Process report research and testing anti lock braking system and traction control system of honda civic 2020 by matlab and carsim software

+ Brake clogs+ Brakes+ Disc brake- Classification by mode of drive+ Mechanical brake drive+ Hydraulic brake drive+ Pneumatic vapor brake drive+ Combined brake drive hydraulic + pneumatic

FACULTY FOR HIGH QUALITY TRAINING

PROCESS REPORT

RESEARCH AND TESTING ANTI LOCK BRAKING SYSTEM AND TRACTION CONTROL SYSTEM OF HONDA CIVIC 2020 BY MATLAB AND CARSIM

SOFTWARE

Ho Chi Minh City, June 2022

FACULTY FOR HIGH QUALITY TRAINING

PROCESS REPORT

RESEARCH AND TESTING ANTI LOCK BRAKING SYSTEM AND TRACTION CONTROL SYSTEM OF HONDA CIVIC 2020 BY MATLAB AND CARSIM

SOFTWARE

VIETNAM Independence – Freedom– Happiness

1 Project title: _

2 Initial materials provided by the advisor: _

3 Content of the project: _

4 Final product:

CHAIR OF THE PROGRAM

(Sign with full name)

ADVISOR

(Sign with full name)

ADVISOR’S EVALUATION SHEET

Student name: Student ID: _ Major: Automotive Engineering

Project title: Research and Testing the Anti Lock Braking System and Traction Control System on Honda Civic 2020 by MATLAB and Carsim SoftwareAdvisor:

EVALUATION

1 Content of the project:

2 Strengths:

3 Weaknesses:

THE SOCIALIST REPUBLIC OF VIETNAM

Independence – Freedom– Happiness

-Ho Chi Minh City, June 12, 2022

The authors gratefully acknowledge the valuable supports from Ph.D Nguyen Manh

Cuong from Ho Chi Minh City University of Technology and Education.

CHAPTER I: OVERVIEW OF CAR BRAKE SYSTEM

1 Purpose and meaning of the topic

Currently, cars have become an important means of transporting passengers and goodsfor national economic sectors, and at the same time have become a private means oftransport in countries with developed economies In our country, the number of peopleusing cars is increasing, along with the growth of the economy, the increasing density ofcars on the road leads to more and more traffic accidents Therefore, to ensure the safety

of traffic accidents is one of the most necessary solutions, always concerned by thedesigners and manufacturers of cars, where the brake system plays a very importantrole Because of that, now the brake system is increasingly improved, the standards forthe design, manufacture and use of the brake system are increasingly strict and strict.For students majoring in traffic mechanics, the survey and testing of the brake system iseven more practical That's why I chose the topic "Surveying, calculating and testing theABS brake system on Honda Civic 2020" To solve this problem, first of all, we need tounderstand the operating principle, structure of details and parts in the brake system.Thereby creating a premise for the design and improvement of the brake system toincrease braking efficiency, increase directional stability and guideability when braking,increase working reliability for the purpose of ensuring movement safety and increasingsafety vehicle performance

2. Uses, classifications and requirements of the brake system.

2.1 Uses

The brake system is used to slow down the vehicle until it comes to a complete stop or

+ Brake clogs

+ Brakes

+ Disc brake

- Classification by mode of drive

+ Mechanical brake drive

+ Hydraulic brake drive

+ Pneumatic (vapor) brake drive

+ Combined brake drive (hydraulic + pneumatic)

+ Power-assisted brake drive

2.3 Requirements

The brake system is an important part of the car that performs "active safety" functions,

so the brake system must satisfy the following requirements:

+Has the highest braking efficiency on all wheels under all circumstances

+Quiet operation to ensure the stability of the car when braking

+Smooth control to reduce the driver's labor intensity

+Has high sensitivity to quickly adapt to dangerous situations

+The brake mechanism has no self-tightening phenomenon

+The brake mechanism must have good heat dissipation

+Has a high and stable coefficient of friction

+Keeping the ratio between the force applied to the brake pedal and the brakingforce generated by the brake mechanism

+The system must have reliability, durability and long life

+Streamlined layout for easy adjustment of care and maintenance

3. Structure of disc brakes

Disc brake mechanism is commonly used on passenger cars (mainly on the frontwheels) Recently, this type of brake began to be used on some types of transport andpassenger cars

Disc brakes are of the following types: closed, open, single disc, multi-disc, rotatinghousing type, rotating disc, rotating friction ring

The disc can be a solid disc, a disc with vented slots, a single layer of metal, or acomposite of two dissimilar metals In automobiles, the main type of open disc is used,and rarely the rotary shell type is used

There are two mounting options for clamps: fixed mounting and optional swimmingstyle mounting Fixed mounting plan has high rigidity, allowing large driving force to

be used However, the cooling condition is poor, and the working temperature of thebrake mechanism is higher

stiffness When the guide pins are deformed, wear and tear will cause the brake pads towear unevenly, reduce the braking efficiency and cause vibration However, it has onlyone hydraulic cylinder with twice the length, so the cooling condition is better, the brakefluid is less hot, the working temperature can be reduced by 30 ÷ 50 ˚C In addition, italso allows deep translation of the brake mechanism into the wheel Thereby reducingthe lever arm acting on the rolling resistance to the vertical cylinder of the guide wheels.

Figure 2 Structural diagram of disc brake with automatic clamp type - fixed cylinder:

1. Brake Pads 5 Guide Pin

2. Fixed Clamp 6 Locating Gauze

3. Piston 7 Brake Disc

4. Sealing Ring 8 Shock Absorber Ring

4. Sealing Ring 8 Ventilation Grooves

+ Simple maintenance since no clearance adjustment is required

+ The axial and self-balancing forces should allow their values to be increased toachieve the required braking effect without being limited by the deformationconditions of the structure Therefore, disc brakes are compact in size and easy toarrange in the wheel

+ The braking effect is independent of rotation direction and more stable

+ Better cooling conditions, especially with the rotating disc type

- Disadvantages of disc brake mechanism compared to drum-hoo brake mechanism:

+ Sensitive to dirt and difficult to seal

+ Open type brake discs are easily oxidized and dirty, causing the brake pads to wearquickly

+ High working pressure makes the brake pads easy to crack and scratch

+ It is often necessary to use vacuum boosters to increase driving force, so when theengine is not working effectively, the brake performance is low and it is difficult

to use them to combine as a stop brake

- Structural characteristics of the main details and parts:

+ Brake disc: usually made of cast iron Solid discs are 8 - 13 mm thick Ventilatedslotted disc 16 - 25 mm thick The coupling disc can have an aluminum or coppercore and a friction surface – gray cast iron

+ Clamp: usually cast in wrought iron

+ Hydraulic cylinders: cast aluminum alloy To increase wear resistance and reducefriction, the working surface of the cylinder is chrome plated When the cylinder ismade of aluminum alloy, it is necessary to reduce the heating temperature of thebrake fluid One of the ways to reduce the temperature of brake fluid is to reducethe contact area between the piston and the brake shoe or to use pistons made ofnon-metallic materials

+ Brake pad bodies: the place where the piston presses up is made of sheet steel

+ Friction plate: of open disc brake pads usually have a surface area of about 12 16% of the disc surface area, so disc cooling conditions are very favorable

-4.1 Causes

One of the most common causes of “brake failure” accidents is a loss of brake fluidpressure The brake is operated by hydraulic pressure inside the system Therefore, ifthere is a leak of brake fluid in the brake fluid line or brake cylinder, the brake systemwill not have enough pressure to perform the deceleration When a serious leak occurs,the brake fault light will light up to warn you and the vehicle will not be safe to operate

in this condition

Check the brake fluid tank, if the oil level is too low, it means there is a serious brakefluid leak, need to check the entire brake system to find out where the leak is and fix it.Leaks have many causes, but if the brake fluid level is too low, it means that the rubberseal in the brake system is broken or the oil line is rusty

If the brake pedal is not effective, there may be air in the system At this time, it isnecessary to vent the brake system to remove air bubbles Sometimes it can also bebecause the piston inside the master cylinder is damaged.

Figure 5: Low oil pressure indicator lightAnother possible cause of brake failure is a faulty ABS controller Due to the leak, theinternal pressure drops and the brake pressure cannot be transferred when the brake isapplied Contamination inside the brake fluid can also enter the control unit and preventthe intake and exhaust valves from opening and closing, causing the brakes to fail

Figure 6: When the ABS controller fails, the light will warn

The cause of brake failure can also be caused by the driver, that is, pressing the brakescontinuously for a long time (usually when the vehicle is going downhill on a pass)causes the brake pads to burn, leading to ineffective braking To avoid this, the drivershould not apply the brakes for a long time, instead can use the engine to reduce thevehicle's speed (by engaging in low gear)

Some unexpected accidents related to brake failure, loss of control

Figure 8: The bus lost its brakes and rolled many motorbikes at the red light

Figure 9 : Passenger car lost the brakeThe brake is the part that helps the vehicle decelerate to reduce motion However, after many accidents, the question often arises, why does the brake lose its effect? Is it

directional stability and guideability when braking, increase working reliability for the purpose of ensuring movement safety and increasing safety vehicle performance It is for these reasons that I have chosen this topic.

CHAPTER II: INTRODUCE ABOUT HONDA CIVIC 2020

1. The Overall of Honda Civic 2020

In the Vietnamese market, the Honda Civic model right after its launch has alwaysreceived positive feedback from consumers Over 10 generations, this small sports C-class sedan has quickly entered the list of Top 10 best-selling cars of all time, HondaCivic has become a typical representative of Honda, in terms of agility, in terms offlexibility and especially in terms of reliability

Figure 10: The exterior appearance of the Honda Civic 2020

Unconventional styling with solid lines but still emotional flexibility along with class details, gives Civic a youthful, modern and sportier appearance than ever In particular, the aerodynamic design style also helps to complete the fuel efficiency and quietness of the cabin

high-This is the most spectacular makeover ever of this small sedan With an all-new fastback design, the most powerful turbo engine in the segment, and many safety-driving assist technologies are notable points in this version.

In Vietnam, Honda Civic is being distributed with 03 versions, which are the standard Civic 1.8E CVT with naturally aspirated gas, the turbocharged Civic 1.8G CVT and the high-end Civic 1.5RS CVT Turbo

2. Honda Civic Overview

2.1 Overview of Honda Civic cars

2.2.1 Honda Civic specifications are listed in the table 1

Table 1: Basic technical parameters of Honda Civic 2020

E CIVIC 1.8 G CIVIC1.5 RS TRANSMISSION ENGINE

ENGINE STYLE

1.8 SOHC VTEC

i-4 cylinders

in line 16valves

1.8 SOHCi-VTEC

4 cylinders

in line 16valves

1.5LDOHCVTECTURBOTRANSMISSION (CVT) EARTH DREAMSTECHNOLOGY

Cylinder capacity (cm3) 1.799 1.799 1.498Maximum power (Hp/rpm) 139/6.500 139/6.500 170/5.500Maximum torque (Nm/rpm) 174/4.300 174/4.300 220/1.700-5.500Fuel tank capacity (litre) 47 47 47Fuel system PGM-FI PGM-FI PGM-FIAcceleration time from 1 to

100km/h (giây) 10 10 8.3

SIZE/WEIGHT

Length x Width X Height (mm) 4.648 x 1.799 x 1.416

The standard long (mm) 2700

Tire size 215/55R16 215/55R16 235/40R18Lazang (inch) 16 16 18Ground clearance (mm) 133 133 133Minimum turning radius (m) 5.3 5.3 5.3

BRAKING SYSTEM

Front brake Disc brake

Rear brake Disc brake

2.2.2 Engine

Figure 12: Engine on Honda Civic 2020The first engine block equipped on the standard versions Civic 1.8E & Civic 1.8G is anaturally aspirated 1.8 SOHC i-VTEC engine, 4 cylinders, 16 valves This engine blockdelivers a maximum power of 139 (hp) at 6,500 rpm (rpm), along with a maximumtorque of 174 (Nm) at 4,300 (rpm) Comes with a CVT automatic transmission usingHonda's Earth Dreams technology In versions 1.8E & 1.8G naturally aspirated with

must trade off fuel consumption to achieve higher power output With the same fuel, theVTEC TURBO engine produces more power than a naturally aspirated engine, byreusing energy from the exhaust gas, which increases the thermal efficiency of theengine.

2.2.3 Powertrain, steering system

Exciting driving experience with MA-EPS (Motion Adaptive Electric Power Steering)

Figure 13: Steering system uses electronic power steering ESP

- MA-EPS is a combination of EPS electronic power steering system with VSA system

- MA-EPS uses data about vehicle speed and steering angle as input signals toanalyze, calculate and make adjustments to the steering system

- Steering force will be gentle when the vehicle is operating at low speed and will

be more compact when the vehicle is operating at high speed

- In the following cases: oversteer, understeer, slippery road, MA - EPS makes iteasier for the driver to steer the steering wheel in a stable direction & difficult tosteer in an unstable direction This helps the car to be more balanced and safe onall roads

With EPS and MA-EPS electronic steering system, Honda vehicles will givecustomers the confidence to operate quickly, accurately and stably during thejourney, customers will feel secure and safe completely when traveling on allroads with a Honda

The Honda Civic 2020 brake system is a hydraulic brake system with vacuum assist,using a disc brake mechanism on the front and rear axles The anti-lock braking system(ABS) combines the electronic brake force distribution system EBD (Electronic BrakeForce Distribution) with internal sensors to ensure optimization on all terrains.

Figure 15: Chassis and suspension system on Honda Civic 2020

- Ventilation, heating, air conditioning systems, wipers, glass washers

- Sound system: 8-speaker audio, the ability to answer phones hands-free, texting, voice commands and navigation maps

CHAPTER III: Braking system on Honda Civic

3.1 General layout diagram of the brake system on the vehicle

Figure 16: General layout diagram of the brake system on the vehicle

times to avoid the above situation However, there is no time to do this duringemergency braking To solve the above problem, manufacturers to create cars with ABSsystem - Anti-lock Braking System.

3.2.2 Diagram of brake system drive

a) General diagram of the main brake system ABS

The anti-lock braking system (ABS) is essentially a brake force regulator with a reverse contact circuit The typical block diagram of an ABS looks like this:

Figure 17: General diagram of the main brake system ABS

1 Brake disc 8 Hydraulic block

2 Sensor gear ring 9 Signal line

3 Master cylinder 10 ABS indicator light

4 Vacuum booster 11 Rear brake fluid line

5 Pedal 12 Rear wheel speed sensor

6 Front wheel speed sensor 13 Wheel brake cylinder

7 Front brake fluid line

- When the brake pedal is pressed, the high pressure oil in the master brake cylinder(3) is amplified by the power assist, which will be transmitted to the wheel cylindersand perform the braking process.

- If one of the wheels shows signs of slowing down compared to the other wheels(about to lock), this signal is processed by the ECU and the brake hydraulic controlECU works to reduce the oil pressure in the wheel cylinder the car so that it doesn'tlock up

- ABS ensures directional stability and control performance during braking

- If there is a fault in the ABS system, the ABS indicator (10) lights up and the checkmust be carried out through the diagnostic machine

During ABS control, the wheels involved are controlled by a total of 4 pressure holdingvalves and 4 pressure reducing valves

b) Diagram of hydraulic control assembly

Figure 18: Diagram of hydraulic control assembly

1 Oil pipelines 10 Rubber ring proportional structure

2 Piston master cylinder 11 Power steering membrane

3 Master cylinder 12 Vacuum booster

4 Engine intake manifold 13 Brake fluid reservoir

5 Vacuum valve 14 Front and rear wheel cylinders

6 Air filtration 15 One way valve

7 Pedals 16 Engine intake line

vacuum When releasing the brake: The vacuum valve (5) opens, so compartment Awill communicate with compartment B through this valve and have the same vacuumpressure When braking: The driver acts on the pedal to push the lever to move to theright, causing the vacuum valve (5) to close and cut off the passage of twocompartments A and B, and the air valve (9) to open to allow air to pass through thefilter element (6) enters compartment A The pressure difference between twocompartments A and B will create a pressure acting on the membrane of the powersteering and thereby create an auxiliary force to support the driver and act on thecomponents piston in the master cylinder (2), presses the oil along the pipes to thewheel cylinders to perform the braking process When the force acting on the powersteering diaphragm (11) increases, the deformation of the rubber ring (10) alsoincreases, causing the piston to move slightly forward relative to the push rod, causingthe air valve (9) to close and hold for a constant differential pressure, i.e constantpower assist To increase braking force, the driver must continue to pedal harder, pushthe lever to move to the right to make the air valve (9) open to allow more air to entercompartment A The pressure difference increases, the rubber ring (10 ) is moredeformed, causing the piston to move forward slightly compared to the rod (8), makingthe air valve (9) close to ensure that the pressure difference or power assist is constantand proportional to the pedal force When the braking force is at its maximum, the airvalve opens completely and the pressure difference or power assist also reaches themaximum value.

3.2.3 Stages of the ABS brake system

Normal braking process

ECU

4

11 10

14

13 12

Figure 19: Diagram of ABS system when braking normally

1 Election of assistants 9 Pulse generating gear

2 Oil pipeline 10 One-way crazy valve 1

3 Non-return valve No 3 11 Oil pump

4 Coil 12 One-way electric valve 2

5 Pressure holding valve 13 Storage tank

6 Valve pressure relief 14 Battery

7 Brake mechanism 15 ECU slide control

8 Speed sensor

During normal braking, the ABS system does not operate and the ABS-ECU does notsend current to the coils of the valves and the pump motor does not operate Thus openthe pressure retaining valve and close the pressure reducing valve and make the valves

in the position as shown

When the brake pedal is pressed, the oil from the master brake cylinder will passthrough the pressure-holding valve into the wheel brake cylinder and perform thenormal braking process.

When the brake is released, the oil from the wheel brake cylinder will return through thepressure retaining valve to return to the master brake cylinder

When performing emergency braking (ABS system will work)

If any wheel appears to be about to lock, the ABS-ECU will send a signal to control thebrake fluid pressure acting on that wheel cylinder in the direction of pressure reduction

to avoid locking

Normally, the process of controlling brake fluid pressure through 3 stages is:

a) Pressure drop stage

10 4 2

5 3

15

13 ECU

14

11

12 6

8

9 7

Figure 20: Diagram of working principle of ABS system (Pressure Reduction Stage)

1 Election of assistants 9 Pulse generating gear

2 Oil pipeline 10 One-way crazy valve 1

3 Non-return valve No 3 11 Oil pump

4 Coil 12 One-way electric valve 2

5 Pressure holding valve 13 Storage tank

6 Valve pressure relief 14 Battery

7 Brake mechanism 15 ECU slide control

8 Speed sensor

When a wheel is about to lock, based on the signal received from the wheel speedsensor The ABS-ECU will send electricity (5V) to the coils of the solenoid valves,generating a strong magnetic force that overcomes the elastic force of the valve springs

As a result, the pressure retaining valve closes and the pressure reducing valve openswhen the oil from the wheel cylinder will return to the oil tank At the same time, the

pump motor continues to run while the ABS is operating thanks to the signal from theECU, so the brake fluid flowing into the reservoir is sucked by the pump back to themaster cylinder.

b) Pressure holding period

8 9 7

When the pressure in the wheel cylinder decreases or increases, the wheel speed sensorsends a signal to the ABS-ECU If the wheel speed is at the desired speed, the ABS-ECU will supply current (5V) to the solenoid valve to keep closing and cut off thecurrent of the pressure reducing valve when

Then the return spring will close the valve, that is, both the pressure retaining valve andthe pressure reducing valve are closed As a result, the oil pressure in the wheelcylinders is kept constant

c) Pressure rise stage

5 3

Figure 22: Diagram of working principle of ABS system (Stage Booster Pressure)

1 Election of assistants 9 Pulse generating gear

2 Oil pipeline 10 One-way crazy valve 1

3 Non-return valve No 3 11 Oil pump

4 Coil 12 One-way electric valve 2

5 Pressure holding valve 13 Storage tank

6 Valve pressure relief 14 Battery

7 Brake mechanism 15 ECU slide control

8 Speed sensor

When the pressure in the cylinder of a wheel decreases, its rotation speed increases,there is a speed difference of that wheel (faster) compared to other wheels, the signalfrom the wheel speed sensor will be sent to the ABS-ECU ABS-ECU will cut off thecurrent to the pressure retaining valve when both the pressure retaining valve and thepressure reducing valve have a voltage of 0V As a result, the pressure-retaining valveopens and the pressure-relief valve closes evenly thanks to the return force of the spring,the oil from the master brake cylinder enters the wheel brake cylinder through thepressure retaining valve At the same time, the pump motor is still operating from thecontrol signal of the ABS-ECU, which supplies oil from the reservoir to the wheelcylinder through the pressure-holding valve, increasing the pressure of the wheelcylinder

3.3 Structure and and main parts

3.3.1 Brake mechanism

All four brake mechanisms working on the vehicle are disc brakes with automaticclamps with Cylinders arranged on the clamps However, there is a structural differencebetween the front brake mechanism and the rear brake mechanism

This type of brake mechanism has a low rigidity, when the guide pins are deformed andworn, the brake pads will wear unevenly, the braking efficiency will be reduced, andthere will be large vibrations However, this type of brake gives better cooling

9

22 20

21

12 A

2

8

14

B-B 19

Figure 23: Front brake mechanism Honda Civic

1 Brake disc 9 Sealing gasket 16 Dust shield

2 Brake pads 10 Protective cushions 17 Bolts catch wheel hub

to brake disc

3 Brake pad body 11 Compartment ring 18 Silver pads

4 Mobile brake fork 12 Bolts to catch brake

calipers and beams 19 Dust shield ring

5 Air release screw 13 Hole to catch brake

assembly on car girder 20 Brake bolt

6 Cylinder 14 Wheel hubs 21 Rings

7 Piston 15 Ventilation grooves 22 Slide pin

8 Oil supply hole

The friction plate of open disc brake pads usually has a small friction area compared tothe disc surface area, so the disc cooling conditions are very favorable Hydrauliccylinders made of aluminum alloy To increase wear resistance and reduce friction, theworking surface of the cylinder is chrome plated When the cylinder is made ofaluminum alloy, it is necessary to reduce the heating temperature of the brake fluid One

of the ways to reduce brake fluid temperature is to reduce the contact area between thepiston and the brake pads or to use pistons made of non-metallic materials The brakepads where the piston presses against are made of sheet steel The hydraulic cylinderpressing mechanism, also known as the child cylinder or wheel cylinder, has a simplestructure and is easy to arrange The cylinder body is made of gray cast iron, theworking surface is polished Piston is made of aluminum alloy

Working principle: When the driver steps on the brake pedal, the oil is pushed from

the master cylinder to the booster, a part directly goes to the wheel cylinders to generatebraking force, partly through the duct to open the air valve of the vehicle the boostercreates a pressure difference between the two compartments in the booster It is that

structures have not high stiffness When the guide pins are worn, deformed, and rusted,the brake pads will wear unevenly, reduce the braking efficiency and cause vibration.The rear brake mechanism of the Honda Civic uses a single piston, so it has better heatdissipation So the type of disc that the rear brake uses is a solid disc In particular, theinner surface of the brake disc is used as a drum for the stopping brake system, so thissurface is designed to be thicker than usual With such a structure, the coolingconditions are better, the working temperature of the brake mechanism is low However,the stiffness is not high When the guide pins are worn, deformed, and rusted, the brakepads will wear unevenly, reduce the braking efficiency and cause vibration The soliddisc brake disc is made of cast iron, the clamp is made of forged cast iron, and thehydraulic cylinder is made of aluminum alloy To increase wear resistance and reducefriction, the working surface of the cylinder is chrome plated When the cylinder ismade of aluminum alloy, it is necessary to reduce the heating temperature of the brakefluid One of the ways to reduce brake fluid temperature is to reduce the contact areabetween the piston and the brake pads or to use pistons made of non-metallic materials

3

13 12 9

4 Brake shoes 13 Bolts to catch brake

calipers and beams 21 Dust shield ring

5 Clamps pad 14 Wheel hubs 22 Pin on which

calipper slides

6 Air release screw 15 Bolts catch wheel hub

to brake disc 23 Sliding Silver Pads

7 Protective cushions 16 Brake caliper 24 Piston

8 Brake pad body 17 Cable 25 Bolts

9 Brake pad

3.3.2 Master cylinder

The brake master cylinder in the vehicle brake drive is a two-piston dual mastercylinder, installed in series with a brake booster with each piston regulating one brakeline

Main brake cylinder structure:

+ The main brake cylinder is a dual cylinder, that is, in the brake cylinder there aretwo pistons, corresponding to them are two separate oil chambers

+ Cylinder body is cast in cast iron, on the body is processed compensation holes,through holes, and this is also a detail to install other details

+ Each chamber of the master cylinder has a piston and each piston has its ownreturn spring Piston is made of die-cast aluminum, the working end has a fixedgasket sealed, each piston has a hole drilled and has an oil chamber tocompensate for oil in the return stroke The rear of the first chamber piston has arecess to accommodate the tip of the push rod

+ Sealing ring: Made of brake fluid-resistant rubber, moving in the cylindertogether with the piston acts as a seal when the oil is under high pressure in thecompression stroke