GB2087775A

GB2087775A - Machining slanting surfaces on crankshafts

Info

Publication number: GB2087775A
Application number: GB8135531A
Authority: GB
Original assignee: GFM Gesellschaft fuer Fertigungstechnik und Maschinenbau AG
Current assignee: GFM Gesellschaft fuer Fertigungstechnik und Maschinenbau AG
Priority date: 1980-11-26
Filing date: 1981-11-25
Publication date: 1982-06-03
Also published as: FR2494610A1; GB2087775B; DE3141846A1; JPS57114308A; AT369301B; ATA576380A; DD201265A5

Abstract

A laterally extending part 2 of a crankshaft 1 is machined along an imaginary surface which is described by an arc of a circle laying in a plane that is normal to the axis of the crankshaft when said arc of a circle is moved axially and radially with respect to said axis along a predetermined path. A milling machine for forming such slanting surfaces on crankwebs comprises a compound tool slide, 4a,b which is movable transversely to the longitudinal axis of the machine and carries an inserted-tooth milling cutter M, preferably an internally cutting annular cutter, and is carried by a carriage 5 which is movable along the machine bed. A control system is provided for controlling the vertical drive means for the tool slide and the drive means for the carriage so as to impart to the cutter a feed movement in radial and axial directions with respect to the axis of the crankshaft. <IMAGE>

Description

SPECIFICATION Method of machining an elongated workpiece having a laterally protruding portion This invention relates to a process of machining a slanting surface on a laterally protruding portion of an elongated workpiece, particularly to machine a slanting surface on a crankweb of a crankshaft, and to milling machine for carrying out the process.

The crankwebs particularly of large and heavy crankshafts are often formed on their outer side faces with slanting surfaces adjacent to the crankpins in order to save material and weight and also to save space, e.g., in the crankcase. These slanting surfaces have previously consisted of planar or conical surfaces and their formation has added considerably to the manufacturing costs. For instance, in the manufacture of crankshafts the cylindrical portions are machined on a conventional crankshaft-milling machine and the crankshafts must then be transferred to a lathe or milling machine specially designed to machine said slanting surfaces in a separate operation.A transfer of the workpiece can only be avoided if the inserted tooth-cutter of the crankshaft-milling machine is replaced after the milling of the cylindrical portions by an accessory which has a drive of its own and serves to machine the slanting surfaces. The tools used for that purpose consist of lathe tools or suitable milling cutters to which a radial recessing feed movement of a feed movement that is radial to the axis of the crankshaft is imparted. It is apparent that the known processes of machining slanting surfaces on crankwebs are time-consuming because that operation must be carried out on a separate machine tool or the conventional crankshaft-milling machine used to mill the cylindrical portions of the crankshaft must be altered before it can be used to machine said slanting surfaces.Besides, these special machines or accessories, fixtures and tools required for that purpose involve a high additional equipmentex- penditure.

It is an object of the invention to eliminate these disadvantages and to provide a process which is of the kind described first hereinbefore and permits a machining of slanting surfaces on laterally protruding portions of elongated workpieces in a timeconsuming, efficient manner virtually without a need for accessories.

This object is accomplished in accordance with the invention in that the laterally protruding portion to be provided with a slanting surface is machined along an imaginary surface that is described by an arc of a circle, which lies in a plane that is normal to the longitudinal axis of the elongated workpiece, when the center of said arc is axially and radially displaced with respect to said longitudinal axis along a predetermined path. For instance, a cylindrical slanting surface will be formed in this manner if the center of the arc of a circle is moved along a straight line. That process can be carried out by means of simple, internally or externally cutting side milling cutters in which the teeth have a flight circle which has the same radius as said arc of a circle.To form the desired slanting surface it will be sufficient to impart to said milling cutter a feed movement along the desired path of the center of the arc of a circle.

Such internally or externally cutting milling cutter may be mounted without difficulty on crankshaft milling machine so that the crankwebs of the crankshaft can be formed with slanting surfaces without a change of the fixation of the workpiece and without a mounting of an accessory. As the saving of material and space by the provision of the slanting surface rather than the shape of said surface is essential, the slanting surfaces need not be conical.

If a conical slanting surface is required in special cases, an approximately conical surface can be machined in the process according to the invention if, for instance, the slanting surface consists of two surface portions and the center of the arc of a circle is moved in two axial planes which are symmetrical to the axial plane that includes the crank radius. The feed movement and the configuration of the path of the center of the arc of a circle can be freely selected so that any desired shape can be imparted to the slanting surfaces. For instance, the center of the arc of a circle may be moved along a straight or convex or concave line.It will be understood that the process according to the invention is not restricted to the formation of slanting surfaces on crankshafts but may be used to machine slanting surfaces on laterally protruding portions on other workpieces that can be machined on crankshaft-milling machines.

In accordance with another aspect of the invention, a milling machine for efficiently carrying out the process comprises a tool slide, which is movable transversely to the longitudinal axis of the machine and carries a milling cutter, preferably an internally cutting annular milling cutter, and a carriage, which is movable along said longitudinal axis and carries said tool slide, and said machine comprises a control system for controlling drive means for driving the tool slide and drive means for driving the carriage so as to impart to the milling cutter a feed movement in radial and axial directions.If a conventional milling machine is provided with such a control system it can be used to machine slanting surfaces on crankwebs without need for further accessories as the required feed movement can be imparted to the tool by the combination of the movements of the tool slide and the carriage. The tool slide may be a compound slide or a cross slide although where a cross slide is used the crankshaft must be suitably angularly indexed so that the cross slide will move in the correct position relative to the radius of each crank in order to impart to the feed movement the desired radial component. Such an indexing of the crankshaft will not be required where a compound slide is provided because the latter can be used to move the tool in any desired radial direction.

Within the scope of the invention, special advantages will be afforded by the use of an inserted-tooth milling cutter which is adapted to machine also the cylindrical portions of the crankshaft and/or the peripheral surfaces of the crankwebs. Where such an inserted-tooth cutter is used, the cylindrical portions and/or the peripheral surfaces of the crankwebs of a crankshaft as well as the slanting surfaces of the crankwebs can be machined with one and the same milling cutter and without need for a change of the fixation of the workpiece or for an alteration. In that case the workpiece which has been fixed once can be machined in a single sequence of operations wherever this is required.

The subject matter of the invention is shown by way of example on the accompanying drawings, in which Figures 1 and 2 are, respectively, a side elevation and an end elevation showing a crankshaft and illustrating the process according to the invention and Figure 3 is a side elevation showing a milling machine for carrying out the process according to the invention.

A conventional crahkshaft-milling machine having a disc-shaped inserted-tooth cutter M is used to machine a substantially cylindrical slanting surface 2 on each crankweb 1a of a crankshaft 1. Forthat purpose the inserted-tooth cutter M consisting in the present example of an internally cutting annular cutter has a feed movement imparted to it in a direction V, which is the resultant of a radial component VR and an axial component VA. As a result of that feed movement in the direction V, the crankweb 1 a milled with the inserted-tooth cutter M is formed with a slanting surface 2, which is defined by the surface described by the flight circle K of the teeth of the cutter M moved in the direction V of the feed movement.The direction V of the feed movement and the path of the center of the inserted-tooth cutter during the milling operation can be freely selected, provided that said center is moved in radial and axial directions. It will be understood that the path of the center of the cutter M may change in direction and may comprise mereiy radial sections and merely axial sections. As the feed movement of the tool must be controlled to move its center along such path, said path and the feed movement must be selected in such a mannerthatthe movement can be performed in practice and in an efficient manner.

In the crank-shaft-milling machine shown in Figure 3, one and the same inserted-tooth cutter M is used to machine a crankshaft 1 at the mainshaft portions 1 b, the crankpins lcandthe peripheral surfaces la' of the crankwebs 1a and also to form the crankwebs with the slanting surfaces 2. For this purpose the internally cutting annular inserted-tooth cutter M is mounted in a tool-holding drum 3, which is mounted in a tool slide 4 consisting of a compound slide. The lamer consists of a horizontal slide 4a and a vertical slide 4b and permits the inserted-tooth cutter M to be moved as desired in a plane that is normal to the longitudinal axis of the machine. The tool slide 4 is mounted on a carriage 5, which is movable along the machine bed 6 and moves the inserted-tooth cutter M in the axial direction.The horizontai and vertical slides 4a, 4b are driven by motors 7 through the intermediary of suitable transmissions 8 and screws 9. The carriage 5 is driven from a motor 10 by a screw 11.

The work supports 12 are mounted on the machine bed 6 of the milling machine and hold the crankshaft 1 in position throughout the time in which the crankshaft is machined. An additional support of the crankshaft 1 during its machining by the inserted-tooth cutter M is provided by a backrest 14, which is also mounted on and slidable along the machine bed 6 and may be coupled to the carriage, if desired.

A control system 13 is provided and is adapted to control the means for driving the carriage and the slides in such a manner that the inserted-tooth cutter M is moved along the bed to the portions which are to be machined and also performs the feed movement required for the desired machining operation.

During the machining of the mainshaft portions 1b and of the crankpins 1c and of the peripheral surfaces la' ofthecrankwebs 1 a, that feed movement is imparted only be the tool slide 4 takes place in a plane that is normal to the longitudinal axis of the machine. For the machining of the slanting surface 2 of the crankwebs, the feed movement must have radial and axial components. For this reason the means for driving the carriage 5 must be operated not only to move the inserted-tooth cutter M along the bed to the portion to be machine but also to impart to the inserted-tooth cutter a component of its feed movement. During the machining of the slanting surfaces 2 of the crankwebs, the direction V of the feed movement of the inserted-tooth cutter is the resultant of the component VR imparted by the tool slide, which moves in a suitable direction in a normal plane, and the component VA, which is imparted by the axial movement of the carriage. The magnitudes of the components of the feed movement and the cooperation of said components can be selected by the control system and are monitored by the latter. In this manner, a single milling machine and a single tool can be used for an efficient machining of the mainshaft portions, crankpins, peripheral surfaces of crankwebs and slanting surfaces of crankwebs.

Claims

1. A process of machining a slanting surface on a laterally protruding portion of an elongated workpiece, characterized in that the laterally protruding portion to be provided with a slanting surface is machined along an imaginary surface that is described by an arc of a circle, which lies in a plane that is normal to the longitudinal axis of the elongated workpiece, when the center of said arc is axially and radially dispiaced with respect to said longitudinal axis along a predetermined path.

2. A process according to claim 1 whenever used to machine a slanting surface on a crankweb of a crankshaft.

3. A process of machining a crankshaft having cylindrical portions and crankwebs and formed with peripheral surfaces at said cylindrical portions and at said crankwebs and with slanting surfaces at said crankwebs, wherein a milling cutter is operated to machine said crankshaft at least at part of said peripheral surfaces, characterized in that said slant ing surfaces are formed in that each of said crankwebs is machined with said milling cutter along an imaginary surface which is described by an arc of circle, which lies in a plane that is normal to the longitudinal axis of crankshaft, when the center of said arc is moved axially and radially with respect to said predetermined axis along a predetermined path.

4. A milling machine for carrying out the process according to claim 1 or 2, comprising a tool slide, which is movable transversely to the longitudinal axis of the machine and carries a milling cutter, preferably an internally cutting annular milling cutter, and a carriage, which is movable along said longitudinal axis and carries said tool slide, characterized by the provision of a control system for controlling drive means for driving the tool slide and drive means for driving the carriage so as to impart to the milling cutter a feed movement in radial and axial directions.

5. A milling machine according to claim 4, which constitutes a crankshaft-milling machine adapted to machine a crankshaft at cylindrical portions and at peripheral surfaces of crankwebs, characterized in that the machine comprises an inserted-tooth milling cutter and is operable to machine said cylindrical portions and the peripheral and slanting surfaces of said crankwebs with said inserted-tooth milling cutter.