suppressed.

In addition, in the present invention, preferably, the electric motor includes a rear electric motor which is mounted to the vehicle body in the rear portion of the vehicle and which drives the rear wheel, and the rear electric motor provided in the rear portion of the vehicle is used as a main drive source.

According to the present invention configured as described above, although a braking force of the regenerative brake which acts on the rear wheel increases, since the rear wheel swinging axis and the second imaginary line extend in a direction parallel to each other, a change in the pitching behavior of the rear portion of the vehicle during use of the regenerative brake and the friction brake on the rear wheel can be suppressed more effectively. In addition, since the rear wheel is driven using the rear electric motor as a main drive source, the front wheel swinging axis and the first imaginary line perpendicular to the direction of extension of the front damper extend in a direction parallel to each other, and the rear wheel swinging axis and the second imaginary line perpendicular to the direction of extension of the rear damper extend in a direction parallel to each other, a lift of the front portion of the vehicle during travel start of the vehicle due to the use of the rear wheel as main drive wheel can be prevented.

Furthermore, in the present invention, preferably, the front wheel swinging axis and the rear wheel swinging axis each extend obliquely upward toward the front of the vehicle in a side view, the electric motor includes a front electric motor which is mounted to the vehicle body in the front portion of the vehicle and a rear electric motor which is mounted to the vehicle body in the rear portion of the vehicle, and the rear electric motor provided in the rear portion of the vehicle is used as a main drive.

According to the present invention configured as described above, a difference in anti-lift angles (anti-dive angles) between the regenerative brake and the friction brake does not occur or can be made extremely small in both the front wheel and the rear wheel, and a change in the behavior of the entire vehicle during use of the regenerative brake and the friction brake can thus be more reliably suppressed. In particular, since the rear electric motor is used as a main drive, due to the anti-lift angle of the rear suspension, a lift of the rear portion of the vehicle body can be suppressed during use of the regenerative brake and the friction brake.

In addition, in the present invention, preferably, the front suspension arm and the rear suspension arm are mounted to a vehicle body frame which extends in the vehicle front-rear direction from a battery case disposed in a lower portion of a center of the vehicle.

According to the present invention configured as described above, support rigidity of each of the front wheel and the rear wheel can be enhanced and a response delay to vehicle behavior (for example, a response delay to a cornering force) can be reduced.

Furthermore, in the present invention, the suspension device is a strut-type suspension device including front and rear wheel hub carriers to which wheel-side end portions of the front suspension arm and the rear suspension arm are respectively coupled and which respectively support the front wheel and the rear wheel, a lower portion of the front damper and a lower portion of the rear damper are respectively mounted to the hub carriers, and upper portions of the front damper and the rear damper are each mounted to the vehicle body.

According to the present invention configured as described above, the strut-type suspension can suppress a change in behavior of the entire vehicle during use of the regenerative brake and the friction brake.

With the suspension device for a vehicle according to the present invention, in a vehicle equipped with an electric motor, a change in a pitching behavior of the entire vehicle during use of regenerative brakes and friction brakes can be suppressed.

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

First, a schematic configuration of a vehicle to which the suspension device for a vehicle according to the embodiment of the present invention has been applied will be described with reference to <FIG> and <FIG>. <FIG> is a side view showing a schematic configuration of the vehicle to which the suspension device for a vehicle according to the embodiment of the present invention has been applied, and <FIG> is a perspective view showing, separated above and below, a vehicle body in an upper part of the vehicle, and a battery assembly, a vehicle body frame, a front suspension device, and a rear suspension device in a lower part of the vehicle shown in <FIG> as seen from a side of and from obliquely above the vehicle.

First, as shown in <FIG> and <FIG>, a vehicle <NUM> includes a vehicle body <NUM> constituted of a monocoque body in an upper part of the vehicle <NUM> and, below the vehicle body <NUM>, a battery assembly <NUM> provided in a center portion in a vehicle front-rear direction, a rear vehicle body frame <NUM> which extends toward the rear of the vehicle from the battery assembly <NUM>, a front vehicle body frame <NUM> which extends toward the front of the vehicle from the battery assembly <NUM>, a rear suspension device <NUM> mounted to the rear vehicle body frame <NUM>, and a front suspension device <NUM> mounted to the front vehicle body frame <NUM>.

The battery assembly <NUM> includes a battery case <NUM> and a battery main body (not illustrated). Although not illustrated in <FIG> and <FIG>, the battery case <NUM> further includes a cover member 14a which includes frame members of four sides constituted of extruded material or the like in the present embodiment, the battery main body being housed inside the frame members of four sides, the cover member 14a covering the battery main body from above and below.

Next, a schematic configuration of each portion of the vehicle will be described with reference to <FIG>. <FIG> is a perspective view showing the battery assembly, the vehicle body frame, and the rear suspension device in the lower part of the vehicle shown in <FIG> as seen from the rear of and from obliquely above the vehicle; <FIG> is a side view of a rear suspension device on a left side of the vehicle in the rear suspension device shown in <FIG> as seen from the left side of the vehicle; <FIG> is a bottom view of the rear suspension device on the left side of the vehicle in the rear suspension device shown in <FIG> as seen from below; <FIG> is a perspective view showing the battery assembly, the vehicle body frame, and the front suspension device in the lower part of the vehicle shown in <FIG> as seen from the rear of and from obliquely above the vehicle; <FIG> is a side view of a front suspension device on the left side of the vehicle in the front suspension device shown in <FIG> as seen from the left side of the vehicle; and <FIG> is a bottom view of the front suspension device on the left side of the vehicle in the front suspension device shown in <FIG> as seen from below.

First, as shown in <FIG>, the rear vehicle body frame <NUM> includes a base member <NUM> which is fixed to a rear end edge of the battery case <NUM>, two rear side frames <NUM> which are integrally formed with the base member <NUM> by welding or the like and which extend in the vehicle front-rear direction, and two rear cross members <NUM> which are mounted to the rear side frames <NUM> by fastening using bolts, welding, and the like.

The base member <NUM> of the rear vehicle body frame <NUM> is directly connected to a frame member 14b at the rear end edge of the battery case <NUM> by fastening using bolts, welding, and the like, and rigidity of a lower portion of the vehicle body is increased by the frame members of four sides of the battery case <NUM> and the rear vehicle body frame <NUM>.

Next, as shown in <FIG>, the rear cross members <NUM> function as rear suspension support members 20a and 20b for supporting the rear suspension device <NUM>. In this manner, the rear suspension device <NUM> is mounted via the rear suspension support members 20a and 20b to the rear side frames <NUM> which are directly connected to the battery case <NUM>.

Next, as shown in <FIG>, <FIG>, and <FIG> to <FIG>, the front vehicle body frame <NUM> includes a base member <NUM> which is fixed to a front end edge of the battery case <NUM>, two front side frames <NUM> which are integrally formed with the base member <NUM> by welding or the like and which extend in the vehicle front-rear direction and extend obliquely in a vehicle width direction, a front cross member <NUM> which is mounted to the front side frames <NUM>, and front suspension support members <NUM> which are integrally formed with the base member <NUM>, which extend forward along each front side frame <NUM>, and for supporting the front suspension device <NUM>.

The base member <NUM>/front suspension support members <NUM> of the front vehicle body frame <NUM> are directly connected to a frame member 14c at the front end edge of the battery case <NUM> by fastening using bolts, welding, and the like, and rigidity of the lower portion of the vehicle body is increased by the frame members of four sides of the battery case <NUM> and the front vehicle body frame <NUM>.

Next, the vehicle body <NUM> constituted of a monocoque body in the upper portion of the vehicle <NUM> shown in <FIG> and <FIG> is mounted to the frame members of the four sides of the battery case <NUM>, the rear cross member <NUM>, the front cross member <NUM>, and the like in the lower portion of the vehicle body by fastening using bolts, welding, and the like to be integrally constructed as the vehicle <NUM>.

Next, as shown in <FIG> and <FIG> to <FIG>, a rear electric motor (motor) <NUM> which has a large output and which is to be used as a main drive source is provided in a rear portion of the vehicle. The rear electric motor <NUM> is connected to rear wheels <NUM> (indicated by imaginary lines in <FIG> and <FIG>) via two output transmission shafts <NUM> which extend to the left and the right from the rear electric motor <NUM> and drives the rear wheels <NUM>. In other words, in the vehicle <NUM> according to the present embodiment, the rear wheels are main drive wheels.

On the other hand, as shown in <FIG> and <FIG> to <FIG>, a front electric motor (motor) <NUM> which has a smaller output than the rear electric motor <NUM> and which is to be used as an auxiliary drive source is provided in a front portion of the vehicle. The front electric motor <NUM> is connected to front wheels <NUM> (indicated by imaginary lines in <FIG> and <FIG>) via two output transmission shafts <NUM> which extend to the left and the right from the front electric motor <NUM> and drives the front wheels <NUM>. Accordingly, in the vehicle <NUM> according to the present embodiment, the front wheels are auxiliary drive wheels.

Next, with reference to <FIG>, a configuration of the rear suspension device <NUM> and a mounting structure thereof to the vehicle body will be explained. <FIG> and <FIG> show the rear suspension device <NUM> on a left side of the vehicle. Since the rear suspension device <NUM> on a right side of the vehicle shares a same configuration as the rear suspension device <NUM> on the left side of the vehicle, hereinafter, a description of the rear suspension device <NUM> on the right side of the vehicle will be omitted.

First, as shown in <FIG>, the rear suspension device <NUM> includes a hub carrier <NUM> for supporting the rear wheel <NUM>. In the hub carrier <NUM>, an opening which holds a hub <NUM> and which is to be penetrated by an output transmission shaft (axle) <NUM> is formed in a center portion thereof.

In addition, the rear suspension device <NUM> includes a rear lower arm <NUM>, a rear damper <NUM>, and a toe control link <NUM> that are each coupled to the hub carrier <NUM>. The rear damper <NUM> constitutes a shock absorber together with a coil spring <NUM>.

As shown in <FIG>, the rear suspension device <NUM> is positioned above a lower end of the battery case <NUM>.

The suspension components described above will now be described in greater detail.

First, the rear lower arm <NUM> is an A-shaped lower arm, and a distal end portion thereof on a side of the wheel <NUM> is coupled via a swinging shaft <NUM> to a portion which protrudes downward from a center portion of the hub carrier <NUM>. In the present embodiment, the swinging shaft <NUM> is constituted of a pillow ball joint.

On the other hand, the A-shaped rear lower arm <NUM> is coupled at two locations thereof on a vehicle body side to the rear suspension support members 20a and 20b via swinging shafts <NUM> and <NUM>, respectively. In the present embodiment, each of the swinging shafts <NUM> and <NUM> is constituted of a bush housing, elastic bushing, a bolt shaft mounted on a vehicle body side, and the like.

In the present embodiment, as shown in <FIG>, a position of each of the swinging shafts <NUM> and <NUM> is set such that a swinging axis A formed by each of the swinging shafts <NUM> and <NUM> extends in a direction coinciding with the vehicle front-rear direction in a bottom view (plan view).

In addition, in the present embodiment, as shown in <FIG>, the position and an inclination of each of the swinging shafts <NUM> and <NUM> are set such that the swinging axis A formed by each of the swinging shafts <NUM> and <NUM> extends in an inclined manner in a direction of a predetermined obliquely-upward angle toward the front of the vehicle in a side view.

Next, as clearly shown in <FIG>, a lower end portion of the rear damper <NUM> is mounted in a vehicle up-down direction in a distal end portion of a portion extending inward in the vehicle width direction above a center portion of the hub carrier <NUM>. On the other hand, an upper end portion of the rear damper <NUM> is mounted to the vehicle body <NUM>.

In the present embodiment, as shown in <FIG>, the rear damper <NUM> is mounted to the hub carrier <NUM> and the vehicle body <NUM> so that a longitudinal direction axis B of the rear damper <NUM> (a direction of extension of the rear damper <NUM>) vertically extends in a direction of <NUM> degrees relative to a direction of extension of the swinging axis A in a side view.

Next, the toe control link <NUM> is coupled to a portion which protrudes rearward from a center portion of the hub carrier <NUM>.

Next, with reference to <FIG>, a configuration of the front suspension device <NUM> and a mounting structure thereof to the vehicle body will be explained. <FIG> and <FIG> show the front suspension device <NUM> on the left side of the vehicle. Since the front suspension device <NUM> on the right side of the vehicle shares a same configuration as the front suspension device <NUM> on the left side of the vehicle, hereinafter, a description of the front suspension device <NUM> on the right side of the vehicle will be omitted.

First, as shown in <FIG>, the front suspension device <NUM> includes a hub carrier <NUM> for supporting the front wheel <NUM>. In the hub carrier <NUM>, an opening which holds a hub <NUM> and which is to be penetrated by an output transmission shaft (axle) <NUM> is formed in a center portion thereof.

In addition, the front suspension device <NUM> includes a front lower arm <NUM>, a front damper <NUM>, and a tie rod (not illustrated) which controls an orientation of a toe direction of the front wheel <NUM> with a steering mechanism (not illustrated) that are each coupled to the hub carrier <NUM>. The front damper <NUM> constitutes a shock absorber together with a coil spring <NUM>.

First, the front lower arm <NUM> is an L-shaped lower arm, and a distal end portion thereof on a side of the wheel <NUM> is coupled via a swinging shaft <NUM> to a portion which protrudes downward from a center portion of the hub carrier <NUM>. In the present embodiment, the swinging shaft <NUM> is constituted of a pillow ball joint.

On the other hand, the L-shaped front lower arm <NUM> is coupled at two locations thereof on a vehicle body side to the front suspension support members <NUM> described above via swinging shafts <NUM> and <NUM>, respectively. In the present embodiment, each of the swinging shafts <NUM> and <NUM> is constituted of a bush housing, elastic bushing, a bolt shaft mounted on a vehicle body side, and the like.

In addition, in the present embodiment, as shown in <FIG>, the position and an inclination of each of the swinging shafts <NUM> and <NUM> are set such that the swinging axis A formed by each of the swinging shafts <NUM> and <NUM> extends obliquely upward at a predetermined angle toward the front of the vehicle in a side view.

Next, as clearly shown in <FIG>, a lower end portion of the front damper <NUM> is mounted in the vehicle up-down direction in a distal end portion of a portion extending inward in the vehicle width direction above a center portion of the hub carrier <NUM>. On the other hand, an upper end portion of the front damper <NUM> is mounted to the vehicle body <NUM>.

In the present embodiment, as shown in <FIG>, the front damper <NUM> is mounted to the hub carrier <NUM> and the vehicle body <NUM> so that a longitudinal direction axis B of the front damper <NUM> (a direction of extension of the front damper <NUM>) vertically extends in a direction of <NUM> degrees relative to a direction of extension of the swinging axis A in a side view.

Next, the tie rod (not illustrated) is coupled to a portion protruding forward from a center portion of the hub carrier <NUM>.

Next, a main geometric configuration of the suspension device according to the embodiment of the present invention will be described with reference to <FIG> is a conceptual diagram for explaining a relationship between an anti-tail-lift angle during friction braking and an anti-tail-lift angle during regenerative braking according to a comparative example (A) and the embodiment of the present invention (B). <FIG> shows the rear suspension device <NUM> (<NUM>). In the present embodiment, since the front suspension device <NUM> also shares a same geometric configuration as the rear suspension device <NUM>, hereinafter, a description of the front suspension device <NUM> will be omitted.

Note that <FIG> shows a state of each portion when the vehicle is stationary (a <NUM> state). <FIG> described above also show a state of each portion when the vehicle is stationary.

First, as shown in <FIG>, in a conventional vehicle according to the comparative example, normally, an instantaneous center of rotation Ic of the rear suspension device <NUM> is set to be positioned higher than and closer to the inside of the vehicle than the rear suspension device <NUM> in a side view so that a predetermined anti-tail-lift force is obtained during braking. Note that the instantaneous center of rotation Ic is an intersection of an imaginary line C1 which is perpendicular to a longitudinal direction axis of a rear damper and an swinging axis A1 of a lower arm.

When using regenerative brakes in a vehicle with an electric motor (a so-called electric car), since an operation point of a braking force thereof is a wheel center Wc, an anti-tail-lift angle is an angle of a line (indicated by a dashed line in <FIG>) connecting the instantaneous center of rotation Ic and the wheel center Wc to each other relative to the ground G. On the other hand, when using friction brakes (such as disk brakes inside the wheels), since an operation point of a braking force thereof is a center of tire-ground contact Gc, the anti-tail-lift angle is an angle of a line (indicated by a dashed line in <FIG>) connecting the instantaneous center of rotation Ic and the center of tire-ground contact Gc to each other relative to the ground G.

Therefore, in comparative examples such as that shown in <FIG>, changing braking forces of friction brakes and regenerative brakes when, for example, the friction brakes and the regenerative brakes are subjected to coordinated control or switching between the friction brakes and the regenerative brakes is carried out causes a pitching behavior of the rear portion of the vehicle to change due to a difference in anti-tail-lift angles and, accordingly, the behavior of the entire vehicle becomes unstable.

Note that, in <FIG>, a reference sign T1 denotes a trajectory of motion of the rear wheel, and the swing trajectory T1 is a trajectory which extends in an arc shape in a direction perpendicular to the line connecting the instantaneous center of rotation Ic and the wheel center Wc to each other.

On the other hand, in the present embodiment, as shown in <FIG> and <FIG>, the longitudinal direction axis B of the rear damper <NUM> extends perpendicular to the swinging axis A in a side view and, accordingly, an imaginary line C which is perpendicular to the longitudinal direction axis B of the rear damper <NUM> extends parallel to the swinging axis A.

In addition, in the present embodiment, as shown in <FIG>, the swinging axis A extends in a direction coinciding with the vehicle front-rear direction in a bottom view (plan view).

Furthermore, in the present embodiment, by causing the swinging axis A to extend in a direction coinciding with the vehicle front-rear direction in a bottom view, as shown in <FIG>, a ball joint <NUM> of the rear lower arm <NUM> and the rear wheel <NUM> linearly swing (a swing trajectory thereof is denoted by a reference sign T) in an up-down direction which coincides with a direction of extension of the longitudinal direction axis B of the rear damper <NUM>. Since the rear lower arm <NUM> swings around the swinging axis A which extends in the vehicle front-rear direction, the swing trajectory T of the ball joint <NUM> on a wheel-side assumes a linear shape in a side view.

In addition, in the present embodiment, as shown in <FIG> and <FIG>, the swinging axis A of the rear lower arm <NUM> is extended obliquely upward toward the front of the vehicle in a side view and, accordingly, an anti-lift angle is formed in the rear suspension device <NUM>.

In the present embodiment, due to a suspension geometry set as described above, as shown in <FIG>, an anti-tail-lift angle when using regenerative brakes and an anti-tail-lift angle when using friction brakes in the vehicle <NUM> with an electric motor are made to be similar angles. Accordingly, in the present embodiment, for example, during coordinated control of the friction brakes and the regenerative brakes, a change in a pitching behavior of the rear portion of the vehicle is suppressed to stabilize the behavior of the vehicle.

In addition, as shown in <FIG>, by configuring the rear damper <NUM> to extend perpendicular to the swinging axis A in a side view, a linear swing direction (trajectory of motion) T of the rear wheel <NUM> and the longitudinal direction axis B of the rear damper are made to coincide with each other. Accordingly, in the present embodiment, a load transmitted from the rear wheel <NUM> is efficiently input to the rear damper <NUM> via the hub carrier <NUM> to operate the rear damper <NUM> in an efficient manner.

Furthermore, in the present embodiment, since the drive of the rear wheel <NUM> is used as a main drive by using the rear electric motor <NUM> as a main drive source with a large output, as shown in <FIG>, due to the anti-lift angle formed in the rear suspension device <NUM>, a lift of particularly the rear portion of the vehicle body can be suppressed during use of the regenerative brakes and the friction brakes.

As described above, the technical idea of the present invention is to, firstly, extend a damper <NUM> in a direction perpendicular to a swinging axis A and cause an imaginary line C which is perpendicular to a longitudinal direction axis B of the damper <NUM> to extend in a direction parallel to the swinging axis A in a side view so as to create a state where an instantaneous center of rotation does not exist or to make an instantaneous center of rotation at a position separated by an infinite distance (in particular, with respect to a position of an instantaneous center of rotation Ic such as that shown in <FIG>) and, accordingly, suppress a change in a pitching behavior of a vehicle even when braking forces of regenerative brakes and friction brakes are changed.

In addition, the technical idea of the present invention is to, secondly, cause the swinging axis A to extend in a direction coinciding with a vehicle front-rear direction in a bottom view (plan view) so as to create a state where an instantaneous center of rotation does not exist or to make an instantaneous center of rotation at a position separated by an infinite distance (in particular, with respect to a position of an instantaneous center of rotation Ic such as that shown in <FIG>) and, accordingly, suppress a change in a pitching behavior of the vehicle even when braking forces of regenerative brakes and friction brakes are changed.

Furthermore, the technical idea of the present invention is to, thirdly, form an anti-lift angle by causing the swinging axis A to extend obliquely upward toward a front of the vehicle in a side view and, accordingly, suppress a change in a pitching behavior of the vehicle (in particular, a change in a pitching behavior of a rear portion of the vehicle) during coordinated control of the regenerative brakes and the friction brake and the like.

Moreover, the technical idea of the present invention is to, fourthly, cause the swinging axis A to extend in a direction coinciding with the vehicle front-rear direction in a bottom view (plan view) and, at the same time, cause the damper <NUM> to extend in a direction perpendicular to the swinging axis A in a side view so that a linear swing direction (trajectory of motion) T of the rear wheel <NUM> (ball joint <NUM>) and the longitudinal direction axis B of a rear damper coincide with each other and, accordingly, enable a load transmitted from the rear wheel <NUM> to be efficiently input to the rear damper <NUM>.

The technical idea of the present invention described above is applied to the front suspension device <NUM> in a similar manner.

As described above, in the present invention, an angle of the longitudinal direction axis B of the damper relative to the swinging axis A in a side view, parallelism of the swinging axis A and the imaginary line C in a side view, and a direction of extension of the swinging axis A in a bottom view are important. On the other hand, these values are not limited to those in the embodiment described above and, for example, when designing a vehicle, performing an experiment with a test vehicle, or the like, the values may be adjusted to ranges (angle, parallelism, and direction) in which a change in a pitching behavior of the vehicle can be substantially suppressed during coordinated control of friction brakes and regenerative brakes and the like in consideration of a length of a wheel base or a position of the center of gravity of the vehicle, motion of each portion during swinging of the suspension, and the like which affect the pitching behavior of the vehicle. For example, the angle formed by the swinging axis A and the longitudinal direction axis B of the rear damper <NUM> is preferably set to a range of <NUM>° ± <NUM>°.

As a modification of the vehicle <NUM> according to the present embodiment, only the front electric motor <NUM> may be provided as the electric motor to drive the front wheels <NUM> and make the vehicle <NUM> a front-wheel drive vehicle, only the rear electric motor <NUM> may be provided as the electric motor to drive the rear wheels <NUM> and make the vehicle <NUM> a rear-wheel drive vehicle, or the front wheels <NUM> and the rear wheels <NUM> may be driven by a single electric motor.

In addition, the present invention is not limited to the strut-type suspension device described above and can also be applied to suspension devices of other types. For example, with a double wishbone-type suspension device, by causing a swinging axis of a lower arm and a swinging axis of an upper arm to extend in directions parallel to each other in a side view and causing the swinging axes to extend in a direction coinciding with the vehicle front-rear direction in a bottom view (plan view), a similar effect of suppressing a change in a pitching behavior of the vehicle even when braking forces of regenerative brakes and friction brakes are changed can be obtained. A similar effect can also be obtained by a measure of causing each swinging axis to extend obliquely upward toward the front of the vehicle in a side view.

Next, a main geometry of the suspension device according to the embodiment of the present invention and an effect thereof will be further described with reference to <FIG> is a conceptual diagram showing a relationship among a swinging axis of a lower arm, a direction of extension of a damper, and an imaginary line perpendicular to the direction of extension of the damper in the front suspension device and the rear suspension device according to the embodiment of the present invention.

As shown in <FIG>, in the present embodiment, in the rear suspension device <NUM> and the front suspension device <NUM>, a direction of extension of the longitudinal direction axes B of the dampers <NUM> and <NUM> is made to be a direction perpendicular to the swinging axes A of the lower arms <NUM> and <NUM>, the imaginary lines C perpendicular to the longitudinal direction axes B of the dampers <NUM> and <NUM> are made to extend in a direction parallel to the swinging axes A, and the swinging axes A of the lower arms <NUM> and <NUM> are made to extend obliquely upward toward the front of the vehicle in a side view. In the present embodiment, by preventing a difference in anti-lift angles (anti-dive angles) between the regenerative brakes and the friction brakes from occurring in the front wheels <NUM> and the rear wheels <NUM> due to such a configuration, a difference in behavior change between the front portion of the vehicle and the rear portion of the vehicle is suppressed and, accordingly, a change in the pitching behavior of the entire vehicle during use of the regenerative brakes and the friction brakes is suppressed.

In the vehicle <NUM> according to the present embodiment, an output of the front electric motor <NUM> is set smaller than an output of the rear electric motor <NUM> so as to prevent a large drive force from being applied to the front wheels <NUM>. As a result, while making the effect of an anti-nose-lift angle of the front portion of the vehicle negligible when being driven due to the smaller output, with respect to the regenerative brakes and the friction brakes which act on the front wheels <NUM> during braking, the imaginary line C perpendicular to the longitudinal direction axis B of the front damper <NUM> is made to extend in a direction parallel to the swinging axis A as described above to suppress a change in the pitching behavior of the entire vehicle during use of the regenerative brakes and the friction brakes.

If the swinging axis A and the imaginary line C are parallel to each other in both the rear suspension device <NUM> and the front suspension device <NUM>, an attitude change of the vehicle during coordinated control of the friction brakes and the regenerative brakes can be suppressed regardless of differences in anti-lift angles and anti-dive angles between the rear suspension device <NUM> and the front suspension device <NUM>.

Next, a working effect of the present embodiment will be described.

The present embodiment provides suspension devices <NUM> and <NUM> of a vehicle <NUM> equipped with electric motors <NUM> and <NUM> for transmitting a drive force to front wheels <NUM> and rear wheels <NUM> (in a modification, at least one of the front wheels <NUM> or the rear wheels <NUM>) via output transmission shafts <NUM> and <NUM>, the suspension devices including: a front lower arm <NUM> capable of swinging in a vehicle up-down direction with reference to a front wheel swinging axis A in a vehicle body-side mounting portion in a front portion of the vehicle; a front damper <NUM> which extends in a direction perpendicular to the front wheel swinging axis A in a side view; a rear lower arm <NUM> capable of swinging in the vehicle up-down direction with reference to a rear wheel swinging axis A in a vehicle body-side mounting portion in a rear portion of the vehicle; and a rear damper <NUM> which extends in a direction perpendicular to the rear wheel swinging axis A in a side view, wherein, in a side view, the front wheel swinging axis A and a first imaginary line C perpendicular to a direction of extension of the front damper <NUM> extend in a direction parallel to each other and, at the same time, the rear wheel swinging axis A and a second imaginary line C perpendicular to a direction of extension of the rear damper <NUM> extend in a direction parallel to each other.

According to the present embodiment configured as described above, in a side view, since the front wheel swinging axis A and the first imaginary line C perpendicular to the direction of extension of the front damper <NUM> extend in a direction parallel to each other and, at the same time, the rear wheel swinging axis A and the second imaginary line C perpendicular to the direction of extension of the rear damper <NUM> extend in a direction parallel to each other, an occurrence of a difference in behavior changes of the front portion of the vehicle and the rear portion of the vehicle can be suppressed during braking of the front and rear wheels <NUM> and <NUM> on which regenerative brakes act (in a modification, during braking of the front and rear wheels <NUM> and <NUM> in which regenerative brakes act on at least one of the front wheels <NUM> or the rear wheels <NUM>) and, accordingly, a change in a pitching behavior of the entire vehicle can be suppressed during use of the regenerative brakes and friction brakes such as when the friction brakes and the regenerative brakes are subjected to coordinated control and a sense of discomfort imparted to an occupant can be reduced.

In addition, according to the present embodiment, since the front wheel swinging axis A and the rear wheel swinging axis A respectively extend in a direction coinciding with the vehicle front-rear direction in a bottom view, an occurrence of a difference in behavior changes of the front portion of the vehicle and the rear portion of the vehicle can be more reliably suppressed and, accordingly, a change in a pitching behavior of the entire vehicle can be suppressed, for example, when the friction brakes and the regenerative brakes are subjected to coordinated control, and a sense of discomfort imparted to an occupant can be reduced. In addition, since (respective wheel centers Wc of) the front wheels <NUM> and the rear wheels <NUM> can each be made to linearly swing in a same direction as the directions of extension of the dampers <NUM> and <NUM>, a change in the behavior of the entire vehicle during use of the regenerative brakes and the friction brakes can be suppressed more effectively.

Furthermore, according to the present embodiment, since the front wheel swinging axis A and the rear wheel swinging axis A each extend obliquely upward toward the front of the vehicle in a side view, an anti-lift angle is particularly formed in the rear suspension device <NUM> and a lift of the rear portion of the vehicle body during use of the regenerative brakes and the friction brakes is suppressed. Moreover, according to the present embodiment, since the front wheel swinging axis A and the first imaginary line C perpendicular to the direction of extension of the front damper <NUM> extend in a direction parallel to each other and the rear wheel swinging axis A and the second imaginary line C perpendicular to the direction of extension of the rear damper extend in a direction parallel to each other, a difference between the behavior of the front portion of the vehicle and the behavior of the rear portion of the vehicle during braking of front and rear wheels can be reduced and, accordingly, a change in a pitching behavior of the entire vehicle during use of the regenerative brakes and friction brakes can be suppressed.

In addition, according to the present embodiment, since the rear electric motor <NUM> which is mounted to the vehicle body in the rear portion of the vehicle and which drives the rear wheels <NUM> is provided and the rear wheels <NUM> are driven using the rear electric motor <NUM> provided in the rear portion of the vehicle as a main drive source, although a braking force of the regenerative brakes which act on the rear wheels <NUM> increases due to the use of the rear wheels <NUM> as main drive wheels, since the rear wheel swinging axis A and the second imaginary line C extend in a direction parallel to each other, a change in the pitching behavior of the rear portion of the vehicle during use of the regenerative brakes and the friction brakes of the rear wheels <NUM> can be suppressed more effectively. In addition, a lift of the front portion of the vehicle during travel start of the vehicle due to the use of the rear wheels <NUM> as main drive wheels can be suppressed.

Furthermore, according to the present embodiment, since the front wheel swinging axis A and the rear wheel swinging axis A respectively extend obliquely upward toward the front of the vehicle in a side view, the front electric motor <NUM> mounted to the vehicle body in the front portion of the vehicle and the rear electric motor <NUM> mounted to the vehicle body in the rear portion of the vehicle are provided, and the rear electric motor <NUM> provided in the rear portion of the vehicle is used as a main drive, a difference in anti-lift angles (anti-dive angles) between the regenerative brakes and the friction brakes can be prevented from occurring or can be made extremely small in both the front wheels <NUM> and the rear wheels <NUM> and, therefore, a change in the behavior of the entire vehicle during use of the regenerative brakes and the friction brakes can be more reliably suppressed. In particular, since the rear electric motor <NUM> is used as a main drive, due to the anti-lift angle of the rear suspension device <NUM>, a lift of the rear portion of the vehicle body can be suppressed during use of the regenerative brakes and the friction brakes.

In addition, according to the present embodiment, since the front lower arm <NUM> and the rear lower arm <NUM> are mounted to the vehicle body frames <NUM> and <NUM> which extend in the vehicle front-rear direction from the battery case <NUM> disposed in a lower portion of the center of the vehicle, support rigidity of each of the front wheels <NUM> and the rear wheels <NUM> can be increased and a response delay to vehicle behavior (for example, a response delay to a cornering force) can be reduced.

Claim 1:
A vehicle (<NUM>) having a vehicle body (<NUM>), front and rear wheels (<NUM>, <NUM>), at least one electric motor (<NUM>) and at least one output transmission shaft (<NUM>), the electric motor (<NUM>) configured for transmitting a drive force to wheels (<NUM>) of the vehicle (<NUM>) via the output transmission shaft (<NUM>), the vehicle (<NUM>) further comprising a suspension device (<NUM>, <NUM>), the suspension device (<NUM>, <NUM>) comprising:
a front suspension arm (<NUM>), which is configured to be movable for swinging in a vehicle up-down direction with reference to a front wheel swinging axis (A) in a vehicle body-side mounting portion in a front portion of the vehicle (<NUM>);
a front damper (<NUM>) which extends in a direction perpendicular to the front wheel swinging axis (A) in a side view;
a rear suspension arm (<NUM>), which is configured to be movable for swinging in the vehicle up-down direction with reference to a rear wheel swinging axis (A) in a vehicle body-side mounting portion in a rear portion of the vehicle (<NUM>); and
a rear damper (<NUM>) which extends in a direction perpendicular to the rear wheel swinging axis (A) in a side view,
wherein the front wheel swinging axis (A) and a first imaginary line (C) perpendicular to a direction of extension of the front damper (<NUM>) extend in a direction parallel to each other and the rear wheel swinging axis (A) and a second imaginary line (C) perpendicular to a direction of extension of the rear damper (<NUM>) extend in a direction parallel to each other in a side view, characterized in that
the suspension device (<NUM>, <NUM>) is a strut-type suspension device including front and rear wheel hub carriers (<NUM>, <NUM>), to which wheel-side end portions of the front suspension arm (<NUM>) and the rear suspension arm (<NUM>) are respectively coupled, and which respectively support the front wheel (<NUM>) and the rear wheel (<NUM>), wherein a lower portion of the front damper (<NUM>) and a lower portion of the rear damper (<NUM>) are respectively mounted to the hub carriers (<NUM>, <NUM>), and upper portions of the front damper (<NUM>) and the rear damper (<NUM>) are each mounted to the vehicle body (<NUM>).