JP4165393B2 - Wheel condition judgment device - Google Patents

Description

  The present invention relates to a wheel state determination device for determining the state of a wheel of a vehicle based on a detected value of a state quantity of the wheel and a reference value, and in particular, initializes a reference value based on the detected value. It is related to the improvement of technology.

  There is already known a wheel state determination device for determining the state of a wheel of a vehicle based on a detected value of the state amount of the wheel and a reference value (for example, see Patent Document 1).

  Specifically, Patent Literature 1 describes a tire pressure drop detection device as a conventional example of the above-described wheel state determination device. In this conventional example, the state of the tire air pressure of a wheel is determined based on an output signal of a wheel speed sensor that detects a wheel speed that is the rotational speed of the wheel.

  Further, in this conventional example, basically, if the tire air pressure changes, the dynamic load radius of the tire changes accordingly, and the change appears as a change in the wheel speed. Is detected. Specifically, the deviation (decompression evaluation value) between the plurality of wheels of the wheel speed in the vehicle is acquired based on the plurality of wheel speeds sampled for each wheel when the tire air pressure is normal. The wheel speed is compared with a deviation (decompression reference value) between a plurality of wheels. The difference between the two deviations is compared with a depressurization determination threshold value, and based on the result, it is determined whether or not the tire air pressure has decreased.

  Further, in this conventional example, the depressurization determination reference value is set in response to the driver operating the initialization switch on the assumption that the tire air pressure is normal. That is, the decompression determination reference value is initialized based on a plurality of wheel speeds sampled during a period when the tire air pressure is normal.

However, in this conventional example, when the vehicle is in a turning state, for example, the wheel speed, that is, the dynamic load radius of the tire may not accurately reflect the tire air pressure. Is now prohibited.
JP 2001-80324 A

  The present inventor has improved a technique for initializing a reference value based on a detected value for a wheel state determination device that determines a state of a wheel of the vehicle based on a detected value of a state quantity of the wheel and a reference value. I did research aiming at.

  As a result, the present inventors have found that the detection accuracy of the sensor that detects the state quantity of the wheel is not always kept constant, and that the detection accuracy may be reduced depending on the environment in which the sensor is placed. I noticed. Furthermore, in spite of such a case, the present inventor does not normally initialize the reference value when the reference value is initialized by using the detection value with low accuracy. I also noticed the fact that there is a possibility that the accuracy of the judgment using a simple reference value may be reduced.

  Based on the above knowledge, the present invention provides a wheel state determination device that determines a state of a wheel of a vehicle based on a detection value of the state amount of the wheel and a reference value, and sets an initial reference value based on the detection value. It was made as an issue to improve the technology to be realized.

  The following aspects are obtained by the present invention. Each aspect is divided into sections, each section is given a number, and is described in a form that cites other section numbers as necessary. This is to facilitate understanding of some of the technical features that the present invention can employ and combinations thereof, and the technical features that can be employed by the present invention and combinations thereof are limited to the following embodiments. Should not be interpreted. That is, although not described in the following embodiments, it should be construed that it is not impeded to appropriately extract and employ the technical features described in the present specification as the technical features of the present invention.

Further, describing each section in the form of quoting the numbers of the other sections does not necessarily prevent the technical features described in each section from being separated from the technical features described in the other sections. It should not be construed as meaning, but it should be construed that the technical features described in each section can be appropriately made independent depending on their properties.
(1) A wheel state determination device for determining a state of a wheel in a vehicle having a wheel configured such that air is sealed under pressure in a tire mounted on the wheel, and the state amount of the wheel is detected. And a determination unit that determines the state of the tire based on a detection value and a reference value of the sensor, and when a setting condition relating to the accuracy of the detection value is satisfied, the reference value based on the detection value The sensor is rotated together with the wheel to detect the state quantity based on the displacement of the movable member, and the setting condition is determined. Includes a condition that is established when the accuracy is lower than normal, and the condition that is established when the accuracy is reduced. The centrifugal force that is established when the centrifugal force acting on the sensor is greater than an allowable centrifugal force. Wheel condition determination apparatus including a pressurized during establishment condition.

  In this apparatus, when the setting condition regarding the accuracy of the detection value of the sensor is satisfied, the initialization of the reference value based on the detection value is executed, whereas when the setting condition is not satisfied, the initialization is not executed.

  Therefore, according to this device, it is possible to prevent the occurrence of the initialization failure and the reference value accuracy failure due to the detection accuracy of the sensor. As a result, the initialization accuracy is improved, and as a result, the wheel state The accuracy of the determination result is also improved.

  For example, the “determination unit” in this section compares the detection value of the sensor with the reference value and determines the state of the vehicle based on the result, or detects the sensor detection value, the reference value, and the vehicle state The vehicle state corresponding to the current value of the detection value of the sensor and the reference value can be used as the current determination result in accordance with a predetermined relationship between is there.

  An example of the “reference value” in this section is a value that the sensor detection value should take when the state of the wheel is normal. For example, the pressure reduction determination reference value in the above-described conventional example is applicable. Also, another example of “reference value” is used to determine the threshold value itself or the threshold value to be compared with the detected value of the sensor to determine whether the state of the wheel is normal. Is the value to be

  The “wheel condition” in this section includes, for example, the wheel tire pressure, the tire temperature, the tire abnormal deformation degree, the tire rubber deterioration degree, the force acting on the tire, the tire vibration state, etc. It is possible to select.

The “sensor” in this section may include, for example, an air pressure sensor that detects tire air pressure. The air pressure sensor is, for example, a sensor including a sensor that is mounted on a tire to detect air pressure, or a sensor that detects a physical quantity different from the air pressure that reflects the air pressure (for example, the wheel speed sensor described above). Thus, it can be used with a signal processing device that detects air pressure indirectly by processing the output signal of the sensor. The former sensor is a type that directly detects air pressure, while the latter sensor is a type that indirectly detects air pressure.
According to this apparatus, when the accuracy of the detection value of the sensor is lower than usual, it is not necessary to use such detection value for initialization, and therefore, initialization failure due to a decrease in detection accuracy of the sensor may occur. You do n’t have to. Furthermore, according to this device, when the centrifugal force acting on the sensor is larger than the allowable centrifugal force, the detected value whose accuracy has decreased due to the fact that the detected value of the sensor does not accurately reflect the true value of the air pressure is initialized. It is not necessary to use it.
(2) Further, it includes a command device that issues an initialization command in accordance with the intention of the user of the vehicle, and the determination device responds to the issued initialization command in response to the issued initialization command when the set condition is satisfied. The wheel state determination device according to item (1), wherein the initialization is not executed when the setting condition is not satisfied.

  According to this device, initialization is performed according to the intention of the user of the vehicle (for example, the driver) when the setting condition regarding the accuracy of the detected value is satisfied, and when the setting condition is not satisfied, the initialization of the vehicle user is performed. On the other hand, initialization is not executed.

The “determinator” in this section is an embodiment in which, for example, when an initialization command is issued when the setting condition is not satisfied, initialization is performed after the setting condition is satisfied without waiting for the next initialization command. When the initialization command is issued when the setting condition is not satisfied, the initialization command can be invalidated and wait for the next initialization command .

(3) the determination unit is the success or failure of the inaccuracy during establishment condition, at least one determined based on (1) or (2) of the temperature of air before Symbol the tire and the rotational speed of the wheel The wheel state determination device according to.

Accuracy of the detection value of the sensor, for example, air at a temperature within the tire depends on the rotational speed of the wheel.

Specifically, for example, when the temperature of the air in the tire is higher than the outside air temperature, thermal expansion causes the air in the tire, the detection value of the sensor does not reflect accurately the true value of the air pressure there is a possibility. In addition, when the sensor has a movable member and the sensor rotates with the wheel, centrifugal force acts on the movable member due to the rotation of the wheel, which causes a detection error. There is a possibility.

Based on such knowledge, in the apparatus according to this section, the success / failure condition when the accuracy is lowered is determined by at least one of a sensor temperature, a tire temperature, an air temperature in the tire, and a wheel rotation speed. It is determined based on.
( 4 ) The wheel condition determination device according to ( 3 ), wherein the condition that is satisfied when the accuracy is reduced includes a condition that is established when the temperature of the sensor deviates from an allowable temperature range.

( 5 ) The state quantity includes the tire air pressure, and the condition that is satisfied when the accuracy is reduced is a first condition that is satisfied when the temperature of the air in the tire is higher than an allowable temperature. The wheel state determination device according to item ( 3 ) or ( 4 ).

According to this device, when the temperature of the air in the tire is higher than the allowable temperature, the detected value whose accuracy has decreased due to the fact that the detected value of the sensor does not accurately reflect the true value of the air pressure is initialized. No need to use it.
( 6 ) The second tire high temperature that is satisfied when the state quantity includes the tire air pressure, and the condition for when the accuracy is lowered is satisfied when the temperature of the air in the tire is higher than an allowable temperature difference by an allowable temperature difference or more. The wheel state determination device according to ( 3) or (4), which includes a time establishment condition.

According to this apparatus, when the temperature of the air in the tire is higher than the outside air temperature by an allowable temperature difference or more, the detected value that is reduced in accuracy because the detected value of the sensor does not accurately reflect the true value of the air pressure. Need not be used for initialization .

(7 ) The wheel state determination device according to any one of ( 1) to (6) , wherein the sensor includes a diaphragm as the movable member.
( 8 ) The wheel condition determination according to any one of ( 3) to (7 ), wherein the condition that is satisfied when the accuracy is reduced includes a condition that is established when the wheel rotation speed is greater than an allowable rotation speed. apparatus.

  According to this device, when the rotational speed of the wheel is larger than the allowable rotational speed, for example, it is not necessary to use a detected value whose accuracy has decreased due to a large centrifugal force acting on the sensor for initialization.

  It is not indispensable that the “rotation speed of the wheel” in this section is a speed inherent to the wheel, and the vehicle speed that is the traveling speed of the vehicle can be substituted.

  Hereinafter, some of more specific embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 schematically shows a wheel state determination device according to a first embodiment of the present invention in a plan view. This wheel state determination device is mounted on a vehicle configured by mounting left and right front wheels 10 (FL, FR) and left and right rear wheels 10 (RL, RR) on a vehicle body 12. However, in FIG. 1, the wheel 10 is representatively shown with respect to only one of the plurality of wheels 10.

  As is well known, each wheel 10 is configured such that air is sealed under pressure in a rubber tire 20 mounted on a metal wheel 16. In the present embodiment, a tire sensor 24 is attached to the wheel 16. Therefore, the tire sensor 24 is rotated together with the wheel 10.

  FIG. 2 conceptually shows the configuration of the tire sensor 24 in a block diagram. The tire sensor 24 is provided for each wheel 10. The tire sensor 24 includes a pressure sensor 30 that directly detects the air pressure of the tire 20.

  As shown in an enlarged view in FIG. 3, the pressure sensor 30 converts the air pressure into a displacement of a diaphragm (for example, a metal or non-metallic elastic thin film) 31 as an elastic movable member to equal the pressure (equal to the air pressure of the tire 20) .) This is a format for detecting P.

  The diaphragm 31 is supported by an IC (capacitance type distance sensor) 34 mounted on the substrate 32 of the tire sensor 24 so as to be elastically deformable. A chamber 35 is formed between the diaphragm 31 and the IC 34 and is blocked from the outside. The diaphragm 31 receives the air pressure P of the tire 20 only on the side opposite to the side facing the IC 34, and is elastically displaced according to the height of the air pressure P. The IC 34 detects a change in the distance d between the surface of the IC 34 and the facing surface of the diaphragm 31 as a change in capacitance. In accordance with such a principle, the pressure sensor 30 detects the pressure P.

  In the present embodiment, as described above, since the pressure sensor 30 rotates together with the wheel 10, a centrifugal force is generated in the diaphragm 31 during traveling of the vehicle. Since this centrifugal force acts to deform the diaphragm 31, it becomes a factor of reducing the detection accuracy of the pressure sensor 30.

  As shown in FIG. 2, the tire sensor 24 further includes a temperature sensor 36. The temperature sensor 36 is provided for detecting the temperature T of the air in the tire 20 (also the temperature of the pressure sensor 30 itself).

  As shown in FIG. 2, the tire sensor 24 further includes a signal processing circuit 38 electrically connected to the pressure sensor 30 and the temperature sensor 36, and a transmitter 40 connected to the signal processing circuit 38. I have. The signal processing circuit 38 has a function of processing signals supplied from the pressure sensor 30 and the temperature sensor 36 with electric power from a power source (not shown) and sending the signals to the transmitter 40. The transmitter 40 is provided to wirelessly transmit signals representing the detected values of the pressure P and the temperature T.

  As shown in FIG. 1, an antenna 42 is installed in the vehicle body 12 in association with each wheel 10. As shown in FIG. 4, each antenna 42 receives a radio wave transmitted from the transmitter 40 of the corresponding wheel 10 and sends a signal represented by the radio wave to the receiver 44.

  As shown in FIG. 1, an electronic control unit (hereinafter simply referred to as “ECU”) 50 is electrically connected to the receiver 44. As shown in FIG. 4, the ECU 50 is composed mainly of a computer 52. As is well known, the computer 52 includes a CPU 54, a ROM 56, and a RAM 58 that are connected to each other via a bus 60. The ROM 56 stores in advance various programs including a wheel state determination program and an initialization program which will be described later.

  As shown in FIGS. 1 and 4, an initialization switch 70 and an alarm device 72 are electrically connected to the ECU 50. The initialization switch 70 is operated by a driver of the vehicle to transmit to the ECU 50 that the tire 20 has normal air pressure for all of the plurality of wheels 10. The alarm device 72 is activated to visually or audibly notify the vehicle driver that the tire 20 is not in normal pressure.

  As shown in FIG. 4, an external air temperature sensor 74 and a wheel speed sensor 76 are further electrically connected to the ECU 50. The outside air temperature sensor 74 is provided for detecting the outside air temperature θ of the vehicle. The wheel speed sensor 76 is provided for each wheel 10 and detects the angular speed of each wheel 10 as the wheel speed V. In the present embodiment, the wheel speed sensor 76 is used to detect the rotation speed of each wheel 10, but a vehicle speed sensor can be substituted to detect the rotation speed common to the plurality of wheels 10. is there.

  FIG. 5 conceptually shows the contents of the aforementioned wheel state determination program in a flowchart. This wheel state determination program is repeatedly executed for each wheel 10 while the ECU 50 is powered on. At the time of execution of each time, first, in step S1 (hereinafter, simply referred to as “S1”, the same applies to other steps), the tires are wirelessly communicated between the ECU 50 and the tire sensor 24 of each wheel 10. A signal representing the detection value of sensor 24 (including a signal representing the detection value of pressure sensor 30 and a signal representing the detection value of temperature sensor 36) is received by receiver 44. Further, the pressure (air pressure) P of the corresponding tire 20 is detected based on the received signal.

  Next, in S2, the latest threshold value Pth is read from the RAM for each wheel 10. The threshold value Pth is determined by execution of an initialization program described in detail later and stored in the RAM.

  Subsequently, in S3, for each wheel 10, it is determined whether or not the detected pressure P is lower than the read threshold value Pth. If it is assumed that the pressure is low this time, the determination is YES. In S4, it is determined that the tire 20 this time is abnormal with respect to the air pressure. Then, in S5, the alarm device 72 is turned on, so that the air pressure is abnormal. The driver is notified that a certain tire 20 exists. The alarm device 72 is operated in a manner that identifies the position of the tire 20 where the air pressure is abnormal.

  This completes one execution of the wheel state determination program.

  On the other hand, this time, if it is assumed that the detected pressure P is not lower than the read threshold value Pth, the determination in S3 is NO, and in S6, the current tire 20 is normal with respect to air pressure. Then, in S7, the alarm device 72 is turned off to notify the driver that the current tire 20 is normal with respect to air pressure.

  This completes one execution of the wheel state determination program.

  FIG. 6 conceptually shows the contents of the initialization program in a flowchart. Hereinafter, the initialization program will be described in detail with reference to FIG. 7, but will be schematically described prior to that.

  The accuracy of the detected value of the pressure P by the pressure sensor 30 depends on the temperature of the pressure sensor 30 (approximate to the temperature of air in the tire 20). The diaphragm 31 of the pressure sensor 30 and the IC 34 for detecting the position thereof tend to undergo thermal expansion / shrinkage. When such thermal expansion / shrinkage occurs, the influence tends to appear in the detected value. is there. For example, as shown in FIG. 7, when the pressure sensor 30 is at a reference temperature (for example, 25 degrees C), if it is assumed that the detected value of the pressure P and the true value match each other, the temperature T of the pressure sensor 30 As the temperature deviates from the reference temperature, the deviation of the detected value of the pressure P from the true value increases.

  The accuracy of the detected value of the pressure P further depends on the centrifugal force acting on the pressure sensor 30 (particularly, its diaphragm 31). This is because if the centrifugal force acts on the diaphragm 31 of the pressure sensor 30, the position of the diaphragm 31 tends not to accurately reflect the true value of the pressure P. For example, as shown in FIG. 8, when the centrifugal force acting on the pressure sensor 30 is 0 [G], if it is assumed that the detected value of the pressure P and the true value match each other, the centrifugal force increases from 0. As a result, the deviation of the detected value of the pressure P from the true value increases.

  Therefore, as shown in the graph of FIG. 9, at time t1, the vehicle is stopped, the temperature T of the pressure sensor 30 is equal to the reference temperature, and the centrifugal force of the pressure sensor 30 is 0 (wheel speed V = 0 [km / h]) and the vehicle started after that, at time t2, the temperature T of the pressure sensor 30 is higher than the reference temperature (T = 50 degrees C) and the centrifugal force of the pressure sensor 30 Are compared with each other under the condition that there is no air leakage from the tire 20, the detected value of the pressure P at time t2 is The detected value of pressure P at time t1 increases by ΔP.

  The increase amount ΔP contributes to the temperature rise of the pressure sensor 30 and the centrifugal force of the pressure sensor 30, and means a detection error of the pressure sensor 30. When the initialization switch 70 is operated by the driver in a situation where such a detection error exists, if the threshold value Pth is initialized based on the detected value of the pressure P at that time in accordance with the operation, The accuracy of initialization is lowered, and as a result, the accuracy of determining whether or not the air pressure of the tire 20 is normal is also lowered.

  On the other hand, in this embodiment, when the initialization switch 70 is operated in a state where the detection error of the pressure sensor 30 is large, the threshold Pth is set to wait for the detection error to return to the normal range. It is initialized. In order to perform such selective initialization, the initialization program shown in FIG. 6 is repeatedly executed for each wheel 10.

  When each initialization program is executed, it is first determined in S31 whether or not the initialization switch 70 has been operated by the driver. If it is assumed that no operation has been performed this time, the determination is no, and one execution of this initialization program is immediately terminated. In contrast, if it is assumed that the initialization switch 70 has been operated this time, the determination in S31 is YES, and the process proceeds to S32.

  In S <b> 32, a signal representing the detection value of the tire sensor 24 is received by the receiver 44 by wireless communication between the ECU 50 and the tire sensor 24 of each wheel 10. Further, based on the received signal, the pressure P and temperature T of the corresponding tire 20 are detected.

  Thereafter, in S33, it is determined whether or not the detection error due to the temperature T of the pressure sensor 30 is small. Specifically, it is determined whether or not the detected temperature T is within an allowable range defined by the lower limit value Tc and the upper limit value Th. If it is assumed that the temperature T is within the allowable range this time, the determination is YES, and the wheel speed V is detected for each wheel 10 based on the output signal of the wheel speed sensor 76 in S34. It is not indispensable to detect the wheel speed V as a value unique to each wheel 10, and it may be detected as a value common to a plurality of wheels 10 (so-called vehicle speed).

Subsequently, in S35, it is determined whether or not the detection error due to the centrifugal force acting on the pressure sensor 30 installed on each wheel 10 is small. Specifically, it is determined whether or not the detected wheel speed V is smaller than a threshold value Vth. If it is assumed that the wheel speed V is smaller than the threshold value Vth this time, the determination is YES, and the threshold value Pth is set based on the detected pressure P in S36. The threshold value Pth is, for example,
Pth = 0.25xP + P0
It is possible to calculate using the following formula. Here, “P0” is a constant.

  This completes one execution of the initialization program.

  On the other hand, if the determination in S33 is NO because the detection error due to temperature T is large, or if the determination in S35 is NO because the detection error due to centrifugal force is large, both return to S32. The execution of S32 to S35 is repeated until both the determinations of S33 and S35 are YES.

  If the determinations in S33 and S35 are both YES, a threshold value Pth is set in S36 based on the last detected pressure P.

  This completes one execution of the initialization program.

  As is apparent from the above description, in the present embodiment, the tire pressure P constitutes an example of the “state quantity” in the item (1), and the pressure sensor 30 constitutes an example of the “sensor” in the item. The threshold value Pth constitutes an example of “reference value” in the same term, and the ECU 50 constitutes an example of “determinator” in the same term. The first condition relating to the temperature T and the second relating to the wheel speed V Each of these conditions constitutes an example of the “setting condition” in the same section.

Further, in the present embodiment, the initialization switch 70 constitutes an example of the “indicator” in the item (2), and the first and second conditions described above are respectively “in the case of reduced accuracy” in the item ( 1 ). An example of the “satisfaction condition” is configured, and the ECU 50 configures an example of the “determination unit” in the item ( 3 ).

Furthermore, in the present embodiment, the allowable range defined by the lower limit value Tc and the upper limit value Th constitutes an example of the “allowable temperature range” in the item ( 4 ), and the temperature T is within the allowable range. Constitutes an example of the “satisfaction condition at the time of departure from the range” in the same section.

Furthermore, in the present embodiment, the centrifugal force acting on the pressure sensor 30 when the wheel rotates at a wheel speed V equal to the threshold value Vth constitutes an example of the “allowable centrifugal force” in the ( 1 ) term, The fact that the wheel speed V is larger than the threshold value Vth constitutes an example of the “satisfaction condition when the centrifugal force increases” in the same term.

Further, in the present embodiment, the threshold value Vth constitutes an example of the “allowable rotational speed” in the above ( 8 ) term, and that the wheel speed V is larger than the threshold value Vth is “established when the speed increases” It constitutes an example of “condition”.

  Next, a second embodiment of the present invention will be described. However, since the present embodiment is different from the first embodiment only in the contents of the initialization program and is common to other elements, only the initialization program will be described in detail, and the common elements are denoted by the same reference numerals. Or, a duplicate description is omitted by quoting using the name.

  In the first embodiment, as setting conditions regarding the detection accuracy of the pressure sensor 30, a first condition that the temperature T of the pressure sensor 30 is within an allowable range and a second condition that the wheel speed V is smaller than the threshold value Vth. Are prepared, and when these two conditions are cumulatively established, initialization is executed.

  On the other hand, in the present embodiment, the setting condition regarding the detection accuracy of the pressure sensor 30 is that the temperature of the air pressure in the tire 20 (equal to the above-described temperature T) is lower than the allowable temperature, specifically, A third condition that is lower than the sum of the temperature θ and the allowable temperature difference ΔTth is also prepared, and initialization is permitted when the first to third conditions are cumulatively established. Yes.

  FIG. 10 is a flowchart showing the contents of the initialization program executed by the computer 52 of the ECU 50 of the wheel state determination device according to the present embodiment. Hereinafter, this initialization program will be described, but steps common to the initialization program shown in FIG. 6 will be briefly described.

  When the initialization program shown in FIG. 10 is executed each time, first, in S101, it is determined whether or not the initialization switch 70 has been operated in the same manner as in S31. If it is assumed that an operation has been performed this time, the determination is YES, and S102 and S103 are executed in the same manner as S32 and S33.

  Subsequently, in S104, the outside air temperature θ is detected by the outside air temperature sensor 74. Thereafter, in S105, it is determined whether or not a value obtained by subtracting the detected outside air temperature θ from the temperature T detected by the execution of S102 (an increase amount from the outside air temperature θ) is smaller than the allowable temperature difference ΔTth. The This determination is equivalent to the determination as to whether or not the temperature T is lower than the sum (variable threshold value) of the outside air temperature θ and the allowable temperature difference ΔTth.

  If it is assumed that the amount of increase from the outside temperature θ is smaller than the allowable temperature difference ΔTth this time, the determination in S105 is YES, and S106 to S108 are executed in the same manner as S34 to S36. On the other hand, if it is assumed that the amount of increase from the outside air temperature θ is not smaller than the allowable temperature difference ΔTth this time, the determination in S105 is NO and the process returns to S102. The execution of S102 to S107 is repeated until the determinations of S103, S105, and S107 are all YES.

As is apparent from the above description, in the present embodiment, the variable threshold value described above constitutes an example of the “allowable temperature” in the item ( 5 ), and the temperature T, the outside air temperature θ, and the allowable temperature difference ΔTth. The above-mentioned third condition defined by the above constitutes an example of the “first tire high temperature condition” in the same section.

Furthermore, in the present embodiment, the allowable temperature difference ΔTth constitutes an example of the “allowable temperature difference” in the item ( 6 ).

  Next, a third embodiment of the present invention will be described. However, since the present embodiment is different from the first embodiment only in the contents of the initialization program and is common to other elements, only the initialization program will be described in detail, and the common elements are denoted by the same reference numerals. Or, a duplicate description is omitted by quoting using the name.

  In the first embodiment, when the initialization switch 70 is operated, the execution of the initialization program in FIG. 6 is repeated until the above two conditions are cumulatively satisfied. Therefore, basically, initialization is performed for each operation of the initialization switch 70.

  On the other hand, in the present embodiment, if the above two conditions are not satisfied cumulatively immediately after the initialization switch 70 is operated, the initialization is performed until the initialization switch 70 is operated next. There is nothing. That is, in this embodiment, the operation of the initialization switch 70 is invalidated when the condition is not satisfied immediately after that.

  FIG. 11 is a flowchart showing the contents of the initialization program executed by the computer 52 of the ECU 50 of the wheel state determination device according to the present embodiment. Hereinafter, this initialization program will be described, but steps common to the initialization program shown in FIG. 6 will be briefly described.

  When the initialization program shown in FIG. 11 is executed each time, it is first determined in S201 whether or not the initialization switch 70 has been operated in the same manner as in S31. If it is assumed that an operation has been performed this time, the determination is YES, and S202 and S203 are executed in the same manner as S32 and S33.

  Since the detection error due to the temperature T is large, if the determination in S203 is NO, one execution of this initialization program immediately ends, and the initialization switch 70 is operated next time in the next execution of this initialization program. Waiting to be done.

  On the other hand, since the detection error due to the temperature T is small, if the determination in S203 is YES, S204 and S205 are executed in the same manner as S34 and S35.

  Since the detection error due to the centrifugal force is large, if the determination in S205 is NO, one execution of this initialization program is immediately terminated, and the initialization switch 70 is operated next in the next execution of this initialization program. Waiting to be done.

  On the other hand, since the detection error due to the centrifugal force is small, if the determination in S205 is YES, in S206, the threshold value Pth is initialized based on the pressure P acquired in S202, as in S206. .

  This completes one execution of the initialization program.

  As described above, some of the embodiments of the present invention have been described in detail with reference to the drawings. However, these are merely examples, and those skilled in the art including the aspects described in the above-mentioned section of [Means for Solving the Problems] will be described. It is possible to implement the present invention in other forms in which various modifications and improvements are made based on the knowledge.

It is a top view which shows roughly the wheel state determination apparatus according to 1st Embodiment of this invention. FIG. 2 is a block diagram conceptually showing a tire sensor 24 in FIG. 1. It is side surface sectional drawing which expands and shows the pressure sensor 30 in FIG. FIG. 2 is a block diagram conceptually showing an ECU 50 and its peripheral elements in FIG. 1. 5 is a flowchart conceptually showing the contents of a wheel state determination program executed by a computer 52 in FIG. 5 is a flowchart conceptually showing contents of an initialization program executed by a computer 52 in FIG. It is a graph for demonstrating the reason initialization is selectively performed in the initialization program of FIG. FIG. 7 is another graph for explaining the reason why initialization is selectively performed in the initialization program of FIG. 6. FIG. 7 is still another graph for explaining the reason why initialization is selectively performed in the initialization program of FIG. 6. It is a flowchart which represents notionally the content of the initialization program performed by the computer 52 of ECU50 of the wheel state determination apparatus according to 2nd Embodiment of this invention. It is a flowchart which represents notionally the content of the initialization program performed by the computer 52 of ECU50 of the wheel state determination apparatus according to 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Wheel 16 Wheel 20 Tire 24 Tire sensor 30 Pressure sensor 31 Diaphragm 36 Temperature sensor 50 Electronic control unit ECU
52 Computer 70 Initialization switch 76 Wheel speed sensor

Claims (8)

A wheel state determination device for determining a state of a wheel in a vehicle including a wheel configured such that air is sealed under pressure in a tire attached to the wheel,
A sensor for detecting a state quantity of the wheel;
A determination unit that determines the state of the tire based on a detection value and a reference value of the sensor, and executes initialization of the reference value based on the detection value when a setting condition regarding the accuracy of the detection value is satisfied On the other hand, when the failure is not established, the initialization is not executed .
Only including,
The sensor rotates with the wheel, detects the state quantity based on the displacement of the movable member,
The setting condition includes a condition for establishment when accuracy is lowered when the accuracy is lower than normal,
The wheel state determination device including a condition for satisfying an increase in centrifugal force, which is satisfied when the condition for decreasing the accuracy is greater than an allowable centrifugal force.   Further, it includes an issuer that issues an initialization command according to the intention of the user of the vehicle, and the determination unit executes the initialization in response to the issued initialization command when the set condition is satisfied. On the other hand, the wheel state determination device according to claim 1, wherein the initialization is not executed when the setting condition is not satisfied.   3. The wheel state determination device according to claim 1, wherein the determination unit determines whether or not the condition for satisfying the accuracy drop is satisfied based on at least one of a temperature of air in the tire and a rotation speed of the wheel. .   The wheel condition determination device according to claim 3, wherein the condition that is satisfied when the accuracy is reduced includes a condition that is established when the temperature in the tire deviates from a permissible temperature range.   The condition quantity includes air pressure of the tire, and the condition that is satisfied when the accuracy is reduced includes a first condition that is satisfied when the temperature of air in the tire is higher than an allowable temperature. The wheel state determination apparatus according to 3 or 4.   Second tire high temperature condition that is satisfied when the state quantity includes air pressure of the tire and the accuracy condition is satisfied when the temperature of the air in the tire is higher than the outside temperature by an allowable temperature difference or more. The wheel state determination apparatus according to claim 3 or 4, comprising:   The wheel state determination apparatus according to any one of claims 1 to 6, wherein the sensor includes a diaphragm as the movable member.   The wheel state determination device according to any one of claims 3 to 7, wherein the condition that is satisfied when the accuracy is reduced includes a condition that is established when the speed of the wheel is greater than an allowable rotation speed.