GB2212174A

GB2212174A - Apparatus for the hardening of crankshafts

Info

Publication number: GB2212174A
Application number: GB8825920A
Authority: GB
Inventors: Edgar Stengel; Waldemar Gezarziek; R Friedhelm Reinke
Original assignee: AEG Elotherm GmbH
Current assignee: SMS Elotherm GmbH
Priority date: 1987-11-06
Filing date: 1988-11-04
Publication date: 1989-07-19
Anticipated expiration: 2008-11-04
Also published as: FR2622897A1; GB2212174B; IT1224299B; GB8825920D0; DE3737694C1; JP2603705B2; JPH01268819A; IT8848527A0; FR2622897B1

Description

1k 1 2212'17,-t "Apparatus for the hardening of crankshafts" The present

invention relates to apparatus for lowdistortion hardening, wherein a crankshaft rotated around its longitudinal axis is inductively heated and then immediately quenched.

It is known that the distortion-free hardening of workpieces, of whatever section or shape, is substantially impossible. The reason is that the expansion of the workpiece during heating and its shrinkage upon quenching result in permanent deformation or distortion. The lowdistortion hardening of flat workpieces, such as flat strips, can be successfully performed, for example, by pressing the heated workpiece during quenching. Previously, engineers in the art have considered this firm clamping of the workpiece to be the optimum method. The basic idea was to deprive the heated and quenched workpiece of the opportunity of yielding to the tendency to become deformed. For this purpose the firm clamping of the workpiece seemed to be the optimum method. However, the method did not mean that the final truing of the hardened workpiece could be eliminated. It is particularly difficult to harden irregularly shaped elongate workpieces, such as crankshafts, camshafts and racks, in which the amount of very various hardening distortion is difficult to predict, clamping providing no usable remedy against hardening distortion. For example, it is not much use to clamp on pivot bearing crankshafts whose crankshaft bearings are to be hardened, 2 since hardening distortion can occur without hinderance on the exposed crankshaft bearings.

It is an object of the prevent invention to minimize at low expense the hardening distortion of crankshafts hardened by the rotary method, so that expensive truing can be dispensed with.

It has now been found that substantially low-distortion hardening can be successfully performed if during heating and quenching the workpiece is given the opportunity to move in its main direction of expansion, namely its longitudinal axis. If then during heating the workpiece becomes elongated, the workpiece can follow this trend, and similarly it can shrink freely during quenching, so that hardly any distortion takes place.

The basic idea of the invention rejects completely the previously predominant opinion of engineers in the art that the workpiece should be clamped as comprehensively as possible in order to avoid hardening distortion. Thus in accordance with the present invention the workpiece is given the opportunity to yield during heating and quenching to the tendency to become deformed.

According to the present invention there is provided apparatus for the hardening of crankshafts which are clamped at both ends in opposite clamping heads to rotate around their axis, said apparatus including: a heating and quenching device; a drive on one of the two clamping heads; a clamping drive on both clamping heads; and a displacing drive for the clamping heads in relation to the crankshaft !t 1 1 3 when it is received for clamping; characterized in that the displacing drive comprises pneumatic or hydraulic actuators which are fixedly located at one end in a first casing and at the other end cooperate with stops on a square spindle sleeve which is floatably mounted in needle bearings to move in a second casing and in which there is rotatably mounted a hollow spindle which carries one of the clamping heads and through which the clamping drive means is actuable by a control device extending coaxially, therewith.

With the above construction it will be appreciated that the other clamping head can be coupled to and uncoupled from its displacing drive and is floatably mounted axially in a low-friction bearing. The crankshaft to be hardened is therefore clamped fixed - i.e. axially immovably - at one is end, while at the opposite end of the pivotably mounted crankshaft the clamping head can move in its axial direction after the clamping drive has been released from the clamping head.

Furthermore, the rotating workpiece may be mounted at at least one of its ends with such low friction that it can move freely in the axial direction with a frictional coefficient lower than 0.01 even at the lowest speeds.

The present invention will now be described in greater detail by way of example with reference to the accompanying drawings, wherein:- Fig. 1 is an elevation view of the hardening apparatus; Fig. 2 is a longitudinal section through the axially movable clamping head; and 4 Fig. 3 is a cross-section through the clamping head.

Referring to the drawings, Fig. 1 shows a complete hardening apparatus having a system 1 (shown in chain dot lines) for heating and quenching a crankshaft 2 to be hardened. The hardening device has clamping heads 3 and 4 for clamping the crankshaft 2 at opposite ends and a central support 5 for the central bearing of the crankshaft 2. The crankshaft 2 is clamped in the clamping heads 3 and 4 by control systems 6 and 7.

The crankshaft 2, which rotates around its longitudinal axis during the hardening operation, is clamped on one side (the right hand side as viewed in Fig. 1) in the clamping head 3 with which a drive 8 for rotating the crankshaft 2 around its longitudinal axis engages and which is mounted is and axially secured in a casing 9. The clamping head 3 which clamps the other end of the crankshaft 2 (the left hand side as viewed in Fig. 1) is mounted floatably, i.e. axially displaceably, in a casing 10, as shown in detail in Figs. 2 and 3.

The clamping head 3 is located at the end of a tubular spindle 11 which can rotate in an antifriction bearing 13 mounted in a square spindle sleeve 12, itself mounted on opposite edges axially displaceable in a needle bearing 14 in the casing 10. A tie rod 15 for actuating the clamping 25 head 3 when the crankshaft 2 is clamped extends coaxially. through the spindle 11.

Pneumatic or hydraulic actuators 17 provided with pistons 16 are located on rigid blocks 19 in the casing 10.

1 v 1 The pistons 16 can be extended in the axial direction of the pivot bearing 2 until they abut stops 18 attached to the square spindle sleeve 12.

Low-impedance bellows 20 secure the inside of the casing 4 against dirt. Alternatively, the casing 10 can be sealed off from the outside contactlessly buy means of barrier air.

To clamp the crankshaft 2, the clamping heads 3 and 4 are advanced in relation to the ends of the crankshaft 2 and then clamped by the control systems 6 and 7 actuating the chuck of the clamping heads 3 and 4. The clamping heads are. advanced by the pistons 16 of the actuators 17, which exert pressure against the stops 18 attached to the square spindle sleeve 12 and thereby axially displace the square spindle sleeve 12 and together therewith the spindle 11 and the clamping head 3 in the casing 10. When the crankshaft 12 is unclamped, the actuator 17 is actuated and pushes the clamping head 3 away from the crankshaft 2. The uncoupling of the displacement drive, formed by the actuators 17, for the clamping heads 3 and 4 after the clamping operating creates the precondition for the low-friction axial displaceability of the clamping heads 3 and 4.

c 6

Claims

CLAIMS:-

Apparatus for the hardening of crankshafts which are clamped at both ends in opposite clamping heads to rotate around their axis, said apparatus including: a heating and quenching device; a drive on one of the two clamping heads; a clamping drive on both clamping heads; and a displacing drive for the clamping heads in relaion to the crankshaft when it is received for clamping; characterized in that the displacing drive comprises pneumatic or hydraulic actuators which are fixedly located at one end in a first casing and at the other end cooperate with stops on a square spindle sleeve which is floatably mounted in needle bearings to move in a second casing and in which there is rotatably mounted a hollow spindle which carries one of the clamping heads and through which the clamping drive means is actuable by a control device extending coaxially, therewith.
2. Apparatus according to claim 1, characterized in that the second casing is outwardly sealed with low impedance by bellows.
3. Apparatus according to claim 1, characterized in that the said one of the clamping heads can be coupled to and uncoupled from its displacing drive and is floatably mounted hydrostatically or anti-friction guided with a frictional coefficient lower than 0.01 even at the lowest speeds in a low-friction bearing sealed outwardly contact-free by means C.

7 of barrier air or with low impedance via bellows.

1
4. Apparatus for the hardening of crankshafts, constructed substantially as herein described with reference to and as illustrated in the accompanying drawings.

0 Published 1989 at The Patent Office, State House, 86171 High Holborn, London WCIR 4TP. FVrther copies maybe obtained from The Patent Office. Was Branch, St Mary Cray, Orpington, Rent BR5 3RD, Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87