Movable structure driving unit

A movable structure driving unit is a movable structure driving unit used for a movable structure, including: an electric motor that is electrically connected to a power supply and that drives a front wheel; a rear-side motive power source that drives a rear wheel; a jump detector that detects a jump of the front wheel from ground; and a motor controller that controls driving of the electric motor. The motor controller stops supply of a driving current from the power supply to the electric motor when the jump of the front wheel from the ground is detected in a state in which driving of the front wheel and the rear wheel is instructed.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application Nos. 2018-130130, 2018-130135, and 2018-130149, all filed on Jul. 9, 2018, the entire content of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a movable structure driving unit which is used for a movable structure having a front wheel and a rear wheel, and in particular to protection of a driving mechanism of the front wheel regardless of jump during travel. The present disclosure also relates to a movable structure driving unit which is used for a movable structure having a front wheel and a rear wheel, and in particular to improving stability of travel on a soft road surface. The present disclosure further relates to a movable structure driving unit which is used for a movable structure having a wheel at each of front and rear sides in a driving direction, and in particular to prevention of stopping of an engine due to excessive load and to improvement of fuel consumption.

BACKGROUND

In the related art, as described in JP 2017-87824 A, a structure is known in which an engine is mounted at a rear side of a vehicle, and a motive power of the engine is transmitted to a rear wheel via an axle driving apparatus. The axle driving apparatus includes a motor and an input shaft. The motive power of the engine can be input to one end side of the input shaft, and a motive power of the motor can be input to the other end side of the input shaft. The motive power of the input shaft is transmitted to the axle of the rear wheel via a gear-type transmission. The motive power of the motor is transmitted to an output shaft via a clutch. The motive power of the output shaft is transmitted to the axle of the front wheel via a PTO shaft, a motive power transmission shaft (propeller shaft), or the like. With this process, a four-wheel drive is enabled in which the rear wheel is driven by the motive power of the engine and the front wheel is driven by the motive power of the motor by connection of the clutch.

In the vehicle described in JP 2017-87824 A, there may be cases where the vehicle jumps in a manner to be lifted off from the ground during high-speed traveling on a rough terrain with the four-wheel drive or the like. In this case, when the vehicle lands on the ground after the vehicle jumps, the high-speed rotation of the front wheel is rapidly suppressed by the ground, and an excessive impact is applied to the driving mechanism of the front wheel. Due to the excessive impact, the strength of the front-wheel driving mechanism may become insufficient or endurance of the driving mechanism may be reduced. On the other hand, increasing the strength of the front-wheel driving mechanism may result in an increase in the size of the front-wheel driving mechanism or an excessive increase of the cost.

In addition, in the vehicle described in JP 2017-87824 A, during travel of a soft road surface such as a swamp, a damp ground, or the like with the four-wheel drive, because the transmission of the motive power of the front wheel to the ground is reduced, it becomes easier for the front wheel to swing left and right according to the topography of the ground. Because of this, the vehicle may fail to travel stably in an intended direction of travel of a driver who is a user, such as a forward direction of a straight movement or the like.

In a movable structure such as a vehicle in which, of the front and rear wheels, a first wheel such as the front wheel is driven by a motor, and a second wheel such as the rear wheel is driven by the engine, if an excessive load is applied to the engine during a period in which only the second wheel is driven and driving of the first wheel by the motor is stopped, there may be cases where the engine stops or the fuel consumption is degraded.

An advantage of the present disclosure lies in provision of a movable structure driving unit which can suppress an increase in the size and cost of the driving mechanism which drives the front wheel and which can protect the driving mechanism of the front wheel regardless of the jump during travel.

Another advantage of the present disclosure lies in provision of a movable structure driving unit which can improve stability of soft road surface traveling of a movable structure of a four-wheel drive, according to an instruction of a user.

Yet another advantage of the present disclosure lies in provision of a movable structure driving unit which can prevent stopping of the engine due to excessive load and which can improve fuel consumption, in a movable structure which drives the wheel by the engine.

SUMMARY

According to one aspect of the present disclosure, there is provided a movable structure driving unit of a first structure, which is used for a movable structure having a front wheel and a rear wheel, comprising: an electric motor that is electrically connected to a power supply and that drives the front wheel; a rear-side motive power source that drives the rear wheel; a jump detector that detects a jump of the front wheel from ground; and a motor controller that controls driving of the electric motor, wherein the motor controller stops supply of a driving current from the power supply to the electric motor when the jump of the front wheel from the ground is detected in a state in which driving of the front wheel and the rear wheel is instructed.

According to another aspect of the present disclosure, there is provided a movable structure driving unit of a second structure, which is used for a movable structure having a front wheel and a rear wheel, comprising: an electric motor that is electrically connected to a power supply and that drives the front wheel; a rear-side motive power source that drives the rear wheel; a detector that detects a change of a weight of a part of the movable structure, acting on a suspension device; and a motor controller that controls driving of the electric motor, wherein the motor controller stops supply of a driving current from the power supply to the electric motor when an amount of reduction of the weight detected by the detector is greater than or equal to a predetermined value in a state in which driving of the front wheel and the rear wheel is instructed.

According to another aspect of the present disclosure, there is provided a movable structure driving unit of a third structure, which is used for a movable structure having a front wheel and a rear wheel, comprising: an electric motor that drives the front wheel; a rear-side motive power source that drives the rear wheel; a mode instructor that instructs switching between a hard road surface mode suited for travel on a hard road surface and a soft road surface mode suited for travel on a soft road surface; and a control device that controls driving of the electric motor and the rear-side motive power source according to an operation of an acceleration instructor which instructs acceleration by an operation of a user, wherein the control device applies a control to match a rotational speed of the front wheel to a rotational speed of the rear wheel when the hard road surface mode is instructed by the mode instructor, and applies a control to set the rotational speed of the front wheel higher than the rotational speed of the rear wheel when the soft road surface mode is instructed by the mode instructor.

According to another aspect of the present disclosure, there is provided a movable structure driving unit of a fourth structure, which is used for a movable structure having a wheel at each of a front side and a rear side of a direction of travel, comprising: an electric motor that drives, of a plurality of the wheels, a first wheel on a first side in a front-and-rear direction; an engine that drives, of the plurality of the wheels, a second wheel on a second side in the front-and-rear direction; a load detector that detects a load of the engine; and a motor controller that controls driving of the electric motor, wherein the motor controller drives the electric motor to drive both of the first wheel and the second wheel when a detected value of the load detector becomes greater than or equal to a first predetermined value in a state in which a two-wheel drive is instructed in which driving of the first wheel by the electric motor is stopped and the second wheel is driven.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present disclosure will now be described with reference to the drawings. In the following description, a case is described in which a movable structure on which a movable structure driving unit is mounted is an off-road utility vehicle having a carriage and which travels on rough terrain such as forests, wastelands, rocky mountains, or the like, but alternatively, the movable structure may be a work vehicle having a working machine which executes at least one type of work among snow removal work, excavation work, civil work, and agricultural work, an all terrain vehicle (ATV), or a recreational vehicle (ROV). In the following, elements similar throughout all drawings are assigned the same reference numerals.

FIG. 1toFIG. 8A-FIG. 8Cshows an embodiment of the present disclosure.FIG. 1is a side view of a vehicle10on which a movable structure driving unit20of the present embodiment is mounted.FIG. 2is a diagram showing an overall structure of the movable structure driving unit20mounted on the vehicle10.FIG. 3is an enlarged view of an A part ofFIG. 2.FIG. 4is an enlarged view of a B part ofFIG. 2.

In the vehicle10shown inFIG. 1, a platform12which is a fundamental structure is fixed at an upper side of a frame11forming a vehicle body, and a front cover13is fixed to a front side (left side ofFIG. 1) of the frame11. In the platform12, a driver seat14is fixed at a rear side of the front cover13, and a carriage19is fixed at a rear side of the driver seat14. The vehicle10comprises two front wheels15on the left and right and two rear wheels16on the left and right, which are wheels supported at a front side and a rear side of the frame11, an operation element group18, and the movable structure driving unit20. As shown inFIG. 1, a battery23to be described later is placed at a space below the driver seat14.

The movable structure driving unit20comprises an engine21and an electric motor22which are motive power sources, the battery23(FIG. 1andFIG. 5) which is a power supply, a power generator GE (FIG. 2) driven by the engine21and for generating electricity to be stored in the battery23, a rear-side motive power transmission unit25(FIG. 2) and a front-side motive power transmission unit41(FIG. 2), a sensor switch group50, and a control device70. The engine21corresponds to a rear-side motive power source. The sensor switch group50has a jump sensor51to be described later. The jump sensor51detects a jump of the front wheel15from the ground, as will be described later. The jump sensor51corresponds to a jump detector.

The control device70controls a motor driving circuit24(FIG. 2andFIG. 5) to stop supply of a driving current from the battery23to the electric motor22when the jump of the front wheel15from the ground is detected in a state where four-wheel drive is instructed by an operation of a drive switching switch52, as will be described later. With this process, the front-side motive power transmission unit41which is a driving mechanism of the front wheels15can be protected.

The operation element group18includes an acceleration pedal60which is an acceleration instructor and a brake pedal which is a brake instructor (not shown) which are provided at a front side of the driver seat14, and a steering operator61which is a turn instructor and a forward/rearward movement lever62provided at the front side of the driver seat14.

The steering operator61is formed from a steering wheel fixed on a steering shaft protruding at an upper side of the front covert13toward a slanted rear side. The steering operator61is connected to the two front wheels15at the left and right in a manner to allow steering of the front wheels15via a steering mechanism of an Ackermann type.

As shown inFIG. 2, the forward/rearward movement lever62is formed to have an operation position switchable among three positions including a forward movement position (F position), a neutral position (N position), and a rearward movement position (R position). The forward/rearward movement lever62is supported on the vehicle body in a manner to allow swinging movement in the front-and-rear direction (up-and-down direction ofFIG. 2). The forward/rearward movement lever62may be formed as a transmission lever which can switch the forward traveling in a plurality of stages of traveling speed ranges such as low speed, high speed, etc.

The engine21is fixed to a lower side of the carriage19at a rear side of the driver seat14on the frame11. The engine21is started by a startup switch (not shown) being operated to ON. As the engine21, any of a plurality of types of engines may be used, including gasoline engines, diesel engines, and the like. The motive power of the engine21is transmitted to the two rear wheels16at the left and right via the rear-side motive power transmission unit25, to drive the two rear wheels16.

The electric motor22is placed inside a front-side case40(FIG. 2) to be described later, which is fixed at the front side of the driver seat14on the frame11. The battery23(FIG. 5) is electrically connected to the electric motor22via the motor driving circuit24(FIG. 2andFIG. 5). The battery23is placed inside the front cover13, or at a lower side of the driver seat14or the carriage19. As will be described later, the electric motor22is started when the startup switch (not shown) is operated to ON and four-wheel drive (4WD) is instructed which is an instruction of driving of the front wheels15and the rear wheels16, by the drive switching switch52(FIG. 2andFIG. 5) to be described later.

For the electric motor22, various types of motors may be used such as a DC motor, a permanent magnet motor, and an induction motor. The motive power of the electric motor22is transmitted to the two front wheels15at the left and right via the front-side motive power transmission unit41, to drive the two front wheels15. With this process, the electric motor22drives the front wheels15.

The rear-side motive power transmission unit25and the front-side motive power transmission unit41will now be described. As shown inFIG. 3, the rear-side motive power transmission unit25includes a CVT26which is a belt-type continuously variable transmission device, a gear transmission device30, a differential device36, an output shaft37, and a rear axle38. The rear-side motive power transmission unit25is connected between the engine21and the rear wheel16(FIG. 2) in a manner to allow transmission of motive power from the engine21to the rear wheel16. For this purpose, the rear wheel16and the engine21are connected via the CVT26.

The CVT26is formed by winding a belt29around an input pulley27and an output pulley28. The input pulley27has a fixed sheave27afixed on an output shaft21aof the engine21, and a movable sheave27bsupported on the output shaft21ain a manner to allow movement in an axial direction and opposing the fixed sheave27a. The output pulley28has a fixed sheave28afixed on an input shaft31of the gear transmission device30, and a movable sheave28bsupported on the input shaft31in a manner to allow movement in an axial direction and opposing the fixed sheave28a. The movable sheave27bof the input pulley27moves in the axial direction by an actuator26aincluding an electric motor. The actuator26acorresponds to an electric actuator. An elastic force is urged to the movable sheave28bof the output pulley28by a spring (not shown) in a direction toward the fixed sheave28a. As the rotational speed of the engine21is increased, the actuator26acauses the movable sheave27bof the input pulley27to be closer to the fixed sheave27a. With this configuration, when the rotational speed of the engine21is low, as shown inFIG. 3, a width between the movable sheave27band the fixed sheave27a(inter-sheave width) is increased. Because of this, the CVT26is continuously variably transmitted, and a ratio (N1/N2) between a rotational speed N1 of the input pulley27and a rotational speed N2 of the output pulley28which is a gear ratio of the CVT26is increased. On the contrary, when the rotational speed of the engine21is increased, the inter-sheave width of the input pulley27is reduced. Thus, the CVT26is continuously variably transmitted, and the gear ratio (N1/N2) of the CVT26is reduced. With this process, a torque of the input shaft31during low-speed travel can be increased, and fuel consumption during high-speed travel can be improved.

The gear transmission device30includes a rear-side case35fixed at a rear side of the engine21on the frame11, and the input shaft31, a transmission shaft32, and a final shaft33placed in the rear-side case35in a rotatable manner. The gear transmission device30enables transmission of motive power from the input shaft31to the final shaft33via a gear mechanism34aand a slide gear34bprovided around the transmission shaft32. The slide gear34bis connected to the forward/rearward movement lever62. According to the operation of the forward/rearward movement lever62, the slide gear34bmoves in the axial direction, and a gear to be engaged is switched, so that the relationship between a rotational direction of the input shaft31and a rotational direction of the final shaft33is switched. The motive power transmitted to the final shaft33is transmitted to a transmission gear36aof the differential device31via a gear mechanism. Two output shafts37at the left and right are differentially connected to the differential device36. The differential device36is placed inside the rear-side case35. Each of the rear wheels16is connected to the output shaft37via a universal joint39and the rear axle38. With this configuration, the rear wheel16is driven by the engine21.

When a forward movement position is selected by the forward/rearward movement lever62(FIG. 2), forward movement of the vehicle10becomes possible. When the rearward movement position is selected by the forward/rearward movement lever62, rearward movement of the vehicle10becomes possible. When the neutral position is selected by the forward/rearward movement lever62, the inter-sheave width of the input pulley27is increased, such that the transmission of motive power is prevented between the output shaft21aof the engine21and the belt29of the CVT26.

As shown inFIG. 4, the front-side motive power transmission unit41includes a gear mechanism42, a differential device43, an output shaft44, and a front axle45. The front-side motive power transmission unit41is connected between the electric motor22and the front wheel15(FIG. 2) in a manner to allow transmission of the motive power from the electric motor22to the front wheel15. A motive power of a rotation shaft22aof the electric motor22is transmitted to a transmission gear43aof the differential device43via the gear mechanism42. Two output shafts44at the left and right are differentially connected to the differential device43. Each of the front wheels15is connected to the output shaft44via a universal joint46and the front axle45. The electric motor22, the gear mechanism42, and the differential device43are placed inside the front-side case40. The front-side case40is fixed at a front side of the frame11(FIG. 1). With this configuration, the front wheel15is driven by the electric motor22.

As shown inFIG. 2, the sensor switch group50includes a lever sensor53(FIG. 5), a pedal sensor54, the drive switching switch52, a rear axle speed sensor55, a front axle speed sensor56, an engine speed sensor57, and the jump sensor51.

The lever sensor53(FIG. 5) detects a position of the forward/rearward movement lever62, and transmits a detection signal thereof to the control device70to be described later. When the control device70judges from the detection signal of the lever sensor53that the forward/rearward movement lever62is at the neutral position, the control device70applies a control to largely separate the movable sheave27bof the input pulley27from the fixed sheave27aso that the motive power of the input pulley27is not transmitted to the belt29by flexure of the belt29. With this process, the neutral state is realized.

The pedal sensor54detects an amount of operation, which is an operation state, of the acceleration pedal60, and transmits a detection signal thereof to the control device70. The control device70has an engine controller71(FIG. 5). The engine controller71controls a throttle valve (not shown) of the engine21so that a degree of opening of the throttle valve is increased as the amount of operation of the acceleration pedal60is increased. In order to drive the throttle valve, a valve driving electric motor which is controlled by the engine controller71may be provided. The degree of opening of the throttle valve changes according to the driving of the valve driving electric motor. The rotational speed of the engine21is adjusted by the degree of opening of the throttle valve, and the rotational speed of the engine21is increased as the degree of opening of the throttle valve is increased. The concept of “rotational speed” includes a rotation number which is a rotational speed per unit time, for example, per minute.

Alternatively, a driving unit of the throttle valve may be connected to the acceleration pedal60via a link or a cable, and the degree of opening of the throttle valve may be increased as the amount of operation of the acceleration pedal60is increased. In this case, the pedal sensor may be provided near the throttle valve and indirectly detect the pedal position of the acceleration pedal60by detecting the degree of opening of the throttle valve, in place of directly detecting the pedal position of the acceleration pedal60.

A brake pedal (not shown) is connected to a hydraulic pressure generation mechanism (not shown) via a link. On one or both of the pair of front wheels15and the pair of rear wheels16, a brake disc (not shown) is fixed, and two brake pads (not shown) at an inner side and an outer side of the vehicle are placed on respective sides of the brake disc. The hydraulic pressure generation mechanism generates a braking force to sandwich the brake disc by applying a hydraulic pressure force to one of the two brake pads.

The drive switching switch52is provided to be operable by the user on a drive panel on which the forward/rearward movement lever62protrudes, and instructs a driving state of the vehicle by an operation. Specifically, with the operation on the drive switching switch52, the instruction is switched between an instruction to set the vehicle in a two-wheel drive (2WD) state and an instruction to set the vehicle in a four-wheel drive (4WD) state. A signal indicating the instruction of the drive switching switch52is transmitted to the control device70. The control device70switches the traveling state between the two-wheel drive and the four-wheel drive according to the switching of the drive switching switch52. Specifically, the control device drives only the rear wheel16when the two-wheel drive is instructed, by driving the engine21and stopping the electric motor22. When the four-wheel drive is instructed, the control device70drives both the engine21and the electric motor22.

Further, the control device70has a motor controller72(FIG. 5). The motor controller72controls the electric motor22so that the rotational speed of the electric motor is increased as the amount of operation of the acceleration pedal60is increased in the state in which the four-wheel drive is instructed.

The rear axle speed sensor55detects a rotational speed of the transmission gear36a(FIG. 3) of the differential device36. The transmission gear36ais fixed to a differential case36bof the differential device36. The differential case36brotates at an average rotational speed of the two rear axles38at the left and right. With this configuration, the rear axle speed sensor55can detect the average rotational speed of the two rear axles38at the left and right. A detection signal of the rear axle speed sensor55is input to the control device70.

The front axle speed sensor56detects a rotational speed of the transmission gear43a(FIG. 4) of the differential device43. The transmission gear43ais fixed on a differential case43bof the differential device43. The front axle speed sensor56corresponds to a first rotational speed detector. The transmission gear43acorresponds to a motive power transmitting rotational structure. The differential case43brotates at an average rotational speed of the two front axles45at the left and right. With this configuration, the front axle speed sensor56can detect the average rotational speed of the two front axles45at the left and right. A detection signal of the front axle speed sensor56is input to the control device70.

The engine speed sensor57detects the rotational speed of the output shaft21aof the engine21, and transmits a detection signal thereof to the control device70. The control device70controls the actuator26ato move the movable sheave27bof the CVT26according to the detected value of the engine speed sensor57.

In the above description, a case is described in which the CVT26is electrically driven and includes the electric motor. Alternatively, the CVT may be of a hydraulic pressure type in which the movable sheave is moved by a hydraulic pressure device, or of a mechanical type in which the movable sheave is moved by a pressurization force generation mechanism including a torque cam.

Further, the jump sensor51detects jump of the two front wheels15at the left and right from the ground; that is, running-off.FIG. 6is a diagram showing a suspension device80and the jump sensor51for the right front wheel15in the present embodiment, as viewed from the front side of the vehicle and with a portion omitted.

The front wheel15is supported on the vehicle body via the suspension device80. The suspension device80includes a plurality of arms81and82, and a rod-cylinder unit84which extends and contracts. The plurality of arms81and82are placed in a separated manner at an upper side and lower side on each of left and right sides. Inner ends, in the width direction of the vehicle, of the arms81and82are respectively supported on the frame11(FIG. 1), in a rotatable manner about axes85and86along the front-and-rear direction. Outer ends, in the vehicle width direction, of the arms81and82are respectively supported on upper and lower ends of a wheel support unit88which rotatably supports the front wheel15, in a rotatable manner about axes89and90along the front-and-rear direction.

The rod-cylinder unit84includes a cylinder case84a, and a rod84bwhich extends from a lower side of the cylinder case84a. A lower end of the rod84bis connected to the arm82at the lower side, in a rotatable manner about an axis91along the front-and-rear direction. An upper end of the cylinder case84ais connected to a portion (not shown) of the frame11(FIG. 1), in a rotatable manner about an axis along the front-and-rear direction. An upper end of the rod84bis connected to a piston (not shown) in the cylinder case84a. Oil or air is sealed between the cylinder and the piston in the cylinder case84a.

The jump sensor51is connected between the cylinder case84aand the lower end of the rod84b, and detects a change of a protrusion length of the rod84bfrom the cylinder case84a. The jump sensor51detects that the front wheel15has jumped from the ground when an amount of extension of the rod-cylinder unit84with respect to a reference length becomes greater than or equal to a predetermined value. The reference length is a length from the upper end to the lower end of the rod-cylinder unit84in a state where a driver rides the vehicle10and the vehicle10is stopped. When the rod-cylinder unit84extends in an amount greater than or equal to the predetermined value, it can be considered that the vehicle10is floating from the ground, and the lower arm82is significantly lowered to the downward direction, and thus, the jump can be detected. A detection signal of the jump sensor51is transmitted to the control device70(FIG. 2andFIG. 5).

The control device70is also called an ECU (Electronic Control Unit), is formed from, for example, a microcomputer, and has a CPU which is a calculation processor, a storage unit including a memory such as a RAM and a ROM, and an input/output port. The CPU has a function to read and execute a control program which is stored in the storage unit in advance. In general, the functions of various means of the control device70are realized by executing a control program. The control device70has the above-described engine controller71(FIG. 5) and motor controller72(FIG. 5).

FIG. 5is a diagram showing a structure of the motor driving circuit24of the electric motor22and the control device70in the present embodiment. The battery23is connected to the electric motor22via the motor driving circuit24. The motor driving circuit24converts a current which is output from the battery23into a drive current of the electric motor22. For example, the motor driving circuit24includes an inverter which converts a DC current which is output from the battery23into a three-phase AC current.

The motor controller72controls the motor driving circuit24in a state where the four-wheel drive is instructed, to control driving of the electric motor22. The motor controller72applies a control such that the electric motor22is rotated in a direction corresponding to a forward movement when the motor controller72judges that the forward movement position is selected by the forward/rearward movement lever62(FIG. 2) based on the detection signal from the lever sensor53and that the acceleration pedal60(FIG. 2) is being operated based on the detection signal from the pedal sensor54(FIG. 2). In this process, the driving current is supplied from the battery23to the electric motor22.

On the other hand, when the motor controller72judges that the rearward movement position is selected by the forward/rearward movement lever62and that the acceleration pedal60is being operated, the motor controller72applies a control to rotate the electric motor in a direction corresponding to the rearward movement. In this process also, the driving current is supplied from the battery23to the electric motor22.

When the motor controller72judges that the neutral position is selected by the forward/rearward movement lever62, the motor controller72stops the supply of current from the battery23to the electric motor22.

When there is the instruction of the four-wheel drive, the motor controller72controls the electric motor22to match the rotational speed of the front wheel15to the rotational speed of the rear wheel16, based on the detection signals of the rear axle speed sensor55and the front axle speed sensor56(FIG. 2).

The control device70controls the actuator26ato change the inter-sheave width of the input pulley27of the CVT26according to the rotational speed of the engine21. Further, when the rotational speed of the engine21is lower than a predetermined value, the control device70increases the inter-sheave width of the input pulley27, to cause the belt29to flex and prevent generation of a tensioning force on the belt29, so that the motive power of the input pulley27is not transmitted to the belt29of the CVT26.

In place of the control device70increasing the inter-sheave width to prevent the generation of the tensioning force on the belt29when the rotational speed of the engine21is lower than the predetermined value, a centrifugal clutch may be provided between the output shaft21aof the engine21and the input pulley27. In this case, the output shaft21aand the input pulley27are disconnected when the rotational speed of the engine21is lower than a predetermined value, and the output shaft21aand the input pulley27are connected via the centrifugal clutch when the rotational speed of the engine21is greater than or equal to the predetermined value.

Further, when the jump of the front wheel(s)15from the ground is detected in a state in which the four-wheel drive is instructed by the operation of the drive switching switch52, the motor controller72controls the motor driving circuit24to stop the supply of the driving current from the battery23(FIG. 5) to the electric motor22. Alternatively, the motor driving circuit24may have a relay switch which is controlled by the motor controller72.

Further, the motor controller72controls the motor driving circuit24so that, after a predetermined time has elapsed without detection of a jump of the front wheel(s)15after the jump of the front wheel(s)15from the ground is detected and the supply of the driving current is stopped, the supply of the driving current from the battery23to the electric motor22is re-started.

FIG. 7is a flowchart showing an example of a control process of the movable structure driving unit20having the above-described structure, and showing a control method during detection of jump. In the following, reference numerals ofFIG. 1˜FIG. 6will be used as suited. Processes of steps S11˜S16are executed by the motor controller72. In step S11, it is judged whether or not there is an instruction of the four-wheel drive. When it is judged that there is the instruction of the four-wheel drive (YES in S11), it is then judged in step S12whether or not jump is detected. When it is judged that jump is detected (YES in S12), in step S13, the supply of the driving current from the battery23to the electric motor22is stopped. With this process, the front wheel15is not driven by the electric motor22, and is set in a state of running on idle by inertia. Because of this, when the vehicle10lands on the ground after the jump as shown in (c) ofFIG. 8AtoFIG. 8Cto be described later, because the front wheel15is not driven by the electric motor22, the front wheel15does not receive an excessively high force from the ground. Therefore, the front-side motive power transmission unit41which is the driving mechanism of the front wheel15can be protected regardless of the jump during the travel. Further, because it is not necessary to excessively increase the strength of the front-side motive power transmission unit41, the increases in the size and the cost of the front-side motive power transmission unit41can be suppressed.

When the judgment of steps S11or S12ofFIG. 7is negative (NO in S11or S12), the process returns to a state before step S11. After the step S13, in step S14, it is judged whether or not non-detection of the jump is realized. When it is judged that the non-detection of the jump is realized (YES in S14), the method proceeds to step S15. When the judgment of step S14is negative (NO in S14), the process of step S14is repeated. In step S15, it is judged whether or not a predetermined time has elapsed from the time when the non-detection of the jump is realized. When it is judged that the predetermined time has elapsed (YES in S15), the method proceeds to step S16. When the judgment of step S15is negative (NO in S15), the process of step S15is repeated. In step S16, the supply of the driving current from the battery23to the electric motor22is re-started. With this process, the application of high power to the front-side motive power transmission unit41can be further suppressed, and, consequently, the front-side motive power transmission unit41can be further protected.

Alternatively, in the structure ofFIG. 1˜FIG. 7, the jump detector may comprise a stroke sensor which detects an amount of extension of the rod-cylinder unit84(FIG. 6) with respect to a reference length, and a jump judgment unit provided on the control device70. A detection signal indicating a detected value of the stroke sensor is transmitted to the control device70. The jump judgment unit detects the jump by judging that the front wheel15has jumped when the amount of extension of the rod-cylinder unit84with respect to the reference length becomes a predetermined value or greater, based on the detection signal of the stroke sensor.

FIG. 8A-FIG. 8Cis a diagram showing a jump state and states before and after the jump of the vehicle10in the present embodiment. As shown in the order ofFIG. 8A,FIG. 8CandFIG. 8CinFIG. 8, during travel on wasteland, when the vehicle10travels over a small mountain at a relatively high vehicle velocity, the front wheels15jump away from the ground1, and then the vehicle10lands on the ground from the front wheels15. When the front wheels15and the rear wheels16are separated from the ground1, the force from the ground1and received by the front wheels15and the rear wheels16vanishes. Because of this, it becomes easier for the acceleration pedal to be stepped on in a large amount. In this process, if the supply of the driving current from the battery23to the electric motor22is continued, the speed of the front wheels15tends to be easily rapidly increased. After the landing of the vehicle10, the front wheels15are rapidly decelerated by the ground1, causing an excessive impact on the front-side motive power transmission unit41. This excessive impact may be a cause of insufficiency of the strength of the front-side motive power transmission unit41or reduction of endurance of the front-side motive power transmission unit41. According to the embodiment described above, when the jump of the front wheels15is detected, the supply of the driving current from the battery23to the electric motor22is stopped, so that the front-side motive power transmission unit41can be protected.

On the other hand, when the vehicle lands on the ground after the jump, because the rear wheels16are driven by the engine21and are rotating, a large impact may be applied also to the rear-side motive power transmission unit25which is the driving mechanism of the rear wheel16. However, because the rear wheel16is driven in both the two-wheel drive and the four-wheel drive during the normal time, normally, the rear-side motive power transmission unit25is designed with high strength. Thus, problems tend to not be caused in the practical use by application of the impact of the landing to the rear-side motive power transmission unit25.

FIG. 9shows an alternative configuration of the present embodiment, and is a diagram corresponding toFIG. 6. In a vehicle10aincluding a movable structure driving unit20aof the present configuration, two jump sensors51aat the left and right are fixed on the frame11(refer toFIG. 1), opposing a lower surface82a, which is a surface to be detected, of the arm82at the lower side. With the movement of the vehicle body in the up-and-down direction, a direction of the lower surface82aof the arm82changes with respect to a reference direction (a direction of an arrow α inFIG. 6) of the lower surface82aof the arm82. The jump sensor51adetects, when the arm82is lowered toward the front wheel15as shown by a two-dots-and-a-chain line ofFIG. 9, an angle γ between the reference direction and an actual direction (a direction of an arrow β ofFIG. 6) of the lower surface82aof the arm82. The jump sensor51adetects a jump when the detected value of the angle γ described above is greater than or equal to a predetermined value. A detection signal of the jump sensor51ais transmitted to the control device70(FIG. 5). The other structures and operations in the present configuration are similar to those of the structure ofFIG. 1˜FIG. 7.

Alternatively, in the structure ofFIG. 1˜FIG. 7or in the structure ofFIG. 9, in place of the jump sensors51and51a, an upper weight sensor corresponding to a detector may be used. The upper weight sensor is connected, for example, between the cylinder case84aand the lower end of the rod84bsimilar to the jump sensor51of the structure ofFIG. 1˜FIG. 7, and detects the change of the protrusion length of the rod84bfrom the cylinder case84a. Further, unlike the jump sensor51, the upper weight sensor does not detect the jump directly, but detects a change of a weight of a part of the vehicle acting on the suspension device80(FIG. 6); that is, a weight of the portion including portions above the suspension device80, by detecting the change of the protrusion length as described above. When the protrusion length is increased, it is detected that a reduction amount of the weight is increased. When the reduction amount of the weight detected by the upper weight sensor is greater than or equal to a predetermined value in a state in which the four-wheel drive is instructed, the motor controller controls the motor driving circuit24, to stop the supply of the driving current from the battery23(FIG. 5) to the electric motor22. With the reduction amount of the weight becoming greater than or equal to the predetermined value, the jump of the vehicle can be detected indirectly. With this structure, similar to the structure ofFIG. 1˜FIG. 7, the increases in the size and in the cost of the front-side motive power transmission unit41which drives the front wheel15can be suppressed, and the front-side motive power transmission unit41can be protected regardless of the jump during the travel.

Alternatively, similar to the jump sensor51aof the structure ofFIG. 9, the upper weight sensor may be fixed on the frame11(refer toFIG. 1), opposing the lower surface82a, which is the surface to be detected, of the arm82at the lower side. Similar to the jump sensor51a, the upper weight sensor detects the angle γ between the reference direction of the lower surface82aof the arm82and the actual direction of the lower surface82a, and detects the change of the weight of the part of the vehicle acting on the suspension device80, through the detection of the angle γ. With the increase in the angle γ, an increase in the reduction amount of the weight is detected. Similar to the above, when the reduction amount of the weight detected by the upper weight sensor is greater than or equal to a predetermined value in a state in which the four-wheel drive is instructed, the motor controller controls the motor driving circuit24, to stop supply of the driving current from the battery23(FIG. 5) to the electric motor22. With this configuration also, the increases in the size and cost of the front-side motive power transmission unit41which drives the front wheel15can be suppressed, and the front-side motive power transmission unit41can be protected regardless of the jump during the travel.

Further, a structure may be employed in which the motor controller controls the motor driving circuit24so that, after a predetermined time has elapsed after the reduction amount of the weight detected by the upper weight sensor becomes lower than the predetermined value after the reduction amount of the weight detected by the upper weight sensor becomes greater than or equal to the predetermined value and the supply of the driving current is stopped, the supply of the driving current from the battery23to the electric motor22is re-started.

FIG. 10is a diagram showing an alternative configuration of an embodiment of the present disclosure, and corresponding toFIG. 1.FIG. 11is a block diagram showing an input for the control device70and a structure of the control device70in the alternative configuration of the embodiment of the present disclosure. In a vehicle10bincluding a movable structure driving unit20bof the present configuration, a wheel support member93is fixed on a rear end of the frame11and extending in a lower side. A driven wheel17which is a driven rotation wheel is supported at a rear end of the wheel support member93, in a rotatable manner about an axis along a left-and-right direction (width direction) (directions into and out of the page ofFIG. 10) of the vehicle10b. The driven wheel17rotates by a force received from the ground during the travel of the vehicle10b.

As shown inFIG. 11, a jump detector94is formed including a driven wheel speed sensor95which detects a rotational speed of the driven wheel17(FIG. 10), and a jump judgment unit73provided on the control device70. The driven wheel speed sensor95corresponds to a second rotational speed detector. The driven wheel speed sensor95transmits a detection signal to the control device70.

The jump judgment unit73judges that jump is detected when a vehicle speed V2 calculated from the rotational speed of the transmission gear43a(FIG. 4) of the front-side motive power transmission unit41(FIG. 4) is greater than a vehicle speed V1 calculated from the rotational speed of the driven wheel17by a predetermined value or by a predetermined ratio, and judges non-detection of the jump in other cases. The vehicle speed V1 calculated from the rotational speed of the driven wheel17is 0 or is significantly reduced upon jump of the vehicle10b. On the other hand, the vehicle speed V2 calculated from the rotational speed of the transmission gear43ais high when the electric motor22is driven, even during the jump of the vehicle10b. Thus, the jump can be detected by an increase in the difference between two vehicle speeds V1 and V2 calculated based on the driven wheel17and the transmission gear43a. The other structures and operations in the present configuration are similar to those of the structure ofFIG. 1˜FIG. 7.

FIG. 12is a block diagram showing an input for the control device70and a structure of the control device70in an alternative configuration of an embodiment of the present disclosure.FIG. 13is a flowchart showing a control method during start of travel in the alternative configuration of the embodiment of the present disclosure.FIG. 14is a diagram showing drive states of the front wheel15(FIG. 1) and the rear wheel16(FIG. 1) during start of travel, a low-speed travel, and a high-speed travel of the vehicle.

A movable structure driving unit of the present configuration is a structure that smoothens the start of the travel of the vehicle in the structure ofFIG. 1˜FIG. 7. In the structure ofFIG. 1˜FIG. 7, when the vehicle is stopped, the fixed sheave27aand the movable sheave27bin the input pulley27of the CVT26are significantly separated from each other. With this structure, no tensioning force is generated in the belt29between the input pulley27and the output pulley28, and the motive power transmission between the engine21and the input shaft31of the gear transmission device30is suspended. In this case, even if the vehicle attempts to start traveling in a state where the two-wheel drive in which the vehicle travels only with the driving of the rear wheel16is instructed, the tensioning force is not generated in the belt29until the rotational speed of the engine21is increased to a predetermined value or greater. Thus, there is a room for improvement in the travel starting capability. In particular, when the user moves his/her feet off both of the acceleration pedal60and the brake pedal (when the pedals are switched OFF) in order to start traveling the vehicle at a very low speed, the vehicle attempts to creep-travel in a state where the engine21is rotated at an idling rotation number. However, because the tensioning force generated in the belt29is low, slipping tends to occur between the input pulley27and the output pulley28and the belt29, and motive power tends to be not transmitted from the input pulley27to the belt29. Because of this, the travel starting capability of the vehicle is low, and, for example, when the motive power is transmitted from the input pulley27to the belt29, the connection of the motive power transmission rapidly changes from a disconnected state to a connected state, and the shock caused thereby is significant. In addition, because slipping tends to occur in the belt29during the start of travel, the belt29tends to be easily worn. The structure shown inFIG. 12FIG. 14resolves such a disadvantage.

As shown inFIG. 12, in the movable structure driving unit of the present configuration, detection signals of the lever sensor53, the drive switching switch52, the pedal sensor54, the engine speed sensor57, the rear axle speed sensor55, and the front axle speed sensor56are transmitted to the control device70. Based on the received detection signals of the sensors53,54,57,55, and56and the switch52, the control device70starts the two-wheel drive of the front wheel15. Specifically, when the control device70judges that the forward movement is selected by the forward/rearward movement lever62(refer toFIG. 2), that the two-wheel drive (2WD) of the rear wheel16is instructed by the drive switching switch52, that an average rotational speed of the left and right rear axles38and an average rotational speed of the left and right front axles45are both zero, that the acceleration pedal60is in the OFF state, and that the engine21is being idle-rotated, the control device70drives the electric motor22to start the two-wheel drive of the front wheels15. In this process, the control device70stops the engine21to stop the driving of the rear wheels16. With this configuration, the start of travel of the vehicle can be smoothened and the wear of the belt29can be suppressed, as will be described later.

Further, the control device70activates the engine21to drive the front wheels15and the rear wheels16and to consequently realize the four-wheel drive (4WD) when the vehicle speed becomes greater than or equal to a first predetermined value. Moreover, the control device70stops the electric motor22and drives the engine21to realize the two-wheel drive of the rear wheel16when the vehicle speed becomes greater than or equal to a second predetermined value higher than the first predetermined value.

The control method during start of travel will now be described with reference toFIG. 13. In the following, reference numerals ofFIG. 2andFIG. 12will be used as suited. The control process ofFIG. 13is executed by the control device70. In step S21, it is judged whether or not the forward movement is selected by the forward/rearward movement lever62and the two-wheel drive (2WD) of the rear wheel16is instructed by the drive switching switch52. When the judgment of step S21is positive (YES in S21), the method proceeds to step S22. In step S22, it is judged, based on the detection signals of the rear axle speed sensor55and the front axle speed sensor56, whether or not the average rotational speeds of the left and right rear axles38and the left and right front axles45are zero. When judgment of step S22is positive (YES in S22), the method proceeds to step S23.

In step S23, it is judged, based on the detection signals of the pedal sensor54and the engine speed sensor57, whether or not the acceleration pedal60is in the OFF state and the engine21is being idle-rotated at the idling rotation number. When judgment of S23is positive (YES in S23), the method proceeds to step S24. If any of the judgments of steps S21, S22, and S23is negative (NO in any of S21, S22, and S23), the process returns to a state before step S21, and the processes are repeated.

In step S24, the electric motor and the engine21are controlled such that the electric motor22is driven but the engine21is stopped. With this process, the two-wheel drive of the front wheel15is started.

Next, in step S25, it is judged whether or not the vehicle speed calculated based on the detection signal(s) of one or both of the rear axle speed sensor55and the front axle speed sensor56is greater than or equal to a first predetermined value. When it is judged that the vehicle speed is greater than or equal to the first predetermined value (YES in S25), the method proceeds to step S26. When the judgment of step S25is negative (NO in S25), the process of step S25is repeated.

In step S26, the electric motor22and the engine21are controlled so that both of the electric motor22and the engine21are driven. With this process, the four-wheel drive is started.

In step S27, it is judged whether or not the vehicle speed calculated based on the detection signal(s) of one or both of the rear axle speed sensor55and the front axle speed sensor56is greater than or equal to a second predetermined value. When it is judged that the vehicle speed is greater than or equal to the second predetermined value (YES in S27), the method proceeds to step S28. When the judgment of step S27is negative (NO in S27), the process of step S27is repeated.

In step S28, the electric motor22and the engine21are controlled so that the electric motor22is stopped and the engine21is driven. With this process, the two-wheel drive of the rear wheel16is started, and the process is completed.

FIG. 14shows driving of each of the front wheels15and the rear wheels16with a circle (o) and stopping of the driving with an x (X). As shown inFIG. 14, during the start of travel, the front wheels15are driven and driving of the rear wheels16is stopped. In a low-speed travel in which the vehicle speed is greater than or equal to the first predetermined value, both of the front wheels15and the rear wheels16are driven. In a high-speed travel in which the vehicle speed is greater than or equal to the second predetermined value, the rear wheels16are driven and driving of the front wheels15is stopped.

According to the structure of the present configuration shown inFIG. 12FIG. 14, the two-wheel drive of the front wheels15by the electric motor22is realized when the forward movement is selected by the forward/rearward movement lever62, the two-wheel drive of the rear wheels16is instructed by the drive switching switch52, the average rotational speeds of the left and right rear axles38and the left and right front axles45are zero, the acceleration pedal60is in the OFF state, and the engine21is being idle-rotated. With this configuration, it is not necessary to drive, during the start of travel of the vehicle, the rear wheels16by the engine21via the CVT26, and thus, the vehicle is not stopped until the rotation number of the engine21is increased to a degree in which the tensioning force is generated in the belt29. Because of this, the start of the travel of the vehicle, in particular, the start of travel at a very low speed, can be smoothened. After the vehicle starts to travel, the engine21is driven when the vehicle speed becomes greater than or equal to the first predetermined value. In this process, with the increase of the rotational speed of the engine21, the motive power of the input pulley27(FIG. 3) of the CVT26is transmitted to the belt29, and, in this process, a shock is generated due to the switching of the transmission of the motive power. On the other hand, in the travel at the vehicle speed of greater than or equal to the first predetermined value, an amount of operation of the acceleration pedal60is large, and thus, the feeling of deceleration due to the shock is small in comparison to the feeling of deceleration of the vehicle due to a change of the amount of operation of the acceleration pedal60, and, consequently, uncomfortable feeling by the driver due to the shock tends not to be generated. Further, according to the structure of the present configuration, because slipping of the belt29tends to be not generated during the start of travel, the wear of the belt29can be suppressed. The other structures and operations in the present configuration are similar to those of the structure ofFIG. 1˜FIG. 7.

FIG. 15is a flowchart showing a control method during rear wheel slipping, in an alternative configuration of an embodiment of the present disclosure. A movable structure driving unit of the present configuration is a structure for improving a rough-road traveling capability in the structure ofFIG. 1˜FIG. 7. In the structure ofFIG. 1˜FIG. 7, there may be cases where the traveling capability is degraded due to slipping of the rear wheels16when the vehicle travels on a rough road such as a damp ground by two-wheel drive of the rear wheels16. The structure of the present configuration to be described with reference toFIG. 15resolves such a disadvantage.

As shown inFIG. 12, in the movable structure driving unit of the present configuration, the detection signals of the lever sensor53, the drive switching switch52, the rear axle speed sensor55, and the front axle speed sensor56are transmitted to the control device70. The control device70starts the four-wheel drive according to the received detection signals of the sensors53,55, and56, and the switch52. Specifically, the control device70judges that the rear wheels16are slipping when the forward movement or the rearward movement is selected by the forward/rearward movement lever62(FIG. 2), the two-wheel drive (2WD) of the rear wheel16is instructed by the drive switching switch52, and the average rotational speed of the left and right rear axles38(FIG. 2) is greater than the average rotational speed of the left and right front axles45(FIG. 2). When the control device70judges the slipping of the rear wheels16, the control device70drives the electric motor22(FIG. 2), to start driving the front wheels15. With this process, the four-wheel drive (4WD) is realized, and the rough-road traveling capability of the vehicle can be improved.

A control method during slipping of the rear wheel will now be described with reference toFIG. 15. In the following, the reference numerals ofFIG. 2andFIG. 12will be used as suited. The control process ofFIG. 15is executed by the control device70. In step S31, it is judged whether or not the forward movement or the rearward movement is selected by the forward/rearward movement lever62, and the two-wheel drive (2WD) of the rear wheel16is instructed by the drive switching switch52. When judgment of step S31is positive (YES in S31), the method proceeds to step S32. When the judgment of step S31is negative (NO in S31), the process returns to a state before step S31, and the process is repeated.

In step S32, it is judged based on the detection signals of the rear axle speed sensor55and the front axle speed sensor56whether or not the average rotational speed of the left and right rear axles38is greater than the average rotational speed of the left and right front axles45. When judgment of step S32is positive (YES in S32), it is judged in step S33that slipping of the rear wheels16has been caused. Then, in step S34, the four-wheel drive is realized in which the front wheels15and the rear wheels16are driven by driving of both the electric motor22and the engine21.

On the other hand, when the judgment of S32is negative (NO in S32), the electric motor22is stopped and the engine21is driven, to realize the two-wheel drive of the rear wheels16. With the completion of step S34or S35, the control process during the slipping of the rear wheel is completed.

According to the structure of the present configuration, because the four-wheel drive (4WD) is realized with the judgment of the slipping of the rear wheels16, the rough-road traveling capability of the vehicle can be improved. The other structures and operations in the present configuration are similar to those of the structure ofFIG. 1˜FIG. 7.

In the structure ofFIG. 12˜FIG. 14or in the structure ofFIG. 15, the numbers of the front wheels15and the rear wheels16of the vehicle are not limited to 2 wheels, and, for example, one of the front wheel and the rear wheel may be only one wheel attached at a center in the left-and-right direction of the vehicle body. For example, in the structure described above with reference toFIG. 15, if the rear wheel is one wheel, the rear axle is provided on a transmission path for transmitting the motive power of the engine21to the rear wheel, and the rear axle speed sensor detects a rotational speed of the rear axle. The slipping of the rear wheel is judged when the rotational speed of the rear axle is greater than the average rotational speed of the left and right front axles. Similarly, in the structure described above with reference toFIG. 15, if the front wheel is one wheel, the front axle is provided on a transmission path for transmitting the motive power of the electric motor22to the front wheel, and the front axle speed sensor detects the rotational speed of the front axle. The slipping of the rear wheel is judged when the average rotational speed of the left and right rear axles is greater than the rotational speed of the front axle.

FIG. 16is a block diagram showing an input for the control device70and a structure of the control device70in an alternative configuration of an embodiment of the present disclosure.FIG. 17is a flowchart showing a control method of a regenerative brake in the alternative configuration of the embodiment of the present disclosure.FIG. 18is a diagram showing a state of a vehicle10cmoving down an inclined road in the alternative configuration of the embodiment of the present disclosure. A movable structure driving unit of the present configuration is a structure for improving a brake force when moving down a hill road and for improving an energy efficiency, in the structure ofFIG. 1˜FIG. 7. In the structure ofFIG. 1˜FIG. 7, with only the sandwiching of the brake disc by the brake pads by stepping-on of the brake pedal during the movement of the vehicle down the hill road, the amount of stepping-on of the brake pedal becomes large, and frequency of stepping-on is also increased. The structure of the present configuration to be described with reference toFIG. 16˜FIG. 18resolves such a disadvantage, and improves the energy efficiency.

As shown inFIG. 16, in the structure of the present configuration, the detection signals of the pedal sensor54and the rear axles speed sensor55are transmitted to the control device70. The control device70has a regenerative brake controller74. The regenerative brake controller74controls the motor driving circuit24(FIG. 5) of the electric motor22according to the received detection signals of the sensors54and55, to cause the electric motor22to function as a power generator, and to recover the regenerative energy during the braking, with the electric motor22. With this process, the regenerative brake force by the electric motor22is generated in the vehicle, and the regenerative energy recovered by the electric motor22is charged to the battery23(FIG. 5) as generated electric power. Specifically, the control device70causes the electric motor22(FIG. 2) to generate the regenerative brake force (switches the regenerative brake ON) regardless of the position of the drive switching switch52, when the acceleration pedal is in the OFF state and the vehicle speed calculated based on the average rotational speed of the left and right rear axles is greater than or equal to a predetermined value.

A control method of the regenerative brake will now be described with reference toFIG. 17. In the following description, reference numerals ofFIG. 2andFIG. 16will be used as suited. The control process ofFIG. 17is executed by the control device70.

In step S42, it is judged based on the detection signal of the pedal sensor54whether or not the acceleration pedal60is in the OFF state. When judgment of step S42is positive (YES in S42), it is judged in step S43whether or not the vehicle speed is greater than or equal to a predetermined value. When judgment of step S43is positive (YES in S43), the method proceeds to step S44. In step S44, the regenerative brake force is generated by the electric motor22(regenerative brake is switched ON).

On the other hand, when judgment of step S42or S43is negative (NO in S42or S43), the generation of the regenerative brake in the electric motor22is stopped in step S45(regenerative brake is switched OFF). With the completion of the processes of steps S44and S45, the control process of the regenerative brake is completed.

According to the above-described structure, when the vehicle10cmoves down the hill road in the four-wheel drive as shown inFIG. 18, with the switching OFF of the acceleration pedal, the regenerative brake force by the electric motor22is generated, and the regenerative energy recovered by the electric motor22is charged to the battery as generated electric power. With this configuration, the braking force of the vehicle10ctraveling down the hill road can be increased, the amount of stepping-on of the brake pedal can be reduced, and the frequency of stepping-on can be reduced. In addition, because the generated electric power can be charged to the battery as the regenerative energy, the energy efficiency of the vehicle10ccan be improved. The other structures and operations in the present configuration are similar to those of the structure ofFIG. 1˜FIG. 7.

In the above-described configuration, the vehicle speed is calculated from the average rotational speed of the left and right rear axles. Alternatively, the average rotational speed of the left and right front axles may be determined based on the detection signal of the front axle speed sensor56(FIG. 16), and the vehicle speed may be calculated based on this average rotational speed.

FIG. 19is a flowchart showing a control method of the regenerative brake in an alternative configuration of an embodiment of the present disclosure. In the structure of the present configuration, as shown inFIG. 16, in the structure ofFIG. 16˜FIG. 18, an inclination sensor96is connected to the control device70. The inclination sensor96is attached to the vehicle body. The inclination sensor96detects a vehicle inclination angle θ (FIG. 18), which is an angle of a direction of travel of the vehicle with respect to a horizontal plane. The vehicle inclination angle θ is coincident with an inclination angle of the ground on which the vehicle is positioned, with respect to the horizontal plane. A detection signal indicating a detected value of the inclination sensor96is transmitted to the control device70. The control device70causes the electric motor22(FIG. 2) to generate the regenerative brake force only when the vehicle inclination angle θ is greater than or equal to a predetermined value. In addition, the control device70in this case changes the regenerative brake force according to the vehicle inclination angle θ. Specifically, the control device70increases the regenerative brake force as the vehicle inclination angle θ becomes larger. With this configuration, it becomes easier to control the behavior of the vehicle during braking.

A control method of the regenerative brake will now be described with reference toFIG. 19. In the following, reference numerals ofFIG. 2andFIG. 16will be used as suited. The control process ofFIG. 19is executed by the control device70. Processes of steps S52˜S53are similar to the processes of steps S42˜S43. After completion of the process of step S53, in step S54, it is judged whether or not the vehicle inclination angle θ with respect to the horizontal plane is greater than or equal to a predetermined value. When judgment of step S54is positive (YES in S54), the method proceeds to step S55. When the judgment of step S54is negative (NO in S54), the regenerative brake is switched OFF in step S56. In step S55, the regenerative brake force is generated by the electric motor22(the regenerative brake is switched ON), and the regenerative brake force is changed according to the vehicle inclination angle θ. Specifically, as the vehicle inclination angle θ becomes larger, the regenerative brake force is set larger.

According to the above-described structure, because the regenerative brake force is generated by the electric motor22only when the vehicle inclination angle θ is greater than or equal to a predetermined value when the vehicle moves down an inclined road, the regenerative brake is not generated during a flat-ground travel which does not require a large brake force as compared to the inclined road. With this configuration, it becomes easier to control the behavior during braking of the vehicle in the flat-ground travel, with the operation of the brake pedal. The other structures and operations in the present configuration are similar to those of the structure ofFIG. 1˜FIG. 7.

FIG. 20is a block diagram showing an input and an output for the control device70and a structure of the control device70in an alternative configuration of an embodiment of the present disclosure.FIG. 21is a flowchart showing a control method of the regenerative brake and the CVT in the alternative configuration of the embodiment of the present disclosure.

A structure of the present configuration is targeted to improving endurance of the belt in a vehicle which generates the regenerative brake force according to the vehicle speed, as in the structure ofFIG. 16andFIG. 17. For this purpose, in the structure of the present configuration, the control device70has a regenerative brake controller74aand a CVT controller76. The CVT controller76controls the driving of the actuator26awhich moves the movable sheave27b(FIG. 3) of the CVT26.

The control device70controls the motor driving circuit24by the regenerative brake controller74ato generate the regenerative brake force by the electric motor22(FIG. 2) (regenerative brake is switched ON) when the acceleration pedal60(FIG. 1) is in the OFF state and a vehicle speed calculated from the average rotational speed of the left and right rear axles38(FIG. 2) is greater than or equal to a predetermined value. Along with this control, the control device70controls the actuator26awith the CVT controller76to set the movable sheave27bshown inFIG. 3to be largely separated from the fixed sheave27a, and to consequently set the tensioning force of the belt29to zero.

Further, when the vehicle speed continues to be greater than or equal to the predetermined value after the above-described process, the control device70controls the actuator26awith the CVT controller76, to move the movable sheave27bofFIG. 3closer to the fixed sheave27a, to consequently increase the tensioning force of the belt29.

A control method of the regenerative brake and the CVT will now be described with reference toFIG. 21. In the following, reference numerals ofFIG. 2,FIG. 3, andFIG. 20will be used as suited. The control process ofFIG. 21is executed by the control device70.

In step S62, it is judged, based on the detection signal of the pedal sensor54, whether or not the acceleration pedal60is in the OFF state. When judgment of step S62is positive (YES in S62), it is judged in step S63whether or not the vehicle speed is greater than or equal to a predetermined value. When judgment of step S63is positive (YES in S63), the method proceeds to step S64. In step S64, the tensioning force of the belt of the CVT26is set to zero, and the regenerative brake force is generated by the electric motor22(the regenerative brake is switched ON).

Next, in step S65, it is again judged whether or not the vehicle speed is greater than or equal to the predetermined value. When judgment of step S65is positive (YES in S65), the method proceeds to step S66. In step S66, the belt tensioning force of the CVT26is increased. With this process, the engine brake is activated along with the regenerative brake of the electric motor22, and the vehicle can be more strongly braked. For example, when the inclination of the hill road on which the vehicle is moving down is large and the vehicle speed is not reduced with the regenerative brake alone, the vehicle can be more strongly braked with the engine brake.

Alternatively, between the steps S64and S65, a step may be provided in which it is judged whether or not a predetermined time has elapsed after execution of step S64, and the method may proceed to step S65only after the predetermined time has elapsed.

On the other hand, when the judgment of step S62is negative (NO in S62), a normal transmission control of the CVT26is executed in step S67, and the process is completed. Moreover, when the judgment of step S63or S65is negative (NO in S63or S65), the generation of the regenerative brake by the electric motor22is stopped in step S68(the regenerative brake is switched OFF). Then, in step S69, the actuator26ais controlled by the CVT controller76to largely separate the movable sheave27bfrom the fixed sheave27aso that the belt tensioning force of the CVT26is set to zero. In this case, the driver of the vehicle can brake the vehicle by sandwiching of the brake disc due to stepping-in of the brake pedal.

According to the above-described structure, when a strong brake force is needed, the brake force of the engine brake can be added to the brake force of the regenerative brake, and when the vehicle speed is reduced, the belt tensioning force of the CVT26is set to zero. Thus, it is not necessary to always generate the engine brake, and, consequently, the endurance of the belt29of the CVT26can be improved in a structure which can generate a strong brake force. The other structures and operations in the present configuration are similar to those of the structure ofFIG. 1˜FIG. 6or the structure ofFIG. 16andFIG. 17.

FIG. 22˜FIG. 25show an alternative configuration of an embodiment of the present disclosure.FIG. 22is a diagram showing an overall structure of a movable structure driving unit20cof the alternative configuration of the embodiment of the present disclosure.FIG. 23is a diagram showing structures of a driving circuit of the electric motor22and the control device70in the alternative configuration of the embodiment of the present disclosure. In a vehicle10don which the movable structure driving unit20cofFIG. 22is mounted, outer sizes of the front wheels15and the rear wheels16are identical or approximately identical to each other. The engine21corresponds to a rear-side motive power source.

The sensor switch group50includes a first lever sensor53a(FIG. 23), and a second lever sensor59(FIG. 23) to be described later. The first lever sensor53ais formed similarly as the lever sensor53of the structure ofFIG. 1˜FIG. 7. The second lever sensor59detects an operation position of a mode lever63for instructing switching between a hard road surface mode and a soft road surface mode, as will be described later. The mode lever63forms the operation element group18, and corresponds to a mode instructor.

The control device70applies a control to set the rotational speed of the front wheels15higher than the rotational speed of the rear wheels16when the four-wheel drive travel is instructed and the soft road surface mode is instructed by the operation of the mode lever63, as will be described later. With this process, stability of the soft road surface travel by the vehicle of the four-wheel drive can be improved.

The steering operator61is connected to the pair of front wheels15at the left and right via a steering mechanism180of an Ackermann type, in a manner to allow steering of the front wheels15.

The mode lever63is provided to instruct switching between the hard road surface mode at a display position of “hard” and the soft road surface mode at a display position of “soft.” The “hard road surface mode” is a mode suited for travel on a hard road surface having a relatively high frictional force with the wheels, and the “soft road surface mode” is a mode suited for travel on a soft road surface having a relatively low frictional force with the wheels. The mode lever63is placed, for example, near the front cover13at a front side of the driver seat14, and is supported on the vehicle body in a manner to allow swing. The second lever sensor59(FIG. 23) corresponds to the mode lever63.

An operation angle sensor58(FIG. 23) detects an operation angle from a neutral position of the steering operator61. The operation angle sensor58outputs, for example, a positive operation angle for a case where the steering operator61is rotated to the right from the neutral position, and a negative operation angle for a case where the steering operator61is rotated to the left from the neutral position. The relationship between the rotational directions of right and left and the positive and negative of the operation angle may alternatively be reversed. A detection signal of the operation angle sensor58is transmitted to the control device70. With this configuration, the control device70can calculate an amount of turn of the steering operator61.

In addition, the second lever sensor59(FIG. 23) detects a position of the mode lever63, and transmits a detection signal thereof to the control device70. The control device70changes the relationship between the rotational speeds of the rear wheel16and the front wheel15as will be described later, according to the road surface mode instructed by the mode lever63.

The control device70has the engine controller71(FIG. 23) and the motor controller72(FIG. 23). The motor controller72changes the relationship between the rotational speeds of the rear wheels16and the front wheels15according to the road surface mode instructed by the mode lever63. Specifically, the motor controller72controls the rotational speed of the electric motor22, to match the rotational speed Vf of the front wheels15to the rotational speed Vr of the rear wheels16, when the four-wheel drive is instructed by the drive switching switch52and the hard road surface mode is instructed by the mode lever63. With this process, the front wheels15and the rear wheels16rotate at the same speed. Here, as the rotational speed Vr of the rear wheels16, an average rotational speed Vrm of the pair of rear wheels16is used. The average rotational speed Vrm of the pair of rear wheels16is determined based on the detection signal which is transmitted from the rear axle speed sensor55to the control device70. In addition, as the rotational speed Vf of the front wheels15, an average rotational speed Vfm of the pair of the front wheels15is used. The average rotational speed Vfm of the pair of the front wheels15is determined based on the detection signal which is transmitted from the front axle speed sensor56to the control device70.

On the other hand, when the soft road surface mode is instructed by the mode lever63, the motor controller72controls the rotational speed of the electric motor22so as to set the rotational speed Vf of the front wheels15to be higher than the rotational speed Vr of the rear wheels16. Similar to the instruction of the hard road surface mode, here also, as the rotational speed of the rear wheels16, the average rotational speed of the pair of the rear wheels16is used. In addition, as the rotational speed of the front wheels15, the average rotational speed of the pair of the front wheels15is used. In a state where the amount of turn of the steering operator61is zero; that is, when a straight movement is instructed, the rotational speed of the front wheels15is set to a value, for example, obtained by increasing the rotational speed of the rear wheel16by a predetermined ratio or by a predetermined amount.

Further, the motor controller72applies a control when the soft road surface mode is instructed by the mode lever63, such that, as the amount of turn by the steering operator61is increased, the amount of increase of the average rotational speed Vfm of the pair of the front wheels15with respect to the average rotational speed Vrm of the pair of the rear wheels16is increased.

FIG. 24is a diagram showing a relationship between the operation angle of the steering operator61and the amount of increase of the front-wheel rotational speed with respect to the rear-wheel rotational speed when the soft road surface mode is instructed in the embodiment of the present disclosure. In the example structure ofFIG. 24, as an absolute amount of the operation angle of the steering operator61is increased, the amount of increase of the rotational speed of the front wheels15with respect to the rotational speed of the rear wheels16is increased linearly. In addition, the relationship between the amount of increase and the operation angle is the same between the case where the steering operator61is rotated to the right and the case where the steering operator61is rotated to the left. Such a relationship between the operation angle of the steering operator61and the amount of increase of the front-wheel rotational speed with respect to the rear-wheel rotational speed is stored in the storage unit of the control device70in advance. The motor controller72controls the electric motor22according to the relationship stored in the storage unit, and to increase the amount of increase of the average rotational speed of the pair of the front wheels15with respect to the average rotational speed of the pair of the rear wheels16, as the amount of turn described above is increased.

The relationship between the amount of increase of the front-wheel rotational speed with respect to the rear-wheel rotational speed and the operation angle described above is not limited to the example ofFIG. 24. For example, the amount of increase of the rotational speed of the front wheels with respect to the rotational speed of the rear wheels may be increased in a curved line shape as the absolute amount of the operation angle is increased.

FIG. 25is a flowchart showing an example of a control process of the movable structure driving unit20chaving the above-described structure, and showing a control method of the driving of the front wheels15and the rear wheels16during travel with four-wheel drive. In the following, the reference numerals ofFIG. 1,FIG. 22, andFIG. 23will be used as suited. Processes of steps S71˜S74are executed by the motor controller72. In step S71, it is judged whether or not there is an instruction of four-wheel drive. When it is judged that there is the instruction of four-wheel drive (YES in S71), in step S72, it is judged whether or not the hard road surface mode is instructed by the mode lever63. When it is judged that the hard road surface mode is instructed (YES in S72), in step S73, the electric motor22is controlled so that the average rotational speed Vfm of the front wheels15matches the average rotational speed Vrm of the rear wheels16. With this configuration, by the driver judging that the ground on which the vehicle is traveling or is about to travel is a hard road surface and switching the mode lever63to the hard road surface mode, a travel can be achieved in which the average rotational speeds of the front wheels15and the rear wheels16are matched. In this manner, wear of the wheels during the travel can be suppressed. When the vehicle travels on a location where the ground does not be wanted to be disturbed such as a lawn, the driver may instruct the hard road surface mode with the mode lever63to set the rotational speed difference between the front and rear wheels to zero, and to consequently suppress disturbance of the ground.

When the judgment of step S71ofFIG. 25is negative (NO in S71), the process of step S71is repeated. When the judgment of step S72ofFIG. 25is negative (NO in S72); that is, when it is judged that the soft road surface mode is instructed by the mode lever63, in step S74, the electric motor22is controlled such that the average rotational speed Vfm of the front wheels15is higher than the average rotational speed Vrm of the rear wheels16. With this configuration, by the driver judging that the ground on which the vehicle is traveling or is about to travel is a soft road surface such as a swamp or damp ground, and switching the mode lever63to the soft road surface mode, the average rotational speed of the front wheels15can be set to be higher than the average rotational speed of the rear wheels16. Because of this, in the travel of the soft road surface with four-wheel drive, the motive power of the front wheels15can be more easily transmitted to the ground, and swinging of the front wheels15can be suppressed. Therefore, because the vehicle can stably travel in a direction of travel intended by the driver such as a forward movement in a straight direction, the stability of the soft road surface travel can be improved according to the instruction of the driver.

Further, in step S74, the electric motor22is controlled so that the amount of increase of the average rotational speed Vfm of the front wheels15with respect to the average rotational speed Vrm of the rear wheels16is increased according to the amount of turn of the steering operator61. With this configuration, when the orientation of the vehicle is to be changed by turning the steering operator61, the vehicle can more easily move in the direction corresponding to the front wheels15, resulting in easier turning. After completion of the processes of steps S73and S74, the method returns to step S71and the processes are repeated. Alternatively, in step S74, the amount of increase of the average rotational speed of the front wheels15with respect to the average rotational speed of the rear wheels16may be set invariable with the amount of turn of the steering operator61.

In addition, in the above, a case is described in which the rotational speed of the electric motor22is controlled with the instruction of the soft road surface mode, such that the rotational speed of the front wheels15is set higher than the rotational speed of the rear wheels16. On the other hand, as an alternative configuration, for example, with the instruction of the soft road surface mode, the control device70may control the CVT26so that the rotational speed of the rear wheels16is lower than the rotational speed of the front wheels15by setting a gear ratio of the CVT26higher than that in the case of the hard road surface mode. The other structures and operations in the present configuration are similar to those of the structure ofFIG. 1˜FIG. 7.

FIG. 26is a block diagram showing an input for the control device70and a structure of the control device70in an alternative configuration of an embodiment of the present disclosure. A movable structure driving unit of the present configuration is a structure for smoothening start of travel of the vehicle in the structure ofFIG. 22˜FIG. 25.

As shown inFIG. 26, in the movable structure driving unit of the present configuration, detection signals of the first lever sensor53a, the drive switching switch52, the pedal sensor54, the engine speed sensor57, the rear axle speed sensor55, and the front axle speed sensor56are transmitted to the control device70.

In the present configuration, the control method during start of travel is similar to that ofFIG. 13. The driving of the front wheels15and the rear wheels16is similar to that ofFIG. 14. Further, the other structures and operations in the present configuration are similar to those of the structure ofFIG. 22˜FIG. 25or the structure ofFIG. 12˜FIG. 14.

The structure ofFIG. 22˜FIG. 25may be combined with the structure ofFIG. 15, to achieve a structure which improves the rough road traveling capability.

In a structure in which the structure ofFIG. 26or the structure ofFIG. 22FIG. 25is combined with the structure ofFIG. 15, the numbers of wheels for the front wheels15and the rear wheels16of the vehicle are not limited to two wheels, respectively, and, for example, one of the front wheel and the rear wheel may be only one wheel attached to the vehicle body at a center in the left-and-right direction. For example, in a structure combined withFIG. 15, if the rear wheel is only one wheel, the rear axle is provided on a transmission path for transmitting the motive power of the engine21to the rear wheel, and the rear axle speed sensor detects the rotational speed of the rear axle. When the rotational speed of the rear axle is larger than the average rotational speed of the left and right front axles, the slipping of the rear wheel is judged. Alternatively, in a structure combined withFIG. 15, if the front wheel is only one wheel, the front axle is provided on a transmission path for transmitting the motive power of the electric motor22to the front wheel, and the front axle speed sensor detects the rotational speed of the front axle. When the average rotational speed of the left and right rear axles is larger than the rotational speed of the front axle, the slipping of the rear wheels is judged.

Alternatively, the structure ofFIG. 22˜FIG. 25or the structure ofFIG. 26may be combined with the structure ofFIG. 16˜FIG. 17to achieve a structure in which the brake force when the vehicle moves down a hill road is improved and the energy efficiency is improved. The state of the vehicle moving down the hill road is similar to that shown inFIG. 18.

Alternatively, the structure ofFIG. 22˜FIG. 25or the structure ofFIG. 26may be combined with the structure ofFIG. 19to achieve a structure to control the regenerative brake.

Alternatively, the structure ofFIG. 22˜FIG. 25or the structure ofFIG. 26may be combined with the structure ofFIG. 20˜FIG. 21to achieve a structure in which the endurance of the belt is improved in a vehicle which generates the regenerative brake force according to the vehicle speed. In this case, the control device70includes the regenerative brake controller and the CVT controller. The CVT controller controls driving of the actuator26awhich moves the movable sheave27b(FIG. 3) of the CVT.

In the configurations described above, the rear wheels16are driven by the engine21, but alternatively, the rear wheels may be driven by a second electric motor serving as the rear-side motive power source. For example, the four-wheel drive is realized by driving of the electric motor22and the second electric motor.

FIG. 27is a diagram showing an overall structure of a movable structure driving unit20din an alternative configuration of an embodiment of the present disclosure.FIG. 28is a diagram showing structures of a driving circuit of the electric motor22and the control device70in the alternative configuration of the embodiment of the present disclosure. In a vehicle10eon which the movable structure driving unit20dshown inFIG. 27andFIG. 28is mounted, outer sizes of the front wheels15and the rear wheels16are identical or approximately identical to each other. The front wheels15correspond to a first wheel, of a plurality of wheels, at a first side in a front-and-rear direction. The rear wheels16corresponds to a second wheel, of the plurality of wheels, at a second side in the front-and-rear direction.

The engine21corresponds to the rear-side motive power source. The sensor switch group50includes a load detector47to be described later. The load detector47detects a load of the engine21. The control device70controls the electric motor22according to a detected value of the load detector47.

The control device70drives the electric motor22to drive all of the front wheels15and the rear wheels16when the detected value of the load detector47becomes greater than or equal to a first predetermined value in a state where the two-wheel drive of the rear wheels16is instructed as will be described below. In this manner, stopping of engine due to excessive load can be prevented, and fuel consumption can be improved.

The CVT26is a belt CVT which achieves continuously variable transmission by changing an amount of tension of the belt by an electric actuator. The differential device43corresponds to a differential device.

As shown inFIG. 27andFIG. 28, the sensor switch group50includes the lever sensor53(FIG. 28) corresponding to the forward/rearward movement lever62, the drive switching switch52, and the pedal sensor54. The pedal sensor54corresponds to a first detector. The sensor switch group50also includes the rear axle speed sensor55, the front axle speed sensor56, and the engine speed sensor57.

The drive switching switch52is provided to be operable by the driver on a drive panel on which the forward/rearward movement lever62protrudes, and instructs a drive state of the vehicle by an operation.

The rear axle speed sensor55corresponds to a third detector. The average rotational speed of a pair of the rear axles38at the left and right matches the average rotational speed of the two rear wheels16at the left and right. A detection signal of the rear axle speed sensor55is input to the control device70. The rear axle speed sensor55corresponds to a detector which detects a rotational speed of a first wheel.

The average rotational speed of the pair of the front axles45at the left and right matches the average rotational speed of the two front wheels15at the left and right. A detection signal of the front axle speed sensor56is input to the control device70. The front axle speed sensor56corresponds to a detector which detects a rotational speed of a second wheel. The engine speed sensor57corresponds to a second detector.

As shown inFIG. 28, the control device70has the engine controller71, the motor controller72, and a load calculation unit75.

The load calculation unit75calculates the load of the engine21based on a combination of a part or all of the detected values of the pedal sensor54, the engine speed sensor57, and the rear axle speed sensor55. For example, the load calculation unit75calculates the load of the engine21based on the detected value of the amount of operation of the acceleration pedal60detected by the pedal sensor54and the detected value of the engine speed sensor57. For example, when the detected value of the engine speed sensor57is lower than that in a normal time in relation to the detected value of the pedal sensor54, the calculated value of the engine load would be high. Alternatively, the load calculation unit75may calculate the load of the engine21based on the detected value of the pedal sensor54and the average rotational speed of the pair of the rear wheels16detected by the rear axle speed sensor55. For example, when the detected value of the rear axle speed sensor55is lower than that in a normal time in relation to the detected value of the pedal sensor54, the calculated value of the engine load would be high. The load detector47is formed including the pedal sensor54, the engine speed sensor57, the rear axle speed sensor55, and the load calculation unit75. The load calculation unit75may calculate the vehicle speed based on the detected value of the rear axle speed sensor55, and may calculate the engine load using the calculated value of the vehicle speed and the detected value of the pedal sensor54or the engine speed sensor57.

The motor controller72drives the electric motor22when the detected value of the load detector47becomes greater than or equal to a first predetermined value in a state where the two-wheel drive is instructed in which the driving of the front wheels15by the electric motor22is stopped and the rear wheels16are driven by the engine21. With this process, the motor controller72drives all of the front wheels15and the rear wheels16, to realize four-wheel drive.

FIG. 29is a flowchart showing an example of a control process of the movable structure driving unit20dhaving the above-described structure, and showing a method of controlling the electric motor22according to the load of the engine21. In the following, the reference numerals ofFIG. 1,FIG. 27, andFIG. 28will be used as suited. Processes of steps S81˜S85are executed by the control device70. In step S81, it is judged whether or not there is an instruction of two-wheel drive (2WD). When it is judged that there is the instruction of the two-wheel drive (YES in S81), in step S82, the load of the engine21is calculated by the load calculation unit75, and the motor controller72judges whether or not the detected value of the load detector47is greater than or equal to a first predetermined value. When it is judged that the detected value of the load detector47is greater than or equal to the first predetermined value (YES in S82), the method proceeds to step S83. In step S83, the four-wheel drive is realized in which the motor controller72drives the electric motor22so that all of the front wheels15and the rear wheels16are driven. With this configuration, because the electric motor22assists the travel of the vehicle10ewhen the load of the engine21is high in the vehicle which drives the rear wheels16by the engine21, stopping of the engine due to excessive load can be prevented and fuel consumption can be improved.

After the four-wheel drive is started in step S83, the method proceeds to S84. In S84, the motor controller72judges whether or not the detected value of the load detector47became lower than or equal to a second predetermined value lower than the first predetermined value. When judgment of step S84is positive (YES in S84), in step S85, the driving of the electric motor22is stopped. With this process, the vehicle returns from the four-wheel drive state in which all of the front wheels15and the rear wheels16are driven to the two-wheel drive state in which only the rear wheels16are driven. Because of this, the electric motor22is stopped when the load of the engine21is reduced, and the electric power consumption of the battery23can thus be suppressed.

On the other hand, when the judgment of step S81ofFIG. 29is negative (NO in S81), the process of step S81is repeated. In addition, when the judgment of step S84is negative (NO in S84), the process of step S84is repeated. Further, when the judgment of step S82is negative (NO in S82); that is, when the detected value of the load detector47is not greater than or equal to the first predetermined value, the two-wheel drive of the rear wheels16is executed in S85.

In the above description, a case is described in which the load calculation unit75calculates the load of the engine21from a combination of a part or all of the detected values of the pedal sensor54, the engine speed sensor57, and the rear axle speed sensor55. Alternatively, the load calculation unit75may have a structure in which the load of the engine21is calculated from a combination of a part or all of the detected values of the pedal sensor54, the engine speed sensor57, and the front axle speed sensor56(FIG. 28). The load calculation unit75may calculate the vehicle speed based on the detected value of the front axle speed sensor56, and may calculate the engine load using the calculated value of the vehicle speed and the detected value of the pedal sensor54or the engine speed sensor57. The other structures and operations in the present configuration are similar to those of the structure ofFIG. 1˜FIG. 7.

An alternative configuration of an embodiment of the present disclosure will now be described with reference toFIG. 28. In the structure of the present configuration, as shown inFIG. 28, the movable structure driving unit has a drive switching switch52ain place of the drive switching switch52(FIG. 27).

The drive switching switch52ais provided in a manner to be operable by the driver, and instructs a drive state of the vehicle with the operation. Specifically, with the operation of the drive switching switch52a, the instruction is switched among an instruction to set the vehicle in the two-wheel drive (2WD) state, an instruction to set the vehicle in the four-wheel drive state according to request of the driver (on-demand 4WD), and an instruction to set the vehicle always in the four-wheel drive state (continuous 4WD). The instruction of the two-wheel drive state of the drive switching switch52aand the instruction of the four-wheel drive state according to the request of the driver are similar to the instruction of the two-wheel drive state and the instruction of the four-wheel drive state of the drive switching switch52in the structure described above with reference toFIG. 27˜FIG. 29.

On the other hand, when the drive switching switch52ais switched to the state of the continuous four-wheel drive state by the operation of the driver, the motor controller72is configured to continuously drive the electric motor22regardless of the detection of the load detector47. The other structures and operations in the present configuration are similar to those of the structure described above with reference toFIG. 27˜FIG. 29.

FIG. 30is a block diagram showing an input for the control device70and a structure of the control device70in an alternative configuration of an embodiment of the present disclosure.FIG. 31is a diagram showing a suspension device80aand a front extension/contraction sensor97afor a right front wheel15in the alternative configuration of the embodiment of the present disclosure, as viewed from the front side of the vehicle, and with a portion omitted.FIG. 32is a diagram showing a suspension device80band a rear extension/contraction sensor97bfor a right rear wheel16in the alternative configuration of the embodiment of the present disclosure, as viewed from the front side of the vehicle, and with a portion omitted.

In the structure of the present configuration, a movable structure driving unit20e(FIG. 31andFIG. 32) comprises the front extension/contraction sensor97aand the rear extension/contraction sensor97b. The front extension/contraction sensor97adetects a degree of extension/contraction of the suspension device80a(FIG. 31) at the front side of a vehicle10f(FIG. 31,FIG. 32). The rear extension/contraction sensor97bdetects a degree of extension/contraction of the suspension device80b(FIG. 32) at the rear side of the vehicle10fThe front extension/contraction sensor97acorresponds to a first extension/contraction detector, and the rear extension/contraction sensor97bcorresponds to a second extension/contraction detector.

Specifically, as shown inFIG. 31, each of the front wheels15is supported on the vehicle body via the suspension device80aat the front side. The suspension device80aincludes a plurality of arms81and82, and a rod-cylinder unit84which extends and contracts. The plurality of arms81and82are placed separated in upper and lower sides in each of left and right sides, and inner ends, in the width direction of the vehicle, of the arms81and82are supported on the frame11(FIG. 1), in a rotatable manner about axes85and86along the front-and-rear direction. Outer ends, in the width direction of the vehicle, of the arms81and82are supported on an upper end and a lower end of a wheel support unit88which rotatably supports the front wheel15, in a rotatable manner about axes89and90along the front-and-rear direction.

The rod-cylinder unit84includes a cylinder case84aand a rod84bwhich extends from a lower side of the cylinder case84a. A lower end of the rod84bis connected to the arm82at the lower side in a rotatable manner about an axis91along the front-and-rear direction. An upper end of the cylinder case84ais connected to a portion (not shown) of the frame11(FIG. 1) in a rotatable manner about an axis along the front-and-rear direction. An upper end of the rod84bis connected to a piston (not shown) in the cylinder case84a. Oil or air is sealed between the cylinder and the piston in the cylinder case84a.

The front extension/contraction sensor97ais connected between the cylinder case84aand the lower end of the rod84b, and detects a degree of extension/contraction of the suspension device80abased on a change of a protrusion length of the rod84bfrom the cylinder case84a. A detection signal of the front extension/contraction sensor97ais transmitted to the control device70(FIG. 30).

As shown inFIG. 32, each of the rear wheels16is supported on the vehicle body via the suspension device80bat the rear side. The structure of the suspension device80bis similar to the structure of the suspension device80a(FIG. 31).

The rear extension/contraction sensor97bis connected between a cylinder case98aof a rod-cylinder unit98of the suspension device80band a lower end of a rod98b, and detects a degree of extension/contraction of the suspension device80bbased on a change of a protrusion length of the rod98bfrom the cylinder case98a. A detection signal of the rear extension/contraction sensor97bis transmitted to the control device70(FIG. 30).

The load calculation unit75of the control device70detects the load of the engine21based on a change in relationship between the detected values of the front extension/contraction sensor97aand those of the rear extension/contraction sensor97b. Specifically, when a large number of pieces of luggage are carried on the carriage19(FIG. 1) of the vehicle, the rear side of the vehicle body is significantly lowered as compared to the front side, as shown by an arrow P inFIG. 32. With this process, the upper end of the cylinder case98aand the axis86, of the arm82at the lower side, on the vehicle body side, of the suspension device80bat the rear side are significantly lowered. In this process, due to a difference between an inclination angle of the rod-cylinder unit98with respect to a vertical direction and an inclination angle of the arm82with respect to the vertical direction, the length of the rod-cylinder unit98is significantly reduced, as shown by an arrow Q inFIG. 32. Thus, the rod-cylinder unit98of the suspension device80bis significantly contracted in comparison to the rod-cylinder unit84of the suspension device80a. Therefore, the amount of luggage can be calculated from the relationship of the degrees of extension/contraction of the rod-cylinder units84and98at the front and the rear, and, consequently, the load calculation unit75can detect the load of the engine21by a calculation based on this relationship. The control device70stores in the storage unit in advance the relationship between the relationship between the degrees of extension/contraction of the rod-cylinder units84and98at the front and the rear, and the load of the engine21.

The motor controller72drives the electric motor22to switch the vehicle to the four-wheel drive when the load of the engine21detected in the manner described above becomes greater than or equal to a first predetermined value in a case where the two-wheel drive of the rear wheel16by driving of the engine21is instructed. The other structures and operations in the present configuration are similar to those of the structure ofFIG. 1˜FIG. 7or those of the structure ofFIG. 27˜FIG. 29.

Alternatively, the structure ofFIG. 27˜FIG. 29or the structure ofFIG. 30FIG. 32may be combined with the structure ofFIG. 12˜FIG. 14, to realize a structure for smoothening the start of travel of the vehicle.

In this case, the control method at the start of travel is similar to that ofFIG. 13. The driving of the front wheels15and the rear wheels16is similar to that ofFIG. 14. The other structures and operations in the present configuration are similar to those of the structure ofFIG. 27˜FIG. 29, the structure ofFIG. 30˜FIG. 32, or the structure ofFIG. 12˜FIG. 14.

Alternatively, the structure ofFIG. 27˜FIG. 29or the structure ofFIG. 30FIG. 32may be combined with the structure ofFIG. 15, to realize a structure for improving the rough road traveling capability.

In the structure ofFIG. 27˜FIG. 29or the structure ofFIG. 30˜FIG. 32, or a structure in which each of these structures is combined with the structure ofFIG. 12˜FIG. 14or the structure ofFIG. 15, each of the front wheels15and the rear wheels16of the vehicle is not limited to two wheels, and for example, one of the front wheel and the rear wheel may be only one wheel attached at the center in the left and right direction of the vehicle body. For example, in the structure combined with the structure ofFIG. 15, if the rear wheel is to be set as one wheel, the rear axle is provided on a transmission path for transmitting the motive power of the engine21to the rear wheel, and the rear axle speed sensor detects the rotational speed of the rear axle. The slipping of the rear wheel is judged when the rotational speed of the rear axle is higher than the average rotational speed of the front axles at the left and right. Similarly, in the structure combined with the structure ofFIG. 15, if the front wheel is to be set as one wheel, the front axle is provided on a transmission path for transmitting the motive power of the electric motor22to the front wheel, and the front axle speed sensor detects the rotational speed of the front axle. The slipping of the rear wheel is judged when the average rotational speed of the rear axle at the left and right is higher than the rotational speed of the front axle.

Alternatively, the structure ofFIG. 271˜FIG. 29or the structure ofFIG. 30FIG. 32may be combined with the structure ofFIG. 16˜FIG. 17, to realize a structure for improving the brake force when moving down the hill road and for improving the energy efficiency. The state of the vehicle moving down the hill road is similar to that shown inFIG. 18.

Alternatively, the structure ofFIG. 27˜FIG. 29or the structure ofFIG. 30FIG. 32may be combined with the structure ofFIG. 19, to realize a structure for controlling the regenerative brake.

Alternatively, the structure ofFIG. 27˜FIG. 29or the structure ofFIG. 30FIG. 32may be combined with the structure ofFIG. 20˜FIG. 21, to realize a structure in which, in a vehicle which generates the regenerative brake force according to the vehicle speed, the endurance of the belt is improved. In this case, the control device70has the regenerative brake controller and the CVT controller. The CVT controller controls driving of the actuator26awhich moves the movable sheave27b(FIG. 3) of the CVT26.

Next, two alternative configurations of an embodiment of the present disclosure will be described. The structures of the two alternative configurations are targeted to preventing disadvantages caused in a vehicle10gby an obstacle100shown inFIG. 33andFIG. 34, respectively. The disadvantages will first be described with reference toFIG. 33andFIG. 34.FIG. 33is a diagram showing a disadvantage caused by the obstacle100during the forward movement of the vehicle10g. When the vehicle10gis moving forward by the driving of the front wheel15and the rear wheel16in a direction of an arrow shown inFIG. 33, there may be a case where one of both of the front wheels15comes in contact with the obstacle100. A load is then applied to the front wheel15, and an excessively large load may be caused in the front-side motive power transmission unit41(FIG. 27) which drives the front wheels15.

FIG. 34shows a disadvantage caused by the obstacle100during a rearward movement of the vehicle10g. When the vehicle10gis moving rearward by driving of the front wheels15and the rear wheels16in a direction of an arrow shown inFIG. 34, there may be a case where one or both of the rear wheels16comes in contact with the obstacle100. A load is then applied to the rear wheel16, and an excessive large load may be caused in the rear-side motive power transmission unit25(FIG. 27) which drives the rear wheels16.

FIG. 35is a flowchart showing a control method of the electric motor22and the engine21in the alternative configuration for preventing the disadvantage shown inFIG. 33. In the following, the reference numerals ofFIG. 1andFIG. 27˜FIG. 29will be used as suited. A control process ofFIG. 35is executed by the control device70. In step S91, it is judged whether or not the forward movement is selected by the forward/rearward movement lever62, and the four-wheel drive (4WD) is instructed by the drive switching switch52. When judgment of step S91is positive (YES in S91), the method proceeds to step S92. When the judgment of step S91is negative (NO in S91), the method returns to a state before step S91, and the process is repeated.

In step S92, both of the electric motor22and the engine21are driven, to realize the four-wheel drive of the forward movement. In this process, the electric motor22receives a detection result of the lever sensor53(FIG. 28) and causes the front axle45to rotate in a direction corresponding to the forward movement, and, at the gear transmission device30(FIG. 27), the rear axle38(FIG. 27) is rotated in a direction corresponding to the forward movement.

In step S93, it is judged, based on the detection signals of the rear axle speed sensor55and the front axle speed sensor56, whether or not the average rotational speed of the left and right front axles45became lower than the average rotational speed of the left and right rear axles38. When judgement of step S93is positive (YES in S93), the rotational speed of the front wheels15became lower than the rotational speed of the rear wheels16, and it is judged in step S94that a high load is caused in the front wheels15. Then, in step S95, the supply of the driving current to the electric motor22is stopped, so that the two-wheel drive of the forward movement is realized in which only the rear wheels16, of the front wheels15and the rear wheels16, are driven.

On the other hand, when the judgment of step S93is negative (NO in S93), the process according to the load of the front wheels15is completed with the four-wheel drive of the forward movement maintained.

According to the structure of the present configuration, even when one or both of the front wheels15comes in contact with the obstacle100and the load of the front-side motive power transmission unit41is about to increase, the increase of the load can be suppressed by the stopping of the electric motor22. With such a structure, the front-side motive power transmission unit41can be protected. The other structures and operations in the present configuration are similar to those of the structure ofFIG. 27˜FIG. 29.

FIG. 36is a flowchart showing a control method of the electric motor22and the engine21in the alternative configuration for preventing the disadvantage shown inFIG. 34. In the following, the reference numerals ofFIG. 1andFIG. 27˜FIG. 29will be used as suited. A control process ofFIG. 36is executed by the control device70. In step S101, it is judged whether or not the rearward movement is selected by the forward/rearward movement lever62, and the four-wheel drive (4WD) is instructed by the drive switching switch52. When judgment of S101is positive (YES in S101), the method proceeds to step S102. When the judgment of S101is negative (NO in S101), the method returns to a state before step S101and the process is repeated.

In step S102, both of the electric motor22and the engine21are driven, to realize the four-wheel drive of the rearward movement. In this process, the electric motor22causes the front axle45to rotate in a direction corresponding to the rearward movement, and, at the gear transmission device30(FIG. 27), the rear axle38(FIG. 27) is rotated in a direction corresponding to the rearward movement.

In step S103, it is judged based on the detection signals of the rear axle speed sensor55and the front axle speed sensor56whether or not the average rotational speed of the left and right rear axles38is lower than the average rotational speed of the left and right front axles45. When judgement of step S103is positive (YES in S103), the rotational speed of the rear wheels16became lower than the rotational speed of the front wheel15, and it is judged in step S104that a high load is caused in the rear wheels16. In step S105, the supply of the driving current to the actuator26aof the CVT26is controlled so that the tensioning force of the belt29of the CVT26is reduced to zero. With this process, the motive power transmission between the rear wheels16and the engine21is suspended. Thus, the two-wheel drive of the rearward movement is realized in which only the front wheels15, of the front wheels15and the rear wheels16, are driven.

When the judgment of step S103is negative (NO in S103), the process according to the load of the rear wheels16is completed with the four-wheel drive of the rearward movement maintained.

According to the structure of the present configuration, even when one or both of the rear wheels16comes in contact with the obstacle100(FIG. 34) and the load of the rear-side motive power transmission unit25is about to increase, because the motive power of the engine21is not transmitted to the rear wheels16, the increase of the load can be suppressed. Thus, the rear-side motive power transmission unit25can be protected. The other structures and operations in the present configuration are similar to those of the structure ofFIG. 27˜FIG. 29.

In the structures ofFIG. 27˜FIG. 32,FIG. 35, andFIG. 36, a case is described in which the front wheels are driven by the electric motor and the rear wheels are driven by the engine. Alternatively, in the structures ofFIG. 27˜FIG. 32,FIG. 35, andFIG. 36, a configuration may be employed in which the front wheels are driven by the engine and the rear wheels are driven by the electric motor. In this case, the rear wheels correspond to the first wheel and the front wheels correspond to the second wheel.

A movable structure driving unit according to at least one of the embodiments described above has the movable structure driving unit of the first structure described above or the movable structure driving unit of the second structure described above. Because of this, the increases in the size and the cost of the driving mechanism which drives the front wheel can be suppressed, and the driving mechanism of the front wheels can be protected regardless of the jump during travel.

A movable structure driving unit according to at least one of the embodiments described above has the movable structure driving unit of the third structure described above. Because of this, the rotational speed of the front wheels is set to be higher than the rotational speed of the rear wheels when the user instructs the soft road surface mode by the mode instructor, and, consequently, the stability of the soft road surface travel by the movable structure of the four-wheel drive can be improved according to the instruction of the user.

A movable structure driving unit according to at least one of the embodiments described above is the movable structure driving unit of the third structure described above, wherein the front wheels and the rear wheels are formed as a pair of the front wheels and a pair of the rear wheels, each connected with interposing a differential device, the rotational speed of the front wheels is an average rotational speed of the pair of the front wheels, and the rotational speed of the rear wheels is an average rotational speed of the pair of the rear wheels.

A movable structure driving unit according to at least one of the embodiments described above further comprises a turn instructor that instructs turning of the movable structure, and a steering mechanism that changes directions of the pair of the front wheels according to the instruction by the turn instructor, wherein the control device applies a control such that, when a soft road surface mode is instructed by the mode instructor, an amount of increase of the average rotational speed of the pair of the front wheels with respect to the average rotational speed of the pair of the rear wheels is increased as an amount of turn by the turn instructor is increased.

A movable structure driving unit according to at least one of the embodiments described above has the movable structure driving unit of the fourth structure described above. Because of this, in the movable structure which drives the wheels by the engine, the electric motor assists the travel of the movable structure when the load of the engine is high, and thus, stopping of the engine due to excessive load can be prevented and fuel consumption can be improved.

A movable structure driving unit according to at least one of the embodiments described above is the movable structure driving unit of the fourth structure described above, wherein the motor controller is configured to be able to continuously drive the electric motor regardless of detection of the load detector, by an operation of the user.

A movable structure driving unit according to at least one of the embodiments described above is the movable structure driving unit of the fourth structure described above, wherein, the load detector comprises a first detector which detects an amount of operation of an acceleration instructor for instructing acceleration by an operation of a user, a second detector which detects a rotational speed of the engine, a third detector which detects a rotational speed of the second wheel or the first wheel, and a load calculation unit which calculates a load of the engine by a combination of a part or all of detected values of the first detector, the second detector, and the third detector.

In a movable structure driving unit according to at least one of the embodiments describe above, the second wheel or the first wheel is formed as a pair of the second wheels or a pair of the first wheels connected with interposing a differential device, and a rotational speed of the second wheel or the first wheel is an average rotational speed of the pair of the second wheels or the pair of the first wheels.

A movable structure driving unit according to at least one of the embodiments described above is the movable structure driving unit of the fourth structure, wherein the load detector includes a first extension/contraction detector which detects a degree of extension/contraction of a suspension device which supports the first wheel, a second extension/contraction detector which detects a degree of extension/contraction of a suspension device which supports the second wheel, and a load calculation unit which calculates a load of the engine based on a change of relationship between detected values of the first extension/contraction detector and the second extension/contraction detector.

A movable structure driving unit according to at least one of the embodiments described above is the movable structure driving unit of the fourth structure, wherein the motor controller returns the vehicle from a state in which all of the first wheel and the second wheel is driven to a state in which only the second wheel is driven, when the detected value of the load detector becomes greater than or equal to a first predetermined value and then becomes lower than or equal to a second predetermined value smaller than the first predetermined value.

A movable structure driving unit according to at least one of the embodiments described above is the movable structure driving unit of the fourth structure, further comprising a detector that detects each of the rotational speeds of the first wheel and the second wheel, wherein, when the rotational speed of the first wheel becomes lower than the speed of the second wheel in a state where all of the first wheel and the second wheel is driven, a supply of a driving current to the electric motor is stopped.

In a movable structure driving unit according to at least one of the embodiments described above, the second wheel and the engine are connected to each other with interposing a belt CVT which continuously variable transmits by changing an amount of tension of the belt by an electric actuator, and, when the rotational speed of the second wheel becomes lower than the speed of the first wheel in a state in which all of the first wheel and the second wheel is driven, supply of a driving current to the electric actuator is controlled to reduce a tensioning force of the belt, and to consequently disconnect the motive power transmission between the second wheel and the engine.