Electricity: electrical systems and devices – Control circuits for electromagnetic devices – For relays or solenoids
Reexamination Certificate
2000-07-10
2002-06-25
Jackson, Stephen W. (Department: 2836)
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
For relays or solenoids
C361S058000, C361S154000
Reexamination Certificate
active
06411488
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an on-board current control device controlling an inductive load such as an electromagnetic powder clutch, an electromagnetic valve controlling an oil pressure, and so on, which are equipped in a vehicle.
In particular, the present invention relates to improvement of controllability and productivity of the on-board current control device.
2. Discussion of Background
FIG. 6
is a circuit diagram illustrating a structure of a conventional on-board current control device, for example, disclosed in Japanese Patent No. 2737449.
FIG. 7
is a chart illustrating a waveform for explaining an operation of the conventional on-board current control device. In
FIG. 6
, numerical reference
1
designates a processing unit including a microcomputer and so on, inputting engine control information SE and driving control formation SD, and making a PWM modulator
1
a
output a current basic pulse width modulating signal S
1
. Numerical reference
10
designates a D/A converter including a buffer amplifier
11
for a digital signal, a smoothing filter
14
having a resistance
12
and a capacitor
13
, and an analog buffer amplifier
15
, wherein the current basic pulse width modulating signal S
1
is inputted in the butter amplifier
11
for digital signals in the D/A converter
10
so that a waveform thereof is modified. A high frequency component of the signal is removed by the smoothing filter
14
. Thus obtained signal is applied to an input terminal (+) of the analog buffer amplifier
15
, and a current command signal Is is outputted from an output terminal of the analog buffer amplifier
15
.
Numerical reference
21
designates a comparator outputting an on/off signal to a transistor in a later stage from a deviation between the current command signal Is and a current feed-back signal IF, to be inputted as described below. Numerical reference
22
designates a resistance connecting the comparator
21
to a power source. Numerical reference
23
designates a transistor for converting signals. Numerical reference
24
designates an output transistor. A base of the transistor
23
, converting signals, receives the on/off signal from the comparator
21
through series resistances
25
and a resistance
26
connected to an earth. A collector of the transistor
23
is connected to a base of the output transistor
24
through a resistance
27
, and an emitter of the transistor
23
is grounded. The base of the output transistor
24
is connected to a power source through a resistance
28
, and an emitter of the output transistor
24
is connected to the power source. The on/off signal from the comparator
21
makes the signal-converting transistor
23
turn on or turn off, whereby the output transistor
24
is turned on or turned off along with the turning-on and turning-off of the signal converting transistor
23
.
A collector of the output transistor
24
is connected to the earth through a circulating diode
31
and simultaneously connected to an output terminal
32
. An exciting coil
35
of an electromagnetic clutch
34
, as a load, is connected between the output terminal
32
and another output terminal
33
through slip rings
36
and
37
. A load current Ic is applied to the exciting coil
35
depending on the turning-on and the turning-off of the output transistor
24
and a turning-on of a quick-break transistor
41
, to be described below, whereby a current value of the load current Ic is controlled by the output transistor
24
.
A collector of the quick-break transistor
41
is connected to the output terminal
33
. A constant-voltage diode
42
is connected between the collector and a base of the quick-break transistor
41
, and an emitter of the constant-voltage diode
42
is grounded through a current detecting resistance
43
. Both ends of the current detecting resistance
43
are respectively connected to an input terminal (+) and an input terminal (−) of a current detecting amplifier
46
respectively through a resistance
44
and a parallel circuit having a resistance
45
and an adjusting resistance
45
a
. Further, a feedback resistance
47
is connected between the input terminal (−) of the current detecting amplifier
46
and an output terminal of the current detecting amplifier
46
. The current detecting amplifier
46
outputs and supplies the current feedback signal IF, corresponding to the load current Ic, to an input terminal (−) of the above-mentioned comparator
21
.
Numerical references
51
and
52
designate signal converting transistors for turning on and turning off the quick-break transistor
41
depending on the signal from the processing unit
1
. A base of the signal converting transistor
51
receives a signal from the processing unit
1
through series resistances
53
and a resistance
54
connected to the earth, a collector of the signal converting transistor
51
is connected to a power source through resistances
55
and
56
. A base of the signal converting transistor
52
is connected to a connecting point between the resistances
55
and
56
, an emitter of the signal converting transistor
52
is connected to the power source, and a collector of the signal converting transistor
52
is connected to the base of the quick-break transistor through a resistance
57
. When the signal from the processing unit
1
is a positive potential, the signal converting transistors
51
and
52
are turned on, and the quick-break transistor
41
is turned on; and when the signal is changed to 0, the signal converting transistors
51
and
52
are turned off, and the quick-break transistor
41
is turned off.
In thus constructed conventional on-board current control device, when the engine control information SE and the driving control information SD are inputted into the processing unit
1
, the processing unit
1
operates a current command value from the two types of the information SE and SD, modulates the current command value to obtain a PWM modulating signal, and outputs the current basic pulse width modulating signal S
1
. This current basic pulse width modulating signal S
1
is a rectangular wave signal having a weight of modulation in proportional to the current command value illustrated in
FIG. 7
a
. However, because a voltage value is not an ideal waveform, being in a range of 0 through V
5
of a voltage of the power source, because of a voltage drop inside a circuit. Therefore, the current basic pulse width modulating signal is converted to a pulse width modulating signal S
2
having an ideal waveform illustrated in
FIG. 5
b
by the buffer amplifier
11
for digital signals.
A high frequency component of the pulse width modulating signal S
2
is removed by the smoothing filter
14
to be converted to a signal like a direct current. Thereafter, the pulse width modulating signal S
2
is applied to the analog buffer amplifier
15
. The analog buffer amplifier
15
outputs the current command signal Is illustrated in
FIG. 7
c
and applies to the terminal (+) of the comparator
21
. Since the current feed-back signal Is is applied from the current detecting amplifier
46
to the terminal (−) of the comparator
21
, the current command signal Is and the current feed-back signal IF are compared. Depending on a difference between these, a signal subjected to the pulse width modulation is outputted from the output terminal of the comparator
21
in response to the difference, the signal converting transistor
23
and the output transistor
24
are turned on or turned off in response to a rate of modulation of the signal to control a current value of the load current Ic, passing through an exciting coil
35
of the electromagnetic clutch
34
.
Further, when the electromagnetic clutch
34
is actuated, the signal applied from the processing unit
1
to the signal converting transistor
51
as a positive tension. Therefore, the signal converting transistors
51
and
52
are turned on, and accordingly the quick-break transistor
41
i
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