JP2692456B2 - Vehicle drive force control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle driving force control device capable of achieving both acceleration performance and turning performance of a vehicle.

[0002]

2. Description of the Related Art When a drive slip occurs on a drive wheel,
A conventional example of a vehicle drive control device for performing a so-called traction control, which variably controls the drive force supplied to the drive wheels according to the drive slip amount, is disclosed in, for example, Japanese Patent Laid-Open No. 61-16136. There is something. In this conventional example, the vehicle speed, the throttle opening, and the steering angle of the steering wheel (front wheel steering angle), which represent the driving state of the vehicle, are used.
Is used as a parameter to variably control the engine driving force to eliminate the driving slip. At that time, the larger the steering angle, the larger the engine driving force reduction amount (hereinafter referred to as the torque reduction amount) becomes. We are in control.

[0003]

In the above-mentioned conventional example, in the front-wheel drive vehicle, the larger the steering angle, the greater the amount of reduction in the driving force, so that the turning performance is more important than the acceleration performance of the vehicle. . However, even if the torque reduction amount is simply increased by the above control, the tire lateral force Q can be maximized as shown in FIG. 6 (a), but in that case, the vehicle lateral force M is the maximum (friction). This is not a vector that touches the circle), and the turning performance will deteriorate. Further, the component F of the tire lateral force Q in the direction of decelerating the vehicle also becomes large, which causes a feeling of deceleration of the vehicle.

An object of the present invention is to solve the above-mentioned problems by variably controlling a target slip state used for drive torque variable control according to the steering amount of the front wheels.

[0005]

To this end, the vehicle driving force control apparatus of the present invention has a steering amount detecting means for detecting a steering amount of a front wheel and a drive wheel driving device as shown in the concept of FIG. In a vehicle that drives at least the front wheels, the drive slip state includes a slip detection unit that detects a slip state and a drive torque control unit that variably controls the drive torque to achieve a target slip state based on the detected drive slip state. In order to maximize the lateral force of the vehicle by the resultant force of the tire lateral force and the tire driving force corresponding to, the target slip setting means is set to be larger as the steering amount is larger. At that time, for example, the target slip state is set in a region below the drive slip state where the tire driving force is maximum. To.

[0006]

According to the present invention, in the first configuration, the driving torque control means sets the target slip on the basis of the driving slip state (for example, the slip ratio) detected by the slip detection means while the vehicle driving the front wheels is running. When the variable control of the drive torque is performed so as to achieve the state, the target slip setting means, based on the steering amount of the front wheel detected by the steering amount detecting means, is set by the target slip setting means, for example, as shown in FIG. 6 (b). The total force of the tire lateral force Q and the tire driving force P corresponding to the state (slip ratio S) is the maximum value M _max of the lateral force M of the vehicle.
Therefore, the target slip state is set larger as the steering amount is larger. This makes it possible to optimize the balance between the tire driving force and the tire lateral force to improve the turning performance of the vehicle even when the vehicle is turning while the lateral acceleration of the vehicle exceeds a predetermined value. It is possible to achieve compatibility with.

In the second configuration, the target slip state is set in a region below the drive slip state where the tire driving force is maximized, so that only the region where the idea of the friction circle is valid is set. As the control target area,
The lateral force of the vehicle can be surely maximized.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 shows the first embodiment of the vehicle driving force control device of the present invention.
FIG. 1 is a diagram showing a configuration of an embodiment, in which 1L and 1R are left front wheels, right front wheels, 2L and 2R are left rear wheels, right rear wheels, and 3 is an engine. This vehicle is a front-wheel drive vehicle in which front wheels 1L and 1R that are drive wheels are driven by an engine 3.
Wheel rotation sensors 4, 5, 6, and 7 are provided near L, 1R, 2L, and 2R, respectively (which may be applied to all-wheel drive vehicles). The wheel rotation sensors 4 to 7 detect the number of revolutions of each wheel as a pulse signal having a frequency corresponding to the number of revolutions. The obtained number of revolutions VFL, VFR,
A pulse signal having a frequency corresponding to VRL and VRR is input to the F / V converter 9 of the driving force control unit 8. The driving force control section 8 comprises an F / V converter 9, an A / D converter 10 and a CPU 11, and the F / V converter 9
Converts the input signal from each of the wheel sensors 4 to 7 and inputs the voltage to the A / D converter 10. The A / D converter 10 digitally converts each input signal and inputs the digital signal to the CPU 11.
Note that the CPU 11 uses, for example, a microcomputer.

In this example, a lateral acceleration (lateral G) sensor 14 for detecting the turning state of the vehicle is provided, and the lateral G signal Y _g detected by the lateral G sensor 14 is input to the A / D converter 10 (here, the vehicle. The lateral G sensor is used as a means for detecting the turning state of the vehicle, but a lateral slip angle sensor for detecting the lateral slip angle of the driven wheels 2L, 2R may be used instead. Further, in this example, a steering angle sensor 15 for detecting the front wheel steering angle θ is provided, and the front wheel steering angle signal θ detected by the steering angle sensor 15 is input to the A / D converter 10.

The CPU 11 executes the control programs of FIGS. 3 and 4 on the basis of the input wheel rotation speeds (wheel speeds) VFL, VFR, VRL, VRR, the lateral G value Y _g and the front wheel steering angle θ, The target slip state used when executing the traction control (driving force variable control) is variably controlled according to the front wheel steering angle θ.

That is, in the control program of FIG. 3, which is repeatedly executed by a timed interrupt every predetermined period by an operation system (not shown), first step
At 101, the rotational speeds VFL and VFR of the left and right front wheels, which are the driving wheels
And the rotational speeds VRL and VRR of the left and right rear wheels that are driven wheels
Are read from the corresponding wheel rotation sensors 4 to 7, and in step 102, the average rotation speeds VF and VR of the front wheels and the rear wheels are calculated as VF = (VFL + VFR) / 2, VR = (VRL + VR).
R) / 2, and in step 103, the slip ratio S is calculated by S = (VF-VR) / VF (this step 103 functions as slip detection means). In the next step 104, the steering angle θ of the front wheels, which are the driving wheels, is read from the steering angle sensor 15 (this step 104 functions as a steering amount detecting means). Based on this θ, the target slip ratio S _d , which is the target slip state, is obtained by looking up the map of FIG. 5 in the next step 105 (or by using a predetermined arithmetic expression). Here, the map of FIG. 5 represents the target slip ratio S _d as a function of the front wheel steering angle θ by S _d = f (θ), and this map is set so that S _d increases as θ increases. Has been done. This map is stored in advance in a memory or the like (not shown). After the control program of FIG. 3 is executed, the control program of FIG. 4 for actually performing engine drive torque control (traction control) is continuously executed.

In the control program of FIG. 4, first, in step 111, the slip ratio S in the slip state calculated in step 103 is read, and in step 112, the target slip ratio S _d obtained in step 105 is read. In the next step 113, the slip ratio S and the target slip ratio S _d
And step 114 depending on the result of this comparison.
Control is passed to any of ~ 116. That is, when the slip ratio S at that time is S> S _d , which is higher than the target slip ratio S _d , the control proceeds to step 114 to issue the engine drive torque decrease command, and the slip ratio S at that time is the target. in the case of S = S _d to match the slip rate S _d is complete the control to step 115 performs a status quo command,
If the slip ratio S at that time is less than the target slip ratio S _d and S <S _d , the control advances to step 116 to issue an engine drive torque recovery (increase) command.

In this embodiment, since the method of cutting the fuel supply to each cylinder 13-1 to 13-6 of the engine is used as the traction control, the control advances when a drive slip of S> S _d occurs, for example, step 114. Then, in order to suppress the drive slip, the CPU 11 outputs the fuel supply cut signal FC to the fuel supply control unit 12, and the signal FC supplies the fuel supply control unit 12 with the fuel supply cut signal FC.
The injection pulse I _P output from 12 to each cylinder is cut off to perform fuel cut. At that time, by executing a control program (not shown), the number of cylinders whose fuel supply is cut according to the slip ratio S at that time (for example, 3/6 cylinder cut → 6/6 cylinder cut or 2 / (6 cylinder cut → 4/6 cylinder cut → 6/6 cylinder cut pattern increases) and the cylinder arrangement and timing of the actual fuel supply cut are determined. If
The fuel supply to the three cylinders out of each cylinder is evenly cut.

The operation of the above control is shown in FIGS. 6 (a), (b) and FIG.
It will be explained by. 6 (a) and 6 (b) schematically show the front wheels, the rear wheels, and the vehicle, and the vector of the tire driving force P corresponding to the engine driving force in the turning state of the front wheels, which are the driving wheels, at the steering angle = θ. Will occur on the center line L of the front wheels in the traveling direction (upper left in the figure). In general, the forces acting on the front wheels, which are the driving wheels, are a tire driving force P and a tire lateral force Q. The tire driving force P and the tire lateral force Q are non-linear as the slip ratio S increases as shown in FIG. Change. The slip ratio S indicated by A in FIG.
Is a region to be controlled, that is, a region where the idea of the friction circle is valid, and is also a region below the drive slip state where the tire driving force P is maximum. In this region, P increases and Q decreases as the slip ratio S increases. Therefore, when the target slip ratio S _d is set so that the slip ratio S becomes 0 and the engine driving force is controlled (reduced) so as to achieve this target slip ratio S _d , as shown in FIG.
As shown in (a), the tire lateral force Q can be maximized, but in that case, the lateral force M of the vehicle is not maximized and the turning performance is deteriorated. The component F also becomes large, causing a feeling of deceleration.

On the other hand, in this example, for example, the slip ratio S
Since the target slip ratio S _d is set so as to be S ₁ in FIG. 7 that is larger than 0, the value of this S ₁ is set to the tire driving force P and the tire lateral force Q corresponding to the slip ratio S.
6B, the resultant force can be set to a value that maximizes the lateral force of the vehicle (M _max ). By the way, the slip ratio S ₁ for obtaining such a maximum lateral force M _max
Since there is always only one point when the characteristic diagram shown in FIG. 7 is created for each front wheel steering angle θ, the target slip ratio S _d that realizes the slip ratio S ₁ is a function of the front wheel steering angle θ. The map of FIG. 5 represents S _d = f (θ). Therefore, step 105 of FIG. 3 for looking up the map of FIG. 5 functions as a target slip setting means, and step 113 of FIG. 4 using step S _d set by the execution of step 105 and step 113 of FIG. The steps 114 to 116 selected as a result of the discrimination function as a driving torque control means, and the tire driving force P and the tire lateral force Q are exerted on the front wheels represented by their resultant force by the variable control of the driving torque. Since the force has a predetermined distribution that maximizes the lateral force of the vehicle, the turning performance of the vehicle is improved and the feeling of deceleration is not caused.

FIG. 8 is a flow chart showing a control program of the target slip amount variable control in the second embodiment of the vehicle driving force control device of the invention. The second embodiment is similar to the first embodiment except that the determination regarding the turning state of the vehicle is added in the setting of the target slip ratio S _d corresponding to FIG. 3 of the first embodiment. That is, in step 121 of FIG. 8, steps 101 to 104 of FIG.
The same control is executed to calculate the slip ratio S and read the front wheel steering angle θ.
The lateral G value Y _g is read from the sensor 14. In the next step 123, it is judged whether or not the lateral G value Y _g is less than a predetermined value (for example, 0.2 g), and if the judgment is NO, that is, Y _g ≧ 0.2 g, that is, the vehicle is in a turning state. If the determination is made, the control proceeds to the target slip ratio setting routine for turning after step 124, and in step 124, the map of FIG. 5 is looked up based on θ similarly to step 105 of FIG. ask for _d . On the other hand, if the determination in step 123 is YES, that is, if Y _g <0.2 g, it can be considered that the vehicle is traveling straight ahead, and in that case, the step that is the target slip ratio setting routine for straight travel is performed. Control is advanced to 124 and the target slip ratio S _d is set to a fixed value of 0.1 (10%), for example. After executing the control program shown in FIG. 8, the control program shown in FIG. 4 for actually increasing / decreasing the engine drive torque is executed as in the first embodiment.

In the second embodiment, the NO-124 of steps 121-122-123 are executed during turning, and the control content becomes the same as that of the first embodiment. Therefore, the same effect as the first embodiment is obtained. Step 121 when obtained straight ahead
YES-125 of -122-123 is executed to set the target slip ratio _Sd to generally maximize the tire driving force of the wheel S.
_{Since d} = 0.1 is set, acceleration performance when driving straight ahead is improved.

In each of the above embodiments, the engine driving force control by cutting the fuel supply is adopted as the traction control, but the invention is not limited to this. For example, a throttle for electrically controlling the throttle valve of the engine is used. The opening control, the ignition timing control of the engine, and the brake control that directly applies pressure to the wheel cylinders may be used. Further, in each of the above-described embodiments, the slip ratio is used as the slip state of the drive wheels, but the present invention is not limited to this, and control may be performed using the slip amount, for example.

[0019]

As described above, in the vehicle driving force control device of the present invention, in the first structure, the target slip state used for the drive torque variable control is the tire lateral force and the tire driving force corresponding to the drive slip state. In order to maximize the lateral force of the vehicle by the resultant force, the target slip state is variably controlled to become larger as the steering amount of the front wheels becomes larger. Therefore, even when turning, the tire driving force and the tire lateral force are balanced. Can be optimized to improve the turning performance of the vehicle, and both acceleration performance and turning performance of the vehicle can be realized. Also, in the second configuration,
By setting the target slip state in a region less than the drive slip state in which the tire driving force is maximum, only the region where the idea of the friction circle is valid is set as the control target region, and the lateral direction of the vehicle is ensured. You can maximize your power.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of the present invention.

FIG. 2 is a diagram showing the configuration of a first embodiment of the vehicle driving force control device of the present invention.

FIG. 3 is a flowchart showing a control program of target slip amount variable control in the same example.

FIG. 4 is a flowchart showing a control program of target slip amount variable control in the same example.

FIG. 5 is a diagram illustrating a map used for setting a target slip ratio in the same example.

FIG. 6A is a diagram for explaining the operation of the conventional example, and FIG. 6B is a diagram for explaining the operation of the first embodiment.

FIG. 7 is a characteristic diagram showing tire longitudinal force and tire lateral force acting on a driving wheel.

FIG. 8 is a flow chart showing a control program of target slip amount variable control in the second embodiment of the vehicle driving force control device of the invention.

[Explanation of symbols]

 1L, 1R front wheels (driving wheels) 3 engine 4 to 7 wheel rotation sensor 11 CPU 12 fuel supply control unit 13-1 to 13-6 cylinder 14 lateral G sensor 15 rudder angle sensor

Claims (2)

(57) [Claims] 1. A steering amount detecting means for detecting a steering amount of a front wheel, a slip detecting means for detecting a drive slip state of a drive wheel, and a drive torque variable so as to achieve a target slip state based on the detected drive slip state. In a vehicle that drives at least the front wheels and that has a driving torque control means for controlling, in order to maximize the lateral force as a vehicle by the combined force of the tire lateral force and the tire driving force corresponding to the driving slip state, the target slip A vehicle driving force control device comprising a target slip setting means for setting a larger state as the steering amount is larger. 2. The vehicle drive force control device according to claim 1, wherein the target slip state is set in a region less than the drive slip state where the tire drive force is maximum.