JP3791525B2 - Four-wheel drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake control device for a battery-less motor four-wheel drive vehicle whose front wheel are driven by an engine and rear wheels are driven by a motor, capable of smoothening the accelerative running at starting on an ultra-low &mu; road. <P>SOLUTION: When the increment rate of the revolving speed of the front wheels as the engine-driven wheels is equal to or over the specified value, first the driving force reducing control is prohibited, and the gearing position of an automatic transmission is made neutral, followed by determining the torque required to drive the vehicle only by the motor, and the electric power necessary for obtaining the torque is determined and also the engine speed necessary for obtaining the electric power is determined to serve for performing the feedback control. When the system has an upper limit for the voltage, the upper limit of the engine speed is set, and the engine speed is controlled in the region under the upper limit, including it. The control is ended when the running speed has attained the vehicle propelling upper limit owing to the motor. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

  The present invention relates to a four-wheel drive vehicle in which either one of the front and rear wheels is driven by an engine and the other one of the front and rear wheels can be driven by an electric motor (motor), and more particularly, the generator is driven by the engine. It is suitable for a battery-less four-wheel drive vehicle that drives an electric motor with the electric power generated by the motor.

As such a four-wheel drive vehicle, for example, one of the front and rear wheels (hereinafter also referred to as a main drive wheel) is driven by an engine, and the other of the front and rear wheels (hereinafter also referred to as a sub drive wheel) is driven by a motor. It is configured to be auxiliary driven, and the generator is driven by the engine, and the motor is directly driven by the power generated by the generator, so-called battery-less (there is no power storage device between the generator and the motor) There is a motor four-wheel drive vehicle (see, for example, Patent Document 1). When the road surface reaction torque is smaller than the driver's required torque, the generator is controlled so that the power generation load torque corresponding to the difference is obtained, and further, the driving force of the engine is reduced when the main drive wheel slips. In performing the control, the control amount is reduced by the generator load torque.
JP 2003-47109 A

However, in the conventional four-wheel drive vehicle, by performing the driving force reduction control of the engine when the main drive wheel slips, the generated power of the generator is reduced, and sufficient power cannot be supplied to the motor. There is a problem that the necessary motor torque cannot be output.
The present invention has been made paying attention to the above-described problems, and an object thereof is to provide a four-wheel drive vehicle capable of obtaining a necessary motor torque by supplying sufficient electric power to the motor. To do.

  In order to solve the above problems, the four-wheel drive vehicle of the present invention drives either one of the front and rear wheels with an engine and the other with an electric motor (motor), and drives a generator with the engine. In a four-wheel drive vehicle that drives a motor with electric power generated by a generator, when the wheels are driven by the motor, the driving force reduction control of the engine is prohibited.

  Thus, according to the braking control device of the present invention, when the wheels are driven by the motor, the engine driving force reduction control is prohibited, so that sufficient engine driving force is obtained and sufficient electric power is generated. Therefore, a necessary motor torque can be obtained by supplying sufficient electric power to the motor.

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a system configuration of a vehicle according to the present embodiment.
As shown in FIG. 1, in the vehicle of this embodiment, front left and right wheels 1L and 1R are main drive wheels driven by an engine 2, and rear left and right wheels 3L and 3R are driven by a motor (electric motor) 4. Possible driven wheel.
The rotational torque Te of the engine 2 is transmitted to the front left and right wheels 1L, 1R through the transmission 30 and the difference gear 31.
The transmission 30 is provided with a shift position detecting means 32 for detecting the current shift range. The shift position detecting means 32 transmits the detected shift position signal to the four-wheel drive (hereinafter also referred to as 4WD) controller 8. Output. In addition, the transmission 30 of this embodiment is an automatic transmission.

A generator 7 is attached to the engine 2. The generator 7 is connected to, for example, a rotation shaft in the engine 2 such as a camshaft or a crankshaft or a gear shaft that rotates together with the shaft via a pulley. The generator 7 rotates at a rotational speed Nh obtained by multiplying the rotational speed Ne of the engine 2 by a pulley ratio, generates a current corresponding to the rotational speed Nh, and generates a field current Ifh adjusted by the 4WD controller 8. Accordingly, a load is applied to the engine 2 and a voltage corresponding to the load torque is generated.
The electric power generated by the generator 7 can be supplied to the motor 4 via an electric wire (power cable) 9. A junction box 10 is provided in the middle of the electric wire 9. The drive shaft of the motor 4 can be connected to the rear wheels 3L and 3R via the speed reducer 11 and the clutch 12. Reference numeral 13 represents a differential.

A throttle valve 15 is interposed in the intake pipe 14 (for example, intake manifold) of the engine 2. The throttle valve 15 is normally controlled to adjust the throttle opening according to the amount of depression of the accelerator pedal 17 or the like. However, the throttle valve 15 is a so-called accelerator-by-wire that is not mechanically linked to the amount of depression of the accelerator pedal 17, and uses a step motor 19 as an actuator. The throttle valve 15 opens at a rotation angle corresponding to the number of steps. The degree is adjusted and controlled. Specifically, the depression amount of the accelerator pedal 17, i.e., the accelerator opening Acc ₁ detected by the accelerator sensor 16, typically such that the throttle opening corresponding to the accelerator opening Acc ₁ which is the detection step The rotation angle of the motor 19, that is, the number of steps is controlled. The rotation angle of the step motor 19 is feedback-controlled by a drive signal from the motor controller 20 based on the throttle opening detection value detected by the throttle sensor. Here, by adjusting the throttle opening of the throttle valve 15 to a throttle opening different from the throttle opening corresponding to the depression amount of the accelerator pedal 17, the engine is operated independently of the driver's operation of the accelerator pedal. 2 output torque can be controlled. Incidentally, when a throttle opening command value is output from the engine controller 18 or the 4WD controller 8, the throttle opening is controlled so that the throttle opening command value is achieved. The accelerator opening Acc ₁ detected by the accelerator sensor 16 is also output to the 4WD controller 8.

The engine rotation speed sensor 21 that detects the rotation speed of the engine 2 is provided, and the engine rotation speed sensor 21 outputs the detected signal to the engine controller 18 and the 4WD controller 8.
The engine controller 18 controls the operating state of the engine 2 so as to obtain a target rotational torque in accordance with the amount of depression of the accelerator pedal 17 detected by the accelerator sensor 16, that is, the accelerator opening, for example, the 4WD controller 8 From the above, when it is requested to control the engine rotation speed so that the generated power of the generator 7, that is, the generated voltage and generated current are in a predetermined state, for example, The throttle opening of the throttle valve 15 is adjusted to control the operating state of the engine 2, that is, the engine speed in this case. Further, when the rotational speed of the front left and right wheels 1L, 1R driven by the engine 2 is excessively slipped in the engine controller 18, the throttle opening of the throttle valve 15 is closed in the closing direction. And a driving force reduction control function that reduces the driving torque of the engine 2 and suppresses the slip of the front left and right wheels 1L, 1R.

Reference numeral 34 denotes a brake pedal, and the stroke amount of the brake pedal 34 is detected by the brake stroke sensor 16. The brake stroke sensor 16 outputs the detected brake stroke amount to the braking controller 36 and the 4WD controller 8.
The braking controller 36 controls the braking torque acting on the vehicle through the braking devices 37FL, 37FR, 37RL, 37RR such as disc brakes equipped on the wheels 1L, 1R, 3L, 3R according to the input brake stroke amount. .

  Further, as shown in FIG. 2, the generator 7 includes a voltage regulator 22 (regulator) for adjusting the output voltage V, and the field current Ifh is adjusted by the 4WD controller 8 so that the engine 2 The generated load torque Th and the generated voltage V are controlled. The voltage regulator 22 receives a generator control command (field current value) from the 4WD controller 8 and adjusts the field current Ifh of the generator 7 to a value according to the generator control command. The output voltage V can be detected and output to the 4WD controller 8.

  In addition, a current sensor 23 is provided in the junction box 10, and the current sensor 23 detects the current value Ia of the electric power supplied from the generator 7 to the motor 4, and outputs the detected armature current signal to 4WD. Output to the controller 8. In addition, a voltage value (voltage of the motor 4) flowing through the electric wire 9 is detected by the 4WD controller 8. The generated current value and generated voltage value of the generator 7 detected by the 4WD controller 8 are also monitored by the engine control unit 18.

Reference numeral 24 denotes a relay, and the cutoff and connection of the voltage (current) supplied to the motor 4 is controlled by a command from the 4WD controller 8.
In the motor 4, the field current Ifm is controlled by a command from the 4WD controller 8, and the drive torque Tm is adjusted by adjusting the field current Ifm.
A motor rotation speed sensor 26 that detects a rotation speed Nm of the drive shaft of the motor 4 is provided, and the motor rotation speed sensor 26 outputs the detected rotation speed signal of the motor 4 to the 4WD controller 8.
Incidentally, in the present embodiment, the motor 4 is regeneratively operated to apply braking torque to the rear wheels 3L and 3R. The regenerative braking torque by the motor 4 is also controlled by adjusting the field current Ifm.

The clutch 12 is a hydraulic clutch or an electromagnetic clutch, and is engaged or released according to a clutch control command from the 4WD controller 8.
Each wheel 1L, 1R, 3L, 3R is provided with a wheel speed sensor 27FL, 27FR, 27RL, 27RR. Each wheel speed sensor 27FL, 27FR, 27RL, 27RR outputs a pulse signal corresponding to the rotation speed of the corresponding wheel 1L, 1R, 3L, 3R to the 4WD controller 8 as a wheel speed detection value.
As shown in FIG. 3, the 4WD controller 8 includes a generator control unit 8A, a relay control unit 8B, a motor control unit 8C, a clutch control unit 8D, a surplus torque calculation unit 8E, a target torque limiting unit 8F, and a surplus torque conversion unit 8G. And a start control unit 8J.

The generator control unit 8A adjusts the field current Ifh of the generator 7 while monitoring the power generation voltage V of the generator 7 through the voltage regulator 22, so that the generator voltage V of the generator 7 is required. Adjust to the voltage of.
The relay control unit 8B controls the power supply from the generator 7 to the motor 4 or the cutoff / connection of the power supply from the motor 4 to the generator 7 when the motor 4 is regeneratively operated.
The motor control unit 8C adjusts the field current Ifm of the motor 4 to adjust the torque of the motor 4 to a required value.

  The clutch control unit 8D controls the state of the clutch 12 by outputting a clutch control command to the clutch 12. Specifically, for example, when it is necessary to drive the rear left and right wheels 3L, 3R by the motor 4 by an arithmetic process described later, the rotational speed matching of the input side rotational speed and the output side rotational speed of the clutch 12 is performed. The clutch is engaged when the is aligned. Further, for example, when it becomes unnecessary to drive the rear left and right wheels 3L, 3R by the motor 4, the clutch 12 is released.

In addition, processing is performed in a cycle of surplus torque calculating unit 8E → target torque limiting unit 8F → surplus torque converting unit 8G at predetermined sampling times in accordance with each input signal.
First, the surplus torque calculation unit 8E calculates the slip speed (acceleration slip amount) by subtracting the average rear wheel speed (≈body speed) of the rear wheels 3L and 3R from the average front wheel speed of the front wheels 1L and 1R, for example, and calculates the front wheel 1L. The absorption torque necessary to suppress the 1R acceleration slip is calculated, the current load torque of the generator 7 is calculated, and the surplus torque, that is, the target generation load torque to be loaded by the generator 7 is obtained.

  Next, the target torque limiting unit 8F determines, for example, whether the target power generation load torque is larger than the maximum load capacity of the generator 7, and determines that the target power generation load torque is larger than the maximum load capacity of the generator 7. In such a case, an excess torque exceeding the maximum load capacity is obtained, an engine torque upper limit value obtained by subtracting the excess torque from the current engine torque is calculated and output to the engine controller 18, and the target power generation load torque is maximized. Set to load capacity.

  Next, the surplus torque conversion unit 8G calculates a target motor field current corresponding to the rotation speed of the motor 4 detected by the motor rotation speed sensor 21, and outputs the target motor field current to the motor control unit 8C. In addition, the induced voltage of the motor 4 is calculated from the target motor field current and the rotation speed of the motor 4, the target motor torque is calculated based on the power generation load torque calculated by the surplus torque calculating unit 8E, and the target motor torque and The corresponding target armature current is calculated using the target motor field current as a variable, the target voltage of the generator 7 is calculated from the target armature current, resistance, and the induced voltage, and the target voltage of the generator 7 is generated. To the machine control unit 8A.

Next, the operation of the apparatus having the above configuration will be described.
When the road surface μ is small or the amount of depression of the accelerator pedal 17 by the driver is large, the front wheels 1L and 1R, which are the main driving wheels, accelerate slip, and the generator 7 generates power with a power generation load torque corresponding to the acceleration slip amount. Thus, the driving torque transmitted to the front wheels 1L, 1R is adjusted, and the electric power generated by the generator 7 is supplied to the motor 4, and the rear wheels 3L, 3R are driven by the driving torque of the motor 4. Is done. As a result, the acceleration slip at the front wheels 1L and 1R which are the main drive wheels is suppressed.

Therefore, for example, when a four-wheel drive control is required by a start control unit 8J, which will be described later, the surplus torque calculation unit 8E, the target torque limiting unit 8F, and the surplus torque conversion unit 8G perform acceleration slip of the front wheels 1L and 1R. Suppressing four-wheel drive control is performed. Further, when it is necessary for the start control unit 8J to control the driving of only the front wheels 1L, 1R by the engine, the clutch 12 is disengaged and the front wheels 1L, 1R are driven by the engine 2 to perform front wheel driving control. Is called.
The start control unit 8J switches between the four-wheel drive control and the front wheel drive control when starting the vehicle by the arithmetic processing of FIG. 4, and performs rear wheel control for driving only the rear wheels 3L and 3R with motor torque. .

  In the calculation process of FIG. 4, first, in step S1, it is determined whether or not the traveling speed of the host vehicle is equal to or higher than the start threshold value. If the traveling speed of the host vehicle is equal to or higher than the start threshold value, the process proceeds to step S2. Otherwise, the process proceeds to step S17. The start threshold is a threshold of a relatively small traveling speed set to, for example, about 10 km / h. In a traveling speed region smaller than this threshold, the rear wheels 3L and 3R are driven by the motor 4 to force four. Wheel drive state. As the traveling speed of the host vehicle, the average rear wheel speed of the rear wheels 3L and 3R detected by the wheel speed sensors 27RL and 27RR is used as the vehicle speed.

  In step S2, it is determined whether or not the four-wheel drive condition is satisfied. If the four-wheel drive condition is satisfied, the process proceeds to step S3. Otherwise, the process proceeds to step S16. The four-wheel drive condition is, for example, that the average front wheel speed of the front wheels 3L and 3R driven by the engine 2 is accelerated and slipped at a speed difference of a predetermined value or more with respect to the traveling speed composed of the average rear wheel speed. Can be mentioned.

  In step S3, it is determined whether or not the traveling speed of the host vehicle is equal to or lower than the vehicle propulsion upper limit value based on the motor torque. The process proceeds to S4, and if not, the process proceeds to step 13. In general, since the output of the motor is constant, as shown by the solid line in FIG. 5, the torque decreases as the rotational speed increases. On the other hand, when the drive torque (converted to the motor output shaft) necessary for propelling the vehicle is as shown by the broken line in FIG. 5, the motor is temporarily set in a region where the rotational speed is larger than the intersection with the motor torque curve. Even if it rotates at high speed, the vehicle cannot be propelled. Therefore, this intersection is the value of the motor rotation speed corresponding to the vehicle propulsion upper limit value, and a value obtained by multiplying this by the reduction ratio becomes the vehicle propulsion upper limit value for the travel speed.

  In step S4, it is determined whether or not the rate of increase in the rotational speed of the engine drive wheels detected by the wheel speed sensors 25FL and 27FR, that is, the front wheels 1L and 1R is greater than or equal to a predetermined value. If the increase rate is equal to or greater than the predetermined value, the process proceeds to step S5, and if not, the process proceeds to step S13. For example, as shown in FIG. 6c, when the rear wheels 3L and 3R are not driven by the motor 4, the driving wheels driven by the engine 2, that is, the front wheels 1L and 1R and the rear wheels 3L and 3R have the same or substantially the same speed. , The front wheels 1L, 1R are not accelerated and slipped, and only the front wheels 1L, 1R can be driven to accelerate. Further, as shown in FIG. 6b, in a state in which the rear wheels 3L and 3R are not driven by the motor 4, the driving wheels by the engine 2, that is, the front wheels 1L and 1R are slightly more than the rear wheels 3L and 3R. When the vehicle is accelerating and slipping, for example, if the driving torque of the engine 2 is reduced by the driving force reduction control, the tires of the front wheels 1L, 1R can recover the gripping force and accelerate. On the other hand, as shown in FIG. 6a, in a state where the rear wheels 3L and 3R are not driven by the motor 4, the driving wheels by the engine 2, that is, the front wheels 1L and 1R are compared with the rear wheels 3L and 3R. In the case of a large acceleration slip, even if the driving torque of the engine 2 is reduced by the driving force reduction control, there is no possibility that the tires of the front wheels 1L and 1R will recover sufficient gripping force. Therefore, when the rate of increase in the rotational speed of the front wheels 1L and 1R, which are engine drive wheels, is greater than or equal to a predetermined value, it is determined that the front wheels 1L and 1R are in a large acceleration slip state, and driving force reduction control is prohibited. The motor 4 travels by driving the rear wheels 3L, 3R.

In step S5, the driving torque required for the vehicle is obtained from the traveling speed of the host vehicle consisting of the average rear wheel speed and the accelerator opening detected by the accelerator sensor 16, and the driving torque is obtained only by the motor 4. After calculating the necessary motor torque necessary for obtaining, the process proceeds to step S6.
In step S6, the necessary motor power necessary to obtain the necessary motor torque calculated in step S5 is calculated, and then the process proceeds to step S7. The required motor power is given in the form of a matrix of required motor voltage and required motor current. In the present embodiment, since the electric power generated by the generator 7 is supplied to the motor 4 as it is, the required motor voltage and the required motor current become the required generated voltage and the required generated current as they are.

  In step S7, the lower limit value of the engine speed for obtaining the required motor power consisting of the required motor voltage and the required motor current calculated in step S6 is calculated as the required engine speed lower limit value, and then the process proceeds to step S8. Transition. For example, when the generated voltage / generated current characteristic for each engine speed (indicated by rpm in the figure) is as shown in FIG. 7, the engine speed required to obtain the required motor power is obtained. This required engine speed is set to the lower limit value of the required engine speed.

  In Step S8, it is determined whether or not the required engine speed lower limit calculated in Step S7 is equal to or lower than the upper limit of the engine speed, and the required engine speed lower limit is equal to or lower than the engine speed upper limit. If so, the process proceeds to step S9. If not, the process proceeds to step S13. The upper limit value of the engine speed is a so-called rev. Limit. As described above, the required engine speed lower limit is the engine speed necessary to obtain the required motor power. Therefore, as shown in FIG. 8, when the required engine rotational speed lower limit exceeds the engine rotational speed upper limit corresponding to the rev limit, the rotational speed cannot be obtained. In that case, prohibition of driving force reduction control, which will be described later, and driving of the rear wheels 3L and 3R driven only by the motor 4 are stopped.

In step S9, after setting the upper limit value of the required engine speed, the process proceeds to step S10. The upper limit value of the required engine speed is set as follows. That is, for example, in this embodiment, as shown in FIG. 9, the upper limit value V _LMT is set for the voltage of the rear wheel drive system by the motor. Since the generated voltage must not exceed the upper limit value V _LMT for the generated power characteristic corresponding to the engine speed, the engine speed is set to the upper limit value of the required engine speed.

In step S10, after the stop command for the driving force reduction control function by the engine controller 18 is output, the process proceeds to step S11.
In step S11, the gear position of the transmission 30 serving as the automatic transmission is set to the N (neutral) position, and then the process proceeds to step S12. In the present embodiment, the vehicle is driven only by driving the rear wheels 3L and 3R by the motor 4 while obtaining the necessary motor power by the engine 2 and the generator 7, so that the engine 2 and its front wheels 1L and 1R are driven wheels. The driving force transmission path of is cut off.

In step S12, the engine controller 18 is instructed to control the engine speed so that the necessary motor torque calculated in step S5 is obtained, and then the process returns to the main program. Specifically, the required engine rotational speed lower limit value is set as a target engine rotational speed, and the engine rotational speed feedback control is performed using the required engine rotational speed upper limit value as a limiter.
On the other hand, in step S13, after the driving force reduction control function of the engine control unit 18 is restored, the process proceeds to step S14.

In step S14, the gear position of the transmission 30, which is the automatic transmission, is set to the D (normal travel) position, and then the process proceeds to step S15.
In step S15, the four-wheel drive control is performed by the surplus torque calculator 8E, the target torque limiter 8F, and the surplus torque converter 8G, and then the process returns to the main program.
In step S16, the clutch 12 is disengaged and the front control (engine drive wheel) drive control by the engine control unit 18 is performed, and then the process returns to the main program.
In step S17, the four-wheel drive control is performed by the surplus torque calculation unit 8E, the target torque limiting unit 8F, and the surplus torque conversion unit 8G, and then the process returns to the main program.

  According to this calculation process, the traveling speed of the host vehicle is equal to or greater than the start threshold value at which the four-wheel drive control can be canceled, and the acceleration slip amount of the drive wheels by the engine 2, that is, the front wheels 1L and 1R is equal to or greater than a predetermined value. When the four-wheel drive conditions are satisfied, the traveling speed is equal to or higher than the vehicle propulsion upper limit value by the motor torque, and the rate of increase in the rotational speed of the front wheels 1L and 1R that are engine driving wheels is equal to or higher than a predetermined value In order to drive the vehicle only by driving the rear wheels 3L and 3R by the motor 4, the necessary motor torque corresponding to the vehicle traveling speed and the accelerator opening is calculated, and further, the necessary motor power necessary to obtain it is calculated. . Then, a lower limit value of the required engine speed for obtaining the necessary motor power is calculated. If the lower limit value of the required engine speed is equal to or lower than the upper limit value of the engine speed, the required engine speed not exceeding the system voltage upper limit value is calculated. Set the upper speed limit. Next, the requested engine rotation speed lower limit is specifically set so that the required motor torque can be obtained after the driving force reduction control function by the engine controller 18 is stopped and the gear position of the transmission 30 as an automatic transmission is set to neutral. The engine controller 18 is instructed to perform feedback control of the engine speed, with the value as the target engine speed and the requested engine speed upper limit as a limiter.

  As a result, the necessary motor power is generated by the engine 2 and the generator 7, the motor 4 is driven by the generated power, and the rear wheels 3L and 3R are driven by the driving force, so that the vehicle travels. At this time, since the driving force reduction control by the engine controller 18 is prohibited, sufficient motor rotation speed is obtained and necessary motor power is generated. Further, since the gear position of the transmission 30 which is an automatic transmission is neutral and transmission of driving force from the engine 2 to the front wheels 1L and 1R is interrupted, the acceleration slip of the front wheels 1L and 1R converges quickly. .

FIG. 10 shows changes over time in the wheel speed, traveling speed, rear wheel (motor) torque, and front wheel (engine) torque when starting an extremely low μ road in the four-wheel drive vehicle of the present embodiment. When the vehicle starts at time t ₀₀ , the front wheel torque increases with the engine torque as the accelerator opening increases, and the rear wheel torque increases together with the motor torque, resulting in a four-wheel drive state. However, since the engine torque when the accelerator opening is large is much larger than the motor torque, the front wheels driven by the engine start to slip and the difference between the front wheel speed and the rear wheel speed becomes remarkably large.

Eventually, at time t ₀₁ when the traveling speed becomes the start threshold, the rate of increase in the rotational speed of the front wheels, which are the engine-driven wheels, was greater than or equal to a predetermined value. That is, engine driving force reduction control is prohibited, the gear position is neutral, and the engine is used only to generate the necessary motor power with the generator, and the rear wheels are driven by driving the motor with the generated power. . As a result, the acceleration slip of the front wheels converges quickly and the vehicle gradually accelerates. Since the engine torque thereafter is used only for power generation by the generator 7 as described above, the torque is small even if the rotational speed is high (see the two-dot chain line in the figure). Further, the motor torque gradually decreases as the traveling speed increases, that is, the motor rotation speed increases.

At time t ₀₃ , the traveling speed becomes the vehicle propulsion upper limit value by the motor torque, the acceleration traveling only by the rear wheel drive by the motor is finished, the gear position is set to the normal traveling position, and the engine torque is changed to the front wheel. Communicated. At this time, the motor torque is still transmitted to the rear wheels and the four-wheel drive state is maintained, but the motor torque continues to decrease and eventually becomes “0” at time t ₀₄ and shifts to the front wheel drive state.
As is apparent from this figure, even on an extremely low μ road where the front wheels driven by the engine are greatly accelerated and slipped, the acceleration slip of the front wheels at the start of the vehicle converges quickly, and the vehicle can be accelerated smoothly.

  On the other hand, FIG. 11 shows an extremely low μ road when the vehicle speed is to be accelerated by the driving force reduction control when the traveling speed is equal to or higher than the start threshold value and the front wheels, which are engine driving wheels, are greatly accelerating and slipping. 3 shows changes with time in wheel speed, traveling speed, rear wheel (motor) torque, and front wheel (engine) torque. In this comparative example, a driving force return region (shaded portion in the figure) having a predetermined width is set for the rear wheel speed equivalent to the traveling speed, and once the driving force reduction control is started, The engine torque is set to “0” when the front wheel rotation speed is larger than the driving force return area, and the engine torque is returned only when the front wheel rotation speed converges in the driving force return area.

Therefore, the vehicle is starting at time t _10, when the running speed at the time t ₁₁ is equal to or higher than the starting threshold value, since the front wheel is greatly acceleration slippage, the engine torque to "0". As a result, the front wheel speed rapidly decreases and enters the driving force return region, so that the engine torque is restored again, and the front wheels are greatly accelerated and slipped accordingly. This repetition is continued until time t ₁₃ the front wheel speed is stabilized by the driving force return area, while the engine is repeatedly sense the rotational speed is reduced or increased, discomfort to the driver.

  As described above, according to the four-wheel drive vehicle of the present embodiment, since the driving force reduction control of the engine is prohibited when the wheels are driven by the motor, the power storage device is particularly interposed between the generator and the motor. In a battery-less four-wheel drive vehicle that is not mounted, it is possible to obtain electric power necessary for driving wheels with a motor, and to supply sufficient electric power to the motor to obtain necessary motor torque.

In addition, since the engine driving force reduction control is prohibited when the increase rate of the engine rotation speed is equal to or higher than a predetermined value, even on an extremely low μ road where the vehicle cannot be accelerated properly by the engine driving force reduction control, The vehicle can be accelerated smoothly.
In addition, while the driving force reduction control of the engine is prohibited, the transmission slip from the engine to the wheels is cut off by setting the gear position of the transmission to neutral, etc., so that the acceleration slip of the driving wheels by the engine converges quickly. And the engine can only be used to generate the necessary power.

  In addition, the motor torque required to drive the vehicle only with the motor is calculated, the generated power necessary to generate the required motor torque is calculated, and the lower limit of the engine rotation speed required to obtain the generated power When the value is calculated and the transmission of the driving force from the engine to the wheels is interrupted, the engine speed is controlled in a region equal to or greater than the lower limit value of the calculated engine speed, so the vehicle is driven only by the motor. It is possible to reliably obtain the motor torque necessary for the above.

In addition, when the upper limit value of the required engine speed is calculated from the voltage upper limit value of the wheel drive system by the motor and the transmission of the driving force from the engine to the wheels is cut off, the calculated engine speed is within an area below the upper limit value. Since the configuration is such that the engine speed is controlled, a voltage higher than the voltage upper limit value of the system is not generated.
In addition, the lower limit value of the engine speed calculated according to the required motor torque is set as the target engine speed, and the target engine is within a range equal to or lower than the upper limit value of the engine speed calculated according to the voltage upper limit value of the system. Since the engine rotational speed is controlled to follow the rotational speed, energy is not wasted when the vehicle is driven only by the motor.

Further, when the vehicle cannot be accelerated only by the torque of the motor, the driving force reduction control of the engine is restored, so that the vehicle can be driven only by the engine or by the engine and the motor.
Further, when the lower limit value of the engine rotation speed calculated according to the necessary motor torque is equal to or higher than the upper limit value of the engine rotation speed set in advance, the engine driving force reduction control is restored, so that only the engine or The vehicle can be driven by the engine and the motor.

  From the above, the 4WD controller 8 of FIG. 1 constitutes the motor driving means of the present invention, and similarly, the engine controller 18 of FIG. 1 constitutes the driving force reduction control means, and the arithmetic processing of FIG. 4 is prohibited. The engine rotation speed sensor 21 in FIG. 1 constitutes an engine rotation speed detection means, the transmission 30 constitutes a driving force cutoff means, and step S5 of the arithmetic processing in FIG. 4, the step S6 of the calculation process of FIG. 4 constitutes a required power calculation means, the step S7 of the calculation process of FIG. 4 constitutes a required engine speed lower limit value calculation means, and the calculation of FIG. Step S9 of the process constitutes the required engine upper limit value calculation means, and step S3 of the calculation process of FIG. 4 constitutes the non-acceleration detection means.

Note that the driving force blocking means of the present invention is not limited to the transmission in the neutral position. For example, a fastening element such as a clutch may be interposed between the engine and the engine drive wheel.
In the above embodiment, the case of a four-wheeled vehicle is exemplified, but the present invention may be applied to a two-wheeled vehicle using the motor 4 as a drive source.
The generator may be coupled to the engine by a spline or a chain.
Further, a reduction gear or a clutch may not be interposed between the slave drive source and the wheel. When the vehicle does not have a clutch and the motor drive wheels are not driven, it is only necessary to apply current to the motor that is the slave drive source.
In addition to driving the front wheels with the engine, the rear wheels may be driven with the engine. In that case, the front wheels are driven by a motor.

It is a schematic device block diagram concerning one embodiment based on the present invention. It is a system configuration figure concerning one embodiment based on the present invention. It is a block diagram which shows the 4WD controller which concerns on one Embodiment based on this invention. It is a flowchart which shows the arithmetic processing for the vehicle start control performed within the 4WD controller of FIG. It is explanatory drawing of the vehicle propulsion upper limit by motor torque. It is explanatory drawing of the front-wheel acceleration slip driven by an engine. It is explanatory drawing of a request | requirement engine speed lower limit. It is explanatory drawing of an engine speed upper limit. It is explanatory drawing of a request | requirement engine speed upper limit. It is a timing chart which shows the time-dependent change of the wheel speed at the time of start by the four-wheel drive vehicle of the present invention, and traveling speed. It is a timing chart which shows the time-dependent change of the wheel speed at the time of starting by the conventional four-wheel drive vehicle, and traveling speed.

Explanation of symbols

1L, 1R Front wheel 2 Engine 3L, 3R Rear wheel 4 Motor 7 Generator 8 4WD controller 9 Electric wire 10 Junction box 11 Reducer 12 Clutch 14 Intake line 15 Throttle valve 16 Accelerator sensor 17 Accelerator pedal 18 Engine controller 19 Step motor 20 Motor Controller 21 Engine speed sensor 22 Voltage regulator 23 Current sensor 26 Motor speed sensor 27FL, 27FR, 27RL, 27RR Wheel speed sensor 30 Transmission 31 Differential gear 32 Shift position detecting means 34 Brake pedal 35 Brake stroke sensor 36 Brake controller 37FL, 37FR, 37RL, 37RR Braking device

Claims (7)

An engine that drives one of the front and rear wheels, an electric motor that can drive either of the front and rear wheels, a generator that drives the electric motor with electric power that is driven by the engine and generated, and driving of the wheels by the electric motor A motor driving means for controlling the state, a driving force reduction control means for reducing the driving force of the engine when the wheel driven by the engine is slipping, and a rotational speed of the wheel driven by the engine; When the engine driving wheel rotational speed detecting means and the motor driving means drive the wheels with an electric motor, and the increase rate of the rotational speed of the engine driving wheel detected by the engine driving wheel rotational speed detecting means is equal to or greater than a predetermined value. A four-wheel drive vehicle comprising: prohibiting means for prohibiting engine driving force reduction control by the driving force reduction control means. Driving force blocking means for cutting off transmission of driving force between the wheel driven by the engine and the engine, and the prohibiting means includes the driving force while the driving force reduction control of the engine is prohibited by the driving force reducing means; The four-wheel drive vehicle according to claim 1 , wherein transmission of driving force from the engine to the wheels is blocked by the blocking means. Necessary electric motor torque calculating means for calculating electric motor torque required for driving the vehicle only by the electric motor, and generated electric power of the generator required for generating the required electric motor torque calculated by the required electric motor torque calculating means The required power calculation means for calculating the required engine rotation speed lower limit value calculation means for calculating the lower limit value of the engine rotation speed required to obtain the generated power calculated by the required power calculation means, and the prohibition means When the transmission of the driving force from the engine to the wheels is interrupted by the driving force interrupting means, the engine speed is reduced in a region equal to or greater than the lower limit value of the engine speed calculated by the required engine speed lower limit calculating means. The four-wheel drive vehicle according to claim 2 , wherein the four-wheel drive vehicle is controlled. A request engine rotational speed upper limit value calculating means for calculating an upper limit value of the required engine rotational speed from a voltage upper limit value when driving the electric motor with the electric power generated by the generator; and the prohibiting means includes the driving force blocking means When the transmission of the driving force from the engine to the wheels is interrupted by the engine, the engine speed is controlled in a region equal to or less than the upper limit value of the engine speed calculated by the required engine speed upper limit value calculating means. The four-wheel drive vehicle according to claim 3 . The prohibiting means sets the lower limit value of the engine speed calculated by the required engine speed lower limit value calculating means as a target engine speed, and the engine speed calculated by the required engine speed upper limit value calculating means. The four-wheel drive vehicle according to claim 4 , wherein the engine rotation speed is controlled so as to follow the target engine rotation speed in a region equal to or less than an upper limit value. A non-acceleration detecting means for detecting that the vehicle cannot be accelerated only by the torque of the electric motor, and the prohibiting means detects the drive when the non-acceleration detecting means detects that the vehicle cannot be accelerated only by the motor torque. The four-wheel drive vehicle according to any one of claims 1 to 5 , wherein the driving force reduction control of the engine by the force reduction control means is permitted . When the lower limit value of the engine rotational speed calculated by the required engine rotational speed lower limit value calculating means is greater than or equal to a preset upper limit value of the engine rotational speed, the prohibiting means is configured to reduce the engine power by the driving force reduction control means. The four-wheel drive vehicle according to any one of claims 3 to 6 , wherein the driving force reduction control is permitted.

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