DE102014207583A1 - Method for stopping an internal combustion engine - Google Patents

Abstract

Method for stopping an internal combustion engine, wherein when the ignition and / or injection is switched off, an air quantity supplied to the internal combustion engine is initially reduced and increased again after a speed (n) of the internal combustion engine has fallen below a predefinable speed threshold value (ns), a first speed value (n1 ) at a first sampling time (t1) and a second speed value (n2) at a second sampling time (t2), the two sampling times (t1, t2) being selected such that the first speed value (n1) is greater and the second speed value (n2) is smaller than the predefinable speed threshold value (ns), and means for generating a rotational movement of the engine braking torque depending on a degraded energy content (E) are controlled, wherein the degraded energy content (E) depends on the first speed value (n1) and second speed value (n2) is determined.

Description

State of the art

From the DE 10 2011 082 196 A1 a method for stopping an internal combustion engine is known, in which via a throttle valve of the internal combustion engine, the amount of air supplied to the engine is reduced after a stop request has been determined, and the air metering means the amount of air supplied to the engine is increased again when a detected speed of the internal combustion engine falls below the predetermined speed threshold value, wherein the predefinable speed threshold value is increased when an inlet cylinder after the increase in the metered amount of air until the engine stops, no bottom dead center passes.

Disclosure of the invention

In practice, the engine speed at the last bottom dead center of the intake cylinder is individually different from engine spout to engine spout. It must therefore be reduced with the last compression of spout to spout different amounts of energy.

The method with the features of claim 1, on the other hand, has the advantage that these differences are adequately taken into account, which makes the positioning of the engine more accurate towards the end of the spout and at the same time reduces the engine's tendency to shake and thus improves comfort, as excessive cylinder fillings are avoided.

Further advantageous embodiments are the subject of the dependent claims.

In further aspects, the invention relates to a computer program which is set up to carry out all the steps of the method according to the invention, a machine-readable storage medium on which the computer program is stored, and a control device which is set up to perform all the steps of the method according to the invention.

Hereinafter, embodiments of the invention will be explained in more detail with reference to the accompanying drawings. In the drawing: Description of the embodiments

Show it:

1 Characteristics of parameters during the discharge of an internal combustion engine;

2 a flowchart according to a first aspect of an embodiment of the invention;

3 a flowchart according to a second aspect of an embodiment of the invention;

4 Characteristics of parameters during further outlets of the internal combustion engine according to a further aspect of an embodiment of the invention;

5 a diagram for determining the leakage behavior of the internal combustion engine depending on determined rotational speeds according to a further aspect of the invention;

6 schematically the electronic control unit for performing the method.

Description of the embodiments

1a shows by way of example for a four-cylinder internal combustion engine, the sequence of the clocks of a first cylinder ZYL1, a second cylinder ZYL2, which immediately precedes the first cylinder ZYL1 in the intake order, and another cylinder ZYL3, which follows the first cylinder ZYL1 in the intake order. The cylinders go through in a known manner intake stroke, compression stroke, power stroke and exhaust stroke.

1b describes the course of a rotational speed N of the internal combustion engine (for example, the rotational speed of the crankshaft) over the time t. At times t1, t2, t3, t4, the internal combustion engine passes through dead centers T1, T2, T3 and T4. The speed of the internal combustion engine shows the outlet of the internal combustion engine, ie ignition and / or injection are switched off. At certain times, in the exemplary embodiment at the dead centers T1, T2, T3, T4, the rotational speed n of the internal combustion engine is determined, for example measured with a rotational speed sensor. At a first sampling time t1, a first rotational speed value n1 results, at a second sampling time t2 a second rotational speed value n2 results. The first speed value n1 is greater than a predefinable speed threshold value ns, the second speed value n2 is less than the predefinable speed threshold value ns.

In 1c the degree of opening DK of an air metering device, for example a throttle valve of the internal combustion engine, is shown. It goes without saying that the Luftzumesseinrichtung can also be designed differently, for example by a variable valve timing. However, the air metering device can also be provided, for example, by an additional electric compressor, which is arranged in the intake pipe of the internal combustion engine.

In the embodiment, the Luftzumesseinrichtung is given by the throttle. First, the throttle is closed or light open, shown in the embodiment by a first opening degree DK0. After it has been determined at the second sampling time t2 that the rotational speed n of the internal combustion engine has fallen below the predefinable rotational speed threshold ns, the throttle valve is opened its time t (corresponding to a crankshaft angle KWauf). At this time, the first cylinder ZYL1 is in its intake stroke and is therefore also referred to as intake cylinder or intake cylinder.

The first cylinder ZYL1 now sucks an increased amount of air, passes the dead center T4, and experiences in its compression stroke due to the compression of the now increased amount of air a strong restoring torque. Conversely, since the expansion force of the second cylinder ZYL2, which is then in its power stroke, is low, because the air charge of the second cylinder ZYL2 is still low, resulting in sum, a strong restoring torque. The speed of the internal combustion engine drops rapidly, passes through the zero speed at a Rückpendelzeitpunkt tosc. The internal combustion engine now shuttles back and comes to a stop time tstop to a standstill.

This means that the energy stored in the rotational movement of the internal combustion engine is reduced within a single stroke of the internal combustion engine. This stored energy is therefore also referred to as the energy content E to be degraded. According to the invention, it is now provided that the energy content to be degraded is determined as a function of the first rotational speed value n1 and second rotational speed value n2, depending on the relative position of the first rotational speed value n1, second rotational speed value n2 and predefinable rotational speed threshold value ns to one another.

There are different extreme cases possible. In an extreme case, it is possible that the first rotational speed value n1 is minimally greater than the predefinable rotational speed threshold value ns, so that the second rotational speed value n2 is relatively low, so that the energy content E to be degraded is relatively low. In this case, for example, be provided that the degree of opening DK2 of the throttle valve is rather low, and thus a softer gas spring is generated. For example, alternatively or additionally, it may also be provided that the throttle valve is not opened at the time tauf for producing a softer gas spring, but rather at a later point in time tauf '. This is in 1c also illustrated.

In a reversed extreme case, however, it is also possible for the second rotational speed value n2 to be only slightly lower than the predefinable rotational speed threshold value ns. In this case, the energy content E to be degraded is large. It can therefore be provided to select the second opening degree DK1 of the throttle valve larger than in the previously illustrated case of a low energy content E to be degraded.

The method according to the invention is carried out particularly advantageously with sampling times at the dead centers, since then the energy content of the unburned internal combustion engine can be determined particularly easily. The energy content consists of rotational energy, potential energy and kinetic energy. In a multi-cylinder internal combustion engine, the positional energies of the individual cylinders cancel each other out. For even number of cylinders, the kinetic energy, i. H. the translational energy given by the up and down movement of the cylinders is zero at the dead centers since all cylinders are either at their top or bottom dead center. The potential energy, ie the compression energy, is almost the same between the dead centers. The energy content E is thus characterized in the dead centers by the rotational energy and thus proportional to the square of the rotational speed n.

In a specific embodiment, the energy content E is given by a quotient Q = D12 / D1S, where D12 = n1 -n2 is the difference between the first speed value n1 and second speed value n2 and D1S = N1-ns is the difference between the first speed value n1 and the speed threshold ns.

If the energy content E is thus determined, it assumes values between 0 and 1, where 0 corresponds to a low energy and 1 to a high energy. The standardization by the difference D12 can optionally be dispensed with. Other ways to determine the degraded energy content E are conceivable.

2 shows a flowchart according to another embodiment of the invention. The procedure starts in step 1000 , In the following step 1010 the degraded energy content E is determined depending on the first speed value n1 and second speed value n2. Advantageously, this determination is made before the time tauf, in addition, the throttle valve is opened. In the following step 1020 it is checked whether the energy content to be degraded is smaller than a first energy content threshold Es. If this is the case, follow step 1030 otherwise step follows 1040 ,

In step 1030 will the procedure as in 1 illustrated performed, ie, the time tauf, at which the throttle valve is opened, corresponds to an opening crankshaft angle KWauf, which lies between the dead centers T3 and T4. The suction cylinder, that is, the cylinder to which the increased amount of air is first supplied is the first cylinder ZYL1. The procedure is as in 1 Illustrates and ends in step 1050 , In step 1040 becomes on the other hand, the throttle valve is not opened between the dead centers T3 and T4, but in the cycle which follows the dead center T4. In this case, the intake cylinder is given by the further cylinder ZYL3, which is later in the intake order, namely immediately following the first cylinder ZYL1. This in 1 described Auspendelverhalten shifts thus by one bar to the rear. The amount of energy dissipated by the compression of the air spring in the intake cylinder is lower, and the tendency of the engine to shake is reduced.

3 shows a flowchart according to another aspect of the invention. The procedure starts in step 2000 , In step 2010 then the energy content E to be degraded is determined. It follows step 2020 in which it is checked whether the energy content E to be degraded is smaller than a second energy content threshold Es2. If this is the case, follow step 2030 otherwise step 2040 , In step 2030 the procedure proceeds as in 1 illustrated, if appropriate according to 2 , There is no separate control of coupled to the crankshaft additional units.

Such additional units include, for example, a (in particular belt-driven or permanently meshed) generator, an electric motor of a valve adjustment or a pump. The term "coupled" can here mean an immediate mechanical coupling, but it can also be understood broadly, for example as in an axle hybrid. There, the coupling is indirect, for example via a torque transmitted via a road

In step 2040 is such a rotational movement of the engine decelerating torque applied by a means for applying this torque (ie, the aforementioned generator, the pump, etc.) is driven. Of course it is also possible that in step 2030 also such a decelerating torque is impressed, and in step 2040 Accordingly, a larger decelerating torque is impressed. After step 2030 respectively. 2040 The method according to this aspect of the invention ends in step 2050 ,

4a and 4b illustrate the leakage behavior of the internal combustion engine according to another aspect of the invention. In 4a and 4b in each case shown are first speed value n1 and second speed value n2 and the difference D12.

This in 4a illustrated discharge behavior corresponds to a case in which the internal combustion engine has four cylinders and as in 1 illustrated leaking.

After determining the second rotational speed value n2, the first cylinder ZYL1 enters its intake stroke A1 at the next dead center T3 of the internal combustion engine. As in 1 illustrates the internal combustion engine still passes through a clock in which between the dead centers T3 and T4, the throttle valve DK is opened, before he commutes in the next cycle and comes to a standstill. That is, after the speed n has fallen below the speed threshold ns, the engine still passes through three dead points T2, T3, T4 before it declines.

4b illustrates the case that is decided on the basis of first speed value n1 and second speed value n2 that the energy to be degraded of the engine is so large that the throttle valve DK is not as in 4a illustrated between the dead centers T3 and T4 is opened, but only one bar later. The rest of the process to a standstill is analogous to that in 4a illustrated case, but offset by one bar. The third cylinder ZYL3 goes to the fourth dead center T4 in its intake stroke A3 and sucks as described the increased amount of air. Thus, after falling below the speed threshold value ns by the speed n, the internal combustion engine still passes through four dead points before settling out.

5 shows by way of example how it is decided in dependence on the second speed value n2 and difference D12, whether the internal combustion engine according to the in 4a illustrated behavior is stopped, ie with three dead points passed through (area B1), or according to the in 4b illustrated method, ie with four traversed dead centers (area B2). With a second speed value n2 greater than a limit value, it is decided that four instead of three dead points are passed through, so that the internal combustion engine can dissipate further energy in the thus additional coasting stroke. With a larger difference D12, this limit value shifts to higher values since the internal braking of the internal combustion engine is greater.

6 shows the controller 1 which is so on a powertrain 2 to which the internal combustion engine belongs, acts to carry out all the steps of the method according to the invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102011082196 A1 [0001]

Claims (13)

Method for stopping an internal combustion engine, wherein when the ignition and / or injection is switched off, an air quantity supplied to the internal combustion engine is initially reduced and increased again after a speed (n) of the internal combustion engine has fallen below a predefinable speed threshold value (ns), characterized in that a first Speed value (n1) at a first sampling time (t1) and a second speed value (n2) at a second sampling time (t2) are determined, wherein the two sampling times (t1, t2) are selected such that the first speed value (n1) and the second rotational speed value (n2) is smaller than the predefinable rotational speed threshold value (ns), and deceleration means for generating a torque decelerating the rotational movement of the internal combustion engine are actuated as a function of the first rotational speed value (n1) and second rotational speed value (n2). The method of claim 1, wherein the braking means are also dependent on a difference (D12) between the first speed value (n1) and the second speed value (n2) are driven.  The method of claim 1 or 2, wherein the braking means are also controlled depending on the speed threshold value (ns) and / or dependent on the first speed value (n1). The method of claim 3, wherein the deceleration means is dependent on a quotient (Q) between the difference (D12) between the first speed value (n1) and the second speed value (n2) divided by a difference (D1s) first speed value (n1) and speed threshold value (ns) be controlled. Method according to one of the preceding claims, wherein the braking means comprise means with which the amount of air supplied to the internal combustion engine is controlled. The method of claim 5, wherein depending on the second speed value (n2) an energy content to be degraded (E) is determined, and wherein the amount of air supplied is increased at a larger energy content to be degraded (E) by a larger amount than at a smaller energy content to be degraded (E) , The method of claim 5 or 6, wherein the supplied amount of air at a larger energy content to be degraded (E) at a later time (bauf ') is performed as a smaller energy content to be degraded (E). The method according to claim 7, wherein the suction cylinder (ZYL1, ZYL3) to which the increased air quantity is first supplied is a first cylinder (ZYL1) if the energy content (E) to be degraded is less than a predeterminable first energy content threshold (Es), and another cylinder (ZYL3) later in the intake order is when the energy content (E) to be degraded is not less than the predefinable first energy content threshold (Es). Method according to claim 8, wherein the energy content (E) to be degraded is newly determined as a function of a third value (n3) of the rotational speed (n), the third value (n3) being determined at a time at which the later cylinder (ZYL3) after the first time (t1) goes into its intake stroke for the first time. Method according to one of the preceding claims, wherein depending on the second speed value (n2) an energy content to be degraded (E) is determined, and wherein the amount of air supplied is increased by a larger amount at a larger energy content to be degraded (E) than at a smaller energy content to be degraded (E), and wherein the braking means comprise means that apply the decelerating torque to a crankshaft of the internal combustion engine, in particular a generator, a valve timing or a pump, and wherein the means are not driven to generate the decelerating torque when the energy content to be degraded ( E) is smaller than a predefinable second energy content threshold (Es2), and be driven to generate the decelerating torque when the energy content to be degraded (E) is not less than the predetermined second energy content threshold (Es2). Computer program which is set up to carry out all the steps of the method according to one of Claims 1 to 10. A machine readable storage medium storing the computer program of claim 11. Control unit which is set up to carry out all the steps of the method according to one of the steps 1 to 10.

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