DE1580583B1 - Device for controlling the automatic engagement and disengagement of an electromagnetically actuated clutch of a motor vehicle - Google Patents

Description

The invention relates to a device for controlling the automatic Engaging and disengaging an electromagnetic clutch of a motor vehicle the im through the interrupter, depending on the engine speed, intermittently interrupted ignition circuit, a primary winding is arranged on an im Circuit of the coil of the electromagnetically operated clutch lying secondary winding Transmits current pulses whose pulse width and voltage level depend on a the secondary winding parallel capacitor can be changed and the Coil are fed through an amplifier, with the electromagnetically actuated Coupling in direct heat-conducting connection with a balancing resistor is a temperature coefficient, the higher the higher the clutch temperature Working current supplies the coil.

A device of this type is known (French additional patent 79 072) in which the balancing resistor has a negative temperature coefficient and is connected in series with the base of a transistor. In order for the working current supplied to the coil to increase, it is necessary that the voltage at the base of the transistor also increases. At a certain engine speed, the current surges are periodically fed to the base of the transistor, among other things via the balancing resistor. The opposite the passage of the base current resistance changes with temperature, and thereby controls, more or less strongly the collector current of the transistor. The result therefore depends to a large extent on the gain of the transistor and leads to a strong heating of the same, which then does not immediately follow when it is switched off and supports both current and voltage. Furthermore, with the known device, at best, linear dependencies of the current intensity on the engine speed are obtained, but not curves with a parabolic character which are particularly well matched to the characteristics of the engine. the addition of the device must be modified, as is the case with the known device, and also insofar as the circuit with the output resistor with a positive temperature coefficient has only weak impedances, so one is not hampered by insulation problems for the resistors. Furthermore, in the device according to the invention, the signal width, namely the ratio of the times in which the transistor conducts to the times in which it does not conduct, can be varied with the temperature of the clutch, within a large range without affecting the function the device changes when it is switched off. Finally, the change in the current intensity with increasing speed results in a parabolic curve which is particularly well adapted to the characteristics of internal combustion engines.

An exemplary embodiment of the device according to the invention, which is explained in more detail in the following description, is shown in the drawings. It shows F i g. 1 shows the electrical circuit diagram of a device according to the invention, FIG. 2 shows a simplified sectional view of a magnetic powder clutch with the associated brushes and a compensation resistor, FIG. 3 shows the course of the voltage over time at a certain point in the circuit diagram of FIG . 1, under the influence of the balancing resistor, F i g. 4 the course of the characteristic curve of the balancing resistor used (or the balancing resistors used) over temperature, FIG. 5 shows the arrangement of a compensation circuit, which consists of ordinary resistors and resistors with a high positive temperature coefficient, FIG. 6 shows the variation of the characteristic of the strength of the coupling current flowing through to the Antriebsmaschinendrebzahl at the moment of start-up and that of the object underlying the invention is to provide a device of the initially mentioned type, which operates with better efficiency d. H. is more economical and is better adapted to the characteristics of the internal combustion engine.

This object is achieved in that the with the electromagnetically actuated coupling in a direct, heat-conducting connection standing balancing resistor has a high positive temperature coefficient and in a bypass circuit .. to the circuit- the coil of the electromagnetically operated Coupling is in which one in a known manner also from the primary winding Affected auxiliary secondary winding is provided, one end of which is connected to one end of the Equalizing resistor, the other end of which is connected to ground, is connected while the other end of which is both connected to a line leading to the battery as well as a resistor with one side of the pulse width and voltage level the current pulse changing capacitor is connected.

This training is very economical in that the feed line for the clutch is not through FIG. 7 shows the curve of the prime mover speed, which corresponds to the balance between the prime mover torque and the torque transmitted by the clutch, plotted against the spool resistance. This speed is essentially that which the prime mover assumes during a considerable part of a start-up process with the accelerator pedal fully depressed.

In Fig. 1 shows an embodiment of a device as it has already become known from French patent specification 1323 553 .

This device includes a battery 1, the primary winding 4 fed via an outgoing from its positive pole line 2 and an outgoing from its negative terminal lead 3 of the ignition coil of an internal combustion engine, the ignition coil having a circuit breaker 5, and a quenching capacitor 6 cooperates. In the positive line 2, the primary winding 7 of a transformer 8 , which has a main and an auxiliary secondary winding 9 and 10 , is connected in front of the primary winding 4. The auxiliary secondary winding 10 has a tap which is connected to the line 2 via a resistor 29. The primary winding 7, the current passage of which is subject to the fluctuations generated by the interrupter, represents the control part of an electronic control unit 11, which is dependent on the engine speed, for the power supply of a magnetic particle clutch 13, which has a coil 12 and a contact 14 actuated when the internal combustion engine and the transmission input shaft are synchronized. This contact is open as long as the engine speed is higher than that of the transmission input shaft. It is connected to the terminals of the auxiliary secondary winding 10 of the transformer 8 via a line 22, together with a compensation resistor 15 , so that both, by being connected to the auxiliary secondary winding 10, modify the voltages occurring at the terminals of the main secondary winding 9 with every movement of the interrupter 5.

A circuit is arranged at the terminals of the main secondary winding 9, which comprises a diode 16, which detects the voltage due to the opening of the interrupter 5 , and a capacitor 17 , the coating of which on the side of the diode 16 is connected to the negative line 3 via a resistor 18 is. The resistor 18 serves to discharge the capacitor mentioned, the charging of which is due to the voltage of the main secondary winding 9 and the battery 1 .

The circuit of the coil 12 is connected to the terminals of the capacitor 17 and feeds the coil 12 via an amplifier 19 from the battery via the lines 20 and 21 as a function of the pulse width of the current pulses generated via the capacitor 17.

F i g. 2 shows an embodiment of the magnetic particle coupling with the coil 12, the contact 14 and the compensation resistor 15 with a positive temperature coefficient.

The driving coupling part 24 is firmly connected to the output shaft 23 of the internal combustion engine. It contains the coil 12, which surrounds a recess 24 a, into which a ring 25 firmly connected to the transmission input shaft 26 is inserted. The remaining cavity is filled with magnetic powder 27 , which enables a progressive coupling of the driving coupling part 24 and the ring 25 under the effect of the induction generated by the coil 12.

In a cover 24 b closing the recess 24 a, the equalizing resistor 15 is arranged, which is divided into a resistor 15 a with a high positive coefficient and an ordinary resistor 15 b connected in series with it. Both resistors are connected in parallel with the contact 14, which opens as soon as the driving clutch part 24 rotates faster than the transmission input shaft 26. The resistor 15 a with a high positive temperature coefficient is in the best possible, thermally conductive connection with the mass of the driving clutch part 24 and is held in position by a spring 28.

The arrangement described above can of course also in other devices for controlling the automatic engagement and disengagement of a solenoid operated clutch are used if there is the possibility of the current pulses applied to coil 12 through a high positive resistor To modify the temperature coefficient, which is in thermally conductive connection with the Clutch is arranged and acts on a control circuit.

For a more detailed description of the mode of operation of the device according to the invention, reference is now made to FIG. Reference is made to FIG. 3 , which shows a voltage oscillogram of the capacitor 17. The opening of the interrupter 5 causes the capacitor to be charged with the voltage U 1 at a time t 1, the resistor 18 completely discharging the capacitor at the time t 2. The amplifier 19 is designed so that it sends current into the coil of the magnetic particle clutch between t 1 and t 2. When the balancing resistor 15 has a low value, some of the energy normally intended for the capacitor 17 is conducted through the auxiliary secondary winding 10 to the balancing resistor 15 , and the charging voltage drops to U 2, with the discharge occurring at t 3 before t 2 , i.e. . That is, each time the circuit breaker is opened, current is sent to the coil 12 for a shorter period of time than before. If the speed of the internal combustion engine is lower than the speed of the transmission input shaft, the contact 14 is closed and thereby short-circuits the compensation resistor 15 , so that the current reaching the coil 12 is very weak. If, on the other hand, the engine speed is even slightly higher than the speed of the transmission input shaft, the contact 14 is open and a strong current flows through the coil 12, which is determined by the value of the compensating resistor 15, which varies depending on the temperature of the clutch will. The amplifier outputs less current at a given speed when the magnetic particle coupling is cold, the coil has a low resistance and the balancing resistance 15 has a lower value than with a warm magnetic particle coupling when the balancing resistor 15 has a higher value.

In Fig. 4, the curve 4 a represents the necessary change in the resistance R as a function of the temperature T. If this characteristic cannot be achieved with a single compensation resistor 15 , an approximate curve composed of two curves can be obtained using the circuit according to FIG . Achieve 5 , in which resistors 15 a 1 and 15 a 2 with a high positive temperature coefficient with the characteristics 4 c and 4 b are used in conjunction with ordinary resistors 15 b 1 and 15 b 2.

These resistors with a high positive temperature coefficient exist mostly made of relatively poorly conductive materials, the Curie point of which is in the operating range lies. They are available in various designs in stores.

In Fig. 6 shows the current intensity I in the coil 12 when starting up as a function of the engine speed N. The curve 6 a corresponds to an ambient temperature T 1. Due to the higher resistance of the coil at the higher temperature T 2, the characteristic curve 6 b is then obtained. The steeper characteristic curve 6 c can be achieved by the value of the balancing resistor 15 increasing with the temperature. The current strength i 2, which at T 2 keeps the torque of the internal combustion engine in equilibrium, is higher than the current strength ! 1, 1 keeps the same torque T in the balance, but in an internal combustion engine speed n 2 obtained which is lower than the temperature T 1 corresponding speed n. 1

In FIG. 7 shows the internal combustion engine speed as a function of the resistance of the coil 12, which changes with the clutch temperature, which corresponds to the equilibrium between the torque of the internal combustion engine and the torque that can be transmitted by the magnetic particle clutch when starting at full throttle. Curve 7 a corresponds to operation with overcompensation, curve 7 b to operation without compensation by a compensating resistor 15, the control values being the same due to the action of resistor 18 at coil resistance r 1.

Claims (2)

Claims: 1. Device for controlling the automatic engagement and disengagement of an electromagnetically actuated clutch of a motor vehicle, in which a primary winding is arranged in the ignition circuit internüttierend interrupted by the interrupter, depending on the engine speed, which is connected to one in the circuit of the coil of the electromagnetically actuated Secondary winding lying on the clutch transmits current pulses whose pulse width and voltage level can be changed depending on a capacitor connected in parallel to the secondary winding and which are fed to the coil via an amplifier, with the electromagnetically actuated clutch being in direct heat-conducting connection with a compensation resistor with a temperature coefficient that corresponds to a higher clutch temperature supplies a higher working current to the coil, characterized in that the A, which is in direct heat-conducting connection with the electromagnetically actuated clutch (13) Equalizing resistor (15) has a high positive temperature coefficient and is located in a secondary circuit to the circuit of the coil (12) of the electromagnetically operated clutch (13) , in which an auxiliary secondary winding (10) is provided, which is also influenced in a known manner by the primary winding (7) one end of which is connected to one end of the balancing resistor (15), the other end of which is connected to ground, while the other end of which is connected both to a line (3) leading to the battery and via a resistor (18) the one side of the pulse width and voltage level of the current pulses changing capacitor (17) is connected. 2. Apparatus according to claim 1, characterized in that the balancing resistor (15) with a high positive temperature coefficient is connected to the terminals of a contact (14) closed in a manner known per se with synchronism between the driving coupling part (24) and the transmission input shaft (26) is, wherein the contact (14) is opened at a higher speed of the driving clutch part (24).