JP2007245995A - Control device for hybrid four-wheel drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow for stable cruise running even on a sand road surface. <P>SOLUTION: A control device for a hybrid four-wheel drive vehicle 1 of which front wheels 10a and 10b are driven by an engine 2, and of which rear wheels 26a and 26b are driven by a motor 20 comprises: a sand road surface judgement means; a cruise running judgment means; a driving force distribution calculating means for calculating the driving force distribution of front and rear wheels; a front and rear revolution difference calculating means for calculating revolution difference of front and rear wheels; an output calculating means for calculating the output of the engine 2 and the motor 20 respectively based on the distribution calculated by the driving force distribution calculating means and the revolution difference of front and rear wheels calculated by the front and rear revolution difference calculating means; and a driving force distribution correcting means for correcting the driving force distribution of front and rear wheels calculated by the driving force distribution calculating means so that, when it is determined that the driver is making cruise running on a sand road surface, the revolution difference of the front and rear wheels become the revolution difference which are obtained by adding a predetermined revolution difference to the revolution difference set when the driver makes the cruise running on a rough road other than a sand road surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for a hybrid four-wheel drive vehicle in which one of front and rear wheels is driven by an engine and / or an electric motor and the other is driven by another electric motor.

In recent years, hybrid four-wheel drive vehicles (hereinafter sometimes simply referred to as four-wheel drive vehicles) in which one of the front and rear wheels is driven by an engine and / or an electric motor and the other is driven by another electric motor have been developed.
As a technology for improving the running stability of this four-wheel drive vehicle, there is a traction control system (hereinafter abbreviated as TCS). The TCS detects the vehicle speed from the rotational speed of the driven wheel (non-main driving wheel), and increases the speed of the main driving wheel rapidly so as to keep the wheel speed difference of the main driving wheel with respect to the driven wheel below a predetermined threshold. While restraining with a brake, it controls the output of the engine and electric motor to limit the torque of the main drive wheels. That is, the TCS prevents excessive idling of the main drive wheel under slippery road conditions such as a snowy road by cooperatively controlling the brake, the engine, and the electric motor.

In addition, as a technology for protecting the electric motor in the hybrid four-wheel drive vehicle, it is provided with a rough road detecting means, and when the rough road is detected by the rough road detecting means, the driving by the electric motor is prohibited, There is one that reduces the drive region (see, for example, Patent Document 1).
Japanese Patent No. 3390475

  However, the TCS that cooperatively controls the brake and the engine mainly assumes a slip state on a snow-capped road surface or a wet paved road surface, and has not been studied in detail until traveling on sand. In running on a general low μ road surface such as a snow-capped road surface or a frozen road surface, the running resistance is equal to or less than that of a normal paved road surface, but in running on sand, the running resistance increases.

This special situation in traveling on sand will be described. When the vehicle travels on dry sand as shown in FIG. 13, since the wheel is buried in the sand, the work of crushing and deforming the sand is generated. As the contact area with the road surface (sand) increases, the contact surface energy loss increases. Now, the shaft torque of the drive wheel is T (Nm), the rotational speed of the drive wheel is ω (rsd / sec), the tractive force is P (N), the straight speed is V (m / sec), and the amount of work to deform the sand is When D (Nm) and the contact surface energy loss are Ef (Nm), Expression (1) is established.
Tω = PV + D + Ef (1)
In this formula (1), the left side is input energy from the drive wheel, and the right side is output energy.
Therefore, the running resistance in running on sand increases compared to a snow-capped road surface or a frozen road surface. On the other hand, as for the road surface friction coefficient (hereinafter referred to as road surface μ), the road surface μ on the sand is determined by the friction coefficient of sand-to-sand, so that the apparent road surface μ is low like the road surface μ of the snow road surface or the frozen road surface. There is a case.

As described above, when traveling on sand, the running resistance increases and the road surface μ decreases. Therefore, when TCS is used, ON / OFF of TCS control is repeated, resulting in an increase in rotational fluctuation and a deterioration in running feeling. There is a fear. In addition, since the TCS aims to stabilize the traveling of the vehicle while securing the driving force, the vehicle efficiency (energy transmission efficiency) at the time of TCS control is not taken into consideration.
In addition, since the running resistance is the same as or less than that of ordinary paved roads on snowy and frozen roads, the driving force required for cruising at low speed (constant speed running) is small, and the driving force is the main drive. Although it can be ensured by two-wheel drive using wheels, traveling resistance on sand increases, so it is necessary to travel by four-wheel drive even when cruising at low speed.
Therefore, the present invention provides a control device for a hybrid four-wheel drive vehicle that enables stable cruise traveling even on a sandy road surface.

The control device for a hybrid four-wheel drive vehicle according to the present invention employs the following means in order to solve the above-described problems.
The invention according to claim 1 is a hybrid four-wheel drive in which one of the front and rear wheels is driven by an engine (for example, an engine 2 in an embodiment described later) and the other is driven by an electric motor (for example, a rear wheel motor 20 in an embodiment described later). In a control device for a vehicle (for example, vehicle 1 in an embodiment described later), a sand road surface determination means (for example, step S102 in an embodiment described later) for determining whether the vehicle is on a sand road, and whether the vehicle is traveling on a cruise. A cruise travel judging means (for example, step S101 in the embodiment described later) and a driving force distribution calculating means for calculating the driving force distribution of the front and rear wheels with respect to the total driving force of the vehicle (for example, step in the embodiment described later). S103) and a front / rear differential speed calculation means (for example, an actual speed described later) for calculating the front / rear wheel differential speed from the front and rear wheel speeds. Step S301) in the example, and the outputs of the engine and the electric motor based on the distribution calculated by the driving force distribution calculating means and the differential rotational speeds of the front and rear wheels calculated by the front / rear differential rotational speed calculating means. When the output calculating means for calculating (for example, step S104 in the embodiment described later) and the sandy road surface determining means are determined to be sandy road surfaces, and the cruise driving determining means is determined to be cruise driving, The driving force distribution calculating means is configured so that the differential rotational speed of the front and rear wheels becomes a differential rotational speed obtained by adding a predetermined differential rotational speed to the differential rotational speed set when cruise traveling on a rough road other than a sandy road surface. It is characterized by comprising driving force distribution correcting means (for example, steps S301 to S306 in the embodiments described later) for correcting the calculated front / rear driving force distribution.
With this configuration, it is possible to continue cruising stably (continuity) on the sandy road surface without increasing the running resistance and the total driving force. In addition, since the driving force sharing of the wheels driven by the electric motor can be reduced, the continuous operation output of the electric motor can be reduced and the temperature rise of the electric motor can be suppressed. In this application, “bad roads other than sandy road surfaces” include wet pavement roads, snow-capped road surfaces, and the like, in other words, all road surfaces in which a rotational difference occurs between the front and rear wheels other than on the sandy road surfaces.

According to a second aspect of the present invention, in the first aspect of the invention, the driving force distribution correcting unit corrects the front / rear driving force distribution so that the differential rotational speed of the front and rear wheels maintains a predetermined value. And
With this configuration, it is possible to continue cruising stably (continuity) on the sandy road surface without increasing the running resistance and the total driving force.

The invention according to claim 3 is the invention according to claim 1, wherein the differential rotational speed obtained by adding the predetermined differential rotational speed is a predetermined value corresponding to a vehicle speed.
By comprising in this way, the stable cruise driving | running | working on a sand road surface is attained in a wide vehicle speed range.

According to a fourth aspect of the present invention, in the first aspect of the invention, when the steering angle of the vehicle is equal to or greater than a predetermined value, the differential rotational speed of the front and rear wheels is decreased and corrected according to the increase amount of the steering angle. It is characterized by that.
By configuring in this way, it is possible to generate a lateral force required when the vehicle turns, and to keep good turning performance on the sandy road surface.

According to a fifth aspect of the present invention, in the first aspect of the invention, when the steering angle of the vehicle is within a predetermined value and the lateral acceleration is equal to or greater than a predetermined value, the front and rear are increased according to the increase amount of the lateral acceleration. It is characterized in that the difference rotational speed of the wheel is reduced and corrected.
When the steering angle of the vehicle is within a predetermined value and the lateral acceleration is greater than or equal to a predetermined value, it is considered that the vehicle is traveling in camber. By configuring as described above, it is possible to generate a lateral force necessary during camber travel, and thus it is possible to continue stable camber travel on the sandy road surface.

According to a sixth aspect of the present invention, in the first aspect of the present invention, when the steering angle of the vehicle is within a predetermined value and the yaw rate of the vehicle is equal to or larger than the predetermined value, the front and rear according to the increase amount of the yaw rate. It is characterized in that the difference rotational speed of the wheel is reduced and corrected.
When the steering angle of the vehicle is within a predetermined value and the yaw rate of the vehicle is greater than or equal to a predetermined value, it is considered that the vehicle is turning with a large turning radius. By configuring as described above, it is possible to generate a lateral force required during a large turn, so that a stable large turn on the sandy road surface is possible.

The invention according to claim 7 is characterized in that, in the invention according to claim 1, the output of the electric motor is reduced in accordance with the temperature rise of the electric motor.
By comprising in this way, the temperature rise of an electric motor can be suppressed and protection of an electric motor can be aimed at.

The invention according to claim 8 is the invention according to claim 1, further comprising a generator capable of generating electric power with at least the power of the engine (for example, the front wheel motor 3 in an embodiment described later) as a power source of the electric motor. The generator reduces the amount of power generation according to the temperature rise of the generator and supplies power to the motor.
By comprising in this way, the temperature rise of a generator can be suppressed and protection of a generator can be aimed at.
In addition, when the output of the motor is reduced as described above, the continuous power output of the generator that is the power source of the motor can be suppressed, so that the temperature rise of the generator is suppressed to protect the generator. be able to.

The invention according to claim 9 is the invention according to claim 8, wherein a battery (for example, a battery 12 in an embodiment to be described later) is provided outside the generator as a power source of the electric motor, and the power generation amount of the generator is reduced. The battery is made up for power that is insufficient for the electric motor when reduced.
By configuring in this way, it is possible to supply necessary electric power to the electric motor even when the electric generator is restricted in power generation.

According to a tenth aspect of the present invention, in the ninth aspect of the invention, when the remaining capacity of the battery is equal to or lower than a predetermined value, or when the temperature of the battery is equal to or higher than a predetermined value, the remaining capacity is reduced. Or the output of the battery is reduced in response to an increase in battery temperature.
By comprising in this way, the temperature rise of a battery can be suppressed and protection of a battery can be aimed at.

According to the first and second aspects of the invention, stable cruising continuation (continuity) on the road surface on the sand is possible without increasing the running resistance and the total driving force. In addition, since the driving force sharing of the wheels driven by the electric motor can be reduced, the continuous operation output of the electric motor can be reduced and the temperature rise of the electric motor can be suppressed.
According to the invention which concerns on Claim 3, the stable cruise driving | running | working on the sand road surface is attained in a wide vehicle speed range.

According to the invention which concerns on Claim 4, the turning performance on a sandy road surface can be kept favorable.
According to the invention which concerns on Claim 5, it becomes possible to continue the stable camber driving | running | working on the road surface on sand.
According to the invention which concerns on Claim 6, the stable large turning on the sand road surface is attained.

According to the invention which concerns on Claim 7, the temperature rise of an electric motor can be suppressed and protection of an electric motor can be aimed at.
According to the invention which concerns on Claim 8, the temperature rise of a generator can be suppressed and protection of a generator can be aimed at.
According to the invention which concerns on Claim 9, even when a generator is restrict | limited to an electric power generation, it becomes possible to supply electric power required for an electric motor.
According to the invention which concerns on Claim 10, the temperature rise of a battery can be suppressed and protection of a battery can be aimed at.

Embodiments of a control device for a hybrid four-wheel drive vehicle according to the present invention will be described below with reference to the drawings of FIGS.
FIG. 1 is a schematic configuration diagram of a drive system of a hybrid four-wheel drive vehicle (hereinafter abbreviated as a vehicle) 1. The vehicle 1 includes a front wheel drive system and a rear wheel drive system.
The front-wheel drive system includes an engine 2, a front-wheel electric motor (generator) 3 that is disposed on the output shaft of the engine 2 and directly connected to the engine 2, and a transmission that is coupled to the output shaft of the engine 2. 5, a differential mechanism 8 connected to the output shaft of the transmission 5 via a clutch or the like (not shown), left and right axle shafts 9 a and 9 b connected to the differential mechanism 8, and connected to the axle shafts 9 a and 9 b It consists of left and right front wheels 10a, 10b. As the transmission 5, either a stepped transmission or a pulley / belt continuously variable transmission can be adopted, and further, either an automatic transmission or a manual transmission can be adopted.

  On the other hand, the rear-wheel drive system includes a rear-wheel motor 20 capable of generating power, a differential mechanism 24 connected to an output shaft of the rear-wheel motor 20 via a clutch (not shown), and right and left connected to the differential mechanism 24. Axle shafts 25a and 25b, and left and right rear wheels 26a and 26b connected to the axle shafts 25a and 25b.

  Both the front wheel motor 3 and the rear wheel motor 20 are electrically connected to a vehicle-mounted battery 12 via a power control unit (hereinafter abbreviated as PDU) 13, and the PDU 13 is an inverter for the front wheel motor 3. And an inverter for the rear wheel motor 20. The front wheel motor 3 can be operated by being supplied with electric power from the battery 12 via the PDU 13, and performs a regenerative operation by rotational driving from the front wheels 10 a and 10 b side during deceleration traveling, or a regenerative operation by the power of the engine 2. The battery 12 can be charged (energy recovery). The rear wheel motor 20 can also be operated by being supplied with electric power from the battery 12 via the PDU 13, and at the time of decelerating traveling, a regenerative operation is performed by rotational driving from the rear wheels 26 a and 26 b to charge the battery 12 (energy Recovery) can be performed.

  In the vehicle 1, the main drive is performed by the front wheel drive system, and therefore, the two-wheel drive is driven by the front wheel drive system. In the front wheel drive system, the power of at least one of the engine 2 and the front wheel motor 3 can be transmitted to the front wheels 10 a and 10 b via the transmission 5. The rear wheel drive system transmits the power of the rear wheel motor 20 to the rear wheels 26a and 26b during four-wheel drive. Further, during four-wheel drive, the front wheel motor 3 is controlled to perform a regenerative operation by the power of the engine 2 to charge the battery 12.

Although not shown, in this vehicle 1, a temperature sensor (temperature detection means) that detects the temperature of the front wheel motor 3 and a temperature that detects the temperature of the rear wheel motor 20 for the purpose of running control on sand, which will be described later. Sensor (temperature detection means), temperature sensor (temperature detection means) for detecting the temperature of the inverter for the front wheel motor 3, temperature sensor (temperature detection means) for detecting the temperature of the inverter for the rear wheel motor 20, a battery 12, a temperature sensor (temperature detection means) for detecting the temperature of the battery 12, a remaining capacity sensor (remaining capacity detection means) for detecting the remaining capacity (hereinafter abbreviated as SOC) of the battery 12, and a wheel for detecting the wheel speed of the front wheels 10a and 10b. Speed sensor (wheel speed detection means), wheel speed sensor (wheel speed detection means) for detecting the wheel speed of the rear wheels 26a, 26b, steering angle sensor (steering angle detection means) for detecting the steering angle of the vehicle, vehicle A yaw rate sensor (yaw rate detecting means) for detecting the yaw rate, a lateral acceleration sensor (lateral acceleration detecting means) for detecting the lateral acceleration (lateral G) of the vehicle, and the like are provided, and the output of these sensors is an electronic control unit (ECU) 50. Is input.
Based on the input from these sensors, the ECU 50 performs operation / stop / output control of the engine 2 and operation (powering / regeneration) / stop / output control of the front wheel motor 3 and the rear wheel motor 20.

  By the way, in this vehicle 1, driving force transmission can be stabilized even when traveling on sand, and deterioration of vehicle efficiency (energy transmission efficiency) can be prevented, so that the running performance as a four-wheel drive vehicle can be maintained without impairing traveling performance. Therefore, the following control is performed when traveling on sand.

(1) When the vehicle is cruising on a sandy road surface, the difference between the rotational speeds of the front and rear wheels (hereinafter referred to as the front-rear differential rotational speed) is set when the TCS cruises on a bad road other than the sandy road surface. Correct the driving force distribution of the front and rear wheels so as to increase the front wheel driving force and decrease the rear wheel driving force so as to be a differential rotational speed obtained by adding a predetermined differential rotational speed to the rotational speed; and The driving force distribution of the front and rear wheels is corrected so that the actual front-rear differential rotational speed (actual front-rear differential rotational speed described later) maintains a predetermined slip ratio (differential rotational speed). As a result, it is possible to continue cruising on a sandy road surface (continuity) without increasing the running resistance and the total driving force. In addition, since the driving force sharing of the rear wheels can be reduced, the continuous operation output of the rear wheel motor 20 can be reduced, and the rear wheel motor 20 and its inverter are prevented from generating more heat than necessary. The “bad road other than the sandy road surface” includes a wet paved road surface, a snow-capped road surface, and the like. In short, it means all road surfaces in which a rotational difference occurs between the front and rear wheels other than the sandy road surface.

(2) The differential rotational speed obtained by adding the predetermined differential rotational speed is a predetermined value set in advance according to the vehicle speed. Thereby, the stable cruise driving | running | working on a sand road surface is enabled in a wide vehicle speed range.
(3) When the steering angle of the vehicle is equal to or greater than a predetermined value, the differential rotational speed of the front and rear wheels is corrected to decrease according to the increase amount of the steering angle. As a result, a lateral force necessary for turning the vehicle is generated to ensure turning performance on the sandy road surface.

(4) When the steering angle of the vehicle is within a predetermined value and the lateral acceleration is greater than or equal to a predetermined value, the front-rear rotational speed is corrected to decrease according to the increase amount of the lateral acceleration. This situation is considered that the vehicle is traveling in camber, but by correcting the differential rotational speed in this way, the lateral force required during camber travel is generated, and the continuity of camber travel on the sandy road surface is increased. Secure.
(5) When the steering angle of the vehicle is within a predetermined value and the yaw rate of the vehicle is greater than or equal to a predetermined value, the differential rotational speed of the front and rear wheels is corrected to decrease according to the increase amount of the yaw rate. This situation is considered that the vehicle is turning with a large turning radius, but by correcting the differential rotation speed in this way, the lateral force required for large turning is generated, and large turning on the sand surface is performed. Make it feasible.

(6) The output of the rear wheel motor 20 is reduced according to the temperature rise of the rear wheel motor 20 or the temperature rise of the inverter for the rear wheel motor 20. Thereby, the temperature rise of the rear wheel motor 20 is suppressed, and the rear wheel motor 20 is protected. Further, since the output of the rear wheel motor 20 is reduced, the continuous power generation output of the front wheel motor 3 which is the power source of the rear wheel motor 20 can be suppressed, so that the heat generation of the front wheel motor 3 is suppressed and the front wheel motor is suppressed. Therefore, the front wheel motor 3 can be protected.
(7) The power generation amount of the front wheel motor 3 is reduced and power is supplied to the rear wheel motor 20 in accordance with the temperature rise of the front wheel motor 3 or the temperature rise of the inverter for the front wheel motor 3. Thereby, the heat generation of the front wheel motor 3 can be suppressed, the temperature increase of the front wheel motor 3 can be suppressed, and the front wheel motor 3 can be protected.

(8) When the power generation amount of the front wheel motor 3 is reduced and power is supplied to the rear wheel motor 20, the battery 12 compensates for the insufficient power in the rear wheel motor 20. As a result, even when the power generation of the front wheel motor 3 is restricted, the necessary power can be supplied to the rear wheel motor 20 and the necessary driving force is secured on the rear wheel side.
(9) However, when the remaining capacity of the battery 12 (hereinafter abbreviated as “SOC”) is not more than a predetermined value, or when the temperature of the battery 12 is not less than a predetermined value, the temperature of the battery 12 or the temperature of the battery 12 is decreased. The output of the battery 12 is reduced according to the increase. Thereby, the temperature rise of the battery 12 is suppressed and the battery 12 is protected.

Next, the sand traveling control in this embodiment will be described with reference to the flowchart of FIG.
The sand running control routine shown in the flowchart of FIG. 2 is executed by the ECU 50 at regular intervals.
First, in step S101, a cruise traveling determination process for determining whether or not the cruise traveling is performed. In the cruise travel determination process, the vehicle body speed (vehicle speed) is calculated based on the output values of the wheel speed sensors of the rear wheels 26a and 26b, and the change in the vehicle speed within a predetermined time is within a predetermined range. It is determined that the vehicle is traveling on a cruise, and if it is not within the predetermined range, it is determined that the vehicle is not traveling on a cruise. If it is determined in step S101 that the vehicle is cruising, the process proceeds to step S102, and a sandy road surface determination process is performed to determine whether the road surface is sandy. The road surface judgment process on the sand will be described in detail later.

As a result of executing the sandy road surface determination process in step S102, if it is determined as a sandy road surface, it is a sandy road surface cruise traveling, so the process proceeds to step S103, and the four-wheel-drive driving is performed with respect to the total driving force required for the vehicle. The basic front and rear wheel driving force distribution ratio is calculated.
Next, the process proceeds to step S104, and based on the actual front / rear differential rotational speed calculated in step S301 in the front / rear differential rotational speed control described later and the basic front / rear wheel driving force distribution ratio calculated in step S103. Each output of the electric motor 20 is calculated.

Next, it progresses to step S105 and it is determined whether the steering angle of a vehicle is smaller than predetermined value based on the output value of a steering angle sensor.
If the determination result in step S105 is “YES” (steering angle <predetermined value), the process proceeds to step S106 to determine whether the lateral acceleration of the vehicle is greater than the predetermined value based on the output value of the lateral acceleration sensor. To do.
If the determination result in step S106 is “NO” (lateral acceleration ≦ predetermined value), the process proceeds to step S107, and it is determined whether or not the yaw rate of the vehicle is greater than the predetermined value based on the output value of the yaw rate sensor.

If the determination result in step S107 is “NO” (yaw rate ≦ predetermined value), the rudder angle is smaller than the predetermined value, and the lateral acceleration and the yaw rate are less than or equal to the set predetermined values. It is determined that the vehicle is traveling straight, and the front-rear differential speed table (shown by the solid line in FIG. 3) shown in FIG. 3 is calculated to calculate the front-rear differential rotational speed corresponding to the vehicle speed. Set to the target front / rear differential speed during driving.
In the sand road surface front / rear difference rotational speed table in this embodiment, the front / rear differential rotational speed is constant regardless of the vehicle speed until the vehicle speed reaches a predetermined value, and when the vehicle speed becomes equal to or higher than the predetermined value, the front / rear difference difference increases. The number of rotations also increases. However, in the entire vehicle speed region, the front-rear differential rotational speed in this table is the differential rotational speed (hereinafter referred to as base TCS target differential rotational speed) that is set when cruise traveling on a rough road other than the sandy road surface in the TCS indicated by the dotted line in FIG. Is set to a value obtained by adding a predetermined number of differential rotations.

On the other hand, if the determination result in step S105 is “NO” (steering angle ≧ predetermined value), it is determined that the vehicle is turning on the sand road surface, and the process proceeds to step S109, where the steering angle increases. Decrease the target front / rear rotational speed and correct the sum of the front / rear wheel differential rotational speed and the base TCS target differential rotational speed, which are generated according to the steering angle and vehicle speed when the vehicle turns on the paved road surface. Set to. Therefore, as a result, the target front-rear differential rotation speed during the turning on the sand road surface is set to a value smaller than the target front-rear rotation speed during the straight road cruise traveling on the sand.
Lateral force is required when the vehicle is turning. Thus, the steering force can be recovered by reducing the front-rear rotational speed and reducing the slip ratio of the front wheels, and turning on the sandy road surface. Performance can be ensured.

On the other hand, if the determination result in step S106 is “YES” (lateral acceleration ≦ predetermined value), the lateral acceleration is larger than the predetermined value even though the steering angle is smaller than the predetermined value, so that the vehicle tilts in the vehicle width direction. It is determined that the vehicle is traveling straight on the sand road surface, that is, a so-called camber traveling state, and the process proceeds to step S110, where the target front-rear differential rotational speed is set according to the lateral acceleration. More specifically, the target longitudinal difference rotational speed is set to decrease as the lateral acceleration increases. As a result, the target front-rear rotational speed at this time is set to a value smaller than the target front-rear differential rotational speed during straight-cruise cruise traveling on the sand at the same vehicle speed.
Lateral force is required during camber travel, but the steering force can be recovered by reducing the front-rear differential rotational speed and reducing the slip ratio of the front wheels in this way. Driving continuity can be ensured.

If the determination result in step S107 is “YES” (yaw rate> predetermined value), the yaw rate is greater than the predetermined value even though the rudder angle is smaller than the predetermined value and the lateral acceleration is less than the predetermined value. Therefore, it is determined that the vehicle is turning with a large turning radius, and the process proceeds to step S110, where the target front-rear differential rotational speed is set according to the yaw rate. More specifically, the target front-rear difference rotational speed is set to decrease as the yaw rate increases. As a result, the target front-rear rotational speed at this time is set to a value smaller than the target front-rear differential rotational speed during straight-cruise cruise traveling on the sand at the same vehicle speed.
Lateral force is required even during a large turn, but the steering force can be recovered by reducing the front-rear differential rotation speed and reducing the slip ratio of the front wheels in this way. Continuity of large turns can be ensured.

After setting the target front-rear differential rotational speed in steps S108 to S110, the process proceeds to step S111, and the driving force of the front wheels 10a, 10b (that is, the driving force of the engine 2) and the driving force of the rear wheels 26a, 26b (that is, for the rear wheels). The driving force by the electric motor 20) is calculated, and these driving forces are summed to calculate the total driving force.
Next, the process proceeds to step S112, where the front / rear rotational speed control is executed, and the front / rear driving speed is controlled so that the actual front / rear differential rotational speed of the front and rear wheels matches the target front / rear differential rotational speed set in steps S108 to S110. Control the distribution ratio. The front-rear differential rotation speed control will be described in detail later.
Next, the process proceeds to step S113, the front and rear motor output limit control is executed, the output limits of the front wheel motor 3 and the rear wheel motor 20 are searched, and the output control of the front wheel motor 3 and the rear wheel motor 20 is executed. Then, the execution of this routine is finished. The front and rear motor output limit control will be described in detail later.
In this embodiment, the ECU 50 executes the processing of step S101 to realize the cruise traveling determination means, and the processing of step S102 realizes the sandy road surface determination means, and executes the processing of step S103. Thus, a driving force distribution calculating unit is realized, and an output calculating unit is realized by executing the process of step S104.

Next, the sandy road surface determination process executed in step S102 will be described with reference to the flowchart of FIG.
The sandy road surface determination processing routine shown in the flowchart of FIG. 4 is executed by the ECU 50 at regular intervals.
First, in step S201, the driving force of the front wheels 10a and 10b (that is, the driving force by the engine 2) and the driving force of the rear wheels 26a and 26b (that is, the driving force by the rear wheel motor 20) are calculated, and these driving forces are calculated. To calculate the total driving force.

Next, the process proceeds to step S202, where the vehicle body speed (vehicle speed) and the longitudinal vehicle body acceleration are calculated based on the output values of the wheel speed sensors of the rear wheels 26a and 26b.
Next, it progresses to step S203, and driving resistance is calculated, and also it progresses to step S204, and subtracts air resistance, acceleration resistance, etc. from driving resistance, and calculates rolling resistance.
Next, it progresses to step S205 and it is determined whether the rolling resistance calculated by step S204 is larger than predetermined value.
If the determination result in step S205 is “YES” (rolling resistance> predetermined value), the process proceeds to step S206, where the front-rear differential rotational speed is greater than the predetermined value and the rolling resistance is greater than the predetermined value, so that the road surface is sandy. This routine is terminated.
If the determination result in step S205 is “NO” (rolling resistance ≦ predetermined value), the process proceeds to step S207, where it is determined that the road surface is not sand and the execution of this routine is terminated.

Next, the front-rear rotational speed control executed in step S112 will be described with reference to the flowchart of FIG.
The front / rear rotational speed control routine shown in the flowchart of FIG. 5 is repeatedly executed by the ECU 50 at regular intervals.
First, in step S301, based on the output values of the wheel speed sensors of the front wheels 10a and 10b and the output values of the wheel speed sensors of the rear wheels 26a and 26b, the actual actual front / rear rotational speed (hereinafter referred to as the actual front / rear differential rotational speed). Calculated). In this embodiment, the ECU 50 executes the process of step S301, thereby realizing a front / rear difference rotational speed calculation means.
Next, the process proceeds to step S302, and it is determined whether or not the actual front-rear rotational speed calculated in step S301 matches the target front-rear differential rotational speed set in steps S108 to S110 in the above-described sand traveling control.

If the determination result in step S302 is “NO” (actual front / rear differential rotational speed ≠ target front / rear differential rotational speed), the process proceeds to step S303, and whether or not the actual front / rear differential rotational speed is smaller than the target front / rear differential rotational speed. judge.
If the determination result in step S303 is “NO” (actual front-rear differential rotational speed ≧ target front-rear differential rotational speed), the process proceeds to step S304, and the rear wheel driving force distribution is increased to reduce the front-rear differential rotational speed. The execution of this routine is once terminated.

If the determination result in step S302 is “YES” (actual front / rear differential rotational speed = target front / rear differential rotational speed), the process proceeds to step S305, and after the sand road surface cruise determination (in other words, differential rotation in the sand road road cruise traveling). It is determined whether or not the current rate of increase in the total driving force relative to the total driving force (before the number increase) is equal to or less than a predetermined value.
If the determination result in step S305 is “YES” (total driving force increase rate ≦ predetermined value), the current state is maintained and the execution of this routine is temporarily terminated.

If the determination result in step S305 is “NO” (total driving force increase rate> predetermined value), if this state is maintained, the expansion control of the forward / backward differential rotation leads to an increase in running resistance, so the process proceeds to step S304. In order to reduce the forward / backward differential rotation in order to suppress the increase in the total driving force, the rear wheel driving force distribution is increased and the execution of this routine is temporarily terminated.
If the determination result in step S303 is “YES” (actual front-rear differential rotational speed <target front-rear differential rotational speed), the process proceeds to step S306, and the rear wheel driving force distribution is decreased to increase the front-rear differential rotational speed. The execution of this routine is once terminated.
In this embodiment, the ECU 50 executes a series of processes in steps S301 to S306, thereby realizing a driving force distribution correcting unit.

Next, the front and rear motor output limit control executed in step S113 will be described with reference to the flowchart of FIG.
The front and rear motor output limit control routine shown in the flowchart of FIG. 6 is executed by the ECU 50 at regular intervals.
First, in step S401, the output correction coefficient (S-Km) of the rear wheel motor 20 is searched based on the temperature of the rear wheel motor 20 with reference to the rear wheel motor temperature output restriction table shown in FIG.
In the rear wheel motor temperature output limit table in this embodiment, the output correction coefficient (S-Km) is 100% (that is, no correction) below the limit start temperature, and the temperature rises above the limit start temperature. Therefore, the output correction coefficient (S-Km) decreases, and the output correction coefficient (S-Km) becomes 0% (output stop of the rear wheel motor 20) above the drive inhibition temperature.

Next, the process proceeds to step S402, with reference to the rear wheel inverter temperature output restriction table shown in FIG. 8, based on the temperature of the inverter for the rear wheel motor 20, the output correction coefficient (S-Ki) of the rear wheel motor 20. )
In the rear wheel inverter temperature output restriction table in this embodiment, the output correction coefficient (S-Ki) is 100% (that is, no correction) below the restriction start temperature, and the temperature rises above the restriction start temperature. Accordingly, the output correction coefficient (S-Ki) decreases, and the output correction coefficient (S-Ki) becomes 0% (output stop of the rear wheel motor 20) above the drive inhibition temperature.

  In step S403, the output correction coefficient (S-Km) searched in step S401 is compared with the output correction coefficient (S-Ki) searched in step S402, and the smaller output correction coefficient is adopted. Then, the output upper limit value A of the rear wheel motor 20 is set based on the output correction coefficient.

Next, the process proceeds to step S404, and the output correction coefficient (E-Km) of the front wheel motor 3 is searched based on the temperature of the front wheel motor 3 with reference to the front wheel motor temperature output restriction table shown in FIG.
In the front wheel motor temperature output limit table in this embodiment, the output correction coefficient (E-Km) is 100% (that is, no correction) below the limit start temperature, and as the temperature increases above the limit start temperature. The output correction coefficient (E-Km) decreases, and the output correction coefficient (E-Km) becomes 0% (power generation stop of the front wheel motor 3) above the drive inhibition temperature.

Next, proceeding to step S405, referring to the front wheel inverter temperature output restriction table shown in FIG. 10, the output correction coefficient (E-Ki) of the front wheel motor 3 is searched based on the temperature of the inverter for the front wheel motor 3. To do.
In the front wheel inverter temperature output restriction table in this embodiment, the output correction coefficient (E-Ki) is 100% (that is, no correction) below the restriction start temperature, and as the temperature rises above the restriction start temperature. The output correction coefficient (E-Ki) decreases, and the output correction coefficient (E-Ki) becomes 0% (power generation stop of the front wheel motor 3) above the drive inhibition temperature.

  In step S406, the output correction coefficient (E-Km) searched in step S404 is compared with the output correction coefficient (E-Ki) searched in step S405, and the smaller output correction coefficient is adopted. Thus, the power generation upper limit B of the front wheel motor 3 is set based on the output correction coefficient.

Next, the process proceeds to step S407, and an output correction coefficient (E-Kb) of the battery 12 is searched based on the temperature of the battery 12 with reference to the battery temperature output restriction table shown in FIG.
In the battery temperature output limit table in this embodiment, the output correction coefficient (E-Kb) is 100% (that is, no correction) below the limit start temperature, and the output increases as the temperature increases above the limit start temperature. The correction coefficient (E-Kb) decreases, and the output correction coefficient (E-Kb) becomes 0% (battery output stop) above the drive inhibition temperature.

Next, the process proceeds to step S408, and the output correction coefficient (E-Ks) of the battery 12 is searched based on the SOC of the battery 12 with reference to the battery SOC output restriction table shown in FIG.
In the battery SOC output restriction table in this embodiment, the output correction coefficient (E-Ks) is 100% (that is, no correction) when the SOC is equal to or higher than the predetermined value B1, and the SOC is decreased when the SOC is equal to or lower than the predetermined value B1. The output correction coefficient (E-Ks) is decreased as the value is reduced. When the SOC is equal to or less than the predetermined value B2, the output correction coefficient (E-Ks) becomes 0% (battery output stop).

In step S409, the output correction coefficient (E-Kb) searched in step S407 is compared with the output correction coefficient (E-Ks) searched in step S408, and the smaller output correction coefficient is adopted. The battery output upper limit C is set based on the output correction coefficient.
Next, the process proceeds to step S410, the output of the rear wheel motor 20 is set, and the execution of this routine is terminated. The output setting of the rear wheel motor 20 is performed as follows. Electricity generated by the front wheel motor 3 under the power generation upper limit B set in step S406 and power output by the battery 12 under the battery output upper limit C set in step S409 are simultaneously supplied to the rear wheel motor 20. The output of the rear wheel motor 20 (hereinafter referred to as “output based on power supply restriction”) is calculated, and this “output based on power supply restriction” and the rear wheel motor 20 set in step S403 are calculated. The output upper limit value A is compared, and the smaller output is set as the output of the rear wheel motor 20.

When the front and rear motor output limit control is executed in this way, the output of the rear wheel motor 20 is as follows.
When the temperature of the rear wheel motor 20 or the temperature of the inverter for the rear wheel motor 20 is equal to or lower than the respective restriction start temperatures, the rear wheel motor 20 basically has no output limitation, and the rear wheel motor 20 When at least one of the temperature of the motor 20 for driving and the temperature of the inverter for the motor 20 for rear wheels becomes equal to or higher than the limit start temperature, the output is limited.

  However, even if the temperature of the rear wheel motor 20 or the temperature of the inverter for the rear wheel motor 20 is not more than the respective restriction start temperature, at least the temperature of the front wheel motor 3 or the temperature of the inverter for the front wheel motor 3 is at least. If any of them becomes equal to or higher than the limit start temperature, the output of the front wheel motor 3 is limited (power generation limited) according to the temperature, and as a result, the output of the rear wheel motor 20 using the front wheel motor 3 as a power source. May also be limited.

  That is, when the temperature of the battery 12 is equal to or lower than the restriction start temperature and the SOC of the battery 12 is equal to or greater than the predetermined value B1, the battery 12 has no output restriction, and therefore the total amount of electric power that is insufficient for the power generation amount of the front wheel motor 3 Can be supplemented by the battery 12, in which case the output of the rear wheel motor 20 is not limited. However, when the temperature of the battery 12 is equal to or higher than the limit start temperature or the SOC of the battery 12 is equal to or less than the predetermined value B1, the output of the battery 12 is limited. In some cases, the battery 12 may not be able to compensate for the insufficient power, and as a result, the rear wheel motor 20 is limited in output by the amount that cannot be supplemented by the battery 12.

  Further, when the temperature of the battery 12 is equal to or lower than the drive prohibition temperature or the SOC of the battery 12 is equal to or lower than the predetermined value B2, the output of the battery 12 is stopped. The rear wheel motor 20 is subjected to output restriction.

It should be noted that at least one of the temperature of the front wheel motor 3 and the temperature of the inverter for the front wheel motor 3 is not less than the drive prohibition temperature, and the temperature of the battery 12 is not less than the drive prohibition temperature or the SOC of the battery 12 is not more than B2. In some cases, the front wheel motor 3 stops generating power and the battery 12 stops outputting, so the rear wheel motor 20 loses power, and as a result, the rear wheel motor 20 stops operating and the vehicle 1 Two-wheel drive of the front wheels 10a and 10b by the power of the engine 2 is performed.
By setting the output of the rear wheel motor 20 in this manner, the output of the rear wheel motor 20 is secured as much as possible while preventing overheating of the front wheel motor 3, the rear wheel motor 20, and the battery 12. Can do.

1 is a schematic configuration diagram of a drive system of an embodiment of a hybrid four-wheel drive vehicle including a control device according to the present invention. It is a flowchart which shows the traveling control on sand in an Example. It is a sand road surface front-and-back differential rotation speed table used in the examples. It is a flowchart which shows the sandy road surface judgment process in an Example. It is a flowchart which shows front-back differential rotation speed control in an Example. It is a flowchart which shows the front-and-rear motor output limit control in an Example. It is a rear-wheel electric motor temperature output restriction table used in an Example. It is a rear-wheel inverter temperature output restriction table used in an Example. It is a front-wheel electric motor temperature output restriction table used in an Example. It is a front-wheel inverter temperature output restriction table used in an Example. It is a battery temperature output restriction table used in an Example. It is a battery SOC output restriction table used in an Example. It is a schematic diagram for demonstrating the energy loss at the time of driving on a sandy road surface.

Explanation of symbols

1 Hybrid four-wheel drive vehicle 2 Engine 3 Front wheel motor (generator)
10a, 10b Front wheel 12 Battery 20 Rear wheel motor (electric motor)
26a, 26b Rear wheel S101 Cruise running judgment means S102 Sand road surface judgment means S103 Driving force distribution calculation means S104 Output calculation means S301 Front / rear difference rotational speed calculation means S301 to S306 Driving force distribution correction means

Claims (10)

In a control device for a hybrid four-wheel drive vehicle in which one of the front and rear wheels is driven by an engine and the other is driven by an electric motor.
A sandy road surface judging means for judging whether or not it is a sandy road surface;
Cruise traveling determination means for determining whether the vehicle is traveling on a cruise,
Driving force distribution calculating means for calculating the driving force distribution of the front and rear wheels with respect to the total driving force of the vehicle;
Front-rear differential rotation speed calculating means for calculating the differential rotation speed of the front and rear wheels from the wheel speeds of the front and rear wheels;
Output calculating means for calculating the outputs of the engine and the electric motor based on the distribution calculated by the driving force distribution calculating means and the differential rotational speed of the front and rear wheels calculated by the front / rear differential rotational speed calculating means;
When the sandy road surface determining means determines that the road is a sandy road surface and the cruise travel determining means determines that the vehicle is traveling on a cruise, the differential rotational speed of the front and rear wheels cruises on a bad road other than the sandy road surface. Driving force distribution correcting means for correcting the front and rear driving force distribution calculated by the driving force distribution calculating means so as to be a differential rotational speed obtained by adding a predetermined differential rotational speed to the differential rotational speed set at the time;
A control device for a hybrid four-wheel drive vehicle, comprising:   2. The control device for a hybrid four-wheel drive vehicle according to claim 1, wherein the driving force distribution correcting unit corrects the front and rear driving force distribution so that the differential rotational speed of the front and rear wheels maintains a predetermined value.   2. The control device for a hybrid four-wheel drive vehicle according to claim 1, wherein the differential rotational speed obtained by adding the predetermined differential rotational speed is a predetermined value corresponding to a vehicle speed.   2. The hybrid four-wheel drive vehicle according to claim 1, wherein when the steering angle of the vehicle is equal to or greater than a predetermined value, the differential rotational speed of the front and rear wheels is corrected to decrease according to the increase amount of the steering angle. Control device.   2. The differential rotational speed of the front and rear wheels is corrected to decrease in accordance with the increase amount of the lateral acceleration when the steering angle of the vehicle is within a predetermined value and the lateral acceleration is greater than or equal to a predetermined value. A control device for a hybrid four-wheel drive vehicle described in 1.   The differential rotational speed of the front and rear wheels is corrected to decrease according to the amount of increase in the yaw rate when the steering angle of the vehicle is within a predetermined value and the yaw rate of the vehicle is greater than or equal to a predetermined value. A control device for a hybrid four-wheel drive vehicle described in 1.   2. The control apparatus for a hybrid four-wheel drive vehicle according to claim 1, wherein an output of the electric motor is reduced in accordance with a temperature rise of the electric motor.   The power source of the electric motor includes at least a generator capable of generating electric power with the power of the engine, and the electric generator reduces the amount of electric power generated according to the temperature rise of the electric generator and supplies electric power to the electric motor. The control device for a hybrid four-wheel drive vehicle according to claim 1.   9. The battery according to claim 8, further comprising: a battery outside the generator as a power source of the motor, wherein the battery compensates for a power shortage with respect to the motor when the power generation amount of the generator is reduced. The control apparatus of the hybrid four-wheel drive vehicle of description.   When the remaining capacity of the battery is equal to or lower than a predetermined value, or when the temperature of the battery is equal to or higher than a predetermined value, the output of the battery is reduced according to a decrease in the remaining capacity or an increase in the battery temperature. The control apparatus for a hybrid four-wheel drive vehicle according to claim 9.

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