JP2006327269A - Tire grounding state estimation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire grounding state estimation device to estimate a grounding state of a tire in high precision. <P>SOLUTION: This tire grounding state estimation device detects relative displacement of a wheel 12 and the tire 14 to be a premise of slip angle formation of the tire 14. The relative displacement of the wheel 12 and the tire 14 is detected by a change of an induced electric current generated by a coil 20 as a tread standard member fixed on the inside of a tread part crossing a magnetic field B generated by a magnet 18 as a rim standard member fixed on the wheel 12 in the cross direction of the tire 14 and estimates a tire slip angle θ by a changing gradient of the induced electric current. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tire ground contact state estimation device, and more particularly to an improvement in a tire ground contact state estimation device that estimates the ground contact state of a tire based on information directly obtained from the tire.

  When a sudden steering operation is performed while trying to avoid an obstacle while the vehicle is running, or when the vehicle enters a slippery road surface curve, the tire may slip sideways. In such a case, in order to suppress the generated side slip, a vehicle stability control system that automatically controls engine output and braking force of each wheel to ensure vehicle stability has been proposed. When this side slip suppression control is performed, the system needs to recognize how much tire slip angle is present in the tire as a whole body and what target the control should be performed. Therefore, it is required to accurately grasp the ground contact state of each wheel tire.

Therefore, there has been a proposal related to an apparatus for estimating the ground contact state of a tire. For example, Patent Document 1 discloses a technique for estimating a side slip angle (tire slip angle) of a tire as a ground contact state of the tire. In Patent Document 1, a tire rotation axis direction speed detection unit that is provided on the side of the vehicle body and detects a moving speed that is collinear with the rotation axis of the ground contact point with respect to the road surface of the tire is the same as the center of the tire at the contact point. A side slip angle acquisition device including a center line direction speed detecting unit that detects a moving speed on a straight line, and a side slip angle calculating unit that calculates a side slip angle based on the detected center line direction moving speed and rotational axis direction moving speed. Are listed. Patent Document 2 discloses a technique for estimating a tire slip angle based on tire lateral acceleration, yaw rate, vehicle speed, and vehicle specification data.
JP-A-6-341822 JP-A-10-281944

  In the tire ground contact state estimation device described above, data such as the movement speed in the center line direction, the travel speed in the rotation axis direction, or the lateral acceleration, yaw rate, speed, etc. are collected to determine the tire slip angle that is in the ground contact state indirectly. Estimated. However, the collected data described above changes due to various external factors (disturbances) other than the tire ground contact state. When the ground contact state of a tire is estimated based on such data, there is a problem that the estimation accuracy is also affected by the influence of disturbance. Further, there is a problem that complicated calculation processing is required and the configuration becomes complicated.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a tire ground contact state estimating device capable of estimating the ground contact state of a tire with high accuracy and a simple configuration.

  In order to solve the above-described problem, in an aspect of the present invention, on a wheel rim of a wheel that supports a tire, a rim reference member provided in a region facing the inner side of the tread portion of the tire, and an inner side of the tread portion of the tire, A tread reference member provided at a position facing the rim reference member, and state estimation means for estimating a ground contact state of the tire based on a change in relative position between the rim reference member and the tread reference member. Features.

  For example, when a wheel is steered and the tire is going to travel in a certain traveling direction, the wheel is directed in the steering direction ahead of the tire while the tire is gripping the road surface. As a result, the rim reference member moves relative to the tread reference member, and the relative position between the two changes. Also, when the grip on the road surface of the tire decreases or disappears, the friction between the tire and the road surface decreases, so the direction in which the tire is facing the wheel so as to cancel the change in the relative position due to the tire shape recovery action. Change direction to follow. At this time, the relative position between the rim reference member and the tread reference member returns to the state before the change, but the tire substantially advances in the traveling direction immediately before the start of the return because the friction with the road surface is low. That is, the relationship between the tire turning angle and the traveling direction can be expressed by a change in the relative position of the tread reference member. As a result, the ground contact state with respect to the road surface of the tire can be estimated based on a change in relative position between the rim reference member and the tread reference member.

  In the above aspect, the state estimation means may estimate a tire slip angle based on a relative displacement in the tire width direction of the rim reference member and the tread reference member. Here, the tire slip angle is an angle formed by the tire turning angle and the tire traveling direction. When the relative displacement of the rim reference member and the tread reference member in the tire width direction occurs, it indicates that the tire is gripping the road surface. When this grip disappears, that is, when the relative displacement in the tire width direction starts to return to the state before the displacement, the tire starts slipping, and the tire is substantially in the traveling direction just before the grip begins to disappear. Will proceed. Therefore, a slip angle, which is an angle formed by the tire turning angle and the tire traveling direction, can be estimated based on the relative displacement in the tire width direction.

  In the above aspect, one of the rim reference member and the tread reference member may be a coil, and the other may be a magnetic member that generates a magnetic field through which the coil can pass. As the relative position of the coil and the magnetic member changes, the coil crosses the magnetic field. As a result, an induced electromotive force is generated in the coil, and a change in relative position appears as a change in current value. Therefore, it is possible to estimate a change in the ground contact state of the tire based on the generated current value.

  In the above aspect, one of the rim reference member and the tread reference member may be an imaging unit, and the other may be a marking member that can be imaged by the imaging unit. According to this aspect, it is possible to accurately detect a change in the relative position between the rim reference member and the tread reference member by photographing the marking with the imaging unit. As a result, a change in the ground contact state of the tire can be estimated.

  Further, in the above aspect, the tire slip angle may be indicated by a change gradient of a relative position between the rim reference member and the tread reference member after a portion corresponding to the arrangement of the tread reference member of the tread portion starts to ground. it can. According to this aspect, the tire slip angle can be easily estimated.

  According to the tire ground contact state estimation device of the present invention, it is possible to directly detect the deformation state of the tire with respect to the wheel based on the change in the relative position between the rim reference member and the tread reference member, and accurately estimate the tire ground contact state. It can be performed.

  Hereinafter, an embodiment of the present invention (hereinafter referred to as an embodiment) will be described with reference to the drawings.

  The tire ground contact state estimation device according to the present embodiment faces a rim reference member provided on a wheel rim of a wheel that supports a tire in a region facing the inner side of the tread portion of the tire, and on the inner side of the tire tread portion. A tread reference member provided at a position, and state estimation means for estimating a ground contact state of the tire based on a change in relative position between the rim reference member and the tread reference member. And it detects that the tread part of the tire was displaced relative to the wheel of the tire, and estimates the ground contact state of the tire.

  FIG. 1 is a conceptual configuration diagram of a vehicle 10 equipped with a tire ground contact state estimation device of the present embodiment. In the vehicle 10, a wheel 16 including at least a wheel 12 and a tire 14 is mounted at a front wheel position and a rear wheel position. As shown in an enlarged view in FIG. 2, on the wheel rim 12 a of the wheel 12 that supports the tire 14, a specific position on the wheel rim 12 a is defined in a region facing the inner side of the tread portion 14 a of the tire 14. For example, a magnetic member that functions as a rim reference member serving as a part of a relative position detection mechanism that obtains data for estimating the ground contact state of the device, in the present embodiment, for example, a magnet 18 is disposed. In addition, a specific position on the tread portion 14a is defined at a position substantially facing the magnet 18 inside the tread portion 14a of the tire 14, and a relative position detection mechanism that obtains data for estimating the ground contact state of the tire 14 is provided. A coil 20 functioning as a tread reference member serving as a portion is supported and fixed by a stay 14b integrally formed with the tread portion 14a.

  FIG. 3 shows the positional relationship between the magnet 18 and the coil 20 in more detail. In the case of this embodiment, the magnets 18 are arranged as a set of two, and are fixed to the wheel rim 12a so as to generate a magnetic field B having a predetermined strength in each set. The coil 20 is fixed to the tread portion 14 a so as to be positioned in the magnetic field B so as to cross the magnetic field B formed by the magnet 18 in the width direction of the tire 14. Therefore, when the magnet 18 is displaced due to deformation of the tire 14 in the width direction, an induced electromotive force is generated in the coil 20 and an induced current flows. This current changes according to the movement amount of the magnet 18. In the tire ground contact state estimation device according to the present embodiment, a change in the relative position of the wheel 12, that is, the rim reference member with respect to the tire 14, that is, the tread reference member, is detected based on the change in the induced current, thereby estimating the ground contact state of the tire 14. I do. In the example shown in FIG. 3, three sets of relative position detection mechanisms including two magnets 18 and coils 20 are arranged at equal intervals, for example, 120 ° intervals. Can be increased or decreased as appropriate. The state estimation of the tire 14 can be performed in more detail by increasing the number of arrangement groups.

  Returning to FIG. 1, a transmitter 22 that transmits data indicating the magnitude of the induced current flowing through the coil 20 to the ECU 24 on the vehicle 10 side is disposed in a part of the wheel 12. The ECU 24 also includes a receiver 26 that receives data transmitted from the transmitter 22 and a state estimation unit 28 that estimates the ground contact state of the tire 14 based on the received data.

  By the way, in a situation where a side slip is likely to occur, such as when the tire 14 is steered by a sudden handle or when the road surface condition easily slips when entering a curve, the tire 14 is in the traveling direction M of the tire 14 as shown in FIG. On the other hand, the original center N of the tire 14, that is, the cutting angle of the tire 14, faces the inside of the turn. That is, the tire 14 proceeds toward the traveling direction M in a state where the tire 14 slips by an angle formed by the traveling direction M and the center N. The angle at this time is the tire slip angle θ.

  When the actually traveling tire 14 is steered, first, the tire 14 grips the road surface by its own grip characteristics. The wheel 12 is directed to the steering direction in advance of the tire 14, and is directed to the original center N of the tire 14 in FIG. 4. As a result, the magnet 18 moves with respect to the coil 20, and the relative position of both changes. Further, when the grip on the road surface of the tire 14 decreases or disappears, the friction between the tire 14 and the road surface decreases, so that the tire 14 changes its direction so as to follow the direction in which the wheel 12 faces by the shape restoration action. That is, the tire 14 changes direction so as to cancel the change in the relative position between the magnet 18 and the coil 20 (center N direction). At this time, the relative position of the magnet 18 and the coil 20 returns to the state before the change, but the tire 14 advances while substantially slipping in the traveling direction immediately before the start of the return because the friction with the road surface is low. That is, the tire 14 proceeds in the traveling direction M with a slip angle. Therefore, in the tire ground contact state estimation device of the present embodiment, the tire slip angle is estimated by detecting the state until the grip is lost in the tire 14.

  As described above, the coil 20 is always located in the magnetic field B formed by the magnet 18 (see FIG. 5A). While the vehicle 10 is traveling, in this state, the tire 14 rotates as shown in FIG. 5B, and the portion where the coil 20 is located repeatedly contacts and separates from the road surface P. At this time, when the wheel 16 is steered, the tire 14 starts to deform as the tire 14 grips the road surface P as described above. This deformation occurs when the wheel 12 turns in the width direction of the tire 14 with respect to the tread portion 14a of the tire 14 gripping the road surface P. That is, the magnet 18 fixed to the wheel rim 12a and generating the magnetic field B moves with respect to the coil 20 fixed to the tread portion 14a. In other words, the coil 20 crosses the magnetic field B, and an induced current corresponding to the movement amount flows through the coil 20. As shown in FIG. 5B, when the tire 14 starts to deform and the current value changes and the tire 14 rolls to some extent, the deformation of the tire 14 is restored to the original state. In this restoration, as the deformation of the tread portion 14a increases, the force to be restored gradually increases. Then, when the static friction force is exceeded, the tire 14 is switched to dynamic friction force and slipping occurs in the tread portion 14a, and the tire 14 is restored. At this time, the shape of the tire 14 is restored by the rigidity of the tire 14.

  As shown in FIG. 5B, the induced current generated in the coil 20 increases almost proportionally when the tire 14 is gripping the road surface P, and the induced current value starts to drop from the portion where the grip starts to be lost. . This state is a region where slipping occurs, and the tire 14 substantially proceeds in the direction in which the tire 14 is traveling at this time. When the tread portion 14a corresponding to the portion where the coil 20 is disposed is separated from the road surface P, the induced current becomes zero completely. As described above, the tire 14 proceeds in the traveling direction when the change in the relative position between the tread portion 14a and the wheel rim 12a is maximized, but slips in a state of turning at an angle that cancels the change in the relative position. ing. Therefore, an angle based on a change in the relative position between the tread portion 14a and the wheel rim 12a can be set as the tire slip angle θ. That is, as shown in FIG. 5B, the relative position between the magnet 18 as the rim reference member and the coil 20 as the tread reference member after the arrangement corresponding portion of the coil 20 of the tread portion 14a of the tire 14 starts to ground. This corresponds to the change gradient and the tire slip angle θ.

  For example, the transmitter 22 arranged on the wheel 12 transmits data based on the induced current generated in the coil 20 to the receiver 26 of the ECU 24 at an interval of 1/1000 second, and the state estimation unit 28 indicates the change gradient of the induced current. The tire slip angle of the tire 14 is calculated. As described above, the tire slip angle estimated in this way is sequentially provided to, for example, a vehicle stability control system, and is used for engine output control and brake force control. Note that the time during which the tire 14 is in contact with the road surface changes according to the speed of the vehicle 10, but the change while the tread portion 14 a corresponding to the arrangement of the coil 20 is in contact with the ground becomes the tire slip angle. The tire slip angle θ can be estimated from the change gradient of the induced current without being affected by the speed of the vehicle 10 or the like. In the case of the wheel 16, a transmitter may be provided to monitor the air pressure in the internal space of the tire 14. Data transmission for the air pressure monitor is performed at a relatively long interval. However, the configuration of the wheel 16 may be simplified by sharing the transmitter 22 for air pressure data transmission.

  Further, as shown in FIG. 3, a plurality of relative position detection mechanisms composed of the magnets 18 and the coils 20 can be arranged in one tire 14, so that the state estimation unit 28 generates induced currents by individual relative position detection mechanisms. The tire slip angle θ for each portion of the tire 14 may be estimated based on the change in the value, or the tire slip angle θ obtained from a plurality of relative position detection mechanisms is comprehensively analyzed, and the tire as the entire tire 14 is analyzed. The slip angle may be estimated. Further, when engine output control is performed using the estimated slip angle, it may be necessary to grasp the tire slip angle of the vehicle 10 as a whole. In such a case, the state estimation unit 28 may estimate the tire slip angle of the entire vehicle 10 based on the tire slip angles estimated for the front wheels and the rear wheels.

  In the above description, the magnet 18 is shown as the rim reference member and the coil 20 is shown as the tread reference member. However, the coil 20 may be arranged as the rim reference member and the magnet 18 may be arranged as the tread reference member. Well, the same effect as described above can be obtained. Moreover, although the structure which forms the magnetic field B with two magnetic fields B was shown, if the magnetic field which the coil 20 can traverse is formed with a magnetic member, the formation method of a magnetic field is arbitrary and the same effect as the above-mentioned Can be obtained.

  As described above, according to the tire ground contact state estimation device of the present embodiment, the tread reference member generates the magnetic field B generated by the magnet 18 as the rim reference member for the displacement of the wheel 12 with respect to the tire 14 which is a premise that the tire 14 slips sideways. Is detected by a change in the induced current caused by the crossing of the coil 20 in the width direction of the tire 14, and the tire slip angle θ is estimated based on the gradient of the induced current. It is possible to accurately detect the relative displacement between 12a and the tread portion 14a, and to estimate the tire slip angle θ with high accuracy based on the relative displacement. Further, since data necessary for estimation can be obtained with a simple configuration of only the magnet 18 and the coil 20, it is possible to contribute to a reduction in system cost.

  FIG. 6 is a conceptual diagram illustrating another configuration of the relative position detection mechanism of the tire ground contact state estimation device of the present embodiment. In FIG. 6, an imaging device (CCD) 30 is disposed as a rim reference member, and, for example, a marking 32 that can be imaged by the imaging device is disposed as a tread reference member. As described above, when the wheel 16 is steered, while the tire 14 is gripping the road surface P, the wheel 12 is turned in the steered direction ahead of the tire 14, and the tread portion 14 a is the tire. 14 in the width direction. As a result, the imaging device 30 moves according to the deformation. That is, the relative position between the imaging device 30 and the marking 32 changes. Further, when the grip of the tire 14 is lost, the shape of the tire 14 returns following the turning direction of the wheel 12. As a result, the relative position between the imaging device 30 and the marking 32 is restored to the original position. The change in the relative position is the same as the change in the induced current shown in FIG. 5B. The vertical axis indicates the amount of displacement of the relative position between the imaging device 30 and the marking 32, and the horizontal axis indicates the time. A displacement gradient based on a change in the relative position between 14a and the wheel rim 12a can be set as the tire slip angle θ. As a result, the tire slip angle of the tire 14 can be estimated by the displacement of the relative position between the imaging device 30 and the marking 32 as in the case where the tire slip angle is estimated by the induced current. In addition, when the induced current generated in the coil 20 is used for estimating the ground contact state of the tire 14, noise is likely to appear in the data because the induced current is weak. Therefore, when estimating the tire slip angle with higher accuracy, it is preferable to employ the configuration of FIG. 6 using the imaging device 30 and the marking 32 using actual displacement data.

  Note that when the image data of the marking 32 is acquired by the imaging device 30, the data size increases and the transmission load on the receiver 26 shown in FIG. 1 tends to increase. Therefore, when using the imaging device 30, the image processing unit 34 is disposed in the wheel 16, for example, on the wheel rim 12 a, and the displacement amount of the marking 32 or the tire slip angle data of the tire 14 is received from the transmitter 22 by the receiver 26. It is desirable to send it toward. When there is no need to consider the transmission load, the imaging data acquired by the imaging device 30 is transmitted as it is to the receiver 26 on the vehicle 10 side, image processing is performed on the vehicle side, and the tire slip angle is estimated. Also good. Moreover, the electric power used by the imaging device 30 or the image processing unit 34 can be provided via, for example, an axle.

  Thus, when it is desired to configure a tire ground contact state estimation device at a low cost, a relative position detection mechanism composed of a magnet 18 and a coil 20 as shown in FIG. 3 is adopted, and a more accurate tire slip angle is required. In this case, it is preferable to employ a relative position detection mechanism configured by the imaging device 30 and the marking 32. Note that a plurality of relative position detection mechanisms configured by the imaging device 30 and the marking 32 can be disposed inside the tire 14 in the same manner as the relative position detection mechanism configured by the magnet 18 and the coil 20. As the number increases, the estimation accuracy of the tire slip angle also improves.

  In FIG. 6, the marking 32 is shown as a protruding member. However, as long as the mark follows the deformation of the tread portion 14 a, the shape is arbitrary, and for example, it is printed planarly on the tread portion 14 a. However, it may be a concave shape, and the same effect as described above can be obtained.

  Thus, according to the tire ground contact state estimation device that employs the relative position detection mechanism configured by the imaging device 30 and the marking 32, it is possible to easily estimate the tire slip angle with high accuracy.

  The configuration of the tire ground contact state estimation device shown in the present embodiment is an example, on the wheel rim of the wheel that supports the tire, on the rim reference member provided in the tread portion inner side facing region of the tire, and on the inner side of the tread portion of the tire, If the configuration includes a tread reference member provided at a position facing the rim reference member, and state estimation means for estimating the ground contact state of the tire based on a change in the relative position between the rim reference member and the tread reference member Other configurations can be changed as appropriate, and the same effects as in the present embodiment can be obtained.

1 is a conceptual diagram of a configuration of a vehicle on which a tire ground contact state estimation device according to an embodiment is mounted. In the tire ground contact state estimation device according to the present embodiment, it is an explanatory diagram for explaining an arrangement relationship between a magnet that is a rim reference member and a coil that is a tread reference member. In the tire ground contact state estimation device according to the present embodiment, it is another explanatory view for explaining an arrangement relationship between a magnet that is a rim reference member and a coil that is a tread reference member. It is explanatory drawing explaining the tire slip angle of a tire. In the tire ground contact state estimation device according to the present embodiment, it is an explanatory diagram for explaining the relationship between an induced current generated in a coil as a tread reference member and a tire slip angle. It is explanatory drawing explaining the arrangement | positioning relationship of the imaging device which is a rim reference member, and the marking which is a tread reference member as another structure of the tire ground-contact-state estimation apparatus which concerns on this embodiment.

Explanation of symbols

  10 vehicle, 12 wheel, 12a wheel rim, 14 tire, 14a tread part, 14b stay, 16 wheel, 18 magnet, 20 coil, 22 transmitter, 24 ECU, 26 receiver, 28 state estimation part, 30 imaging device, 32 Marking, 34 Image processing unit.

Claims (5)

A rim reference member provided in a region facing the inner side of the tread portion of the tire on a wheel rim of a wheel that supports the tire;
A tread reference member provided at a position facing the rim reference member inside the tread portion of the tire;
State estimating means for estimating a ground contact state of the tire based on a change in relative position between the rim reference member and the tread reference member;
A tire ground contact state estimation device comprising:   2. The tire ground contact state estimating device according to claim 1, wherein the state estimating means estimates a tire slip angle based on a relative displacement in the tire width direction of the rim reference member and the tread reference member.   3. The tire ground contact according to claim 1, wherein one of the rim reference member and the tread reference member is a coil, and the other is a magnetic member that generates a magnetic field through which the coil can pass. State estimation device.   3. The tire ground contact state estimation according to claim 1, wherein one of the rim reference member and the tread reference member is an imaging unit, and the other is a marking member that can be imaged by the imaging unit. apparatus.   The tire slip angle is indicated by a change gradient of a relative position between the rim reference member and the tread reference member after the arrangement corresponding portion of the tread reference member of the tread portion starts to contact the ground. 5. The tire ground contact state estimation device according to any one of items 4 to 5.

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