Electric Brake System

Abstract

To provide an electric brake system that monitors, with a simple configuration, a decrease in braking performance of an electric brake and secures traveling safety of a mobility.SOLUTION: An electric brake system is used in a mobility 900 that uses a main battery as a power source, has a maximum movement speed of lower than 25 km / h, and has a plurality of wheels 91 to 94. Electric brakes 81 to 84 generate a clamping force for the corresponding wheels 91 to 94 by using electric power. A braking performance monitoring unit 36 monitors a decrease in braking performance of the electric brakes 81 to 84 that is caused by an electrical factor and a mechanical factor. A movement speed limiting unit 37 sets an upper limit value of a movement speed of the mobility 900. The movement speed limiting unit 37 changes the upper limit value of the movement speed of the mobility 900 in accordance with information on the decrease in the braking performance of the electric brakes 81 to 84 estimated by the braking performance monitoring unit 36.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electric brake system. [Background technology]

[0002] Conventionally, there are known technologies that ensure the safety of a vehicle when a brake system including a friction brake fails. For example, a vehicle control device disclosed in Patent Document 1 enables an autonomous vehicle to continue autonomous driving with safety guaranteed for a certain period of time even if a failure occurs in a brake actuator equipped with a friction brake assist motor, a drive motor, and a parking brake. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6536852 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, green slow mobility has been promoted as a form of mobility aimed at resolving regional transportation issues and realizing a low-carbon society. Green slow mobility is defined as a small transportation service that utilizes electric vehicles that can travel on public roads at speeds of less than 20 km / h, and is a general term that includes these vehicles (Reference: Ministry of Land, Infrastructure, Transport and Tourism website).

[0005] This invention focuses on electric mobility vehicles with a maximum speed of less than 25 km / h, which is slightly faster than the speed limit on public roads, from the perspective of functionality that assumes use off public roads. As a specific example, we focus on passenger golf carts that run on golf courses. In this specification, we use the term "traveling speed" to distinguish the speed of mobility vehicles from the "vehicle speed" of ordinary vehicles.

[0006] The conventional technology in Patent Document 1 is targeted at autonomous vehicles, and is equipped with a large number of sensors for sensing information about the vehicle's surroundings, such as cameras, around-view cameras, laser range finders, etc. Therefore, the control system is complex and expensive to apply to small-scale mobility.

[0007] The main failure modes of electric mobility brake systems are expected to be a decrease in braking performance due to a decrease in brake motor torque in the electric brakes that apply frictional braking to each wheel and wear of the clamping parts. Therefore, if a decrease in braking performance of the electric brakes occurs, it is necessary to detect it early and appropriately ensure the driving safety of the mobility. Therefore, the challenge is to realize a fail-safe function for the electric brake system with a simple configuration suitable for small-scale mobility.

[0008] The present invention was created in consideration of the above points, and its purpose is to provide an electric brake system that has a simple configuration and monitors the deterioration of braking performance of an electric brake, thereby ensuring the driving safety of mobility vehicles. [Means for solving the problem]

[0009] The present invention is powered by a main engine battery, and has a maximum travel speed of less than 25 km / h; It includes some wheels (93, 94) that rotate together with the drive shaft (96) by the drive motor (5) driven by the main engine battery. A brake system for use in a mobility (900) having a plurality of wheels (91-94), comprising: electric brakes (81-84); a braking performance monitor (36); an electromagnetic brake (6); and a movement speed limiter (37).

[0010] Electric brakes use electrical power to generate a clamping force on the corresponding wheel. The electromagnetic brake is provided separately from the electric brake and operates as a parking brake by locking the rotation of the drive shaft. The braking performance monitoring unit monitors the deterioration of braking performance of the electric brake due to electrical and mechanical factors. The movement speed limiting unit sets an upper limit for the movement speed of the mobility.

[0011] The movement speed limiting unit changes the upper limit of the movement speed of the mobility in accordance with the braking performance degradation information of the electric brake estimated by the braking performance monitoring unit. If the current speed exceeds the upper limit, the movement speed limiting unit controls the supply of electricity to the drive motor so that the rotation speed of the drive motor is below a predetermined value, and also uses an electromagnetic brake to decelerate the mobility.

[0012] The present invention does not use a camera or laser device that senses information about the vehicle's surroundings as in Patent Document 1, but limits the scope to deterioration in braking performance due to electrical and mechanical factors, and can monitor deterioration in braking performance of electric brakes with a simple configuration. Furthermore, the traveling safety of mobility vehicles can be appropriately ensured by lowering the upper limit of the travel speed as the braking performance of the electric brakes deteriorates. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a configuration diagram of an electric rake system according to an embodiment. [Figure 2] 4 is a flowchart for estimating a decrease in braking performance of an electric brake due to an electrical factor. [Figure 3] 4 is a flowchart for estimating a decrease in braking performance of an electric brake due to a mechanical factor. DETAILED DESCRIPTION OF THE INVENTION

[0014] (One embodiment) An electric brake system according to one embodiment of the present invention will be described with reference to the drawings. This brake system is used for mobility that uses a main battery as a power source and has a maximum travel speed of less than 25 km / h, i.e., green slow mobility. Specifically, in this embodiment, a golf cart is assumed as the green slow mobility. However, the general term "mobility" will be used in the description of the embodiment.

[0015] 1 shows the configuration of an electric brake system 800 used in a mobility 900. The mobility 900 has four wheels in the longitudinal direction: two front wheels 91, 92, left and right, and two rear wheels 93, 94, left and right. The left and right front wheels 91, 92 are labeled "FL, FR," and the left and right rear wheels 93, 94 are labeled "RL, RR."

[0016] The drive motor 5 is driven by the main battery and rotates the drive shaft 96 via the transmission. The main battery and transmission are not shown in the figure. The rotation of the drive shaft 96 causes the rear wheels 93, 94 to rotate, causing the mobility 900 to move forward or backward. When the mobility 900 decelerates, if the rotation of the drive shaft 96 is input in reverse to the drive motor 5, the drive motor 5 operates regeneratively, thereby generating a regenerative brake function. A wheel speed sensor 59 that detects the wheel speed of the mobility 900 is provided near the output shaft of the drive motor 5 or the drive shaft 96.

[0017] In addition, in this embodiment, electric brakes 81-84 are provided on the wheels 91-94 to brake the wheels 91-94.

[0018] The electric brakes 81-84 are composed of a motor, a reducer, a linear actuator, etc. The motor may be a brushed DC motor or a three-phase brushless motor. The electric brakes 81-84 use electric power to rotate the motor, and the torque output by the motor is converted into linear force by the linear actuator to press the brake pads against the wheel discs, thereby generating a clamping force for the corresponding wheels 91-94. The electric power for the electric brakes 81-84 may be supplied by stepping down the voltage of the main engine battery, or may be supplied from an auxiliary battery installed separately from the main engine battery.

[0019] The electromagnetic brake 6 is attached to, for example, the transmission. The electromagnetic brake 6 acts as a parking brake by locking the rotation of the drive shaft 96 when the speed of the mobility 900 is zero.

[0020] The braking control device 35 corresponds to the brake ECU and controls the operation of the electric brakes 81-84 to brake the mobility 900. In normal braking control, the driver operates the brakes or a braking signal from the automatic driving control device 20 is input to the braking control device 35. In manual driving by the driver, the driver steps on the brake pedal to input a braking signal to the braking control device 35. In the case of golf carts that move along a fixed driving route within a golf course, electromagnetic guidance type automatic driving is used. In this method, a magnetic sensor attached to the bottom of the golf cart detects magnetic markers installed along the driving route.

[0021] The braking control device 35 calculates torque command values ​​for the motors of the electric brakes 81-84 based on the required braking force, and further calculates current command values ​​to control the drive of the motors. Note that Fig. 1 merely shows the signal input / output relationship between the braking control device 35 and the electric brakes 81-84, and does not specify the physical arrangement. For example, the main body of each electric brake 81-84 and the braking control device 35 may be configured as an electromechanical integrated module.

[0022] Here, the main failure modes of the electric brake system 800 are expected to be a decrease in braking performance due to a decrease in brake motor torque and wear of the clamps. Therefore, it is necessary to detect any decrease in braking performance of the electric brakes 81-84 early on and appropriately ensure the traveling safety of the mobility 900. In response to this need, the brake control device 35 of this embodiment has a braking performance monitoring unit 36 ​​and a travel speed limiting unit 37 that monitor for any decrease in braking performance of the electric brakes 81-84 due to electrical and mechanical factors.

[0023] The braking performance monitoring unit 36 ​​estimates a deterioration in the braking performance of the electric brakes 81-84 due to electrical factors based on the voltages applied to the electric brakes 81-84 or the currents passed through the electric brakes 81-84. The braking performance monitoring unit 36 ​​also estimates a deterioration in the braking performance of the electric brakes 81-84 due to mechanical factors based on the clamp loads generated by the electric brakes 81-84.

[0024] When the braking performance monitoring unit 36 ​​determines that the braking performance of the electric brakes 81-84 has deteriorated, it instructs the movement speed limiting unit 37 to change the upper limit of the movement speed.

[0025] The movement speed limiting unit 37 sets an upper limit value for the movement speed of the mobility 900. For example, the motor ECU that controls the drive motor 5 functions as the movement speed limiting unit 37. When instructed by the braking performance monitoring unit 36 ​​to change the upper limit value of the movement speed, the movement speed limiting unit 37 changes the upper limit rotation speed of the drive motor 5, for example.

[0026] The travel speed limiting unit 37 also acquires the current speed of the mobility 900 based on, for example, the wheel speed detected by the wheel speed sensor 59. If the current speed exceeds the upper limit, the travel speed limiting unit 37 outputs a deceleration command. Specifically, the travel speed limiting unit 37 controls the supply of electricity to the drive motor 5 so that the rotation speed of the drive motor 5 is equal to or less than a predetermined value. Furthermore, regenerative braking may be generated in the drive motor 5 by downshifting the transmission, and the electromagnetic brake 6 may also be used in combination. Note that, since it is assumed that the braking performance of the electric brakes 81-84 has deteriorated, braking by the electric brakes 81-84 may not be effective.

[0027] The estimation of the deterioration of braking performance of an electric brake due to electrical and mechanical factors will be described with reference to the flowcharts of Figures 2 and 3. In the explanation of the flowcharts, the symbol "S" denotes a step. Steps specific to Figure 2 have the letter "E" added to the end of the step number, and steps specific to Figure 3 have the letter "M" added to the end of the step number. Steps common to Figures 2 and 3 have the same step number and will not be described again. The braking performance monitoring unit 36 ​​may perform the monitoring steps of Figures 2 and 3 simultaneously or alternately.

[0028] FIG. 2 shows an estimation of the deterioration of braking performance of electric brakes 81-84 due to electrical factors. In S1E, the braking performance monitor 36 acquires the voltage or current between the terminals of the brake motor. Here, the brake motor is assumed to be a brushed DC motor. In S2E, the maximum clamp load Fmax is calculated based on, for example, a voltage-load map.

[0029] In S3E, it is determined whether the maximum clamp load Fmax is equal to or greater than a threshold value. If the answer is YES in S3E, the current braking performance is determined to be normal, and the process returns to S1E, where monitoring is repeated, for example, at a predetermined interval. Basically, the decision in S3E is YES if the answer is YES for all electric brakes 81-84, and NO if the answer is NO for any one or more electric brakes.

[0030] If the result in S3E is NO, i.e., if the maximum clamp load Fmax is less than the threshold value, the braking performance monitoring unit 36 ​​determines that braking performance has deteriorated, and instructs the movement speed limiting unit 37 to change the upper limit of the movement speed in S4. The braking performance monitoring unit 36 ​​also displays a warning lamp in S5. A warning lamp may be displayed for each electric brake so that an abnormal electric brake can be identified.

[0031] In S6, the movement speed limiting unit 37 determines whether the current speed exceeds the upper limit. If the answer is YES in S6, the movement speed limiting unit 37 outputs a deceleration command in S7 by controlling the energization of the drive motor 5 or by regenerative braking, etc. The deceleration command in S7 is repeated until the current speed falls below the upper limit and the answer in S6 is NO.

[0032] In the flowchart of Figure 2, the braking performance is estimated by converting the terminal voltage of the brake motor into the maximum clamp load Fmax, but the braking performance may also be estimated directly using the voltage under certain operating conditions as a parameter. The same applies when using the current.

[0033] Figure 3 shows an estimation of the deterioration of braking performance of the electric brakes 81-84 due to mechanical factors. At S1M, the braking performance monitoring unit 36 ​​starts sensing the clamp load of the electric brakes 81-84. At S2M, the braking performance monitoring unit 36 ​​starts braking so that the clamp load becomes the target load.

[0034] In S3M, it is determined whether the detected clamp load F is equal to or greater than a threshold value. In both cases where the result in S3M is YES or NO, the following explanation is the same as in FIG. 2 and will therefore be omitted.

[0035] As described above, the electric brake system 800 of this embodiment can monitor the deterioration of braking performance of the electric brakes 81-84 with a simple configuration, limiting the target to deterioration of braking performance due to electrical and mechanical factors, without using a camera or laser device that senses information about the surroundings of the vehicle as in Patent Document 1. Furthermore, the traveling safety of the mobility 900 can be appropriately ensured by lowering the upper limit of the travel speed as the braking performance of the electric brakes 81-84 deteriorates.

[0036] (Other embodiments) (a) In the flowcharts of Figures 2 and 3, one threshold value is used to determine whether braking performance has deteriorated, but two or more threshold values ​​may be set to distinguish between, for example, mild and severe braking performance deterioration. In the case of mild braking performance deterioration, the upper limit of the travel speed may be set relatively high, and in the case of severe braking performance deterioration, the upper limit of the travel speed may be set relatively low (including the case where the upper limit is zero). In other words, the travel speed limiting unit 36 ​​may change the upper limit of the mobility's travel speed in multiple stages in accordance with the braking performance deterioration information of the electric brakes 81-84.

[0037] (b) In the above embodiment, the failure mode in which the braking performance of the electric brakes 81-84 deteriorates is mainly assumed to be a case in which the braking force is insufficient relative to the target value due to a decrease in torque of the brake motor or wear of the clamping portion. However, it is also possible to assume that the braking force exceeds the target value depending on the failure condition. Therefore, the term "deterioration in braking performance" is to be interpreted to include a case in which the braking force deviates from the target value to the excessive side.

[0038] (c) "Mobility vehicles with a maximum travel speed of less than 25 km / h" to which the electric brake system of the present invention is applicable include golf carts, tourist vehicles, unmanned vehicles for delivering mail, etc. In the case of mobility vehicles that can freely select their destinations and routes, an automatic driving control device 20 having information input functions such as cameras and position sensors, navigation functions, etc., similar to ordinary vehicles, may be used instead of electromagnetically guided automatic driving. In addition, mobility vehicles are not limited to those with four wheels, and may be any vehicle with multiple wheels.

[0039] The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. [Explanation of symbols]

[0040] 36...Braking performance monitoring department, 37. Travel speed limiter, 800···Electronic brake system, 81-84···Electric brake, 900···Mobility, 91-94···Wheels.

Claims

1. A brake system used in a mobility (900) that is powered by a main engine battery, has a maximum travel speed of less than 25 km / h, and has a plurality of wheels (91-94) including some wheels (93, 94) that rotate together with a drive shaft (96) by a drive motor (5) driven by the main engine battery, Electric brakes (81-84) that use electric power to generate clamping forces on the corresponding wheels; an electromagnetic brake (6) provided separately from the electric brake and operating as a parking brake by locking the rotation of the drive shaft; a braking performance monitoring unit (36) that monitors the deterioration of braking performance of the electric brake due to electrical and mechanical factors; a movement speed limiting unit (37) that sets an upper limit value of the movement speed of the mobility; Equipped with the travel speed limiting unit changes an upper limit value of the travel speed of the mobility in accordance with braking performance degradation information of the electric brake estimated by the braking performance monitoring unit; When the current speed exceeds the upper limit, the travel speed limiting unit controls the supply of electricity to the drive motor so that the rotation speed of the drive motor is below a predetermined value, and further uses the electromagnetic brake in combination to slow down the mobility.

2. 2. The electric brake system according to claim 1, wherein the braking performance monitoring unit estimates a deterioration in braking performance of the electric brake due to an electrical cause based on a voltage applied to the electric brake or a current passed through the electric brake.

3. The electric brake system according to claim 1 , wherein the braking performance monitoring unit estimates a deterioration in braking performance of the electric brake due to a mechanical cause based on a clamp load generated by the electric brake.

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