Air compressor and method for controlling the same
An air compressor includes: a tank portion for reserving compressed air used in a pneumatic tool; a compressed air generation portion for generating compressed air and supplying the compressed air to the tank portion; a drive portion including a motor for driving the compressed air generation portion; a control circuit portion for controlling the drive portion; and a pressure sensor for detecting pressure of the compressed air reserved in the tank portion. The control circuit portion includes a unit for controlling the rotational speed of the motor multistageously on the basis of a detection signal output from the pressure sensor.
1. A method of controlling an air compressor, said air compressor including a tank portion for reserving compressed air used in a pneumatic tool, a compressed air generation portion for generating compressed air and supplying said compressed air to said tank portion, a drive portion including a motor for driving said compressed air generation portion, and a control circuit portion for controlling said drive portion, the method comprising:
detecting pressure P of said compressed air reserved in said tank portion;
storing a plurality of values indicating different rotational speeds of the motor;
calculating a rate ΔP/ΔT between pressure change ΔP and time ΔT;
selecting one of the values based on the pressure P of said tank portion and the rate ΔP/ΔT of pressure change; and
controlling the rotational speed of said motor in accordance with the selected value.
2. The method according to claim 1 , wherein the plurality of values comprise integral times of a predetermined rotational speed.
3. The method according to claim 1 , wherein said controlling comprises:
judging whether the pressure P in the tank is higher than a predetermined value; and
controlling the motor to stop when the pressure P is higher than the predetermined value.
4. The method according to claim 1 , wherein said calculating includes calculating a first rate ΔP 1 /ΔT 1 of pressure change ΔP 1 to a relatively short time ΔT 1 and a second rate ΔP 2 /ΔT 2 of pressure change ΔP 2 to a time ΔT 2 longer than the time ΔT 1 , and
wherein said selecting includes selecting one of the rotational speeds based on the first and second rates of pressure change.
5. The method according to claim 1 , further comprising:
storing a plurality of patterns indicating relations among the pressure P of said tank portion, the rate ΔP/ΔT of pressure change, and the rotational speeds of said motor; and
selecting one of the patterns based on a currently operating motor speed.
6. A method of controlling an air compressor, said air compressor including a tank portion for reserving compressed air used in a pneumatic tool, a compressed air generation portion for generating compressed air and supplying said compressed air to said tank portion, a drive portion including a motor for driving said compressed air generation portion, and a control circuit portion for controlling said drive portion, the method comprising:
detecting pressure P of said compressed air reserved in said tank portion;
calculating a rate ΔP/ΔT between pressure change ΔP and time ΔT;
storing a plurality of tables each indicating relations among the pressure P, the rate ΔP/ΔT and different rotational speeds of the motor;
selecting one of the plurality of tables based on a currently operating motor speed; and
searching for the rotational speed of the motor by referring to the selected table.