Liquid temperature control apparatus comprising initial temperature dependent high power heater drive

• US 4,467,183 A
• Filed: 12/15/1981
• Issued: 08/21/1984
• Est. Priority Date: 12/19/1980
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Ishima, Kazumi
• Primary Examiner(s): PASCHALL, MARK H
• Application Number:
  US06/330,981
• Time in Patent Office: 980 Days
• Field of Search: 219/501, 219/508, 219/330, 219/497, 219/492, 219/493, 219/494, 219/490, 219/510, 236/46 R, 236/46 F, 99/327, 99/332, 99/325 R
• US Class Current: 219/497
• CPC Class Codes: G05D 23/1912 whose output amplitude can take more than two discrete values

Abstract

A liquid temperature control apparatus controllably heats a liquid from a temperature before a control to a desired reference temperature by varying the magnitude and/or application time period of a power for energizing a heater on the basis of a difference between a voltage corresponding to the actual temperature before a control and a reference voltage corresponding to the reference temperature. The parameter on which the magnitude and/or application time period of the heater power is to be based may be the sum of a first voltage differential between a voltage corresponding to the actual temperature before a control and the reference voltage and a second voltage differential between a voltage corresponding to an actual temperature after the start of a control and the reference voltage.

Claims

1. A liquid temperature control apparatus for controlling the temperature of a liquid to a predetermined level comprising:

heater means for heating the liquid;

reference means for producing a reference output signal indicative of the predetermined level;

first sensor means for sensing an initial temperature of the liquid upon energization of the apparatus to produce a first sensing output signal indicative of the initial temperature level;

first differential amplifier means for comparing the first sensing output signal with the reference output signal to produce a first differential output signal representing the difference between the predetermined level and the initial temperature level;

second sensor means for sensing a controlled temperature of the liquid which is being heated by the heater means to produce a second sensing output signal indicative of the varying controlled temperature level;

second differential amplifier means for comparing the second sensing output signal with the reference output signal to produce a second differential output signal representing the difference between the predetermined level and the varying controled temperature level;

timer means for producing a pulse output signal upon energization of the apparatus;

heater drive circuit means for initially applying a high drive power to the heater means in response to the pulse output signal from the timer means for a pulse duration of the timer means and for subsequently producing a heater drive power output signal in response to the second differential output signal to apply a variable heater drive power to the heater means, the high drive power being higher than the variable heater drive power; and

control means for controlling the timer means and the heater drive circuit means such that at least one of the pulse duration of the timer means and the high drive power of the heater drive circuit means is varied depending on the first differential output signal.

2. An apparatus as claimed in claim 1, in which the first and second sensor means comprise a single sensor, and the first and second differential amplifier means comprise a single differential amplifier.

3. An apparatus as claimed in claim 1, in which said first differential output comprises a voltage output, said heater drive circuit means comprising a voltage-to-current converter for producing a current proportional to the voltage output.

4. An apparatus as claimed in claim 3, in which said heater drive circuit means further comprises a current limiter connected between the heater means and the heater drive circuit means.

5. An apparatus as claimed in claim 3, in which said heater drive circuit means further comprises a series connection of a current limiter and a reverse current flow preventing means, the series connection being connected between the second differential amplifier means and the heater means.

6. An apparatus as claimed in claim 1, in which said heater drive circuit means comprises a first series connection of a power amplifier and a first current limiter and a second series connection of a second current limiter and a reverse current flow preventing means, the first series connection being connected between the first differential amplifier means and the heater means, the second series connection being connected between the second differential amplifier means and the heater means.

7. An apparatus as claimed in claim 1, in which said heater drive circuit means comprises a first series connection of a first power amplifier, a first reverse current flow preventing means and a current limiter and a second series connection of a second power amplifier and a second reverse current flow preventing means, the first series connection being connected between the first differential amplifier means and the heater means, the second series connection being connected between the second differential amplifier means and the current limiter.

8. An apparatus as claimed in claim 1, in which said heater drive circuit means comprises a first series connection of a power amplifier and a first heater driver and a second series connection of a second heater driver and a reverse current flow preventing means, the first series connection being connected between the first differential amplifier means and the heater means, the second series connection being connected between the second differential amplifier means and the heater means.

9. An apparatus as claimed in claim 1, in which said heater drive circuit means comprises a first heater driver connected between the first differential amplifier means and the heater means and a series connection of a second heater driver and a reverse current flow preventing means, the series connection being connected between the second differential amplifier means and the heater means.

10. An apparatus as claimed in claim 9, in which said heater drive circuit means further comprises a current limiter connected between the first heater driver and the heater means.

11. An apparatus as claimed in claim 9, in which said heater drive circuit means further comprises a voltage-to-current converter connected between the first differential amplifier means and the first heater driver.

12. An apparatus as claimed in claim 1, in which said heater drive circuit means comprises a voltage-to-current converter connected between the first differential amplifier means and the heater means and a series connection of a heater driver and a reverse current flow preventing means, the series connection being connected between the second differential amplifier means and the heater means.

13. An apparatus as claimed in claim 1, further comprising an adder connected between the first differential amplifier means and the timer means for summing up the first and second differential output signals to produce a summation output signal which is applied to the timer means, said heater drive circuit means comprising a first heater drive connected between the timer means and the heater means and a series connection of a second heater driver and a reverse current flow preventing means, the series connection being connected between the second differential amplifier means and the heater means.

14. An apparatus as claimed in claim 13, in which said heater drive circuit means further comprises a current limiter connected between the first heater driver and the heater means.

15. An apparatus as claimed in claim 1, further comprising an adder connected between the first differential amplifier means and the heater drive circuit means for summing up the first and second differential output signals to produce a summation output signal, said heater drive circuit means comprising a first heater driver connected between the adder and the heater means and a series connection of a second heater driver and a reverse current flow preventing means, the series connection being connected between the second differential amplifier means and the heater means.

16. An apparatus as claimed in claim 15, in which said heater drive circuit means further comprises a current limiter connected between the first heater driver and the heater means.

17. An apparatus as claimed in claim 1, further comprising an adder connected between the first differential amplifier means and the heater drive circuit means for summing up the first and second differential output signals to produce a summation output signal, said heater drive circuit means comprising a voltage-to-current converter connected between the adder and the heater means and a series connection of a heater driver and a reverse current flow preventing means, the series connection being connected between the second differential amplifier means and the heater means.

18. An apparatus as claimed in claim 17, in which said heater drive circuit means further comprises a current limiter connected between the voltage-to-current converter and the heater means.

19. An apparatus as claimed in claim 1, further comprising an adder connected between the first differential amplifier means and the heater drive circuit means for summing up the first and second differential output signals to produce a summation output signal, said heater drive circuit means comprising a first series connection of a power amplifier and a first heater driver and a second series connection of a second heater driver and a reverse current flow preventing means, the first series connection being connected between the power amplifier and the heater means, the second series connection being connected between the second differential amplifier means and the heater means.

20. An apparatus as claimed in claim 1, further comprising an adder connected between the first differential amplifier means and the heater drive circuit means for summing up the first and second differential output signals to produce a summation output signal, said heater drive circuit means comprising a first series connection of a power amplifier and a current limiter and a second series connection of a heater driver and a reverse current flow preventing means, the first series connection being connected between the adder and the heater means, the second series connection being connected between the second differential amplifier means and the current limiter.

21. An apparatus as claimed in claim 1, further comprising an adder connected between the first differential amplifier means and the heater drive circuit means for summing up the first and second differential output signals to produce a summation output signal, said heater drive circuit means comprising a voltage-to-current converter connected between the adder and the heater means, and a series connection of a heater driver and a reverse current flow preventing means, the series connection being connected between the second differential amplifier means and the heater means.

22. An apparatus as claimed in claim 21, in which said heater driver circuit means further comprises a current limiter connected between the voltage-to-current converter and the heater means.