JP4816181B2 - Tire condition processing device - Google Patents

Description

  The present invention relates to an apparatus for processing information related to a tire condition, and more particularly to a technique for estimating a tire contact area and a road surface friction coefficient.

Conventionally, in order to control the braking and posture of a vehicle based on information obtained from the tire, the road surface is determined based on the ratio of the slip area and the adhesion area of the tire obtained from the output of a strain sensor embedded in the tread portion of the tire. A method for estimating the friction coefficient is known (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2005-238961 JP 2004-359203 A JP 2005-205956 A

  When controlling the attitude of the vehicle, it is possible to control the braking / driving force in a direction in which the dangerous behavior is converged by detecting whether or not the dangerous behavior has occurred. However, it is in contact with the road surface and knows in real time the tire generation force that is directly involved in the behavior and convergence force, and the road surface friction coefficient that affects the tire generation force (hereinafter referred to as “road surface μ” as appropriate). Since there is no such thing, only post hoc control after the occurrence of the dangerous behavior can be performed, and there may be a scene that is not necessarily sufficient in terms of avoiding danger.

  The present invention has been made in view of these circumstances, and an object thereof is to provide an apparatus for monitoring a road surface friction coefficient for appropriate control of a vehicle.

In order to solve the above-described problems, a tire condition processing device according to an aspect of the present invention includes an acceleration detection unit that is provided in a tire and detects acceleration, and calculates a value of a contact length of the tire based on the detected acceleration. a tire state quantity acquisition unit that acquires a vertical load detecting means for detecting a vertical load of the tire, and the map storage means for storing previously measured relationship between the contact load and the contact length ground plane product for said tire, With reference to the correspondence relationship between the stored grounding load, grounding length and grounding area, grounding state estimating means for estimating the grounding area of the tire corresponding to the acquired grounding load and grounding length, the grounding area and the grounding Friction coefficient estimating means for estimating a road surface friction coefficient based on the ground contact load.

Here, the contact state estimation means directly derives the contact area of the tire from the acquired contact length by referring to the correspondence relationship between the contact load, the contact length, and the contact area. It is not intended to hinder the method of deriving the contact area after estimating the contact shape of the tire and the rectangular ratio of the contact surface. The friction coefficient estimating means may store a correspondence relationship between the contact area and the contact load in advance, and estimate the road surface friction coefficient based on the correspondence relationship.

  According to this aspect, the change in the friction coefficient between the road surface and the tire can be recognized by monitoring the change in the contact length over time, and the dangerous behavior of the vehicle can be immediately detected from the tendency of the change, and the safety of the vehicle can be detected. It is possible to improve the performance.

The acceleration detection means is provided at a plurality of locations in the width direction of the tire, the tire condition quantity acquisition means acquires the contact length of the tire for each of the plurality of locations of the tire, and the map storage means storing the ground contact load and the contact length of the correspondence between the ground plane product for location, the contact state estimation unit refers to correspondence between the ground plane product and the ground length and the vertical load on the plurality of locations, said plurality of locations The contact area of the tire corresponding to the contact length obtained with respect to may be estimated. The grounding state estimating means may estimate a grounding shape of the grounding surface based on a plurality of grounding lengths acquired from a plurality of locations on the tire and obtain a grounding area based on the grounding shape. According to this aspect, by obtaining multiple contact lengths for one tire, it is possible to more accurately grasp the contact shape and determine the contact area, and therefore recognize changes in the road surface friction coefficient with higher accuracy. Thus, the safety of the vehicle can be improved.

Air pressure acquisition means for acquiring the value of the air pressure of the tire may be further provided. The map storage means stores a correspondence relationship between the contact length, the air pressure, and the contact area, and the contact state estimation means refers to a correspondence relationship between the contact length, the air pressure, and the contact area, and The tire contact area corresponding to the acquired contact length and the acquired air pressure may be estimated. The grounding state estimating means may estimate the grounding shape of the grounding surface based on the grounding length, the grounding load, and the air pressure, and obtain the grounding area based on the grounding shape. According to this aspect, it is possible to recognize the contact shape and the contact area more accurately by accurately grasping the tire air pressure. Therefore, it is possible to recognize the change in the friction coefficient of the road surface with higher accuracy and to improve the safety of the vehicle. Improvements can be made.

The contact state estimation means, the detected based on the vertical load before Symbol obtained contact length and pressure estimates the lateral force applied to the tire, the ground contact area is estimated based on the lateral force and the estimated May be. The grounding state estimation means may estimate the lateral force based on the grounding load, the grounding length, and the air pressure. Alternatively, the grounding state may be estimated based on the grounding shape after estimating the grounding shape based on the lateral force. You may ask for. According to this aspect, by obtaining the contact area after more accurately grasping the lateral force applied to the tire, it is possible to recognize the change in the road surface friction coefficient with higher accuracy and to improve the safety of the vehicle.

  According to the tire condition processing apparatus of the present invention, it is possible to improve the safety of the vehicle by recognizing a change in the friction coefficient with higher accuracy.

(First embodiment)
FIG. 1 shows an overall configuration of a vehicle 10 provided with a tire condition processing apparatus according to the present embodiment. The vehicle 10 includes first wheels 20A, second wheels 20B, third wheels 20C, and fourth wheels 20D as traveling wheels, and a vehicle body 12. Each of the first wheel 20A, the second wheel 20B, the third wheel 20C, and the fourth wheel 20D includes a state quantity sensor including an acceleration sensor that detects acceleration, and information about the detected acceleration together with the ID of the state quantity sensor. A communication device that transmits to the vehicle body 12 is provided as a wheel side device. As the state quantity sensors, the first state quantity sensor 30A, the second state quantity sensor 30B, the third state quantity sensor 30C, and the fourth state quantity sensor 30D are the first wheel 20A, the second wheel 20B, the third wheel 20C, the first state quantity sensor. It is provided on each of the four wheels 20D. As the communication device, the first wheel side communication device 40A, the second wheel side communication device 40B, the third wheel side communication device 40C, the fourth wheel side communication device 40D, the first antenna 50A that is a communication antenna, the first Two antennas 50B, a third antenna 50C, and a fourth antenna 50D are provided on each of the first wheel 20A, the second wheel 20B, the third wheel 20C, and the fourth wheel 20D.

  Hereinafter, when the configuration is described without distinguishing each wheel, reference signs A to D for distinguishing the positions of the wheels are appropriately omitted. For example, the first wheel 20A, the second wheel 20B, the third wheel 20C, and the fourth wheel 20D are collectively referred to as the wheel 20, and the first state quantity sensor 30A, the second state quantity sensor 30B, the third state quantity sensor 30C, The four state quantity sensor 30D is collectively referred to as a state quantity sensor 30. The first wheel side communicator 40A, the second wheel side communicator 40B, the third wheel side communicator 40C, and the fourth wheel side communicator 40D are collectively referred to as the wheel side communicator 40, and the first antenna 50A, second The antenna 50B, the third antenna 50C, and the fourth antenna 50D are collectively referred to as the antenna 50.

  The wheel 20 includes a tire, a wheel, and other wheel components. The wheel side communication device 40 and the antenna 50 may be configured integrally with the state quantity sensor 30. The value detected by the state quantity sensor 30 is sent to the wheel side communicator 40 and transmitted from the antenna 50 to the vehicle body side communicator 200 by radio.

  The acceleration sensor included in the state quantity sensor 30 is realized by, for example, a piezoelectric vibration sensor, a strain gauge, a piezoelectric film, a piezoelectric cable, or the like. Only one acceleration sensor in the present embodiment is provided for each tire, and is embedded, for example, in the center of the tread portion in the tire width direction.

  The vehicle body 12 includes a first wheel side communication device 40A, a second wheel side communication device 40B, and a third wheel provided on each of the first wheel 20A, the second wheel 20B, the third wheel 20C, and the fourth wheel 20D. Vehicle side communication for receiving information on wheel state quantities such as acceleration and ID of the state quantity sensor 30 (hereinafter, these pieces of information are collectively referred to as “wheel information”) from the side communicator 40C and the fourth wheel side communicator 40D. Machine 200, receiving vehicle body side antenna 210, electronic control device (hereinafter referred to as "ECU") 64 for comprehensively controlling vehicle 10, and buzzer 70 and warning lamp 72 as warning output means. Provided. The vehicle body 12 includes a first ground load sensor 60A, a second ground load sensor 60B, and a third ground load at positions corresponding to the first wheel 20A, the second wheel 20B, the third wheel 20C, and the fourth wheel 20D. A sensor 60C and a fourth ground load sensor 60D (hereinafter collectively referred to as “ground load sensor 60”) are provided. The ground load sensor 60 is provided, for example, on a suspension, a shock absorber, a spring seat, and the like, and detects the tire ground load based on the spring reaction force of the suspension suspension, the axial force of the shock absorber, the pressure of the spring seat portion, and the like.

  The vehicle body side communication device 200 receives wheel information from the first wheel 20A, the second wheel 20B, the third wheel 20C, and the fourth wheel 20D that are mounted as traveling wheels via the vehicle body antenna 210, and receives the wheel information. The information is sent to the ECU 64. The ECU 64 grasps the state of the tire based on the wheel information received from the vehicle body side communication device 200. The ID of the state quantity sensor 30 that the ECU 64 receives from each wheel 20 is recognized as the tire ID of each wheel 20 in the subsequent processing, and is used for various processes and determinations to recognize from which wheel the wheel information is acquired. . The ECU 64 controls the vehicle 10 by executing calculations necessary for controlling the vehicle 10 based on the wheel information received from the state quantity sensor 30 via the wheel side communication device 40 and the vehicle body side communication device 200.

  FIG. 2 is a functional block diagram showing a configuration relating to acquisition of wheel information and vehicle control in the ECU 64. The ECU 64 has functions of a tire state quantity acquisition unit 220, a map storage unit 222, a ground contact state estimation unit 224, a friction coefficient estimation unit 226, a warning output unit 302, and a vehicle control unit 304. Each process described below is processed independently for each tire of the first wheel 20A, the second wheel 20B, the third wheel 20C, and the fourth wheel 20D, and can be controlled independently. Assuming

  The tire state quantity acquisition unit 220 acquires the value of the contact length of the tire based on the acceleration of each tire received from the state quantity sensor 30 via the vehicle body side communication device 200. Here, the tread portion and the shoulder portion of the traveling tire are divided into a portion that is in contact with the road surface and a portion that is not in contact with the road surface, and the contact portion is displaced as the wheel rotates. When the portion where the state quantity sensor 30 is embedded in the tread portion starts to ground with the rotation of the wheel, a peak appears in the acceleration detected by the state quantity sensor 30 due to vibration accompanying the start of grounding. Similarly, when the portion where the state quantity sensor 30 is provided in the tread portion ends the grounding with the rotation of the wheel, a peak also appears in the acceleration detected by the state amount sensor 30 due to the vibration accompanying the end of the grounding. The tire state quantity acquisition unit 220 measures the time from the peak at the start of contact to the peak at the end of contact, and obtains the contact length that is the length of the contact portion in the rotational direction from the relationship with the vehicle speed at that time.

Map storage unit 222 has been previously measured for each tire, and stores the correspondence between the contact area of the contact length change rate tire against the ground load heavy as the contact length change rate map. Contact length change rate here is a relationship between the time change until the state of the contact length and the contact length with respect to the ground load, mainly of the tire size, shape, material, elements such as oblateness It depends on. The contact length change rate map is measured in advance for each tire mounted on the vehicle body 12 before the vehicle is shipped and stored in the map storage unit 222. The contact length change rate map may be generated as a table or as a function. Since the contact length change rate varies depending on the magnitude of the tire air pressure, a contact length change rate map sampled at a plurality of air pressure values is stored in the map storage unit 222. The tire state quantity acquisition unit 220 calculates an air pressure value other than the sampled value by interpolating the sample value.

  The ground contact state estimation unit 224 receives the tire ground contact length from the tire state quantity acquisition unit 220, receives the tire ground contact load from the ground load sensor 60, and reads the tire contact length change rate map from the map storage unit 222. Since the change rate of the contact length with respect to the change in the contact load varies depending on the tire air pressure at that time, the contact state estimation unit 224 monitors the change in the contact length with respect to the actual change in the contact load as time passes, The tire pressure is estimated based on the magnitude of the change gradient.

  The warning output unit 302 outputs a warning indicating a decrease in tire air pressure via the buzzer 70 and the warning lamp 72 when the tire air pressure estimated by the ground contact state estimating unit 224 falls below a predetermined low pressure value. As a result, the driver can be informed of the danger caused by the tire pressure reaching the low pressure range, and the safety of the vehicle can be further improved, and the air pressure can be estimated without providing a tire pressure sensor for each tire. Can contribute to improving safety.

The contact state estimation unit 224 refers to the contact length change rate map, and estimates the contact area of the tire corresponding to the acquired contact length and the detected contact load. Here, in the process of obtaining the ground contact area from the ground contact length and the ground load, it is originally necessary to consider factors such as the ground shape of the ground surface, the rectangular ratio of the ground surface, and the influence of lateral force. The contact length change rate map is formed in a manner that reflects such factors as the contact shape, rectangular rate, and lateral force. Therefore, if at least the contact length and the contact load are known, the contact area can be directly determined by referring to the contact length change rate map. However, as a modification, the ground contact state estimation unit 224 may estimate the lateral force based on the ground load, the ground contact length, and the air pressure, and the ground contact area is estimated based on the acquired ground contact length and the estimated lateral force. To do.

  The ground contact state estimation unit 224 determines whether the vehicle 10 is turning left or right depending on the difference in the contact length between the left and right wheels. When the difference between the contact lengths of the left and right wheels exceeds a predetermined value, the ground contact state estimation unit 224 determines that the vehicle is turning right if the left wheel is longer, and is turning left if the wheel on the right side is longer. It is determined that When the ground contact state estimation unit 224 determines that the vehicle 10 is turning due to the difference in contact length between the left and right wheels, the contact state estimation unit 224 determines the degree of turn according to the magnitude of the difference in the contact length. As a modification, the ground contact state estimation unit 224 may determine whether or not the vehicle 10 is turning left or right depending on the difference in the ground contact load between the left and right wheels. In that case, the ground contact state estimation unit 224 determines that the left wheel is turning right if the ground load is higher, and determines that the right wheel is turning left if the ground load is higher. . The vehicle control unit 304 controls the attitude of the vehicle 10 based on the determination of the presence / absence of turning by the ground contact state estimation unit 224 and the degree of turning.

  The friction coefficient estimation unit 226 estimates the road surface μ by estimating the contact surface pressure per unit area based on the contact area and the contact load. At this time, the friction coefficient estimation unit 226 may estimate the road surface μ based not only on the contact area and the contact load, but also on the contact shape. When the ground contact shape is a shape with a high rectangular rate, the surface pressure difference tends to be small and the road surface μ tends to be high between the center in the tread width direction and the shoulder side, and conversely, the ground contact shape is a rounded shape with a low rectangular rate In this case, there is a large difference in surface pressure between the center in the tread width direction and the shoulder portion side, and the road surface μ tends to be low. The friction coefficient estimation unit 226 estimates the road surface μ in consideration of the tendency of the relationship between the ground contact shape and the road surface μ. When the ground contact state estimation unit 224 determines that the vehicle 10 is turning left or right, the friction coefficient estimation unit 226 estimates the road surface μ separately for the front-rear direction component and the lateral direction component. When the rainfall amount and the rainfall time obtained from a raindrop sensor (not shown) exceed predetermined values, the friction coefficient estimation unit 226 estimates the road surface μ in consideration of the wet and dry conditions of the road surface based on the information on the rainfall amount and the rainfall time.

  The vehicle control unit 304 controls various devices such as the suspension device 306, the steering device 308, the braking device 310, the drive device 312, and the drive transmission device 314 based on the road surface μ estimated by the friction coefficient estimation unit 226. The attitude and braking of the vehicle 10 are controlled. The vehicle control unit 304 recognizes a change in the road surface μ as time elapses, determines that a dangerous behavior occurs when the road surface μ attempts to fall below a predetermined threshold, and avoids the dangerous behavior. Execute control. This makes it possible to realize preventive control in advance and enhance vehicle safety, compared to the case where the behavior and braking of the vehicle are controlled according to the behavior after the actual dangerous behavior occurs. be able to.

FIG. 3 is a diagram illustrating the relationship between the contact length with respect to the contact load and the change time until the contact length is reached. This figure is a three-axis graph in which the contact load, the contact length, and the change time are taken as axes. Here, the contact length change rates are shown for three cases of air pressure P1, P2, and P3. The air pressure P1 is the tire air pressure on the high pressure side, and the contact length change rate when the contact load is F in this case is indicated by a straight line 100. The air pressure P3 is the tire air pressure on the low pressure side, and the contact length change rate when the contact load is F in this case is indicated by a straight line 104. The air pressure P2 is an intermediate tire air pressure, and the contact length change rate when the contact load is F in this case is indicated by a straight line 102. If the grounding loads are all F, when the air pressure is P1, P2, P3, the grounding lengths are a, b, c, respectively, and the change times until reaching the grounding lengths a, b, c are A, B , C. The relationship between a, b, c and A, B, C is a <b <c and A <B <C, respectively. In the case of the high pressure air pressure P1, the change gradient of the contact length is the smallest, and the air pressure is low pressure. In the case of P3, the change gradient of the contact length is the largest. Further, since the magnitude of the change gradient of the contact length increases almost linearly as the air pressure value decreases, the contact state estimation unit 224 also performs the contact length change rate by interpolation processing even when the air pressure is other than P1, P2, P3. Can be determined. In the map storage unit 222, the correspondence relationship between the contact load, the contact length, and the contact area based on the contact length change rate as shown in the figure is stored in the form of a map.

  FIG. 4 is a flowchart showing a process of estimating the road surface μ and controlling the vehicle in the first embodiment. First, the tire state quantity acquisition unit 220 acquires the contact length of the tire (S10), and the contact load sensor 60 detects the contact load (S12). The ground contact state estimation unit 224 performs turning determination based on the difference between the contact lengths of the left and right wheels (S13), obtains the change rate of the contact length with respect to the change of the contact load (S14), (Y of S16), it is determined that the air pressure is low, and the warning output unit 302 gives a warning to that effect (S18). If the contact length change rate is less than or equal to the predetermined value, S18 is skipped (N in S16). When the contact state estimation unit 224 estimates the tire contact area based on the contact length, contact load, and contact length change rate (S20), the friction coefficient estimation unit 226 estimates the road surface μ based on the contact area and contact load ( S22). The vehicle control unit 304 controls the attitude and braking of the vehicle 10 based on the road surface μ (S24).

  FIG. 5 is a flowchart showing in detail the turning determination process of S13 in FIG. First, when the difference between the contact lengths of the left and right wheels is greater than or equal to a predetermined value, the ground contact state estimation unit 224 determines that the vehicle 10 is turning left or right and proceeds to S100 (Y in S90). When the difference in length is smaller than the predetermined value, it is determined that the vehicle 10 is not turning, and the processing after S100 is skipped (N in S90). In S100, the ground contact state estimation unit 224 determines that the vehicle 10 is turning leftward (S102) when the right wheel has a longer contact length than the left wheel (Y in S100). When the contact length of the wheel on the right side of the wheel is shorter (N in S100), it is determined that the vehicle 10 is turning right (S104).

  As described above, in the present embodiment, the ground contact state estimation unit 224 monitors the change in the contact length over time, so that the friction coefficient estimation unit 226 can recognize the change in the road surface μ, and the vehicle control The unit 304 can immediately detect the dangerous behavior of the vehicle from the tendency of the change in the road surface μ and improve the safety of the vehicle. Furthermore, since each wheel can be independently controlled based on information obtained from each wheel, safety can be improved by more accurate attitude or braking control.

(Second Embodiment)
In the present embodiment, the state quantity sensor includes an air pressure sensor, and the ground contact area and the road surface μ of the tire are estimated based on the air pressure information. This is different from the estimation of the road surface μ. Hereinafter, description of points common to the first embodiment will be omitted, and differences will be mainly described.

  In FIG. 1, the first state quantity sensor 30A, the second state quantity sensor 30B, the third state quantity sensor 30C, and the fourth state quantity sensor 30D each further include an air pressure sensor in addition to the acceleration sensor. The air pressure sensor may be provided to provide tire pressure information to the tire pressure monitoring system. The first state quantity sensor 30A, the second state quantity sensor 30B, the third state quantity sensor 30C, and the fourth state quantity sensor 30D may each further include a temperature sensor that detects the temperature of air in the tire and the temperature of the tire tread. Good. The air pressure sensor and the temperature sensor included in the state quantity sensor 30 are attached to a wheel, a tire tread, a rim, or the like.

  In FIG. 2, the map storage unit 222 stores a correspondence relationship between the contact length change rate, the air pressure, and the contact area as a contact length change rate map. The contact state estimation unit 224 refers to the correspondence relationship between the contact length change rate, the air pressure, and the contact area, and estimates the contact area of the tire corresponding to the acquired contact length and the acquired air pressure. The friction coefficient estimation unit 226 estimates the road surface μ based on the ground contact area, the ground contact length, and the ground contact load estimated by the ground contact state estimation unit 224.

  FIG. 6 is a flowchart showing a process of estimating the road surface μ and controlling the vehicle in the second embodiment. First, the tire condition quantity acquisition unit 220 acquires the contact length of the tire (S30), the contact load sensor 60 detects the contact load (S32), and the tire condition quantity acquisition unit 220 acquires information on the air pressure (S34). . The grounding state estimation unit 224 estimates lateral force based on the grounding length, grounding load, air pressure, and grounding length change rate (S36), and estimates the grounding area (S38). The ground contact state estimation unit 224 performs turning determination based on the difference between the contact lengths of the left and right wheels (S39), and the friction coefficient estimation unit 226 estimates the road surface μ based on the ground contact area and the ground load (S40). The vehicle control unit 304 controls the attitude and braking of the vehicle 10 based on the road surface μ (S42). The details of the turning determination process in S39 are as shown in FIG. In this flowchart, the process in which the ground contact state estimation unit 224 estimates the lateral force in S36 and then estimates the ground contact area in S38 is shown. However, the ground contact state estimation unit 224 estimates the lateral force at an intermediate stage. Alternatively, the contact area may be directly estimated according to the contact length change rate map in which the estimation of the lateral force is reflected in advance.

  As described above, in the present embodiment, the ground contact state estimation unit 224 monitors the change in the contact length over time, so that the friction coefficient estimation unit 226 can recognize the change in the road surface μ, and the vehicle control The unit 304 can immediately detect the dangerous behavior of the vehicle from the tendency of the change in the road surface μ and improve the safety of the vehicle. Also, by accurately grasping the tire air pressure, it is possible to recognize the contact shape and contact area more accurately, so it is possible to recognize changes in the road surface μ with higher accuracy and improve vehicle safety. it can.

(Third embodiment)
The present embodiment is different from the state quantity sensor and the estimation of the ground contact area and road surface μ in the first and second embodiments in that a plurality of acceleration sensors are provided for each tire. Hereinafter, description of points common to the first and second embodiments will be omitted, and differences will be mainly described.

  The state quantity sensor 30 in FIG. 1 includes a plurality of acceleration sensors per tire. For example, the acceleration sensor detects acceleration from at least two locations on the outer side and the inner side in the tire width direction.

  In FIG. 2, the tire state quantity acquisition unit 220 acquires at least two contact lengths from one tire based on the acceleration information received from the state quantity sensor 30. The map storage unit 222 stores a contact length change rate map indicating a correspondence relationship between the contact length change rate and the contact area for a plurality of locations on the tire. The contact state estimation unit 224 can estimate the contact shape more accurately by referring to the plurality of contact lengths and the contact length change rate map, so that the contact area and the road surface μ can be estimated more accurately. In particular, if the contact length can be obtained from two locations on the outer and inner sides of the tire, the contact shape can be estimated more accurately. The ground contact state estimation unit 224 determines turning of the vehicle 10 based not only on the difference between the contact lengths of the left and right wheels, but also on the difference between a plurality of contact lengths in one tire. That is, the presence / absence of turning is determined based on whether at least one of the difference between the contact lengths of the left and right wheels or the difference between the plurality of contact lengths in one tire is a predetermined value or more, and depending on which of the contact lengths is longer It is determined whether the turn is left or right. Further, the ground contact state estimation unit 224 can more accurately determine the turning state and the degree of turning based on the contact length difference obtained individually from each tire.

  FIG. 7 is a flowchart showing a process of estimating the road surface μ and controlling the vehicle in the third embodiment. First, the tire state quantity acquisition unit 220 acquires the contact length from a plurality of locations on the tire (S50), and the contact load sensor 60 detects the contact load (S52). The ground contact state estimation unit 224 performs turning determination based on the difference in the contact lengths of the left and right wheels or the plurality of contact length differences for one tire (S56), and obtains a plurality of contact length change rates with respect to changes in the ground load ( If the rate of change is greater than a predetermined value (S58), it is determined that the air pressure is low, and the warning output unit 302 issues a warning to that effect (S62). If the contact length change rate is equal to or less than the predetermined value, S62 is skipped (N in S60). When the contact state estimation unit 224 estimates the contact area of the tire based on a plurality of contact lengths, contact loads, and contact length change rates (S64), the friction coefficient estimation unit 226 estimates the road surface μ based on the contact area and the contact load. (S66). The vehicle control unit 304 controls the attitude and braking of the vehicle 10 based on the road surface μ (S68). The details of the turning determination process in S56 are as shown in FIG. However, in S90 in FIG. 5, the ground contact state estimation unit 224 determines that the vehicle 10 is turning left or right when the difference in contact length between the left and right sides of each tire is greater than or equal to a predetermined value. Good. In S100 of the figure, the ground contact state estimation unit 224 determines that the vehicle 10 is turning leftward when the contact length is longer on the right side than on the left side of each tire (Y in S100) (S102). ) When the contact length is shorter on the right side than on the left side (N in S100), it may be determined that the vehicle 10 is turning right (S104).

  As described above, in the present embodiment, the ground contact state estimation unit 224 monitors the change in the contact length over time, so that the friction coefficient estimation unit 226 can recognize the change in the road surface μ, and the vehicle control The unit 304 can immediately detect the dangerous behavior of the vehicle from the tendency of the change in the road surface μ and improve the safety of the vehicle. In addition, by acquiring multiple contact lengths from a single tire, it is possible to more accurately recognize the contact shape and contact area, so that changes in the road surface μ can be recognized with higher accuracy, improving vehicle safety. Can be planned.

  The present invention is not limited to the above-described embodiment. Various modifications such as design changes can be added to the embodiments based on the knowledge of those skilled in the art, and embodiments to which such modifications are added can also be included in the scope of the present invention. Examples of such modifications are given below.

  In the second embodiment, a configuration has been described in which air pressure information is acquired from each tire in addition to the ground contact length and the ground load, and the ground contact area and the road surface μ are estimated based on the air pressure information. In the third embodiment, a configuration has been described in which a plurality of contact lengths are acquired from each tire in addition to the contact length and the contact load, and the contact area and the road surface μ are estimated based on the plurality of contact lengths. . In a modification, it is good also as a structure which acquires the information of air pressure from each tire, acquires several contact lengths, and estimates the contact area and road surface micro | micron | mu based on these air pressure and several contact lengths. In that case, the ground contact area and the road surface μ can be estimated with higher accuracy, and the safety of the vehicle can be further improved.

  In 3rd Embodiment, the structure which acquires the contact length from two places of the outer side and inner side in one tire was shown. In a modified example, the contact length may be acquired from three or more locations on the outer side, the inner side, and the center in one tire. In this case, since the contact shape, the contact area, and the road surface μ can be estimated with higher accuracy based on more contact lengths, the safety of the vehicle can be further improved.

It is a figure showing the whole vehicle composition provided with the tire condition processing device concerning this embodiment. It is a functional block diagram which shows the structure which concerns on acquisition of the wheel information in ECU, and vehicle control. It is a figure which shows the relationship between the contact length with respect to a contact load, and the change time until it becomes the state of the contact length. It is a flowchart which shows the process of estimation of the road surface (micro | micron | mu) in the 1st Embodiment, and vehicle control. It is a flowchart which shows the turning determination process of S13 in FIG. 4 in detail. It is a flowchart which shows the process of estimation of road surface (micro | micron | mu) in 2nd Embodiment, and vehicle control. It is a flowchart which shows the process of estimation of the road surface (micro | micron | mu) and vehicle control in 3rd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Vehicle, 12 Car body, 20 Wheel, 30 State quantity sensor, 60 Ground load sensor, 64 ECU, 70 Buzzer, 72 Warning lamp, 220 Tire state quantity acquisition part, 222 Map storage part, 224 Ground state estimation part, 226 Friction coefficient An estimation unit; 302 a warning output unit; 304 a vehicle control unit;

Claims (4)

Acceleration detecting means provided on the tire for detecting acceleration;
Tire state quantity acquisition means for acquiring a value of a contact length of the tire based on the detected acceleration;
A contact load detecting means for detecting a contact load of the tire;
A map storage means for storing a correspondence between the ground plane product with a previously measured vertical load and the contact length on the tire,
A grounding state estimating means for referring to the correspondence relationship between the stored grounding load, the grounding length, and the grounding area, and estimating the grounding area of the tire corresponding to the acquired grounding load and the grounding length;
Friction coefficient estimating means for estimating a road surface friction coefficient based on the contact area and the contact load;
A tire condition processing apparatus comprising: The acceleration detecting means is provided at a plurality of locations in the width direction of the tire,
The tire state quantity acquisition means acquires the contact length of the tire for each of a plurality of locations of the tire,
It said map storage means stores correspondence between the ground plane product and the ground load and the contact length of the plurality of locations,
The contact state estimation means to estimate a ground contact area of the tire in which the ground load of the plurality of locations and ground contact length with reference to the correspondence between the ground plane products, corresponding to the ground contact length obtained for the plurality of locations The tire condition processing apparatus according to claim 1, wherein An air pressure acquisition means for acquiring a value of the tire air pressure;
The map storage means stores a correspondence relationship between the contact length, the air pressure, and the contact area,
The contact state estimation means to estimate the ground contact area of the tire where the reference to the correspondence relation between the contact length and the pressure and the contact area, corresponding to the the obtained contact length and the obtained air pressure The tire condition processing device according to claim 1 or 2. The contact state estimation means, the detected based on the vertical load before Symbol obtained contact length and pressure estimates the lateral force applied to the tire, and estimates the ground contact area on the basis of the lateral force obtained by the estimated The tire condition processing device according to claim 3 .

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