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Abstract: In this study, a gear shifting mechanism was designed and applied to make the shifting process
faster and less destructible for the driver. The new device must be reliable, has a small dimensions, low
construction and maintenance cost. This paper aims to improve gear shifting process using devices as: a
manual four speed gear box, two pneumatic double acting cylinders, Programmable Logic Controller (PLC), an
electrical motor , limit switches, push buttons, bulbs, a table (holder) and power supply. According to suggested
gear_ shifting method the control unit chooses optimum gear shifting ratio for an automobile without operating
it manually (using relays). Using this method leaves to the driver the excitement of choosing the shifting
moment
Introduction
At present due to the extended difficulties in manual operations, the technology has shifted from
manual to automatic; few of them include ABS system, active steering system e.t.c., in order to increase
passenger safety and comfort. Increasing demands on performance, quality and cost are the main challenge for
today’s automotive industry, in an environment where movement, component and every assembly operation
must be immediately and automatically recorded, checked and documented for maximum efficiency. One of the
automatic applications includes pneumatic gear changer. This study describes in detail in an understandable way
to how to convert the traditional manually gear shifting mechanism by using microcontroller (control unitrelays).
A method of controlling a gear change of an automobile, said automobile comprising an internal
combustion engine; an automatic transmission connected to an output rotation shaft of said engine so as to
transmit the rotational output of said engine to drive wheels of said automobile through any selected one of a
plurality of gear ratios; a load device selectively connectable to said output rotation shaft of said engine via
selectively-connecting means; and means for generating a gear change control signal for selecting one of said
gear ratios of said automatic transmission in accordance with one of operational conditions of said automobile
and said engine said method comprising the steps of controlling said selectively-connecting means when said
gear change signal-generating means generates the control signal for shifting up the gear in said automatic
transmission, in such a manner that said selectively-connecting means connects said load device to said output
rotation shaft of said engine.
For some drivers, the gear shifting can cause some confusing at driving especially at critical situations.
A crowded road on a hill or a sudden detour makes a lot of tension on the driver. One of the difficulties in this
situation is to choose right reduction ratio and engaging it at the right time. This design helps the driver to
increase his focusing on the road. Also reduces the time needed to engage the required reduction ratio, which
increases the vehicles’ response.
II. Objective
The main objective of this system is to minimize the human errors in operating the gears with the help
of automatic technology. Other objectives include optimum gear ratios, reducing wear and tear of the gears,
shifting the gear effectively, optimum performance of the gear box, optimum force exerted by the cylinders to
move the shifting levers (pedals).
III. Model Components
1) A manual 4- speed gear box
2) Pneumatic cylinders
3) Programmable Logic Controller (PLC) - Micro controller
4) Directional Control Valves (DCV)
5) An electric motor (to simulate a combustion engine rotation)
6) Transformer
7) 12 Volt DC power supply
8) Proximity sensor
9) Liquid Crystal Display
10) Relays
11) Solenoid Valve
3.1 Model Components
1. Manual 4- speed gear box:
Manual gear box is a synchronizer type with helical gears. It has one input shaft and one output shaft. It
has three shifting arms; one for first and second speeds, the second one for the third and fourth speeds, third one
for the neutral as shown in (Fig.1). There are three connecting rods for each arm. Every connecting rod connects
its shifting arm with a common shifting lever as shown in (Fig.2). The common arm is 80 mm length with
ability of sliding and axial motions. The axial motion is 35 mm forwards and 35 mm backwards
(35mm8.35mm). The sliding motion is 15 mm to the left and 15 mm to the right (15mm²15mm÷). The arm is
connected from the top with the front and rear pistons rod.
Pneumatic Cylinders:
Pneumatic cylinders (sometimes known as air cylinders) are mechanical devices which use the power
of compressed gas to produce a force in a reciprocating linear motion.
It consists of two openings one on the top and another on its side below , when a compressed air is
passes through the valve the piston present inside the pneumatic cylinder gets energized and ejects the piston
head out. The pressure used in this pneumatic cylinder should be 2 bar , but due to large openings and leakage
of the air from the cylinder the pressure can be increased to 4-5 bar.
Generally we prefer pneumatic cylinder than fluid cylinder as pneumatic cylinder has no fluid
drippings and it will not affect he surroundings. As with the categorization pneumatic cylinders can be divided
into 2 types
Single acting cylinder (sac)
Double acting cylinder(dac)
Single-acting cylinders:
Single-acting cylinders (SAC) use the pressure imparted by compressed air to create a driving force in
one direction (usually out), and a spring to return to the "home" position. More often than not, this type of
cylinder has limited extension due to the space the compressed spring takes up. Another downside to SACs is that part of the force produced by the cylinder is lost as it tries to push against the spring. Fig. 4 shows the
schematic diagram of single acting cylinder.