汽车差速器英文

Engineering Failure Analysis 13 (2006)1422–1428

www.elsevie /locate/engfailanal

Failure analysis of an automobile differential pinion

shaft

H. Bayrakceken *

Afyon Kocatepe University, Technical Education Faculty, 03200 Afyon, Turkey

Received 8 July 2005; accepted 14July 2005

Available online 2 September2005

Abstract

Differential is used to decrease the speed and to provide moment increase for transmitting the movement coming from the engine to the wheels by turning it according to the suitable angle in vehicles and to provide that inner and outer wheels turn differently. Pinion gear and shaft at the entrance are manufactured as a single part whereas they are in different forms according to automobile types. Mirror gear which will work with this gear should become familiar before the assembly. In case of any breakdown,they should be changed as a pair. Generally, in these systems there are wear damages in gears. The gear inspected in this study has damage as a form of shaft fracture.

In this study, failure analysis of the differential pinion shaft is carried out. Mechanical characteristics of the material are obtained first. Then, the microstructure and chemical compositions are determined. Some fractographic studies are

carried out to asses the fatigue and fracture conditions.

2005 Elsevier Ltd. All rights reserved.

Keywords: Differential; Fracture; Power transfer; Pinion shaft

1. Introd uction

The final-drive gears may be directly or indirectly driven from the output gearing of the gearbox. Di- rectly driven final drives are used when the engine and transmission units are combined together to form an integral construction. Indirectly driven final drives are used at the rear of the vehicle being either sprung and attached to the body structure or unsprung and incorporated in the rear-axle casing. The final-dr ive gears are used in the transmission system for the following reasons [1]:

(a) to redirect the drive from the gearbox or propeller shaft through 90and,

(b) to provide a permanent gear reduction between the engine and the driving road-wheel s.

* Tel.: +90 272 228 1311; fax: +90 272 228 1319.

E-mail address: bceken@.tr.

1350-6307/$ - see front matter 2005 Elsevier Ltd. All rights reserved.

doi:10.1016/j.engfailan al.2005.07.019

H. Bayrakceken / Engineering Failure Analysis 13 (2006) 1422–1428 1423

In vehicles, differential is the main part which transmits the movement coming from the engine to the wheels. On a smooth road, the movement comes to both wheels evenly. The inner wheel should turn less and the outer wheel should turn more to do the turning without lateral slipping and being flung.Di fferen- tial, which is generally placed in the middle part of the rear bridge, consists of pinion gear,mirror gear, differential box, two axle gear and two pinion spider gears.

A schematic illustration of a differential is given in Fig. 1. The technical drawing of the fractured pinion shaft is also given in Fig. 2. Fig. 3 shows the photograph of the fractured pinion shaft and the fracture sec- tion is indicated.

In differentials, mirror and pinion gear are made to get used to each other during manufacturing and the same serial number is given. Both of them are changed on condition that there are any problems. In these systems, the common damage is the wear of gears [2–4].In this study, the pinion shaft of the differential of a minibus has been inspected. The minibus is a diesel vehicle driven at the rear axle and has a passenge r capacity of 15 people. M aximum engine power is 90/4000HP/rpm, and maximum torque is 205/1600

Nm/rpm. Its transmission box has manual system (5 forward, 1 back). The damage was caused by stoppi ng and starting the minibus at a traffic lights. In this differential, entrance shaft which carries the pinion gear was broken. Various studies have been made to determine the type and possible reasons of the damage. These are:

studies carried out to determine the material of the

shaft;

studies carried out to determine the micr o-structur e;

studies related to the fracture

surface.

There is a closer photograph of the fractured surfaces and fracture area in Fig. 4. The fracture was caused by taking out circular mark gear seen in the middle of surfa ces.

Fig. 1. Schematic of the analysed differential.