JP2000259254A - Flow rate controller for diluted gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flow rate controller for diluted gas capable of automatically setting initial pressure even when no initial pressure setting line with a needle valve, etc., is arranged. SOLUTION: In the flow rate controller for diluted gas provided with plural branch flow passages 7, 8 with filters 9, 10 to collect PM to be contained in sample gas S extracted by branching from a tunnel 2 to dilute the sample gas respectively and connected with each other in parallel, a flow passage switching means 26 to switch the branch flow passages 7, 8 so that the sample gas S flows to one of the branch flow passages 7, 8 and a suction pump 15 the rotation frequency of which is controlled so that the flow rate of the sample gas becomes constant by an instruction from an inverter 20 in which a control value from a PI controller or a PID controller 21 is inputted, initial pressure loss in the filters 9. 10 is electrically measured and the suction pump is f controlled based on data to be obtained at the time off measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to PM contained in gas discharged from a diesel engine of an automobile or the like.
The present invention relates to a dilution gas flow control device used for quantitative analysis of (particulate matter, particulate matter such as soot).

[0002]

2. Description of the Related Art One of the techniques for measuring PM in exhaust gas is based on a filter weight method. In this type of measurement device, in order to collect PM in exhaust gas in a steady state where the engine speed is constant, to collect PM contained in sample gas branched and collected from a tunnel for diluting the sample gas. In parallel with the sample gas flow path provided with the above filter, a dilution gas flow control device provided with a bypass flow path for flowing exhaust gas in an unsteady state where the engine speed is unstable is used.

FIG. 4 schematically shows a configuration of a conventional dilution gas flow control device. In FIG. 4, reference numeral 1 denotes a diesel engine mounted on, for example, an automobile, and reference numeral 2 denotes an exhaust pipe connected to the diesel engine. A probe 3 is inserted and connected to the exhaust pipe 2, and is a probe for sampling the exhaust gas G flowing through the exhaust pipe 2. The downstream side thereof is connected to a dilution tunnel 4 for diluting the sampled exhaust gas G. Reference numeral 5 denotes a supply pipe for air for dilution connected to the upstream side of the dilution tunnel 4.

[0004] 6 is connected downstream of the dilution tunnel 4,
A gas flow path through which diluted exhaust gas (hereinafter, referred to as a sample gas S) flows.
8, filters 9 and 10 and electromagnetic valves 11 and 12 for trapping PM contained in the sample gas S are provided in the respective channels 7 and 8, and one of the channels 7 is provided with a stationary exhaust gas. And the other flow path 8 is formed as a bypass flow path for flowing unsteady exhaust gas.

A three-way solenoid valve 13 is provided on the downstream side of the sample gas flow path 7 and the bypass flow path 8 as a flow path switching means.
The port 13b is connected to the bypass flow path 8 and the port 13c is connected to the gas flow path 14 downstream of the three-way solenoid valve 13.

In the gas flow path 14, a suction pump (for example, a roots blower pump) 15 whose suction capacity can be changed by controlling the number of revolutions, and a flow meter (for example, a Venturi meter) 16 having high measurement accuracy are provided in this order. ing.
Reference numeral 17 denotes a pressure sensor for detecting the pressure of the gas flowing through the gas passage 14, reference numeral 18 denotes a differential pressure sensor, and reference numeral 19 denotes a temperature sensor.

Further, reference numeral 20 denotes an inverter (frequency converter) for controlling the suction pump 15, and reference numeral 21 denotes a PID controller, which outputs a command to the inverter 20. The constants (P, I, D) in the PID controller 21 are set according to the gas flow rate and the capacity of the suction pump 15. Reference numeral 22 denotes an interface unit,
An output from the microcomputer 9 and a command from a microcomputer 23 which will be described later are input so that some calculations such as a flow rate calculation can be performed, and a command is output to the PID controller 21. Reference numeral 23 denotes a microcomputer as an arithmetic control unit that controls the entire apparatus.

FIG. 5 schematically shows a control system of the suction pump 15 in the dilution gas flow control device. In FIG. 5, E _INV is a voltage to the inverter 20 and E _FF.
Is the feedforward voltage, E _PID is the PID control voltage,
Q _act is the actual flow rate (actual flow rate) of the gas in the flow path 14, Q _tgt is the target flow rate, and R is an integrated reset signal output from the interface unit 22 to the PID controller 21. It is formed based on the switching signal. Note that T, P, and dP are detection outputs from the sensors 17 to 19.

In the dilution gas flow control device configured as described above, the command value output by the PID controller 21 is output to the inverter 20, and based on the command value output from the inverter 20 based on this command. The roots blower pump 15 is controlled and the gas flow paths 6 and 14 are controlled.
Is controlled so that the flow rate of the sample gas flowing through is always constant. In this case, the flow rate of the sample gas S passing through the filter 9 (or 10) needs to be always constant. Conventionally, as shown in FIG. Three-way solenoid valve 13
Immediately before, the initial pressure setting lines 24 and 25 were respectively connected.

That is, the initial pressure setting lines 24, 2
5 have the same configuration as each other, and have a filter 2 for air suction.
4F, 25F, needle valve 24N, 2 for setting pressure loss
5N, connected to the sample gas flow path 7 and the bypass flow path 8 immediately upstream of the three-way solenoid valve 13 via the two-way solenoid valves 24V and 25V, and configured to take in the atmosphere via the filters 24F and 25F. Have been. The opening of the needle valves 24N and 25N is manually adjusted to generate initial pressure loss of the filters 9 and 10 provided in the sample gas flow path 7 and the bypass flow path 8, respectively.

[0011]

However, in the above-mentioned conventional dilution gas flow control device, the filter 24
F, 25F and needle valves 24N, 25 for setting pressure loss
Since the initial pressure setting lines 24 and 25 provided with N are provided, and the needle valves 24N and 25N are manually adjusted in opening to set the initial pressure, the overall configuration of the apparatus becomes complicated and it takes time. In addition to the inconvenience, when filters having different initial pressure losses are used, there is a problem that the configuration of the flow becomes so complicated that it is necessary to provide the initial pressure setting lines 24 and 25 for the types of the filters.

On the other hand, the needle valve 24
It is conceivable to automate the setting of the initial pressure loss by driving the N and 25N with a motor. However, even with such a configuration, it is necessary to provide an initial pressure setting line for each type of filter. Will remain.

[0013] The present invention has been made in consideration of the above-mentioned matters, and an object thereof is to automatically perform initial pressure setting without providing an initial pressure setting line including a needle valve and the like. It is an object of the present invention to provide a dilution gas flow control device that can perform the above.

[0014]

In order to achieve the above object, according to the present invention, there are provided filters for collecting PM contained in a sample gas branched and collected from a tunnel for diluting the sample gas. A plurality of branch flow paths connected in parallel; flow path switching means for switching the branch flow paths so that the sample gas flows into one of the branch flow paths; a PI controller or a PID
A dilution gas flow control device including a suction pump whose rotation speed is controlled so that the sample gas has a constant flow rate by a command from an inverter to which a control value is input from a controller. And the suction pump is controlled based on the data at that time.

[0015]

Embodiments of the present invention will be described with reference to the drawings. 1 to 3 show one embodiment of the present invention. First, FIG. 1 schematically shows the overall configuration of the dilution gas flow control device of the present invention, in which the same components as those in FIG. 4 indicate the same members. In FIG. 1, reference numeral 26 denotes a three-way solenoid valve provided as a flow path switching means provided on the downstream side of the sample gas flow path 7 and the bypass flow path 8.
a is connected to the sample gas flow path 7, the port 26 b is connected to the bypass flow path 8, and the port 26 c is connected to the gas flow path 14. 27 is the gas flow path 1
4 is a standby line connected between the three-way solenoid valve 26 and the suction pump 15, and includes a two-way solenoid valve 28 and a filter 29, and is configured to take in the atmosphere via the filter 29.

Next, the operation of the dilution gas flow control device having the above configuration will be described. The setting of the initial pressure loss is based on the following facts. That is, generally, the flow rate passing through the filter and the pressure loss in the filter are in a proportional relationship. FIG. 3 shows data showing this fact.
Fluid velocity (cm / sec) when flowing a fluid (for example, air) using a 7 mm (effective diameter 35 mm) filter
c) and the pressure loss (mmH ₂ O) were measured. The numbers shown on the margins of the horizontal axis indicate the fluid flow per minute at an outer diameter of 47 mm and an outer diameter of 70 mm (effective diameter of 60 mm).

For example, in order to set the initial pressure loss of the filter using the sample gas flow channel 7, the initial pressure loss may be set in the following sequence.

(1) First, a new filter is set in the filter holder.

(2) The electromagnetic valve 26 is operated to make the sample gas flow path 7 and the gas flow path 14 communicate with each other. Then, a signal is output from the inverter 20 and the suction pump 15
Is operated to flow air through the gas flow path 14. At this time, the flow rate at this time is measured by the flow meter 16. Then, the minimum flow rate Q _min and the maximum flow rate Q _max are set, and the microcomputer 23 stores the voltage value V _min and the maximum flow rate V _max applied to the inverter 20 at that time.

(3) Two sets of data obtained in the above (2), that is, flow rate and voltage data (Q _min ,
V _min), indicating (Q _max, from V _max), the relationship between flow rate and voltage in a linear expression.

In this case, when the types of filters (outer diameter, effective diameter, etc.) are the same, the equation obtained in the above (3) can be applied to all filters, and the types of filters are different. In this case, the relational expression (primary expression) between the flow rate and the voltage may be obtained by executing the above-described procedures (1) to (3) for each of the different filters.

FIG. 2 shows an example of a screen of the microcomputer 23 when the initial pressure loss of the filter is set. In this example, a case where the type of the filter is different is shown.

As described above, in the dilution gas flow control device according to the present invention, the initial pressure loss of the filter can be set by the above procedures (1) to (3). The feedforward value (voltage) corresponding to the set flow rate is obtained from the above-described linear expression, and this voltage value is given to the PID controller 21 to obtain the PI.
The output supplied from the D controller 21 to the inverter 20 starts from the voltage value. Therefore,
The delay time is shorter than when no feedforward value is given.

In the above procedure, the suction pump 15
Is operated to allow predetermined air to flow through the gas flow path 14, the electromagnetic valve 28 is opened to allow the standby flow path 27 to communicate with the gas flow path 14, and the air from the standby flow path 27 When the flow rate in the gas flow path 14 is stabilized, the electromagnetic valve 28
May be closed, and the solenoid valve 26 may be operated to allow the sample gas flow path 7 to communicate with the gas flow path 14. In this case, the flow rate flowing through the sample gas flow path 7 can be controlled more quickly.

In the dilution gas flow control device, when collecting PM, the following control is performed. In the steady state, the sample gas S
Although the opening and closing states of the three-way electromagnetic valve 13 to flow is set in this state, given from the interface unit 23 and a target flow rate Q _tgt and the actual flow rate Q _act on the PID controller 22, based on these differences PID output E _{PI D} from the controller 22 is output as a command value _INV to the inverter 20. The inverter 20 receiving the command value E _INV outputs a command to the suction pump 15.
As a result, the suction pump 15 operates at a predetermined rotation speed, and the flow rate of the sample gas flowing through the flow paths 7 and 14 is constantly controlled.

When the flow path is switched from the above state and the sample gas S is caused to flow through the bypass flow path 8, first, a command value E _INV to the inverter 20 according to the pressure loss before the flow path is switched. Is stored.

Next, an integrated reset signal R based on the flow path switching signal is input from the interface unit 23 to the PID controller 22 simultaneously with or slightly after the flow path switching signal. As a result, the output E _PID from the PID controller 22 to the inverter 20 disappears. At the same time, the stored command value E _INV is
The feedforward signal E without the controller 22
_This is given to the inverter 20 as _FF .

As described above, in the dilution gas flow control device of the present invention, the sequence of the initial pressure setting can be automatically performed, so that the number of steps for setting the initial pressure can be reduced as compared with the conventional case. Further, unlike the related art, there is no need to provide an initial pressure setting line including a needle valve and the like, so that the configuration of the gas line is simplified, the configuration of the entire apparatus is simplified, and the miniaturization is promoted. Further, it is not necessary to reset the initial pressure every time the flow rate changes.

In the above embodiment, the PI
Although the D controller 21 was used, instead of this,
An I controller may be used.

[0030]

According to the dilution gas flow control apparatus of the present invention, the initial pressure can be automatically set without providing an initial pressure setting line having a needle valve and the like, and the whole apparatus can be controlled. Inexpensive and compact.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an example of a configuration of a dilution gas flow control device of the present invention.

FIG. 2 is a diagram showing an example of a screen of a microcomputer when an initial pressure loss of a filter is set in the device.

FIG. 3 is a diagram showing a relationship between fluid velocity and pressure loss in a filter.

FIG. 4 is a diagram schematically showing a configuration of a conventional dilution gas flow control device.

FIG. 5 is a diagram schematically showing a control system of a suction pump in the dilution gas flow control device.

[Explanation of symbols]

2: dilution tunnel, 7, 8: branch channel, 9, 10: filter, 15: suction pump, 20: inverter, 21: P
ID controller, 26: flow path switching means.

Claims (1)

[Claims] 1. A plurality of branch flow paths connected in parallel to each other, each having a filter for collecting PM contained in a sample gas branched and collected from a tunnel for diluting the sample gas, and Flow path switching means for switching a branch flow path so that the sample gas flows through one of the flow paths; and a command from an inverter to which a control value from a PI controller or a PID controller is input. In a dilution gas flow control device including a suction pump whose rotation speed is controlled so that a constant flow rate is obtained, an initial pressure loss in the filter is electrically measured, and the suction pump is controlled based on data at that time. A dilution gas flow control device, characterized in that: