Air supply apparatus for stable air supply

Abstract

An air supply apparatus supplies atmospheric air to an external apparatus such as an air demander. The air supply apparatus comprises a pump, an actuator, a power consumption detector, an air pressure detector, and a controller. The pump takes in atmospheric air and discharges the atmospheric air to the external apparatus. The actuator actuates the pump. The power consumption detector detects a measurement value corresponding to a power consumption of the actuator. The air pressure detector detects a discharge pressure of the atmospheric air discharged by the pump. The controller calculates a criterion value of the measurement value when the pump takes in the atmospheric air at 1 atmospheric pressure and discharges the atmospheric air at the discharge pressure based on the rotational frequency of the pump and the measurement value. The controller also adjusts the rotational frequency based on the measurement value and the criterion value.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of Japanese Patent Applications No. 2004-017039 filed on Jan. 26, 2004, the content of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an air supply apparatus, which intakes, compresses, and discharges air to be supplied to another apparatus.

BACKGROUND OF THE INVENTION

JPH07-025337A discloses an air supply apparatus, which controls the airflow volume thereof according to an atmospheric pressure detected by an atmospheric pressure sensor. This air supply apparatus requires the atmospheric pressure sensor and, therefore, includes increased complexity and cost.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an air supply apparatus capable of supplying air according to an atmospheric pressure by comprising a simple structure.

To achieve the above object, an air supply apparatus according to the present invention comprises a pump, an actuator, a power consumption detector, an air pressure detector, and a controller.

The pump takes in atmospheric air and discharges it to an air demander. The actuator actuates the pump. The power consumption detector detects a measurement value corresponding to a power consumption of the actuator. The air pressure detector detects a discharge pressure of the atmospheric air discharged by the pump. The controller calculates a criterion value of the measurement value when the pump takes in the atmospheric air at 1 atmospheric pressure and discharges the atmospheric air at the discharge pressure. This criterion values is based on the rotational frequency of the pump and the measurement value. The controller then adjusts the rotational frequency based on the measurement value and the criterion value.

Other features and advantages of the present invention will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following detailed description, the appended claims, and the drawings, all of which form a part of this application. In the drawings:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view of an air supply apparatus according to a first embodiment of the present invention;

FIG. 2 is an enlarged cut-away perspective view of a pair of screw rotors of the air supply apparatus of FIG. 1;

FIG. 3 is a flowchart of a process for controlling an intake air pressure with the air supply apparatus of FIG. 1;

FIG. 4 is a cross-sectional side view of an air supply apparatus according to a second embodiment of the present invention; and

FIG. 5 is a flowchart of a process for controlling an intake air pressure with the air supply apparatus of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An air supply apparatus of a first embodiment shown in FIGS. 1 to 3 is for supplying air to a catalytic combustion apparatus. The air supply apparatus is a screw pump having male and female screw rotors 1 and 2, respectively, (refer to FIG. 2), a torque transmitter 3 for rotating the screw rotors 1, 2 by a torque of a driver (not shown), a casing 4 enclosing the screw rotors 1, 2 and the torque transmitter 3, and a driveshaft 5 transmitting the torque of the driver to the torque transmitter 3. In FIG. 1, the female screw rotor 2 is located behind the male screw rotor 1.

As shown in FIG. 2, each of the male and the female screw rotors 1, 2 has a male screw thread having a spiral-shaped projection. The screw threads of the male and the female screw rotors 1, 2 meshingly engage each other. As shown in FIG. 1, the torque transmitter 3 driven by an electric motor 100 rotates the male screw rotor 1 on a shaft 1a. The male screw rotor 1 rotates the female screw rotor 2 engaged therewith on a shaft 2a. The electric motor 100 is driven by an electric power supplied via an inverter from a power sources (not shown).

The casing 4 includes a lubricating box 6, a rotor housing 7, and a cover 8 arranged from the electric motor 100 to the screw rotors 1, 2. The lubricating box 6, the rotor housing 7, and the cover 8 are securely fastened to one another by fasteners such as bolts (not shown). The rotor housing 7 contains the screw rotors 1, 2 therein and the lubricating box 6 contains the torque transmitter 3 therein. Therefore, the screw rotors 1, 2 and the torque transmitter 3 are arranged separate from each other in the casing 4.

The lubricating box 6 defines a lubricating chamber 9 around the torque transmitter 3 and contains lubricating oil to be supplied to the torque transmitter 3. Oils having a viscosity generally equal to that of typical engine oil can serve as the lubricating oil. The splashing of lubricating oil in the lubricating box 6 lubricates gears and/or other components constituting the torque transmitter 6.

The lubricating box 6 further rotatably supports the driveshaft 5 driven by the electric motor 100. The lubricating box 6 holds a first bearing 11 near the electric motor 100 and a second bearing 12 near the lubricating chamber 9. The first and the second bearings 11, 12 rotatably support the driveshaft 5. The casing 4 has a first oil seal 13 disposed in an internal circumference of a through hole locating the driveshaft 5. The first oil seal 13 prevents the lubricating oil supplied to the first and the second bearings 11, 12 from leaking out of the casing 4.

The rotor housing 7 has a rotor chamber 10 therein enclosing the screw rotors 1, 2. The rotor housing 7 further has an intake port 7a for supplying air into the rotor chamber 10 and a discharge port 7b for discharging air out of the rotor chamber 10. The intake port 7a is located at the side of the cover 8 and the discharge port 7b is located at the side of the lubricating box 6. Downstream of the discharge port 7b is a catalytic combustion apparatus 200, which is also referred to herein as an air demander.

An outermost circumference of the threads of the screw rotors 1, 2 are infinitesimally smaller than an internal surface of the rotor chamber 10 to define a clearance therebetween, which has a sealing function. Air compression chambers 10a are defined by the annular spaces between the threads of the screw rotors 1, 2 and the internal surface of the rotor chamber 10. The air compression chambers 10a are for compressing the intake air supplied from the intake port 7a.

According to the above-described configuration, the torque transmitter 3 transmits the torque of the driveshaft 5 to the shafts 1a, 2a and rotates the male and the female screw rotors 1, 2 in synchronization with each other.

The torque transmitter 3 has first and second gears 14, 15 for transmitting the rotational torque of the driveshaft 5 to the shaft 1a of the male screw rotor 1, and third and fourth gears 16, 17 for transmitting the rotation of the shaft 1a to the shaft 2a of the female screw rotor 2. The third and fourth gears 16, 17 are timing gears for synchronously rotating the male and female screw rotors 1, 2.

The rotor housing 7 holds third and fourth bearings 18, 19 rotatably supporting one end of each of the shafts 1a, 2a. The cover 8 holds fifth and sixth bearings 20, 21 rotatably supporting ends of the shafts 1a, 2a that are opposite to those supported by the third and fourth bearings 18, 19. The rotor housing 7 holds second and third oil seals 22, 23 disposed in internal circumferences of through holes and locating the ends of the shafts 1a, 2a supported by the third and fourth bearings 18, 19. The second and third oil seals 22, 23 prevent the lubricating oil supplied to the third and the fourth bearings 18, 19 from leaking into the rotor chamber 10. The cover 8 holds fourth and fifth oil seals 24, 25 disposed in internal circumferences of through holes and locating the ends of the shafts 1a, 2a supported by the fifth and sixth bearings 20, 21. The fourth and fifth oil seals 24, 25 prevent grease filled in the fifth and sixth bearings 20, 21 from leaking into the rotor chamber 10.

The rotor housing 7 further has a pressure sensor 26 disposed at the discharge port 7b for detecting the pressure of the discharge air. The pressure sensor 26 serves as a discharge air pressure detector of the present invention.

The air supply apparatus further has an ECU (electric control unit) 40 composed of a microcomputer having a CPU, a ROM, a RAM, external circuitries, and other components necessary to serve the principles of the present invention. The ECU 40 receives an electric signal outputted by the pressure sensor 26 and controls the rotation of the electric motor 100. A PWM (pulse width modulation) control conducted by an inverter regulates the rotational frequency of the electric motor 100. The ECU 40 receives a current value flowing to the motor coil of the electric motor 100, which is detected for the PWM control. The ECU 40 operates based on a control program stored in the memory devices such as the ROM and outputs control signals to the electric motor 100. The ECU 40 serves as a power consumption detector and a controller of the present invention.

Following is a description of how the air supply apparatus operates.

The torque transmitter 3 rotates the screw rotors 1, 2 synchronously, so as to take a given volume of air into the air compression chamber 10a through the intake port 7a. The rotation of the screw rotors 1,2 axially translates the air compression chambers 10a from the side of the cover 8 to the side of the lubricating chamber 9. This simultaneously decreases the volume of the air compression chamber 10a, thereby, compressing the air in the air compression chamber 10a.

When the number of revolutions of the screw rotors 1, 2 reaches a predetermined value, the air compression chamber 10a arrives at the discharge port 7b located at the side of the lubricating chamber 9 of the rotor housing 7. Thus, the air enclosed in the air compression chamber 10a is released through the discharge port 7b to be supplied to the catalytic combustion apparatus 200 located downstream of the air flow passage for performing a chemical catalysis therein.

FIG. 3 shows the flow of the air supply compression control performed by the air supply apparatus of the first embodiment and performed by the CPU of the ECU 40 based on a control program.

In step S10, an operator sets a rotational frequency of the electric motor 100 according to a target air pressure and airflow volume to be supplied to the catalytic combustion apparatus 200. In step S11, the electric motor 100 starts rotating based on the rotational frequency set in step S10. In step S12, the ECU 40 detects an air pressure value at the discharge port 7b.

In step S13, the ECU 40 determines a criterion current value that is required to adjust the pressure of the air discharged through the discharge port 7b detected in step S12. The criterion value is an amount of current required to produce the target discharge air pressure and is based on a standard atmospheric pressure (1 atmospheric pressure).

In step S14, the ECU 40 detects a current value flowing to the motor coil of the electric motor 100. In step S15, the ECU 40 determines whether the current value detected in step S14 is greater than the criterion current value. If No in step S15, the process returns to the start. If Yes in step S15, the work done by the electric motor is large so that the outer air pressure is considered to be lower than 1 atmospheric pressure and the process goes to step S16.

In step S16, the ECU 40 increases the rotational frequency of the electric motor 100 by a predetermined increment. The increment of the rotational frequency may be set to a value according to the apparatus condition, for example, 100 rpm. Thus, the apparatus prevents the pressure of the air supplied to the catalytic combustion apparatus 200 from decreasing when the atmospheric pressure is lower than 1 atmospheric pressure.

As described above, the air supply apparatus of the first embodiment operates to adjust the pressure of the discharging air based on the atmospheric pressure without directly detecting the atmospheric pressure. The adjustment is done by comparing an actual current with the criterion current at 1 atmospheric pressure and is calculated based on the rotational frequency of the motor and the discharging air pressure. Accordingly, the air supply apparatus described above can adjust the air supplied by the electric motor 100 according to the atmospheric pressure by using a simple configuration that does not require a sensor for detecting the atmospheric pressure.

In the first embodiment, the program may operate to decrease the rotational frequency of the motor when the flowing current detected in step S14 is less than the criterion current calculated in step S13.

FIG. 4 depicts a cross-sectional side view of an air supply apparatus according to a second embodiment. This air supply apparatus of the second embodiment is mostly identical to that of the first embodiment, except that it further includes an air discharge conduit 27 and an air pressure control valve 28 in the air discharge conduit 27. The air pressure control valve is for adjusting the air flowing from the discharge port 7b toward a target pressure to be supplied to the catalytic combustion apparatus 200.

A large opening degree of the air pressure control valve 28 makes the air pressure supplied to the catalytic combustion apparatus 200 large, while a small opening degree makes the air pressure small. The ECU 40 operates according to a program stored in its memory such as the ROM and outputs a control signal to the air pressure control valve 28. In this embodiment, the air pressure sensor 26 detects a pressure in the air discharging conduit 27 at a point between the discharge port 7b and the air pressure control valve 28.

FIG. 5 shows the flow of the air supply compression control conducted by the air supply apparatus of the second embodiment and performed by the CPU of the ECU 40 based on a control program.

Each of steps S20 to S26 is equivalent to steps S10 to S16 of the first embodiment.

In step S26, the ECU increases the rotational frequency of the electric motor 100 by a predetermined increment. In step S27, the ECU 40 decreases the opening degree of the air pressure control valve 28. Thus, the apparatus prevents the pressure of the air supplied to the catalytic combustion apparatus 200 from decreasing when the atmospheric pressure is lower than 1 atmospheric pressure.

Accordingly, the air supply apparatus described above can adjust the air supplied by the electric motor 100 according to the atmospheric pressure by using a simple configuration and not requiring a sensor for detecting the atmospheric pressure.

In the second embodiment, step 26, which increases the rotational frequency of the electric motor 100, is not always necessary. The program may operate to decrease the rotational frequency of the motor and increase the opening degree of the air pressure control valve 28 when the flowing current detected in step S24 is smaller than the criterion current calculated in step S23.

The first and the second embodiments utilize the criterion current and the flowing current of the electric motor 100. These directly relate to the electric power consumed by the electric motor 100. In an alternative embodiment, instead of using the criterion current and the flowing current, the program can use the electric power consumed by the electric motor 100 as the criterion and actual value.

In another alternative embodiment, instead of the catalytic combustion apparatus 200, the air supply apparatus may supply air to other apparatuses requiring air such as a fuel cell or other air demanding accessories, or even a vehicular cabin. In the case of a fuel cell powered car, the air supply apparatus of the present invention may be used to prevent a decrease in power output when the vehicle is traveling in a highland where the air pressure is relatively low.

The present invention can be applied not only for an air supply apparatuses having a screw rotor compressor but also for those having other volume compressors such as root compressors and/or scroll compressors.

Claims

1. An air supply apparatus for supplying air to an air demander comprising:

a pump taking in atmospheric air and discharging the air to the air demander;

an actuator for actuating the pump;

a power consumption detector for detecting a measurement value corresponding to an amount of power consumed by the actuator;

an air pressure detector for detecting a discharge pressure of the air discharged by the pump; and

a controller for calculating a criterion value of the measurement value when the pump takes in the air from the atmosphere at 1 atmospheric pressure and discharges the air at the discharge pressure based on the rotational frequency of the pump and the measurement value, and

adjusting the rotational frequency based on the measurement value and the criterion value.

2. The air supply apparatus according to claim 1,

wherein the controller increases the rotational frequency of the pump when the measurement value is greater than the criterion value.

3. The air supply apparatus according to claim 1,

wherein the actuator is an electric motor and the measurement value is a current value flowing through the electric motor.

4. The air supply apparatus according to claim 1,

wherein the pump is a compressor.

5. The air supply apparatus according to claim 4,

wherein the compressor has an airtight structure reducing an amount of flow loss of air therein.

6. The air supply apparatus according to claim 1, further comprising:

a pressure valve adjusting the air discharged from the pump, and

wherein the controller further adjusts an opening degree of the pressure valve.

7. An air supply apparatus for supplying air to an air demander comprising:

a pump taking in atmospheric air and discharging the air to the air demander;

an actuator actuating the pump;

a power consumption detector detecting a measurement value corresponding to an amount of power consumed by the actuator;

an air pressure detector for detecting a discharge pressure of the air discharged by the pump;

a pressure valve for adjusting a pressure of the air discharged by the pump; and

a controller for calculating a criterion value of the measurement value when the pump takes in the air from the atmosphere at 1 atmospheric pressure and discharges the air at the discharge pressure based on the rotational frequency of the pump and the measurement value, and

adjusting an opening degree of the pressure valve based on the measurement value and the criterion value.

8. An air supply apparatus for supplying air to an air demander comprising:

a pump having an air inlet for taking in atmospheric air and an air outlet for delivering the air to the air demander;

an actuator for actuating the pump;

a power consumption detector for detecting a measurement value corresponding to an amount of power consumed by the actuator;

an air pressure detector for detecting a discharge pressure of the air delivered from the pump; and

a controller for calculating a criterion value of the measurement value when the pump takes in the air from the atmosphere at 1 atmospheric pressure and discharges the air at the discharge pressure based on the rotational frequency of the pump and the measurement value, and

adjusting a pressure of the sir discharged by the pump toward the air demander based on the measurement value and the criterion value.

9. The air supply apparatus according to claim 8, wherein the controller adjusts the pressure of the air delivered to the air demander by adjusting the rotational frequency of the pump.

10. The air supply apparatus of claim 8, wherein the controller adjusts the pressure of the air delivered to the air demander by adjusting an opening value of a pressure valve disposed between the pump and the air demander.