JP2012106516A - Abs control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ABS control device for a vehicle capable of eliminating the uncomfortable feeling of a driver accompanied by the deceleration insufficiency feeling of the vehicle when the ABS is operated during the traveling of the vehicle on a low-friction road surface such as a frozen road.SOLUTION: The ABS control device for the vehicle includes an ABS controller 8 for calculating the optimum rotational speed of each wheel on the basis of the detected value of a G sensor 4 or a wheel speed sensor 5, and an ABS actuator 10 for controlling brake pressure so that a slip rate reaches a control target value by controlling the opening/closing of a solenoid valve 9 according to a control signal from the ABS controller 8. In the ABS control device, when an outside air temperature and a vehicle speed are equal to or lower than set values, the control target slip rate is changed to a lock side with respect to a control target slip rate during traveling at a normal temperature and at high speed.

Description

  The present invention relates to an ABS control device for controlling an ABS (anti-lock brake system) for preventing a wheel from being locked during sudden braking in a vehicle.

  The vehicle is equipped with an ABS for preventing the wheels from locking even when a sudden brake is applied, for example, when traveling on a frozen road surface. This ABS detects the deceleration of the vehicle. G sensor (acceleration sensor), wheel speed sensor for detecting the rotational speed of each wheel, an ABS controller for calculating the optimum rotational speed of each wheel based on the detected values of these G sensor and wheel speed sensor, from the ABS controller It is constituted by an ABS actuator or the like that controls the brake pressure by controlling the opening and closing of the electromagnetic valve by a control signal.

  By the way, if the brake is applied while the vehicle is running, the rotational speed of the wheel decreases from the vehicle speed, and slip occurs between the wheel (tire) and the road surface. The magnitude of this slip is defined by the following equation as the slip ratio s. Is done.

Slip rate s = (vehicle speed V−wheel speed W) / vehicle speed V
Here, the relationship between the friction coefficient μ between the tire and the road surface and the slip ratio s is indicated by a solid line in FIG. 4 with the road surface condition (dry road surface, wet road surface, snow road and on ice) as a parameter, as shown in FIG. In all road surface conditions, the friction coefficient μ between the tire and the road surface becomes maximum when the slip ratio s = 0.1 to 0.3, and the braking force also becomes maximum. When the wheels are completely locked (slip rate s = 1.0), the braking force becomes small.

  Further, the side force (cornering force) generated by the tire when the vehicle turns is shown by a broken line in FIG. 4, and this side force becomes maximum when the slip rate s = 0, and decreases as the slip rate s increases. The slip ratio s = 1.0 at which the wheel locks is minimum. Therefore, even if steering is performed with the front wheels locked, the direction of the front wheels changes, but the vehicle slides on the road surface and the traveling direction does not change.

  Therefore, the ABS controller uses the range of the slip ratio s = 0.1 to 0.3 (the hatched range in FIG. 4) in which the friction coefficient μ between the tire and the road surface is maximum during ABS operation as the control target value. A control signal is transmitted to the actuator, and the ABS actuator receives the control signal from the ABS actuator to control opening and closing of the solenoid valve, and controls the brake pressure so that the slip ratio s becomes the control target value (0.1 to 0.3). To do.

  By the way, in patent document 1 regarding the ABS control device, when the outside air temperature detected by the outside air temperature sensor is low, the initial value of the road surface μ used for the slip ratio control of the wheel is changed to a smaller value than the normal time. In addition, there has been proposed a technique for improving the responsiveness of the slip control by executing the slip control at an early stage when traveling on a frozen road or the like where the drive wheels are likely to slip.

JP-A-3-258647

  However, in the control by the conventional ABS control device, the control target slip rate is uniformly set and is suppressed to a relatively small slip rate (0.1 to 0.3). When the ABS is activated during driving, there is a problem that the vehicle has a feeling of deceleration and the driver feels uncomfortable, such as a feeling of running idle and poor braking. In the slip control proposed in Patent Document 1, when the ABS is operated while the vehicle is traveling on a low friction road surface such as a frozen road, the initial value of the road surface μ used for wheel slip ratio control is changed to a small value. Such a problem is likely to occur.

  The present invention has been made in view of the above problems, and can eliminate the driver's uncomfortable feeling due to insufficient deceleration of the vehicle when the ABS is activated while the vehicle is traveling on a low friction road surface such as a frozen road. An object is to provide an ABS control device for a vehicle.

  In addition, the present invention can ensure high running stability even if the wheel control target slip ratio is changed to the lock side when the ABS is activated while the vehicle is running on a low friction road surface such as a frozen road. An object of the present invention is to provide a vehicle ABS control device.

  In order to achieve the above object, an invention according to claim 1 is directed to an ABS controller that calculates an optimum rotational speed of each wheel based on a detection value of a G sensor or a wheel speed sensor, and a solenoid valve based on a control signal from the ABS controller. In an ABS control device for a vehicle including an ABS actuator that controls the brake pressure so that the slip ratio becomes a control target value by controlling the opening and closing of the vehicle, the control is performed when the outside air temperature and the vehicle speed are both lower than the set value. The target slip ratio is changed to the lock side with respect to the control target slip ratio at normal temperature and high speed.

  The invention according to claim 2 is the invention according to claim 1, wherein the control target slip ratio is set to the control target slip ratio at normal temperature and high speed when the vehicle traveling path is flat and the vehicle is traveling straight. It is characterized by changing to the lock side.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the friction coefficient between the wheel and the road surface is estimated based on a detection value of the G sensor or the wheel speed sensor, and the estimated value is less than a set value. In some cases, the control target slip ratio is changed to the lock side with respect to the control target slip ratio at normal temperature and high speed.

  According to the first aspect of the present invention, when the ABS is operated while the vehicle is traveling at a low speed (25 km / h or less) on a low friction road surface such as a freezing road when the outside air temperature is low (the outside air temperature is 1 ° C. or less). Since the control target slip ratio is changed to the lock side with respect to the control target slip ratio at normal temperature and high speed, the lack of deceleration of the vehicle is compensated, and the driver feels idling and braking is not effective. The problem of feeling uncomfortable is prevented.

  According to the second aspect of the present invention, the ABS control is started to change the control target slip ratio to the lock side with respect to the control target slip ratio at normal temperature and high speed when the outside air temperature and the vehicle speed are both lower than the set values. As a result, even if the side force generated in the tire during turning of the vehicle decreases, the ABS control for changing the control target slip ratio to the lock side is performed only when the vehicle traveling path is flat and the vehicle is traveling straight. Therefore, high running stability can be ensured for the vehicle.

  According to the third aspect of the present invention, the ABS control is performed to change the control target slip ratio to the lock side when the road surface is slippery because the estimated friction coefficient between the wheel and the road surface is equal to or less than the set value. Therefore, the driver's uncomfortable feeling can be eliminated without a great increase in the braking distance of the vehicle.

It is a see-through | perspective perspective view of the vehicle which shows arrangement | positioning of the component of the ABS control apparatus which concerns on this invention. It is a block diagram which shows the system configuration | structure of the ABS control apparatus which concerns on this invention. It is a flowchart which shows the control flow of the ABS control apparatus which concerns on this invention. FIG. 5 is a diagram (μ-s characteristic diagram) showing a relationship between a tire / road surface friction coefficient μ and a slip ratio s with a road surface condition as a parameter.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a vehicle showing an arrangement of components of an ABS control device according to the present invention, FIG. 2 is a block diagram showing a system configuration of an ABS control device according to the present invention, and FIG. 3 is an ABS control according to the present invention. FIG. 4 is a diagram (μ-s characteristic diagram) showing the relationship between the tire / road surface friction coefficient μ and the slip ratio s with the road surface condition as a parameter.

  In the vehicle 1 shown in FIG. 1, for example, an ABS is mounted in the engine room so that the front wheels 2 and the rear wheels 3 do not lock even when a sudden brake is applied when traveling on a frozen road surface. However, this ABS detects a vehicle deceleration G sensor (acceleration sensor) 4, a total of four wheel speed sensors 5 for detecting the rotational speeds of the left and right front wheels 2 and rear wheels 3, and detects the outside air temperature. The outside air temperature sensor 6 (see FIG. 2), the steering angle sensor 7 (see FIG. 2) for detecting the steering angle of the steering, the optimum of the front wheels 2 and the rear wheels 3 based on the detected values of the G sensor 4 and the wheel speed sensor 5 The ABS controller 8 (see FIG. 2) for calculating the respective rotation speeds and the four electromagnetic valves 9 (see FIG. 2) are controlled to open and close by a control signal from the ABS controller 8 so that the slip rate s becomes the control target value. Control pressure It is configured to include an ABS actuator 10.

  Further, as shown in FIG. 1, in an engine room of the vehicle 1, a brake booster 11 as a booster device that assists a driver's brake operation force, and a master cylinder 12 that generates a brake pressure by the driver's brake operation. A front brake 13 and a rear brake 14 are provided on the pair of left and right front wheels 2 and rear wheels 3, respectively. Here, the wheel speed sensors 5 are respectively arranged in the vicinity of the brake disks 13a and 14a of the front brake 13 and the rear brake 14, and each wheel speed sensor 5 detects the rotational speed of the brake disks 13a and 14a. A detection signal is transmitted to the ABS controller 8.

  Further, as shown in FIG. 1, the vehicle 1 is provided with an ABS warning lamp 15 and a stop lamp switch 16, and these ABS warning lamp 15 and stop lamp switch 16 are connected to the ABS controller 8.

  The master cylinder 12 is connected to the ABS actuator 10 by two brake pipes 17, and the four brake pipes 18 extending from the ABS actuator 10 are respectively connected to wheel cylinders (not shown) of the front brake 13 and the rear brake 14. It is connected. Here, the ABS actuator 10 includes the electromagnetic valve 9 for controlling the brake pressure supplied to the wheel cylinders of the front brake 13 and the rear brake 14 via the brake pipe 18 and the ABS controller 8 (see FIG. 2). Is built-in.

  FIG. 2 shows a system configuration of the ABS control device according to the present invention. A wheel speed sensor 5, an outside air temperature sensor 6 and a steering angle sensor 7 are connected to the input side of the ABS controller 8, and an electromagnetic side is connected to the output side. A valve 9 and an ABS warning lamp 15 are connected.

  Here, in FIG. 4, the relationship between the friction coefficient μ of the tire and the road surface and the slip ratio s is indicated by a solid line with the road surface condition (dry road surface, wet road surface, snow road and on ice) as a parameter. The side force (cornering force) that occurs is shown by a broken line. As shown in the figure, the friction coefficient μ between the tire and the road surface becomes maximum at a slip ratio s = 0.1 to 0.3 in all road surface conditions. The braking force is also maximized. For this reason, the ABS controller 8 has a slip ratio s = 0.1 to 0.3 in which the friction coefficient μ between the tire and the road surface is maximized during ABS operation at normal time (normal temperature / high speed) (hatched line in FIG. 4). The control signal is sent to the ABS actuator 10 as a control target value, and the ABS actuator 10 receives the control signal from the ABS controller 8 to control the opening and closing of the electromagnetic valves 9, respectively, and the slip ratio s is the control target. The brake pressure is controlled to be a value (0.1 to 0.3).

  However, when the ABS is activated while the vehicle 1 is traveling on a low friction road surface at a low speed, there is a problem that the vehicle 1 lacks a feeling of deceleration, and the driver feels uncomfortable such as a feeling of idling and poor braking. This is as described above.

  Therefore, in the present embodiment, when the following conditions 1 to 5 are satisfied, the control target slip ratio is in a range of control target slip ratio s = 0.1 to 0.3 at normal temperature and high speed (in FIG. The range is changed to the lock side (arrow direction in FIG. 4) with respect to the hatched range.

Condition 1: Outside air temperature ≦ 1 ℃
Condition 2: vehicle speed ≦ 25 km / h
Condition 3: Estimated road friction coefficient μ ≦ 0.3G
Condition 4: The road is flat. Condition 5: The vehicle goes straight. The outside air temperature is detected by the outside air temperature sensor 6, the vehicle speed is calculated based on the detection values of the G sensor 4 and the wheel speed sensor 5, and the road surface friction coefficient .mu. It is estimated from the detection value of the G sensor 4 or the detection value of the wheel speed sensor 5. In addition, the fact that the traveling road is a flat road is judged by the front-rear G value before braking being -0.15 G or more (when down is a negative value), and the fact that the vehicle is traveling straight is the steering angle. This is determined by the steering angle detected by the sensor 7 being ± 45 ° or less.

  Here, the ABS control by the ABS controller 8 will be described below based on the flowchart shown in FIG.

  When braking 3 is started (step S1), whether or not the outside air temperature ≦ 1 ° C. (step S2), whether the vehicle speed ≦ 25 km / h (step S3), the estimated road surface friction coefficient μ ≦ 0 .3G (step S4), whether the traveling road is a flat road (step S5), and whether the vehicle 1 is traveling straight (step S6) are sequentially determined. If Yes (when conditions 1 to 5 are all satisfied), the control target slip ratio is changed to the lock side (step S7), and ABS control is executed (step S8).

  On the other hand, if one of the determinations in steps S2 to S6 is No (if any one of conditions 1 to 5 is not satisfied), the control target slip ratio is not changed to the lock side (step S9). The ABS control is executed as it is (step S10).

  Thus, in the present embodiment, when the outside air temperature is low (the outside air temperature is 1 ° C. or less), the ABS is activated while the vehicle 1 is traveling on a low friction road surface such as a frozen road at a low speed (25 km / h or less). In some cases, the control target slip rate is changed to the lock side with respect to the control target slip rate at normal temperature and high speed (s = 0.1 to 0.3), so that the lack of deceleration of the vehicle 1 is compensated, Occurrence of problems that the driver feels uncomfortable, such as a feeling of idling and poor braking, is prevented.

  Further, when the outside temperature and the vehicle speed are both lower than the set values, the ABS control for changing the control target slip ratio to the lock side with respect to the control target slip ratio at the normal temperature / high speed is started. Even when the side force generated in the tire decreases, the ABS control for changing the control target slip ratio to the lock side has a flat traveling path (G value before and after braking is −0.15 G or more) and the vehicle 1 goes straight (steering angle). Therefore, the vehicle 1 can ensure high running stability.

  Further, in the present embodiment, the road surface slips because the friction coefficient μ between the tire and the road surface estimated by the detection value of the G sensor 4 or the detection value of the wheel speed sensor 5 is equal to or less than the set value (0.3G). Since the ABS control for changing the control target slip ratio to the lock side is performed in the case where it is easy, the driver can feel uncomfortable without greatly increasing the braking distance of the vehicle 1.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Front wheel 3 Rear wheel 4 G sensor 5 Wheel speed sensor 6 Outside air temperature sensor 7 Steering angle sensor 8 ABS controller 9 Solenoid valve 10 ABS actuator 11 Brake booster 12 Master cylinder 13 Front brake 14 Rear brake

Claims (3)

An ABS controller that calculates the optimum rotational speed of each wheel based on the detection values of the G sensor and the wheel speed sensor, and a brake that controls the opening and closing of the electromagnetic valve by a control signal from the ABS controller so that the slip ratio becomes the control target value In an ABS control apparatus for a vehicle configured to include an ABS actuator for controlling pressure,
An ABS control device for a vehicle, characterized in that when both the outside air temperature and the vehicle speed are equal to or less than a set value, the control target slip ratio is changed to the lock side with respect to the control target slip ratio at normal temperature and high speed.   2. The vehicle according to claim 1, wherein the control target slip ratio is changed to a lock side with respect to the control target slip ratio at normal temperature and high speed when the vehicle traveling path is flat and the vehicle is traveling straight. ABS control device. The friction coefficient between the wheel and the road surface is estimated based on the detected value of the G sensor or the detected value of the wheel speed sensor, and if this estimated value is less than the set value, the control target slip ratio is controlled at normal temperature and high speed. 3. The ABS control apparatus for a vehicle according to claim 1, wherein the target slip ratio is changed to a lock side.

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