JPH11139292A - Vehicle stop judging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle stop judging device which can judge with more reliability the stop of a vehicle, while detecting the locked states of wheels in every running condition of the vehicle. SOLUTION: This device includes wheel speed sensors 3a, 3b, 3c, 3d placed at the wheels of a vehicle to detect the rotating speeds of the wheels, a false vehicle body speed calculation means 4 for calculating a false vehicle body speed based on the outputs of the wheel speed sensors for all the wheels, and an all-wheel lockup detection means which detects whether or not all the wheels are locked up according to at least the outputs of the wheel speed sensors. When all the wheel speeds detected by the wheel speed sensors are zero for a predetermined time and the all-wheel lockup detection means detects that all the wheels are not locked up and the false vehicle body speed calculated by the false vehicle body speed calculation means 4 is zero, the device judges that the vehicle is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle stop judging device for judging a stop state of a vehicle, and more particularly to a technique for improving the accuracy of a vehicle stop judgment.

[0001]

2. Description of the Related Art A conventional vehicle stop judging device is disclosed, for example, in Japanese Patent Application Laid-Open No. 61-229660. This vehicle stop determination device controls the operation of a braking force holding device provided between a master cylinder associated with a brake pedal and a brake device. When the vehicle stops, the braking device is controlled by the braking force holding device. Is controlled so as to maintain the braking force. The held braking force is released when the driver steps down on the accelerator when starting the vehicle.

Further, Japanese Utility Model Laid-Open No. 49-10574 discloses an unexpected stop such as a sudden stop of a vehicle in which wheels are locked and stops while slipping on a road surface, a failure of a vehicle speed sensor, a disconnection of a meter cable, and the like. A vehicle stop determination device that controls so as not to maintain the braking force when a situation occurs is disclosed. When the vehicle stops beyond the set deceleration, the vehicle stop determination device performs control so that the vehicle may not be determined to be in the stopped state because the vehicle may be in a wheel locked state while the vehicle is running. This is because, if the braking force is maintained before the vehicle stops, there is a risk that the sudden braking state continues and there is a danger that the vehicle will be hit and the steering wheel will be taken. The basic operation of the braking force holding device using such a vehicle stop determination device will be described with reference to FIG. The braking force holding device 40 controls the flow of braking oil into a wheel cylinder 41 connected to a wheel brake device (not shown). First, when the brake pedal 42 is depressed,
The braking force is applied to the wheels by causing the brake oil to flow into the wheel cylinders through the hydraulic paths 43 and 44. And
When the driver's foot is released from the brake pedal, the braking oil from the wheel cylinder is caused to flow backward through the hydraulic path 43 to release the braking force. A control valve 45 whose valve opening and closing is controlled by a control device 46 is provided in the middle of the hydraulic passage 43, and controls whether or not the brake oil can flow backward. A check valve 44a is provided in the middle of the hydraulic path 44 so that the brake oil does not flow backward in the hydraulic path 44.

Here, when the braking force is maintained,
The control valve 45 is set to the open state by a command from the control device 46, and the wheel cylinder is depressed by depressing the brake pedal 42.
After the brake oil flows into the 41, the control valve 45 is closed to prevent the brake oil from flowing back. That is, the brake pressure is maintained without releasing the brake oil once flowing. This control device 46
Accelerator switch 47 for detecting depression of accelerator pedal 47
The opening and closing of the control valve is controlled in accordance with the setting state of the brake switch 42a for detecting the depression of the brake pedal and the output state of the speed sensor 48. For example, when the vehicle stops on an uphill road, when the brake pedal 42 is depressed and the vehicle stops, the control valve 45 is closed so that the brake oil flowing into the wheel cylinder 41 does not flow backward to maintain the braking force. To Then, when the accelerator pedal 47 is depressed at the start, the control valve 45 is opened to release the braking force by causing the brake oil flowing into the wheel cylinder 41 to flow backward.

[0004]

By the way, as a device utilizing such a conventional vehicle stop judging device, for example, in a braking force holding device, it is used for a speedometer for detecting a vehicle speed from rotation of a drive shaft. The stop state of the vehicle is determined by the speed sensor, and control is performed to maintain the brake pressure. However, it was difficult to determine whether or not the vehicle was stopped when the wheels were locked with this speed sensor. First of all, when it is assumed that the wheels are in a locked state, this braking force holding device emphasizes the danger caused by the wheel lock even if the wheels are not actually locked, and stops the wheels. Is not determined to be the stop of the vehicle, and the control method does not hold the braking force. Here, "the wheels are in the locked state" is determined as a case where the deceleration detected by the speed sensor exceeds an upper limit set value (for example, 0.2 to 0.3 G) of the deceleration generated during general braking. doing. The reason for this value is that when such a large deceleration occurs, the possibility of occurrence of a slip state due to wheel lock increases. Therefore, at the time of sudden braking of the vehicle exceeding the upper limit set value, even if the speed signal from the speed sensor becomes zero, there is a possibility that the wheels are locked, and the actual vehicle state is in a stopped / non-stop state. Regardless of whether there is, the vehicle is not determined to be in the stopped state.

Therefore, when the vehicle is stopped suddenly without locking the wheels at the time of sudden braking of the vehicle exceeding the upper limit set value, the vehicle is not determined to be in the stopped state, and as a result, the braking force is not maintained after the vehicle stops. The convenience of the braking force holding device is impaired. The present invention has been made in order to solve such a conventional problem, and provides a vehicle stop determination device capable of detecting a lock state of a wheel and determining a stop state of a vehicle more accurately. It is an object.

[0006]

In order to achieve the above object, a vehicle stop judging device according to the first aspect of the present invention includes a wheel speed sensor disposed on each wheel of a vehicle for detecting a rotation speed of the wheel, Pseudo vehicle speed calculating means for calculating a pseudo vehicle speed based on the output from the wheel speed sensor of each wheel, and all wheel lock detection for detecting whether all wheels are locked based on at least the output of the wheel speed sensor Means, all the wheel speeds detected by the respective wheel speed sensors become zero for a predetermined time, and it is detected that all the wheels are not in a locked state by the all wheel lock detecting means,
And a vehicle stop determining means for determining that the vehicle is in a stopped state when the pseudo vehicle speed by the pseudo vehicle speed calculating means is zero.

Further, the invention according to a second aspect of the present invention includes a vehicle speed sensor for detecting a vehicle speed from rotation of a drive shaft, and the vehicle stop determining means determines that the vehicle speed detected by the vehicle speed sensor is a first predetermined speed. When the vehicle is faster, it is determined that the vehicle is not stopped.

Further, in the invention according to a third aspect, the all-wheel lock detecting means is configured such that the pseudo-vehicle speed calculated by the pseudo-vehicle speed calculating means is equal to or higher than a second predetermined speed, and the all-wheel speed is zero for a predetermined time. And when the vehicle speed detected by the vehicle speed detecting means is lower than or equal to a first predetermined speed, all wheels are recognized as being in a locked state.

[0009]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the vehicle stop determination device according to the present invention. The vehicle stop determination device in the present embodiment is an example applied to control of a braking force holding device of a vehicle equipped with a general wheel lock prevention device (ABS: Antilock Brake System). The present invention is not limited to this, and can be applied to other control targets such as driving force control and suspension control.

[0010] Vehicle stop determination device 1 in the present embodiment
Is a vehicle speed sensor 2 for a speedometer that detects a vehicle speed based on a rotation speed of a drive shaft (for example, a rotation speed of a rear wheel), and is disposed on each wheel of a four-wheel vehicle to detect the rotation speed of each wheel. Wheel speed sensors 3a, 3
b, 3c, 3d, and pseudo vehicle speed calculating means 4 for calculating the pseudo vehicle speed by integrating the outputs from the wheel speed sensors 3a, 3b, 3c, 3d, and the vehicle speed sensor 2 And a control unit 5 which receives each speed information from the wheel speed sensors 3a, 3b, 3c, 3d and the pseudo vehicle speed calculating means 4 and outputs a stop determination signal of the vehicle based on the speed information. The control unit 5 in the present embodiment is a control unit for, for example, an ABS control that outputs a vehicle stop determination signal to the vehicle braking force holding device 6, and is configured by a programmable electronic circuit including a CPU and a memory (not shown). be able to.

When the driver depresses the brake pedal while the vehicle is running to decelerate the vehicle, for example, the vehicle stop determination device 1 stops the vehicle based on the vehicle speed and the wheel speed. It is determined whether the vehicle is in the locked state and whether all the wheels are in the locked state. When it is determined that the vehicle is in the stopped state, the braking force is held by the braking force holding device 6 even when the driver releases his / her foot from the brake pedal. The present invention more accurately performs such vehicle stop determination processing for determining the vehicle stop state and all-wheel lock detection processing for detecting the lock state of all wheels of the vehicle, and appropriately performs subsequent vehicle control. It is intended to provide a vehicle stop judging device adapted to be operated.

Next, a procedure for determining whether or not the vehicle has stopped by the vehicle stop determination apparatus according to the present embodiment will be described with reference to FIGS. FIG. 2 is a flowchart showing a vehicle stop determination procedure. First, while the vehicle is running, the wheel speed sensor
2 is the first predetermined speed (for example, 1 k / h)
m) It is determined whether it is equal to or less than (step 21, and thereafter S2
1). Specifically, it is determined whether or not no pulse of the speed signal output from the vehicle speed sensor 2 has been output within a certain predetermined time. For example, the vehicle speed sensor 2 according to the present embodiment has a speed of 0.
A speed sensor output as 7 km or less is used. The speed signal from this speed sensor is, for example, 1 k / h
m or less, it is determined that there is a possibility that the vehicle is stopped. S2 when the vehicle speed is 1 km / h or less
If the speed is higher than the above speed, the vehicle is not in a stopped state, and the current vehicle stop determination process is stopped.
Note that S21 may be omitted in some cases. In this case, the processing can be speeded up.

In S22, a timer in the control unit 5 is initialized to prepare for clocking. In S23, the speed of each wheel is detected from each wheel speed sensor 3a, 3b, 3c, 3d. Next, in S24, it is determined whether or not all the wheels are in a stopped state based on the wheel speeds of the respective wheels repeatedly detected within the predetermined time. That is, it is confirmed that the wheel speeds output from the respective wheel speed sensors are all zero. This step is performed, for example, when braking is performed on an extremely low friction road, when the rear two wheels that are drive shafts are locked, that is, when an engine stall occurs when braking is performed in a gear-in state, or when braking is performed using a parking brake. And the like to detect that the vehicle is not stopped.

Then, a timer is added in S25 and S2
In step 6, it is determined whether a predetermined time (for example, 700 ms) that has been set in advance has elapsed. If the predetermined time has not elapsed, S2
3 and the detection of the wheel speed is repeated. If the predetermined time has elapsed, the process proceeds to S27. Here, for the determination of the stop state, for example, a wheel speed sensor for ABS control
Speed signals from 3a, 3b, 3c, 3d are used. Since it is difficult for a general wheel speed sensor to determine whether or not the speed is zero within a short time, in this embodiment, the speed signals of all the wheels become zero for a predetermined time (for example, 700 ms). Is a condition for stopping the vehicle. For this reason, the process proceeds to S27 only when all the wheel speeds remain zero after the lapse of the predetermined time. If at least one of the wheel speeds is other than zero after the elapse of the predetermined time, it means that the wheels are rotating, and the current vehicle stop determination process is stopped because the wheels are not in a stopped state.

In S27, it is determined whether or not all wheels of the vehicle are locked. This step is for preventing the vehicle from being determined to be in a stopped state even when the vehicle speed is detected to be zero, when all the wheels are locked and the vehicle is moving while the four wheels are slipping. This all-wheel locked state means that all the wheels are locked while the vehicle is traveling and the wheel speeds are all zero, and therefore, based on the outputs from the wheel speed sensors 3a, 3b, 3c, 3d, What is necessary is just to judge. However, in the present embodiment, detection is performed according to the procedure shown in FIG. 3 in order to more accurately detect the locked state of all wheels. Specifically, as shown in the flowchart of FIG. 3, first, in S31, in order to confirm whether or not the vehicle is traveling with the all-wheel locked state being regarded as a problem, the vehicle travels using the pseudo vehicle speed. Determine the status. That is, the pseudo vehicle speed is set to the second predetermined speed (for example, 10 kph / h).
m) It is determined whether or not it is not less than.

The pseudo vehicle speed is a pseudo vehicle speed calculated from the rotation speed of each wheel. For example, the maximum wheel speed or the average wheel speed detected from each wheel is converted into a vehicle speed. Is the pseudo vehicle speed. Of course,
Other various calculation methods may be used. When the pseudo vehicle body speed is set based on the maximum wheel speed, it is possible to determine that all the wheels are not in the locked state as soon as at least one wheel rotates, and to detect the vehicle locked state from the vehicle speed sensor 2. This has the effect of further improving the detection sensitivity. Here, for example, 40k / h
m, when all the wheels are locked and the output speed from the speed sensor suddenly becomes zero, that is, when the vehicle continues running with all the wheels locked after the sudden braking. However, the pseudo vehicle speed calculating means 4 does not immediately set the pseudo vehicle speed to zero although the detected speed is zero. When the detected speed suddenly becomes zero in this way, for example, assuming that the vehicle is braked at a deceleration of 1 G, the speed reduced during the braking is set as the pseudo vehicle speed. Thereby, even when the correct speed is not detected from the speed sensor, a more realistic speed can be set. Note that the second predetermined speed of the above-described pseudo vehicle body speed is set because it is necessary to set the second speed to be equal to or higher than the lower limit speed at which the ABS can operate in order to prevent frequent wheel lock detection on a low friction road surface. Value. If the pseudo vehicle speed is equal to or higher than the second predetermined speed, the process proceeds to S32 because the vehicle is indeed running and it is necessary to detect the locked state of all wheels. When the speed is lower than the second predetermined speed, it is not necessary to particularly detect the locked state of all the wheels, so that the locked wheel state detection process is stopped.

In S32, a timer is initialized as in S22, and wheel speeds are detected by the wheel speed sensors 3a, 3b, 3c, 3d in S33. In S34, it is determined whether all the wheel speeds are each zero. If all wheel speeds are zero, a timer is added in S35 and the process proceeds to S36. If at least one of the wheel speeds is other than zero, the all-wheel lock state is not established, and the all-wheel lock state detection process is stopped. In S36, it is determined whether a predetermined time (for example, 700 ms) has elapsed. If the predetermined time has elapsed with all wheel speeds kept at zero, the process proceeds to S37, and if less than the predetermined time, the process returns to S33 to detect the wheel speed again. In S37, it is determined whether or not the vehicle speed detected by the vehicle speed sensor 2 is equal to or lower than a first predetermined speed (for example, 1 km / h). This is because, after all the wheels are determined to be in the locked state in S36, when the wheels start to rotate again with the passage of time, the vehicle speed is equal to or lower than the first predetermined speed for vehicle braking when the wheels are locked. It is determined whether or not the vehicle has been decelerated. When the vehicle speed is equal to or lower than the first predetermined speed, the process proceeds to S38, and it is determined that all the wheels are in the locked state. When the speed is higher than the first predetermined speed, it is determined that the wheels are not continuously locked, and the all wheel lock state detection process is stopped.

In this way, it is determined whether or not all the wheels are locked, and if it is determined that the wheels are not locked,
Proceeding from S27 to S28 in FIG. 2, when it is determined that all the wheels are locked, the current vehicle stop determination process is stopped in order not to determine that the vehicle is in the stopped state. In S28, the pseudo vehicle speed, which is the pseudo speed of the vehicle, is calculated in S31.
Similarly, the pseudo vehicle speed calculating means 4 calculates the speed based on the output from each wheel speed sensor 3a, 3b, 3c, 3d. If the pseudo vehicle speed is zero, the process proceeds to S29 and determines that the vehicle is in a stopped state. If it is faster than this, the current vehicle stop determination process is stopped. Note that the above-described vehicle stop determination process is constantly repeated. Then, the determination result is initialized when the determination process is repeated again.

As described above, in this embodiment, it is possible to accurately determine whether or not the vehicle is in a stopped state by determining whether all the wheels are locked. Therefore, even when the vehicle stops suddenly without locking the wheels, the braking force of the vehicle can be held, and the braking force holding device can be operated safely.
In the above-described embodiment, the vehicle stop state is determined using the speed signal from the wheel speed sensor for the ABS control in addition to the speed signal from the vehicle speed sensor for the speedometer. Without being limited to the above, the same effect can be obtained by using any other type of wheel speed sensor. Further, the present invention is applicable not only to a four-wheeled vehicle but also to other types of vehicles such as a two-wheeled vehicle.

[0020]

According to the first aspect of the present invention, since the stop state of the vehicle can be accurately determined by detecting the wheel lock state, even if the vehicle stops suddenly without locking the wheels. The stop state of the vehicle can be determined more accurately. According to the second aspect of the present invention, the vehicle stop state is determined using the speed signal from the vehicle speed sensor, so that the vehicle is immediately stopped without detecting the wheel speed when the vehicle is clearly running. Is not determined, a less wasteful determination process can be performed, and the speed of the vehicle stop determination process can be further increased. According to the third aspect of the invention, it is possible to accurately detect the locked state of the wheel while preventing complicated detection of the wheel lock on the low friction road.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a vehicle stop determination device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a procedure for determining a vehicle stop state.

FIG. 3 is a flowchart illustrating a procedure for determining whether all wheels are in a locked state.

FIG. 4 is a diagram showing a configuration of a conventional braking force holding device.

[Explanation of symbols]

 1 Vehicle stop judging device 2 Vehicle speed sensor 3a, 3b, 3c, 3d Wheel speed sensor 4 Pseudo vehicle speed calculating means 5 Control unit 6 Braking force holding device

Claims (3)

[Claims] 1. A wheel speed sensor disposed on each wheel of a vehicle for detecting a rotation speed of the wheel, and a pseudo vehicle speed calculating means for calculating a pseudo vehicle speed based on an output from the wheel speed sensor of each wheel. And all-wheel lock detecting means for detecting whether or not all wheels are locked based on at least the output of the wheel speed sensor, wherein all wheel speeds detected by the wheel speed sensors become zero for a predetermined time. In addition, when the all-wheel lock detecting means detects that all the wheels are not in the locked state, and when the pseudo vehicle speed by the pseudo vehicle speed calculating means is zero, it is determined that the vehicle is in the stopped state. Characteristic vehicle stop determination device. 2. A vehicle speed sensor for detecting a vehicle speed, wherein the vehicle stop determining means determines that the vehicle is in a stopped state when the vehicle speed detected by the vehicle speed sensor is equal to or lower than a first predetermined speed. The vehicle stop determination device according to claim 1, wherein 3. The all-wheel lock detecting means, wherein the pseudo-vehicle speed calculated by the pseudo-vehicle speed calculating means is equal to or higher than a second predetermined speed, all the wheel speeds are zero for a predetermined time, and 3. The vehicle stop judging device according to claim 2, wherein all the wheels are recognized as being in a locked state when the vehicle speed by the means is equal to or lower than a first predetermined speed. [0001]