Patent Description:
In recent years, exhaust gas regulations for vehicles have been enhanced and demands for fuel efficiency and carbon dioxide emissions per travel distance for vehicles have become strict in various countries in the world. In addition, some cities regulate entry of vehicles traveling by an internal combustion engine into urban areas. To satisfy these requests, hybrid-drive vehicles having an internal combustion engine and motors and electric vehicles driven only by motors have been developed and widely used.

<CIT> (PTL <NUM>) describes a drive control device for vehicles. In this drive control device, a drive device is provided on the rear wheel side of the vehicle and two motors provided in this drive device drive the rear wheels of the vehicle, respectively. In addition to this drive device, a drive unit formed by connecting an internal combustion engine and a motor are in series is provided in the front portion of the vehicle. The power of the drive unit is transmitted to the front wheels via the transmission and the main drive shaft and the power of the drive device is transmitted to the rear wheels of the vehicle. In addition, in this drive control device, the two motors of the drive device are driven when the vehicle starts, and these driving forces are transmitted to the rear wheels of the vehicle, respectively. In addition, the driving unit also generates a driving force during acceleration of the vehicle and the four-wheel drive is achieved by the driving unit and the two motors of the drive device. As described above, in the drive control device described in PTL <NUM>, the two motors provided mainly for the rear wheels of the vehicle generate the driving forces.

<CIT> describes a method and apparatus for an all-electric vehicle using a primary drive system and a secondary drive system is provided. While the primary drive system utilizes a single electric motor, the secondary drive system utilizes a pair of electric motors.

<CIT> describes that the vehicular power output device is connected to a power transmission system to transmit the power to wheels and has power regenerative mechanisms to control the torque provided on the power transmission system.

<CIT> describes a motor drive device for a vehicle. This motor drive device for a vehicle includes a reactor also used for a vehicle-mounted coil spring for resiliently supporting a heavy load and a switching element connected with the reactor. The coil spring supports the vehicle body by mounting on a suspension arm. The motor drive device drives an in-wheel type motor IWM placed near a wheel.

<CIT> describes that the reconfigurable energy storage system comprises a first energy storage system, a second energy storage system and a power converter.

<CIT> describes that an apparatus includes a multi-channel DC bus assembly comprising a first channel and a second channel, a first electromechanical device coupled to a positive DC link of the first channel, and a second electromechanical device coupled to a positive DC link of the second channel.

<CIT> describes that the apparatus includes a series circuit for a battery and an electric storage portion, a DC/DC converter connected so as to charge and discharge the electric storage portion, a switch which is connected to the series circuit and the battery and switches to one of them, a motor connected to output of the switch through a power converter, and a control circuit connected to the DC/DC converter, the switch and the power converter.

<CIT> describes that an electric vehicle driving system includes an energy-storage apparatus, a first motor, a speed regulating motor and a single row planetary mechanism.

<CIT> describes a plug-in type power system of a hybrid electric vehicle and a controlling method thereof. The plug-in type power system of the hybrid electric vehicle comprises a front shaft driving device, a rear shaft driving device, an energy storing device and a controller.

Since the driving of a vehicle by motors does not emit carbon dioxide during a travel, emission regulations that are enhanced each year can be advantageously satisfied, but it is difficult to ensure a sufficiently long distance travel because the electric power that can be stored in the battery is limited. Accordingly, a hybrid drive device having an internal combustion engine together with motors is widely used as a drive device for vehicles. In addition, even in such a hybrid drive device, in order to reduce carbon dioxide emissions during a travel, vehicles that mainly utilize the driving forces of motors like the vehicle described in PTL <NUM> are increasing.

Such a hybrid drive device driven mainly by the driving forces of motors as described above needs to have a large capacity battery to obtain sufficient travel performance. In addition, in order to obtain a sufficient driving forces by motors, the motors need to be operated at a relatively high voltage. Accordingly, in a hybrid drive device driven mainly by the driving forces of motors, since a large capacity battery is necessary and the electrical system that supplies a high voltage to the motors needs to be electrically insulated sufficiently, the overall weight of the vehicle increases and the fuel efficiency of the vehicle reduces. Furthermore, in order to drive the vehicle with a heavy weight by the motors, a larger capacity battery and a higher voltage are required, thereby causing a vicious cycle that further increases the weight.

In addition, in the drive control device of the vehicle described in PTL <NUM>, the motors that drive the rear wheels are directly connected to the drive shafts of the rear wheels, but the motors may be built into the rear wheels to form so-called in-wheel motors. Since the drive shafts that couple the motors and the wheels are not required when using in-wheel motors, it is advantageous in that the weight of the drive shafts can be reduced. However, only use of in-wheel motors as the motors cannot obtain a sufficient driving force and cannot configure a vehicle drive device that utilizes the advantage of in-wheel motors.

For example, when in-wheel motors are driven by a constant voltage, large driving current needs to be supplied to the in-wheel motors to obtain sufficient output power. Since electric power is supplied to the in-wheel motors through wire harnesses extending from the body side to the wheels, thick wire harnesses having a large conductor cross section need to be provided to supply large current to the in-wheel motors. However, if the wire harnesses extending from the body side to the wheels are formed by conductors having a large cross section, it is difficult to obtain the flexibility and durability of the wire harnesses.

Accordingly, an object of the present invention is to provide a vehicle drive device capable of effectively driving a vehicle by using in-wheel motors without falling into the vicious cycle between enhancement of driving by motors and an increase in vehicle weight.

To solve the problem described above, according to the present invention, there is provided a vehicle drive device as defined in claim <NUM>.

In the present invention, the voltage of the battery is applied to the body side motor that drives the wheel of the vehicle and the voltage of the battery and the capacitor connected in series is applied to the in-wheel motor provided in the wheel of the vehicle.

In the present invention, since the voltage of the battery is applied to the body side motor provided in the body of the vehicle, the insulating member that electrically insulates the power supply system for supplying electric power to the body side motor can be simple when the voltage of the battery is low, thereby making the power supply system lightweight. In addition, when the body side motor is driven by a low voltage, it is difficult to obtain high output power by the body side motor, but insufficient output power can be made up for by using the in-wheel motor. Furthermore, since the driving current becomes large when the in-wheel motor is driven by a low voltage, the wire harness for supplying electric power from the body side to the in-wheel motor provided in the wheel becomes thick. When the wire harness becomes thick, it is difficult to obtain the flexibility and durability thereof. In the present invention configured as described above, since the voltage of the battery and the capacitor connected in series is applied to the in-wheel motor, the in-wheel motor can be driven by a voltage higher than in the body side motor and the wire harness does not become excessively thick. This enables the in-wheel motor to efficiently drive the vehicle.

In the present invention, preferably, a maximum inter-terminal voltage of the capacitor is higher than an inter-terminal voltage of the battery.

Since the maximum inter-terminal voltage of the capacitor is higher than the inter-terminal voltage of the battery, the in-wheel motor can be driven by a voltage sufficiently higher than in the body side motor. As a result, the driving current of the in-wheel motor can be suppressed and the load on the wire harness that supplies electric power to the in-wheel motor can be reduced sufficiently.

In the present invention, preferably, the vehicle drive device further includes a first voltage converting unit connected between the capacitor and the battery, in which the first voltage converting unit performs at least one of an operation that raises the voltage of the battery and charges the capacitor with electric power stored in the battery and an operation that lowers the voltage of the capacitor and charges the battery with electric power stored in the capacitor.

Particularly, the body side motor consumes the electric power stored in the battery and the in-wheel motor consumes the electric power stored in the battery and the capacitor. Accordingly, depending on the driving conditions of the body side motor and the in-wheel motor, the electric power stored in the battery and the capacitor may become unbalanced. Since the first voltage converting unit particularly charges the capacitor with the electric power stored in the battery or charges the battery with the electric power stored in the capacitor, the amounts of electric power stored in the battery and the capacitor can be adjusted so that electric power stored in the capacitor and the battery is used effectively.

In the present invention, preferably, the vehicle drive device further includes a second voltage converting unit connected between the battery and an electric component provided in the vehicle, in which the second voltage converting unit lowers the voltage of the battery and supplies electric power to the electric component.

Since the second voltage converting unit lowers the voltage of the battery and supplies the electric power to the electric component, the battery for driving the body side motor can be shared with the electric component provided in the vehicle, the vehicle can be made lightweight.

In the present invention, preferably, the in-wheel motor is an induction motor.

Generally, an induction motor can obtain a large output torque in the high rotation range and can be made lightweight. Accordingly, when the in-wheel motor is used so that a large torque is not requested in the low rotation range, the motor capable of generating a sufficient torque in the required rotation range can be made lightweight by adopting an induction motor as the in-wheel motor.

In the present invention, preferably, the in-wheel motor directly drives the wheel in which the in-wheel motor is provided, without intervention of a deceleration mechanism.

Since the wheel is directly driven without intervention of a deceleration mechanism, the deceleration mechanism with very heavy weight can be omitted and an output loss due to the rotation resistance of the deceleration mechanism can be avoided.

In the present invention, preferably, the in-wheel motor generates maximum output power in a high revolutions range equal to or more than a predetermined number of revolutions that is more than zero.

By using the driving force of an internal combustion engine or other motor for a travel requested for output power in the low revolutions range such as, for example, starting or a low speed travel and using the in-wheel motor for a travel requested for output power in the high revolutions range such as a high speed travel, the vehicle can be efficiently driven by using a small in-wheel motor.

In the present invention, preferably, the body side motor is a permanent magnet motor.

Generally, a permanent magnet motor has a relatively large starting torque and can obtain large output power in the low rotation range. Accordingly, when the vehicle side motor is used so that a large torque is requested in the low rotation range, the motor capable of generating a sufficient torque in the required rotation range can be made lightweight by using a permanent magnet motor as the body side motor.

The vehicle drive device according to the present invention can efficiently drive a vehicle using an in-wheel motor without causing the vicious cycle between enhancement of driving by a motor and an increase in vehicle weight.

Next, preferred embodiments of the present invention will be described with reference to the attached drawings.

<FIG> is a layout diagram illustrating a vehicle in which a hybrid drive device according to a first embodiment of the present invention is installed. <FIG> is a perspective view, as seen from the side, illustrating the front portion of a vehicle in which the hybrid drive device according to the embodiment is installed and <FIG> is a perspective view, as seen from the side, illustrating the front portion of the vehicle. <FIG> is a sectional view taken along line iv-iv in <FIG>.

As illustrated in <FIG>, a vehicle <NUM> having the hybrid drive system, which is a vehicle drive device according to the first embodiment of the present invention, is a so-called FR (front engine rear drive) vehicle in which an engine <NUM> as an internal combustion engine is installed in the front portion (in front of the driver's seat) of the vehicle and a pair of left and right rear wheels 2a as main drive wheels is driven. In addition, as described later, the rear wheels 2a are also driven by the main drive motor, which is the main drive electric motor, and a pair of left and right front wheels 2b, which are auxiliary drive wheels, is driven by the auxiliary drive motors, which are the auxiliary drive electric motors.

A hybrid drive device <NUM> according to the first embodiment of the present invention installed in the vehicle <NUM> includes the engine <NUM> that drives the rear wheels 2a, a power transmission mechanism <NUM> that transmits a driving force to the rear wheels 2a, a main drive motor <NUM> that drives the rear wheels 2a, a battery <NUM> that is an electric storage unit, auxiliary drive motors <NUM> that drive the front wheels 2b, a capacitor <NUM>, and a control device <NUM> that is a controller.

The engine <NUM> is an internal combustion engine for generating a driving force for the rear wheels 2a, which are the main drive wheels of the vehicle <NUM>. As illustrated in <FIG>, in the embodiment, an in-line <NUM>-cylinder engine is adopted as the engine <NUM> and the engine <NUM> disposed in the front portion of the vehicle <NUM> drives the rear wheels 2a via the power transmission mechanism <NUM>. In addition, as illustrated in <FIG>, in the embodiment, the engine <NUM> is a flywheel-less engine that does not include a flywheel and installed on a subframe 4a of the vehicle <NUM> via engine mounts 6a. Furthermore, the sub-frame 4a is fastened and fixed to the lower portions of front side frames 4b and the lower portion of a dash panel 4c at the rear ends thereof.

The power transmission mechanism <NUM> is configured to transmit the driving force generated by the engine <NUM> to the rear wheels 2a, which are the main drive wheels. As illustrated in <FIG>, the power transmission mechanism <NUM> includes a propeller shaft 14a connected to the engine <NUM>, a clutch 14b, and a transmission 14c, which is a stepped transmission. The propeller shaft 14a extends from the engine <NUM> disposed in the front portion of the vehicle <NUM> toward the rear of the vehicle <NUM> in a propeller shaft tunnel 4d (<FIG>). The rear end of the propeller shaft 14a is connected to the transmission 14c via the clutch 14b. The output shaft of the transmission 14c is connected to the axle shaft (not illustrated) of the rear wheels 2a and drives the rear wheels 2a.

In the embodiment, the transmission 14c is provided in so-called transaxle arrangement. As a result, since the main body of the transmission with a large outer diameter is not present immediately behind the engine <NUM>, the width of the floor tunnel (propeller shaft tunnel 4d) can be reduced, the foot space in the middle of the occupant can be obtained, and the lower body of the occupant can take a symmetrical posture that faces directly the front. Furthermore, the outer diameter and the length of the main drive motor <NUM> can easily have sufficient sizes according to the output power thereof while keeping this posture of the occupant.

The main drive motor <NUM> is an electric motor for generating a driving force for the main drive wheels, provided on the body of the vehicle <NUM>, disposed behind the engine <NUM> adjacently to the engine <NUM>, and functions as a body side motor. In addition, an inverter (INV) 16a is disposed adjacently to the main drive motor <NUM> and the inverter 16a converts the current from the battery <NUM> into alternating current and supplies the alternating current to the main drive motor <NUM>. Furthermore, as illustrated in <FIG> and <FIG>, the main drive motor <NUM> is connected in series to the engine <NUM> and the driving force generated by the main drive motor <NUM> is also transmitted to the rear wheels 2a via the power transmission mechanism <NUM>. Alternatively, the present invention may be configured so that the driving force is transmitted to the rear wheels 2a via a part of the power transmission mechanism <NUM> by connecting the main drive motor <NUM> to an intermediate point of the power transmission mechanism <NUM>. In addition, the embodiment adopts, as the main drive motor <NUM>, a <NUM> kW permanent magnet motor (permanent magnet synchronous motor) driven by <NUM> V.

The battery <NUM> is an electric storage unit that stores electric power for mainly operating the main drive motor <NUM>. In addition, as illustrated in <FIG>, the battery <NUM> is disposed inside the propeller shaft tunnel 4d so as to surround the torque tube 14d that covers the propeller shaft 14a in the embodiment. Furthermore, in the embodiment, a <NUM> V <NUM> kWh lithium ion battery (LIB) is used as the battery <NUM>.

Since the transaxle arrangement is adopted in the embodiment as described above, the volume for accommodating the battery <NUM> can be expanded toward the space in front of the floor tunnel (propeller shaft tunnel 4d) created by this arrangement. This can obtain and expand the capacity of the battery <NUM> without reducing the space in the middle of the occupant by increasing the width of the floor tunnel.

As illustrated in <FIG>, the auxiliary drive motors <NUM> are provided in the front wheels 2b under the springs of the vehicle <NUM> so as to generate driving forces for the front wheels 2b, which are the auxiliary drive wheels. In the embodiment, the front wheel 2b is supported by a double wishbone type suspension and is suspended by an upper arm 8a, a lower arm 8b, a spring 8c, and a shock absorber 8d. The auxiliary drive motors <NUM> are in-wheel motors and are housed in the wheels of the front wheels 2b. Accordingly, the auxiliary drive motors <NUM> are provided in the so-called "under-spring portions" of the vehicle <NUM> so as to drive the front wheels 2b. In addition, as illustrated in <FIG>, the current from the capacitor (CAP) <NUM> is converted into alternating current by inverters 20a and supplied to the auxiliary drive motors <NUM>. Furthermore, in the embodiment, the auxiliary drive motors <NUM> are not provided with deceleration machines that are deceleration mechanisms, the driving forces of the auxiliary drive motors <NUM> are directly transmitted to the front wheels 2b, and the wheels are directly driven. In addition, in the embodiment, 17kW induction motors are adopted as the auxiliary drive motors <NUM>.

The capacitor (CAP) <NUM> is provided so as to store the electric power regenerated by the auxiliary drive motors <NUM>. As illustrated in <FIG> and <FIG>, the capacitor <NUM> is disposed immediately in front of the engine <NUM> and supplies electric power to the auxiliary drive motors <NUM> provided in the front wheels 2b of the vehicle <NUM>. As illustrated in <FIG>, in the capacitor <NUM>, brackets 22a projecting from both side surfaces thereof are supported by the front side frames 4b via a capacitor mount 6b. In addition, a harness 22b extending from the auxiliary drive motor <NUM> to the capacitor <NUM> passes through the upper end of the side wall of the wheel house and is led to the engine room. In addition, the capacitor <NUM> is configured to store electric charge at a voltage higher than in the battery <NUM> and is disposed in a region between the left and right front wheels 2b, which are the auxiliary drive wheels. The auxiliary drive motors <NUM>, which are driven mainly by the electric power stored in the capacitor <NUM>, are driven by a voltage higher than in the main drive motor <NUM>.

The control device <NUM> controls the engine <NUM>, the main drive motor <NUM>, and the auxiliary drive motors <NUM> to execute a motor travel mode and an internal combustion engine travel mode. Specifically, the control device <NUM> can include a microprocessor, a memory, an interface circuit, a program for operating these components (these components are not illustrated), and the like. Details on control by the control device <NUM> will be described later.

In addition, as illustrated in <FIG>, a high voltage DC/DC converter 26a and a low voltage DC/DC converter 26b, which are voltage converting units, are disposed near the capacitor <NUM>. The high voltage DC/DC converter 26a, the low voltage DC/DC converter 26b, the capacitor <NUM>, and the two inverters 20a are unitized to form an integrated unit.

Next, the overall structure, the power supply structure, and the driving of the vehicle <NUM> by the individual motors in the hybrid drive device <NUM> according to the first embodiment of the present invention will be described with reference to <FIG>.

<FIG> is a block diagram illustrating the inputs and outputs of various signals in the hybrid drive device <NUM> according to the first embodiment of the present invention. <FIG> is a block diagram illustrating the power supply structure of the hybrid drive device <NUM> according to the first embodiment of the present invention. <FIG> is a diagram schematically illustrating one example of changes in voltages when electric power is regenerated into the capacitor <NUM> in the hybrid drive device <NUM> according to the embodiment. <FIG> is a diagram illustrating the relationship between the output power of the motors used in the hybrid drive device <NUM> according to the embodiment and the vehicle speed.

First, the inputs and outputs of various signals in the hybrid drive device <NUM> according to the first embodiment of the present invention will be described. As illustrated in <FIG>, the control device <NUM> receives the detection signals detected by a mode selection switch <NUM>, a vehicle speed sensor <NUM>, an accelerator position sensor <NUM>, a brake sensor <NUM>, an engine RPM sensor <NUM>, an automatic transmission (AT) input rotation sensor <NUM>, an automatic transmission (AT) output rotation sensor <NUM>, a voltage sensor <NUM>, and a current sensor <NUM>. In addition, the control device <NUM> controls the inverter 16a for the main drive motor, the inverters 20a for the auxiliary drive motors <NUM>, the high voltage DC/DC converter 26a, the low voltage DC/DC converter 26b, a fuel injection valve <NUM>, a spark plug <NUM>, and a hydraulic solenoid valve <NUM> of the transmission 14c by control signals to these components.

Next, the power supply structure of the hybrid drive device <NUM> according to the first embodiment of the present invention will be described. As illustrated in <FIG>, the battery <NUM> and capacitor <NUM> included in the hybrid drive device <NUM> are connected in series to each other. The main drive motor <NUM> is driven by approximately <NUM> V, which is the reference output voltage of the battery <NUM>, and the auxiliary drive motors <NUM> are driven by a maximum voltage of <NUM> V, which is the sum of the output voltage of the battery <NUM> and the output voltage (inter-terminal voltage) of the capacitor <NUM>. That is, the maximum inter-terminal voltage of the capacitor <NUM> is <NUM> V in the embodiment. Therefore, the auxiliary drive motors <NUM> are always driven by the electric power supplied via the capacitor <NUM>.

In addition, the inverter 16a is mounted to the main drive motor <NUM> and converts the output of the battery <NUM> into alternating current through which the main drive motor <NUM>, which is a permanent magnet motor, is driven. Similarly, the inverters 20a are mounted to the auxiliary drive motors <NUM> and convert the outputs of the battery <NUM> and the capacitor <NUM> into alternating current through which the auxiliary drive motors <NUM>. which are induction motors, are driven. Since the auxiliary drive motors <NUM> are driven by a voltage higher than in the main drive motor <NUM>, high insulation is necessary for the harnesses (electric wires) 22b through which electric power is supplied to the auxiliary drive motors <NUM>. However, since the capacitor <NUM> is disposed close to the auxiliary drive motors <NUM>, an increase in the weight due to high insulation of the harnesses 22b can be minimized.

Furthermore, when, for example, the vehicle <NUM> decelerates, the main drive motor <NUM> and the auxiliary drive motors <NUM> function as generators and generate electric power by regenerating the kinetic energy of the vehicle <NUM>. The electric power regenerated by the main drive motor <NUM> is stored in the battery <NUM> and the electric power regenerated by the auxiliary drive motors <NUM> is stored mainly in the capacitor <NUM>.

In addition, the high voltage DC/DC converter 26a, which is the first voltage converting unit, is connected between the battery <NUM> and the capacitor <NUM> and this high voltage DC/DC converter 26a charges the capacitor <NUM> by raising the voltage of the battery <NUM> when the electric charge stored in the capacitor <NUM> is insufficient (when the inter-terminal voltage of the capacitor <NUM> drops). In contrast, when the inter-terminal voltage of the capacitor <NUM> rises to a predetermined voltage or higher due to regeneration of energy by the auxiliary drive motors <NUM>, the battery <NUM> is charged by reducing the electric charge stored in the capacitor <NUM> and applying the electric charge to the battery <NUM>. That is, the electric power regenerated by the auxiliary drive motors <NUM> is stored in the capacitor <NUM>, and then the battery <NUM> is charged with a part of the stored electric charge via the high voltage DC/DC converter 26a.

Furthermore, the low voltage DC/DC converter 26b, which is the second voltage converting unit, is connected between the battery <NUM> and 12V electric components <NUM> of the vehicle <NUM>. Since many of the control device <NUM> of the hybrid drive device <NUM> and the electric components <NUM> of the vehicle <NUM> operate at a voltage of 12V, the voltage of the electric charge stored in the battery <NUM> is reduced to 12V by the low voltage DC/DC converter 26b and supplied to these devices.

Next, charging and discharging of the capacitor <NUM> will be described with reference to <FIG>.

As illustrated in <FIG>, the voltage of the capacitor <NUM> is the sum of the base voltage of the battery <NUM> and the inter-terminal voltage of the capacitor <NUM> itself. When, for example, the vehicle <NUM> decelerates, the auxiliary drive motors <NUM> regenerate electric power and the capacitor <NUM> is charged with the regenerated electric power. When the capacitor <NUM> is charged, the inter-terminal voltage rises relatively rapidly. When the inter-terminal voltage of the capacitor <NUM> rises to a predetermined voltage or more due to the charging, the voltage of the capacitor <NUM> is reduced by the high voltage DC/DC converter 26a and the battery <NUM> is charged. As illustrated in <FIG>, the charging to the battery <NUM> from the capacitor <NUM> is performed relatively slowly than the charging to the capacitor <NUM> and the voltage of the capacitor <NUM> drops to a proper voltage relatively slowly.

That is, the electric power regenerated by the auxiliary drive motors <NUM> is temporarily stored in the capacitor <NUM> and then the battery <NUM> is slowly charged with the regenerated electric power. Depending on the time when the regeneration is performed, the regeneration of electric power by the auxiliary drive motors <NUM> may overlap with the charging from the capacitor <NUM> to the battery <NUM>.

In contrast, the battery <NUM> is directly charged with the electric power regenerated by the main drive motor <NUM>.

Next, the relationship between the vehicle speed and the output power of the motors in the hybrid drive device <NUM> according to the first embodiment of the present invention will be described with reference to <FIG> is a graph illustrating the relationship between the speed of the vehicle <NUM> and the output power of the motors in the hybrid drive device <NUM> according to the embodiment. In <FIG>, the output power of the main drive motor <NUM> is represented by a dotted line, the output power of one of the auxiliary drive motors <NUM> is represented by a dot-dash line, the sum of the output power of the two auxiliary drive motors <NUM> is represented by a dot-dot-dash line, and the sum of the output power of all motors is represented by a solid line. Although <FIG> illustrates the speed of the vehicle <NUM> on the horizontal axis and the output power of the motors on the vertical axis, since there is a certain relationship between the speed of the vehicle <NUM> and the number of revolutions of each of the motors, the output power of the motors draws curves similar to those in <FIG> even when the number of revolutions of each of the motors is represented on the horizontal axis.

Since a permanent magnet motor is adopted as the main drive motor <NUM> in the embodiment, as represented by the dotted line in <FIG>, the output power of the main drive motor <NUM> is large in a low vehicle speed range in which the number of revolutions of the motor is low and the motor output power that can be output reduces as the vehicle speed increases. That is, in the embodiment, the main drive motor <NUM> is driven by approximately <NUM> V, outputs a torque (maximum torque) of approximately <NUM> up to approximately <NUM> rpm, and the torque reduces with the increase in the number of revolutions at approximately <NUM> rpm or more. In addition, in the embodiment, the main drive motor <NUM> is configured to obtain a continuous output power of approximately <NUM> kW and a maximum output power of approximately <NUM> kW in the lowest low speed range.

In contrast, since induction motors are used as the auxiliary drive motors <NUM>, the output power of the auxiliary drive motors <NUM> is very small in the low vehicle speed range, the output power increases as the speed becomes higher, the maximum output power is obtained at a vehicle speed close to <NUM>/h or so, and then the motor output power reduces, as represented by the dot-dash line and the dot-dot-dash line in <FIG>. In the embodiment, the auxiliary drive motors <NUM> are driven by approximately <NUM> V, and each of them obtains an output power of approximately <NUM> kW and the two motors obtain a total output power of approximately <NUM> kW at a vehicle speed close to <NUM>/h or so. That is, in the embodiment, each of the auxiliary drive motors <NUM> has a peak of the torque curve and obtains a maximum torque of approximately <NUM> at approximately <NUM> to <NUM> rpm.

As described above, the auxiliary drive motors <NUM>, which are the in-wheel motors, generate the maximum output power in the high revolutions range equal to or more than the predetermined number of revolutions that is more than zero and the main drive motor <NUM>, which is the body side motor, generates the maximum output power in the low revolutions range less than the predetermined number of revolutions. For example, the auxiliary drive motors <NUM> preferably generate the maximum output power in the high revolutions range equal to or more than approximately <NUM> rpm.

The solid line in <FIG> represents the sum of the output power of the main drive motor <NUM> and the two auxiliary drive motors <NUM>. As is clear from this graph, in the embodiment, a maximum output power of approximately <NUM> kW is obtained at a vehicle speed close to <NUM>/h or so and the travel condition requested in the WLTP test at this vehicle speed is satisfied at this maximum output power. In addition, although the output power values of the two auxiliary drive motors <NUM> are summed up even in the low vehicle speed range as represented by the solid line in <FIG>, the auxiliary drive motors <NUM> are actually not driven in the low vehicle speed range as described later. That is, the vehicle is driven only by the main drive motor <NUM> at startup and in a low vehicle speed range and the two auxiliary drive motors <NUM> generate output power only when large output power is required in the high vehicle speed range (for example, when the vehicle <NUM> is accelerated in the high vehicle speed range). By using the induction motors (auxiliary drive motors <NUM>) capable of generating large output power in the high revolutions range only in the high speed range as described above, sufficient output power can be obtained when necessary (for example, when acceleration at a predetermined speed or more is performed) while an increase in vehicle weight is kept low.

Next, the structure of the auxiliary drive motors <NUM> adopted in the hybrid drive device <NUM> according to the first embodiment of the present invention will be described with reference to <FIG> is a sectional view schematically illustrating the structure of the auxiliary drive motor <NUM>.

As illustrated in <FIG>, the auxiliary drive motor <NUM> is an outer rotor type induction motor including a stator <NUM> and a rotor <NUM> that rotates around this stator.

The stator <NUM> includes a substantially discoid stator base 28a, a stator shaft 28b extending from the center of the stator base 28a, and a stator coil 28c attached around the stator shaft 28b. In addition, the stator coil 28c is housed in an electrical insulating liquid chamber <NUM>, immersed in electrical insulating liquid 32a that fills the electrical insulating liquid chamber, and subject to boiling cooling via the liquid.

The rotor <NUM> is formed in a substantially cylindrical shape so as to surround the periphery of the stator <NUM> and has a substantially cylindrical rotor body 30a with one end closed and a rotor coil 30b disposed on the inner peripheral wall surface of the rotor body 30a. The rotor coil 30b is disposed facing the stator coil 28c so as to generate induction current by the rotational magnetic field generated by the stator coil 28c. In addition, the rotor <NUM> is supported by a bearing <NUM> attached to the end of the stator shaft 28b so as to rotate smoothly around the stator <NUM>.

The stator base 28a is supported by an upper arm 8a and a lower arm 8b (<FIG>) that suspend the front wheels of the vehicle <NUM>. In contrast, the rotor body 30a is directly fixed to the wheels of the front wheels 2b (not illustrated). Alternating current converted by the inverters 20a flows through the stator coil 28c and generates a rotational magnetic field. This rotational magnetic field causes an induced current to flow through the rotor coil 30b and generates a driving force that rotates the rotor body 30a. As described above, the driving forces generated by the auxiliary drive motors <NUM> rotationally drive the wheels of the front wheels 2b (not illustrated) directly.

Next, the operation of the motor travel mode and the operation of the internal combustion engine travel mode performed by the control device <NUM> will be described with reference to <FIG> and <FIG>. <FIG> is a flowchart illustrating control by the control device <NUM> and <FIG> is a graph illustrating examples of the operations of these modes. The flowchart illustrated in <FIG> is repeatedly executed at predetermined time intervals while the vehicle <NUM> operates.

The graph illustrated in <FIG> represents, in order from the top, the speed of the vehicle <NUM>, the torque generated by the engine <NUM>, the torque generated by the main drive motor <NUM>, the torque generated by the auxiliary drive motors <NUM>, the voltage of the capacitor <NUM>, the current of the capacitor <NUM>, and the current of the battery <NUM>. In the graph representing the torque of the main drive motor <NUM> and the torques of the auxiliary drive motors <NUM>, positive values mean the state in which motors generate torques and negative values mean the state in which motors regenerate the kinetic energy of the vehicle <NUM>. In addition, in the graph representing the current of the capacitor <NUM> and the current of the battery <NUM>, negative values mean the state in which electric power is supplied (discharged) to motors and positive values mean the state of charging with the electric power regenerated by motors.

First, in step S1 in <FIG>, it is determined whether the vehicle <NUM> has been set to the internal combustion engine travel mode (ENG mode). That is, the vehicle <NUM> has the mode selection switch <NUM> (<FIG>) that selects either the internal combustion engine travel mode or the motor travel mode (EV mode) and it is determined in step S1 which mode has been set. Since the motor travel mode is set at time t<NUM> in <FIG>, the processing of the flowchart in <FIG> proceeds to step S2.

Next, in step S2, it is determined whether the speed of the vehicle <NUM> is equal to or more than a predetermined vehicle speed. The processing proceeds to step S6 when the speed is equal to or more than the predetermined vehicle speed or the processing proceeds to step S3 when the speed is less than the predetermined vehicle speed. Since the driver has started the vehicle <NUM> and the vehicle speed is low at time t<NUM> in <FIG>, the processing of the flowchart proceeds to step S3.

Furthermore, in step S3, it is determined whether the vehicle <NUM> is decelerating (whether the brake pedal (not illustrated) of the vehicle <NUM> is being operated). The processing proceeds to step S5 when the vehicle <NUM> is decelerating or the processing proceeds to step S4 when the vehicle <NUM> is accelerating or traveling at a constant speed (when the brake sensor <NUM> (<FIG>) does not detect the operation of the brake pedal). Since the driver has started the vehicle <NUM> and is accelerating the vehicle <NUM> (accelerator position sensor <NUM> (<FIG>) has detected that the accelerator pedal of the vehicle <NUM> has been operated by a predetermined amount or more) at time t<NUM> in <FIG>, the processing of the flowchart proceeds to step S4 and the processing of the flowchart in <FIG> is completed once. In step S4, the main drive motor <NUM> generates a torque and the vehicle speed increases (from time t<NUM> to time t<NUM> in <FIG>). At this time, since discharge current flows from the battery <NUM> that supplies electric power to the main drive motor <NUM> and discharge current from the capacitor <NUM> remains zero because the auxiliary drive motors <NUM> do not generate torques, the voltage of the capacitor <NUM> does not change. The current and voltage are detected by the voltage sensor <NUM> and the current sensor <NUM> (<FIG>) and input to the control device <NUM>. In addition, from time t<NUM> to time t<NUM> in <FIG>, the engine <NUM> is not driven because the motor travel mode is set. That is, since the control device <NUM> stops fuel injection via the fuel injection valve <NUM> of the engine <NUM> and does not perform ignition via the ignition plug <NUM>, the engine <NUM> does not generate a torque.

In the example illustrated in <FIG>, the vehicle <NUM> accelerates from time t<NUM> to time t<NUM> and then travels at a constant speed until time t<NUM>. In this period, the processing of steps S1, S2, S3, and S4 in the flowchart in <FIG> is repeatedly executed. During this low speed travel, the torque generated by the main drive motor <NUM> becomes smaller than the torque during the acceleration, the current discharged from the battery <NUM> also becomes smaller.

Next, when the driver operates the brake pedal (not illustrated) of the vehicle <NUM> at time t<NUM> in <FIG>, the processing of the flowchart in <FIG> proceeds to step S5 from step S3. In step S5, the driving by the main drive motor <NUM> is stopped (no torque is generated) and the kinetic energy of the vehicle <NUM> is regenerated as electric power by the auxiliary drive motors <NUM>. The vehicle <NUM> is decelerated by the regeneration of the kinetic energy, the discharge current from battery <NUM> becomes zero, the charge current flows through the capacitor <NUM> because the electric power is regenerated by the auxiliary drive motors <NUM>, and the voltage of the capacitor <NUM> rises.

When the vehicle <NUM> stops at time t<NUM> in <FIG>, the charge current to the capacitor <NUM> becomes zero and the voltage of the capacitor <NUM> also becomes constant. Next, the vehicle <NUM> is started again at time t<NUM> and reaches a constant speed travel (time t<NUM>), and the processing of steps S1, S2, S3, and S4 in the flowchart in <FIG> is repeatedly executed until the deceleration of the vehicle <NUM> is started (time t<NUM>). When the deceleration of the vehicle is started at time t<NUM>, the processing of steps S1, S2, S3, and S5 in the flowchart in <FIG> is repeatedly executed and the auxiliary drive motors <NUM> regenerate electric power. As described above, the motor travel mode is set while the vehicle starts and stops repeatedly at a relatively low speed in urban areas or the like, the vehicle <NUM> functions purely as an electric vehicle (EV) and the engine <NUM> does not generate a torque.

Furthermore, when the vehicle <NUM> is started at time t<NUM> in <FIG>, the processing of steps S1, S2, S3, and S4 in the flowchart in <FIG> is repeatedly executed and the vehicle <NUM> is accelerated. Next, when the speed of the vehicle <NUM> detected by the vehicle speed sensor <NUM> (<FIG>) exceeds a predetermined first vehicle speed at time t<NUM>, the processing of the flowchart proceeds to step S6 from step S2. In step S6, it is determined whether the vehicle <NUM> is decelerating (the brake pedal is being operated). Since the vehicle <NUM> is not decelerating at time t<NUM>, the processing of the flowchart proceeds to step S7. In step S7, it is determined whether the vehicle <NUM> is accelerating by a predetermined value or more (whether the accelerator pedal of the vehicle <NUM> has been operated by a predetermined amount or more). In the embodiment, the predetermined first vehicle speed is set to approximately <NUM>/h, which is more than a travel speed of <NUM>/h.

Since the vehicle <NUM> is accelerating by a predetermined value or more at time t<NUM> in the example illustrated in <FIG>, the processing proceeds to step S8, in which the main drive motor <NUM> is driven and the auxiliary drive motors <NUM> are also driven. When the vehicle <NUM> is accelerated by a predetermined value or more at the predetermined first vehicle speed or more in the motor travel mode as described above, electric power is supplied to the main drive motor <NUM> and the auxiliary drive motors <NUM> to obtain the required power, and this drives the vehicle <NUM>. In other words, the control device <NUM> starts the vehicle <NUM> (time t<NUM>) by causing the main drive motor <NUM> to generate a driving force and then causes the auxiliary drive motors <NUM> to generate driving forces when the travel speed of the vehicle <NUM> detected by the vehicle speed sensor <NUM> reaches the first vehicle speed (time t<NUM>). At this time, the battery <NUM> supplies electric power to the main drive motor <NUM> and the capacitor <NUM> supplies electric power to the auxiliary drive motors <NUM>. Since the capacitor <NUM> supplies electric power as described above, the voltage of the capacitor <NUM> drops. While the vehicle <NUM> is driven by the main drive motor <NUM> and the auxiliary drive motors <NUM> (from time t<NUM> to time t<NUM>), the processing of steps S1, S2, S6, S7, and S8 in the flowchart is repeatedly executed.

As described above, the auxiliary drive motors <NUM> generate driving forces when the travel speed of the vehicle <NUM> is equal to or more than the predetermined first vehicle speed and are prohibited from generating driving forces when the travel speed is less than the first vehicle speed. Although the first vehicle speed is set to approximately <NUM>/h in the embodiment, the first vehicle speed may be set to any vehicle speed that is equal to or more than approximately <NUM>/h according to the output characteristics of the adopted auxiliary drive motors <NUM>. In contrast, the main drive motor <NUM> generates a driving force when the travel speed of the vehicle <NUM> is less than a predetermined second vehicle speed including zero or when the travel speed is equal to or more than the second vehicle speed. The predetermined second vehicle speed may be set to a vehicle speed identical to or different from the first vehicle speed. In addition, in the embodiment, the main drive motor <NUM> always generates a driving force when the driving force is requested in the motor travel mode.

Next, when the vehicle <NUM> shifts to a constant speed travel (when the accelerator pedal is operated by less than a predetermined amount) at time t<NUM> in <FIG>, the processing of steps S1, S2, S6, S7, and S9 in the flowchart is repeatedly executed. In step S9, driving by the auxiliary drive motors <NUM> is stopped (no torque is generated) and the vehicle <NUM> is driven only by the main drive motor <NUM>. Even when the vehicle <NUM> travels at the predetermined vehicle speed or more, the vehicle <NUM> is driven only by the main drive motor <NUM> if the acceleration is less than the predetermined amount.

In addition, since the voltage of the capacitor <NUM> drops to the predetermined value or less because the capacitor <NUM> has driven the auxiliary drive motors <NUM> from time t<NUM> to time t<NUM>, the control device <NUM> sends a signal to the high voltage DC/DC converter 26a at time t<NUM> to charge the capacitor <NUM>. That is, the high voltage DC/DC converter 26a raises the voltage of the electric charge stored in the battery <NUM> and charges the capacitor <NUM>. This causes the current for driving the main drive motor <NUM> and the current for charging the capacitor <NUM> to be discharged from the battery <NUM> from time t<NUM> to time t<NUM> in <FIG>. If large electric power is regenerated by the auxiliary drive motors <NUM> and the voltage of the capacitor <NUM> rises to a predetermined value or more, the control device <NUM> sends a signal to the high voltage DC/DC converter 26a to reduce the voltage of the capacitor <NUM> and charges the battery <NUM>. As described above, the electric power regenerated by the auxiliary drive motors <NUM> is consumed by the auxiliary drive motors <NUM>, or stored in the capacitor <NUM> and then used to charge the battery <NUM> via the high voltage DC/DC converter 26a.

When the vehicle <NUM> decelerates (the brake pedal is operated) at time t<NUM> in <FIG>, the processing of steps S1, S2, S6, and S10 in the flowchart will be repeatedly executed. In step S10, the kinetic energy of the vehicle <NUM> is regenerated as electric power by both the main drive motor <NUM> and the auxiliary drive motors <NUM>. The electric power regenerated by the main drive motor <NUM> is stored in the battery <NUM> and the electric power regenerated by the auxiliary drive motors <NUM> is stored in the capacitor <NUM>. As described above, when the brake pedal is operated at the specified vehicle speed or more, electric power is regenerated by both the main drive motor <NUM> and the auxiliary drive motors <NUM> and electric charge is stored in the capacitor <NUM> and the battery <NUM>.

Next, at time t<NUM> in <FIG>, the driver switches the mode of the vehicle <NUM> from the motor travel mode to the internal combustion engine travel mode by operating the mode selection switch <NUM> (<FIG>) and depresses the accelerator pedal (not illustrated). When the mode of the vehicle <NUM> is switched to the internal combustion engine travel mode, the processing of the flowchart in <FIG> by the control device <NUM> proceeds to step S11 from step S1, and the processing of step S11 and subsequent steps is executed.

First, in step S11, it is determined whether the vehicle <NUM> stops. When the vehicle <NUM> does not stop (the vehicle <NUM> is traveling), it is determined in step S12 whether the vehicle <NUM> is decelerating (whether the brake pedal (not illustrated) is being operated). Since the vehicle <NUM> is traveling and the driver is operating the accelerator pedal at time t<NUM> in <FIG>, the processing of the flowchart in <FIG> proceeds to step S13.

In step S13, the supply of fuel to the engine <NUM> starts and the engine <NUM> generates a torque. That is, since the output shaft (not illustrated) of the engine <NUM> is directly connected to the output shaft (not illustrated) of the main drive motor <NUM> in the embodiment, the output shaft of the engine <NUM> always rotates together with driving by the main drive motor <NUM>. However, the engine <NUM> does not generate a torque in the motor travel mode because fuel supply to the engine <NUM> is performed, but, in the internal combustion engine travel mode, the engine <NUM> generates a torque because fuel supply (fuel injection by the fuel injection valve <NUM> and ignition by the ignition plug <NUM>) starts.

In addition, immediately after switching from the motor travel mode to the internal combustion engine travel mode, the control device <NUM> causes the main drive motor <NUM> to generate a torque for starting the engine (from time t<NUM> to time t<NUM> in <FIG>). This torque for starting the engine is generated to cause the vehicle <NUM> to travel until the engine <NUM> actually generates a torque after fuel supply to the engine <NUM> is started and suppress torque fluctuations before and after the engine <NUM> generates a torque. In addition, in the embodiment, when the number of revolutions of the engine <NUM> at the time of switching to the internal combustion engine travel mode is less than a predetermined number of revolutions, fuel supply to the engine <NUM> is not started and the fuel supply is started when the number of revolutions of the engine <NUM> is equal to or more than the predetermined number of revolutions due to the torque for starting the engine. In the embodiment, when the number of revolutions of the engine <NUM> detected by the engine RPM sensor <NUM> rises to <NUM> rpm or more, fuel supply is started.

While the vehicle <NUM> accelerates or travels at a constant speed after the engine <NUM> is started, the processing of steps S1, S11, S12, and S13 in the flowchart in <FIG> is repeatedly executed (from time t<NUM> to time t<NUM> in <FIG>). As described above, in the internal combustion engine travel mode, the engine <NUM> exclusively outputs the power for driving the vehicle <NUM> and the main drive motor <NUM> and the auxiliary drive motors <NUM> do not output the power for driving the vehicle <NUM>. Accordingly, the driver can enjoy the driving feeling of the vehicle <NUM> driven by the internal combustion engine.

Next, when the driver operates the brake pedal (not illustrated) at time t<NUM> in <FIG>, the processing of the flowchart in <FIG> proceeds to step S14 from step S12. In step S14, fuel supply to the engine <NUM> is stopped and fuel consumption is suppressed. Furthermore, in step S15, the main drive motor <NUM> and the auxiliary drive motors <NUM> regenerate the kinetic energy of the vehicle <NUM> as electric energy and charge current flows through the battery <NUM> and the capacitor <NUM>. As described above, during deceleration of the vehicle <NUM>, the processing of steps S1, S11, S12, S14, and S15 is repeatedly executed (from time t<NUM> to time t<NUM> in <FIG>).

During deceleration of the vehicle <NUM> in the internal combustion engine travel mode, the control device <NUM> performs downshift torque adjustment by driving the auxiliary drive motors <NUM> in switching (shifting) of the transmission 14c, which is a stepped transmission. The torque generated by this torque adjustment complements an instantaneous torque drop or the like and is not equivalent to the torque that drives the vehicle <NUM>. Details on torque adjustment will be described later.

On the other hand, when the vehicle <NUM> stops at time t<NUM> in <FIG>, the processing of the flowchart in <FIG> proceeds to step S16 from step S11. In step S16, the control device <NUM> supplies the minimum fuel required to maintain the idling of the engine <NUM>. In addition, the control device <NUM> generates an assist torque via the main drive motor <NUM> so that the engine <NUM> can maintain idling at a low number of revolutions. As described above, while the vehicle <NUM> stops, the processing of steps S1, S11, and S16 is repeatedly executed (from time t<NUM> to time t<NUM> in <FIG>).

Although the engine <NUM> is a flywheel-less engine in the embodiment, since the assist torque generated by the main drive motor <NUM> acts as a pseudo flywheel, the engine <NUM> can maintain smooth idling at a low number of revolutions. In addition, adoption of a flywheel-less engine makes the response of the engine <NUM> high during a travel in the internal combustion engine travel mode, thereby enabling driving with a good feeling.

In addition, when the vehicle <NUM> starts from a stop state in the internal combustion engine travel mode, the control device <NUM> increases the number of revolutions of the main drive motor <NUM> (the number of revolutions of the engine <NUM>) to a predetermined number of revolutions by sending a signal to the main drive motor <NUM>. After the number of revolutions of the engine is increased to the predetermined number of revolutions, the control device <NUM> supplies the engine <NUM> with fuel for driving the engine, causes the engine <NUM> to perform driving, and performs a travel in the internal combustion engine travel mode.

Next, torque adjustment during switching (shifting) of the transmission 14c will be described with reference to <FIG>.

<FIG> is a diagram that schematically illustrates changes in the acceleration that acts on the vehicle when transmission 14c downshifts or upshifts, and represents, in order from the top, examples of downshift torque down, downshift torque assistance, and upshift torque assistance.

In the internal combustion engine travel mode, the hybrid drive device <NUM> according to the first embodiment of the present invention causes the control device <NUM> to automatically switch the clutch 14b and the transmission 14c, which is an automatic transmission, according to the vehicle speed and the number of revolutions of the engine when the automatic shift mode is set. As illustrated in the upper part of <FIG>, when the transmission 14c downshifts (shifts to a low speed) with negative acceleration acting on the vehicle <NUM> during deceleration (time t<NUM> in <FIG>), the control device <NUM> disconnects the clutch 14b to disconnect the output shaft of the engine <NUM> from the main drive wheels (rear wheels 2a). When the engine <NUM> is disconnected from the main drive wheels in this way, since the rotation resistance of the engine <NUM> no longer acts on the main drive wheels, the acceleration acting on the vehicle <NUM> instantaneously changes to a positive side, as indicated by the dotted line in the upper part of <FIG>. Next, the control device <NUM> sends a control signal to the transmission 14c and switches the built-in hydraulic solenoid valve <NUM> (<FIG>) to increase the reduction ratio of the transmission 14c. Furthermore, when the control device <NUM> connects the clutch 14b at time t<NUM> at which the downshift is completed, the acceleration changes to a negative side again. Although the period from the start to the completion of a downshift (from time t<NUM> to time t<NUM>) is generally <NUM> to <NUM> msec, the occupant is given an idle running feeling and may have a discomfort feeling due to a so-called torque shock in which the torque acting on the vehicle instantaneously changes.

In the hybrid drive device <NUM> according to the embodiment, the control device <NUM> makes torque adjustment by sending a control signal to the auxiliary drive motors <NUM> at the time of a downshift to suppress the idle running feeling of the vehicle <NUM>. Specifically, when the control device <NUM> performs a downshift by sending a signal to the clutch 14b and the transmission 14c, the control device <NUM> reads the number of revolutions of the input shaft and the number of revolutions of the output shaft of the transmission 14c detected by the automatic transmission input rotation sensor <NUM> and the automatic transmission output rotation sensor <NUM> (<FIG>), respectively. Furthermore, the control device <NUM> predicts changes in the acceleration generated in the vehicle <NUM> based on the number of revolutions of the input shaft and the number of revolutions of the output shaft that have been read and causes the auxiliary drive motors <NUM> to regenerate energy. This suppresses an instantaneous rise in the acceleration (change to the positive side) of the vehicle <NUM> due to a torque shock as indicated by the solid line in the upper part of <FIG>, thereby suppressing an idling running feeling. Furthermore, in the embodiment, the torque shock in the main drive wheels (rear wheels 2a) caused by a downshift is complemented by the auxiliary drive wheels (front wheels 2b) via the auxiliary drive motors <NUM>. Accordingly, torque adjustment can be made without being affected by the dynamic characteristics of the power transmission mechanism <NUM> that transmits power from the engine <NUM> to the main drive wheels.

In addition, as indicated by the dotted line in the middle part of <FIG>, when a downshift is started at time t<NUM> with positive acceleration acting on the vehicle <NUM> during acceleration, the output shaft of the engine <NUM> is disconnected from the main drive wheels (rear wheels 2a). Accordingly, since the drive torque by the engine <NUM> does not act on the rear wheels 2a and a torque shock occurs, the occupant may be given a stall feeling by the time the downshift is completed at time t<NUM>. That is, the acceleration of the vehicle <NUM> instantaneously changes to the negative side at time t<NUM> at which a downshift is started and the acceleration changes to the positive side at time t<NUM> at which the downshift is completed.

In the hybrid drive device <NUM> according to the embodiment, when performing a downshift, the control device <NUM> predicts changes in the acceleration caused in the vehicle <NUM> based on detection signals from the automatic transmission input rotation sensor <NUM> and the automatic transmission output rotation sensor <NUM> and causes the auxiliary drive motors <NUM> to generate driving forces. As indicated by the solid line in the middle part of <FIG>, this suppresses an instantaneous drop (change to the negative side) of the acceleration of the vehicle <NUM> by a torque shock and suppresses a stall feeling.

Furthermore, as indicated by the dotted line in the lower part of <FIG>, when an upshift is started at time t<NUM> with positive acceleration acting on the vehicle <NUM> (positive acceleration reduces with time) during acceleration, the output shaft of the engine <NUM> is disconnected from the main drive wheels (rear wheels 2a). Accordingly, since the drive torque by the engine <NUM> does not act on the rear wheels 2a and a torque shock occurs, the occupant may be given a stall feeling by the time the upshift is completed at time t<NUM>. That is, the acceleration of the vehicle <NUM> instantaneously changes to the negative side at time t<NUM> at which the upshift is started and the acceleration changes to the positive side at time t<NUM> at which the upshift is completed.

In the embodiment, when performing an upshift, the control device <NUM> predicts changes in the acceleration caused in the vehicle <NUM> based on detection signals from the automatic transmission input rotation sensor <NUM> and the automatic transmission output rotation sensor <NUM> and causes the auxiliary drive motors <NUM> to generate driving forces. As indicated by the solid line in the lower part of <FIG>, this suppresses an instantaneous drop (change to the negative side) of the acceleration of the vehicle <NUM> due to a torque shock and suppresses a stall feeling.

As described above, the adjustment of the drive torque by the auxiliary drive motors <NUM> during a downshift or an upshift of the transmission 14c is performed in a very short time and does not substantially drive the vehicle <NUM>. Therefore, the power generated by the auxiliary drive motors <NUM> can be generated by the electric charge regenerated by the auxiliary drive motors <NUM> and stored in the capacitor <NUM>. In addition, the adjustment of the drive torque by the auxiliary drive motors <NUM> can be applied to an automatic transmission with a torque converter, an automatic transmission without a torque converter, an automated manual transmission, and the like.

In the hybrid drive device <NUM> according to the first embodiment of the present invention, since the voltage of the battery <NUM> is applied to the main drive motor <NUM>, which is the body side motor, the insulating member that electrically insulates the electric power supply system for supplying electric power to the main drive motor <NUM> from the battery <NUM> with a low voltage of 48V is not requested for a high degree of insulation and the electric power supply system can be made lightweight. In addition, it is difficult to obtain large output power using only the main drive motor <NUM> because the main drive motor <NUM> is driven by a low voltage, but insufficient output power can be made up for by using the in-wheel motors as the auxiliary drive motors <NUM>.

Furthermore, since the driving current increases when the auxiliary drive motors <NUM> are driven by a low voltage, the harnesses 22b (<FIG>) for supplying electric power from the body side to the in-wheel motors provided in the front wheels 2b become thick and it is difficult to obtain flexibility and durability. In the hybrid drive device <NUM> according to the embodiment, since the voltage of the battery <NUM> and the capacitor <NUM> connected in series is applied to the auxiliary drive motors <NUM> (<FIG>), the auxiliary drive motors <NUM> can be driven by a voltage higher than in the main drive motor <NUM>. As a result, the wire harnesses do not become excessively thick and the vehicle can be efficiently driven using the in-wheel motors.

In addition, in the hybrid drive device <NUM> according to the embodiment, since the maximum inter-terminal voltage of the capacitor <NUM> is <NUM> V higher than <NUM> V, which is the inter-terminal voltage of the battery <NUM> (<FIG>), the auxiliary drive motors <NUM> can be driven by a voltage sufficiently higher than in the main drive motor <NUM>. As a result, the driving current of the auxiliary drive motors <NUM>, which are the in-wheel motors, can be suppressed, thereby enabling sufficient reduction in the load on the harnesses 22b through which electric power is supplied to the in-wheel motors.

Furthermore, in the hybrid drive device <NUM> according to the embodiment, the main drive motor <NUM> consumes the electric power stored in the battery <NUM> and the auxiliary drive motors <NUM> consume the electric power stored in the battery <NUM> and the capacitor <NUM> (<FIG>). Accordingly, depending on the driving conditions of the main drive motor <NUM> and the auxiliary drive motors <NUM>, the electric power stored by the battery <NUM> and the capacitor <NUM> may become unbalanced. Since the hybrid drive device <NUM> according to the embodiment has the high voltage DC/DC converter 26a, which is the first voltage converting unit that charges the capacitor <NUM> with the electric power stored in the battery <NUM> or charges the battery <NUM> with the electric power stored in the capacitor <NUM> (<FIG>), the amounts of electric power stored in the battery <NUM> and the capacitor <NUM> can be adjusted so that the electric power stored in the battery <NUM> and the capacitor <NUM> is used effectively.

Furthermore, in the hybrid drive device <NUM> according to the embodiment, since the low voltage DC/DC converter 26b, which is the second voltage converting unit, reduces the voltage of the battery <NUM> and supplies electric power to the electric components <NUM> (<FIG>), the battery <NUM> for driving the main drive motor <NUM> can be shared with the electric components <NUM> provided in the vehicle and the vehicle <NUM> can be made lightweight.

Furthermore, in the hybrid drive device <NUM> according to the embodiment, the auxiliary drive motors <NUM>, which are the in-wheel motors, are used in the high rotation range (from time t<NUM> to time t<NUM> in <FIG>) and a large torque is not requested in the low rotation range. Accordingly, by adopting induction motors as the in-wheel motors, motors capable of generating a sufficient torque in the required rotation range can be made lightweight.

Furthermore, in the hybrid drive device <NUM> according to the embodiment, since the auxiliary drive motors <NUM>, which are the in-wheel motors, directly drive the wheels without intervention of a deceleration mechanism (<FIG>), the deceleration mechanism with very heavy weight can be omitted and an output loss due to the rotation resistance of the deceleration mechanism can be avoided.

Furthermore, in the hybrid drive device <NUM> according to the embodiment, the auxiliary drive motors <NUM>, which are the in-wheel motors, are not used for a travel such as starting or a low speed travel requested for output power in the low revolutions range and the in-wheel motors are used for a travel such as a high speed travel requested for output power in the high revolutions range (<FIG>). In the hybrid drive device <NUM> according to the embodiment, since the in-wheel motors generate the maximum output power in the high revolutions range equal to or more than the predetermined number of revolutions that is more than zero, the vehicle can be efficiently driven by the small in-wheel motors (<FIG>).

In addition, the hybrid drive device <NUM> according to the embodiment adopts, as the main drive motor <NUM>, the permanent magnet motor that has a relatively large starting torque and large output power in the low rotation range. In the hybrid drive device <NUM> according to the embodiment, since the driving force of the main drive motor <NUM> is used for starting in which a large torque is requested in the low rotation range or a low speed travel, the motor capable of generating a sufficient torque in the required rotation range can be made lightweight.

The vehicle drive device according to the first embodiment of the present invention has been described above. Although the vehicle drive device according to the present invention is applied to an FR vehicle in the first embodiment described above, the present invention is applicable to various types of vehicles such as a so-called FF vehicle in which an engine and/or a main drive motor are disposed in the front portion of the vehicle and the front wheels are the main drive wheels or a so-called RR vehicle in which an engine and/or a main drive motor are disposed in the rear portion of the vehicle and the rear wheels are the main drive wheels.

When the present invention is applied to an FF vehicle, it is possible to adopt a layout in which, for example, the engine <NUM>, the main drive motor <NUM>, and the transmission 14c are disposed in the front portion of a vehicle <NUM> and front wheels 102a are driven as the main drive wheels, as illustrated in <FIG>. In addition, the auxiliary drive motors <NUM> can be disposed as in-wheel motors in the left and right rear wheels 102b, which are the auxiliary drive wheels. As described above, the present invention can be configured so that the main drive motor <NUM>, which is the body side motor, drives the front wheels 102a, which are the main drive wheels, and the auxiliary drive motors <NUM>, which are the in-wheel motors, drive the rear wheels 102b, which are the auxiliary drive wheels. In this layout, the main drive motor <NUM> can be driven by the electric power supplied via the inverter 16a and stored in the battery <NUM>. In addition, an integrated unit formed by integrating the capacitor <NUM>, the high voltage DC/DC converter 26a and the low voltage DC/DC converter 26b, which are voltage converting units, and the two inverters 20a can be disposed in the rear portion of the vehicle <NUM>. Furthermore, the auxiliary drive motors <NUM> can be driven by the electric power supplied via the inverters 20a and stored in the battery <NUM> and the capacitor <NUM> that are disposed in series.

When the present invention is applied to an FF vehicle, it is possible to adopt a layout in which, for example, the engine <NUM>, the main drive motor <NUM>, and the transmission 14c are disposed in the front portion of a vehicle <NUM>, and the front wheels 202a are driven as the main drive wheels, as illustrated in <FIG>, which is not part of the present invention. In addition, the auxiliary drive motors <NUM> can be disposed as in-wheel motors in the left and right front wheels 202a, which are the main drive wheels. As described above, the present invention can be configured so that the main drive motor <NUM>, which is the body side motor, drives the front wheels 202a, which are the main drive wheels, and the auxiliary drive motors <NUM>, which are the in-wheel motors, also drive the front wheels 202a, which are the main drive wheels. In this layout, the main drive motor <NUM> can be driven by the electric power supplied via the inverter 16a and stored in the battery <NUM>. In addition, an integrated unit formed by integrating the capacitor <NUM>, the high voltage DC/DC converter 26a and the low voltage DC/DC converter 26b, which are voltage converting units, and the two inverters 20a can be disposed in the rear portion of the vehicle <NUM>. Furthermore, the auxiliary drive motors <NUM> can be driven by the electric power supplied via the inverters 20a and stored in the battery <NUM> and the capacitor <NUM> that are disposed in series.

In contrast, when the present invention is applied to an FR vehicle, it is possible to adopt a layout in which, for example, the engine <NUM> and the main drive motor <NUM> are disposed in the front portion of a vehicle <NUM> and rear wheels 302b are driven as the main drive wheels by leading electric power to the rear portion of the vehicle <NUM> via the propeller shaft 14a, as illustrated in <FIG>, which is not part of the present invention. The rear wheels 302b are driven by the power led to the rear portion by the propeller shaft 14a via the clutch 14b and the transmission 14c, which is a stepped transmission. In addition, the auxiliary drive motors <NUM> can be disposed as in-wheel motors in the left and right rear wheels 302b, which are the main drive wheels. As described above, the present invention can be configured so that the main drive motor <NUM>, which is the body side motor, drives the rear wheels 302b, which are the main drive wheels, and the auxiliary drive motors <NUM>, which are the in-wheel motors, also drive the rear wheels 302b, which are the main drive wheels. In this layout, the main drive motor <NUM> can be driven by the electric power supplied via the inverter 16a and stored in the battery <NUM>. In addition, an integrated unit formed by integrating the capacitor <NUM>, the high voltage DC/DC converter 26a and the low voltage DC/DC converter 26b, which are voltage converting units, and the two inverters 20a can be disposed in the front portion of the vehicle <NUM>. Furthermore, the auxiliary drive motors <NUM> can be driven by the electric power supplied via the inverters 20a and stored in the battery <NUM> and the capacitor <NUM> that are disposed in series.

Claim 1:
A vehicle drive device (<NUM>) comprising:
in-wheel motors (<NUM>) that are provided in auxiliary drive wheels (2b; 102b; 202a; 302b) of the vehicle (<NUM>) and drives the auxiliary drive wheels (2b; 102b; 202a; 302b);
a body side motor (<NUM>) that is provided in a body of the vehicle (<NUM>) and drives main drive wheels (2a; 102a; 202a; 302b) of the vehicle (<NUM>);
a battery (<NUM>); and
a capacitor (<NUM>),
wherein the battery (<NUM>) and the capacitor (<NUM>) are connected in series, and a voltage of the battery (<NUM>) is applied to the body side motor (<NUM>) and a voltage, which is sum of the voltage of the battery (<NUM>) and a voltage of the capacitor (<NUM>), is applied to the in-wheel motor (<NUM>) and
wherein the in-wheel motors (<NUM>) drive the auxiliary drive wheels (2b; 102b, 202b, 302b) only when a vehicle speed is higher than a predetermined speed.