DE4106247C1 - Starter circuit for IC engine - incorporates NTC resistor in parallel with relay to inhibit starting at very low temp. - Google Patents

Abstract

The starter motor is operated via a relay (1) which displaces a pinion to bring it into alignment with a gearwheel to activate the motor. At least one energising winding (H, E) of the relay (1) is connected in series with a parallel circuit comprising at least one negative temp. coefficient resistor (2) and at least one ohmic varistor (3). Pref. the n.t.c. resistor (2) has a resistance of 0.5 Ohm, the ohic resistor (3) a resistance value of 0.1 Ohm, the relay operating winding (E) a resistance of 0.37 Ohm and the relay holding winding (4), a resistance of 1.7 Ohm. USE/ADVANTAGE - Vehicle engine starter circuit. Prevents operation at extremely low temp. to prevent damage to pinion or gearwheel.

Description

A starting device according to the preamble of the patent claim is known from the publication "Startanlagen, Bosch-Technische Unterleitung" 1984, pages 22, 23. Such a starting system of an internal combustion engine consists, according to Figure 1, of a starter motor, a back relay 1 and a screw-push device. When switched on, the relay armature advances the pinion into the toothed ring of the internal combustion engine. In the case of the engagement relay, the relay current depends very much on the temperature and thus also the tightening force. This leads to tracking problems and damage to the pinion and ring gear, especially in the cold, because then the engagement process takes place almost instantaneously.

With the present invention, the temperature-related changes the pulling forces of the engagement relay when the starter is engaged be balanced by ritzels.

This is due to the characterizing features of the claim reached.

An embodiment is shown in Figure 2 and explained in the following description with the help of Figure 3.

A starting device for an internal combustion engine has a back relay 1 for engaging the pinion in the ring gear of the internal combustion engine. So that despite the temperature-dependent change in the relay resistance, an almost uniform current and thus a tightening force that is adapted to the requirements is achieved even over a large temperature range, a combination of at least one NTC resistor 2 and at least one pure ohmic resistor 3 is connected in parallel to limit temperature-related Changes in the relay current of the pull-in and holding winding 1 upstream.

Core and advantages of the invention

Figure 3 shows the relative maximum current during the pull-in process on an engagement relay without and with different series resistors at -30 ° C, 23 ° C and 100 ° C. Without a series resistor, the relay current in the so-called series relay, ie after the previous series production, increases sharply with falling temperature.

With an NTC resistor alone, the desired effect is not reached. As is known, the NTC resistor has no constant Temperature coefficient. At -30 ° C the NTC resistance increases enormous and reduces the relay current to such an extent that the armature can no longer move.

Only with the parallel connection of a thermistor and a pure one Ohmic resistance leads the experiments to the desired success. It is exploited that the resulting resistance at a Parallel connection always smaller than the smallest resistance of the Parallel connection is.

At high temperatures, the value of the NTC counter almost disappears befitting. This will increase the resistance of the relay windings compensated. At low temperature, the NTC resistance is on Multiple of the ohmic series resistor: The relay current flows almost exclusively through the ohmic series resistor. This is so dimensioned that he then with the low winding resistance supplies the excitation current required for soft tracking.  

It is advantageous with this version that the relay is no longer for to design the maximum limit temperature. Functionality at Normal temperature is sufficient. The relay current is at low temperature higher, but deviates less than 10% from its target with less than 10% worth that the friction of the single-track system, which ver in cold weather larger, compensated by the increased relay current in this case becomes. The tightening force of the anchor can thus be in the entire temperature area to be adapted to requirements.

The following values apply to the example according to Figure 2 at 23 ° C.

NTC resistor 2 = 0.5 Ω
Parallel resistance 3 = 0.1 Ω
Pull-in winding E of relay 1 = 0.37 Ω
Holding winding H of relay 1 = 1.7 Ω

Claims (1)

Starting device for internal combustion engines with an electric starter motor, an engagement relay with at least one excitation winding and a screw-and-push device, which is able to mesh with a pinion connected to the starter motor in a gear of the internal combustion engine, with the engagement of the engagement relay, the pinion into the Gear meshes and the starter motor is switched on, characterized in that the at least one excitation winding (H, E) of the engagement relay ( 1 ) is connected in series with a parallel connection of at least one NTC resistor ( 2 ) and at least one ohmic resistor ( 3 ) .