DE2120887C3 - Speed measuring device - Google Patents

Description

The present invention relates to a speed measuring device consisting of a dependent the speed of a rotating element generating pulses with sloping edges Pulse shaping unit, a downstream integration unit and one with the integration unit connected threshold value circuit.

There are already speed measuring devices known (see French patent specification 1448 945 and German Offenlegungsschrift 1 523 172), in which an integration of the depending on a rotating Element generated pulses is made. The integrated signals then become one Threshold circuit supplied, which determines whether the speed of the rotating element in question is above or below a predetermined threshold value.

In view of the prior art, it is the object of the present invention to provide a speed measuring device To create a relatively simple structure, with which a plurality of different speed values can be set.

According to the invention, this is achieved in that the integration unit has a plurality of individual Has integration circles which have a plurality of pulse trains with different decay characteristics generate, and that a selector switch is provided with which the various pulse trains selectively the Threshold circuit can be supplied.

In connection with catalytic exhaust gas cleaning devices, it proves to be / wake-up when the selector switch is one of an operating parameter, for example the temperature, of an internal combustion engine actuated switch is ..

To achieve that such a speed measurement

device has a certain hysteresis, proves

• It is useful if the selector switch through Semiconductor elements is formed in dependence

of the output signal of the threshold value circuit are controlled.

The invention will now be explained in more detail on the basis of exemplary embodiments, with reference to the Drawing is referred to. It shows

Fi g. 1 is a schematic circuit diagram of a first Embodiment of the invention,

F i g. 2 is a schematic circuit diagram of a second embodiment of the invention,

FIGS. 3a and 3b are graphical representations of waveforms occurring within the range shown in FIG. 2 shown Switching arrangement occur,

F i g. 4 shows a schematic circuit arrangement of a third embodiment of the invention,

F i g. 5 a and 5 b are graphical representations of waveforms occurring within the switching arrangement

ao of Fig. 4 occur.

In Fig. 1 shows an integration unit which comprises a parallel connection of a charging resistor 42 or 42 'and a semiconductor discharge diode 44 or 44' and a capacitor 46 or 46 '. the

»5 capacitor 46 is connected to the junction of resistor 42 'and capacitor 46'. The resistors 42 and 42 'differ from one another in their resistance value and are to the respective output semiconductor diodes 48 and 48 'and then to the zener diode 52 in FIG Threshold value circuit 50 connected; the diode 48 'is on via a normally open switch 49 Earth switched on.

It is assumed that switch 49 is in the open position shown in FIG. During the operation of an internal combustion engine, not shown, control pulses with a repetition frequency f 1 are applied to the monostable multivibrator 20, as a result of which the transistor 24 becomes conductive for a predetermined, fixed time interval t 1. The two capacitors 46 and 46 'are then completely discharged. When the monostable multivibrator 20 has returned to its stable initial state in which the transistor 24 is non-conductive

is, the capacitors 46 and 46 'from the current source 14 through the collector resistor 28 and their own resistors 42 and 42 'are charged with different time constants and time delays, respectively.

The voltage on the capacitor 46 then reaches the Zener voltage of the Zener diode 52 in the threshold value _circuit 50, namely after a time interval i rP after the monostable multivibrator 20 has returned to its stable state. In a similar manner, the voltage across the capacitor 46 'reaches the same Zener voltage after a time interval r _r2 which, according to the illustration, is smaller than the time interval f _r1 .

In this way, capacitors 46 and 46 'are repeatedly charged and discharged. If the speed of the machine, not shown, is so low that the period t _{s of} the control pulses supplied to the monostable multivibrator 20 is longer than the sum of the time interval t _o resulting from the semi-stable state of the multivibrator 20 plus one of the rise times f _rl and results in f _r2 , ie if *,>('"+ _frl )>(t" + t _r2 ) , then the voltages on the capacitors 46 and 46' are greater than the Zener voltage

at the diode 52. The threshold value circuit 50 supplies then to the output terminal 54 an output voltage which corresponds to the actual speed of the machine per unit of time.

If the speed of the internal combustion engine then increases per unit time, so that the relationship (t _u + t _ri )> f _s - (t _o + / _r2 ) is maintained, then the voltage on the capacitor 46 is across the conductive transistor 24 discharged before it reaches the Zener voltage of the diode 52. This then results in a zero voltage at the output terminal 54. The voltage on the capacitor 46 'then exceeds the Zener voltage of the diode 52. The Zener diode 52 is then conductive, so that an output voltage is generated at the output terminal 54 which is also different from the actual The speed of the machine per unit of time depends.

With a further increase in the speed of the machine, the relationship r _s ■ {t " + i _r ,) ■ (r" + t _ti ) applies. As a result, the two capacitors 46 and 46 'are then discharged before the voltages across them reach the Zener voltage of diode 52. This then leads to no output signal at the output connection 54.

The integration unit 40 thus has two capacitors 46 and 46 'and corresponding charging circuits with different time constants «. If the time interval f 1 between two control signals is greater or less than the sum of the time interval f ₍₎ , then the integration unit 40 can determine the predetermined value of the speed of the machine per unit of time. The predetermined value is determined in that the time constant of an integration circuit is smaller.

If the switch 49 is now closed, the capacitor 46 'is short-circuited so that the integration circuit in question can no longer carry out integration. At the same time, diode 48 'is reverse biased; this does not affect the threshold value circuit 50. The greater time constant ^T having ntegrationskreis with the capacitor 46 provides a time delay, is determined by whether the time interval is larger or smaller than the time interval (/ "+ r _rl) /. In this way, another predetermined value of the speed of the machine is determined, which, however, differs from the speed when the switch 49 is open.

If so desired, more than two integration circuits connected in parallel can be used in order to achieve several speeds the associated machine per unit of time according to a respective operating parameter determine. In this case there are then individual, normally open switches - corresponding to the one in FIG. 1 switch 49 shown - connected to each of the capacitors connected in series, except for the Capacitor that ensures the maximum delay. Although the switch 49 shown in FIG is a mechanical switch, a semiconductor switch can of course also be used.

Although the invention is based on an integration unit is described in the form of a capacitor charging circuit, the invention can in in practice, of course, by an integration unit in the form of a capacitor discharge circuit be trained; such a circuit is described in the following in connection with FIG. 2 described.

In Fig. 2, the same reference numerals are used for the components that correspond to those shown in Fig. 1; the integration unit 40 contains

two integration circuits connected in parallel, each of which has a semiconductor diode 44 or 44 ', a discharge resistor 42 and 42 'and a semiconductor output diode 48 and 48', respectively, in the aforementioned Are connected in series. The connecting

The connection point of the diode 44 or 44 'and the resistor 42 or 42' is via the capacitor 46 or 46 'connected to earth.

The diodes 44 and 44 'have their anode electrodes attached to the collector of the normally conductive Transistor 22 turned on in monostable multivibrator 20; this multivibrator is compatible with the in Fig. 1 shown identical. The output diodes 48 and 48 'have their cathode electrodes connected to one Base of a transistor 52 turned on. The transit

disturbance 52 contains an emitter connected to ground and a collector which is connected to the current source 14 via a collector resistor 54; the transistor represents the threshold value circuit 50.
The collector of transistor 52 is connected to a control circuit 60. The circuit 60 has a series shadow of a semiconductor diode 62 and a discharge resistor 64 connected to the anode electrode of the diode 62; the cathode of the diode 62 is connected to the collector of the transistor 52. The connection point between the diode 62 and the resistor 64 is connected to ground via a holding capacitor 66.

According to FIG. 2 a circuit 70 is also provided, which contains a switching transistor 72 with a base electrode connected to the resistor 64 of the timing circuit 60 is turned on. The emitter, however, is connected to earth, while the collector is connected to a winding of an integration unit 74 is connected to the current source 14. The integration unit

Unit 74 is in turn connected to a semiconductor diode 76. A resistor 78 is connected to the base and the Emitter of transistor 72 turned on.

The collector of transistor 72 is also connected to a gate circuit 80. The gate circuit 80

consists of a semiconductor diode 82 with a cathode electrode connected to the collector of transistor 72 and having an anode electrode connected to the anode electrode of one of the output diodes is, in turn, in the capacitor discharge

decircle with the larger time constant is arranged when the diode 48 'is at a lower voltage is applied.

The operation of the arrangement shown in Fig. 2 is described below in connection with the

Fig. 3a and 3b described. The actual speed N of the associated internal combustion engine, not shown, may be smaller than a predetermined value N _ON . Similar to the arrangement shown in FIG. 1, a sentence speaks

chcrkontakte 10 to the rotary movement of the machine, whereby the contacts are opened and closed and voltages of the in F i g. 3 provide a waveform shown under A; these voltages are applied to the monostable multivibrator 20 and switch it to the semi-stable state for a predetermined fixed duration I ₀ with a predetermined subsequent period t _s . When the multivibrator 20 is in the semi-stable state,

transistor 22 is non-conductive and the collector voltage is high according to waveform B in Fig. 3a. During the time interval i ", the current source 14 fully charges the capacitors 46 and 46 'via the collector resistor 26 and via the corresponding diodes 44 and 44'; this voltage is then applied to the base of the transistor 52 in the threshold value circuit 50 via the resistors 42 and 42 'and via the diodes 48 and 48', as a result of which this transistor becomes conductive. At the end of the time interval or as soon as the monostable multivibrator 20 has returned to its stable state, the capacitors 46 and 46 'are discharged with different time constants, as shown schematically by waveforms C and D in FIG. 3a. Under these circumstances, the discharge current of the capacitor 46, which has a low discharge time constant t _H , is applied to the base of the transistor 52 via the resistor 42 and the diode 48 and thereby keeps the transistor 52 in the conductive state.

After the time interval t _H and after the monostable multivibrator 20 has returned to its stable state, the capacitor 46 'is completely discharged and switches the transistor 52 into the non-conductive state. This then increases the voltage at the collector electrode of transistor 52, as shown in FIG. 3a by waveform E. When transistor 52 is in the non-conductive state, capacitor 66 is charged from current source 14 through collector resistor 54 and diode 62, which is illustrated by waveform F in FIG. 3a. At the same time, a base current is applied to the transistor 72 from the current source 14 via the resistor 54, the diode 62 and the resistor 64, whereby it becomes conductive. The collector electrode of transistor 72 is then at zero potential, as shown in Fig. 3a at G; the winding of the relay 74 is excited by the current source 14, so that the contacts of the relay are switched to the working position. It will thus emit an output signal.

Each time a control signal is fed to transistor 24, the above-described process is repeated, so that transistor 52 remains in the conductive state for the period of time (r + t _H ) after the control signal has been applied. If the discharge time of the holding capacitor 66 is greater than the time interval (r "+ t _H ) , then the transistor 72 remains in the switched-on state because of the continuously applied base current. The transistor 72 therefore keeps the relay 47 in the operating state as long as the duration I _{1 of} the control signal is greater than the sum of the time / ". This means, however, that the arrangement has an operating speed N _oh which is the reciprocal of the time (r _o + i ").

As described above, the transistor 72 remains in the switched-on state as long as the associated internal combustion engine rotates at a speed N which is less than the speed Ν _υΝ . The discharge current of the capacitor 46 ′, the discharge time constant L _{1 of which is} greater, flows through the control diode 82 into the now conductive transistor 72, but not into the transistor 52.

If the speed N of the machine is higher than the predetermined speed N " _s , then the circuit arrangement according to FIG. 2 produces waveforms A to (Ζ as shown in FIG. 3b, these waveforms corresponding to those shown in FIG. 3a correspond to waveforms A to G. Since the sequence duration t _{s is} less than the time (r + t _H ) and consequently the base current is continuously applied to its base electrode, the measuring transistor 52 remains continuously conductive -

. switched state because no base current is applied. The relay 46 is also not switched on and therefore does not provide an output signal.

When the transistor 72 is in the switched-off state, the control diode 82 is reverse biased and the capacitor 46 'supplies a discharge current to the base electrode of the transistor 52. Since the discharge time t _{L of} the capacitor 46' is longer

»5 is set as the discharge time t _H for the capacitor 46, base current is continuously fed to the transistor 52 before the sequence duration t _{s of} the control signals becomes equal to the interval (r _o + t _L ) . This means, however, that the arrangement has a rotational speed N _OFf which is the reciprocal of the interval (f + t _L ) .

The arrangement according to FIG. 2 accordingly has a hysteresis characteristic whose operating speed N _{ON is} equal to 1 / (i "+ f") and whose reset speed N _{OFt is} equal to 1 / (f "+ f,), the value t _{L being} greater than the value t ".

Although in the arrangement according to Fi g. 2 the discharge of the transistors is used, the circuit arrangement can can of course also be modified in such a way that the charge of the capacitors is used will.

In Fig. 4 are the components similar to those in FIG. 1 or 2 shown are the same or similar to the same Provided with reference numerals; the normally non-conductive transistor 24 of the monostable multivibrator 20 is connected to the integration unit 40, which is shown in FIG. 1 or 2 with that shown Integration unit matches, except that the one Capacitor 46 having a smaller time constant is connected to control diode 82. The threshold value circuit 50 has a normally non-conductive transistor 53 which is connected to the zener diode 52 and a normally conductive transistor 56 is connected which is coupled directly to transistor 53 is. The transistor 53 includes one connected to the anode electrode the Zener diode 52 connected base electrode, an emitter electrode connected to earth and a collector electrode connected to the current source 14 via a resistor 54. The transistor 56, on the other hand, has a base electrode connected to the collector electrode of transistor 53, a Earth lying emitter electrode and one connected to the current source 14 via a resistor 58 Collector electrode on.

The control circuit 70 in FIG. 4 contains a semiconductor diode 82 with an anode electrode attached to the junction of the capacitor 46 and the output diode 48 is turned on. The cathode electrode, however, is normally attached to the collector of one non-conductive transistor 84, whose collector is also connected via a collector resistor 86 is connected to the current source 14 The emitter of this transistor 84 is connected to ground, while the base electrode is connected to the collector of the transistor 72. Otherwise the scarf is correct processing arrangement with the shown in Fig. 2! match.

The machine, not shown, may rotate at a speed N which is below a predetermined one

Speed is N _ON . As in the arrangements described above, the monostable multivibrator 20 is supplied with control pulses with a sequence duration t _s corresponding to waveform A in Fig. 5a. The transistor 24 becomes conductive for a predetermined, fixed time interval J ₀ , as is shown by the waveform B in FIG. 5a; once transistor 24 has returned to its non-conductive state, capacitors 46 and 46 'are charged with the appropriate time constants, as shown schematically by waveforms C and D in FIGS. 5 a is shown. The voltages on the capacitors 46 and 46 'then reach a predetermined fixed voltage V _D , which is measured by the threshold value circuit 40 - or by the Zener voltage of the diode 52 - after the time intervals t _H and t _{t have} elapsed, after the transistor 24 in FIG the non-conductive state or the monostable multivibrator 20 has returned to the stable state. At this time, the diode 52 turns on and supplies a base current to the transistor 53, whereby it becomes conductive. As soon as the transistor 53 becomes conductive, the transistor 56 becomes non-conductive, which is shown in the waveform E ui F i g. 5 a is shown. Then the process as described in connection with FIGS. 2, 3 a and 3 b is repeated to set the relay 74 in the energized state. In Figure 5a, waveforms F and G represent the voltage across capacitor 66 and the voltage across the collector of transistor 72.

As in the circuit arrangement of FIG. 2, the discharge time of the capacitor 66 is selected to be greater than the duration (r _o + t _H ). The transistor 72 therefore remains in the conductive state and the relay 74 is kept in the operating state. The arrangement therefore has an operating speed / V _ON> the reciprocal of the interval

On the other hand, transistor 84 in control circuit 80 is in a non-conductive state because transistor 72 is kept on. As a result, the diode 82 is reverse biased, which is why the integration time supplied by the integration unit 40 is determined by the discharge time i _H which is required to charge the capacitor 46 to the predetermined voltage. This charging time t _H is therefore shorter than the corresponding charging time t _L for the other capacitor 46 '.

If the rotational speed N is greater than the predetermined, fixed rotational speed N _ON , then the circuit arrangement of FIG. 4 produces waveforms which are denoted by the reference letters A through G in FIG. 5b. In this case , the time interval t 1 between the control signals is shorter than the time interval (t + r _H ), so that the output voltage of the integration unit 40 does not reach the threshold voltage V _{0 of} the threshold circuit 50. The transistor 53 then remains non-conductive, while the transistor 56 is kept in the conductive state. No base current is then fed to transistor 72, so that it remains in the switched-off state. The relay also remains in the de-energized state.

Since the transistor 72 is also in the switched-off state, the transistor 84 in the control circuit 80 is conductive, so that the control diode 82 is operated in the forward direction. The charging voltage on the capacitor 46 is then fixed to the sum of the forward voltage on the diode 82 and the saturation voltage of the transistor 84 and always remains lower than the threshold voltage V _{0 of} the threshold circuit 50.

Therefore, if the actual speed N decreases to the predetermined, fixed speed N _m , then the arrangement remains in the operating mode in which N is equal to N _ON because the output voltage of the integration unit 40 is below the threshold voltage V _{n of} the threshold circuit 50. If the speed N decreases further, the period t _s becomes equal to the time interval (r "+ t _L ), so that the voltage on the capacitor 46 'reaches the threshold voltage V ₁₁ . If the following period I ₁ then becomes greater than the time interval (i _o + r,), base current is fed to transistor 53 and the above-described process is repeated, with relay 74 being energized. The in Fi g. The circuit arrangement shown in FIG. 4 has a reset speed N _OFF , which is reciprocal to the interval (f "+ t") . The arrangement therefore has a hysteresis characteristic with the operating speed ^N n \ - VU _n + * η) ^{and with the} reset speed Λ ', «=! ('" + '") And N _flFt = l / (r "+ R,).

In the context of the present invention, the control signals can be generated by a reed switch which is opened and closed according to the speed of the machine. In this case you can then the ignition coil, the breaker contacts and the monostable multivibrator are omitted. Likewise can the threshold value circuit can be designed as a Schmitt trigger circuit. Finally, the invention is the same well applicable for measuring the speed of a vehicle. In this case a Wheel of the vehicle driven by the internal combustion engine can be used to control the monostable Generate multivibrator applied control pulses.

For this purpose 3 sheets of drawings 309ιδ44 / 355

Claims (3)

Patent claims: 1. Speed measuring device, consisting of a depending on the speed of a rotating Element's pulse shaping unit, a downstream integration unit as well as a threshold value circuit connected to the integration unit, characterized in that the integration unit has a plurality of individual integration circles (42,44,46,48 or 42 ', 44', 46 ', 48 ^ having a plurality of Generate pulse trains with different decay characteristics, and that a selector switch (49, 72, 84) is provided, with which the various pulse trains can optionally be sent to the threshold value circuit (50) are supplied. 2. Speed measuring device according to claim 1, characterized in that the selector switch is on of an operating parameter, for example the temperature, of an internal combustion engine actuated switch (49) is. 3. Speed measuring device according to claim 1, characterized in that the selector switch is formed by semiconductor elements (72, 84) that depend on the output signal of the threshold value circuit (50) are controlled.