JP2009154869A - Braking force control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent performance of unnecessary brake assist control by performing brake assist control in consideration of a physical quantity other than master cylinder pressure representing the braking manipulated variable of a driver. <P>SOLUTION: In a braking force control device, the target deceleration Gt of a vehicle is calculated based on the master cylinder pressure Pm1, Pm2 representing the braking manipulated variable of the driver and a brake pedal pressing stroke St as the physical quantity other than the master cylinder pressure representing the braking manipulated variable of the driver (S40-60). The brake assist control is started (S140) when a normal control start condition is satisfied regarding to the master cylinder pressure (S90) and the target deceleration Gt is a start reference value or more (S100). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle braking force control device, and more particularly to a so-called electronically controlled braking force control device.

  As one of braking force control devices for vehicles such as automobiles, for example, as described in Patent Document 1 below, the master cylinder pressure becomes equal to or higher than its start reference value, and the rate of change of the master cylinder pressure is its start reference value. Brake assist control is configured so that the brake assist control starts when the master cylinder pressure falls below the end reference value and the rate of change of the master cylinder pressure falls below the end reference value. Devices are conventionally known.

  According to such a braking force control device, when a sudden braking operation is performed by the driver as in danger avoidance, brake assist control is executed, and the braking pressure of each wheel is controlled to a pressure higher than the master cylinder pressure, Alternatively, since the ratio of the wheel cylinder pressure to the master cylinder pressure is increased, it is possible to effectively prevent the vehicle from being braked quickly due to insufficient pedaling force of the driver.

Japanese Patent Laid-Open No. 11-189139

[Problems to be Solved by the Invention]
In the braking force control apparatus as described above, for example, an orifice may be provided in the master cylinder for the purpose of improving the brake operation feeling. In such a configuration, even if the brake operation by the driver is light, the brake is controlled. When the operation is quick, the master cylinder pressure suddenly increases and then decreases rapidly, so unnecessary brake assist control is executed or necessary brake assist control ends early. Sometimes.

  For example, FIG. 6A shows changes in the master cylinder pressure Pm and the brake pedal stroke St when the driver performs the brake operation relatively slowly, and FIG. 6B shows a quicker brake operation by the driver. This shows changes in the master cylinder pressure Pm and the brake pedal stroke St when. As can be seen from the comparison of these figures, when the brake operation is performed relatively slowly by the driver, the master cylinder pressure Pm changes in the same manner as the stroke St of the brake pedal, but the driver performs a quick brake operation. Then, the master cylinder pressure Pm increases rapidly and then decreases rapidly, and then changes in the same manner as the stroke St of the brake pedal.

In the present invention, when the master cylinder pressure becomes equal to or higher than the start reference value and the rate of change of the master cylinder pressure becomes equal to or higher than the start reference value, the brake assist control is started, and the master cylinder pressure becomes equal to or lower than the end reference value. The present invention has been made in view of the above-described problems in the conventional braking force control device configured to terminate the brake assist control when the rate of change of the cylinder pressure becomes equal to or less than the termination reference value. An important issue is that unnecessary brake assist control is executed and necessary brake assist control is completed early by performing brake assist control in consideration of physical quantities other than the master cylinder pressure that represents the driver's braking operation amount. It is to prevent it.
[Means for Solving the Problems and Effects of the Invention]

  According to the present invention, the main problem described above is that a master cylinder representing a driver's braking operation amount in a vehicle braking force control device that starts brake assist control when a predetermined start condition is established for the master cylinder pressure. A vehicle braking force control device that detects a physical quantity other than pressure and starts brake assist control when the predetermined start condition is satisfied and the physical quantity is equal to or greater than a reference value. In a vehicle braking force control device that starts brake assist control when a predetermined start condition is established for the master cylinder pressure, a physical quantity other than the master cylinder pressure that represents the driver's braking operation amount is detected, and at least Based on the physical quantity, a target deceleration of the vehicle is calculated, the predetermined start condition is satisfied, and the target deceleration of the vehicle becomes equal to or greater than a reference value. It is achieved by the braking force control apparatus for a vehicle, characterized in that to start the brake assist control (the second aspect) when.

  In general, when a light and quick braking operation is performed by the driver, the master cylinder pressure suddenly increases rapidly, but physical quantities other than the master cylinder pressure representing the driver's braking operation amount do not increase rapidly. Therefore, the brake assist control is started in a situation where the brake assist control is unnecessary by determining whether or not the brake assist control should be started in consideration of a physical quantity other than the master cylinder pressure in addition to the master cylinder pressure. It is possible to reduce the possibility of determining that the power should be.

  According to the configuration of the first aspect, when a physical quantity other than the master cylinder pressure representing the driver's braking operation amount is detected, a predetermined start condition is established for the master cylinder pressure, and the physical quantity is equal to or greater than a reference value. Therefore, unnecessary brake assist control may be performed when the driver performs a light and quick braking operation, compared to the conventional case where the physical quantity is not considered. This can be reliably reduced.

  According to the second aspect of the present invention, a physical quantity other than the master cylinder pressure representing the amount of braking operation of the driver is detected, a target deceleration of the vehicle is calculated based on at least the physical quantity, and a predetermined start is made for the master cylinder pressure. Since the brake assist control is started when the condition is satisfied and the target deceleration of the vehicle becomes equal to or higher than the reference value, the target deceleration of the vehicle based on the physical quantity is considered as in the case of the configuration of claim 1 above. Compared to the conventional case where the brake operation is not performed, it is possible to reliably reduce the possibility that unnecessary brake assist control is performed when a light and quick brake operation is performed by the driver.

  According to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 1 or 2, a predetermined end condition is established for the master cylinder pressure after the start of the brake assist control, and The brake assist control is configured to end when the amount of decrease in the physical quantity is equal to or greater than a reference value with reference to the physical quantity at the start of the brake assist control.

  In general, when the driver performs a light and quick braking operation, the master cylinder pressure increases suddenly and then decreases rapidly, but a physical quantity other than the master cylinder pressure that represents the driver's braking operation amount. Does not increase suddenly, and when the brake operation amount is reduced by the driver, the physical quantity other than the master cylinder pressure and the master cylinder pressure decreases in the same way when the brake operation amount decreases. By determining whether brake assist control should be terminated in consideration of physical quantities other than the cylinder pressure in addition to the cylinder pressure, brake assist control should be terminated in situations where it is necessary to continue brake assist control. The risk of determination can be reduced.

  According to the third aspect of the present invention, a predetermined end condition is established for the master cylinder pressure after the start of the brake assist control, and the amount of decrease in the physical quantity is a reference value with reference to the physical quantity at the start of the brake assist control. Since the brake assist control is terminated when the above is reached, it is possible to reliably reduce the possibility that the necessary brake assist control will be terminated, compared to the conventional case where the amount of decrease in the physical quantity is not considered. .

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claim 1 or 2, the physical quantity is an operation force with respect to a brake operator or an operation displacement amount of the brake operator. It is comprised so that it may exist (structure of Claim 4).

According to the configuration of the fourth aspect, since the physical quantity is an operation force with respect to the brake operator or an operation displacement amount of the brake operator, the physical quantity is considered in addition to the master cylinder pressure. It is possible to reliably achieve the operational effects.
[Preferred embodiment of problem solving means]

  According to one preferred aspect of the present invention, in the configuration according to claim 1 or 2, the predetermined start condition is that the master cylinder pressure is equal to or higher than the start reference value, and the rate of change of the master cylinder pressure is the start reference. It is comprised so that it may be the conditions of being more than a value (Preferred aspect 1).

  According to another preferred aspect of the present invention, in the configuration of claim 2 described above, a target deceleration of the vehicle is calculated based on the master cylinder pressure and the physical quantity (preferred aspect 2).

  According to another preferred aspect of the present invention, in the configuration of claim 1, the predetermined start condition is satisfied, the physical quantity is equal to or greater than a start reference value, and the increase rate of the physical quantity is The brake assist control is configured to start when the start reference value is exceeded (preferred aspect 3).

  According to another preferred aspect of the present invention, in the configuration of claim 2, the predetermined start condition is satisfied, the target deceleration of the vehicle is equal to or greater than the start reference value, and the target decrease of the vehicle is achieved. The brake assist control is configured to start when the speed increase rate becomes equal to or higher than the start reference value (preferred aspect 4).

  According to another preferred aspect of the present invention, in the configurations of the first and second aspects, a predetermined end condition is satisfied for the master cylinder pressure after the start of the brake assist control, and the physical quantity is the end reference value. The brake assist control is configured to end when the following occurs (preferred aspect 5).

  According to another preferred aspect of the present invention, in the configuration of claim 4, the physical quantity is configured to be an operation displacement amount of a braking operator (preferred aspect 6).

1 is a schematic configuration diagram showing a hydraulic circuit of an embodiment of a vehicle braking force control apparatus according to the present invention and a block diagram showing a control system. It is a flowchart which shows the braking force control routine in an Example. It is a graph which shows the relationship between the average value Pma of a master cylinder pressure, and target deceleration Gpt. It is a graph which shows the relationship between the depression stroke St of a brake pedal, and the target deceleration Gst. It is a graph which shows the relationship between the weight (alpha) with respect to the last final target deceleration Gtf and the target deceleration Gpt. Examples of changes in the master cylinder pressure Pm and the brake pedal stroke St when the driver performs a brake operation relatively slowly (A) and when the driver performs a quick brake operation (B) It is a graph to show.

  The present invention will now be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram showing a hydraulic circuit of an embodiment of a vehicle braking force control apparatus according to the present invention and a block diagram showing a control system. In FIG. 1, the solenoid of each valve is not shown for the sake of simplicity.

  In FIG. 1, reference numeral 10 denotes an electrically controlled hydraulic brake device. The brake device 10 includes a master cylinder 14 that pumps brake oil in response to a driver's depressing operation of the brake pedal 12. Have. A dry stroke simulator 16 is provided between the brake pedal 12 and the master cylinder 14.

  The master cylinder 14 has a first master cylinder chamber 14A and a second master cylinder chamber 14B, and these master cylinder chambers have a brake hydraulic pressure supply conduit 18 for the left front wheel and a brake hydraulic pressure control conduit for the right front wheel, respectively. One end of 20 is connected. Wheel cylinders 22FL and 22FR for controlling the braking force of the left front wheel and the right front wheel are connected to the other ends of the brake hydraulic pressure control conduits 18 and 20, respectively.

  In the middle of the brake hydraulic pressure supply pipes 18 and 20, normally open type electromagnetic on / off valves (master cut valves) 24L and 24R are provided, respectively. The electromagnetic on / off valves 24L and 24R are respectively connected to the first master cylinder chamber 14A and the second It functions as a shut-off valve that controls communication between the master cylinder chamber 14B and the corresponding wheel cylinders 22FL and 22FR. A wet stroke simulator 28 is connected to the brake hydraulic pressure supply conduit 18 between the master cylinder 14 and the electromagnetic open / close valve 24FL via a normally closed electromagnetic open / close valve (normally closed valve) 26.

  A reservoir 30 is connected to the master cylinder 14, and one end of a hydraulic pressure supply conduit 32 is connected to the reservoir 30. An oil pump 36 driven by an electric motor 34 is provided in the middle of the hydraulic supply conduit 32, and an accumulator 38 that accumulates high-pressure hydraulic pressure is connected to the hydraulic supply conduit 32 on the discharge side of the oil pump 36. One end of a hydraulic discharge conduit 40 is connected to the hydraulic supply conduit 32 between the reservoir 30 and the oil pump 36. The reservoir 30, the oil pump 36, the accumulator 38, and the like function as a high pressure source for increasing the pressure in the wheel cylinders 22FL, 22FR, 22RL, and 22RR as will be described later.

  Although not shown in FIG. 1, a conduit is provided for connecting the suction-side hydraulic supply conduit 32 and the discharge-side hydraulic supply conduit 32 of the oil pump 36, and an accumulator 38 is provided in the middle of the conduit. A relief valve is provided that opens when the pressure exceeds a reference value and returns oil from the discharge-side hydraulic supply conduit 32 to the suction-side hydraulic supply conduit 32.

  The hydraulic pressure supply conduit 32 on the discharge side of the oil pump 36 is connected to the brake hydraulic pressure supply conduit 18 between the electromagnetic on-off valve 24L and the wheel cylinder 22FL by a hydraulic control conduit 42, and the electromagnetic on-off valve 24R and the wheel by a hydraulic control conduit 44. It is connected to a brake hydraulic pressure supply conduit 20 between the cylinder 22FR, a hydraulic control conduit 46 to a left rear wheel wheel cylinder 22RL, and a hydraulic control conduit 48 to a right rear wheel wheel cylinder 22RR. .

  Normally closed electromagnetic linear valves 50FL, 50FR, 50RL, and 50RR are provided in the middle of the hydraulic control conduits 42, 44, 46, and 48, respectively. The hydraulic control conduits 42, 44, 46, 48 on the side of the wheel cylinders 22FL, 22FR, 22RL, 22RR with respect to the linear valves 50FL, 50FR, 50RL, 50RR are connected to the hydraulic discharge conduit 40 by the hydraulic control conduits 52, 54, 56, 58, respectively. And normally closed electromagnetic linear valves 60FL and 60FR are provided in the middle of the hydraulic control conduits 52 and 54, respectively, and normally closed electromagnetic solenoids are provided in the middle of the hydraulic control conduits 56 and 58, respectively. There are provided normally-open electromagnetic linear valves 60RL and 60RR that are cheaper than the conventional linear valves.

  The linear valves 50FL, 50FR, 50RL, 50RR function as pressure-increasing valves (holding valves) for the wheel cylinders 22FL, 22FR, 22RL, 22RR, respectively. The linear valves 60FL, 60FR, 60RL, 60RR are wheel cylinders 22FL, 22FR, 22RL, respectively. The linear valves function as pressure reducing valves for 22RR, so that these linear valves form a pressure increasing / decreasing control valve for controlling supply / discharge of high pressure oil to / from each wheel cylinder from the accumulator 38 in cooperation with each other.

  Note that the electromagnetic on / off valves 24L and 24R are kept open during non-control when no drive current is supplied to the electromagnetic on / off valves, linear valves and motor 34, and the electromagnetic on / off valves 26, linear valves 50FL to 50RR, linear valves 60FL and 60FR is maintained in a closed state, and linear valves 60RL and 60RR are maintained in an open state (non-control mode). In addition, when any one of the linear valves 50FL to 50RR and the linear valves 60FL to 60RR is lost and the pressure in the corresponding wheel cylinder cannot be normally controlled, each electromagnetic on-off valve is set to the non-control mode. As a result, the pressure in the wheel cylinders of the left and right front wheels is directly controlled by the master cylinder 14.

  As shown in FIG. 1, a brake hydraulic pressure control conduit 18 between the first master cylinder chamber 14A and the electromagnetic on-off valve 24L detects a pressure in the control conduit as a first master cylinder pressure Pm1. One pressure sensor 66 is provided. Similarly, the brake pressure control conduit 20 between the second master cylinder chamber 14B and the electromagnetic on-off valve 24R is provided with a second pressure sensor 68 for detecting the pressure in the control conduit as the second master cylinder pressure Pm2. It has been. The brake pedal 12 is provided with a stroke sensor 70 for detecting a brake pedal depression stroke St by a driver, and a pressure for detecting the pressure in the conduit as an accumulator pressure Pa is provided in a hydraulic supply conduit 32 on the discharge side of the oil pump 34. A sensor 72 is provided.

  Pressure sensors for detecting the pressure in the corresponding conduits as the pressures Pfl and Pfr in the wheel cylinders 22FL and 22FR are provided in the brake hydraulic pressure supply conduits 18 and 20 between the electromagnetic on-off valves 24L and 24R and the wheel cylinders 22FL and 22FR, respectively. 74FL and 74FR are provided. Further, in the hydraulic control conduits 46 and 48 between the electromagnetic on-off valves 50RL and 50RR and the wheel cylinders 22RL and 22RR, respectively, pressure sensors for detecting the pressure in the corresponding conduits as the pressures Prl and Prr in the wheel cylinders 22RL and 22RR. 74RL and 74RR are provided.

  The electromagnetic open / close valves 24L and 24R, the electromagnetic open / close valve 26, the electric motor 34, the linear valves 50FL to 50RR, and the linear valves 60FL to 60RR are controlled by an electronic control unit 78. The electronic control unit 78 includes a microcomputer 80 and a drive circuit 82. Although not shown in detail in FIG. 1, the microcomputer 80 has, for example, a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other via a bidirectional common bus. It may be.

  In the microcomputer 80, a signal indicating the first master cylinder pressure Pm1 and the second master cylinder pressure Pm2 from the pressure sensors 66 and 68, a signal indicating the depression stroke St of the brake pedal 12 from the stroke sensor 70, and a pressure sensor 72, respectively. A signal indicating the accumulator pressure Pa and a signal indicating the pressure Pi (i = fl, fr, rl, rr) in the wheel cylinders 22FL-22RR are input from the pressure sensors 74FL-74RR, respectively.

  The microcomputer 80 stores a braking force control routine according to the flowchart shown in FIG. 2 as will be described later. When the brake pedal 12 is depressed, the electromagnetic opening / closing valve 26 is opened and the electromagnetic opening / closing valves 24L and 24R are opened. In this state, the vehicle target deceleration Gt is calculated based on the master cylinder pressures Pm1 and Pm2 detected by the pressure sensors 66 and 68 and the depression stroke St detected by the stroke sensor 70, and the vehicle target reduction is performed. Based on the speed Gt, the target wheel cylinder pressure Pti (i = fl, fr, rl, rr) of each wheel is calculated to be higher than the master cylinder pressures Pm1, Pm2, and the braking pressure Pi of each wheel is calculated as the target wheel cylinder pressure Pti. The linear valves 50FL to 50RR and 60FL to 60RR are controlled so that

  As will be understood from the above description, the microcomputer 80 calculates the target wheel cylinder pressure of each wheel based on the braking operation amount of the driver, and the electromagnetic on / off valves 24L and 24R, the electromagnetic on / off valve 26, the electric motor 34, and the linear valves 50FL to 50RR. In addition, the solenoid valves 24L and 24R are closed using the pressure of the high pressure source in cooperation with the sensors such as the linear valves 60FL to 60RR, the electronic control device 78, and the pressure sensor 66. Control means for controlling the wheel cylinder pressure to become the corresponding target wheel cylinder pressure is configured.

  In the illustrated embodiment, the microcomputer 80 performs brake assist control by increasing the target wheel cylinder pressure Pti of each wheel higher than usual when the driver performs an abrupt braking operation. When the sudden braking operation by is released, the brake assist control is terminated. The brake assist control itself does not form the gist of the present invention, and may be executed in any manner known in the art.

  In this case, the microcomputer 80 performs the brake assist control when the normal brake assist control start condition is satisfied with respect to the average value Pma of the master cylinder pressures Pm1 and Pm2, and the target deceleration Gt of the vehicle is equal to or greater than the start reference value. The brake pedal 12 is depressed with reference to the depression stroke Sto of the brake pedal 12 when the normal brake assist control end condition is satisfied with respect to the average value Pma of the master cylinder pressures Pm1 and Pm2. The brake assist control is ended when the return amount of the stroke St becomes equal to or greater than the end reference value.

  Next, the braking force control in the embodiment will be described with reference to the flowchart shown in FIG. Note that the control according to the flowchart shown in FIG. 2 is started when the microcomputer 80 is activated, and is repeatedly executed at predetermined time intervals.

  First, in step 10, it is determined whether or not there is a braking request by the driver. If a negative determination is made, the process proceeds to step 20, and if an affirmative determination is made, the process proceeds to step 30. Whether or not there is a braking request by the driver is determined by, for example, whether the average value Pma of the master cylinder pressures Pm1 and Pm2 detected by the pressure sensors 66 and 68 is equal to or greater than the start reference value Pms (positive constant) or It may be performed by determining whether or not the stepping stroke St detected by the stroke sensor 70 is greater than or equal to the start reference value Sts (positive constant).

  In step 20, the electromagnetic on-off valve 26 is closed, and the electromagnetic on-off valves 24L and 24R are opened, whereby the communication between the master cylinder 14 and the wet stroke simulator 28 is shut off and the master cylinder 14 is opened. And wheel cylinders 22FL, 22FR, 22RL, and 22RR of each wheel are connected in communication. In step 30, the electromagnetic on-off valve 26 is opened or maintained, and the electromagnetic on-off valves 24L and 24R are closed or maintained, whereby the master cylinder 14 and the wet stroke are maintained. The simulator 28 is connected in communication, and communication between the master cylinder 14 and the wheel cylinders 22FL, 22FR, 22RL, and 22RR of each wheel is blocked.

  In step 40, a signal indicating the master cylinder pressure Pm1 detected by the pressure sensor 66 is read, and a map corresponding to the graph shown in FIG. 3 based on the average value Pma of the master cylinder pressures Pm1 and Pm2. Thus, the target deceleration Gpt based on the master cylinder pressure is calculated.

  In step 50, based on the depression stroke St detected by the stroke sensor 70, a target deceleration Gst based on the depression stroke is calculated from a map corresponding to the graph shown in FIG.

In step 60, the weight α (0 ≦ α ≦ 1) for the target deceleration Gpt is calculated from the map corresponding to the graph shown in FIG. 5 based on the previous final target deceleration Gtf, and the following equation is used: According to 1, the final target deceleration Gt is calculated as a weighted sum of the target deceleration Gpt and the target deceleration Gst. In the illustrated embodiment, the weight α is calculated based on the previous final target deceleration Gtf, but may be modified to be calculated based on the target deceleration Gpt or Gst.
Gt = α · Gpt + (1−α) Gst (1)

In step 70, Ki (i = fl, fr, rl, rr) is defined as a coefficient of the target wheel cylinder pressure of each wheel with respect to the final target deceleration Gt (a positive coefficient considering the braking effectiveness coefficient of each wheel). The target wheel cylinder pressure Pti (i = fl, fr, rl, rr) of each wheel is calculated according to the following formula 2.
Pti = Ki ・ Gt (2)

  In step 80, it is determined whether or not the brake assist control is being performed. If an affirmative determination is made, the process proceeds to step 120. If a negative determination is made, the process proceeds to step 90.

  In step 90, it is determined whether or not a normal brake assist control start condition is satisfied. If a negative determination is made, the process proceeds to step 160. If an affirmative determination is made, the process proceeds to step 100. .

  In this case, it is determined whether or not the normal brake assist control start condition is satisfied, for example, when a stop lamp switch not shown in FIG. 1 is in an on state and the average value Pma of the master cylinder pressure is The stop may be performed by determining whether or not the change rate ΔPma of the average value Pma of the master cylinder pressure is equal to or greater than the start reference value ΔPmbas (positive constant). The condition that the lamp switch is in the on state may be omitted.

  In step 100, it is determined whether or not the final target deceleration Gt is equal to or greater than the start reference value Gtba (positive constant). If an affirmative determination is made, the brake pedal 12 is determined in step 110. After the stepping stroke St is stored in the RAM as the stepping stroke Sto of the brake pedal 12 at the start of the brake assist control, the routine proceeds to step 140. When a negative determination is made, the routine proceeds to step 160.

  In step 120, it is determined whether or not a normal brake assist control termination condition is satisfied. If a negative determination is made, the process proceeds to step 140. If an affirmative determination is made, the process proceeds to step 130. .

  In this case, it is determined whether or not the normal brake assist control end condition is satisfied, for example, the average value Pma of the master cylinder pressure is equal to or less than the end reference value Pmbae (a positive constant smaller than Pmbas) and This may be performed by determining whether or not the change rate ΔPma of the average value Pma of the master cylinder pressure is equal to or less than the end reference value ΔPmbae (negative constant).

  In step 130, the return amount ΔSt (= Sto−St) of the depression stroke St of the brake pedal 12 with reference to the depression stroke Sto of the brake pedal 12 at the start of the brake assist control is the end reference value Stbae (correct If the determination is negative, a brake assist control is executed in step 140, and if an affirmative determination is made, the process proceeds to step 150.

  In step 150, the brake assist control is terminated, and in step 120, control is performed by hydraulic feedback so that the wheel cylinder pressure Pi of each wheel becomes the corresponding target wheel cylinder pressure Pti.

  Thus, according to the illustrated embodiment, when a normal braking operation is performed by the driver, an affirmative determination is made in step 10, and in steps 40 to 70, the vehicle target is determined based on the amount of braking operation performed by the driver. The deceleration Gt is calculated, the target wheel cylinder pressure Pti of each wheel is calculated based on the target deceleration Gt of the vehicle, a negative determination is made in step 90, and the wheel cylinder pressure Pi of each wheel is determined in step 120. Is controlled by a brake-by-wire system with the electromagnetic on-off valves 24L and 24R closed so that the target braking pressure Pti is higher than the master cylinder pressures Pm1 and Pm2.

  On the other hand, when the driver performs a sudden braking operation, an affirmative determination is made in step 10 as in the case where a normal braking operation is performed by the driver, and in steps 40 to 70, the driver is determined. The target wheel cylinder pressure Pti of each wheel corresponding to the braking operation amount is calculated, and a negative determination is made in step 80.

  In this case, when the driver's braking operation is caused by a strong depression of the brake pedal, both of the average value Pma of the master cylinder pressure and the depression stroke St of the brake pedal 12 are rapidly increased to be higher than those during a normal braking operation. Therefore, an affirmative determination is made in steps 90 and 100, whereby the brake assist control is executed in step 140.

  On the other hand, when the driver's braking operation is rapid but is caused by a light brake pedal depression, the average value Pma of the master cylinder pressure rises abruptly, but the depression stroke St of the brake pedal 12 is the master cylinder pressure. Since the pressure does not increase as rapidly as the average pressure value Pma, an affirmative determination is made in step 90, but a negative determination is made in step 100, and thus the brake assist control is not executed and step 160 is executed. In this case, normal braking force control based on the final target deceleration Gt is performed.

  Therefore, when the driver's braking operation is due to a strong depression of the brake pedal, the brake assist control can be reliably performed to effectively decelerate the vehicle, and the driver's braking operation can be performed quickly but with a light brake pedal depression. Therefore, it is possible to effectively prevent unnecessary brake assist control from being executed.

  Further, when the brake operation amount is reduced by the driver in a situation where the brake assist control is being executed by a strong depression of the brake pedal, both the average value Pma of the master cylinder pressure and the depression stroke St of the brake pedal 12 are both used. Similarly, since it decreases, an affirmative determination is made in steps 120 and 130, whereby the brake assist control is terminated in step 150.

  On the other hand, when the brake operation amount is reduced by the driver in a situation where the brake assist control is being executed by the brake pedal being depressed very quickly, the average value Pma of the master cylinder pressure rapidly decreases. Since the depression stroke St of the brake pedal 12 does not decrease as rapidly as the average value Pma of the master cylinder pressure, an affirmative determination is made at step 120, but a negative determination is made at step 130, thereby It is possible to effectively prevent the assist control from being ended too early.

  In particular, according to the illustrated embodiment, it is determined in step 90 that the normal brake assist control start condition is satisfied, and in step 100, the final target deceleration Gt is equal to or greater than the start reference value Gtba. Since it is determined that the brake assist control is started, a physical quantity other than the master cylinder pressure representing the braking operation amount of the driver and the depression force on the brake pedal 12 that changes in substantially the same manner as the master cylinder pressure are used. It is possible to accurately determine whether or not to start the brake assist control as compared to the case where

  Further, according to the illustrated embodiment, it is determined in step 120 that the normal brake assist control termination condition is satisfied, and in step 100, the return amount ΔSt of the depression stroke St of the brake pedal 12 is terminated. Since the brake assist control is terminated when it is determined that the reference value Stbae is equal to or greater than the reference value Stbae, it is compared with the case where it is determined in step 100 whether or not the depression stroke St of the brake pedal 12 is equal to or less than the reference value. Thus, it can be accurately determined whether or not the brake assist control should be terminated.

  Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

  For example, in the above-described embodiment, it is determined in step 100 whether or not the final target deceleration Gt is equal to or greater than the start reference value Gtba. It may be modified so that it is determined whether or not the increase is equal to or greater than the start reference value Gtba, and whether or not the depression stroke St of the brake pedal 12 is equal to or greater than the reference value. The determination may be made to determine whether or not the braking operation amount of the driver based on the depression stroke St of the brake pedal 12 and the depression force Fb on the brake pedal 12 is greater than or equal to a reference value. It may be modified to be done.

  In the above embodiment, the return amount ΔSt of the depression stroke St of the brake pedal 12 with reference to the depression stroke St of the brake pedal 12 at the start of the brake assist control in step 130 is the end reference value. Although it is determined whether or not it is greater than or equal to Stbae, it may be modified so as to determine whether or not the depression stroke St of the brake pedal 12 has become equal to or less than its end reference value.

  In the above-described embodiment, the target braking pressure Pti of each wheel is operated based on the average value Pma of the master cylinder pressures Pm1 and Pm2 as a value indicating the amount of braking operation by the driver and the depression amount St of the brake pedal. The driver's required deceleration Gt is calculated, and the target braking pressure Pti of each wheel is calculated based on the driver's required deceleration Gt, but the control of the braking force itself forms the gist of the present invention. Rather, it may be performed in any manner known in the art.

  In the above-described embodiment, the pressure increasing / reducing control valve for controlling the wheel cylinder pressure Pi of each wheel is composed of the linear valves 50FL to 50RR as pressure increasing control valves and the linear valves 60FL to 60RR as pressure reducing control valves. However, these valves may be replaced with control valves having functions of increasing and decreasing pressure and holding.

  Furthermore, although the master cylinder pressure is detected by the two pressure sensors 66 and 68, the master cylinder pressure may be corrected so as to be detected by one pressure sensor.

  DESCRIPTION OF SYMBOLS 10 ... Brake device, 12 ... Brake pedal, 14 ... Master cylinder, 22FL-22RR ... Wheel cylinder, 24F, 24R, 26 ... Electromagnetic on-off valve, 50FL-50RR ... Linear valve, 60FL-60RR ... Linear valve, 66, 68 ... Pressure sensor, 70 ... Stroke sensor, 72, 74FL to 74RR ... Pressure sensor, 78 ... Electronic control unit

Claims (7)

  In a vehicle braking force control apparatus that starts brake assist control when a predetermined start condition including a condition for the master cylinder pressure is satisfied, a physical quantity other than the master cylinder pressure representing the amount of braking operation by the driver is set as the predetermined physical quantity. A braking force control device for a vehicle, wherein the brake assist control is started when a target deceleration of the vehicle calculated based on at least the predetermined physical quantity is equal to or greater than a reference value.   In a vehicle braking force control device that starts brake assist control when a predetermined start condition is satisfied, when starting brake assist control, start based on the master cylinder pressure and the operation displacement amount of the brake operator. A vehicle braking force control device.   In a vehicle equipped with a braking force control device that starts brake assist control when a predetermined start condition is satisfied, the brake assist control is started based on the master cylinder pressure and the operation displacement amount of the brake operator. A vehicle characterized by that.   2. The vehicle braking force control apparatus according to claim 1, wherein the physical quantity includes an operation displacement amount of a brake operator.   2. The vehicle braking force control apparatus according to claim 1, wherein the target deceleration is calculated based on a master cylinder pressure and the physical quantity.   6. The vehicle braking force control device according to claim 5, wherein the target deceleration is a sum of weights of a target deceleration calculated based on a master cylinder pressure and a target deceleration calculated based on the physical quantity. .   The vehicle braking force according to claim 5 or 6, wherein the target deceleration is calculated every predetermined time, and the target deceleration is calculated based on the previously calculated target deceleration. Control device.

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