JPS588735B2 - Constant volume dilution sampling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention dilutes a gas to be measured such as automobile exhaust gas with air to obtain a constant flow rate of diluted gas, and collects a portion of the diluted gas.
A constant volume dilution sampling device (Constant Volume S
ampler, hereafter C. V. S. (abbreviated as) Koseki,
In particular, it relates to a device using a constant volume pump as a means for diluting automobile exhaust gas or the like with air to achieve a constant flow rate.

The constant volume pump is of this type C. V. S. This is an important factor that determines the measurement accuracy of an analyzer using a gas analyzer, and it must be operated so that a constant flow rate of dilution gas is drawn in at all times during operation.

On the other hand, C. V. S. For example, when applying this to automobiles with different displacements, the suction amount of the constant volume pump must be increased or decreased according to the displacement of the automobile, and the pump must be operated in such a state to maintain a constant flow rate. .

In order to operate a constant volume pump as described above, it is necessary to maintain and adjust the rotation speed of the electric motor as its drive source at a constant level. Conventionally, pole switching induction motors or electromagnetic coupling type induction motors This was done by directly connecting the induction motor and constant volume pump, or by using a belt and changing the diameter of the pulley.

However, since all of the conventional means are based on induction motors, they have the following drawbacks.

■Since the rotation speed changes greatly due to changes in the load, power supply voltage, and frequency, the suction amount of the constant volume pump also changes, causing measurement errors.

2 In addition to the above-mentioned disadvantages, in the case of using an electromagnetic coupling type induction motor, the number of revolutions changes due to changes in the ambient temperature of the control panel, and in the case of a belt-operated type, slippage in the belt transmission causes problems with constant-displacement pumps. There is a drawback that a predetermined number of rotations cannot be transmitted.

(3)C. V. S. As a performance test of the C. V. S. Although the flow rate is calculated, C. V. S. This will result in an error in the flow rate and the graph will no longer be usable.

■Since the rotational speed changes due to changes in load, it is necessary to measure the rotational speed every time the load changes.

■When changing the load, it takes at least 3 minutes for the rotational speed to become stable, and it takes a long time to perform the test.

■If it is necessary to change to a special rotation speed, it cannot be done easily using the belt hooking method, and mechanical change work (for example, changing the pulley and belt) is required.

Also, it cannot be changed in the direct connection system of a pole number switching induction motor.

Therefore, the present invention provides a new and useful means for solving all of the above-mentioned drawbacks.

An embodiment of the present invention will be described below.

Figure 1 shows C. V. This is a diagram showing the whole of C.S. ■． S denotes a dilution chamber 18 for diluting the gas to be measured such as the exhaust gas of the automobile 1 with air, a heat exchanger 4 for heating or cooling the dilution gas diluted in the chamber 18 to maintain a constant temperature, and a heat exchanger 4 for keeping the dilution gas at a constant temperature. It is equipped with a constant volume pump 5 that sucks at a constant flow rate, and a sample collection pump 13 that collects a part of the dilution gas behind the heat exchanger 4.

The dilution chamber 18 has a filter chamber 2 through which air passes for diluting exhaust gas, and a cyclone 3 at the rear.
is provided.

The cyclone 3 is for separating and removing dust and mist in the diluent gas, so if the diluent gas does not contain dust or mist, the cyclone is not necessary.

In this embodiment, a roots blower is used as the constant volume pump 5.

In the present invention, a synchronous motor is used as the drive source 6 for driving the same, and its rotating shaft is directly connected to the rotating shaft of the Roots blower 5.

The synchronous motor 6 is connected to an inverter 7 and an electrical circuit 1 as shown in FIG.

In the figure, 8 is an AC signal (triangular wave) generated by inverter 7
9 is a command unit that commands the inverter 7 to increase or decrease the rotational speed of the synchronous motor 6 when the vehicle type is different.

Further, in FIG. 1, 10 is a silencer, 11 is a digital counter that detects the rotation speed of the Roots blower 5, 12 is an analyzer that measures the weight values of components (HC, CO, NOx, etc.) of automobile exhaust gas, and 14. ...is sample collection bag, 15
, 15 is an air sampling pump, 16 . . . is an air sampling bag, and 17 is a temperature and pressure sensor.

As explained above, the constant volume dilution sampling device according to the present invention uses a synchronous motor as the driving source of the constant volume pump, and therefore has the effect of eliminating all of the conventional drawbacks listed below.

■Synchronous motors are driven by an inverter, so they are not affected by fluctuations in power supply voltage or frequency.

■Since the inverter has a circuit configuration that is completely unaffected by ambient temperature, synchronous motors are not affected by changes in ambient temperature.

Furthermore, if the rotating shaft of the synchronous motor and the rotating shaft of the constant displacement pump are directly connected as in the embodiment described above, slipping due to belt hooking will not occur.

■Since the rotational speed of the synchronous motor does not change as mentioned in ■ and ■, C. V. The graph showing the correlation between the load fluctuation at the rotation speed according to the displacement and the volume sucked per rotation ■0 as an S performance test can be used as is.
Accurate C. ■． S flow rate can be calculated.

■In the case of a synchronous motor, there is almost no change in the rotation speed even if the load fluctuates, so there is no need to measure the rotation speed every time the load changes.

In addition, the measurement error is reduced and the final result is C. V. S.
Flow rate error is reduced.

■The rotational speed stabilizes immediately even when the load is changed, which greatly reduces test time.

■ Changing the special number of revolutions can be easily done by using an electrical signal from the command unit (usually by operating a variable resistor, etc.), and the number of revolutions can be changed continuously.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, with FIG. 1 being a flowchart and FIG. 2 being a connection diagram showing the main parts. 5... Constant volume pump, 6... Synchronous motor, 18...
・Dilution room.

Claims (1)

[Claims] 1. A dilution chamber that dilutes the gas to be measured such as automobile exhaust gas with air, a heat exchanger that heats or cools the diluted gas in the chamber to maintain a constant temperature, and a constant flow chamber that sucks the dilution gas at a constant flow rate. A constant volume dilution sampling device comprising a volumetric pump and a sample collection pump that collects a portion of the dilution gas behind the heat exchanger, wherein the constant volume pump is driven by a synchronous motor. Characteristic constant volume dilution sampling device.