Vehicle speed limiting device

Abstract

To provide a vehicle speed limiting device capable of suppressing the occurrence of a fade phenomenon.SOLUTION: A vehicle speed limiting device that imposes limits on a vehicle speed of a vehicle includes: a rotation speed measurement unit which measures the rotation speed of a drive source mounted on the vehicle; a weight measurement unit which measures the vehicle weight of the vehicle; a gradient information acquisition unit which acquires gradient information about the road surface gradient during travel of the vehicle; a deceleration torque measurement unit which measures the deceleration torque of the drive source; a vehicle speed measurement unit which measures the vehicle speed of the vehicle; and a vehicle speed limiting unit which limits the vehicle speed of the vehicle. The vehicle speed limiting unit controls the drive source so as to limit the vehicle speed if the deceleration energy of the vehicle calculated from the rotation speed of the drive source, vehicle weight, road surface gradient, deceleration torque, and vehicle speed is equal to or greater than a prescribed value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle speed limiting device. [Background technology]

[0002] For example, when driving down a long slope, excessive use of the foot brake causes the brake pads to overheat, reducing the coefficient of friction and resulting in a fade phenomenon that reduces the braking force. Regarding this fade phenomenon, technologies for providing an early warning to the driver are known, such as those described in the following Patent Documents 1 and 2. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Public Relations No. 7-19042 [Patent Document 2] JP2005-226659 Public Relations Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, even if a fade warning is given in advance as in Patent Documents 1 and 2, depending on the driver's skill, the driver may continue to use the foot brake excessively.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a vehicle speed limiting device that can suppress the occurrence of the fade phenomenon. [Means for solving the problem]

[0006] The present invention has been made to solve at least some of the problems described above, and can be realized in the following aspects or application examples.

[0007] The vehicle speed limiting device of this application example is a vehicle speed limiting device that sets a limit on the vehicle speed, and includes a rotation speed measuring unit that measures the rotation speed of a driving source mounted on the vehicle, a weight measuring unit that measures the vehicle weight of the vehicle, a gradient information acquisition unit that acquires gradient information related to the road surface gradient while the vehicle is traveling, a deceleration torque measuring unit that measures the deceleration torque of the driving source, a vehicle speed measuring unit that measures the vehicle speed of the vehicle, and a vehicle speed limiting unit that limits the vehicle speed of the vehicle, wherein the vehicle speed limiting unit controls the driving source to limit the vehicle speed when the deceleration energy of the vehicle calculated from the rotation speed of the driving source, the vehicle weight, the road surface gradient, the deceleration torque, and the vehicle speed is equal to or greater than a predetermined value.

[0008] According to this application example, by limiting the vehicle speed when the deceleration energy of the vehicle is equal to or greater than a predetermined value, braking by the brake mechanism (foot brake) is suppressed, and the fade phenomenon can be prevented in advance. In this way, by limiting the vehicle speed as necessary, excessive use of the brake mechanism can be suppressed, and the occurrence of the fade phenomenon can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a configuration of a vehicle. [Diagram 2] FIG. 4 is a flow chart showing an example of the operation of the vehicle speed limiting device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] 1. Configuration of the vehicle speed limiter Fig. 1 is a schematic diagram showing the configuration of a vehicle 10. Fig. 1 also shows, in a block diagram, the electrical configuration of a vehicle speed limiting device 40 provided in the vehicle 10. Hereinafter, the vehicle 10 provided with the vehicle speed limiting device 40 will be described with reference to Fig. 1.

[0011] The vehicle 10 is an engine-powered truck. In other words, the vehicle 10 has, as a drive system configuration, an internal combustion engine 12 that is a drive source, a transmission 14 that transmits the driving force of the engine 12 to wheels 22, a propeller shaft 16, a differential 18, and axles (wheel shafts) 20.

[0012] The engine 12 is, for example, a diesel engine. The driving force generated by the engine 12 is transmitted to the inside of an axle 20 via a transmission 14, a propeller shaft 16, a differential 18, etc., and drives wheels 22. For this reason, the wheels 22 are also called driving wheels.

[0013] Although FIG. 1 shows only driving wheels as the wheels 22, the vehicle 10 also includes other driven wheels (not shown).

[0014] The vehicle 10 also includes a brake pedal (foot brake) 24 and a brake mechanism 26. The brake mechanism 26 corresponds to a drum brake type, but may also be a disc brake type. The amount of operation of the brake pedal 24 is correlated with the brake pressure generated by the brake mechanism 26, that is, the braking force. Therefore, the greater the amount of operation of the brake pedal 24, the greater the braking force generated by the brake mechanism 26. The vehicle may also be equipped with an auxiliary brake (exhaust brake, retarder, etc.) that is independent of the operation of the brake pedal 24.

[0015] Furthermore, the vehicle 10 includes a shift mechanism 28. In the shift mechanism 28, for example, gear shifting is possible by operating a shift lever. The shift mechanism 28 in this embodiment is of an automatic type, and is capable of selecting, for example, a parking range (P range), a reverse range (R range), a neutral range (N range), a drive range (D range), a first range (first-speed range), and a second range (second-speed range). Note that the shift mechanism 28 is not limited to an automatic type, and may be of a so-called manual type in which the driver directly selects and operates each gear stage.

[0016] Furthermore, the vehicle 10 is equipped with a vehicle speed limiting device 40. The vehicle speed limiting device 40 is a device for setting a limit on the vehicle speed of the vehicle 10, and includes a navigation unit 42, an RPM sensor 44, a shift sensor 46, a weight sensor 48, a gradient sensor 50, a vehicle speed sensor 52, a brake sensor 54, an ECU (Electronic Control Unit) 56, and a memory unit 58.

[0017] The ECU 56 is connected to each of the navigation unit 42, the RPM sensor 44, the shift sensor 46, the weight sensor 48, the gradient sensor 50, the vehicle speed sensor 52, the brake sensor 54, and the memory unit 58, etc., so as to be able to communicate with each other via a CAN (Controller Area Network) communication means.

[0018] The navigation unit 42 is equipped with a GPS (Global Positioning System) (not shown), and uses the GPS and map information to appropriately acquire and present information regarding the current position of the vehicle 10, the distance from the current position to the destination, and the terrain on which the vehicle 10 is traveling.

[0019] An application software included in an information processing terminal such as a smartphone or a tablet, or a terminal equipped with a dedicated car navigation system may be used as the navigation unit 42. The map information is stored in advance in the navigation unit 42 or the storage unit 58.

[0020] The map information also includes altitude information. Therefore, the navigation unit 42 can use the GPS and the map information to obtain gradient information, which is information about the gradient of the road surface on which the vehicle 10 is traveling.

[0021] The rotation speed sensor 44 measures the rotation speed of the engine 12, which is a drive source. The rotation speed sensor 44 measures the rotation speed of, for example, a flywheel, a camshaft, a crank pulley, or the like (not shown).

[0022] The shift sensor 46 detects the shift position selected by the shift mechanism 28. From the shift position detected by the shift sensor 46, the current gear ratio in the transmission 14 can be detected.

[0023] The weight sensor 48 measures the weight of the vehicle 10. Specifically, the weight sensor 48 measures the weight of the cargo on the vehicle 10 and adds the weight of the vehicle 10 itself to the weight to measure the current weight of the vehicle 10. The weight of the vehicle 10 itself can also be estimated by the ECU 56 from an equation of motion using the gradient sensor 50, the vehicle speed sensor 52, etc., and is stored in advance as data in the storage unit 58. The weight sensor 48 is provided, for example, on a suspension (not shown) of the vehicle 10.

[0024] The gradient sensor 50 measures the gradient of the road surface on which the vehicle 10 runs. The gradient sensor 50 is a sensor that detects the degree of inclination of the vehicle 10, for example.

[0025] The vehicle speed sensor 52 measures the vehicle speed of the vehicle 10. Specifically, the vehicle speed sensor 52 measures the number of rotations of the drive train that rotates as the vehicle 10 travels, and then measures the current vehicle speed of the vehicle 10 based on the number of rotations of the wheels 22 or the number of rotations of the output shaft, for example. In addition, the brake sensor 54 measures the amount of operation of the brake pedal 24.

[0026] The ECU 56 is an information processing unit that executes various processes in the vehicle 10. The ECU 56 may be composed of only a CPU (Central Processing Unit), or may be configured to further include a storage unit 58, for example.

[0027] The storage unit 58 is composed of a volatile memory such as a random access memory (RAM) and a non-volatile memory such as an embedded multi media card (eMMC). Programs and data for implementing the operations of various components of the vehicle 10 are stored in the storage unit 58, and are read out by the ECU 56 as necessary. Data output from the various components is stored in the storage unit 58 by the ECU 56.

[0028] The ECU 56 executes the programs stored in the memory unit 58 to function as a deceleration torque measurement unit 60, a deceleration energy calculation unit 62, and a vehicle speed restriction unit 64.

[0029] The deceleration torque measurement unit 60 measures the deceleration torque that acts to decelerate the vehicle speed of the vehicle 10. The deceleration torque measurement unit 60 acquires the output results of the various sensors described above, and calculates the indirect deceleration torque due to auxiliary brakes such as the engine brake, and the direct deceleration torque due to the brake mechanism 26. Note that, in addition to the engine brake, there are also exhaust brakes, retarders, and the like as auxiliary brakes, but in this embodiment, the engine brake will be used as a representative example to simplify the explanation.

[0030] Specifically, the deceleration torque measuring unit 60 obtains information on the current engine speed, gear ratio of the transmission 14, vehicle weight, road surface gradient, and vehicle speed from, for example, the rotation speed sensor 44, the shift sensor 46, the weight sensor 48, the gradient sensor 50, and the vehicle speed sensor 52, and calculates the load (deceleration torque) generated by the engine brake during deceleration.

[0031] In addition, the deceleration torque measurement unit 60 acquires information on the current vehicle weight, road surface gradient, vehicle speed, and brake operation amount from, for example, the weight sensor 48, gradient sensor 50, vehicle speed sensor 52, and brake sensor 54, and calculates the load (deceleration torque) generated by the brake mechanism 26 during deceleration. The deceleration torque measurement unit 60 may calculate the deceleration torque from a preset calculation formula, or may calculate it from a relationship map stored in the storage unit 58.

[0032] The deceleration energy calculation unit 62 measures the amount of deceleration energy that acts to decelerate the vehicle speed of the vehicle 10. The deceleration energy calculation unit 62 calculates the deceleration energy by acquiring the deceleration torque calculated by the deceleration torque measurement unit 60 as well as output results from the navigation unit 42, the rotation speed sensor 44, the weight sensor 48, the gradient sensor 50, the vehicle speed sensor 52, the deceleration torque measurement unit 60, etc. Specifically, the deceleration energy calculation unit 62 extracts downhill roads on the travel route from the navigation unit 42, acquires distance information and gradient information of the downhill roads, and calculates the deceleration energy required to descend the slope while maintaining a predetermined speed (e.g., legal speed) from the current vehicle speed. For example, the deceleration energy calculation unit 62 calculates the final deceleration energy by subtracting the deceleration energy required to maintain a predetermined speed using only the auxiliary brake until the vehicle reaches the bottom of the downhill road (deceleration torque by the auxiliary brake × distance downhill) from the deceleration energy required to maintain a predetermined speed using only the brake mechanism 26 until the vehicle reaches the bottom of the downhill road (deceleration torque by the auxiliary brake × distance downhill).

[0033] The vehicle speed limiting unit 64 limits the vehicle speed of the vehicle 10. Specifically, the vehicle speed limiting unit 64 acquires the output result of the deceleration energy calculation unit 62, i.e., the deceleration energy, and controls the engine 12 to limit the vehicle speed of the vehicle 10 if the deceleration energy is equal to or greater than a predetermined value.

[0034] As described above, the deceleration energy calculated by the deceleration energy calculation unit 62 is the difference between the deceleration energy caused by the brake mechanism 26 and the deceleration energy caused by the auxiliary brake. The deceleration energy caused by the brake mechanism 26 corresponds to energy in a direction that heats the friction material of the brake mechanism 26, while the deceleration energy caused by the auxiliary brake is energy in a direction that cools the friction material of the brake mechanism 26. Therefore, when the deceleration energy, which is the difference, is positive, it is not possible to maintain a predetermined speed using only the auxiliary brake, and heating of the brake mechanism 26 is involved. It is known that when the friction material of the brake mechanism 26 reaches or exceeds a predetermined temperature, a fade phenomenon occurs.

[0035] Therefore, the predetermined value of the deceleration energy in the vehicle speed limiting unit 64 is preferably set to, for example, a value corresponding to the temperature at which fade occurs in the brake mechanism 26. In other words, if the deceleration energy calculated by the deceleration energy calculation unit 62 is less than the predetermined value, it means that the vehicle can descend a slope without fade occurring. On the other hand, if the deceleration energy calculated by the deceleration energy calculation unit 62 is equal to or greater than the predetermined value, it means that there is a possibility that fade will occur, and therefore the vehicle speed limiting unit 64 limits the vehicle speed to reduce the deceleration energy.

[0036] The vehicle speed limit by the vehicle speed limiting unit 64, for example, limits the vehicle speed until the deceleration energy calculated by the deceleration energy calculation unit 62 becomes equal to or less than a predetermined value. A vehicle speed limit map is stored in the storage unit 58, in which the degree of the vehicle speed limit is set to increase according to the degree to which the deceleration energy exceeds a predetermined value, and the vehicle speed limiting unit 64 limits the vehicle speed of the vehicle 10 according to the vehicle speed limit map. By limiting the vehicle speed in this way, the shift mechanism 28 can select a lower gear, and the deceleration energy by the auxiliary brake can be increased. Specifically, the vehicle speed limit can be limited by, for example, forcing the brake mechanism 26 to operate the shift mechanism 28 to a lower gear stage regardless of the brake pedal operation, limiting the amount of fuel injected into the engine 12, or limiting the amount of intake air.

[0037] 2. Flowchart Fig. 2 is a flow diagram showing an example of the operation of the vehicle speed limiting device 40. The flow shown in Fig. 2 is started, for example, when the engine 12 of the vehicle 10 starts.

[0038] In step S1, the deceleration energy calculation unit 62 of the ECU 56 extracts a downhill road on the travel route from the navigation unit 42. Note that the deceleration energy calculation unit 62 may return the flow while a downhill road with a predetermined gradient or more is not extracted within a predetermined distance on the travel route.

[0039] In step S2, the deceleration energy calculation unit 62 of the ECU 56 calculates the deceleration energy on the extracted downhill road. Specifically, the deceleration energy calculation unit 62 acquires the output results of the deceleration torque measurement unit 60, the navigation unit 42, the rotation speed sensor 44, the weight sensor 48, the gradient sensor 50, the vehicle speed sensor 52, and the deceleration torque measurement unit 60, and calculates the deceleration energy as described above.

[0040] In step S3, the vehicle speed limiting unit 64 of the ECU 56 determines whether the deceleration energy calculated in step S2 is equal to or greater than a predetermined value. If the determination in step S2 is "NO", that is, if the deceleration energy is less than the predetermined value, the vehicle speed limiting unit 64 proceeds to step S4. If the determination in step S2 is "YES", that is, if the deceleration energy is equal to or greater than the predetermined value, the vehicle speed limiting unit 64 proceeds to step S5.

[0041] In step S4, the vehicle speed limiting unit 64 does not limit the vehicle speed. Specifically, if the vehicle speed limiting unit 64 is not imposing a vehicle speed limit at this point, the vehicle speed limiting unit 64 returns the flow as is. On the other hand, if the vehicle speed limiting unit 64 is imposing a vehicle speed limit at this point, the vehicle speed limiting unit 64 cancels the vehicle speed limit and returns the flow.

[0042] In step S5, the vehicle speed limiting unit 64 limits the vehicle speed of the vehicle 10. Specifically, the vehicle speed limiting unit 64 limits the vehicle speed to a predetermined vehicle speed by forcibly driving the brake mechanism 26 regardless of the brake pedal operation, operating the shift mechanism 28 to a lower gear, limiting the amount of fuel injected into the engine 12, or limiting the amount of intake air, in accordance with the vehicle speed limit map, and then returns the flow.

[0043] According to such a vehicle speed limiting device 40, when the deceleration energy on a downhill road on the travel route is equal to or greater than a predetermined value, the vehicle speed of the vehicle 10 is limited, thereby forcibly driving the brake mechanism 26 regardless of the brake pedal operation, operating the shift mechanism 28 to a lower gear stage, or suppressing braking by the brake mechanism 26, thereby preventing the fade phenomenon from occurring. Therefore, by limiting the vehicle speed as necessary, excessive use of the brake mechanism 26 can be suppressed, and the occurrence of the fade phenomenon can be suppressed.

[0044] It should be noted that the specific configuration shown in this embodiment is merely an example, and the aspects of the present invention are not limited to the configuration shown in this embodiment.

[0045] For example, the gradient information used by the deceleration energy calculation unit 62 to calculate the deceleration energy is not limited to gradient information acquired by the navigation unit 42, and gradient information acquired by the gradient sensor 50 may be used.

[0046] In the above embodiment, a truck is used as an example of the vehicle 10, but the vehicle to which the vehicle speed limiting device of the present invention is applied is not limited to a truck, and may be, for example, a bus or a passenger car. In the above embodiment, the vehicle 10 uses an engine as a drive source, but the vehicle is not limited to this, and may be an electric vehicle or a fuel cell vehicle using an electric motor, or a hybrid vehicle using an engine and an electric motor. [Explanation of symbols]

[0047] 10 Vehicles 12 Engine 40 Vehicle speed limit section 42 Navigation Section 44 Rotational speed sensor 46 Shift sensor 48 Weight Sensor 50 Gradient Sensor 52 Vehicle speed sensor 54 Brake sensor 60 Deceleration torque measurement section 62 Deceleration energy calculation unit 64 Vehicle speed control unit

Claims

[Claim 1] In a vehicle speed limiting device that limits the vehicle speed, a rotation speed measuring unit for measuring the rotation speed of a drive source mounted on the vehicle; a weight measuring unit for measuring a vehicle weight of the vehicle; a gradient information acquisition unit that acquires gradient information regarding a road surface gradient while the vehicle is traveling; a deceleration torque measurement unit for measuring a deceleration torque of the driving source; a vehicle speed measurement unit for measuring the vehicle speed of the vehicle; a vehicle speed limiting unit that limits the vehicle speed of the vehicle; Equipped with the vehicle speed limiting unit controls the driving source to limit the vehicle speed when a deceleration energy of the vehicle calculated from the rotation speed of the driving source, the vehicle weight, the road surface gradient, the deceleration torque, and the vehicle speed is equal to or greater than a predetermined value. A vehicle speed limiting device characterized by the above.

Images