GB2218285A - Motor driven fan control - Google Patents
Motor driven fan control Download PDFInfo
- Publication number
- GB2218285A GB2218285A GB8810626A GB8810626A GB2218285A GB 2218285 A GB2218285 A GB 2218285A GB 8810626 A GB8810626 A GB 8810626A GB 8810626 A GB8810626 A GB 8810626A GB 2218285 A GB2218285 A GB 2218285A
- Authority
- GB
- United Kingdom
- Prior art keywords
- electric motor
- control circuit
- processing unit
- central processing
- variable
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P7/00—Arrangements for regulating or controlling the speed or torque of electric DC motors
- H02P7/06—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current
- H02P7/18—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power
- H02P7/24—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices
- H02P7/28—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices
- H02P7/285—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices controlling armature supply only
- H02P7/29—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices controlling armature supply only using pulse modulation
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01P—COOLING OF MACHINES OR ENGINES IN GENERAL; COOLING OF INTERNAL-COMBUSTION ENGINES
- F01P7/00—Controlling of coolant flow
- F01P7/02—Controlling of coolant flow the coolant being cooling-air
- F01P7/04—Controlling of coolant flow the coolant being cooling-air by varying pump speed, e.g. by changing pump-drive gear ratio
- F01P7/048—Controlling of coolant flow the coolant being cooling-air by varying pump speed, e.g. by changing pump-drive gear ratio using electrical drives
Abstract
A control circuit (20) for a fan driven by an electric motor (22) driven by a dc power supply, the control circuit comprising actuating means (24, 26); a computer controlled central processing unit (28) having a first input (30) which receives a variable signal from the actuating means; and a digital-to-analogue converter (32) and a power amplifier (36) connected to an output (34) of the computer controlled central processing unit for providing a pulse-width modulated output signal (48) having a mark-space ratio for powering the electric motor, the size of the mark-space ratio, and hence the power supplied to the electric motor, being variable by the computer controlled central processing unit in accordance with the variable signal from the actuating means. Has particular application for the cooling fan for an engine of a motor vehicle. Provides variable fan speed for variations in monitored engine temperature. <IMAGE>
Description
FAN CONTROL CIRCUIT
This invention relates to a control circuit for a fan driven by an electric motor. The present invention has particular application as a control circuit for a cooling fan for an engine in a motor vehicle, or for a vehicle blower fan.
In a conventional engine cooling system, the cooling fan, which is driven by an electric motor is either fully on or fully off. See Figures 1 and 2 of the accompanying drawings. When the temperature of the engine exceeds predetermined temperature (TON), the electric motor is turned on and runs at full power. The electric motor, which is powered by a dc power supply, remains switched on until the temperature of the engine falls below a predetermined temperature (TOFF), when the electric motor is switched off. TOFF is usually a few degrees below
TON due to hysteresis in the temperature-activated switch which controls the actuation of the electric motor.In practice, it is only necessary for the electric motor to run at full power if the engine is somewhere near its maximum operating temperature which results in an unnecessary drain in power if the temperature of the engine is between TON and TMAX- In conventional systems for blower fans for motor vehicles, the speed of the fan is normally controlled by a manually operable switch having two or more actuating positions. In the actuating positions, one or more ballast resistors are switched in series with the electric motor. The power drain on the vehicle power supply remains the same no matter what the speed of the fan since any excess power is simply dissipated in the ballast resistor(s).
It is an object of the present invention to provide a control circuit for a fan driven by an electric motor driven by a dc power supply which minimises the power drain from the power supply.
To this end, a control circuit in accordance with the present invention comprises actuating means; a computer controlled central processing unit having a first input which receives a variable signal from the actuating means; and a digital-to-analogue converter and a power amplifier connected to an output of the computer controlled central processing unit for providing a pulse-width modulated output signal having a mark-space ratio for powering the electric motor, the size of the mark-space ratio, and hence the power supplied to the electric motor, being variable by the computer controlled central processing unit in accordance with the variable signal from the actuating means.
With the present invention, the speed of the fan can be controlled in accordance with the signal from the actuating means, and hence is variable over a predetermined required range. This arrangement minimises the power drain from the power supply.
The computer controlled central processing unit preferably has a second input for receiving a signal from the electric motor, the computer control central processing unit varying the size of the mark-space ratio of the pulse-width modulated output signal in accordance with the signal from the electric motor. This arrangement will maintain a substantially constant speed for the fan at substantially constant input signals from the actuating means, thereby substantially preventing undesirable oscillatory noise from the fan.In this case, the second input preferably comprises two terminals each connectabie by way of an analogue-to-digital converter to a power input terminal of the electric motor, the computer controlled central processing unit determining the mean voltage on the electric motor, comparing the mean voltage with a predetermined stored value for the required power supply to the electric motor, and adjusting, if necessary, the mark-space ratio.
Alternatively, the computer controlled central processing unit may be such that it interrupts the pulse-width modulated output signal, determines the voltage generated by the electric motor at the second input, compares the generated voltage with a predetermined stored value for the required power supply to the electric motor, and reapplies the pulse-width modulated output signal with adjusted mark-space ratio if necessary.
Preferably, the actuating means comprises a temperature transducer and an analogue-to-digital converter, the temperature transducer producing the variable signal, the variable signal varying in accordance with the temperature monitored by the temperature transducer, the size of the mark-space ratio being variable in accordance with the temperature monitored by the temperature transducer.
This arrangement has particular application where the fan is a cooling fan for the engine of a motor vehicle. The temperature transducer is mounted such that it monitors the temperature of the engine block and/or the water cooling the engine, and produces a signal, the magnitude of which is dependent on the temperature monitored by the temperature transducer.
The computer controlled central processing unit varies the size of the mark-space ratio of the pulse-width modulated output signal in accordance with the magnitude of the signal from the temperature transducer. The power supplied to the electric motor, and hence the speed of the fan, is therefore variable in accordance with the required amount of cooling, which is determined by the monitored temperature.
Alternatively, the actuating means may comprise a manually operable switch having two or more actuating positions, or a potentiometer having variable actuating positions, each actuating position providing a different signal at the first input to the computer controlled central processing unit, the size of the mark-space ratio being variable in accordance with the selected actuating position of the switch. This arrangement has particular application where the fan is a blower fan in a motor vehicle. In this case, the computer controller central processing unit monitors the position selected on the switch, and sets the size of the mark-space ratio in accordance with the required fan speed as selected on the switch. This arrangement removes the need for ballast resistor(s), and only provides enough power to the electric motor as is required to produce the selected fan speed.
When the present invention is used in a motor vehicle, the computer controlled central processing unit may also monitor other conditions, for example, air conditioning, vehicle speed, etc., and vary the size of the mark-space ratio in accordance with these other monitored conditions as required.
The present invention also includes fan driven by an electric motor driven by a dc power supply which is controlled by a control circuit as herein defined, and, in particular, a cooling fan for the engine of a motor vehicle.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a conventional control circuit for a cooling fan driven by an electric motor;
Figure 2 is a plot of temperature T against voltage V across the electric motor shown in Figure 1;
Figure 3 is a control circuit in accordance with the present invention for a cooling fan for an engine in a motor vehicle; and
Figure 4 is a plot of temperature against voltage across the electric motor shown in Figure 3.
Referring to Figure 1, the control circuit 10 is of conventional design for use in driving a cooling fan for an engine of a motor vehicle. The cooling fan is driven by an electric motor 12 which is powered by the battery 14 of the motor vehicle. A temperature actuated switch 16 switches on power to the electric motor 12 when the engine temperature reaches TON (Figure 2), and switches off power when the engine temperature falls to TOFF. The plot of temperature against voltage is shown in Figure 2.
Voltage V5 is the supply voltage across the battery 14. TMAX is the maximum temperature reached by the engine. As can be see from Figure 2, the electric motor is either off, or operating at full power.
The control circuit 20 shown in Figure 3 is in accordance with an embodiment of the present invention. The control circuit 20 is for use in driving a cooling fan for an engine of a motor vehicle. The cooling fan is driven by an electric motor 22. The control circuit 20 comprises actuating means in the form of a temperature transducer 24 and an analogue-to-digital converter 26; a computer controlled central processing unit (CPU) 28 having a first input 30 connected to the actuating means; a digital-to-analogue converter 32 connected between an output 34 of the CPU 28 and a power amplifier 36.
The power amplifier 36 is connected to one 38 of the power input terminals of the electric motor 22, the other power input terminal 40 being connected to the voltage supply V8 from the vehicle battery (not shown). The control circuit 20 further comprises two analogue-to digital converters 42,44 each connected between the power input terminals 40,38 respectively of the electric motor 22 and a second input 46 to the
CPU 28 defined by two separated terminals.
In use, the temperature transducer 24 monitors the temperature of the water cooling the engine of the motor vehicle, and produces a signal which varies with monitored temperature. This variable signal is received by the first input 30 of the CPU 28 via the analogue-to-digital converter 26.
When the variable signal indicates a temperature in excess of TON (see Figure 4), the CPU 28 produces a pulse-width modulated output signal (trace 48 in
Figure 3) at output terminal 34 which is fed through the digital-to-analogue converter 32 and power amplifier 36 to the electric motor 22 to begin powering the electric motor. As the monitored temperature continues to rise, the mark-space ratio of the pulse-width modulated output signal is altered by the CPU 28 (as shown by the dotted lines in trace 48) to provide additional power to the electric motor 22. This situation continues up to a maximum monitored temperature TAX at which the electric motor 22 is being driven at full power (see Figure 4).As the monitored temperature decreases, the power supplied to the electric motor 22 is gradually reduced until the monitored temperature reaches TOFFi at which point the electric motor 22 is switched off.
As can be seen from the plot in Figure 4, the electric motor 22 is only driven at full power when the monitored temperature is at TMAX, hence minimising the power drain on the vehicle battery.
Analogue-to-digital converters 42,44 are in a feedback loop from the electric motor 22 to the CPU 28. The CPU 28 monitors the mean voltage on the electric motor 22, and compares this mean voltage with a predetermined stored value for the required power supply to the electric motor. If any discrepancy is found between the monitored mean voltage and the stored voltage, the CPU 28 adjusts the mark-space ratio of the pulse-width modulated output signal to correct the error in the power supply to the electric motor 22. This arrangement maintains a substantially constant fan speed for a substantially constant monitored temperature, preventing the risk of oscillatory noise from the cooling fan.
The CPU 28 may also monitor additional analogue signals from, for example, an air conditioning monitoring circuit 50 via an analogue-to-digital converter 52, and/or digital signals from, for example, a vehicle speed monitoring circuit 54, and vary the pulse-width modulated output signal accordingly.
As can readily be seen, the power supply to the electric motor 22 can be varied, to provide variable fan speeds, in accordance with monitored conditions at any instance in time, substantially minimising the power drain on the vehicle battery.
Claims (9)
1. A control circuit for a fan driven by an electric motor driven by a dc power supply, the control circuit comprising actuating means; a computer controlled central processing unit having a first input which receives a variable signal from the actuating means; and a digital-to-analogue converter and a power amplifier connected to an output of the computer controlled central processing unit for providing a pulse-width modulated output signal having a mark-space ratio for powering the electric motor, the size of the mark-space ratio, and hence the power supplied to the electric motor, being variable by the computer controlled central processing unit in accordance with the variable signal from the actuating means.
2. A control circuit as claimed in Claim 1, wherein the computer controlled central processing unit has a second input for receiving a signal from the electric motor, the computer controlled central processing unit varying the size of the mark-space ratio of the pulse-width modulated output signal in accordance with the signal from the electric motor.
3. A control circuit as claimed in Claim 1 or Claim 2, wherein the actuating means comprises a temperature transducer and an analogue-to-digital converter, the temperature transducer producing the variable signal, the variable signal varying in accordance with the temperature monitored by the temperature transducer, the size of the mark-space ratio being variable in accordance with the temperature monitored by the temperature transducer.
4. A control circuit as claimed in Claim 1 or Claim 2, wherein the actuating means comprises a manually operable switch having two or more actuating positions, or a potentiometer having variable actuating positions, each actuating position providing a different signal at the first input to the computer controlled central processing unit, the size of the mark-space ratio being variable in accordance with the selected actuating position of the switch.
5. A control circuit as claimed in any one of Claims 2 to 4, where the second input comprises two terminals each connectable by way of an analogue-to-digital converter to a power input terminal of the electric motor, the computer controlled central processing unit determining the mean voltage on the electric motor, comparing the mean voltage with a predetermined stored value for the required power supply to the electric motor, and adjusting, if necessary, the mark-space ratio.
6. A control circuit as claimed in any one of Claims 2 to 4, wherein the computer controlled central processing unit interrupts the pulse-width modulated output signal, determines the voltage generated by the electric motor at the second input, compares the generated voltage with a predetermined stored value for the required power supply to the electric motor, and reapplies the pulse-width modulated output signal with adjusted mark-space ratio if necessary.
7. A control circuit substantially as hereinbefore with reference to, and as shown in,
Figures 3 and 4 of the accompanying drawings.
8. A fan driven by an electric motor driven by a dc power supply which is controlled by a control circuit as claimed in any one of Claims 1 to 7.
9. A fan as claimed in Claim 8 which is a cooling fan for an engine of a motor vehicle.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8810626A GB2218285A (en) | 1988-05-05 | 1988-05-05 | Motor driven fan control |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8810626A GB2218285A (en) | 1988-05-05 | 1988-05-05 | Motor driven fan control |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8810626D0 GB8810626D0 (en) | 1988-06-08 |
| GB2218285A true GB2218285A (en) | 1989-11-08 |
Family
ID=10636389
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8810626A Withdrawn GB2218285A (en) | 1988-05-05 | 1988-05-05 | Motor driven fan control |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2218285A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2693231A1 (en) * | 1992-07-06 | 1994-01-07 | Valeo Thermique Moteur Sa | Cooling device for a motor vehicle engine |
| EP0638724A1 (en) * | 1993-08-12 | 1995-02-15 | Hitachi, Ltd. | Vortex blower |
| ES2171129A1 (en) * | 2000-11-08 | 2002-08-16 | Aux De Componentes Electricos | System for speed control of motors, used for coolant circuits of vehicle engines |
| EP1726464A3 (en) * | 2005-05-24 | 2007-01-03 | BorgWarner Inc. | Self-learning control system and method for controlling fan speed |
| CN103953563A (en) * | 2014-05-20 | 2014-07-30 | 国家电网公司 | Fan control circuit for electric power monitoring equipment room |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2178256A (en) * | 1985-05-30 | 1987-02-04 | Sanyo Electric Co | Brushless motor control |
-
1988
- 1988-05-05 GB GB8810626A patent/GB2218285A/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2178256A (en) * | 1985-05-30 | 1987-02-04 | Sanyo Electric Co | Brushless motor control |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2693231A1 (en) * | 1992-07-06 | 1994-01-07 | Valeo Thermique Moteur Sa | Cooling device for a motor vehicle engine |
| EP0578564A1 (en) * | 1992-07-06 | 1994-01-12 | Valeo Thermique Moteur | Cooling device for a motor car engine |
| EP0638724A1 (en) * | 1993-08-12 | 1995-02-15 | Hitachi, Ltd. | Vortex blower |
| US5569023A (en) * | 1993-08-12 | 1996-10-29 | Hitachi, Ltd. | Vortex blower |
| ES2171129A1 (en) * | 2000-11-08 | 2002-08-16 | Aux De Componentes Electricos | System for speed control of motors, used for coolant circuits of vehicle engines |
| EP1726464A3 (en) * | 2005-05-24 | 2007-01-03 | BorgWarner Inc. | Self-learning control system and method for controlling fan speed |
| CN103953563A (en) * | 2014-05-20 | 2014-07-30 | 国家电网公司 | Fan control circuit for electric power monitoring equipment room |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8810626D0 (en) | 1988-06-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |