JP2007153278A - Braking force control device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable the improvement of an initial responsiveness even in a braking force control so as to stabilize the turning. <P>SOLUTION: A braking force control device preloads a braking fluid pressure before decelerating control is actuated. There, the greater a lateral acceleration Yg becomes, a predetermined time Δt is set to a greater value (step S34). An estimated target turning vehicle speed V<SP>*</SP><SB>prefill</SB>after a predetermined time Δt of a target turning speed V<SP>*</SP>is calculated (step S35). When the vehicle speed is greater than the estimated target turning vehicle speed V<SP>*</SP><SB>prefill</SB>(V>V<SP>*</SP><SB>prefill</SB>) (step S38), the braking fluid pressure is preloaded. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a braking force control device for a vehicle that enables the vehicle to stably turn.

  2. Description of the Related Art Conventionally, as a braking force control device aimed at ensuring stability during vehicle turning, for example, there is a device described in Patent Document 1. The braking force control device described in Patent Document 1 detects the amount of turning state of the vehicle from the driving state of the vehicle, instead of simply detecting the acceleration slip of the driving wheel and suppressing the acceleration slip as in the case of traction control. The target deceleration required for the vehicle to maintain a stable turning when the turning state amount approaches a predetermined braking operation threshold with respect to the turning limit state amount at which the vehicle can stably travel. And a braking force for realizing the target deceleration is applied to the vehicle.

As a result, the vehicle is controlled so that it does not exceed the limit turning amount that allows the vehicle to turn stably regardless of the driver's intention, resulting in overshooting when the corner is suddenly contrary to the driver's expectation. Even when the vehicle enters the corner at a speed, the vehicle can be secured stably by quickly decelerating the vehicle appropriately.
However, as an actuator that applies braking to a vehicle, for example, a hydraulic brake device that applies a braking force to a wheel is assumed, and a hydraulic brake actuator including a motor pump as a pressure generation source of the hydraulic brake device, a so-called pump In the up system, even if the braking force control starts to operate, it takes time until the brake fluid is boosted on the wheel cylinder side after the motor pump is operated, so that there is a problem that the initial response is delayed.

In order to solve this problem, conventionally, for example, a technique for applying a preload to the brake fluid pressure as described in Patent Document 2 is known.
Japanese Patent Laid-Open No. 02-171373 JP 2001-63541 A

However, as described in Patent Document 2, a second operation threshold lower than the target first operation threshold is simply set, and the first operation is determined from the second operation threshold. When the preload control is executed when it is determined that the state is between the threshold values, it is determined that the second operation threshold value has been exceeded in cases such as when the change in the output value from the means for determining braking is fast. Even if the preload control is shifted from the preload control, the first operation threshold value may be exceeded without taking sufficient time to apply the preload. In such a case, the effect of the preload control may not be sufficiently obtained. There is a problem that there is.
Further, if the interval between the second operation threshold and the first operation threshold is set large, the preload control is operated unnecessarily.
An object of the present invention is to make it possible to reliably improve initial responsiveness without waste in braking force control for the purpose of turning stability.

  In the vehicle braking force control device according to the first aspect of the present invention, it is determined that the turning state quantity of the vehicle has exceeded a braking operation threshold value set in accordance with a limit turning state quantity at which the vehicle can stably travel. Determining means for calculating, a calculating means for calculating a target deceleration required for maintaining a stable turning of the vehicle, and when the determining means determines that the turning state of the vehicle has exceeded the braking operation threshold value. Control means for applying a braking force according to the target deceleration obtained by the computing means to the vehicle.

  This vehicle braking force control device estimates whether or not the amount of turning state of the vehicle exceeds the braking operation threshold after a predetermined time has elapsed from the present time, and determines the predetermined time based on the running state of the vehicle. Set by setting means, the control means starts a preliminary operation for increasing the braking force application responsiveness when the estimation means estimates that the braking operation threshold is exceeded after the predetermined time has elapsed.

  According to the first aspect of the present invention, it is possible to reliably improve the initial response of the control, and it is possible to decelerate with good response to a vehicle speed at which the vehicle can stably turn. Moreover, it is possible to prevent the initial response of the control from being unnecessarily increased by setting the predetermined time based on the traveling state of the vehicle.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described in detail with reference to the drawings.
(First embodiment)
(Constitution)
FIG. 1 is a block diagram showing a schematic configuration of a braking force control apparatus according to a first embodiment to which the present invention is applied. An electromagnetic induction type wheel speed sensor 1 for detecting the wheel speed Vwi (i = FL, FR, RL, RR) of each wheel, and an optical / non-contact type steering angle sensor 2 for detecting the steering angle θ of the steering wheel. When a yaw rate sensor 3 for detecting a vehicle yaw rate phi _D, an accelerator sensor 4 to detect an accelerator opening Acc of the accelerator pedal, the lateral acceleration sensor 5 is connected to the controller 6.

The controller 6 is composed of, for example, a microcomputer, and executes a turning traveling control process, which will be described later, based on detection signals from the respective sensors, and drives and controls the engine output control device 7 and the braking force control device 9. Automatic deceleration is performed according to the turning state.
Here, the engine output control device 7 is configured to control the engine output (the number of revolutions and the engine torque) by adjusting the throttle valve opening, the fuel injection amount, the ignition timing, and the like in the engine 8. .

FIG. 2 shows the configuration of the braking force control device 9.
As shown in FIG. 2, the braking force control device 9 is interposed between the master cylinder 10 and each wheel cylinder 11 i (i = FL, FR, RL, RR).
The master cylinder 10 is a tandem type that produces two systems of hydraulic pressure according to the driver's pedaling force. The master cylinder 10 transmits the primary side to the front left and rear right wheel cylinders 11FL and 11RR, and the secondary side transmits the right front wheel and A diagonal split system is used for transmission to the left rear wheel cylinders 11FR and 11RL.

Each of the wheel cylinders 11FL to 11RR is incorporated in a disc brake that presses a disc rotor with a brake pad to generate a braking force, or a drum brake that generates a braking force by pressing a brake shoe against the inner peripheral surface of the brake drum. Yes.
The braking force control device 9 uses a braking fluid pressure control circuit used for anti-skid control (ABS), traction control (TCS), stability control (VDC: Vehicle Dynamics Control), and the like. Regardless of the operation, the hydraulic pressure in each of the wheel cylinders 11FL to 11RR can be increased, held and reduced.

  The primary side has a normally open type first gate valve 12A capable of closing a flow path between the master cylinder 10 and the wheel cylinder 11FL (11RR), and a flow path between the first gate valve 12A and the wheel cylinder 11FL (11RR). A normally open type inlet valve 13FL (13RR) that can be closed, a reservoir 14 communicated between the wheel cylinder 11FL (11RR) and the inlet valve 13FL (13RR), and a flow path between the wheel cylinder 11FL (11RR) and the reservoir 14 are provided. A normally closed outlet valve 15FL (15RR) that can be opened, and a normal channel that can open a flow path that communicates between the master cylinder 10 and the first gate valve 12A and between the reservoir 14 and the outlet valve 15FL (15RR). The pump 17 has a suction side communicating between the second gate valve 16A of the nozzle type, the reservoir 14 and the outlet valve 15FL (15RR), and a discharge side communicating between the first gate valve 12A and the inlet valve 13FL (13RR). And. A damper chamber 18 is disposed on the discharge side of the pump 17 to suppress pulsation of discharged brake fluid and weaken pedal vibration.

Similarly to the primary side, the secondary side also has a first gate valve 12B, an inlet valve 13FR (13RL), a reservoir 14, an outlet valve 15FR (15RL), a second gate valve 16B, a pump 17, A damper chamber 18.
The first gate valves 12A and 12B, the inlet valves 13FL to 13RR, the outlet valves 15FL to 15RR, and the second gate valves 16A and 16B are two-port, two-position switching, single solenoid, and spring offset type electromagnetic operations, respectively. The first gate valves 12A and 12B and the inlet valves 13FL to 13RR open the flow path at a non-excited normal position, and the outlet valves 15FL to 15RR and the second gate valves 16A and 16B are non-excited. The flow path is closed at the normal position.

The pump 17 is a positive displacement pump such as a gear pump or a piston pump that can ensure a substantially constant discharge amount regardless of the load pressure.
With the above configuration, the primary side will be described as an example. When the first gate valve 12A, the inlet valve 13FL (13RR), the outlet valve 15FL (15RR), and the second gate valve 16A are all in the non-excited normal position. Then, the hydraulic pressure from the master cylinder 2 is transmitted as it is to the wheel cylinder 11FL (11RR) and becomes a normal brake.

  Even when the brake pedal is not operated, the first gate valve 12A is energized and closed while the inlet valve 13FL (13RR) and the outlet valve 15FL (15RR) are kept in the non-excited normal position. The second gate valve 16A is excited and opened, and the pump 17 is further driven to suck the hydraulic pressure of the master cylinder 2 through the second gate valve 16A and discharge the hydraulic pressure to the inlet valve 13FL (13RR). ) To the wheel cylinder 11FL (11RR) to increase the pressure.

  If the inlet valve 13FL (13RR) is excited and closed when the first gate valve 12A, the outlet valve 15FL (15RR), and the second gate valve 16A are in the non-excited normal position, the wheel cylinder 11FL (11RR) is closed. ) To the master cylinder 2 and the reservoir 14 are blocked, and the hydraulic pressure of the wheel cylinder 11FL (11RR) is maintained.

  Further, when the first gate valve 12A and the second gate valve 16A are in the non-excited normal position, the inlet valve 13FL (13RR) is excited and closed, and the outlet valve 15FL (15RR) is excited and opened. The hydraulic pressure of the wheel cylinder 11FL (11RR) flows into the reservoir 14 and is reduced. The hydraulic pressure flowing into the reservoir 14 is sucked by the pump 17 and returned to the master cylinder 2.

Regarding the secondary side, the normal braking, pressure increasing, holding, and pressure reducing operations are the same as the operations on the primary side, and thus detailed description thereof is omitted.
Therefore, the controller 6 controls each wheel by drivingly controlling the first gate valves 12A and 12B, the inlet valves 13FL to 13RR, the outlet valves 15FL to 15RR, the second gate valves 16A and 16B, and the pump 17. The fluid pressure in the cylinders 11FL to 11RR is increased / held / reduced.
In this embodiment, a diagonal split method is used that divides the brake system into front left / rear right and front right / rear left, but a front / rear split method that divides front left / right and rear left / right is adopted. May be.

  In the present embodiment, the first gate valves 12A and 12B and the inlet valves 13FL to 13RR open the flow path at the non-excited normal position, and the outlet valves 15FL to 15RR and the second gate valves 16A and 16B are non-excited. The flow path is closed at the normal excitation position. However, it is only necessary to open and close each valve, so the first gate valves 12A and 12B and the inlet valves 13FL to 13RR open the flow path at the excited offset position, and the outlet valves 15FL to 15RR and the The two gate valves 16A and 16B may close the flow path at the excited offset position.

Next, turning control processing executed by the controller 6 will be described.
FIG. 3 shows a flowchart of the processing procedure.
The turning control process is executed as a timer interruption process at predetermined time intervals (for example, 10 msec). As shown in FIG. 3, first, in step S1, each wheel speed Vwi, steering angle θ, and yaw rate detection value φ _D Then, the accelerator opening Acc is read.

Subsequently, in step S2, the turning speed V is calculated based on each wheel speed Vwi. In this embodiment, the turning speed V is calculated based on each wheel speed Vwi. However, the longitudinal speed of the vehicle body is detected by an acceleration sensor, and the turning speed V is calculated by taking this longitudinal acceleration into account. good.
Subsequently, in step S3, the yaw rate φ of the vehicle body is calculated according to the block diagram of FIG.

First, with reference to the control map shown in FIG. 5, to calculate the yaw rate estimated value phi _E in accordance with the turning speed V and the steering angle theta. The control map used for calculating the yaw rate estimated value phi _E, as shown in FIG. 5, the horizontal axis steering angle theta, the vertical axis is the yaw rate estimated value phi _E, as steering angle theta increases yaw rate phi _E The rate of increase is set so that the rate of increase decreases as the turning speed V increases.

Then, as shown in the following (1) to calculate a final yaw rate phi by the select high between an absolute value of the absolute value and the yaw rate estimated value phi _E of the yaw rate detection value phi _D. Here, for performing select-high of the estimated value phi _D and the detection value phi _E, for example to the steering angle at low roads road surface friction coefficient mu theta is not too large when a slow spin mode in which yaw rate phi increases This is because the deceleration control can be intervened earlier.
φ = max [| φ _D |, | φ _E |] (1)

Subsequently, in step S4, as shown in the following equation (2), a target turning speed V ^* for the current turning state is calculated. Here, μ is a road surface friction coefficient, which is estimated based on a slip ratio and a brake operation amount (master cylinder pressure), estimated based on road surface image data and air temperature, or a road surface discrimination sensor (GVS: It is estimated based on the detection result of (Grand View Censor), and further acquired from the infrastructure. Yg _L is a limit lateral acceleration and is set to a predetermined value (eg, 0.45 G) at which the vehicle can stably turn, but may be variable according to the slip ratio of each wheel.
V ^* = μ × Yg _L / | φ | (2)
According to the equation (2), the target turning speed V ^* decreases as the yaw rate φ increases, that is, as the steering angle θ or the estimated yaw rate value φ _E calculated based on the steering angle θ increases.

Subsequently, in step S5, the target deceleration Xg ^* is calculated as shown in the following equation (3). Here, ΔV is a deviation (V−V ^* ) between the turning speed V and the target turning speed V ^* , t is a predetermined time, and k is a coefficient.
Xg ^* = k × ΔV / t (3)
Here, the target deceleration Xg ^* is simply calculated based on the deviation ΔV between the turning speed V and the target turning speed V ^* . However, as shown in the following equation (4), the deviation ΔV increases in the increasing direction. The target deceleration Xg ^* may be calculated in consideration of the change speed (change amount per unit time) dΔV. Here, k1 and k2 are coefficients. Further, the change rate dΔV may be a change amount for each calculation cycle, or may be an average change amount within a predetermined time.
Xg ^* = (k1 × ΔV + k2 × dΔV) / t (4)
According to the equation (3) or (4), as the yaw rate φ increases, the target turning speed V ^* decreases and the deviation ΔV increases, so the target deceleration Xg ^* increases.

Subsequently, in step S30, preload control, which is a preliminary operation for braking fluid pressure, is performed. The brake fluid pressure preload control process will be described in detail later.
Subsequently, in step S6, it is determined whether or not the target deceleration Xg ^* is greater than zero. When the determination result is Xg ^* ≦ 0, it is determined that deceleration control, that is, automatic deceleration is unnecessary, and the process proceeds to step S15 described later. On the other hand, when the determination result is Xg ^* > 0, it is determined that deceleration control is necessary because the braking operation threshold set in accordance with the limit turning state amount at which the vehicle can stably travel is exceeded, The process proceeds to step S7.

Further, when the determination in relation to the yaw rate phi, according to the above (3) or (4), the yaw rate phi increases, because the target deceleration Xg ^* becomes larger than the target deceleration Xg ^* is 0 It becomes easy to determine that it is large. As will be described later, since the deceleration control is activated when the target deceleration Xg ^* is greater than 0, the deceleration control increases as the yaw rate φ increases, that is, as the steering angle θ or the yaw rate estimated value φ _E increases. Becomes easier to operate.
In step S7, the deceleration control flag Fc is set to “1”.
Subsequently, in step S8, the calculated increase the target braking force F ^* which is required to achieve the target deceleration Xg ^*. However, the target braking force F ^* is increased at a predetermined change speed so that the braking force increases to such an extent that a stable vehicle behavior can be maintained.

Subsequently, in step S9, as shown in the following equation (5), the target engine torque T ^* is calculated by subtracting a predetermined amount _Tdown from the target engine torque T ^* _(n-1) before one sampling. However, the initial value of T ^* _(n−1) is set to the driver request engine torque T _driver according to the accelerator opening Acc of the driver.
T ^* = T ^* _(n−1) −T _down (5)

Subsequently, in step S10, a lower limit value T ^* _MIN of the target engine torque is calculated according to the turning speed V with reference to a control map as shown in the flowchart. Here, the horizontal axis represents the turning speed V, the vertical axis represents the lower limit value T ^* _{MIN of the} target engine torque, and the lower limit value T ^* _MIN of the target engine torque increases as the turning speed V increases. ing.

Subsequently, in step S11, it is determined whether or not the target engine torque T ^* is smaller than the lower limit value T ^* _MIN . When the determination result is T ^* <T ^* _MIN , it is determined that the target engine torque T ^* is too narrow, and the process proceeds to step S12.
In step S12, as shown in the following formula (6), the target engine torque T ^* is limited to the lower limit value T ^* _MIN , and then the process proceeds to step S13.
T ^* ← T ^* _MIN (6)

On the other hand, when the determination result in step S11 is T ^* ≧ T ^* _MIN , the process proceeds to step S13 as it is.
In step S13, as shown in the following equation (7), the target engine torque ^{T *,} the final target engine torque by select low and the driver required engine torque _{T Draiver} corresponding to the accelerator opening Acc by the driver ^{T *} Is calculated.
T ^* = min [T ^* , T _driver ] (7)

Subsequently, in step S14, the target engine torque T ^* and the target braking force F ^* are output as control commands to drive the engine output control device 7 and the braking force control device 9, and then return to a predetermined main program. To do.
On the other hand, in step S15 which moves from the step S6, it is determined whether or not the deceleration control flag Fc is set to “1”. When the determination result is Fc = 0, it is determined that the deceleration control, that is, the automatic deceleration has not been started or has already ended, and the process returns to the predetermined main program. On the other hand, when the determination result is Fc = 1, it is determined that the deceleration control is started, and the process proceeds to step S16.

In step S16, the target braking force F ^* is decreased by the amount increased in the process of step S8. However, the target braking force F ^* is reduced at a predetermined change speed so that the braking force is reduced to such an extent that a stable vehicle behavior can be maintained.
Subsequently, in step S17, as shown in the following equation (8), the target engine torque T ^* is calculated by adding a predetermined amount _Tup to the target engine torque T ^* _(n-1) before one sampling.
T ^* = T ^* _(n−1) + T _up (8)

Subsequently, in step S18, whether or not the deceleration control is completed, that is, the increase in the target braking force F ^* is canceled in step S16, and the target engine torque T ^* is determined as a current driver request by the processing in step S17. It is determined whether or not the engine torque has returned to T _driver . Here, when the increase in the target braking force F ^* is released and the target engine torque T ^* is restored to T _driver , it is determined that the deceleration control is completed, and the process proceeds to step S19.

In step S19, the deceleration control flag Fc is reset to “0”, and then the process proceeds to step S14.
On the other hand, when the increase in the target braking force F ^* is not canceled or the target engine torque T ^* has not returned to T _driver in step S18, it is determined that the deceleration control has not ended, and the above-described process continues. The process proceeds to step S14.

Next, the preload control process executed by the controller 6 will be described.
FIG. 6 shows a flowchart of the processing procedure.
As shown in FIG. 6, first, in step S31, the vehicle speed V is read. For example, the turning speed V calculated in step S2 is read.
Subsequently, in step S32, the target turning speed (target vehicle speed) V ^* is read. For example, the target turning speed V ^* calculated in step S4 is read.

In step S33, the lateral acceleration Yg is read. For example, the lateral acceleration generated in the vehicle is detected by the lateral acceleration sensor 5.
Subsequently, in step S34, a predetermined time Δt necessary for the preload control is set. The predetermined time Δt is set as a value that exhibits the effect by the preload control. For example, Δt is 300 msec.

Further, a predetermined time Δt is set based on the lateral acceleration Yg read in step S33. Specifically, the predetermined time Δt is increased as the lateral acceleration Yg increases. Note that the predetermined time Δt may be set based on the yaw rate φ. In this case, the predetermined time Δt is increased as the yaw rate φ increases.
FIG. 7 shows an example of a characteristic diagram (table) for setting the predetermined time Δt based on the lateral acceleration Yg (or yaw rate φ). As shown in FIG. 7, the predetermined time Δt becomes a small value in a region where the lateral acceleration Yg is small, and when the lateral acceleration Yg becomes a certain value, it has a proportional relationship that increases with the lateral acceleration Yg, and then increases to a certain lateral acceleration Yg. When it reaches, it becomes a constant value with a large value. Thus, as a rule, the larger the lateral acceleration Yg, the larger the predetermined time Δt.

Subsequently, in step S35, a target turning vehicle speed (target vehicle speed, hereinafter referred to as an estimated target turning vehicle speed) V ^* _prefill after a predetermined time Δt is calculated using the following equation (9).
V ^* _prefill = V ^* + dV ^* / dt × Δt (9)
Subsequently, in step S36, the vehicle speed V read in step S32 is compared with the estimated target turning vehicle speed V ^* _prefill calculated in step S35. If the vehicle speed V is _higher than the estimated target turning vehicle speed V ^* _prefill (V> V ^* _prefill ), the process proceeds to step S37, and if the vehicle speed V is _{equal to} or less than the estimated target turning vehicle speed V ^* _prefill (V ≦ V ^* _prefill ). The process proceeds to step S39.

In step S37, the preload control determination flag _Fprefill is set to ON ( _Fprefill = ON).
Subsequently, in step S38, preload control (braking fluid pressure increase control) is performed. Then, the process shown in FIG. 6 ends.
Here, in the preload control (braking fluid pressure increase control), when the brake fluid pressure is increased, the driver does not give a feeling of deceleration of the vehicle, or the brake pad of the brake device does not transmit force to the rotor. Increase the brake fluid pressure to the extent of contact.
In step S39, the preload control determination flag _Fprefill is set to OFF ( _Fprefill = OFF). And the process shown in the said FIG. 6 is complete | finished, without performing the preload control of the said step S38.

As described above, the preload control of the brake fluid pressure is performed.
If the preload control has already been executed (if the preload control has been executed in step S38), the condition for proceeding to step S39 (the preload control end condition) is the vehicle speed V is the estimated target turn. The vehicle speed V ^* _prefill may be equal to or less than a value _obtained by adding a predetermined value V ^* _offset1 (V ≦ V ^* _prefill + V ^* _offset1 ).

Further, under the following conditions, preload control is prohibited because it is not necessary (F _prefill = OFF).
(1) When the turning control itself is in the OFF mode state.
(2) The vehicle speed V is equal to or lower than a predetermined low vehicle speed V _low1 (for example, 30 km / h), and one wheel speed Vwi is a low vehicle speed V _low2 (for example, 3 km / h) among the wheel speeds. However, this condition is a condition only at the start of the preload control, and this condition is excluded during the preload control.
(3) The driver is depressing the brake pedal. For example, when the master cylinder pressure Pm is larger than a predetermined value _Pmin (Pm> _Pmin ).

  In the description of the first embodiment, the processing of step S6 to step S14 of the controller 6 is the braking in which the turning state amount of the vehicle is set according to the limit turning state amount that allows the vehicle to travel stably. A determination means for determining that the operation threshold has been exceeded, a calculation means for calculating a target deceleration necessary for maintaining a stable turning of the vehicle, and a turning state of the vehicle by the determination means When it is determined that the vehicle has exceeded, a control unit that applies a braking force according to the target deceleration obtained by the calculation unit to the vehicle is realized, and the process of step S36 of the controller 6 is performed after a predetermined time has elapsed from the present time. An estimation means for estimating whether or not the amount of turning state of the vehicle exceeds the braking operation threshold value is realized, and the process of step S34 of the controller 6 is performed based on the traveling state of the vehicle. A setting means for setting the interval is realized, whereby when the control means estimates that the estimation means exceeds the braking operation threshold after the predetermined time has elapsed, the response for applying braking force is improved. The preliminary operation is realized.

Here, the target turning vehicle speed V ^* is the braking operation threshold value, the turning vehicle speed V is the turning state quantity of the vehicle, Δt is the predetermined time, and the estimated target turning vehicle speed V ^* _prefill has passed the predetermined time. It is a later braking operation threshold value, and the lateral acceleration Yg (or yaw rate φ) is a value indicating the running state of the vehicle.

(Operation, action and effect)
Next, the operation, action, and effect will be described.
Now assume that the vehicle is turning. At this time, when the target deceleration Xg ^* is 0 or less (determination in Step S6 is “No”), it is determined that deceleration control, that is, automatic deceleration is not necessary because stable turning is maintained. Therefore, the engine output control device 7 is brought into a non-driving state so that the normal engine torque according to the driver's accelerator operation is obtained, and the braking force control device 9 is set so as to be a normal brake according to the driver's brake operation. To the non-driven state.

From this state, when the driver's steering operation amount increases or the driver's accelerator operation amount increases and the target deceleration Xg ^* becomes larger than 0 (the determination in step S6 is “Yes”). That is, when the turning vehicle speed V that is the amount of turning state of the vehicle reaches the target turning vehicle speed V ^* that is the braking operation threshold value, the turning state of the vehicle is approaching the limit of turning performance. Judge that deceleration is required.

Therefore, in order to achieve the target deceleration Xg ^* , the braking force control device 9 is driven to increase the hydraulic pressure of each wheel cylinder 11i, and the engine output control device 7 is driven to reduce the engine torque. Thus, automatic deceleration is performed to achieve a stable turning (step S8, step S9, step S14).
At this time, if the driver is stepping on the accelerator pedal, the engine torque may be reduced to zero when the braking force is generated by automatic deceleration, but if the engine torque is reduced to zero, the accelerator pedal is It gives a driver a feeling of stall. Conversely, if the deceleration control is terminated with priority given to the driver's intention to accelerate, there is a risk that stable turning of the vehicle cannot be ensured.

The engine torque required to maintain the vehicle speed is higher when the vehicle speed is higher than when the vehicle speed is low. Therefore, in reducing the engine torque to the lower limit value ^T _{* MIN,} it sets the lower limit value ^T _{* MIN} engine torque as turning velocity V of the vehicle is high to a high value (step S10).
As a result, when the engine torque is reduced to the lower limit value T ^* _MIN , excessive torque reduction is prevented, and the driver who has performed the accelerator operation is not given a sense of unnecessary stall. Conversely, by setting the lower limit value T ^* _MIN of the engine torque to a lower value as the turning speed V is lower, excessive engine torque can be eliminated and stable turning traveling of the vehicle can be ensured.

Thus, when the target deceleration Xg ^* is reduced to 0 or less and the vehicle can return to a stable turning state by the deceleration control by increasing the braking force and decreasing the engine torque (the determination in step S6 is “No”). ) The braking force increased by the deceleration control is gradually decreased, and the engine torque is gradually increased to the driver request engine torque T _driver (steps S16 and S17).

When the braking force increased by the deceleration control is released and the engine torque returns to the driver request engine torque T _driver (determination in step S18 is “Yes”), the braking force control device 9 and the engine Both the output control device 7 and the output control device 7 are brought into a non-driven state, and the deceleration control is finished.
As described above, deceleration control is performed based on the turning state when the vehicle is turning.

When the vehicle speed V is larger than the estimated target turning vehicle speed V ^* _prefill, which is the target turning vehicle speed V ^* after a predetermined time Δt (determination in Step S36 is “Yes”), the brake fluid pressure preload control is performed. Here, in the preload control (brake hydraulic pressure increase control), when the braking force is increased, the driver does not give the driver a feeling of deceleration of the vehicle, or the brake pad of the brake device makes contact without transmitting the force to the rotor. Increase the brake fluid pressure to the extent you want. On the other hand, when the vehicle speed V is _{equal to} or less than the estimated target turning vehicle speed V ^* _prefill (determination in Step S3 is “No”), such preload control of the brake fluid pressure is not performed.

There is an initial delay time until the deceleration control effectively generates deceleration (until the brake fluid pressure can be increased). In this embodiment, preload control is performed to reduce the delay time and improve the initial response. In the preload control of the present embodiment, a preload start timing is not simply set, but a delay time Δt that can ensure the target preload before the shift to the deceleration control is assumed, and as shown in FIG. When the turning vehicle speed V (actual vehicle speed) of the vehicle is estimated to exceed the target turning vehicle speed V ^* _prefill , the brake fluid pressure preload is started.

  In other words, regardless of the turning state at that time or the target turning state, the preload control of the deceleration control is effectively activated by a predetermined time Δt before the timing at which the deceleration control is to be started stably. As a result, the brake hydraulic pressure is increased, and the hydraulic pressure responsiveness at the initial stage where the deceleration control is to be activated is remarkably improved. FIG. 9 shows an example of a time chart of control based on this embodiment.

In this embodiment, the predetermined time Δt is set based on the lateral acceleration Yg (or yaw rate φ). Specifically, the predetermined time Δt is increased as the lateral acceleration Yg increases. Here, as the predetermined time Δt increases, the estimated target turning vehicle speed V ^* _prefill is set to be larger (formula (9)), and when the vehicle speed V is _higher than the estimated target turning vehicle speed V ^* _prefill , the brake fluid pressure Therefore, as the lateral acceleration Yg increases, the braking fluid pressure preload becomes easier to operate, and as the lateral acceleration Yg decreases, the braking fluid pressure preload becomes difficult to operate.

For example, when driving on a straight road, a rough road such as a wandering road or an uneven road, the driver maintains the driving state while giving minute correction steering. On the other hand, the steering reaction force becomes small near the steering neutral point. For this reason, when the driver near the steering neutral point is the modified steering, the steering speed is momentarily increased, as described above, calculates a yaw rate estimated value phi _D based on the steering angle theta, the by calculates the target turning velocity V ^* on the basis of the yaw rate estimated value phi _D (larger yaw rate estimated value phi _D is by the target turning velocity V ^* decreases), the vehicle speed V is estimated target turning vehicle speed V ^* becomes larger than the _prefill, as a result, in spite of being a straight-ahead driving, etc., resulting in preload the unnecessary braking fluid pressure. In this case, the durability and sound vibration of the actuator are affected.

  However, as the lateral acceleration Yg becomes smaller as in the present embodiment, the braking fluid pressure preload becomes harder to operate, and the braking fluid pressure preload in the traveling scene where deceleration control is not necessary in the first place, such as during straight traveling. As described above, the driver performs the correction steering near the steering neutral point, so that the steering speed is instantaneously increased, and as a result, the braking hydraulic pressure is preloaded. The malfunction of the preload control of the brake fluid pressure can be prevented.

Further, as described above, as the preload control termination condition, the vehicle speed V is equal to or less than a value _obtained by adding a predetermined value V ^* _offset1 to the estimated target turning vehicle speed V ^* _prefill (V ≦ V ^* _prefill + V ^* _offset1 ). Thus, hysteresis can be provided between the start condition and the end condition of the preload control, thereby preventing hunting due to repetition of the preload control operating state and non-operating state.

(Second Embodiment)
Next, a second embodiment will be described.
(Constitution)
The second embodiment is a braking force control device to which the present invention is applied. The configuration of the braking force control device of the second embodiment is the same as the configuration of the braking force control device of the first embodiment (see FIG. 1). Further, the braking force control device of the second embodiment performs a turning traveling control process, and the content of the processing is the turning traveling control processing by the braking force control device of the first embodiment (FIG. 3). The same. However, in the braking force control apparatus of the second embodiment, the processing content of the preload control in step S30 is different from the processing content of the preload control in step S30 in the first embodiment (see FIG. 6).

  FIG. 10 shows a flowchart of a processing procedure of preload control processing by the braking force control apparatus of the second embodiment. In the second embodiment, steps S41 to S45 are provided instead of the steps S35 and S36 in the first embodiment. In the following description, in the processing of the braking force control device of the second embodiment, the same reference numerals as those of the processing of the braking force control device of the first embodiment are the same unless otherwise specified. The explanation is omitted as it is.

As shown in FIG. 10, in step S41, the reciprocal 1 / V of the vehicle speed V read in step S1 is calculated. Subsequently, in step S42, the reciprocal 1 of the target turning speed V ^* read in step S32. / V ^* is calculated, and then, in step S43, a change amount d (1 / V ^* ) / dt of the reciprocal 1 / V ^* of the target turning speed V ^* calculated in step S42 is calculated.

Then at step S44, by using the amount of change ^{d (1 / V *) /} dt of the calculated target turning velocity ^{V *} reciprocal 1 / ^{V *} and the calculated at the step S43 in step S42, the following (10 ) To calculate the reciprocal estimated value 1 / V ^* _prefill of the target turning vehicle speed V ^* after a predetermined time Δt.
1 / V ^* _prefill = 1 / V ^* + d (1 / V ^* ) / dt × Δt (10)
Subsequently, in step S45, the reciprocal 1 / V of the vehicle speed V calculated in step S41 is compared with the reciprocal estimated value 1 / V ^* _prefill calculated in step S45. If the reciprocal 1 / V is larger than the reciprocal estimated value 1 / V ^* _prefill (1 / V> 1 / V ^* _prefill ), the process proceeds to step S37, where the reciprocal 1 / V is reciprocal estimated 1 / V. If V ^* _prefill or less (1 / V ≦ 1 / V ^* _prefill ), the process proceeds to step S39.

As in the first embodiment, in step S37, the preload control determination flag _Fprefill is set to ON ( _Fprefill = ON), and in the subsequent step S38, preload control (brake hydraulic pressure increase control) is performed. . In step S39, the preload control determination flag _Fprefill is set to OFF ( _Fprefill = OFF), and the processing shown in FIG. 6 ends without performing the preload control in step S38.

In the second embodiment as well, when the preload control is already executed (when the preload control is executed in step S38), the condition for proceeding to step S39 (condition for terminating the preload control) is set. The reciprocal 1 / V may be equal to or less than a value _obtained by adding a predetermined value V ^* _offset2 to the reciprocal estimated value 1 / V ^* _prefill (V ≦ V ^* _prefill + V ^* _offset2 ). Thereby, hysteresis can be provided between the start condition and the end condition of the preload control, and hunting due to repetition of the preload control operation state and the non-operation state can be prevented.

(Operation, action and effect)
Next, the operation, action, and effect will be described.
In particular, in the second embodiment, as described above, when the reciprocal 1 / V of the vehicle speed V is larger than the reciprocal estimated value 1 / V ^* _prefill of the target turning vehicle speed V ^* after the predetermined time Δt (in step S45). When the determination is “Yes”), the brake fluid pressure preload control is performed.
Here, the estimated target turning vehicle speed V ^* _prefill target turning velocity V used to calculate the ^*, when running straight, it may become infinite equivalent value. For example, according to the equation (2), the target turning speed V ^* increases as the yaw rate φ decreases. Therefore, when the vehicle is traveling straight (when the yaw rate φ is approximately 0), the target turning speed V ^* is infinite. It becomes a considerable value.

If an estimated target turning vehicle speed V ^* _prefill , which is a target turning speed V ^* after a predetermined time Δt is to be predicted using such a target turning speed V ^* , the vehicle goes straight from a straight drive to a slightly turning state, and is greatly increased. The estimated target turning vehicle speed V ^* _prefill changes, and the subsequent change in the estimated target turning vehicle speed V ^* _prefill cannot be accurately predicted.
For this reason, in the second embodiment, when going straight from turning straight, the reciprocal estimated value 1 / V ^* _{prefill of} the target turning vehicle speed V ^* increases from 0. The estimated target turning vehicle speed V ^* _prefill , which is the target turning speed V ^* after a predetermined time Δt, can be accurately predicted by a simple prediction method. In addition, since it does not become infinite, the slope does not become discontinuous when hitting a limiter or the like, and accurate prediction can be performed in this region.

The embodiments of the present invention have been described above. However, the present invention may be realized as an embodiment with the following configuration.
That is, in the embodiment, the predetermined time Δt is set based on the lateral acceleration Yg and the yaw rate φ. On the other hand, for example, the predetermined time Δt may be set based on the vehicle speed V. FIG. 11 shows an example of a characteristic diagram (table) for setting the predetermined time Δt based on the lateral acceleration Yg (or yaw rate φ) using the vehicle speed (turning vehicle speed) V as a parameter.

  As shown in FIG. 11, as the lateral acceleration Yg (or yaw rate φ) increases, the predetermined time Δt is increased, and as shown by a change from a solid line to a dotted line in FIG. The predetermined time Δt is increased as the vehicle speed V increases. As a result, as the vehicle speed V increases, the braking fluid pressure preload becomes easier to operate, and as the vehicle speed V decreases, the braking fluid pressure preload becomes difficult to operate.

  For example, when the vehicle speed is high, the vehicle behavior changes more quickly than when the vehicle speed is low, and therefore deceleration control with higher responsiveness is required. On the other hand, when the vehicle speed is high, background noise becomes larger than when the vehicle speed is low, thereby reducing the driver's uncomfortable feeling with respect to sound vibration. For this reason, as in the present embodiment, as the vehicle speed V increases, it becomes easier to operate the preload of the brake fluid pressure, thereby ensuring the responsiveness of the deceleration control when the vehicle speed is high, and against the vibration. The driver's uncomfortable feeling can be reduced.

Moreover, in the said embodiment, the drive torque which acts on a drive wheel is reduced by reducing an engine torque. On the other hand, for example, the drive torque acting on the drive wheels may be reduced by controlling the transmission torque in the transmission.
In the above-described embodiment, the target deceleration Xg ^* is calculated based on the deviation ΔV between the turning speed V and the target turning speed V ^* . When the target deceleration Xg ^* is greater than 0, deceleration control, that is, automatic It is slowing down. On the other hand, for example, the deceleration control may be performed when the turning speed V becomes larger than the target turning speed V ^* (V> V ^* ). Further, not only the turning speed but also the turning radius and the target turning radius may be calculated, and automatic deceleration may be performed when the turning radius becomes smaller than the target turning radius. It is only necessary that the deceleration control can be performed so as not to exceed the limit of the turning performance capable of stably turning.

  Moreover, in the said embodiment, the hydric brake which used hydraulic pressure as the transmission medium is employ | adopted as a braking mechanism which applies a brake. On the other hand, a cable, a link, or any other braking mechanism using air pressure may be adopted as the transmission medium. Furthermore, even if the disc rotor is not a friction brake that generates a braking force by a frictional resistance, such as pressing the disc rotor with a brake pad or pressing a brake shoe against the inner peripheral surface of the brake drum, an electromagnetic that generates a braking force by a magnetic resistance. Any other braking mechanism such as a brake, an aerodynamic brake that generates a braking force by air resistance, and a regenerative brake that generates a braking force by power generation may be employed.

It is a block diagram which shows schematic structure of the braking force control apparatus of embodiment of this invention. FIG. 3 is a hydraulic circuit diagram of the braking force control device. It is a flowchart which shows the turning traveling control process by the said braking force control apparatus. It is a block diagram which shows the calculation procedure of a yaw rate. It is a control map used for calculation of a yaw rate estimated value. It is a flowchart which shows the preload control process of the brake fluid pressure by the said braking force control apparatus. It is a characteristic view showing the relationship between the lateral acceleration Yg (or yaw rate φ) and the predetermined time Δt. It is a time chart example for demonstrating 1st Embodiment. It is a time chart example for demonstrating 1st Embodiment. It is a flowchart which shows the preload control process of the braking hydraulic pressure by the braking force control apparatus of 2nd Embodiment. FIG. 5 is a characteristic diagram showing a relationship between a vehicle speed V and a predetermined time Δt.

Explanation of symbols

  1 wheel speed sensor, 2 steering angle sensor, 3 yaw rate sensor, 4 accelerator sensor, 5 lateral acceleration sensor, 6 controller, 7 engine output control device, 9 braking force control device, 10 master cylinder, 11FL to 11RR wheel cylinder, 12A 12B 1st gate valve, 13FL-13RR inlet valve, 14 accumulator, 15FL-15RR outlet valve, 16A, 16B 2nd gate valve, 17 pump, 18 damper chamber

Claims (6)

A determination means for determining that the turning state amount of the vehicle has exceeded a braking threshold value set in accordance with a limit turning state amount at which the vehicle can stably travel; and for maintaining stable turning of the vehicle And a calculation means for calculating a required target deceleration, and when the determination means determines that the turning state of the vehicle has exceeded the braking operation threshold value, the control according to the target deceleration obtained by the calculation means. A control means for applying power to the vehicle, and a braking force control device for the vehicle,
An estimation means for estimating whether a turning state amount of the vehicle exceeds the braking operation threshold after a predetermined time has elapsed from the present time, and a setting means for setting the predetermined time based on the running state of the vehicle,
The control means starts a preparatory operation for increasing the braking force application responsiveness when the estimating means estimates that the braking operation threshold is exceeded after the lapse of the predetermined time. Braking force control device.   The braking force control device for a vehicle according to claim 1, wherein the traveling state of the vehicle is a lateral acceleration or a yaw rate of the vehicle.   3. The vehicle braking force control apparatus according to claim 1, wherein the setting unit lengthens the predetermined time as the lateral acceleration or yaw rate of the vehicle as the traveling state of the vehicle increases. 4.   4. The vehicle braking force control apparatus according to claim 2, wherein the setting means lengthens the predetermined time set according to the lateral acceleration or yaw rate as the vehicle speed increases. 5.   The estimation means estimates whether or not the turning state amount of the vehicle exceeds the braking operation threshold value after a predetermined time has elapsed from the present time, based on the reciprocal number of the turning state amount and the reciprocal number of the braking operation threshold value. The vehicle braking force control device according to any one of claims 1 to 4, wherein the vehicle braking force control device is a vehicle braking force control device. When it is determined that the turning state of the vehicle has exceeded a braking operation threshold value set in accordance with a limit turning state amount at which the vehicle can stably travel, a vehicle braking force control device that applies a braking force to the vehicle is provided. And
When it is estimated that the amount of turning state of the vehicle exceeds the braking operation threshold after a predetermined time has elapsed from the present time, a preliminary operation for increasing the braking force application responsiveness is started, and the predetermined time is A braking force control device for a vehicle, wherein the braking force control device is set based on a traveling state of the vehicle.

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