GB2275351A - Motor speed controller - Google Patents

Abstract

In a system eg a mail handling system comprising at least one motor M1 to MN, the speed of the motor is reduced when the temperature of an element in the system exceeds a threshold. Preferably the reduction in speed is effected when the temperature of the motor as measured by a thermistor 304 - 312 exceeds the threshold. A multi-channel A/D converter 302 may be used so that the reduction can be effected if the temperature of any one of the elements in the system exceeds a threshold. The system allows reduced operational performance upon failure of system elements such as cooling fans without the need to use components having enough tolerance to operate in worst case conditions. <IMAGE>

Description

APPARATUS INCuJDING SYSTEM CONTROL OF MOTOR TEMPERATURE Field of the Invention The invention relates to processing systems having at least one motor whose speed is controllable by a central control for controlling throughput and more particularly to mail processing systems having a plurality of brushless motors controlled by speed information from a system controller.

Background of the Invention Electronic mailing machines which are used in conjunction with postage meters are well known. Such devices operate under microcomputer control to perform mail transport, envelope printing and accounting operations associated with the printing of a postal indicia on an envelope. A detailed description of such a mailing machine postage meter is provided, for example, in U.S. Patent No.

4,935,078 entitled High Throughput Mailing Machine Timing.

The mailing machine described in the foregoing patent includes various brushless motors for operation of the transport system and the like. In many situations, there can be potential motor problems due, for example, to high ambient temperature, excessive load and the like which can cause the motor to fail and require a service call for repair.

U.S. Patent No. 4,982,143 describes a phase control circuit for a motor. In the teaching of this reference, when a limit temperature is exceeded, the phase window during which the motor is energized is reduced by way of a semiconductor switch which is actuated by a sensor placed in the airstream cooling the motor. In U.S. Patent No.

4,983,897 a PTC device is connected in series in the motor energizing circuit to block the current flow in the event of overheating due to excessive current or by sensing of excessive ambient temperatures. While each of these devices can protect the individual motor, it will be appreciated that many times the shutdown of an individual motor can disrupt a system operation.

Summarv of the Invention According to a first aspect of the invention, there is provided in an apparatus comprising a system controller and at least one motor for providing a determined system throughput in accordance with information provided by the system controller, the improvement comprising a temperature sensor arranged in conjunction with a determined element of the system for measuring a temperature representative of a temperature of the element, means connected to the temperature sensor and to the system controller for providing to the system controller a signal representative of the temperature measured by the temperature sensor, and wherein in response to the signal representative of measured temperature exceeding a predetermined temperature, said system controller is operative to control said motor to reduce system throughput in order to reduce the temperature of the element.

In another aspect, the invention comprises a method for controlling the temperature of an element of a system, the system having at least one motor for providing a determined system throughput, the method comprising the steps of arranging a temperature sensor in conjunction with a determined element of the system for measuring a temperature representative of a temperature of the element, connecting an output signal from the temperature sensor to a system controller for providing to the system controller a signal representative of the temperature measured by the temperature sensor, and, i in response to the signal representative of measured temperature exceeding a predetermined temperature, controlling said motor to reduce system throughput in order to reduce the temperature of the element.

Thus there is advantageously provided apparatus in which there is an automatic reduction in throughput of the system in response to a measured temperature of an element that is higher than a desired temperature in order to reduce the operating temperature of the element.

There is also advantageously provided a method and apparatus for operating a motor in a system such that the motor does not have to be designed to operate for all possible combinations of extreme operating conditions.

In accordance with the invention, the system processor can determine from the sensor data whenever a system element such as a motor is getting too hot and can reduce the system throughput to prevent permanent damage to the motor or to even shut the system down if a motor or other element shows a temperature profile that indicates a major problem. It will be appreciated that the temperature may also be displayed in order to inform a service person of potential problems.

It will also be appreciated that a major advantage of the invention described and claimed herein is that, for instance, a motor of the system does not have to be designed to work under all worst-case operating conditions such as maximum ambient temperature combined with maximum load, maximum throughput, minimum cooling and the like. The system can be designed to handle full operation when only some of the extreme conditions, but not all, are simultaneously encountered. The system in accordance with the invention serves to prevent abuse such as by operating the system outside the specified ambient temperature range or blocking of the air ducts. It also enables some level of operation upon failure of other components, for example the fans, without causing permanent damage.

It will be understood that the placement of sensors is not limited to motors; other system components may also have sensors that may similarly be used to provide a signal for modifying system operation.

There now follows a description of a preferred embodiment of the invention, by way of example, with reference being made to the accompanying drawings in which: Fig 1. is a perspective view of a postage meter and a suitable mailing machine in which the invention may reside.

Fig. 2 is a schematic block diagram of a mailing machine microcontroller system in which the temperature system control in accordance with the invention may be incorporated.

Fig. 3 is a block diagram of a system temperature sensor arrangement.

Fig. 4 is a flow chart of the operation of the system in accordance with the invention.

Description of the Preferred Embodiment In Fig. 1, there is shown generally at 1 a mailing machine comprising feeder section 2 and an electronic postage meter section at 3. Envelopes are placed on the hopper 4 where they are serially fed to the meter section 3 for imprint of a meter indicia by a printing mechanism not visible in this Figure. In the preferred embodiment, mailing machine includes scale 5 for weighing the envelope and communicating the weight to a microprocessor control so that the proper postage value may be imprinted on the envelope. In the preferred embodiment illustrated here, the meter section 3 comprises a detachable meter which may be easily removed and replaced by a similar meter.

The mailing machine 1 has a user interface indicated at 6. This illustrated user interface includes visual display 7 and a plurality of soft keys 8 aligned with respective portions of the display screen as well as the hard keys indicated at 9 of a keyboard or keypad.

Typically, as shown there will be "enter" key 11 and "return" key 13. A "start" key is shown at 16. The interface may also include further displays such as those shown at 10 and 12 along with associated keys illustrated at 14 and 15.

Fig. 2 shows a suitable microprocessor control system 100 for the mailing machine comprising, for example, a board 102 having motor controller 104 communicating via bus 106 with ROM 107, motor specific chip 108 and shared non-volatile memory (NVM) controller 112. Host controller 116 communicates via bus 118 with NVM controller 112. The NVM controller 112 communicates via bus 113 with shared NVM 115. The motor controller 104 also communicates via bus 126 with the meter through meter board 128, dater board 130 and scale board 132. Bus 118 also allows communication between the host controller 116 and DUAL UART module 150 and the Echoplex communication module 152.

Microprocessor based sensor controller 119 is in bus communication with NVM controller 112 via bus 136. Sensor bus 142 enables communication from sensor controller 119 and A/D converter to harness coupler 144 from which connection a suitable flex harness 146 is connected to the respective drive motors and sensors of the mailing machine 1 indicated generally at 148. A more detailed description of such a mailing machine-postage meter is provided in U.S. Patent No.

4,935,078 entitled High Throughput Mailing Machine Timing specifically incorporated by reference herein.

"Personality" module 160 communicates with host controller bus 118 through bus 162 via coupler 120. This module includes Expansion NVM 164, Graphics controller 166, combination keyboard and MIMIC I/O port 168. The man-machine interface module 170 includes a liquid-crystal display board 172 as well as a keyboard and MIMIC board 174 which are in respective bus 176 and 178 communication with graphics controller 166 and I/O board 168 through respective couplers 180 and 182. It will be appreciated that other means of display, such as for example, LED or CRT displays, and data entry means may be used. NVM accounting cartridges 184 and 186 are in communication with the NVM expansion I/O board 164 through coupled busses 188 and 190, respectively.

Dual communication module 150 permits coupling of weighing platform with rating 200, rating board 202, a service device 204 or printer 206 or other such general purpose devices. An echoplex output from a scale device 208 may be coupled to Echoplex module 152 via bus 210.

System bus controller 220 communicates via bus 222 with the host controller bus 118 by way of coupler 123. ROM module 221 is coupled by bus 223 with host controller bus 118 through coupler 122. System bus 224 enables communication of the system bus controller 220 with I/O expansion module 226 from which may be coupled, for example, parallel printer interface 228, general purpose interface 230 and custom parallel interface 223. Optional devices such as, for instance, a modem 236, inserter module 238, OCR module 242, addresser module 224, and an additional stacker module may be attached for communication via bus 224.

Referring to Fig. 3, a block diagram of a suitable temperature sensor input to the system controller is shown.

The system controller 300, which may suitably be the system controller shown in Fig. 2, is connected to receive temperature signal inputs from multi-channel A/D converter 302. The A/D converter 302 is in turn connected respectively to a plurality of temperature sensors associated with or juxtaposed to elements or components of the system, a representative example being shown. In the illustrated embodiment of Fig. 3, the respective sensors 304 through 312 are shown in conjunction with motor No. 1 indicated at 314, motor No. 2 at 316, a representative motor No. N at 318, a power supply at 320, and in association with other assemblies at block 322.

Suitably each of the sensors 304 through 312 may comprise a Negative Temperature Coefficient (NTC) surface mount thermistor with for example a nominal resistance of 5K at 25 degrees C. The thermistor may be configured as part of a resistive divider network such that an analog signal proportional to temperature may be generated and provided to the A/D converter 302. For best results, the resistor ratio is selected to provide maximum dynamic range over the temperature range of interest, suitably 100 degrees C. In the case where the motors are of the brushless type a suitable mounting arrangement is shown in our copending U.S. Patent Application entitled COMMUTATION BOARD FOR A BRUSHLESS MOTOR filed on 17th February 1993.

Fig. 4 is a flow chart illustrating the operation of the system in accordance with the invention. The temperature monitoring routine at 400 begins with the reading of sensor inputs from the multi-channel A/D converter at block 405 and falls to evaluate data and determine temperature profile for each monitored component at block 410. If a diagnostic test is called, the YES branch from decision block 415 selects block 420 to display the desired temperatures. The NO branch from block 415 falls to decision block 425 to test whether the temperature exceeds a determined temperature and if YES the motor speed is reduced by the motor controller at block 430 to reduce the system throughput. The NO branch returns to the main sequence.

Claims (13)

1. In an apparatus comprising a system controller and at least one motor for providing a determined system throughput in accordance with information provided by the system controller, the improvement comprising a temperature sensor arranged in conjunction with a determined element of the system for measuring a temperature representative of a temperature of the element, means connected to the temperature sensor and to the system controller for providing to the system controller a signal representative of the temperature measured by the temperature sensor, and wherein in response to the signal representative of measured temperature exceeding a predetermined temperature, said system controller is operative to control said motor to reduce system throughput in order to reduce the temperature of the element.

2. The apparatus of claim 1 wherein the element is said at least one motor.

3. The apparatus of claim 1 or claim 2 wherein the means connected to the temperature sensor and the system controller includes an A/D converter.

4. The apparatus of any preceding claim wherein the temperature sensor is a thermistor.

5. The apparatus of any preceding claim further comprising additional sensors arranged in respective juxtaposition to respective additional components of the system and wherein the means connected to the temperature sensor and the system controller is connected to receive inputs from said additional sensors and said means comprises a multi-channel A/D Converter.

6. In an apparatus comprising a system controller and at least one motor for providing a determined system throughput in accordance with information provided by the system controller, the improvement comprising a temperature sensor arranged in conjunction with the motor for measuring a temperature representative of the temperature of the motor, means connected to the temperature sensor and to the system controller for providing to the system controller a signal representative of the temperature measured by the temperature sensor, and wherein in response to the measured temperature exceeding a predetermined temperature, said system controller being operative to control said motor to reduce system throughput in order to reduce the temperature of the motor.

7. A method for controlling the temperature of an element of a system, the system having at least one motor for providing a determined system throughput, the method comprising the steps of arranging a temperature sensor in conjunction with a determined element of the system for measuring a temperature representative of a temperature of the element, connecting an output signal from the temperature sensor to a system controller for providing to the system controller a signal representative of the temperature measured by the temperature sensor, and wherein in response to the signal representative of measured temperature exceeding a predetermined temperature, controlling said motor to reduce system throughput in order to reduce the temperature of the element.

8. The method of claim 7 wherein the element is said at least one motor.

9. The method of claim 7 wherein connecting the output signal from the temperature sensor to the system controller includes connecting the signal from the sensor to an A/D converter.

10. The method of any of claims 7 to 9 wherein the temperature sensor is a thermistor.

11. The apparatus of any of claims 7 to 10 further comprising the step of arranging additional sensors in respective juxtaposition to respective additional components of the system and connecting the outputs to the system controller to provide signals from said additional sensors for monitoring component temperatures.

12. Apparatus generally as herein described, with reference to or as illustrated in the accompanying drawings.

13. A method generally as herein described, with reference to or as illustrated in the accompanying drawings.