Method for lapping valve seats using a single point cutting tool

• US 6,382,883 B1
• Filed: 03/09/2000
• Issued: 05/07/2002
• Est. Priority Date: 04/13/1998
• Status: Expired due to Term

• Current Assignee: The Harmand Family Limited Partnership
• Original Assignee: The Harmand Family Limited Partnership
• Inventors: Harmand, Brice, Harmand, Pierre
• Primary Examiner(s): Hughes, S. Thomas
• Assistant Examiner(s): Omgba, Essama
• Application Number:
  US09/521,333
• Time in Patent Office: 789 Days
• Field of Search: 408/1.R, 408/3, 408/82, 408/83.5, 298/884.4, 298/901.22
• US Class Current: 408/1.00R
• CPC Class Codes: B23C 3/055 for engines
• CPC Class Codes: F01B 1/12 Separate cylinder-crankcase elements coupled together to form a unit
• CPC Class Codes: F02F 1/24 Cylinder heads
• CPC Class Codes: F02F 7/0031 Construction kit principle (modular engines)
• CPC Class Codes: Y10T 29/49306 Valve seat making
• CPC Class Codes: Y10T 29/49405 Valve or choke making
• CPC Class Codes: Y10T 408/03 Processes
• CPC Class Codes: Y10T 408/08 with means to regulate operation by use of templet, tape, card, or other replaceable information supply
• CPC Class Codes: Y10T 408/5584 Engaging surface axially advanced of tool-action
• CPC Class Codes: Y10T 408/5587 Valve fitting
• CPC Class Codes: Y10T 408/85 to move radially
• CPC Class Codes: Y10T 82/125 Tool simultaneously moving axially

Abstract

The cutting tool for machining valve seats comprises a driving system, a spindle assembly, and a system controller. The driving system provides rotational movement and vertical movement for the spindle assembly which is controlled by the system controller. The spindle assembly further comprises a spherical sheath providing capability to align a spindle to any valve seat orientation, the spindle for rotating a universal cutting blade, a machining head attachable to the spindle, a tool holder carriage for holding the universal cutting blade, and a pinion feed driving assembly or set of connecting rods for controlling the cutting radius of the universal cutting blade. The pinion feed driving assembly is driven by a servo motor which moves the spindle vertically and independent from the vertical movement of the spindle assembly and the rotational movement of the spindle. The system controller includes memory and programming for controlling the operation of the universal cutting blade. An operator can input the parameters that define the geometry of the valve seat profile. These parameters are used by the system controller to determine the rotational speed, the vertical feed of the machine spindle, and the inward or outward feed of the universal cutting tool.

Claims

1. A method for lapping a valve seat of a plurality of pre-existing valve seats with corresponding valve guides in an engine cylinder head utilizing a spindle assembly in a machining apparatus, the spindle assembly having a spindle adapted for rotation around a vertical axis, the method comprising:

providing a carriage head at a lower portion of the spindle assembly, the carriage head having a carriage head control mechanism for effecting radial feed of the carriage head relative to the vertical axis;

attaching a universal cutting tool to the carriage head, the universal cutting tool having a single cutting point;

attaching a pilot at the lower portion of the spindle assembly so that the pilot is centered on the vertical axis, wherein the pilot is adapted to fit within a valve guide;

centering the spindle assembly with respect to the valve seat by inserting the pilot into the valve guide corresponding to the valve seat;

providing lapping parameters for a desired valve seat profile to a system controller, the desired valve seat profile comprising a plurality of segments, each segment having a segment length and at least one segment angle;

in the system controller, using the segment length and at least one segment angle for each of the plurality of segments to calculate each of a carriage head feed rate of the carriage head and a vertical feed rate and rotational speed of the spindle for lapping each segment of the valve seat profile using the lapping parameters; and

separately for each segment of the desired valve seat profile, generating control signals in the system controller for controlling the vertical feed rate and the rotational speed of the spindle and controlling the carriage head feed rate independent of the vertical feed rate and the rotational speed.

2. The method of claim 1 wherein the step of controlling the vertical feed rate further comprises adjusting both the rotational speed and the vertical feed rate of the spindle for each segment of the desired valve seat profile.

3. The method of claim 2 wherein adjusting both the rotational speed and the vertical feed rate provides a circular interpolation capability.

4. The method of claim 1 wherein the step of providing machining parameters further comprises the step of reading a memory card having stored machining parameters using a memory card reader connected to the system controller.

5. The method of claim 1 wherein the step of controlling the vertical feed rate further comprises adjusting the vertical feed rate of the spindle while keeping the rotational speed of the spindle constant for each segment of the desired valve seat profile.

6. The method of claim 1 wherein the step of controlling the vertical feed rate further comprises adjusting the rotational speed of the spindle while keeping the vertical feed rate constant.

7. The method of claim 1 wherein the radial movement of the carriage head is outward from the vertical axis.

8. The method of claim 1, wherein the radial movement of the carriage head is inward toward the vertical axis.

9. The method of claim 1, wherein the at least one segment is curved and the system controller decomposes the curved segment into a plurality of straight lines.

10. The method of claim 1, wherein the carriage head has a plurality of mounting holes and the step of attaching the universal cutting tool comprises selecting a mounting hole according to a radius of the desired valve seat profile.

11. The method of claim 1, wherein the carriage head is disposed at an angle relative to a horizontal plane perpendicular to the vertical axis.

12. A method for lapping a valve seat in an engine cylinder head comprising:

determining a target valve seat profile, the target valve seat profile comprising a plurality of segments, each segment having a segment length and a segment angle;

providing a machine head having a spindle assembly adapted for rotation around a vertical axis and a carriage disposed at a lower portion of the spindle assembly at an inclination angle relative to a horizontal plane perpendicular to the vertical axis, the carriage adapted for radial movement relative to the vertical axis;

attaching a cutting tip to the carriage, the cutting tip having a single cutting point;

centering the vertical axis within the valve seat;

in a system controller, calculating a radial feed rate of the carriage and a vertical feed rate, a vertical displacement and a rotational speed of the spindle for creating each segment of the plurality of segments;

for each segment, generating control signals comprising a carriage control signal for moving the carriage at the calculated radial feed rate and a spindle control signal for moving the spindle assembly at the calculated vertical feed rate and the calculated rotational speed for the calculated vertical displacement; and

lapping the plurality of segments one segment at a time to produce the target valve seat profile.

13. The method of claim 12, wherein the step of calculating comprises using the segment length and segment angle for calculating vertical feed rate per revolution of the spindle assembly, for calculating the number of spindle rotations, and for calculating an amount of vertical displacement of the spindle assembly, all for completion of the at least one segment.

14. The method of claim 13, wherein the step of calculating further comprises using the inclination angle of the carriage.

15. The method of claim 12, wherein the radial feed rate is independent of the vertical feed rate and the rotational speed.

16. The method of claim 12, wherein the step of generating control signals further comprises changing at least one of the radial feed rate, the vertical feed rate, and the rotational speed when proceeding from one segment to another segment in the valve seat profile.

17. The method of claim 12, wherein the step of centering comprises attaching a pilot to the lower portion of the spindle assembly along the vertical axis and inserting the pilot into a valve guide corresponding to the valve seat.

18. The method of claim 12 wherein the radial movement of the carriage head is outward from the vertical axis.

19. The method of claim 12, wherein the radial movement of the carriage head is inward toward the vertical axis.

20. The method of claim 12, wherein the at least one segment is curved and the step of calculating further comprises decomposing the curved segment into a plurality of straight lines.

21. The method of claim 12 further comprising the step of reading a memory card having stored machining parameters comprising the radial feed rate of the carriage and the vertical feed rate and the rotational speed of the spindle assembly for obtaining the target valve seat profile using a memory card reader connected to the system controller.

22. The method of claim 12, wherein the carriage has a plurality of mounting holes and the step of attaching the cutting tip comprises selecting a mounting hole according to a radius of the target valve seat profile.