JP2005264814A - Fuel injection control device of multi-cylinder diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device of a multi-cylinder diesel engine capable of reducing the sound pressure level of a sound emitted from an engine in a specific frequency band. <P>SOLUTION: This fuel injection control device comprises a noise meter 16 measuring the sound emitted from the multi-cylinder diesel engine 10, an FFT 17 analyzing the frequency of an emitted sound signal measured by the noise meter 16, and an ECU 15 controlling the injection of a fuel for each cylinder 11. The ECU 15 interferes combustion/radiation noises from the cylinders 11 with each other by changing the fuel injection control constants of the specific cylinder based on the results of the analysis of the FFT 17. The fuel injection control constants are corrected in the order of pilot injection timing, pilot injection amount, main injection timing, and injection pressure until an actual frequency component analyzed by the FFT 17 matches a specified target value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel injection control device for a multi-cylinder diesel engine, and more particularly to a fuel injection control device for a multi-cylinder diesel engine that can reduce the sound pressure level in a specific frequency band of engine radiated sound.

  Conventionally, as a technique for reducing combustion noise of a multi-cylinder diesel engine (hereinafter simply referred to as an engine), the combustion mode is changed by changing an injection system control constant such as multi-stage injection (pilot injection, multi-injection). Internal pressure control is performed.

  For example, a technique for reducing noise of a specific frequency component of in-cylinder pressure by causing a pilot combustion pressure wave and a main combustion pressure wave to interfere with each other, or pilot injection based on combustion noise caused by pilot injection A technique for reducing combustion noise by controlling the amount has been proposed (for example, see Patent Document 2).

  By the way, the combustion pressure in the cylinder is transmitted to pistons, cranks, cylinder blocks, cylinder heads, etc., which are structural transmission members of the engine, and is heard by the human ear as pressure fluctuations via air, that is, engine radiated sound. Therefore, it is necessary to reduce the sound pressure level in a specific frequency band (for example, 1 to 3 kHz) that is of interest to humans in the audible range.

  Therefore, conventionally, the combustion noise has been reduced by improving the hardware specifications of the engine, by taking hard measures to reduce engine noise with a sound absorbing material, etc., or by improving the fuel injection control to reduce the combustion variation between cylinders as much as possible. Has been implemented.

JP 2002-47975 A JP 2001-123871 A

  However, in recent years, it has been required to cope with exhaust gas regulations and fuel efficiency improvements that have become more and more strict, and there has been a large contradiction with combustion noise caused by combustion pressure, making it difficult to achieve both. In particular, the conventional combustion adaptation reduces the noise level by reducing the in-cylinder pressure. However, even if the in-cylinder pressure level is reduced, the pressure fluctuation transmitted through the engine body is amplified by the resonance of the structural transmission system member. There was a problem that it deteriorated at the actual radiation sound level.

  The present invention has been made in view of the above, and an object of the present invention is to provide a fuel injection control device for a multi-cylinder diesel engine that can reduce the sound pressure level in a specific frequency band of engine radiated sound.

  In order to solve the above-described problems and achieve the object, a fuel injection control device for a multi-cylinder diesel engine according to claim 1 of the present invention includes a noise meter for measuring a radiated sound of a multi-cylinder diesel engine, and the noise meter. And a control device for controlling the fuel injection for each cylinder, the control device being controlled with the same fuel injection control constant for each cylinder. The combustion radiation sound between the cylinders is made to interfere by changing the fuel injection control constant of the specific cylinder based on the analysis result of the frequency analysis device from the combustion state.

  A fuel injection control device for a multi-cylinder diesel engine according to claim 2 of the present invention relates to pilot injection for generating a combustion environment in the cylinder and generation of engine torque according to claim 1. Control means for controlling each injector for fuel injection so as to perform main injection, and the fuel injection control constant is pilot injection until the actual frequency component analyzed by the frequency analysis device matches a predetermined target value. The correction is made in the order of timing, pilot injection amount, main injection timing, and injection pressure.

  According to a third aspect of the present invention, a fuel injection control device for a multi-cylinder diesel engine combusts from an in-cylinder pressure sensor provided in each cylinder of the multi-cylinder diesel engine and an output signal of the in-cylinder pressure sensor. A combustion pressure specifying means for specifying a pressure frequency component, and a control device for controlling fuel injection for each cylinder, wherein the control device is a predetermined map for engine radiation sound control in addition to a normal injection control map. And switching the engine radiation sound control map for one cylinder or a plurality of cylinders based on the combustion pressure frequency component specified by the combustion pressure specifying means, thereby changing the combustion state for each cylinder, and This is characterized in that the combustion radiated sound of this is made to interfere.

  According to a fourth aspect of the present invention, there is provided a fuel injection control device for a multi-cylinder diesel engine, wherein the resonance frequency band of the structural transmission system of the engine is specified in advance and the sound of the resonance frequency band is specified. The engine radiation sound control map is set so as to reduce the pressure level.

  According to a fifth aspect of the present invention, there is provided a fuel injection control device for a multi-cylinder diesel engine according to the fourth aspect, wherein the engine emission sound control map is switched in a specific cylinder in a high engine speed range of the engine. The control is stopped.

  According to the fuel injection control device for a multi-cylinder diesel engine according to the present invention (claim 1), the sound pressure level in a specific frequency band of engine radiated sound can be reduced.

  According to the fuel injection control device for a multi-cylinder diesel engine according to the present invention (claim 2), the fuel injection control constant can be corrected and changed efficiently.

  Further, according to the fuel injection control device for a multi-cylinder diesel engine according to the present invention (claim 3), the sound pressure level in a specific frequency band of the engine radiated sound can be reduced.

  According to the fuel injection control device for a multi-cylinder diesel engine according to the present invention (claim 4), the sound pressure level in the resonance frequency band can be accurately reduced.

  According to the fuel injection control device for a multi-cylinder diesel engine according to the present invention (Claim 5), the control can be simplified in a region where the contribution of the combustion noise to the engine emission noise is small.

  Embodiments of a fuel injection control device for a multi-cylinder diesel engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  The present invention changes a fuel injection control constant of a specific cylinder from a combustion state controlled with the same fuel injection control constant for each cylinder by an injection control device capable of performing fuel injection control for each cylinder of a pressure accumulating multi-cylinder diesel engine. In this way, the combustion radiation sound (specific frequency) between the cylinders is made to interfere, and noise reduction is realized. As this pressure accumulating multi-cylinder diesel engine, a four-cylinder diesel engine (hereinafter simply referred to as an engine) will be described as an example.

  1 is a block diagram showing a fuel injection control device for a multi-cylinder diesel engine according to Embodiment 1 of the present invention. As shown in FIG. 1, the engine 10 includes four cylinders 11, and each cylinder 11 is provided with an injector 12 capable of multistage injection (pilot injection and main injection). The injector 12 is supplied with fuel from a common rail 13 serving as a pressure accumulating chamber, and is driven and controlled by an electronic drive unit (hereinafter referred to as EDU) 14.

  The common rail 13 is provided with a sensor (not shown) that detects the pressure and temperature of the fuel. The engine 10 includes various components (not shown) such as an intake system and an exhaust system.

  Although not shown in the figure, the engine 10 includes an engine rotation sensor that detects the engine speed NE (rpm) and an accelerator sensor that detects the accelerator opening degree accp (%). Various sensors for detecting the pressure, temperature, flow rate, etc. are provided.

  An electronic control unit (hereinafter referred to as “ECU”) 15 as a control device issues a control command to the EDU 14 based on output information from the above-described various sensors, a frequency analysis device (hereinafter referred to as “FFT”) 17 described later, and the like. 10 is controlled. The ECU 15 includes a normal control map for controlling the engine 10 and also includes an experimentally obtained engine radiated sound frequency control map.

  The sound level meter 16 is provided in an engine room (not shown) and measures the radiated sound of the engine 10. The sound level meter 16 is connected to the ECU 15 via an FFT 17 that analyzes the frequency. That is, the frequency of the radiated sound signal measured by the sound level meter 16 is analyzed by the FFT 17, and the ECU 15 performs various control calculations based on the analyzed signal and issues a control command to the EDU 14.

  Next, a control operation according to the first embodiment will be described with reference to FIG. Here, FIG. 2 is a flowchart showing a control method. The following control operation is executed by the ECU 15 and the engine 10 is described as N cylinders (N and n are arbitrary integers, and the cylinder numbers are hereinafter expressed as #n, # n + 1,...).

  The engine 10 is in a combustion state controlled by the same fuel injection control constant (pilot injection amount, injection timing, injection pressure, etc.) for each cylinder 11.

First, the values of the engine speed NE (rpm), the accelerator opening degree accp (%), and the injection amount Qfin (mm ³ / st) are read from the sensors according to the operating state of the engine 10 (step S10).

  Next, the engine radiation sound signal is read by the sound level meter 16 (step S11). Then, the actual frequency component Fact (dB) of the read radiated sound signal is calculated by the FFT 17 (step S12).

Next, the target value Ftrg (dB) of the frequency component of the radiated sound is calculated by the ECU 15 from the engine speed NE (rpm) and the injection amount Qfin (mm ³ / st) read in step S10 (step S13). The target value Ftrg (dB) is set so that the radiated sound can be reduced to a predetermined sound pressure level by causing interference with the radiated sound related to the actual frequency component Fact (dB).

  Here, the concept of the means for reducing the sound pressure level will be described with reference to FIGS. FIG. 3 is an explanatory diagram showing the state of the radiated sound level of the entire engine when the conventional technology is used to adjust the sound pressure level of each cylinder. For example, in the case of a two-cylinder engine, the combustion pressure analysis result of the front injection cylinder And the combustion pressure analysis result of the next injection cylinder show the state of the radiated sound level of the entire engine as indicated by the arrow.

  FIG. 4 is an explanatory diagram showing a state in which the radiated sound level of the entire engine is reduced by the combustion control of the next injection cylinder that generates a frequency that cancels the combustion sound of the pre-injection. From the result of the combustion pressure analysis and the result of the combustion pressure analysis of the next injection cylinder that generates a frequency that cancels the combustion sound of the pre-injection, it is shown that the radiated sound level of the entire engine is reduced as indicated by the arrows. In the first embodiment, the control means shown in FIG. 4 is employed.

  Comparing the two figures, it can be seen that in FIG. 4 that employs the control means according to the first embodiment, the radiated sound pressure level of the entire engine can be reduced compared to the case of FIG. 3. From such a viewpoint, the target value Ftrg (dB) of the frequency component of the radiated sound is set.

  Next, based on the calculation result of step S13, the actual frequency component Fact (dB) of the radiated sound signal is compared with the target value Ftrg (dB) of the frequency component, and if they are equal (step S14), the above step is performed. Return to S10.

  On the other hand, if the actual frequency component Fact (dB) of the radiated sound signal and the target value Ftrg (dB) of the frequency component are not equal (No in step S14), the following operation is performed for one cylinder.

That is, the pilot injection timing Ainjpl (° C. A ATDC), the pilot injection amount Qpl (mm ³ / st), the main injection timing Ainjm (° C. A ATDC), and the injection pressure Pc (MPa) are corrected in this order. This correction is performed until the actual frequency component Fact (dB) matches the target value Ftrg (dB) (steps S15 and S16).

  Further, the same correction is performed for the second cylinder, and finally the same correction is performed up to the number of cylinders N of the engine 10 (N = 4 in the illustrated example) (steps S15 and S16). As described above, the number of cylinders for which constant correction is performed is increased until the actual frequency component Fact (dB) matches the target value Ftrg (dB), and the final injection control constant for each cylinder is determined.

  Here, the tendency of the change in the radiated sound pressure level when the injection control constant of the specific cylinder is changed is shown in FIGS. 5 to 8 for the engine radiated sound of 3 KHz, for example. FIG. 5 is a map showing a change tendency of the radiated sound pressure level when the pilot injection timing is changed, and FIG. 6 is a map showing a change tendency of the radiated sound pressure level when the pilot injection amount is changed.

  FIG. 7 is a map showing a change tendency of the radiated sound pressure level when the injection pressure is changed, and FIG. 8 is a map showing a change tendency of the radiated sound pressure level when the main injection timing is changed. .

  As shown in FIG. 5, the pilot injection timing does not have a linearity in tendency, and becomes minimum at a specific point P1. Further, as shown in FIG. 6, the pilot injection amount also has no linearity in tendency, and becomes minimum at a specific point P2.

  Further, as shown in FIG. 7, when the injection pressure is reduced, the sound pressure level also tends to be reduced. Further, as shown in FIG. 8, the sound pressure level tends to be reduced by the main injection timing retard. Thus, the tendency of the change in the sound emission sound pressure level when the injection control constant of the specific cylinder is changed is previously mapped to the engine sound emission of the specific frequency, and this is stored in the ECU 15. The ECU 15 performs the injection control with the optimum value of the injection control constant based on this map.

  As described above, according to the fuel injection control device for a multi-cylinder diesel engine according to the first embodiment, the specific fuel injection control is performed from the combustion state (see the A pattern in FIG. 9) controlled with the same fuel injection control constant for each cylinder. By changing the injection control constant of the cylinder, the combustion radiation sound (specific frequency) between the cylinders can be made to interfere and noise reduction can be realized (see the B pattern in FIG. 9). Here, FIG. 9 is a graph showing how the sound pressure level at a specific frequency can be reduced by changing the injection control constant.

  FIG. 10 shows how the sound pressure level at a specific frequency can be reduced at a certain pilot interval as the injection control constant, and FIG. 11 shows how the sound pressure level at a specific frequency can be reduced with a certain pilot injection amount. That is, both figures show that at a certain point, the frequency f2 can reduce the sound pressure level more than the frequency f1.

  Here, FIG. 10 is a graph showing how the sound pressure level at a specific frequency can be reduced at a predetermined pilot interval, and FIG. 11 is a graph showing how the sound pressure level at a specific frequency can be reduced with a predetermined pilot injection amount. It is.

  12 is a block diagram showing a fuel injection control device for a multi-cylinder diesel engine according to Embodiment 2 of the present invention, FIG. 13 is a flowchart showing a control method, and FIG. 14 is a cylinder switching control based on the operating state of the engine. It is a map which shows an area | region. In the following description, members that are the same as or correspond to those already described are denoted by the same reference numerals, and redundant description is omitted or simplified.

  In the second embodiment, in addition to a normal control map (not shown) in the ECU 15, an experimentally obtained engine radiated sound frequency control map (not shown) is provided, and a map of one cylinder or a plurality of cylinders is provided. By switching, the combustion state for each cylinder 11 is changed, and the frequency level of the combustion noise radiated from each cylinder 11 is changed. Combustion with frequency characteristics that interfere with the noise generated by the combustion of the previous cylinder 11 is generated in the next cylinder 11, that is, the combustion for each cylinder 11 is changed so as to shift the phase of the specific frequency. Thus, the radiated sound level of the entire engine 10 is reduced.

  In order to perform such control, as shown in FIG. 12, each cylinder 11 is provided with an in-cylinder pressure sensor 20 for measuring the in-cylinder pressure. The ECU 15 includes a normal control map for controlling the engine 10 and an experimentally obtained engine radiated sound frequency control map (engine radiated sound control map). It also has a function as combustion pressure specifying means for specifying the combustion pressure frequency component from the output signal.

  Also, this engine radiated sound frequency control map is set so that the resonance frequency band of the structural transmission system of the engine is specified in advance and the sound pressure level of the resonance frequency band is reduced. It can be reduced with high accuracy.

Further, the ECU 15 includes a map (see FIG. 14) in which a cylinder switching procedure is set based on the operating state of the engine. In FIG. 14, predetermined values α1 (threshold with the middle rotation range) and α2 (threshold with the high rotation range) related to the engine speed NE (rpm) and a predetermined amount related to the injection amount Qfin (mm ³ / st). Values β1 (threshold with the middle injection amount range) and β2 (threshold with the high injection amount range) are experimentally determined in advance as optimum values.

Next, a control operation according to the second embodiment will be described with reference to FIG. First, values of the engine speed NE (rpm), the accelerator opening degree accp (%), and the injection amount Qfin (mm ³ / st) are read from the operating state of the engine 10 (step S20).

A normal injection control constant is read from the signal read in step S20 and a map (not shown) stored in the ECU 15 (step S21). That is, injection pressure Pc (base) (MPa), main injection timing Ainjm (base) (° C. A ATDC), pilot injection amount Qp (base) (mm ³ / st), pilot injection timing Ainjpl pilot injection timing Ainjpl (base) Read (° C A ATDC).

  Next, the injection control constant for each cylinder (#n, # n + 1,...) Whose frequency of combustion sound is changed is read from the signal read in step S21 and the map (not shown) stored in the ECU 15 ( Step S22). This is because for the noise generated by the combustion of the previous cylinder 11, combustion of a frequency characteristic that interferes with the noise is generated in the next cylinder 11 (for example, the phase of a specific frequency is shifted), and the combustion for each cylinder is changed. It is to do.

That is, injection pressure Pc (#n, # n + 1, ...) (MPa), main injection timing Ainjm (#n, # n + 1, ...) (° C A ATDC), pilot injection amount Qp (#n, # n + 1, ...) (Mm ³ / st), pilot injection timing Ainjpl (#n, # n + 1,...) (° C. A ATDC) is read (step S22).

Next, with reference to the map shown in FIG. 14, it is determined whether or not to perform cylinder 11 switching control based on the operating state of the engine 10. If the engine speed NE (rpm) is smaller than the predetermined value α1 and the injection amount Qfin (mm ³ / st) is smaller than the predetermined value β1 (Yes at step S23), #n, # n + 1 , # N + 2,..., Switch cylinders (step S24), and return to step S20.

When the engine speed NE (rpm) is smaller than the predetermined value α1 and the injection amount Qfin (mm ³ / st) is not in the region smaller than the predetermined value β1 (No at Step S23), the engine speed NE ( rpm) is greater than the predetermined value α1 and less than the predetermined value α2, and it is determined whether or not the injection amount Qfin (mm ³ / st) is in the region exceeding the predetermined value β1 and less than the predetermined value β2 (step S25). .

If the engine speed NE (rpm) exceeds the predetermined value α1 and is less than the predetermined value α2 and the injection amount Qfin (mm ³ / st) is in the region exceeding the predetermined value β1 and less than the predetermined value β2 (step) (Yes in S25), #n, # n + 1, # n + 2,..., Change cylinders (step S26), and return to step S20.

If the engine speed NE (rpm) exceeds the predetermined value α1 and is less than the predetermined value α2, and the injection amount Qfin (mm ³ / st) exceeds the predetermined value β1 and is not in the region less than the predetermined value β2 (step) S25 negative), it is considered that the engine speed NE (rpm) exceeds the predetermined value α2 and the injection amount Qfin (mm ³ / st) exceeds the predetermined value β2 (step S27).

  When the engine is in this high speed region, the contribution of combustion noise to engine radiated sound is reduced, so that normal injection control is performed without performing cylinder switching (step S27), and the process returns to step S20. Thereby, control can be simplified. In this way, the final injection control constant for each cylinder is determined.

  As described above, according to the fuel injection control device for a multi-cylinder diesel engine according to the second embodiment, in addition to the normal control map (not shown) in the ECU 15, engine radiated sound frequency control obtained experimentally. It is possible to change the combustion state of each cylinder 11 by changing the map of one cylinder or a plurality of cylinders and to change the frequency level of the combustion noise radiated from each cylinder 11.

  Therefore, with respect to the noise generated by the combustion of the previous cylinder 11, the combustion of the frequency characteristic that interferes with the noise is generated in the next cylinder 11, that is, the combustion for each cylinder 11 is changed so as to shift the phase of the specific frequency. By doing so, the radiation sound level of the whole engine 10 can be reduced.

  As described above, the fuel injection control device for a multi-cylinder diesel engine according to the present invention is useful for a multi-cylinder diesel engine that can reduce the sound pressure level in a specific frequency band of engine radiated sound. It is suitable for a multi-cylinder diesel engine that can reduce the sound pressure level in a frequency band (for example, 1 to 3 KHz).

1 is a block diagram showing a fuel injection control device for a multi-cylinder diesel engine according to Embodiment 1 of the present invention. FIG. It is a flowchart which shows a control method. It is explanatory drawing which shows the mode of the radiation level of the whole engine at the time of controlling by a prior art so that the sound pressure level of each cylinder may be equalized. It is explanatory drawing which shows a mode that the radiated sound level of the whole engine reduced by the combustion control of the next injection cylinder which generate | occur | produces the frequency which cancels the combustion sound of a front injection. It is a map which shows the change tendency of a radiated sound pressure level at the time of changing pilot injection timing. It is a map which shows the change tendency of a radiation sound pressure level in the case of changing pilot injection quantity. It is a map which shows the change tendency of a radiation sound sound pressure level at the time of changing injection pressure. It is a map which shows the change tendency of a radiated sound pressure level when the main injection timing is changed. It is a graph which shows a mode that the sound pressure level in a specific frequency can be reduced by the change of an injection control constant. It is a graph which shows a mode that the sound pressure level in a specific frequency can be reduced by a predetermined pilot interval. It is a graph which shows a mode that the sound pressure level in a specific frequency can be reduced with predetermined pilot injection quantity. It is a block diagram which shows the fuel-injection control apparatus of the multicylinder diesel engine which concerns on Example 2 of this invention. It is a flowchart which shows a control method. It is a map which shows the switching control area | region of the cylinder based on the driving | running state of an engine.

Explanation of symbols

10 engine (multi-cylinder diesel engine)
11 cylinder 12 injector 13 common rail 14 EDU
15 ECU (control device)
16 Sound level meter 17 FFT (frequency analyzer)
20 In-cylinder pressure sensor

Claims (5)

A sound level meter that measures the radiated sound of a multi-cylinder diesel engine;
A frequency analyzer for analyzing the frequency of the radiation signal measured by the sound level meter;
A control device for controlling fuel injection for each cylinder;
With
The control device changes the fuel injection control constant of a specific cylinder from the combustion state controlled with the same fuel injection control constant for each cylinder, based on the analysis result of the frequency analysis device, thereby causing combustion between the cylinders. A fuel injection control device for a multi-cylinder diesel engine, characterized by causing radiation noise to interfere. Control means for controlling each injector for fuel injection so as to perform pilot injection for forming a combustion environment in the cylinder and main injection related to generation of engine torque;
The fuel injection control constant is corrected in the order of pilot injection timing, pilot injection amount, main injection timing, and injection pressure until the actual frequency component analyzed by the frequency analysis device matches a predetermined target value. The fuel injection control device for a multi-cylinder diesel engine according to claim 1. An in-cylinder pressure sensor that is provided in each cylinder of the multi-cylinder diesel engine and measures the in-cylinder pressure;
Combustion pressure specifying means for specifying a combustion pressure frequency component from the output signal of the in-cylinder pressure sensor;
A control device for controlling fuel injection for each cylinder;
With
The control device includes an engine emission sound control map set in advance in addition to a normal injection control map, and the one or a plurality of cylinders is configured based on the combustion pressure frequency component specified by the combustion pressure specifying means. A fuel injection control device for a multi-cylinder diesel engine, wherein a combustion state for each cylinder is changed by interchanging an engine radiation sound control map to cause interference between combustion radiation sounds between the cylinders.   The resonance frequency band of the engine structure transmission system is specified in advance, and the engine radiation sound control map is set so that the sound pressure level in the resonance frequency band is reduced. Fuel injection control device for multi-cylinder diesel engines.   5. The fuel injection control device for a multi-cylinder diesel engine according to claim 4, wherein switching control of the engine radiation sound control map for a specific cylinder is stopped in a high engine speed range.

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