Failure detection device for spindle head of machine tool including a plurality of sensors

A failure detection device for detecting an abnormality of a spindle head of a machine tool, comprising:

• a first sensor that detects generation of a predetermined first gas in the spindle head;
• a second sensor that detects a change in a state of the spindle head that is different from the generation of the first gas;
• and
• a controller that determines whether a bearing arranged in the spindle head is abnormal or not, wherein
• the controller is configured to determine occurrence of the abnormality in the bearing and a cause of the abnormality based on a change in an output value of the first sensor over time and a change in an output value of the second sensor over time,
• the bearing is a motor bearing that supports a shaft of a spindle motor,
• the motor bearing includes urea grease disposed in the motor bearing,
• the first sensor is a gas sensor or an odor sensor that detects nitrogen oxide,
• the second sensor is one of a vibration sensor that detects vibration of the spindle head or a sensor that detects an elastic wave generated in the spindle head, and
• the controller determines that the motor bearing is abnormal due to deterioration of the urea grease if the output value of the second sensor increases after the output value of the first sensor increases.

A failure detection device for detecting an abnormality of a spindle head of a machine tool, comprising:

• a first sensor that detects generation of a predetermined first gas in the spindle head;
• a second sensor that detects a change in a state of the spindle head that is different from the generation of the first gas;
• and
• a controller that determines whether an oil seal arranged in the spindle head is abnormal or not, wherein
• the controller is configured to determine occurrence of the abnormality in the oil seal and a cause of the abnormality based on a change in an output value of the first sensor over time and a change in an output value of the second sensor over time,
• the oil seal is disposed so as to seal an inner space of a spindle motor and includes an elastic member that is in contact with a shaft of the spindle motor and is made of nitrile rubber,
• the first sensor is a first gas sensor or a first odor sensor that detects hydrogen sulfide,
• the second sensor is a humidity sensor that detects humidity in the spindle head, and
• the controller determines that the oil seal is abnormal due to biting of a foreign matter if the output value of the second sensor increases after the output value of the first sensor increases.