Air conditioner

Details Air conditioner Air conditioner

2003-07-18

2004-11-23

Doerrler, William (Department: 3744)

Refrigeration

With alternately usable energy sources

C062S498000

Reexamination Certificate

active

06820437

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an air conditioner equipped with an electric compressor and an electric compressor driving device.
BACKGROUND ART
A conventional electric compressor driving device used in a car is described hereinafter with reference to drawings. FIG.
15
(
a
) shows a perspective view illustrating an appearance of an electric compressor driving device. Case
24
made of metal has a waterproof construction and accommodates the device. Coupling-line output port
47
which has also a waterproof structure and is mounted to case
24
passes coupling line
55
therethrough. Coupling line
55
includes two wires coupled to a battery, e.g., a direct-current (DC) power supply of approximately 300V, three wires coupled to an electric compressor, two wires coupled to a 12V power supply, and three wires carrying controlling signals and coupled to an air-conditioner controller.
In case
24
, an inverter circuit converting a current from the battery into an alternate-current (AC) current is located. This inverter circuit generates heat due to DC/AC converting loss. This heat dissipates into cooling water running through water-cooling tube
56
mounted to case
24
. The heat dissipation is not limited to the water cooling method, but an air cooling method can be used.
The above construction allows the electric compressor driving device to be placed in a car with few restrictions, so that the driving device can be disposed at a place away from the power supply, the battery.
FIG.
15
(
b
) illustrates the inside of case
24
of the electric compressor driving device. Circuit board
57
having electric components mounted thereon and electrolytic capacitor
41
are located in case
24
. Capacitor
41
is generally used as a power-current smoothing capacitor for smoothing the current supplied from the battery to the inverter circuit. An outline of the appearance is shown as line
53
.
FIG. 16
shows a perspective view illustrating circuit board
57
shown in FIG.
15
(
b
) and its related components. Circuit board
57
is coupled to an inverter circuit
54
as an inverter block which generates a heat greater than other components, so that inverter circuit
54
is mounted to a cooling structure related to water-cooling tube
56
.
FIG. 17
shows a circuit diagram of the electric compressor driving device.
As shown in the drawing, battery
1
is coupled to compressor driving device
5
as a power supply through current-carrying device
2
. Compressor driving device
5
includes inverter circuit
9
and electrolytic capacitor
41
for smoothing the current supplied from battery
1
to inverter circuit
9
.
Inverter circuit
9
is coupled to a load, i.e., electric compressor
23
. Current-carrying device
2
charges electrolytic capacitor
41
through charging resistor
10
up to a voltage of battery
1
, and then closes main relay
11
for passing the current from battery
1
to inverter circuit
9
. Current-carrying device
2
may be built in compressor driving device
5
.
A voltage supplied from battery
1
to compressor driving device
5
is divided by upper bleeder resistor
13
and lower bleeder resistor
14
, is insulated by voltage detector
16
, and is then fed into inverter controlling microprocessor
19
. The current passing through inverter circuit
9
is detected by current sensor
15
, is insulated by current detector
17
, and is fed into inverter controlling microprocessor
19
.
Air-conditioner controller
21
calculates a capacity (such as a rotation speed) of compressor
23
necessary for an air-conditioner, and the capacity is input to microprocessor
19
via communication circuit
20
.
Inverter controlling microprocessor
19
sends signals to gate driver
18
based on at least the inputs, thereby activating switching elements of inverter circuit
9
for driving compressor
23
.
Gate driver
18
electrically insulates inverter circuit
9
from microprocessor
19
. Inverter controlling microprocessor
19
receives sequential temperature data supplied from a thermistor temperature sensor of compressor
23
. Switching power supply
12
produces a power for gate driver
18
and others. Current sensor
15
includes a current-carrying coil having an inductance component. This coil produces magnetic field detected by a Hall element, so that a current is determined.
This is not shown in the drawings, but a traction motor driving device is coupled to compressor driving device
5
in parallel, and current-carrying device
2
works similarly on a current-smoothing capacitor and an inverter circuit both equipped to the traction motor driving device.
12V power supply
22
is used as a power supply mainly for inverter controlling microprocessor
19
and communication circuit
20
. 12V power supply
22
is also used as a power supply for many electric devices, such as air-conditioner controller
21
, audio equipment, and a navigation system. 12V power supply
22
is electrically insulated from battery
1
; and is however powered from battery
1
via a DC converter (not shown).
FIG.
18
(
a
) shows a current flowing into inverter circuit
9
, and FIG.
18
(
b
) shows a current flowing into compressor driving device
5
.
The waveform of the current flowing into inverter circuit
9
is like a rectangular wave. The waveform of the current flowing into compressor driving device
5
includes a constant current although having ripples due to the current flowing into inverter circuit
9
smoothed by electrolytic capacitor
41
. Actual waveforms are more complicated, and
FIG. 18
shows just outlines. As shown in FIG.
18
(
c
), a DC voltage of battery
1
is applied to inverter circuit
9
.
FIG. 19
is a schematic diagram of electric compressor
23
shown in FIG.
17
. Compressor
23
includes metallic case
8
accommodating compressing mechanism
4
and motor
7
. Refrigerant is sucked from intake
45
, and motor
7
drives compressing mechanism
4
(a scroll compressing mechanism), so that the refrigerant is compressed.
The compressed refrigerant cools motor
7
before being discharged from outlet
46
. Terminal
27
coupled to a winding of motor
7
in compressor
23
is connected to compressor driving device
5
shown in FIG.
17
.
Electrolytic capacitor
41
discussed above has a large size to increase the size of the compressor driving device and to make the driving device heavy. Electrolytic capacitor
41
is vulnerable to vibrations and heat, thus preventing the compressor driving device from having an improved vibration proof and heat resistance.
A vehicle having a limited space, such as a compact electric vehicle and a hybrid electric vehicle, requires small components mounted in the vehicle. Further, the hybrid electric vehicle has a smaller space since having a space for an engine. Thus, no electrolytic capacitor
4
be mounted in the vehicle is proposed, but the following problems occur in this case.
The current supplied from battery
1
to inverter circuit
9
would not be smoothed without electrolytic capacitor
41
. Then, the current of rectangular waveform passing through a power supply lead wire radiates electromagnetic-wave noises. As a result, a surge voltage is generated in the power supply lead wire, thereby damaging the circuit of compressor driving device
5
.
FIG. 20
shows a circuit diagram in which electrolytic capacitor
41
is excluded (detailed structure is omitted). The case and junction connectors lengthen the power supply lead wire, so that a large and unstable inductance component
58
is generated in the lead wire.
Since the current is not smoothed by electrolytic capacitor
41
shown in
FIG. 17
, the current shown in FIG.
21
(
a
) and flowing into inverter circuit
9
passes through the power supply lead wire. This current passes through inductance component
58
, so that surge occurs as shown in FIG.
21
(
c
) when the current is turned off.
This surge has a high voltage and may damage inverter circuit
9
. Electrolytic capacitor
41
shortens the path for the current flowing into inverter circuit
9
just between capacitor
41
and

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