CN112413015A

CN112413015A - Chassis brake module mechanical structure for multiple vehicle types and hydraulic control system

Info

Publication number: CN112413015A
Application number: CN202011398007.5A
Authority: CN
Inventors: 高镇海; 于桐; 高菲; 胡宏宇; 王雨蒙
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2020-12-01
Filing date: 2020-12-01
Publication date: 2021-02-26

Abstract

The invention provides a chassis brake module mechanical structure and a hydraulic control system for multiple vehicle types, and relates to the field of vehicle braking. The screw box module comprises a reduction box module, wherein the reduction box module is directly connected with an output shaft of an external motor and used for reducing speed and increasing torque, one side of the reduction box module is butted with the screw box module through a convex edge and a concave edge and is fixed through a bolt, and one side of the reduction box module is matched with the screw box module in size. The invention reduces the cost of the active braking module. The invention simplifies the structure, simplifies the installation process, can be suitable for various vehicle types such as garden express trucks, garden snow plows, forklifts and the like, improves the hydraulic structure of the existing brake system and the hydraulic structure of systems such as ABS and the like, cancels the design of brake cylinders and more hydraulic valves, simplifies the structure and reduces the cost.

Description

Chassis brake module mechanical structure for multiple vehicle types and hydraulic control system

Technical Field

The invention relates to the technical field of vehicle braking, in particular to a chassis braking module mechanical structure and a hydraulic control system for multiple vehicle types.

Background

The unmanned technology is expected to be used not only for passenger vehicles, but also for commercial vehicles. Under the scenes of warehouse fork goods taking, campus express taking and delivering, snow sweeping in a factory and the like, the unmanned vehicle has obvious advantages. Great numbers of research have also been conducted in these areas by the major automobile industries such as Toyota, crown, Boshi, etc. The brake-by-wire system suitable for unmanned driving is an important component of an intelligent vehicle chassis and mainly comprises an Electronic Mechanical Brake (EMB) and an Electronic Hydraulic Brake (EHB).

The scholars such as the Goshichong and the like summarize the EHB into two structures, one structure is that a motor pump and a high-pressure accumulator supply pressure to a braking system, namely the traditional EHB; in the other structure, the master cylinder is connected with the motor through the transmission mechanism and is directly driven by the motor to build pressure, namely the motor direct-drive brake-by-wire system. The motor direct-drive brake-by-wire system is rapid and accurate in pressure build-up, the integration level is higher than that of a transmission EHB, active braking is easier to realize, and the system is convenient to match with an unmanned function.

In recent years, some foreign manufacturers of known automobile parts have made some research on direct drive-by-wire braking of motors. The iboster of BOSCH is an electromechanical Brake booster independent of a vacuum pump, and Integrated Brake Control (IBC) of ZF TRW and e-ACT Brake actuators of HITACHI (HITACHI) all use an air-core motor to directly drive for building pressure. Related research is also carried out in colleges and universities. For example, chinese patent publication No. CN104071142A discloses a technique for realizing brake-by-wire by using a hollow motor and an energy accumulator.

But the existing scheme is developed for the traditional passenger car, and compared with a small unmanned vehicle, the passenger car has the advantages of large occupied space, complex structure and difficult installation. The existing solutions all involve a brake pedal related design, which is superfluous in small unmanned vehicles. Meanwhile, the existing brake system modules can only be used for single or similar vehicle types, and cannot be simultaneously applied to small commercial or special vehicles such as forklifts, express delivery vehicles, snow plows and the like. In addition, the existing brake-by-wire system has high requirements on a motor and a lead screw, and brings great problems to the reduction of the overall cost and the wide popularization of the technology.

Disclosure of Invention

Technical problem to be solved

In order to overcome the defects in the prior art, the invention provides a chassis brake module mechanical structure and a hydraulic control system for multiple vehicle types, which aim to solve the problems in the background art.

(II) technical scheme

In order to achieve the purpose, the invention is realized by the following technical scheme: chassis brake module mechanical structure for multiple vehicle types, comprising:

the speed reduction box module is directly connected with an output shaft of an external motor and is used for reducing speed and increasing torque;

the screw box module is characterized by comprising a screw box module, a reduction box module and a screw box module, wherein one side of the reduction box module is butted with the screw box module through convex and concave edges and is fixed through bolts, and one side of the reduction box module is matched with the screw box module in size;

the speed reduction box module comprises a speed reduction box body, a gear shaft, a two-stage soft-tooth-surface gear pair, a bearing and the like, and comprises a speed reduction box, an output shaft large gear, a cylindrical roller, an input shaft small gear, a speed reduction box cover, an input shaft bearing end cover, an input shaft, an intermediate shaft bearing end cover, an intermediate shaft, a 6303 bearing, an intermediate shaft large gear, an intermediate shaft small gear, a shaft sleeve, an output shaft bearing end cover, a felt ring, an output shaft, a 6306 bearing, a sealing gasket, an M10 hexagon socket head cap screw and an M12 hexagon socket head cap screw;

the lead screw box module comprises a lead screw box, a ball screw pair, an output push disc (700), a bearing and other supporting elements, and comprises the lead screw box, a combined bearing support, a combined bearing, a lead screw nut, a second felt ring, a second M10 socket head cap screw, the output push disc, a second M12 socket head cap screw, a spring washer, a nut push rod, a bearing end cover, a 6013 bearing, an M12X socket head cap screw, a ball screw and an M16X socket head cap screw.

Preferably, the reduction box body consists of a reduction box and a reduction box cover, and the reduction box cover are combined to form a flat cuboid.

Preferably, the gear shaft comprises an input shaft, an intermediate shaft and an output shaft, the input shaft is connected with the output shaft of the motor through a flat key, and the output shaft is connected with the ball screw through a spline shaft.

Preferably, the double-stage soft-tooth-surface gear pair consists of an input shaft pinion, an intermediate shaft gearwheel 11, an intermediate shaft pinion and an output shaft gearwheel, and the input shaft pinion, the intermediate shaft gearwheel 11, the intermediate shaft pinion and the output shaft gearwheel are fixedly connected with the gear shaft through flat keys.

Preferably, the left side of the input shaft is arranged on the reduction gearbox through a 6303 bearing, the right side of the output shaft is arranged on the reduction gearbox through a 6306 bearing 17, and the input shaft and the output shaft are sleeved through a cylindrical roller.

Preferably, the ball screw pair consists of a ball screw and a screw nut, the left end of the ball screw is machined and formed into a spline hub, and the ball screw is matched with the output shaft of the reduction gearbox.

Preferably, one end of the ball screw is supported on the screw box through a 6013 bearing, the middle of the ball screw is supported at the bottom of the screw box through a combined bearing and a special combined bearing support, and one side of the screw box is connected with an external piston push rod through an output push disc.

Preferably, the screw nut is fixedly connected with 6 nut push rods through nuts, and the nut push rods are uniformly distributed on a flange of the screw nut.

Preferably, one end of the nut push rod penetrates through a through hole in the lead screw box, the other side of the nut push rod is fixedly connected with the output push disc through a nut, and threads are machined on two sides of the nut push rod.

The hydraulic control system for the chassis brake module of multiple vehicle types is characterized by comprising an ECU module, a double-cavity brake master cylinder, an oil storage tank, a brake oil path, a switch valve, a reversing valve, a front wheel cylinder, a rear wheel cylinder and a pressure sensor;

the dual-cavity brake master cylinder comprises a first working cavity and a second working cavity;

the brake oil path comprises a front shaft oil path and a rear shaft oil path, the first working cavity is connected with the front shaft oil path, and the second working cavity is connected with the rear shaft oil path;

the reversing valve is provided with two downlink oil paths, one downlink oil path of the reversing valve is connected to the rear wheel cylinder, the other downlink oil path of the reversing valve is connected back to the oil storage tank, and the reversing valve is set to be a 2-position 3-way electromagnetic valve;

the pressure sensors are distributed and installed on one of the front wheel cylinder and the rear wheel cylinder respectively;

one switching valve is installed in the front axle oil circuit, a switching valve and a reversing valve are respectively installed in the rear axle oil circuit, and 2-position 2-way electromagnetic valves of the switching valves are arranged.

The invention provides a chassis brake module mechanical structure and a hydraulic control system for multiple vehicle types, which have the following beneficial effects:

1. the invention realizes the design of a mechanical device of the chassis brake module of the unmanned vehicle in the small park, completes the active brake function, successfully reduces the requirements of the brake module on the motor and the screw rod, improves the working conditions of related elements and reduces the cost of the active brake module. The invention simplifies the structure and the installation process, and can be suitable for various vehicle types such as garden express delivery vehicles, garden snow sweeper, fork trucks and the like.

2. The system improves the hydraulic structure of the existing brake system and the hydraulic structure of the ABS and other systems, cancels the design of a brake cylinder and a plurality of hydraulic valves, simplifies the structure and reduces the cost. Meanwhile, the design scheme of the hydraulic system provided by the invention can be well combined with an automatic driving system, and provides braking system parameters such as different braking modes, braking force distribution coefficients and the like for different vehicle types such as a forklift, a snow sweeper, an express delivery vehicle and the like under the condition of matching with a corresponding control algorithm.

Drawings

FIG. 1 is a schematic view of the reduction gearbox of the present invention;

FIG. 2 is a schematic view of the mounting structure of the M10 socket head cap screw according to the present invention;

FIG. 3 is a schematic view of the mounting structure of the M12 socket head cap screw according to the present invention;

FIG. 4 is a schematic view of a screw box according to the present invention;

FIG. 5 is a schematic view of the mounting structure of the socket head cap screw M16X according to the present invention;

FIG. 6 is a flow chart of a control system according to the present invention;

FIG. 7 is a graph of comparative data according to the present invention.

In the figure: 1. a reduction gearbox; 2. an output shaft bull gear; 3. a cylindrical roller; 4. an input shaft pinion; 5. a reduction box cover; 6. an input shaft bearing end cap; 7. an input shaft; 8. an intermediate shaft bearing end cover; 9. an intermediate shaft; 10. 6303 bearings; 11. a countershaft bull gear; 12. a countershaft pinion; 13. a shaft sleeve; 14. an output shaft bearing end cover; 15. a felt ring; 16. an output shaft; 17. 6306 bearings; 18. sealing gaskets; 19. m10 socket head cap screw; 20. m12 socket head cap screw; 101. a speed reduction box module; 102. a lead screw box module; 100. a lead screw box; 200. a combined bearing support; 300. a combination bearing; 400. a lead screw nut; 500. a second felt; 600. a second M10 socket head cap screw; 700. outputting a push disc; 800. a second M12 socket head cap screw; 900. a spring washer; 1000. a nut push rod; 110. a bearing end cap; 120. 6013 a bearing; 130. M12X hex head bolt; 140. a ball screw; 150. M16X socket head cap screw.

Detailed Description

An embodiment of the present invention provides a chassis brake module mechanical structure for multiple vehicle types, as shown in fig. 1 to 7, including:

the reduction box module 101 is directly connected with an output shaft of an external motor, is used for reducing speed and increasing torque, can be matched with a solid motor for use, and reduces the requirement on the motor;

the brake master cylinder comprises a lead screw box module 102, wherein one side of the reduction box module 101 is butted with the lead screw box module 102 through convex and concave edges and fixed through bolts, one side of the reduction box module 101 is matched with the lead screw box module 102 in size so as to be convenient to place and arrange in an equipment compartment, and the lead screw box module 102 is connected with the reduction box module 101 and is used for converting rotation into translation to push a piston push rod of the brake master cylinder;

the speed reducer module 101 comprises a speed reducer box body, a gear shaft, a double-stage soft-tooth-surface gear pair, a bearing and the like, wherein the speed reducer box module 101 comprises a speed reducer box 1, an output shaft gearwheel 2, a cylindrical roller 3, an input shaft pinion 4, a speed reducer box cover 5, an input shaft bearing end cover 6, an input shaft 7, an intermediate shaft bearing end cover 8, an intermediate shaft 9, a 6303 bearing 10, an intermediate shaft gearwheel 11, an intermediate shaft pinion 12, a shaft sleeve 13, an output shaft bearing end cover 14, a felt ring 15, an output shaft 16, a 6306 bearing 17, a sealing gasket 18, an M10 hexagon socket head cap screw 19 and an M12 hexagon socket head screw 20;

the lead screw box module 102 is composed of a lead screw box 100, a ball screw pair, an output push disc (700), a bearing and other supporting elements, wherein the lead screw box module 102 comprises the lead screw box 100, a combined bearing support 200, a combined bearing 300, a lead screw nut 400, a second felt ring 500, a second M10 socket head cap screw 600, an output push disc 700, a second M12 socket head cap screw 800, a spring washer 900, a nut push rod 1000, a bearing end cover 110, a 6013 bearing 120, an M12X hexagon head bolt 130, a ball screw 140 and an M16X socket head cap screw 150.

The reduction box body consists of a reduction box 1 and a reduction box cover 5, wherein the reduction box 1 and the reduction box cover 5 are combined to form a flat cuboid to realize modular design and play a supporting role.

The gear shaft comprises an input shaft 7, an intermediate shaft 9 and an output shaft 16, the input shaft 7 is connected with the output shaft of the motor through a flat key, and the output shaft 16 is connected with the ball screw 140 through a spline shaft.

The double-stage soft-tooth-surface gear pair is composed of an input shaft pinion 4, an intermediate shaft gearwheel 11, an intermediate shaft pinion 12 and an output shaft gearwheel 2, wherein the input shaft pinion 4, the intermediate shaft gearwheel 11, the intermediate shaft pinion 12 and the output shaft gearwheel 2 are fixedly connected with a gear shaft through flat keys.

The left side of the input shaft 7 is arranged on the reduction gearbox 1 through a 6303 bearing 10, the right side of the output shaft 16 is arranged on the reduction gearbox 1 through a 6306 bearing 17, and the input shaft 7 and the output shaft 16 are sleeved through a cylindrical roller 3, so that the structure is compact and cantilever beams are avoided.

The ball screw pair is composed of a ball screw 140 and a screw nut 400, the left end of the ball screw 140 is machined and formed into a spline hub, and the ball screw 140 is matched with the output shaft 16 of the reduction gearbox.

One end of the ball screw 140 is supported on the screw box 100 through a 6013 bearing 120, the middle part of the ball screw 140 is supported at the bottom of the screw box 100 through a combined bearing 300 and a specially-made combined bearing support 200, and one side of the screw box 100 is connected with an external piston push rod through an output push plate 700.

The lead screw nut 400 is fixedly connected with 6 nut push rods 1000 through nuts, and the nut push rods 1000 are uniformly distributed on a flange of the lead screw nut 400, so that the problem that the stress of the lead screw is uneven is solved, the dynamic load of the lead screw is reduced, and the requirements for the lead screw are reduced.

One end of the nut push rod 1000 penetrates through a through hole in the lead screw box 100, the other side of the nut push rod 1000 is fixedly connected with the output push disc 700 through a nut, the motion is transmitted to the output push disc 700, threads are machined on both sides of the nut push rod 1000 so as to be matched with the nut, and the output push disc 700 finally pushes a main cylinder piston to move, so that the pressure build-up of a brake system is realized.

The working principle is as follows: the motor starts to rotate under the instruction of the controller, the input shaft 7 is driven to rotate through the flat key, the input shaft 7 transmits the rotation to the two-stage soft-tooth-surface gear pair, and finally, the output shaft 16 outputs enough torque and rotating speed; the output shaft 16 is connected with the ball screw 140 through a special spline shaft, the rotation is transmitted to the ball screw 140, the ball screw 140 converts the rotation into translation, the translation motion is output by the screw nut 400, the screw nut 400 transmits the force and the motion to the nut push rod 1000, and the nut push rod 1000 drives the output push plate 700 to move; finally, the output push plate 700 pushes the master cylinder piston to realize the pressure build-up of the brake system,

the design of a mechanical device of the chassis brake module of the unmanned vehicle in the small park is realized, the active brake function is completed, the requirements of the brake module on a motor and a lead screw are successfully reduced, the working conditions of related elements are improved, and the cost of the active brake module is reduced. The invention simplifies the structure, simplifies the installation process and realizes the modular design.

As shown in fig. 6, the hydraulic control system for a chassis brake module of a multi-vehicle type is characterized by comprising an ECU module, a dual-chamber brake master cylinder, an oil storage tank, a brake oil path, a switching valve, a reversing valve, front and rear wheel cylinders and a pressure sensor;

The implementation mode is specifically as follows: the first working cavity of the double-cavity brake master cylinder is connected with a front shaft oil path, and the second working cavity is connected with a rear shaft oil path. A pressure sensor is respectively arranged in the front wheel cylinder and the rear wheel cylinder to determine whether the pressure reaches a limit pressure, a 2-position 2-way electromagnetic valve, namely an on-off valve, is additionally arranged in the front axle oil path, and whether the pipeline is closed is determined according to a signal transmitted by a control unit. A 2-position 3-way electromagnetic valve, namely a reversing valve, and a 2-position 2-way electromagnetic valve, namely a switch valve, are additionally arranged in a rear axle oil path, and a downlink oil path of the reversing valve 1 is connected to a rear wheel cylinder, namely an express delivery vehicle and a snow sweeper oil path; and the other downlink oil way is connected back to the oil storage tank, namely a forklift oil return way. The design of returning oil circuit is because under the fork truck motorcycle type, the rear axle does not brake, if directly blocks up the rear axle through the ooff valve, so valve both sides pressure differential is too high, can reduce the life of valve on the one hand, and on the other hand also can have certain oil leak phenomenon, can't make the pipeline totally enclosed.

The control method of the system comprises the following steps:

firstly, a vehicle owner selects a working mode of a braking system through a switch, an ECU adjusts the working state of a 2-to-3 way valve in a rear shaft pipeline according to the working mode, if the mode is a forklift mode, the 2-to-3 way valve is communicated with an oil return path of the forklift, and if the mode is other modes, the 2-to-3 way valve is communicated with an oil path of a rear wheel cylinder;

secondly, in the braking process, the wheel cylinder pressure sensor transmits the pressure in the pipeline back to the ECU in real time;

thirdly, the ECU judges whether the pressure of the front shaft and the rear shaft reaches the upper limit value under the model mode, if the single shaft reaches the upper limit value, a control signal is sent to the electromagnetic valve corresponding to the shaft, and if the two shafts all reach the upper limit value, a control signal is sent to the brake motor and each electromagnetic valve;

fourthly, the motor stops working after receiving the control signal, the 2-position 2-way electromagnetic valve enters a closing mode after receiving the signal, and the brake system enters a pressure maintaining working state;

fifthly, when the system or the operator judges that the brake can be released or the brake strength is reduced, under the control of the ECU, the electromagnetic valve is opened, and the brake oil pushes the main cylinder piston to return under the action of high pressure or the motor reversely rotates to drive the piston to return to actively release the pressure.

In addition, when the failure of the front axle brake pipeline is detected, if the front axle brake pipeline is in a forklift working mode, the system automatically exits the mode and starts the rear axle brake pipeline so as to ensure that certain braking force can be provided. Moreover, the braking system can perform gentle braking according to the requirement: when the automatic driving system or an operator judges that the vehicle needs to be gently braked and provides expected braking force according to the state and the surrounding environment of the whole vehicle, the braking system can enter a pressure maintaining mode in advance according to the expected value to maintain lower braking force so as to gently brake and save energy.

As shown in fig. 7, the upper limit of the braking force of the front axle and the rear axle in operation of the chassis brake module for a plurality of vehicle types is related to the vehicle type.

The system improves the hydraulic structure of the existing brake system and the hydraulic structure of the ABS and other systems, cancels the design of a brake cylinder and a plurality of hydraulic valves, simplifies the structure and reduces the cost. Meanwhile, the design scheme of the hydraulic system provided by the invention can be well combined with an automatic driving system, and provides braking system parameters such as different braking modes, braking force distribution coefficients and the like for different vehicle types such as a forklift, a snow sweeper, an express delivery vehicle and the like under the condition of matching with the control algorithm.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A chassis brake module mechanical structure for multiple vehicle types, comprising:

the speed reducer module (101), the speed reducer module (101) is directly connected with an output shaft of an external motor and is used for reducing speed and increasing torque;

the screw box module (102), one side of the reduction box module (101) is butted with the screw box module (102) through convex and concave edges and is fixed through bolts, and one side of the reduction box module (101) is matched with the screw box module (102) in size;

the reduction box module (101) comprises a reduction box body, a gear shaft, a double-stage soft-tooth-surface gear pair, a bearing and the like, wherein the reduction box module (101) comprises a reduction box body (1), an output shaft large gear (2), a cylindrical roller (3), an input shaft small gear (4), a reduction box cover (5), an input shaft bearing end cover (6), an input shaft (7), an intermediate shaft bearing end cover (8), an intermediate shaft (9), a 6303 bearing (10), an intermediate shaft large gear (11), an intermediate shaft small gear (12), a shaft sleeve (13), an output shaft bearing end cover (14), a felt ring (15), an output shaft (16), a 6306 bearing (17), a sealing gasket (18), an M10 inner hexagonal screw (19) and an M12 inner hexagonal screw (20);

the lead screw box module (102) comprises a lead screw box (100), a ball screw pair, an output push disc (700), a bearing and other supporting elements, wherein the lead screw box module (102) comprises the lead screw box (100), a combined bearing support (200), a combined bearing (300), a lead screw nut (400), a second felt ring (500), a second M10 hexagon socket head cap screw (600), the output push disc (700), a second M12 hexagon socket head cap screw (800), a spring washer (900), a nut push rod (1000), a bearing end cover (110), a 6013 bearing (120), an M12X hexagon head bolt (130), a ball screw (140) and an M16X hexagon socket head cap screw (150).

2. The mechanical chassis brake module structure for multiple vehicle types according to claim 1, wherein the reduction box body is composed of a reduction box (1) and a reduction box cover (5), and the reduction box (1) and the reduction box cover (5) are combined to form a flat rectangular parallelepiped.

3. The mechanical chassis brake module for a multi-vehicle type according to claim 1, wherein the gear shaft includes an input shaft (7), an intermediate shaft (9), and an output shaft (16), the input shaft (7) is connected to the motor output shaft by a flat key, and the output shaft (16) is connected to the ball screw (140) by a spline shaft.

4. The mechanical structure of the chassis brake module for the multiple vehicle types according to claim 1, wherein the double-stage soft-toothed gear pair is composed of an input shaft pinion (4), an intermediate shaft gearwheel (11), an intermediate shaft pinion (12) and an output shaft gearwheel (2), and the input shaft pinion (4), the intermediate shaft gearwheel (11), the intermediate shaft pinion (12) and the output shaft gearwheel (2) are fixedly connected with a gear shaft through flat keys.

5. The chassis brake module mechanical structure for the multiple vehicle types according to claim 1, wherein the left side of the input shaft (7) is arranged on the reduction gearbox (1) through a 6303 bearing (10), the right side of the output shaft (16) is arranged on the reduction gearbox (1) through a 6306 bearing 17, and the input shaft (7) and the output shaft (16) are sleeved through a cylindrical roller (3).

6. The chassis brake module mechanical structure for multiple vehicle types according to claim 1, characterized in that the ball screw pair is composed of a ball screw (140) and a screw nut (400), the left end of the ball screw (140) is machined and formed into a spline hub, and the ball screw (140) is matched with the output shaft (16) of the reduction gearbox.

7. The mechanical structure of a chassis brake module for a multi-vehicle type according to claim 1, wherein one end of the ball screw (140) is supported on the screw box (100) through a 6013 bearing (120), the middle part of the ball screw (140) is supported at the bottom of the screw box (100) through a combination bearing (300) and a special combination bearing support (200), and one side of the screw box (100) is connected with an external piston push rod through an output push disk (700).

8. The chassis brake module mechanical structure for multiple vehicle types according to claim 1, wherein the lead screw nut (400) is fixedly connected with 6 nut push rods (1000) through nuts, and the nut push rods (1000) are uniformly distributed on a flange of the lead screw nut (400).

9. The chassis brake module mechanical structure for the multiple vehicle types according to claim 1, wherein one end of the nut push rod (1000) passes through a through hole on the lead screw box (100), the other side of the nut push rod (1000) is fixedly connected with the output push disc (700) through a nut, and threads are machined on both sides of the nut push rod (1000).

10. The hydraulic control system for the chassis brake module of multiple vehicle types is characterized by comprising an ECU module, a double-cavity brake master cylinder, an oil storage tank, a brake oil path, a switch valve, a reversing valve, a front wheel cylinder, a rear wheel cylinder and a pressure sensor;