# US 8,784,070 B2 · Air compressor

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- Number: US 8,784,070 B2
- Document ID: US8784070B2
- Status: Granted
- Kind: B2
- Application number: 13/123,375
- Filed: 2009-10-09
- Published: 2011-08-25
- Granted: 2014-07-22
- Earliest claimed: 2008-10-09
- Assignees: Hitachi Koki Co., Ltd.
- Applicants: Tomoyoshi Yokota; Seiichi Kodato; Kenichi Matsunaga
- Inventors: Tomoyoshi Yokota; Seiichi Kodato; Kenichi Matsunaga
- Web page: https://patentgrep.com/patent/US8784070B2

## CPC

- F04B 49/065: {and making use of computers}
- F04B 41/02: having reservoirs
- F04B 49/00: Control {, e.g. of pump delivery, or pump pressure} of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B 49/022: {by means of pressure}
- F04B 2203/0209: Rotational speed
- F04B 2205/05: Pressure after the pump outlet
- F04B: POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS (machines for liquids, or pumps, of rotary-piston or oscillating-piston type F04C; non-positive-displacement pumps F04D; pumping of fluid by direct contact of another fluid or by using inertia of fluid to be pumped F04F)

## Abstract

When an air pressure in a tank part (5) drops from a maximum set pressure value (A1) to or below at least one restart set pressure value defined to lie in a range between the maximum set pressure value and a minimum set pressure value, a control circuit part (2) operates an electric motor (3b) at a predetermined revolving speed. When the air pressure in the tank part (5) drops from the restart set pressure value to or below the minimum set pressure value, the control circuit part (2) operates the electric motor (3b) at the predetermined revolving speed or a revolving speed lower than N2 until the air pressure in the tank part (5) reaches the maximum set pressure value.

## Claims

### Claim 1

An air compressor comprising:
a tank part that stores compressed air to be supplied to a pneumatic tool;
a compressed-air generation part for generating the compressed air and supplying the compressed air to the tank part;
a drive part with a motor for driving the compressed-air generation part;
a pressure sensor for detecting an air pressure inside the tank part; and
a control circuit part for controlling the motor of the drive part based on a detection signal from the pressure sensor,
wherein the control circuit part:
stops operating the motor when a detected pressure indicating the air pressure in the tank part acquired from the detection signal is higher than a maximum set pressure value,
sets, as restart set pressure values, a first restart set pressure value and a second restart set pressure value lower than the first restart set pressure value,
operates the motor at a first predetermined revolving speed if a pressure drop rate calculated based on the detected pressure is greater than a set pressure drop rate and when the detected pressure drops from the maximum set pressure value to or below the first restart set pressure value,
operates the motor at a second predetermined revolving speed that is lower than the first predetermined revolving speed if the pressure drop rate is less than the set pressure drop rate and when the detected pressure drops from the maximum set pressure value to or below the second restart set pressure value, and
forcibly operates the motor at the first predetermined set revolving speed independent of the pressure drop rate, when the detected pressure becomes equal to or less than a minimum set pressure value, independent of the operation of the motor, and does so until the detected pressure reaches the maximum set pressure value.

### Claim 2

An air compressor comprising:
a tank part that stores compressed air to be supplied to a pneumatic tool;
a compressed-air generation part for generating the compressed air and supplying the compressed air to the tank part;
a drive part with a motor for driving the compressed-air generation part;
a pressure sensor for detecting an air pressure inside the tank part; and
a control circuit part for controlling the motor of the drive part based on a detection signal from the pressure sensor,
wherein the control circuit part:
stops operating the motor when a detected pressure indicating the air pressure in the tank part acquired from the detection signal is higher than a maximum set pressure value,
sets, as restart set pressure values, a first restart set pressure value and a second restart set pressure value lower than the first restart set pressure value,
operates the motor at a first predetermined revolving speed if a pressure drop rate calculated based on the detected pressure is greater than a set pressure drop rate,
operates the motor at a second predetermined revolving speed that is lower than the first predetermined revolving speed if the pressure drop rate is less than the set pressure drop rate, and
forcibly operates the motor at the first predetermined set revolving speed independent of the pressure drop rate, when the detected pressure becomes equal to or less than a minimum set pressure value, independent of the operation of the motor, and does so until the detected pressure reaches the maximum set pressure value.