JPS6050212A - Burner air controller for diesel exhaust emission control device - Google Patents

Abstract

PURPOSE:To make a rate of weight flow of secondary air so as to keep it constant in an accurate manner, by installing an escape valve and a flow control valve being controlled in accordance with downstream pressure in the flow control valve, in an air flow passage ranging from an air pump to a regenerating burner. CONSTITUTION:An air flow passage 12 makes the air discharged out of an air pump 11 flow into a regenerating burner 4 of a Diesel particulate filter 5. An escape valve 23 makes a part of inflow air into the flow control valve 24 discharge into the atmosphere so as to cause pressure inside the air flow passage at the inflow side of the flow control valve 24 to become constant in terms of gauge pressure. The flow control valve 24 is controlled so as to increase or decrease its opening area according to variations in downstream pressure since pressure at the downstream side is led into a diaphragm chamber 34 via a pipe 35 and thereby constant pressure is led into a diaphragm chamber 36.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a quiz purifying device that collects particulates contained in diesel exhaust gas using a filter, and regenerates the filter by re-burning the collected particulates using a burner. The present invention relates to a burner air control device for controlling the burner air.

Particulates discharged from diesel engines are usually removed from the exhaust by a ceramic diesel particulate filter due to pollution, and are re-burned at specified times to regenerate the filter itself.
It is discharged as a non-polluting substance. This re-combustion of particulates requires air that maintains an appropriate combustion flow rate and appropriate amount of oxygen, that is, a predetermined air excess ratio.If the heating temperature is low, particulates will not be removed; There is an inconvenience that excessive heating causes the filter itself to melt and make noise.

Incidentally, a burner is often used as a heating source for the filter, and in the burner, the fuel is atomized using high-pressure, small-flow primary air, and the secondary air of a low-pressure hole flow meter is used to perform sivaticulate combustion. Type burners are the most improved technology. The primary air supplied to the burner is approximately proportional to the fuel flow rate, and in order to keep this fuel flow rate constant, a portion of the air amount is normally kept constant. On the other hand, secondary air has a low pressure but requires a large flow of mold, and must be controlled so that only a predetermined weight flow rate of air necessary for combustion of particulates is supplied. This secondary air is usually
A positive displacement air pump is used to supply the air, but if only the rotational speed is kept constant, the volumetric flow rate will be constant.
The weight flow rate is susceptible to changes in response to changes in atmospheric pressure and temperature. For this reason, it is necessary to take advantage of the advantage of positive displacement air pumps, which is ensuring a large discharge amount, while also correcting changes in weight flow rate. For example, as shown in Figure 1, atmospheric pressure decreases as altitude increases, and accordingly, the differential pressure before and after the air pump, that is, the differential pressure between atmospheric pressure and air flow path internal pressure △P
changes in the same way. Hikoori indicates pressure loss on the exhaust side. Second
The figure shows an example of the volumetric flow rate/discharge pressure characteristics of a positive displacement air pump, and it can be seen that the discharge pressure increases by reducing the flow rate on the discharge side. Furthermore, Fig. 3 shows an example of the weight flow rate/discharge pressure characteristics when the positive displacement air pump is located at a low altitude, indicated by a solid line, and when it is located at a high altitude, indicated by a broken line.When obtaining the same weight flow rate, It has been shown that it is necessary to lower the discharge pressure at high altitudes, that is, to lower the discharge pressure by widening the restriction of the air supply path than at low altitudes. Similarly, as shown in FIG. 4, even if the discharge pressure is constant, the weight flow rate fluctuates due to variations in the pump itself, changes in atmospheric temperature, etc.

Next, an example of a conventional burner air control device using such a positive displacement air pump as a secondary air pump will be described with reference to FIG. The diesel engine 1 includes a turbocharger 2, a burner 4 and a filter 5 on the downstream side of an exhaust path 3, and discharges exhaust gas through a muffler (not shown) on the downstream side. A bypass 7 having a switching valve 6 at its starting end is connected in the middle of the exhaust path 3, and its terminal end is connected to the downstream side of the filter 5. The burner 4 has an ignition device using an ignition coil 8, and atomizes the fuel from the fuel pump 10 with air from the primary air pump 9.
It is configured to maintain the excess air ratio of high-temperature gas at a predetermined value with air from the secondary air pump 11, and burns the particulate with excess oxygen.

The flow area of the secondary air supply path 12 is increased or decreased by a flow rate control valve 13, and a vacuum chamber for opening and closing this valve is connected to a vacuum pump 14 via a vacuum adjustment valve 15 and a solenoid valve 16. In addition, the reference numeral 19 indicates a fuel regulating valve, the reference numeral 20 indicates a pressure regulating valve, and the reference numerals 21 and 22 indicate an air cleaner.

Filter 5 of engine 1 like this is particulate)
ff: If excessive adhesion occurs, the controller 17 starts re-combustion, even if it detects that the exhaust passage pressure on the upstream side of the filter 5 has exceeded the set value. In this case, if the atmospheric pressure is low at a high altitude, the controller 17 outputs an output to the solenoid valve 16 based on the input signal from the atmospheric pressure sensor 18, and controls the flow area of the secondary air to increase by a certain amount from the reference value. This is it! A decrease in the weight flow rate due to a decrease in air density can be prevented by increasing the volumetric flow rate. However, this system in which changes in atmospheric pressure are simply controlled by a diaphragm type flow control valve 13 that receives a constant negative pressure has the disadvantage that the degree of flow MWI of the secondary air is poor due to variations in the secondary air pump 11 itself. Furthermore, while the filter 5 is being regenerated, the switching valve 6 is operated to allow the exhaust gas to pass through the bypass 7 so that the exhaust gas from the engine 1 does not adversely affect the combustion conditions in the burner 4. but,
When the engine is operating under high load, the exhaust gas pressure increases.
Since this acts as a back pressure on the filter 5 and the burner 4, the flow rate of the secondary air changes.

Of course, if another muffler is attached to the bypass 7 to make the system independent, this problem will not occur, but an additional muffler will be required.

The object of the present invention is therefore to provide an improved burner air control device capable of accurately maintaining constant the weight flow rate of secondary air supplied to a filter regeneration burner in a diesel exhaust gas purification device equipped with a diesel particulate filter. Our goal is to provide the following.

The burner air control device according to the present invention is equipped with a relief valve and a flow rate control valve in the air flow path that guides the air discharged from the positive displacement air pump to the regeneration burner of the diesel particulate filter. The upstream pressure of the flow control valve is controlled to an absolutely constant pressure using the relief valve so that the weight flow rate is constant, and the valve opening area of the flow control valve is increased or decreased according to the downstream pressure of the flow control valve, in other words, the downstream pressure decreases. When this occurs, the valve opening area is decreased, and when the downstream pressure increases, the valve opening area is controlled to increase.

In this invention, since the upstream pressure of the flow control valve is maintained at an absolutely constant pressure, variations in the flow rate of the air pump can be absorbed, and the lift amount of the flow control valve is controlled according to the downstream pressure of the flow control valve, so the burner Fluctuations in flow rate due to back pressure and changes in atmospheric pressure can be corrected.

An embodiment of the present invention will be described below with reference to FIG. The basic configuration of the burner combustion system is the same as the conventional example shown in FIG. 5, but the control system for supplying secondary air to the burner 4 is different from the conventional example. Air passage 12 from air cleaner 22 to burner 4 via secondary air pump 11
The relief valve 23 and the flow control valve 2 are installed in order from the upstream side.
4 are provided. Diaphragm 25 of relief valve 23
The lower chamber 26 is connected to the air flow path 12 upstream of the relief valve 23 by an upstream pressure intake means such as a conduit 27, and the upper chamber 28 is connected to the air flow path 12 upstream of the relief valve 23 by a constant pressure valve CPv which generates an absolutely constant pressure. or an aneroid bellows. A compression coil spring 31 is provided in the upper chamber 28 for constantly pressing the valve body 29 connected to the diaphragm 25 in a direction to close the valve opening 30. The strength of the spring 31 is balanced with the operating pressure of this relief valve 23, and a portion of the air in the air flow path 12 is released to the atmosphere through the relief path 32. On the other hand, the flow control valve 24 on the downstream side of the relief valve 23 has a lower chamber 3475 partitioned off by the diaphragm 33.
The upper chamber 36 is connected to the air passage 12 on the downstream side by a downstream pressure intake means such as a conduit 35, and the upper chamber 36 is connected to a constant pressure valve C.
This leads to constant pressure holding means such as PV and aneroid bellows.

A compression coil spring 39 is provided in the upper chamber 36 to constantly press the valve body 37 connected to the diaphragm 33 in a direction to close the valve opening 38.

Next, the operation of this air control device will be explained.

The upstream pressure of the relief valve 23 is applied to the chamber 26 below the relief valve 23, and the absolute constant pressure from CPv is applied to the upper chamber 28, so the operating pressure of the relief valve 23 is set to, for example, 800 yuHg. Then, when the upstream pressure becomes higher than this, the upstream pressure chamber 26 pushes up the diaphragm 25, so the valve body 29 rises and a part of the air on the upstream side is released to the atmosphere, and the upstream pressure decreases.

Conversely, when the upstream pressure becomes lower than 8001+1Hg, the constant pressure chamber 28 pushes down the diaphragm 25, so the valve body 29 descends to suppress the release of air, and the upstream pressure increases.

In this way, the upstream pressure of the flow control valve 24 is maintained at an absolutely constant pressure. When the upstream pressure is maintained at an absolutely constant pressure in this way, even if there is a variation in the performance of the air pump 11, this can be absorbed and the weight flow rate control of the secondary air supplied to the burner 4 can be kept constant. However, the flow control valve 24
If the total upstream pressure of
At low altitude conditions of 0111Hg, the discharge pressure of the air pump 11 is 401! 11Hg, and under high altitude conditions where the atmospheric pressure is 60011Hg, the discharge pressure of the pump 11 is 200ffillllHg.
g, and in the case of high altitude conditions, a large flow of secondary air will be supplied. In the present invention, such fluctuations in flow rate caused by fluctuations in atmospheric pressure are self-corrected by applying a constant pressure to the upper chamber 36 of the flow control valve 24 and the downstream pressure to the lower chamber 34. Ru. That is, when the downstream pressure of the flow rate control valve 24 becomes lower than its operating pressure due to high altitude conditions, the upper chamber 36 pushes down the diaphragm 33 and the valve body 37 narrows the valve opening 38, thereby reducing the weight flow rate of the secondary air. is saved. On the other hand, when the downstream pressure becomes higher than the operating pressure due to low altitude conditions, the lower chamber 34 pushes up the diaphragm 33 and the valve body 37 widens the valve opening 38.
The weight flow rate of secondary air increases. If there is only one muffler, when the engine is under high load during burner operation, the exhaust gas passing through the bypass 7 becomes back pressure and pushes up the downstream pressure of the flow control valve 24, so the valve body 37 rises at this time as well. The amount of secondary air is increased.

In an alternative embodiment of the invention shown in FIG. 7, the operation of the relief valve 23 is more precisely controlled by an associated vacuum regulating valve 40. Negative pressure from a vacuum pump is applied to the chamber 28 above the relief valve 23 via a restriction 41, and atmospheric pressure is applied to the chamber 26 below. A left chamber 43 partitioned by a diaphragm 42 of one vacuum regulating valve 40 is connected to a flow control valve 2 through a conduit 44.
4 upstream pressure is applied, and a constant pressure valve CP is applied to the right chamber 45.
A constant pressure is applied from a constant pressure holding means such as a V or an aneroid bellows. The end of a conduit 47 leading to the chamber 28 above the relief valve 23 is opposed to the surface of the diaphragm 42 facing the right chamber 45 having the compression coil spring 46 .

When the upstream pressure of the flow control valve 24 increases, the vacuum adjustment valve 40
diaphragm 42 is pushed down to block the end of conduit 47. This releases all the negative pressure from the vacuum pump to the relief valve 2.
3, the diaphragm 25 is sucked and the valve body 29 is lifted, releasing some of the air in the flow path to the atmosphere and reducing the upstream pressure of the flow control valve 24. When the upstream pressure decreases in this way, the vacuum regulating valve 4
0 diaphragm 42 is pushed back by the pressing force of the spring 46 provided in the right chamber 45, and the end of the conduit 47 is opened, so that a portion of the absolute pressure in the right chamber 45 escapes through the conduit 47, causing a restriction. 41 enters the chamber 28 above the relief valve 23 and pushes down the diaphragm 25, so the valve body 29 throttles the valve opening 30 to maintain the upstream pressure of the flow control valve 24 at an absolutely constant pressure.

As described above, according to the burner air control device of the present invention, the upstream pressure of the flow rate control valve is kept absolutely constant and positive, so even if the air pump flow rate varies, the constant air weight necessary for stable combustion in the burner can be maintained. Since the flow rate is obtained and the flow rate control valve is controlled using the downstream pressure and an absolutely constant pressure, it is possible to follow fluctuations in atmospheric pressure and back pressure, and furthermore, it is possible to follow fluctuations in atmospheric pressure and back pressure. Even if there is, the upstream pressure is kept at an absolutely constant pressure, so the load on the air pump becomes constant, improving the durability of the pump.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between altitude changes and atmospheric pressure.
The figure shows the discharge pressure/discharge pressure at different drive voltages of a positive displacement pump.
A graph showing the volumetric flow rate characteristics, Figure 3 is a graph showing the discharge pressure/weight flow rate characteristics at high and low altitudes, and Figure 4 shows the discharge pressure/weight flow rate characteristics to explain the variation in the flow rate of the air pump itself. The graph and FIG. 5 are control circuit diagrams showing an example of a conventional burner air control device, and FIGS. 6 and 7 are control circuit diagrams showing examples of a burner air control device in the present invention. 1...Engine, 3...Exhaust path, 4...Bar 1-
．． 5...Filter, 6...Switching valve, 7...Bypass, 11...Secondary air pump, 12...Air flow path,
22... Air cleaner, 23... Relief valve, 24...
...Flow control valve, 40...Vacuum adjustment valve.

Claims (1)

[Claims] A burner air control device for a diesel exhaust gas purification device, comprising a relief valve and a flow control valve sequentially from upstream in an air flow path that guides air discharged from a positive displacement air pump to a regeneration burner of a diesel particulate filter,
The relief valve includes means for taking in the pressure upstream of the flow control valve and releasing a portion of that pressure so as to maintain it at an absolutely constant pressure, and the flow control valve has means for taking in the pressure upstream of the flow control valve and releasing a portion of the pressure so as to maintain it at an absolutely constant pressure. A burner air control device comprising means for taking in downstream pressure on one side so as to reduce the valve opening area when the pressure decreases, and means on the other side for taking in a constant pressure in opposition thereto.