GB1565035A

GB1565035A - Machine for the fine-machining of gearwheels

Info

Publication number: GB1565035A
Application number: GB7929/78A
Authority: GB
Original assignee: Hurth Verwaltungs GmbH
Current assignee: Hurth Verwaltungs GmbH
Priority date: 1977-03-15
Filing date: 1978-02-28
Publication date: 1980-04-16
Also published as: JPS53115994A; JPS5854935B2; FR2383743A1; FR2383743B1; IT7847518A0; DE2711282A1; IT1155755B

Description

(54) MACHINE FOR THE FINE-MACHINING OF GEARWHEELS (71) We, HURTH VERWALTUNGS GmbH, of 36 Moosacher Strasse, 8 Munich 40, Germany, a German Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described, in and by the following statement: The invention relates to a machine for the fine-machining (finishing) of gearwheels by running them in mesh with a toothed tool with contact at only one flank of each tool and workpiece tooth, e.g. by honing or grind ing. In the past numerous methods have been disclosed for the fine-machinging of gearwheels, as have many different kinds of machine, in order to meet the constantly increasing demands of the users as regards the quality of the workpiece toothing.

Nevertheless, slight errors, for example flank errors, still occur and their cause lies inter alia in the conditions governing the relative movement of the tool and the workpiece.

It is therefore the object of the invention to provide a machine capable of achieving a further improvement of the tooth quality.

Usually, in known machines the tool is driven and the workpiece is entrained by the tool. This applies to machining with singleflank contact, e.g. honing, as well as to machining with two-flank contact, e.g. by shaving. In single-flank contact only one flank of a tooth of the driving wheel, in this case usually the tool, directly contacts only one flank of the tooth of a driven wheel, and the other flank of the same workpiece tooth is situated at a specific distance from the corresponding flank of the next tool tooth: the tool and workpiece mesh with each other with flank clearance. In two-flank contact both tooth flanks on each side of a tooth gap of the workpiece are in direct contact with both flanks of a workpiece tooth, or vice versa: there is no flank clearance between the tool and the workpiece.

In the machining methods involving single-flank contact the first contact between the tool and the workpiece - the direction in which the tool is drivingly driven is of no consequence in this context - always takes place between a workpiece tooth tip and a tool tooth base. The ensuing slip between the two touching flanks, which diminishes to zero towards the pitch circle and subsequently again increases, necessarily leads to irregularities in the shape of the flank i.e. the tooth flanks of the workpiece deviate from the ideal involute shape. Previously, allowance was made for such effects by corresponding correction of the tool.

If the workpiece instead of the tool is driven and the tool is entrained by the workpiece, the first contact between the tool and the workpiece will take place between the workpiece tooth base and the tool tooth tip, i.e. in the order which is the reverse of the above-described case of the driven tool. Slip of the two flanks upon each other also takes place in the opposite manner, so that the deviations from the ideal ivolute shape. are also orientated in the direction which is opposite to that of the driven tool.

Because there is contact at only one flank and a small clearance at the other flank of each tooth, it is possible for the normally contacting flanks of the tool and workpiece to separate briefly, for example because of irregularities on the flanks of the workpiece.

The separation and restoration of contact involve changes of angular velocity and may involve impact between the tooth flanks, and the separated workpiece flank will not be fully machined. The machined workpiece will therefore have tooth flank errors, which are very difficult to avoid or remove.

The present invention resides in a machine for fine-machining of gearwheels by rotating the workpiece and a toothed tool in mesh with contact between the tool and workpiece teeth at only one flank of each tooth, in which machine the means for rotating the tool and workpiece are such that both the tool and the workpiece meshing therewith can be rotatingly driven in such a manner that the contacting flanks can be subjected to changing, adjustable contact forces by acceleration or retardation of the tool and/or workpiece.

By suitable selection of the contact force applied, errors due to flank separation during machining can be reduced or eliminated.

A further improvement of the gear-cutting quality is achieved by the provision of flywheel masses for the tool drive and/or the workpiece drive.

One embodiment of the invention will be described herein below by reference to the accompanying drawings, in which: Figure 1 shows a machine for the finemachining of gearwheels in accordance with the invention; Figures 2 to 5 show different meshing relationships between tool and workpiece in single-flank contact, namely In Figure 2: the tool drives and rotates anti-clockwise, In Figure 3: the workpiece drives and rotates clockwise, In Figure 4: the tool drives and rotates clockwise, and Th Figure 5: the workpiece drives and rotates anticlockwise.

A machine which operates by the plungcutting process, i.e. without longitudinal feed, as shown in Figure 1, may be used as an example of a machine according to the invention for the fine-machining of gearwheels.

The machine has a tool carrier 2 in which the tool 3 is held in known manner, the tool carrier being pivotably (about a vertical axis) and lockably supported in a C-shaped machine frame 1. The drive for the tool will be described subsequently. The machine frame 1 also supports a carriage 8 which is slidable in a guide perpendicularly to the pivoting plane of the tool carrier and can also be locked in some circumstances. A worktable 7 which can tilt about a pivot 10 is disposed on the carriage. The - workpiece 4, which meshes with the tool 3, usually with crossed axes, and can be driven by a motor 21 as will be described subsequently, is held between tailstocks 5, 6. Tilting of the worktable 7 about the pivot 10 enables crowned teeth to be produced on the workpiece. The tilting device is known and is therefore not illustrated or described.

The carriage 8 can be driven in known manner by a motor 11 or by a handwheel 13 through various transmissidn elements, whereby it can be made to traverse vertically for the purpose of applying workpiece feed.

The means required to this end are also known and are therefore not illustrated.

The tool 3 is driven by a variable-speed electric motor 14 via a gear transmission 15, a pair of spur gears 16, 17 and a pair of bevel gears 18, 19. A variable-speed hydraulic motor can be employed in place of an electric motor. The provision of a clutch 20 between the motor and the transmission is in general appropriate.

The workpiece 4 is driven by means of a variable-speed electric motor 21 of the same kind as the motor 14 is used for driving the tool. A variable-speed hydraulic motor can be employed instead. The motor is followed by a transmission 21' and it is appropriate to provide a clutch 22 between the motor and the transmission. The motor 21, the transmission 21' and the clutch 22 if provided can be flange-mounted on the tailstock 6 as an integral unit or can be independently mounted on the worktable 7 and can be coupled to the tailstock 6 by means of a suitable shaft connection. The machine is provided with means for indicating the rotational speed of the tool and the workpiece to facili- tate monitoring by the operating personnel; thus tachometers 44, 45 or the like can be connected to the shafts on which the above-mentioned parts are held.A digital display can be provided in place of the tachometers.

The motors 14, 21 are provided with regulating apparatus 23, 24 with which - inde pendenfly of each other - the rotational speed as well as a braking torque which remains constant or varies with the speed can be steplessly adjusted for each motor. The tool and the workpiece can thus be pressed one against the other during fine-machining with changing and adjustable forces of single-flank contact. For example if the tool is driven it will not merely entrain the workpiece but must also overcome the resistance produced by the braking torque of the motor 21 on the driving flank or flanks.

As already mentioned the drive can be applied to the tool or to the workpiece and the non-driven part can be retarded. By virtue of this fact and owing to the possibility of changing the direction of rotation of the motors it is therefore possible to obtain four machining steps for fine-machining with flank clearance (two on each flank) which steps are illustrated in Figures 2 to 5.

The tool 3 is driven anticlockwise (arrow 25) as shown in Figure 2 and the workpiece is retarded, the first contact between a tooth 27 of the workpiece 4 and the tool will always take place at point 26 at the workpiece tooth tip. Motion of the region of contact will then take place in the arrow direction 29 from the tip to the base of the left flank 28 of the tooth 27.

If the workpiece is then driven clockwise as shown by arrow 30 in Figure 3 while maintaining the same direction of rotation and the tool is retarded, the first contact of the workpiece tooth 27 with the tool will take place at point 31 at the base of the tooth 27. The contact region will then move in the arrow direction 32 from the base to the tip of the rirght-hand flank 33 of the tooth 27. If the direction of rotation is then reversed (Figure 4) and the tool is again driven (arrow 34) while the workpiece is retarded the first contact of the tooth 27 with the tool will take place at point 35 at the tip of the tooth and the contact will move in the arrow direction 36 down the right-hand flank 33 to the base of the tooth.

Finally, the workpiece is driven, with the same direction of rotation as in Figure 4 (arrow 37 in Figure 5) and the tool is retarded. The first contact of the workpiece tooth 27 with the tool takes place at 38 at the base of the workpiece tooth left flank 28, the contact moves in accordance with the arrow 39 from the base to the tip of the flank 28.

Changing over the motors from "driving" to "retarding" and vice versa or from "clockwise" to "anticlockwise" or vice versa can of course proceed automatically. To this end the motors 14 and 21 are interconnected by known control devices 40 so that the different machining steps can take place automatically one after the other in the described or some other sequence. The duration of the individual machining steps can be controlled, for example by means of a known counting mechanism 41 in dependence on the number of rotations of the tool, the counting mechanism delivering corresponding signals to the control device.Although it is possible to start smoothly with the driving motor and for the retarding motor to operate with a constant braking torque from the commencement of starting it is more advantageous, in view of the masses that have to be accelerated, to initially commence operation with both motors driving and for one of the motors to be changed over to retarding after a specific time has elapsed. Conveniently the full braking torque is not applied suddenly but the torque is allowed to rise from zero to a preselected maximum value so as to protect the tool.

Varying the braking torque on the tool enables the contact force conditions on the flanks of a workpiece tooth to be changed.

The initially described appearance of flank errors resulting from motion which takes place in only one direction on each workpiece tooth flank can be substantially avoided on a machine according to the invention by applying the processing steps described hereinabove. To further ensure results which are as perfect as possible, the motors 14, 21 can be provided with additional flywheel masses 14, 43 in order to stabilize the drive, i.e. in order to obtain a driving speed which is uniform and unaffected by unintentional changes.

The invention, explained herein by reference to the example of a machine which operates by the plunge-cutting method for the fine-machining of gearwheels, can also be applied to all other machines for the finemachining of gearwheels. The machines themselves can also be provided with all other devices required for their operation and the appropriate machining procedure, for example they can be provided with known cooling and lubricating means or with a horizontally movable table to provide an additional transverse motion between the tool and the workpiece and the like.

WHAT WE CLAIM IS: 1. A machine for fine-machining of gearwheels by rotating the workpiece and a toothed tool in mesh with contact between the tool and workpiece teeth at only one flank of each tooth, in which machine the means for rotating the tool and workpiece are such that both the tool and the workpiece meshing therewith can be rotatingly driven in such a manner that the contacting flanks can be subjected to changing, adjustable contact forces by acceleration or retardation of the tool and/or workpiece.

2. A machine as claimed in claim 1 including means for reversing the rotation af the tool and workpiece.

3. A machine according to claim 1 or 2, characterised in that the two driving motors are connected to suitable regulating apparatus which permit different speeds and torques to be adjusted.

4. A machine according to any of claims 1 to 3 characterised in that the two driving motors are interconnected through suitable control devices so that different machining steps take place automatically and successively in a sequence which is variable but can be fixed at pre-defined times.

5. A machine according to any of claims 1 to 4, characterized in that a flywheel mass is disposed on the driving motor for the tool and/or on the driving motor for the workpiece.

6. A gear-finishing machine, constructed and operable substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. point 31 at the base of the tooth 27. The contact region will then move in the arrow direction 32 from the base to the tip of the rirght-hand flank 33 of the tooth 27. If the direction of rotation is then reversed (Figure 4) and the tool is again driven (arrow 34) while the workpiece is retarded the first contact of the tooth 27 with the tool will take place at point 35 at the tip of the tooth and the contact will move in the arrow direction 36 down the right-hand flank 33 to the base of the tooth. Finally, the workpiece is driven, with the same direction of rotation as in Figure 4 (arrow 37 in Figure 5) and the tool is retarded. The first contact of the workpiece tooth 27 with the tool takes place at 38 at the base of the workpiece tooth left flank 28, the contact moves in accordance with the arrow 39 from the base to the tip of the flank 28. Changing over the motors from "driving" to "retarding" and vice versa or from "clockwise" to "anticlockwise" or vice versa can of course proceed automatically. To this end the motors 14 and 21 are interconnected by known control devices 40 so that the different machining steps can take place automatically one after the other in the described or some other sequence. The duration of the individual machining steps can be controlled, for example by means of a known counting mechanism 41 in dependence on the number of rotations of the tool, the counting mechanism delivering corresponding signals to the control device.Although it is possible to start smoothly with the driving motor and for the retarding motor to operate with a constant braking torque from the commencement of starting it is more advantageous, in view of the masses that have to be accelerated, to initially commence operation with both motors driving and for one of the motors to be changed over to retarding after a specific time has elapsed. Conveniently the full braking torque is not applied suddenly but the torque is allowed to rise from zero to a preselected maximum value so as to protect the tool. Varying the braking torque on the tool enables the contact force conditions on the flanks of a workpiece tooth to be changed. The initially described appearance of flank errors resulting from motion which takes place in only one direction on each workpiece tooth flank can be substantially avoided on a machine according to the invention by applying the processing steps described hereinabove. To further ensure results which are as perfect as possible, the motors 14, 21 can be provided with additional flywheel masses 14, 43 in order to stabilize the drive, i.e. in order to obtain a driving speed which is uniform and unaffected by unintentional changes. The invention, explained herein by reference to the example of a machine which operates by the plunge-cutting method for the fine-machining of gearwheels, can also be applied to all other machines for the finemachining of gearwheels. The machines themselves can also be provided with all other devices required for their operation and the appropriate machining procedure, for example they can be provided with known cooling and lubricating means or with a horizontally movable table to provide an additional transverse motion between the tool and the workpiece and the like. WHAT WE CLAIM IS:

1. A machine for fine-machining of gearwheels by rotating the workpiece and a toothed tool in mesh with contact between the tool and workpiece teeth at only one flank of each tooth, in which machine the means for rotating the tool and workpiece are such that both the tool and the workpiece meshing therewith can be rotatingly driven in such a manner that the contacting flanks can be subjected to changing, adjustable contact forces by acceleration or retardation of the tool and/or workpiece.