JPH0820339B2 - Method and apparatus for measuring operating state of displacement machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and a device for measuring the state of a positive displacement machine, and more particularly to a method and device for simply measuring the indicated mean effective pressure in an automobile engine. Regarding

Here, the positive displacement machine is a machine in which a working fluid is positively flowed into a space inside the machine every cycle to generate power and pressure by moving a boundary surface of the volume of the space. That is, the positive displacement machine is not limited to the heat engine, but includes a fluid machine (compressor, pump, hydraulic motor, hydraulic motor, etc.), a refrigerator having a reverse cycle of the heat engine, and the like.

[Conventional technology]

Along with the rapid development of semiconductor technology, computer control of automobile engines has become widespread.
One purpose of such computer control is to improve fuel economy, and for that purpose it is necessary to operate the engine as close to the lean limit as possible.

However, when attempting to perform such engine control, there is a problem that control is difficult because the lean limit itself, which is a control target, deteriorates due to rotational speed, load, atmospheric conditions, and the like. Further, when the lean limit is exceeded, a drastic change in drivability and exhaust characteristics due to an increase in combustion fluctuations and misfires is also a big problem. Therefore, in the conventional engine control focusing only on the air-fuel ratio, the control target is set to the rich side from the lean limit, and high-precision control is often not performed.

Therefore, in order to improve control accuracy in the lean range while maintaining drivability and exhaust characteristics at a certain level, it is useful to use the indicated mean effective pressure Pi, which directly indicates the combustion state of the engine, as engine control information. Yes and desired.

The indicated mean effective pressure Pi is defined as follows, where P is the pressure in the combustion chamber, V is its volume, and V _s is the stroke volume.

In order to actually obtain this, P _i is calculated by the following equation (2) obtained by discretizing equation (1).

Here, P _j is, for example, the j-th pressure data counted from the top dead center among the n pieces of data sampled for each equal crank angle (for example, 1 °) by the A / D converter, and V _j
Means the volume of the combustion chamber at that time. That is, the product of the pressure value read from the acupressure diagram and the change in the volume of the combustion chamber determined from the engine specifications may be numerically integrated over one cycle.

Expression (2) can be executed by using a microprocessor or the like, and an apparatus based on such a method is commercially available as a P _i meter.

[Problems to be Solved by the Invention]

However, in this method, an A / D converter for sampling pressure data in synchronization with the crank angle and a volume data for the angle must be stored in the memory. For example, in the case of a 4-cycle engine, if sampling is performed every 1 °, a total of 720 data of pressure and volume must be handled. As a result, the memory capacity and the calculation time are inevitably increased.

Therefore, even though this method is sufficient for laboratory use, it is difficult to apply it to P _i control of an actual automobile engine.

Therefore, an object of the present invention is to provide a method for measuring an operating state of a positive displacement machine and a device therefor capable of easily and quickly obtaining information indicating an operating state.

[Means for solving the problem]

According to the operating state measuring method for a positive displacement machine according to the present invention, a finger pressure waveform signal, which is related to the stroke cycle of the positive displacement machine in the operating state and represents a pressure change in the combustion chamber, is used to extract the fundamental wave component. A bandpass filter and a second bandpass filter that extracts a harmonic component that is an integral multiple of the previous fundamental wave component are filtered, and the instantaneous values sampled at the angles related to the stroke cycle are expressed by the following equation, However Is an amplitude and ₁ , ₂ , ₄ are combined according to a phase difference to obtain an indicated mean effective pressure value representing an operating state of the positive displacement machine.

The filtering is a process of passing through a first filter for extracting a fundamental wave component and a second filter for extracting a double frequency component, and using the fundamental wave component and the double frequency component, A simpler measurement is possible by synthesizing in accordance with the above and obtaining an approximate value of the indicated mean effective pressure value.

According to the operating state measuring method of the positive displacement machine according to the present invention, the finger pressure waveform signal representing the pressure change in the combustion chamber is related to the stroke cycle of the positive displacement machine in the operating state by the bandpass filter for extracting the fundamental wave component. Filtered,
The instantaneous value obtained by sampling this at the angle related to the stroke cycle is However, Is amplitude and ₁ is a phase difference. By obtaining a rough approximate indicated mean effective pressure value, a simpler measurement is possible.

The positive displacement machine may be a reciprocating engine, and the angle associated with the stroke cycle may be obtained with reference to top dead center.

Further, according to the operating state measuring apparatus for a displacement type machine according to the present invention, a fundamental wave component is extracted from a finger pressure waveform signal representing a pressure change in the combustion chamber, which is related to a stroke cycle of the displacement type machine in an operating state. No. 1 band filter and a second band filter for taking out a harmonic component that is an integral multiple of the fundamental wave component, and sampling means for sampling the values filtered by these filters at angles associated with stroke cycles to obtain instantaneous values. And the sampling result of this sampling means is However Is an amplitude, and ₁ , ₂ , and ₄ are combined according to a phase difference to provide an arithmetic means for obtaining an indicated mean effective pressure value representing an operating state of the positive displacement machine.

The filtering means is a first filter for extracting a fundamental wave component and a second filter for extracting a double frequency component, and the computing means uses the following equation based on the fundamental wave component and the double frequency component. The approximate value of the indicated mean effective pressure value may be obtained by synthesizing according to.

According to the working state measuring device of the positive displacement machine according to the present invention, regarding the finger pressure waveform signal representing the pressure change in the combustion chamber, which is related to the stroke cycle of the positive displacement machine in the working state,
Sampling means for sampling the values filtered by the bandpass filter for extracting the fundamental wave component at an angle associated with the stroke cycle to obtain an instantaneous value, and the sampling result by this sampling means, However, Is an amplitude and ₁ is a calculation means for obtaining a rough approximate indicated mean effective pressure value according to a phase difference.

Preferably, the positive displacement machine is a reciprocating engine and the angle associated with the stroke cycle is determined with reference to top dead center.

Rotation detecting means for generating a voltage proportional to a stroke cycle of the positive displacement machine may be further provided, and the bandpass filter may be of a type in which a center frequency thereof rises according to an output of the rotation detecting means.

[Action]

According to the research conducted by the inventor, the acupressure diagram includes various frequency components, which also includes information related to the heat engine state. Therefore, it has been found that the information indicating the state of the heat engine can be extracted by extracting the specific component. For example, as will be described later, the indicated mean effective pressure Pi can be easily and accurately extracted by extracting and synthesizing frequency components of 1, 2, and 4 times the rotational speed of the engine from the finger pressure waveform.

〔Example〕

 First, the principle of the present invention will be described in detail.

Here, the case of a reciprocating engine in which power is transmitted by a piston / crank mechanism is taken up.

Generally, the phenomenon repeated at a certain cycle T is the angular velocity ω
It can be expressed in the form of a Fourier series as a composition of harmonic vibrations having an angular velocity that is an integer multiple of (= 2π / T).

Now, between the angular velocity ω of the combustion chamber pressure change (acupressure waveform) P (ωt) and the engine angular velocity ω _e , ω = hω
_e (4 cycle engine: h = 1/2, 2 cycle engine: h = 1)
Considering that there is a relationship, P (ωt) can be expressed in the form of Fourier series. Is.

Here, t is time, C _k and φ _k are the amplitude and phase of each harmonic component, and a ₀ is the average value of P (ωt).

On the other hand, if the crank angle based on the top dead center is represented by θ _e , and the cylinder cross-sectional area and the clearance volume are represented by A and V _c , respectively,
Combustion chamber volume V omits higher order elements However, r: crank radius, l: connecting rod length, λ = 1 / r, and therefore the volume change dV can be expressed as follows by differentiating equation (4).

Relationship where θ _e = ω _e t, as well as the formula (3), (5)
By using the equation (1) (where the integration interval is 0 ≦ θ _e ≦
2π / h), the indicated mean effective pressure P _i is obtained as follows.

Here, when paying attention to the equation (6) and extracting the frequency component related to P _i from the equation (3), it is h in the 4-cycle engine.
= 1/2 than _{C 2 sin (ω e t +} φ 2), C 4 sin (2ω e t + φ 4), C 8
Meanwhile _{sin (4ω e t + φ 8} ) (7), in 2-cycle engine than _{h = 1, C 1 sin (} ω e t + φ 1), C 2 sin (2ω e t + φ 2), C 4
_{sin (4ω e t + φ 4} ) and made (8).

That is, it is clear that in both 4-cycle and 2-cycle engines, P _i is determined only by the frequency components 1, 2, and 4 times the engine angular velocity included in the pressure waveform. In order to unify the symbols for both 4-cycle and 2-cycle engines, the amplitudes of the 1st, 2nd, and 4th order components of the rotation speed are If the phase difference is set to ₁ , ₂ , and ₄ , the indicated mean effective pressure P
_{After all, 1} can be expressed by the following equation (6).

From the acupressure waveform, the formula (9) is calculated as 1, which is the engine speed
It suggests that P _i can be detected by extracting frequency components of 2 or 4 times and calculating the equation (9) based on these waveforms.

It is clear from the results in Table 1 that such a measurement principle is valid.

The table shows a Shibaura 4-cycle air-cooled gasoline engine as a heat engine (bore * stroke: 78mm * 62mm, stroke volume: 296c
Using m ² , compression ratio: 7.4, ignition timing: BTDC 23 deg), the acupressure diagram obtained from this was used to confirm the validity of equation (9). The operating condition is the rotation speed.
2430-2510rpm, throttle opening 4/4, and air-fuel ratio A / F
8.7 to 17.2.

The reference value for comparison in Table 1 is the indicated mean effective pressure {P obtained by numerically integrating Equation (1) according to Simpson's 1/3 rule using 720 pressure data sampled for each 1 degree of crank angle. _i } ₀ , and from the amplitude and phase of each component obtained by harmonic analysis of the same pressure data, P _i is Equation (9), and {P _i } ₁₂ is 1/2 of the second term on the right side of Equation (9). Equation (10) in which 4λ ² and the third term are omitted and {P _i } ₁ are average effective pressures calculated from Equation (11) in which all the terms other than the first term on the right side of Equation (9) are omitted. The error e (%) is calculated as | {P _i } ₀ -calculated value | * 100 / {P _i } ₀ .

As is clear from the table, the difference between the reference value {P _i } ₀ , which is the result of numerical integration of formula (1), and P _i according to formula (9) is within 0.05%, and {P _i } ₀ and {P _i } The difference from ₁₂ is within 0.2%. From this, the validity of the above-mentioned measurement principle was confirmed, and the values of P _i and {P _i } ₁₂ were values that were sufficiently practical. Also, {P _i } ₁ is within 9%, which is a practical value depending on the measurement application.

FIG. 1 is a block diagram showing an outline of a Pi meter according to an embodiment of the present invention. Here, for simplification, a type using frequency components up to the second order is shown.

Input Shiatsu waveform P (hω _{e t)} is applied to the input terminal 1, the finger pressure waveform is inputted to the two band pass filters 2 and 3 corresponding to the first-order component and the second order component. The center frequency of these bandpass filters (for example, about 100 Hz for the first-order component) is controlled by the FV converter 5 based on the engine speed detected by the engine speed detector 4 such as a rotary encoder. It is automatically changed according to the value. That is, when the engine speed increases, the voltage generated from the FV converter rises, and the center frequency of the filter rises in proportion to this voltage. This is because it has been found by experiments by the inventor that the setting accuracy of the center frequency has a great influence on the measurement accuracy of Pi.

In this way, the necessary information can be easily obtained only by filtering the acupressure waveform with the filter.

Output of bandpass filter 2 Is a sample hold circuit 6 that operates with the output signal of the ATDC 90deg detection circuit 7 that detects the crank angle 90 ° after top dead center
Causes the first-order component to be sampled and held, Is output. Similarly, the output of bandpass filter 3 Detects a crank angle of 45 ° or 225 ° after top dead center A
The second-order component is sample-held in the sample-hold circuit 6 that operates by the output signal of the TDC45deg detection circuit 9, Is output. this Is multiplied by 1 / 2λ by the multiplier 10 using λ given from the λ setter 11. This value and the output signal of the sample hold circuit 6 Are added in the adder 12, and the coefficient π or π / 2 is further multiplied in the multiplier 13. As a result, the output of the multiplier 13 becomes Pi expressed by the equation (10) and is output from the output terminal 14.

A computer is used to simulate the theoretical values of the first-order frequency component and the second-order frequency component in the case of using such a device, and the acupressure diagram obtained by combining them.
The obtained results are shown in FIG.

FIG. 3 illustrates the error between the theoretical values for the first-order component and the second-order component shown in FIG. 2 and both components obtained by the apparatus of FIG. As can be seen from the figure, these errors are small at 5% or less, and the accuracy of the method of the present invention is sufficiently high. Further, referring to the above-mentioned table, it was proved that practically sufficient accuracy can be obtained by using up to the second-order component.

FIG. 4 is a block diagram showing a part of the configuration of the Pi meter according to another embodiment of the present invention. This figure shows a modified example of the sample hold circuit in FIG. From the sample hold unit 21 And the peak hold unit 22 And calculate from these with the calculator 24 Can be calculated as

FIG. 5 is a block diagram showing a part of the configuration of the Pi meter according to another embodiment of the present invention. In this configuration, the acupressure waveform is differentiated by the differentiator 15 before being input to the bandpass filter, and the output of the adder 12 is multiplied by Vs information to show the output Li shown.
FV converter 5 from the output of multiplier 17 and adder 12
It is almost the same as the embodiment shown in FIG. 1 except that it has a multiplier 18 for removing the frequency component by using the output of FIG.

Next, the operation of this circuit will be described. When the acupressure waveform is passed through BPFs 2 and 3 with cutoff frequencies ω _e , 2ω _e , the output is When Becomes

From there readings of each component in the top dead point given by the TDC detection circuit 7 ', from ω _{e t =} θ _c = 0 Becomes

Since ω _e is included in the above equation, 1 / ω _{e in the} multiplier 18
Is calculated. However, if ω _e is left as it is, the illustrated output Li can be calculated. Considering that the period of one cycle is T, and T = Te / h, the illustrated output Li can be expressed as follows.

Therefore, And the same formula is obtained in 4 cycles and 2 cycles. When a simple measuring device as shown in each of the above examples is used, the amount of data to be handled is small, so a large memory capacity is not required and the calculation time is short. And you can get information for engine control.

 Various modifications can be made to the above embodiments.

First, in order to change the center frequency of the bandpass filter, in the embodiment, a rotary encoder capable of detecting rotations every 1 °, for example, is used. However, if measurement accuracy is not so required, rotations can be detected in some form. It is possible to use things such as rotary pick-ups for electronic fuel injection (EFI). In addition, the ignition signal can be used indirectly.

Further, although the crank angle of 90 °, 45 ° or 25 ° is used for detecting the high frequency component in the above-mentioned embodiment, another crank angle can be selected depending on the characteristics of the engine.

In the embodiment, the acupressure waveform is used as the input waveform,
Although the device is electrically configured by using an electrical component such as a bandpass filter, the present invention is not limited to this.

That is, the present invention is characterized in that information relating to the operating state of the machine is obtained by extracting and synthesizing frequency components from the wave related to the stroke cycle in the positive displacement machine. As a mechanical signal, for example, the engine sound is taken out using an acoustic pickup attached to an arbitrary place of the machine, or a knock sensor or a plug washer type indicator,
A frequency component can be obtained by passing the output signal through a mechanical filter having a specific frequency characteristic. In this case, the above-mentioned first-order frequency component is the center and the accuracy is not always good, but in the case of this configuration, there is an advantage that information can be obtained without performing any calculation. Moreover, in such a configuration, if the shape of the mechanical filter is appropriately designed, it can be integrated with the acoustic pickup, and the size and weight can be made extremely small. Such a simple measuring device can be sufficiently used as a monitor.

As the mechanical signal, a cylinder block deformation signal generated in association with the acupressure waveform can be used.

The first-order component and the second component included in the indicated mean effective pressure Pi
The secondary component tends to increase as Pi increases. According to the inventor's experiments, the ratio of Pi to the first-order component is always
Values around 1.2 are shown. Therefore, it is possible to obtain Pi even with only one bandpass filter in the above embodiment.

Furthermore, in the above-described embodiment, the fundamental wave component and the high frequency component are combined and extracted, but it is possible to extract the information related to the state of the machine only by the amplitude or the phase. In this case, the amplitude can be easily obtained by the configuration shown in the embodiment, and the phase can be easily obtained only by adding a zero cross circuit and a comparator.

[Effects of the Invention] As described above, according to the operating state measuring method for a positive displacement machine according to the present invention, the acupressure waveform signal indicating the pressure change in the combustion chamber is related to the stroke cycle of the positive displacement machine in the operating state. Are filtered by a first bandpass filter for taking out a fundamental wave component and a second bandpass filter for taking out a high frequency component of an integral multiple of the fundamental wave component, and the instantaneous values obtained by sampling these at an angle associated with a stroke cycle are calculated as follows. Since the indicated mean effective pressure value representing the operating state of the positive displacement machine is obtained by combining according to the formula, the operating state of the positive displacement machine can be known easily and with high accuracy.

Further, according to the operating state measuring apparatus for a displacement type machine according to the present invention, a fundamental wave component is extracted from a finger pressure waveform signal representing a pressure change in the combustion chamber, which is related to a stroke cycle of the displacement type machine in an operating state. No. 1 band filter and a second band filter for taking out a high frequency component which is an integral multiple of the fundamental wave component, sampling means for sampling the instantaneous value filtered by these filters at an angle associated with each stroke cycle, and this sampling means. Since the sampling means in (1) is combined according to a predetermined formula to obtain the indicated mean effective pressure value representing the operating state of the positive displacement machine, the result can be obtained at high speed with a simple structure.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an indicated average effective pressure measuring device as an embodiment of a state measuring apparatus for a displacement type machine according to the present invention, and FIG. 2 is a graph showing theoretical values of a method of the present invention, and FIG. FIG. 4 is a graph showing the usefulness of the present invention, FIG. 4 is a block diagram showing the configuration of another embodiment of the state measuring apparatus for a positive displacement machine according to the present invention, and FIG. 5 is a positive displacement type according to the present invention. It is a block diagram which shows the structure of the other Example of the state measuring device of a machine. 1 ... input terminal, 2,3 ... band filter, 4 ... encoder, 5 ... FV converter, 6,8,21 ... sample and hold circuit, 7,7 ', 9,23 ... angle detection circuit, 10,10 ', 12,1
3,13 ′, 17,18,24 …… Calculator, 11 …… λ setter, 14 ……
Output terminal, 15 ... Differentiator, 22 ... Peak hold circuit.

Claims (9)

[Claims] Claim: What is claimed is: 1. A finger-pressure waveform signal, which is related to a stroke cycle of a positive displacement machine in an operating state and which represents a pressure change in a combustion chamber,
A first bandpass filter for extracting a fundamental wave component and a second bandpass filter for extracting a harmonic component that is an integral multiple of the fundamental wave component are filtered, and instantaneous values obtained by sampling these at an angle associated with a stroke cycle are expressed as follows. , However Is an amplitude, and ₁ , ₂ , and ₄ are combined according to a phase difference to obtain an indicated mean effective pressure value representing an operating state of the positive displacement machine, and an operating state measuring method for the positive displacement machine. 2. A first filter for extracting a fundamental wave component and a second filter for extracting a double frequency component.
Process of passing through the filter of
With the double frequency component, 2. An operating state measuring method for a positive displacement machine according to claim 1, wherein an approximate value of the indicated mean effective pressure value is obtained by synthesizing in accordance with. 3. A finger pressure waveform signal, which is associated with the stroke cycle of the positive displacement machine in operation and is representative of pressure changes in the combustion chamber,
The instantaneous value obtained by filtering with a bandpass filter that extracts the fundamental wave component and sampling this at an angle related to the stroke cycle is given by However, Is an amplitude and ₁ is a rough approximation of the indicated mean effective pressure value according to the phase difference. 4. The positive displacement machine is a reciprocating engine,
The operating state measuring method for a positive displacement machine according to claim 1 or 3, wherein the angle associated with the stroke cycle is obtained with reference to top dead center. 5. A first bandpass filter for extracting a fundamental wave component and an integral multiple of the fundamental wave component for a finger-pressure waveform signal relating to a stroke cycle of a positive displacement machine in an operating state and representing a pressure change in a combustion chamber. A second band-pass filter for extracting a harmonic component, a sampling means for obtaining an instantaneous value by sampling the values filtered by these filters at angles associated with the stroke cycle, and a sampling result by this sampling means, However Is an amplitude, and ₁ , ₂ , and ₄ are combined according to a phase difference, and an operating state measuring device for a positive displacement machine is provided, which is provided with a calculating means for obtaining an indicated mean effective pressure value representing an operating state of the positive displacement machine. . 6. The filtering means is a first filter for extracting a fundamental wave component and a second filter for extracting a double frequency component, and the computing means uses the fundamental wave component and the double frequency component. , The following formula The operating state measuring device for a positive displacement machine according to claim 5, wherein an approximate value of the indicated mean effective pressure value is obtained by synthesizing in accordance with the above. 7. A bandpass filter for extracting a fundamental wave component and a value filtered by the bandpass filter for a finger pressure waveform signal representing a pressure change in a combustion chamber in relation to a stroke cycle of a positive displacement machine in an operating state. Sampling means for obtaining an instantaneous value by sampling at an angle related to the cycle, and the sampling result by this sampling means are However, Is an amplitude, and ₁ is a phase-difference operation device for measuring the working state of the positive displacement machine, which is provided with a computing means for obtaining a rough approximate indicated effective pressure value. 8. The positive displacement machine is a reciprocating engine,
8. The operating state measuring method for a positive displacement machine according to claim 5, wherein the angle related to the stroke cycle is obtained with reference to top dead center. 9. A rotation detecting means for generating a voltage proportional to a stroke cycle of the positive displacement machine is further provided, and the bandpass filter is of a type in which a center frequency thereof rises according to an output of the rotation detecting means. The operating state measuring device according to claim 5 or 7.