orca汽车英语

2021年1月16日发(作者：丁雪松)
Automo
tive Belts,
Fittings, and Hoses
INTRODUCTION

On the automobile, especially on the engine, there are many types of belts, fittings, and hoses.
Belts are used to connect
two
rotating shafts togethei Various types of fit- tings are also used
to connect tubes and hoses together. This chapter introduces you to the basic types of belts,
fit- tings, and hoses used on today’s automobiles. In addition, service information is included
that shows how to check and change belts, fittings, hoses, and tubing.
7.1 AUTOMOTIVE BELTS
PURPOSE OF AUTOMOTIVE BELTS
Automotive belts have been used for years to connect one rotating shaft to another. As
technology improves, stronger, more flexible belts were developed for new uses. The basic
purpose of using an automotive belt is to connect
two
shafts that are not necessarily next to
each other. For example, if
two
shafts are next to each other
and
one needs to be driven from
the other, gears could be used. Butwhen the shafts are farther apart, belts will be used. In
addition, belts are quiet as compared to gears or chains. They are also much less expensive.
The use of automotive belts gives flexibility to where rotating shafts can be placed. On
today’s automotive engine, belts are used to turn alternators, power steering pumps, water
pumps, air-conditioning compressors, and various pollution equipment.
Figure 7-1
shows an
example of common components that can be driven by belts on the front ofan automotive
engine.

TYPES OF BELTS
There are several types of belts used on automotive engin
The exact type used depends on several consideration&
These include the following:

（1）
The distance between the two rotating shafts
（2）The speed of the belts .
（3）The load on the helts

FIGURE 7-1The belt on the front of an automotive engine can be used to drive many components and accessories.


FIGURE 7-3 Depending on the car manufacturer, from one to four belts may be used to drive various
components.

FIGURE 7-4 Beltsare constructed with rubber, FIGURE 7-5 This cogged timing belt
fabric, and metal cords strength. keep the camshaft and crankshaft the
with each other.


FIGURE 7-2
Various types of belts are used on automofive engines.
(1)
The need for timing or keeping the
two shafts
in time with each other
(2)

The direction of rotation between the
two
shafts
(3)
The costs of the application
(4)
The length of service required


Common belts used on the automobile are shown in
Figure 7-2.
The conventional V belt
is used to drive alternators on some cars. The alternator needs to be driven by the crankshaft
of the engine. To do this a simple V belt may be used. Note that the V belt will not keep the
two
rotating
shafts
timed together. There may be slippage between the
two.
The V belt is a
low-cost and effective way to connect
two
rotating shafts together.
The cogged V belt has a series of ribs cut into it. These ribs have a tendency to reduce
slippage between
two
rotating shafts during heavier loads. The serpentine
belt
is corn- mon
today on engines that require several rotating shafts to be turned by a single belt. The
serpentine belt is so named because it can be snaked around several rotating shafts. The
serpentine belt has several (usually four to seven) angled grooves in the belt surface. The
number of grooves is determined by the width and load on the belt. These grooves increase
the surface area of the belt so slippage is reduced. In addition, the serpentine belt is wide
enough so that pulleys
can
run on either side of the belt.

BELT SYSTEMS
Each
car manufacturer may use a different belt system.
Figure
7-3 shows a one-, two-,
three-, and four-belt system. Depending on the shafts that must be rotated, a serpentine belt,
V belt, or other belt may be used. In each case, the crankshaft is the drive component, while
the other cornponents

are the driven components. Note that similar diagrams can usually be
found in the service manual or under the hood of the car to help the service technician service
belts and pulleys.

/
. .
CUSTOMER CONCERN:
Alternator Light Comes On
A driver says that while driving home from work, the alternator light came on
suddenly. Being only a few blocks from home, the driver continued home and shut the
car off. What could be the problem?
SOLUTION: Often the alternator belt is driven from the crankshaft. Sometimes this
belt is very hard to see. lt is a serpentine-type belt and, if not checked for cracks and
other damage, may easily break. The most likely cause of this problem is that the
alternator belt broke. Replacing the alternator belt with a new one will easily fix the
problem. In this particular case the air- conditioning compressor belt will also have to
be removed because it rides on the outer end of the crankshaft pulley. The alternator
belt rides on the center ofthe crankshaft pulley.

BELT CONSTRUCTION
Various materials are used to ensure that automotive belts are strong. All belts are constructed
of several materials including rubber, fabric, and rubber-impregnated fabric (rubber and fabric
mixed together). Also, some belts are strengthened by using reinforcing fabric or steel cords
in- side the belt. These materials help to reduce stretch and slippage under heavier loads such
as air compressors.
Fig- ure
7-4 shows the internal makeup of a typical V belt. Note that
there are fiber or metal reinforcement sections, rubber- impregnated sections, and laminated
fabric sections.
TIMING BELTS
In addition to the belts just mentioned, many automotive engines also use a cogged timing
belt. The purpose of the cogged timing belt is to keep the camshaft exactly in time with the
crankshaft. This is important so that the valves keep in time with the position of the piston
during normal operation.
Figure 7-5
shows one example of a timing belt in place on the
engine. The cogs in the belt act like a chain, keeping the
two
rotating shafts from slipping out
of time with each other.
SERVICING BELTS
There are many important things to know about servicing belts. For example, when ordering
V belts it is very important to replace an existing damaged belt with the correct belt. V belts
typically have a certain width and a certain

.

FIGURE 7-6 Always make sure the replacement belt is the correct size recommended by the manufacturer.

pitch or angle of the V. Figure 7-6 shows three examples of V belts fitting into a pulley. Note
that the belt is too narrow in diagram A, too wide in diagram B, and the correct size in
diagram C.
A V belt may be identified as A, B, C, or D. These letters indicate the width of the belt. A
is the narrowest; D is the widest. A belt may also be identified by its length. For example,
A35 means a narrow belt that is 35 inches in length. In addition, vehicle manufacturers
always provide part numbers for specific belt applications.
When installing serpentine belts always make sure the belt is placed completely on the
pulley. It is very easy to have the belt slightly offthe pulley as shown inFigure 7-7. In the top
drawing, the belt is installed correctly. In the middle drawing, the belt is installed too far in
toward the engine. In the bottom drawing, the belt is installed too far out, away from the
engine.

FIGURE 7-8
Always check belts for cracks peeling Oil tears msing teeth and so
O
n
.

FIGURE 7-7 When installing a serpentine belt, be sure to instaW it correctly as shown.

It is always important to check the condition of belts on the automobile engine.
Figure 7-8
shows
typical damage to loolc for on automobile belts. Problems to look for in- dude the following:
（1）Cracks in the belt
（2）Oil soaked into the belt
（3）Glazing caused by excessive slippage
-
（4）Tears or splits
（5）Peeling

(6)
Outerwear
(7) Missing teeth
(8) Inside cracks
(9)Outside cracks
If there are any visible cracks in the belt, it should be replaced immediately. In fact, most
manufacturers recommend that if one belt needs replacement, all other belts should be
replaced. Often damage to the belt can be better observed if it is held in both hands and then
twisted. The twisting helps to expose some of the possible problems with a belt.
ADJUSTING BELTS
Some belts may have a tension device that keeps them at the correct tension. There are many
designs of belt-tension devices. In most cases, these tensioners work against the belt under
.