JP2002310910A - Gas concentration measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the measuring accuracy of a gas concentration measuring instrument which detects the concentration of a specific component of gas inside a pipe based on the attenuation of infrared rays caused by the in-pipe gas. SOLUTION: A microcomputer 45 makes the in-pipe gas and a reference gas the concentration of which is already known to be supplied repeatedly to a cell 21 by controlling switching valves 34-36, and resets the correlation between the signal of a detector 23 which receives infrared rays transmitted through the cell 21 and the concentration of the reference gas whenever the reference gas is supplied so that the correlation may always be reviewed even when the measuring period becomes longer. In addition, the actual existing time of the in-pipe gas containing oil, etc., that easily cause contamination in the cell 21 is shortened and, at the same time, the inside contamination of the cell 21 is prevented by means of the purging action of the reference gas. In this way, the measuring accuracy of the gas concentration measuring instrument is maintained at a high level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas concentration measuring device used for analyzing in-cylinder gas of an internal combustion engine.

[0002]

2. Description of the Related Art Analysis of the gas composition in a cylinder is important in the analysis of the combustion mechanism of an internal combustion engine and the development of an internal combustion engine. A gas concentration measuring device is used for analyzing such a gas composition, and an infrared absorption type is expected from the viewpoint of high responsiveness.

An infrared absorption type gas concentration measuring device irradiates an infrared ray from one end into a cell into which a sample gas is introduced, and receives the infrared ray from a detector provided at the other end. The concentration of a specific component of the sample gas that absorbs infrared light is measured from the attenuation of infrared light known from the instrument. The cell allows the gas flowing from the inlet to flow through the cell and is discharged from the outlet, so that the instantaneous value of the concentration of the flowing gas can be measured. The concentration of the specific component of the sample gas is quantified based on a calibration curve indicating the correspondence between the concentration and the magnitude of the detection signal of the detector.

[0004] As described above, the infrared absorption type gas concentration measuring device uses the attenuation of infrared light due to the absorption of infrared light by the sample gas. It is necessary to perform calibration for resetting the correspondence using zero gas or the like.

Japanese Patent Application Laid-Open No. 7-63682 discloses a gain-adjustable amplifier circuit for amplifying and outputting the output of a detector. The output of the amplifier circuit when a reference gas is supplied to a cell prior to measurement is provided. Is disclosed that realizes calibration using zero gas by adjusting the gain so that the reference voltage value becomes a reference voltage value.

[0006]

However, depending on the required measurement accuracy, the irradiation intensity of the infrared light source and the drift of the detection sensitivity are not always sufficient.

The gas in the cylinder of the internal combustion engine contains soot, oil, fuel and moisture in addition to the combustion gas.
During the measurement period, the contamination in the cell may progress, and the measurement error may increase.

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a gas concentration measurement device that can obtain sufficient measurement accuracy.

[0009]

According to the first aspect of the present invention, there is provided a cell in which gas flowing from an inlet flows and is discharged from an outlet, an infrared light source for irradiating infrared light from one end of the cell into the cell, A detector for detecting the intensity of infrared light emitted from the other end, a signal processing means for receiving an output signal of the detector as an input, and outputting a gas concentration signal corresponding to a concentration of a specific gas component in the gas; In a gas concentration measuring device having a correspondence setting means for setting a correspondence between a detector output signal and a gas concentration signal of the means, the supply gas into the cell is supplied with a known concentration of a sample gas and a specific gas component. A supply gas switching means for repeatedly switching with the reference gas, wherein the correspondence setting means is provided for each time the supply gas switching means is switched to the reference gas side with the concentration of the specific gas component in the reference gas. Scan density signal and is configured to reconfigure the correspondence relation to be consistent.

[0010] Even if the measurement period is long, the calibration with the reference gas is repeatedly performed during that period, and high measurement accuracy can be realized even if the irradiation intensity of the infrared light source changes over time during the measurement period. . In addition, since the inside of the cell is not always filled with the sample gas, and the reference gas and the sample gas are alternately periodically replaced, the actual time in which the sample gas is present in the cell is shortened. In addition, the reference gas flowing in the cell has an effect of removing dirt in the cell, and measurement errors due to dirt in the cell can be reduced. Thus, even if the sample gas includes a gas that is likely to cause contamination, such as a gas in a cylinder, a long-time measurement can be performed.

In the invention according to a second aspect, in the configuration according to the first aspect of the invention, the supply gas into the cell includes a purge gas for purging the inside of the cell, and the supply gas switching means can be switched to the purge gas. Make up,
By controlling the supply gas switching means, when a reset value of a parameter defining the correspondence deviates from a preset allowable range, for a certain period, purge command means for using supply gas into the cell as purge gas. I will prepare it.

When the inside of the cell is contaminated, the influence setting means tries to absorb the influence by resetting the relation between the detector output signal and the gas concentration signal. At this time, the degree of the influence of dirt in the cell is reflected on the magnitude of the reset value of the parameter defining the correspondence. By supplying a purge gas into the cell when the reset value of such a parameter deviates from a preset allowable range, even if the sample gas contains many substances that are likely to cause contamination, the contamination in the cell becomes excessive. Before that, the stain is removed and the inside of the cell is kept clean. Since the timing for supplying the purge gas into the cell is appropriately determined, the actual measurement time during the measurement period is not excessively reduced.

According to a third aspect of the present invention, in the configuration of the first or second aspect, the supply gas into the cell is:
A purge gas for purging the inside of the cell, and two kinds of reference gases having different concentrations of specific gas components are included as the reference gas, and the supply gas switching means is configured to be switchable to a purge gas. Controlling, when the concentration change when switching from one type of reference gas to the other type of reference gas is smaller than a preset threshold value, the supply gas into the cell is used as the purge gas for a certain period of time. Purge command means is provided.

If the sample gas contains a large amount of gas which is likely to cause contamination, the passage cross-sectional area of the pipe which forms a gas flow passage together with the cell decreases due to the adhesion of the contamination, and the gas is replaced in the cell. Responsiveness decreases.
When the change in concentration when switching from one type of reference gas to the other type of reference gas is smaller than a preset threshold, the purge gas is supplied into the cell, so that the sample gas is likely to cause contamination. Even if it contains a lot of dirt, the dirt is removed before the dirt in the cell becomes excessive,
The inside of the cell is kept clean. Since the timing for supplying the purge gas into the cell is appropriately determined, the actual measurement time during the measurement period is not excessively reduced.

According to a fourth aspect of the present invention, in the configuration of the first to third aspects, the supply source of the sample gas is the internal combustion engine, and the gas in the cylinder is the sample gas.

The in-cylinder gas contains a large amount of gas which tends to cause contamination such as fuel and oil. When the present invention is applied to a gas concentration measuring device using the gas as a sample gas, a particularly preferable structure is obtained.

According to a fifth aspect of the present invention, in the configuration of the fourth aspect of the present invention, the supply gas switching means is provided with a replacement gas supply system in which a reference gas or a purge gas flows through a communication path that connects the inside of the cylinder with the inside of the cell. While connecting the passage, provided in the middle of the replacement gas supply passage, a switching valve for switching between supply and stop of the reference gas, and a switching valve control means for controlling the switching valve,
The switching valve control means is set to have a reference gas supply stop period in a range from the compression stroke to the expansion stroke.

The range from the compression stroke to the expansion stroke is a period during which the in-cylinder pressure is positive. During the reference gas supply stop period, the in-cylinder gas can be supplied by the in-cylinder pressure.

According to a sixth aspect of the present invention, in the configuration of the fifth aspect of the present invention, the communication path is provided with a switching valve for switching between communication and cutoff between the inside of the cylinder and the inside of the cell, and the switching valve control means is provided. After the measurement of the sample gas is completed, the switching valve is set to close.

After the measurement of the sample gas is completed, the inside of the cell and the inside of the cylinder are shut off, so that no dirt is brought into the cell thereafter even if the in-cylinder pressure is a positive pressure. The inside of the cell can be kept even cleaner.

[0021]

(First Embodiment) FIGS. 1, 2 and 3 show a gas concentration measuring apparatus of the present invention applied to in-cylinder gas analysis of an internal combustion engine. In FIG. 2 showing the overall configuration of the gas concentration measuring device, in the gas concentration measuring device 1, a high-speed analyzer 11, which is a main body, has an analyzer 111 for introducing a sample gas sampled from the internal combustion engine 5, and receives an output signal thereof. And a controller 112.

The controller 112 determines a specific component to be measured, for example, the concentration of CO 2 (hereinafter referred to as gas concentration) based on the output signal, and outputs the data signal to the data recording device 14. The synchronization circuit 12 is provided with a crank angle sensor 13 provided in the internal combustion engine 5 as an input.
The controller 112 outputs a control signal to the controller 2, and the controller 112 controls the analyzer 111 based on the control signal. Further, the crank angle signal is output from the synchronization circuit 12 to the data recording device 14, and the gas concentration is stored in association with the crank angle.

In FIG. 1 showing the electrical configuration of the analysis unit 111 and the controller 112, and FIG. 3 showing the analysis unit 111, the internal combustion engine 5 has a cylinder 501 formed in a cylinder block 51 in which a cylinder head 52 is covered. 501
A piston 53 is slidably held therein. The cylinder head 52 includes an injector 54 for fuel injection,
Intake valve 55 and exhaust valve 5 for intake and exhaust
6 are provided. The distal end 311 of the sampling passage 31, which is a communication passage, penetrates the cylinder head 52,
The intake port faces a combustion chamber 502 formed above the piston 53. The sampling passage 31 is connected to the inlet 21a of the cell 21 at the base end. The cell 21 has a transparent window 21 made of calcium fluoride or the like at both ends of the cylindrical body 211.
The entrance 21a is formed at a position near one of the transmission windows 212. The exit 2 is located at a position near the transmission window 213 opposite to the entrance 21a.
1b is provided, and the outlet 21b is connected to the discharge passage 33. The gas introduced from the inlet 21a is supplied to the cell 2
1, and is discharged from the outlet 21b after flowing in the length direction.

A replacement gas supply passage 32 is connected to the sampling passage 31 so that various gases stored in a cylinder 38 can be supplied into the cell 21 in addition to the sample gas. The gas that can be supplied through the replacement gas supply passage 32 includes a zero gas as a reference gas having no infrared absorption such as N2 gas, a span gas and a purge gas as a reference gas containing a certain amount of a specific component and having a known gas concentration.

Behind the transmission window 213 of the cell 21, an infrared light source 2 for irradiating infrared rays into the cell 21 from the transmission window 213.
2 is provided, and behind another transmission window 212, a transmission window 2 is provided.
A detector 23 for detecting the intensity of the infrared light emitted from the light source 12 is provided. In addition, a rotating sector (not shown) is provided between the infrared light source 22 and the cell 21 to prevent intermittent irradiation of infrared light into the cell 21 and prevent the characteristics of the detector 23 from changing over time in a certain direction. It has become. In addition, it goes without saying that a known filter or the like for improving the measurement accuracy of the specific component can be used.

The controller 112 includes the preamplifier circuit 4
1, peak hold circuit 42, variable gain amplifier circuit 4
3, an AD conversion circuit 44, and a microcomputer 45, which process the output signal of the detector 23 when the sample gas is flown into the cell 21 to correspond to the gas concentration of the in-cylinder gas. The signal processing means 4a for outputting the gas concentration signal to the data recording device 14 is constituted. The controller 112 also includes a decoder 46. The decoder 46, together with the microcomputer 45, constitutes a correspondence setting means 4b for setting a correspondence between the output signal of the detector 23 and the gas concentration signal.

The microcomputer 45 outputs a control signal to the valve driving circuit 47 to output the control signals to the valves 34, 35, 3.
6, 37 are switched between open and closed. The valves 34 to 37 include a main valve 34 for opening and closing the replacement gas supply passage 32, a zero gas valve 35 for switching between supply and stop of zero gas, a span gas valve 36 for switching between supply and stop of span gas, and supply and stop of purge gas. Is provided. When these valves 34 to 37 are closed and the pressure in the cylinder 501 (hereinafter referred to as the in-cylinder pressure) is a positive pressure, the cylinder 501
A sample gas is supplied into the cell 21 from the inside. When any one of the main valve 34 and the replacement gas supply valves 35 to 37 is open, a selected replacement gas such as zero gas is supplied into the cell 21.

The control signal from the microcomputer 45 to the valve drive circuit 47 is output based on the control signal from the synchronous circuit 12, and the valves 34 to 37 are opened and closed when the crank angle is at a predetermined crank angle. The opening / closing timing will be described later. Microcomputer 4
5. Valve drive circuit 47, crank angle sensor 13, sampling passage 31, replacement gas supply passage 32, valve 34
37 constitute supply gas switching means 4c for switching the supply gas into the cell 21.

The signal processing means 4a and the correspondence setting means 4b will be described in detail. The output signal of the detector 23 is amplified by the preamplifier circuit 41 and
Enter 2 The output voltage of the preamplifier circuit 41 becomes an AC signal having a constant cycle synchronized with the rotation of the rotating sector.
The peak hold circuit 42 is reset at a constant cycle in synchronization with the rotation of the rotating sector, and the peak hold voltage of each cycle is input to the variable gain amplifier 43. The peak hold voltage is amplified by the variable gain amplifier 43, digitized by the AD converter 44, and
It is taken in. As described later in detail, the microcomputer 45 calculates the gas concentration based on the taken data.

The variable gain amplifier circuit 43 includes an operational amplifier 43.
The peak hold voltage output from the peak hold circuit 42 is input to its + input terminal. Further, the − input terminal is connected to the output terminal of the operational amplifier 431 via the switching circuit 433, and when the switching circuit 433 is switched to the first switching contact 433a, the output voltage of the operational amplifier 431 is −
It becomes an input voltage of the input terminal, and becomes a voltage follower circuit in which the output voltage of the operational amplifier 431, that is, the output voltage Vs of the variable gain amplifier 43 becomes the output voltage Vp of the peak hold circuit 42. On the other hand, when the switching circuit 433 is switched to the second switching contact 433b side, the resistance circuit 4 is connected between the-input terminal and the output terminal of the operational amplifier 431.
32. At this time, assuming that the resistance of the resistance circuit 432 is Rf and the resistance of the input resistor 434 connected to the minus input terminal of the operational amplifier 431 is R, the gain of the variable gain amplifier 43 is given by (1 + Rf / R). When the output voltage Vs of the variable amplifier circuit 43 is (1 + Rf / R) V
p.

The resistor circuit 432 includes a plurality of resistors 4321.
Has a resistor string connected in series, and each resistor 4
One of the terminals 321 is connected to a second switching contact 433b of the switching circuit 433 via a switching element 4322 provided in one-to-one correspondence with the terminal. One end of the resistor string is connected to the input resistor 434.

A control signal is input from the decoder 46 to the gate of each switching element 4322, and each switching element 4322 is turned on and off. From the switching element 4322 connected to the resistor 4321 near the minus input terminal of the operational amplifier 431, Switching element 432 to be turned on
2 are sequentially switched, the resistance value R of the resistance circuit 432 is changed.
f increases sequentially, and the gain of the variable gain amplifier 43 can be freely set according to the number and resistance value of the resistors 4321.

The microcomputer 45 comprises a decoder 46
, And the decoder 46 sets the resistance Rf of the resistance circuit 432 based on the gain adjustment signal.

The microcomputer 45 has an AD
The correspondence between the data of the output voltage Vs from the conversion circuit 44 and the gas concentration is stored as a look-up table. The look-up table is created based on a previously obtained calibration curve.

A method for preparing a calibration curve will be described. First, a plurality of types of calibration gases having different gas concentrations, including zero gas, are sequentially supplied into the cell 21 while being replaced, and the output voltage Vs of the variable gain amplifier 43 at that time is obtained. At this time, the switching circuit 433 is switched to, for example, the first switching contact 433a. Using this as a tentative calibration curve, the output voltage Vs when the gas concentration is zero gas and zero gas
The output voltage Vs at the time of each calibration gas is also multiplied by a constant so that the reference voltage VREF becomes a reference voltage VREF.

Since the reference voltage VREF is an output voltage when the gas concentration is 0, the reference voltage VREF is the maximum voltage.
Should be set in accordance with the specifications of the AD conversion circuit 44 so that the A / D converter operates in the full range.

The controller 111 is also provided with an operation panel section 48, which is connected to the microcomputer 45. The operation panel unit 48 includes various setting switches and a display, and serves as an interface with a person who performs measurement.

FIG. 4 is a flowchart of a control program executed by the microcomputer 45, and FIG.
5 is a timing chart showing an operation state of each part and the like of the gas concentration measurement device. Thereby, the microcomputer 4
The operation of the present gas concentration measuring device will be described together with the setting of 5.

The zero gas valve 35 is turned on to start supplying the zero gas (step S101). The timing of turning on is after the crank angle reaches 90 ° CA at the compression top dead center (° A
TDC). Next, calibration is performed (step S10).
2). In the zero calibration, the switching circuit 433 is set to the first switching contact 433a side, and the output voltage Vp of the peak hold circuit 42 is taken in. Then, the switching circuit 433 is connected to the second
The gain is set so that the output voltage Vs of the gain variable amplifier circuit 43 when the switching contact 433b is switched to the reference voltage VREF. That is, VREF / Vp = 1
Rf is calculated so as to satisfy + Rf / R, and the decoder 46
Set the gain adjustment signal to. This completes the zero calibration. The gain is held until the next gain setting.

When the temperature reaches 360 ° ATDC, the zero gas valve 35 is turned off (step S103), and the span gas valve 36 is turned on (step S104).
The gas supplied to the cell 1 is switched to span gas,
Is replaced with zero gas from span gas. By substitution,
The gas concentration in the cell 21 increases from 0 toward the gas concentration of the span gas. The response time T90 at this time is measured (step S105). The response time T90 is a time required for the gas concentration to change from 10% to 90% of the span gas concentration. Further, the gas concentration at the time when the replacement is completed is measured (step S106). This measurement timing is set to a timing at which the gas concentration can be considered to have converged to the span gas concentration. For example, the gas concentration is 90% of the span gas concentration
May be brought after a lapse of a predetermined time from the arrival at.
In calculating the response time T90 and the measured concentration Dsp of the span gas, a reference value, for example, 1 is used as a correction coefficient described later.

Next, the measured concentration Dsp of the span gas is compared with a preset threshold value X, and whether the measured concentration Dsp is smaller than the threshold value X and the response time T90 are set at the preset threshold value X. It is determined whether the measured response time T90 is greater than the threshold value T1 by comparing with T1 (step S107). If a positive determination is made, step S108
Proceed to and perform span calibration. In the calibration, the true value of the concentration of the span gas / the measured concentration Dsp is calculated to obtain a correction coefficient. This correction coefficient is a coefficient for multiplying the gas concentration obtained from the look-up table to obtain a final measurement result of the gas concentration.

When the crank angle reaches 90 ° BTDC,
The span gas valve 36 is turned off, and the supply of the span gas is stopped. Thereby, the inside of the cell 21 is filled with the cylinder 5 of the internal combustion engine 5.
It communicates only with 01. The gas concentration in the cylinder 501 at this time is, for example, the residual gas (internal EGR) of the previous cycle of the internal combustion engine 5 and the intake and exhaust gas recirculation (external EGR).
And the EGR gas concentration in each cycle. The pressure in the cell 21 gradually decreases by stopping the supply of the span gas. Conversely, the in-cylinder pressure increases with the progress of the compression stroke. When the in-cylinder pressure rises to a certain degree or more, the cylinder 501 having a lower concentration than the span gas.
The gas in the cell 21 flows into the cell 21, the gas concentration in the cell 21 rapidly decreases, and the gas in the cell 21 is replaced with the gas in the cylinder 501. Thereafter, the gas in the cylinder 501 passes through the sampling passage 31, circulates in the cell 21 and is discharged to the discharge passage 33, and the cell 21 always has new gas in the cylinder 501.

Then, the air-fuel mixture burns in the substantially compressed TDC, the cylinder pressure increases, and the cell pressure also increases. And
Also in the expansion stroke, the cylinder 5
The gas in the cell 01 continues to flow into the cell 21, and the gas from the cylinder 501 continues to flow into the cell 21 during the substantially expansion stroke.

The microcomputer 45 sets an actual measurement period within a period in which gas from the cylinder 501 flows into the cell 21, and measures the gas concentration (step S11).
0). That is, the data of the output voltage Vs from the variable gain amplifier 43 is converted into data of the gas concentration in the in-cylinder gas based on the look-up table and the correction coefficient. The data of the gas concentration is sequentially taken into the data recording device 14 and stored in association with the crank angle known from the synchronization circuit 12. 45 ° B in the example shown
The period from TDC to 45 ° ATDC is set as the actual measurement period, and data on the behavior in the cylinder 501 before and after combustion is obtained.

If there is a measurement end command from the outside (step S111), the measurement ends. The measurement end command is issued by the operation panel unit 48 provided on the front surface of the controller 111, and is also generated when a predetermined time has elapsed after the start of the measurement. Alternatively, it is generated when the number of rotations of the engine reaches a predetermined number. The time and the number of times can be set by, for example, a setting switch of the operation panel unit 48 or the like. When the measurement is completed, all the valves 34 to 37 are turned off.

If there is no measurement end command, step S10
1, and according to the control signal from the synchronization circuit 12,
It is repeated from the time when the zero gas valve 35 is turned on. Thereby, the cell internal pressure rises again to the pressure specified by the passage cross-sectional area of the passages 31 to 33, and the inside of the cell 21 is replaced by the zero gas.

If the determination in step S107 is negative, that is, if the response time T90 is larger than the threshold value T1 or if the measured concentration Dsp of the span gas is larger than the threshold value X, the span gas The valve 36 is turned off (step S112) and the span gas valve 37 is turned on (step S113), and the purging of the cell 21 is executed. Also, the passage cross-sectional area becomes narrow due to contamination of the sampling passage 31 and the like, and the gas flow rate into the cell 21 decreases accordingly, the replacement of the zero gas with the span gas is delayed, and the response time T90 becomes longer. Further, when the contamination of the transmission window 212 on the emission side advances due to the contamination in the cell 21, the infrared rays attenuate more than the absorption by the sample gas, and shift to a higher concentration side than the true gas concentration. Therefore, when the shift to the high concentration side and the increase in the response time T90 exceed a certain limit (step S107), the purging is executed to prevent the stain from excessively progressing.

When the purge has been performed for a predetermined time T (step S114), the purge gas valve 37 is turned off to terminate the purge and return to step S101. Then, when a negative determination is made again in step S107, the process is performed again. As a result, the purge amount is properly performed according to the degree of contamination.

In the above flow, step S1
01, S103, S104, S109, S112, S1
13 and S115 are operating procedures as switching valve control means, steps S102 and S108 are operating procedures as part of the correspondence setting means, and step S110 is an operating procedure as part of the signal processing means. Steps S105 to S107 are an operation procedure as purge command means.

The gas concentration measuring apparatus 1 is configured as described above. Even if the measuring period is long, the calibration with the reference gas is repeatedly performed during the measuring period, and the irradiation intensity of the infrared light source 22 is reduced during the measuring period. High measurement accuracy can be realized even if the time varies during the measurement.

In this embodiment, since the sample gas in the cell 21 is from the cylinder 501 and contains soot, oil, fuel and moisture in addition to the combustion gas, the inside of the cell 21 is easily contaminated. Situation. FIG. 6 is a timing chart showing an operation state of each part in a case where the inside of the cell 21 and the inside of the cylinder 501 are always in a communication state (conventional example) during the measurement period without performing calibration during the measurement period. The in-cylinder gas concentration is constant before and after, because the exhaust gas remains in the cylinder 501. In addition to the period before and after the combustion to be measured, this residual exhaust gas causes
Inside will be dirty. In the present gas concentration measuring apparatus 1, as described above, the period sandwiching the existence period of the sample gas is sufficiently replaced by the reference gas, and this is repeated, so that the actual time when the sample gas exists in the cell 21 is Be shortened. Further, when the reference gas flows from the inlet 21a to the outlet 21b in the cell 21, the inside of the cell 21 is purged to prevent the sample gas that induces contamination in the cell 21 from staying in the cell 21. It works. Thereby, the progress of the stain in the cell 21 can be suppressed.

In addition, the progress of the dirt in the cell 21 is monitored based on the response at the time of measuring the span gas and the measured concentration, and when the dirt in the cell 21 is accumulated, the purge is automatically executed before the dirt becomes severe. Accordingly, it is possible to prevent the analysis unit 111 from being so dirty as to be required to be disassembled and cleaned to become unmeasurable.

(Second Embodiment) FIG. 7 shows a configuration of an analyzer and a controller of a gas concentration measuring device according to a second embodiment of the present invention. The switching of the supply gas to the cell is performed by means different from that of the first embodiment. Parts that operate in the same manner as in the first embodiment are given the same numbers and differ from the first embodiment. This will be mainly described.

The gas concentration measuring device 1A is connected to the inside of the cylinder 501 and the cell 21 by a main valve 34A composed of a three-way valve.
The controller 45A outputs a control signal to the valve drive circuit 47A corresponding to the actual measurement period defined by the crank angle, during which the main valve 34A is connected to the cylinder 501. Side so that the sample gas in the cylinder 501 is introduced into the cell 21. Other settings of the controller 45A are the same as those of the first embodiment.

As a result, the time during which the sample gas that induces contamination in the cell 21 can be further reduced. For example, if the purpose is to measure the gas concentration before the start of combustion, the supply start timing of the zero gas is advanced until about the time of ignition, and the flow of the sample gas from the cylinder 501 to the cell 21 is cut off. Contamination in the cell 21 can be further reduced.

In each of the above embodiments, the contamination in the cell 21 is determined based on the response time T90 and the measured concentration Dsp of the span gas when there is no correction (correction coefficient = 1). Good. Further, when the peak hold voltage in the calibration using the zero gas becomes larger than the lower limit value or when the calculated gain becomes larger than the upper limit value, it may be determined that purging is to be performed.

The structure may be simplified by using the purge gas also as, for example, a zero gas.

Further, when the purge is executed, a warning may be displayed on the operation panel section 48 or output to the data recording device 14 and recorded in the data recording device 14 together with the output timing.

It is also possible to simplify the configuration and control by not performing the purge by the purge gas. in this case,
In order to enhance the purge effect of the reference gas, it is desirable to set the supply flow rate of the reference gas into the cell to be relatively large.

The present invention can also be applied to a simple apparatus for performing calibration with only zero gas or only with span gas.

The actual measurement period is from the compression stroke to the expansion stroke in which the in-cylinder pressure can be used. However, as long as a suction pump can be provided in the discharge passage 33, the actual measurement period is not limited to this period. The position is also arbitrary, and further rich data can be obtained. Thereby, the combustion mechanism of the internal combustion engine and the like can be analyzed in more detail. For example, when shifting from the exhaust stroke to the intake stroke, the exhaust valve 55 is opened due to the negative pressure at the intake port downstream of the throttle valve 57 (FIG. 3) while the exhaust gas is at a positive pressure. When the cylinder 50
A blow-back occurs from the inside to the intake port side, and the behavior at this time can be known from the viewpoint of the gas concentration.

Although the present invention has been described as applied to the analysis of in-cylinder gas of an internal combustion engine, it can also be applied to the measurement of the gas concentration of other sample gases.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a gas distribution system and an electric signal system of a first gas concentration measurement device of the present invention applied to analysis of in-cylinder gas of an internal combustion engine.

FIG. 2 is an overall configuration diagram of the gas concentration measurement device.

FIG. 3 is a configuration diagram of an analysis unit of the gas concentration measurement device.

FIG. 4 is a flowchart showing control contents executed by a microcomputer of the gas concentration measuring device.

FIG. 5 is a timing chart showing operating states of respective parts of the gas concentration measuring device and the internal combustion engine.

FIG. 6 is a timing chart of a comparative example.

FIG. 7 is a configuration diagram showing a gas distribution system and an electric signal system of a second gas concentration measurement device of the present invention.

[Explanation of symbols]

Reference Signs List 1, 1A gas concentration measuring device 11 high-speed analyzer 111 analyzer 112 controller 12 synchronization circuit 13 crank angle sensor 14 data recording device 21 cell 211 cylindrical body 212, 213 transmission window 21a inlet 21b outlet 22 infrared light source 23 detector 31 sampling Passage (communication passage) 32 Replacement gas supply passage 33 Discharge passage 34, 34A Main valve (switching valve) 35 Zero gas valve (switching valve) 36 Span gas valve (switching valve) 37 Purge gas valve (switching valve) 4a Signal processing means 4b Correspondence relationship Setting means 4c supply gas switching means 41 preamplifier circuit 42 peak hold circuit 43 variable gain amplifier circuit 44 AD conversion circuit 45, 45A microcomputer (switching valve control means, purge command means) 46 decoder 47, 7A valve drive circuit 48 operation panel 5 an internal combustion engine 501 cylinder

Continued on the front page F term (reference) 2G059 AA01 BB01 DD12 DD13 EE01 HH01 MM01 MM05 MM09 MM12 MM15 MM16 3G084 BA24 DA04 EA04 EA08 EA11 EB02 EB06 FA28 FA38

Claims (6)

[Claims] 1. A cell through which gas flowing from an inlet flows and is discharged from an outlet, an infrared light source for irradiating infrared light into the cell, a detector for detecting the intensity of infrared light emitted from the cell, and an output of the detector. A signal processing means for inputting a signal and outputting a gas concentration signal corresponding to the concentration of a specific gas component in the gas, and a correspondence setting between the detector output signal and the gas concentration signal of the signal processing means; A gas concentration measuring device having a relation setting means, comprising: a supply gas switching means for repeatedly switching a supply gas into the cell between a sample gas and a reference gas having a known concentration of a specific gas component. Each time the supply gas switching means is switched to the reference gas side, the correspondence is reset so that the concentration of the specific gas component in the reference gas matches the gas concentration signal. Configured gas concentration measuring apparatus characterized by a. 2. The gas concentration measuring apparatus according to claim 1, wherein the supply gas to the cell includes a purge gas for purging the inside of the cell, and the supply gas switching means is configured to be switchable to a purge gas. Purge command means for controlling the supply gas switching means so that the supply gas into the cell is a purge gas for a certain period when the reset value of the parameter defining the correspondence deviates from a preset allowable range. Gas concentration measuring device. 3. A gas concentration measuring apparatus according to claim 1, wherein two kinds of gas having different concentrations of a specific gas component are used as a supply gas into the cell, a purge gas for purging the inside of the cell, and the reference gas. And the supply gas switching means is configured to be switchable to a purge gas, and the supply gas switching means is controlled to switch from one type of reference gas to the other type of reference gas. A gas concentration measuring device comprising: purge command means for using a supply gas into a cell as a purge gas for a certain period when a concentration change is smaller than a preset threshold value. 4. The gas concentration measuring apparatus according to claim 1, wherein the supply source of the sample gas is an internal combustion engine, and the gas in the cylinder is the sample gas. 5. The gas concentration measuring device according to claim 4, wherein the supply gas switching means connects a replacement gas supply passage through which a reference gas or a purge gas flows to a communication passage that connects the inside of the cylinder with the inside of the cell. And a switching valve provided in the middle of the replacement gas supply passage for switching between supply and stop of the reference gas, and switching valve control means for controlling the switching valve. A gas concentration measuring device set to have a reference gas supply stop period within a range from a stroke to an expansion stroke. 6. The gas concentration measuring device according to claim 5, wherein the communication path is provided with a switching valve for switching between communication and shutoff between the inside of the cylinder and the inside of the cell. A gas concentration measuring device set so that the switching valve closes after the measurement is completed.