GB2240941A - Crankshaft grinding - Google Patents

Abstract

A method and apparatus for crankshaft grinding permits crankshafts of different throws to be mounted for grinding on the same apparatus. The grinding shaft 24 for rotating the crankshaft 12 during grinding has located co-axially therein indexing and clamping shafts 32, 68 transmitting drive to indexing and clamping mechanisms driven by electric and pneumatic motors respectively. The indexing drive is transmitted through an off-set mechanical drive coupling 34 in the throwblock. The coupling can accommodate differing degrees of off-set of the grinding and indexing axes 16, 18, and hence differing crankshaft throws. The clamping shaft drives a pair of clamping arms through a mechanical drive 62. Hydraulic drives are eliminated. Speed and accuracy of operation are improved. <IMAGE>

Description

METHOD AND APPARATUS FOR CRANKSHAFT GRINDING This invention relates to a method and apparatus for crankshaft grinding.

The operation of grinding the crankshaft for an internal combustion engine requires, so far as each individual crank is concerned, the positioning of that crank in a co-axial relationship with a grinding axis about which the crankshaft is rotated during grinding. In a typical crankshaft for a four cylinder engine, the two pairs of two cranks are located 180 degrees apart and are ground in pairs with an indexing operation of 180 degrees between the pairs.

To the best of the Applicant's knowledge, all presently in-use systems of crankshaft grinding provide for the crankshaft to be mounted on support means for rotation about the grinding axis, and a specific support means or, crankshaft mounting assembly is provided for each particular crankshaft type, having regard to the throw of its cranks, and thus the off-set between the grinding and indexing axes. The result of this dedicated use of the crankshaft support assembly is, of course, limited utilisation of same, reduced efficiency, and correspondingly increased costs with respect to the grinding of a series of different crankshaft types or sizes.

One reason for the limited utility of existing crankshaft support systems for grinding operations arises from the difficulty of accurately indexing the crankshaft between the successive grinding operations, and notably the difficulty of providing an indexing drive which does not interfere with or compromise the main drive for rotating the crankshaft assembly. Analogous problems arise in relation to clamping the crankshaft on the support means so that it is securely and accurately retained in position during the grinding operation.

Previously used systems for indexing the crankshaft and clamping same on its support means have been based on hydraulic actuators. Thus, for example, to effect the necessary degree of angular movement of the crankshaft during indexing, there have been provided hydraulic actuators within the throwblock or head on which the crankshaft is mounted at each end, these actuators causing indexing angular movement of the crankshaft by effecting linear movement of a rack and pinion drive connected to the crankshaft and serving to turn it about the indexing axis. It will be understood that such a rack and pinion drive provides little or no facility for accommodating movement of the indexing axis towards or away from the grinding axis to accommodate different crankshaft throws - hence the limited utility of this previously used apparatus.

Likewise, in the case of the clamping means for securing the crankshaft on its support means, previously used systems have employed hydraulic actuators operating pivoted clamping arms. The shortcoming of such hydraulic actuation, which applies equally to the hydraulic actuator of the rack and pinion drive for indexing, includes not only very limited speed of operation, but also variable operating characteristics arising from changes in hydraulic oil viscosity due to temperature changes during use.

An object of the present invention is to provide a method and apparatus for crankshaft grinding providing improved flexibility for accommodating different crankshaft throws, and/or improved speed or controllability of the indexing or clamping operations, and/or one or more other improvements in relation to matters discussed herein or generally.

According to the invention there is provided a method and apparatus for crankshaft grinding as defined in the accompanying claims.

In a preferred embodiment, a mechanical drive is provided interconnecting shafts on the grinding and indexing axes and which transmits drive between these shafts by means of an offset drive coupling permitting drive at varying off-sets. In this way, a variety of different crankshaft throws can be readily accommodated, without any adjustment of the off-set drive coupling. The drive coupling comprises three discs interconnected by pivoted links. Such a drive coupling has been previously proposed for use in transmitting power to mechanisms requiring a driven component to be power rotated at differing radial distances from a relatively fixed drive shaft.However, in the preferred embodiment of the present invention, this off-set drive coupling is employed in a mechanism in which the main power transmission (for grinding) is effected about a fixed and constant grinding axis, and the transmission of torque for indexing effects turning movement only through a limited angular distance. There is no significant power transmission through the coupling to the crankshaft, save that required for the indexing movement, and thus this use of the coupling represents a non powertransmitting application in a mainly fixed-axis system and thus represents an unconventional application of the coupling.

In the preferred embodiment the indexing shaft extends co-axially with the grinding shaft, and indeed is located radially within same, whereby the indexing shaft can be conveniently driven from the end of the grinding shaft, whereby a simple and effective control system employing an electric motor can be employed.

Likewise, in the preferred embodiment, a clamping shaft extends co-axially with the grinding shaft and is drivable from the end of the grinding shaft, thereby permitting simple and effective control of the clamping force by employing a pneumatic motor which can be driven to its stall point.

Also in the preferred embodiment, the absence of hydraulic systems greatly simplifies the construction and operation of the apparatus. Previously used hydraulic systems are somewhat messy in-use and inherently slow in operation.

The rack and pinion indexing system has had to be driven back to the start of the rack after each operation.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which : Fig 1 shows a longitudinal section through crankshaft grinding apparatus; Fig 2 shows an axial view of a pawi-and-ratchet system for defining the indexed position of a crankshaft, the direction of viewing being generally as indicated by arrow II in Fig 1; Fig 3 is a perspective view of an off-set drive coupling employed in the drive to the indexing mechanism of Fig 1; Fig 4 shows a section through crankshaft clamping means in Fig 1, the section being taken generally on the line IV-IV in Fig 1; Fig 5 shows a side elevation view of the clamping means of Fig 4, the direction of viewing being generally as indicated by arrow V-V in Fig 4; and Fig 6 shows an end elevation view of the apparatus, the direction of viewing being as indicated by arrow VI-VI in Fig 1.

As shown in the drawings, apparatus 10 for grinding a crankshaft 12 comprises support means 14 for supporting the crankshaft for rotation about a grinding axis 16 and for limited angular indexing movement about an indexing axis 18.

Indexing axis 18 is also the axis of rotation of the crankshaft when in use. It will be understood that complementary support means, corresponding to support means 14 is provided at the opposite end of crankshaft 12.

In order to grind the cranks 20 of crankshaft 12, the cranks are brought, in sequence, into co-axial relationship with grinding axis 16. In Fig 1, one of the cranks 20 is indeed shown in that position ready for grinding. Rotation of the assembly is effected by means of a belt drive (not shown) to a grinding pulley 22 which is connected via a tubular grinding shaft 24 to a head or housing 26 known as a throwblock, having a coupling 28 for connection to crankshaft 12. Grinding is effected by driving pulley 22 and hence rotating crankshaft 12 about grinding axis 16. A grinding wheel (not shown) is radially advanced and effects controlled grinding of crank 20.

The mechanism for indexing the crankshaft about indexing axis 18 will now be described.

A mechanical drive interconnects a shaft 30 on indexing axis 18, and an indexing shaft 32 which extends co-axially through grinding shaft 24. The mechanical drive comprises an off-set drive coupling 34, shown in more detail in Fig 3.

Coupling 34 operates on a parallel crank principle, transmitting rotary motion between shafts 32 and 30 via discs 36, 38, 40 and two sets of three parallel pivoted links 42 and 44, interconnecting the discs. Indexing shaft 32 is coupled to an electric motor 46. It will be understood that coupling 34 can accept significant variation in the degree of off-set between indexing axis 18 and grinding axis 16 to accommodate differing crankshaft throws.

To define the indexed position of crankshaft 12 there is provided pawl and ratchet means 46 seen in Fig 2 and comprising a rotary ratchet disc 48 through which drive is transmitted from coupling 34 to crankshaft 12, and a cooperating fixed but pivotable and spring-biased pawl 50.

In operation, the crankshaft is driven slightly beyond its required indexing position, and then motor 46 is reversed so that pawl 50 lodges against one of two shoulders 52, defining the required indexed position.

The arrangement for clamping crankshaft 12 in position for grinding will now be described.

A pair of clamping arms 54, 56 pivoted at 58 and 60 are actuated by a mechanical actuation mechanism 62 powered by a pneumatic motor 64 coupled via a belt and pulley drive 66 to a tubular indexing shaft 68, and hence via pinions 70, 72, a shaft 74 and a flexible coupling 76 to actuation mechanism 62.

Coupling 62 comprises a worm 78 and a pinion 80 driving a shaft 82 having oppositely threaded complementary actuation sleeves 84, 86 at its ends, acting on clamping arms 54 and 56.

To compensate for any mismatch in closure of the clamping arms 54, 56, the arms have schnorr discs 88 (or belleville washers) to apply clamping load to the crankshaft with a degree of resilience.

In use, crankshaft 12 is located on support means 14, pneumatic motor 64 is energised to cause arms 54, 56 to effect clamping, motor 46 is then energised to index the crankshaft to its required first grinding position, the motor being reversed to cause pawl 50 to engage the relevant shoulder 52.

Then, the drive to grinding shaft 24 is engaged and grinding proceeds. Subsequent grinding steps are performed merely by indexing the crankshaft about axis 18 by energising motor 46.

A different crankshaft having a different throw can be readily mounted on coupling 28, and the difference in crankshaft throw is automatically accommodated by coupling 34. As shown in Fig 6 coupling 28 is vertically adjustable by means of slots 90, 92 for the purpose.

Interestingly, the above embodiment provides simple accommodation of differing crankshaft throws in a single set of apparatus. Crankshaft clamping is effected simply and mechanically, and rapidly. The complications of hydraulic drives are avoided, and yet the apparatus provides more flexibility employing fewer internal mechanisms and this therefore leading to improved reliability.

Claims (16)

1 A method of crankshaft grinding comprising : a) mounting a crankshaft on support means for rotation about a grinding axis, and for limited angular indexing movement about an indexing axis, which is co-axial with the crankshaft axis; b) causing said limited angular indexing movement of said crankshaft about said indexing axis to bring two or more angularly spaced cranks sequentially into co-axial relationship with said grinding axis; and c) grinding said cranks in sequence when in said coaxial relationship; characterised by d) the step of effecting said limited angular indexing movement, or at least a major art thereof, by means of a mechanical drive interconnecting shafts on said grinding and indexing axes, and transmitting drive between said shafts by means of an off-set drive coupling permitting drive at varying off-sets; and e) mounting a second crankshaft on said same support means and repeating the above sequence of steps for said second crankshaft, said second crankshaft having a different throw and hence a different spacing between the said grinding and indexing axes.

2 A method of crankshaft grinding characterised by the step of causing indexing movement of a crankshaft by means of a mechanical drive interconnecting shafts on the grinding and indexing axes of the crankshaft.

3 A method of grinding a crankshaft according to claim 1 or claim 2 characterised by transmitting drive for effecting said limited angular movement by driving a shaft co-axial with said grinding axis and extending lengthwise of a grinding shaft which is drivable to effect said grinding.

4 A method of crankshaft grinding according to any one of claims 1 to 3 characterised by transmitting drive for clamping said crankshaft on said support means by driving a shaft which is co-axial with said grinding axis and which extends lengthwise of a grinding shaft which is drivable to effect said grinding.

5 A method of crankshaft grinding according to claim 4 characterised by transmitting said drive for clamping said crankshaft on said support means, from a pneumatic motor, and the method including the step of permitting said motor to stall on clamping said crankshaft.

6 A method of crankshaft grinding substantially as described herein with reference to Figs 1 and 3 of the accompanying drawings.

7 A method of crankshaft grinding substantially as described herein with reference to Fig 1 as modified by Figs 4 and 5 of the accompanying drawings.

8 Apparatus for crankshaft grinding comprising : a) support means for mounting a crankshaft for rotation about a grinding axis and for limited angular indexing movement about an indexing axis, which is the crankshaft axis; and b) indexing means to cause said limited angular indexing movement of said crankshaft about said indexing axis and thereby bring two or more angularly spaced cranks sequentially into co-axial relationship with said grinding axis, to enable same to be ground in sequence; characterised by c) a mechanical drive interconnecting shafts on said grinding and indexing axes and adapted to transmit drive between said shafts by means of an off-set drive coupling permitting drive at varying off-sets.

9 Apparatus for crankshaft grinding characterised by a mechanical drive to effect indexing movement of a crankshaft being ground and interconnecting shafts on the grinding and indexing axes of the apparatus.

10 Apparatus according to claim 8 or claim 9 characterised by an indexing shaft to transmit drive for said limited angular indexing movement and extending co-axially with said grinding axis lengthwise of a grinding shaft which is drivable during said grinding.

11 Apparatus according to any one of claims 8 to 10 characterised by a clamping shaft for transmitting drive for clamping said crankshaft on said support means, said clamping shaft extending co-axially with said grinding axis and lengthwise of a grinding shaft which is drivable to effect said grinding.

12 Crankshaft grinding apparatus according to claim 11 characterised by a pneumatic motor coupled to said clamping shaft for transmitting drive for clamping said crankshaft on said support means, said pneumatic motor being suitable to be stalled during drive on clamping said crankshaft.

13 Apparatus for crankshaft grinding substantially as described herein with reference to Figs 1 and 3 of the accompanying drawings.

14 Apparatus for crankshaft grinding substantially as described herein with reference to Fig 1 as modified by Figs 4 and 5 of the accompanying drawings.

15 A method of crankshaft grinding characterised by the step of effecting clamping of the crankshaft on support means therefore by driving a clamping shaft co-axial with the grinding axis.

16 Apparatus for crankshaft grinding comprising a clamping shaft extending co-axially with the grinding axis and drivable to effect clamping of a crankshaft by mechanical means.