WO2018033282A1

WO2018033282A1 - Starting apparatus, which is equipped with a ntc resistor, for an internal combustion engine

Info

Publication number: WO2018033282A1
Application number: PCT/EP2017/065477
Authority: WO
Inventors: Sven Hartmann; Harun Erismis
Original assignee: Seg Automotive Germany Gmbh
Priority date: 2016-08-15
Filing date: 2017-06-23
Publication date: 2018-02-22
Also published as: DE102016215142A1

Abstract

The invention relates to a starting device (100) for an internal combustion engine of a motor vehicle having an electrical machine (110) which is designed to start the internal combustion engine, and having an on-board electrical system (105) with a voltage supply (120), in which on-board electrical system the electrical machine (110) and at least one load (140, 141) are incorporated, wherein at least one NTC resistor (130) is provided in an electrical circuit (160) as part of the on-board electrical system (105) via which a current for operating the electrical machine (110) flows, wherein the electrical circuit (160) has a thermal resistance behaviour, based on a specially designed thermal network, of the kind that a dip in voltage in the on-board electrical system (105) during a short-circuit current flow when starting the internal combustion engine is so low that voltage which is sufficient for normal operation can be supplied to the at least one load (140, 141) at the same time, and that a power output by the electrical machine (110) after the short-circuit current is so large that starting of the internal combustion engine can be completed.

Description

EQUIPPED WITH AN NTC RESISTOR

STARTING DEVICE FOR A INTERNAL COMBUSTION ENGINE

Description title

Starting device for an internal combustion engine of a motor vehicle

The present invention relates to a starting device for an internal combustion engine of a motor vehicle with an electric machine that is set up to start the internal combustion engine.

State of the art

Internal combustion engines in motor vehicles can be started by means of an electric machine, for example in the form of a starter. Since an electrical machine causes a high current flow ("short-circuit current") just when it starts up, voltage drops can occur in the electrical system of the motor vehicle.

From DE 103 17 466 A1 and DE 10 2012 215 338 A1 starting devices for internal combustion engines are known in which an NTC resistor is provided in the circuit of the starter.

From DE 41 06 247 C1, DE 41 22 252 A1 and DE 10 2007 036 789 A1 starting devices for internal combustion engines are known in which an NTC resistor in the circuit of a relay, which serves to engage the starter, is provided.

Disclosure of the invention

According to the invention, a starting device for an internal combustion engine of a motor vehicle with the features of patent claim 1 is proposed. Advantageous embodiments are the subject of the dependent claims and the following description. Advantages of the invention

A starting device according to the invention for an internal combustion engine of a motor vehicle has an electrical machine which is set up to start the internal combustion engine, and an electrical system with a power supply, in which the electric machine and at least one consumer are integrated. In this case, at least one NTC resistor is provided in a circuit as part of the vehicle electrical system, via which a current flows to operate the electric machine. The circuit has such a thermal resistance behavior that a voltage drop in the electrical system during a short-circuit current flow when starting the internal combustion engine is so low that at the same time the at least one consumer can be supplied with sufficient for normal operation voltage, and that a power output of the electrical machine see after the short circuit current is so great that starting the

Internal combustion engine can be completed.

An NTC resistor, also referred to as a thermistor, is a resistance or resistance element which, in contrast to conventional conductors such as most metals, has lower resistance with increasing temperature. The abbreviation NTC stands for Negative Temperature Coefficient. NTC resistors are mostly semiconductor materials, some compound semiconductors, and various metallic alloys. An NTC resistor can be produced, for example, by film casting or powder sintering.

By simply introducing an NTC resistor, which serves as a dropping resistor, into the circuit, the resistance during the short-circuit current, that is to say during the start of the starting of the internal combustion engine, can be chosen large enough so that voltage dips are reduced or prevented, but reduced The resistance of the NTC element by the current flow and the associated heating then not far enough, so that an optimal power output of the electric machine can be achieved. If the simple NTC resistor is chosen lower, you can a good power output can be achieved after the short-circuit current, however, the resistance is lower even during the short-circuit current, whereby a voltage dip can not be prevented. By suitable choice and / or tuning of the NTC resistor and in particular also other components in the circuit, however, can be achieved that both a voltage dip during the short-circuit current prevented and then a good power output can be achieved. In particular, by such a resistance behavior, for example, even frequent starting operations of the internal combustion engine in short intervals, as this example. In

Framework of so-called start-stop systems, especially in city traffic occur, are taken into account.

Preferably, the thermal resistance behavior of the circuit is essentially due to the at least one NTC resistor, materials of

Contacts of the at least one NTC-Wderstands, electrical properties of the at least one NTC-Wderstands and / or materials determined by contacts of the electrical machine. Contact here can be understood as meaning both a stranded wire on the component and a connection means such as solder. By suitable coordination of the components involved in the resistance behavior, the desired behavior can be achieved. In particular, a significantly better behavior can thus be achieved than by simply introducing an NTC-Wderstandes different ambient temperatures should be considered for the starting process of the internal combustion engine. For example. the internal combustion engine is operated in the temperature range from -40 ° C to 150 ° C. The temperature-dependent variation of the NTC heat resistance should therefore not lead to a required voltage breakdown requirement or power output can not be guaranteed. For this purpose, in addition to the appropriate NTC selection an overall design of a heating network, ie the circuit, advantageous in which the individual heat capacities and thermal resistances of the components should be designed accordingly. Advantageously, the at least one NTC resistor is provided inside and / or outside the electric machine. It takes into account the fact that it does not primarily depend on the exact arrangement of the NTC resistor in the circuit. Rather, for example, a structurally advantageous arrangement can be selected. Also, the thermal connection, in particular the influence of the chosen location of the arrangement on the temperature behavior of the NTC-Wderstands be considered. Furthermore, it is also possible, for example, to arrange two NTC-Wderstände at different positions.

It is preferred if a logarithmic resistance-temperature profile of the at least one NTC resistor has a substantially constant gradient. Conveniently, there is a slope of Wderstands- temperature curve in logarithmic representation between 1000 K and 3500 K. By a suitable design of the circuit or the heating network, the desired effect can be achieved in this way.

Advantageously, in this case are a heat capacity of at least one NTC resistor between 0.06 J / K and 0, 18 J / K, a specific Wderstand the least NTC Wderstandes between 2, 1 ücm and 2.8 ücm at a

Temperature of 298 K, a heat capacity of a contact of the at least one NTC-Wderstandes between 0, 15 J / K and 0.3 J / K and / or a heat capacity of lines in the circuit between 0, 15 J / K and 0.4 J. / K. One class of materials that have the corresponding thermal and electrical properties are the so-called perovskites. These have the general structural formula ABO3, where A = (La _x Sr _y ) and B = Fe correspond to the respective chemical elements. The values for x can in this case preferably move in an interval of 0.6 to 0.8 and for y between 0.2 and 0.4. Other perovskites with AB = LaCaFe or AB = LaSrFeMn, with a suitable

Weighting of the respective chemical elements, also meet the aforementioned electrical and thermal properties. In particular, by one of the aforementioned material combinations can be achieved in particular in a warm start (at a temperature of 273 K to 298 K) that the NTC resistor resistance at the beginning of the starting phase, before the short-circuit current, in a range between 5 and 20 mfi, in a range of short-circuit current between 3 and 10 mfi and at the end of starting in a range between 0.2 and 0.5 mQ (or alternatively up to 2 mQ).

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described below with reference to the drawing.

Brief description of the drawings

Figures 1a and 1b schematically show a starting device according to the invention in two preferred embodiments as an electrical circuit.

Figures 2a and 2b show current and voltage curves when starting an internal combustion engine with non-inventive starting devices.

FIG. 3 shows current and voltage curves when starting an internal combustion engine with a starting device according to the invention in a preferred embodiment.

Figures 4a and 4b show an exemplary thermal resistance behavior of an NTC-Wderstands in a starting device according to the invention in a preferred embodiment.

Embodiment (s) of the invention

FIG. 1 a schematically illustrates a starting device 100 according to the invention in a preferred embodiment as an electrical circuit. The starting device 100 has an electrical system 105 into which an electrical machine 110 and a voltage supply 120 designed as a battery are integrated. they are. The electric machine 110 is configured to start an internal combustion engine of a motor vehicle, in which the starting device 100 can be integrated. The electric machine is referred to in this context as a starter. It is understood that the electric machine must be coupled or coupled for torque transmission to the internal combustion engine.

Furthermore, two consumers 140 and 141 are shown, which are integrated into the electrical system 105. For example. For example, the load 140 may be an engine control unit configured to drive both the electric machine 110 and the engine (not shown). The consumer 141 can be an example of consumers who are usually present in a motor vehicle, such as, for example, further control devices, and in particular must or must also function properly during starting of the internal combustion engine.

Furthermore, an internal resistance Rtatt of the battery 120 and a resistance Rßord (line resistance) are shown, the latter being representative of the resistance of the electrical system 105. With 160, a circuit is referred to as a part of the electrical system 105, in which in the operation of the electric machine 1 10th

Electricity flows. In this circuit 160, an NTC resistor 130 and a switch 135 are further provided.

The switch 135 is provided to close the circuit 160 to operate the electric machine 110 to start the engine. The switch 135 can be controlled by the control unit of the electric machine 110, that is, for example, by the engine control unit 140.

The NTC Wderstand 130 is exemplified in the circuit 160 between the electrical machine see 1 10 and the switch 135 is arranged. The switch 135 is typically part of the starter relay and is usually controlled via pilot control relay. Thus, the NTC-Wderstand 130 in the electrical machine 110, ie, for example, on or within the housing, can be arranged. Furthermore, a current I, which flows in the circuit 160, and a voltage U, which is applied to the electrical system 105 and thus also to the circuit 160, shown.

In Figure 1 b, the starting device 100 of Figure 1a is shown again, but with the difference that the NTC resistor 130 is arranged here in front of the switch 135 and thus outside of the electric machine.

FIG. 2 a schematically shows current and voltage curves when starting an internal combustion engine with a starting device not according to the invention. For this purpose, the current I in A and the voltage U in V are plotted against the time t in s.

With a schematic current waveform is referred to, as it can occur when starting the engine and thus the operation of the electric machine without using an NTC resistor in the circuit. Beginning with the start of the starting at t = 0 s, the current increases from zero to, for example, approximately 1030 A at the time t "0.005 s. At this time, therefore, the maximum current is reached. This corresponds to the so-called short-circuit current or is just below it, since the starter usually begins to turn already. Then the current drops, in the example shown to about 400 A at t «0.1 s. Ui is the associated voltage curve. It can clearly be seen that the voltage at the time of the short-circuit current drops to about 6.8 V, for example. According to the decay of the current, the voltage rises again after the short-circuit current.

With is now called a current waveform, as it can occur when starting the internal combustion engine and thus the operation of the electric machine using a simple NTC resistor in the circuit, but not according to the invention.

Beginning with the start of the starting at t = 0 s, the current increases from zero to, for example, about 700 A at time t << 0.01 s. At this time, the so-called short-circuit current is reached. Then the power drops again. With U2 is the associated voltage curve is called. It can clearly be seen that the voltage at the time of the short-circuit current only breaks down to about 9V.

This shows that using a relatively large NTC resistor, in the example shown at about 50 mfi at time t = 0 s, can prevent a voltage dip. The resistance of the NTC resistor is at time t = 0.005 s in about even greater than 5 mfi. However, it can also be seen that the NTC-Wderstand remains relatively large, for example, at about a little over 2 mfi at time t = 0, 1 s, whereby the current flow in the electric machine is low and leads to a low power output.

FIG. 2 b shows current and voltage curves during starting of an internal combustion engine with a further starter device not according to the invention. For this purpose, the current I in A and the voltage U in V are plotted against the time t in s. Current flow and voltage curve Ui correspond to the

Gradients without using an NTC resistor, as shown in Figure 2a.

With now another current characteristic is called, as it can occur when starting the internal combustion engine and thus the operation of the electric machine using a simple NTC-Wicking in the circuit, but not according to the invention.

Beginning with the start of the starting at t = 0 s, the current increases from zero to about 1000 A at the time t "0.005 s. At this time, the so-called.

Short-circuit current reached. Then the power drops again. U3 is the associated voltage curve. It can clearly be seen that the voltage at the time of the short-circuit current here drops to about 6.9 V. This shows that using a relatively small NTC resistor, in the example shown at about 3 mfi at time t = 0 s, can not prevent a voltage dip. The resistance of the NTC resistor is at time t = 0.005 s in about 0.5 mfi. However, it can also be seen that the NTC resistor is therefore relatively low even after the short-circuit current, For example, in about 0.2 mfi at the time t = 0, 1 s, whereby the current flow in the electric machine in comparison to, for example, without NTC resistance is hardly lower and thus leads to a desired power output.

In comparison with FIGS. 2a and 2b, it can be seen that a simple use of an NTC resistor can not simultaneously prevent a voltage dip in the short-circuit current and subsequently ensure a desired power output of the electrical machine.

FIG. 3 shows current and voltage curves when starting an internal combustion engine with a starting device according to the invention in a preferred embodiment. For this purpose, the current I in A and the voltage U in V are plotted against the time t in s. Current profile and voltage curve Ui correspond to the curves without using an NTC resistor, as shown in Figures 2a and 2b.

With U is now called a current waveform, as it can occur when starting the internal combustion engine and thus the operation of the electric machine with the use of an NTC resistor in the circuit in an embodiment of the invention.

Beginning with the start of the starting at t = 0 s, the current increases from zero to about 880 A at the time t "0.005 s. At this time, the so-called short-circuit current is reached. Then the power drops again. With U the associated voltage curve is designated. It can clearly be seen that the

Voltage at the time of short-circuit current only to about 7.8 V breaks.

This shows that use of a suitable NTC resistor, in the example shown with about 5 to 20 mfi at the time t = 0 s, can prevent a voltage drop, at least to the extent that proper operation, for example, of the engine control unit is still possible , The resistance of the NTC resistor is at time t = 0.005 s in about 3 to 10 mfi. Furthermore, it can also be seen that the NTC resistor after the short-circuit current is relatively low, for example. In about 0.2 to 0.5 mfi at time t = 0, 1 s, whereby the current flow in the electric machine compared to for example without NTC resistance is hardly lower and leads to a desired power output.

It should be noted that the shown thermal Wderstandsverhalten with the associated curves U and U ₄ not only by the NTC-Wderstand itself, but also by a vote of the materials of the contacts of the NTC resistor, the electrical properties of the NTC resistor and the Contacts of the terminals of the electrical machine is characterized. Thus, a detailed design of a suitable thermal network for the function is crucial (thermal network see previous pages). For a more detailed description of the NTC resistor itself, reference is made to the following description.

FIG. 4 a shows schematically an exemplary thermal resistance behavior of an NTC-Wderstands of a starting device according to the invention in a preferred embodiment. For this, the resistance R of the NTC resistor in Ω and in logarithmic representation over the temperature T in K is shown.

In this case, B shows a profile of a constant typical for an NTC resistor, with which reference to the formula

the temperature-dependent resistance of the NTC resistor can be described at least approximately. In this case, RN denotes a resistance of the NTC-Wderstands at the temperature TN, which is usually a nominal temperature of 298 K is. In the following, briefly advantageous parameters are described, from which a suitable NTC module can be derived, which satisfies the required requirements and has a thermal resistance behavior as shown in FIG.

For a maximum heat capacity C of the NTC-resistance, the following assumptions are made for a density Q, a volume V and a specific heat capacity c: C = mc = pVc = 6000 ^ · 3.19 cm ² - 0.1 \ 2mm W0 ^ - = 0.1715-

m ³ kg-K K

For a minimum heat capacity C of the NTC resistance results:

C = mc = pV-c = 6000 ^■ 2, 15cm ^{2 ■} 0, 067mm · 800- = 0, 069-

m ³ kg-K K

A specific resistance of the NTC resistor is, for example, between 2.1 and 2.8 .mu.m at room temperature, ie. 2998 K. This results in a temperature coefficient or B value of between 2500 K and 3500 K.

For a maximum heat capacity of a contact or an electrode of the NTC resistor made of copper, the following results:

J J

C = mc = pV-c =% 930 ^ - 3, \ 9cm ² -0.2mm -400 0.228

m kg-K K For a minimum heat capacity of a contact or an electrode of the

NTC resistance of copper results:

C = m ^■ c = pV -c = 8930 ^ -2.15cm ^{2 ■} 0, 2mm ^■ 400 --- = 0.154

m ³ kg-K K For a maximum heat capacity of a heat channel, ie a conductor in the

Circuit of copper results: C = m ^■ c = p - V - c = 8930 ^ - · 0, 056m ^{2 ■} 19, 2mm · 400 --- = 0, 384-

m ³ kg - KK

For a minimum heat capacity of a heat channel, i. of a conductor in the copper circuit results:

J

8930 ^ · 0, 05m ^{2 ■} 10, 3mm · 400 - 0.184

m kg - K K

In Figure 4b is a measured thermal resistance behavior of an NTC resistor for an exemplary parameter set within the mentioned

Shown limits. The temperature T is indicated here in ° C.

One class of materials that have the corresponding thermal and electrical properties are the so-called perovskites. These have the general structural formula ABO3, where A = (La _x Sr _y ) and B = Fe the respective chemical

Correspond to elements. The values for x can in this case preferably move in an interval of 0.6 to 0.8 and for y between 0.2 and 0.4. Other perovskites with AB = LaCaFe or AB = LaSrFeMn, with a suitable weighting of the respective chemical elements, also fulfill the aforementioned electrical and thermal properties.

Claims

Starting device (100) for an internal combustion engine of a motor vehicle with an electric machine (1 10), which is set up to start the internal combustion engine, and an electrical system (105) with a power supply (120), in which the electric machine (110) and at least one Consumers (140, 141) are involved,

wherein at least one NTC resistor (130) is provided in a circuit (160) as part of the vehicle electrical system (105), via which a current flows for operation of the electric machine (110),

characterized in that the circuit (160) has such a thermal resistance behavior that a voltage drop in the electrical system (105) during a short-circuit current flow when starting the internal combustion engine is so low that at the same time the at least one consumer (140, 141) with sufficient for normal operation Voltage is supplied, and

that a power output of the electric machine (110) after the short-circuit current is so large that the starting of the internal combustion engine can be completed.

The starting device (100) according to claim 1, wherein the thermal resistance behavior of the circuit (160) is substantially determined by the at least one NTC resistor (130), materials of contacts of the at least one NTC resistor (130), electrical properties of the at least one NTC resistor. Resistor (130) and / or materials of contacts of the electric machine (1 10) is determined.

The starting device (100) according to claim 1 or 2, wherein the at least one NTC resistor (130) is provided inside and / or outside the electric machine (110).

4. Starting device (100) according to one of claims 1 to 3, wherein a logarithmic resistance-temperature curve of the at least one NTC resistor (130) has a substantially constant gradient.

5. Starting device (100) according to claim 4, wherein a slope of the Wderstands- temperature curve in logarithmic representation between 1000 K and 3500 K.

6. Starting device (100) according to any one of the preceding claims, wherein a heat capacity of the at least one NTC-Wderstandes between 0.06 J / K and 0.18 J / K, a specific resistance of at least NTC resistor between 2, 1 ücm and 2.8 μcm at a temperature of 298 K, a heat capacity of a contact of the at least one NTC resistor between 0.15 J / K and 0.3 J / K and / or a heat capacity of lines in the circuit between 0.15 J / K and 0.4 J / K lie.