JP3428419B2 - Braking / driving 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 constant speed traveling device having an actuator capable of controlling a braking force or a braking / driving force control device for an inter-vehicle distance control device.

[0002]

2. Description of the Related Art Conventionally, there is known a travel control method in which a vehicle distance to a preceding vehicle is detected and a vehicle speed or a braking / driving force is controlled so that the vehicle distance becomes an appropriate value. Also,
2. Description of the Related Art There is known a device that cuts off fuel supply to an engine (hereinafter referred to as a fuel cut) in order to improve fuel efficiency when the engine speed is higher than a certain level and the throttle valve is fully closed.

In addition to this fuel cut device, a vehicle equipped with a constant speed traveling device or an inter-vehicle distance control device,
When traveling on a downhill or when decelerating to follow a preceding vehicle, the throttle valve may be returned to near full closure.

In such a case, the driving torque sharply decreases in steps due to the fuel cut, and the vehicle speed falls below the target vehicle speed. Therefore, the vehicle speed control device controls the throttle valve to open. As a result, fuel is supplied again, the driving torque increases stepwise, and the vehicle speed increases rapidly, so the throttle valve is controlled to close again,
The fuel supply to the engine is cut off again and the vehicle speed drops sharply. In this way, since the fuel cut is repeatedly turned on and off, the engine torque fluctuates and the riding comfort deteriorates. To solve this problem, Japanese Patent Laid-Open No. 6-087
According to Japanese Patent No. 355, the above problem is prevented by setting a large engine speed for fuel cut to make it difficult to operate the fuel cut during execution of engine brake control. Also, JP-A-63-134832
In the publication, the above problem is prevented by stopping the fuel cut during traveling at a constant speed.

[0005]

However, in such a conventional braking / driving force control device, hunting by the front / rear G added to the vehicle is prevented, which improves the riding comfort but deteriorates the fuel consumption. was there.

The present invention has been made in view of the above,
An object of the present invention is to provide a braking / driving force control device capable of preventing hunting due to front / rear G added to a vehicle even when performing on / off control of fuel cut, and achieving both improvement of fuel efficiency and improvement of riding comfort. To do.

[0007]

The invention according to claim 1 is
To solve the above problems, a torque control unit that controls a shaft torque generated by a vehicle, a braking force control unit that controls a braking force of the vehicle, and the shaft torque have a value according to a predetermined shaft torque command value. As described above, a shaft torque control means for calculating a command signal to the torque control means and the braking force control means, and a fuel cut means for cutting off fuel supply to the engine when a predetermined fuel cut condition is satisfied are provided. In a braking / driving force control device of the traveling control device having, fuel cut stop means for stopping the operation of the fuel cut means in accordance with a result of comparison between the shaft torque command value and a shaft torque calculation value at the time of fuel cut. And a braking force correction unit that corrects the braking force by the braking force control unit according to the operating state of the fuel cut stop unit.

According to a second aspect of the present invention, in order to solve the above-mentioned problems, in the braking / driving force control device according to the first aspect, when the braking force correcting means is interrupting the fuel supply to the engine. Is to correct the command signal so as to weaken the braking force according to the calculated shaft torque at the time of the fuel cut.

According to a third aspect of the present invention, in order to solve the above problems, in the braking / driving force control device according to the first aspect, the axial torque command value and the axial torque calculation value at the time of fuel cut have negative values. However, the calculated shaft torque at the time of fuel cut is
There is a relationship of calculated shaft torque at fuel cut> second shaft torque reference value> first shaft torque reference value, and the fuel cut stopping means has a first shaft torque reference value rather than the shaft torque command value. When the value is larger, the fuel cut means is operated, while when the second shaft torque reference value is smaller than the shaft torque command value, the operation of the fuel cut means is stopped. And

[0010]

According to the present invention, the fuel supply to the engine is cut off when a predetermined fuel cut condition is satisfied, and the shaft torque command value and the shaft at the time of fuel cut are set. The fuel cut operation is stopped according to the result of comparison with the calculated torque value, and the fuel cut on / off control is performed by correcting the braking force to the vehicle according to the operation state of the fuel cut stop. Even if
It is possible to prevent hunting due to the front and rear G added to the vehicle, and it is possible to improve both fuel efficiency and riding comfort.

According to the second aspect of the present invention, when the fuel supply to the engine is being cut off, the command signal is corrected so as to weaken the braking force according to the shaft torque calculation value at the time of fuel cut. By doing so, hunting by the front and rear G at the time of fuel cut can be avoided.

According to the third aspect of the present invention, when the first shaft torque reference value is larger than the shaft torque command value, the fuel cut operation is performed while the second shaft torque command value is used. When the shaft torque reference value is smaller, by stopping the fuel cut operation, hunting due to the front and rear G due to the fuel cut can be avoided, and on / off of the fuel cut is determined according to the shaft torque command value, so fuel consumption is reduced. Can be improved.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram for explaining a configuration of functional elements of a braking / driving force control device according to a first embodiment of the present invention. FIG. 2 is a block diagram showing components and their connections of the braking / driving force control device according to the first embodiment of the present invention.

In FIG. 1, an inter-vehicle distance command value calculation unit 1
Calculates an appropriate inter-vehicle distance according to the vehicle speed. The inter-vehicle distance measuring unit 3 measures the inter-vehicle distance. The inter-vehicle distance control unit 5
A vehicle speed command value is calculated to make the inter-vehicle distance measurement value a value corresponding to the inter-vehicle distance command. The vehicle speed control unit 7 calculates a wheel torque command value for setting the measured vehicle speed value to a value corresponding to the vehicle speed command value.

The shaft torque control unit 9 calculates a throttle opening command value and a brake fluid command value for making the shaft torque a value according to the wheel torque command value, and a fuel from a fuel cut judging unit 11 described later is supplied. Input a cut stop signal and correct the brake fluid pressure command value to weaken the braking force. Specifically, as shown in FIG. 7, the fuel cut stop signal from the fuel cut determination unit 11 is input to the engine brake torque correction unit 43 provided inside, and the shaft torque component T _eb is _calculated from the shaft torque command value T _wr. Correct by subtracting to reduce the braking force.

The fuel cut judgment unit 11 is a characteristic part of the present invention, and judges whether the fuel cut is on or off according to the shaft torque command value and the vehicle operation signal, and determines the shaft torque control unit 9 and the engine controller 83 which will be described later. The fuel cut stop signal is output to. The brake fluid pressure servo system 13 sets the brake fluid pressure to a value according to the brake fluid pressure command value. The throttle opening servo system 15 sets the throttle opening to a value according to the throttle opening command value. Vehicle 1
7 will be described later.

As shown in FIG. 2, the brake fluid pressure servo system 13 comprises a fluid pressure control calculation unit 21, a brake actuator 23, and a fluid pressure detection unit 25. Further, the throttle opening servo system 15 includes a throttle opening positioning control calculation unit 51 and a throttle opening sensor 53.
And a throttle actuator 55.

Further, the vehicle 17 includes an engine 61, an automatic transmission AT63, a differential gear 65, a wheel cylinder 67, and tires 6.
9, a vehicle body 81, and an engine controller 83 that inputs a fuel cut stop signal from the fuel cut determination unit 11 to perform on / off control of the fuel cut.

Next, the operation of each component will be described in more detail. First, the inter-vehicle distance command value computing unit 1 wants to secure the inter-vehicle time T to match the inter-vehicle distance L with the preceding vehicle measured by the radar or the like provided in the inter-vehicle distance measuring unit 3 with the inter-vehicle distance command value Lr. And based on the own vehicle speed Vsp, the inter-vehicle distance command value Lr is derived,

[Equation 1] It is output to the inter-vehicle distance control unit 5.

Here, the vehicle speed control system uses the vehicle speed command value Vspr.
The response of the actual vehicle speed Vsp to the time constant τv (= 1 / ω)
If it can be approximated by the first-order lag system, the configuration of the inter-vehicle distance control unit 5 is as shown in the block diagram of FIG. 3, for example. In this case, from the inter-vehicle distance command value Lr to the actual inter-vehicle distance L
The transfer characteristic up to v is as follows.

[0021]

[Equation 2] However, s is a Laplace operator. From the equation (2), the inter-vehicle distance control system can match the following response with a desired response by setting the constants Kv and KL to appropriate values.

The vehicle speed control unit 7 matches the actual vehicle speed with the vehicle speed command value from the inter-vehicle distance control unit 5. The configuration of the vehicle speed control system is, for example, as shown in the block diagram of FIG. However, the transmission delay of the shaft torque control system 43 shown in FIG. 4 can be ignored.

The running resistance estimator 41 shown in FIG. 4 estimates the running resistance Fdh using the following equation (3) based on the driving force command value Fwr and the vehicle speed Vsp, and feeds back the gradient or the air. Eliminate the effects of resistance and rolling resistance.

[0024]

[Equation 3] However, H (s) is a low-pass filter with a steady gain of 1. If the disturbance to the control system is eliminated by estimating the running resistance F _dh , the transfer characteristic from the vehicle speed command value to the actual vehicle speed is given by the following equation.

[0025]

[Equation 4] From equation (4), by setting the constant Ksp to an appropriate value,
The responsiveness of the vehicle speed control system can be matched with a desired response.

The shaft torque control unit 9 calculates a throttle opening command value for realizing the shaft torque calculated by the vehicle speed control unit 7 and a brake fluid command value. It is assumed that the constant speed traveling device and the inter-vehicle distance control device have relatively gentle acceleration / deceleration of the engine speed, and the influence of the engine inertia can be ignored. In this case, the engine torque command value T _{eng with} respect to the shaft torque command value Twr is calculated based on the torque converter torque ratio Ktrk, the differential gear ratio Kdef, and the automatic transmission gear ratio Kat.

[Equation 5] Becomes

Next, based on the engine torque command value and the engine speed calculated by the equation (5), the throttle opening command value θcmd is calculated using an engine map as shown in FIG.

On the other hand, if the brake is operated when the throttle opening is zero, the axial torque Twrc due to the brake must be subtracted from the axial torque command value Twr by the axial torque Teb due to the engine brake. Therefore,
The axial torque Twrc is

[Equation 6] Becomes The shaft torque Teb shown in the equation (6) is based on the engine torque Teng 0 when the throttle opening is zero,

[Equation 7] Becomes

Engine torque Teng 0 shown in equation (7)
Is obtained by referring to a table map of engine torque related to engine speed as shown in FIG. 6, for example. However, since the magnitude of the engine torque Teng 0 varies depending on the fuel cut operation state, the fuel cut determination unit 6
It receives a signal from, a configuration for switching the T _{FC_OFF} (fuel cut is not operated engine torque) and T _{FC_ON} (fuel cut operation engine torque).

Next, with respect to the shaft torque command value Twrc, the brake fluid command value Pbr is the brake cylinder area Sb,
Based on the brake rotor effective radius Rb and the brake pad friction coefficient μb,

[Equation 8] Becomes However, the master cylinder fluid shall be distributed equally to the four wheels. The shaft torque control system described above is summarized as shown in FIG. Here, when the fuel cut is activated, the engine torque is reduced stepwise, so it becomes impossible to output the shaft torque between the time when the fuel cut is activated and the time when the fuel cut is not activated.

FIG. 10 is a diagram showing a simulation result in the conventional braking / driving force control device. In this simulation result, the control for performing the fuel cut under the usual experimental conditions is selected. In the conventional braking / driving force control device, when the vehicle speed reaches the command value when the throttle is fully closed, the fuel cut signal is repeatedly turned on and off, which results in hunting due to front and rear G applied to the vehicle. Becomes worse. By the way, in the conventional example in which the fuel cut is not performed, hunting due to the front and rear G does not occur, but the fuel consumption is obviously deteriorated.

Therefore, as shown in FIG. 8, until the axial torque command value that exceeds the axial torque due to the fuel cut is input, the fuel cut is deactivated and the braking torque is generated by the brake. On the other hand, when a shaft torque command value larger than that is input, the fuel cut may be operated and at the same time, the brake fluid corresponding to the shaft torque due to the fuel cut may be reduced.

FIG. 9 is a flow chart for explaining the operation of the fuel cut determination section 11 of the braking / driving force control device according to the first embodiment of the present invention. First, in step S1, the fuel cut determination unit 11 is used to determine whether or not the conditions are for fuel cut. If the fuel cut is not performed, the fuel cut operation flag is set to 0 in step S15, and the routine returns.

In the case of the condition that the fuel cut is performed, the process proceeds to step S3, and as shown in FIG. 6, the engine torque during the fuel cut operation is referred to from a table map or the like, or is calculated by a calculation formula. Next, step S
In 5, the shaft torque T _wfc during the fuel cut operation is calculated from the following equation.

[0035]

[Equation 9] Here, in step S7, the shaft torque Twfc calculated by the equation (9) is compared with the shaft torque command value Twr, and the shaft torque command value Twr is, for example, 1.5 times the reference value (first value) of the shaft torque Twfc. A value smaller than the shaft torque reference value (at this time T
Since wr and Twfc are negative values, the absolute value of Twr is Twfc
Value greater than 1.5 times the absolute value of),
In step S9, set the fuel cut operation flag to 1
And allow fuel cut.

On the other hand, the shaft torque command value Twr is equal to the shaft torque Twf.
If it is not smaller than the value of 1.5 times c, for example, the process proceeds to step S11, where the shaft torque command value Twr is equal to
For example, it is compared whether or not the value is larger than a reference value (second shaft torque reference value) that is 1.2 times wfc.
In step S13, the fuel cut operation flag is set to 0 and the fuel cut is stopped. On the other hand, when the shaft torque command value Twr is not larger than, for example, 1.2 times the shaft torque Twfc, the fuel cut operation flag is restored without being changed.

The first and second shaft torque reference values are
It goes without saying that the value changes according to the change in the shaft torque Twfc. In this way, in order to avoid frequent changes in the front and rear G applied to the vehicle by turning the fuel cut on and off, and in the brake fluid pressure, when the engine speed is above a certain level and the throttle valve is fully closed, the fuel cut Hysteresis characteristics are provided for the operating conditions.

That is, when the shaft torque command value becomes equal to or greater than a reference value (first shaft torque reference value) which is, for example, 1.5 times the reduction amount of the shaft torque due to the fuel cut, the fuel cut is turned on, for example, 1 A hysteresis characteristic is provided in which the fuel cut is turned off when the value becomes equal to or less than the double standard value (second shaft torque standard value). By the way, at least when the relationship of (shaft torque command value> shaft torque due to fuel cut) is established, the fuel cut is turned off.

The fuel cut operation flag obtained by the fuel cut determination unit 11 as described above is input to the shaft torque control unit 9 as a fuel cut stop signal and is substituted into Teng 0 shown in the equation (7) T _{FC_OFF.} And T
At the same time when _{FC_ON} is switched, it is input to the engine controller 83 provided in the vehicle 17 to command the operation or non-operation of the fuel cut in the engine 61.

In this way, the fuel cut determination unit 11
Then, the fuel cut operation is stopped according to the result of comparison between the shaft torque command value and the shaft torque calculation value at the time of fuel cut. The hysteresis characteristics as described above are merely examples, and for example, the axial torque command value is a reference value (first
The shaft torque reference value), the fuel cut is turned on, and for example, when it becomes 1.5 times the reference value (second shaft torque reference value) or less, the fuel cut is turned off. Good.

As a result, even when the on / off control of the fuel cut is performed, the hunting due to the front and rear G applied to the vehicle can be prevented, and the improvement of the fuel consumption and the improvement of the riding comfort can both be achieved.

FIG. 11 is a diagram showing a simulation result in the braking / driving force control device according to the first embodiment of the present invention. As shown in FIG. 11, until the axial torque command value that exceeds the axial torque due to the fuel cut is input, the fuel cut is deactivated and the brake fluid pressure increases to generate the braking torque.

On the other hand, when a shaft torque command value greater than that is input, the fuel cut signal is turned on to activate the fuel cut, and at the same time, the brake fluid corresponding to the shaft torque due to the fuel cut is reduced.

From this simulation result, it is understood that the vehicle 17 is not hunted by the front and rear G even if the fuel cut signal is turned on and off.

(Second Embodiment) FIG. 12 is a block diagram for explaining the configuration of a braking / driving force control device according to a second embodiment of the present invention as seen from the functional elements, and FIG.
FIG. 6 is a block diagram showing constituent devices of a braking / driving force control device and connections thereof according to a second embodiment of the present invention.

In the present embodiment, the case where the braking / driving force control device of the present invention is applied to a system having no mechanical link between the accelerator pedal and the throttle valve will be described. In the present embodiment, the signals output by the shaft torque control unit 209 are the engine torque command value and the brake fluid pressure command value, and the throttle opening control system is included in the engine controller. The fuel cut determination unit 211 is configured to input a fuel cut request from the engine controller and output a fuel cut permission to the engine controller 93.

First, only the part of the configuration different from that of the first embodiment will be described. Axis torque control unit 209
Calculates an engine torque command value and a brake fluid command value for the shaft torque to be a value according to the command value, and sends a fuel cut stop signal from a fuel cut determination unit 211, which will be described later, to the engine brake torque correction unit 43. Input to correct the brake fluid pressure command value.

The fuel cut judgment unit 211 judges whether the fuel cut is on or off in response to a shaft torque command value, a vehicle operation signal, and a fuel cut request from an engine controller 93 described later, and the shaft torque control unit 209.
Then, a fuel cut stop signal is output to the engine controller 93 described later. Engine controller 93
So that the engine torque becomes a value according to the command value,
It controls the throttle opening, ignition timing, and fuel injection amount. Further, the engine controller 93 outputs a fuel cut request to the fuel cut determination unit 211, and turns on / off the fuel cut according to the fuel cut permission signal. The other components are the same as those of the braking / driving force control device according to the first embodiment, and thus the description thereof is omitted.

Next, the operation of each component will be described in more detail. In the axial torque control unit 9 in the braking / driving force control device according to the first embodiment, the throttle opening command value is calculated, but in the present embodiment, the axial torque control unit 209
The engine torque command value Teng is output. Therefore,
The engine torque command value Teng calculated by the equation (5) may be output to the engine controller 93 as a command value.
The brake fluid pressure command value is the same as that of the braking / driving force control device according to the first embodiment.

Further, as shown in FIG. 13, the fuel cut determination section 211 is configured to receive a fuel cut request signal from the engine controller 93 and return a fuel cut operation flag to the engine controller 93. Note that FIG. 14 is a diagram showing a configuration in which the operating characteristics of the shaft torque control unit 209 are summarized.

FIG. 15 is a flow chart for explaining the operation of the fuel cut determination unit 211 of the braking / driving force control device according to the second embodiment of the present invention.

This flowchart is based on the modification of the fuel cut determination in step S1 shown in FIG. That is, in step S21, the fuel cut determination unit 211 determines whether or not there is a fuel cut request signal received from the engine controller 93. If there is no fuel cut request signal, the process proceeds to step S15, the fuel cut operation flag is set to 0, and the process ends. On the other hand, if there is a fuel cut request signal,
The steps following step S3 are executed to operate to return the fuel cut operation flag to the engine controller 93. In addition, about the operation after step S3,
The operation is the same as that of the fuel cut determination unit 211 of the braking / driving force control device according to the first embodiment, and thus the description thereof is omitted.

As a result, it can be seen from the simulation result shown in FIG. 11 that the vehicle 17 is not hunted by the front and rear G even when the fuel cut signal is turned on and off. In the description of the operation of the braking / driving force control device according to the present embodiment, the case where the brake is used as the braking device has been described, but the present invention is not limited to such a case, and the braking force is controlled. It is also applicable to possible motors. For example, if the motor is installed at the wheel, the motor torque command may be calculated using the equation (6) as in the braking / driving force control device according to the first embodiment. If the motor is mounted on the output shaft of the transmission, the motor torque command may be calculated by dividing the equation (6) by Rdef. In this way, the motor torque command value may be calculated by selecting an appropriate gear ratio according to the mounting location of the motor, and it is also applicable to a hybrid vehicle in which a braking / driving force control device of this type can be mounted. .

[Brief description of drawings]

FIG. 1 is a block diagram for explaining a configuration of a braking / driving force control device according to a first embodiment of the present invention viewed from a functional element.

FIG. 2 is a block diagram showing constituent devices of the braking / driving force control device according to the first embodiment of the present invention and their connections.

FIG. 3 is a block diagram showing operating characteristics of an inter-vehicle distance control system 3.

FIG. 4 is a block diagram showing a configuration of a vehicle speed control system.

FIG. 5 is an engine map for obtaining a throttle opening command value θcmd from an engine torque command value and an engine speed.

FIG. 6 is a table map of engine torque related to engine speed.

FIG. 7 is a block diagram summarizing operating characteristics of an axial torque control system.

FIG. 8: Fuel cut operation status and shaft torque command value,
6 is a time chart showing a relationship between a brake fluid pressure command value and a throttle opening command value.

FIG. 9 is a flowchart for explaining the operation of a fuel cut determination unit of the braking / driving force control device according to the first embodiment of the present invention.

FIG. 10 shows a simulation result in a conventional braking / driving force control device.

FIG. 11 shows a simulation result in the braking / driving force control device according to the first embodiment of the present invention.

FIG. 12 is a block diagram for explaining a configuration of a braking / driving force control device according to a second embodiment of the present invention viewed from a functional element.

FIG. 13 is a block diagram showing constituent components of a braking / driving force control device according to a second embodiment of the present invention and their connections.

FIG. 14 is a diagram showing a configuration in which operating characteristics of a shaft torque control unit are summarized.

FIG. 15 is a flowchart for explaining an operation of a fuel cut determination unit of the braking / driving force control device according to the second embodiment of the present invention.

[Explanation of symbols]

1 Inter-vehicle distance command value calculator 3 Distance measurement unit 5 Inter-vehicle distance control unit 7 Vehicle speed control section 9,209 Axis torque control unit 11, 211 Fuel cut judgment unit 13 Brake fluid pressure servo system 15 Throttle opening servo system 17,217 vehicles 61 engine 63 Automatic transformer 65 differential gear 67 Brake wheel shilling 69 tires 81 car body 83,93 engine controller

Continuation of front page (51) Int.Cl. ⁷ identification code FI F02D 41/12 330 330 F02D 41/12 330M (58) Fields investigated (Int.Cl. ⁷ , DB name) B60T 8/00-8/96 B60T 7/12-7/22 B60K 41/20 F02D 29/02 F02D 41/04 F02D 41/12

Claims (3)

(57) [Claims] 1. A torque control means for controlling a shaft torque generated in a vehicle, a braking force control means for controlling a braking force of the vehicle, and the shaft torque having a value according to a predetermined shaft torque command value. Traveling having axial torque control means for calculating a command signal to the torque control means and the braking force control means, and fuel cut means for cutting off fuel supply to the engine when a predetermined fuel cut condition is satisfied In the braking / driving force control device of the control device, according to the result of comparing the shaft torque command value and the shaft torque calculation value at the time of fuel cut, fuel cut stop means for stopping the operation of the fuel cut means, A braking / driving force control device comprising: a braking force correction unit that corrects the braking force by the braking force control unit according to the operating state of the fuel cut stop unit. 2. The braking force correcting means corrects the command signal so as to weaken the braking force according to the shaft torque calculation value at the time of the fuel cut when the fuel supply to the engine is being cut off. The braking / driving force control device according to claim 1, wherein 3. The shaft torque command value and the shaft torque calculated value at the time of fuel cut have negative values, and the shaft torque calculated value at the time of fuel cut is the shaft torque calculated value at the time of fuel cut> second
Shaft torque reference value> first shaft torque reference value, and the fuel cut stop means is configured to perform the fuel cut when the first shaft torque reference value is larger than the shaft torque command value. The braking / driving force control according to claim 1, wherein the operation of the fuel cut means is stopped when the second shaft torque reference value is smaller than the shaft torque command value while the means is operated. apparatus.