JP2006138764A - Apparatus and method for monitoring wheel condition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for monitoring wheel condition capable of improving accuracy in detecting alignment deviations. <P>SOLUTION: An action force sensor grounded to a wheel detects action forces acting on the wheel in directions in parallel with a road surface. An alignment generation force computation part 112 computes an alignment generation force generated in a grounded part of the wheel due to wheel alignment through the use of the detected action forces. An estimate value computation part 106 makes reference to a previously stored setting value of wheel alignment and computes an estimate value of the alignment generation force. An alignment determination part 116 determines the difference between the alignment generation force and the estimate value, compares the difference with a predetermined threshold value, and determines whether wheel alignment deviates from the setting value or not. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wheel state monitoring apparatus and method, and more particularly to a technique for detecting a wheel alignment shift by monitoring a wheel of a running vehicle.

  The tire is mounted on a wheel and attached to the vehicle, and is combined with a suspension mechanism to form the vehicle's legs. Among the wheels, particularly the front wheels, angles such as a toe angle and a camber angle are preset in order to improve steering operability, steering stability, and straight running performance of the vehicle, and this is called wheel alignment.

  If this wheel alignment deviates from the initial set value, tire wear is accelerated and the driving efficiency of the vehicle is reduced. Therefore, it is preferable to detect the alignment misalignment early. Conventionally, the detection of misalignment has been performed by a skilled worker visually inspecting the axle or using a dedicated measuring device. For this reason, if the driver of the vehicle is not inspected, the misalignment state may continue for a long time, so it is advantageous if the misalignment can be automatically detected.

Patent Document 1 discloses a technique for detecting axle misalignment by monitoring the acceleration of a vehicle. Patent Document 2 discloses a technique for detecting an alignment change based on a fluctuation state of a wheel speed. Patent Document 3 discloses a technique for detecting misalignment of a wheel using an alignment function determined based on the rotation speed of the wheel.
JP 2002-156212 A JP-A-6-305316 JP 2001-260619 A

  However, in the techniques disclosed in Patent Documents 1 to 3, since the misalignment is detected using information related to the rotation speed of the wheel such as acceleration and wheel speed, it depends on the road surface condition and the traveling condition. It is considered that the influence of wheel rotation speed fluctuation is large, and it is difficult to improve the alignment detection accuracy.

  The present invention has been made in view of such a situation, and an object thereof is to provide a technique capable of accurately detecting a misalignment of a vehicle without depending on the number of rotations of a wheel.

  One embodiment of the present invention relates to a wheel state monitoring device. This device is installed on a wheel and uses an action force sensor that detects an action force that is a force acting in a direction parallel to the road surface with respect to the wheel, and the detected action force. Alignment generation force calculation means for calculating an alignment generation force generated at the ground contact portion of the wheel, and an estimated value calculation means for calculating an estimated value of the alignment generation force with reference to a preset value of wheel alignment stored in advance. Alignment determining means for determining whether or not wheel alignment is deviated from the set value based on a comparison between the alignment generation force and the estimated value.

  According to this aspect, the alignment generation force calculated using the action force actually generated on the wheel and the estimated value of the alignment generation force estimated that the wheel alignment remains at the initial setting value are obtained. By comparing, it is determined whether or not the wheel alignment has shifted, so that the alignment shift can be detected more accurately than before.

  The “alignment generation force” includes a generation force due to a toe angle and a generation force due to a camber angle. Therefore, if the generated force for each of the toe angle and the camber angle is calculated by the alignment generating force calculation means, it can be determined whether the toe angle or the camber angle is shifted.

  The alignment determination means preferably performs alignment determination when the vehicle goes straight. By doing so, it is not necessary to consider tire slip due to the steering angle, so that the detection accuracy of misalignment can be further increased.

  The wheel state monitoring device may further include load detection means for detecting a load applied to the wheel from the vehicle. In this case, the estimated value calculation means may calculate the estimated value with reference to map data representing the relationship between the detected load and the set value of the alignment. The estimated value calculation means can always calculate the estimated value by using the same value as the load applied from the vehicle to the wheel, but by calculating the estimated value by using the actual load, the alignment deviation detection accuracy can be increased. Can be increased. The load detection means here includes any sensor that detects an amount related to the load applied to the wheel from the vehicle, such as a stroke sensor that detects the stroke amount of the suspension or a tire air pressure sensor that detects the pressure of the tire air chamber. Device included.

  Another aspect of the present invention relates to a wheel state monitoring method. This method detects an applied force that is a force acting in a direction parallel to the road surface with respect to the wheel, and uses the detected applied force to be generated in the ground contact portion of the wheel due to wheel alignment. Based on a step of calculating an alignment generation force, a step of calculating an estimated value of the alignment generation force with reference to a preset value of wheel alignment stored in advance, and a comparison between the alignment generation force and the estimated value Determining whether the wheel alignment is deviated from the set value.

  According to this aspect, the alignment generation force calculated using the action force actually generated on the wheel and the estimated value of the alignment generation force estimated that the wheel alignment remains at the initial setting value are obtained. By comparing, it is determined whether or not the wheel alignment has shifted, so that the alignment shift can be detected more accurately than before.

  According to the wheel state monitoring device and the wheel state monitoring method according to the present invention, since the determination of the misalignment is performed using the acting force actually acting on the wheel, the wheel state monitoring method and the wheel state monitoring method are not easily affected by fluctuations in the wheel rotational speed. Therefore, it is possible to make a more accurate determination than in the past.

  In one embodiment of the present invention, an alignment generation force that is calculated using an acting force that is actually generated on a wheel, and an estimated value of the alignment generation force that is estimated that the wheel alignment remains at the initial setting value. Is a wheel state monitoring device that detects misalignment. Hereinafter, the present invention will be described with reference to embodiments.

  FIG. 1 shows a four-wheel vehicle 10 provided with a wheel state monitoring device according to an embodiment. The vehicle 10 has wheels 14 composed of tires, wheels, and the like. Each wheel 14 is coupled to the vehicle body 12 in a known manner by a suspension device (not shown) including a suspension, a knuckle, a tie rod, an upper arm, a lower arm, and the like.

  Each wheel 14 is provided with a wheel-side device 20 for detecting an acting force acting on the wheel and transmitting it to the vehicle body 12 side. The vehicle body 12 is provided with a receiver 30 that receives information transmitted from the wheel side device 20 at a position facing each wheel 14. Information acquired by each receiver 30 is sent to an electronic control device 100 (hereinafter referred to as “ECU 100”).

  The vehicle body 12 is also provided with a vehicle speed sensor 32 that determines the vehicle speed by detecting the number of rotations of the wheels. The vehicle speed sensor 32 may be provided so as to face any one of the wheels, or a vehicle speed sensor may be provided so as to face each of the plurality of wheels, and each detected value is processed to calculate the vehicle speed. May be. The vehicle body 12 is also provided with a steering sensor 34 for detecting a steering angle θ of a steering wheel (not shown). Detection signals from the vehicle speed sensor 32 and the steering sensor 34 are sent to the ECU 100.

  FIG. 2 is a diagram for explaining the components of the wheel-side device 20 and how the components are arranged in the wheels. FIG. 2 shows a part of the radial cross section of the wheel 14. The bead portion 50 of the tire 40 is mounted on the wheel rim 44 of the wheel 42 and is fixed to the wheel 42 by filling the inside of the tire 40 with air. The tread portion 46 of the tire 40 is a portion that contacts the ground and receives the load of the vehicle. The wheel 42 is connected to the vehicle body via a suspension device (not shown).

  An action force sensor 22 for detecting action force is embedded in the tread portion 46 of the tire. The acting force sensor 22 is preferably disposed in the vicinity of the groove portion 48 extending in the circumferential direction of the tread portion 46. The value detected by the acting force sensor 22 is sent to the processing device 24 provided on the outer peripheral surface of the wheel rim 44. The processing device 24 calculates the acting force from the detected value. The calculated acting force is sent by the transmitter 26 to the receiver 30 on the vehicle body 12 side.

  In this specification, “acting force” refers to a force generated in a direction parallel to the road surface from the road surface to the tire when the vehicle travels. The acting force sensor 22 is a sensor that detects an acting force in the front-rear or left-right direction on the tire, and is, for example, a strain gauge. A change in the length of the strain gauge is taken out as an electrical signal, and the processing device 24 calculates a corresponding force with reference to a strain-force diagram stored in advance as a table. Alternatively, an electrical signal indicating a change in length of the strain gauge is transmitted to the vehicle body side by the transmitter 26 without passing through the processing device 24, and conversion into force with reference to the strain-force diagram is executed in the ECU 100 on the vehicle body side. May be.

  The acting force sensor 22 is preferably arranged in a direction parallel to the circumferential direction of the tire and a direction perpendicular thereto. The acting force sensor 22 is preferably provided along the rotation center line of the tire circumference.

  The acting force sensor 22 may be manufactured as a finished product, embedded in the rubber layer of the tread portion 46 of the tire, or directly formed in the rubber layer of the tire. In the latter case, as an example, after the rubber layer is extruded, the acting force sensor 22 is inserted into a predetermined position inside the tread portion 46, and then molded while being vulcanized to form the tire 40. This is feasible.

  The processing device 24 and the transmitter 26 operate by receiving power supply from a battery (not shown). The processing device 24 and the transmitter 26 may be an integrated unit formed on the same substrate. This unit may be configured as a transponder that operates by receiving power from the receiver 30 on the vehicle body 12 side.

  The acting force sensor 22 may be a piezoelectric element. In this case, the piezoelectric element is disposed in the tread portion 46 so that the detection surface is perpendicular to the front-rear and left-right directions in order to detect the acting force in the front-rear or left-right direction of the tire.

  Next, wheel alignment will be described with reference to FIG. The front wheels of the vehicle are attached at a certain angle from the beginning in order to provide straight running stability and steering restoration. The attachment angle given to this wheel is called wheel alignment. FIG. 3A illustrates the toe angle. FIG. 3A shows a state when the front wheels are viewed from above the vehicle, and the upper side of the figure is the traveling direction of the vehicle. The toe angle refers to the inclination of the left and right tires when the vehicle is viewed from above. As shown in the drawing, the case where the left and right wheels are in front of each other (that is, B> A) is called toe-in. FIG. 3B illustrates the camber angle. FIG. 3B shows a state when the front wheel on one side is viewed from the front of the vehicle. The camber angle refers to the inclination of the wheel with respect to a smooth road surface when the vehicle is viewed from the front. As shown in the figure, a state in which the wheel is inclined outwardly of the vehicle body with respect to the vertical line, that is, a state in which the wheel is opened upward is called a positive camber, and conversely, the wheel is inclined inward of the vehicle body. The state, that is, the state where the wheel is opened downward is called a negative camber. In the figure, θ is a camber angle.

  FIG. 4 is a diagram for explaining the force generated on the contact surface of the wheel with the road surface of the tire. As described above, since the wheels have a toe angle and a camber angle, a force parallel to the road surface is applied to the contact surface with the road surface of the tire even when the vehicle is traveling straight. appear. Hereinafter, the force generated due to the toe angle (hereinafter referred to as “toe angle generating force”) is expressed as Ft, and the force generated due to the camber angle (hereinafter referred to as “camber angle generating force”) is expressed as Fc. . The toe angle generating force and the camber angle generating force are collectively referred to as “alignment generating force”. In FIG. 4, the X axis is taken in the circumferential direction of the tire, and the Y axis is taken so as to pass through the center point of the contact surface between the tire and the road surface perpendicular to the X axis. The X component of the toe angle generating force Ft is expressed as Ftx, and the Y component is expressed as Fty. Further, let the traveling direction of the wheel be the X ′ axis.

  As for the toe angle and camber angle, appropriate initial setting values are selected in the vehicle design stage in consideration of the influence on various characteristics of the vehicle. Therefore, if the vehicle load is known, it is possible to analytically estimate the toe angle generating force and camber angle generating force generated on the tire contact surface.

  Further, “β” in FIG. 4 is an angle formed by the traveling direction X ′ of the wheel and the direction X of the tire, and is called a “slip angle”. The slip angle β can be calculated based on the change amount δ in the circumferential direction of the tire and the road surface friction coefficient μ. This method will be described later. The slip angle β of the tire can be measured from a photographed image provided with a camera for photographing the wheel on the vehicle body.

  By the way, wheel alignment such as toe angle and camber angle is impacted by the wheel climbing on the curb or passing through a large hole on the road surface, the bolt for alignment adjustment is removed, the arm holding the wheel is deformed May deviate from the initial setting value. If the toe angle or camber angle is shifted, the neutral position of the steering wheel is deviated, the tire is unevenly worn, or the vehicle oversteer characteristic or understeer characteristic is changed.

  Therefore, in the wheel state detection device according to the present embodiment, an alignment deviation is detected by comparing the actual generated force obtained from the detection value of the acting force sensor and the estimated force obtained analytically. did.

  FIG. 5 is a functional block diagram showing a configuration of a part of the ECU 100 shown in FIG. 1 that is involved in the alignment deviation detection process according to the present embodiment. Each block shown here can be realized in hardware by an element and a mechanical device including a computer CPU and memory, and in software by a computer program or the like. It is drawn as a functional block to be realized. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by a combination of hardware and software. ECU 100 may be provided independently of other ECUs that execute brake control and vehicle stability control, or may be provided integrally.

  The ECU 100 calculates a travel state determination unit 104 that determines a travel state of the vehicle, a calculation unit 130 that calculates an alignment generation force resulting from alignment, and an estimated value that is estimated from an initial alignment value. An estimation unit 140, an alignment determination unit 116 for determining whether or not the alignment is normal, a notification unit 118 for notifying the passenger of the result, and a map storage unit 110 for storing various map information .

  The traveling state determination unit 104 receives detection signals from the steering sensor 34 and the vehicle speed sensor 32, and determines whether the vehicle is traveling at a low speed and whether the vehicle is traveling straight. Then, only when a certain condition is met, an instruction to start calculation is issued to the estimated value calculation unit 106 and the alignment generation force calculation unit 112.

  The calculation unit 130 includes a slip angle calculation unit 108, an acting force reception unit 114, and an alignment generation force calculation unit 112. The acting force receiving unit 114 receives the detection value of the acting force sensor 22 embedded in the tread portion of the tire via the wheel side device 20 and the receiver 30. The slip angle calculation unit 108 calculates the above-described slip angle β using the detection value of the acting force sensor 22 or the like. The alignment generation force calculation unit 112 calculates the toe angle generation force Ft and the camber angle generation force Fc using the detection value of the acting force sensor 22 and the slip angle β calculated by the slip angle calculation unit 108. The calculated alignment generation force is passed to the alignment determination unit 116.

Specifically, the alignment generation force calculation unit 112 calculates the alignment generation force as follows. When the detection values by the acting force sensors 22 arranged in the X-axis and Y-axis directions in FIG. 4 are respectively expressed as Sx and Sy, referring to FIG. 4, the X component Ftx and the Y component Fty of the toe angle generating force It can be seen that the following equation holds.
Ftx = Sx (1)
Fty + Fc = Sy (2)
From the equation (2), the camber angle generating force Fc is expressed by the following equation.
Fc = Sy-Fty (3)
Here, the following equation is established from the relationship between the toe angle generating force and the slip angle β.
tanβ = Ftx / Fty (4)
Therefore, the camber angle generating force Fc can be calculated from the following equation.
Fc = Sy-Ftx / tanβ
= Sy-Sx / tan β (5)

  The estimation unit 140 includes a signal acquisition unit 102 and an estimated value calculation unit 106. The signal acquisition unit 102 acquires various signals necessary for calculating the estimated value of the alignment generation force. This signal includes, for example, a value related to a load applied to the wheel from the vehicle, such as a stroke amount of a suspension device (not shown) and a tire pressure detected by a pneumatic sensor (not shown). The estimated value calculation unit 106 refers to a table prepared in advance corresponding to the load obtained from the stroke amount and the tire pressure in the map storage unit 110, and estimates of the toe angle generation force and the camber angle generation force Are calculated respectively. The calculated estimated value of the alignment generation force is passed to the alignment determination unit 116.

  The alignment determination unit 116 takes the difference between the estimated value obtained from the estimated value calculation unit 106 and the actual alignment generation force obtained from the alignment generation force calculation unit 112, and the difference exceeds a predetermined threshold value. It is determined that the toe angle or camber angle is deviated from the initial setting value. The notification unit 118 issues a warning to the occupant when the alignment determination unit 116 determines that there is an alignment shift. For example, the notification unit 118 may drive a speaker and emit a sound to warn an occupant, or may display a warning on a monitor installed in the passenger compartment. Alternatively, a signal may be periodically issued to notify the inspection system outside the vehicle of the occurrence of the abnormality.

  Next, a method for determining the slip angle β of the vehicle will be described with reference to FIGS. As described above, a toe angle and a camber angle are attached to the front wheels of the vehicle. On the other hand, as shown in FIG. 6, the contact surface with the road surface of the tread portion of the tire tends to be in the traveling direction X ′ of the wheel, so that the traveling direction does not coincide with the direction X of the rotating surface of the tire. An angle formed by the traveling direction X ′ and the direction X of the rotating surface is a slip angle β. In a state where the wheel rolls with a slip angle β, a lateral force, that is, a lateral force is generated between the tread portion of the tire and the road surface. This lateral force increases as the slip angle β increases.

As shown in FIG. 7, when the wheel rolls with a slip angle β, the center line of the tire is displaced by y _{0 in} the lateral direction while maintaining the contact width w and the contact length L. The point on the center line of the wheel rotates along the points A, E, and C, and the contact point of the tire is moved along the locus of the points A, B, and C by the force from the road surface. The contact point moves from point A to point B while in contact with the road surface. In this region, the tread portion of the tire is elastically deformed by the road surface and the carcass inside the tread portion. At this time, the distortion increases as the point A moves from the point A, and an acting force corresponding to the distortion is generated in the tread portion. In a region where this acting force is smaller than the maximum frictional force on the road surface, the contact point of the tire is moved along the traveling direction, and the acting force increases as the strain increases. When the acting force exceeds the frictional force on the road surface, the contact point with respect to the road surface of the tire slides from point B to point C.

Point A is a contact start point of the tire with a predetermined point on the road surface, point B is a point where the deformation force exceeds the maximum frictional force, and point C is on the road surface of the tire with a predetermined point. This is the point at which the contact ends. The distance between the points AC is the contact length. Further, a region where the contact point of the road surface of the tire is moved from point A to point B is referred to as a pressure-sensitive zone La, the contact point is referred to as the point C and the sliding range L _b regions glide up from point B.

  When the friction coefficient μ of the road surface is the same, the larger the slip angle β, the smaller the ratio γ = La / Lb of the adhesive area La to the slip area Lb. Further, as the road surface friction coefficient μ increases, the ratio γ increases. The relationship between the friction coefficient μ of the road surface and the ratio γ is obtained in advance by experiments and simulations, and can be stored in a table.

  Assuming that the acting force sensor 22 embedded in the tread portion of the tire is a strain gauge, this strain gauge detects a value corresponding to the amount of change in the actual length of the strain gauge caused by the frictional force on the road surface. . This amount of change can be said to be the amount of change caused by the frictional force of the road surface of the actual length of the portion where the strain gauge is provided in the entire circumference of the tire. This corresponds to the difference δ = ML.

As shown in FIG. 8, when the trajectories A to B to C of the tire contact points are approximated by a straight line, the lengths of the adhesion area La and the slip area Lb are as follows using the contact length L and the ratio γ. It can be expressed by a formula.
La = L · γ / (1 + γ) (6)
Lb = L / (1 + γ) (7)
If the slip angle β is used, the detected value δ of the strain gauge can be expressed by the following equation.
δ = ML
= {L / (1 + γ)} · {γ / cos β + √ (1 + γ ² tan ² β)} − L (8)
Therefore, the slip angle β can be calculated using the contact length L, the detected value δ, and the ratio γ.

  FIG. 9 is a detailed functional block diagram of the slip angle calculation unit 108. The road surface μ estimation unit 150 estimates a road surface friction coefficient μ. For example, the road surface μ can be estimated based on the road surface state detected by a sensor that detects the surface state of the road surface. Alternatively, the road surface μ may be estimated based on a braking force or a driving force when a slip occurs during braking or driving. The contact length acquisition unit 152 acquires the contact length with respect to the road surface of the tire. The contact length acquisition unit 152 may adopt a contact length determined in advance from the shape, size, etc. of the tire, or the shape, size, etc. of the tire, the load applied to each wheel, and the tire The contact length may be calculated based on air pressure or the like. In the latter case, the contact length acquisition unit 152 includes at least one of a load sensor that detects a load or an air pressure sensor that detects a tire air pressure. The ratio calculation unit 154 calculates the ratio γ based on μ estimated by the road surface μ estimation unit 150 and the above-described table. The calculation unit 156 calculates the slip angle β using Expression (8).

  Another method for obtaining the slip angle β is described in detail in Japanese Patent Application No. 2004-050875 filed by the present applicant.

  FIG. 10 is a flowchart of processing for detecting an alignment shift according to the present embodiment. First, the traveling state determination unit 104 determines whether the vehicle is traveling at a low speed (S10) or whether the vehicle is traveling straight (S12). If either S10 or S12 is not established (N in S10 or N in S12), this routine is terminated. Whether or not the vehicle is traveling at a low speed is determined only when the vehicle is traveling at a low speed (for example, 20 km / h or less) so that the influence of the driving force of the vehicle on the acting force of the tire is as small as possible. This is because it is preferable to execute detection. However, for example, the driving force of the vehicle may be estimated from the rotational speed of the engine, and the driving force may be subtracted from the acting force of the tire. Or you may make it detect the action force of a tire at the time of inertia driving | running | working which seems to have comparatively little influence of a driving force. The reason for determining whether or not the vehicle is traveling straight is that when the steering wheel is steered, the magnitude of the acting force of the tire changes due to the influence of the steering angle.

  If both S10 and S12 are satisfied (Y of S10, Y of S12), the signal acquisition unit 102 acquires a signal necessary for calculating the estimated force (S14). By referring to the acquired signal and the vehicle alignment information previously mapped and stored in the map storage unit 110, the estimated value calculation unit 106 estimates the estimated value of the alignment generation force, that is, the estimation of the toe angle generation force. A value Ftxi and an estimated value Fci of the camber angle generating force are calculated (S16). The acting force receiving unit 114 receives the acting force generated in the tire via the wheel side device 20 and the vehicle body side receiver 30 (S18), and the alignment generating force calculating unit 112 is a slip angle calculating unit 108. With reference to the calculated slip angle β, an alignment generation force, that is, a toe angle generation force Ftx in the X direction and a camber angle generation force Fc are calculated (S20).

Subsequently, the alignment determination unit 116 compares the estimated value Ftxi of the X-direction toe angle generating force obtained in S16 with the actual toe angle generating force Ftx obtained in S20, and calculates the absolute difference between these differences. It is determined whether or not the value is greater than a predetermined threshold value Tt (S22). That is,
| Ftxi-Ftx |> Tt (9)
It is determined whether or not holds. Note that the threshold value Tt is a value that can be recognized that a toe angle shift has occurred even when calculation errors are taken into account, and can be obtained experimentally. When Expression (9) is satisfied (Y in S22), since the actual generated force greatly deviates from the estimated value, it is determined that a toe angle shift has occurred, and the notification unit 118 determines the toe angle shift to the occupant. An alarm is issued (S24).

When Expression (9) does not hold (N in S22), the alignment determination unit 116 continues the estimated camber angle generation force Fci obtained in S16 and the actual camber angle generation force Fc obtained in S20. Are compared to determine whether the absolute value of these differences is greater than a predetermined threshold value Tc (S26). That is,
| Fci-Fc |> Tc (10)
It is determined whether or not holds. Note that the threshold value Tc is a value that can be recognized as a camber angle shift even when an error is taken into consideration, and can be obtained experimentally. When Expression (10) is satisfied (Y in S26), the alignment determination unit 116 determines that the camber angle has shifted because the actual generated force greatly deviates from the estimated value. A camber angle deviation warning is issued (S28). If equation (10) does not hold (N in S26), this routine is terminated.

  As described above, according to the present embodiment, the alignment generation force calculated using the action force actually generated on the wheel and the alignment estimated that the wheel alignment remains at the initial setting value. Since it is determined whether or not the wheel alignment has been deviated by comparing the estimated value of the generated force, the misalignment can be detected more accurately than before. Further, according to the present embodiment, the generated force detected by the sensor embedded in the tire can be used for vehicle control such as brake control.

  The present invention has been described above based on the embodiment. It should be understood by those skilled in the art that these embodiments are exemplifications, and that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention.

It is a figure which shows the vehicle provided with the wheel state monitoring apparatus which is one Embodiment of this invention. It is a figure which shows the structure of a wheel side apparatus. (A) is a figure explaining a toe angle among wheel alignments, (b) is a figure explaining a camber angle. It is a figure which shows the force which generate | occur | produces on a tire. It is a functional block diagram of ECU regarding the detection process of misalignment by one Embodiment of this invention. It is a figure which shows the contact state to the road surface of the tire of the modeled wheel. It is a figure which shows a grounding state in detail. It is a figure which shows notionally the relationship between the deformation | transformation state of a tire, and slip angle (beta). It is a detailed functional block diagram of a slip angle calculation part. It is a flowchart of the alignment shift detection process by one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Vehicle, 12 Car body, 14 Wheel, 20 Wheel side apparatus, 22 Action force sensor, 24 Processing apparatus, 26 Transmitter, 30 Receiver, 32 Vehicle speed sensor, 34 Steering sensor, 40 Tire, 42 Wheel, 44 Wheel rim, 46 Tread section, 48 groove section, 100 ECU, 102 signal acquisition section, 104 running state determination section, 106 estimated value calculation section, 108 slip angle calculation section, 110 map storage section, 112 alignment generation force calculation section, 114 action force reception section, 116 alignment determination unit, 118 notification unit, 130 calculation unit, 140 estimation unit, 150 road surface μ estimation unit, 152 contact length acquisition unit, 154 ratio calculation unit, 156 calculation unit.

Claims (4)

An action force sensor that is installed on the wheel and detects an action force that acts on the wheel in a direction parallel to the road surface;
Alignment generation force calculation means for calculating an alignment generation force generated in the ground contact portion of the wheel due to wheel alignment using the detected acting force;
An estimated value calculating means for calculating an estimated value of the alignment generating force with reference to a preset value of wheel alignment stored in advance;
Alignment determination means for determining whether wheel alignment is deviated from the set value based on a comparison between the alignment generation force and the estimated value;
A wheel state monitoring device comprising:   The wheel state monitoring apparatus according to claim 1, wherein the alignment determination unit performs alignment determination when the vehicle travels straight. Load detecting means for detecting a load applied to the wheel from the vehicle,
The wheel state monitoring apparatus according to claim 1, wherein the estimated value calculating means calculates the estimated value with reference to map data representing a relationship between the detected load and the set value of the alignment. . Detecting an acting force which is a force acting in a direction parallel to the road surface with respect to the wheels;
Calculating an alignment generation force generated in the ground contact portion of the wheel due to the wheel alignment using the detected acting force;
A step of calculating an estimated value of the alignment generation force with reference to a preset value of wheel alignment stored in advance;
Determining whether wheel alignment is deviated from the set value based on a comparison between the alignment generation force and the estimated value;
A wheel condition monitoring method comprising:

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