WO2014044147A1

WO2014044147A1 - Method, system and vehicle for implementing hill hold control based on abs

Info

Publication number: WO2014044147A1
Application number: PCT/CN2013/083384
Authority: WO
Inventors: Fei Yu; Xiansong FEI; Xinchun Lin; Franke MIRKO; Yuhui HE
Original assignee: Bosch Automotive Products (Suzhou) Co., Ltd.
Priority date: 2012-09-18
Filing date: 2013-09-12
Publication date: 2014-03-27
Also published as: CN103661333B; CN103661333A

Abstract

Provided are a method, a system and a vehicle for implementing hill hold control based on ABS, wherein the method comprises the steps of: providing a check valve (7) having a return spring (17) in the ABS; keeping an inlet valve (6) and an outlet valve (12) being closed and by means of a force of the return spring (17) of the check valve (7), maintaining a pressure of a wheel cylinder (13) under a target pressure to keep the vehicle stopped on a slope within a preset period of time, when it is determined that the vehicle has been braked and stopped on the slope and a brake pedal (3) has been fully released; and opening the outlet valve (12) so that the pressure of the wheel cylinder (13) is reduced to zero, when it is determined that a accelerator pedal has been pushed and a current driving torque is greater than a rolling torque on the slope. This method achieves HHC function in a vehicle equipped merely with ABS. It is not only easy to be implemented, but also reliable to operate with high efficiency and helpful to enhance a comfort and safety for driving.

Description

Method, System and Vehicle for Implementing Hill Hold Control Based on ABS

FIELD OF THE INVENTION

[0001] The present invention pertains to the technical field of automobile, and in particular, to a method, system and vehicle for implementing Hill Hold Control (hereinafter referred to as HHC for abbreviation) based on ABS (Anti-Lock Braking System).

BACKGROUND

[0002] The main function of HHC is to prevent vehicle from rolling backward when the vehicle is on a slope. The HHC enables the vehicle to be held automatically after the driver releases the brake pedal by maintaining brake pressure of a wheel cylinder so that it is ensured the driver will have sufficient time to perform driving operation during that time period. This is a very useful function, and is especially beneficial for new drivers who lack driving experience or female drivers.

[0003| At present, most vehicles having HHC functions are based on ESP/ESC system, meaning that customs can only use this function on vehicles which are equipped with software and hardware such as ESP/ESC sensor or the like. However, since the ESP/ESC system is expensive in price (for example, it typically comprises 12 valves) and it imposes high demands on vehicle sensors and ECU or the like, the installation rate of ESP/ESC system is very low in some market areas, thus considerably affecting a widespread application of the advantageous HHC function.

SUMMARY OF THE INVENTION

[0004] In view of the above, according to a first aspect of the invention, a method for implementing HHC based on ABS is provided so as to effectively address the above problems and other problems existing in the prior art. The method according to the invention comprises the steps of:

A. providing a check valve having a return spring in the ABS used to prevent wheels from being locked during braking and including an inlet valve and an outlet valve which are provided between master and wheel cylinders, and the check valve being arranged in parallel with the inlet valve in order to form a bypass for the brake fluid to flow from the wheel cylinder to the main cylinder;

B. keeping the inlet and outlet valves closed and by means of the force of the return spring of the check valve, maintaining the wheel cylinder at a target pressure to keep vehicle stopped on a slope within a preset period of time, when it is determined that a first condition which means the vehicle has been braked and stopped on the slope and the brake pedal has been fully released, has been established; and

C. opening the outlet valve so that the pressure of the wheel cylinder is reduced to zero, when it is determined that a second condition which means the accelerator pedal has been pushed and the current driving torque is greater than the rolling torque on the slope, has been established.

[0005] In an advantageous embodiment of the method according to the invention, whether the first condition in the step B is established is determined by obtaining the following signals: a pressure signal of the master cylinder detected by a pressure sensor, rotational speed signals of the wheels detected by wheel sensors and a signal indicating whether the vehicle is on the slope detected by a slope sensor. Alternatively, whether the first condition in the step B is established is determined by obtaining the following signals: a travel distance or rotational angle signal of the brake pedal detected by a brake pedal sensor, rotational speed signals of the wheels detected by wheel sensors and a signal indicating whether the vehicle is on the slope detected by a slope sensor.

[0006] In another advantageous embodiment of the method according to the invention, whether the second condition in the step C is established is determined by obtaining the following signals: a first signal at least comprising information on transmission type of the transmission, gear state and clutch state, and a second signal at least comprising information on engine rotational speed and engine torque. Optionally, the first signal is a transmission control unit (TCU) signal. Optionally, the second signal is an engine management system (EMS) signal. Optionally, the transmission control unit (TCU) signal and the engine management system (EMS) signal origin from an in-vehicle network including CAN and FlexRay. [0007] In further another advantageous embodiment of the method according to the invention, the above preset period of time is set to be 2 seconds. [0008] Moreover, according to a second aspect of the invention, a system for implementing HHC based on ABS is also provided, comprising an ABS used to prevent wheels from being locked during braking and including an inlet valve and an outlet valve which are provided between master and wheel cylinders, the system for implementing HHC based on ABS further comprising:

a check valve having a return spring and arranged in parallel with the inlet valve in order to form a bypass for the brake fluid to flow from the wheel cylinder to the main cylinder; and

a controller associated with the ABS and being configured to: i) keep the inlet and outlet valves closed and by means of the force of the return spring of the check valve, maintain the wheel cylinder at a target pressure to keep vehicle stopped on a slope within a preset period of time, when it is determined that a first condition which means the vehicle has been braked and stopped on the slope and the brake pedal has been fully released, has been established; and ii) open the outlet valve so that the pressure of the wheel cylinder is reduced to zero, when it is determined that a second condition which means the accelerator pedal has been pushed and the current driving torque is greater than the rolling torque on the slope, has been established.

[0009] In an advantageous embodiment of the system according to the invention, the controller determines whether the first condition is established by obtaining the following signals: a pressure signal of the master cylinder detected by a pressure sensor, rotational speed signals of the wheels detected by wheel sensors and a signal indicating whether the vehicle is on the slope detected by a slope sensor. Alternatively, the controller determines whether the first condition is established by obtaining the following signals: a travel distance or rotational angle signal of the brake pedal detected by a brake pedal sensor, rotational speed signals of the wheels detected by wheel sensors and a signal indicating whether the vehicle is on the slope detected by a slope sensor.

[0010] In another advantageous embodiment of the method according to the invention, the controller determines whether the second condition is established by obtaining the following signals: a first signal at least comprising information on transmission type of the transmission, gear state and clutch state, and a second signal at least comprising information on engine rotational speed and engine torque. [0011] In further another advantageous embodiment of the system according to the invention, the above preset period of time can be set to be 2 seconds.

[0012] In still another advantageous embodiment of the system according to the invention, the controller is an electronic control unit (ECU). The first signal is a transmission control unit (TCU) signal and/or the second signal is an engine management system (EMS) signal. Optionally, the transmission control unit (TCU) signal and the engine management system (EMS) signal origin from an in-vehicle network including CAN and FlexRay.

[0013] Furthermore, according to a third aspect of the invention, a vehicle is provided, which is equipped with a system for implementing hill hold control based on ABS according to any of the above aspects, or a vehicle is provided in which a method for implementing hill hold control based on ABS according to any of the above aspects is implemented.

[0014] The present invention inventively achieves HHC function in a vehicle based on existing Anti-Lock Braking System (ABS) so that in addition to a dynamic anti-lock function, the current Anti-Lock Braking System (ABS) can also have a Hill Hold Control function, thus further expanding the comfort and safety or the like of vehicle. The system and method of the invention is not only easy to achieve, but also operate reliably and efficiently. Therefore, more end users can achieve a very practical HHC function in their vehicles equipped merely with low cost Anti-Lock Braking System (ABS), particularly facilitating enhancing safety performance of driving.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The technical solutions of the invention will be further described hereinafter in connection with accompanying drawings and illustrated embodiments. [0016] Fig. 1 is a schematic view showing the components of an embodiment of the system for implementing HHC based on ABS according to the invention.

[0017] Fig. 2 is a schematic view showing operational time sequence of an embodiment of the method for implementing HHC based on ABS according to the invention.

[0018] Fig. 3 is a schematic view showing the structure of a check valve having a return spring in the example of Fig. 1.

[0019] Fig. 4 is a schematic view showing the constituent modules of controller in the example of Fig. 1.

DETAILED DESCRIPTION OF THE INVENTION [0020] Firstly, it is noted that the basic principle, characteristics and advantages of the method and system of the invention will be specifically described in an exemplary way; however, all the description is for illustrative purpose only and should not be considered as limiting the invention in any way. Moreover, for any single technical feature described or implicated in each of the embodiments described herein or for any single technical feature shown or implicated in the accompanying drawings, any combination or cancellation can also be made among these technical features (or their equivalents) to thereby obtain more other embodiments that may not have been mentioned directly herein. Moreover, the term "Anti-Lock Braking System" or "ABS" used herein each generally refers to all kinds of various systems, devices and apparatuses or the like that can achieve the function of prevent wheels from being locked during braking in driving.

[ 0021] Fig. 1 schematically shows a basis constituent structure of an embodiment of the system according to the invention. In this example, the hydraulic brake system of vehicle is designed to have two brake conduits 1 and 2, both of which are connected with a master cylinder 4 and can have completely the same configuration or similar configurations. Therefore, only one of the brake conduits 1 will be described hereinafter.

[0022] As shown in Fig. 1, the brake conduit 1 enables the master cylinder 4 and a wheel cylinder 13 to be fluidly communicated with each other, thus providing a flow path for braking fluid. An inlet valve 6, a backflow pump 8, an electric motor 9, a suction valve 10, an accumulator 11 and an outlet valve 12 or the like are disposed in the brake conduit 1. It is understood that the function, type and arrangement of these components that are associated with existing hydraulic brake and anti-lock brake technology are known by those skilled in the art and can be adjusted and adapted (for example, in other applications, the inlet valve 6 and/or the outlet valve 12 are not necessarily selected as the 2-position- 2-way solenoid valve shown in the figures, or an isolation valve can be added between the main cylinder 4 and the backflow pump 8, or more than two brake conduits can also be provided, and so on); detailed description will not be given herein for the aforesaid since they are not the key points of the invention.

[0023] In addition to the Anti-Lock Braking System (ABS), the system of the invention is inventively provided with a check valve having a return spring in the hydraulic brake conduits and is provided with a controller associated with the Anti-Lock Braking System. Taking the above brake conduit 1 as an example, in the system of the invention, the check valve 7 having the return spring 17 is arranged in parallel with the inlet valve 6 so as to form a bypass 18. Therefore, brake fluid can flow from the wheel brake cylinder 13 unidirectionally to the master cylinder 4 via the bypass 18 and will be restrained by a spring force applied by the return spring 17 when it passes through the bypass 18.

[0024] Fig. 3 shows more clearly a substantial configuration of the above check valve 7, and the following relational expression (1) shows a relationship among the force of the return spring in the check valve, the pressure PI in the master cylinder and the pressure P2 in the wheel cylinder:

K * Ax = (Ρ2 - Ρ 1) * π * (ϋ/2) ² (1)

Where the parameter K represents the spring constant, Δχ represents the amount of deformation of the return spring, d represents the diameter of a sealed circle formed of the spool 20 of the check valve. The operational principle of the invention will be described with more details with reference to the relational expression (1) hereinafter.

[0025] The controller 16 is an important component of the system of the invention which is associated with the Anti-Lock Braking System (ABS) and achieves a control function in the system of the invention. Taking the brake conduit 1 as an example, the controller 16 is designed to control the opening or closing operations of the inlet valve 6 and the outlet valve 12 in the brake conduit 1 by determining whether the first condition (meaning that the vehicle has been braked and stopped on the slope and the brake pedal has been fully released) and the second condition (meaning that the accelerator pedal has been pushed and the current driving torque is greater than the rolling torque on the slope) are established, thus achieving a desired hill hold control by means of the check valve 7 having the return spring 17. Specifically, when the controller 16 determines that the first condition has been established according to an input signal, it sends an instruction to place both the inlet valve 6 and the outlet valve 12 in a closed state, and then by means of the force of the return spring 17 in the check valve 7, the controller 16 enables the wheel cylinder 13 to be maintained at a target pressure to keep vehicle stopped on a slope within a preset period of time (for example, 2 seconds or another appropriate value), thus achieving the HHC function; moreover, when the controller 16 determines that the second condition has been established, it sends an instruction to open the outlet valve 12, thus reducing the pressure of the wheel cylinder 13 to be zero, that is, the brake fluid backflows to the accumulator 11 and the master cylinder 4 via the outlet valve 12, thus completing the operation of HHC function. [0026] With respect to the determination of the first condition and the second condition, various technical means offered by different automobile manufactures and development departments or the like can be used to make the determination, and various signals comprising useful information and input to the controller 16 to be used therefor are collectively represented as Si_nput in Fig. 1. Therefore, the above determination is merely for exemplary purpose and some optional embodiments are given hereinafter.

[0027] For the first condition, for example, the controller 16 can determine whether the first condition has been established by obtaining a pressure signal of the master cylinder 4 detected by a pressure sensor 5, rotational speed signals of the wheels detected by wheel sensors 15 and a signal indicating whether the vehicle is on the slope detected by a slope sensor (not shown). Besides, the controller 16 can also determine whether the first condition has been established by obtaining a travel distance or rotational angle signal (i.e., the brake demand imposed by the driver) of the brake pedal 3 detected by a brake pedal sensor 19, rotational speed signals of the wheels detected by wheel sensors 15 and a signal indicating whether the vehicle is on the slope detected by a slope sensor. [0028] For the second condition, for example, the controller 16 can determine whether the second condition has been established by obtaining a signal at least comprising information on transmission type of the transmission, gear state and clutch state (for example, a transmission control unit (TCU) signal, etc.), and a signal at least comprising information on engine rotational speed and engine torque (for example, an engine management system (EMS) signal, etc.). These above signals can be for example obtained via an in-vehicle network (for example, CAN, FlexRay, etc.). [0029] While an independent control device which is specially designed can be provided for achieving the function of the above described controller 16, in some preferable examples, the electronic control unit (ECU) in the automobile can be used as the controller of the system of the invention. [0030] As a further example, as shown in Fig. 4, the modules to be described below can be specially provided in the controller 16 to specifically achieve respective control functions of the controller, i.e., transforming an input signal Si_nput which is input to the controller 16 into an output signal S_0UtpUt of the controller 16 by processing: a vehicle speed information calculating module 21 , which is designed to calculate the actual speed of vehicle according to the input signal from the wheel sensors 15; a slope information calculating module 22, which is designed to calculate whether the vehicle is on the slope and vehicle upslope driving information according to the input signal from the slope sensor and the transmission control unit (TCU); a HHC calculating module 23, which is designed to detect upslope driving condition and calculate a target pressure at which the wheel cylinder is required to be maintained during the implementation of HHC control according to each output information from the vehicle speed information calculating module 21 and the slope information calculating module 22, the transmission control unit (TCU) signal, the engine management system (EMS) signal, a pressure signal of the master cylinder 4 detected by the pressure sensor 5 (or the travel distance or rotational angle signal of the brake pedal 3 detected by the brake pedal sensor 19); a hydraulic actuation output module 24, which is designed to receive the output signal of the HHC calculating module 23 and transforms the above target pressure into the amount of load and operational duration required for each inlet valve and outlet valve in the brake conduits, that is, the hydraulic actuation output module 24 outputs a signal to determine when to open or close the inlet valve and outlet valve. In the hydraulic actuation output module 24, it is also required to calculate the flow rate of brake fluid when the outlet valve pressure is released so as to thereby control the operation of electric motor 9, thus pumping brake fluid back to the master cylinder from the wheel cylinder. [0031 ] The calculation of the target pressure in the above HHC calculating module 23 will be further discussed hereinafter so that the design and operational principle of the invention will become more clearly understood through the exemplary description. Firstly, assuming that the vehicle stays still on a slope having an inclination of a and the vehicle is in a state of not being driven, the minimum hill hold brake pressure P_mi_n that can be provided by the brake pressure at this moment should keep identical to the component force generated the gravity of vehicle in the direction parallel with the slope surface of the slope in magnitude, but opposite in direction. Therefore, it is known that the following relational expression (2) holds:

where the parameter

represents the minimum hill hold brake pressure in the unit of bar, and the value of P_mi_n calculated according to the above expression can be used an the value of the above target pressure at which the wheel cylinder is required to be maintained; the parameter C_p is brake efficacy factor which represents brake torque generated by unit brake pressure, C_p is related to the basic brake system of vehicle and can be derived from measurement in the unit of N*m/bar; the parameter m represents the mass of the whole vehicle in the unit of kg; the parameter g represents acceleration of gravity, i.e., 9.8m/s²; the parameter R represents the rolling radius of wheels in the unit of m; and the parameter a represents the inclination of the slope, i.e., a ratio between the height of slope and the length of base in the unit of %. [0032] The following relational expression (3) can be obtained by a transformation of expression (2):

P mi-i- - m *g *.sb[tan ^"l (3)

Whereby, if the above expression (1) is considered in combination, when the pressure PI of the master cylinder is reduced to zero, it can be deducted that at this moment, the

pressure P2 of the wheel cylinder is

, i.e., the above target pressure value.

For example, when P_mi_n = P2 is set and the inclination a of slope is set to be 20% or another suitable value according to relevant regulations or standards such as GB21670-2008 "Passenger Car Braking System Technical Requirements and Test Methods", the selection of return spring 17 in the check valve 7 can be determined with reference to the following relational expression (4):

ηχϊ

In this manner, when the check valve 7 having the return spring 17 is arranged in the hydraulic brake conduits in the manner as described above, the above controller 16 can perform control according to specific conditions during driving so that the pressure value of the wheel cylinder can be maintained at the target pressure value on a slope having an inclination no greater than a when necessary, thus avoiding the situation of moving downslope of vehicle. [0033] With reference to the schematic view of operational time sequence shown in Fig. 2, it is shown a vehicle speed V curve, a pressure PI curve of the master cylinder and a pressure P2 curve of the wheel cylinder in four time intervals A-D corresponding to operations of braking on a slope, stopping, maintaining and activating. The method for implementing HHC based on ABS according to the invention will be described through this exemplary view, which will also facilitate better understanding the operational principle and advantages of the above described system of the invention.

[0034] In the method according to the invention, as described previously, a check valve having a return spring should be firstly provided in the Anti-Lock Braking System (ABS) of vehicle; then, when the driver operates the brake pedal to brake the vehicle and maintains it on the slope, both the pressure PI of the master cylinder and the pressure P2 of the wheel cylinder increase, and PI = P2 since the inlet valve and the outlet valve in the brake conduits are both in a normal state; the above process corresponds to the time interval A in Fig. 2; next, the driver releases the brake pedal and the pressure PI in the master cylinder is then to be released; the above process corresponds to the time interval B in Fig. 2; thereafter, the driver will fully release the brake pedal and the HHC function is now activated; the controller will send an instruction to close the inlet valve in the brake conduit and then the pressure PI in the master cylinder will decrease gradually; however, since the return spring in the check valve provides a spring force, the pressure P2 in the wheel cylinder can be maintained at a target pressure and the target pressure will be maintained for a preset period of time (for example, 2 seconds or another suitable value) so that rolling is prevented between the operation of releasing brake pedal and the operation of engaging clutch, i.e., the vehicle is thereby maintained on the slope; now, the pressure P2 in the wheel cylinder > the pressure PI in the master cylinder (as described above,

when PI is reduced to zero, the pressure P2 in the wheel cylinder is ^πί1 , i.e.,

P2 is maintained at a desired target pressure value); the above process corresponds to the time interval C in Fig. 2; later, when it is determined that the vehicle has enough driving torque for driving (i.e., when it is determined that the acceleration pedal is pushed and the current driving torque is greater than the rolling torque on the slope), the controller sends an instruction to open the outlet valve in the brake conduit so that the pressure P2 in the wheel cylinder is released until it is reduced to zero, i.e., the brake fluid is delivered to the accumulator in the brake conduit; then, the brake fluid is again pumped back to the master cylinder by the operation of backflow pump; the above process corresponds to the time interval D in Fig. 2.

[0035] In the above-described method, with respect to the determination of whether the vehicle has been braked and stopped on the slope and the brake pedal has been fully released (i.e., the above first condition), whether the acceleration pedal has been pushed and the current driving torque is greater than the rolling torque on the slope (i.e., the above second condition), etc., please refer to corresponding description of the system of the invention provided previously, and no repeated description is given herein.

[0036] In summary, the invention inventively achieves HHC function based on existing Anti-Lock Braking System (ABS) so that not only the inherent function of ABS is effectively expanded, but also a technical solution for implementing Hill Hold Control that is more convenient, more reliable and low in cost is provided for massive end users, and the invention is thus particularly advantageous for improving the comfort and safety of driving.

[0037] The above description expounds in detail the method, system and vehicle for implementing Hill Hold Control based on ABS of the invention in an exemplary manner only. These examples are used merely for the purpose of explaining the principle of the invention and the embodiments thereof, rather than liming the invention. Those skilled in the art can make various modifications and variations thereto without departing from the spirit and scope of the invention. Therefore, all the equivalent technical solutions should fall within the scope of the invention and are defined by individual claims of the invention.

Claims

1. A method for implementing hill hold control based on ABS, characterized in that, the method comprising the steps of:

2. The method according to claim 1, characterized in that, whether the first condition in the step B is established is determined by obtaining the following signals: a pressure signal of the master cylinder detected by a pressure sensor, rotational speed signals of the wheels detected by wheel sensors and a signal indicating whether the vehicle is on the slope detected by a slope sensor; or

whether the first condition in the step B is established is determined by obtaining the following signals: a travel distance or rotational angle signal of the brake pedal detected by a brake pedal sensor, rotational speed signals of the wheels detected by wheel sensors and a signal indicating whether the vehicle is on the slope detected by a slope sensor.

3. The method according to claim 1, characterized in that, whether the second condition in the step C is established is determined by obtaining the following signals: a first signal at least comprising information on transmission type of the transmission, gear state and clutch state, and a second signal at least comprising information on engine rotational speed and engine torque.

4. The method according to claim 1, 2 or 3, characterized in that, said preset period of time is set to be 2 seconds.

5. A system for implementing hill hold control based on ABS, comprising an ABS used to prevent wheels from being locked during braking and including an inlet valve and an outlet valve which are provided between master and wheel cylinders, characterized in that, the system further comprising:

a controller associated with the ABS and being configured to: i) send a signal to keep the inlet and outlet valves closed and by means of the force of the return spring of the check valve, maintaining the wheel cylinder at a target pressure to keep vehicle stopped on a slope within a preset period of time, when it is determined that a first condition which means the vehicle has been braked and stopped on the slope and the brake pedal has been fully released, has been established; and ii) send a signal to open the outlet valve so that the pressure of the wheel cylinder is reduced to zero, when it is determined that a second condition which means the accelerator pedal has been pushed and the current driving torque is greater than the rolling torque on the slope, has been established.

6. The system according to claim 5, characterized in that, the controller determines whether the first condition is established by obtaining the following signals: a pressure signal of the master cylinder detected by a pressure sensor, rotational speed signals of the wheels detected by wheel sensors and a signal indicating whether the vehicle is on the slope detected by a slope sensor; or

the controller determines whether the first condition is established by obtaining the following signals: a travel distance or rotational angle signal of the brake pedal detected by a brake pedal sensor, rotational speed signals of the wheels detected by wheel sensors and a signal indicating whether the vehicle is on the slope detected by a slope sensor.

7. The system according to claim 5, characterized in that, the controller determines whether the second condition is established by obtaining the following signals: a first signal at least comprising information on transmission type of the transmission, gear state and clutch state, and a second signal at least comprising information on engine rotational speed and engine torque.

8. The system according to claim 5, 6 or 7, characterized in that, said preset period of time is set to be 2 seconds.

9. The system according to claim 5, 6 or 7, characterized in that the controller is an electronic control unit (ECU), the first signal is a transmission control unit (TCU) signal and/or the second signal is an engine management system (EMS) signal.

10. A vehicle equipped with a system for implementing hill hold control based on ABS according to any one of claims 5 to 9, or a vehicle in which a method for implementing hill hold control based on ABS according to any one of claims 1 to 4 is implemented.