WO2000019213A1

WO2000019213A1 - Device for determining the position of a battery operated control motor with commutator

Info

Publication number: WO2000019213A1
Application number: PCT/DK1999/000477
Authority: WO
Inventors: Per Gregor Zacho; Per Elgård PEDERSEN
Original assignee: Danfoss A/S
Priority date: 1998-09-28
Filing date: 1999-09-09
Publication date: 2000-04-06
Also published as: AU5504499A; DE19844330A1; DE19844330B4

Abstract

In a device for determining the position of a battery operated control motor (2) with commutator, a pulse voltage is deflected from the current outages caused by the commutator in the supply line (3) of the control motor (2), which pulse voltage is led to the counting inlet of a counter (6) via a pulse shaping step (5), the counter value of the counter being a measure for the position of the control motor (2). To avoid an ohmic resistor or blind resistor in the supply line (3) for the registration of the pulse voltage, the pulse voltage is tapped directly from the battery 1, utilising its inner resistance.

Description

Device for determining the position of a battery operated control motor with commutator

The invention concerns a device for determining the posi- tion of a battery operated control motor with commutator, in which a pulse voltage is deflected from the current outages caused by the commutator in the supply line of the control motor, which pulse voltage is led to the counting- inlet of a counter via a pulse shaping step, the counter value of the counter being a measure for the position of the control motor.

In a known device of this kind (US-PS 4,924,166 or EP 0 379 193 Al), the pulse voltage is tapped at an ohmic resistor or a parallel oscillatory circuit. Both of these are not only expensive, they also cause an additional load on the battery, which may be exhausted relatively fast, particularly when small standard batteries are concerned, which are normally only required for relatively small control motors, which must be arranged in a housing together with the regulating unit driven by them, and therefore must have very small dimensions. In particular, this goes for remote controlled control motors in thermostatic valves for radiators.

Thus, the task of the invention is to provide a device of the kind described, whose power consumption is lower, meaning that the battery is less loaded.

According to the invention, this is solved in that the pulse voltage is tapped directly from the battery.

Thus, an additional measuring resistor and its power loss between battery and control motor can be avoided, as a battery also has an inevitable internal resistance, at which a power drop appears in connection with a load, said power drop causing corresponding variations in the output voltage of the battery due to the current outages caused by the commutator in the supply line of the control motor, which variations can be counted as a measure for the position of the motor when having been submitted to a corresponding pulse shaping.

Preferably, it is provided that the operating voltage of ^• the pulse shaping step taken from the battery is automati- cally interrupted in connection with a standstill of the control motor. Thus, it is ensured that the pulse shaping step does not load the battery when the motor stands still, meaning that there is no pulse voltage and thus no pulses to count.

This can, for example, be achieved in that the operating voltage is only led to the operating voltage inlet of the pulse shaping step via a switching element, when the control motor works. The current consumption of such a switching element can be kept relatively low, so that the additional load on the battery caused by the switching element is small.

Preferably, it is provided that the switching element is connected on the outlet side of the counter, that the battery voltage is led to a voltage transformer stepping it up, the outlet of said voltage transformer transmitting the stepped up voltage being connected with the current supply connection of the switching element, and that before reaching the predetermined counting value the switching element turns on the operating voltage of the control motor and the pulse shaping step, and turns it off again when the predetermined counting value has been reached. Thus, the pulse shaping step is on the one hand supplied with a relatively high voltage when compared with the battery voltage, and on the other hand it is ensured that the pulse shaping step is only supplied with current during operation of the motor until reaching the predetermined counting value, meaning only until the motor is turned off.

Further, it can be provided that the outlet signal of a timer is led to the inlet of an antivalence circuit, converting it to two non-equivalent signals, of which one- is led to one inlet of a first gate and the other to one inlet of a second gate, and both being led via an OR-link to a reset inlet of the counter, that the outlet of the switching element is connected with the other inlets of the gates, whose outlets are connected in bridge circuit with control connections of semiconductor switching ele- ments with low forward voltage, the control motor being arranged in the bridge cross branch of said semiconductor switching elements and the operating voltage of the control motor being commutated or turned off in dependence of the output signals of the gates via said semiconductor switching elements. Thus, the operation of the control motor can be controlled by means of the timer, for example, for central different settings of the desired value regulating unit of a thermostatic valve by day and by night. The commutation via controllable semiconductor switching elements with low forward voltage, particularly via MOS field-effect-transistors (MOS-FET) , of the operating voltage of the control motor to reverse its rotation direction has the advantage that in the blocked state it has a high resistance and in the open state it has a very low resistance between the main connections causing its power loss to be small. Further, MOS-FETs only need a very small control current. As, however, they need a relatively high control voltage, the gates controlling them are supplied with the stepped up output voltage of the voltage transformer, the output voltage of the gates depending on this high supply voltage. Preferably, it is provided that the pulse shaping step has a differential amplifier, whose reversing inlet is connected with one connection of the battery via an ohmic inlet resistor of the differential amplifier and a coupling capacitor, that the connecting point of the inlet resistor and the coupling capacitor is connected with the outlet of the differential amplifier via two anti-parallel- connected diodes, and that the non-reversing inlet of the differential amplifier is connected with the tap of a voltage divider. This embodiment also ensures that the battery is only slightly loaded by the inlet of the pulse shaping step. At the same time, the anti-parallel connection of the diodes in the return of the differential amplifier ensures that the amplifier has a high total amplification, the return resistance still being low, so that a delay of the output pulses of the pulse shaping step in relation to the start of the motor is avoided due to the low time constants of the charging of the coupling capacitor caused by the low return resistance.

The outlet of the differential amplifier can be connected with the reversing inlet of an additional differential amplifier, whose non-reversing inlet is connected with the tap of the voltage divider and whose outlet is connected with the counting inlet of the counter. Thus, the edge steepness of the output pulses of the first differential amplifier is increased.

Preferably, the device is used for a control motor, which is arranged in the housing of a thermostatic element and drives its regulating unit.

In the following the invention and its embodiments are explained in detail on the basis of the enclosed drawings, showing: Fig. 1: a wiring diagram of an embodiment of a device according to the invention

Fig. 2: a schematic view of the time course of signals occurring in the device according to Fig. 1

The device according to Fig. 1 serves the purpose of determining the position of a control motor 2 with commu- tator, driven by a battery 1. The control motor 2 is used for the setting of the regulating unit determining the desired temperature value of a thermostatic radiator valve, and is arranged in the housing of the thermostatic element of the valve together with the regulating unit and the battery 1. Due to the lack of space in the housing, both the battery 1 and the control motor 2 are very small. Thus, the battery 1 consists of two series-connected standard cells, each 1.5 Volt. The control motor 2 is a DC motor with commutator, for which the battery voltage of 3 Volt is sufficient.

Due to the current outages in the supply line 3 caused by the commutator and the inevitable inner resistance of the battery 1, the battery voltage varies during operation of the control motor 2. These variations are tapped immediately at the battery 1 and led to a pulse shaping step 5 via a line 4 and mass GND as a pulse voltage (pulsating direct voltage) . The pulses created by the pulse shaping step 5 are led to the counting inlet of a counter 6 as counting pulses ZP. The counting value of the counter is then a measure for the position of the control motor.

In the present case, however, only the reaching of a predetermined counting value of the counter 6 is regis- tered by a switching element 7, here a NAND-element, being connected on the outlet side of the counter, and transmit- ting a high output signal (1-signal) from the start of the control motor 2 until reaching the predetermined counting value, and a low output signal (0-signal) from the reaching of the predetermined counting value. The high output signal of the switching element 7 is led to the pulse shaping step as operating voltage. The reaching of the predetermined counting value of the counter 6 thus means that the operating voltage for the pulse shaping step 5 is turned off.

The control motor 2 is arranged in the cross branch of a bridge connection of four controllable semiconductor switching elements with very low forward voltage, here MOS field effect transistors 8, 9, 10 and 11, whose parallel series connections are also connected to the battery 1 via the supply line 3 and mass GND. The gates of the MOS field effect transistors 8 and 11 connected in series with the control motor 2 are connected with the outlet of a gate 12, and the gates of the two remaining MOS field effect transistors 9 and 10 also connected in series with the control motor 2 are connected with the outlet of a second gate 13.

A binary output signal S_u of a timer 14 is converted to two antivalent (reverse) signals S_v and S_r via an antiva- lence circuit 15, which signals determine the rotation direction of the control motor 2, that is, forward or backward. The signal S_v determining the forward rotation is led to one inlet of the gate 12, and the signal S_r determining the backward rotation is led to one inlet of the second gate 13. The output signal of the switching element 7 is led to the other inlets of the two gates 12 and 13.

When the output signal of the switching element 7 is high, there is a high turn-on-signal S_ve for the forward rotation direction at the outlet of the gate 12, or a turn-on- signal S_re for the backward rotation direction at the outlet of the gate 13, depending on which of the two signals S_v or S_r is high.

Simultaneously, each of the output signals S_v and S_r is led via differential elements 16 and 17, respectively, consisting of a capacitor in series with a diode poled in the • blocked direction, to an OR element 18, from whose outlet the reset inlet of the counter 6 receives a reset pulse R on the occurrence of either the signal S_v or the signal S_r.

This gives the following mode of operation of the device according to Fig. 1, with reference to Fig. 2:

At the time t₀ the output signal S_u of the timer 14 is high, and consequently also the signal S_v at the outlet of the antivalence circuit 15, whereas all other signals shown in Fig. 2 are low. This means that the counting value of the counter 6 has been reached and that the low output signal ZW of the switching element 7 blocks both gates 12, 13, so that the MOS field effect transistors 9 to 11 are all blocked by the low signals S_ve and S_re and the control motor 2 stands still. At the same time, also the operating voltage of the pulse shaping step 5 corresponding to the output signal ZW of the switching element 7 is turned off, so that the pulse shaping step 5 consumes no current. This state continues until the time ti, when the input signal S_u and thus also the signal S_r change to a high value. Through the differential element 16 the 0 to 1 change of the signal S_r is differentiated and the differentiated signal is led to the reset inlet of the counter 6 as a reset pulse R. The resetting of the counting value of the counter 6 to zero caused by this means that the output signal ZW of the switching element 7 goes high, both gates 12, 13 are pulsed on, and the operating voltage of the pulse shaping step 5 is turned on. As, further, at the time ti the signal S_v has become low, also the signal S_ve remains low, so that the MOS field effect transistors 8 and 11 remain blocked. Contrary to that, the signal S_re increases, so that the MOS field effect transistors 9 and

10 are open and the control motor 2 starts in the backward direction. Then, the battery voltage starts varying, so that the pulse shaping step 5 leads counting pulses ZP to the counter 6. At the time t₂ the counter 6 has counted the predetermined number of counting pulses ZP, meaning that the predetermined counting value has been reached, so that the output signal ZW of the switching element 7 now changes to a lower value, both gates 12, 13 are blocked and simultaneously the operating voltage of the pulse shaping step 5 is removed. The blocking of the gates 12, 13 also causes the signal S_re to change to a lower value, while the signal S_ve still remains low, as the low output signal S_u of the timer and thus also the low signal S_v still remain. Accordingly, the control motor 2 stops at the time t₂, until at the time t₃ the output signal S_u of the timer 14 changes to a higher value again, so that also the signal S_v changes to a higher value, and the counter 6 receives a reset pulse R via the differential element 17 and the OR element 18. While the control motor 2 ran backward in the period from tj to t₂ and stood still in the period from t₂ to t₃, it now runs forwards until the time t₄, at which the counter 6 reaches the predetermined counting value and the control motor 2 is stopped again.

Thus, the selection of the ON and OFF durations of the output signal S_u of the timer 14 and the predetermined counting value of the counter 6 will determine how far the control motor 2 runs forwards or backward and for how long it stands still. When the motor drives the desired value regulating unit of the thermostat of a radiator valve, the timer can determine the times of readjusting the radiator temperature from day temperature to night temperature and vice versa, and the extent of the temperature change can be determined by the selection of the predetermined counting value of the counter 6.

As the battery 1, just like the control motor 2, must have very small dimensions, to enable the arrangement of it, together with the control motor 2, in the housing of the thermostat for the purpose of central remote control, the use of traditional standard battery cells will only produce a small voltage, here approximately 3 Volt. Such a low operating voltage will be sufficient for the control motor 2, but it would not be sufficient, if controllable semiconductor switching elements were used in the bridge connection for the control of the control motor 2. For this reason, the MOS field effect transistors 9 to 11 are used, as in the open state they only cause a very small voltage drop. On the other hand, however, they need a relatively high control voltage for the opening.

Therefore, the battery voltage is stepped up through a voltage transformer 19, whose stepped-up output voltage, here about 9 Volt, is used for the current supply of the counter 6, the switching element 7, the gates 12 and 13 and the antivalence circuit 15. As the high output signal ZW of the switching element 7 is then also almost equal to the stepped-up output voltage of the voltage transformer 19, the high output signal ZW can at the same time be used as current supply for the pulse shaping step 5.

The voltage transformer 19 is constructed in the traditional way, and only causes a very small load on the battery 1. For this purpose the voltage transformer 19 comprises an oscillator with an unijunction transistor 20, connected in series with an ohmic resistor 21 and a capacitor 22 on the battery voltage. Further, it comprises an NPN-transistor 23 in series with a winding 24 of a ferrite core transformer on the battery voltage. The control connection of the NPN-transistor 23 is connected with the connecting point of resistor 21 and capacitor 22 via a further winding 25 of the transformer. Parallel to the winding 24 an additional ohmic resistor 26 is arranged. The output voltage of the oscillator is tapped at the collector of the transistor 23 and rectified through a ^■ diode 27 and firstly led to a control connection of the unijunction transistor 20 via a high-ohmic resistor 28 and secondly smoothed through a capacitor 29 with a high capacity. Further, the positive pole of the battery 1 is connected with the control connection of the unijunction transistor 20 via an additional high-ohmic resistor 30. The stepped-up, smoothed output voltage of the voltage transformer 19, here about 9 Volt, is tapped at the capacitor 29. Having 40 windings, the winding number of the winding 24 is about twice as high as that of the winding 25. An additional winding 31 of the transformer, whose winding number is about half the winding number of the winding 25, produces a lower output voltage, which is rectified over an additional diode 32 and smoothed through an additional capacitor 33 with higher capacity. The lower output voltage of about 1.5 Volt serves as current supply for the timer 14.

The pulse shaping step 5 comprises a differential amplifier 34, whose reversing inlet (-) is connected with one connection (the positive pole) of the battery 1 via an inlet resistor 35 of the differential amplifier 34 and a coupling capacitor 36 with very low capacity as well as via an additional resistor 37. The connecting point of inlet resistor 35 and coupling capacitor 36 is connected with the outlet of the differential amplifier 34 via two anti-parallel connected diodes 38 and 39. The non- reversing inlet (+) of the differential amplifier 34 is connected with the tap of a voltage divider having two identical series connected high-ohmic resistors 40 and 41.

The outlet of the differential amplifier 34 is connected with the reversing inlet (-) of an additional differential amplifier 42, whose non-reversing inlet (+) is connected with the tap of the voltage divider 40, 41 and whose outlet is connected with the counting inlet of the counter

6. The operating voltage of the pulse shaping step 5 formed by the output signal ZW is firstly led to the operating voltage connections of the differential amplifiers 34 and 40 and secondly to the voltage divider 40, 41. Thus, half the operating voltage of the pulse shaping step 5 lies on the tap of the voltage divider. As the switching element 7 receives an operating voltage of about 9 Volt, the high output signal ZW is somewhat lower than 9 Volt, and the voltage at the tap of the voltage divider is thus somewhat lower than 4.5 Volt. The resistors 35, 40 and 41 have a very high value of about 330 kΩ, whereas the capacity of the capacitor 36 amounts to about 33 nF and the value of the resistor 37 to about 4 kΩ. Thus, these resistors cause only a minimum load on the battery 1.

When the control motor 2 is not operating, and the operating voltage of the differential amplifiers 34 and 42 is thus turned off, the output voltage of the differential amplifier 34 is 0 Volt. The connecting point between the inlet resistor 35 and the coupling capacitor 36 has the same potential. The coupling capacitor 36 thus carries the battery voltage of about 3 Volt. When the control motor starts, also the differential amplifiers 34 and 42 receive the operating voltage (about 9 Volt) . At the non-reversing inlet (+) of the differential amplifier 34 then lies the voltage of about 4.5 Volt of the voltage divider tap divided by the voltage divider. As the reversing inlet (-) of the differential amplifier 34 initially still carries the potential of the connecting point of inlet resistor 35 and coupling capacitor 36, also the output voltage of the differential amplifier 34 increases (to about 9 Volt) . As the coupling capacitor 36 cannot be charged stepwise via the diode 38, the potential of the non-reversing inlet (+) of the differential amplifier remains about 4.5 Volt higher than that of its reversing inlet, so that the variations of the battery voltage are not registered, and • the voltage on the outlet of the differential amplifier 34 remains high.

While now the coupling capacitor 36 starts charging via the diode 38, so that the potential of the connecting point between the inlet resistor 35 and the coupling capacitor 36 increases, also the voltage at the reversing inlet of the differential amplifier 34 increases from 0 Volt. As soon as the voltage at the reversing inlet exceeds the value of about 4.5 Volt, the pulse shaping step 5 transfers counting pulses ZP to the counter 6. The increase speed of the voltage at the reversing inlet of the differential amplifier 34 is determined by the return resistor of the differential amplifier 34 and the capacity of the coupling capacitor 36. To obtain a large amplification, the return resistor could be very large, about 1 MΩ. Supposing a resistor of 1 MΩ was provided instead of the two diodes 38 and 39, the resulting time constant would be so large that the first pulses of the pulse voltage occurring at the battery 1 could not be counted.

However, with the two diodes 38 and 39 it is achieved that the return resistance is very low, when the voltage difference at the inlets of the differential amplifier exceeds 0.7 Volt the diode collector saturation voltage, but it is high, when the voltage difference is lower than 0.7 Volt. Thus, it is ensured that the coupling capacitor 36 is charged via a very low resistance with correspondingly small time constant. When the coupling capacitor has been charged, the diodes 38 and 39 act as very large resistors, so that the differential amplifier 34 works normally, though it must be considered that a diode is only conducting, when its collector saturation voltage is exceeded and provides a very high resistance at low voltage.

Therefore, the pulse shaping step 5 already registers the first pulse of the pulse voltage produced when starting the control motor 2, so that a miscounting is avoided.

The antivalence circuit 15 comprises two reversing amplifiers (NOT elements) 44 and 45 connected in series via a high-ohmic resistor 43 of, for example, about 10 MΩ, the output of the outlet side reversing amplifier 45 being fed back to the input of the inlet side reversing amplifier 44 via an additional high-ohmic resistor 46 of, for example, about 10 MΩ. Both reversing amplifiers 44 and 45 are supplied with the stepped-up output voltage of the voltage transformer 19.

Between the inlet of the reversing amplifier 45 and mass there is an NPN-transistor 47, whereas between the inlet of the reversing amplifier 44 and the basis of the transistor 47 the collector-emitter-path of an additional NPN- transistor 48 is arranged in series with a high-ohmic resistor 49 of about 1 MΩ. Via a high-ohmic resistor 50 of about 1 MΩ the basis of the transistor 48 lies at the lower output voltage of the voltage transformer 19. The outlet of the timer 14 is connected with the connecting point between the emitter of the transistor 48 and the resistor 49. When the output signal S_u of the timer 14 is high, the transistor 47 is open, so that a low potential on the inlet of the reversing amplifier 45 is enforced, causing its output signal S_v to assume a high value, which is fed back to the inlet of the reversing amplifier 44 via the resistor 46, and on the one hand reduces the output potential of the reversing amplifier 44 and on the other hand keeps the voltage at the collector of the transistor 48 high, so that it is opened at its basis by the operating voltage of the timer via the resistor 50 and sends an additional basic current to the basis of the transistor 47, to keep the through-connection of this transistor as safe as possible.

When, however, the output signal S_u of the timer 14 drops to the low value of about 0 Volt, the transistor 47 is blocked via the resistor 49, and the transistor 48 continues to be open for some time, so that at the inlet of the reversing amplifier 44 the potential drops to zero, and at its outlet the high signal S_r occurs. The consequence of this is that the output signal S_v of the reversing amplifier 45 drops and thus, that the input voltage of the reversing amplifier 44 is still kept low via the feed back resistor 46, until the output signal S_u of the timer in- creases again.

The counter 6, the switching element 7, the gates 12, 13 and the differential amplifiers 34, 42 and also the reversing amplifiers 44 and 45 can be made as integrated circuits, which, in connection with the high-ohmic resistors, including the diodes in the differential elements 16 and 17, only cause a small load on the battery 1.

Therefore, the battery 1 cannot only have a low voltage, but also very small dimensions, meaning at the same time that it has a long life. Variations could, for example, mean that the gates 12, 13 are made as NAND-elements, each connected in series with a NOT-element (reversing step) . Also the switching element 7 can be made as a NAND-element with two series-connected NOT-elements . The alternative and additional elements can also be supplied with the stepped-up output voltage of the voltage transformer 19, without loading the battery 1 significantly, when they are made as integrated circuits. The latter also applies for the counter 6 and the antivalence circuit 15.

Instead of the MOS field effect transistors, bipolar transistors can be used.

All resistors mentioned are ohmic resistors being relatively high-ohmic.

Claims

Patent claims

1. Device for determining the position of a battery operated control motor (2) with commutator, in which a pulse voltage is deflected from the current outages caused by the commutator in the supply line (3) of the control motor (2), which pulse voltage is led to the counting inlet of a counter (6) via a pulse shaping step (5), the counter value of the counter being a measure for the position of the control motor (2) , characterised in that the pulse voltage is tapped directly from the battery (1) .

2. Device according to claim 1, characterised in that the operating voltage of the pulse shaping step (5) taken from the battery (1) is automatically interrupted in connection with a standstill of the control motor (2) .

3. Device according to claim 1 or 2, characterised in that the operating voltage is only led to the operating voltage inlet of the pulse shaping step (5) via a switching element (7), when the control motor (2) works .

4. Device according to claim 3, characterised in that the switching element (7) is connected on the outlet side of the counter (6), that the battery voltage is led to a voltage transformer (19) stepping it up, the outlet of said voltage transformer transmitting the stepped up voltage being connected with the current supply connection of the switching element (7), and that before reaching the predetermined counting value the switching element (7) turns on the operating voltage of the control motor (2) and the pulse shaping step (5) , and turns it off again when the predetermined counting value has been reached.

5. Device according to claim 4, characterised in that the outlet signal (S_u) of a timer (14) is led to the inlet of an antivalence circuit (15), converting it to two non-equivalent signals (S_v, S_r) , of which one is led to one inlet of a first gate (12) and the other to one inlet of a second gate (13), and both being led via an OR-link (18) to a reset inlet of the counter (6), that the outlet of the switching element (7) is connected with the other inlets of the gates (12, 13), whose outlets are connected in bridge circuit with control connections of semiconductor switching elements (9 to 11) with low forward voltage, the control motor (2) being arranged in the bridge cross branch of said semiconductor switching elements and the operating voltage of the control motor (2) being commutated or turned off in dependence of the output signals of the gates (12, 13) via said semiconductor switching elements .

6. Device according to claim 5, characterised in that the semiconductor switching elements are MOS field effect transistors (9 to 11) and that the operating voltage of the gates (12, 13) is the stepped-up output voltage of the voltage transformer (19) .

7. Device according to one of the claims 1 to 6, charac- terised in that the pulse shaping step (5) has a differential amplifier (34), whose reversing inlet (-) is connected with one connection of the battery via an ohmic inlet resistor (35) of the differential amplifier (34) and a coupling capacitor (36), that the con- necting point of the inlet resistor (35) and the cou- pling capacitor (36) is connected with the outlet of the differential amplifier (34) via two anti-parallel connected diodes (38, 39) , and that the non-reversing inlet (+) of the differential amplifier (34) is con- nected with the tap of a voltage divider (40, 41) .

8. Device according to claim 7, characterised in that the outlet of the differential amplifier (34) is connected with the reversing inlet (-) of an additional differ- ential amplifier (42), whose non-reversing inlet (+) is connected with the tap of the voltage divider (40, 41) and whose outlet is connected with the counting inlet of the counter (6) .

9. Application of the device according to one of the claims 1 to 8 for a control motor (2), which is arranged in the housing of a thermostatic element of a radiator valve and operates its regulating unit.