JPH10236290A - Braking control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a shift shock at shift-down time in a power-off condition by automatically adding braking force until a prescribed time passes after shift-down is completed from foreseeing time by foreseeing information on the shift-down of an automatic transmission, and reducing an adding quantity of the braking force when the shift-down is performed. SOLUTION: A target speed change stage preset in a storage device of an electronic control unit(ECU) 10 is read out according to car speed of a car speed sensor 12 and accelerator opening by an accelerator opening sensor 22, and is supplied to a corresponding solenoid valve in an oil pressure controller 6, and speed change is attained. Fuzzy inference is realized in the ECU 10, and when shift-down is foreseen, a brake actuating signal is gradually supplied to a brake control unit 60, and the shift-down is performed after a prescribed time passes, and since addition of braking force is interrupted for a speed change period simultaneously when the shift-down is started, a speed reduction difference between pre-speed change time and speed change time is reduced, and a shift shock can be sharply reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake control device for a vehicle provided with an automatic transmission, and more particularly to a brake control device capable of reducing shift shock during shifting.

[0002]

2. Related Art In an automatic transmission for a vehicle such as an automobile, a transmission mechanism using a planetary gear is generally used, and a sun gear or a planetary carrier is connected by a hydraulic friction engagement element such as a hydraulic wet multi-plate clutch. Alternatively, a desired gear is obtained by fixing.

[0003] In such an automatic transmission, the shift control is performed based on a shift map using the accelerator opening and the vehicle speed as parameters. That is, a shift command is output when the operation state becomes a downshift timing or an upshift timing on the shift map, and the operating oil pressure discharged from the disengagement-side hydraulic friction engagement element in accordance with the shift command, The operating hydraulic pressure supplied to the hydraulic friction engagement element on the side is controlled to change the gear.

[0004] By the way, when the hydraulic friction engagement element on the disengagement side and the hydraulic friction engagement element on the coupling side are exchanged in this way, a so-called shift shock occurs during the shift because the gear ratio is different before and after the shift. Occur. This shift shock is very unpleasant for the occupants of the vehicle, and it is desired to reduce the shift shock as much as possible. Therefore, a braking control device that uses a braking device such as a brake to apply a braking force to the vehicle during gear shifting, thereby lowering the rotation speed on the output shaft side and reducing shift shock at low cost has been proposed. It is disclosed in JP-A-8-85373.

[0005]

However, the braking control disclosed in the above publication is mainly applied at the time of an upshift during acceleration running, that is, at the time of a power-on upshift while depressing an accelerator pedal. Therefore, the apparatus disclosed in the above publication is effective when, for example, the downshift is performed when the accelerator pedal is decelerated and decelerated, that is, when the power-off downshift is performed. It has not become.

That is, for example, when a downshift is performed while the driver is releasing the accelerator pedal and decelerating the vehicle during traveling, the gear ratio of the lower gear is set lower. Is large, a deceleration shock similar to sudden braking occurs, but such a shock cannot be avoided. It is extremely uncomfortable that such a deceleration shock is generated particularly during high-speed running, and it is not preferable because the running stability of the vehicle is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vehicle brake control device capable of preventing a shift shock during a downshift in a power-off state. is there.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, a first aspect of the present invention is a braking control for a vehicle having an automatic transmission mounted on the vehicle and a braking device for applying a braking force to the vehicle. A shift-down forecasting means for foreseeing a downshift of the automatic transmission; and, based on information from the shift-down foreseeing means, the braking from the foreseeing to a predetermined time after the completion of the downshift. Braking force addition control means for automatically adding a braking force to the device;
An additional amount limiting means for reducing the additional amount of the braking force by the braking force additional control means during the downshift is provided.

Therefore, when the downshift of the automatic transmission is foreseen, the braking force is applied by the braking force adding control means, but when the downshift is actually performed, the braking force is applied by the additional amount limiting means. The added amount is reduced. As a result, the vehicle is decelerated before the downshift is started, and at the time of the downshift, the engine brake is prevented from increasing due to a rotational speed difference based on the difference in the gear ratio between before and after the shift. The deceleration difference of the vehicle can be kept small. Therefore, the shift shock caused by the engine brake during downshifting is greatly reduced, and the occupant is preferably prevented from feeling uncomfortable during downshifting.

Further, in the invention of claim 2, the additional amount limiting means cancels the application of the braking force by the braking force applying means. Therefore, when downshifting is performed, an increase in engine brake caused by a rotational speed difference based on a gear ratio difference before and after shifting is completely prevented, and a difference in deceleration between the vehicle before shifting and during shifting is extremely small. Therefore, it is possible to more suitably prevent the occupant from feeling uncomfortable when downshifting.

In the invention according to a third aspect, the braking force adding control means gradually increases the braking force from the time of the prediction and gradually reduces the braking force after the completion of the downshift. Therefore, when a downshift of the automatic transmission is predicted, the braking force is gradually increased by the braking force adding control means, and the vehicle gradually decelerates without abrupt deceleration before the downshift. The feeling of strangeness is prevented. Further, after the downshift is completed, the braking force is gradually reduced, and the occupant is prevented from feeling uncomfortable even after the downshift.

[0012] In the invention according to claim 4, the vehicle includes:
An accelerator pedal for performing an acceleration operation, and an accelerator operation state detection unit for detecting an operation state of the accelerator pedal, wherein the braking force addition control unit includes an accelerator operation state detection unit that returns the accelerator pedal to a return state. It is characterized in that a braking force is applied when it is detected that there is something.

Accordingly, when the downshift of the automatic transmission is predicted when the vehicle is decelerating while the accelerator pedal is returned, that is, in the power-off state, the braking force adding control is performed. Shift shock during deceleration traveling of the vehicle is reduced, and the occupant is preferably prevented from feeling uncomfortable during deceleration traveling. Further, when the vehicle is traveling at a relatively high speed, the traveling stability of the vehicle is not impaired by reducing the shift shock.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a power plant of a vehicle (a passenger car or the like) including a braking control device according to the present invention. As shown in the figure, an automatic transmission (A /
T) 2 is connected, and the automatic transmission 2 is connected to drive wheels (not shown) via the output shaft 3.

The automatic transmission 2 mainly includes a torque converter 4, which is a fluid coupling, a transmission main body 5, and a hydraulic controller 6. The transmission body 5 incorporates a plurality of hydraulic friction engagement elements such as a hydraulic clutch and a hydraulic brake, in addition to a plurality of sets of planetary gears, according to a combination of engagement of the plurality of hydraulic friction engagement elements. The gear position is determined.

The hydraulic controller 6 has a hydraulic circuit (not shown) corresponding to each of the plurality of hydraulic friction engagement elements, in addition to a hydraulic circuit integrally formed, and corresponding to the plurality of hydraulic friction engagement elements. A plurality of solenoid valves for supplying and releasing hydraulic pressure from the solenoid valve are housed. The plurality of solenoid valves of the hydraulic controller 6 are electrically connected to an electronic control unit (ECU) 10, and are switched and controlled according to a drive signal from the ECU 10.

The structures of the torque converter 4, the transmission main body 5, and the hydraulic controller 6 are known, and a detailed description thereof will be omitted. The ECU 10 includes an input / output device (not shown), a storage device (non-volatile RAM, ROM, etc.) containing a large number of control programs, and a central processing unit (CP).
U), a timer counter, etc., on its input side, a vehicle speed sensor 12 for detecting a vehicle speed V, an operation amount of an accelerator pedal 20 for adjusting the output of the engine 1 and performing an acceleration operation of the vehicle, that is, an accelerator opening. The accelerator opening sensor (accelerator operation state detecting means) 22 for detecting θA, the operation amount of a steering wheel (not shown) for steering the vehicle, that is, the steering wheel angle sensor 30 for detecting the steering wheel angle θH, and the current state of the automatic transmission 2 The shift speed sensor 40 and the like for detecting the shift speed are connected.

The vehicle speed sensor 12 detects, for example, the rotation speed of the output shaft 3, and the rotation speed of the output shaft 3 is converted into a vehicle V in the ECU 10. Also,
As shown in FIG. 1, the vehicle has a shift mode of the automatic transmission 2 which is an automatic shift mode, that is, a traveling range (D range).
A select lever 7 is provided which can be switched to a manual shift mode, that is, a manual range (M range), a parking range (P range), a neutral range (N range), and a reverse range (R range) of the first speed and the second speed. And
The input side of the ECU 10 is also connected to an inhibitor switch 8 for detecting the selected position of the select lever 7.

The input side of the ECU 10 is also connected to road condition detecting means 50 for detecting road conditions in addition to the above. The road condition detecting means 50 mainly detects a road gradient correlation value XR. Specifically, the road condition detecting means 50 includes, for example, an engine driving force,
A gradient correlation value XR is calculated from the following equation (1) based on the aerodynamic resistance, the rolling resistance, and the acceleration resistance, and the calculated value is supplied to the ECU 10.

Gradient correlation value XR = engine driving force−aerodynamic resistance−rolling resistance−acceleration resistance (1) Hereinafter, each term on the right side will be briefly described. The engine driving force is calculated by the following equation (2). Engine driving force = TE.iCON.μ.iT.iF / r (2) where, TE is the engine torque, iCON is the torque ratio of the torque converter 4, μ is the transmission efficiency of the automatic transmission 2, and iT is the automatic transmission. The current gear ratio of the machine 2, iF is the gear ratio (final gear ratio) of a differential gear (not shown), and r is the moving radius of the wheel (tire).

The aerodynamic resistance is calculated by the following equation (3). The aerodynamic drag = ρa · S · Cd · V 2/2 ... (3) where, .rho.a air density, S is the vehicle frontal projected area, Cd is the air resistance coefficient, V is a vehicle speed. The rolling resistance is calculated by the following equation (4).

Rolling resistance = R 0 + (CF ² / CP) (4) where R 0 is the rolling resistance during free rolling, CF is the cornering force, and CP is the cornering power. The rolling resistance R0 during free rolling is calculated from the following equation (5). R0 = μr · W (5) In the equation, μr is a rolling resistance coefficient, and W is a vehicle weight.

The acceleration resistance is calculated by the following equation (6). Acceleration resistance = (W + ΔW) · Gx (6) where W is the vehicle weight, ΔW is a weight equivalent to a rotating portion,
Gx is the vehicle longitudinal acceleration (longitudinal G). The larger the gradient correlation value XR, the higher the slope of the road, the higher the slope.

On the other hand, the output side of the ECU 10 is connected to a plurality of solenoid valves of the hydraulic controller 6 and a brake control unit 60 for applying a braking force to a brake device (for example, a disc brake) 62 provided on wheels. I have. The brake control unit 60
A hydraulic master cylinder (not shown), an electric actuator (not shown) for operating the hydraulic master cylinder, and a brake actuator (not shown) which is connected to the hydraulic master cylinder by a high-pressure oil passage and brakes the brake device 62 by hydraulic pressure. And the ECU 10 is actually connected to the electric actuator. Therefore, when a drive signal is supplied from the ECU 10 to the electric actuator, the hydraulic master cylinder automatically operates to generate a high-pressure oil pressure, and the high-pressure oil pressure activates the brake actuator to generate the braking force in the brake device 62. . The hydraulic master cylinder is connected not only to an electric actuator but also to a brake pedal 64 as in a normal vehicle, so that the brake device 62 can be braked by a driver's operation.

Hereinafter, the operation of the braking control device configured as described above will be described. First, the shift control when the automatic transmission 2 is in the automatic shift mode, that is, when the select position is in the D range, will be briefly described. A shift map (not shown) for setting a target shift speed for selecting and setting a shift speed during automatic shifting is stored in the storage device of the ECU 10. On the shift map for setting the target shift speed, an appropriate shift speed based on the vehicle speed V and the accelerator opening θA, that is, a target shift speed, is set in advance.

Therefore, when the selected position is in the D range during running of the vehicle, first, the target gear position is determined according to the vehicle speed V detected by the vehicle speed sensor 12 and the accelerator opening θA detected by the accelerator opening sensor 22. The target shift speed is read from the setting shift map. Then, the target gear position signal (shift signal) read out and set in this way is supplied to a corresponding solenoid valve in the hydraulic controller 6, whereby the corresponding hydraulic friction among the hydraulic clutch, the hydraulic brake and the like of the transmission body 5 is transmitted. The reengaging of the engagement element is performed, and the shift is achieved.

More specifically, in the gripping of the hydraulic friction engagement element, when the target gear position signal is supplied, first, the engagement of the hydraulic friction engagement element on the releasing side is released, and the transmission main body 5 is temporarily moved. The neutral state is set. Then, thereafter, the engagement of the hydraulic friction engagement element on the coupling side will be performed,
This completes the shift. It should be noted that the timing at which the hydraulic friction engagement element is grasped is constantly learned and controlled so that the engine 1 does not suddenly blow up when the vehicle enters the substantially neutral state.

Further, here, the shift of the automatic transmission 2 can be performed not only based on the target shift speed but also by control based on fuzzy inference according to the driver's intention. Here, fuzzy inference is performed mainly with the information from the road condition detecting means 50 and the steering wheel angle sensor 30 as the antecedent part, and if fuzzy inference is established, the shift control according to the inferior part is performed thereafter. You. Specifically, for example, if the gradient correlation value XR output from the road condition detecting means 50 is large and the road gradient is large and it can be determined that the vehicle is traveling or trying to travel on an uphill road, the gear position is set to the target gear. Even if the gearshift is controlled to the lower gear regardless of the gear, and the steering wheel angle θH output from the steering wheel angle sensor 30 is large and it can be determined that the vehicle is running or about to run on a curved road, the gear is still the same. The shift is controlled to the lower gear irrespective of the target gear.

By the way, when the shift is performed as described above, the gear ratio iT changes before and after the shift, so that when shifting from the lower gear to the higher gear (upshift), the engine rotation on the engine 1 side is performed. The rotation speed of the output shaft 3 becomes faster than the speed Ne. On the other hand, during a shift (downshift) from the higher gear to the lower gear, the rotation speed of the output shaft 3 becomes larger than the engine rotation speed Ne of the engine 1. Slows down. That is, during an upshift, if the output of the engine 1 is constant, the vehicle is rapidly accelerated, and during a downshift, if the output of the engine 1 is constant, the vehicle is rapidly decelerated.

In this case, during an upshift, the driver usually accelerates (power-on upshift) by stepping on the accelerator pedal 20 in many cases. , The engine speed Ne can easily be made to substantially match the rotation speed of the output shaft 3, so that the occupant can continue smooth running without much discomfort due to sudden acceleration.

On the other hand, during a normal downshift other than kick down (power-on downshift) in which the downshift is performed while the accelerator pedal 20 is depressed as in the case of traveling on an uphill road, the driver operates the accelerator pedal 20. In many cases, the vehicle is decelerating (power-off downshift) without returning to stepping on. In this case, a so-called shift shock occurs in the vehicle due to a large engine brake having a difference between the engine speed Ne and the rotation speed of the output shaft 3. The shift shock due to the action of the engine brake tends to increase as the speed is relatively high (for example, the third speed or higher) and the difference between the rotational speeds before and after the shift is increased. The effect increases as the rotation speed of the output shaft 3 increases, that is, as the vehicle speed V increases.

Therefore, in order to reduce the shift shock at the time of such a power-off downshift, a braking force adding control as described below is performed. Referring to FIG. 2, there is shown a flowchart of a braking force addition control routine executed by the ECU 10, and the braking force addition control at the time of a power-off downshift according to the present invention will be described below with reference to FIG. It should be noted that here, from the relatively high gear, the fourth gear, to the third gear
A description will be given of an example of downshifting to a gear.

First, in step S10, the accelerator pedal 20 is returned, and there is no output from the accelerator opening sensor 22, and a downshift from the fourth gear to the third gear is foreseen in the power-off state (accelerator pedal returned state). It is determined whether or not there is a shift down prediction means. Here, the ECU 10
When the fuzzy inference is established and the downshift is expected to be performed, it is assumed that the downshift by power-off is predicted. Therefore,
In this step S10, it is determined whether or not fuzzy inference has been established.

The determination result of step S10 is true (Yes)
If a downshift is foreseen in step S, then step S
At 12, the braking force gradual increase control is performed (braking force addition control means). That is, in this step S12, a brake operation signal is gradually supplied to the brake control unit 60 to apply a braking force. That is, the deceleration a is gradually added to the vehicle. At this time, it is desirable to gradually increase the deceleration a so that the rate of increase da / dt is constant so that the braking proceeds smoothly without giving the occupant an uncomfortable feeling. Note that, regarding the braking force gradual increase control, a control routine separately provided is actually performed.

Referring to FIG. 3, the time change of the shift speed, the amount of braking force applied and the deceleration a at the time of downshifting from the fourth speed to the third speed are shown in (a), (b) and (c), respectively. As described above, when a downshift is foreseen, braking force gradual increase control is performed to apply the braking force as shown in (a) and the rate of change as shown by the solid line in (b). da / dt
The deceleration a is gradually increased at a constant value.

In the next step S14, a braking force gradual increase control continuation signal is output, and the braking force gradual increase control is continuously performed. In the next step S16, it is determined whether or not the downshift command from the fourth gear to the third gear is output from the ECU 10 and the downshift is actually started. As shown in FIG. 3, when a downshift is predicted, a downshift command is normally supplied from the ECU 10 to the brake control unit 60 after a predetermined time ta has elapsed. Then, after the operation delay time td (for example, 0.6 sec) has elapsed, the downshift is actually started. Therefore, here, for example, it is determined whether or not the predetermined time ta and the operation delay time td have elapsed (t> ta + td).

The determination result of step S16 is false (No)
If it is determined that the predetermined time ta and the operation delay time td have not yet elapsed and that the downshift has not actually been started, the braking force gradual increase control is continuously performed. on the other hand,
If the result of the determination in step S16 is true (Yes), and it is determined that the predetermined time ta and the operation delay time td have elapsed and that the downshift has actually been started, then step S1 is performed.
Proceed to 8.

Here, for example, the predetermined time ta
It is determined whether or not the downshift has been started by determining whether or not the operation delay time td has elapsed (t> ta + td). However, the present invention is not limited to this.
The determination may be made based on information from 0. That is, it may be determined that the downshift has been started when the signal corresponding to the fourth gear is turned off.

In step S18, braking force reduction control is performed (addition amount limiting means). That is, in step S18, as shown in FIG. 3C, the application of the braking force is interrupted simultaneously with the start of the downshift (the application of the braking force is released). As described above, if the application of the braking force is interrupted while the downshift is actually being performed, the deceleration a due to the braking is made substantially zero over the interruption period.

Normally, when a downshift is performed, FIG.
As shown in (b), the gripping of the hydraulic friction engagement element is performed, and as described above, the engine brake suddenly acts, and the deceleration a temporarily increases suddenly to the deceleration a2. Therefore,
If the braking force is continuously applied during the downshift (for example, during the time ts), the braking force will be added in accordance with the deceleration a2 by the engine brake. However, as described above, this shift period (during time ts)
By interrupting the application of the braking force over a period of time, the deceleration a2 due to the engine brake can be prevented from increasing. As for the braking force reduction control, a control routine separately provided is actually performed.

In this case, the application of the braking force is interrupted during the downshift, and no braking force is applied. However, actually, the braking force is applied in accordance with the braking force application condition during the braking force gradual increase control. It is better to control to reduce the amount by an appropriate amount. As a result, the difference Δa between the deceleration a1 immediately before the execution of the downshift and the deceleration a2 caused by the engine brake during the downshift is increased by the braking force gradual increase control.
Is the difference .DELTA.a 'between the deceleration a0 (shown by the broken line in FIG. 3) and the deceleration a2 when the braking force is not applied as in the prior art.
(For example, about 0.1 G). For example, according to the experimental results shown in FIG. 3B, the deceleration difference Δa is reduced by about 50% from the conventional deceleration difference Δa ′, and the value is, for example, 0.05 G. Therefore, the shift shock generated during downshifting is reduced, and the occupant is preferably prevented from feeling uncomfortable.

As a result of repeating the experiment, it has become clear that in the braking device of the present invention, the peak value of the deceleration a caused by the engine brake during the downshift is smaller than the deceleration a2. (For example, reduced by about 0.02 G), it can be said that the effect of the present invention is very large. Then, in step S20, it is determined whether or not the shift time ts (for example, 0.3 sec) has elapsed, that is, whether or not the downshift has been completed. If the determination result is false (No), the downshift has been completed. If not, the braking force reduction control is continued. on the other hand,
If the result of the determination is true (Yes) and it is determined that the downshifting has been completed, the process proceeds to step S22.

In step S22, the application of the braking force, which has been suspended, is resumed, and the application of the braking force is continued for a predetermined time t.
The speed is gradually reduced to the normal deceleration a at the third speed stage over c. That is, braking force gradual decrease control is performed (braking force addition control means). Here, the predetermined time tc may be set arbitrarily. As a result, the deceleration a2 caused by the engine brake during the downshift does not suddenly decrease, and the occupant is also suitably prevented from feeling uncomfortable.

Here, as shown in FIG. 3, the braking force addition amount at the time of resumption is substantially the same as the braking force addition amount immediately before interruption, but it is not always necessary to make the same. Also, in this braking force gradual decrease control, similarly to the case of the braking force gradual increase control, the decreasing rate da / d of the deceleration a is set so that the braking force is smoothly released without giving the occupant an uncomfortable feeling.
It is desirable to control t to be constant. Note that, also for this braking force gradual decrease control, a separately provided control routine is actually performed.

If the result of the determination in step S10 is false (No), and a downshift at power-off is not foreseen, the process proceeds to step S30. In step S30, it is determined whether or not a downshift command has been output without foreseeing a downshift. If the determination result is false (N
In o), if there is no downshift prediction and no downshift command output, the routine exits without performing any operation.

On the other hand, if the decision result in the step S30 is true (Y
In es), when the downshift command is output without foreseeing the downshift, the process proceeds to step S32, and the braking force gradual increase control is performed as in step S12. That is, even when the downshift is performed without the fuzzy inference being established, the braking force gradual increase control is performed as in the case where the downshift is predicted.

However, if the braking force gradual increase control is performed after the downshift command is output in this manner, the start timing of the application of the braking force is delayed, and the braking force is sufficiently reduced by the time the downshift is performed. It cannot be added. Therefore, in the next step S34,
The temporarily output downshift command is held in the ECU 10. Thus, a sufficient time can be obtained from the start of the braking force gradual increase control to the execution of the downshift, and the deceleration a can be sufficiently increased to the extent indicated by the solid line in FIG. For example, the hold period of the downshift command is preferably set to the above-mentioned predetermined time ta, and in this case, the braking force is added in exactly the same manner as when the braking force gradual increase control is started in anticipation of the downshift, and Similar effects can be obtained.

Then, in the next step S36, it is determined whether or not the time ta has elapsed, and the determination result is false (No).
In the case of, the braking force gradual increase control is continued, while if the determination result is true (Yes), in the next step S38,
The suspension of the downshift command executed in step S34 is released, and the downshift command is supplied to the brake control unit 60.

When the downshift command is supplied in step S38, the process proceeds to step S14, and the braking force gradually increasing control is continued. By the way, in this case, the actual shift down execution timing is delayed by a predetermined time ta compared to the case where the braking force gradual increase control is started based on the preview of the shift down, but this time ta is an extremely short time. (Ta <1 sec), which is sufficiently within a practical range.

As described above, according to the braking control device of the present invention, at the time of the power-off downshift, the downshift is actually performed after the downshift is predicted or the downshift command is output. (The predetermined time ta + the operation delay time td), the braking force is gradually added (gradually increased), and the braking force is reduced while the downshift is actually performed (time ts) (in the above embodiment, the braking force is increased). The addition of the braking force is interrupted), and after the downshift is completed, the application of the braking force is restarted, and the braking force is gradually reduced (gradually reduced).

Accordingly, as shown in FIG. 3 (b), the deceleration a suddenly increases to the deceleration a2 with the change of the hydraulic friction engagement element during downshifting, and the engine brake acts on the vehicle. However, before the downshift is performed, the deceleration a is gradually increased to the deceleration a1, and the difference Δa between the deceleration a2 and the deceleration a1 when the engine brake is applied is determined without control. It is made smaller than in the case (about 50% reduction), and the shift shock is kept small. Therefore, the occupant is preferably prevented from feeling uncomfortable.

In particular, when the vehicle is running at a relatively high speed as in the present embodiment, if the shift shock accompanying the downshift is reduced, a good driver can be obtained without impairing the running stability of the vehicle. Ability can be maintained continuously. For example, in a vehicle equipped with an inter-vehicle distance control system that maintains a constant inter-vehicle distance from a preceding vehicle, braking is automatically performed during high-speed driving, and in many cases, the vehicle is decelerated and shifted down in a power-off state. However, if the braking control device of the present invention is also applied to such a vehicle, the traveling performance of the vehicle can be further improved.

In the above-described embodiment, the automatic transmission 2 is configured to be able to control the shift in accordance with the fuzzy inference, and the shift down at power-off is foreseen based on the establishment of the fuzzy inference. The down prediction is not limited to this, and other methods may be used as long as the down can be predicted. Further, even if there is no means for predicting downshifting, the present invention can be suitably implemented by executing the steps after step S30 in FIG.

In the above embodiment, the power off downshift from the fourth speed to the third speed has been described. However, the present invention is not limited to this, and the power off downshift is performed regardless of the speed. It is better to always perform the braking control.

[0055]

As described above in detail, according to the vehicle braking control apparatus of the first aspect of the present invention, the vehicle is decelerated before the start of the downshift, and when the downshift is performed, before and after the shift is performed. The increase in engine brake caused by the rotational speed difference based on the gear ratio difference can be prevented, and the difference in deceleration between the vehicle before and during the shift can be reduced.

Therefore, the shift shock caused by the engine brake during downshifting can be greatly reduced, and the discomfort felt by the occupant during downshifting can be suppressed. According to the vehicle braking control device of the second aspect, when downshifting is performed, it is possible to completely prevent the engine brake from increasing due to a rotational speed difference based on a difference in gear ratio between before and after the shift, so that the shift before and after the shift is performed. The difference in the deceleration of the vehicle at the time can be kept very small. Therefore, the uncomfortable feeling felt by the occupant at the time of downshifting can be more suitably suppressed.

According to the third aspect of the present invention, when the downshift of the automatic transmission is predicted, the braking force is gradually increased by the braking force adding control means, and the vehicle suddenly stops before the downshift. The vehicle gradually decelerates without decelerating, so that the occupant does not feel discomfort like a deceleration shock. Also, after the downshift is completed, the braking force is gradually reduced,
Even after the downshift, the occupants can be prevented from feeling uncomfortable.

According to the vehicle braking control device of the present invention, when the downshift of the automatic transmission is foreseen when the vehicle is decelerating in the power-off state, the braking force adding control is performed. Therefore, shift shock during deceleration traveling of the vehicle can be reduced, and discomfort felt by the occupant during deceleration traveling can be suitably prevented. Also, if the vehicle is traveling at a relatively high speed,
Deterioration of running stability of the vehicle due to reduction of shift shock can be suitably prevented, and good drivability can be maintained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a braking control device according to the present invention.

FIG. 2 is a flowchart illustrating a control routine of braking force addition control during a power-off downshift.

3 is a time chart showing a time change of a shift speed, a deceleration a, and a braking force addition amount during a power-off downshift based on an execution result of a control routine of FIG. 2;

[Explanation of symbols]

Reference Signs List 1 engine 2 automatic transmission 3 output shaft 4 torque converter 5 transmission body 6 hydraulic controller 7 select lever 8 inhibitor switch 10 electronic control unit (ECU) 12 vehicle speed sensor 20 accelerator pedal 22 accelerator opening degree sensor (accelerator operation state detecting means) 60 Brake control unit 62 Brake device 64 Brake pedal

Claims (4)

[Claims] 1. A brake control device for a vehicle, comprising: an automatic transmission mounted on a vehicle; and a braking device for applying a braking force to the vehicle, wherein a shift-down prediction unit for predicting a shift-down of the automatic transmission; Braking force addition control means for automatically applying a braking force to the braking device from the time of the preview until a predetermined time elapses after the completion of the downshift, based on information from the downshift prediction means, A braking control device for a vehicle, comprising: an additional amount limiting unit that reduces an additional amount of the braking force by the braking force additional control unit during the down operation. 2. The method according to claim 1, wherein the additional amount limiting unit cancels the application of the braking force by the braking force applying unit.
The vehicle braking control device according to claim 1. 3. The braking control device for a vehicle according to claim 1, wherein the braking force adding control means gradually increases the braking force from the time of the foreseeing and gradually reduces the braking force after the completion of the downshift. 4. The vehicle further includes an accelerator pedal for performing an acceleration operation, and accelerator operation state detecting means for detecting an operation state of the accelerator pedal, wherein the braking force adding control means detects the accelerator operation state. 4. The braking control device for a vehicle according to claim 1, wherein a braking force is applied when it is detected by the means that the accelerator pedal is returned.