JP6248477B2 - Vehicle control device - Google Patents

Description

  The present invention relates to a vehicle control device that controls the braking force of each wheel so as to keep the vehicle body speed low.

  Conventionally, there has been proposed a vehicle control device that performs control to keep the vehicle body speed at a low speed by controlling the braking force of each wheel (see, for example, Patent Document 1). For example, as a control to keep the vehicle speed at a low speed, the vehicle speed on the road surface that requires speed adjustment such as off-road such as sand, dirt, rocky road, snowy road, steep slope, etc., called crawl control. Control for maintaining the vehicle speed at a constant speed, and control for maintaining the vehicle body speed at a constant speed on a downhill road called DAC (Downhill Assist Control). For example, in crawl control and downhill assist control, the vehicle body speed is kept low by feedback controlling the braking force of each wheel based on the deviation between the target speed and the vehicle body speed.

Japanese Patent Laid-Open No. 2004-90679

  Like crawl control and downhill assist control, high responsiveness is required in the low-speed region, so it is necessary to quickly increase the wheel cylinder (hereinafter referred to as W / C) pressure. For example, when traveling off-road, the W / C pressure can be increased more quickly because frequent occurrence of a sudden change in the slope or road surface of the vehicle and a sudden change in the vehicle's driving state occurs. It is desirable.

  However, in the conventional method in which the braking force of each wheel is feedback-controlled based on the deviation between the target speed and the vehicle body speed, the target braking force cannot be changed in accordance with the change in the running state of the vehicle. The driver may not be able to respond sufficiently and may make the driver feel uncomfortable. In particular, when a brake system having a high boosting capability such as a hydro booster is used, the W / C pressure can be quickly boosted. However, when a system with a low boosting capability is used, the W It is difficult to increase the / C pressure. For this reason, generating a delay in boosting the W / C pressure gives the driver a sense of incongruity due to a delay in applying the brake, and the braking force varies due to a delay in boosting the W / C pressure or a delay in removing the W / C pressure. Thus, speed hunting in which the vehicle body speed fluctuates around the target speed may occur.

  The present invention has been made in view of the above points, and it is an object of the present invention to provide a vehicle control device that can alleviate a driver's uncomfortable feeling when performing control to maintain the vehicle body speed at a low speed by controlling the braking force of each wheel. And

  In order to achieve the above object, according to the first aspect of the present invention, the feedback braking force is calculated based on the deviation between the vehicle body speed and the target speed every predetermined control period, and the feedback braking force is generated to generate the vehicle body. A feedback control means for performing feedback control to bring the speed close to the target speed, a traveling state determination means for determining whether the vehicle is in a normal traveling state or a stopped vehicle stopped state, and a vehicle stopped state When the determination is made, there is provided a gain correction means for correcting the feedback braking force decreasing-side gain higher for use in the calculation of the feedback braking force than in the normal running state.

  In this way, the vehicle stop state and the normal running state are determined, and correction is performed so that the feedback braking force is more quickly reduced when the vehicle stop state is determined. When the driver sets a target speed and performs vehicle control so that the target speed is reached, for example, when performing crawling control during off-road, the driver basically stops the vehicle. Since it is considered that the vehicle has not been stopped, there is a possibility that the vehicle has stopped even though the vehicle has not been stopped. In such a case, the responsiveness is increased so that the brake can be released more quickly by performing a correction that reduces the feedback braking force more quickly. As a result, the driver's uncomfortable feeling can be alleviated.

In the first aspect of the present invention, the brake operation determining means for determining whether or not the driver has performed a brake operation is provided, and the gain correcting means is configured such that the brake operation is performed when the vehicle is stopped. If determined, the reduction-side gain is corrected to be higher.

  For example, when the feedback braking force is generated so that the vehicle body speed becomes the target speed, when the brake operation is performed, the feedback braking force is quickly released and the W / C pressure is increased based on the driver's brake operation. The braking force that matches the driver's operation can be generated by changing to. For this reason, when a braking operation is performed while the vehicle is stopped, the feedback braking force in the crawl control can be released quickly by performing a correction to further increase the decreasing gain, and a braking force that matches the driver's operation is generated. It becomes possible to make it.

In the second aspect of the invention, the slope acquisition means for acquiring the slope of the road surface of the vehicle is provided, and the gain correction means has a gentler slope when the slope is steep when the vehicle is stopped. Compared to a certain time, the reduction side gain is corrected to be low.

  When the slope of the slope is steep, acceleration is facilitated when the braking force is reduced and the brake is released, but the vehicle cannot be stopped immediately after acceleration. For this reason, when the slope is steep, it is preferable that the gain on the decrease side is made lower than that when the slope is gentle so that the braking force can be gradually reduced so that the vehicle is difficult to accelerate.

The invention according to claim 3 is characterized in that the gain correction means corrects the decrease-side gain high for only one of the two braking systems when correcting the decrease-side gain high.

  In this way, it is possible to prevent excessive brake release that occurs when the brakes are quickly released from all four wheels.

  In this case, when the braking system is a front / rear pipe, the correction for increasing the decrease side gain is not performed for both front wheels, and the correction for increasing the decrease side gain is performed only for both rear wheels. It is preferable. For example, on a downhill, the stability of the vehicle becomes higher if the brakes are released before both front wheels than both front wheels. For this reason, by performing the correction to increase the decrease side gain only for both rear wheels, the brake can be released before both front wheels for both rear wheels, and the stability of the vehicle can be improved. .

1 is a diagram illustrating a system configuration of a braking / driving system of a vehicle to which a vehicle control device according to a first embodiment of the present invention is applied. It is the figure which showed an example of the map which showed the relationship between vehicle stop time and the reduction | decrease side gain BrakeDownGain. It is the figure which showed an example of the map which showed the relationship between a road surface gradient and the reduction | decrease side gain BrakeDownGain. It is the figure which showed an example of the map which shows the relationship between the reduction | decrease side gain BrakeDownGain and the reduction | decrease side gain BrakeDownGainRear of the rear-wheel RR and RL side. It is the flowchart which showed the whole crawl control including TRC. It is the flowchart which showed the whole crawl control including TRC following Fig.5 (a). It is the flowchart which showed the detail of correction | amendment calculation processing of the reduction | decrease side gain BrakeDownGain. It is the time chart which showed the case where correction of decrease side gain BrakeDownGain in feedback control is executed in the downhill. It is the time chart which showed the case where correction of decrease side gain BrakeDownGain in feedback control is executed on the steep downhill.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
FIG. 1 is a diagram showing a system configuration of a braking / driving system of a vehicle to which a vehicle control device according to a first embodiment of the present invention is applied. Here, a case where the vehicle control device according to an embodiment of the present invention is applied to a front drive-based four-wheel drive vehicle in which the front wheel side is a main drive wheel and the rear wheel side is a slave drive wheel will be described. However, the present invention can also be applied to a rear drive base four-wheel drive vehicle in which the rear wheel side is a main drive wheel and the front wheel side is a slave drive wheel.

  As shown in FIG. 1, the drive system of a four-wheel drive vehicle includes an engine 1, a transmission 2, a driving force distribution control actuator 3, a front propeller shaft 4, a rear propeller shaft 5, a front differential 6, a front drive shaft 7, It has a configuration including a differential 8 and a rear drive shaft 9, and is controlled by an engine ECU 10 serving as engine control means.

  Specifically, when the operation amount of the accelerator pedal 11 is input to the engine ECU 10, the engine control is performed by the engine ECU 10, and the engine output (engine torque required for generating the driving force corresponding to the accelerator operation amount) ) Is generated. The engine output is transmitted to the transmission 2 and converted by a gear ratio corresponding to the gear position set in the transmission 2, and then transmitted to the driving force distribution control actuator 3 serving as driving force distribution control means. The transmission 2 includes a transmission 2a and a sub-transmission 2b. During normal traveling, an output corresponding to the gear position set by the transmission 2a is transmitted to the driving force distribution control actuator 3, and during off-road traveling. When the sub-transmission 2b is operated during traveling on a slope or the like, an output corresponding to the gear position set by the sub-transmission 2b is transmitted to the driving force distribution control actuator 3. The driving force is transmitted to the front propeller shaft 4 and the rear propeller shaft 5 in accordance with the driving force distribution determined by the driving force distribution control actuator 3.

  Thereafter, a driving force according to the driving force distribution on the front wheel side is applied to the front wheels FR and FL through the front drive shaft 7 connected to the front propeller shaft 4 via the front differential 6. A driving force according to the driving force distribution on the rear wheel side is applied to the rear wheels RR and RL through a rear drive shaft 9 connected to the rear propeller shaft 5 via a rear differential 8.

  The engine ECU 10 is configured by a known microcomputer including a CPU, ROM, RAM, I / O, and the like, and performs various calculations and processes according to a program stored in the ROM or the like, thereby generating engine output (engine torque). And the driving force generated in each wheel FL to RR is controlled. For example, the engine ECU 10 inputs an accelerator opening by a known method, and calculates an engine output based on the accelerator opening and various engine controls. The engine ECU 10 outputs a control signal to the engine 1 to adjust the fuel injection amount and control the engine output. The engine ECU 10 can determine that the accelerator pedal 11 is on when the accelerator opening exceeds the accelerator-on threshold, but in this embodiment, an accelerator indicating whether or not the accelerator pedal 11 is being operated. A switch 11a is provided, and it is detected that the accelerator pedal 11 is turned on by inputting a detection signal of the accelerator switch 11a. The engine ECU 10 also executes traction control (hereinafter referred to as TRC). For example, the engine ECU 10 acquires information on wheel speed and vehicle body speed (estimated vehicle body speed) from a brake ECU 19 described later, and outputs a control signal to the brake ECU 19 so that acceleration slip represented by these deviations is suppressed. The driving force is reduced by applying a braking force to the wheel to be controlled. Thereby, acceleration slip is suppressed and the vehicle can be accelerated efficiently.

  Although not shown here, the transmission 2 is controlled by the transmission ECU, and the driving force distribution control is performed by the driving force distribution ECU or the like. These ECUs and the engine ECU 10 exchange information with each other through the in-vehicle LAN 12. In FIG. 1, information on the transmission 2 is directly input to the engine ECU 10. For example, gear position information of the transmission 2 output from the transmission ECU is input to the engine ECU 10 through the in-vehicle LAN 12. May be.

  On the other hand, the service brake constituting the braking system includes a brake pedal 13, a master cylinder (hereinafter referred to as M / C) 14, a brake actuator 15, W / C 16FL to 16RR, calipers 17FL to 17RR, disk rotors 18FL to 18RR, and the like. The brake ECU 19 serving as the brake control means is configured.

  Specifically, when the brake pedal 13 is depressed and operated, a brake fluid pressure is generated in the M / C 14 in accordance with the amount of brake operation, and the brake hydraulic pressure is generated via the brake actuator 15 from W / C16FL to 16RR. To be told. Accordingly, the disc rotors 18FL to 18RR are sandwiched by the calipers 17FL to 17RR, so that a braking force is generated. The service brake having such a configuration may be any one as long as it can automatically pressurize W / C 16FL to 16RR. Here, a hydraulic service brake that generates W / C pressure by hydraulic pressure is taken as an example. However, it may be an electric service brake such as a brake-by-wire that electrically generates a W / C pressure.

  The brake ECU 19 is configured by a known microcomputer including a CPU, ROM, RAM, I / O, and the like, and executes various calculations and processes according to a program stored in the ROM or the like to thereby apply a braking force (braking torque). And the braking force generated in each of the wheels FL to RR is controlled. Specifically, the brake ECU 19 receives detection signals from the wheel speed sensors 20FL to 20RR provided in the wheels FL to RR, calculates various physical quantities such as the wheel speed and the vehicle body speed, A detection signal is input, and brake control is performed based on a physical quantity calculation result and a brake operation state. The brake ECU 19 receives the detection signal of the M / C pressure sensor 22 and detects the M / C pressure.

  The brake ECU 19 also performs crawl control, which is vehicle control in off-road, etc., based on the control of the braking force. Specifically, the brake ECU 19 inputs a detection signal of the crawl switch 23 and the target speed setting switch 24 that are operated when the driver requests crawl control, and a detection signal of the acceleration sensor 25 that detects longitudinal acceleration. Crawl control is executed based on the detection signal. The crawl switch 23 is basically considered to be pressed when performing off-road traveling, but the same control is performed even when pressed on a steep slope. The target speed setting switch 24 is used for setting a target speed when the crawl control is executed, and sets the target speed in a speed range of 1 to 5 km / h, for example. In FIG. 1, detection signals from the M / C pressure sensor 22 and the acceleration sensor 25 are input to the brake ECU 19 via the brake actuator 15, but are configured to be input directly from each sensor to the brake ECU 19. It may be.

  As described above, the vehicle braking / driving system system to which the vehicle control device according to the present embodiment is applied is configured. Next, the operation of the vehicle control device configured as described above will be described. In the vehicle control device according to the present embodiment, normal engine control and brake control are also performed as vehicle control. However, since these are the same as conventional ones, crawl control related to features of the present invention will be described here. To do. In the case of the present embodiment, the brake control of the crawl control is executed as the vehicle control, and the brake ECU 19 executes the control. Therefore, the brake ECU 19 constitutes a vehicle control device.

  The crawl control is executed when the driver depresses the crawl switch 23, sets the target speed TBV with the target speed setting switch 24, and makes a crawl control execution request. In the vehicle control apparatus according to the present embodiment, as the crawl control, when the driver sets the target speed TBV, feedback control is performed by setting the control amount of the brake control based on the deviation between the vehicle body speed V0 and the target speed TBV. In addition to the above, processing is performed to improve responsiveness. The target speed TBV can be set by the driver as the crawl switch 23 is operated, and can be arbitrarily set in a speed range of 1 to 5 km / h, for example. The vehicle body speed V0 is calculated by the brake ECU 19, and is calculated by a well-known method based on the wheel speeds obtained from the detection signals of the wheel speed sensors 20FL to 20RR provided in the wheels FL to RR. Basically, based on the deviation between the vehicle speed V0 and the target speed TBV, the control amount of the feedback control increases as the vehicle speed V0 becomes larger than the target speed TBV so that the vehicle speed V0 approaches the target speed TBV. It is trying to become.

  However, if the vehicle's running condition suddenly changes due to a sudden change in the slope or road condition of the vehicle, such as when driving off-road, the responsiveness will be adjusted to the sudden change in the driving condition. It is desirable to change the target braking force well so that the W / C pressure can be increased more quickly. For this reason, in simple feedback control, the target braking force cannot be changed in accordance with the change in the running state of the vehicle, and the driver cannot respond sufficiently, giving the driver a sense of incongruity. If the control amount in feedback control is set large, high responsiveness can be obtained, but the vehicle speed V0 constantly increases and decreases around the target speed TBV and frequent acceleration / deceleration is repeated. It is not preferable to increase.

  Therefore, here, the vehicle stop state and the normal running state are determined as follows, and correction is performed so that the brake control amount in the feedback control is more quickly reduced when the vehicle stop state is determined. In other words, when crawling control is being performed during off-road, etc., it is considered that the driver is basically not trying to stop the vehicle, so it may have stopped without trying to stop the vehicle. There is sex. In such a case, by making a correction so that the control amount of the brake control in the feedback control decreases more quickly, the responsiveness can be increased so that the brake can be released more quickly, and the driver's uncomfortable feeling can be alleviated. To do. Specifically, the following controls (1) to (4) are executed. In this specification, a feedback braking force is described as a control amount of brake control by feedback control, but a braking torque is assumed as the feedback braking force. However, another control amount that can be used as a control amount corresponding to the braking torque, such as a W / C pressure, may be used.

  (1) Deciding between the vehicle stop state and the normal running state. When it is judged that the vehicle is in the stopped state, the feedback braking force FBbrakeForce is reduced more quickly than the normal running state. Perform correction to increase For determining the vehicle stop state and the normal running state, for example, the vehicle body speed V0 is calculated from the wheel speed obtained based on detection signals from the wheel speed sensors 20FL to 20RR, and if the vehicle body speed V0 is 0, the vehicle is stopped. If the state is not 0, the normal running state can be determined. For the decrease side gain BrakeDownGain in feedback control, for example, a map showing the relationship between the vehicle stop time and the decrease side gain BrakeDownGain is created, and the decrease side corresponding to the vehicle stop time using the map gain BrakeDownGainMAP shown in the map Gain BrakeDownGain can be set.

FIG. 2 is a diagram showing an example of a map showing the relationship between the vehicle stop time and the decrease side gain BrakeDownGain. As shown in this figure, the map gain BrakeDownGainMAP is such that the decrease side gain BrakeDownGain becomes a larger value as the vehicle stop time increases, and the decrease side gain BrakeDownGain can be set to this map gain BrakeDownGainMAP.
Here, the map gain BrakeDownGainMAP is increased at a predetermined gradient as the vehicle stop time becomes longer until the vehicle stop time reaches a first predetermined time (for example, 0.5 s), and the vehicle stop time is longer than the first predetermined time. In this case, the map gain BrakeDownGainMAP is further increased and the map gain BrakeDownGainMAP is set to a constant value when the vehicle stop time reaches a second predetermined time (for example, 1.0).

  (2) When the brake pedal 13 is depressed while the vehicle is stopped, the decrease gain BrakeDownGain in the feedback control is increased so that the feedback braking force FBbrakeForce decreases more quickly than in the control in (1). Make corrections.

  When the braking operation is performed when the feedback braking force FBbrakeForce is generated so that the vehicle body speed V0 becomes the target speed TBV, the feedback braking force FBbrakeForce is quickly released and the W / C pressure based on the driver's braking operation is reduced. The braking force that matches the driver's operation can be generated by changing to boosting. For example, when the brake operation is performed is the crawl control termination condition, in that case, the feedback braking force FBbrakeForce in the crawl control is quickly canceled and changed to the increase in the W / C pressure based on the driver's brake operation. One can generate a braking force that matches the driver's operation. For this reason, when the brake pedal 13 is depressed in the vehicle stop state, the feedback braking force in the crawl control can be quickly released by performing a correction to further increase the decreasing side gain BrakeDownGain.

  (3) When the slope of the road surface on which the vehicle is stopped in the vehicle stop state is a steep slope, correction is performed to lower the decrease-side gain BrakeDownGain in the feedback control as compared with a gentle slope. When the slope of the slope is steep, acceleration is facilitated when the braking force is reduced and the brake is released, but the vehicle cannot be stopped immediately after acceleration. For this reason, when the slope of the slope is steep, the reduction gain BrakeDownGain is made lower than when the slope is gentle, so that the braking force can be gently lowered and the vehicle is difficult to accelerate. For the decrease side gain BrakeDownGain in the feedback control, for example, a map showing the relationship between the slope gradient and the decrease side gain BrakeDownGain can be created, and the decrease side gain BrakeDownGain can be set using the map gain BrakeDownSlopeGainMAP shown in the map.

  FIG. 3 is a diagram showing an example of a map showing the relationship between the road surface gradient and the decrease-side gain BrakeDownGain. As shown in this figure, for example, the map gain BrakeDownSlopeGainMAP can be set such that the decreasing gain BrakeDownGain becomes smaller as the road surface gradient increases. Here, the map gain BrakeDownSlopeGainMAP is decreased at a predetermined gradient as the road gradient increases to the negative side until the road gradient becomes a predetermined value (for example, -11.5 deg), and the map gain BrakeDownSlopeGainMAP is decreased when the road gradient becomes a predetermined value or less. This is a map with a larger decline slope. The reduction gain BrakeDownGain can be corrected by multiplying the map gain BrakeDownSlopeGainMAP by the reduction gain BrakeDownGain.

  (4) When performing correction to increase the decrease side gain BrakeDownGain by the control of (1) and (2), the decrease side gain BrakeDownGain is changed for the braking system divided into two systems.

  For example, correction is performed to increase the decrease-side gain BrakeDownGain for only one of the two systems, and correction is not performed for the other systems. In this way, it is possible to prevent excessive brake release that occurs when the brakes are quickly released from all four wheels. In this case, when the braking system is a front and rear pipe, correction for increasing the reduction side gain BrakeDownGainFront is not performed for both front wheels FR and FL, and the reduction side gain BrakeDownGainRear is only applied to both rear wheels RR and RL. It is preferable to perform correction to increase the value. For example, on a downhill, the stability of the vehicle becomes higher if the brakes are released before both front wheels FR and FL on both rear wheels RR and RL. For this reason, it is possible to make the brakes come off before both front wheels FR and FL by correcting the rear gain rake and lower gain BrakeDownGainRear only for both rear wheels RR and RL. It becomes possible to improve the stability of the.

  FIG. 4 is a diagram showing an example of a map showing the relationship between the decrease side gain BrakeDownGain and the rear wheel RR, RL side decrease side gain BrakeDownGainRear. As shown in this figure, for example, as the decrease side gain BrakeDownGain increases, the rear wheel RR and the decrease side gain BrakeDownGainRear on the RL side also increase. However, as the decrease side gain BrakeDownGain increases, the rear wheel RR exceeds the decrease side gain BrakeDownGain. The map gain BrakeDownGainMAPRear in which the rate of increase in the decreasing gain BrakeDownGainRear on the RL side decreases can be obtained.

  The same operation can be performed when the braking system is an X pipe, and the reduction gain BrakeDownGain is set for one of the combination of the right front wheel FR and the left rear wheel RL and the combination of the left front wheel FL and the right rear wheel RR. It is possible to perform correction to increase, and not to perform correction to increase the decrease side gain BrakeDownGain for the other. Furthermore, the correction of the decrease side gain BrakeDownGain may be changed before and after regardless of the piping of the braking system.

  As described above, when the crawl control is executed, the above-described controls (1) to (4) are executed. Next, details of the crawl control executed in this way will be described. FIGS. 5A and 5B are flowcharts showing the entire crawl control including the TRC. The details of the crawl control including the TRC will be described below with reference to this figure.

  First, in step 100, various input processes are performed. Specifically, by inputting the detection signals of the wheel speed sensors 20FL to 20RR and the detection signal of the acceleration sensor 25, the wheel speed VW ** of each wheel FL to RR is calculated and the longitudinal acceleration Gx of the vehicle is calculated. To do. The subscript ** attached to the wheel speed VW ** indicates any of FL to RR, and VW ** is a comprehensive description of the wheel speed of each corresponding wheel FL to RR. is there. In the following description, it is assumed that the subscript ** indicates any of FL to RR.

  In addition, the detection signal of the M / C pressure sensor 22 is input to detect the M / C pressure, or the accelerator opening, the driving force, the gear position of the auxiliary transmission 2b, that is, whether it is located at H4 or L4. Is input from the engine ECU 10 or the like through the in-vehicle LAN 12. Further, detection signals from the crawl switch 23 and the target speed setting switch 24 are input to detect whether or not the driver is requesting crawl control and selecting a target speed.

  Next, the routine proceeds to step 105, where it is determined whether or not the crawl control execution condition is satisfied. Specifically, the gear position of the sub-transmission 2b is set to L4, that is, the gear ratio of the low-speed gear used for off-road or the like. It is determined whether the crawl switch 23 is turned on. Here, if the determination is affirmative, the execution condition for crawl control is satisfied, and therefore the process proceeds to step 110 to set a flag indicating permission for crawl control. If the determination is negative, the execution condition for crawl control is not satisfied. Proceed to, and set a flag indicating that crawl control is prohibited.

  Subsequently, the routine proceeds to step 120, where the vehicle body speed V0 is calculated based on each wheel speed VW **. In step 125, the vehicle body speed DV0 is calculated by time differentiation of the vehicle body speed V0.

Then, it progresses to step 130 and calculates slope slope SLOPE. First, since the difference between the vehicle body acceleration DV0 and the longitudinal acceleration Gx of the vehicle calculated based on the detection signal of the acceleration sensor 25 in step 100 corresponds to the gravitational acceleration component, the slope gradient SLOPE = sin ⁻¹ {(Gx−DV0 ) /9.8} is used to calculate the slope gradient SLOPE.

  Subsequently, the routine proceeds to step 135, where the braking force FOOTBRAKE by the driver's braking operation is calculated. For example, based on the M / C pressure input at step 100, the braking force FOOTBRAKE corresponding to the M / C pressure is calculated. Since the relationship between the M / C pressure and the braking force FOOTBRAKE can be examined in advance by experiments, a map showing the relationship is created and the braking force FOOTBRAKE corresponding to the M / C pressure is used using the map. Can be calculated.

  In step 140, the target speed TBV is calculated. The target speed TBV is basically a speed within a speed range (for example, 1 to 5 km / h) set by the driver with the target speed setting switch 24, but when the driver switches the target speed TBV. Instead of suddenly changing to the target speed TBV after switching, a filter is applied so that the target speed TBV before switching is gradually changed to the target speed TBV after switching. For example, the target speed TBV before switching is changed with a constant gradient from the target speed TBV after switching to the target deceleration (or target acceleration).

  In this way, when the calculation of various parameters is completed, it is determined in step 145 whether or not crawl control is prohibited. If it is prohibited, the feedback braking force FBbrakeForce in the feedback calculation is set to 0 [N] in step 150, and the target pressure TargetPress ** of the W / C pressure of each wheel FL to RR is set to 0 [MPa in step 155. ] To prevent crawling control, and if not prohibited, the process proceeds to step 160.

  In step 160, normal control gain setting is performed. That is, the feedback gain BrakeGain that is normally set to execute the brake control by feedback control, for example, the gains of the P term, I term, and D term in PID control are set. The gain at this time is set to a normal gain that is generally performed as brake control.

  Subsequently, the process proceeds to step 165, and the correction calculation of the decrease side gain BrakeDownGain in the feedback gain BrakeGain is performed by the above-described controls (1) to (4). FIG. 6 is a flowchart showing details of this processing. Here, the flowchart assumes a case where the braking system is configured by front and rear piping.

  First, in step 165a, it is determined whether or not the vehicle body speed V0 is 0 km / h, that is, whether the vehicle is in a stopped state or a normal running state. If a negative determination is made here, the vehicle is in a normal running state, and it is not necessary to perform the controls (1) to (4) described above. The correction values to be applied to the decrease side gain BrakeDownGainFront in the wheels RR and RL are both set to 1.0 so that the decrease side gain BrakeDownGain remains the normal control gain. If the determination in step 165a is affirmative and the vehicle is in a stopped state, the process proceeds to step 165c.

  In step 165c, since the vehicle is in a stopped state based on the determination result in step 165a, the reduction gain BrakeDownGain in the feedback control is increased so that the braking torque decreases more quickly than in the normal running state as the control in (1). Make corrections. Specifically, the map gain BrakeDownGainMAP corresponding to the vehicle stop time is selected from the map shown in FIG. 2 described above, and is set to the decrease side gain BrakeDownGain.

  Thereafter, the process proceeds to step 165d to determine whether or not the vehicle is in a braking state, that is, whether or not the brake pedal 13 has been depressed by the driver. If an affirmative determination is made here, the process proceeds to step 165e, and as the control in (2), the decrease-side gain BrakeDownGain in the feedback control is increased so that the braking torque decreases more quickly than in the control in (1). Make corrections. Specifically, in order to increase the decreasing gain BrakeDownGain set in step 165c, a value obtained by multiplying the decreasing gain BrakeDownGain by a braking gain increase coefficient KGain (for example, 2.0) is set as a new decreasing gain BrakeDownGain. And Then, the process proceeds to Step 165f. On the other hand, if a negative determination is made in step 165d, the process proceeds to step 165f without passing through step 165e.

  In step 165f, as the control in (3), the decreasing gain BrakeDownGain in the feedback control is corrected according to the slope of the slope. Specifically, a map BrakeDownSlopeGainMAP corresponding to the slope of the slope is selected using the map shown in FIG. 3 described above, and is newly multiplied by the decrease side gain BrakeDownGain to obtain a new decrease side gain BrakeDownGain.

  Then, the process proceeds to step 165g, and in the control of (4), when the correction for increasing the reduction side gain BrakeDownGain is performed by the control of (1) and (2), the braking side divided into two systems is reduced. Change the gain BrakeDownGain. Here, correction for increasing the reduction-side gain BrakeDownGainFront is not performed for both front wheels FR and FL, and correction for increasing the reduction-side gain BrakeDownGainRear is performed only for both rear wheels RR and RL. That is, for the front wheels FR and FL, the reduction gain BrakeDownGain calculated up to step 165f is set as the reduction gain BrakeDownGainFront as it is. For the reduction side gain BrakeDownGainRear of both rear wheels RR and RL, using the map shown in FIG. 4 described above, the reduction side of the rear wheels RR and RL corresponding to the reduction side gain BrakeDownGain calculated up to step 165f. Select the gain BrakeDownGainMapRear and set it as the decreasing gain BrakeDownGainRear.

  In this manner, the correction value of the decreasing gain BrakeDownGain based on the controls (1) to (4) is calculated. Thereafter, the process proceeds to step 170 in FIG. 5B, and in the brake control in the crawl control, the gain correction at the time of pressure reduction for decreasing the W / C pressure is performed with respect to the normally set feedback gain BrakeGain set in step 160. Thus, the feedback gain BrakeGain of each of the front wheels FR and FL and the rear wheels RR and RL is corrected by multiplying the reduction gain BrakeDownGainFront or the reduction gain BrakeDownGainRear calculated in step 165.

  In step 175, the final feedback braking force FBbrakeForce is calculated. Specifically, using the feedback braking force FBbrakeForce (previous value) at the previous control cycle, the difference between the vehicle body speed V0 and the target speed TBV is determined in step 170 with respect to this feedback braking force FBbrakeForce (previous value). The final feedback braking force FBbrakeForce is calculated by adding the value obtained by multiplying the feedback gain BrakeGain calculated in step 1 and the braking force conversion coefficient.

  Further, the process proceeds to step 180 where the feedback braking force FBbrakeForce calculated in step 175 is converted into each wheel braking force. Here, each wheel braking force BrakeForce ** is calculated by multiplying the feedback braking force FBbrakeForce by each wheel braking force gain EachBrakeGain ** that determines the distribution of each wheel FL to RR. Each wheel braking force gain EachBrakeGain ** is usually ¼ so as to be uniform among the four wheels FL to RR, but the distribution of the front wheels FR and FL is larger than that of the rear wheels RR and RL. The distribution may be changed between the front and rear wheels. Then, the process proceeds to step 185, and the target pressure TargetPress ** of the W / C pressure of each wheel FL to RR is calculated by multiplying each wheel braking force BrakeForce ** calculated in step 180 by the hydraulic pressure converted value. .

  After this, as a control including TRC, it is determined in step 190 whether or not the TRC is being controlled. If the control is being performed, the process proceeds to step 195 and is requested by the TRC as a TRC required hydraulic pressure calculation. Calculate TRC required hydraulic pressure TrcTargetPress **. Then, the process proceeds to step 200, and the TRC required hydraulic pressure TrcTargetPress ** is added to the target pressure TargetPress ** of the W / C pressure of each wheel FL to RR obtained in step 195, and finally the crawl control and TRC are added. The target pressure TargetPress ** of the W / C pressure of each of the wheels FL to RR is calculated. Whether or not the TRC is being controlled and the TRC required hydraulic pressure TrcTargetPress ** can be acquired from the ECU executing the TRC (either the brake ECU 19 or the engine ECU 10).

  As described above, when the final target pressure TargetPress ** of the W / C pressure of each wheel FL to RR in consideration of crawl control and TRC is calculated, the target pressure TargetPress ** can be generated. Then, the brake actuator 15 is controlled, and the W / C pressures of W / C 16FL to 16RR are controlled.

  FIG. 7 and FIG. 8 are time charts showing a case where the reduction side gain BrakeDownGain is corrected in the feedback control described in the present embodiment.

  As shown in FIG. 7, on the downhill, when the vehicle body speed V0 decreases and the vehicle stops, the decrease gain BrakeDownGain in the feedback control increases at that time, and the W / C pressure is sharply decreased. For this reason, when the vehicle is in a stopped state in a situation where the driver is not supposed to stop the vehicle as in the case of performing crawl control, the control amount of the brake control in the feedback control is basically Can be corrected so as to decrease more quickly. As a result, the responsiveness can be increased so that the brake can be released more quickly, and the driver's uncomfortable feeling can be alleviated.

  Then, when the vehicle body speed V0 returns, the decrease side gain BrakeDownGain in the feedback control is again returned to the value at the time of normal traveling, and feedback control based on the deviation between the vehicle body speed V0 and the target speed TBV is performed. . In FIG. 6, the control pressure of the W / C pressure based on the feedback control gradually increases even though the vehicle body speed V0 is below the target speed TBV after the vehicle body speed V0 becomes positive again (V0> 0). There is a period. This is because there is a braking force feedback according to the acceleration component by the D term of the feedback control performed by PID control or the like, and the control pressure of the W / C pressure increases even when the vehicle body speed V0 is equal to or lower than the target speed TBV. It is to be made.

  On the other hand, as shown in FIG. 8, when the slope of the road surface on which the vehicle is stopped is a steep slope, the decrease gain BrakeDownGain in the feedback control is smaller than in the case of a gentle slope. The pressure drop becomes gradual. As a result, when the slope of the slope is steep, it is possible to prevent the W / C pressure from being sharply reduced despite the fact that the braking force is reduced and acceleration is facilitated when the brake is released. .

(Other embodiments)
The present invention is not limited to the embodiment described above, and can be appropriately changed within the scope described in the claims.

  For example, in the above embodiment, the crawl control is given as an example of the control for keeping the vehicle body speed at a low speed by controlling the braking force of each of the wheels FL to RR. However, this is merely an example, and the same can be said for other controls such as downhill assist control (DAC). The downhill assist control is similar to the crawl control, and all the crawl control portions described in the first embodiment may be replaced with the downhill assist control.

  In addition, including the steps shown in the drawings, the portion in the brake ECU 19 that executes various processes corresponds to the means for executing the various processes. For example, the part that executes the process of step 165a corresponds to the traveling state determination means, the part that executes the processes of steps 165c to 165g corresponds to the gain correction means, and the part that executes the process of step 165d corresponds to the brake operation determination means. Further, the step 130 for obtaining the gradient and the part for executing the processing of step 170 correspond to the feedback control means.

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Transmission, 2a ... Transmission, 2b ... Sub transmission, 3 ... Driving force distribution control actuator, 10 ... Engine ECU, 11 ... Accelerator pedal, 11a ... Accelerator switch, 12 ... LAN, 13 ... Brake pedal , 14 ... M / C, 15 ... Brake actuator, 16 ... W / C, 19 ... Brake ECU, 20FL-20RR ... Wheel speed sensor, 21 ... Brake switch, 21 ... Brake pedal, 22 ... M / C pressure sensor, 23 ... switch, 23 ... crawl switch, 24 ... target speed setting switch, 25 ... acceleration sensor

Claims (3)

Feedback control means for performing feedback control for calculating a feedback braking force based on a deviation between the vehicle body speed and the target speed for each predetermined control cycle and causing the vehicle body speed to approach the target speed by generating the feedback braking force;
Traveling state determination means for determining whether the vehicle is traveling in a normal traveling state or a stopped vehicle stopped state;
Gain correction means for correcting a decrease gain of the feedback braking force used for calculation of the feedback braking force higher than that in the normal running state when it is determined that the vehicle is stopped;
Brake operation determination means for determining whether or not a brake operation by the driver has been performed,
The vehicle control apparatus according to claim 1 , wherein the gain correction unit corrects the decrease-side gain higher when it is determined that the brake operation is performed in the vehicle stop state . Feedback control means for performing feedback control for calculating a feedback braking force based on a deviation between the vehicle body speed and the target speed for each predetermined control cycle and causing the vehicle body speed to approach the target speed by generating the feedback braking force;
Traveling state determination means for determining whether the vehicle is traveling in a normal traveling state or a stopped vehicle stopped state;
Gain correction means for correcting a decrease gain of the feedback braking force used for calculation of the feedback braking force higher than that in the normal running state when it is determined that the vehicle is stopped;
Anda gradient obtaining means for obtaining the slope gradient of the traveling road surface of the vehicle,
Said gain correcting means in the vehicle stop state, the slope gradient is compared with when the direction of time is steep is gentle gradient, vehicles you and corrects lower the decreasing side gain Control device. Feedback control means for performing feedback control for calculating a feedback braking force based on a deviation between the vehicle body speed and the target speed for each predetermined control cycle and causing the vehicle body speed to approach the target speed by generating the feedback braking force;
Traveling state determination means for determining whether the vehicle is traveling in a normal traveling state or a stopped vehicle stopped state;
Gain correction means for correcting the decrease gain of the feedback braking force used for calculation of the feedback braking force higher than that in the normal running state when it is determined that the vehicle is stopped. And
It said gain correcting means, when a higher correcting the reduction side gain, 2 for only one system of the systems is the brake system, vehicle both controller you characterized by a higher correcting the reduction side gain.

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