Patent Description:
There is known a vehicle behavior control device that detects a state of a tire and controls the traveling of a vehicle (see, for example, <CIT>).

In this vehicle behavior control device, control that reduces the speed of the vehicle is carried out in a case in which a run-flat tire enters into a run-flat state.

<CIT> discloses tire over- or under-inflation can create problems in vehicle operation. To limit the effects of out-of-range tire pressure, vehicle speed is automatically controlled if the vehicle speed is not appropriate for either or both of measured tire air pressure and measured tire temperature.

<CIT> discloses a method for ensuring safe tire emergency running operation in a motor vehicle that is equipped with tires that have emergency running properties when the tire pressure is greatly reduced or absent altogether, a device is provided for detecting an emergency running mode of the motor vehicle. The device for limiting the driving speed limits the driving speed of the motor vehicle whenever emergency running is detected.

<CIT> discloses an arithmetic model generation system includes a sensor information acquisition unit, a tire force calculator, and an arithmetic model update unit. The sensor information acquisition unit acquires acceleration of a tire. The tire force calculator includes an arithmetic model for calculating tire force based on the acceleration, and calculates the tire force by inputting the acceleration acquired by the sensor information acquisition unit. The arithmetic model update unit compares tire axial force measured by the tire and the tire force calculated by the tire force calculator, and updates the arithmetic model.

By the way, due to traveling, the rubber that structures a pneumatic tire deforms repeatedly and generates heat. The amount of heat that is generated also becomes great at a region where the deformation (strain, stress) of the rubber is great. If the temperature of the rubber becomes excessively high, there are cases in which the vicious cycle of the rubber softening, tire deformation increasing, and the tire temperature rising arises. Therefore, if traveling is continued in a state in which the temperature of the rubber has become high, the rubber will ultimately be destroyed, and traveling of the vehicle will become difficult, and there are cases in which the vehicle will not be able to travel to its destination.

In the prior art, although it is possible to reduce the speed of the vehicle at the time when a tire is punctured, consideration is not given to the generation of heat at the tire. Therefore, there is the possibility that traveling will be continued in a state in which the rubber of the tire has become an excessively high temperature, and ultimately, the tire breaking down can be imagined.

Further, in the prior art, there are cases in which the speed of the vehicle is reduced excessively in order to control the behavior of the vehicle, and there is also the possibility that the traveling time to the destination will be extended.

In order to suppress destruction of the rubber, the generation of heat of the rubber must be suppressed. Further, if the speed can be raised in a range in which the generation of heat at the rubber can be suppressed such that the aforementioned vicious cycle does not occur, it is possible to reach the destination without causing breakdown of the tire, and the traveling time to the destination can be shortened.

In consideration of the above-described circumstances, an object of the present invention is to provide a vehicle speed control system that takes tire temperature into consideration and can shorten the traveling time to a destination without causing the tire to break down.

According to a first aspect of the invention there is provided a vehicle speed control system as specified in claim <NUM>.

Due to traveling, the elastic body such as rubber or the like that structures the tire elastically deforms and generates heat, and the temperature thereof rises. If the temperature of the rubber rises excessively, the rubber softens. If the rubber softens, there are cases in which this results in the vicious cycle of tire deformation increasing and moreover the temperature of the rubber rising. Further, if the temperature of the rubber rises excessively, there are cases in which the rubber deteriorates or the rubber is destroyed, which leads to a deterioration in the durability of the tire.

In the vehicle speed control system relating to the first aspect, the control device controls the speed of the vehicle on the basis of the measured temperature of the tire and suppresses generation of heat of the rubber, so that the above-described vicious cycle does not arise. By suppressing generation of heat of the rubber in this way, the aforementioned vicious cycle is suppressed, the speed can be raised within a range in which the tire does not break down, and it is possible shorten the traveling time to the destination without causing the tire to break down.

As described above, in accordance with the vehicle speed control system of the present invention, the temperature of a tire is taken into consideration, and the traveling time to a destination can be shortened without the causing the tire to break down.

A vehicle <NUM>, to which a vehicle speed control system <NUM> not according to the present invention, but useful for understanding the present invention, is described by using <FIG>.

As illustrated in <FIG>, a tire / rim wheel assembly <NUM> is provided at the vehicle <NUM> (not illustrated in <FIG>; refer to <FIG>) is a structure in which a pneumatic tire <NUM> is mounted on a rim 12A of a rim wheel <NUM>. Note that the pneumatic tire <NUM> is a usual tire for a passenger vehicle. In <FIG>, arrow IN indicates the vehicle inner side direction, and arrow OUT indicates the vehicle outer side direction.

The pneumatic tire <NUM> has a carcass <NUM> that spans in a toroidal form over a pair of bead portions <NUM>. The carcass <NUM> is structured from a single carcass ply 18P in which plural cords are lined-up parallel to one another and coated with rubber.

A belt <NUM>, which is formed from two belt plies that are a first belt ply 20A and a second belt ply 20B, is disposed at the tire radial direction outer side of the carcass <NUM>.

Note that the end portions of the belt <NUM> are covered by belt reinforcing layers <NUM>.

A tread rubber layer <NUM> is disposed at the tire radial direction outer side of the belt <NUM>. Further, side rubber layers <NUM> are disposed at the tire axial direction outer sides of the carcass <NUM>.

The end portions of the carcass ply 18P are wound upwardly on bead cores <NUM> of the bead portions <NUM> toward the tire radial direction outer side.

Here, the portion, which extends from the one bead core <NUM> to the another bead core <NUM> of the carcass ply 18P, is main body portion 18A. The portions that are wound upward and extend from the bead cores <NUM> toward the tire radial direction outer side are upwardly-wound portions 18B. Bead fillers <NUM>, which are formed from a rubber of a high hardness and which extend from the bead cores <NUM> toward the tire radial direction outer side, are disposed between the main body portion 18A and the upwardly-wound portions 18B of the carcass ply 18P.

A thermometer <NUM> and a transmitter <NUM> are mounted to the outer peripheral portion of the rim 12A. The thermometer <NUM> is, as an example, a non-contact-type infrared thermometer.

As illustrated in <FIG>, measured temperature data that is measured by the thermometer <NUM> is transmitted wirelessly by the transmitter <NUM> to a receiver <NUM> provided at a vehicle body 36A.

A control device <NUM> that controls the output of an engine 36B is provided at the vehicle body 36A.

The schematic structure of the control device <NUM> that can be made to function as a vehicle speed control device as an example is illustrated in <FIG>. Note that the control device <NUM> can be applied to a computer for engine control that is installed in the vehicle <NUM> that is an automobile or the like as an example.

The control device <NUM> is structured by a computer that includes a CPU 40A that is an example of a hardware processor, a RAM 40B, a ROM 40C, an I/O 40D and the like. The CPU 40A, the RAM 40B, the ROM 40C and the I/O 40D are connected to a bus 40E that can transmit and receive data and commands. Further, a computing program 40F is stored in the ROM 40C.

Further, the engine (fuel injection device) 36B, the receiver <NUM>, a display device <NUM>, a warning lamp <NUM>, and the like are connected to an I/O 42D.

The measured temperature data that is transmitted by the transmitter <NUM> is sent to the control device <NUM> via the receiver <NUM>. Note that the display device <NUM> is provided at the instrument panel of the vehicle <NUM>, and various types of information relating to the vehicle <NUM> can be displayed on the display device <NUM>.

Upper limit temperature T1 of the pneumatic tire <NUM>, lower limit pressure P1 of the pneumatic tire <NUM>, upper limit temperature T2 at the time of reduced internal pressure, and the like are stored in advance in the ROM 40C of the control device <NUM>.

At the control device <NUM>, the CPU 40A reads-out the computing program 40F stored in the ROM 40C, and expands the computing program 40F in the RAM 40B, and the expanded computing program 40F is executed.

Speed control at the vehicle speed control system <NUM> is described next on the basis of the flowchart shown in <FIG>.

By executing speed limiting in this way, the bead portions <NUM> becoming high temperature, and the rubber of the bead fillers <NUM> softening and deteriorating, can be suppressed, and the durability of the bead portions <NUM> can be ensured.

Note that, in order to inform the driver that speed limiting is carried out, in step <NUM>, a warning by characters or the like may be displayed on the display device <NUM>, or the warning lamp <NUM> may be turned on.

(<NUM>) In next step <NUM>, it is judged whether or not the temperature of the bead portion <NUM> has become less than or equal to the upper limit temperature T1 that is set in advance. Here, if the temperature of the bead portion <NUM> has become less than or equal to the upper limit temperature T1 that is set in advance, the routine moves on to step <NUM>, and if the temperature of the bead portion <NUM> has not become less than or equal to the upper limit temperature T1 that is set in advance, the routine returns to step <NUM>.

(<NUM>) In step <NUM>, the control device <NUM> cancels the speed limiting. Due thereto, the driver can make the vehicle <NUM> travel at greater than or equal to the speed limit (V1) that is set in advance.

In this way, by using the vehicle speed control system <NUM>, at the time of traveling of the pneumatic tire <NUM>, generation of heat of the bead portions <NUM> can be suppressed, the vehicle <NUM> can be made to travel fast within a range that does not cause breakdown of the bead portions <NUM>, the traveling time to the destination can be shortened, and the vehicle <NUM> can go to the destination quickly.

Note that the temperature of the bead portion <NUM> is measured, and speed limiting is executed in a case in which the temperature of the bead portion <NUM> exceeds the upper limit temperature T1 that is set in advance. However, speed limiting may be executed in a case in which the temperature of a region other than the bead portion <NUM> is measured, and the measured temperature of the region exceeds the upper limit temperature T1 that is set in advance.

The temperature of the bead portion <NUM> at the vehicle outer side is measured, but the temperature of the bead portion <NUM> at the vehicle inner side may be measured, or the temperatures of the bead portions <NUM> at both the vehicle outer side and the vehicle inner side may be measured.

A region where it is easy for the rubber to generate heat, or in other words, a region where the strain during traveling is large, for example, the cord end portions (vicinities of the belt ends), the tire maximum width portion, and the like are regions other than the bead portion <NUM>.

For example, in vicinities of the cord end portions of the carcass or the belt, there are portions having and portions not having cords that have a higher Young's modulus than the rubber, and these are portions where the rigidity as a structural body varies sharply and regions where large stress and strain arise when traveling. It is easy for a rise in temperature to occur at such portions where there is large strain. Therefore, by measuring the temperature at such a portion and controlling the traveling speed by using this as a reference, the vicious cycle can be prevented more, and breakdown of the pneumatic tire <NUM> can be suppressed.

Further, in a case of traveling at high speed in a state in which excessive load is applied to the pneumatic tire <NUM>, there are cases in which the tread rubber layer <NUM> generates heat excessively. In cases in which such a situation is envisaged, the temperature at the tread inner surface side may be measured.

Note that, in the vehicle speed control system <NUM>, the place where the temperature of the pneumatic tire <NUM> is measured is not limited to one place, and may be plural places. Further, as needed, the upper limit temperature T1 can be made to differ per region of the pneumatic tire <NUM>.

The vehicle speed control system <NUM> relating to a first embodiment of the present invention is described next in accordance with <FIG> and <FIG>. Note that structures that are the same as those of the first example are denoted by the same reference numerals, and description thereof is omitted.

As illustrated in <FIG>, a so-called side-reinforced-type run-flat tire <NUM> is mounted to the rim 12A of the present embodiment. Side reinforcing rubbers <NUM> are provided at tire side portions <NUM>.

In addition to the thermometer <NUM>, a pressure gauge <NUM> that measures the internal pressure of the tire is provided at the rim 12A. The measured pressure data that is measured by the pressure gauge <NUM> is transmitted from the transmitter <NUM> to the receiver <NUM>. Note that the pressure gauge <NUM> may be mounted to the air valve of the rim 12A.

In the present embodiment, the control device <NUM> controls the speed of the vehicle <NUM> on the basis of measured temperature data and measured pressure data.

Speed control at the vehicle speed control system <NUM> of the present embodiment is described next on the basis of the flowchart illustrated in <FIG>.

By executing speed limiting at the time of run-flat traveling in this way, the side reinforcing rubbers <NUM> becoming high temperature, the rubbers thereof softening and deteriorating, the side reinforcing rubbers <NUM> no longer being able to exhibit their original functions, and traveling becoming impossible due to destruction of the rubbers can be suppressed. Due thereto, the traveling distance at the time of running on a flat can be extended.

Further, in order to inform the driver that speed limiting due to a decrease in internal pressure is carried out, in step <NUM>, a warning by characters or the like may be displayed on the display device <NUM>, or the warning lamp <NUM> may be turned on.

(<NUM>) In next step <NUM>, it is judged whether or not the temperature of the tire inner surface at the tire maximum width portion has become less than or equal to the upper limit temperature T2 at the time of reduced internal pressure that is set in advance. Here, if the temperature of the tire inner surface at the tire maximum width portion has become less than or equal to the upper limit temperature T2 at the time of reduced internal pressure that is set in advance, the routine moves on to step <NUM>, and, if the temperature of the tire inner surface at the tire maximum width portion has not become less than or equal to the upper limit temperature T2 at the time of reduced internal pressure that is set in advance, the routine returns to step <NUM>.

(<NUM>) In step <NUM>, the control device <NUM> cancels the speed limiting. Due thereto, the driver can make the vehicle <NUM> travel at greater than or equal to the speed limit (V2) at the time of reduced internal pressure that is set in advance.

Note that, in order to inform the driver that speed limiting has been cancelled, in step <NUM>, the fact that the speed limiting has been cancelled may be displayed by characters or the like on the display device <NUM>. However, the warning that the internal pressure has decreased is continued.

In this way, by using the vehicle speed control system <NUM> of the present embodiment, at the time of run-flat traveling on the run-flat tire <NUM>, generation of heat of the side reinforcing rubbers <NUM> is suppressed, the vehicle <NUM> can be made to travel fast within a range that does not cause breakdown of the run-flat tire <NUM>, the traveling time to the destination can be shortened, and the vehicle <NUM> can go to the destination quickly.

Note that estimation of the run-flat traveling distance in accordance with an ISO run-flat test was carried out by assuming usage of a side-reinforced-type run-flat tire (tire size: <NUM>/45RF17).

It is assumed that a temperature sensor is affixed to the tire innermost surface side of the portion that juts out furthest toward the outer side in the tire width direction, and that the measured temperature data is transmitted by using a wireless device mounted to the rim wheel, and that measurement can be carried out at an external device, and, under the premise of measuring the traveling distance on a drum tester, the traveling distance at a speed of <NUM>/h until traveling becomes impossible is predicted.

Running is carried out for one hour at a speed of <NUM>/h under ISO testing conditions (ISO <NUM>: <NUM>) that are the certification criterion for run-flat tires.

Estimation of the extent to which the traveling distance is extended when speed limiting is carried out as in the present embodiment on the basis of these test standards, is described hereinafter.

Estimation is carried out under the assumption that, after running at <NUM>/h, at the point in time when the results of temperature measurement become <NUM>, the speed is lowered to <NUM>/h and running is continued.

First, at the drum tester, the test tire is made to run at <NUM>/h, and running is continued until the temperature becomes <NUM>. In a case in which the running time at the time when the temperature reaches <NUM> is <NUM>, the traveling distance is <NUM>/h × <NUM> = <NUM>.

Thereafter, if running is carried out with the speed lowered to <NUM>/h that is half of <NUM>/h, the generation of heat is halved, and therefore, predicting of the traveling distance is carried out by estimating that the traveling distance is <NUM> times that.

Accordingly, assuming that, after running for <NUM> at <NUM>/h, traveling for <NUM> at <NUM>/h is possible, the traveling distance is <NUM> + <NUM>/h × <NUM> = <NUM>, and it can easily be predicted that the traveling distance can be extended by carrying out speed limiting.

Although an embodimen has been described above, the present invention is not limited to the above, and can, of course, be implemented by being modified in various ways other than the above, within a scope that does not depart from the gist thereof.

The vehicle to which the present invention can be applied is not limited to a passenger vehicle, and may be a bus, a truck, construction equipment, a motorcycle, a vehicle of a new transportation system or the like, and can be applied to all vehicles that use pneumatic tires.

In the first embodiment, the pneumatic tire is the side-reinforced-type run-flat tire <NUM>, but the present invention can be applied also to a run-flat tire using a core. In a run-flat tire that uses a core, at the time of run-flat traveling, there are cases in which the outer peripheral surface of the core contacts the tire inner peripheral surface of the tire width direction central portion of the tread, and the tread generates heat. Therefore, the generation of heat at the region that contacts the core can be suppressed by measuring the temperature of the tread inner surface of that tire and carrying out speed control.

In the above-described embodiment, the non-contact-type thermometer <NUM> is mounted to the rim 12A, but the non-contact-type thermometer <NUM> may be mounted to the vehicle body 36A (the wheel house, the suspension or the like) and may measure the tire temperature from the tire outer side.

In the above-described embodiment, an infrared thermometer is used as the thermometer <NUM> in order to measure the temperature of the pneumatic tire <NUM> or the run-flat tire <NUM>, without contact. However, a contact-type thermometer may be mounted to the tire inner surface and the tire temperature measured.

The vehicle speed control systems <NUM> of the above-described embodiment can also be applied to autonomous vehicles in which the vehicle <NUM> can be driven automatically. By incorporating the vehicle speed control system <NUM> into an autonomous vehicle, in a case in which the tire temperature or internal pressure or the like becomes abnormal, the traveling speed of the autonomous vehicle is lowered automatically, and the autonomous vehicle can be made to travel safely.

The vehicle speed control systems <NUM> of the present invention are not limited to vehicles that travel on public roads, and can also be applied to vehicles for racing or the like that make hard use of tires. Due thereto, for example, a tire breaking down and the vehicle becoming unable to travel in the middle of the course can be suppressed, and the vehicle can be made to travel to the pit.

Note that the above embodiment describes examples of suppressing breakdown of the pneumatic tire <NUM> and the run-flat tire <NUM> that use rubber as an elastic body, but the vehicle speed control systems <NUM> can also suppress breakdown of pneumatic tires that use a thermoplastic elastomer as the elastic body.

Claim 1:
A vehicle speed control system (<NUM>) comprising:
a thermometer (<NUM>) measuring a temperature of a tire (<NUM>);
a pressure determining section (<NUM>) that determines an internal pressure of the tire; and
a control device (<NUM>) controlling a speed of a vehicle (<NUM>) based on a measured temperature of the tire obtained by the thermometer;
wherein the control device carries out speed limiting of the vehicle in a case in which the measured temperature exceeds an upper temperature limit (T1) that is set in advance; and
wherein the control device carries out speed limiting of the vehicle in a case in which the internal pressure obtained at the pressure determining section is less than a lower pressure limit (P1), that is set in advance, and the temperature of the tire measured by the thermometer exceeds an upper temperature limit at a time of reduced internal pressure (T2) that is set in advance;
wherein the lower pressure limit is indicative of a puncture of the pneumatic tire.