Main-shaft malfunction-state detector in an air bearing type machine tool

• US 6,212,935 B1
• Filed: 08/03/1998
• Issued: 04/10/2001
• Est. Priority Date: 04/23/1996
• Status: Expired due to Term

• Current Assignee: Toshiba Kikai Kabushiki Kaisha
• Original Assignee: Toshiba Kikai Kabushiki Kaisha
• Inventors: Shiozaki, Masahito, Fujie, Hideo, Momochi, Takeshi, Nagashima, Kazuo
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US09/127,779
• Time in Patent Office: 981 Days
• Field of Search: 735/87, 735/93, 736/49, 736/58, 736/60, 735/99, 736/00, 73/375, 73/376, 73/379, 738/623.81, 738/626.8, 73/9, 408/6, 408/5, 408/11, 408/10
• US Class Current: 73/9
• CPC Class Codes: B23Q 1/38 using fluid bearings or fluid cushion supports
• CPC Class Codes: B23Q 1/70 Stationary or movable members for carrying working-spindles for attachment of tools or work B23Q1/01 takes precedence; designed to be moved by using particular mechanisms B23Q1/44
• CPC Class Codes: B23Q 17/09 for indicating or measuring cutting pressure or for determining cutting-tool condition, e.g. cutting ability, load on tool arrangements preventing overload of tools B23Q11/04; devices for indicating failure of drills during boring B23B49/00
• CPC Class Codes: F16C 2322/39 General build up of machine tools, e.g. spindles, slides, actuators in general B23Q
• CPC Class Codes: F16C 32/06 with moving member supported by a fluid cushion formed, at least to a large extent, otherwise than by movement of the shaft, e.g. hydrostatic air-cushion bearings
• CPC Class Codes: G01M 13/045 Acoustic or vibration analysis

Abstract

A main-shaft malfunction-state detector in an air bearing type machine tool, in which an abnormal contact of a main shaft with a housing is reliably and automatically detected. The contacting state of the main shaft 11 and the housing 13 is detected through the presence of electric conductivity by a contact detection device 31. A contact decision device 32 determines the contact of the main shaft 11 with the housing 13 based on the detected conductivity, thus automatic and certain preventative measures, such as the main shaft of the machine tool stops and so on, are based on the above decision.

Claims

1. A main-shaft malfunction-state detector in an air bearing type machine tool, for detecting an abnormal contact of a main shaft of the machine tool with a housing supporting the main shaft through an air bearing, the malfunction-state detector comprising:

contact sensor for detecting contact of the main shaft and the housing when the main shaft and the housing physically contact each other; and

contact decision device for determining the detected contact of the main shaft and the housing by using the output signal sent from said contact sensor.

2. The main-shaft malfunction-state detector in the air bearing type machine tool according to claim 1,

wherein said contact sensor is an AE sensor detecting acoustic emission created in the housing; and

wherein said contact decision device determines the contact when the output signal sent from said AE sensor exceeds a predetermined threshold value.

3. The main-shaft malfunction-state detector in the air bearing type machine tool according to claim 2, wherein said contact decision device has an amplifying circuit amplifying the output signal sent from said AE sensor, an amplitude discriminating circuit measuring a value of amplitude of an output value of said amplifying circuit, a threshold value memory storing the predetermined threshold value, and a comparing circuit comparing the threshold value stored in the threshold value memory and an output value of said amplitude discriminating circuit.

4. The main-shaft malfunction-state detector in the air bearing type machine tool according to claim 2, wherein said contact decision device has an amplifying circuit amplifying the output signal sent from said AE sensor, an amplitude discriminating circuit measuring a value of amplitude of an output value of said amplifying circuit, an A/D converting circuit converting the output value of said amplitude discriminating circuit from an analog form to a digital form, a threshold value memory storing the predetermined threshold value, and a comparison arithmetic area comparing the threshold value stored in said threshold value memory and an output value of said A/D converting circuit, said threshold value memory and said comparison arithmetic area being provided in an NC system controlling the machine tool.