JPH06237509A - Driving force controller of electric vehicle - Google Patents

Abstract

PURPOSE:To make it possible to obtain a proper creep torque automatically in accordance with a steering angle by providing a steering angle sensor detecting the steering angle of a steering wheel and a steering-angle- corresponding torque control means which generates a larger creep torque as the steering angle becomes larger. CONSTITUTION:A torque control of an electric motor 12 is conducted so that a creep torque be generated when prescribed creep control conditions are satisfied. This driving force control device is equipped, in particular, with a steering angle sensor 70 which detects the steering angle of a steering wheel and with a steering-angle-corresponding torque control means, e.g. a computer 54 for a motor control, which conducts the torque control of the electric motor 12 so that a larger creep torque be generated as the steering angle becomes larger. According to this constitution, a vehicle can be made to run on the basis of the creep torque even when the steering angle is large and, for instance, garaging or the like can be executed easily only by an ON-OFF operation of a brake.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving force control device for an electric vehicle, and more particularly to an improvement of the control device for generating creep torque when the accelerator is off.

[0002]

2. Description of the Related Art In an electric vehicle, torque control of an electric motor is generally performed with an accelerator operation amount and a motor rotation speed as parameters. When the accelerator operation amount is zero, the motor torque is also zero. For this reason, there is no creep torque like in an automatic vehicle with a torque converter, and when starting up a slope, you must instantly switch from the brake pedal to the accelerator pedal or use the side brakes. It is not always easy for a person who is accustomed to driving an automatic vehicle, such as having to repeat the accelerator operation and the brake operation. In contrast,
It has been considered to perform torque control of the electric motor so as to generate creep torque when the vehicle speed is substantially zero or when the accelerator is off. The control device described in Japanese Patent Application Laid-Open No. 3-253202 is an example, and the driver can manually adjust the creep torque according to the inclination of the road surface.

[0003]

However, in such a conventional creep torque control, the creep torque is constant regardless of the steering angle of the steering wheel, so that the vehicle speed is reduced due to the change in the running resistance due to the steering wheel operation. And the steering angle of the steering wheel becomes large, for example, when the vehicle is parked, the vehicle may stop. If the creep torque is set to a large value, the vehicle will travel even if the steering angle is large, but if the steering angle is small, the vehicle speed will be unnecessarily high, and the driving operability will be worsened. Even if the driver can manually adjust the creep torque, it is difficult to adjust the torque while operating the steering wheel, and it is virtually impossible to obtain an appropriate creep torque according to the steering angle.

The present invention has been made in view of the above circumstances, and an object thereof is to automatically obtain an appropriate creep torque according to a steering angle.

[0005]

In order to achieve such an object, the creep torque may be controlled according to the steering angle of the steering wheel, and the present invention provides a predetermined value as shown in the claim correspondence diagram of FIG. In a driving force control device for an electric vehicle, which controls torque of an electric motor so as to generate creep torque when a creep control condition is satisfied, (a) a steering angle sensor for detecting a steering angle of a steering wheel; And a steering angle corresponding torque control means for controlling the torque of the electric motor so that a larger creep torque is generated as the steering angle is larger.

[0006]

In such a driving force control device for an electric vehicle, the steering angle sensor detects the steering angle of the steering wheel, and the steering angle corresponding torque control means operates the electric motor of the electric motor in accordance with the steering angle. By performing the torque control, a larger creep torque is generated as the steering angle is larger. As a result, even when the steering angle is large, the vehicle is caused to travel on the basis of the creep torque, and, for example, garage parking can be easily performed only by turning the brake on and off. In addition, since the creep torque is controlled according to the size of the steering angle, the vehicle speed does not increase more than necessary when the steering angle is small. Is reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 2 is a block diagram illustrating a control system of an electric vehicle to which the present invention is applied, and FIG. 3 and FIG.
[Fig. 2] is a cross-sectional view and a skeleton view showing an example of the drive device 10 in detail. The drive device 10 is configured to include an electric motor 12 and a speed reducer 16, and the power output from the output shaft 14 of the electric motor 12 is used as the planetary gear type speed reducer 1.
After being decelerated in 6, the planetary gear type differential 18 is distributed to the left and right drive systems. One power is transmitted to the left drive wheel 26L supported by a suspension device (not shown) via the left first constant velocity joint 20L, the left axle 22L, and the left second constant velocity joint 24L, and the other power is cylindrical. To the suspension device (not shown) through the intermediate shaft 28 penetrating the output shaft 14 of the above and arranged concentrically with the output shaft 14, the right first constant velocity joint 20R, the right axle 22R, and the right second constant velocity joint 24R. It is adapted to be transmitted to the supported right drive wheel 26R. Drive wheels 26L, 26R are 4
It constitutes the front or rear wheels of an electric vehicle consisting of two wheels.

The electric motor 12 includes a cylindrical housing 30 and a first side housing 3 fitted to both ends thereof.
The output shaft 14 is housed in a housing composed of the second side housing 34 and the second side housing 34, and the output shaft 14 is arranged in a posture parallel to the left-right direction of the vehicle. A stator 36 having a coil is fixed to the inner peripheral surface of the cylindrical housing 30, and a rotor 40 is fixed to the output shaft 14 concentrically with the stator 36. Such an electric motor 12
As the motor, various motors such as a permanent magnet type AC motor, an induction motor, a synchronous motor, a DC motor, etc. can be used.

The speed reducer 16 is, as is clear from FIG.
A first sun gear 42 connected to the shaft end of the output shaft 14.
S, a planetary gear 42P that is rotatably supported by the first carrier 42C and meshes with the first sun gear 42S, and a ring gear 42R that meshes with the planetary gear 42P.
The planetary gear device 42, a second sun gear 44S connected to the first carrier 42C, a second planet gear 44P that meshes with the second sun gear 44S, a second fixed ring gear 44R that meshes with the second planet gear 44P, and a second planet gear 44R. The second planetary gear 44P is rotatably supported to support the first ring gear 42.
And a second planetary gear set 44 consisting of a second carrier 44C connected to R. As a result, the speed reducer 16
Reduces the rotation input from the electric motor 12 to the first sun gear 42S according to a predetermined reduction ratio, and from the second carrier 44C to the third stage of the planetary gear type differential device 18 of the subsequent stage.
Output to ring gear 46R.

The differential device 18 is a double pinion type planetary gear device, and includes a third sun gear 46S connected to the right end of the left first constant velocity joint 20L and the second carrier 4.
4C, a third ring gear 46R, a third sun gear 46S, and a third ring gear 46R, and a plurality of pairs of third planetary gears 46P and 46P that mesh with one and the other of the third ring gear 46R, and that mesh with each other.
The third carrier 46C is rotatably supported and connected to the left end of the intermediate shaft 28. As a result, the differential device 18 distributes the power input to the third ring gear 46R and is operatively connected to the third sun gear 46S operatively connected to the left drive wheel 26L and the right drive wheel 26R. To the third carrier 46C.

Returning to FIG. 2, the electric motor 12 is rotationally driven in both forward and reverse directions by supplying drive power from a power source 50 such as a battery via a motor drive control circuit 52. The motor drive control circuit 52 is an inverter or the like, and controls the torque of the electric motor 12 by changing the frequency and current of the drive power according to a command signal ST supplied from the motor control computer 54, and at the same time, controls the electric motor 12 Controls the regenerative braking torque that accumulates in the power supply 50 the electric power generated by the forced rotation. The motor control computer 54 includes a CPU 56,
A RAM 58, a ROM 60, a clock signal source 62 such as a crystal oscillator, an A / D converter (not shown), an input / output interface circuit, and the like are provided, and the temporary storage function of the RAM 58 is used while a signal is stored according to a program previously stored in the ROM 60. The electric motor 12 is processed by outputting the command signal ST to the motor drive control circuit 52.
Output torque and regenerative braking torque are controlled.

In the motor control computer 54,
Accelerator operation amount sensor 64, Motor rotation speed sensor 6
6, shift position sensor 68, steering angle sensor 70,
An inclination angle sensor 72, a mode selection switch 74, etc. are connected, and an accelerator operation amount signal SAc indicating the operation amount Ac of the accelerator pedal, a motor rotation speed signal SNm indicating the rotation speed Nm of the electric motor 12, and an operation range of the shift lever. The shift position signal SSh, the steering angle signal Sφ indicating the steering angle φ of the steering wheel, the inclination angle signal Sθ indicating the inclination of the road surface, that is, the inclination angle θ in the front-rear direction of the vehicle, and the mode signal SM indicating whether or not the garage entry mode is selected. Are supplied respectively. The shift lever is arranged in the vicinity of the driver's seat and has a D (drive) range for moving the vehicle forward, an R (reverse) range for moving the vehicle backward, a P (parking) range for parking, and an N allowing free rotation of the electric motor 12.
(Neutral) Range is selected. The steering angle sensor 70 is configured by a rotary encoder or the like that detects the rotation amount of the steering shaft, and detects the rotation amount from the original position where the steered wheels are oriented in the front-rear direction of the vehicle as the steering angle φ. Further, the mode selection switch 74 is a push button type switch provided in the vicinity of the driver's seat, for example, on the shift lever or the like, and is pushed in to select the garage entry mode to turn on / off the mode signal SM. Can be switched.

Next, the motor control computer 54 is used.
Driving force control by means of will be described with reference to the flowchart of FIG. The flowchart of FIG. 5 is repeatedly executed at a predetermined cycle time of, for example, several tens of msec.

First, in step S1, it is determined whether the shift lever is operated to the D range or the R range based on the shift position signal SSh. If the shift lever is in the D range or the R range, the vehicle speed V is determined in step S2. Is determined to be equal to or lower than a predetermined determination vehicle speed V1. Vehicle speed V
Is the motor rotation speed N represented by the motor rotation speed signal SNm.
The determination vehicle speed V1 is determined based on m, and a value of, for example, several kilometers per hour is set. Also, in step S3,
Based on the accelerator operation amount Ac represented by the accelerator operation amount signal SAc, for example, it is determined whether or not the accelerator operation amount Ac is about several% or less in the accelerator off state, and if both determinations in steps S2 and S3 are YES, step If S4 and subsequent steps are executed, otherwise, the normal torque control of step S13 is performed. In this normal torque control, basically, a torque control value Ta is calculated based on the accelerator operation amount Ac and the motor rotation speed Nm according to a data map as shown in FIG. 6, and the torque control value Ta is set to the target torque To. By outputting the command signal ST as, the torque of the electric motor 12 is controlled to match the target torque To, that is, the torque control value Ta. In addition, when a predetermined braking condition is satisfied, a command signal ST for generating a regenerative braking torque is output to generate a braking torque similar to the engine brake in an automobile having an internal combustion engine, and the magnitude thereof is controlled. , Electric power corresponding to the braking torque is stored in the power source 50.

In step S4, which is executed when the determinations in steps S2 and S3 are both YES, it is determined whether or not the garage entry mode is selected by the mode signal SM, and if the garage entry mode is selected. Step S5 and subsequent steps are executed, but if the garage entry mode is not selected, the normal creep control of Step S12 is executed. This normal creep control is performed by the motor rotation speed Nm according to the data map as shown in FIG. 7, for example.
The torque of the electric motor 12 is calculated based on the torque control value Tb and the torque control value Tb is used as the target torque To to output the command signal ST.
That is, control is performed so as to match the torque control value Tb.
In this case, in this embodiment, one of three types of maps MA, MB, MC is selected according to the inclination angle θ represented by the inclination angle signal Sθ, and a flat road having a relatively small inclination angle θ is selected. For downhill slope, torque control according to map MA,
The torque control is performed according to the map MB when the climbing gradient is moderate and the torque is controlled according to the map MC when the climbing gradient is large. As a result, an appropriate creep torque that prevents the vehicle from sliding down is generated regardless of the slope of the road surface. Note that the negative torque control value Tb in FIG. 7 means the regenerative braking torque that suppresses the rotation of the electric motor 12. Further, when the shift lever is operated to the R range, the torque control value Tb = 0 and the creep control is not performed.

On the other hand, in step S5 executed when the garage entry mode is selected, the steering angle φ and the vehicle speed V are detected by reading the steering angle signal Sφ and the motor rotation speed signal SNm, and in the next step S6, The torque control value Tc is calculated from a data map stored in advance in the ROM 60 or the like using the steering angle φ and the vehicle speed V as parameters. In this data map, for example, as shown in FIG. 8, the torque control value Tc increases as the steering angle φ increases and the vehicle speed V decreases, and even if the steering angle φ is large and the running resistance of the vehicle is large, the vehicle is flat It is determined in advance by experiments, simulations, arithmetic expressions, etc. so that the vehicle can run. Also,
This torque control value Tc is positive when the operation range of the shift lever is the D range, but is set to a negative value with the same magnitude when it is the R range. Instead of the vehicle speed V, the data map of FIG. 8 may be set using the motor rotation speed Nm as a parameter.

In the next step S7, the torque control value Tc obtained in step S6 is a value obtained by subtracting a predetermined constant value α1 from the current target torque To (To-α1).
If it is smaller than Tc <(To−α1), a constant value α1 is subtracted from the target torque To in step S8 to obtain a new target torque To, and a command signal representing the target torque To. By outputting ST, the torque of the electric motor 12 is reduced by a constant value α1. The constant value α1 is a torque reduction width of the electric motor 12 that can be changed while preventing a shock. This prevents a sudden change in torque, and the motor torque is torque controlled by repeatedly executing the steps. The value can be smoothly approximated to Tc.

When Tc ≧ (To-α1), step S9 is executed after step S7, and the torque control value Tc
Is greater than a value (To + α2) obtained by adding a predetermined constant value α2 to the current target torque To. If (To + α2) <Tc, a constant value α2 is added to the target torque To in step S10 to obtain a new target torque To, and a command signal ST representing the target torque To is output to drive the motor. The torque of the motor 12 is increased by a constant value α2. The constant value α2 can change the electric motor 1 while preventing shock.
With the torque increase width of 2, a rapid change in torque is prevented, and the motor torque is smoothly approached to the torque control value Tc by repeatedly executing such steps. This constant value α2 may be the same value as the constant value α1. Also, (To−α1) ≦ Tc ≦ (To + α
In the case of 2), that is, when the determinations in steps S7 and S9 are both NO, step S11 is executed, the torque control value Tc is set as the target torque To, and the command signal ST representing the target torque To is output. , Electric motor 1
The torque of 2 is controlled to be the torque control value Tc.
Note that steps S7 to S10 may be omitted and step S11 may be directly executed following step S6.

In the electric vehicle of this embodiment, the steering angle φ and the vehicle speed V are detected in step S5, and the steering angle φ and the vehicle speed V are used as parameters in step S6 according to the data map of FIG. The torque control value Tc is obtained, and the torque control of the electric motor 12 is performed according to the torque control value Tc in step S11, so that a larger creep torque is generated as the steering angle φ increases. As a result, even if the steering angle φ is large, the vehicle is caused to travel based on the creep torque, and, for example, garage parking can be easily performed only by turning the brake on and off. Further, since the creep torque is controlled according to the magnitude of the steering angle φ, the vehicle speed V will not be unnecessarily increased when the steering angle φ is small. The change in vehicle speed is reduced.

Further, in this embodiment, even if the steering angle φ is large, as the vehicle speed V increases, the torque control value Tc approaches the value when the steering angle φ = 0, and the creep torque is reduced, so that the torque control value Tc becomes excessive. The increase in vehicle speed is suppressed, and the driving operation when entering the garage becomes easier. Further, in the present embodiment, the creep torque control that reflects the steering angle φ is performed only when the garage entry mode is selected by the mode selection switch 74, so that, for example, normal creep torque control is performed. The vehicle speed V does not decrease against the driver's intention that the vehicle speed V decreases when the steering angle φ increases, and high safety can be obtained.

In the present embodiment, steps S5 to S1 of the series of signal processing by the motor control computer 54.
The part that executes each step of 1 corresponds to the steering angle-corresponding torque control means, and the fact that the determinations in steps S2, S3, and S4 are all YES means that the creep torque control corresponding to the steering angle φ is executed. It is a control condition.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be implemented in other modes.

For example, in the above embodiment, the shift lever is R
Even when the range is operated, the creep torque in the backward direction of the vehicle is generated in the garage entry mode, but it is not always necessary to perform the creep control when the range is operated. .

In the above embodiment, the creep torque control corresponding to the steering angle φ is performed when the three conditions of V ≦ V1, accelerator off, and garage entry mode selection are satisfied. The control condition may be changed as appropriate, and for example, the creep control may be started when the brake is turned off from the vehicle stopped state where the brake is turned on. It is also possible to separately set the start condition and the release condition of the creep control.

Further, in the above-described embodiment, the normal creep torque control is performed in step S12, but the content of this torque control can be changed appropriately and can be omitted. In the normal creep torque control as in step S12, the torque control value T is set according to the steering angle φ.
It is also possible to correct b and obtain the torque control value Tb using the steering angle φ as a parameter so that a larger creep torque is generated as the steering angle φ increases.

In the above embodiment, the torque control value Tc is obtained using the steering angle φ and the vehicle speed V as parameters, but the torque control value Tc is obtained using only the steering angle φ as a parameter.
c may be obtained, or the inclination angle θ, etc. may be set so that the vehicle moves at a slow speed regardless of the inclination angle θ and the vehicle weight.
Other operating conditions such as vehicle weight may be added to the torque control parameters. When the vehicle travels by its own weight with the inclination angle θ being a negative downward slope, the creep torque may be set to zero or the regenerative braking torque may be applied.
The vehicle weight can be detected from the amount of flexural displacement of the suspension device.

Instead of using the data map, the torque control value Tc may be obtained by using fuzzy inference using the steering angle φ, the vehicle speed V and the like as parameters, arithmetic expressions and the like. Even during normal torque control or creep control, the torque control values Ta, Tb are calculated by fuzzy reasoning or arithmetic expressions.
It is possible to ask for.

In the data map of FIG. 8, the torque control value Tc remains positive even if the vehicle speed V increases, but FIG.
Vehicle speed V as in the normal creep torque data map
Is excessively large, the torque control value Tc = 0 or the regenerative braking torque may be applied.

In the above embodiment, the electric vehicle having the electric motor 12, the speed reducer 16, and the differential device 18 coaxially arranged between the pair of drive wheels 26L and 26R has been described. The configuration of the drive device can be appropriately changed, such as a multi-shaft reducer or a bevel gear type differential device, a device without a reducer, or a transmission that can change the reduction ratio.

Although not illustrated one by one, the present invention can be carried out in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is a block diagram illustrating a control system of an electric vehicle including a driving force control device that is an embodiment of the present invention.

3 is a cross-sectional view showing a drive device of the electric vehicle of FIG.

FIG. 4 is a skeleton diagram illustrating a power transmission path of the drive device in FIG.

5 is a flowchart illustrating driving force control of the electric vehicle of FIG.

6 is an example of a data map used in step S13 of FIG.

FIG. 7 is an example of a data map used in step S12 of FIG.

8 is an example of a data map used in step S6 of FIG.

[Explanation of symbols]

 12: electric motor 54: motor control computer 70: steering angle sensor φ: steering angle Steps S5 to S11: steering angle corresponding torque control means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiji Ichioka 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Koujiro Kuramochi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd.

Claims (1)

[Claims] 1. A steering angle sensor for detecting a steering angle of a steering wheel, in a driving force control device for an electric vehicle for controlling a torque of an electric motor so as to generate a creep torque when a predetermined creep control condition is satisfied, A driving force control device for an electric vehicle, comprising: a steering angle corresponding torque control means for controlling the torque of the electric motor so that a larger creep torque is generated as the steering angle is larger.