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12. Electric expansion valve
CN15 , 16
Electric expansion valve 1
• The electric expansion valve is driven by DC 12V. Power is supplied to 1 or 2 phases of 4-phase winding to switch
magnetic pole of winding in order to control opening degree.
• Relationship between power switching direction of phase and open/close direction is shown below.
When power is supplied, voltages at pins
power is supplied. When power is reset, initialization is performed for 10 or 20 seconds.
During initialization, measure all voltages at pins
voltage that has not changed from around 0.9V or 12V, expansion valve or microcomputer is defective.
• Fig 12-2 shows logic waveform when expansion valve is operating.
Pin No.
With explosion valve control, opening degree is adjusted to stabilize target temperature, by detecting temperature of
compressor head.
The period of control is about once per 20 seconds, and output a few pulses.
12V
6
5
4
3
2
1
4
Pin
Lear
phase No.
wire
1
2
④
White
ON
ON
③
OFF
ON
Yellow
②
Orange
OFF
OFF
OFF
①
Blue
OFF
Operation mode
1→2→3→4→5→6→7→8 VALVE CLOSE
8→7→6→5→4→3→2→1 VALVE OPEN
42 , 38
41 , 37
40 , 36
39 , 35
50ms
12V
R208
C225
16
9
R209
2
15
7
10
4
5 12 13
Fig. 12-1
to
of CN15 and CN16 are about 0.9V; they are about 12V when no
1
to
of CN15 and CN16 using tester. If there is any pin with
4
1
Table 12-1
Drive status
3
4
5
OFF
OFF
OFF
OFF
ON
ON
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
75ms
200ms
Fig. 12-2
– 122 –
5V
1
8
Microcomputer
IC6 , 7
Valve A
3
35
Valve B
14
36
Valve A
6
37
Valve B
11
38
0V
6
7
8
ON
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
12V
0.9V
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