RU2258917C2 - Piston machine current cylinder volume converter device - Google Patents

Abstract

FIELD: internal combustion engines.

SUBSTANCE: device has serially connected optical position indicator, pulse set-point generator, low frequency filter, control signal generator, differential cascade, saw-shaped signal generator and sinα function generator, which through commutating device are connected to filters packet input, output of which is connected to inputs of generators of sin2α, sin²α, cosα and to first input of first adder device. Outputs of generators of sin2α and sin²α are connected respectively to first inputs of first and second multiplication devices. Scale converter of λ_d value is connected to second inputs of first and second multiplication devices, output of first of which is connected to second input of first adder device, while outputs of second one, generator of cosα and time scale converter of value ε are connected to inputs of second adder device, output of which is connected to first input of third multiplication device, and its second input - to V_h value scale converter. Control of converters for λ_d, ε and V_h is performed by operator using device control panel.

EFFECT: simplified construction, higher precision, higher efficiency.

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Description

The invention relates to the field of testing internal combustion engines (ICE), reciprocating compressors, in particular to measuring devices for assessing the technical condition of heat engines, and can be used in the design of these devices when diagnosing ICE and compressors in operating conditions.

Known measuring devices for assessing the technical condition of ICEs, where magnetic devices, photoelectric circuits, etc. are used as converters of the current cylinder volume [1, 2]. Such converters, if, on the one hand, additionally, there are optoelectronic junctions and electrical circuits, and on the other hand there are disks with special slots, they are quite complex and practically not applicable on operating engines.

There are also transducers built into the measuring complexes for monitoring the technical state of the internal combustion engine, where pulses are generated using, for example, the 31st or 361st mark [3] mounted on the flywheel, especially for controlling the collection of dynamic information. Further, through analog-to-digital conversion, information (corrected in frequency) is fed to the microcomputer. However, this method of forming the function of the volume of gases in the cylinder V (α), winning in accuracy, is difficult in its constructive implementation (a large number of marks on the flywheel, the complexity of installation and devices for each specific engine).

Thus, the complication of the transducers of the cylinder volume and the movement of the piston in the cylinder and the higher prices for them lead to the fact that the degree of their use in measuring systems for monitoring the technical condition of the piston ICE and compressor during testing is practically limited only by laboratory or bench conditions.

Among the known devices, the closest in technical essence to the claimed converter is the device of the converter of the current cylinder volume described in [4] and intended to generate the function V (α). This device contains a generator of the function sinα, scale converters of constant values λ _∂ , ε, V _h , generators sin2α, cosα and sin ² α, the first, second and third multiplying devices, the first and second summing devices, and the outputs of the generators sin2α and sin ² α respectively connected to the first input of the first and second multiplying devices, and a scale converter λ _{∂ is} connected to the second input of the first and second multiplying devices, the output of the first multiplying device is connected to the second input of the first sum of the multiplying device, and the outputs of the second multiplying device, the shaper cosα and the scale converter ε are connected to the inputs of the second summing device, the output of which is connected to the first input of the third multiplying device, and its second input to the scale converter V _h .

A disadvantage of the known Converter is the following. Since the synchronous AC machines used in it - tachogenerators are not specially designed to reproduce the sinα function in measuring devices, the signal is received with interference. The percentage of high-frequency components is high (up to 30%). Therefore, in practice, it is necessary to introduce a filter into the circuit [1]. Great interference also occurs when using magnetic drums mounted on the crankshaft of the engine as a sinα generator [2, 4].

The second disadvantage is the dependence of the output voltage on the rotational speed of the motor shaft. Obtaining a voltage-stable signal using an automatic gain controller with deep adjustment, as experiments show, is difficult due to the unreliability of the electronic circuit.

The invention solves the problem of eliminating the above-mentioned disadvantages, as well as simplifying and optimizing the operation of the device of the converter of the current volume of the cylinder of the piston machine and the possibility of its use on the internal combustion engines and compressors.

This is achieved by the fact that to obtain the function of the volume of gases in the cylinder V (α), only one mark is "removed" from the shaft (flywheel) of the engine during the working cycle. The engine top dead center (TDC) was selected as the only label. To do this, in the device of the converter of the current cylinder volume of the piston machine containing the generator of the function sinα, constant-scale converters λ _∂ , ε, V _h , the formers sin2α, cosα and sin ² α, the first, second and third multiplying devices, the first and second summing devices moreover, the output of the shaper sinα is connected to the inputs of the shapers sin2α, cosα and sin ² α, as well as to the first input of the first summing device, the outputs of the shapers sin2α and sin ² α are connected respectively to the first input of the first and second multiplying their devices, and the scale converter λ _{∂ is} connected to the second input of the first and second multiplying devices, the output of the first multiplying device is connected to the second input of the first summing device, and the outputs of the second multiplying device, cosα former and the scale converter ε are connected to the inputs of the second summing device the output of which is connected with the first input of the third multiplying device, and its second input with a scale converter of the magnitude V _h , according to the invention, Additionally, there is a TDC position sensor made optically and connected in series with a master pulse generator, a differential cascade, a sawtooth signal generator, a sinα driver, through a low-pass filter (LPF) and a control signal driver with a switching unit with a Chebyshev filter package.

The theoretical justification of the method on which the operation of the inventive device is based is given in graphs I and II. These graphs show the calculated dependences of the methodological relative error in determining the average indicator pressure p _i and the recorded heat-release rate curves when implementing the proposed method for generating the function V (α). Along with the method for determining p _i and phases of the combustion process during operation of the device from one TDC mark removed from the flywheel, methods based on the collection of more detailed information (31, 61, 361 labels and more) followed by analog-to-digital conversion were considered. As the calculations show, the relative errors in determining p _i do not exceed 1.0%, and the studies were carried out at different degrees of uneven rotation of the motor shaft and for a different number of cylinders. Errors that occur during registration of heat-release intensity curves practically do not affect the phase characteristics of the combustion process.

It should be noted that the functionally converting the current cylinder volume of the piston engine is performed depending on the geometry of the crank mechanism of the engine.

In the case of the most common axial mechanisms, we have:

where V _h is the working volume of the cylinder, ε is the compression ratio, λ _δ is the ratio of the radius of the crank to the length of the connecting rod, α is the angle of rotation of the crankshaft of the engine.

The invention is illustrated graphically (figure 1-4). Figure 1 presents a block diagram of a device. As follows from figure 1, in addition to the cylinder of the engine 1 and the crankshaft with the flywheel 2, the device includes a BMT 3 optical position sensor, a pulse generator 4, a low-pass filter (LPF) 4.1, a driver of the control signal 4.2, a differential cascade 5, a sawtooth signal generator 6, a generator of the function sinα 7, which are connected through the switching device 8 to the input of the Chebyshev filter package 9, the output of which is connected to the inputs of the formers sin2α 13, sin ² α 14, cosα 15, as well as to the first input First Adder 17.

The outputs of the formers sin2α 13, sin ² α 14 are connected respectively to the first input of the first and second multiplying devices 16, and the scale converter λ _∂ 10 is connected to the second input of the first and second multiplying devices 16.

The output of the first multiplying device 16 is connected to the second input of the first summing device 17, and the outputs of the second multiplying 16, the shaper cosα 15 and the scale converter ε 11 are connected to the inputs of the second summing device 17, the output of which is connected to the first input of the third multiplying device 16, and the second its input is connected to a scale converter V _h 12.

The control of the scale converters λ _∂ , ε and V _{h is} carried out by the operator from the remote control 18 of the device. These values are set each time before testing, depending on the type of engine.

Figure 2 shows the timing diagrams of the sinα generator and uses the following notation: U _o - output voltage of the signal, V; τ - current time, s.

The device Converter operates as follows. The pulse corresponding to the TDC from the output of the optical sensor 3 through the master pulse generator 4 is converted into a square wave and fed to the input of the differential cascade 5. The output signal after the differential cascade 5 is fed to a sawtooth signal generator 6, then to the generator of the function sinα 7 and through a low-pass filter ( Low-pass filter) 4.1 and the driver of the control signal 4.2, the pulses are applied to the inputs of packet 9, which consists of third-order active Chebyshev filters. As a result, the signal sinα is generated, which is fed to the inputs of the formers sin2α 13, sin ² α 14, cosα 15, as well as to the first input of the first summing device 17. As a result, through the scale converters λ _∂ 10, ε 11, V _h 12 and summing 17, as well as multiplying 16 devices at the output of the Converter we have the function V (α).

The control of the switching device 8 is carried out by means of blocks 4.1 and 4.2 as follows. The signal sinα from output 7 is fed to the low-pass filter 4.1, which is tuned to a cutoff frequency of 30 Hz. If the engine shaft speed is lower than 30 Hz, the control signal shaper 4.2 generates a control pulse for connection from the low-pass filter package of the Chebyshev filter at _fg = 15 Hz, i.e. designed for a lower frequency and vice versa. Thus, the driver of the control signal 4.2 gives pulses to the switching device 8, which closes the keys K1 or K2.

The numbers of the outputs 3, 4, 5, 6, 7, and 9 in FIG. 2 correspond to the block designations adopted in FIG. 1.

Figure 3 shows the amplitude-frequency characteristics of active Chebyshev filters (third order), collected for the frequencies of the "cut" f _gr = 15 Hz and f _gr = 30 Hz. U _max is the maximum voltage level corresponding to the reproduced sinα, measured in mV. The choice of Chebyshev filters is associated with the features of their amplitude-frequency characteristics, characterized by small voltage fluctuations (ripples) around a given level within specified limits, in a frequency bandwidth from 0 to f _gr . As follows from the experimentally constructed amplitude-frequency characteristics of the filters, the quality of the obtained sinα strongly depends on the rotational speed of the shaft of the piston machine and, as studies show, is sharply worsened outside the passband. In the passband, δsinα <0.5 ... 1.0%, which is proved by a harmonic analysis of the function sinα and is acceptable. Moreover, the coefficient of nonlinear distortion is 5.0%, and the measured one is 0.5%.

However, in order to obtain sinα with a given error of less than 1.0% for a wide range of engine shaft rotation frequencies, a whole package of filters with intersecting passbands is needed, which is done in the device. Figure 3 shows as an example two such filters.

Figure 4 shows an example of a specific implementation of the device of the generator sinα, integrated in the Converter of the current cylinder volume of the piston machine. In figure 4, the following notation: R1 ... R8 - fixed resistors; R9 is a variable resistor; C1 ... C3 - capacities; P1, P2 - switches; KT 801A - transistor; 140 UD8 - amplifier; Low-pass filter - 15, Low-pass filter - 30 - low-pass filters designed for cutoff frequencies of 15 and 30 Hz.

The proposed device in comparison with the prototype is structurally simpler and not expensive, and also adapted to the operating conditions of the piston machines. The technical and economic effect expected from the use of the device is to improve the process of setting up engines, to speed up the process of fine-tuning new and used samples of heat engines.

SOURCES OF INFORMATION

1. Hardware implementation of the heat emission curve on the oscilloscope screen. Magnitsky Yu.A., Ludvikevich E.A .: Proceedings of the RIIZhT, Interuniversity. topics collection, issue 180. - Rostov-on-Don, 1985, p.14-17.

2. Magnitsky Yu.A. etc. A device for registering a heat-release curve in a cylinder of an internal combustion engine. A.S. No. 1508123, publ. 09/15/89 in BI No. 34.

3. Kaare Aaen. Monitoring the technical condition of diesel engines. Engine building. L. No. 6, 1989, p. 27-29.

4. Magnitsky Yu.A. et al. A device for recording a heat release curve in a cylinder of a piston engine. A.S. No. 1012068, publ. 04/15/83 in BI No. 14.

Claims (1)

A device for a converter of the current cylinder volume of a piston machine, comprising a function generator sinα, constant scale converters λ _∂ , ε, V _h , sin2α, cosα and sin ² α formers, first, second and third multiplying devices, first and second summing devices, and the output the shaper sinα is connected to the inputs of the shapers sin2α, cosα and sin ² α, as well as to the first input of the first summing device, the outputs of the shapers sin2α and sin2α are connected respectively to the first input of the first and second multiplying devices and the scale converter λ _{∂ is} connected to the second input of the first and second multiplying devices, the output of the first multiplying device is connected to the second input of the first summing device, and the outputs of the second multiplying device, cosα former and the scale converter ε are connected to the inputs of the second summing device, the output which is connected with the first input of the third multiplying device, and its second input - with a scale transducer of magnitude V _h , characterized in that it has an additional but it contains a TDC position sensor made optically and connected in series with a master pulse generator, a differential cascade, a sawtooth signal generator, a sinα function shaper, through a low-pass filter (LPF) and a control signal shaper with a switching unit with a Chebyshev filter package.

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