Patent Description:
In recent years, from the viewpoint of reducing the environmental load, in the field of commercial vehicles such as trucks, there has been developed an electric truck which does not have an internal combustion engine and is driven only by an electric motor (see Patent Literature <NUM>). As a drive device used for such an electric truck, for example, as shown in Patent Literature <NUM>, a drive device in which a driving motor and a reducer are integrally provided in a differential gear has been considered.

<CIT> discloses a drive device for an electric truck comprising a drive unit housing which integrally accommodates a motor that generates drive power, a reducer that reduces a rotation speed of the motor, and a final gear that is connected to the reducer and transfers the drive power of the motor to a drive wheel of the electric truck.

<CIT> provides an oil-gas spring, a wheel steering mechanism provided with the oil-gas spring, a wheel provided with the oil-gas spring and a vehicle adopting the wheel.

<CIT> discloses a truck having a frame with a forward end and a rearward end. The rearward end of the frame is supported by at least two wheels coupled to part of the frame. The truck also has a forward strut support coupled to the frame near the forward end. The truck has at least first and second struct modules coupled to the forward strut support. The first and second strut modules each have an independent steering mechanism and at least one wheel and tire assembly. Each of the first and second strut modules can also have one or more motors for driving a respective wheel and tire assembly independent of each other wheel and tire assembly of that strut module and of the other strut module.

<CIT> each disclose an electric truck comprising a drive device having drive units each of which includes a drive unit housing integrally accommodating a motor that generates drive power, a reducer that reduces a rotation speed of the motor, and a final gear that is connected to the reducer and transfers the drive power of the motor to a drive shaft of the double-tire.

For commercial vehicles such as trucks, there is a market demand to improve the steering performance of vehicles by increasing the steering angle of wheels to <NUM>° or more, preferably to about <NUM>°. If such a steering angle can be realized, there is an advantage that the turning radius can be reduced, and if the steering of <NUM>° is possible, the vehicle can be moved and parked in the left-right direction.

However, in an electric truck which is actually produced up to now, since a suspension device of a leaf spring type, a rigid axle, or the like is often employed, it is difficult to realize the steering angle described above. In addition, since the electric truck is required to have a higher torque than that of a passenger car, it is necessary to provide a speed reduction mechanism, which increases the size of the drive device. From this point of view as well, it is difficult to realize the steering angle described above.

An electric truck has a tendency of having larger vehicle-body vibration while traveling than a passenger car, and for this reason, a demand arises to improve drive feeling.

With the foregoing problems in view, it is an object of the present disclosure to provide a drive device for an electric truck having a steering performance of a steering angle of <NUM>° to <NUM>° while improving drive feeling.

The present disclosure is made in order to solve at least part of the above problems and can be carried out in the following embodiment or application.

The present disclosure makes it possible to provide a drive device for an electric truck having a steering performance of a steering angle of <NUM>° to <NUM>° while improving drive feeling.

A drive device for an electric truck according to an embodiment will now be described with reference to accompanying drawings. The following embodiment is merely example, so there is no intention to exclude various modifications and applications of techniques not explicitly described in the following embodiment. Each of the structures of the present embodiment can be variously modified without departing from the scope of the structure. The structures may be appropriately selected, omitted, or combined according to the requirement.

As illustrated in <FIG>, the drive device according to the present embodiment is applied to an electric truck <NUM> that travels only by the drive power of a motor <NUM> (see <FIG>) without an internal combustion engine. In <FIG>, the electric truck <NUM> (hereinafter simply referred to as the "truck <NUM>") including a pair of left and right side frames 1A (also referred to as chassis frames) extending in the front-rear direction of the vehicle and a cab 1B disposed in the front part of the vehicle is illustrated, and the illustration of the body is omitted. In addition to the side frames 1A, a frame extending in the vehicle widthwise direction may be provided, or the side frames 1A may be omitted.

In the following description, the forward direction of the truck <NUM> will be referred to as the "front", and the opposite direction to the front will be referred to as the "rear". In addition, the left-right direction is determined with reference to the state of the truck <NUM> facing forward. The left-right direction is orthogonal to the front-rear direction of the vehicle. Hereinafter, the left-right direction is referred to as a "vehicle width direction", and the front-rear direction of the vehicle is simply referred to as a "front-rear direction".

As illustrated in <FIG> and <FIG>, the truck <NUM> of the present embodiment includes double-tires <NUM> each consisting of two drive wheels 2A (drive wheels). In the truck <NUM> of the present embodiment, a pair of left and right double-tires <NUM> are provided on the front side (front wheel side) of the vehicle, and two pairs of left and right double-tires <NUM> are provided side by side on the rear side (rear wheel side) of the vehicle, but the number of double-tires <NUM> in the front-rear direction is not limited to this. Each double-tire <NUM> is provided with one drive unit <NUM> including the motor <NUM>, and the drive power of the motor <NUM> is transmitted to the double-tire <NUM> (drive wheels 2A). The configuration of the drive unit <NUM> will be described below.

The truck <NUM> of the present embodiment includes a body frame casing <NUM> composed of a pair of mounting frame bodies 5A extending in the vehicle width direction, a pair of cross members 5B and a pair of cross members 5C connecting the mounting frame bodies 5A, and body-connecting parts <NUM> and <NUM> for connecting the drive unit <NUM> disposed in the frame of the body frame casing <NUM> to the respective mounting frame bodies 5A.

The pair of mounting frame bodies 5A are disposed apart from each other in the front-rear direction. Each of the cross members 5B and 5C connects the front and rear mounting frame bodies 5A. The pair of left and right drive units <NUM> are disposed in the frame of the body frame casing <NUM> so as to be adjacent to each other in the vehicle width direction. In the truck <NUM> of the present embodiment, one body frame casing <NUM> is provided on the front side (front wheel side) of the vehicle, and two body frame casings <NUM> are provided on the rear side (rear wheel side) of the vehicle, but the number of body frame casings <NUM> in front and that in rear are not limited to these. As described above, in the truck <NUM> of the present embodiment, the body frame casing <NUM> in which the pair of left and right drive units <NUM> are connected by the body-connecting parts <NUM> and <NUM> constitutes a front axle and a rear axle of the vehicle.

The body frame casing <NUM> of the present embodiment is formed of a rectangular flat plate member in which the front and rear mounting frame bodies 5A extend in the vehicle width direction and the vertical direction. The cross members 5B located above the body frame casing <NUM> are each formed of a member having a U-shaped or hat-shaped cross section extending in the front-rear direction, and connects the flanges at the upper ends of the front and rear mounting frame bodies 5A. On the other hand, the cross members 5C located on the sides of the body frame casing <NUM> are each formed of a flat plate member extending in the front-rear direction and the vertical direction and having a concave portion formed so as to surround the drive wheel 2A. Any one of the cross members 5B and 5C may be omitted.

As illustrated in <FIG>, the front body-connecting part <NUM> connects the front side of the drive unit <NUM> in the frame to the front mounting frame body 5A, and the rear body-connecting part <NUM> connects the rear side of the drive unit <NUM> in the frame to the rear mounting frame body 5A. As illustrated in <FIG> and <FIG>, the front and rear body-connecting parts <NUM> and <NUM> are formed in the same manner (front and rear symmetric). Each of the body-connecting parts <NUM> and <NUM> extends in the front-rear direction and is connected to the mounting frame body 5A to constitute a part of the frame of the truck <NUM>.

At the front end portion of the front body-connecting part <NUM>, a planar mounting face 32a extending in a direction orthogonal to the front-rear direction is provided. At the rear end portion of the front body-connecting part <NUM>, a pair of connecting side protruding portions 32b protruding rearward is provided. The mounting face 32a is a part to be attached to the mounting frame body 5A, and has a fastening hole (not shown). The pair of connecting side protruding portions 32b are separated from each other in the vehicle width direction, and have holes 32c penetrating in the vehicle width direction. The connecting side protruding portion 32b constitutes a part of a hinge part <NUM>, which will be described below, and is connected to a steering gear part <NUM>, which will also be described below.

At the rear end portion of the rear body-connecting part <NUM>, a planar mounting face 33a extending in a direction orthogonal to the front-rear direction is provided. At the front end portion of the rear body-connecting part <NUM>, a pair of connecting side protruding portions 33b protruding forward and each having a hole 33c are provided. The configuration of the mounting face 33a and the connecting side protruding portions 33b are the same as the configuration of the mounting face 32a and the connecting side protruding portions 32b, respectively.

As illustrated in <FIG> and <FIG>, the drive unit <NUM> includes the motor <NUM> that generates drive power, a reducer <NUM> that reduces a rotation speed of the motor <NUM>, a final gear <NUM> that is connected to the reducer <NUM> and transfers the drive power of the motor <NUM> to a drive shaft <NUM> of the double-tire <NUM>, and a drive unit housing <NUM> that integrally accommodates these units. That is, the drive unit housing <NUM> integrally houses the motor <NUM>, the reducer <NUM>, and the final gear <NUM>.

The motor <NUM> functions as an electric motor when the vehicle is driven, and functions as an electric generator when the vehicle is decelerated. The reducer <NUM> decelerates the rotation speed of the motor <NUM> to amplify the motor torque (drive power). The drive shaft <NUM> is extended in the vehicle width direction with the truck <NUM> traveling straight forward, and is arranged in pairs on the left and right across the final gear <NUM>. The final gear <NUM> is positioned substantially at the center of the two drive wheels 2A in the vehicle width direction, and distributes the drive power of the motor <NUM> amplified by the reducer <NUM> to the two drive wheels 2A. The final gear <NUM> may be included in a differential gear. However, in the double-tire <NUM>, the differential gear can be omitted because the two drive wheels 2A are closer to each other than the normal left and right wheels.

In addition to the drive units <NUM> disposed on the left and right sides of the truck <NUM>, the drive device of the truck <NUM> includes a suspension part <NUM> provided over the final gear <NUM> in the drive unit housing <NUM>, and a steering gear part <NUM> provided over the suspension part <NUM>. Further, the drive device includes the pair of hinge parts <NUM> provided one on each of the vehicle front side and the vehicle rear side of the steering gear part <NUM>, respectively, and the body-connecting parts <NUM> and <NUM> described above.

The suspension part <NUM> functions as a suspension for absorbing vertical vibration of the double-tire <NUM>. The steering gear part <NUM> is configured to be able to steer the double-tire <NUM>, and has a function of steering the double-tire <NUM> around a steering shaft 30a (changing a steering angle). The double-tire <NUM> may be steered manually or automatically. Each double-tire <NUM> is individually driven and individually steered. The hinge part <NUM> has a function of suppressing the vertical vibration of the double-tire <NUM> from being transmitted to the vehicle body. The body-connecting parts <NUM> and <NUM> are for connecting the steering gear part <NUM> and the vehicle body of the truck <NUM> through the pair of hinge parts <NUM>. A pair of the front and rear body-connecting parts <NUM> and <NUM> are provided across the steering shaft 30a.

In the present embodiment, as illustrated in <FIG>, both the suspension part <NUM> and the steering gear part <NUM> are located above a space between the two drive wheels 2A constituting the double-tire <NUM>. Further, in the drive device shown in <FIG>, the motor <NUM> is disposed in front of the final gear <NUM> and above the reducer <NUM>, but the position of the motor <NUM> may be set according to the specification and the size of the motor <NUM>, the space in which the motor <NUM> can be disposed, and the like. For example, the motor <NUM> may be disposed behind the final gear <NUM>, or may be disposed obliquely above the final gear <NUM>. Alternatively, the output shaft (not shown) of the motor <NUM> may be disposed in a downward extending posture.

First, the suspension part <NUM> will be described in detail. As illustrated in <FIG> and <FIG>, the suspension part <NUM> of the present embodiment is an air suspension including an outer tube <NUM> centered at the steering shaft 30a of the double-tire <NUM>, and an inner tube <NUM> being concentric with the outer tube <NUM>. The inner tube <NUM> is slidable along an inner circumference face of the outer tube <NUM> in an axis direction and incapable of relatively rotating with respect to the outer tube <NUM>. The steering shaft 30a is a shaft portion having a steering center Cs when the double-tire <NUM> is steered, and extends in the vertical direction. The steering center Cs coincides with the centers of the outer tube <NUM> and the inner tube <NUM>.

As illustrated in <FIG>, the suspension part <NUM> may also have a coil spring <NUM> surrounding the outer tube <NUM> and the inner tube <NUM>. The suspension part <NUM> having the coil spring <NUM> is applied to the relatively lightweight truck <NUM>. On the other hand, the suspension part <NUM> without the coil spring <NUM> shown in <FIG> and <FIG> is applied to the truck <NUM> which has a relatively large weight because the suspension part <NUM> has a larger capacity of air than that of the suspension part <NUM> having the coil spring <NUM>. The suspension part <NUM> shown in <FIG> is basically the same as the suspension part <NUM> shown in <FIG> and <FIG> except that the coil spring <NUM> is provided. Therefore, hereinafter, <FIG> will be described with reference to one of the embodiments.

As illustrated in <FIG>, each of the outer tube <NUM> and the inner tube <NUM> has a vertically-long cylindrical shape, and the inner diameter of the outer tube <NUM> is slightly larger than the outer diameter of the inner tube <NUM>. The upper opening of the outer tube <NUM> is sealed by a cover part 30b to which the steering shaft 30a is fixed, and the lower opening of the outer tube <NUM> communicates with the inner tube <NUM> by insertion of the upper portion of the inner tube <NUM>. The upper opening of the inner tube <NUM> enters the lower portion of the outer tube <NUM> and communicates with the outer tube <NUM>, the lower opening of the inner tube <NUM> is sealed with a flat drive head <NUM>. Air is sealed inside the outer tube <NUM> and the inner tube <NUM>.

As illustrated in <FIG>, the drive head <NUM> may have a stepped shape so that the drive head <NUM> is also fixed to the inner circumference face at the lower end of the inner tube <NUM>. In this case, the fixation between the inner tube <NUM> and the drive head <NUM> becomes strong, and it becomes possible to resist a load in the lateral direction. A stopper <NUM> that prevents the inner tube <NUM> from coming off and that seals the lower end of the outer tube <NUM> is fixed to the lower end of the outer tube <NUM>. When the coil spring <NUM> is provided on the suspension part <NUM>, the coil spring <NUM> is arranged around the outer tube <NUM> and the inner tube <NUM>, as illustrated in <FIG>.

The outer tube <NUM> and the inner tube <NUM> are relatively displaced (slide) in the axial direction (vertical direction) according to the vertical vibration of the truck <NUM> (vertical movement of the double-tire <NUM>). As illustrated in <FIG>, the suspension part <NUM> of the present embodiment includes a low frictional member <NUM> being arranged at a point where the outer tube <NUM> is brought into slidable contact with the inner tube <NUM>. The low frictional member <NUM> is a member that reduces sliding friction of the outer tube <NUM> with inner tube <NUM>, and is attached to, for example, the inner circumference face of the outer tube <NUM> or the outer circumference face of the inner tube <NUM>. The low frictional member <NUM> avoids direct contact between the outer tube <NUM> and the inner tube <NUM>, and reduces the friction when these slide relatively in the vertical direction.

As illustrated in <FIG> and <FIG>, in the present embodiment, an annular attaching part <NUM> is fixed to the outer circumference face of the upper portion of the outer tube <NUM>, and the attaching part <NUM> and the drive head <NUM> are linked by a stabilizer <NUM> (also referred to as a steering arm). Thereby, the relative rotation of the outer tube <NUM> and the inner tube <NUM> is restricted. Further, by linking the upper part of the outer tube <NUM> and the lower part of the inner tube <NUM> to each other, relative vertical movement of the outer tube <NUM> and the inner tube <NUM> is allowed, and these movements are smoothed.

In the suspension part <NUM> of the present embodiment, shock absorbers <NUM> are provided on both left and right sides of the stabilizer <NUM>, respectively. The shock absorber <NUM> has an upper end connected to the attaching part <NUM> and a lower end connected to the drive head <NUM> via mounting components.

Next, the steering gear part <NUM> will be described in detail. The steering gear part <NUM> of the present embodiment is configured to be capable of steering the double-tire <NUM> up to <NUM>° leftward and rightward on an assumption that a steering angle of the double-tire <NUM> under a state where the truck <NUM> is traveling straight forward (that is, when the drive shaft <NUM> extends in the vehicle width direction) is <NUM>° (reference). That is, the double-tire <NUM> can be steered by <NUM>° by the steering gear part <NUM>, and when the double-tire <NUM> is steered <NUM>° leftward or rightward from the forward direction, the extending direction of the drive shaft <NUM> becomes the front-rear direction, and the truck <NUM> can move in the left-right direction.

As illustrated in <FIG> and <FIG>, the steering gear part <NUM> includes the steering shaft 30a fixed to the cover part 30b, a spur gear 30c fixed to the steering shaft 30a, an annular gear 30d that meshes with the spur gear 30c, a tube portion 30e concentrically arranged with the steering shaft 30a, and a driving part <NUM> connected to the annular gear 30d to rotate the annular gear 30d. The driving part <NUM> is an actuator such as a hydraulic cylinder or a stepping motor.

In the example of <FIG>, when the driving part <NUM> rotates the annular gear 30d clockwise in a top view, the spur gear 30c also rotates clockwise. Accordingly, since the steering shaft 30a also rotates clockwise, the double-tire <NUM> is steered rightward. Conversely, when the driving part <NUM> rotates the annular gear 30d counterclockwise, the spur gear 30c also rotates counterclockwise. Accordingly, since the steering shaft 30a also rotates counterclockwise, the double-tire <NUM> is steered leftward. As illustrated in <FIG>, the steering shaft 30a is disposed equidistant from each of the pair of mounting frame bodies 5A.

As illustrated in <FIG>, a pair of front and rear protruding portions 30f are formed on the tube portion 30e and connected to the connecting side protruding portions 32b and 33b of the body-connecting parts <NUM> and <NUM>, respectively. The protruding portion 30f protrudes in the front-rear direction from each of the outer circumference face on the front side and the outer circumference face on the rear side of the tube portion 30e, and forms the hinge part <NUM> together with the above-mentioned connecting side protruding portions 32b and 33b. That is, the front protruding portion 30f is interposed between the pair of connecting side protruding portions 32b, and a portion functioning as a rotating center Ch of the hinge parts <NUM> is inserted into the hole 32c of each connecting side protruding portion 32b. In the protruding portions 30f of the present embodiment, a cylindrical portion (not shown) having a through hole <NUM> penetrating in the vehicle width direction is inserted into the hole 32c.

Similarly, the rear protruding portion 30f is interposed between the pair of connecting side protruding portions 33b, and a cylindrical portion functioning as the rotating center Ch of the hinge part <NUM> is inserted into the hole 33c of each connecting side protruding portion 33b. A bush (not shown) that absorbs a load to be transmitted to the vehicle body is interposed in the hinge parts <NUM> of the present embodiment. With the bush interposed, the load to be transmitted to the vehicle body is absorbed, and the drive feeling is further improved.

As illustrated in <FIG> and <FIG>, in the tube portion 30e, the cover part 30b and the upper portion of the outer tube <NUM> are concentrically arranged and rotatably supported with respect to the tube portion 30e. That is, the outer tube <NUM>, the inner tube <NUM>, the cover part 30b, and the drive head <NUM> rotate integrally about the steering shaft 30a with respect to the tube portion 30e. A thrust plate <NUM> that receives a vertical load is interposed between the inner circumference face of the tube portion 30e and the outer circumference face of the outer tube <NUM>. At the upper end of the thrust plate <NUM>, a stopper <NUM> for preventing the outer tube <NUM> from coming off is fixed.

The thrust plate <NUM> of the present embodiment includes a cylinder portion 34a located between the tube portion 30e and the outer tube <NUM>, and a flange portion 34b projecting radially outward from a lower end of the cylinder portion 34a. The flange portion 34b is sandwiched between the upper surface of the attaching part <NUM> and the lower surface of the tube portion 30e. The thrust plate <NUM> is a metal component that is not fixed to any component and functions as a spacer, and avoids direct contact between the tube portion 30e on the fixed side and the outer tube <NUM> and the attaching part <NUM> on the rotating side. The thrust plate <NUM> is made replaceable due to wear.

The steering gear part <NUM> of the present embodiment includes a low frictional member <NUM> arranged at a point where the outer tube <NUM> is brought into slidable contact with the thrust plate <NUM>. The low frictional member <NUM> is a member that reduces friction between the outer tube <NUM> and the thrust plate <NUM>, and is attached to, for example, the outer circumference face of the outer tube <NUM> or the inner circumference face of the thrust plate <NUM>. The friction at the time of relative displacement between the outer tube <NUM> and the thrust plate <NUM> is reduced by the low frictional member <NUM>.

According to the drive device for the above truck <NUM>, it is possible to obtain the following actions and effects.

The above-described drive device and the truck <NUM> are all examples. For example, although the suspension part <NUM> is an air suspension including the outer tube <NUM> and the inner tube <NUM>, or a hybrid of an air suspension and the coil spring <NUM>, the suspension part can be selected based on the load and application. Alternatively, a hydraulic suspension or an electromagnetic suspension may be employed.

The low frictional members <NUM> and <NUM> and the thrust plate <NUM> are not essential and can be omitted. The structure for restricting the relative rotation between the outer tube <NUM> and the inner tube <NUM> is not limited to the link connection by the stabilizer <NUM>. The steering gear part <NUM> may be realized using gears other than the spur gear 30c and the annular gear 30d. The range of the steering angle of the double-tire <NUM> may be set according to the required turning radius.

Claim 1:
An electric truck (<NUM>) comprising a drive device comprising:
drive unit housings (<NUM>) each of which integrally accommodates a motor (<NUM>) that generates drive power, a reducer (<NUM>) that reduces a rotation speed of the motor (<NUM>), and a final gear (<NUM>) that is connected to the reducer (<NUM>) and transfers the drive power of the motor (<NUM>) to a drive wheel (2A) of the electric truck (<NUM>),
wherein
the drive unit housings (<NUM>) are provided to each of the drive wheels (2A) of left and right sides of the electric truck (<NUM>); and
the drive device further comprises
suspension parts (<NUM>) positioned over the respective final gears (<NUM>),
steering gear parts (<NUM>) positioned over the respective suspension parts (<NUM>) and configured to steer the respective drive wheels (2A),
characterized in that the drive device further comprises pairs of hinge parts (<NUM>), each pair disposed one to each of a vehicle front side and a vehicle rear side of each of the steering gear parts (<NUM>), and
pairs of body-connecting parts (<NUM>, <NUM>), one of the pairs connecting each of the steering gear parts (<NUM>) to a vehicle body of the electric truck (<NUM>) through each of the pairs of hinge parts (<NUM>).