JP2005201723A - Vehicle speed computing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle speed computing device determining the correct vehicle speed from the angular velocities of the wheels and the internal pressures of the tires. <P>SOLUTION: A vehicle 10 is equipped with pressure sensors 25-28 for detecting the internal pressures P(n) of the tires n(n=1 to 4) and wheel velocity sensors 21-24 for detecting the angular velocities ωn of the wheels (n). The device calculates the changing rate DP(n) of the dynamic load radius based on the difference ΔTP(n) between the reference pressure PS(n) and the internal pressures P(n) of the tires respectively detected by the pressure sensors to determine the vehicle speed computing wheel speed SPDH(n) based on the angular velocities ωn of the wheels respectively detected by the wheel speed sensors and the DP(n). The vehicle speed SPDH is calculated from the SPDH(n) to be outputted to a speed meter 19. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vehicle speed calculation device that calculates the speed of a vehicle based on an angular speed of a wheel provided in the vehicle and an internal pressure of a tire mounted on the wheel.

In the anti-lock braking system (ABS) control of a vehicle, an electronic control device controls brake hydraulic pressure applied to the brake device of each wheel in order to avoid locking of the wheel during braking. In order to perform this control, a wheel speed sensor for detecting the angular speed of the wheel is attached to the rotating shaft of the wheel, and a technique for calculating the speed of the vehicle using this wheel speed sensor has been proposed. More specifically, the ABS control microcomputer (electronic control unit) calculates a vehicle speed pulse based on the wheel speed pulse output from the wheel speed sensor for ABS control, and uses the vehicle speed pulse as an AC signal (vehicle The technique of converting to (speed) and outputting to a speedometer is proposed (for example, refer patent document 1).
JP-A-8-268252 (columns 0025 and 0027, FIGS. 2 and 4)

By the way, even if the angular velocity of the wheels is constant, the vehicle speed changes if the tire dynamic load radius is different. Further, the dynamic load radius greatly varies depending on the internal pressure (air pressure) of the tire.
However, since the above-described prior art uniformly calculates the vehicle speed based on the angular velocity of the wheels regardless of the internal pressure of the tire, the vehicle speed displayed on the speedometer is an inaccurate value.
An object of the present invention is to obtain a more accurate vehicle speed based on the angular velocity of a wheel and the internal pressure of a tire.

The vehicle speed calculation device of the present invention is made to achieve the above object,
Angular velocity detection means for detecting the angular velocity of wheels provided in the vehicle;
Pressure detecting means for detecting the internal pressure of the tire mounted on the wheel;
And calculating means for calculating a vehicle speed based on the detected angular velocity of the wheel and the detected internal pressure of the tire.

  According to this, since the vehicle speed is calculated based on the angular velocity of the wheel and the internal pressure of the tire, a more accurate vehicle speed can be obtained in consideration of fluctuations in the internal pressure of the tire.

The vehicle speed calculation device of the present invention further includes:
Input means for inputting a value corresponding to the internal pressure of the tire in response to an operation signal from the outside as a reference pressure;
The calculation means calculates a value representing a change in a dynamic load radius based on a deviation of the detected internal pressure of the tire from the input reference pressure based on the deviation, and detects the angular velocity of the detected wheel The vehicle speed is calculated based on the calculated dynamic load radius change value.

  The dynamic load radius of the tire varies depending on the type of tire and the like, and therefore is not uniquely determined only from the internal pressure of the tire. However, the change in the dynamic load radius according to the deviation of the internal pressure of the tire from the reference pressure can be determined as a substantially constant value regardless of the type of tire. Therefore, this device calculates a value representing the change in the dynamic load radius based on the deviation of the internal pressure of the tire from the reference pressure based on the deviation, and calculates the calculated change in the dynamic load radius as well as the angular velocity of the wheel. The vehicle speed is determined based on the value to be expressed. As a result, since the variation of the dynamic load radius due to the variation of the internal pressure of the tire is taken into account, a more accurate vehicle speed can be obtained.

The angular velocity detection means detects angular velocities of a plurality of wheels provided in the vehicle,
The pressure detecting means detects internal pressures of a plurality of tires mounted on the plurality of wheels,
The input means inputs a value corresponding to the internal pressure of each of the plurality of tires in response to an operation signal from the outside as a reference pressure of each tire,
The computing means is
The detected internal pressure of the tire does not satisfy a given pressure condition. A value representing a change in the dynamic load radius for a tire is set to the input reference pressure of the tire and the detected internal pressure of the tire. A vehicle speed calculation wheel that is calculated based on the deviation and that is based on the detected angular velocity of the wheel on which the tire is mounted and a value representing the calculated change in the dynamic load radius according to the speed of the tire outer periphery of the wheel. For calculating the speed and calculating the vehicle speed according to the speed of the outer circumference of the tire from the detected angular speed of the wheel on which the tire in which the internal pressure of the detected tire satisfies the given pressure condition is mounted A wheel speed is calculated, and a vehicle speed is calculated based on a plurality of vehicle speed calculation wheel speeds calculated for each of the plurality of wheels.

  According to this, when the internal pressure of the focused tire does not satisfy the given pressure condition, the vehicle speed calculation device calculates the change in the angular velocity of the wheel corresponding to the tire and the change in the dynamic load radius for the wheel. The vehicle speed calculation wheel speed (the tire outer peripheral speed) for calculating the vehicle speed is calculated from the expressed value. On the other hand, when the internal pressure of the tire satisfies the same condition, this device calculates the vehicle speed calculation wheel speed from the angular speed of the wheel corresponding to the tire without using the value representing the change in the dynamic load radius. Since the vehicle speed is calculated based on the plurality of vehicle speed calculation wheel speeds determined in this manner, a more accurate vehicle speed can be determined in consideration of the state of the internal pressure of the tire.

The vehicle speed calculation device of the present invention is
Angular velocity detection means for detecting angular velocities of a plurality of wheels provided in the vehicle;
Pressure detecting means for detecting internal pressures of a plurality of tires mounted on the plurality of wheels,
The detected angular velocity of a wheel on which a tire in which the detected tire internal pressure does not satisfy a given pressure condition is mounted is excluded from the object for calculating the vehicle speed, and the detected tire Calculating means for calculating the speed of the vehicle on the basis of the detected angular speed of the wheel on which the tire having the internal pressure satisfying the given pressure condition is mounted.

  According to this, the vehicle speed calculation device excludes the detected angular speed of a wheel on which a tire that does not satisfy a given pressure condition from a plurality of tires from a target for calculating the speed of the vehicle. Then, the speed of the vehicle is calculated based on the detected angular speed of only the wheels on which the remaining tires are mounted. Accordingly, it is possible to obtain a more accurate vehicle speed in consideration of the state of the internal pressure of the tire.

The vehicle speed calculation device of the present invention is
Angular velocity detection means for detecting angular velocities of a plurality of wheels provided in the vehicle;
Temperature detecting means for detecting internal temperatures of a plurality of tires mounted on the plurality of wheels, respectively.
The detected angular velocity of a wheel on which a tire in which the detected tire internal temperature does not satisfy a given temperature condition is mounted is excluded from the object for calculating the vehicle speed, and the detected tire Calculating means for calculating the speed of the vehicle based on the detected angular speed of the wheel on which the tire having the internal temperature satisfying the given temperature condition is mounted.

  According to this, the vehicle speed calculation device excludes tires that do not satisfy a given temperature condition from a plurality of tires from the target for calculating the vehicle speed, and only the wheels on which the remaining tires are mounted. The speed of the vehicle is calculated based on the angular speed. Accordingly, it is possible to obtain a more accurate vehicle speed in consideration of the state of the internal temperature of the tire.

  Furthermore, since the vehicle speed calculation device of the present invention outputs the calculated vehicle speed to a speedometer provided in the vehicle, the speedometer can display a vehicle speed closer to the true vehicle speed. .

Embodiments of a vehicle speed calculation device according to the present invention will be described below with reference to the drawings.
(First embodiment)
First, the vehicle speed calculation device according to the first embodiment of the present invention will be described. As shown in FIG. 1, the vehicle 10 includes a first wheel 11 and a second wheel 12 positioned on the left and right sides of the vehicle 10, and a third wheel 13 positioned on the left and right of the vehicle 10, respectively. And a first wheel 15 to a fourth tire 18 and a speedometer 19 mounted on the fourth wheel 14, the first wheel 11 to the fourth wheel 14, respectively.
The first wheel 11 and the second wheel 12 are drive wheels, and the third wheel 13 and the fourth wheel 14 are driven wheels.

  The vehicle speed calculation device includes a first wheel speed sensor 21 to a fourth wheel speed sensor 24, a first tire 15 to a fourth wheel, which are attached to the rotation shafts of the first wheel 11 to the fourth wheel 14, respectively. Direct pressure type first pressure sensor 25 to fourth pressure sensor 28 attached to the tire 18, a receiver 30 for receiving a signal output from the pressure sensor via the receiving antenna 31 a and the receiving antenna 31 b, An operation switch 40 and an electronic control unit 50 that are operated to set the internal pressure of the tire at a predetermined time as a reference pressure are provided.

The speedometer 19 is provided on an instrument panel in front of the vehicle 10 and displays the speed of the vehicle 10 (vehicle speed SPDH).
The first wheel speed sensor 21 to the fourth wheel speed sensor 24 correspond to changes in the magnetic field obtained by the rotation of sensor rotors (not shown) attached to the rotation shafts of the first wheel 11 to the fourth wheel 14, respectively. The change in the voltage of the coil is detected, and the change in the voltage is output as a speed signal corresponding to the angular speeds ω1 to ω4 of the first wheel 11 to the fourth wheel 14, respectively. The first wheel speed sensor 21 to the fourth wheel speed sensor 24 correspond to angular speed detecting means for detecting the angular speeds ω1 to ω4 of the first wheel 11 to the fourth wheel 14, respectively.

  The first pressure sensor 25 to the fourth pressure sensor 28 are respectively attached to the tire valve holes of the wheel rims fixed to the hubs of the first wheel 11 to the fourth wheel 14. The first pressure sensor 25 to the fourth pressure sensor 28 include a pressure detector that detects an internal pressure P (n) of each tire, a temperature detector that detects an internal temperature T (n) of each tire, and a transmitter. Each has. The transmitter provided in each of the first pressure sensor 25 to the fourth pressure sensor 28 transmits the internal pressure P (n) as a pressure signal, and transmits the internal temperature T (n) as a temperature signal. It is like that. Here, the variable n indicates the numbers of wheels and tires to be processed later. For example, the internal pressure of the first tire 15 is represented by P (1).

  The first pressure sensor 25 to the fourth pressure sensor 28 are internal pressures P (n) of the first tire 15 to the fourth tire 18 attached to each of the first wheel 11 to the fourth wheel 14. ), And the internal temperatures T (n) of the first tire 15 to the fourth tire 18 mounted on each of the first wheel 11 to the fourth wheel 14 respectively. This corresponds to temperature detecting means for detecting.

  The receiver 30 transmits pressure signals (P (1)) respectively transmitted from the first pressure sensor 25 and the second pressure sensor 26 via a receiving antenna 31a provided at a substantially central portion in the vehicle left-right direction in front of the vehicle 10. , P (2)) and temperature signals (T (1), T (2)). In addition, the receiver 30 receives pressure signals (P () transmitted from the third pressure sensor 27 and the fourth pressure sensor 28 via a receiving antenna 31b provided at a substantially central portion in the vehicle lateral direction behind the vehicle 10, respectively. 3), P (4)) and temperature signals (T (3), T (4)).

  The operation switch 40 is disposed in the vehicle interior, and instructs that the tire pressure after adjustment to the reference pressure is input as the reference pressure of each tire when a serviceman or an occupant of a maintenance shop replaces the tire. When the operation is performed, an operation signal for setting the internal pressure PS (n) serving as a reference for the nth tire is output.

The electronic control unit 50 includes a microcomputer mainly composed of a CPU 51, a ROM 52, a RAM 53, a back up RAM 54, and an input / output circuit (interface 55). The electronic control device 50 is connected to the first wheel speed sensor 21 to the fourth wheel speed sensor 24, the receiver 30 and the operation switch 40, and the speed signal output from each wheel speed sensor, from the receiver 30. The output pressure signal and temperature signal, and the operation signal output from the operation switch 40 are input.
The electronic control unit 50 is connected to the speedometer 19 and outputs a signal for displaying the vehicle speed SPDH on the speedometer 19.

  Next, the operation of the vehicle speed calculation device configured as described above will be described with reference to FIG. FIG. 2 is a flowchart showing a main routine (program) executed by the CPU 51 of the electronic control unit 50 shown in FIG. 1 to control the vehicle speed SPDH displayed on the speedometer 19. The CPU 51 is configured to repeatedly execute this program every elapse of a predetermined time.

  Determination flags F (1) to F (4) described later are used for calculating the vehicle speed SPDH by the wheel speeds SPD (1) to SPD (4) of the first wheel 11 to the fourth wheel 14. Are each set to a value of “0” in advance in an initial routine executed when an ignition switch (not shown) is turned on from off. The determination flags F (1) to F (4) are subjected to calculations for the wheel speeds SPD (1) to SPD (4) of the first wheel 11 to the fourth wheel 14 to calculate the vehicle speed SPDH. In this case, the value is set to “0”, and when the target is not set, the value is set to “1”.

  (1) First, when the vehicle 10 is shifted from a stopped state to a traveling state, the state of the first wheel speed sensor 21 to the fourth wheel speed sensor 24 and the first tire 15 to the fourth tire. The case where the internal temperature of 18 is normal will be described.

  The CPU 51 starts the process from step 200 in FIG. 2 at a predetermined timing, proceeds to step 205, and sets a value of “1” to the variable n. Next, the CPU 51 proceeds to step 210 and determines whether or not there is an instruction to input the reference pressure of the first tire 15 based on the operation signal output from the operation switch 40. If there is an input instruction, the CPU 51 determines “Yes” in step 210 and proceeds to step 215 to determine the internal pressure of the first tire 15 detected by the first pressure sensor 25 as the reference pressure PS ( 1) and proceed to step 220. On the other hand, if there is no input instruction when the CPU 51 proceeds to step 210, the CPU 51 determines “No” in step 210 and immediately proceeds to step 220. In this case, the reference pressure PS (1) is set to a value predetermined as an initial value or a value of the internal pressure of the first tire 15 when an input is previously instructed by a serviceman, a passenger, or the like. Yes.

  Next, the CPU 51 inputs the angular speed ω1 of the first wheel 11 based on the speed signal output from the first wheel speed sensor 21 in step 220, and proceeds to step 225 to determine the angular speed ω1 and the dynamic load radius RSstd. Is multiplied by the wheel speed SPD (1). Here, the wheel speed is the peripheral speed of the tire outer periphery. Further, RSstd is a dynamic load radius of the tire, which is a predetermined reference in the vehicle design stage. This reference dynamic load radius RSstd can be considered to correspond to the reference value PSstd of the internal pressure of the tire required for the assumed type of tire.

  Next, the CPU 51 proceeds to step 230 to determine whether or not the variable n is equal to the value “4”. At this time, since the value of the variable n is “1”, the CPU 51 determines “No” in step 230 and proceeds to step 235, adds “1” to the variable n, and returns to the processing of step 210. Thereafter, the CPU 51 repeats the processing of steps 210 to 235 until the CPU 51 determines “Yes” at step 230. When the variable n reaches the value “4”, the CPU 51 determines “Yes” at step 230 and proceeds to step 240. As described above, the wheel speeds SPD (1) to SPD (4) are obtained.

Next, in step 240, the CPU 51 sends a pressure signal indicating the internal pressures P (1) to P (4) of the first tire 15 to the fourth tire 18 and the internal temperature T (1) of the tire from the receiver 30. ) To T (4) are input.
Next, the CPU 51 proceeds to step 245 to call a subroutine for correcting the wheel speed SPD (n). FIG. 3 is a flowchart showing a subroutine (program) executed by the CPU 51 to correct the wheel speed SPD (n).
The CPU 51 starts processing from step 300 of the called subroutine, proceeds to step 305 and sets a value of “1” to the variable n, and then proceeds to step 310 and the first wheel speed sensor 21 is in a normal state. It is determined whether or not there is. According to the premise, since the first wheel speed sensor 21 is normal, the CPU 51 determines “Yes” at step 310 and proceeds to step 315, where the internal temperature T (1) of the first tire 15 is determined. Whether or not the temperature is equal to or lower than a given upper limit temperature is determined based on a temperature signal indicating the internal temperature T (1).

  According to the premise, since the internal temperature T (1) of the first tire 15 is normal, the CPU 51 determines “Yes” in step 315 and proceeds to step 320, where the first tire 15 is based on the pressure signal. A deviation ΔTP (1) of the internal pressure P (1) of the first tire 15 from the 15 reference pressure PS (1) is obtained. In the correlation diagram (Map1) between the tire air pressure and the dynamic load radius in FIG. 4, the tire dynamic load radius corresponding to the difference ΔTP (n) between the tire internal pressure P (n) and the reference pressure PS (n) is shown. The amount of change between R (n) and RS (n) is shown. Here, the dynamic load radius of the tire refers to a value obtained by dividing a travel distance per one rotation of the tire when the vehicle is driven at a constant speed by applying a specified load by 2π. Further, the correlation diagram (Map1) is determined by experiments, and these relationships are defined (approximate) so that the dynamic load radius R (n) of the tire is proportional to the internal pressure P (n) of the tire. Yes.

  Next, the CPU 51 proceeds to step 325 and substitutes the deviation ΔTP (1) into the function f shown in the correlation diagram (Map2) between the tire air pressure deviation ΔTP (n) and the dynamic load radius change rate DP (n) in FIG. As a result, the dynamic load radius change rate (change in dynamic load radius) DP (1) (= R (1) / RS (1)) corresponding to the deviation ΔTP (1) is obtained. The dynamic load radius change rate DP (1) is an example of a value corresponding to a change in the dynamic load radius of the tire based on the deviation ΔTP (1). The correlation diagram (Map2) is determined based on the relationship shown in FIG.

  Next, the CPU 51 proceeds to step 330 and multiplies the wheel speed SPD (1) by the dynamic load radius change rate DP (1) (the wheel speed SPD (1) becomes the dynamic load radius change rate DP (1). A vehicle speed calculating wheel speed SPDH (1) for calculating the vehicle speed is calculated. As a result, the vehicle speed calculation wheel speed SPDH (1) becomes a value very close to the true wheel speed of the first wheel 11 (the speed of the outer periphery of the first tire 15).

  Next, the CPU 51 proceeds to step 335 to determine whether or not the variable n is equal to the value “4”. At this time, since the variable n is “1”, the CPU 51 determines “No” in step 335, proceeds to step 340, adds “1” to the variable n, and returns to the processing of step 310. . According to the premise, the internal temperatures T (2) to T (4) of the second wheel speed sensor 22 to the fourth wheel speed sensor 24 and the second tire 16 to the fourth tire 18 are all normal. The CPU 51 repeats the processing of steps 310 to 340 until the CPU 51 determines “Yes” in step 335. When the variable n becomes a value of “4”, the CPU 51 determines “Yes” in step 335, proceeds to step 395, and once executes the processing of this subroutine until it is called from the main routine. finish. Thus, vehicle speed calculation wheel speeds SPDH (1) to SPDH (4) are obtained.

  Next, the CPU 51 proceeds to step 250 of the main routine as the return destination, and calls a subroutine for calculating the vehicle speed SPDH. FIG. 6 is a flowchart showing a subroutine (program) executed by the CPU 51 to calculate the vehicle speed SPDH.

  The CPU 51 starts processing from step 600 of the subroutine, proceeds to step 605, and determines whether or not both the determination flag F (1) and the determination flag F (2) are set to the value “0”. . At this point, these determination flags are all set to a value of “0” in the initial routine and have not been changed thereafter. Accordingly, the CPU 51 makes a “Yes” determination at step 605 and proceeds to step 610 to calculate the vehicle speed SPDH (1) of the first wheel 11 and the vehicle speed of the second wheel 12 (drive wheel). The average value of the wheel speed SPDH (2) is calculated as the vehicle speed SPDH, and the process proceeds to step 695, and the process of this subroutine is temporarily ended until it is called from the main routine next.

  Next, the CPU 51 proceeds to step 255 of the main routine as the return destination and outputs the vehicle speed SPDH to the speedometer 19, and then proceeds to step 295 to end the processing of this routine once. Accordingly, the speed meter 19 displays the average value of the output vehicle speed calculation wheel speeds SPDH (1) and SPDH (2) of the two driving wheels.

(2) Next, the case where the internal temperature of the tire becomes abnormal (the internal temperature T (n) of the tire n> the given upper limit temperature) while the vehicle 10 is traveling will be described separately.
First, (a) the case where only the internal temperature T (1) of the first tire 15 is abnormal will be described. The CPU 51 starts processing from step 200, and in step 245 following steps 205 to 240, FIG. Call the subroutine shown in.
When the CPU 51 proceeds to step 315 following steps 300 to 310 of the subroutine, the internal temperature T (1) of the first tire 15 is larger than a given upper limit temperature on the premise, so that the CPU 51 determines in step 315. It determines with "No" and progresses to step 345, and sets the value of "1" to the determination flag F (1). Next, the CPU 51 returns from Steps 335 and 340 to Step 310. According to the premise, since the internal temperatures T (2) to T (4) of the second tire 16 to the fourth tire 18 are all normal, step 310 is performed until the CPU 51 determines “Yes” in step 335. After repeating the processes of .about.340, the CPU 51 once ends the process of this subroutine.

  When the CPU 51 calls the subroutine shown in FIG. 6 at step 250 as the return destination and starts the processing from step 600 and proceeds to step 605, the determination flag F (1) is “1”, and the determination flag F (2) is The value is set to “0”. Therefore, the CPU 51 makes a “No” determination at step 605 to proceed to step 615 to determine whether or not the determination flag F (1) or the determination flag F (2) is set to a value of “0”. judge. As described above, since the determination flag F (2) is set to a value of “0”, the CPU 51 determines “Yes” in step 615 and proceeds to step 620, where the determination flag F (1) is set. It is determined whether or not the value is set to “0”. As described above, since the determination flag F (1) is set to a value of “1”, the CPU 51 determines “No” in step 620, proceeds to step 625, and sets the second wheel 12 to the vehicle speed SPDH. The vehicle speed calculation wheel speed SPDH (2) of (driving wheel) is set, and the routine proceeds to step 695 to end the processing of this subroutine once.

  In step 255, the CPU 51 outputs the vehicle speed SPDH to the speedometer 19. Accordingly, among the drive wheels, the drive wheel (first wheel 11) having an abnormal tire internal temperature is excluded from the object for calculating the vehicle speed, and the CPU 51 determines in step 255 the vehicle speed of the drive wheel having the normal tire internal temperature. The calculation wheel speed SPDH (2) is output to the speedometer 19.

  When the internal temperatures of the first tire 15, the third tire 17, and the fourth tire 18 are abnormal, the CPU 51 determines “No” in step 315 when the variable n is 3 or 4, and (step In the case where only the internal temperature of the first tire 15 is abnormal in that the value of “1” is set to each of the determination flags F (3) and (4) in step 345 (without performing the processing of 320 to 330). Is different. However, in this case as well, since the CPU 51 sets the vehicle speed calculation wheel speed SPDH (2) to the vehicle speed SPDH in step 625, the vehicle speed SPDH output to the speedometer 19 is abnormal only in the internal temperature of the first tire 15. It is the same speed as the case.

  Next, (b) the case where only the internal temperature of the second tire 16 is abnormal will be described. When the variable n is set to a value of “2” in the subroutine processing shown in FIG. Therefore, the internal temperature T (2) of the second tire 16 is higher than the given upper limit temperature, so “No” is determined in Step 315, the process proceeds to Step 345, and the determination flag F (2) is set to “1” "Is set.

  At this time, the CPU 51 calls the subroutine shown in FIG. 6 at step 250, which is the return destination, starts processing from step 600, and proceeds to step 605 and step 615. Then, the determination flag F (1) is “0”, The determination flag F (2) is set to a value of “1”. Therefore, the CPU 51 determines “Yes” in step 615 and proceeds to step 620, determines “Yes” in step 620, proceeds to step 630, and sets the first wheel 11 (drive wheel) to the vehicle speed SPDH. Vehicle speed calculation wheel speed SPDH (1) is set, and the routine proceeds to step 695 to end the processing of this subroutine once.

  Therefore, among the drive wheels, the drive wheel (second wheel 12) having an abnormal tire internal temperature is excluded from the object for calculating the vehicle speed, and the CPU 51 determines in step 255 the vehicle speed of the drive wheel having the normal tire internal temperature. The calculation wheel speed SPDH (1) is output to the speedometer 19.

  Even when the internal temperatures of the second tire 16, the third tire 17, and the fourth tire 18 are abnormal, the vehicle speed SPDH is set to the vehicle speed calculation wheel speed SPDH (1) in step 630. The vehicle speed SPDH output to the speedometer 19 is the same as that when only the internal temperature of the second tire 16 is abnormal.

  Next, (c) the case where the internal temperatures of the first tire 15 and the second tire 16 are both abnormal and the internal temperatures of the third tire 17 and the fourth tire 18 are both normal will be described. When the variable n is set to 1 or 2 in the processing of the subroutine shown in FIG. 3, in step 345, the determination flags F (1) and F (2) are each set to a value of “1”.

  At this point, when the CPU 51 proceeds to step 615 following steps 600 and 605 of the subroutine shown in FIG. 6, since the determination flags F (1) and (2) are both set to the value “1”, the CPU 51 Determines “No” in step 615 and proceeds to step 635 to determine whether or not the determination flag F (3) and the determination flag F (4) are each set to a value of “0”. Since both of the determination flags F (3) and (4) are set to “0”, the CPU 51 determines “Yes” in step 635, proceeds to step 640, and proceeds to the third wheel 13. The vehicle speed calculation wheel speed SPDH (3) and the vehicle speed calculation wheel speed SPDH (4) of the fourth wheel 14 (driven wheel) are calculated as the vehicle speed SPDH, and the process proceeds to step 695 to execute the processing of this subroutine. Exit once.

  Therefore, the two drive wheels (the first wheel 11 and the second wheel 12) having an abnormal tire internal temperature are excluded from the object for calculating the vehicle speed, and the CPU 51 determines that the tire internal temperature is normal in step 255. The average values of the vehicle speed calculation wheel speeds SPDH (3) and SPDH (4) of the two driven wheels are output to the speedometer 19.

  Next, (d) the case where the internal temperatures of the first tire 15 to the third tire 17 are abnormal will be described. The CPU 51 sets the variable n to 1 to 3 in the subroutine processing shown in FIG. In step 345, the determination flags F (1) to F (3) are each set to a value of “1”.

  At this point, when the CPU 51 proceeds in the order of steps 600, 605, 615, and 635 of the subroutine shown in FIG. 6, the determination flag F (3) is set to “1” and the determination flag F (4) is set to “0”. Has been. Therefore, the CPU 51 determines “No” in step 635 and proceeds to step 645 to determine whether or not the determination flag F (3) or the determination flag F (4) has a value of “0”. Since the determination flag F (4) is set to a value of “0”, the CPU 51 determines “Yes” in step 645 and proceeds to step 650, where the determination flag F (3) has a value of “0”. It is determined whether or not. Since the determination flag F (3) is set to “1”, the CPU 51 determines “No” in step 650 and proceeds to step 655 to calculate the vehicle speed of the fourth wheel 14 (driven wheel). The wheel speed SPDH (4) is set to the vehicle speed SPDH, and the routine proceeds to step 695 to end the processing of this subroutine once. In step 255, the CPU 51 outputs the vehicle speed SPDH calculated by excluding the wheel speeds of the first wheel 11 to the third wheel 13 whose tire internal temperature is abnormal to the speedometer 19.

  Next, (e) the case where the internal temperatures of the first tire 15, the second tire 16, and the fourth tire 18 are abnormal will be described. The CPU 51 sets the variable n to 1 in the subroutine processing shown in FIG. , 2 and 4, in step 345, the determination flags F (1), (2) and (4) are each set to a value of “1”.

At this point, when the CPU 51 proceeds in order of steps 600, 605, 615, 635, and 645 of the subroutine shown in FIG. 6, the determination flag F (3) is “0” and the determination flag F (4) is “1”. Is set to Therefore, the CPU 51 determines “Yes” in Step 645 and proceeds to Step 650, determines “Yes” in Step 650, proceeds to Step 660, and moves to the vehicle speed SPDH at the third wheel 13 (driven wheel). Vehicle speed calculation wheel speed SPDH (3) is set, and the process proceeds to step 695 to end the process of this subroutine once.
In step 255, the CPU 51 outputs the vehicle speed SPDH to the speedometer 19. Therefore, wheels having abnormal tire internal temperatures (the first wheel 11, the second wheel 12, and the fourth wheel 14) are excluded from the object for calculating the vehicle speed, and the speedometer 19 includes the tire internal temperature. The vehicle speed calculation wheel speed SPDH (3) of the normal driven wheel (third wheel 13) is displayed.

  Finally, (f) the case where the internal temperatures of all tires are abnormal will be described. When the variable n is set to 1 to 4 in the processing of the subroutine shown in FIG. A value of “1” is set in each of F (1) to (4).

  At this point, when the CPU 51 proceeds in the order of steps 600, 605, 615, 635, and 645 of the subroutine shown in FIG. 6, the CPU 51 determines that both of the determination flags F (3) and (4) are “1”. Therefore, it is determined as “No” in step 645, and the process proceeds to step 665. In step 665, a value of “0” is set in the vehicle speed SPDH. In step 255, the CPU 51 outputs a value “0” to the speedometer 19.

(3) Next, the case where the state of the wheel speed sensor becomes abnormal while the vehicle 10 is traveling will be described. For example, the case where the state of the first wheel speed sensor 21 becomes abnormal will be described. The CPU 51 calls a subroutine shown in FIG. 3 in step 245 following steps 200 to 240, and step 310 following steps 300 and 305. Proceed to Since the state of the first wheel speed sensor 21 is not normal due to the premise, the CPU 51 determines “No” in step 310, proceeds to step 345, and sets the determination flag F (1) to a value of “1”. Set. Subsequent processing is the same as that in the case where the internal temperature of the first tire 15 is abnormal, and a description thereof will be omitted.
Note that the processing when the state of the other wheel speed sensors becomes abnormal is the same as that when the internal temperature of the other tire is abnormal, and thus the description thereof is omitted.

  As described above, the angular velocity detection means (nth wheel speed sensor) for detecting the angular velocity ωn of the wheel n (nth wheel) provided in the vehicle, and the tire n (nth tire) attached to the wheel. The vehicle speed SPDH is calculated on the basis of the pressure detection means (nth pressure sensor) for detecting the internal pressure P (n) and the detected angular velocity of the wheel and the detected internal pressure of the tire. A vehicle speed calculation device including calculation means (steps 210 to 225, 240, 320 to 330, 250) for performing the above has been described.

  According to this, since the vehicle speed calculation device calculates the vehicle speed SPDH based on the angular speed ωn of the wheel n and the internal pressure P (n) of the tire n, the internal pressure P (n) of the tire n is taken into consideration. Therefore, a more accurate vehicle speed SPDH is required (considering changes in the dynamic load radius based on changes in the internal pressure P (n) of the tire n).

  Furthermore, input means (steps 210 and 215) for inputting a value corresponding to the internal pressure of the tire n as a reference pressure PS (n) in response to an operation signal from the outside (operation switch 40), The calculation means calculates a value DP (n) representing a change in dynamic load radius based on a deviation ΔTP (n) of the detected tire internal pressure P (n) from the input reference pressure PS (n). A vehicle speed calculation device has been described which calculates based on the deviation and calculates the vehicle speed SPDH based on the detected angular velocity ωn of the wheel and the calculated value DP (n).

  The change in the dynamic load radius according to the deviation of the actual tire internal pressure from the reference pressure can be determined regardless of the type of tire and the absolute value of the tire internal pressure. Therefore, according to the vehicle speed calculation device of the present invention, the value representing the change in the dynamic load radius based on the deviation of the tire internal pressure from the reference pressure is calculated based on the deviation. Based on the calculated value representing the change in the dynamic load radius, a more accurate vehicle speed SPDH can be obtained in consideration of the change in the dynamic load radius due to the change in the internal pressure of the tire.

  Also, angular velocity detection means (first wheel speed sensor 21 to fourth wheel) for detecting angular velocities (ω1 to ω4) of a plurality of wheels (first wheel 11 to fourth wheel 14) provided in the vehicle, respectively. A speed sensor 24) and temperature detecting means for detecting internal temperatures T (1) to T (4) of a plurality of tires (first tire 15 to fourth tire 18) mounted on the plurality of wheels, respectively. The first pressure sensor 25 to the fourth pressure sensor 28) and a tire in which the detected internal temperature of the tire does not satisfy a given temperature condition (internal temperature T (n) ≦ upper limit temperature of the tire n) The detected angular velocity of the detected wheel is excluded from the target for calculating the vehicle speed SPDH (steps 315 and 345), and the tire whose internal temperature satisfies the given temperature condition is mounted. The detected wheel being The vehicle speed calculation device including calculation means (steps 320 to 330, 250) for calculating the vehicle speed based on the angular velocity has been described.

  When the driving of the vehicle is continued in a state where the tire pressure P (n) is reduced, a large distortion may occur in the sidewall portion and the tire may burst. This phenomenon often occurs when the temperature of the sidewall portion where a large strain is generated becomes abnormally high. As described above, when the internal temperature of the tire is abnormal (the internal temperature T (n) of the tire n> the upper limit temperature), the vehicle speed calculation device calculates the vehicle speed SPDH for the tire in such an unstable state. Since the vehicle speed SPDH is calculated on the basis of the wheel speed SPD (n) of the wheel on which the remaining tire n is mounted, the vehicle speed SPDH is calculated in consideration of the internal temperature of the tire.

  Further, since the vehicle speed calculation device of the present invention outputs the calculated vehicle speed SPDH to the speedometer 19 provided in the vehicle, the speedometer 19 can display a vehicle speed closer to the true vehicle speed. it can.

  The CPU 51 determines whether or not each state of the first wheel speed sensor 21 to the fourth wheel speed sensor 24 is abnormal from each of the first wheel speed sensor 21 to the fourth wheel speed sensor 24. The determination is made based on the output speed signal. For example, when the wiring connecting any one of the wheel speed sensors and the electronic control unit 50 is disconnected or short-circuited, or when the detection result of any one of the wheel speed sensors contains more noise than necessary, Since the wheel speed sensor outputs an abnormal pulse speed signal, the CPU 51 determines that the wheel speed sensor is abnormal from the state of the pulse.

(Second Embodiment)
Next, a vehicle speed calculation device according to the second embodiment of the present invention will be described. The vehicle speed calculation device of the first embodiment is a target for calculating the vehicle speed of the wheel speed SPD (n) of the corresponding wheel when the state of the wheel speed sensor n or the internal temperature T (n) of the tire n is abnormal. The vehicle speed calculation wheel speed SPDH (n) is calculated based on the wheel speed SPD (n) and the rate of change DP (n) of the remaining wheels. The apparatus is further implemented in that it adopts a calculation method of the vehicle speed calculation wheel speed SPDH (n) depending on whether the internal pressure P (n) of the tire satisfies the given pressure condition or not. This is different from the vehicle speed calculation device of the embodiment. Accordingly, hereinafter, the second embodiment will be described focusing on this difference. In the following, steps that perform the same processing as the steps already described are given the same reference numerals, and detailed descriptions thereof are omitted.

  The CPU 51 starts processing from step 700 of FIG. 7 instead of FIG. 3 when the predetermined timing comes, and proceeds to step 705 following steps 305 to 315, and the internal pressure P (n) of the tire n is determined in advance. It is determined whether or not it is larger than the upper limit pressure. Since the internal pressure P (n) is equal to or lower than the upper limit pressure in the normal tire state, the CPU 51 makes a “No” determination at step 705 to proceed to step 710 where the internal pressure P (n) of the tire n is previously set. It is determined whether or not the pressure is smaller than a predetermined lower limit pressure. Since the internal pressure P (n) is equal to or higher than the lower limit pressure in the normal tire state, the CPU 51 makes a “No” determination at step 710 to proceed to step 715 and set the dynamic load radius change rate DP (n) to “ A value of “1” is set. Thereafter, the CPU 51 proceeds to step 330 to multiply the wheel speed SPD (n) by the dynamic load radius change rate DP (n) (= 1) to obtain a vehicle speed calculation wheel speed SPDH (n) (wheel speed SPD ( n) is set to the vehicle speed calculation wheel speed SPDH (n) as it is), and after proceeding to Steps 335 and 340, the process returns to Step 310.

  Thereafter, when the internal pressure P (n) of the tire n becomes larger than the upper limit pressure, the CPU 51 determines “Yes” in step 705 following steps 305 to 315, and proceeds to steps 320 and 325 to change the dynamic load radius. The rate DP (n) is obtained. Next, the CPU 51 proceeds to step 330 and multiplies the wheel speed SPD (n) by the dynamic load radius change rate DP (n) (the wheel speed SPD (n) is corrected by the dynamic load radius change rate DP (n). The vehicle speed calculation wheel speed SPDH (n) is obtained. Then, the CPU 51 proceeds to steps 335 to 340 and then returns to step 310.

  When the internal pressure P (n) of the tire n becomes smaller than the lower limit pressure, the CPU 51 determines “Yes” in step 710 following steps 305 to 315 and 705. And CPU51 performs the process of step 320-330 similarly to the case where the internal pressure P (n) of the tire n becomes larger than an upper limit pressure, calculates | requires the vehicle speed calculation wheel speed SPDH (n), and steps 335-340 Then, the process returns to step 310. Then, the CPU 51 repeats the processing from step 310, and when it determines “Yes” in step 335, the CPU 51 proceeds from step 335 to step 795 to end the processing of this subroutine once.

  In step 250 of the routine of FIG. 2 (actually, the routine of FIG. 6), the CPU 51 determines the vehicle speed SPDH from the vehicle speed calculation wheel speed SPDH (n) obtained by a different method depending on the internal pressure of the tire as described above. In step 255, the vehicle speed SPDH is output to the speedometer 19.

  As described above, the angular velocity detection means (the first wheel speed sensor 21 to the fourth wheel speed sensor 24) is the angular velocity of a plurality of wheels (the first wheel 11 to the fourth wheel 14) provided in the vehicle 10. (Ω1 to ω4) are respectively detected, and the pressure detecting means (first pressure sensor 25 to fourth pressure sensor 28) is configured to include a plurality of tires (first tire 15 to first tire) mounted on the plurality of wheels. Each of the plurality of tires 18 is detected in response to an operation signal from the outside (operation switch 40). A value corresponding to the internal pressure is input as a reference pressure PS (n) (steps 210 and 215), and the calculating means is configured to provide a predetermined pressure condition (upper limit pressure ≧≧) among the detected internal pressures of the plurality of tires. Satisfies the internal pressure P (n) ≧ lower limit pressure of the tire n) A vehicle speed calculation wheel speed SPDH (n) of the tire n is calculated from the detected angular speed ωn of the wheel n on which the tire n is mounted and the calculated dynamic load radius change rate DP (n); The dynamic load radius change rate DP (n) is set to “1” from the detected angular velocity ωn of the wheel n on which the tire n satisfying the pressure condition is mounted (without using the dynamic load radius change rate DP (n)). ) The vehicle speed calculation wheel speed SPDH (n) of the tire n is calculated, and the vehicle speed SPDH is calculated based on the calculated vehicle speed calculation wheel speed SPDH (n) (steps 705 to 715, 320 to 330, 250) The vehicle speed calculation device has been described.

  The dynamic load radius of the tire varies greatly depending on the internal pressure of the tire. For this reason, the error of the wheel speed SPD (n) with respect to the true wheel speed increases as the internal pressure P (n) of the tire deviates from the internal pressure of the tire in a normal state. In consideration of this, in the vehicle speed calculation device of the present embodiment, the first tire 15 to the fourth tire 18 satisfy a given pressure condition (upper limit pressure ≧ inner pressure P (n) of tire n ≧ lower limit pressure). If not, the wheel speed SPD (n) of the wheel on which the tire n is mounted (the wheel having a large error in the wheel speed SPD (n)) is corrected by the dynamic load radius change rate DP (n), and the vehicle speed calculation wheel speed. SPDH (n) is obtained. Further, when the tire n satisfies the pressure condition, the vehicle speed calculation device uses the value of the wheel speed SPD (n) of the wheel on which the tire n is mounted (the wheel having a small error in the wheel speed SPD (n)) as it is. The vehicle speed calculation wheel speed SPDH (n) is set. In this embodiment, since the vehicle speed SPDH is calculated from the vehicle speed calculation wheel speed SPDH (n) obtained by these two methods, a more accurate vehicle speed SPDH is obtained. The given pressure condition mentioned above is “the difference between the detected tire internal pressure and the presumed tire internal pressure is small, and therefore the actual dynamic load radius and the presumed dynamic load”. Since the difference in radius is small, it can be said that it is within a pressure range that does not require correction of the wheel speed based on the internal pressure of the tire.

(Third embodiment)
Next, a vehicle speed calculation device according to the third embodiment of the present invention will be described. In the second embodiment, when the internal pressure P (n) of the tire n is higher than the upper limit pressure or lower than the lower limit pressure, the wheel speed SPD (n) is set at the dynamic load radius change rate DP (n). By correcting, the vehicle speed calculation wheel speed SPDH (n) was obtained. On the other hand, in the third embodiment, when the internal pressure P (n) of the tire n is larger than the abnormal high pressure or smaller than the abnormal low pressure, the wheel speed of the wheel n on which the tire n is mounted. This is different from the second embodiment in that SPD (n) is excluded from the calculation target of the vehicle. Therefore, hereinafter, the third embodiment will be described focusing on this difference.

  The CPU 51 starts processing from step 800 of FIG. 8 instead of FIG. 7 when the predetermined timing comes, and proceeds to step 805 following steps 305 to 315, where the internal pressure P (n) of the tire n is abnormally high pressure. Determine if greater than. In the normal state, the internal pressure P (n) of the tire n is equal to or lower than the abnormally high pressure. Therefore, the CPU 51 determines “No” in Step 805 and proceeds to Step 810 to internal pressure P (n) of the tire n. It is determined whether or not is smaller than abnormally low pressure. Since the internal pressure P (n) of the tire n is not less than an abnormally low pressure in a normal state, the CPU 51 determines “No” in Step 810 and proceeds to Step 815 to set the wheel speed SPD (n). The vehicle speed calculation wheel speed SPDH (n) is set, and after proceeding to steps 335 to 340, the process returns to step 310.

  When the internal pressure P (n) of the tire n becomes larger than the abnormally high pressure, the CPU 51 determines “Yes” in Step 805 following Steps 305 to 315 and proceeds to Step 345 to determine the determination flag F (n). A value of “1” is set in, and the process proceeds to steps 335 and 340 and then returns to step 310. If the internal pressure P (n) of the tire n becomes smaller than the abnormally low pressure, the CPU 51 determines “Yes” in step 810 following steps 305 to 315 and 805, and proceeds to step 345 to determine the determination flag. A value of “1” is set in F (n), the process proceeds to steps 335 and 340, and then returns to step 310. Then, the CPU 51 repeats the processing from step 310, and when it determines “Yes” in step 335, it proceeds from step 335 to step 895 to end the processing of this subroutine once.

  Next, the CPU 51 performs the process of step 250 (FIG. 6). As a result, when the predetermined condition is not satisfied (the wheel speed sensor is abnormal, the tire is abnormal in internal temperature, the tire is abnormal in internal pressure), the tire is excluded from the calculation target of the vehicle, and the vehicle speed calculation wheel of the remaining tire A vehicle speed SPDH is calculated based on the speed SPDH (n), and the vehicle speed SPDH is output to the speedometer 19 in step 255.

  As described above, angular velocity detection means (first wheel speed sensor 21 to fourth wheel speed sensor 24) for detecting angular velocities (ω1 to ω4) of a plurality of wheels provided in the vehicle, and the plurality of wheels (first Pressure detecting means for detecting internal pressures P (1) to P (4) of a plurality of tires (first tire 15 to fourth tire 18) mounted on the wheels 11 to 14) of The first pressure sensor 25 to the fourth pressure sensor 28) and given pressure conditions (abnormally high pressure ≧ internal pressure P (n) of tire n ≧) of the detected internal pressures of the plurality of tires Tires having an internal pressure that does not satisfy (abnormally low pressure) are excluded from the target for calculating the vehicle speed SPDH, and the vehicle speed SPDH is calculated based on the detected angular velocity ωn of the wheel n on which the remaining tire n is mounted. Arithmetic means (steps 805-815,345) It has been described vehicle speed calculation apparatus comprising a 250) and.

  In the vehicle speed calculation device of the present embodiment, since the internal pressure of the tire deviates significantly from the internal pressure of the normal tire, the error between the wheel speed SPD (n) of the wheel on which the tire is mounted and the true wheel speed is significant. In consideration of the case where it becomes large, the wheel speed SPD (n) of the wheel corresponding to the tire n that does not satisfy the given pressure condition among the first tire 15 to the fourth tire 18 is calculated as a vehicle calculation target. Since the vehicle speed SPDH is calculated based on the wheel speed SPD (n) of only the wheel on which the remaining tire n is mounted (the wheel having a small error in the wheel speed SPD), a more accurate vehicle speed SPDH is obtained. It is done.

  In all the embodiments described above, the given upper limit temperature (given temperature condition) means that the CPU 51 uses the angular velocity ωn and the dynamic load radius R (n) of the tire to correspond to the wheel speed SPD of the wheel n. When determining (n), since the dynamic load radius of the tire greatly varies depending on the internal temperature of the tire, the error of the wheel speed SPD corresponding to the tire increases as the internal temperature of the tire deviates from the internal temperature of the normal tire. Therefore, it refers to the internal temperature of the tire corresponding to the wheel when it is preferable that the wheel speed SPD (n) of the wheel is not used for the calculation of the vehicle speed SPDH.

  In the second embodiment, the CPU 51 uses the angular velocity ωn and the dynamic load radius R (n) of the tire as the given upper limit pressure and the given lower limit pressure (given pressure conditions). When the wheel speed SPD (n) of the corresponding wheel n is obtained and the vehicle speed SPDH is calculated using the wheel speed SPD (n), the dynamic load radius of the tire varies due to the pressure inside the tire. Since a large error occurs in the calculated vehicle speed, it means the internal pressure of the tire corresponding to the wheel when it is preferable to correct the wheel speed SPD (n) of the wheel corresponding to the tire in order to reduce the error.

  In the third embodiment, the given abnormally high pressure and the given abnormally low pressure (given conditions for the given pressure) mean that the CPU 51 uses the angular velocity ωn and the dynamic load radius R (n) of the tire. When the wheel speed SPD (n) of the wheel is obtained using the above, the tire dynamic pressure greatly varies depending on the tire internal pressure as described above, so that the tire internal pressure deviates significantly from the normal tire internal pressure. Accordingly, the error of the wheel speed SPD (n) corresponding to the tire becomes remarkably large, so that it is preferable that the wheel speed SPD (n) of the wheel is not used for the calculation of the vehicle speed SPDH. The internal pressure of the tire.

  In all the above embodiments, the CPU 51 of the vehicle speed calculation device calculates the vehicle speed SPDH in addition to the tire internal pressure P (n), An occupant or the like needs a tire reference pressure PS (n) instructed to input the tire pressure after being adjusted to the reference pressure as the reference pressure of each tire. This is based on the fact that the dynamic load radius of the tire cannot be uniquely determined only from the internal pressure P (n) of the tire.

  More specifically, the vehicle can be equipped with various tires. As described above, if the tire type is different, the dynamic load radius is different even at the same tire internal pressure. That is, the tire dynamic load radius R (n) varies depending on the type of tire and the like, and therefore is not uniquely determined only from the tire internal pressure P (n). On the other hand, since the signal obtained from the wheel speed sensor is the angular velocity ω of the wheel, the dynamic load radius RS is required to convert this into the vehicle speed.

  Therefore, in the design stage, a dynamic load radius RS of a tire that will be mounted on the target vehicle is assumed. Hereinafter, the assumed dynamic load radius RS will be referred to as a design dynamic load radius RSstd. That is, the design dynamic load radius RSstd is determined based on the prediction that the vehicle will travel with such a dynamic load radius. The design dynamic load radius RSstd determined in this way is incorporated in advance in a program executed by the CPU 51 in order to obtain the wheel speed SPD (n) (see step 225). At this time, the internal pressure of the tire with respect to the design dynamic load radius RSstd is not uniquely determined, but can be considered to be within a pressure range having a certain width.

  On the other hand, the present inventor, in a vehicle production factory, service factory, or the like, if the tire internal pressure is adjusted to the reference pressure PS (n) within the pressure range, the actual pressure from the reference pressure PS (n) It has been found that the change DP (n) in the dynamic load radius according to the deviation ΔTP (n) of the tire internal pressure P (n) can be determined almost uniquely regardless of the type of tire. . On the other hand, an operator such as a production factory or a maintenance factory adjusts the actual internal pressure of the tire to the internal pressure of the tire indicated in advance. Although the actually adjusted internal pressure varies somewhat, it can be easily estimated that it will be within the above pressure range.

  Therefore, the vehicle speed calculation device inputs the reference pressure PS (n) based on the operation signal of the operation switch 40 that is operated after the internal pressure is adjusted by the operator, and thereafter, from the reference pressure PS (n). The deviation ΔTP (n) of the actual tire internal pressure P (n) is obtained, and the change DP (n) of the dynamic load radius corresponding to the deviation ΔTP (n) is obtained.

  Specifically, when the vehicle travels, the CPU 51 inputs the tire internal pressure P (n) at every predetermined elapsed time (step 240), and the tire internal pressure P (n) from the reference pressure PS (n). n) deviation ΔTP (n) is obtained (step 320), and the tire dynamic load radius change rate DP (n) is obtained corresponding to the deviation ΔTP (n) (step 325).

  The CPU 51 obtains a vehicle speed calculation speed SPDH (n) by multiplying the change rate DP (n) (= R (n) / RS (n)) by the wheel speed SPD (n) (step 330). As described above, the wheel speed SPD (n) is obtained by multiplying the angular speed ωn of the wheel by the design dynamic load radius RSstd. Therefore, the process of step 330 can be said to be a process for obtaining the vehicle speed calculation speed SPDH (n) based on the following equation (1).

SPDH (n) = SPD (n) × DP (n)
= SPD (n) × {R (n) / RS (n)}
= (Ωn × RSstd) × {R (n) / RS (n)}
= Ωn × {RSstd × R (n) / RS (n)}
= Ωn × Rst (n) (1)
In (1), Rst (n) is a dynamic load radius corrected based on the internal pressure P (n) of the actual tire, and the actual tire pressure corresponding to the internal pressure P (n) of the actual tire. This value is very close to the dynamic load radius.

Further, the CPU 51 uses the deviation ΔRn (= R (n) −RS (n)) of the dynamic load radius R (n) with respect to the dynamic load radius RS (n) instead of the change rate DP (n) to calculate the vehicle speed. The service speed SPDH (n) may be obtained. Specifically, the above equation (1) can be approximated to the following equation (2) as follows.
SPDH (n) = SPD (n) × DP (n)
= SPD (n) × R (n) / RS (n)
= SPD (n) × (RS (n) + ΔRn) / RS (n)
= (Ωn × RSstd) × (RS (n) + ΔRn) / RS (n)
= (Ωn × RSstd) × {1 + ΔRn / RS (n)}
= Ωn × RSstd + ωn × RSstd × ΔRn / RS (n)
≒ ωn (RSstd + ΔRn) (2)
(Approximate to RSstd / RS≈1.)

  Therefore, the CPU 51 calculates a value very close to the actual dynamic load radius by adding the change ΔRn of the dynamic load radius to the design dynamic load radius RSstd determined at the time of design using the above equation (2). A method of obtaining the vehicle speed calculation speed SPDH (n) by multiplying the value (= RSstd + ΔRn) by the angular speed ωn of the wheel n may be employed. In this case, the deviation ΔRn can be said to be an example of a value corresponding to a change in the dynamic load radius of the tire based on the deviation ΔTP (n), similarly to the change rate DP (n).

As described above, the CPU 51 executes processing for obtaining a value very close to the actual dynamic load radius from the dynamic load radius RSstd determined at the time of design in steps 320 to 330 and the change in the dynamic load radius. However, parameters other than the tire internal pressure P (n), such as the type of tire that affects the dynamic load radius of the tire, are specified. As a result, the actual tire internal pressure P (n ) Can be uniquely determined by the function of R (n) = g (P (n)), the CPU 51 does not need to execute the processes of steps 320 to 330 described below. The vehicle speed calculation speed SPDH (n) can be calculated by executing a program incorporating the equation (3).
SPDH (n) = ωn × g (P (n)) = ωn × R (n) (3)

  The embodiment of the vehicle speed calculation device according to the present invention has been described above. In addition, this invention is not limited to the said embodiment, A various modification can be employ | adopted within the scope of the present invention. For example, the operation switch 40 includes means for inputting a numerical value and means for specifying the number of tires. When the operator adjusts the internal pressure of the tire, the operator can input the adjusted internal pressure numerically. You may input by. Further, the operation switch 40 may be provided with a tire type input means for inputting a tire type, and the correlation diagram (Map2) may be switched according to the tire type input by the tire type input means. .

It is the schematic of the vehicle speed calculating apparatus which concerns on 1st Embodiment. It is the flowchart which showed the program which CPU shown in FIG. 1 performs in order to control a speedometer. It is the flowchart which showed the program which CPU shown in FIG. 1 performs in order to correct | amend wheel speed SPD (n). FIG. 4 is a correlation diagram between tire air pressure and tire dynamic load radius. FIG. 5 is a correlation diagram between a tire air pressure deviation and a tire dynamic load radius change rate. It is the flowchart which showed the program which CPU shown in FIG. 1 performs in order to calculate the vehicle speed output to a speedometer. It is the flowchart which showed the program performed in order to correct | amend wheel speed SPD (n) which concerns on 2nd Embodiment. It is the flowchart which showed the program performed in order to correct | amend wheel speed SPD (n) which concerns on 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Vehicle, 11 ... 1st wheel, 12 ... 2nd wheel, 13 ... 3rd wheel, 14 ... 4th wheel, 15 ... 1st tire, 16 ... 2nd tire, 17 ... 3rd Tires, 18 ... fourth tire, 19 ... speedometer, 21 ... first wheel speed sensor, 22 ... second wheel speed sensor, 23 ... third wheel speed sensor, 24 ... fourth wheel speed sensor. 25 ... first pressure sensor, 26 ... second pressure sensor, 27 ... third pressure sensor, 28 ... fourth pressure sensor, 30 ... receiver, 31a, 31b ... receiving antenna, 40 ... operation switch, 50: Electronic control device.

Claims (6)

Angular velocity detection means for detecting the angular velocity of wheels provided in the vehicle;
Pressure detecting means for detecting the internal pressure of the tire mounted on the wheel;
A vehicle speed calculation device comprising: calculation means for calculating a vehicle speed based on the detected angular velocity of the wheel and the detected internal pressure of the tire. The vehicle speed calculation device according to claim 1, further comprising:
Input means for inputting a value corresponding to the internal pressure of the tire in response to an operation signal from the outside as a reference pressure;
The calculation means calculates a value representing a change in a dynamic load radius based on a deviation of the detected internal pressure of the tire from the input reference pressure based on the deviation, and detects the angular velocity of the detected wheel A vehicle speed calculation device that calculates the speed of the vehicle based on the calculated dynamic load radius change value. The vehicle speed calculation device according to claim 2,
The angular velocity detection means detects angular velocities of a plurality of wheels provided in the vehicle,
The pressure detecting means detects internal pressures of a plurality of tires mounted on the plurality of wheels,
The input means inputs a value corresponding to the internal pressure of each of the plurality of tires in response to an operation signal from the outside as a reference pressure of each tire,
The computing means is
The detected internal pressure of the tire does not satisfy a given pressure condition. A value representing a change in the dynamic load radius for a tire is set to the input reference pressure of the tire and the detected internal pressure of the tire. A vehicle speed calculation wheel that is calculated based on the deviation and that is based on the detected angular velocity of the wheel on which the tire is mounted and a value representing the calculated change in the dynamic load radius according to the speed of the tire outer periphery of the wheel. For calculating the speed and calculating the vehicle speed according to the speed of the outer circumference of the tire from the detected angular speed of the wheel on which the tire in which the internal pressure of the detected tire satisfies the given pressure condition is mounted A vehicle speed calculation device that calculates a wheel speed and calculates a vehicle speed based on a plurality of vehicle speed calculation wheel speeds calculated for each of the plurality of wheels. Angular velocity detection means for detecting angular velocities of a plurality of wheels provided in the vehicle;
Pressure detecting means for detecting internal pressures of a plurality of tires mounted on the plurality of wheels,
The detected angular velocity of a wheel on which a tire in which the detected tire internal pressure does not satisfy a given pressure condition is mounted is excluded from the object for calculating the vehicle speed, and the detected tire A vehicle speed calculation device comprising: calculation means for calculating a vehicle speed based on the detected angular speed of a wheel on which a tire having a tire whose internal pressure satisfies the given pressure condition is mounted. Angular velocity detection means for detecting angular velocities of a plurality of wheels provided in the vehicle;
Temperature detecting means for detecting internal temperatures of a plurality of tires mounted on the plurality of wheels, respectively.
The detected angular velocity of a wheel on which a tire in which the detected tire internal temperature does not satisfy a given temperature condition is mounted is excluded from the object for calculating the vehicle speed, and the detected tire A vehicle speed calculation device comprising: calculation means for calculating a vehicle speed based on the detected angular speed of a wheel on which a tire having an internal temperature satisfying the given temperature condition is mounted. The vehicle speed calculation device according to any one of claims 1 to 5, further comprising:
A vehicle speed calculation device comprising output means for outputting the calculated vehicle speed to a speedometer provided in the vehicle, and configured to display the output vehicle speed on the speedometer.

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