DE102007047723A1 - Pressure change determining method for engine cylinder of internal combustion engine i.e. four-stroke engine, in vehicle, involves detecting whether pressure change takes place within engine cylinder - Google Patents

Abstract

The method involves providing a non-actively controlled actuator (50) with sensory characteristics in a surrounding of an engine cylinder. The voltage at the non-actively controlled actuator is measured within a predetermined voltage range. The measured voltage is compared with a reference voltage. The detection is made whether the pressure change takes place within the engine cylinder when the measured voltage deviates from the reference voltage. The movement of a piston in the engine cylinder is determined based on the detected pressure change. An independent claim is also included for a pressure change determining device comprising an actuator.

Description

The The invention relates to a method for determining a pressure change within an engine cylinder of an internal combustion engine. Furthermore it concerns the invention a device for determining a pressure change within an engine cylinder of an internal combustion engine.

The EP 1 138 902 B1 describes a method and a device for time-controlled voltage measurement in a charge circuit of a piezoelectric element. With the aid of such a method and a corresponding device, it should be possible to monitor the application of a voltage to the piezoelectric element for operating the piezoelectric element.

The The problem underlying the invention will be described below by way of example a four-stroke engine described. However, the invention is not on limited to a four-stroke engine, but also to others Motor types applicable.

In front injecting a fuel into a four-stroke engine for starting of the four-stroke engine, it is necessary to determine in which rotational position itself a crankshaft with respect to a rotational position of a camshaft of the four-stroke engine is located. This is necessary because the crankshaft of the four-car engine at twice the angular velocity turns as the camshaft. Most is the top dead center of a Piston determined. Dead centers are the positions of the Crankshaft of the four-stroke engine, in which the piston no movement in the axial direction. One differentiates between the top and the bottom dead center. Is the piston in the top dead center, so is an upper surface of the piston near the cylinder head. At bottom dead center is a distance between the top of the piston and the cylinder head bigger.

traditionally, is the top dead center of the piston of the first cylinder means determined a donor wheel, which is attached to the camshaft is and acts on a fixed camshaft sensor. The The sender wheel and the camshaft sensor together are relative, however expensive. To additionally claimed attaching the camshaft sensor on a four-stroke engine additional space.

Desirable It would therefore be more cost effective and / or less space requiring possibility to determine of top dead center of at least one piston.

The The invention provides a method for determining a pressure change within an engine cylinder of an internal combustion engine with the Features of claim 1 and a corresponding device with the features of claim 11.

The The present invention is based on the recognition that a movement a piston of an internal combustion engine, a pressure change inside the engine cylinder and / or a mechanical movement causes the cylinder head in the form of structure-borne sound. there is also provided in the area, cheaper Actuator deformed at least slightly.

By this slight deformation of the actuator becomes a voltage change generated at the non-actively activated actuator. This voltage change can be combined with a cost-effective and Determine little space requiring electronics. As is the actor only a small size must exist thus a cost-effective and no additional Space requiring possibility to determine an upper Dead center of at least one piston of the internal combustion engine. By the Use of this sensitive effect can be the camshaft sensor and the Nockenwellengeberrad omitted.

One additional advantage is that in the majority of engines the actuator outside the oil-wetted camshaft housing is appropriate. This eliminates oil-tight cable guides or connectors for signal line.

Of the Actuator can be a piezoelectric actuator, a magnetostrictive Actuator or an actuator made of a magnetic shape memory alloy. For example, the actuator is a single piezocrystal. Such a Actuator behaves by the mechanical bias means a spring like a spring-mass system. Likewise, several can Piezocrystals, magnetorestrictive crystals or multiple layers a shape memory alloy in non-actively operated State to a voltage, a voltage change, a Current and / or a current change are examined to to detect a pressure change.

It It is hereby noted that it is to carry out the process of the invention is not necessary is to determine a current pressure in the cylinder as a numerical value. It is sufficient to determine the times or crankshaft angles in which a significant pressure changes occurs. Indeed For example, the present invention can also be used to control the pressure progression during operation of the internal combustion engine.

In one embodiment of the method, it is recognized that an actual pressure within the engine cylinder increases, as far as the measured Voltage is greater than the reference voltage. In this case, the comparison voltage is provided by at least one previous time, a voltage applied to the non-actively driven actuator voltage is measured. As an alternative or in addition to the comparison voltage, a comparison voltage change, a comparison current and / or a comparison current change can also be specified.

In A preferred embodiment of the method becomes available measuring the voltage applied to the non-driven actuator a voltage picked up on the actuator to the predetermined voltage range filtered. In particular, the act taken on the actuator is Voltage to a voltage range between -1 V and 1 V, preferably to a range between -300 mV and 300 mV, filtered. In this way, those through the Pressure change in the vicinity of the actuator caused voltage changes be detected without a measuring device thereby obstructed too high positive or negative interference voltages becomes. Above all, the possibility exists for reliable Measuring small amounts of voltage up to to 200 mV with fast edges, the z. B. with respect to the Actuator voltage during operation are voltage resistant. In this case, the actuator voltage in Operation have an amount between 100 V to 500 V.

additionally be in a training before measuring radio frequency interference filtered out. This is beneficial because high frequency noise, such as for example, mobile phone signals, voltages in the connected to the actuator, can produce relatively long lines. By filtering out this Radio frequency interference is prevented by mistake caused by the interference signals, for example cell phone signals, caused voltage changes as pressure changes within the cylinder.

In A preferred embodiment of the method is by means of detected pressure change a movement of a in the engine cylinder arranged piston determined. For example, it is recognized that the piston is in its top dead center in the engine cylinder, if the measured voltage assumes a maximum voltage value.

When Alternatively, by means of a sudden change of direction the pressure change the top dead center of the piston in the engine cylinder be determined. Due to the movement of the piston, the air in the Cylinder compressed or decompressed. This results in voltage edges at the measured voltage. The top dead center can be thus reliably determine.

In a preferred embodiment is considered, that it is also an interference pulse at voltage edges can act on the measuring input of the microcomputer. That's why at least one wait second pulse before the dead point is determined. The location of the two pulses is in accordance with the defined ignition sequences the cylinder. By detecting the crankshaft gap are clear references regarding the position of the crankshaft to the camshaft possible. If the assignment is implausible, so another impulse must be awaited until a plausible Determine assignment. That way a reliable reference of the crankshaft position with respect to Determine camshaft position.

In Another preferred embodiment is as an actuator provided with an injector actuator with sensory properties. By a pressure change in the area of the engine cylinder it comes with a compression or a decompression at least a slight deformation of the cylinder, for example on the cylinder head. This deformation affects the built-in cylinder head Injector and the integrated actuator in it. This way will a voltage in a not actively driven at this time Actuator built. In this preferred embodiment eliminates the need to attach an additional sensor, such as a camshaft sensor, for determining a Reference for the crankshaft positions. It offers one space saving and cost effective way to Determine this reference as a conventionally already existing actuator of an injector used back can be. This additionally guarantees a multifunctionality the actuator of the injection valve.

The The advantages described in the upper sections also apply to a corresponding device. The previous circuit concept to control the injection output stages of actuators can be easily add a measuring circuit. by virtue of The circuit concept will be the power output stages in their principle of action not changed.

The inventive method and the corresponding Device also make it possible to reverse the polarity of an injector, a deformed piezoelectric actuator, a broken piezo element or a layer delamination based on the measured voltage signals determine. Furthermore, it can also be interrupted Lines, leaking engine valves or poor compression of a single cylinder prove.

Further Features and advantages of the present invention will become apparent below explained with reference to the figures. Show it:

1 a circuit diagram of an embodiment of the apparatus for detecting a pressure change within an engine cylinder of an internal combustion engine; and

2a to 2d and 3 Diagrams with voltage curves, which are measured with the embodiment of the device and simultaneously measured pressure curves.

1 shows a circuit diagram of an embodiment of the device for detecting a pressure change within an engine cylinder of an internal combustion engine. The device comprises a piezoelectric actuator device 10 connected to a vehicle battery 12 and to a central ground 14 connected. Between the vehicle battery 12 and the actuator device 10 is a filter 15 arranged. On both sides of the filter 15 are capacitors 16 and 18 arranged.

The piezoelectric actuator device 10 may be part of an injection valve, not shown, for filling a fuel in the internal combustion engine. Likewise, a part of the piezoelectric actuator device 10 be arranged away from the internal combustion engine. For example, in this case, only the piezocrystals 46 . 48 and 50 Components of the injection valve. It is expressly pointed out here that the piezoelectric actuator device 10 not like in 1 shown, must be designed as a compact unit.

The piezoelectric actuator device 10 consists of a DC-DC converter 20 , a power amp 22 and an actuator and selector circuit 24 , The DC-DC converter 20 , the power amp 22 and the actuator and selector circuit 24 be from a controller 26 controlled so that the injection valve is opened or closed.

The DC-DC converter 20 includes a voltage converter 28 , a diode arranged behind it 30 and a capacitor 32 , Furthermore, the DC-DC converter 20 a transistor 34 on, which is parallel to the diode 30 and to the capacitor 32 is arranged.

Within the power amp 22 is a charge switch 36 and a discharge switch 38 appropriate. The switches 36 and 38 be from the controller 26 connected. In addition, the power amplifier indicates 22 a diode 40 , a throttle 42 and a resistance 44 on.

Through the interaction of the vehicle battery 12 , the capacitor 32 , the charging switch 36 and the discharge switch 38 voltages are applied to the piezocrystals 46 . 48 and 50 the actuator and selection circuit 24 created. With the help of the selector switch 52 to 56 the actuator and selection circuit 24 can be at least one of the piezocrystals 46 to 50 to be selected. Furthermore, the actuator and selection circuit 24 another resistance 58 on.

To determine the crankshaft position, a measurement of a pressure change with a piezoelectric actuator is sufficient. In this case, the piezoelectric actuator, for example, the piezoelectric crystal 50 , not actively activated. The not actively controlled piezoelectric crystal 50 is with respect to the power amplifier 22 for controlling the injection stages with the charging switch 36 and the discharge switch 38 There is therefore no low-resistance connection of the piezocrystal 50 to a supply voltage or to a ground.

According to the invention is within the two lines, which with the piezoelectric crystal 50 are connected, a first coupling point 60a and a second coupling point 60b arranged. To the first coupling point 60a a capacitor C1 is connected. Behind the capacitor C1 is a ground G1. Between the ground G1 and the capacitor C1, a transistor T1 is arranged. The transistor T1 is, for example, a MOSFET or an analog switch consisting of a plurality of MOSFETs.

The circuit S1 composed of the capacitor C1, the transistor T1 and the grounding G1 serves the piezocrystal 50 high frequency or with respect to a high frequency to ground. At the same time, the capacitor C1 prevents overloading of the transistor T1, since DC voltage currents are filtered out due to residual charges.

To the second coupling point 60b another circuit S2 is connected. In this case, the circuit S2 consists of a capacitor C2, which directly to the second coupling point 60b connected is. The capacitor C2 is used with the capacitor C1, a measuring device described in more detail below 66 in normal operation of the injector from the up to 500 V high voltages for controlling the injection output stages to decouple.

Behind the capacitor C2, a resistor R1 is attached. This resistor R1 is used to limit high-voltage pulses. On the side facing away from the capacitor C2 of the resistor R1 is a first branch point 62a arranged. The first branch point 62a connects the line to the capacitor C2 and the resistor R1 to another line which leads to a ground G2. Between ground G2 and the first branch point 62a is a diode D1 on whose flow direction from the ground G2 to the first branch point 62a is directed. Furthermore, the first branch point connects 62a the line with the capacitor C2 and the resistor R1 with another line with a diode D2 and a battery 64 , The flow direction of the diode D2 is from the first branch point 62a to the battery 64 directed. The voltage clamp composed of the ground G2 and the two diodes D1 and D2 serves to derive voltages outside a predetermined voltage range to the battery 64 ,

Behind the first branch point 62a is a second branch point 62b arranged. The second branch point 62b is via a first line with a measuring device 66 connected. Via a second line is the second branch point 62b connected to a capacitor C3 and a grounding G3 arranged behind it.

The capacitor C3, together with the resistor R1, serves as a filter for suppressing high-frequency noise to that of the measuring device 66 measured voltages. Due to the relatively long lines of in 1 sketched embodiment of the device, high-frequency signals, such as mobile phone signals, induce voltages in the lines. With the help of the resistor R1 and the capacitor C3, a low-pass filter can be realized, which filters out unwanted high-frequency interference.

The circuits S1 and S2 ensure that only voltages within a predetermined voltage range at the measuring device 66 issue. The voltage range can be between -1 V and U _BAT +1 V. This is important because the stresses that occur at a pressure on the piezocrystal 50 be induced in this, are relatively small compared to the operating voltage of the piezoelectric crystal 50 , If the circuits S1 and S2 were not present, these relatively low voltages could be used with the one not shown, between the first coupling point 60a and the capacitor C1 arranged voltage divider for measuring the piezoelectric voltages in normal operation hardly detect. By the circuits S1 and S2, however, even low voltages and voltage edges can be detected. Furthermore, there is the risk that the relatively high operating voltages during normal operation of the piezoelectric crystal 50 the relatively sensitive measuring device 66 would damage quickly.

The measuring device 66 Forwards the applied voltages to an AD converter and a microcomputer connected to it. Alternatively, a capture-compare unit of a microcomputer can be used. In a further step, based on the measured voltages on a cylinder head, on which the piezoelectric crystal 50 is attached, acting current pressure or pressure change are determined. The specific pressure can be used to determine when the piston is close to the cylinder head. In this way, a clear reference with respect to the position of the crankshaft to the camshaft can be derived.

It should be pointed out once again that to implement the present invention, only the circuits S1 and S2 must be coupled to a conventional device for controlling an actuator with at least one actuator. Since the elements of the circuits S1 and S2 are inexpensive and require little space, thus provides an easy-to-implement way to detect a pressure change within a cylinder head of an internal combustion engine and thus to determine the top dead center of the piston. For example, the circuits S1 and S2 can be easily mounted in a central control unit and via a cable harness with the piezoelectric crystal 50 connect.

In All circuits may be useful in series with a ground switch install a current limiting resistor to those in the fast and high switching edges during normal operation of the Power output stage occurring capacitive displacement currents in the parasitic capacitances of the transistors to limit.

Using the basis of the 1 described device can be obtained even more information. For example, it can be detected with the device a polarity reversal of the piezoelectric actuator, since in this case the signals are inverted. Likewise, a deformed piezoelectric actuator, a broken piezoelectric element or a layer delamination can be detected on the basis of too small signals. Furthermore, the device can detect broken lines, leaking engine valves or poor compression of a single cylinder. With a low-side line break, a selected assignment is also possible.

The 2a to 2d show diagrams with voltage curves, which are measured with the embodiment of the device and simultaneously measured pressure curves. In this case, a rotational speed of a crankshaft of an internal combustion engine to which the embodiment of the apparatus is mounted varies in a range of 50 rotations per minute up to 200 rotations per minute.

As based on the 2a to 2d can be seen, the voltage curves U at all un different rotational speeds pronounced maxima on. The maxima can be used to determine the times, angles of rotation or crankshaft angles at which a pressure p has a maximum value or a maximum change. These maximum pressure values or maximum pressure changes are always detected when the crankshaft is at top dead center and the piston top is close to the cylinder head. Accordingly, the angle at which the piston is at top dead center can also be determined.

in the Case of a capacitive coupling of the measuring circuit, which in particular is necessary for actuators with high operating voltages, creates a Differentiation of the waveform. This results in the signal pieces with the greatest change speeds the largest output amplitudes. This can be beneficial be exploited to only above a certain detection threshold to deliver a digital signal to the evaluation computer. The flat Flanks generate only small voltages and are therefore below the threshold. Depending on the speed, for example from a crankshaft signal, a threshold shift can occur to increase the evaluation security.

at Such an evaluation circuit can be based on a capacitive blocking to be dispensed with. It is particularly advantageous the evaluation of the zero crossings of the useful signal by means a method known for inductive incremental sensors, in which these zero crossings are evaluated and a Activation wave from a maximum value of the signal or the previous one Signals is derived.

there can also be a shift of the reference value "zero crossing" occur when closely spaced two similar zero crossings or smaller signals or noise between the wanted signals must be hidden. A shift of the reference value in Direction of a negative value can be here despite double edges to one lead to safe evaluation, since the amplitude of an applied Vibration or noise in the signal is considerably smaller. The threshold shift may be in addition to the known Dependence on an amplitude maximum value or a previous signal also still dependent on the current one Pulse frequency, which represents the speed executed become.

3 shows a further example of a voltage curve U measured with the first embodiment of the device and a simultaneously measured pressure p in the cylinder. In this example, the rotational speed of the crankshaft is increased. It can be seen that regardless of the rotational speed of the crankshaft, the top dead center of the crankshaft is detectable due to a pronounced maximum.

In an alternative embodiment, the invention can also be used to determine the pressure prevailing in the engine cylinder pressure based on the voltage curve U. In this case, pressure values, as they are for the pressure p in the 2 and 3 shown, calculate.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1138902 B1 [0002]

Claims (22)

Method for determining a pressure change within an engine cylinder of an internal combustion engine, comprising the steps of: - providing an actuator ( 50 ) with sensory properties in an environment of the engine cylinder; - Measuring an actuator that is not actively activated ( 50 ) applied voltage (V) within a predetermined voltage range; - Providing a comparison voltage; - comparing the measured voltage (V) with the reference voltage; and - detecting that a pressure change has taken place within the engine cylinder, as far as the measured voltage (V) deviates from the comparison voltage. The method of claim 1, wherein it is recognized that a current pressure within the engine cylinder increases, provided the measured voltage (V) is greater than the reference voltage is. A method according to claim 1 or 2, wherein the comparison voltage is provided by at least one preceding time an on the non-actively activated actuator ( 50 ) applied voltage (V) is measured. Method according to one of the preceding claims, wherein prior to measuring the actuator which is not actively actuated ( 50 ) voltage (V) on the actuator ( 50 ) is filtered to the predetermined voltage range. The method of claim 4, wherein the at the actuator ( 50 ) voltage is filtered to a voltage range between -1 V and 1 V, preferably to a range between -300 mV and 300 mV. A method according to claim 4 or 5, wherein before measuring Radio frequency interference are filtered out. Method according to one of the preceding claims, wherein by means of the detected pressure change a movement a piston arranged in the engine cylinder is determined. The method of claim 7, wherein it is recognized that the piston is in its top dead center in the engine cylinder, provided the measured voltage (V) has a maximum voltage value accepts. Method according to one of the preceding claims, wherein by means of a sudden change in direction of the Pressure change the top dead center of the piston in the engine cylinder is determined. Method according to one of the preceding claims, wherein as actuator ( 50 ) is provided with an injector actuator with sensory properties. Device for determining a pressure change within an engine cylinder of an internal combustion engine - having an actuator which can be fastened in an environment of the engine cylinder ( 50 ) with sensory properties; - with a measuring device ( 66 ) for measuring an actuator which is not actively actuated ( 50 ) with an evaluation device, which is designed to compare the measured voltage (V) with a comparison voltage provided, and to detect that a pressure change has taken place within the motor cylinder, provided the measured Voltage (V) deviates from the reference voltage. Apparatus according to claim 11, wherein the evaluation device additionally designed by means of the measured voltage (V) a movement of a piston arranged in the engine cylinder to investigate. Apparatus according to claim 12, wherein the evaluation device additionally designed to be a top dead center of Recognize the piston by means of a maximum of the measured voltage (V). Apparatus according to claim 11 or 12, wherein the Evaluation device is designed in addition to a Change of direction and a steep slope that follows to recognize the measured voltage (V). Apparatus according to claim 14, wherein the evaluation device in addition to this, based on the change of direction and the steep edge of the measured voltage (V) top dead center to recognize the piston. Device according to one of claims 11 to 15, wherein the device comprises a filter device (S1, S2) for filtering one on the actuator ( 50 ) has picked up voltage to the predetermined voltage range. Device according to claim 16, wherein the filter device (S1, S2) is designed to be connected to the actuator ( 50 ) to a voltage range between -1 V and 1 V, preferably to a voltage range between -300 mV and 300 mV. Apparatus according to claim 16 or 17, wherein the Filter means (S1, S2) a low pass filter (R1, C3, G3) for Filtering out high frequency noise. Apparatus according to claim 18, wherein the filter means (S1, S2) comprises the following components: - a first input for coupling to a first contact point ( 60a ) of the actuator ( 50 ) with a first capacitor (C1) connected to the first input, with a first ground (G1) connected to the first capacitor (C1) on the side of the first capacitor (C1) remote from the first input, and with one between the first capacitor (C1) and the first ground (G1) arranged first transistor (T1), and - a second input for coupling to a second contact point ( 60b ) of the actuator ( 50 ) with a second capacitor (C2) connected to the second input, with a first output, which is connected to the second capacitor (C2) on the side of the second capacitor (C2) remote from the second input, for coupling to the measuring device ( 66 ), comprising a voltage clamp (G2, D1, D2) arranged between the second capacitor (C2) and the first output for deriving voltages outside the predetermined voltage range and at least partially between the second capacitor (C2) and the first output arranged low-pass filter (R1, C3, G3). The device of claim 19, wherein the voltage clamp (G2, D1, D2) comprises two series-aligned and equally-aligned diodes (D1, D2), one contact point (G2, D1, D2). 62a ) between the two diodes (D1, D2) between the second capacitor (C2) and the first output, wherein the first diode (D1) between a second ground (G2) and the contact point ( 62a ), wherein the flow direction of the first diode (D1) from the ground (G2) to the contact point () 62a ) and the second diode (D2) is connected between a second output for coupling to a voltage storage unit (12). 64 ) and the contact point ( 62a ), wherein the flow direction of the second diode (D2) from the contact point ( 62a ) is directed to the second output. An apparatus according to any one of claims 18 to 20, wherein the low-pass filter (R1, C3, G3) comprises a third capacitor (C3) having a third ground (G3) disposed on one side of the third capacitor (C3) and one on the other side of the third capacitor (C3) arranged branch point ( 62b ) for arranging at least parts of the low-pass filter (R1, C3, G3) in the filter means (S1, S2). Method according to one of claims 11 to 21, wherein the actuator ( 50 ) with sensory properties is an injector actuator.