Vehicle speed control system

Abstract

This vehicle speed control system comprises: a thermometer that measures the temperature of a tire; and a control device that controls the speed of a vehicle on the basis of the measured temperature of the tire obtained by the thermometer.

Description

Technical Field

[0006]

[0001] The present disclosure relates to a vehicle speed control system.

Background Art

[0002] A vehicle behavior control device that detects the state of a tire and controls the running of a vehicle (see, for example, Japanese Patent No. 4466386) is known.

[0003] In this vehicle behavior control device, when a run-flat tire enters the run-flat state, control is performed to reduce the speed of the vehicle.

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the rubber that constitutes a pneumatic tire repeatedly deforms and generates heat due to running. The portion where the deformation (strain, stress) of the rubber is large has a larger amount of heat generation. When the temperature of the rubber becomes excessively high, the rubber may soften, tire deformation may increase, and a vicious cycle in which the tire temperature rises may occur. Therefore, if driving continues in a state where the temperature of the rubber is high, the rubber may ultimately be destroyed, making it difficult for the vehicle to run and possibly unable to reach the destination.

[0005] In the prior art, it is possible to suppress the speed of the vehicle when the tire punctures, but the heat generation of the tire is not considered. For this reason, there is a possibility that driving continues in a state where the rubber of the tire has become excessively hot, and ultimately the tire is assumed to fail. Also, in the prior art, the speed of the vehicle may be excessively suppressed in order to control the behavior of the vehicle, which may also extend the driving time to the destination.

[0006] To prevent rubber breakdown, it is necessary to suppress the heat generated by the rubber. Furthermore, if the speed can be increased within a range that suppresses rubber heat generation to prevent the above vicious cycle from occurring, it will be possible to reach the destination without tire failure and shorten the travel time to the destination.

[0007] This disclosure aims to provide a vehicle speed control system that takes the above facts into consideration, takes tire temperature into account, and can shorten the travel time to the destination without causing tire failure. [Means for solving the problem]

[0008] A vehicle speed control system according to the first embodiment includes a thermometer for measuring the temperature of a tire, and a control device for controlling the speed of the vehicle based on the measured temperature of the tire obtained by the thermometer.

[0009] In the vehicle speed control system according to the first embodiment, the thermometer can measure the temperature of the tire. The control device can control the vehicle's speed based on the tire temperature measured by a thermometer.

[0010] The elastic materials that make up tires, such as rubber, deform elastically during driving, generating heat and raising their temperature. If the rubber temperature rises excessively, it softens. When the rubber softens, tire deformation increases, which can lead to a vicious cycle where the rubber temperature rises even further. Furthermore, if the rubber temperature rises excessively, it can deteriorate or even break down, leading to a decrease in tire durability.

[0011] In the vehicle speed control system according to the first embodiment, the control device controls the vehicle speed based on the measured temperature of the tire to prevent the above-mentioned vicious cycle from occurring, thereby suppressing the overheating of the rubber. By suppressing the overheating of the rubber in this way, the above-mentioned vicious cycle is suppressed, the speed can be increased within a range that does not cause tire failure, and the travel time to the destination can be shortened without causing tire failure. [Effects of the Invention]

[0012] As explained above, the vehicle speed control system of this disclosure takes tire temperature into consideration and can shorten the travel time to the destination without causing tire failure. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view along the tire rotation axis showing a tire-rim wheel assembly used in a vehicle speed control system according to the first embodiment. [Figure 2A] This is a block diagram showing the overall configuration of the vehicle speed control system according to the first embodiment. [Figure 2B] This is a block diagram showing the schematic configuration of a control device for a vehicle speed control system according to the first embodiment. [Figure 3] This is a flowchart showing the control of the vehicle speed control system according to the first embodiment. [Figure 4] This is a cross-sectional view along the tire rotation axis showing a tire-rim-wheel assembly used in a vehicle speed control system according to the second embodiment. [Figure 5] This is a flowchart showing the control of the vehicle speed control system according to the second embodiment. [Modes for carrying out the invention]

[0014] [First Embodiment] A vehicle 36 to which the vehicle speed control system 8 according to the first embodiment of this disclosure is applied will be described with reference to Figures 1 to 3. As shown in Figure 1, the tire-rim-wheel assembly 10 of this embodiment, provided on the vehicle 36 (not shown in Figure 1; see Figure 2A), has a pneumatic tire 14 mounted on the rim 12A of the rim wheel 12. The pneumatic tire 14 in this embodiment is a standard passenger car tire. In Figure 1, the arrow IN indicates the direction towards the inside of the vehicle, and the arrow OUT indicates the direction towards the outside of the vehicle.

[0015] The pneumatic tire 14 of the present embodiment includes a carcass 18 that straddles a pair of bead portions 16 in a toroidal shape. The carcass 18 of the present embodiment is composed of a single carcass ply 18P in which a plurality of cords are arranged parallel to each other and rubber-coated.

[0016] On the outer side in the tire radial direction of the carcass 18, in the present embodiment, a belt 20 composed of two belt plies, a first belt ply 20A and a second belt ply 20B, is disposed.

[0017] Note that the end portions of the belt 20 are covered with a belt reinforcing layer 22.

[0018] A tread rubber layer 24 is disposed on the outer side in the tire radial direction of the belt 20. Also, a side rubber layer 26 is disposed on the outer side in the tire axial direction of the carcass 18.

[0019] At the bead core 28 of the bead portion 16, the end portion of the carcass ply 18P is wound upward in the tire radial direction.

[0020] Here, the portion from one bead core 28 to the other bead core 28 of the carcass ply 18P is defined as a main body portion 18A, and the wound-up portion extending outward in the tire radial direction from the bead core 28 is defined as a wound-up portion 18B. Between the main body portion 18A and the wound-up portion 18B of the carcass ply 18P, a bead filler 30 made of high-hardness rubber extending outward in the tire radial direction from the bead core 28 is disposed.

[0021] A thermometer 32 and a transmitter 34 are attached to the outer peripheral portion of the rim 12A. The thermometer 32 is, as an example, a non-contact infrared radiation thermometer.

[0022] As shown in FIG. 2A, the temperature measurement data measured by the thermometer 32 is wirelessly transmitted by the transmitter 34 to a receiver 38 provided on the vehicle body 36A.

[0023] A control device 40 for controlling the output of the engine 36B is provided on the vehicle body 36A.

[0024] Figure 2B shows a schematic configuration of a control device 40 that can function as a vehicle speed control device as an example. The control device 40 can be applied, for example, to an engine control computer installed in a vehicle 36 such as an automobile.

[0025] The control unit 40 is composed of a computer including a CPU 40A, RAM 40B, ROM 40C, and I / O 40D, which are examples of hardware processors. The CPU 40A, RAM 40B, ROM 40C, and I / O 40D are connected to a bus 40E so that data and commands can be sent and received. The ROM 40C also stores an arithmetic program 40F.

[0026] Additionally, the I / O42D is connected to the engine (fuel injection system) 36B, receiver 38, display device 42, warning lamp 50, and other components. The temperature measurement data transmitted by the transmitter 34 is sent to the control device 40 via the receiver 38. The display device 42 is located on the instrument panel of the vehicle 36 and can display various information related to the vehicle 36.

[0027] The ROM 40C of the control device 40 has pre-stored information such as the upper limit temperature T1 of the pneumatic tire 14, the lower limit pressure P1 of the pneumatic tire 14, and the upper limit temperature T2 when the internal pressure drops. In the control device 40, the CPU 40A reads the arithmetic program 40F stored in the ROM 40C, loads it into the RAM 40B, and then executes the loaded arithmetic program 40F.

[0028] (Effect, Action) Next, the speed control in the vehicle speed control system 8 of this embodiment will be explained based on the flowchart shown in Figure 3.

[0029] (1) In step 100, the thermometer 32 starts measuring the temperature of the inner surface of the tire bead 16. The temperature measurement data measured by the thermometer 32 is transmitted wirelessly to the receiver 38 by the transmitter 34. For example, the temperature measurement starts when the ignition key of the vehicle 36 (the main power switch of the vehicle 36) is turned on and continues until it is turned off.

[0030] (2) In step 102, it is determined whether the measured temperature of the bead portion 16 exceeds the preset upper limit temperature T1. If the measured temperature of the bead portion 16 exceeds the preset upper limit temperature T1, the process proceeds to step 104; otherwise, the process returns to step 102.

[0031] (3) In step 104, the control device 40 implements a speed limit. When a speed limit is implemented, the engine 36B is controlled so that even if the driver presses the accelerator of the vehicle 36, the vehicle 36 will not exceed the preset speed limit (V1). This makes it possible to suppress the heat generation of the bead portion 16 (especially the bead filler 30) and to lower the temperature of the bead portion 16.

[0032] By implementing speed restrictions in this manner, it is possible to suppress the bead portion 16 from becoming too hot, which can cause the rubber of the bead filler 30 to soften or deteriorate, thereby ensuring the durability of the bead portion 16.

[0033] In addition, in step 104, a warning message such as text may be displayed on the display device 42, or the warning lamp 50 may be illuminated, in order to inform the driver that a speed limit has been imposed.

[0034] (4) In the next step 106, it is determined whether the temperature of the bead portion 16 has fallen below the preset upper limit temperature T1. If the temperature of the bead portion 16 has fallen below the preset upper limit temperature T1, the process proceeds to step 108. If the temperature of the bead portion 16 has not fallen below the preset upper limit temperature T1, the process returns to step 106.

[0035] (5) In step 108, the control device 40 releases the speed limit. This allows the driver to drive the vehicle 36 at or above the preset speed limit (V1).

[0036] Thus, by using the vehicle speed control system 8 of this embodiment, when the pneumatic tire 14 is in motion, the heat generation of the bead portion 16 is suppressed, and the vehicle 36 can be driven faster within a range that does not cause damage to the bead portion 16, thereby shortening the travel time to the destination and allowing the vehicle to reach its destination sooner.

[0037] In this embodiment, the temperature of the bead portion 16 is measured, and speed restriction is implemented when the temperature of the bead portion 16 exceeds a preset upper limit temperature T1. However, the temperature of a part other than the bead portion 16 may be measured, and speed restriction may be implemented when the temperature of the measured part exceeds a preset upper limit temperature T1.

[0038] In this embodiment, the temperature of the bead portion 16 on the outside of the vehicle was measured, but the temperature of the bead portion 16 on the inside of the vehicle may also be measured, or the temperature of both the outside and inside bead portions 16 may be measured.

[0039] Other areas besides the bead section 16 include areas where the rubber is prone to generating heat, in other words, areas where there is significant deformation during driving, such as the cord ends (near the belt ends) and the widest part of the tire.

[0040] For example, near the ends of the cords in the carcass and belt, there are areas with and without cords that have a higher Young's modulus than rubber, resulting in a rapid change in structural rigidity. These areas experience significant stress and strain during driving. Such areas of high strain are prone to temperature increases. Therefore, by measuring the temperature in these areas and using this as a reference to limit the driving speed, a vicious cycle can be prevented, and failures of the pneumatic tire 14 can be suppressed.

[0041] Furthermore, if the pneumatic tire 14 is subjected to excessive load during high-speed driving, the tread rubber layer 24 may overheat. In cases where such a situation is anticipated, the temperature of the inner surface of the tread may be measured.

[0042] In the vehicle speed control system 8 of this embodiment, the location for measuring the temperature of the pneumatic tire 14 is not limited to one location, but may be multiple locations. Also, the upper limit temperature T1 can be varied for each part of the pneumatic tire 14 as needed.

[0043] [Second Embodiment] Next, a vehicle speed control system 8 according to the second embodiment of this disclosure will be described with reference to Figures 4 and 5. Components identical to those in the first embodiment are denoted by the same reference numerals, and their descriptions are omitted.

[0044] As shown in Figure 4, a so-called side-reinforced run-flat tire 15 is mounted on the rim 12A of this embodiment. Side-reinforcement rubber 44 is provided on the tire side portion 43.

[0045] In addition to the thermometer 32, the rim 12A is equipped with a pressure gauge 46 for measuring the internal pressure of the tire. The pressure measurement data measured by the pressure gauge 46 is transmitted from the transmitter 34 to the receiver 38. The pressure gauge 46 may also be attached to the air valve of the rim 12A.

[0046] In this embodiment, the control device 40 controls the speed of the vehicle 36 based on temperature measurement data and pressure measurement data. The program is

[0047] Next, the speed control in the vehicle speed control system 8 of this embodiment will be explained based on the flowchart shown in Figure 5.

[0048] (1) In step 200, the pressure gauge 46 starts measuring the internal pressure of the tire. The internal pressure measurement data is transmitted to the receiver 38 by the transmitter 34. For example, the measurement of the internal pressure of the tire starts when the ignition key of the vehicle 36 (the main power switch of the vehicle 36) is turned on and continues until it is turned off.

[0049] (2) In step 202, it is determined whether the measured internal pressure is less than the preset lower limit pressure P1. If the measured internal pressure is less than the preset lower limit pressure P1, proceed to step 204; otherwise, return to step 202. One example of a situation where the internal pressure falls below the predetermined lower limit pressure P1 is when the pneumatic tire 14 has a puncture.

[0050] (3) In step 204, the temperature of the inner surface of the tire at the widest part of the tire (where the side reinforcement rubber 44 is thickest) is measured by the thermometer 32. The temperature measurement data is transmitted to the receiver 38 by the transmitter 34. In step 204, in order to inform the driver that the internal pressure of the tire has decreased, a warning message such as text may be displayed on the display device 42, or the warning lamp 50 may be illuminated.

[0051] (4) In step 206, it is determined whether the temperature of the inner surface of the tire at the widest part of the tire measured exceeds the preset upper limit temperature T2 when the internal pressure drops. If the temperature of the inner surface of the tire at the widest part of the tire measured exceeds the preset upper limit temperature T2 when the internal pressure drops, proceed to step 208; otherwise, return to step 206.

[0052] (5) In step 208, the control device 40 implements a speed limit. As a result, even if the driver presses the accelerator of the vehicle 36, the vehicle 36 will not exceed the preset internal pressure drop speed limit (V2). This suppresses the heat generation of the side reinforcement rubber 44, and makes it possible to lower the temperature of the side reinforcement rubber 44 to below the preset internal pressure drop upper temperature T2.

[0053] In this way, by implementing a speed limit during run-flat driving, it is possible to prevent the side reinforcement rubber 44 from becoming too hot, softening, deteriorating, or failing to perform its intended function, thus preventing the vehicle from becoming inoperable due to rubber failure. This allows for an extension of the driving range during run-flat driving.

[0054] Furthermore, in order to inform the driver that a speed limit has been imposed due to a drop in internal pressure, a warning message such as text may be displayed on the display device 42, or the warning lamp 50 may be illuminated in step 208.

[0055] (6) In the next step 210, it is determined whether the temperature of the inner surface of the tire at the widest point of the tire has fallen below the preset upper limit temperature T2 when the internal pressure drops. If the temperature of the inner surface of the tire at the widest point of the tire has fallen below the preset upper limit temperature T2 when the internal pressure drops, the process proceeds to step 212. If the temperature of the inner surface of the tire at the widest point of the tire has not fallen below the preset upper limit temperature T2 when the internal pressure drops, the process returns to step 210.

[0056] (7) In step 212, the control device 40 releases the speed limit. This allows the driver to drive the vehicle 36 at or above the preset internal pressure drop speed limit (V2). Furthermore, in order to inform the driver that the speed limit has been lifted, the display device 42 may display text or other information indicating that the speed limit has been lifted in step 212. However, the warning regarding the decrease in internal pressure should continue.

[0057] Thus, by using the vehicle speed control system 8 of this embodiment, when the run-flat tire 15 is running in a run-flat state, the heat generation of the side reinforcement rubber 44 is suppressed, and the vehicle 36 can be driven faster within a range that does not cause damage to the run-flat tire 15, thereby shortening the travel time to the destination and allowing the vehicle to reach its destination sooner.

[0058] Furthermore, assuming the use of side-reinforced run-flat tires (tire size: 225 / 45RF17), we conducted an estimate of the run-flat driving distance in accordance with ISO run-flat test standards. A temperature sensor is attached to the innermost side of the tire at the outermost part in the tire width direction. Temperature measurement data is transmitted using a wireless device attached to the rim wheel, and measurements can be taken by an external device. Assuming that the mileage is measured using a drum testing machine, the mileage until the vehicle becomes inoperable is predicted at a speed of 80 km / h.

[0059] According to the ISO test conditions (ISO 16992:2018) that serve as the certification standard for run-flat tires, the test involves driving at a speed of 80 km / h for one hour. Based on these test standards, the following is an estimate of how much the driving distance will increase when a speed limit is imposed as in this embodiment. The estimate was based on the assumption that after driving at 80 km / h, the speed would be reduced to 40 km / h once the temperature measurement reached 140°C, and driving would continue.

[0060] First, the test tire was driven at 80 km / h on a drum testing machine until its temperature reached 140°C. Continue driving until the temperature reaches 140°C. If the driving time is 0.5 hours, the distance traveled is 80 km / h × 0.5 hours = 40 km. After that, if you reduce the speed to half of 80 km / h, which is 40 km / h, the heat generated will be halved. Therefore, the estimated mileage was calculated based on the assumption that the mileage would double. Therefore, if it is possible to travel at 80 km / h for 0.5 hours and then at 40 km / h for 1 hour, the total distance traveled would be 40 km + 40 km / h × 1 hour = 120 km. It is easy to see that the distance traveled can be extended by imposing a speed limit.

[0061] [Other embodiments] Although two embodiments of this disclosure have been described above, this disclosure is not limited to those described above, and it is of course possible to implement it in various modified forms without departing from its spirit.

[0062] For example, in the run-flat tire 15, control may be performed by combining the control of the first embodiment and the control of the second embodiment.

[0063] Furthermore, the vehicles to which this disclosure can be applied are not limited to passenger cars, but may also include buses, trucks, construction machinery, motorcycles, vehicles of new transportation systems, etc., and can be applied to all vehicles that use pneumatic tires.

[0064] In the second embodiment, the pneumatic tire was a side-reinforced run-flat tire 15, but this disclosure is also applicable to run-flat tires using a core. In run-flat tires using a core, the outer surface of the core may come into contact with the inner surface of the tire at the center of the tread in the tire width direction during run-flat driving, causing the tread to heat up. Therefore, by measuring the temperature of the inner surface of the tire tread and controlling the speed, it is possible to suppress the heat generation at the part in contact with the core.

[0065] In the above embodiment, a non-contact thermometer 32 was attached to the rim 12A, but the non-contact thermometer 32 may also be attached to the vehicle body 36A (wheel well, suspension, etc.) to measure the tire temperature from the outside of the tire.

[0066] In the above embodiment, an infrared radiation thermometer was used in the thermometer 32 to measure the temperature of the pneumatic tire 14 or run-flat tire 15 in a non-contact manner. However, a contact-type thermometer may also be attached to the inner surface of the tire to measure the tire temperature.

[0067] The vehicle speed control system 8 of the above embodiment can also be applied to an autonomous vehicle (autonomous vehicle) (vehicle 36). By incorporating the vehicle speed control system 8 into an autonomous vehicle, if the tire temperature, internal pressure, etc. become abnormal, the driving speed of the autonomous vehicle can be automatically suppressed, making it possible to drive the autonomous vehicle safely.

[0068] The vehicle speed control system 8 disclosed herein can be applied not only to vehicles that travel on public roads, but also to racing vehicles that put heavy stress on their tires. This makes it possible to prevent, for example, a tire failure midway through a race, which would render the vehicle unable to continue, and to allow the vehicle to reach the pit.

[0069] In the above embodiment, examples were described for suppressing failures of pneumatic tires 14 and run-flat tires 15 using rubber as the elastic material. However, the vehicle speed control system 8 of this embodiment can also suppress failures of pneumatic tires using thermoplastic elastomer as the elastic material.

[0070] In the above embodiment, a puncture (decrease in internal pressure) was detected by directly measuring the internal pressure of the pneumatic tire 14 with a pressure gauge 46. However, a decrease in the internal pressure of the pneumatic tire 14 is not limited to direct measurement with a pressure gauge 46; it can also be detected indirectly by changes in the rotational speed of the pneumatic tire 14 (comparison with other tires), etc. A decrease in the internal pressure of the pneumatic tire 14 can be detected using a known indirect TPMS (Tire Pressure Monitoring System). [Explanation of Symbols]

[0071] The disclosure of Japanese Patent Application No. 2020-176887, filed on 21 October 2020, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. A vehicle speed control system applied to run-flat tires, A thermometer to measure the temperature of the tires, A control device that controls the vehicle speed based on the measured temperature of the tire obtained by the thermometer, A pressure determination unit that determines the internal pressure of the tire, Equipped with, The control device is If the internal pressure obtained by the pressure determination unit is less than a preset lower limit pressure, and the tire temperature measured by the thermometer exceeds a preset upper limit temperature for internal pressure drop, the vehicle's speed limit will be imposed. The aforementioned lower limit pressure is the internal pressure at the time of tire puncture. The control device further releases the speed limit after the speed limit has been imposed, if the measured temperature falls below the upper limit temperature during internal pressure reduction. Vehicle speed control system.

2. The thermometer measures the temperature of the bead portion of the tire. The vehicle speed control system according to claim 1.

3. The thermometer measures the temperature of the tire surface closest to the end of the tire belt. A vehicle speed control system according to claim 1 or claim 2.

4. The vehicle speed control system according to any one of claims 1 to 3, wherein the thermometer is a non-contact thermometer and is provided on the rim on which the tire is mounted.

5. A transmitter provided on the rim transmits temperature measurement data measured by the thermometer, A receiver provided on the vehicle body for receiving the temperature measurement data, The control device provided on the vehicle body, Having, A vehicle speed control system according to any one of claims 1 to 4.

6. The pressure determination unit has a pressure gauge provided on the rim on which the tire is mounted. The transmitter transmits pressure measurement data measured by the pressure gauge. The vehicle speed control system according to claim 5.

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