Clutches
Clutches are mechanical devices used to connect and disconnect rotating shafts in machinery. They are commonly found in vehicles to engage and disengage the engine from the transmission, allowing for gear changes and smooth operation. Clutches are essential for controlling power transmission and are designed to withstand high levels of friction and heat.
6 Key excerpts on "Clutches"
eBook - ePub- M J Nunney(Author)
- 2007(Publication Date)
- Routledge(Publisher)
...13 Friction Clutches 13.1 TYPES OF SINGLE-PLATE CLUTCH General requirements A clutch is a device used in engineering to engage smoothly two shafts in relative motion, one of which may be stationary, and to release them quickly or slowly at will. The purpose of fitting a clutch between the engine and gearbox of a motor vehicle is to satisfy the following requirements: 1 To connect a running engine smoothly and gradually to the remainder of the transmission system. 2 To permit gear changing when a vehicle is in motion. 3 To allow the engine to continue running when a vehicle is temporarily halted in gear with the clutch pedal depressed to disengage. A friction type of clutch is used in motor vehicles with manually operated gearboxes. Its functioning depends upon sufficient friction being developed between the contact surfaces of two or more members to transmit the desired torque without their slipping relative to each other. Their ability to slip before full engagement is, nevertheless, a decided advantage because it allows shock-free connection to be made between engine and gearbox. Heat is necessarily generated during any slipping of the clutch, but with fairly infrequent use there is usually sufficient time for it to cool. An important consideration in the design of Clutches is that the driven member connected to the gearbox should behave as little like a flywheel as possible. It should therefore be of lightweight construction and thus possess the minimum of inertia to ensure that it can be rapidly slowed down or speeded up, thereby assisting changing into higher or lower gears respectively...
eBook - ePub- Dick Jeffrey(Author)
- 2013(Publication Date)
- Routledge(Publisher)
...assembly Interference Contamination Overload 7.5 Clutches Clutches are devices that enable two shafts or rotating elements to be connected or disconnected while at rest or in relative motion. They must be capable of transmitting the maximum torque requirement of the drive system, and of disengaging completely and allowing one shaft to rotate independently of the other. Some Clutches allow transmission of motion in one direction only. The best known application of a clutch is in the transmission system of a motor vehicle. There are many other industrial applications in which Clutches are critical machine elements, and they play a particularly important role in the operation of automatically controlled machinery. Principles of Operation There are two aspects to clutch operation: torque transmission and clutch actuation. Torque transmission There are three principle ways in which torque and motion are transmitted from one shaft to another: positive engagement, friction and wedging action. Positive engagement The simplest and most basic arrangement is one which relies on positive engagement by means of teeth on coupling halves such as the one shown in Fig. 7-80. Engagement is achieved by allowing one of the clutch halves to slide axially along the shaft This mechanism has the advantage of being unable to slip but is very limited in its ability to allow engagement on the run, although this can be achieved at low speeds with certain tooth designs. Fig. 7-80 Engagement by teeth. Friction Many types of clutch rely on friction to transmit torque. This is the principle used in most motor vehicle Clutches. A typical arrangement involves bringing two contacting surfaces together and relying on the friction between them to transmit the torque...
eBook - ePubAutomotive Systems
Principles and Practice
- G.K. Awari, V.S. Kumbhar, R.B. Tirpude(Authors)
- 2021(Publication Date)
- CRC Press(Publisher)
...4 Automotive Clutches Outcome Learning Objectives Necessity and functions of the clutch Working principle of the clutch Requirements of the Clutches Construction and working of various types of Clutches Operating mechanism of the clutch Design of the clutch 4.1 Introduction The clutch is a device used to connect the two co-axial (collinear axis) shafts having relative motion (different speeds). The meaning of the word clutch is to grip tight or grasp. Clutch engages and disengages the engine to the transmission system from the gear box. The clutch is always in the engage position. At the time of moving from stationary or when necessary changes are required in the gear box as per traction requirements, the driver presses the clutch pedal to disengage it. 4.2 Necessity and Functions of the Clutch Traction requirement of a vehicle continuously changes with the resistances offered by the vehicle. It is necessary to transfer the maximum torque smoothly to the wheel through the various controls of the transmission system. The clutch is the link between the engine and the transmission system, which plays an important role in the following cases: When, due to certain limitations the engine is unable to run at very low rpm. The engine cannot provide sufficient torque for positive engagement of the transmission. Initially, at the time of starting the vehicle, it is in the neutral position, and when the vehicle is started, engine rotates with certain speed and the remaining transmission system from the clutch is stationery. When the driver needs to shift from a lower to a higher gear and vice versa. In both these cases, when the shaft is connected directly there are chances of jerk and damage to the system...
eBook - ePub- Peter Childs(Author)
- 2018(Publication Date)
- Butterworth-Heinemann(Publisher)
...Clutch connection can be achieved by a number of techniques from direct mechanical friction, electromagnetic coupling, hydraulic or pneumatic means or by some combination. There are various types of Clutches as outlined in Fig. 13.6, developed following a classification originally developed by Hindhede et al. (1983). The devices considered here are of the friction type. Fig. 13.6 Clutch classification. Clutches must be designed to satisfy four main requirements: 1. the necessary actuation force should not be excessive, 2. the coefficient of friction should be constant, 3. the energy converted to heat must be dissipated, 4. wear must be limited to provide reasonable clutch life. Alternatively the objective in clutch design can be stated as maximisation of a maintainable friction coefficient and minimisation of wear. Correct clutch design and selection is critical because a clutch that is too small for an application will slip and overheat and a clutch that is too large will have a high inertia and may overload the drive. Example 13.1 Calculate the torque a clutch must transmit to accelerate a pulley with a moment of inertia of 0.25 kg m 2 to (a) 500 rpm in 2.5 s. (b) 1000 rpm in 2 s. Solution The torque is given by T = Iα. The angular acceleration is α = Δ n /t. The mass moments of inertia I = 0.25 kg m 2. T = 0.25 500 2 π / 60 2.5 = 5.236 N m T = 0.25 1000 2 π / 60 2 = 13.10 N m Positive contact Clutches have teeth or serrations, which provide mechanical interference between mating components. Fig. 13.7 shows a square jaw and Fig. 13.8 shows a multiple serration positive contact clutch. This principle can be combined with frictional surfaces as in an automotive synchromesh clutch. As helical gears cannot be shifted in and out of mesh easily, the pragmatic approach is to keep the gears engaged in mesh and allow the gear to rotate freely on the shaft when no power is required but provide positive location of the gear on the shaft when necessary (Section 8.3.1). Fig...
eBook - ePub- Peter Childs(Author)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
...Chapter 13 Clutches and Brakes Abstract A clutch is a device that permits the smooth, gradual connection of two shafts rotating at different speeds. A brake enables the controlled dissipation of energy to slow down, stop, or control the speed of a system. This chapter describes the basic principles of frictional Clutches and brakes and outlines design and selection procedures for disc Clutches as well as disc and drum brakes. Keywords Band; Brake; Clutch; Design; Disc; Drum; Friction; Long; Multiple; Power; Shoe; Short; Transmission Chapter Outline 13.1 Introduction 13.2 Clutches 13.2.1 Design of Disc Clutches 13.3 Brakes 13.3.1 Disc Brakes 13.3.2 Drum Brakes 13.3.3 Short-Shoe External Drum Brakes 13.3.4 Long-Shoe External Drum Brakes 13.3.5 Long-Shoe Internal Drum Brakes 13.3.6 Band Brakes 13.4 Conclusions References Further Reading Nomenclature 13.1 Introduction When a rotating machine is started it must be accelerated from rest to the desired speed. A clutch is a device used to connect or disconnect a driven component from a prime mover such as an engine or motor. A familiar application is the use of a clutch between an engine's crankshaft and the gearbox in automotive settings. The need for the clutch arises from the relatively high torque requirement to get a vehicle moving and the low torque output from an internal combustion engine at low levels of rotational speed. The disconnection of the engine from the drive enables the engine to speed up unloaded to about 1000 rpm, where it generates sufficient torque to drive the transmission. The clutch can then be engaged, allowing power to be transmitted to the gearbox, transmission shafts, and wheels. A brake is a device used to reduce or control the speed of a system or bring it to rest. Typical applications of a clutch and brake are illustrated in Figure 13.1. Clutches and brakes are similar devices providing frictional, magnetic, or mechanical connection between two components...
eBook - ePub- Sayed M. Metwalli(Author)
- 2021(Publication Date)
- Wiley(Publisher)
...If the clutch-brake is operated and operating differently, the previously indicated seals and fixations must be considered, and fluid passages may also be relocated. Several alternative constructions may be available over the Internet or the associated patents. In addition, several available manufacturers provide OEM clutch-brake products that can be acquired. 18.10 Summary Clutches, brakes, and flywheels are important machine elements that control power transmission. The synthesis of these, consequently, is not necessarily dependent on other machine elements. Therefore, this chapter has been pushed back after so many other machine elements in this text. The initial synthesis of each of the Clutches, brakes, and flywheels is dependent mainly on power transmission variation. Classification of Clutches and brakes as positive, friction, or mixed friction-positive indicates the importance of the friction in the design of these components. The basic treatment in this chapter has been on the friction activated Clutches and brakes. Relations for developed torques and axial forces according to the assumptions of uniform wear and uniform pressure have been introduced. Applications in conical and plane disks provide needed information to synthesize single or multi-disk configurations for Clutches and brakes. The initial synthesis of disk Clutches and brakes depends on optimum ratio of inner to outer diameters. Knowing the transmitted power and the rotational speed is enough to initially synthesize the single or multi-disk configurations for Clutches and brakes using usual or selected materials in these applications. Information about these materials is provided to evaluate, modify, or verify the design. Wide ranging graphs provide tools to initially synthesize the single or multi-disk configurations for Clutches and brakes. These would also be potentially useful in the initial designs of caliper disk brakes...
