JP2007276641A - Drive unit for vehicle and four-wheel drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive unit for a vehicle, controlling the driving force of the vehicle in slope traveling according to the slope. <P>SOLUTION: In this drive unit, when the four-wheel drive vehicle is traveling on a slope, the rear wheel torque in slope traveling of the four-wheel drive vehicle 100 is increased and decreased with respect to the rear wheel torque in flat road traveling of the four-wheel drive vehicle 100 depending on whether the slope in the traveling direction of the vehicle 100 is uphill or downhill. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vehicle drive device and a four-wheel drive vehicle equipped with the vehicle drive device, and more particularly to a technique for controlling the drive force of a vehicle in accordance with the travel path of the vehicle.

  As background art for controlling the driving force of a vehicle in accordance with the traveling path of the vehicle, for example, those described in Patent Literature 1 and Patent Literature 2 are known. Among these, Patent Document 1 describes a technique for controlling the output torque of an electric motor based on a start acceleration obtained according to a road surface condition when the vehicle starts. Patent Document 2 describes a technique for selecting a motor with a large output as the slope of the slope increases.

JP-A-5-131858 Japanese Patent No. 3206038

  When a vehicle that drives by driving a plurality of wheels, for example, a four-wheel drive vehicle travels on a slope, the vehicle load applied to the road surface through the front wheels and the vehicle load applied to the road surface through the rear wheels It depends on the slope of the slope with respect to the direction. For this reason, even on the road surface having the same friction coefficient, the maximum driving force of the vehicle that can be transmitted from the front wheels to the road surface is different from the maximum driving force of the vehicle that can be transmitted from the rear wheels to the road surface. For example, when the vehicle moves uphill on a forward road, the vehicle load received by the road surface via the rear wheel increases more than the vehicle load received by the road surface via the front wheel. The load of the vehicle that the road surface receives through the vehicle increases more than the load of the vehicle that the road surface receives through the rear wheels.

  From the above, in order to make a vehicle run stably on a slope as well as on a flat road, the driving force output from the vehicle drive device to the wheels is optimally set according to the state of the slope with respect to the traveling direction of the vehicle. Need to control. If the driving force is not optimally controlled, the running of the vehicle on the slope may not be stable, and the following state may be reached. For example, when the vehicle is traveling forward and climbs a slope, if the driving force output to the rear wheels is small, the vehicle cannot climb the vehicle and stalls. Further, when the vehicle moves forward and descends the slope, particularly when the road surface is a low μ road, if the driving force output to the rear wheels is large, the rear wheels slip and the vehicle slides sideways. Therefore, it is necessary to optimally control the driving force output from the vehicle driving device to the wheels in accordance with the state of the slope with respect to the traveling direction of the vehicle, and to stabilize the traveling of the vehicle on the slope.

  In this regard, the technique described in Patent Document 1 does not consider stable traveling of the vehicle on a slope. In the technique described in Patent Document 2, although the driving force of the vehicle can be improved by traveling on a hill by selecting a motor, slip during traveling on a hill is not taken into consideration and a plurality of motors must be mounted.

  The present invention provides a vehicle drive device that can control the driving force of a vehicle when the vehicle is traveling on a slope according to the slope.

  In providing the vehicle drive device, it is preferable that both improvement in drive performance and suppression of slip can be achieved.

  In providing the vehicle drive device, when slip occurs in the drive wheels, it is preferable that the drive force of the vehicle controlled in accordance with the traveling slope can be changed so that the slip is contained.

  Here, according to the present invention, when the vehicle travels on a hill, the electric power when the vehicle travels on a flat road depends on whether the slope with respect to the traveling direction of the vehicle is an uphill road or a downhill road. The electric power is increased or decreased with respect to the electric power.

  According to the present invention having such a feature, for example, when traveling on an uphill road due to forward movement of a vehicle or traveling on a downhill road due to backward travel of the vehicle, the electric power during traveling on the slope road of the vehicle is changed to the electric power when traveling on the flat road of the vehicle. When driving on a downhill road due to forward movement of the vehicle or traveling on an uphill road due to backward travel of the vehicle, the electric power when the vehicle travels on a slope road is reduced more than the electric power when the vehicle travels on a flat road. The driving force of the vehicle when the vehicle is traveling on a slope can be controlled according to the slope.

  The present invention also provides a four-wheel drive vehicle equipped with the vehicle drive device.

  According to the present invention described above, since the driving force of the vehicle when the vehicle is traveling on a slope can be controlled according to the slope, for example, the driving force of the vehicle is improved when climbing and the vehicle is driven while suppressing slipping when descending. As described above, a vehicle drive device capable of stably driving a vehicle on a slope can be provided as on a flat road.

  Further, according to the present invention, a four-wheel drive vehicle equipped with the vehicle drive device can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the following description of the embodiments, the front wheels of the front and rear wheels (four wheels) are driven by the power of the engine which is an internal combustion engine, and only the front wheel drive (engine drive only) from a part of the vehicle traveling region, for example, from the start of the vehicle. The electric vehicle drive device mounted on the four-wheel drive vehicle that drives the rear wheels by electric power until the vehicle travels at a traveling speed (from the start of the vehicle to a vehicle speed of 30 km / h). A case where the configuration is applied will be described as an example.

  In the four-wheel drive vehicle, the front wheels are driven by engine power and the rear wheels are driven by electric power. However, the rear wheels may be driven by engine power and the front wheels may be driven by electric power.

  Further, the configuration described below may be applied to an electric vehicle driving device mounted on a vehicle having six or more wheels.

  An embodiment of the present invention will be described with reference to FIGS.

  First, the configuration of the drive system of the four-wheel drive vehicle 100 of this embodiment will be described with reference to FIG.

  FIG. 4 shows the overall configuration of the drive system of the four-wheel drive vehicle 100 of this embodiment.

  A front wheel axle 13 is rotatably supported on the front side of the vehicle body 10. Front wheels 11 and 12 are attached to both ends of the front wheel axle 13. A front wheel side differential gear 23 (hereinafter referred to as a front wheel side DEF 23), which is a differential power transmission mechanism, is provided at the center of the front wheel axle 13.

  In the front wheels 11 and 12, the rotational power of the engine 20, which is an internal combustion engine, is shifted by an automatic transmission including a torque converter 21 and a transmission mechanism 22 and transmitted to the front wheel DEF 23. By being transmitted to 13, the vehicle is driven in the entire travel range of the vehicle. In other words, the power system that includes the automatic transmission including the engine 20, the torque converter 21 and the transmission mechanism 22 and the front-wheel side DEF 23 has the same configuration as a so-called front-wheel drive vehicle, and constitutes the main drive system. .

  The automatic transmission may be either multi-stage or continuously variable.

  A rear wheel axle 16 is rotatably supported on the rear side of the vehicle body 10. Rear wheels 14 and 15 are attached to both ends of the rear wheel axle 16. A rear wheel side differential gear 35 (hereinafter referred to as a rear wheel side DEF 35), which is a differential power transmission mechanism, is provided at the center of the rear wheel axle 16.

  In the rear wheels 14 and 15, the rotational power of the electric motor 30 is decelerated by the speed reducer 33 and transmitted to the rear wheel DEF 35 via the electromagnetic clutch 34, and is transmitted from the rear wheel DEF 35 to the rear wheel axle 16. Drive during a part of the vehicle travel, for example, from the start of the vehicle until it reaches the travel speed by driving only the front wheels 11 and 12 (only the drive of the engine 20) (from the start of the vehicle to the vehicle speed of 30 km / h) Is done. The rear wheels 14 and 15 are also driven when a slip occurs on the front wheels 11 and 12. That is, the power system composed of the electric motor 30, the speed reducer 33, the electromagnetic clutch 34, and the rear wheel DEF 35 constitutes a slave drive system.

  The speed reducer 33 and the electromagnetic clutch 34 may be provided integrally with the rear wheel side DEF 35.

  The engine 20 is mechanically connected to a vehicle-mounted electrical generator 40 and a drive-only generator 31. Both generators operate in response to the rotational power of the engine 20 and generate electric power having different uses. The in-vehicle electric generator 40 constitutes an in-vehicle 14-volt power supply, and includes an in-vehicle battery having a nominal voltage of 12 volts and an electric load (radio, light, etc.) electrically connected to the in-vehicle battery. DC power to be supplied to 41 is generated. The dedicated drive generator 31 constitutes an electric power source for the electric motor that exclusively generates electric power for driving the electric motor 30, and constitutes an in-vehicle 42-volt power supply that can output higher electric power than the in-vehicle electric generator 40. The output voltage can be varied from 0 to 60 volts in accordance with the driving state of the vehicle.

  The in-vehicle electrical generator 40 and the drive-only generator 31 are disposed in the engine room together with the engine 20. The drive-only generator 31 is a water-cooled hermetic type having a Rundel-type rotor (claw-shaped magnetic pole rotor) having field windings and permanent magnets, and is mounted on one auxiliary machine mounting side of the engine 20. It is attached. The on-vehicle electrical generator 40 is an air-cooled open type having a Rundel-type rotor with field windings, and is attached to the other accessory mounting side of the engine 20.

  The in-vehicle electrical generator 40 and the drive-only generator 31 are configured such that one pulley belt 25 is hung between the pulley 24 of the engine 20, the pulley 44 of the in-vehicle electrical generator 40, and the pulley 32 of the drive-only generator 31. By being mounted, it is mechanically connected to the engine 20 and can receive the power of the engine 20.

  In the present embodiment, since the drive-dedicated generator 31 is provided as a drive power source for the electric motor 30, a dedicated large-capacity battery for driving the electric motor 30 is not mounted, and the in-vehicle space can be used effectively accordingly. (In other words, the vehicle-mounted space for the drive-dedicated battery of the electric motor 30 can be eliminated). In addition, in this embodiment, a large and expensive device such as a propeller shaft is unnecessary as compared with a conventional mechanical four-wheel drive vehicle (a vehicle in which front and rear wheels are driven by an engine). In this embodiment, the power system of the rear wheels can be configured easily and inexpensively.

  An electric compressor 61 constituting an in-vehicle air conditioner 60 is mounted in an engine room provided in the vehicle body 10. In the present embodiment, by adopting the electric compressor 61, an empty space can be formed in the accessory mounting side near the one side of the engine 20, and the drive-only generator 31 is disposed close to the space. The drive-only generator 31 is driven by the power of the engine 20 while avoiding interference between the drive-only generator 31 and other in-vehicle auxiliary devices that drive the engine. Therefore, in this embodiment, since the degree of freedom of the mounting position with respect to the engine 20 is improved, the mountability of the drive generator 31 to the vehicle can be improved, and the types of vehicles on which the electric vehicle drive device can be mounted can be expanded.

  In this embodiment, the on-vehicle air conditioning compressor is targeted as the engine driven auxiliary machine to be electrified, but other engine driven auxiliary machines such as a hydraulic pump may be targeted. In this embodiment, the engine-driven auxiliary machine is targeted as an in-vehicle auxiliary machine that forms a free space for mounting a dedicated drive generator in the vicinity of the engine, but the in-vehicle electrical component arranged in the vicinity of the engine is targeted. It doesn't matter.

  The DC power output from the drive generator 31 is directly input to the armature side of the motor 30 via the power distributor 36. Further, the DC power output from the drive-only generator 31 is directly input to the electric compressor 61 via the power distributor 36. In this way, in this embodiment, by using the drive-only generator 31 as a power source other than the motor 30, the electrical energy of the drive-only generator 31 that is exclusively used as the drive power source for the motor 30 is other than the motor drive. Can be used effectively. Therefore, in this embodiment, the engine 20 becomes a useless load other than the motor drive, and the drive-dedicated generator 31 that was wasting fuel for the engine 20 is made an effective load of the engine 20 other than the motor drive. This can make the fuel consumption of the engine 20 effective.

  Further, in this embodiment, since the electric compressor 61 is operated by supplying high-voltage power to the electric compressor 61 from the drive-only generator 31 that can supply higher power than the battery, the operating efficiency of the electric compressor 61 can be improved. . Accordingly, when the electric energy of the drive-only generator 31 is effectively used, an on-vehicle auxiliary device that can be improved in operating efficiency by supplying high-voltage power, such as the electric compressor 61, is supplied with the high-voltage power of the drive-only generator 31. It is preferable to select the target.

  Furthermore, in this embodiment, the electric compressor 61 is driven by supplying the electric power generated by the drive-only generator 31 to the electric compressor 61 having a drive scene independent of the drive scene of the vehicle. In the state where the electric compressor 61 is driven by the generated electric power, even when it is necessary to drive the vehicle by the electric motor 30, the electric power generated by the dedicated drive generator 31 is immediately supplied regardless of the driving of the electric compressor 61. The electric motor 30 can be driven by switching to the electric motor 30.

  The electric motor 30 is a DC machine having a field winding on a stator (field), is installed in a narrow space under the floor from the rear seat of the vehicle to the trunk room, and is disposed in the vicinity of the rear wheel DEF 35. .

  In the present embodiment, a case where a field winding type DC motor is used as the motor 30 will be described as an example. As the electric motor 30, a field winding type AC electric motor may be used. In this case, an inverter device (converter that converts DC power into AC power) is provided for driving the AC motor, and the DC power output from the drive-only generator 31 is passed through the power distributor 36 to the AC motor. Are directly supplied to an electric motor unit including the inverter device and input directly to the input side (DC side) of the inverter device. As the AC motor, one having a Rundel type rotor (claw-shaped magnetic pole rotor) having a field winding and a permanent magnet is used. By using this electric motor, a driving force larger than that of the DC electric motor can be output. Moreover, the output of the rotation speed higher than a direct current motor can be output, and a rear wheel can be driven to a traveling speed (for example, 60 km / h) larger than the time of a direct current motor.

  The power distributor 36 distributes input power to power corresponding to each of the plurality of electrical loads, and supplies the power distributed to each of the plurality of electrical loads. The semiconductor switch and the drive for driving the semiconductor switch It consists of a circuit. The drive-only generator 31 is electrically connected to the input side of the power distributor 36, and the electric motor 30 and the electric compressor 61 are electrically connected to the output side thereof.

  Inside the four-wheel drive vehicle 100, a plurality of in-vehicle control devices including a four-wheel drive control device 50, an engine control device 51, a transmission control device 52, an antilock brake system control device 53, and an in-vehicle air conditioning control device 54 are provided. It has been. The plurality of in-vehicle control devices are electrically connected by an in-vehicle communication network (not shown) and can share information owned by each control device with each other by signal transmission.

  The engine control device 51 controls the operation of engine devices such as a throttle valve and a fuel injection valve mounted on the engine 20 to control the power output from the engine 20 and the operation of the voltage regulator of the in-vehicle electrical generator 40. This is for controlling the field current supplied to the field winding of the in-vehicle electrical generator 40 and controlling the power output from the in-vehicle electrical generator 40. The transmission control device 52 is for controlling the power transmitted from the automatic transmission to the front wheel side DEF 23 by controlling the operation of the transmission mechanism 3 of the automatic transmission. The anti-lock brake system control device 53 controls the braking force of the front wheels 11 and 12 and the rear wheels 14 and 15, and operates an anti-lock brake system (not shown) that avoids locking of each wheel due to strong depression of the brake pedal. Is for controlling. The in-vehicle air conditioning control device 54 is for controlling the operation of the in-vehicle air conditioning device 60 including the operation of the electric compressor 61 and the cooling unit.

  The four-wheel drive control device 50 controls the operation of the voltage regulator of the drive-only generator 31 and controls the field winding of the drive-only generator 31 from the battery, the on-vehicle electrical generator 40, or a part of the self-generated power generation current. The function for controlling the field current supplied to the wire and the power output from the on-vehicle electrical generator 40 and the operation of the H-bridge circuit to control the motor from the battery or the on-vehicle electrical generator 40 The function for controlling the field current supplied to the 30 field windings and the operation of the voltage regulator are controlled to control the excitation current supplied to the excitation coil from the battery or the in-vehicle electrical generator 40. The switching operation of the semiconductor switch is controlled by controlling the function of controlling the engagement state (complete engagement, slip engagement, disconnection) of the electromagnetic clutch 34 and the operation of the drive circuit of the semiconductor switch of the power distributor 36. Gyoshi, and a function for controlling the distribution of power supplied to each electric load.

  In the four-wheel drive control device 50, an accelerator opening signal, which is a driver's request value for the vehicle, is sent from the engine control device 51, an A / T shift signal indicating the position of the shift lever is sent from the transmission control device 52, and the front wheels 11 , 12 and the rear wheel 14, 15 wheel speed signals indicating wheel speed values from the anti-lock brake system control device 53, and a power consumption signal indicating a power value required for driving the electric compressor 61 from the in-vehicle air conditioning control device 54. A gradient signal indicating the gradient θ of the uphill / downhill road is input from the gradient detection device 70 and a rotation signal indicating the rotation speed of the motor 30 is input from the rotation detection device 37, respectively. The four-wheel drive control device 50 calculates a control value necessary for controlling each control target of the drive-only generator 31, the motor 30, the electromagnetic clutch 34, and the power distributor 36 based on these input signals, and each control target A control signal corresponding to the control value is output to each of the above.

  Next, a specific control operation of the four-wheel drive control device 50 will be described with reference to FIG.

  FIG. 1 shows the flow of control executed by the four-wheel drive control device 50.

  In S101 to S105, based on various signals, various information, and calculation information input to the four-wheel drive control device 50, calculation processing is performed to obtain information necessary for condition determination and calculation processing in subsequent steps.

  First, in S <b> 101, a calculation process for obtaining the rotation speed of the electric motor 30 based on the output signal of the rotation detection device 37 is performed.

  Thereafter, in S102, calculation processing for obtaining the gradient angle θ of the traveling road surface of the four-wheel drive vehicle 100 based on the output signal of the gradient detection device 70 is performed. The gradient of the traveling road surface may be obtained by providing a sensor dedicated to gradient detection as in this embodiment, but may be obtained by using another sensor such as an acceleration sensor instead.

  Thereafter, in S103, calculation processing is performed to obtain the torque request values of the rear wheels 14 and 15 based on a command from the driver. Specifically, the generated torque amount of the electric motor 30 is calculated from a predetermined arithmetic expression based on the accelerator opening amount based on the accelerator opening signal output from the engine control device 51 and the rotation speed of the electric motor 30 calculated in S101. And ask. The rear wheel torque request value may be obtained using a predetermined arithmetic expression as in the present embodiment, or may be obtained using a map for searching for a value set on the program.

  Thereafter, in S104, the wheel speeds of the front wheels 11, 12 (the speed of the front wheel axle 13) and the wheel speeds of the rear wheels 14, 15 (the rear wheel axle 16) based on the wheel speed signal output from the antilock brake system control device 53. The calculation processing is performed to obtain the speed. Here, the front wheel speed is an average value of the wheel speed of the front wheel 11 and the wheel speed of the front wheel 12. The rear wheel speed is an average value of the wheel speed of the rear wheel 14 and the wheel speed of the rear wheel 15.

  Thereafter, in S105, a calculation process for comparing the front wheel speed and the rear wheel speed calculated in S104 to obtain the difference (wheel speed difference) is performed, and in S106, the wheel speed difference calculated in S105. Based on the above, a determination process is performed to determine whether or not slip has occurred in the rear wheels 14 and 15. If the result of determination in S106 is affirmative (YES), the process proceeds to S107, and if negative (NO), the process proceeds to S108.

  If the determination result in S106 is affirmative (YES), in S107, the increase / decrease correction amount of the rear wheel torque request value is corrected so that the slip of the rear wheels 14, 15 is settled. The specific increase / decrease correction amount correction processing in S107 will be described later with reference to the drawings.

  Thereafter, in S119, calculation processing for controlling the electric motor 30 and the drive-only generator 31 (driving the rear wheels) is performed based on the corrected rear wheel torque request value calculated in S107. As a result, the fields of the electric motor 30 and the drive-only generator 31 are controlled (in the case of an AC type vehicle driving device using an AC type electric motor, the drive of the inverter device is also controlled), and the rear wheels 14 and 15 from the electric motor 30 are controlled. The torque transmitted to the rear wheel 14 is controlled to contain the slip of the rear wheels 14 and 15.

  If the determination result in S106 is negative (NO), the processing flow from S108 to S118 is executed. This processing flow is for correcting the rear wheel torque request value calculated in S103.

  First, in S108, it is determined whether or not the gradient θ calculated in S102 is greater than or equal to a predetermined value. If the result of determination in S108 is affirmative (YES), the process proceeds to S111, and if negative (NO), the process proceeds to S109.

  If the determination result in S108 is negative (NO), in S109, the traveling road of the four-wheel drive vehicle 100 is a flat road (not a slope), and the rear wheel torque request value correction process is not required. A setting process for setting the torque correction amount Rhosei = 1 is performed.

  Thereafter, in S110, calculation processing for multiplying the rear wheel torque request value calculated in S103 by the rear wheel torque correction amount Rhosei set in S109 to obtain a corrected rear wheel torque request value is performed.

  Thereafter, in S119, calculation processing for controlling the electric motor 30 and the drive-only generator 31 (driving the rear wheels) is performed based on the corrected rear wheel torque request value calculated in S110. As a result, the fields of the electric motor 30 and the drive-only generator 31 are controlled (in the case of an AC type vehicle driving device using an AC type electric motor, the drive of the inverter device is also controlled), and the rear wheels 14 and 15 from the electric motor 30 are controlled. The torque transmitted to is controlled so as to be the rear wheel torque request value calculated in S110.

  If the determination result in S108 is affirmative (YES), the processing flow from S111 to S118 is executed. This processing flow is for determining the correction amount of the rear wheel torque request value calculated in S103 according to the traveling direction of the four-wheel drive vehicle 100 and the state of the slope with respect to that direction.

  First, in S111, determination processing is performed as to whether or not the traveling direction of the four-wheel drive vehicle 100 is forward based on the wheel speeds of the front and rear wheels calculated in S104. If the result of determination in S111 is affirmative (YES), the process proceeds to S112, and if negative (NO), the process proceeds to S116.

  If the determination result in S111 is affirmative (YES), in S112, if negative (NO), in S116, the slope with respect to the traveling direction of the four-wheel drive vehicle 100 is ascending based on the gradient θ calculated in step 102. Judgment processing of whether or not. When the result of determination in S112 is affirmative (YES), the process proceeds to S113 (forward climbing correction routine), and when negative (NO), the process proceeds to S115 (forward downward slope correction routine). If the determination result in S116 is affirmative (YES), the process proceeds to S117 (backward climbing correction routine), and if negative (NO), the process proceeds to S118 (reverse descending slope correction routine).

In S113, S115, S117, and S118, arithmetic processing for obtaining the rear wheel vertical increase from a predetermined mathematical formula is performed.

  Thereafter, in S114, calculation processing is performed to obtain the rear wheel torque correction amount Rhosei from a predetermined mathematical formula based on the rear wheel vertical increase calculated in any of S113, S115, S117, and S118.

  Thereafter, in S110, a calculation process is performed to multiply the rear wheel torque request value calculated in S103 by the rear wheel torque correction amount Rhosei calculated in S114 to obtain a corrected rear wheel torque request value.

  Thereafter, in S119, calculation processing for controlling the electric motor 30 and the drive-only generator 31 (driving the rear wheels) is performed based on the corrected rear wheel torque request value calculated in S110. As a result, the fields of the electric motor 30 and the drive-only generator 31 are controlled (in the case of an AC type vehicle driving device using an AC type electric motor, the drive of the inverter device is also controlled), and the rear wheels 14 and 15 from the electric motor 30 are controlled. The torque transmitted to is controlled so as to be the rear wheel torque request value calculated in S110.

  Next, a specific calculation processing method in S113, S115, S117, S118, and S114 will be described with reference to FIG.

  FIG. 2 shows the relationship between forces acting on the four-wheel drive vehicle 100 on an uphill road.

  Here, the meaning of each symbol is as follows.

θ: slope of the uphill road relative to the ground plane h: height of the center of gravity of the vehicle relative to the uphill road surface W: total vehicle weight l: wheel base m: tire radius μ: friction coefficient of the uphill road surface Wf: front wheel load Wr: rear wheel load Ff: Front wheel driving force Fr: Rear wheel driving force Tf: Front wheel torque Tr: Rear wheel torque Wsinθ: Horizontal component of total vehicle weight with respect to uphill road surface (gradient resistance to vehicle)
Wcosθ: vertical component of the total vehicle weight with respect to the uphill road surface Wfcosθ: vertical component of the front wheel load with respect to the uphill road surface Wrcosθ: vertical component of the rear wheel load with respect to the uphill road surface The four-wheel drive vehicle 100 is allowed to travel on the flat road without slipping the rear wheels. For this purpose, it is necessary that the rear wheel driving force Fr generated at the rear wheel does not exceed the slip limit. Here, the slip limit can be expressed by Equation 1 from the relationship of the rear wheel driving force Fr, the friction coefficient μ, and the rear wheel load Wr with respect to the uphill road surface.

Fr = μ · Wr (Formula 1)
Further, the rear wheel torque (transmission torque) Tr at the slip limit can be expressed by Expression 2 from the relationship between Expression 1 and the tire radius m.

Tr = Fr · m
= M (μ · Wr) (Formula 2)
However, on the uphill road with the gradient θ, the vehicle body is inclined by the gradient θ and the load applied to the rear wheel changes, so the slip limit changes even on the road surface with the same friction coefficient μ. The amount of change can be expressed by Equation 3.

Fr ′ = μ (Wr cos θ + (h / l) · W sin θ) (Formula 3)
In addition, although Formula 3 shows the driving force of the rear wheel in the forward climbing slope, the driving force is the same in the case of the backward descending slope. That is, the calculation method of the vertical load of the rear wheel is determined by the gradient and the positional relationship between the front wheel and the rear wheel, and therefore, the driving force is the same in the case of the reverse descending slope. As a result, the calculation method of the forward climbing correction routine in S113 is the same as the calculation method of the reverse descending slope correction routine in S118, and Equation 3 is applied to the reverse descending slope correction routine in S118 as well as the forward climbing correction routine in S113. it can.

  As can be seen from Equation 3, the slip limit increases on forward climbing and reverse descending. Therefore, the torque of the electric motor that drives the rear wheels can be increased by the increase.

  On the other hand, in the case of forward descent, the influence on the rear wheel is reversed from that of the uphill road. Therefore, the amount of change in the slip limit on the forward and downward slope can be expressed by Equation 4.

Fr ′ = μ (Wr cos θ− (h / l) · W sin θ) (Formula 4)
In addition, although Formula 4 shows the driving force of the rear wheel in the forward descending slope, the driving force is the same also in the backward traveling uphill. That is, as described above, the calculation method for the vertical load of the rear wheel is determined by the gradient and the positional relationship between the front wheel and the rear wheel. As a result, the calculation method of the forward descending slope correction routine in S115 is the same as the calculation method of the reverse upward slope correction routine in S117, and Equation 4 is applied to the backward descending slope correction routine in S117 as in the forward descending slope correction routine in S115. Applicable.

  As can be seen from Equation 4, the slip limit is reduced and the slip is likely to occur on the forward and downward slopes and the backward slope. Therefore, it is necessary to reduce the torque of the electric motor that drives the rear wheels accordingly.

  Further, the rear wheel torque (transmission torque) Tr ′ at the slip limit including the gradient can be expressed by Formula 5 from the relationship between Formula 3 and Formula 4 and the tire radius m.

Tr ′ = Fr ′ · m
= M (μ (Wrcosθ ± (h / l) · Wsinθ)) (Formula 5)
By the way, in order to establish Expression 5, it is necessary to detect the friction coefficient μ of the road surface or to detect the vertical component Wr ′ of the rear wheel load with respect to the uphill road surface using a load sensing valve or the like. However, it may be difficult to detect with a simple vehicle drive device, and the transmission torque (rear wheel torque) at the time of running on a slope is directly obtained using Equation 5, and the driving of the rear wheels is controlled according to the torque. It can be difficult.

  Therefore, in this embodiment, even in a simple vehicle drive device, the transmission torque at the slip limit is directly obtained by using Equation 5, and the rear wheel drive is equivalent to the one that controls the drive of the rear wheel according to the torque. Can be controlled. That is, in this embodiment, the ratio of the transmission torque of Expression 5 to the transmission torque of Expression 2 is obtained as shown in Expression 6, and the ratio is defined as the increase / decrease amount of the slip limit corresponding to the gradient θ with respect to the flat road (rear wheel torque correction amount Rhosei). The required rear wheel torque value is corrected based on the ratio.

Rhosei = Tr '/ Tr
= M (μ (Wrcosθ ± (h / l) · Wsinθ) / m (μ · Wr)
= (Wrcosθ ± (h / l) · Wsinθ) / Wr (Formula 6)
As can be seen from Equation 6, the rear wheel torque correction amount Rhosei can be finally expressed by the amount of change in the vertical load of the rear wheel due to the gradient θ with respect to the rear wheel load Wr (rear wheel vertical increase).

  Here, in Expression 6, the wheel base l is a fixed value, the total vehicle weight W, and the center of gravity h are also substantially fixed values. Further, since the rear wheel load Wr can be set to a fixed value if it is a weight when the vehicle is empty, there is no need to detect it. Furthermore, since the friction coefficient μ is canceled in the process of deriving the final right term of Equation 6, it is not necessary to detect it. The tire radius m is also canceled out. For this reason, it is possible to detect only the gradient θ as a fluctuation value and obtain the rear wheel torque correction amount Rhosei from Equation 6 based on the gradient θ.

  Therefore, in this embodiment, the calculation is performed in S102 in any one of S113, S115, S117, and S118 depending on the traveling direction of the four-wheel drive vehicle 100 and whether the slope with respect to the traveling direction is uphill or downhill. Based on the gradient θ, the rear wheel vertical increase is calculated from the numerator arithmetic expression of Formula 6, and in S114, the rear wheel vertical increase is calculated based on the rear wheel vertical increase calculated in any of S113, S115, S117, and S118. The rear wheel torque correction amount Rhosei is calculated. In the present embodiment, in S110, the rear wheel torque correction amount Rhosei calculated in S114 is multiplied by the rear wheel torque request value calculated in S103 to obtain a corrected rear wheel torque request value.

  The rear wheel torque request value is generally set so that slip does not occur even when the rear wheel torque is generated according to the rear wheel torque request value on a dry flat road. Therefore, on forward climbing and reverse descending, no slip occurs even if the rear wheel torque request value is increased by an increase ratio of the slip limit. Further, on forward descending slopes and backward climbing slopes, slip occurs unless the rear wheel torque request value is reduced by the reduction ratio of the slip limit.

  According to the torque control on the hill road of the present embodiment described above, the rear wheel drive torque at the time of the four-wheel drive vehicle 100 traveling on the hill is obtained when the four-wheel drive vehicle 100 is traveling on the uphill road or when the four-wheel drive vehicle 100 is traveling on the downhill road. Since the four-wheel drive vehicle 100 is made to increase more than the rear wheel drive torque when running on a flat road, the drive performance can be improved. Further, when the four-wheel drive vehicle 100 travels on a downhill road due to a forward movement or when the four-wheel drive vehicle 100 travels on an uphill road, the rear-wheel drive torque when the four-wheel drive vehicle 100 travels on a slope road is the rear wheel drive torque when the four-wheel drive vehicle 100 travels on a flat road. Since the wheel driving torque is reduced, the slip of the rear wheels 14 and 15 can be suppressed. Thus, in the present embodiment, it is possible to achieve both improvement in driving performance on a slope and suppression of slip. Therefore, according to the present embodiment, when the four-wheel drive vehicle 100 travels on a slope, the driving force of the rear wheels 14 and 15 can be optimally controlled according to the traveling direction of the four-wheel drive vehicle 100 and the state of the slope with respect to that direction. Even on slopes, the four-wheel drive vehicle 100 can be stably driven in the same way as on flat roads.

  FIG. 5 shows the effect. FIG. 5 shows the relationship between the change in the gradient% and the change in the required rear wheel torque with and without the control of this embodiment. The solid line represents the required rear wheel torque when the rear wheel torque correction control is performed in the present embodiment, and the dotted line represents the required rear wheel torque when the rear wheel torque correction control is not performed in the present embodiment.

  As is clear from FIG. 5, when traveling on an uphill road where the gradient greatly increases, the rear wheel torque correction control (solid line) is the rear of the rear wheel torque correction control without the rear wheel torque correction control (solid line). It can be seen that the required torque of the wheel is large and the driving performance is improved. Also. When traveling on downhill roads where the gradient is greatly reduced, the rear wheel torque correction control (solid line) is less for the slip prevention and the rear wheel required torque is smaller than the rear wheel torque correction control (dotted line). It turns out that it is suppressing.

  Next, the rear wheel torque increase / decrease correction processing in S107 will be described with reference to FIG.

  FIG. 3 shows the flow of the rear wheel torque increase / decrease correction processing.

  If the determination result in S106 is affirmative (YES), the process proceeds to S107, and the processes in S201 to S210 are executed. In the processing from S210 to S203, S207 to S210, the same judgment and calculation processing as S111 to S113 and S115 to S118 shown in FIG.

  As described above, the slip limit is higher on the forward climb in S203 and the reverse descent in S210 than on a flat road. For this reason, in order to reduce the rear wheel torque and accommodate the slip of the rear wheel, it is necessary to perform correction so as to reduce the rear wheel torque correction amount (increase amount). For this reason, the rear wheel torque correction amount (increase amount) is corrected using the change amount (rear wheel vertical increase amount) of the rear wheel vertical load due to the gradient θ with respect to the rear wheel load Wr. That is, the concept of Equation 3 is applied.

  In the forward descent in S207 and the reverse descent in S209, as described above, the slip limit is lower than that on a flat road. For this reason, in order to reduce the rear wheel torque and accommodate the slip of the rear wheel, it is necessary to perform correction so that the rear wheel torque correction amount (decrease amount) becomes large. For this reason, the rear wheel torque correction amount (decrease amount) is corrected using the change amount of the rear wheel vertical load due to the gradient θ with respect to the rear wheel load Wr (rear wheel vertical increase amount). That is, the concept of Formula 4 is applied.

  In S204, in order to correct the rear wheel torque correction amount (increase / decrease amount), a calculation process for obtaining the slip correction gain Shosei is performed.

  Also in this calculation, the ratio of the rear wheel torque (transmission torque) at the slip limit in Expression 2 and the rear wheel torque (transmission torque) at the slip limit including the gradient in Expression 5 is used. However, the slip correction gain Shosei is a correction gain that reduces the slip by reducing the rear wheel torque, and is therefore the reciprocal of equation (6). Therefore, the slip correction gain Shosei can be expressed by the rear wheel load Wr with respect to the change amount of the rear wheel vertical load due to the gradient θ (rear wheel vertical increase) as shown in Equation 7.

Shosei = Tr / Tr '
= M (μ · Wr) / m (μ (Wrcosθ ± (h / l) · Wsinθ)
= Wr / (Wrcosθ ± (h / l) · Wsinθ) (Formula 7)
In S205, in order to reduce the rear wheel torque and contain the slip of the rear wheel, a slip torque reduction amount (rear wheel torque required value reduction amount) SLP is obtained based on the slip correction gain Shosei calculated in S204. The arithmetic processing is performed. In this calculation processing, the slip torque reduction amount SLP is obtained by multiplying the predetermined reference value SLPbase for obtaining the rear wheel torque request value reduction amount by the slip correction gain Shosei calculated in S204.

  In S206, a calculation process for obtaining a new rear wheel torque request value for converging the rear wheel slip based on the slip torque decrease amount SLP calculated in S205 is performed. In this calculation process, a new rear wheel torque request value is obtained by subtracting the slip torque decrease amount SLP calculated in S205 from the previous corrected rear wheel torque request value calculated in S110.

  Thereafter, in S119, the rear wheel drive control is executed based on the new rear wheel torque request value in which the increase / decrease amount is corrected.

  According to the rear wheel torque increase / decrease amount correction of the present embodiment described above, the rear wheel torque correction amount (increase amount) can be reduced when the four-wheel drive vehicle 100 travels on an uphill road or travels downhill. The rear wheel drive torque when the four-wheel drive vehicle 100 is traveling on a slope can be reduced. Further, when the four-wheel drive vehicle 100 travels on a downhill road, or when the four-wheel drive vehicle 100 travels on an uphill road, the rear wheel torque correction amount (decrease amount) can be increased. Can be reduced. As described above, in this embodiment, when slip occurs on the rear wheel on the slope, the rear wheel drive torque is reduced by correcting the rear wheel torque increase / decrease amount, and the rear wheel slip can be converged. Therefore, it is possible to suppress a decrease in traveling performance on the slope of the four-wheel drive vehicle 100.

  In the embodiment described above, the case where the rear wheel torque correction control is applied to a simple vehicle driving apparatus has been described as an example, but the vehicle driving apparatus equipped with a system capable of detecting the friction coefficient of the road surface and the load of the rear wheel is described. When the rear wheel torque correction control is applied to the rear wheel, the slip limit transmission torque may be obtained directly using Equation 5, and the rear wheel drive control may be performed using the transmission torque as the rear wheel torque request value.

  In the embodiment described above, the rear wheel torque is reduced by correcting the rear wheel torque increase / decrease when the rear wheel slips. However, the clutch control such as weakening or disconnecting the electromagnetic clutch 34 is performed. The rear wheel torque may be reduced.

The control flowchart which shows the rear-wheel torque correction control of the vehicle drive device for four-wheel drive vehicles which is an Example of this invention. It is a figure which shows the principle of the rear-wheel torque correction control of FIG. 1, Comprising: The relationship of the force which acts on a four-wheel drive vehicle is shown. The control flowchart which shows the rear-wheel torque increase / decrease amount correction control at the time of the rear-wheel slip of the vehicle drive device for four-wheel drive vehicles which is an Example of this invention. The block diagram which shows the structure of the vehicle drive device for four-wheel drive vehicles which is an Example of this invention. It is a figure for demonstrating the effect of the rear-wheel torque correction control of FIG. 1, Comprising: The change of a gradient and the change of a rear-wheel request torque are shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 12 ... Front wheel, 13 ... Front wheel axle, 14, 15 ... Rear wheel, 16 ... Rear wheel axle, 20 ... Engine, 30 ... Electric motor, 31 ... Electric drive generator, 50 ... Four-wheel drive control apparatus, 100 ... a four-wheel drive vehicle.

Claims (7)

A drive device mounted on a vehicle for driving a first axle, which is at least one of a plurality of axles, with the power of an internal combustion engine and driving a second axle, which is at least one of the remaining axles, with electric power,
An electric motor that generates the electric force;
Power supply means for supplying power to the motor;
Control means for controlling the drive of the electric motor,
When the vehicle is traveling on a slope, the electric power when the vehicle is traveling on a flat road is increased or decreased depending on whether the slope with respect to the traveling direction of the vehicle is an uphill road or a downhill road. A vehicle drive device characterized by being made to cause. The vehicle drive device according to claim 1,
When driving on an uphill road due to a forward movement of a vehicle or when traveling on a downhill road due to a backward movement of the vehicle, an electric power during driving on the slope of the vehicle is increased more than that during driving on a flat road of the vehicle. . The vehicle drive device according to claim 1,
A vehicle drive device characterized in that when the vehicle travels on a downhill road or when the vehicle travels on an uphill road, the electric power when the vehicle travels on a slope is less than the electric power when the vehicle travels on a flat road. . The vehicle drive device according to claim 1,
When the wheel provided on the second axle slips, the increase / decrease amount of the electric power when the vehicle travels on a slope is corrected depending on whether the slope with respect to the traveling direction of the vehicle is an uphill road or a downhill road. The vehicle drive device characterized by these. The vehicle drive device according to claim 4,
A vehicle driving apparatus characterized by reducing an increase in electric power when the vehicle is traveling on an uphill road or when the vehicle is traveling on a downhill road. The vehicle drive device according to claim 4,
A vehicle drive device characterized by increasing the amount of decrease in electric power when the vehicle is traveling on a downhill road due to forward movement of the vehicle or when traveling on an uphill road due to backward travel of the vehicle. 7. A four-wheel drive vehicle in which one axle of front and rear wheels is driven by an internal combustion engine and the other axle is driven by an electric force, wherein the electric force is a vehicle drive according to any one of claims 1 to 6. A four-wheel drive vehicle characterized by being supplied from a device.

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