JP2013203152A - Vehicle driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle driving device capable of simply suppressing a slip of a wheel.SOLUTION: A target front wheel driving (braking) torque Ff (Ff') of a driving source 20 when switching from a rear wheel only driving/braking state to a front and rear wheel driving/braking state is controlled to be reduced to less than a slip torque X (X') by a torque control unit 42, and thereby occurrence of a slip of a front wheel Wf driven by the driving source 20 can be suppressed without calculation of a road surface friction coefficient, and the like. Furthermore, the slip torque X (X') acquired by a slip torque acquisition unit 32 is a rear wheel driving (braking) torque Fr (Fr') of an electric motor 10 in occurrence of a slip of a rear wheel Wr driven/braked by the electric motor 10 and thereby can be more accurately detected, and occurrence of a slip of the front wheel Wf in the front and rear wheel driving/braking state can be more reliably suppressed.

Description

  The present invention relates to a vehicle drive device.

  Patent Document 1 discloses an electric motor that independently drives each of a plurality of wheels provided in a vehicle, and a driving torque that is output from the electric motor so that the wheels slip while maintaining the vehicle in a stopped state. A road surface friction coefficient is calculated based on a driving torque control unit that adjusts the driving torque, a driving torque detection unit that detects the driving torque of each of the plurality of wheels, and a driving torque of the wheel when any of the wheels starts to slip. A road surface friction coefficient detection device including a friction coefficient calculation unit is described, and the road surface friction coefficient is detected when the vehicle stops before traveling.

JP 2005-207953 A

  By the way, when a vehicle travels on a road surface with a low coefficient of friction such as a snowy road surface or a wet road surface, a wheel slip may occur when the accelerator pedal opening is increased by the driver, and the vehicle's running performance is reduced. There was a problem that it could not be maintained properly. Therefore, it is conceivable to detect the road surface friction coefficient by using the invention described in Patent Document 1 described above and control the braking / driving of the wheel based on the road surface friction coefficient to suppress the wheel slip. .

  However, in the technique described in Patent Document 1, when calculating the road surface friction coefficient, the calculation method is complicated, such as driving torque at the start of slip, wheel radius, and wheel load must be taken into account. There was a possibility that the value was not accurate.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a vehicle drive device capable of easily suppressing wheel slip.

In order to achieve the above object, the invention described in claim 1
One of the front wheels (for example, the front wheel Wf of the embodiment described later) and the rear wheel (for example, the rear wheel Wr of the embodiment described later) of the vehicle (for example, the vehicle 3 of the embodiment described later) is braked / driven. An electric motor (for example, an electric motor 10 in an embodiment described later), a drive source for braking / driving one of the front wheels and the rear wheels (for example, a drive source 20 in an embodiment described later), and a predetermined value for the one wheel A slip acquisition device (for example, a slip acquisition device 30 in an embodiment described later) that acquires that an excess slip that is the above slip has occurred;
A vehicle control device that controls braking and driving of the wheels by the electric motor and the drive source (for example, a vehicle control device 40 according to an embodiment described later);
With
The slip acquisition device is a slip torque (for example, an embodiment described later) that is a torque of the electric motor (for example, a rear wheel driving torque Fr, a rear wheel braking torque Fr ′ described later) when the excess slip occurs. Slip torque acquisition means (for example, slip torque acquisition unit 32 of an embodiment described later)
The vehicle control device includes:
Torque control means for controlling the torque generated by the electric motor and the torque generated by the drive source (for example, a torque control unit 42 in an embodiment described later);
The one-wheel single braking / driving state in which the total torque of the vehicle (for example, the total driving torque and total braking torque in the embodiments described later) is generated only by the electric motor, and the total torque of the vehicle is generated by the electric motor and the driving source. Braking / driving state control means for switching between front and rear wheel braking / driving states (for example, braking / driving state control unit 44 in an embodiment described later);
A vehicle drive device (for example, a vehicle drive device 1 of an embodiment described later),
The braking / driving state control means switches to the front / rear wheel braking / driving state when the slip acquisition device acquires that the excess slip has occurred in the one-wheel single braking / driving state,
The torque control means includes torque of the drive source when the single wheel single braking / driving state is switched to the front / rear wheel braking / driving state (for example, a target front wheel driving torque Ff, a target front wheel braking torque Ff ′ in an embodiment described later). ) Is controlled to be less than the slip torque.

Moreover, in addition to the structure of Claim 1, the invention of Claim 2 is
The torque control means cancels the suppression control when the rotational speed difference between the one wheel and the other wheel becomes a predetermined threshold value or less during execution of the suppression control.

In addition to the configuration described in claim 1 or 2, the invention described in claim 3
The drive source is an internal combustion engine (for example, an internal combustion engine 22 of an embodiment described later).

According to the first aspect of the present invention, the braking / driving state control means enters the front / rear wheel braking / driving state when the slip acquisition device acquires that one wheel has slipped in the one-wheel single braking / driving state. Since switching is performed, it is possible to improve the driving performance and braking performance of the vehicle when a slip occurs.
Furthermore, the torque control means has torque suppression means for controlling the torque of the drive source to be less than the slip torque when switching from the one-wheel single braking / driving state to the front / rear wheel braking / driving state. Therefore, it is possible to suppress the occurrence of slipping on the wheel (the other wheel) driven and controlled by the drive source.
Further, the slip torque acquired by the slip torque acquisition means is the torque of the motor when a slip is generated on the wheel (one wheel) driven and controlled by the motor, so that it can be detected more accurately, and the front and rear wheel control It is possible to more reliably suppress the occurrence of slipping on the other wheel in the driving state.

  According to the second aspect of the present invention, the torque control means releases the suppression control when the rotational speed difference between the one wheel and the other wheel becomes equal to or less than a predetermined threshold during the execution of the suppression control. Accordingly, it is possible to increase the torque of the drive source and increase the total torque of the vehicle while suppressing the occurrence of slipping of the other wheel in the front and rear wheel braking drive state.

  According to the third aspect of the present invention, one of the front wheels and the rear wheels is controlled by the electric motor, and the other wheel is controlled by the internal combustion engine. It is possible to change the driving efficiency.

1 is a block diagram showing an embodiment of a vehicle on which a vehicle drive device according to the present invention can be mounted. It is a graph showing the relationship between time and each parameter, (a) is an accelerator pedal opening, (b) is a torque, (c) is a graph which shows a 4WD request flag and a slip determination flag. It is a figure which shows the control flow which suppresses the slip of a wheel. It is a graph showing the relationship between the time which concerns on a comparative example, and each parameter, (a) is an accelerator pedal opening degree, (b) is a torque, (c) is a 4WD request flag and a slip determination flag, (d) is a wheel speed. It is a graph which shows.

First, an embodiment of a vehicle drive device according to the present invention will be described with reference to the drawings.
The vehicle drive device 1 according to the present invention is used, for example, in a hybrid vehicle 3 having a drive system as shown in FIG. 1, and brakes or drives the rear wheels Wr (RWr, LWr) of the vehicle 3 (hereinafter referred to as “braking and driving”). The electric motor 10 and the drive source 20 for braking / driving the front wheels Wf are provided.

  The electric motor 10 includes first and second electric motors 10A and 10B. The powers of the first and second electric motors 10A and 10B are decelerated by the speed reducers 12A and 12B and transmitted to the rear wheels RWr and LWr, respectively. The drive source 20 is configured by connecting an internal combustion engine 22 and an electric motor 24 in series, and the power is transmitted to the front wheels Wf via the transmission 26. Further, the first and second electric motors 10A and 10B and the electric motor 24 are connected to the battery 5 so that power supply from the battery 5 and energy regeneration to the battery 5 are possible.

  The rear wheel Wr is provided with a slip acquisition device 30 that can acquire that an acceleration slip or a deceleration slip (hereinafter, simply referred to as “slip”) that exceeds a predetermined value has occurred. The slip acquisition device 30 includes a slip torque acquisition unit 32 that acquires and stores the rear wheel drive (braking) torque Fr (Fr ′) when the slip occurs in the rear wheel Wr as the slip torque X (X ′). Have. The acquisition of the rear wheel drive (braking) torque Fr (Fr ′) of the electric motor 10 by the slip torque acquisition unit 32 may be based on actual measurement or estimation based on the current value, the rotational speed, etc. of the electric motor 10.

  Further, the vehicle drive device 1 determines the vehicle state based on the input shift position, vehicle speed, accelerator pedal opening, brake pedal depression amount, and the like, and the rear wheel Wr and front wheel by the electric motor 10 and the drive source 20. A vehicle control device 40 that controls braking / driving of Wf is provided. The vehicle control device 40 controls the torque (rear wheel driving torque Fr or rear wheel braking torque Fr ′) generated by the electric motor 10 and the torque (front wheel driving torque or front wheel braking torque) generated by the drive source 20. And a braking / driving state control unit 44 for switching the braking / driving states of the electric motor 10 and the drive source 20. The braking / driving state control unit 44 includes a rear wheel single braking / driving state (one-wheel single braking / driving state) in which the total torque (total driving torque or total braking torque) of the vehicle 3 is generated only by the electric motor 10, and the electric motor 10 and the driving source. It is possible to switch between a front and rear wheel braking / driving state in which the total torque of the vehicle 3 is generated by 20 and a front wheel single braking / driving state in which the total torque of the vehicle 3 is generated only by the drive source 20.

  For example, when driving the vehicle 3, the braking / driving state control unit 44 switches to the rear wheel single drive state (RWD) in the low vehicle speed range to start EV and accelerate, and when the accelerator pedal is stepped on deeply, In the situation where acceleration is required, such as when the rear wheel Wr slips, the front-wheel drive state (4WD) is switched, and in the situation where the vehicle speed increases and the engine efficiency is high, the front-wheel alone drive state ( FNG) is switched to ENG traveling.

  Next, a method for suppressing the occurrence of slippage of the front wheels Wf and the rear wheels Wr by the vehicle drive device 1 configured as described above will be described with reference to FIGS. .

  First, when starting the vehicle 3, as shown in FIG. 2A, the target total drive torque FCar of the vehicle 3 is set based on the accelerator pedal (AP) opening (step S1). Then, the braking / driving state control unit 44 changes the driving state of the vehicle 3 to the rear wheel single driving state (RWD), and the torque control unit 42 makes the rear wheel driving torque Fr of the electric motor 10 equal to the target total driving torque FCar ( Fr = FCar) (step S2). Accordingly, the target total drive torque FCar and the rear wheel drive torque Fr increase as the driver increases the accelerator pedal opening.

  Here, the slip acquisition device 30 detects in real time whether or not an acceleration slip has occurred in the rear wheel Wr (step S3), and if no acceleration slip has occurred, the process proceeds to step S10 to drive the rear wheel alone. Continue running in normal mode with the state (RWD).

  On the other hand, if the slip acquisition device 30 detects the occurrence of acceleration slip of the rear wheel Wr when the vehicle 3 has started in step S3 and time Ts has elapsed, the slip determination flag is set and at the same time the 4WD request flag is set. Stand up (see FIG. 2C). Then, the slip torque acquisition unit 32 acquires the rear wheel drive torque Fr when the acceleration slip of the rear wheel Wr occurs and stores it as the slip torque X (step S4). Thereafter, in order to prevent acceleration slip of the rear wheel Wr, the torque control unit 42 controls the rear wheel drive torque Fr of the electric motor 10 to be less than the slip torque X (Fr <X).

  Next, in order to prevent the occurrence of acceleration slip of the front wheel Wf, the torque control unit 42 controls the target front wheel drive torque Ff of the drive source 20 to be less than the above-described slip torque X (Ff <X) (step S5). A 4WD request is made (step S6), and the driving state of the vehicle 3 is switched to the front and rear wheel driving state (4WD) by the braking / driving state control unit 44 to travel in the slip 4WD mode (step S7). FIG. 2B shows an example in which the target front wheel drive torque Ff is set to be about 0.9 times the slip torque X (Ff≈0.9X). The gain is not particularly limited as long as the gain is set to be less than (Ff = aX, 0 <a <1).

  Here, as shown in FIG. 2B, when the target total drive torque FCar is twice or more the slip torque X (Fcar ≧ 2X), the sum of the rear wheel drive torque Fr and the target front wheel drive torque Ff is Since it is less than twice the slip torque X (Fr + Ff <2X), it becomes less than the target total drive torque FCar (Fr + Ff <FCar). As described above, if the vehicle travels in the slip 4WD mode at the time of starting, it may not be able to sufficiently cope with the torque required by the driver and may give an impression that the feeling of acceleration is dull.

  Therefore, in the present invention, the difference between the rotational speeds of the front wheel Wf and the rear wheel Wr becomes equal to or less than a preset threshold value during execution of the control for suppressing the target front wheel drive torque Ff to be less than the slip torque X (Ff <X). At this time, it is determined that the slip has converged, and the suppression control of the target front wheel drive torque Ff is released. Then, the target front wheel driving torque Ff is gradually increased, and control is performed so that the sum of the rear wheel driving torque Fr and the target front wheel driving torque Ff becomes equal to the target total driving torque FCar (Ff = Fcar−Fr). By controlling in this way, it becomes possible to respond to the driver's acceleration request while suppressing the occurrence of slipping at the start.

  Although not shown, when the target total driving torque Fcar is less than twice the slip torque X (Fcar <2X), the sum of the rear wheel driving torque Fr and the target front wheel driving torque Ff is set as the target total driving torque Fcar. Since they can be made equal (Fr + Ff = FCar), the above-mentioned problem does not occur.

  Further, the vehicle drive device 1 of the present invention can suppress the occurrence of deceleration slip of the front wheels Wf and the rear wheels Wr even when the vehicle 3 is braked. More specifically, when the vehicle 3 is braked, first, the target total braking torque FCar ′ of the vehicle 3 is set based on the depression amount of the brake pedal. The braking / driving state control unit 44 changes the braking state of the vehicle 3 to the rear wheel single braking state (one wheel single braking state), and the torque control unit 42 applies the rear wheel braking (regeneration) torque Fr ′ to the vehicle 3. The target total braking torque FCar 'is controlled to be equal to (Fr' = Fcar '). Next, the slip torque acquisition unit 32 acquires, as the slip torque X ′, the rear wheel braking torque Fr ′ when the deceleration slip (lock) occurs in the rear wheel Wr in the rear wheel single braking state. Then, after the target front wheel braking torque Ff ′ of the drive source 20 is suppressed to be less than the slip torque X ′ by the torque control unit 42 (Ff ′ <X ′), the braking / driving state control unit 44 switches to the front and rear wheel braking state. . By configuring in this way, it is possible to prevent a deceleration slip from occurring on the front wheel Wf when shifting to the front and rear wheel braking state.

(Comparative example)
Next, as a comparative example, when the rear wheel single drive state (RWD) is switched to the front and rear wheel drive state (4WD), the target front wheel drive torque Ff of the drive source 10 is suppressed to less than the slip torque X (Ff <X). A case where the control is not performed will be described with reference to FIG.

  As in the above-described embodiment, when the vehicle 3 is started, the target total drive torque FCar of the vehicle 3 is set based on the accelerator pedal opening, the rear wheel single drive state (RWD) is set, and the rear wheel drive of the electric motor 10 is performed. The torque Fr is controlled to be equal to the target total drive torque FCar (Fr = Fcar). When the occurrence of acceleration slip of the rear wheel Wr is detected, the 4WD request flag is set at the same time as the slip determination flag is set.

  Here, when the target total driving torque FCar is more than twice the slip torque X (Fcar ≧ 2X), the sum of the rear wheel driving torque Fr and the target front wheel driving torque Ff is equal to the target total driving torque Fcar. When the target front wheel drive torque Ff is set to (Ff = FCar−Fr), the target front wheel drive torque Ff becomes larger than the slip torque X (Ff> X), and the front wheel Wf is accelerated as shown in FIG. Slip occurs. When such vehicle start and acceleration control is applied to a road surface having a low road surface friction coefficient such as a snowy road, the start / acceleration performance is extremely inferior as 4WD. From the above, it can be seen that the vehicle drive device 1 of the present invention is very suitable for starting and acceleration on a road surface having a low road surface friction coefficient.

As described above, according to the vehicle drive device 1 of the present embodiment, when the braking / driving state control unit 44 acquires that the slip acquisition device 30 has slipped in the rear wheel single braking / driving state, Since the front / rear wheel braking drive state is switched, it is possible to improve the driving performance and braking performance of the vehicle 3 when a slip occurs.
Further, the torque control unit 42 reduces the target front wheel drive (braking) torque Ff (Ff ′) of the drive source 20 when the rear wheel single braking / driving state is switched from the rear wheel independent braking / driving state to less than the slip torque X (X ′). Therefore, the slip generation of the front wheels Wf driven by the drive source 20 can be suppressed without calculating the road surface friction coefficient.
Further, the slip torque X (X ′) acquired by the slip torque acquiring unit 32 is the rear wheel drive (braking) torque Fr (Fr ′) when the slip occurs in the rear wheel Wr driven by the motor 10. Therefore, it is possible to detect more accurately, and it is possible to more reliably suppress the occurrence of slip of the front wheel Wf in the front and rear wheel braking drive state.

  Further, when the rotational speed difference between the front wheel Wf and the rear wheel Wr becomes equal to or smaller than a predetermined threshold during the execution of the suppression control by the torque control unit 42, the suppression control is released, so the front wheel in the front and rear wheel braking drive state It is possible to increase the total torque of the vehicle 3 by increasing the rear wheel drive (braking) torque Fr (Fr ′) of the drive source 10 while suppressing the occurrence of slip of Wf.

  Further, since the rear wheel Wr is braked and driven by the electric motor 10 and the front wheel Wf is braked and driven by the internal combustion engine 22 of the drive source 20, the output ratio of the electric motor 10 and the internal combustion engine 22 is changed depending on the traveling conditions, and the efficiency is high. Driving is possible.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably.

  The drive source 20 for braking / driving the front wheels Wf is configured by connecting the internal combustion engine 22 and the electric motor 24 in series. However, the drive source 20 may be configured by only the internal combustion engine 22 or only the electric motor 24, and from other prime movers. It is good also as composition which becomes.

  Although the electric motor 10 that brakes and drives the rear wheel Wr is configured by the first and second electric motors 10A and 10B, the electric motor 10 may be configured by only a single electric motor.

  The electric motor 10 may brake / drive the front wheel Wf, and the drive source 20 may brake / drive the rear wheel Wr. In this case, for example, in the low vehicle speed range, EV start and EV acceleration are performed in the front wheel single drive state (FWD), and when the front wheel Wf slips, the target rear wheel drive of the drive source 20 is performed to suppress the slip of the rear wheel Wr. It is possible to switch to the front and rear wheel drive state (4WD) after controlling the torque to be below the slip torque. In such a configuration, when the vehicle is started and accelerated by the front wheel drive (FWD) in the steered state and switched to the front and rear wheel drive state (4WD), the rear wheel Wr is particularly easily slipped and may be in a spin state. Therefore, it is considered to be particularly effective.

DESCRIPTION OF SYMBOLS 1 Vehicle drive device 3 Vehicle 5 Battery 10, 10A, 10B Electric motor 12A, 12B Reducer 20 Drive source 22 Internal combustion engine 24 Electric motor 26 Transmission 30 Slip acquisition device 32 Slip torque acquisition part (slip torque acquisition means)
40 Vehicle control device 42 Torque control unit (torque control means)
44 Braking / driving state control unit (braking / driving state control means)
Fcar Target total driving torque Fcar 'Target total braking torque Fr Rear wheel driving torque Fr' Rear wheel braking torque Ff Target front wheel driving torque Ff 'Target front wheel braking torque Wf Front wheels Wr, RWr, LWr Rear wheels X, X' Slip torque

Claims (3)

An electric motor for braking / driving any one of the front wheels and the rear wheels of the vehicle; a drive source for braking / driving either the front wheels or the rear wheels; and an excess slip which is a predetermined slip or more on the one wheel A slip acquisition device for acquiring that occurred,
A vehicle control device for controlling braking / driving of the wheels by the electric motor and the drive source;
With
The slip acquisition device has slip torque acquisition means for acquiring a slip torque that is a torque of the electric motor when the excess slip occurs,
The vehicle control device includes:
Torque control means for controlling the torque generated by the electric motor and the torque generated by the drive source;
Braking / driving state control means for switching between a one-wheel single braking / driving state in which the total torque of the vehicle is generated only by the electric motor and a front / rear wheel braking / driving state in which the total torque of the vehicle is generated by the electric motor and the driving source. ,
A vehicle drive device comprising:
The braking / driving state control means switches to the front / rear wheel braking / driving state when the slip acquisition device acquires that the excess slip has occurred in the one-wheel single braking / driving state,
The vehicle drive apparatus according to claim 1, wherein the torque control means suppresses and controls the torque of the drive source to be less than the slip torque when the one-wheel single braking / driving state is switched to the front / rear wheel braking / driving state. The torque control means cancels the suppression control when a rotational speed difference between the one wheel and the other wheel becomes a predetermined threshold value or less during execution of the suppression control. Item 2. The vehicle drive device according to Item 1. The vehicle drive device according to claim 1, wherein the drive source is an internal combustion engine.

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