Hydraulic brake

The hydraulic brake is an arrangement of braking mechanism which uses brake fluid, typically containing ethylene glycol, to transfer pressure from the controlling unit, which is usually near the operator of the vehicle, to the actual brake mechanism, which is usually at or near the wheel of the vehicle.

Construction:- 

                                     The most common arrangement of hydraulic brakes for passenger vehicles, motorcycles, scooters, and mopeds, consists of the following:
Brake pedal or lever
A pushrod (also called an actuating rod)
A master cylinder assembly containing a piston assembly (made up of either one or two pistons, a return spring, a series of gaskets/ O-rings and a fluid reservoir)
Reinforced hydraulic lines
Brake caliper assembly usually consisting of one or two hollow aluminum or chrome-plated steel pistons (called caliper pistons), a set of thermally conductive brake pads and a rotor (also called a brake disc) or drum attached to a axle.

The system is usually filled with a glycol-ether based brake fluid (other fluids may also be used).

At one time, passenger vehicles commonly employed disc brakes on the front wheels and drum brakes on the rear wheels. However, because disc brakes have been shown a better stopping performance and are therefore generally safer and more effective than drum brakes, four-wheel disc brakes have become increasingly popular, replacing drums on all but the most basic vehicles. Many two-wheel vehicles designs, however, continue to employ a drum brake for the rear wheel.

For simplicity, the braking system described hereafter uses the terminology and configuration for a simple disc brake.

System Operation :-

                                                 Within a hydraulic brake system, as the brake pedal is pressed/ brake lever is squeezed, a pushrod exerts force on the piston(s) in the master cylinder causing fluid from the brake fluid reservoir to flow into a pressure chamber through a compensating port which results in an increase in the pressure of the entire hydraulic system. This forces fluid through the hydraulic lines toward one or more calipers where it acts upon one or two additional caliper pistons secured by one or more seated O-rings which prevent the escape of any fluid from around the piston.

The brake caliper piston(s) then apply force to the brake pads. This causes them to be pushed against the spinning rotor, and the friction between the pads and the rotor causes a braking torque to be generated, slowing the vehicle. Heat generated from this friction is often dissipated through vents and channels in the rotor and through the pads themselves which are made of specialized heat-tolerant materials (kevlar, sintered glass, et al.).

Subsequent release of the brake pedal/ lever allows the spring(s) within the master cylinder assembly to return that assembly's piston(s) back into position. This relieves the hydraulic pressure on the caliper allowing the brake piston in the caliper assembly to slide back into its housing and the brake pads to release the rotor. Unless there is a leak somewhere in the system, at no point does any of the brake fluid enter or leave.

Component specifics :-

                                        (For typical light duty automotive braking systems)

The brake pedal is a simple lever. One end is attached to the framework of the vehicle, a pushrod extends from a point along its length, and the foot pad is at the other end of the lever. The rod either extends to the master cylinder (manual brakes) or to the vacuum booster (power brakes).

In a four-wheel car, the master cylinder is divided internally into two sections, each of which pressurizes a separate hydraulic circuit. Each section supplies pressure to one circuit. Passenger vehicles typically have either a front/rear split brake system or a diagonal split brake system (the master cylinder in a motorcycle or scooter may only pressurize a single unit, which will be the front brake).

A front/rear split system uses one master cylinder section to pressurize the front caliper pistons and the other section to pressurize the rear caliper pistons. A split circuit braking system is now required by law in most countries for safety reasons; if one circuit fails, the other circuit can stop the vehicle.

Diagonal split systems were used initially on American Motors automobiles in the 1967 production year. The right front and left rear are served by one actuating piston while the left front and the right rear are served, exclusively, by a second actuating piston (both pistons pressurize their respective coupled lines from a single foot pedal). If either circuit fails, the other, with at least one front wheel braking (the front brakes provide most of the speed reduction) remains intact to stop the mechanically-damaged vehicle. Just before 1970, diagonally split systems had become universal for automobiles sold in the United States.

The diameter and length of the master cylinder has a significant effect on the performance of the brake system. A larger diameter master cylinder delivers more hydraulic fluid to the caliper pistons, yet requires more brake pedal force and less brake pedal stroke to achieve a given deceleration. A smaller diameter master cylinder has the opposite effect.

A master cylinder may also use differing diameters between the two sections to allow for increased fluid volume to one set of caliper pistons or the other.

Power brakes:-
                                        The vacuum booster or vacuum servo is used in most modern hydraulic brake systems which contain four wheels. The vacuum booster is attached between the master cylinder and the brake pedal and multiplies the braking force applied by the driver. These units consist of a hollow housing with a movable rubber diaphragm across the center, creating two chambers. When attached to the low-pressure portion of the throttle body or intake manifold of the engine, the pressure in both chambers of the unit is lowered. The equilibrium created by the low pressure in both chambers keeps the diaphragm from moving until the brake pedal is depressed. A return spring keeps the diaphragm in the starting position until the brake pedal is applied. When the brake pedal is applied, the movement opens an air valve which lets in atmospheric pressure air to one chamber of the booster. Since the pressure becomes higher in one chamber, the diaphragm moves toward the lower pressure chamber with a force created by the area of the diaphragm and the differential pressure. This force, in addition to the driver's foot force, pushes on the master cylinder piston. A relatively small diameter booster unit is required; for a very conservative 50% manifold vacuum, an assisting force of about 1500 N (200n) is produced by a 20 cm diaphragm with an area of 0.03 square meters. The diaphragm will stop moving when the forces on both sides of the chamber reach equilibrium. This can be caused by either the air valve closing (due to the pedal apply stopping) or if "run out" is reached. Run out occurs when the pressure in one chamber reaches atmospheric pressure and no additional force can be generated by the now stagnant differential pressure. After the run out point is reached, only the driver's foot force can be used to further apply the master cylinder piston.

The fluid pressure from the master cylinder travels through a pair of steel brake tubes to a pressure differential valve, sometimes referred to as a "brake failure valve", which performs two functions: it equalizes pressure between the two systems, and it provides a warning if one system loses pressure. The pressure differential valve has two chambers (to which the hydraulic lines attach) with a piston between them. When the pressure in either line is balanced, the piston does not move. If the pressure on one side is lost, the pressure from the other side moves the piston. When the piston makes contact with a simple electrical probe in the center of the unit, a circuit is completed, and the operator is warned of a failure in the brake system.

From the pressure differential valve, brake tubing carries the pressure to the brake units at the wheels. Since the wheels do not maintain a fixed relation to the automobile, it is necessary to use hydraulic brake hose from the end of the steel line at the vehicle frame to the caliper at the wheel. Allowing steel brake tubing to flex invites metal fatigue and, ultimately, brake failure. A common upgrade is to replace the standard rubber hoses with a set which are externally reinforced with braided stainless-steel wires; these have negligible expansion under pressure and can give a firmer feel to the brake pedal with less pedal travel for a given braking effort.

HYDRAULIC BRAKES:-                                                                                            The hydraulic brake system used in the automobile is a multiple piston system. A multiple piston system allows forces to be transmitted totwo or more pistons in the manner indicated in figure 2-21. Note that the pressure set up by the force applied to the input piston (1) is transmitted undiminished to both output pistons (2 and 3), and that the resultant force on each piston is proportional to its area. The multiplication of forces from the input piston to each output piston is the same as that explained earlier.
The hydraulic brake system from the master cylinders to the wheel cylinders on most automobiles operates in a way similar to the system illustrated in figure 2-22.

Figure 2-21.—Multiple piston system.When the brake pedal is depressed, the pressure on the brake pedal moves the piston within the master cylinder, forcing the brake fluidfrom the master cylinder through the tubing and flexible hose to the wheel cylinders. The wheel cylinders contain two opposed output pistons, each of which is attached to a brake shoe fitted inside the brake drum. Each output piston pushes the attached brake shoe against the wall of the brake drum, thus retarding the rotation of the wheel. When pressure on the pedal is released, the springs on the brake shoes return the wheel cylinder pistons to their released positions. This action forces the displaced brake fluid back through the flexible hose and tubing to the master cylinder.
The force applied to the brake pedal produces a proportional force on each of the output pistons, which in turn apply the brake shoesfrictionally to the turning wheels to retard rotation.
As previously mentioned, the hydraulic brake system on most automobiles operates in a similar way, as shown in figure 2-22. It is beyond the scope of this manual to discuss the various brake systems.

Brake Pedal The brake pedal is directly attached to the master cylinder. Pedal pulsation, excessive pedal travel, a "soft" or "hard" pedal can be indicators of serious problems, including a leak in the hydraulic system, low fluid levels, or unevenly worn shoes or pads.

1. 

Master Cylinder

The master cylinder acts as a holding tank for brake fluid until it is needed. When the brake pedal is depressed, the master cylinder forces fluid to each of the vehicle's wheels.

Wear on the master cylinder's moving parts may allow brake fluid to leak, causing unreliable stopping or possible system failure.

Combination Valve

A vehicle's wheel can lock up if the front and rear brake systems are not working together properly. Comprised of a metering valve, proportioning valve, and brake warning light, the combination valve helps regulate the amount of pressure on each set of wheels -- making sure both front and rear brakes are applied at the same time.

Wheel Cylinder

The wheel cylinder is a critical element in the drum brake assembly. It contains fluid-activated pistons that push the shoes against the drums to slow the wheels.

The wheel cylinder is also the source of many brake problems. If brake fluid leaks from the wheel cylinder, the vehicle could experience unreliable stopping, damage to new brake shoes, or partial brake system failure. A sticking wheel cylinder may cause brake drag, excessive pedal effort, and reduced braking efficiency.

Drum Brake Assembly

A drum brake assembly is used to bring the rear wheels of most vehicles to a stop. Fluid pressure from the master cylinder causes the wheel cylinder to push the brake shoes against the brake drums which are attached to the vehicle's rear wheels. The friction between the stationary shoes and the revolving drums causes the drums to slow and stop the rear wheels.

Worn drums and shoes, however, can cause unreliable stopping, excessive pedal effort, or brake pedal pulsation.

Disc Brake Assembly

Because a disc brake assembly can absorb more heat than a drum brake assembly, most cars use disc brakes for their front brake systems. When the brake pedal is pushed, brake fluid from the master cylinder compresses the brake pads against the rotors attached to the vehicle's front wheels. The friction between the stationary pads and the revolving rotors causes the rotors and wheel to slow and stop.  In day-to-day driving, these rotors and pads are subject to much abuse, and should be checked periodically for wear. Faulty disc brakes can cause excessive pedal travel, pumping or fighting pedal, vibration during braking action, and brake failure.

HINO Trucks and Buses

History of Hino Trucks

The Hino Motors that we know of today is a subsidiary of the Toyota Motor Corporation and a leading manufacturer of buses, trucks, and engines. To understand the steps that Hino took to reach the company that we know, we are going to look at the history of Hino trucks and commercial vehicles.

The Road to Hino

The origins of the Hino Motor Company begin with the Tokyo Gas Industry Company, which started in 1910. As a leader in its industry, the company was able to expand its line of products and eventually built the model TGE A type Truck in 1917. By 1937, this company decided to merge itself with several other Japanese companies to form the Tokyo Automobile Industry Company, which was later renamed the Diesel Motor Industry Company.

Interestingly enough these are the same founding companies that went on to create Isuzu motors, but in 1942 a portion of the company was spun off to create Hino Heavy Industry Company Limited, which marked the beginning of the company as we know it. Its name derived from the company headquarters location of Hino City within Tokyo.

The Growth of Hino

From its beginning, Hino focused on diesel engines, heavy duty trucks, and buses. There is a brief period where they attempt to enter the private car industry through a partnership with Renault, but that is quickly put aside around 1967 when Hino first partners with the Toyota group. By 1984 Hino trucks enters the US market with a medium duty truck designed with the cab over engine. Their first attempt at a practical use for a hybrid vehicle occurs in 1991 with a hybrid diesel and electric engine system to power a bus in Japan.

Today’s Hino Trucks

In 2003 Hino officially becomes a subsidiary of Toyota Motor Company, and its medium duty and heavy duty trucks are re-introduced into the US. That same year Toyota and Hino jointly develop the first hydrogen fuel cell bus service in Japan. Over the next two years Hino introduces hybrid light duty and medium duty trucks to Japan.

This commitment to hybrid and electric technologies places Hino on a path to develop some of the most cutting edge commercial vehicles in the world. Currently, the company is testing a method of hybrid electric bus that does not require a plug for charging. Instead, a wireless system is built into the road to charge the batteries of the bus, so that it can continue to operate without the need for additional fuel.

Today, Hino is 3rd when it comes to the largest truck manufacturers in the world. As the fastest growing medium duty and heavy duty truck manufacturer in the US, and a leader in both diesel and hybrid technologies the Hino brand has a bright future ahead of it.

FY	Management/Production	Products	Environmental Events and Activities
1990	December ■Hino Plant introduced cogeneration equipment
1991	July □Establishment of the Hino Green Fund Foundation	April Release of Hybrid Inverter controlled Motor & Retarder (HIMR) vehicles equipped with hybrid diesel electric engine systems
1992	April ■Establishment of the Hamura Clean Center May ■Total elimination of specified chlorofluorocarbon refrigerant (CFC113) used as a mold release agent for forged parts		◆Rio de Janeiro Earth Summit ◇Establishment of medium-term brake regulations
1993	March □Formulation of the Hino Global Environment Charter □Formulation of the Hino Global Environment Action Plan □Establishment of the Hino Environment Committee ■Establishment of the Production Environment Working Group	March Establishment of the Environment Technology Working Group May Issuance of advance assessment implementation guidelines based on the Recycling Law; completion of switch from specified CFCs for air conditioning to CFC substitutes	◇Enactment of the Basic Environment Law ◇Enforcement of the Law Concerning Special Measures for Total Emission Reduction of Nitrogen Oxides from Automobiles in Specified Areas
1994	June ■Total elimination of trichloroethane used in cleaning parts December ■Hamura Plant introduced cogeneration equipment #2		◇Emission regulations for 1994
1995		February Release of vehicles equipped with common rail fuel injection systems
1996	March □Hino Global Environment Action Plan, 1st revision
1997	March ■Nitta Plant introduced casting sand recycling equipment		◇The Third Conference of the Parties (COP3) held in Kyoto
1998	November ■Elimination of small-size incinerators as a dioxin countermeasure	February Announcement of the voluntary action plan, an end-of-life vehicle recycling initiative
1999	March ○Hamura Plant acquired ISO 14001 certification		◇Emission regulations for 1999
2000	March ○Nitta Plant acquired ISO 14001 certification September □Issuance of an environmental report	February Release of vehicles equipped with Pulse Exhaust Gas Recirculation (EGR) systems
2001	February □Hino Global Environment Charter, 1st revision □Formulation of Hino Motors Environmental Voluntary Plan March ■Achievement of zero emissions at all three plants ○Headquarters and Hino Plant acquired ISO 14001 certification	December Release of first vehicles in Japan equipped with five-cylinder turbo intercooler engine	◇Noise regulations for 2001
2002	January ○Oume Parts Center and Hidaka Delivery Center acquired ISO 14001 certification □Establishment of the Recycling Working Group  □Establishment of the Dealer Environment Working Group  July □Issuance of Dealer Environmental Guidelines September □Issuance of Environmental Procurement Guidelines	February Receipt of the Director-General's Award, the Natural Resources and Energy Agency, the Energy Conservation Award for new model HIMR system route buses	◇Enforcement of the revised Law Concerning Special Measures for Total Emission Reduction of Nitrogen Oxides and Particulate Matters from Automobiles in Specified Areas ◆Johannesburg Earth Summit
2003	April ○Tamachi Office acquired ISO 14001 certification January	August Release of ultra-low PM certified four-star medium- and heavy-duty trucks  October Release of ultra-low PM certified four-star light-duty trucks	◇Emission regulations for 2003
2004	August ■Hino Plant introduced frame deodorizing equipment September ■Nitta Plant introduced cogeneration equipment	April Release of newly developed medium-duty hybrid trucks August Release of ultra-low PM certified four-star small size buses	◇Emission regulations for 2004
2005	April ■Nitta Plant reinforced waste water treatment facilities	May Release of medium-duty trucks compatible with 2005 emission regulations August Release of large-size touring coaches compatible with 2005 emission regulations	◇Enforcement of Law for the Recycling of End-of-Life Vehicles ◇Validation of the Kyoto Protocol ◇Emission regulations for 2005 ◇Exposition of Global Harmony
2006	September ■Shutdown of the Hamura Clean Center ■Issuance of the Hino Green Purchasing Guidelines	February Release of heavy-duty trucks compatible with 2005 emission regulations September Release of light-duty trucks compatible with 2005 emission regulations November Release of medium-duty trucks compatible with low-emission heavy-duty vehicle standards	◇Enactment of the revised Energy Conservation Law
2007	March ■Hino Plant renovated cogeneration equipment August ■Hamura Plant completed new painting facility construction September ■Commencement of demonstration runs along city-operated routes using latest model hybrid buses fueled by second generation bio diesel November ■Recipient at the 4th Eco-Products Awards (Committee Chairperson's Award in the Eco-Products Category) for its "External Power Supply Type Idling-Stop Air-Conditioning System"	January Release of large-sized touring coaches compatible with low-emission heavy-duty vehicle standards February Practical application of second-generation biodiesel; implementation of collaborative projects Release of large-sized route buses compatible with 2005 emission regulations December Addition of the medium-duty truck "Hino Ranger" to the list of heavy-duty trucks compliant with fuel economy standards; Implementation of on-road fleet trial using synthetic liquid Fischer-Tropsch Diesel (FTD) fuel; Addition of the light-duty truck "Hino Dutro" to the list of heavy-duty trucks compliant with fuel economy standards January 2008 Release of the medium-duty truck "Hino Ranger Hybrid" compatible with New Long-Term Emission Regulations	◇Eco Car World 2007 held ◆Issuance of the fourth assessment report from the Intergovernmental Panel on Climate Change (IPCC) ◆Agreement to the COP13 "the Bali Road Map"  ◆Commencement of the first commitment period of the Kyoto Protocol  ◆G20 meeting held, a gathering of cabinet ministers from 20 leading nations to discuss the issue of global warming
2008	April ■Established a truck sales joint-venture company as a part of efforts to enter the Russian market ■Newly introduced a light-duty truck to the Vietnamese market August ■Groundbreaking ceremony held by the Company's local Mexican subsidiary commemorating the planned construction of a new plant ■Established a truck sales joint-venture company as a part of efforts to enter the Indian market December  ■Line-off ceremony held by the Company's local Columbian subsidiary to mark the start of production ○Shanghai Hino Engine Co., Ltd. acquires ISO 14001 certification January 2009 □Hino Motors participates in the Dakar Rally for the 18th successive year February 2009 □Hamura Plant receives an award from Japan's Minister of Economy, Trade and Industry in recognition of its efforts to promote energy conservation activities	May Release of the large Hino Selega Hybrid tour bus following a full model change September Introduced in the line of "Hino Ranger" medium-duty trucks a model equipped with "Pro Shift 6"  December  Steps completed to reinforce the fuel efficiency capabilities offered by Hino Compass	◆The Great Sichuan Earthquake ◇The Hokkaido Toyako Summit established a CO2 reduction target of 50% for 2050 ◇Enforcement of the Basic Act on Biological Diversity 2009 ◆Inauguration of Barack Obama as President of the United States

HINO BUSES

Hino Motors, Ltd. to provide shuttle buses for the G8 Hokkaido Toyako Summit

Hino Motors, Ltd. (“Hino”) will provide the following vehicles as shuttle buses for the G8 Hokkaido Toyako Summit that will be held in July 2008: two different versions of a large-sized hybrid touring coach called the “Hino S’elega Hybrid” and a single hybrid bus equipped with Inductive Power Transfer¹.

The G8 Hokkaido Toyako Summit has been dubbed the “Environment Summit” and environmental concerns are planned to be a major focus. Hino recognizes the importance of such an intention so has decided to provide shuttle buses for the summit. 
Hino will continue to work to actively prevent global warming and provide trucks and buses that are useful for our customers.

Outline of the new “Hino S’elega Hybrid”

The “Hino S’elega Hybrid” is a large-sized high-output hybrid touring coach that is designed to contribute to reducing CO2 emissions. The new model introduces an “A09C-1M” type power unit with a total piston displacement of 8.9 L. This is a combination of a new lightweight, high-output engine and Hino’s special hybrid system². With this power unit, the new model has succeeded in reducing emission gases and improving fuel efficiency.
This has enabled the Hino S’elega Hybrid to meet the 2005 (new long-term) emission regulations and earn it “NOx & PM 10% Reduction Low Emissions Heavy Vehicle” certification from the Ministry of Land, Infrastructure, Transport and Tourism.
With regard to PM emissions, the new model has succeeded in a 50% reduction beyond the values stipulated by regulations and has achieved the fuel efficiency standards for FY2015.

Fig.1: Exterior of the “Hino S’elega Hybrid” (artist’s impression)

 

About the inductive power transfer hybrid bus

This hybrid bus runs on electricity normally to reduce emission gas and CO2 as much as possible while it’s running. It is environmentally-friendly and has succeeded in suppressing internal noise for passengers. In areas where there are no electrical power feeding centers, this model can also run as a normal hybrid bus.

Fig.2: Structure of a hybrid bus equipped with inductive power transfer

Notes:
1: A low-floor hybrid large-sized route bus developed under the “Initiative for the Promotion of Development and Practical Application of Next-generation Low-pollution Vehicles.” Since 2002, this initiative has been promoted by the Ministry of Land, Infrastructure, Transport and Tourism as an Industry-Government-Academia Collaboration Group whose research body is the National Traffic Safety and Environment Laboratory.
In this model, a great amount of electricity is quickly fed from a primary coil built into the road to a secondary coil equipped beneath the floor. The electricity is then stored in batteries built into its roof. The bus can then run on electricity stored in these rooftop batteries.
In areas where there are no electrical power feeding centers, this model can also run as a hybrid bus. The touring coach was demonstrated in an operational service at Tokyo International Airport (Haneda) in February 2008.

2: Introducing Hino’s own parallel hybrid system, which is powered by a normal engine in combination with an electric motor. During normal operation, the Hino S’elega Hybrid is powered only by the engine. When starting to move or accelerating, the electric motor assists the engine. This enables the Hino S’elega Hybrid to improve fuel efficiency and to contribute to reducing CO2 emissions.

BUSES IN PAKISTAN

The largest Manufacturer of Buses in Pakistan, Hinopak is fully-equipped to design and manufacture a wide range of Bus Chassis and all types of Bus Bodies. Hinopak’s Bus Line Up includes the Roadliner Supreme Luxury Bus for long journeys, Citiliner Intercity Buses, Citiliner Urban Buses and the luxury Senator Coach and Rapidliner Deluxe Coaches.

Hinopak delivers only the safest most reliable products and remains the Pioneer in supplying the largest number of Urban Buses those are successfully facilitating the commuters of Punjab and Sindh.Hinopak is fully-equipped to design and manufacture a wide range of Bus Chassis and all types of Bus Bodies.

Hinopak’s Bus Line Up includes the Roadliner Supreme air-condition Super Luxury Bus, Citiliner Intercity Buses, Citiliner Urban Buses, Senator Pride, air-condition luxury coach and Rapidliner Deluxe Coach.