JP5109796B2 - Vehicle stop holding device - Google Patents

Description

  The present invention relates to a stop holding device applied to a vehicle in order to smoothly start a stopped vehicle. More specifically, when the vehicle starts on a slope or starts on a road with a low coefficient of friction (hereinafter sometimes referred to as a low μ road), the vehicle can start smoothly even in situations where starting is difficult than usual. The present invention relates to a vehicle stop holding device that assists a driver so that the driver can perform the operation.

2. Description of the Related Art Various types of vehicle stop and hold devices have been proposed that assist driving operations when starting a vehicle, such as smoothly starting a vehicle that has stopped on a hill without “backwarding (retreating)”. This kind of vehicle stop and hold device can hold the braking force (braking force) even if the foot is released from the brake pedal after stopping the vehicle, preventing "rearward" when stopping on an uphill. Some are designed to start smoothly.
The vehicle stop holding device includes, for example, an accelerator detection means for detecting depression of an accelerator pedal, a rotation detection means for detecting wheel rotation, and a brake hydraulic pressure holding means for holding brake hydraulic pressures of four front and rear wheels. . When the wheel is stopped in the released state of the accelerator pedal, that is, when the vehicle is stopped, the brake hydraulic pressure holding means is operated to prevent the wheel from being "rearly pushed", and when the vehicle starts to move on the slope, the brake hydraulic pressure is maintained by depressing the accelerator pedal. Release the operation of the means to ensure a smooth start. Note that the function intended for smooth start on the slope as described above is particularly referred to as a slope start assist function (Hill Start Assist (or Aid)) or “HSA function”.

  However, even when the vehicle stop holding device is configured to perform the HSA function, the brake hydraulic pressure holding means is used when traveling on a road with a low friction coefficient μ (low μ road) such as a snowy road or a frozen road in winter. There was concern that it would cause malfunctions. That is, when driving on a low μ road, the wheel is locked easily even by a light depression of the brake pedal. When a wheel lock occurs due to the depression of the brake pedal, there is still a movement due to the inertia of the vehicle, that is, the vehicle speed. Nevertheless, the rotation detection means erroneously detects that the vehicle is at a stop, and the brake hydraulic pressure holding means malfunctions. Therefore, even if the driver subsequently releases the brake pedal, the wheels remain locked. As a result, there is a concern that wheel slip or vehicle spin is likely to occur, which is undesirable in terms of traveling safety.

In contrast to the above, for example, a vehicle stop holding device according to Patent Document 1 has been proposed. This device is designed so that rotation can be secured with respect to a predetermined wheel (rotation detection wheel), and a rotation detection sensor is provided so as to detect the rotation state. Furthermore, the hydraulic pressure by the brake hydraulic pressure holding means acts on the other wheels excluding the rotation detection wheel. In this apparatus, after the brake pedal is released, the rotation detection sensor can detect the rotation of the rotation detection wheel. Therefore, even if the situation where the wheel locks due to malfunction of the brake hydraulic pressure holding means, etc., the movement of the vehicle is confirmed by the rotation detection wheel even without the accelerator pedal being depressed. it can. Therefore, by subsequently stopping the braking force holding control for the other wheels held by the brake hydraulic pressure holding means, it is possible to quickly release the locked state of the wheels and suppress the occurrence of slip and thus the vehicle spin. Yes.
Japanese Patent Laid-Open No. 61-253252

  By the way, assuming that a vehicle traveling on a low μ road slips with respect to the road surface when the vehicle starts after stopping on a slope, the driver not only depresses the brake, but also performs steering operation. Usually, the coping action is taken to correct the attitude of the vehicle (correct the orientation). At this time, if the wheel steered by the steering wheel is rotating without being locked, it is possible to suppress spin and skidding and is effective for reestablishing the vehicle posture.

  However, the vehicle stop and hold device disclosed in Patent Document 1 simply ensures the rotation of the vehicle for rotation detection wheels during a slip. That is, it does not propose a technique intended to restore the vehicle posture by steering operation. Therefore, a wheel (rear wheel in a general vehicle) that does not respond to the driver's steering operation may be set as a rotation detection wheel. In this case, since the front wheels are locked and held so as not to rotate by the brake hydraulic pressure holding means, the steering operation of the driver does not have an effect for preventing spin and skidding.

  Further, in the case of the vehicle stop holding device proposed in Patent Document 1, after the brake operation of the driver who applies a braking force to all the wheels is released, the brake stop holding device is always used for detecting the rotation. The wheels are set to rotate. For this reason, since the rotation detection wheel does not contribute to obtaining the braking force for holding the stop, the stop state of the vehicle is held by the other wheels (other three wheels in the case of a general four-wheel vehicle). There is concern about insufficient braking force.

  Therefore, the object of the present invention is to assist the driver's steering operation by reliably detecting the presence or absence of movement of the vehicle with respect to the traveling road, assuming that the vehicle having the braking force holding function starts on a slippery road. It is to provide a vehicle stop holding device capable of (assist).

For the above purpose, the vehicle stop holding device according to the present invention has a braking force holding means for holding the braking force of the wheel when the stepping operation is released after the brake pedal is depressed. Assuming that
When the braking force holding means is activated, a movement detecting means for detecting the presence or absence of movement of the vehicle with respect to the road, and when the movement detecting means detects movement of the vehicle, it responds to a steering operation by the driver. for particular wheel which comprises a braking force reduction means for executing a control to reduce the braking force by the braking force retaining means,
The movement detecting means includes a steering angle detecting means for detecting a steering angle of the vehicle and a wheel speed detecting means for detecting a wheel speed of each wheel of the vehicle, and all the wheels detected by the wheel speed detecting means are detected. the wheel speed of zero, and wherein when the steering angle steering angle detection means for detecting is a predetermined or more, characterized by Rukoto detecting the movement of the vehicle by releasing the braking force of at least one of said wheels It is what is done.

  According to such a vehicle stop holding device of the present invention, when the movement detecting means detects the movement of the vehicle, the rotation of the specific wheel (steering wheel) to be turned in response to the steering operation by the driver is ensured. Since the driver assists the steering operation, it is possible to deal with the problem of slipping when starting after the vehicle stops on a slippery road.

Hereinafter, an example suitable as one embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a system configuration of a vehicle stop holding device according to an embodiment of the present invention. In FIG. 1, FL and FR indicate left and right front wheels of the vehicle, and RL and RR indicate left and right rear wheels of the vehicle, respectively. A brake device (hereinafter referred to as a brake device) is provided on each of the wheels, that is, front and rear (F: front, R: rear) and left and right (L: left, R: right). The driving of each brake device is controlled by the controller CONT.

  The brake device provided in each wheel includes, for example, a brake disc BD that rotates with the wheel, a wheel cylinder WC that frictionally clamps the brake disc BD with a brake pad based on the brake fluid pressure (braking pressure), and brakes the brake cylinder WC. It is prepared. In FIG. 1, the brake hydraulic system BS is illustrated in a simplified manner, but in this brake hydraulic system BS, the wheel cylinders WC arranged on each wheel are connected to a hydraulic supply source (not shown) via a hydraulic path, A brake operating device such as a brake actuator is arranged in the middle of the path. The controller CONT controls the brake actuator to adjust the braking force of each brake device. Each brake device may be integrally controlled by the controller CONT, or may be set so that the braking force can be controlled individually for each brake device.

  The controller CONT is supplied with output signals from various sensors that detect the state of the vehicle. The controller CONT controls the brake device arranged on each wheel based on these outputs. In FIG. 1, each wheel is provided with a wheel sensor WSS that detects the number of rotations. The wheel sensor WSS includes a gear pulsar that rotates together with the wheel, a search coil portion that includes a high magnetic permeability magnetic core and a coil, and a permanent magnet that has a search coil portion disposed on the opposite side of the gear pulsar. Thereby, the magnetic flux which changes with wheel rotation is detected by a search coil part. The output signal of the wheel sensor WSS is supplied to the controller CONT. The wheel sensor WSS is generally incorporated in an ABS (anti-lock brake system) or the like, and is widely adopted as a sensor that detects that a sudden brake has been depressed.

  Information regarding the hydraulic pressure of the master cylinder MC that changes as the brake pedal BP is depressed is also supplied to the controller CONT. In addition, a steering angle sensor SAS that detects the steering angle (rotation angle) of the steering shaft when the driver steers the steering hole SW is provided, and the output thereof is also supplied to the controller CONT.

  The main components such as the brake device and the sensor assembled in the vehicle have been described above. However, the vehicle stop holding device according to the present embodiment is a control for assisting the vehicle so that the vehicle can start smoothly from the stopped state. It is assumed that a braking force (braking force) holding device is provided as power holding means. This braking force holding device can hold the braking force to the wheel when the brake pedal is depressed and then the depression is released. By providing such a device, when the vehicle starts on a slope, it is possible to prevent the vehicle from slipping back and make a smooth start. In the configuration shown in FIG. 1, a wheel cylinder WC that brakes each wheel and a controller CONT that controls driving thereof are the main components of the braking force holding device.

  Further, the vehicle stop holding device of the embodiment according to the present invention is further inconvenience expected when the vehicle stops on a slippery road (low μ road) and starts when the braking force holding device is activated. It has a new configuration to deal with. More specifically, for example, when the vehicle stops on a hill that is frozen and has a low μ road, the braking force holding device operates to hold the braking force, and the vehicle slips backward or forward when starting. This is a technique for dealing with problems such as lowering (wheels slip on the road surface). In such a situation, the driver tries to correct the posture of the vehicle by operating the steering (handle). However, if the wheel (generally the front wheel) that is steered in accordance with the steering operation remains locked by the vehicle stop holding device, the steering operation by the driver will not be successful.

  In consideration of the above situation, the vehicle stop holding device of the present embodiment includes a movement detection unit that detects whether or not the vehicle moves relative to the travel path when the braking force holding device is activated, and the movement detection unit is a vehicle. There is further provided braking force reducing means for executing control for reducing the braking force by the braking force holding device for a specific wheel (hereinafter referred to as a specific wheel) that responds to the steering operation by the driver when the movement of the vehicle is detected. The configuration is as follows. The movement detecting means and the braking force reducing means here can be realized by appropriately combining the components shown in FIG. For example, when the controller CONT realizes the braking force reducing means, and when realizing a part of the movement detecting means and the braking force reducing means, there are various specific forms.

  Hereinafter, the plurality of forms will be described more specifically with reference to the drawings. At that time, in addition to the system configuration shown in FIG. 1, an inclination angle sensor serving as an inclination angle estimation means for detecting the inclination angle of the traveling road, an imaging camera for detecting the external environment around the vehicle, an external environment such as a radar Reference is also made to an example in which detection means and vehicle relative speed calculation means for calculating the relative speed of the vehicle with respect to the outside world are further provided. In this case, reference will be made to the sensors and devices added to the system configuration shown in FIG.

  Hereinafter, a routine that is executed mainly by the controller CONT will be described to clarify the features of the vehicle stop and hold device of the present embodiment. However, in order to facilitate the understanding of the invention, the vehicle is in a situation where it is stopped on a low μ road, and is in a situation where it slips and moves backward (hereinafter simply referred to as “sliding down”) at the time of departure. It will be explained as a premise.

FIG. 2 is a main flowchart showing an outline of the braking force control executed for assisting the driver's operation in the vehicle stop holding device of the embodiment. This flowchart is based on the premise that the braking force holding device functions and the braking force to each wheel is held as described above.
First, it is detected by the movement detection means of the vehicle stop holding device whether or not the vehicle is moving with respect to the travel path (slipping because the braking force holding device brakes the wheels as described above). The In the case illustrated in FIG. 2, it is detected whether or not the low μ road is “sliding down” (step S1). Then, when “sliding down” is detected, that is, when the movement detecting means detects the movement of the vehicle, the braking force reducing means controls the specific wheel (generally, the front wheel) that responds to the steering operation by the driver. A process of reducing power is executed (step S2). Preferably, the specific wheels are a pair of wheels (generally, the left and right front wheels FL, FR), but the effect of assisting the driver's steering operation even when rotation of one of the wheels is ensured. I can expect.
As is clear from the above, the flowchart of FIG. 2 is based on the assumption that the braking force holding device is functioning, and when the vehicle is confirmed to move, the rotation of the steered wheels is secured and This clearly shows that the steering operation is assisted.

Furthermore, the process by the component part which concerns on the movement detection means and braking force reduction means which comprise a vehicle stop holding | maintenance apparatus is demonstrated in order with reference to figures below.
FIG. 3 is a flowchart relating to the movement detection means of the first example and showing vehicle movement detection ("sliding down" detection in this embodiment) executed by the movement detection means. Here, the movement detection means in FIG. 1 includes a steering angle sensor SAS for detecting the steering angle of the steering shaft, a wheel sensor WSS for detecting the rotation speed of the wheel, and a controller CONT. The wheel rotation speed is detected based on the output of the wheel sensor WSS.
In addition, the steering angle sensor SAS is included in the movement detection means, and unnecessary braking force reduction operation is suppressed by setting to execute the subsequent braking force release only when a predetermined steering angle is input. it can.

  In FIG. 3, the movement detecting means detects the steering angle θ based on the output of the steering angle sensor SAS (step S101), and detects the wheel rotation speed based on the output of the wheel sensor WSS (step S102). Further, it is confirmed whether or not the braking force (braking force) is being held, that is, whether or not the above-described braking force holding device has been activated and is assisting the start of the hill (step S103). Then, when the braking force holding device is being activated (Y in Step S103: Yes), it is further confirmed whether the wheel rotation speed (MAX speed of the four wheels) is less than a predetermined low speed Vmin (Step S104). . By this step S104, the case of the gentle slip movement that occurs at the start is targeted. The step S104 is more preferably set in order to more reliably detect the “sliding down” state of the vehicle starting on the low μ road. Therefore, this step S104 can be omitted.

  Then, by confirming whether the steering angle θ detected by the steering angle sensor SAS is larger than the predetermined steering angle θ1, it is confirmed whether the driver is performing a steering operation (step S105). Thereby, only when there is a steering angle input, an unnecessary braking force reduction operation is suppressed by releasing the subsequent braking force.

  If the result of the determination in steps S103 to S105 is YES, the movement detection unit further executes processing for determining a braking force release wheel (step S106). In addition, when the braking force holding device is activated as described above, when the movement of the vehicle is detected with the predetermined wheel being freely rotatable, the braking force is held by the remaining three wheels, so there is a concern about insufficient braking force. become. Therefore, in this embodiment, when the braking force holding device is activated, it is executed by all the wheels, and the braking force of the detection wheels is released only when the vehicle movement is detected.

  Here, in general, the front wheel corresponds to the steering operation of the vehicle. According to the present invention, when a vehicle slips on a low μ road on a slope, the wheel to be steered is rotated in response to a driver's steering operation to assist. Therefore, if it is set in advance so that the movement of the vehicle is detected by any of the front wheels, the braking force of the front wheels may be released. In this case, step S106 in the flowchart in FIG. 3 can be omitted.

  After determining the wheel for releasing the braking force as described above (step S106), the movement detecting means is provided with an additional wheel (switching from braking with four wheels to braking with three wheels). A braking force correction amount is determined (step S107). Then, release of the braking force for the wheel that has been determined to be released and the pressure increase of the wheel cylinder WC of the other wheel are executed in order to compensate for the braking force (step S108). As a result, the necessary braking force can be secured with the remaining three wheels. That is, here, the movement detection means further functions as a total braking force compensation means, and changes the braking force other than the braking force reduction wheel so that the total braking force does not decrease. As a result, even when the braking force is released, it is possible to effectively detect the sliding on the low μ road without causing the vehicle to slide down due to insufficient braking force.

Finally, the movement detection means checks whether or not the output signal (vehicle speed pulse) of the wheel sensor WSS disposed on the opened wheel exceeds a predetermined number (for example, 5 pulses) (step S109). That the output of the wheel sensor WSS exceeds a predetermined pulse means that the vehicle is moving at a certain speed or more with respect to the traveling path, in this case “sliding down”.
The movement detection means sets the determination flag to 1 when detecting “sliding down” (step S110). On the other hand, if “sliding down” is not detected, the determination flag is set to 0 (step S111).
In connection with the above flowchart, the wheel speeds of all the wheels detected by the steering angle sensor SAS (wheel speed detecting means) are zero, and the steering angle detected by the steering angle sensor SAS (steering angle detecting means) is If it is greater than or equal to the predetermined value, the movement of the vehicle can be reliably detected by releasing the braking force of at least one wheel.

  FIG. 4 is a flowchart showing an example of a routine that can be adopted when determining a wheel for releasing the braking force in step S106 in FIG. In steps S201 to S206 shown in this flowchart, “j” is changed in the order of the left and right front wheels FL and FR, and the left and right rear wheels RL and RR to identify the steered wheels, and the identified wheels are drive wheels. In this case, the driving force is further released (step S206), and the open wheel is set (step S205). According to this flowchart, it is possible to reliably detect the movement of the vehicle by determining the wheel whose braking force should be released.

In addition, since the driving force (torque) is applied to the front wheels that serve as the steered wheels in 4-wheel drive vehicles and front-wheel steered front-wheel drive vehicles, even if the braking force of an inappropriate wheel is released during movement detection In some cases, the rotation cannot be secured and the presence or absence of movement of the vehicle cannot be detected accurately. As described above, the braking force (braking force) and the driving force (torque) can be released at the same time to ensure the rotation of the wheels and improve the accuracy of the movement detection.
However, step S106 in FIG. 3 is merely a matter of determining a freely rotating wheel for detection of vehicle movement. On the other hand, in the present invention, as will be described later, the rotation of the specific wheel to be steered in response to the steering operation by the driver is ensured to assist the operation, so that the wheel that releases the braking force is similarly determined. is required. FIG. 4 is a flowchart for securing the rotation by releasing the braking force of the specific wheel. Therefore, when the movement detection means detects the movement based on the flowchart shown in FIG. 4 when detecting the movement of the vehicle, the subsequent processing becomes smooth because the wheel is the specific wheel. .

  Note that step S202 in FIG. 4 is a step that is confirmed in order to set the outer wheel (outer wheel) as an open wheel when the vehicle is steered. If it is confirmed that it is an outer wheel in this way, it is an effective step when releasing the braking force of only one specific wheel, but when ensuring the rotation of the wheel only for the movement detection means, When the specific wheels that respond to the steering operation by the driver are a pair of wheels, this step S206 can be omitted.

  FIG. 5 is a flowchart relating to the movement detection means of the second example and showing the “sliding down” detection of the vehicle executed by the movement detection means. The movement detection means here includes a side view monitor and a back view monitor as the external environment detection means for detecting the external environment around the vehicle in addition to the configuration shown in FIG. 1, and the relative speed of the vehicle with respect to the external environment detected by these monitors is determined. The vehicle relative speed calculating means for calculating is realized by the controller CONT to constitute a movement detecting means.

In FIG. 5, based on the input of the side view monitor (step S301) and the input of the back view monitor (step S302) for detecting the external environment around the vehicle, the controller CONT determines the amount of movement of the vehicle based on the image recognition process. Calculation is performed (step S303).
Then, it is confirmed whether or not the movement amount d detected by the above calculation exceeds a predetermined movement amount (d1) (step S304). When the movement amount d exceeds d1, it can be estimated that the vehicle is moving with respect to the traveling path, here “sliding down”. The movement detection means sets the determination flag to 1 when “sliding down” is estimated as a result (step S305). On the other hand, if “sliding down” cannot be estimated, the determination flag is set to 0 (step S306).

  The monitor in the example of the flowchart of FIG. 5 includes a camera, a back sonar, and the like, acquires an image around the vehicle by these external world detection means, and performs image processing techniques and arithmetic processing to detect the relative movement amount of the vehicle with respect to the traveling road. And estimate the sliding down. As a result, it is possible to easily detect sliding down on a low μ road without performing a detection operation such as releasing the braking force of the wheels.

FIG. 6 is a flowchart relating to the movement detection means of the third example and showing the “sliding down” detection of the vehicle executed by the movement detection means. However, it is assumed that the vehicle here is equipped with a steering assist device (so-called power steering device).
In addition to the configuration shown in FIG. 1, the movement detection means is further provided with, for example, an inclination angle sensor and an acceleration (G) sensor as an inclination angle estimation means for estimating the inclination angle of the traveling road on which the vehicle travels. The movement detection means here includes the steering angle sensor SAS for detecting the steering angle of the steering shaft in FIG. 1, the tilt angle sensor, and the controller CONT, and further includes the steering assist device. It is assumed that it also functions as steering assist estimation means for estimating the steering assist force.

In FIG. 6, the movement detection means estimates the inclination angle ψ of the travel path from the output of the inclination angle sensor (step S401), detects the steering angle θ based on the output of the steering angle sensor SAS (step S402), and further, the steering assist device. The steering assist force by is detected (step S403). Here, the movement detection means estimates the friction coefficient μ of the travel path on which the vehicle is traveling by calculation based on the steering angle θ and the steering assist force detected as described above (step S404).
And it is confirmed whether the said friction coefficient (micro | micron | mu) exceeds tan (psi) about the inclination-angle (psi) of a travel path (step S405). When the friction coefficient μ exceeds tan ψ, it can be estimated that the vehicle is moving with respect to the traveling path, in this case “sliding down”. The movement detection means sets the determination flag to 1 when “sliding down” is estimated as a result (step S406). On the other hand, if “sliding down” cannot be estimated, the determination flag is set to 0 (step S407).

  The flowchart example of FIG. 6 estimates the friction coefficient μ of the travel path from the steering assist force when the vehicle is stopped, for example, and determines that the friction coefficient μ is so small that the stop state of the vehicle cannot be maintained with respect to the inclination of the travel path. In such a case, it is estimated that the vehicle is sliding down. Accordingly, it is possible to detect a low μ road slip without releasing the braking force of the wheels, that is, without causing a vehicle slip due to a decrease in the braking force.

FIG. 6 includes a steering assist estimating unit that includes a vehicle equipped with a steering assist device, and the movement detecting unit estimates an assist amount by the steering assist device. When the steering assist device is operating, The friction coefficient of the travel road is obtained from the estimated steering assist force with respect to the amount of change, and the movement of the vehicle is estimated when it is determined that the friction coefficient is not sufficient to keep the vehicle stationary with respect to the inclination angle. It was something to do.
The same applies to a vehicle equipped with an anti-lock brake system (ABS) and vehicle dynamics control (VDC: hereinafter referred to as a VDC system) for stabilizing the steering of the vehicle.

That is, in the case of a vehicle equipped with an ABS device, the movement detection means estimates the inclination angle of the traveling road on which the vehicle is traveling, and the ABS device prevents the wheel braking lock by braking pressure control. When the control of the ABS device is operating when the vehicle stops, it is determined that the friction coefficient of the travel path is not sufficient for the vehicle to stop with respect to the inclination angle. In such a case, the movement of the vehicle may be estimated.
Thus, when the friction coefficient (road surface μ) of the traveling road is estimated from the control of the ABS device immediately before the stop and it is determined that the road surface μ is so small that the stop state of the vehicle cannot be maintained with respect to the road surface inclination, the vehicle moves. Presumed to be “sliding down”. By doing so, it is possible to detect movement on a low μ road without releasing the braking force of the wheels, that is, without risking that the vehicle will be “sliding down” due to a decrease in the braking force.

In the case of a vehicle equipped with a VDC, the movement detection means determines an inclination angle estimation means for estimating the inclination angle of the traveling road on which the vehicle is traveling, and determines whether the steering stability of the vehicle is good or not. And a vehicle behavior stability control system that generates a yaw moment in a direction to secure the vehicle, and when the control by the vehicle behavior stability control system is operating immediately before the vehicle is stopped, the vehicle If it is determined that the friction coefficient of the travel path is not sufficient to keep the vehicle stopped, the movement of the vehicle may be estimated.
Accordingly, the friction coefficient (road surface μ) of the traveling road is estimated from the control of the VDC system immediately before the stop, and the vehicle moves when it is determined that the road surface μ is so small that the stopped state of the vehicle cannot be maintained with respect to the road surface inclination. Presumed to be “sliding down”. By doing so, it is possible to detect movement on a low μ road without releasing the braking force of the wheels, that is, without risking that the vehicle will be “sliding down” due to a decrease in the braking force.

FIG. 7 is a flowchart relating to the movement detection means of the fourth example, showing the “sliding down” detection of the vehicle executed by the movement detection means. However, the vehicle here is based on the premise that an ABS (anti-brake system) device is mounted.
The movement detection means will be described as a case including the steering angle sensor SAS for detecting the steering angle of the steering shaft, the tilt angle sensor, and the controller CONT in FIG.

  In FIG. 7, when the vehicle stops (step S501), the movement detecting means further confirms the output of the steering angle sensor SAS (step S502), and confirms the steering angle when the ABS device is activated (step S503). . In step S503, if the difference between the steering angle θ0 when the vehicle is stopped and the subsequent steering angle θ is larger than a predetermined value θ2 (Y: YES), the driver steers after the vehicle stops. You are doing the operation. This is because the vehicle is “sliding down” because the road is a low μ road, so it can be expected that the driver is steering. Therefore, in this case, the movement detection unit sets the determination flag “down” to 1 (step S509).

  On the other hand, if it is determined that the answer is N (No) in Step S503, the movement detection unit further accumulates the steering angle θ for a certain period of time (Step S504), and confirms whether or not the accumulated value θ exceeds the predetermined value θ3. (Step S505). If the cumulative ∫θ exceeds θ3, the driver continues the steering operation. In this case, the vehicle is “sliding down” because the road is a low μ road. Therefore, it can be expected that the driver is steering. Therefore, the movement detection unit similarly sets the “sliding down” determination flag to 1 (step S509).

Furthermore, the movement detection unit, when it is determined that N (NO) in step S505, further by angular change dθ of the steering angle sensor SAS calculates the number of reversals N _theta steering (step S506), the number of reversals N _theta is It is confirmed whether or not the predetermined value n1 is exceeded (step S507). In this case, the reversal number N _theta is greater than n1 would driver continues steering operation to the left and right. This can be expected that the driver is steering because the road is a low μ road and the vehicle is “sliding down”. Therefore, the movement detection unit similarly sets the “sliding down” determination flag to 1 (step S509).

  If the result of step S503, step S505, or step S507 is N (no), the movement detection means does not estimate "slip" and sets the determination flag to 0 (step S508). .

  In the example of the flowchart according to FIG. 7 described above, for example, when the ABS device is operated immediately before the vehicle is stopped, it is estimated that the vehicle is caused to slide from the steering operation of the driver thereafter. In this case as well, it is possible to detect a low μ road slip without releasing the braking force of the wheels, that is, without causing a vehicle slip due to a decrease in the braking force. The flowchart illustrated in FIG. 7 confirms the magnitude of the steering angle θ, the integration of the steering angle θ, and further the steering operation (the steering wheel operation that reverses left and right), so that the vehicle is accurately detected based on the steering operation of the driver. Can detect movement.

  The flowcharts of FIGS. 3 to 7 described above show an example of a routine that is executed when the movement detection means of the vehicle stop and hold device detects “sliding down” of the vehicle. Hereinafter, a flowchart of the braking force reducing means of the vehicle stop holding device will be described. The braking force reducing means executes control to reduce the braking force of the wheel (specific wheel) that responds to the driver's steering operation when the movement detecting means detects the movement of the vehicle. At that time, the braking force reducing means determines a specific wheel and then executes control to reduce the braking force.

FIG. 8 is a flowchart showing an example of a routine executed when the braking force reducing means determines a specific wheel whose braking force should be reduced. In this flowchart, “i” is changed in the order of the left and right front wheels FL and FR and the left and right rear wheels RL and RR of the vehicle. First, in step S601, the steering wheel is specified for the left and right front wheels FL and FR and the left and right rear wheels RL and RR. Then, the wheel is set as a pressure reduction target wheel (step S605).
For the sake of certainty, the wheels that are not steering outer wheels at the time of steering (step S602) and that are not non-driven wheels (step S603) are not decompressed, that is, the braking force is not reduced. According to this flowchart, the braking force of the steered wheel that responds to the steering operation can be released.

  When the braking force reducing means determines a specific wheel, if the driving force (torque) transmission from the engine to the specific wheel can be released together, the rotation of the steering wheel can be reliably ensured. In other words, the tire lock state may not improve if the driving force is applied even if the braking force is released at the time of "sliding down". Control becomes possible. For this purpose, the flowchart for determining the rotating wheel by the movement detecting means shown in FIG. 4 may be used. Therefore, further explanation here is omitted.

  However, the control executed by the braking force reducing means to reduce the braking force of the specific wheel includes both a case where the braking force is released and a case where a low braking force is maintained. When braking force is applied to the steered wheels, the vehicle “slides” downward on the slope with the tires locked on low μ roads. However, in this embodiment device, it is possible to effectively generate a tire lateral force by reducing the braking force of the steered wheels, and it is possible to control the direction of the vehicle by assisting the driver's steering operation. Become. At that time, the braking force of the specific wheel may be completely released or a low braking force may be maintained.

  FIG. 9 is a diagram schematically showing a control example that is preferably executed by the braking force reducing means. Here, FIG. 9A shows a case where the control is performed to periodically change the braking force of the specific wheel, and FIG. 9B shows a case where the vehicle speed is controlled to be constant.

  As shown in the upper part of FIG. 9 (a), when the braking force reducing means periodically executes a control for changing the set pressure (target pressure) of the braking force (P) for the specific wheel corresponding to the driver's steering operation, By releasing the braking force, the lateral force of the wheel (tire) can be effectively used to control the vehicle spin state by steering. Further, by periodically changing the braking force, it is possible to suppress inconveniences that occur when the total braking force of each wheel is reduced at a stroke. As a result, as shown in the lower part of FIG. 9A, the vehicle speed detected by the wheel sensor WSS can be made constant.

  As shown in the upper part of FIG. 9 (b), the braking force reducing means makes the set vehicle speed (target vehicle speed) constant for the specific wheel according to the steering operation of the driver, that is, the wheel speed becomes constant. When the control is executed, the vehicle spin state by steering can be controlled by effectively using the lateral force of the wheel (tire) by the rotation of the wheel. As a result, as shown in the lower part of FIG. 9B, a braking force corresponding to the ABS device can be achieved. As a result, it is possible to suppress inconveniences that occur when the total braking force of all the wheels is reduced at once by applying the braking force.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.
In the above-described embodiment, the case where the vehicle is stopped on a low μ road is explained for the purpose of understanding the invention. Therefore, the premise is HSA (hill starting assistance function), but the present invention is not limited to application to HSA. The present invention is similarly applied to various systems that may apply braking force to wheels with a predetermined intention, for example, a VDC (vehicle dynamics control) system, an automatic parking system, a BBW (brake by wire) system, and the like. Applicable.

  As described above, according to the vehicle stop holding device of the present invention, when the movement detection unit detects the movement of the vehicle, the rotation of the specific wheel (steering) that responds to the steering operation by the driver is ensured, Since the steering operation by the driver is assisted, it is possible to effectively cope with the slip that occurs when the vehicle starts after stopping on a slippery road.

  The movement detection means includes a steering angle detection means for detecting a steering angle of the vehicle, and a wheel speed detection means for detecting a wheel speed of each wheel of the vehicle, and all of the detections by the wheel speed detection means. When the wheel speed of each of the wheels is zero and the steering angle detected by the steering angle detecting means is greater than or equal to a predetermined value, the braking force of at least one of the wheels is released to detect the movement of the vehicle. Also good.

  The movement detecting means includes driving force releasing means for releasing the driving force transmitted to the wheels of the vehicle, and detects the movement of the vehicle by releasing the driving force when the braking force of the wheels is released. You may do it.

  The movement detecting means includes an inclination angle estimating means for estimating an inclination angle of a traveling road on which the vehicle is traveling, and an anti-lock brake system for preventing wheel braking lock by braking pressure control, and the vehicle stops. Sometimes, when the control by the anti-lock brake system is operating, the vehicle travels when it is determined that the friction coefficient of the travel path is not sufficient for the vehicle to maintain a stop with respect to the inclination angle. May be estimated.

  The movement detecting means includes an inclination angle estimating means for estimating an inclination angle of a traveling road on which the vehicle is traveling, and a yaw moment in a direction for determining whether the steering stability of the vehicle is good and ensuring the steering stability. A vehicle behavior stabilization control system for generating the vehicle, and when the control by the vehicle behavior stability control system is operating immediately before the vehicle is stopped, the vehicle travels to maintain the stop with respect to the inclination angle. If it is determined that the road friction coefficient is not sufficient, the movement of the vehicle may be estimated.

  The movement detection means includes an external environment detection means for detecting an external environment around the vehicle and a vehicle relative speed calculation means for calculating a relative speed of the vehicle with respect to the external environment, and the vehicle relative speed is equal to or greater than a predetermined value. Based on this, the movement of the vehicle may be estimated.

  Further, the movement detection means assists steering operation by the driver, steering angle detection means for detecting the steering angle of the vehicle, inclination angle estimation means for estimating the inclination angle of the traveling road on which the vehicle is traveling, and Steering assist estimation means for estimating the amount of assist by the steering assist device, and when the steering assist device is operating, the friction coefficient of the travel path is calculated from the estimated amount of steering assist force with respect to the amount of change in the steering angle. Thus, the movement of the vehicle may be estimated when it is determined that the friction coefficient is not sufficient for the vehicle to maintain a stop with respect to the inclination angle.

  The movement detection means includes steering angle detection means for detecting a steering angle of the vehicle and an anti-lock brake system for preventing wheel braking lock by brake hydraulic pressure control. When the control by the lock brake system is operating, the movement of the vehicle may be estimated when it is determined that the change in the steering angle is greater than or equal to a predetermined value.

  In addition, the movement detection means may reduce the braking force of the wheels other than the wheel that has reduced or released the driving force so that the total braking force does not decrease when the braking force of the wheel is reduced or released to detect the movement of the vehicle. It may further include a total braking force compensating means for increasing and changing.

  Moreover, it is preferable that the said braking force reduction means performs control when releasing the said braking force and maintaining the said braking force.

  Moreover, it is preferable that the said braking force reduction means performs control which changes the said braking force periodically about the said specific wheel.

  Preferably, the braking force reducing means includes wheel speed detecting means for detecting a wheel speed of the vehicle, and the braking force holding means is controlled so that the wheel speed is constant for the specific wheel.

  The driving force releasing means for releasing the driving force transmitted to the specific wheel is further provided, and the braking force reducing means controls the driving force releasing means when executing the control for reducing the braking force. Then, the driving force transmitted to the specific wheel may be released.

It is the figure which showed the system configuration | structure of the vehicle stop holding | maintenance apparatus which concerns on the Example of this invention. It is the main flowchart which showed the outline of the braking force control performed for a driver | operator's operation assistance with the vehicle stop holding | maintenance apparatus of an Example. It is a flowchart shown about the movement detection of the vehicle performed by the movement detection means of the 1st example. FIG. 4 is a flowchart showing an example of a routine that can be adopted when determining a wheel that releases braking force in step S106 in FIG. 3; It is a flowchart shown about the movement detection of the vehicle performed by the movement detection means of the 2nd example. It is a flowchart shown about the movement detection of the vehicle performed by the movement detection means of the 3rd example. It is a flowchart shown about the movement detection of the vehicle performed by the movement detection means of the 4th example. It is the flowchart which showed an example of the routine performed when a braking force reduction means determines the specific wheel which should reduce braking force. FIG. 9 is a diagram schematically showing a control example that is preferably executed by the braking force reducing means. FIG. 9A shows a case where the braking force of a specific wheel is changed periodically, and FIG. It is a figure shown about the case where it controls so that it may become fixed.

Explanation of symbols

FL Left front wheel FR Right front wheel RL Left rear wheel RR Right rear wheel SW Steering hole CONT controller WC Wheel cylinder WSS Wheel sensor (wheel speed detection means)
SAS steering angle sensor (steering angle detection means)

Claims (2)

In the vehicle stop holding device having a braking force holding means that can hold the braking force of the wheel when the depression operation is released after the depression of the brake pedal,
A movement detecting means for detecting the presence or absence of movement of the vehicle with respect to the travel path when the braking force holding means is activated;
Braking force reducing means for executing control to reduce the braking force by the braking force holding means for a specific wheel that responds to a steering operation by a driver when the movement detecting means detects the movement of the vehicle ;
The movement detecting means includes
Steering angle detection means for detecting the steering angle of the vehicle, and wheel speed detection means for detecting the wheel speed of each wheel of the vehicle,
When the wheel speeds of all the wheels detected by the wheel speed detecting means are zero and the steering angle detected by the steering angle detecting means is greater than or equal to a predetermined value, the braking force of at least one of the wheels is released to vehicle stop holding apparatus characterized that you detect the movement of the vehicle. It said movement detecting means, when the braking force of the wheels for the movement detection of the vehicle is released to open, the total of the total braking force increases changing the braking force of the wheels other than the wheel is released to open the driving force so as not to decrease further comprising a braking force compensation means, the vehicle stop-maintenance unit according to claim 1, characterized in that.

Images