JPH10151920A - Tire air pressure reduction detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To practice ABS processing and air pressure reduction judging processing by a single microcomputer, and inexpensively incorporate a tire air pressure reduction detecting device into an ABS by providing a processing control means to practice the air pressure reduction judging processing by using a spare time of the ABS processing. SOLUTION: A control unit 1 inputs sine wave signals from wheel speed sensors 3 with respective tires, and practices ABS processing and tire air pressure reduction judging processing (DWS processing) on the basis of a wheel speed pulse by performing binarizing processing on the signals. That is, in a CPU 11a, the ABS processing and DWS control are practiced in time sharing by an interrupt signal outputted from a period timer 11d according to an ABS processing program or a DWS processing program stored in a ROM 11c, and a liquid operated unit 5 is controlled through a driver 12 on the basis of a practice result of the ABS processing. In the DWS processing, when an air pressure reduced tire is judged, it is announced to a driver through a display unit 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire pressure suitable for mounting on a vehicle together with an antilock brake system (ABS) for avoiding a locked state of four tires mounted on a four-wheeled vehicle. The present invention relates to a drop detection device.

[0002]

2. Description of the Related Art As one of safety devices for four-wheel vehicles such as passenger cars and trucks, a device for detecting a decrease in tire air pressure has been developed. The tire pressure drop detector is
The rotational angular velocities of four tires are detected, and a tire whose air pressure is relatively reduced is detected based on the rotational angular velocities of the respective tires (for example, see Japanese Patent Application Laid-Open No. Sho 63-305011).

In this tire pressure drop detecting device, the rotational angular velocities of the respective tires are obtained based on wheel speed sensors for detecting the rotational state of the four tires, and the average value of the rotational angular velocities of a pair of tires on a diagonal line is calculated. The average of the rotational angular velocities of another pair of tires on the other diagonal is subtracted, and if the result falls within, for example, 0.05% of the average of the sum of the four tires, a reduced pressure tire is determined. It has been like that.

On the other hand, ABS for safety of vehicle running
(Antilock-Braking-System) is being used and is currently spreading. The ABS has a wheel speed sensor for detecting the rotation state of four tires, and detects whether or not the tire is in a slipping state in which the tire spins and controls the hydraulic pressure of the brake. As described above, since both the tire pressure drop detecting device (hereinafter, referred to as "DWS") and the ABS use the wheel speed sensor, there is a plan to share the wheel speed sensor.

When the wheel speed sensors are used in common, the detection signals of the four wheel speed sensors 1 are shaped through a binarization circuit and supplied to an ABS microcomputer and a DWS microcomputer, respectively. The two microcomputers perform unique processing according to their respective roles (see JP-A-6-92116).

[0006]

However, when two microcomputers are used, the number of parts is increased, the size of the apparatus is increased, the degree of freedom in designing a printed circuit board pattern is limited, and the productivity of the design work is reduced. . Therefore,
SUMMARY OF THE INVENTION An object of the present invention is to provide a tire air pressure drop detecting device that can implement an ABS process and an air pressure drop determining process with a single microcomputer when the vehicle is equipped with an ABS and a tire air pressure drop detecting device.

[0007]

According to the present invention, there is provided a tire pressure drop detecting apparatus according to the present invention, in which an ABS cycle including an ABS processing time for actually performing processing and an idle time for waiting for timing is one cycle. AB for executing ABS processing for avoiding the tire lock state
S processing means, and D for executing a pneumatic pressure decrease determination process for determining whether or not the tire air pressure is reduced.
WS processing means and the air pressure drop determination processing executed by the DWS processing means are performed by the ABS processing means by ABS processing.
A processing control means for distributing and executing the idle time repeatedly when the processing is executed (claim 1).

According to the present invention, the air pressure drop determination processing is executed by utilizing the idle time of the ABS processing. Therefore, for example, when the vehicle is equipped with the ABS and the tire pressure drop detecting device, the ABS processing and the air pressure drop determination are performed. The processing can be realized by one microcomputer. It is preferable that the tire pressure drop detecting device further includes a signal output unit for outputting an interrupt signal every ABS cycle. In this case, the processing control unit recognizes a start timing of the idle time. In response to the recognition of the start time of the free time,
Means for causing the DWS processing means to execute the air pressure reduction determination processing, and in response to the output of the interrupt signal from the signal output means, temporarily suspending the air pressure reduction determination processing in the DWS processing means, It is preferable that the ABS processing means include means for executing ABS processing.

[0009] Initial check processing means for executing an initial check processing for determining whether or not the apparatus functions normally, and while the initial check processing is being performed in the initial check processing means, Desirably, the apparatus further includes means for prohibiting the execution of the air pressure drop determination processing by the DWS processing means.

According to the present invention, while the initial check process is being performed, the air pressure drop determination process is not performed, so that an erroneous determination as to whether the tire air pressure has dropped can be avoided. That is, during the execution of the initial check process, it is not known whether the hardware configuration for obtaining the wheel speed pulse necessary for executing the air pressure drop determination process, for example, is functioning properly. This is because there is a possibility that the executed wheel speed pulse may include an error.

The memory further includes a memory check means for checking a memory used by the ABS processing means for the ABS processing and a memory used by the DWS processing means for the air pressure drop judgment processing. It is desirable that the processing be performed in accordance with either the program for performing the processing or the program for performing the air pressure drop determination processing.

In the present invention, the program for performing the air pressure drop determination processing can detect the failure of the memory used for the ABS processing, or the program for performing the ABS processing can detect the failure of the memory used for the air pressure reduction determination. Can save computing resources. Note that the memory includes a ROM, a RAM, and a nonvolatile memory. When a memory failure is detected, an ABS warning light, DW
If one or both of the S warning lamps are turned on (claim 5), the user can be notified of the faulty part in an easy-to-understand manner.

The ABS processing means and the DWS processing means execute the ABS processing and the air pressure reduction judgment processing while sharing the memory used by the ABS processing means for the ABS processing and the memory used by the DWS processing means for the air pressure reduction judgment processing. It is desirable to perform (claim 6). In the present invention, since the ABS processing unit and the DWS processing unit share the memory and execute the AB processing and the air pressure drop determination processing, respectively, the configuration is simpler than in the case where a memory is provided for each processing unit. Become.

The tire pressure drop detecting device is
Further, it is preferable to include a pulse acquisition unit for acquiring a wheel speed pulse corresponding to the rotational angular velocity of a tire mounted on the vehicle. In this case, the ABS processing unit includes a wheel acquisition unit that acquires the wheel speed pulse acquired by the pulse acquisition unit. Means for counting the number of pulses in the ABS cycle of the fast pulse, means for determining the time from the start of counting the number of pulses to the end of the counting as a pulse interval, the number of pulses counted one cycle before and one cycle before And a means for executing ABS processing based on the determined rotational angular velocity based on the determined pulse interval. The DWS processing means includes: , The ABS
Means for totalizing the number of pulses counted by the processing means and the determined pulse interval over a DWS cycle;
Means for calculating the tire rotational angular velocity based on the number of pulses and the pulse interval collected one cycle before, and means for executing the air pressure drop determination process based on the determined tire rotational angular velocity It is more preferable to include them.

According to this configuration, since the rotational angular velocity of the tire is obtained by the DWS processing means using the number of pulses and the pulse interval obtained by the ABS processing means, the wheel speed obtained by the pulse obtaining means in each processing means is obtained. The processing is simplified as compared with a configuration in which the pulse is separately acquired and the rotational angular velocity is obtained.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram of a vehicle equipped with a tire pressure drop detecting device according to one embodiment of the present invention. The tire pressure drop detecting device includes four tires W ₁ , W ₂ , W
_3, W is determined pneumatic pressure drop judging function whether the air pressure is decreased in _4, and the tire W _{i (i} = 1,2,3,4) is ABS for preventing lock, such as by sudden braking
It has a function. Tires W ₁ and W ₂ correspond to front left and right tires, respectively. The tires W ₃ and W ₄ correspond to rear left and right tires, respectively.

The tire pressure drop detecting device includes a control unit 1 which is a control center of the device. An initialization switch 2 is connected to the control unit 1. The initialization switch 2 is operated by the driver when obtaining an initial correction coefficient required for an initial correction process included in the air pressure drop determination function. The initial correction process is performed for the tire W
Each tire W of the effective rolling radius within the standard included in _i
This is a process for eliminating variations (initial differences) between _i (Japanese Patent Laid-Open Nos. 7-156621 and 6-183).
227). The "effective rolling radius" refers to a tire W _i that is freely rolling under a load.
Is the value obtained by dividing the distance traveled by one rotation by 2π.

[0018] The control unit 1 is made from the wheel speed sensor 3 provided with respect to the tire W _i on the output of the sine wave is applied. When an output is provided from the wheel speed sensor 3, the control unit 1 performs a binarization process on the output to generate a wheel speed pulse. Further, based on the generated wheel speed pulse, an ABS process and a tire pressure drop determination process (hereinafter, referred to as “DWS process”) are executed.

In the ABS processing, based on the wheel speed pulse,
Tire W_iRotational angular velocity F_iIs required. Then
Rotational angular velocity F obtained_iTire W based on_iSpeed
Degree V _iAnd the speed V of the vehicle are obtained.
_iSpeed V_iAnd the slip which is the ratio or difference of the speed V of the vehicle.
The slip rate Rs is determined, and the slip rate Rs
Based on the tire W_iTo determine if it is likely to lock
Separated. Then, according to the determination result, the tire W_iTo
The brake transmitted to the brake 4 provided in association
The hydraulic pressure is controlled. More specifically, the control unit 1
Is controlled by controlling the hydraulic unit 5.
Control pressure. The hydraulic unit 5 has a brake pedal 6
The brake generated in the master cylinder 7 when depressed
It controls the hydraulic pressure.

[0020] In DWS processing, the rotational angular velocity F _i of the tires W _i is calculated based on the wheel speed pulse. Thereafter, a determination value for determining a decrease in air pressure is determined based on the determined rotational angular velocity F _i , and it is determined whether the air pressure of any of the tires W _i has decreased based on the determination value. You. As a result, the air pressure of any of the tires W _i is determined to be decreased, the determination result display 8
Will be displayed.

FIG. 2 is a block diagram showing the electrical configuration of the tire pressure drop detecting device. As described above, the output of the wheel speed sensor 3 is given to the control unit 1. The output of the wheel speed sensor 3 is subjected to a binarization process in a binarization circuit 10 and converted into a wheel speed pulse. The wheel speed pulse has a pulse width inversely proportional to the rotational angular speed F _i of the tire W _i , and is given to the control microcomputer 11.

The control microcomputer 11 includes a CPU 11a which is a center of arithmetic processing, a RAM 11b functioning as a work area, an initial correction coefficient calculation program,
ROM 11c in which various programs including an ABS processing program and a DWS processing program are stored, and an interrupt signal is generated every time a predetermined interrupt time t _TH elapses.
It includes a period timer 11d for outputting to the PU 11a.

When the ignition key switch is turned on, the CPU 11a reads AB stored in the ROM 11c.
According to either the S processing program or the DWS processing program, a memory check of the ROM 11c, the RAM 11b, and the nonvolatile memory 14 described later is performed. Then, according to the ABS processing program and the DWS processing program stored in the ROM 11c, the periodic timer 1
The ABS process and the DWS process are executed in a time-division manner using the interrupt signal output from 1d as described later.

The CPU 11a controls the hydraulic unit 5 by driving the driver 12 based on the execution result of the ABS processing. As a result, even during a sudden braking operation, the tire W
It is avoided that _i becomes locked. On the other hand, CPU
11a as a result of performing the DWS processing, when the air pressure is judged that there is a tire W _i with a reduced turns on the DWS for monitoring lamp 8a included in the display unit 8, the tire W _i whose air pressure has dropped is Notify the driver of this.

The control unit 1 is also provided with a monitoring microcomputer 13. The monitoring microcomputer 13 includes a CPU 13 which is a center of arithmetic processing.
a, a ROM 13b in which a monitoring program for ABS monitoring processing is stored. When the ignition key switch is turned on, the CPU 13a reads a monitoring program stored in the ROM 13b, and monitors processing in the control microcomputer 11 in accordance with the program. Specifically, it monitors whether the control of the hydraulic unit 5 by the control microcomputer 11 is not abnormally long, whether the arithmetic function of the control microcomputer 11 is functioning properly, and the like. As a result, when an abnormality occurs in the processing in the control microcomputer 11, A
The BS monitoring lamp 8b is turned on to notify the driver of the occurrence of the abnormality.

When the ABS processing program or the DWS processing program detects a memory failure, the CPU 13a turns on one or both of the ABS monitoring lamp 8b and the DWS monitoring lamp 8a to notify the driver of an abnormality. Inform. If one of the monitoring lamps is switched on depending on the location of the failure, the user can know which system is abnormal, and can know that the other systems are operating normally. Further, when one unit (for example, ABS) is housed in the other unit (for example, ABS) in appearance, only one lamp (ABS) is turned on regardless of the failure part. It is enough. This is because the operator checks (replaces) the ABS unit whose lamp is lit.

The control unit 1 further includes an EEPRO
A nonvolatile memory 14 composed of M or the like is provided. Fixed data necessary for executing the DWS processing is stored in the nonvolatile memory 14 in advance. Specifically, in the corner rig correction process included in the DWS process, a correction coefficient used for eliminating an error included in cornering from a determination value is stored.

Variable data necessary for executing DWS processing and ABS processing is written to the nonvolatile memory 14 as needed. The variable data in the DWS processing includes an initial correction coefficient. Initial correction factor are those based on the arbitrary tires W _i, corresponding to the effective rolling radius of the ratio of other tire W _i with respect to the effective rolling radius of the tire W _i which is in this reference at a normal internal pressure.

The initial correction coefficient is obtained, for example, when the driver operates the initialization switch 2 when the tire _Wi is replaced. More specifically, the driver
When all the tires _Wi have the normal internal pressure, the vehicle is driven in a straight line, and the initialization switch 2 is operated in this state.
The CPU 11a reads the initial correction coefficient calculation program from the ROM 11c in response to this, and operates in accordance with the program. That is, based on the wheel speed pulse, the tire W _i
Obtains the rotational angular velocity F _i, further, a primary tire W
determining the ratio of the rotational angular velocities F _i of other tires W _i for _i rotational angular velocities F _i of. Then, the ratio of such rotational angular velocities F _i plurality retrieve and calculate the average. This average value is used as an initial correction coefficient and is written in a predetermined area of the nonvolatile memory 14.

[0030] In order to calculate the initial correction factor is required proportion of a plurality of rotational angular velocities F _i, is before calculation is complete take some time. Therefore, C
The PU 11a writes the progress of the calculation of the initial correction coefficient in the nonvolatile memory 14 one by one. Thereby, even if the power is turned off during the calculation, the continuation can be resumed later.

The variable data in the ABS processing includes a failure code. The failure code indicates an abnormal location when an abnormality occurs in the ABS actuator such as the hydraulic unit 5, the control microcomputer 11, or the like. Whether or not there is an abnormality is determined by, for example, the control microcomputer 1 by the monitoring microcomputer 13.
1 is determined.

FIG. 3 is a conceptual diagram for describing the writing of variable data into the nonvolatile memory 14. CPU
11a, when data to be written necessary for the DWS processing such as an initial correction coefficient occurs (A),
The data is once written in the DWS buffer provided in the PU 11a (A1). At this time, D inside the CPU 11a
A WS access request flag is set (A2). This indicates that there is data to be written to the nonvolatile memory 14. Further, the access address, which is the address of the nonvolatile memory 14 to which data is to be written, is
The data is written to the DWS address buffer provided in U11a (A3).

Thereafter, the CPU 11a determines whether or not the DWS access request flag is set according to an access handler which is a lower program (C1). If it is determined that the DWS access request flag is set, the data to be written is determined. Is determined, and the data and the access address are processed in accordance with the driver which is a higher-level program (C2). Then, data is written to the address area of the nonvolatile memory 14 specified by the access address (C3).

Similarly, when data to be written necessary for ABS processing such as a failure code is generated (B), the CPU
11 writes the data into the ABS buffer once (B1), sets the ABS access request flag (B2), and writes the access address into the ABS address buffer (B3). Thereafter, the access handler and the driver are executed (C1, C2), and data is written to the address area of the nonvolatile memory 14 specified by the access address (C3).

As described above, according to the tire pressure drop detecting device, the nonvolatile memory 14 is subjected to the ABS processing and the DW
Since the processing is shared by the S processing, both the ABS processing and the DWS processing can be realized with a simple configuration. Figure 4 shows the ABS
It is a figure for explaining timing control of processing and DWS processing. The ABS process is performed with a predetermined ABS cycle Δt ₁ (for example, Δt ₁ = 10 (msec)) as one cycle. However, the arithmetic processing is not actually performed over the ABS period Δt ₁ , but the arithmetic processing is actually performed only for the first ABS processing time t _g (for example, t _g = 8 (msec)), and the remaining idle time t _n (for example, t _n = 2 (msec))
Is reserved for time to wait for timing.
Therefore, in this embodiment, so as to execute a DWS processing free time t _n of the ABS process.

On the other hand, the minimum time (actual execution time) required to execute the DWS processing is the free time t _{n of the} ABS processing.
Therefore, all of the DWS processes cannot be completed within one free time t _n . That is, a general DWS process is executed with a DWS cycle Δt ₂ (for example, Δt ₂ = 1 (sec)) longer than the ABS cycle Δt ₁ as one cycle. Among these, the actual execution time of the DWS process is the DWS cycle. It is about several tens of Δt ₂ . Specifically, 200 (mse
c) degree.

Therefore, in this embodiment, a series of DW
Rather than being a S processing is executed once free time t _n, respectively DWS processing to a plurality of idle time t _n (1), D
WS processing (2),..., DWS processing (k-1), DWS processing
(k) is executed in a distributed manner. To realize this control, in this embodiment, the ABS processing and higher priority process than DWS processing, priority end timing of the middle running low DWS processing priority idle time t _n Of high ABS processing,
From this interrupt timing ABS processing time t _g is so as to return to the low priority DWS processing at the start timing of the idle time t _n to end.

In this embodiment, in order to realize the interruption of the ABS processing, the interruption time t _TH of the period timer 2 e is set.
Is set to the same length as the ABS cycle Δt _1, and the measurement start timing of the cycle timer 2 e and the start timing of the ABS cycle Δt ₁ are synchronized. 5 and 6 show a memory check process, an ABS process and D
It is a flow chart for explaining timing control of WS processing more concretely. When the ignition key switch is turned on and the tire pressure drop detecting device is started, the CPU 11a responds to the
The ABS processing program or the DWS processing program stored in is read, and according to the read ABS processing program or the DWS processing program,
The memory check process for both the ABS process and the DWS process is executed (step S1).

Although the memory check method is well known, it will be briefly described as shown in the flowcharts of FIGS. 7, 8, and 9. The flowchart of FIG. 7 explains a method of checking the RAM. The address area of the memory to be checked is called CKADR. In step U1, the start address of CKADR is specified. Then, the check data is written to the address (step U2). Check data, 00 _H, 55 _H, AA
Lower byte of _H or CKADR. Then, the check data is read (step U3), compared with the written check data (step U4), and if they do not match, abnormal processing is performed (step U5). If there is a match, the address is advanced (step U6), and the above processing is repeated until the final address is reached (step U7).

FIG. 8 is a flowchart for explaining a method of checking the ROM. The start address of the CKADR is specified (step V1), and the data at that address is read out and written into the work area of the CPU 11a to be set as S _buf (step V2). Then, the address is advanced (step V4), data is read, and addition to the work area is continued. When the last address is reached, the written total value S
It is determined whether or not _buf has reached a predetermined value (step V5). If the predetermined value has not been reached, an abnormal process is performed (step V6).

The flowchart of FIG. 9 explains a method of checking a nonvolatile memory. The start address of CKADR is specified (step W1), and the data at that address is read and saved in Buf in the work area of the CPU 11a (step W2). Then, check data is written to the address (step W3), the check data is read (step W4), and the check data is compared with the written check data (step W5). If they do not match, an abnormal process is performed (step W6). B if they match
The data of uf is returned (step W7), the address is advanced (step W8), and the above processing is repeated until the address reaches the final address (step W9).

Abnormal processing includes ABS processing and DWS to be continued.
While the processing is interrupted, the ABS monitoring lamps 8b and D
Switching is performed by turning on one or both of the WS monitoring lamps 8a, or by turning on or off one of the monitoring lamps depending on whether the CKADR is in the ABS area or the DWS area. Next, the ABS processing and the DWS processing will be described.

The CPU 11a executes an initial check process according to the ABS processing program (step S3). The initial check processing is performed by the wheel speed sensor 3,
This is a process for determining whether an input / output device such as the display 8 is normal. At this time, when it is determined that any of the input / output devices has a failure, the CPU 11a writes a failure code indicating the failure location in the nonvolatile memory 14 by the above-described method.

The CPU 11a starts the period timer 11d during the initial check process. As described above, the period timer 11d determines the ABS period Δ
The same time as t ₁ is set as the interrupt time t _TH and the CPU
And it outputs an interrupt signal every start timing of the ABS cycle Delta] t ₁ to 11a. When the initial check processing is completed and it is determined that all the input / output devices are normal, the CPU 1
1a executes DWS processing with a low priority according to the DWS processing program (step S4).

As described above, the DWS process is started after the initial check process is completed.
DWS processing can be executed accurately. That is, since the initial check process is a process for determining whether or not the input / output device is normal as described above, the wheel speed pulse obtained from the wheel speed sensor 3 is not used until this process is completed. This is because it may not be accurate.

The cycle timer 11d started during the execution of the initial check processing outputs the interrupt signal to the CPU 11a when the interrupt time t _TH has elapsed from the start timing.
Output to When this interrupt signal is given, the CPU 11a determines that an interrupt request has been made, temporarily suspends the DWS processing being executed, and executes ABS processing according to the ABS processing program.
The process is executed (Step T1 in FIG. 6).

When the ABS processing is executed over the ABS processing time t _g and the start timing of the idle time t _n is reached,
The CPU 11a returns to the DWS processing, and resumes the continuation after the interruption. That is, the ABS processing program includes A
BS process includes a return instruction from the interrupt at the end timing (start timing of the idle time t _n) of time t _g, CPU 11a is DWS by executing this instruction
Return to processing.

On the other hand, as described above, the cycle timer 11d outputs an interrupt signal to the CPU 11a every time the interrupt time t _TH set at the same time as the ABS cycle Δt ₁ elapses. then an interrupt signal after the resumption DWS processing at the start timing of the idle time t _n is CPU11
being output to a is the end timing of the idle time t _n corresponding to the start timing of the next ABS cycle Delta] t _1. Therefore, DWS processing is resumed at the same time as the start timing of the idle time t _n at the same time is again interrupted and the end timing of the idle time t _n. Then, an ABS process is executed instead of the DWS process.

As described above, the ABS processing is performed by the periodic timer 1
The DWS process is repeatedly executed at every ABS cycle Δt ₁ by the interrupt signal from 1d, and the DWS processing is executed in a distributed manner over the free time t _n within the ABS cycle Δt ₁ . Since this DWS processing is executed in a distributed manner over a plurality of idle times t _n ,
The time allowed for WS processing is the DWS cycle Δt ₂
Will be shorter. For example, if the ABS period Δt ₁ is included m times in the DWS period Δt ₂ , the time allowed for the DWS processing is m × t _n . More specifically, Δt ₂ = 1 (sec), Δt ₁ = 10 (msec), and t
_{When n} = 2 (msec), the time allowed for the DWS processing is 100 × 2 = 200 (msec).

On the other hand, the actual execution time of the DWS processing is about several tens of the DWS cycle Δt ₂ as described above. Therefore, even if the time allowed for the DWS processing is short, it is possible to end all of the DWS processing within the DWS cycle Δt ₂ . Also, in view of the fact that the ABS process is performed a plurality of times while the series of DWS processes is performed,
In this embodiment, method of calculating the rotational angular velocities F _i have been devised which are required in any of the process of the DWS processing and ABS processes.

[0051] That is, CPU 11a, when executing the ABS processing, two numbers of a given wheel speed pulses from D conversion circuit 10 while counting over ABS cycle Delta] t _1, time until the terminal count from the count start (pulse The interval T) is measured. Then, in order to use the pulse number N and pulse interval T obtained as a result as data for calculating the rotational angular velocity F _i in the next ABS cycle Δt ₁ , R
It is held in AM 11b.

Incidentally, the rotational angular velocity F _i is obtained by the following equation (1). However, in the following equation (1), α
Is a coefficient determined effective rolling radius depending on the number of teeth of the rotor used in the wheel speed sensor 3 of the tire W _i. F _i = α × (N / T) (1) Further, when executing the DWS processing, the CPU 11a accumulates the pulse number N and the pulse interval T held in the RAM 11b in the immediately preceding ABS processing, Further, an average value is obtained at the time of this accumulation. The accumulation processing and the averaging processing are performed over the DWS cycle Δt ₂ . And
In the next DWS cycle Δt ₂ , a rotational angular velocity F _i is obtained using the obtained average value. Specifically, by substituting the obtained average value into the above equation (1), the rotational angular velocity F
_i is required.

As described above, the pulse number N and the pulse interval T obtained in the ABS processing are used in the DWS processing. Therefore, the processing is simplified as compared with the case where the number of pulses N and the pulse interval T are separately obtained in the ABS processing and the DWS processing to obtain the rotational angular velocity F _i . As described above, according to the apparatus for determining a decrease in tire air-pressure according to the present embodiment, the idle time t _n of the ABS process is
Since the WS processing is distributed and executed, AB
The S processing and the DWS processing can be realized by one CPU 11a. Therefore, for example, when an ABS is pre-equipped in a vehicle and a tire pressure drop detecting device is added later, a microcomputer for the ABS can be used as a control center of the tire pressure drop detecting device. Therefore, the tire pressure drop detecting device can be incorporated in the ABS with low cost and simple configuration.

The nonvolatile memory 14, the ROM 11c
And the RAM 11b are shared by the DWS processing and the ABS processing. Therefore, for example, when the ABS is pre-installed in the vehicle, the non-volatile memory 14 for the ABS can be used when the tire pressure drop detecting device is added later. Therefore, the tire pressure drop detecting device can be incorporated in the ABS with a lower cost and a simpler configuration.

Also, an ABS processing program or DWS
Since the memory check processing for both the ABS processing and the DWS processing is performed in accordance with one of the processing programs, it is possible to save computation resources. Further, in the abnormality processing, it is easy for the user to understand if the monitoring lamp is turned on or switched depending on whether the failure is in the ABS area or the DWS area.

The description of one embodiment of the present invention is as described above.
However, the present invention is limited to the above-described embodiment.
There is no. For example, in the above embodiment, when the ABS process is idle
Interval t _nThe case where the DWS process is executed
However, for example, in the monitoring microcomputer 13,
Execute DWS processing during idle time of the executed ABS monitoring processing.
May be performed. ABS processing for ABS monitoring processing
There is a free time to wait for timing as well as
The DWS process is executed using the idle time.

As shown in FIG. 10, the control unit 1 according to this configuration includes a CPU 30a, a RAM 30b,
A control microcomputer 30 including a ROM 30c in which a BS processing program is stored;
A ROM 40b in which a BS monitoring program and a DWS processing program are stored, and a monitoring microcomputer 40 including a cycle timer 40c that outputs an interrupt signal to the CPU 40a every time the interrupt time t _TH elapses. The nonvolatile memory 14, the DWS monitoring lamp 8a, and the initialization switch 2 are connected to a monitoring microcomputer 40.

In this configuration, the CPU 40b of the monitoring microcomputer 40 provides an interrupt permission signal to the control microcomputer 30 when receiving an interrupt signal from the cycle timer 40c during the DWS process. At the same time, the DWS processing is temporarily suspended. The CPU 30a of the control microcomputer 30 executes ABS processing in response to the interrupt permission signal. Then, a return signal to the DWS processing is given to the monitoring microcomputer 40 at the end timing of the ABS processing time t _g . In response, the monitoring microcomputer 40 sets the DW
S processing is restarted.

According to this configuration, the monitoring microcomputer 13 originally required to execute the ABS processing is also provided.
As a result, DWS processing is multitasked with time sharing, so that computational resources can be used effectively. Also, regarding the memory check, the AB processing is performed according to either the ABS processing program or the DWS processing program.
If the memory check processing for both the S processing and the DWS processing is performed, it is possible to save computation resources.

In the embodiment of FIG. 10, as in the embodiment of FIG. 2, the number of pulses N and the pulse interval T obtained in the ABS processing are used in the DWS processing, but in the embodiment of FIG. Since the control microcomputer 30 that performs the ABS processing and the monitoring microcomputer 40 that performs the DWS processing are separate, the output of the binarization circuit 10 may be input to the monitoring microcomputer 40 as well. . In this case, the number of pulses N and the pulse interval T are separately obtained in the ABS processing and the DWS processing to obtain the rotational angular velocity F _i .

In the above-described embodiment, the case where the nonvolatile memory 14 is connected to the microcomputer that executes the DWS processing is described. However, for example, the nonvolatile memory 14 may be connected to the microcomputer that does not execute the DWS processing. In this case, when data to be written such as an initial correction coefficient is generated, the data is temporarily stored in a microcomputer that does not execute the DWS process, and then written to the nonvolatile memory 14.

Various other design changes can be made within the scope of the present invention.

[0063]

As described above, according to the present invention, the air pressure drop judgment processing is executed in a distributed manner during the idle time of the ABS processing. The ABS processing and the air pressure drop determination processing can be realized by one microcomputer. For example, when the tire pressure drop detecting device is added later with the ABS pre-installed in the vehicle,
AB prepared for ABS just by changing the program
The microcomputer for S can execute the air pressure drop determination processing.

As described above, since the originally provided microcomputer can be effectively used, the tire pressure drop detecting device can be incorporated in the ABS with low cost and a simple configuration. According to the third aspect of the present invention, since the air pressure drop determination process is not performed while the initial check process is being performed, it is possible to avoid an erroneous determination as to whether or not the tire air pressure has dropped. Therefore, a highly accurate tire pressure drop detecting device can be provided.

According to the fourth aspect of the present invention, the memory check of the memory used by the ABS processing means for the ABS processing and the memory used by the DWS processing means for the air pressure reduction determination processing are performed by the ABS processing program or the air pressure reduction determination. Since it is performed according to any of the programs that perform the processing, A
The program for performing the air pressure drop determination processing can detect the failure of the memory used for the BS processing, or the program for performing the ABS processing can detect the failure of the memory used for the air pressure reduction determination processing. Save money.

According to the fifth aspect of the present invention, when a failure in the memory is detected, one or both of the ABS warning light and the DWS warning light are turned on, so that the user can easily recognize the failure portion. I can let you know. Also,
According to the invention described in claim 6, the ABS processing means and the DW
Since the S processing means executes the ABS processing and the air pressure drop determination processing while sharing the memory,
For example, when the tire pressure drop detecting device is added later while the ABS is already installed in the vehicle, the memory provided in the ABS can be used together. Therefore, the tire pressure drop detecting device can be incorporated in the ABS with a cheaper and simpler configuration.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a vehicle equipped with a tire pressure drop detecting device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the tire pressure drop detecting device.

FIG. 3 is a conceptual diagram for describing writing of data to a nonvolatile memory.

FIG. 4 is a diagram for explaining timing control of ABS processing and DWS processing.

FIG. 5 is a flowchart for explaining timing control of ABS processing and DWS processing more specifically;

FIG. 6 is a flowchart for further specifically explaining the timing control of the ABS processing and the DWS processing.

FIG. 7 is a flowchart illustrating a method of checking a RAM.

FIG. 8 is a flowchart illustrating a method of checking a ROM.

FIG. 9 is a flowchart illustrating a method of checking a nonvolatile memory.

FIG. 10 is a block diagram showing an electrical configuration of a tire pressure drop detecting device according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control unit 11 Control microcomputer 11a CPU 11d Period timer 13 Monitoring microcomputer 13a CPU 14 Non-volatile memory

Claims (6)

[Claims] An ABS cycle including an ABS processing time at which processing is actually performed and an idle time for timing wait is set to one.
ABS to avoid the tire lock state with the cycle
ABS processing means for executing processing, DWS processing means for executing air pressure reduction determining processing for determining whether or not the tire air pressure has decreased, and air pressure reduction executed by the DWS processing means A tire control apparatus for detecting a decrease in tire air pressure, comprising: processing control means for executing the determination processing in a vacant time repeatedly visited by the execution of the ABS processing by the ABS processing means. 2. The apparatus according to claim 1, further comprising: signal output means for outputting an interrupt signal every ABS cycle; wherein said processing control means includes means for recognizing a start timing of said idle time; Means for causing the DWS processing means to execute an air pressure drop determination process in response to the recognition; and an air pressure in the DWS processing means in response to an interrupt signal being output from the signal output means. 2. The apparatus for detecting a decrease in tire air pressure according to claim 1, further comprising means for temporarily suspending the decrease determination processing and causing the ABS processing means to execute the ABS processing. 3. An initial check processing means for executing an initial check processing for determining whether or not the apparatus functions normally, and while the initial check processing is being performed by the initial check processing means, The tire pressure drop detecting device according to claim 1, further comprising means for prohibiting execution of the air pressure drop determining process by said DWS processing means. 4. A memory checking means for checking a memory used by the ABS processing means for ABS processing and a memory used by the DWS processing means for air pressure drop judgment processing, wherein the memory checking means checks the memory. , A
The tire pressure drop detection device according to claim 1, wherein the detection is performed in accordance with one of a program for performing a BS process and a program for performing an air pressure drop determination process. 5. When an error is detected in a memory used for ABS processing or a memory used for air pressure drop determination processing, one or both of an ABS warning light and a DWS warning light are turned on. The tire pressure drop detecting device according to claim 4, wherein 6. The ABS processing means and the DWS processing means share the memory used by the ABS processing means for the ABS processing and the memory used by the DWS processing means for the air pressure reduction determination processing while performing the ABS processing and the air pressure reduction determination processing. 2. The apparatus for detecting a decrease in tire air pressure according to claim 1, wherein the detection is executed.