In a machine of the abovementioned type, the object on which the invention
is based is achieved by the grinding surface of the grinding tool being considerably wider than the circumferential surfaces to be ground on the cam. Features of continuations, embodiments and further developments of the machine according to the invention are contained in sub-claims 7 to 11. Claims 7 to 9 relate to different embodiments of the grinding tool with several grinding surface sections and controlled use thereof for grinding various cam configurations. Claims 10 and 11 relate to the choice and construction of the grinding tools.
By the axial enlargement of the grinding surface, a prolonging of the life of the grinding tools when grinding cams results. This is particularly important for belt grinding machines, the grinding belts of which can be used for longer, so that the belt changing cycles can be prolonged considerably. In the case of grinding belts, there is the further important advantage that the wider belts have a higher tear strength and are therefore 4.
more stable, so that they can be subjected to a higher load during grinding. Both the longer belt changing cycles and the higher loading capacity increase the productivity of machines fitted with these belts.
The invention will now be described by way of example only, with reference to the accompanying drawings.
Figure 1 shows a diagrammatic side view of one embodiment of belt grinding machine according to the invention, Figures 2 and 3 each show a plan view of a grinding situation in the process according to the invention and Figure 4 shows a plan view of a modification of the machine of Fig. 1.
A belt grinding machine with a wide grinding belt as the grinding tool is shown as an example of the present invention in Figure 1. It has a machine bed 1, on which a workpiece table 2 can be moved in the direction of the longitudinal axis 3 of a camshaft 4 clamped in a manner suitable for working. For clamping the camshaft 4, a customary workpiece holder, of which only the workpiece spindle carrier 6 is shown in the drawing, is provided on the workpiece table 2. The camshaft 4 is rotated around its longitudinal axis 3 (C axis) by means of a rotary drive 7. The workpiece table 2 can be moved by means of a spindle pinion 8 and a motor 8a in the direction of the camshaft axis 3 (machine axis Z). The rotary drive 7 of the camshaft and the table drive 8a are controlled by a control arrangement 9.
Guides 11 on which a slide 12 can be moved at right angles to the camshaft axis 3 in the Xl direction are attached to the machine bed 1. A motor 13 which moves the slide by a gear means, which is known and not shown in the drawing, serves as the drive for moving the slide 12. A carrier 14 in the form of a vertical plate 16 or another corresponding holding device is mounted on the slide 12. The holding plate 16 is aligned orthogonally to the camshaft axis 3 and carries a belt grinding unit 17 for grinding a cam or pair of cams 18 of the camshaft 4. As many belt grinding units 17 as there are cams or pairs of cams to be ground simultaneously on the camshaft can be arranged orthogonally to the camshaft axis 3 and parallel to one another on the holding plate 16, which is not shown.
The belt grinding unit 17 has a grinding belt 19 which circulates around stationary deflection rollers 21 and 22, around a movable deflection roller 23 for compensation of the belt length and around a drive roller 24. The stationary deflection rollers 21 and 22 are pivoted freely on shafts 26 and 27 respectively, which are fixed on one side cantilevered to the holding i S plate 16 and extend parallel to the camshaft axis 3. The drive roller 24 of the belt grinding unit 17 sits on a drive shaft 28 pivoted in the holding plate 16, the opposite end of which, behind the holding plate, carries a belt pulley 29 of a synchronous belt drive 31, via which the grinding belt 19 is driven by a motor 32. The motor is also arranged behind the holding plate 16 on the tool slide 12 and can be moved, together with this and the holding plate 16, at right angles to the camshaft axis 3 in the direction of the arrow X1.
A tool head 33 which is also attached cantilevered like a beam parallel to the camshaft axis 3 is arranged on the holding plate 16. The tool head carries, in the plane of the circulating grinding belt 19, a support element 34 which can be moved essentially radially to the camshaft at right angles to the camshaft axis 3 in the direction of an arrow X2. For this, the support element is attached to the front end of a sleeve 36 which can be moved in the X2 direction by means of a drive 37. The drive 37 of the support element 34 is connected to the control arrangement 9, preferably the machine control, and, as is customary in numerically controlled grinding of cams, is moved backwards and forwards in the X2 direction in cutting contact with the cams of the camshaft, according to the angular position thereof, such that the desired cam shapes are in each case formed.
38 designates a working area cover. 39 is a machine housing which surrounds the belt grinding unit and the units carrying and driving it, and which is held by a frame 41.
According to the invention, grinding tools of which the grinding surfaces are considerably wider than the cam surfaces to be ground are employed for grinding the cams of camshafts. Figure 2 shows a camshaft 4 which is to be worked and has several pairs of cams 18A, 18B, 18C etc., each with two cams 18a, l8b, 18c etc. The two cams of each pair of cams are ground simultaneously with the wide grinding belt 19. This operation is shown in plan view in Figure 2 as an "instantaneous picture", which coincides with the diagram in Figure 1. For grinding the pairs of cams of the camshaft 4, a wide grinding belt 19 is provided, the width of which is at least twice the total width of the cam surf aces to be ground. This results in four grinding surface sections 43a, 44a, 43b and 44b running side by side on the grinding belt 19. The cams 18a of the pair of cams 18A are ground, as shown, on grinding surface sections 43a and 43b. When grinding of the cams 18a of the pair of cams 18A has ended, further pairs of cams are brought into cutting contact and ground with grinding surface sections 43a (0 and 43b by longitudinal positioning of the camshaft 4 in the Z direction. When working of the camshaft 4 is complete, a new camshaft 4a is inserted and positioned in a manner suitable for working, such that the cams 18a of the pair of cams 18A on camshaft 4a are now brought into cutting contact with the previously unused grinding surface sections 44a and 44b of the grinding belt 19. These and the following cams are now ground in contact with these grinding surface sections 44a and 44b.
As can be seen, this procedure increases the life of the grinding belts and therefore the profitability of the machine. Furthermore, wide belts have a higher tear strength than narrow belts, so that the loading capacity of the grinding belts is also increased by the proposal according to the invention. This opens up the possibility of providing higher material removal rates on the workpiece, which likewise increases the profitability of the machine.
There are of course various possibilities for using the grinding surface sections. In connection with Figures 2 and 3, it has been described that initially exclusively the grinding surface sections 43a and 43b are used, until they have reached a state where they are no longer usable for grinding cam surfaces. In Figure 3, this is indicated at 43a and 43b. Exclusively grinding surface sections 44a and 44b are then used for further grinding, until these are also no longer usable. It is also possible for the grinding surface sections to be used simultaneously, by using the grinding surfaces in alternation for successive pairs of cams to be worked. It is also possible for all the cams of a camshaft to be ground on the first grinding surface sections 43a, b and all the cams of a second camshaft to be ground on the second grinding surface sections 44a and b.
The simultaneous grinding of the cams of pairs of cams has been shown and described in Figures 2 and 3. The same process can of course also be used for grinding individual cams. In this case, a grinding belt which is e.g. about twice as wide as a cam surface to be ground is employed. This belt then comprises two grinding surface sections, on which the cams are ground in succession. The procedure coincides with that described in connection with Figures 2 and 3. Belts of more than twice the cam surface width can also be employed according to the invention in this manner.
A cam grinding machine with a grinding disc as the grinding tool is shown in a plan diagram in Figure 4 as a variant of the invention. On a machine table 46, which can be positioned in the Z direction in guides 47, a camshaft 53 with cams 54 is clamped rotatably between the tip 48 of a workpiece spindle carrier 49 and the tip 51 of a footstock 52 in the 1 7 customary manner. A grinding head 56 with a rotating grinding disc 57 can be moved in the X direction on the machine bed, which is not shown, at right angles to the axis of the camshaft. The grinding surface of the grinding disc 57 is at least twice as wide as the surfaces of the cam 54 which are to be ground. This results in two grinding surface sections 58 and 59 on the grinding surface of the grinding disc, which can be brought in succession into cutting contact with cams to be ground. In the diagram of Figure 4, the grinding surface section 58 is in use on a cam 54a. Working of another cam 54b in a different angular position using the second grinding surface section 59 is shown as a broken line, the associated positions of the grinding head 56 and the workpiece table 46 also being indicated as broken lines. Grinding discs with a wider grinding surface than the cam width can thus also be employed as grinding tools for working cams, in order to prolong the service life of the grinding tool and to increase the profitability of the machine.
13 CLAIMS:
1. Process for grinding the cams of camshafts, in which a camshaft is clamped into a workpiece receiver and is rotated around its longitudinal axis (C axis) and the grinding tool and a cam are brought into cutting contact and moved relatively to one another essentially radially to the rotational axis of the cam in the context of generation of a desired cam shape, characterized in that the cams are ground successively with different axially adjacent grinding surface sections of a grinding tool having a wide grinding surf ace.
2. Process according to Claim 1, characterized in that a cam to be ground is brought into cutting contact and ground with the grinding surface of a grinding tool, the axial width of which is greater than that of the cam surface to be ground, and in that the grinding tool and the workpiece are moved axially relatively to one another during grinding, which means that the contact line of the workpiece on the grinding tool is moved in the axial direction along the grinding surface, in addition to its movement in the circumferential direction of the grinding tool.
3. Process according to Claim 1, characterized in that a cam to be ground is brought into cutting contact with the grinding surface of a grinding tool which is at least twice as wide as the cam, in that at least one cam is ground with a first axial cutting surface section, in that the camshaft and the grinding tool are displaced relatively to one another in the axial direction such that a further cam to be ground is brought into cutting contact with a second grinding surface section of the grinding tool which is displaced axially with respect to the first, and in that at least this further cam is ground an this second grinding surface section of the same grinding tool.
4- Process according to Claim 1 or 3, characterized in that a group of adjacent cams of the same shape and angular position on a camshaft having several such groups of cams is ground simultaneously on first grinding surface sections of a wide grinding tool, and in that, after grinding of this group of cams, the camshaft and the grinding tool are displaced relatively to one another in the axial direction such that the cams of a further group 9 of cams are simultaneously brought into cutting contact and ground with second grinding surface sections of the same grinding tool lying axially alongside the first, at least one of the second grinding surface sections lying between two first grinding surface sections.
5. Process according to one of Claims 1 to 4, characterized in that all the cams of a first camshaft are ground on the first grinding surface sections of the grinding tool, and in that all the cams of at least one further camshaft are ground on the second grinding surface sections of the same grinding tool displaced axially with respect to the first.
6. Machine for grinding the cams of camshafts, having a workpiece receiver with a means for holding and rotating a camshaft around its longitudinal axis (C axis) in a manner suitable for working, a grinding unit with a circulating grinding tool having a grinding surface, drives for rotation of the camshaft and the circulatory movement of the grinding tool, guides and drive -means for moving the grinding tool and the camshaft relatively to one another essentially radially and axially to the camshaft axis, and a control arrangement for controlling the drive means in the context of generation of a desired cam shape, characterized in that the grinding surface of the grinding tool (19, 57) is considerably wider than the circumferential surfaces to be ground on the cams (18, 54).
7. Grinding machine according to Claim 6, characterized in that the grinding tool (19, 57) and the camshaft (4, 53) can be moved transversely in the axial direction (Z) relatively to one another during grinding, and in that the control arrangement (9) controls the transverse movement, in addition to the relative movement generating the cam shape, and the contact line of the workpiece and grinding tool shifts in the axial direction along the grinding surface.
8. Grinding machine according to Claim 6, characterized in that the grinding surface of the grinding tool (19, 57) is at least twice as wide as the cam surfaces to be ground, and in that it has at least two grinding surface sections (43, 44; 58, 59) side by side, with which cam surfaces to be ground can be brought into cutting contact in succession.
9. Grinding machine according to one of Claims 6 to 8, characterized in that the grinding surface of the grinding tool (19) has at least four grinding surface sections (43a, b, 44a, b) axially side by side, each of which is at least as wide as the surface to be ground on a cam (18), in that at least two cams (18a) of the same shape and alignment of a group of cams (18A) on a camshaft (4, 4a) can be brought simultaneously into cutting contact with the corresponding number of first grinding surface sections (43a, b), and in that the cams (18a) of a further group of cams (18A) of the same or another camshaft (4a) can be brought into cutting contact with the corresponding number of second grinding surface sections (44a, b), at least one of which lies between two first cutting surface sections.
10. Grinding machine according to one of Claims 6 to 9, characterized in that a continuous circulating grinding belt (19) is provided as the grinding tool having a wide grinding surface.
11. Grinding machine according to one of Claims 6 to 9, characterized in that a rotating grinding disc (57) having a wide grinding surface is provided as the grinding tool.
12. A process for grinding the cams of camshafts, substantially as herein described with reference to the accompanying drawings.
13. A machine for grinding the cams of camshafts, substantially as herein described with reference to the accompanying drawings.