JP4618040B2 - Braking control device - Google Patents

Description

  The present invention relates to a technical field of a braking control device that controls braking means for braking a vehicle.

  As this type of technique, a technique for maintaining a stopped state of a vehicle has been proposed (see, for example, Patent Document 1). According to the slope stopping device disclosed in Patent Document 1 (hereinafter referred to as “conventional technology”), when the vehicle stops on the slope, by adding a stopping force according to the slope angle of the slope to the wheel, It is said that it is possible to prevent the vehicle from moving backward.

  In addition, the technique of changing the pressure reduction gradient at the time of canceling | releasing braking force according to the opening degree and operation speed of an accelerator pedal is also proposed (for example, refer patent document 2).

JP-A-7-69102 JP 2002-283997 A

  When the vehicle starts from a state where the stop state is maintained, for example, the wheel may be steered by a driver's steering operation or the like. In this case, the longitudinal acceleration caused by the cornering drag is generated, and the driver may feel uncomfortable as if the braking state of the vehicle is not released. That is, the conventional technique has a technical problem that maintaining the stop state may result in discomfort to the driver.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a braking control device that can reduce driver discomfort.

In order to solve the above-described problem, a braking control device according to the present invention is a braking control device that controls braking means for braking a vehicle, and according to an input to maintain the vehicle stop state, First control means for controlling the braking means to apply a braking force for maintaining the stop state to the vehicle, and a value corresponding to a running resistance when the vehicle starts from the stop state In accordance with an input for specifying the damping characteristic determining means for determining the damping characteristic of the braking force when the stop state is released based on the specified value, and the input for releasing the stop state, Second control means for controlling the braking means so that the braking force is attenuated with the determined damping characteristic, and the specifying means is a value of at least one of the values corresponding to the running resistance of the vehicle. Steering angle value And identifies.

  The braking means according to the present invention is a concept including a mechanism, a device, or a system capable of braking the vehicle by applying a braking force to the vehicle, preferably a wheel provided on the vehicle. As long as the concept is secured, the form is not limited. Preferably, the brake device of a vehicle is pointed out. In this case, the mode of the brake device is not limited at all, and various systems such as a drum system, a disk system, or a ventilated disk system may be adopted according to the use or required performance of the vehicle. Alternatively, the braking means may be incorporated into various travel stabilization devices such as an ABS (Antilock Braking System) or a VSC (Vehicle Stability Control) device depending on the use or required performance of the vehicle, You may have a form which gives braking power in cooperation.

  According to the steering control device of the present invention, during the operation, the first control means applies a braking force for maintaining the stop state to the vehicle in response to an input indicating that the stop state of the vehicle is maintained. So as to control the braking means.

  Here, “input to maintain the stopped state” means a physical, electrical, mechanical or mechanical trigger signal or a signal equivalent thereto for instructing, commanding or requesting to maintain the stopped state. For example, it refers to an electrical signal generated by an artificial operation through various operation keys, operation buttons, operation levers, operation dials, or the like by a vehicle occupant including a driver. Alternatively, it refers to an electrical signal generated by a driver of a vehicle, such as stepping on a brake pedal or various pedal devices similar to the brake pedal. The input may be performed while the vehicle is running or may be performed while the vehicle is stopped. When an input related to the traveling of the vehicle is performed, the stopped state is maintained once the vehicle stops. That is, “in response to an input” means that the stop state of the vehicle is always maintained at a time close in time series to the time when the input is made as long as it is in the future from the time when the input is made. It is not necessary.

  Further, “maintaining the stopped state” preferably means that after the vehicle has stopped once, the stopped state is continued regardless of an operation (for example, a stepping operation on a brake pedal) that should stop the normal vehicle. Means that. That is, for example, in a vehicle in which an automatic transmission is adopted, the creep torque is suppressed and the vehicle is stopped in an idling state even when the driver removes his / her foot from the brake pedal.

  The mode in which the first control means controls the braking means is not limited as long as the braking force for maintaining the stop state is finally applied to the vehicle by the braking means. For example, the hydraulic pressure in the master cylinder or the wheel cylinder that defines the braking force applied to each wheel of the vehicle, preferably the driving wheel, may be controlled to a value that can maintain the stop state.

  The stop state of the vehicle maintained by the action of the first control means is canceled in response to an input for canceling the stop state. At this time, the second control unit controls the braking unit so that the braking force applied to the vehicle to maintain the stopped state is attenuated, thereby releasing the stopped state.

  Note that “an input to cancel the stop state” is a physical instruction for instructing, instructing or requesting to cancel the stop state based on the same meaning as the input to maintain the stop state described above. It is a concept that includes an electrical, mechanical, or mechanical trigger signal or a signal based on the trigger signal, but preferably, depending on an operation for the driver to start the vehicle, for example, depression of an accelerator pedal, etc. Represents the electrical signal that is generated. In this case, since the braking force for maintaining the stopped state of the vehicle is attenuated according to the driver's intention to start the vehicle, a relatively linear operational feeling can be realized.

  On the other hand, when the braking force for maintaining the stopped state of the vehicle is attenuated, that is, preferably when the vehicle is started again from the state where the stopped state is maintained, for example, the steering operation of the driver, etc. When the wheels are being steered by, a running resistance such as a cornering drag may act as a kind of braking force on the vehicle. This running resistance may cause acceleration in the longitudinal direction of the vehicle. Also, the vehicle may pitch. For this reason, the passenger may feel uncomfortable. Therefore, the braking control device according to the present invention reduces such discomfort as follows.

  That is, according to the braking control apparatus of the present invention, the value corresponding to the running resistance when the vehicle starts from the stop state is specified by the specifying unit. Further, based on the specified value, the damping characteristic of the braking force when the stop state is released is determined by the damping characteristic determining means.

  Here, “running resistance” is a concept that includes a force that acts to prevent the vehicle from moving when the vehicle starts from a stopped state. Typically, when the vehicle moves forward and turns. It refers to the force corresponding to the reverse direction component (i.e., the direction opposite to the forward direction) of the lateral force generated on the steered wheel, that is, the cornering drag.

Further, the “value corresponding to the running resistance” is a concept including values having some correspondence that can define the running resistance as such a concept, and preferably a value that defines the cornering drag. Point to. Examples of such a value include a vehicle steering angle. However, in view of such a concept, the “value defining the running resistance” may include the running resistance itself.

  The “specific” in the present invention means physical, mechanical, electrical or chemical as well as direct or indirect detection or measurement by physical, mechanical, electrical or chemical means. Including estimation or estimation based on some physical value detected or measured by other means, and further, for example, means for physically, mechanically, electrically, or chemically detecting the value of interest From this, it is also a concept including determining a value (that is, simply recognizing it as a detection result in other words) by receiving some signal (for example, an electrical signal) according to the detected value. Therefore, the specifying means according to the present invention may be at least a part of a controller device such as an ECU (Electronic Control Unit). When the specifying means takes the form of an ECU or the like, the running resistance itself is obtained numerically based on the electrical output corresponding to the value corresponding to the running resistance output from various sensor devices. It is also possible to do.

  The damping characteristic determining means determines the damping characteristic of the braking force based on the specified value. Here, the “damping characteristic” may have any form as long as the damping aspect of the braking force can be defined. For example, the damping characteristic may be given as a time function for damping the braking force in a linear function (ie, linearly) or in a multi-order function (ie, curvilinear).

  The attenuation characteristic may be determined in any way as long as it is determined based on the value specified by the specifying means. For example, the damping characteristic may be such that the braking force is quickly released as the running resistance increases. In this case, it is relatively easy to match the sensibility of the passenger, and discomfort can be suitably reduced. However, the attenuation characteristic is not limited to this, and in the case where the attenuation characteristic that can suitably reduce the discomfort given to the occupant can be specified in advance experimentally, empirically, or based on simulation, etc. Such attenuation characteristics may be determined. By at least determining the damping characteristic of the braking force based on the value corresponding to the running resistance in this manner, the consistency with the sensibility of the occupant can be dramatically improved.

  The second control means described above controls the braking means so that the braking force is attenuated at the determined damping rate. Accordingly, it is possible to attenuate the actual braking force with obviously various attenuation characteristics as compared with the case where no consideration is given to the running resistance of the vehicle. That is, it is possible to appropriately reduce the uncomfortable feeling given to the occupant by appropriately controlling the braking force that tends to be excessive as a result of running resistance such as cornering drag.

  Each of the first control means and the second control means according to the braking control device according to the present invention may have an individual hardware configuration, for example, each as at least a part of the ECU or the like. You may have a hardware structure integrated with each other.

Here, in particular, in the braking control device according to the present invention, the steering angle of the vehicle is specified as at least one of the values corresponding to the running resistance. Since the steering angle of the vehicle has a deep relationship with the running resistance, it is preferable that the damping characteristic of the braking force can be determined efficiently and effectively.

  Note that the steering angle of the vehicle according to the present invention may be an actual steering angle of a wheel, or a rotation angle of a steering wheel (hereinafter referred to as “handle” as appropriate) (hereinafter referred to as “handle angle” as appropriate). ). Of course, in view of the fact that the running resistance is the resistance force acting on the wheel, the element that directly defines the running resistance is not the steering wheel angle but the actual steering angle. Is uniquely defined by the steering gear ratio, and by specifying one value, the other value can also be specified. Therefore, the attenuation characteristics determined by the attenuation rate determining means can be equal to each other regardless of which value is determined.

In one aspect of the braking control apparatus according to the present invention, the damping characteristic determining means is based on the specified value when the specified value is a value corresponding to the running resistance equal to or greater than a predetermined value. To determine the attenuation characteristic.

  According to this aspect, when the specified value is a value corresponding to the running resistance equal to or greater than the predetermined value, the attenuation characteristic is determined based on the specified value. In vehicle conditions where the running resistance is relatively low, for example, when the steering angle is so small that it can be regarded as zero or zero, discomfort due to running resistance is unlikely to occur, so an attenuation characteristic based on the specified value By making this determination under such limited conditions, it is possible to reduce the processing load on the braking control device and effectively reduce discomfort.

  The “value corresponding to a running resistance greater than or equal to a predetermined value” may be a value of the running resistance greater than or equal to a predetermined value as long as the running resistance can be detected or calculated as a result of numerical calculation. . In addition, when the correspondence relationship between the specified value and the running resistance is set in advance experimentally, empirically, or based on simulation, for example, the running resistance greater than a predetermined value based on the correspondence relationship. It may be a value corresponding to. That is, although it is a value corresponding to a running resistance of a predetermined value or more, the running resistance value itself does not necessarily have to be grasped as a physical numerical value.

  The predetermined value may be determined in advance experimentally, empirically, or based on a simulation or the like, for example, as a value that cannot disregard the possibility of discomfort to the passenger.

  In another aspect of the braking control apparatus according to the present invention, the damping characteristic determining means determines the damping characteristic so that the braking force is attenuated earlier as the running resistance increases.

  According to this aspect, as the running resistance increases, the braking force attenuates faster, so that discomfort can be efficiently and effectively reduced. Note that “decay quickly” does not necessarily mean that the time required for the braking force to become zero is relatively short, but at least the braking force does not cause discomfort to the passenger. This means that the time required for attenuation is relatively short.

  In this aspect, the damping characteristic may be a damping rate of the braking force, and the damping characteristic determining unit may determine the damping rate so that the damping resistance increases as the running resistance increases.

  In this case, the load applied to the attenuation rate determining means is reduced, and the braking force can be attenuated simply and effectively.

  In another aspect of the braking control device according to the present invention, the damping characteristic determining means is specified when the vehicle is maintained in a stopped state at a place other than an uphill road having an inclination angle equal to or greater than a predetermined value. The attenuation characteristic is determined based on the value to be determined.

  For example, when the vehicle is stopped on an uphill road, a time delay due to the influence of gravitational acceleration occurs when the vehicle starts from a maintained stop state. Such a time delay is an event that can easily be assumed based on the fact that the passenger is stopped on the uphill road, and the passenger does not need to execute the braking force control in consideration of the running resistance. The possibility of feeling such discomfort is extremely low. According to this aspect, when the stop state is maintained at a place other than the uphill road having an inclination angle equal to or greater than the predetermined value, the attenuation characteristic is determined based on the specified value, which is efficient and effective. is there.

  Note that such an inclination angle is not particularly limited as long as it is an inclination angle that defines an uphill road, but is a value that does not cause discomfort to the passenger based on an experiment, experience, or simulation in advance. May be set to such a value. Alternatively, it may be set so that the attenuation characteristic is determined based on the specified value only on the flat road and the downhill road. The determination of the tilt angle may be performed based on, for example, the tilt angle or the longitudinal acceleration detected by the tilt angle sensor or the acceleration sensor that detects the longitudinal acceleration of the vehicle.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

<Embodiment of the Invention>
Preferred embodiments of the present invention will be described below with reference to the drawings as appropriate.

<Configuration of Embodiment>
First, with reference to FIG. 1, the structure of the vehicle 10 which concerns on one Embodiment of this invention is demonstrated. FIG. 1 is a schematic configuration diagram of the vehicle 10. Here, the configuration of the vehicle 10 will be described with a part of its operation.

  In FIG. 1, a vehicle 10 is a vehicle that includes a left front wheel FL, a right front wheel FR, a left rear wheel RL, and a right rear wheel RR, and travels by the power of an engine (not shown).

  The vehicle 10 includes a handle 11, a shaft 12, and a steering device 13.

  The handle 11 is a device for transmitting a steering operation (hereinafter referred to as “handle operation” as appropriate) by a driver (not shown) to the shaft 12. The handle operation by the driver is transmitted to the shaft 12 as rotational power. Is done. The rotational power received by the shaft 12 is transmitted to the steering device 13.

  The steering device 13 is a rack-and-pinion type steering device, and the reciprocating motion of the rack (not shown) meshed with the pinion gear in the left-right direction shown in the figure is caused by the rotational motion of the pinion gear (not shown) provided at the tip portion of the shaft 12. Thus, the steering angles of the left front wheel FL and the right front wheel FR, which are drive wheels, are controlled in accordance with the driver's steering operation.

  In FIG. 1, the vehicle 10 further includes an ECU 100, a longitudinal G sensor 200, a start switch 300, a brake actuator 400, a brake pedal 500, a brake pedal sensor 510, an accelerator pedal 600, an accelerator pedal sensor 610, a handle angle sensor 700, and a braking device 800FL. , 800FR, 800RL and 800RR and wheel cylinders 810FL, 810FR, 810RL and 810RR.

  The ECU 100 includes an unillustrated ROM (Read Only Memory), RAM (Random Access Memory), and the like, and is an electronic control unit that controls the entire operation of the vehicle 10, and is an example of a braking control device according to the present invention. The ECU 100 is configured to be able to execute a braking control process, which will be described later, according to a program stored in the ROM, and can temporarily store various data generated in the execution process of the braking control process in the RAM. It is configured.

  The front-rear G sensor 200 is a sensor that detects an acceleration Gx in the front-rear direction of the vehicle. The front-rear G sensor 200 is electrically connected to the ECU 100, and the sensor output is constantly monitored by the ECU 100.

  The activation switch 300 is an input device that is installed at a predetermined location (for example, a console panel) in the vehicle interior of the vehicle 10 and is operated by a driver or the like, and is electrically connected to the ECU 100. In the present embodiment, when the start switch 300 is operated, an input signal that prompts the ECU 100 to execute the braking control process (that is, an example of “an input to maintain the vehicle stop state” according to the present invention). It is configured to output.

  The brake actuator 400 is an example of the “braking means” according to the present invention that is electrically connected to the ECU 100 and configured to be able to control the hydraulic pressure Pwc of each wheel cylinder according to the upper control by the ECU 100.

  The brake pedal 500 is a pedal for operating each braking device. The brake pedal 500 is a pedal operated by the driver, and the amount of depression is detected by the brake pedal sensor 510 and transmitted as an electric signal to the ECU 100 electrically connected to the brake pedal sensor 510. It has become.

  The accelerator pedal 600 is a pedal that is stepped on by the driver of the vehicle 10 and controls the opening / closing state of the throttle valve in the engine of the vehicle 10. The amount of depression is detected by an accelerator pedal sensor 610 and transmitted as an electric signal to the ECU 100 electrically connected to the accelerator pedal sensor 610.

  The handle angle sensor 700 is a sensor that detects the rotation angle (that is, the handle angle) of the handle 11. The detected handle angle is output to the ECU 100 electrically connected to the handle angle sensor 700 as an electrical signal representing the handle angle. Note that the ECU 100 can acquire the steering angle Ds of the wheels FL and FR as the steering wheels based on the detected steering wheel angle and the steering gear ratio in the steering device 13.

  The braking device 800FL is a disc brake device that is provided on the left front wheel FL and brakes the left front wheel FL by pressing a disc (not shown) by a brake pad (not shown) according to the hydraulic pressure Pwc of the wheel cylinder 810FL. Similarly, the braking devices 800FR, 800RL and 800RR and the wheel cylinders 810FR, 810RL and 810RR are disc brake devices corresponding to the right front wheel FR, the left rear wheel RL and the right rear wheel RR, respectively.

  Each wheel cylinder is configured to transmit the hydraulic pressure of the brake oil via a master cylinder (not shown) and the brake actuator 400. Normally, when the driver depresses the brake pedal 500, the hydraulic pressure corresponding to the depressing amount is transmitted to each wheel cylinder via the master cylinder. On the other hand, the ECU 100 can also control the hydraulic pressure Pwc of each wheel cylinder by controlling the brake actuator 400 regardless of the driver's brake pedal operation. Each braking device and each wheel cylinder together with the brake actuator 400 constitute an example of the “braking means” according to the present invention.

<Operation of Embodiment>
In the vehicle 10 according to the present embodiment, the ECU 100 controls the braking force of the vehicle 10 by executing a braking control process according to a program stored in the ROM. Here, the details of the braking control process will be described with reference to FIG. FIG. 2 is a flowchart of the braking control process.

  In FIG. 2, the ECU 100 determines whether or not the start switch 300 is operated (step A10). When start switch 300 is not operated (step A10: NO), ECU 100 repeats step A10 until start switch 300 is operated. In this case, braking of the vehicle 10 is based on a normal braking mode in which the brake actuator 400 transmits hydraulic pressure corresponding to the amount of depression of the brake pedal 500 to each wheel cylinder.

  When start switch 300 is operated (step A10: YES), ECU 100 starts the stop maintaining mode (step A11). The stop maintenance mode is a braking mode in which, when the vehicle 10 stops once, the stop state is maintained regardless of the depression of the brake pedal 500.

  When the start switch 300 is operated, the ECU 100 determines whether or not the vehicle 10 has stopped (step A12). Whether or not the vehicle 10 has stopped is determined based on the output of a vehicle speed sensor (not shown) in FIG. If the vehicle 10 has not yet stopped (step A12: NO), the ECU 100 repeats step A12 until the vehicle 10 stops, and the process enters a standby state. When the vehicle 10 stops (step A12: YES), the ECU 100 controls the brake actuator 400 so that the stopped state of the vehicle 10 is maintained (step A13).

  At this time, the ECU 100 maintains the stop state of the vehicle 10 by maintaining the oil pressure Pwc of each wheel cylinder at the oil pressure Pw0 of each wheel cylinder at the time when the vehicle 10 stops at least. Here, “at least” means that if the oil pressure Pwc determined based on the amount of depression of the brake pedal 500 by the driver is larger than the oil pressure Pw0, each wheel cylinder is directly reflected by the oil pressure reflecting the driver's intention. Even if the hydraulic pressure Pwc determined by the amount of depression of the brake pedal 500 is smaller than the hydraulic pressure Pw0 even in the extreme case, even if the driver lifts his / her foot from the brake pedal 500, each wheel cylinder is operated at the hydraulic pressure Pw0. It means being driven. The ECU 100 stores the hydraulic pressure Pw0 when the vehicle is stopped as a control value of the brake actuator 400.

  During the period in which the vehicle 10 is kept stopped, the ECU 100 always determines the presence or absence of a release input (step A14). The release input refers to an input for releasing the vehicle stop maintaining state, and in this embodiment, an input indicating that the driver starts the vehicle 10, that is, an electric signal generated by stepping on the accelerator pedal 600. Point to. The amount of depression of the accelerator pedal 600 is detected by an accelerator pedal sensor 610 that is electrically connected to the accelerator pedal 600. The ECU 100 cancels the stop state of the vehicle 10 when the amount of depression of the accelerator pedal 600 detected by the accelerator pedal sensor 610 exceeds a predetermined amount. Therefore, when there is no release input yet (step A14: NO), the ECU 100 repeats steps A13 and A14 until there is a release input, and the stop state of the vehicle 10 is maintained.

  On the other hand, when there is a release input (step A14: YES), the ECU 100 controls the brake actuator 400 so that the hydraulic pressure Pwc of each wheel cylinder is attenuated at a predetermined attenuation rate. At this time, the damping rate of the hydraulic pressure Pwc is determined in consideration of a cornering drag that acts on the front wheels FL and FR of the vehicle 10 (that is, an example of “running resistance” according to the present invention).

  Here, the cornering drag will be described with reference to FIG. FIG. 3 is a schematic diagram of the cornering drag that acts on the vehicle 10. In the figure, the same reference numerals are assigned to the same parts as those in FIG. 1, and the description thereof is omitted.

  In FIG. 3, the left front wheel FL and the left rear wheel RL, which are the left wheels of the vehicle 10, are shown. The left front wheel FL is steered at the steering angle Ds. At this time, the lateral force Fs acts on the left front wheel FL in a direction perpendicular to the arrow direction steering direction. The cornering drag CD is a force corresponding to a component in the front-rear direction of the lateral force Fs, and is represented by the following equation (1).

CD = Fs · sinDs = M · Gx (1)
Here, M is a vehicle mass, which is a fixed value for each vehicle 10. The cornering drag CD is a force acting in the direction opposite to the direction in which the vehicle 10 starts, and becomes a virtual braking force that acts on the front wheel FL when the vehicle 10 tries to start. The longitudinal acceleration Gx of the vehicle 10 generated by the cornering drag CD is finally expressed by the following equation (2).

Gx = Fs · sinDs / M (2)
Eventually, when starting the vehicle 10 from the stop state, the longitudinal acceleration Gx acts on the vehicle 10. This longitudinal acceleration Gx leads to an uncomfortable feeling given to the driver when starting the vehicle 10. On the other hand, in view of the fact that the cornering drag CD acts as a virtual braking force, in order to reduce the uncomfortable feeling when starting the vehicle 10 from the stop maintenance state, the braking force of each braking device is defined. It is only necessary to attenuate the hydraulic pressure Pwc of each wheel cylinder relatively quickly. Therefore, in the brake control process, such a sense of incongruity is reduced by controlling the damping rate of the hydraulic pressure Pwc.

  Returning to FIG. 2, when there is a release input, the ECU 100 first determines whether the place where the vehicle 10 is stopped is a flat road or a downhill road (that is, “uphill road having an inclination angle of a predetermined value or more according to the present invention It is determined whether it is an example of “a place other than” (step A15). Such a determination is made based on the output value of the front-rear G sensor 200. That is, the ECU 100 compares and discriminates the reference value of acceleration corresponding to the uphill road having a predetermined inclination angle stored in advance in the ROM and the output value of the front / rear G sensor 200. The acceleration corresponding to the uphill road is an acceleration acting in the rear direction of the vehicle 10.

  In view of the action of the cornering drag CD shown in FIG. 3, when the vehicle 10 is stopped on the uphill road, the gravitational acceleration acts in the same direction as the cornering drag CD. That is, it is necessary to control the braking force (that is, here, the hydraulic pressure Pwc of the wheel cylinder) because the driver understands sensuously that it is difficult to start compared to a flat road or a descending road. Does not occur. The reference value stored in the ROM is set in advance to a value that defines an uphill road that can be considered to have little need to control the braking force experimentally, empirically, or by simulation.

  When the place where the vehicle 10 is stopped is not a flat road or a descending road (step A15: NO), the ECU 100 defines the attenuation rate of the hydraulic pressure Pwc of each wheel cylinder with normal pressure reduction characteristics for the reasons described above. The attenuation rate A is set (step A17). The brake actuator 400 controls the hydraulic pressure Pwc according to the determined damping rate A to attenuate the braking force.

  Here, in addition to FIG. 2, the subsequent description will be made with reference to FIG. 4 as appropriate. FIG. 4 is a diagram illustrating characteristics of the hydraulic pressure Pwc of each wheel cylinder in the execution process of the braking control process.

  In FIG. 4, the vertical axis and the horizontal axis represent the hydraulic pressure Pwc and time of the wheel cylinder, respectively. For example, the start switch 300 is operated at time T0 in FIG. 4 to start the stop maintenance mode. Thereafter, the driver starts to depress the brake pedal 500 at time T1, and the vehicle 10 stops at time T2. That is, the hydraulic pressure Pwc at this time becomes the aforementioned Pwc0. Thereafter, the driver ends the depression of the brake pedal 500 at time T4. That is, the period ΔTA is a depression period of the brake pedal 500 by the driver.

  On the other hand, as described above, the hydraulic pressure Pwc of each wheel cylinder is maintained at least equal to or higher than Pwc0 during the period in which the stop maintaining mode is activated. Therefore, the hydraulic pressure Pwc corresponding to the depression of the brake pedal 500 at time T3. Even if the pressure falls below Pwc0, the hydraulic pressure Pwc is maintained at Pwc0.

  Here, the release of the braking force (that is, the hydraulic pressure Pwc) is started when the driver depresses the accelerator pedal 600 by a predetermined amount at the time T5 when the period ΔTB that is the stop period of the vehicle 10 has elapsed from the time T3. Is done. The damping rate A set in step A17 in FIG. 2 is equal to the gradient when the hydraulic pressure Pwc is linearly attenuated from Pwc0 to zero in the period ΔTC from time T5 to time T6 (from time T5 to T6 shown in the figure). Equivalent to solid line).

  Returning to FIG. 2, when the place where the vehicle 10 is stopped is a flat road or a descending road (step A15: YES), the ECU 100 determines that the steering angle Ds of the left and right front wheels is greater than a preset steering angle threshold Dsth. Is also larger (step A16).

  As is apparent from the above equation (1), the cornering drag CD increases as the steering angle Ds increases (in the range of 0 ° ≦ Ds ≦ 90 °). The steering angle threshold value Dsth is previously set experimentally, empirically, or based on simulation as a value at which the influence of the cornering drag CD cannot be ignored when the braking force is attenuated according to the above-described attenuation rate A. And stored in the ROM of the ECU 100.

  When the steering angle Ds is equal to or smaller than the steering angle threshold value Dsth (step A16: NO), the ECU 100 executes the process according to step A17 and attenuates the braking force according to the attenuation rate A. On the other hand, when the steering angle Ds is larger than the steering angle threshold value Dsth (step A16: YES), the ECU 100 attenuates the attenuation rate of the hydraulic pressure Pwc of each wheel cylinder larger than the attenuation rate A that defines the normal pressure reduction characteristics described above. The rate B is set (step A18). The brake actuator 400 attenuates the hydraulic pressure Pwc according to the damping rate B and attenuates the braking force of each braking device.

  Here, in FIG. 4, the damping rate B is, for example, when the hydraulic pressure Pwc is linearly attenuated from Pwc0 to zero in a period from time T5 to time T7 closer to time T5 in time series than time T6. (Corresponding to the broken line from the time T5 to T7 in the figure).

  4 is an example, and the value of the attenuation rate B is a variable value corresponding to the value of the steering angle Ds that defines the value of the cornering drag CD. That is, as the steering angle Ds is relatively large, the damping rate B is relatively large, that is, a value that attenuates the wheel cylinder hydraulic pressure Pwc to zero in a relatively short time. Such attenuation rate values are stored in the ROM in advance in association with the steering angle. In addition to the fact that the value of the element that defines the cornering drag in advance (for example, the steering angle) and the attenuation rate are associated with each other in this way, for example, the ECU 100 calculates the above formula (1) each time so that the cornering drag is calculated. May be associated with the cornering drag value and the attenuation factor. Alternatively, such association may not be performed in advance, and an appropriate attenuation rate may be set according to some algorithm each time. In the present embodiment, the threshold value Dsth is set for the steering angle Ds. However, the hydraulic pressure Pwc may be constantly variably controlled according to the steering angle Ds without providing such a threshold value.

  It should be noted that an upper limit value may be set in advance for the length of the period ΔTB in which the hydraulic pressure Pwc of each wheel cylinder is maintained by the processing related to the stop maintaining mode, that is, the braking force is maintained. For example, when the accelerator pedal 600 is clearly depressed for a long time, that is, when there is no input to cancel the stop maintenance mode, the vehicle 10 can be regarded as parked rather than stopped (ie, stopped). . If such a determination is established, the ECU 100 may automatically operate a parking brake device such as a parking brake.

  Returning to FIG. 2, when the attenuation rate is set by the process according to step A17 or step A18, the ECU 100 returns the process to step A10 and the series of processes is repeated.

  As described above, according to the braking control process according to the present embodiment, the braking force of each braking device is considered in consideration of the effect of the cornering drag CD that acts on the left and right front wheels when the vehicle 10 starts from the stop maintaining state. Is set, that is, the damping rate of the hydraulic pressure Pwc of each wheel cylinder is set, so that the longitudinal acceleration acting on the vehicle 10 is reduced. That is, the uncomfortable feeling given to the driver is suitably reduced.

<Second Embodiment>
In the first embodiment, the input for starting the stop maintaining mode is performed through the operation of the start switch 300, but the starting form of the stop maintaining mode is not limited to this. Here, a second embodiment according to the present invention will be described with reference to FIG. FIG. 5 is a diagram illustrating another characteristic of the hydraulic pressure Pwc of each wheel cylinder in the execution process of the braking control process. In the figure, the same parts as those in FIG.

  In FIG. 4, after time T2 when the vehicle 10 is stopped, the brake pedal 500 is stepped on in the process of the driver stepping on the brake pedal 500, and the hydraulic pressure Pwc of each wheel cylinder is preset at the threshold value Pwc1 at time T0 ′. Suppose that The ECU 100 activates the stop maintenance mode in the same manner as in the first embodiment when the wheel cylinder hydraulic pressure Pwc has reached the threshold value Pwc1. After that, the process is the same as in the first embodiment.

  In this case, it is efficient because the driver can activate the stop maintaining mode only by stepping on the brake pedal 500 without operating the activation switch 300.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification. Moreover, it is included in the technical scope of the present invention.

1 is a schematic configuration diagram of a vehicle according to a first embodiment of the present invention. 3 is a flowchart of a braking control process executed by an ECU in the vehicle of FIG. It is a schematic diagram of the cornering drag which acts on the vehicle of FIG. It is a figure which illustrates the characteristic of the oil pressure of each wheel cylinder in the execution process of the brake control processing of FIG. It is a figure which illustrates the other characteristic of the oil_pressure | hydraulic of each wheel cylinder in the execution process of the brake control process of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Vehicle, 100 ... ECU, 200 ... Front / rear G sensor, 300 ... Start switch, 400 ... Brake actuator, 500 ... Brake pedal, 510 ... Brake pedal sensor, 600 ... Accelerator pedal, 610 ... Accelerator pedal sensor, 700 ... Steering angle Sensor, 800FL, 800FR, 800RL, 800RR ... braking device, 810FL, 810FR, 810RL, 810RR ... wheel cylinder.

Claims (6)

A braking control device for controlling braking means for braking a vehicle,
First control means for controlling the braking means to apply a braking force for maintaining the stopped state to the vehicle in response to an input to maintain the stopped state of the vehicle;
A specifying means for specifying a value corresponding to a running resistance when the vehicle starts from the stop state;
Damping characteristic determining means for determining a damping characteristic of the braking force when the stop state is released based on the specified value;
Second control means for controlling the braking means so that the braking force is attenuated by the determined damping characteristic in response to an input to release the stop state;
The braking control device according to claim 1, wherein the specifying unit specifies a value of a steering angle of the vehicle as at least one of values corresponding to the running resistance. The attenuation characteristic determining means determines the attenuation characteristic based on the specified value when the specified value is a value corresponding to the running resistance equal to or greater than a predetermined value. Item 4. The braking control device according to item 1 . The attenuation characteristic determination means, the brake control apparatus according to the damping characteristic, in claim 1 or 2, wherein the determining as the braking force as the running resistance is larger is attenuated quickly. The damping characteristic is a damping rate of the braking force,
The braking control device according to claim 3 , wherein the damping characteristic determination unit determines the damping rate so that the damping resistance increases as the running resistance increases. The attenuation characteristic determining means determines the attenuation characteristic based on the specified value when the vehicle is maintained in a stopped state other than an uphill road having an inclination angle equal to or greater than a predetermined value. The braking control device according to any one of claims 1 to 4 , wherein the braking control device is characterized in that: A braking control device for controlling braking means for braking a vehicle,
First control means for controlling the braking means to apply a braking force for maintaining the stopped state to the vehicle in response to an input to maintain the stopped state of the vehicle;
Damping characteristic determining means for determining a damping characteristic of the braking force when the stop state is released so that the braking force is attenuated earlier as the steering angle of the vehicle is larger;
And a second control means for controlling the braking means so that the braking force is attenuated by the determined damping characteristic in response to an input for releasing the stop state. .

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