JPH04146819A - Drive force controller - Google Patents

Abstract

PURPOSE:To prevent idle running of tires in turning and improve the running limit, response of steering, and driving stability by predicting the load on each wheel according to the cross acceleration predicted and positively controlling the drive force rate of a right wheels and left wheels. CONSTITUTION:A four wheel drive car is not provided with a differential gear, and the right and left front wheels FL and FR and right and left rear wheels RL and RR are directly connected to an engine E through clutches 10 to 13 respectively. An electronic controller 40 controls a hydraulic controller 20 while monitoring the drive signals from the drive force sensors 41 to 44 of respective wheel to adjust the pressure of working oil of the clutches 10 to 13 and feeds back the drive force of each wheel and controls it to an objective drive force. In this case, the cross acceleration generated in the car is predicted based on the steering angle detected by a steering angle detector 55 and the car speed detected by the car speed sensors 41 to 44. In addition, the load acted on each wheel is predicted according to the cross acceleration. Each of the transmission force of clutches 10 to 13 is controlled according to the predicted load of each wheel is controlled.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention provides a drive shaft that transmits driving force (driving torque) to the left and right wheels of the front and rear wheels. The present invention relates to a driving force control device equipped with a clutch device.

(Conventional technology) In order to improve the driving performance of automobiles and the ability to drive on rough roads,
Conventionally, four-wheel drive vehicles are known. In a conventional four-wheel drive vehicle, for example, as shown in FIG. CL2 distributes torque between the front and rear wheels. And clutch CLI,
The driving force from CL2 to the front and rear wheels is provided by differential gear DI.
, D2 to the left and right wheels, and these differential gears DI and D2 absorb the rotational speed difference between the left and right wheels.

This conventional four-wheel drive vehicle determines the distribution of driving force between the front and rear wheels according to the rotational speed difference between the front and rear wheels, yaw rate, lateral acceleration, etc., in an attempt to achieve dynamic performance that suits various driving conditions. There is.

(Problems to be Solved by the Invention) However, in conventional four-wheel drive vehicles, the achievable driving range is not sufficiently expanded by distributing the driving force between the front and rear wheels alone. In particular, the steering response and handling stability during turns were not satisfactory.

The present invention was made to solve these problems, and in particular, actively controls the drive force ratio of the left and right wheels to an optimal value to improve steering response and steering stability. The purpose of the present invention is to provide a driving force control device.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides a clutch device installed on each drive shaft that transmits driving force to left and right wheels, and a steering angle of a steering device. a steering angle sensor that detects the vehicle speed; a vehicle speed sensor that detects the vehicle speed; and a vehicle speed sensor that predicts the lateral acceleration that will occur in the vehicle based on the steering angle that the steering angle sensor detects and the vehicle speed that the vehicle speed sensor detects. and control means for predicting the load on each wheel according to the amount of load on each wheel predicted in this way, and controlling the transmission driving force of each of the clutch devices respectively according to the predicted load amount on each wheel. A control device is provided.

Preferably, the control means is capable of directly controlling the transmission driving force of each of the clutch devices according to the predicted load of each wheel, and also includes a torque sensor for detecting the driving force of each wheel, and The driving force ratio of the left and right wheels is calculated according to the predicted load on each wheel, and the driving force transmitted by each clutch device is adjusted so that each driving force detected by the torque sensor matches the calculated driving force ratio. It is also possible to control the feed rate.

Furthermore, the drive shaft of each wheel includes a brake device, and the control means controls the braking force of each brake device according to the predicted load on each wheel, thereby improving vehicle motion performance during deceleration. can be further improved.

(Function) The clutch device installed on each drive shaft that transmits the driving force to the left and right wheels can arbitrarily control the ratio of the driving force transmitted to the left and right wheels by connecting/disconnecting it or controlling the amount of slip. can be controlled. Then, the control means predicts the load amount of each wheel according to the lateral acceleration calculated based on the steering angle and the vehicle speed, and transmits the driving force of each clutch device according to the predicted load amount of each wheel. By controlling this, the driving force ratio between the left and right wheels is controlled to an optimum value.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows an example of a four-wheel independent drive vehicle as a first embodiment of the present invention. The vehicle of this first embodiment is not equipped with a differential device, and only the left and right front wheels FL.

FR and left and right rear wheels RL and RR are each clutch 1.
It is connected to engine E via 0-13.

More specifically, the driving force of the engine E is transmitted back and forth through a gear 15 fixed to the engine output shaft, a gear 16a meshing with this gear 15 and fixed to the propeller shaft 16, and the propeller shaft 16. Axle shaft 18.
19.

The axle shaft 18 on the front wheel side is provided with a clutch 10 on the left wheel FL side and a clutch 11 on the right wheel FR side.
Engine E transmitted to the axle shaft 18 on the front wheel side
The driving force from is passed through these clutches 10 and 11,
The driving force is distributed to each wheel FL according to the transmission drive force ratio of the left and right wheels determined by the engagement/disengagement state or slip state of each clutch.

It is transmitted to FR. The transmission torque of each front wheel FL, FR is determined by driving force sensors 41, 42 attached to each wheel.
This detected value is detected by the electronic control unit (ECU)
40. Note that various types of driving force sensors can be used, and for example, a strain gauge type or a magnetostrictive type may be used.

Similarly, the axle shaft 19 on the rear wheel side is provided with a clutch 12 on the left wheel RL side and a clutch 13 on the right wheel RR side, and the driving force from the engine E transmitted to the axle shaft 19 on the rear wheel side is as follows. Through these clutches 12 and 13, each wheel RL, R
transmitted to R. The transmission torque of each of the rear wheels RL and RR is detected by driving force sensors 43 and 44 attached to each wheel, and this detected value is supplied to the electronic control unit 40.

In addition, by controlling the rotation speed ratio by connecting/disconnecting or slipping each clutch 10 to 13, the left and right wheels or the four
It is also possible to control the drive force ratio of the wheels. The rotational speed of each wheel is detected by wheel speed sensors 46 to 49 attached to each wheel, and the detected values are supplied to the electronic control device 40.

The clutches 10 to 13 described above may be electromagnetic ones or electromagnetic powder clutches, but in this embodiment, wet multi-disc hydraulic clutches are applied, and these clutches are controlled by the hydraulic control device 20.
The drive torque is transmitted through frictional engagement using high-pressure oil pressure supplied from the engine. The hydraulic control device 20 includes a hydraulic pump that generates hydraulic pressure by driving the engine E, a control valve that controls supply and discharge of working hydraulic pressure to each clutch based on a control signal from the electronic control device 40, and the like, although none of them are shown. It is equipped with

In addition to the above-mentioned sensors, the electronic control device 40 includes various sensors, such as a torque sensor that detects the driving force of the engine E, a yaw rate sensor 51 that detects the yaw rate generated in the vehicle body, and a longitudinal G sensor that also detects the longitudinal acceleration. 5
2. A lateral G sensor 53 that detects lateral acceleration, a steering angle sensor 55 that detects the steering angle, a brake sensor 56 that detects the depression of the brake, and the valve opening of the throttle valve disposed in the intake passage of the engine E. An accelerator opening sensor 57 and the like for detecting this are connected, and detection signals from these sensors are supplied to the electronic control unit 4°.

The electronic control device 40 is a central processing unit (CPU) that executes a driving force control program and calculates the amount of clutch operation, etc.
, a storage device (ROM) that stores the aforementioned control program, various constant values, calculation results, etc.

RAM, etc.), input/output devices (I10 interface) that input detected values from the various sensors mentioned above, perform input processing such as filtering, signal amplification, A/D conversion, etc., and output control signals based on calculation results. It consists of

Next, a lateral acceleration estimation control procedure executed by the electronic control device 40 will be described with reference to FIGS. 2A and 2B. Note that the electronic control device 40 constantly monitors the input signal of the steering angle sensor 55, and when the absolute value of the steering angle exceeds a predetermined value, starts executing the lateral acceleration prospective control shown in FIGS. 2A and 2B. and repeats this routine until control is complete.

When this lateral acceleration prospective control is executed, first, the electronic control unit 40 reads each wheel speed signal from the wheel speed sensors 46 to 49 (step 5IO), calculates the vehicle speed vW by averaging these values ( Step 512). Next, the steering angle signal is read from the steering angle sensor 55 (step 514), and from the vehicle speed Vw and steering angle δS obtained as described above, the lateral acceleration Gy generated in the vehicle body is predicted based on the following formula (AI). Calculate (step 516).

Gy=-KI X (δs x Vw”) /L...
(AI) Here, L is the wheel base and K is a constant.

Next, the load movement amount Δwy of the left and right wheels is predicted and calculated from the lateral acceleration Gy calculated as described above using the following equation (A2) (step 518).

ΔWy = Kt x (MxH/d) x Gy -----
-.(A2) Here, d is the tread, M is the vehicle weight, H is the height of the center of gravity, and K is a constant.

Then, it is determined whether the engine E is in a driving state or a braking state based on the positive or negative value of the driving torque T8 of the engine E detected by the torque sensor 50, and each A driving force distribution ratio α proportional to the wheel load is calculated (step 520).

When the calculation of the driving force distribution ratio α is completed, the electronic control device 40
reads the longitudinal acceleration signal from the longitudinal G sensor 52 (
Step 522) From this longitudinal acceleration, calculate the longitudinal load shift amount to calculate the driving force distribution ratio β between the front and rear wheels.Step 524) From this distribution ratio β, the driving force Ty, T of the front and rear wheels is calculated.
m and target driving force for each front and rear left and right wheels TFLI TFL
TRLI TRI is calculated using the following equations (A3) to (A8), respectively (step 826).

Tr"β×TE ・・・・・・(A
3) Tm=(+-β)XTE...
(A4) TFL=α×T, ・・
...(A5) Tri=(1-α) X TF
--(A6)TRL=αXT,
・・・・・・(A7)T□=(1-α
)x"ri... (A8) The electronic control unit 40 monitors the driving force signals from the driving force sensors 41 to 44 of each wheel based on the target driving force of each wheel calculated in this way. At the same time, a control signal is output to the hydraulic control device 20 to adjust the working oil pressure of each clutch 10 to 13, and the driving force of each wheel is feedback-controlled to the target driving force (step 828).

There are various feedback control methods, and there are no particular limitations on which method to adopt.

In the above embodiment, when the steering angle exceeds a predetermined value range, the lateral acceleration prospective control shown in FIGS. 2A and 2B is started, but the starting conditions for this lateral acceleration prospective control are as follows: The determination may be made based on the angle and vehicle speed.

Figure 3 shows a map that defines the straight-ahead region of the vehicle, in other words, the region in which the above-mentioned lateral acceleration predictive control is not executed, based on the steering angle and vehicle speed, and the vehicle is traveling in the shaded region in the figure. It is determined that the vehicle is traveling straight,
When the vehicle deviates from this shaded area, lateral acceleration predictive control is started.

In the embodiment shown in FIGS. 2A and 2B, a target driving force for each wheel is determined from the calculated load movement amount, and each clutch 10 to 13 is adjusted so that the driving force for each wheel matches this target driving force.
Although the engagement force or the amount of slip is feedback-controlled, each step in FIG. 2B is replaced with the step shown in FIG. 4, and the oil pressure command value of the left and right wheel clutches is directly calculated from the amount of load movement. Each oil pressure may be directly controlled based on the command value (step 522a). That is, in step 522a, each valve command value of the hydraulic control device 20 is subjected to open loop control.

Although such control may be somewhat inferior in control accuracy to the control method shown in FIGS. 2A and 2B, the driving force sensor for each wheel is not required, and the configuration can be simplified.

Furthermore, the driving force ratio of the left and right wheels (step 520 in Fig. 2B)
The valve command value (step 520a in FIG. 4) may be read out as a map value from the above-mentioned storage device according to the calculated lateral acceleration and load movement amount.

As shown in FIG. 5, the present invention provides a brake device 2 for each wheel.
2 to 25 are configured to be individually controllable, and in addition to controlling the driving force of each wheel in the lateral acceleration predictive control described above, the braking force ratio of each wheel during braking is set according to the predicted load of each wheel. , the hydraulic pressure of each brake device may be controlled according to the set braking force ratio. With this configuration, the responsiveness of the steering during deceleration is further improved, the driving limit is improved, and the vehicle driving performance is significantly improved. Although the electronic control device 40 and sensors are omitted in FIG. 5, the corresponding components in FIG. 1 are given the same reference numerals, and the driving force control method and braking force control method are Since it can be easily deduced from the description of the above-mentioned embodiment, detailed description thereof will be omitted.

FIG. 6 shows a configuration in which a center differential 28 is interposed on the propeller shaft 16 of the four-wheel drive vehicle shown in FIG.
In this case, the distribution of driving force to the front and rear wheels is determined by the center differential 28.
There is no need to use clutch devices for the front and rear wheels. In the four-wheel independent drive group shown in Figure 1,
In order to achieve optimal torque distribution while absorbing the differential during turning, that is, the difference in rotational speed between each wheel, it is necessary to directly connect one wheel and control the remaining wheels by slipping, which may complicate control. However, by interposing the center differential 28, there is no need to consider the distribution of driving force between the front and rear wheels by the electronic control unit 40, and there is an advantage that control of the driving force distribution becomes easier. In this case, center differential 28
It is also effective to provide a differential limiting device such as a so-called viscous coupling (VCU) and to apply differential limiting using this differential limiting device.

FIG. 7 shows another embodiment of the present invention, in which a clutch device 10.11 is installed only on the front wheel side, and the rear wheel side is connected to the engine E via a differential device 30 and an operation limiting device 32. The configuration is as follows. More specifically, the driving force of the engine E is transmitted from the rear wheels from the propeller shaft 16 to the left and right axle shafts 19a, 19 via the actuating device 30.
b, and drives each wheel RL and RR. The operation limiting device 32 is interposed between the left and right axle shafts 19a and iQb, and its operation is electronically controlled.

In a four-wheel independent drive vehicle configured as shown in Figure 1, even in normal driving where there is no need to independently control the driving force of each wheel, if the steering angle is exceeded a predetermined value, the clutch Operation control of the device is started, and clutch engagement/disengagement and slip amount control must be performed.

On the other hand, in the configuration shown in FIG. 7, during normal driving, the front wheel side clutches 10, 11 and the differential limiting device 32 are turned off, and the vehicle runs only with rear wheel drive. In addition to performing the driving force distribution control of .11 (for example, the aforementioned lateral acceleration prospective control), differential limiting control can be performed by operating the differential limiting device 32 on the rear wheel side. That is, in the case of the configuration shown in FIG. 7, since the differential device 30 is provided on the rear wheel side, it is not necessarily necessary to perform drive force distribution control using a clutch even during steering.

Note that various known devices can be used as the differential limiting device 32 shown in FIG. 7. Furthermore, there is no particular limitation on which of the front and rear wheels the clutch device is installed on, and the clutch device is installed on the axle shaft on the rear wheel side, and the differential device and differential limiting device are installed on the front wheel side. may be arranged.

FIG. 8 shows the characteristics calculated by simulation for a conventional 4-wheel drive vehicle with a center differential (C/D) and a 4-wheel independent drive vehicle of the present invention. This is a comparison of changes in actual steering angle over time when deceleration is performed. In addition,
As shown in Figure 9, the calculation conditions are as follows: approach distance La is 15 m, initial speed is 30 km/h, acceleration (Gx
) was 0.2G, deceleration was -1.5G, road surface μ was 1.0, and calculations were performed assuming that the area between points X and Y in FIG. 9 was in an acceleration state and the area after point Y was in a deceleration state.

Conventional four-wheel drive vehicles with center differentials tend to understeer (US) when accelerating, and oversteer (US) when decelerating.
O8) Since this characteristic has a strong tendency, it is necessary to turn the steering wheel back significantly when decelerating. On the other hand, in the case of the lateral acceleration predictive control of the present invention, it is not affected by acceleration/deceleration ((
, has characteristics close to neutral steering (NS).

In the case of lateral acceleration prospective control, the steering operation directly distributes the torque between the left and right wheels and generates a yaw moment, so it is thought that the corrective steering works effectively and the amount of steering operation is small.

In the above simulation results, the front and rear torque distribution ratios were obtained as proportional to the load, but the front and rear torque distribution ratios were changed to 5.
Even if it is fixed at 0:50, there is almost no effect. That is,
When turning, the influence of front-rear torque distribution is originally smaller than that of left-right torque distribution, and the load shift 4 degrees forward is smaller than the left-right load shift, and changes in the distribution ratio due to acceleration and deceleration are small. This is probably due to the small size. As is clear from this result, the left and right torque distribution of the vehicle equipped with the driving force control device of the present invention is better than the control of front and rear torque distribution in a conventional four-wheel drive vehicle having a center differential (C/D). This shows that control is more effective.

(Effects of the Invention) As detailed above, according to the driving force control device of the present invention, the load on each wheel is predicted according to the predicted lateral acceleration, and the load on each wheel is predicted according to the predicted lateral acceleration. Since the system actively controls the drive force ratio between the left and right wheels, it prevents the tires from spinning when turning, improving the driving limit, improving steering response, and improving handling stability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of a driving force control device of the present invention, and FIGS. 2A and 2B show a control procedure of lateral acceleration prospective control executed by the electronic control device 40 of FIG. 1. The flowchart, FIG. 3 is a graph showing the straight-ahead region of the vehicle divided by steering angle and vehicle speed, and FIG. 4 shows a modification of FIG. 2B, in which the clutch device is directly operated according to the predicted load movement FIG. 5 is a flowchart showing a control procedure for controlling, and FIG. 6
FIG. 7 is a block diagram showing a modification of the driving force control device according to the present invention, in which the driving force is distributed between the front and rear wheels by a center differential, and FIG. FIG. 8 is a block diagram showing a modification of the driving force control device according to the present invention, which controls the driving force distribution between the left and right wheels of the
Comparing the driving performance of a conventional four-wheel drive vehicle with a center differential and a four-wheel independent drive vehicle of the present invention, it shows 180° turning behavior,
The graph of the change in actual steering angle over time, Figure 9, is shown at 180 in Figure 8.
A graph showing the turning course, Figure 10, shows the conventional 4
FIG. 1 is a block diagram showing the configuration of a wheel drive vehicle. 11-13...Clutch, 18...Front wheel side axle shaft, 19...Rear wheel side axle shaft, 20.
... Hydraulic control device, 28-25 ... Brake device, 2
8゜30...Differential device, 32...Differential limiting device, 4
0...Electronic control unit (ECU), 41-44...
Wheel speed sensor, 47-49... Driving force sensor, 50.
... Torque sensor, 51 ... Yaw rate sensor, 52
...Front and rear G sensor, 53...Lateral G sensor, 55...
・Steering angle sensor. Applicant Mitsubishi Motors Corporation Agent Patent Attorney Kanji Nagado

Claims (4)

[Claims] (1) A clutch device installed on each drive shaft that transmits driving force to the left and right wheels, a steering angle sensor that detects the steering angle of the steering device, a vehicle speed sensor that detects vehicle speed, and a steering angle sensor The lateral acceleration generated in the vehicle is predicted based on the detected steering angle and the vehicle speed detected by the vehicle speed sensor, and the load on each wheel is predicted according to the predicted lateral acceleration. A driving force control device comprising: control means for controlling the transmission driving force of each of the clutch devices according to the amount. (2) A torque sensor is installed on each wheel to detect the driving force,
The control means calculates a driving force ratio between the left and right wheels according to the predicted load on each wheel, and controls each clutch so that each driving force detected by the torque sensor matches the calculated driving force ratio. 2. The driving force control device according to claim 1, wherein the driving force control device performs feedback control of the transmitted driving force of the device. (3) The driving force control device according to claim 1, wherein the control means directly controls the transmission driving force of each of the clutch devices according to the predicted load of each wheel. (4) A brake device is included in the drive shaft of each of the wheels, and the control means controls the braking force of each of the brake devices according to the predicted load on each wheel. 3. The driving force control device according to any one of 3.