JP4957380B2 - Vehicle control device - Google Patents

Description

  The present invention relates to a vehicle control device, and more particularly to a vehicle control device that controls the behavior of a vehicle.

In general, in a vehicle anti-skid control device, when there is a risk of control hunting in which high pressure reduction and pressure increase are repeated during anti-skid control, the amount of increase in the brake pressure is reduced to suppress the increase in the brake pressure. Control hunting is suppressed. However, if the increase in braking pressure is suppressed to suppress control hunting when the vehicle travels on a road surface with high running resistance such as gravel roads and sandy roads, the deceleration of the vehicle decreases and the braking of the vehicle May degrade performance. For this reason, for example, when it is determined that the vehicle is traveling on a road surface with high running resistance, a vehicle anti-skid control device that reduces the amount of suppression of increase in braking pressure has been proposed (for example, a patent) Reference 1). In addition, for example, in a vehicle anti-slip device that performs slip control based on the speed difference between the driving wheel speed and the driven wheel speed, the allowable range of the speed difference between the driving wheel speed and the driven wheel speed is manually changed. A technique for providing a manual switch has been proposed (for example, Patent Document 2). Further, for example, it is determined whether the vehicle is traveling on a gravel road or a dirt road based on the output of the linear longitudinal acceleration sensor, and the brake fluid pressure control when it is determined that the vehicle is traveling on a gravel road and the dirt road are determined. There has been proposed an anti-skid control device that adjusts the actuator on the pressure increasing side compared to the brake fluid pressure control during pavement traveling under different conditions from the brake fluid pressure control when it is determined that the vehicle is traveling (for example, And Patent Document 3).
JP 2005-138737 A JP-A-6-341334 JP-A-11-180278

  As described in Patent Document 1 described above, a technique for determining whether the vehicle is traveling on a road surface with high traveling resistance or a normal road such as a paved road is known. However, if it is erroneously determined that the vehicle is traveling on a road surface with high running resistance even though the vehicle is running on a normal road, ABS control (Antilock Brake System) that should be performed while driving on a road surface with high running resistance. Such anti-skid control is performed while traveling on a normal road. Therefore, if such a misjudgment may occur, there is a possibility that the vehicle cannot travel under optimal control on a normal road where there are many opportunities to travel. For this reason, a threshold for determining the road surface condition where the vehicle is traveling is set so that it is not erroneously determined that the vehicle is traveling on a road surface with high traveling resistance despite traveling on a normal road. May have been.

  However, when such a threshold value is set, there is a risk that it may be determined that the vehicle is traveling on a normal road even though the vehicle is traveling on a road surface with high traveling resistance. When such an erroneous determination occurs, it becomes difficult to travel under optimal control on a road surface with a large traveling resistance.

  This invention is made | formed in view of such a subject, The objective is to implement | achieve appropriate vehicle control according to a vehicle state.

In order to solve the above problems, a vehicle control apparatus according to an aspect of the present invention includes an estimated acceleration calculation unit that calculates an estimated acceleration of a vehicle, an actual acceleration calculation unit that calculates an actual acceleration of the vehicle, and a calculated estimated acceleration. And a road surface state determination unit for determining whether the road surface state on which the vehicle is traveling is a normal road or a sandy road having a greater running resistance than the normal road based on the actual acceleration, and the road surface state on which the vehicle is traveling is a normal road. When it is determined that there is a road, the target slip ratio is set to the first slip ratio to control the braking force applied to the vehicle, and when the road surface state on which the vehicle is traveling is determined to be a sandy road, the target slip ratio is set to the first slip ratio. A braking control unit configured to control the braking force applied to the vehicle by setting the two-slip ratio.

When there is an suggestion input that suggests that the road surface state on which the vehicle is traveling is likely to be a sandy road, the road surface state determination unit determines that the road surface state on which the vehicle is traveling is a normal road if there is no suggestion input. Even in such a case, if the calculated estimated acceleration and actual acceleration satisfy predetermined conditions, it is determined that the road surface state where the vehicle is running is in an intermediate state between the normal road and the sandy road.

When it is determined that the vehicle is in the intermediate state, the braking control unit sets the target slip ratio to a third slip ratio that is an intermediate value between the first slip ratio and the second slip ratio, and applies the control to the vehicle. Control power.

In recent years, development of vehicle control using an off-road switch, a car navigation system, and the like has been advanced. For example, when the off-road switch is turned on, it can be said that the vehicle is likely to travel off-road, and the car navigation system causes the vehicle to travel in sandy areas. If it is detected, it can be said that the vehicle is likely to travel on a sandy road.

According to this aspect, for example, using such suggestion input, the target slip ratio is set to the third slip ratio, which is an intermediate value between the first slip ratio and the second slip ratio, and applied to the vehicle. Can be controlled. For this reason, for example, it is determined that the vehicle is actually on a sandy road even though it is on a sandy road, and the behavior of the vehicle is controlled so as to adapt to a state greatly different from the actual state of the vehicle. And stable vehicle control can be realized.

When there is a suggestion input, the road surface state determination unit calculates the calculated estimated acceleration and the actual acceleration even if the road surface state where the vehicle is traveling is determined as a normal road if there is no suggestion input. If the difference is within a predetermined range, it may be determined that the road surface state where the vehicle is traveling is in an intermediate state between the normal road and the sandy road.

The estimated acceleration calculation unit may calculate an estimated acceleration of the vehicle based on an output of a driving source for driving the vehicle.

According to this aspect, the estimated acceleration of the vehicle can be calculated appropriately.

You may further provide the manual input means on / off-operated by the user. Manual input means that is turned on and off by the user may be provided. The road surface state determination unit may determine that the suggestion input has been made when an on signal indicating that the manual input unit is turned on is acquired.

In recent years, a switch that can be turned on and off by a user, such as an off-road switch or a differential lock switch, is sometimes provided in a vehicle cabin. When such a switch is turned on, it is considered that there is a high possibility that the vehicle will travel on a road surface having higher travel resistance than a normal road. According to this aspect, it is highly likely that the road is actually a sandy road even if it is determined that the manual input means is operated by the user in this way, for example, it is normally determined as a normal road. It is possible to appropriately determine that the state is intermediate.

The manual input means may be an off-road switch operated by a user so as to control the behavior of the vehicle adapted to off-road driving.

Since the off-road switch is turned on during off-road driving, it is considered that the vehicle is likely to go off-road when the off-road switch is turned on. According to this aspect, using such an off-road switch operated by the user, for example, even when it is determined that the road is normally a normal road, there is a high possibility that the road is actually a sand road. It is possible to appropriately determine that the state is intermediate.

  ADVANTAGE OF THE INVENTION According to this invention, suitable vehicle control according to a vehicle state is realizable.

  Hereinafter, embodiments of the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing a vehicle to which a vehicle travel path determination device according to the present invention is applied. The vehicle 1 shown in the figure has wheels FL, FR, RL, and RR. Here, the wheel FR indicates the front right side, the wheel FL indicates the front left side, the wheel RR indicates the rear right side, and the wheel RL indicates the rear left side as viewed from the driver's seat. The vehicle 1 has an internal combustion engine 2 that is a gasoline engine or a diesel engine, a transaxle 4 that includes a transmission 3 that is an automatic transmission or a continuously variable transmission, and a transfer (not shown). That is, the vehicle 1 of the present embodiment is configured as a four-wheel drive vehicle such as an RV vehicle or a so-called pickup truck, and the front wheels FL and FR are provided with a transfer, a front differential (not shown), and drive shafts 5L and 5R. The power is transmitted from the internal combustion engine 2 through this. The output shaft 6 of the transaxle 4 is connected to a rear differential 7. The rear differential 7 is connected to rear wheels RL and RR via drive shafts 8L and 8R. In addition, it cannot be overemphasized that the vehicle 1 of this embodiment can be comprised as what is called a hybrid vehicle and an electric vehicle.

  The vehicle 1 also includes a braking device 10 including disc brake units 9FR, 9FL, 9RR, and 9RL provided for each of the wheels FR to RL. The braking device 10 is configured as an anti-skid control device (ABS) with a so-called EBD (Electronic Brake force Distribution). Each of the disc brake units 9FR to 9RL includes a brake disc 11 and a brake caliper 12, and each brake caliper 12 incorporates a wheel cylinder 41, 42, 43, or 44. Further, the wheel cylinders 41 to 44 of each brake caliper 12 are connected to the brake actuator 20 via independent hydraulic lines.

  The brake actuator 20 is connected to two output ports of the master cylinder 14, and a brake pedal 16 is connected to the master cylinder 14 via a booster 15. In the present embodiment, the brake pressure of the wheel cylinders 41 to 44 included in each brake caliper 12 can be set independently regardless of the hydraulic pressure supplied from the master cylinder 14. A master cylinder pressure sensor 13 is provided in the master cylinder 14, and the master cylinder pressure sensor 13 detects the pressure of brake oil in the master cylinder 14. The brake pedal 16 is provided with a brake lamp switch 17 that is turned on when the pedal is depressed. Further, the wheels FR to RL are provided with a wheel speed sensor 18 that outputs a signal corresponding to each rotation speed, that is, the wheel speed.

  FIG. 2 is a system diagram of the brake actuator 20 included in the braking device 10. As shown in the figure, the hydraulic circuit in the brake actuator 20 is configured as a diagonal system in which the system for the right front wheel FR and the left rear wheel RL and the system for the left front wheel FL and the right rear wheel RR are independent. The Thereby, even if some trouble is caused in one system, the function of the other system is reliably maintained.

  Normally open solenoid valves 31 and 37 are connected in parallel to one output port of the master cylinder 14, and a wheel cylinder 41 for the right front wheel FR is connected to the solenoid valve 31 via a hydraulic path. A wheel cylinder 44 for the left rear wheel RL is connected to 37 via a hydraulic path. A discharge port of the hydraulic pump 21 is connected between the electromagnetic valves 31 and 37 and the master cylinder 14. Further, normally open solenoid valves 33 and 35 are connected in parallel to the other output port of the master cylinder 14, and a wheel cylinder 42 for the left front wheel FL is connected to the solenoid valve 33 via a hydraulic path. A wheel cylinder 43 for the right rear wheel RR is connected to the electromagnetic valve 35 via a hydraulic path. A discharge port of the hydraulic pump 22 is connected between the electromagnetic valves 33 and 35 and the master cylinder 14. The hydraulic pumps 21 and 22 are driven by an electric motor 23, and when these hydraulic pumps 21 and 22 are operated, brake fluid whose pressure has been increased to a predetermined pressure is supplied to the wheel cylinders 41 to 44. The

  The wheel cylinder 41 is further connected with a normally closed solenoid valve 32, and the wheel cylinder 44 is further connected with a normally closed solenoid valve 38. The downstream ports of the electromagnetic valves 32 and 38 are connected to the reservoir 24 and are connected to the suction port of the hydraulic pump 21 via the check valve CV. A normally closed electromagnetic valve 34 is connected to the wheel cylinder 42, and a normally closed electromagnetic valve 36 is connected to the wheel cylinder 43. The downstream ports of the electromagnetic valves 34 and 36 are connected to the reservoir 25 and are connected to the suction port of the hydraulic pump 22 via the check valve CV. Each of the reservoirs 24 and 25 includes a piston and a spring, and accommodates brake fluid from the wheel cylinders 41 to 44 flowing through the electromagnetic valves 32 to 38.

  Each of the electromagnetic valves 31 to 38 is a two-port two-position electromagnetic switching valve provided with a solenoid coil. The solenoid valves 31 to 38 are set to the first position shown in FIG. 2 when the solenoid coil is not energized, whereby the wheel cylinders 41 to 44 communicate with the master cylinder 14. The solenoid valves 31 to 38 are set to the second position when the solenoid coil is energized, whereby the wheel cylinders 41 to 44 are disconnected from the master cylinder 14 and communicate with the reservoir 24 or 25. In FIG. 2, DP is a damper, CV is a check valve, OR is an orifice, and FT is a filter. The check valve CV allows the brake fluid to flow from the wheel cylinders 41 to 44 and the reservoirs 24 and 25 to the master cylinder 14 while blocking the flow in the opposite direction.

  Then, by controlling the energization state of the solenoid coils of the solenoid valves 31 to 38, the brake fluid pressure of the wheel cylinders 41 to 44 can be increased, reduced or held. That is, when the solenoid coils of the solenoid valves 31 to 38 are not energized, the brake fluid is supplied from the master cylinder 14 and the hydraulic pump 21 or 22 to the wheel cylinders 41 to 44, and thereby the brake fluid pressure of the wheel cylinders 41 to 44 is increased. Is increased. When the solenoid coils of the solenoid valves 31 to 38 are energized, the wheel cylinders 41 to 44 communicate with the reservoir 24 or 25, and the brake fluid pressure of the wheel cylinders 41 to 44 is reduced. Further, if the solenoid coils of the solenoid valves 31, 33, 35 and 37 are energized while the solenoid coils of the other solenoid valves 32, 34, 36 and 38 are de-energized, the brake fluid pressure of the wheel cylinders 41 to 44 is increased. Retained. The brake fluid pressure of the wheel cylinders 41 to 44 can be gradually increased (pulse increase) by adjusting a time interval between energization and non-energization of the solenoid coil, that is, a duty.

  The brake actuator 20 configured as described above is controlled by an electronic control unit (hereinafter referred to as “ECU”) 100 as shown in FIGS. 1 and 2. That is, ECU 100 executes anti-skid control (hereinafter referred to as “ABS control”) for increasing or decreasing the brake pressure for applying a braking force to each wheel FR to RL based on the slip ratio of wheels FR to RL. The ECU 100 includes a CPU, a ROM, a RAM, an input / output interface, a storage device, and the like (not shown), and controls the energization state of the solenoid coils of the electromagnetic valves 31 to 38 constituting the brake actuator 20. The electric motor 23 of the hydraulic pumps 21 and 22 is also controlled by the ECU 100.

  FIG. 3 is a control block diagram of the braking device 10 provided in the vehicle 1. The ECU 100 includes a CPU that executes various arithmetic processes, a ROM that stores various control programs, and a RAM that is used as a work area for data storage and program execution. In FIG. It is depicted as a functional block realized by cooperation of hardware such as RAM and software. Therefore, these functional blocks can be realized in various forms by a combination of hardware and software.

  The ECU 100 is connected to the wheel speed sensors 18 of the wheels FR to RL described above. Each wheel speed sensor 18 outputs to ECU 100 a signal indicating the rotational speed of the corresponding wheels FL to RR, that is, the wheel speed and the rotational direction.

  In addition, the ECU 100 is connected with a G sensor 45, a shift position sensor 46, an engine speed sensor 47, and an offload switch 50. The G sensor 45 is a so-called biaxial acceleration sensor that detects acceleration (acceleration / deceleration) in the front-rear direction of the vehicle 1, that is, the traveling direction, and acceleration in the lateral direction of the vehicle 1, that is, the width direction. G sensor 45 outputs a signal indicating acceleration in the front-rear direction and the lateral direction of the vehicle to ECU 100. Instead of the G sensor 45 that is a biaxial acceleration sensor, a sensor that detects only acceleration in the front-rear direction of the vehicle 1 and a sensor that detects only acceleration in the lateral direction of the vehicle 1 may be used.

  The shift position sensor 46 detects the shift range of the transmission 3 set by the driver, and outputs a signal indicating the detected range to the ECU 100. The engine speed sensor 47 detects the speed of the internal combustion engine 2 and outputs a signal indicating the detected value to the ECU 100.

  The off-road switch 50 is disposed on an instrument panel in the vicinity of the driver's seat in the vehicle cabin. The off-road switch 50 is connected to the ECU 100 and outputs an on signal or an off signal to the ECU 100 when the driver performs an on / off operation.

  The ECU 100 performs ABS control and traction control suitable for off-road driving when the off-road switch 50 is pressed. Since the ABS control and the traction control when the offload switch 50 and the offload switch 50 are turned on are known techniques, the description thereof is omitted.

  Further, the vehicle 1 is provided with an engine ECU (not shown) for controlling the opening degree of the throttle valve (not shown) of the engine and a transmission ECU (not shown) for controlling the shift change timing of the automatic transmission. It has been. When the off-road switch 50 is turned on, the engine ECU changes the timing for opening the throttle valve to be suitable for off-road driving, and the transmission ECU sets the shift change timing to be suitable for off-road driving. change. Since the method for changing the timing of the throttle valve and the method for changing the shift change timing when the off-road switch 50 is turned on are also known techniques, description thereof will be omitted.

  As shown in FIG. 3, the ECU 100 includes a slip ratio acquisition unit 101, a wheel cylinder pressure control unit (hereinafter referred to as “W / C pressure control unit”) 102, a vehicle speed acquisition unit 103, an estimated acceleration calculation unit 104, an actual acceleration. A calculation unit 105 and a road surface state determination unit 106 are constructed. The slip ratio acquisition unit 101 acquires the slip ratios of the wheels FR to RL by selecting appropriate data from data indicating the slip ratio stored in a storage unit such as a ROM. The W / C pressure control unit 102 determines the target wheel cylinder pressures of the wheel cylinders 41 to 44 according to the slip rates of the wheels FR to RL acquired by the slip rate acquisition unit 101. The ECU 100 is connected to the electromagnetic valves 31 to 38 via a drive circuit (not shown), and is connected to the electric motor 23 via a relay (not shown). The W / C pressure control unit 102 outputs a control current to the drive circuit and controls the duty of the current supplied from the battery (not shown) to each of the solenoid valves 31 to 38, thereby causing the solenoid valves 31 to 38 to turn on. The valve is opened or closed, and the wheel cylinder pressure of the wheel cylinders 41 to 44 is increased or decreased. Thus, the slip ratio acquisition unit 101 and the W / C pressure control unit 102 function as a braking control unit that controls the braking force applied to the vehicle.

  The vehicle speed acquisition unit 103 acquires the vehicle body speed Vs as the speed of the vehicle 1 (vehicle body) and the wheel acceleration Dw as the rotational acceleration of each wheel based on the detection value of each wheel speed sensor 18.

  The estimated acceleration calculation unit 104 first drives the drive wheel based on the rotational speed of the internal combustion engine 2 detected by the engine speed sensor 47 and the gear ratio of the transmission 3 obtained based on the signal from the shift position sensor 46. The estimated wheel speed of each of the wheels FR to RL is obtained every predetermined sampling time. The estimated acceleration calculation unit 104 calculates the estimated wheel acceleration based on the calculated estimated wheel speed and the sampling time, and calculates the estimated wheel acceleration of the average value of the estimated wheel accelerations of the wheels FR to RL. . The estimated acceleration calculation unit 104 calculates the estimated acceleration Ge of the vehicle 1 using this estimated wheel acceleration. The actual acceleration calculation unit 105 calculates an actual acceleration Gx as an actual acceleration of the vehicle 1 based on a signal from the G sensor 45. The road surface state determination unit 106 determines the state of the road surface on which the vehicle 1 is traveling (hereinafter referred to as “traveling road”) based on the calculated estimated acceleration Ge and actual acceleration Gx. Thus, the ECU 100 functions as a vehicle control unit that controls the braking force applied to the vehicle.

  When the vehicle 1 is traveling on a sandy road, it cannot be smoothly accelerated even when the same engine output is generated compared to when traveling on a normal road, and the actual acceleration Gx is greater than the estimated acceleration Ge. Is also greatly reduced. The road surface state determination unit 106 of the ECU 100 uses this to compare the estimated acceleration Ge and the actual acceleration Gx, thereby determining whether the traveling path of the vehicle 1 is a “normal road” or a “sand road”. . In addition, a normal road shall mean the pavement road and flat road whose traveling resistance is smaller than a sandy road.

  The road surface state determination unit 106 determines the road surface state based on the estimated acceleration Ge and the actual acceleration Gx, and does not determine by looking at the actual road surface state, so it actually travels on a normal road. Nevertheless, there is a possibility of misjudgment that it is determined that the vehicle is traveling on a sandy road, or an erroneous determination that it is actually determined that the vehicle is traveling on a normal road even though the vehicle is traveling on a sandy road. There is. If the former misjudgment occurs, ABS control suitable for sandy road travel will be carried out despite actually traveling on a normal road, and the latter misjudgment occurs. In fact, ABS control suitable for normal road travel is performed even though the vehicle is traveling on a sandy road.

  Here, it is generally considered that there are more opportunities to travel on normal roads than opportunities to travel on road surfaces with high travel resistance such as sandy roads. Therefore, when the former erroneous determination occurs, the influence on the operability of the vehicle by the ABS control performed based on the erroneous determination result is greater than when the latter erroneous determination occurs. For this reason, in order to reduce the possibility of the former misjudgment, that is, the misjudgment in which it is judged that the car is actually traveling on a sandy road despite actually traveling on a normal road, A threshold for determining whether the road is sandy is set.

  However, when the threshold value for determination is set in this way, the latter is erroneously determined, that is, it is determined that the vehicle is traveling on a normal road despite actually traveling on a sandy road. There is a possibility that the possibility that the determination will occur increases. When such an erroneous determination occurs, the operability of the vehicle traveling on the sandy road may be lowered. For this reason, the development of a technique that can realize appropriate ABS control according to the road surface state of the traveling path of the vehicle 1 is currently strongly demanded.

  For this reason, when the off-road switch 50 is turned on by the driver, the road surface state determination unit 106 according to the present embodiment has a value of the estimated acceleration Ge and the actual acceleration Gx that is normally the road on which the vehicle 1 is traveling. Even when the value is determined, when the other predetermined condition is satisfied, the traveling path of the vehicle 1 is a road surface on which both the normal road and the sandy road can travel. Judged to be a pre-sandy road. Further, when the slip ratio acquisition unit 101 and the W / C pressure control unit 102 determine that the vehicle 1 is traveling on a normal road when it is determined that the vehicle 1 is traveling on a pre-sand road. An ABS control intermediate between the ABS control performed in step S3 and the ABS control performed when it is determined that the vehicle 1 is traveling on a sandy road is performed. Hereinafter, such a control procedure will be described in detail with reference to FIGS.

  FIG. 4 is a flowchart showing a determination procedure of the traveling path of the vehicle 1 by the road surface condition determination unit 106. The processing in this flowchart is repeatedly performed every predetermined time while the ABS control is being performed. Note that the processing in this flowchart is started when an ignition switch (not shown) is turned on, and may be repeatedly performed every predetermined time until the ignition switch is turned off.

  The estimated acceleration calculation unit 104 first calculates the estimated acceleration Ge (S10), and the actual acceleration calculation unit 105 calculates the actual acceleration Gx (S12). When the estimated acceleration Ge and the actual acceleration Gx are calculated, the road surface state determination unit 106 determines whether or not the value obtained by subtracting the actual acceleration Gx from the estimated acceleration Ge is equal to or greater than the first threshold value A1 (S14).

  When it is determined that the value obtained by subtracting the actual acceleration Gx from the estimated acceleration Ge is equal to or greater than the first threshold A1 (Y in S14), the road surface state determination unit 106 determines that the vehicle 1 is traveling on a sandy road, and a sandy road flag Is set to ON (S16).

  Here, the off-road switch 50 is turned on by the driver when the vehicle travels off-road. For this reason, the fact that the off-road switch 50 is turned on by the driver is a case where the vehicle 1 is already traveling on an off-road having a running resistance larger than that on a normal road or is still traveling on a normal road. It can be thought of as suggesting that you will be driving off-road soon. For this reason, when it is determined that the value obtained by subtracting the actual acceleration Gx from the estimated acceleration Ge is smaller than the first threshold value A1 (N in S14), the road surface state determination unit 106 has the off-road switch 50 turned on by the driver. It is determined whether or not (S18).

  When the off-road switch 50 is turned on (Y in S18), even if the value obtained by subtracting the actual acceleration Gx from the estimated acceleration Ge is a value that is determined to be traveling on a normal road, the vehicle 1 Is likely to travel on sandy roads. Therefore, the road surface state determination unit 106 determines whether or not the traveling path of the vehicle 1 is a pre-sand road by determining whether or not the value obtained by subtracting the actual acceleration Gx from the estimated acceleration Ge is equal to or greater than the second threshold A2. (S20). The second threshold A2 is set to a value smaller than the first threshold A1. When the value obtained by subtracting the actual acceleration Gx from the estimated acceleration Ge is equal to or greater than the second threshold value A2 (Y in S20), the road surface state determination unit 106 determines that the vehicle 1 is traveling on the pre-sand road, and sets the pre-sand road flag. Set to ON (S22).

  When the off-road switch 50 is turned off (N in S18), it is considered that the possibility that the vehicle 1 travels on the pre-sand road is low. Even when the off-road switch 50 is turned on, if the value obtained by subtracting the actual acceleration Gx from the estimated acceleration Ge is smaller than the second threshold value A2 (N in S20), the vehicle 1 immediately becomes a normal road. The possibility of driving is considered low. Therefore, the road surface state determination unit 106 determines that the vehicle 1 is traveling on a normal road in these cases, and sets the normal road flag to ON (S24).

  FIG. 5A shows a relationship between a normal road determination area determined as a normal road and a sand road determination area determined as a sand road when the off-road switch 50 is turned off. (B) shows the relationship among the normal road determination area, the sandy road determination area, and the pre-sandy road determination area when the off-road switch 50 is turned on. 5A and 5B, the horizontal axis represents the estimated acceleration Ge, and the vertical axis represents the actual acceleration Gx.

  When the off-road switch 50 is turned off, the lower right region is a sandy road determination region, with the estimated acceleration Ge−actual acceleration Gx = first straight line A1 (hereinafter referred to as “straight line L1”) as a boundary. The upper left area is the normal road determination area. When the off-road switch 50 is turned on, the lower right region with the straight line L1 as a boundary is a sandy road determination region as in the case where the off-road switch 50 is turned off. However, in the upper left area with the straight line L1 as a boundary, the straight line of the estimated acceleration Ge−actual acceleration Gx = second threshold A2 is defined as the straight line L2, and the upper left area from the straight line L1 is the normal path determination area, and the straight lines L1 and L2 A region surrounded by is a pre-sand road determination region.

  In this way, the road surface state determination unit 106 turns on the area close to the sand road determination area in the area that is the normal road determination area when the off-road switch 50 is off. When it is, it is set as a pre-sandy road judgment area. This makes it possible to effectively reduce erroneous determinations that are determined to be normal roads even though the vehicle is actually traveling on sandy roads.

  FIG. 6 is a flowchart showing a control procedure of ABS control according to the present embodiment. It is started when the ignition switch is turned on, and is repeatedly performed every predetermined time until the ignition switch is turned off.

  For example, the slip ratio acquisition unit 101 determines whether or not the ABS control is being performed by determining whether or not the ABS flag indicating whether or not the ABS control is being performed (S30). (N of S30), the process in this flowchart is once complete | finished. Data indicating the first slip ratio St1 to the fourth slip ratio St4 described below is stored in advance in a storage unit such as a ROM.

  When ABS control is being performed (Y in S30), the slip ratio acquisition unit 101 first determines whether or not the vehicle 1 is traveling on a normal road by determining whether or not the normal road flag is set to ON. Determine (S32). When it is determined that the vehicle 1 is traveling on a normal road (Y in S32), the slip ratio acquisition unit 101 sets the target slip ratio to the first slip ratio St1, which is the lowest value (S34).

  When it is determined that the vehicle 1 is not traveling on a normal road (N in S32), the slip rate acquisition unit 101 determines whether the pre-sand road flag is set on, thereby determining that the vehicle 1 is It is determined whether or not the vehicle is traveling on a pre-sand road (S36). When it is determined that the vehicle 1 is traveling on the pre-sand road (Y in S36), the slip ratio acquisition unit 101 sets the target slip ratio to the above-described first slip ratio St1 and the off-road switch 50 is also turned off. Is set to the second slip ratio St2, which is an intermediate value to the third slip ratio St3 set when it is determined that the vehicle 1 is traveling on a sandy road (S38).

  By setting the target slip ratio to such a value, when the first slip ratio St1 is to be set due to an erroneous determination, the third slip ratio St3 is set, or when the third slip ratio St3 is to be set It is possible to avoid setting the target slip ratio to a value greatly different from the originally set slip ratio, such as the first slip ratio St1 being set. As a result, it is possible to suppress the ABS control that is not suitable for the actual road surface condition.

  When it is determined that the vehicle 1 is not traveling on the pre-sand road (N in S36), the slip ratio acquisition unit 101 determines that the vehicle 1 is traveling on the sand road, and then the off-road switch 50 is turned on. It is determined whether or not it is turned on (S40). When the off-road switch 50 is turned off (N in S40), the slip ratio acquisition unit 101 sets the target slip ratio to the third slip ratio St3 (S44), and the off-road switch 50 is turned on. In the case (Y in S40), the target slip ratio is set to the fourth slip ratio St4, which is a value larger than the third slip ratio St3 (S42).

  When the target slip ratio is set, the W / C pressure control unit 102 determines the target wheel cylinder pressure of each of the wheel cylinders 41 to 44 based on the set target slip ratio (S46). In addition, since the determination method of target wheel cylinder pressure is a well-known technique, description is abbreviate | omitted. When the target wheel cylinder pressure is determined, the W / C pressure control unit 102 controls the wheel cylinder pressure of each of the wheel cylinders 41 to 44 so as to achieve the determined target wheel cylinder pressure (S48).

  FIG. 7 is a diagram illustrating a relationship between the S-μ characteristic of the braking apparatus 10 according to the present embodiment and the first slip ratio St1 to the fourth slip ratio St4. In FIG. 7, the horizontal axis represents the slip ratio S, and the vertical axis represents the friction coefficient μ with the road surface. As shown in FIG. 7, in the S-μ characteristic of the normal road, as the slip ratio S increases, the friction coefficient μ with the road surface initially increases rapidly and then gradually decreases. On the other hand, the S-μ characteristic of the sandy road gradually increases as the slip ratio S increases.

  Therefore, normally, when it is determined that the vehicle 1 is traveling on a normal road, the first slip ratio St1 is set low so that the friction coefficient μ with the road surface becomes a high value in the S-μ characteristics of the normal road. When it is determined that the vehicle 1 is traveling on a sandy road, the third slip ratio St3 is set so that the friction coefficient μ with the road surface becomes a high value in the S-μ characteristic of the sandy road. A value higher than 1 slip ratio St1 is set. In this way, it is possible to always maintain a high coefficient of friction μ with the road surface and realize good ABS control.

  However, for example, if it is erroneously determined that the vehicle 1 is actually traveling on a sandy road even though the vehicle 1 is traveling on a normal road, the target slip ratio should be originally set to the first slip ratio St1 is third. The slip rate St3 is set. For this reason, the coefficient of friction μ with the road surface decreases from μ4 to μ3, and it is difficult to realize good ABS control that should be originally realized.

  In addition, when it is erroneously determined that the vehicle 1 is actually traveling on a normal road even though the vehicle 1 is traveling on a sandy road, the target slip ratio should originally be set to the third slip ratio St3. The slip rate St1 is set. For this reason, the coefficient of friction μ with the road surface decreases from μ2 to μ1, and in this case as well, it is difficult to realize good ABS control that should be originally realized.

  As in this embodiment, when it is determined that the vehicle 1 is traveling on a pre-sand road, the target slip ratio is set to the second slip ratio St2, so that the friction coefficient μ with such a road surface is large. It becomes possible to suppress fluctuations. As a result, even when the road surface condition is erroneously determined, it is possible to avoid performing ABS control that is significantly different from the ABS control that should be originally performed.

  Further, when the off-road switch 50 is turned on, it is considered that there is a low possibility that the vehicle 1 is determined to be traveling on a sandy road even though the vehicle 1 is actually traveling on a normal road. For this reason, in this embodiment, when it is determined that the vehicle 1 is traveling on a sandy road with the off-road switch 50 turned on, the target slip ratio is larger than the third slip ratio St3. The fourth slip ratio St4 is set. As described above, when it is determined that the vehicle 1 is traveling on a sandy road with the off-road switch 50 turned on, the target slip ratio is larger than that when the off-road switch 50 is turned off. Thus, the friction coefficient μ with the road surface is set to a larger value, and it is possible to perform better ABS control.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added to the embodiments based on the knowledge of those skilled in the art. Embodiments described may also fall within the scope of the present invention. Here are some examples.

  In a modification, a diff lock switch (not shown) is provided on the instrument panel around the driver's seat in the passenger compartment of the vehicle 1. When the differential lock switch is turned on, the differential is locked, and the operation of the left and right wheels is restricted. As a result, the vehicle 1 can be escaped when, for example, one wheel gets muddy. Since the diff lock switch and such vehicle control when the diff lock switch is turned on are well-known techniques, description thereof will be omitted. The road surface state determination unit 106 may be different even when the driving path of the vehicle 1 is determined to be a normal road when the diff lock switch is turned on by the driver or when the diff lock switch is turned off. When the predetermined condition is satisfied, it is determined that the travel path of the vehicle 1 is a pre-sand road. The predetermined condition in this case may be that the estimated acceleration Ge and the actual acceleration Gx become values between the straight line L1 and the straight line L2 in FIG. 5B as in the above-described embodiment.

  Similar to the off-road switch 50, such a differential lock switch is turned on by the driver when the vehicle 1 travels on a road surface having a large running resistance such as off-road. For this reason, when the differential lock switch is turned on, the vehicle 1 is actually off-road even if it is determined from the estimated acceleration Ge and the actual acceleration Gx that the vehicle 1 is traveling on a normal road. It can be said that the vehicle is traveling on a road surface having a large running resistance, or that the possibility of traveling on such a road surface is high immediately after. For this reason, it is a case where a diff lock switch is turned on, Comprising: When the predetermined condition is satisfy | filled, it determines that it is a pre-sand road, and the influence on ABS by the misjudgment of a road surface state can be suppressed.

  In another modification, the vehicle 1 is equipped with a car navigation system. The car navigation system includes an electronic control unit having a CPU, a ROM, and a RAM. The electronic control unit acquires position information of the vehicle 1 by GPS (Global Positioning System), and acquires the acquired position information of the vehicle 1. Is used to acquire map information around the vehicle 1 from map information stored in a storage unit such as a DVD or a hard disk. Since the car navigation system is a well-known technique, further detailed description regarding its configuration is omitted.

  ECU100 acquires the positional information on the vehicle 1 which the electronic control part of the car navigation system acquired, and the map information around the vehicle 1. The road surface state determination unit 106 determines whether the vehicle 1 is traveling on a road surface with high traveling resistance such as a sandy road, a gravel road, or a dirt using the acquired position information and map information of the vehicle 1. . When it is determined that the vehicle 1 is traveling on a road surface having such a high driving resistance, the road surface state determination unit 106 is normally configured to determine that the traveling path of the vehicle 1 is a normal road. When other predetermined conditions are satisfied, it is determined that the travel path of the vehicle 1 is a pre-sand road. Note that the predetermined condition in this case may also be that the estimated acceleration Ge and the actual acceleration Gx are values between the straight line L1 and the straight line L2 in FIG. 5B as in the above-described embodiment.

  As described above, when it is detected by the car navigation system that the vehicle 1 is traveling on a road surface with high traveling resistance, it is determined from the estimated acceleration Ge and the actual acceleration Gx that the vehicle 1 is traveling on a normal road. Even in such a case, it can be said that the vehicle 1 is traveling on a road surface having a large running resistance such as off-road, or that it is highly likely that the vehicle 1 will travel on such a road surface immediately afterward. . For this reason, even when it is detected by the car navigation system that the vehicle 1 is traveling on a road surface with a high running resistance, it is determined that the road surface state is a pre-sand road when a predetermined condition is satisfied. The influence on the ABS due to erroneous determination can be suppressed.

  In another modification, the engine ECU also includes a road surface state determination unit. Like the road surface state determination unit 106 of the ECU 100, whether the traveling path of the vehicle 1 is a normal road, a sand road, or a pre-sand road. Determine. When it is determined that the vehicle 1 is traveling on the pre-sand road, the engine ECU opens the throttle valve when it is determined that the vehicle 1 is traveling on the normal road, and the vehicle 1 is on the sand path. The throttle valve is opened at a timing intermediate to the timing of opening the throttle valve when it is determined that the vehicle is traveling. As a result, even when the traveling path of the vehicle 1 is erroneously determined, it is possible to avoid opening the throttle valve at a timing greatly deviating from the timing suitable for the road surface state on which the vehicle 1 travels.

  In another modification, the transmission ECU also has a road surface state determination unit, and, like the road surface state determination unit 106 of the ECU 100, whether the travel path of the vehicle 1 is a normal road, a sand road, or a pre-sand road. Determine. When it is determined that the vehicle 1 is traveling on the pre-sand road, the transmission ECU performs the shift change timing when it is determined that the vehicle 1 is traveling on the normal road, and the vehicle 1 is traveling on the sand path. Shift change is performed at a timing intermediate to the shift change timing when it is determined that the Thus, even when the traveling path of the vehicle 1 is erroneously determined, it is possible to avoid the shift change being performed at a timing greatly deviating from the timing suitable for the road surface state on which the vehicle 1 travels.

1 is a schematic configuration diagram illustrating a vehicle to which a vehicle travel path determination device according to the present invention is applied. It is a systematic diagram of the brake actuator contained in a braking device. It is a control block diagram of the braking device provided in the vehicle. It is a flowchart which shows the determination procedure of the traveling path of the vehicle by a road surface state determination part. (A) is a figure which shows the relationship between the normal road determination area | region determined to be a normal road, and the sandy road determination area | region determined to be a sandy road when the off-road switch is turned off, (b) ) Is a diagram showing a relationship among a normal road determination area, a sandy road determination area, and a pre-sandy road determination area when the off-road switch is turned on. It is a flowchart which shows the control procedure of ABS control which concerns on this embodiment. It is a figure which shows the relationship between the S-micro characteristic of the braking device which concerns on this embodiment, and 1st slip ratio St1-4th slip ratio St4.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Vehicle, 2 Internal combustion engine, 13 Master cylinder pressure sensor, 17 Brake lamp switch, 18 Wheel speed sensor, 20 Brake actuator, 45 G sensor, 47 Engine speed sensor, 100 ECU, 101 Slip ratio acquisition part, 102 W / C A pressure control unit, 103 a vehicle speed acquisition unit, 104 an estimated acceleration calculation unit, 105 an actual acceleration calculation unit, and 106 a road surface state determination unit.

Claims (2)

An estimated acceleration calculation unit for calculating an estimated acceleration of the vehicle;
An actual acceleration calculator for calculating the actual acceleration of the vehicle;
A road surface state determination unit that determines whether the road surface state on which the vehicle is traveling is a normal road or a sandy road with a greater running resistance than the normal road, based on the calculated estimated acceleration and actual acceleration;
When it is determined that the road surface state on which the vehicle is traveling is a normal road, the target slip ratio is set to the first slip ratio to control the braking force applied to the vehicle, and the road surface state on which the vehicle is traveling is sandy. A braking control unit that controls the braking force applied to the vehicle by setting the target slip ratio to the second slip ratio when it is determined as a road ;
With
When the road surface condition determination unit has an input suggesting that the road surface state on which the vehicle is traveling is likely to be a sandy road, the road surface state on which the vehicle is traveling is normally displayed without the suggestion input. Even if the road is determined to be a road , if the calculated estimated acceleration and actual acceleration satisfy a predetermined condition, the road surface on which the vehicle is traveling is determined to be in an intermediate state between a normal road and a sandy road. And
When it is determined that the vehicle is in the intermediate state , the braking control unit sets the target slip ratio to a third slip ratio that is an intermediate value between the first slip ratio and the second slip ratio. A vehicle control device that controls a braking force to be applied. When the suggestion input is received, the road surface state determination unit is configured to calculate the estimated acceleration even if the road surface state where the vehicle is traveling is determined to be a normal road if the suggestion input is not provided. 2. The vehicle control device according to claim 1, wherein when the difference from the actual acceleration is within a predetermined range, it is determined that the road surface state on which the vehicle is running is an intermediate state between the normal road and the sandy road.

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