JPH0429849B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a burner air control device for a burner used for reburning a diesel particulate filter.

To prevent pollution, particulate matter emitted by diesel engines is usually removed from the exhaust by a ceramic diesel particulate filter (hereinafter simply referred to as a filter), which also regenerates the filter itself at designated times and re-burns it. It is removed as a non-polluting substance. This re-burning of the particulate yulate requires a moderate combustion temperature and a suitable amount of oxygen, that is, air that maintains a predetermined amount of excess air.If the heating temperature is low, the particulate yate will not be removed, and on the contrary, it will not be heated too much. Then, there is an inconvenience that the filter itself is damaged by melting.

By the way, burners are often used as heating sources for filters, and in particular, atomizer burners are often used, which atomize fuel with high-pressure, small-flow primary air and burn particulate with low-pressure, large-flow secondary air. ing. 1 supplied to this burner
The optimum supply amount of primary air is approximately proportional to the fuel flow rate, and in order to keep this fuel flow rate constant, the primary air amount is usually kept constant. On the other hand, secondary air is required to have a low pressure but a large flow rate, and must be controlled so that only a predetermined weight flow rate value necessary for combustion of the particulate is supplied. This secondary air is normally supplied using a positive displacement air pump, and although this air pump has a constant volumetric flow rate by keeping only the rotation speed constant, it responds to changes in atmospheric pressure, atmospheric temperature, and engine exhaust pressure. It is susceptible to changes in weight flow rate. 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, a general positive displacement air pump has characteristics as shown in FIGS. 1 to 3.

FIG. 1 shows an example of the volumetric flow rate-discharge pressure characteristic of a positive displacement air pump, and it is clear that by narrowing down the passage area on the discharge side, the volumetric flow rate is reduced, while the discharge pressure increases relatively greatly. Furthermore, Figure 2 shows the case where the positive displacement air pump is located at a low altitude (indicated by a solid line) and the case where it is located at a high altitude (indicated by a dashed line).
The figure shows an example of the gravimetric-discharge pressure characteristics of , and shows that in order to obtain the same weight flow rate, it is necessary to lower the discharge pressure at high altitudes, that is, to widen the restriction of the air supply passage and lower the discharge pressure from low altitudes. ing. Similarly, as shown in FIG. 3, even if the altitude is constant, the weight flow rate fluctuates as shown by the two broken lines due to fluctuations in the pump itself, atmospheric temperature, etc.

Two positive displacement air pumps with these characteristics
An example of a conventional device used as an air pump is shown in the 4th section.
Shown in the figure. A diesel engine (hereinafter simply referred to as engine) 1 includes a turbocharger 2, a filter 5 on the downstream side of an exhaust path 3, and discharges exhaust gas through a muffler 200 on the downstream side. 4 is a burner provided upstream of the exhaust path 3 of the filter 5, and the burner 4 is connected to the ignition coil 6.
The fuel from the fuel pump 8 is atomized using the air from the primary air pump 7, which is metered by the pressure regulating valve 201, and the air from the secondary air pump 9 is used to atomize the excess air in the high-temperature gas. It is configured to maintain the rate at a predetermined value and burns the particulate with excess oxygen. The flow area of the secondary air supply path 10 is increased or decreased by a flow control valve 11, and the vacuum chamber that opens and closes this valve is a vacuum pump 12 that is a negative pressure source.
and is connected via a vacuum regulating valve 13 and a solenoid valve 14.

Additionally, in such a system, it is necessary to ensure that the flow of exhaust gas does not affect the regeneration of the particulate. For this reason, as shown in FIG. 1, exhaust bypass passages 202 are provided on the upstream and downstream sides of the filter 5 of the exhaust passage 3, respectively, and are connected to the exhaust passage 3. At the upstream branch of road 202,
An exhaust switching valve 210 is provided. The exhaust switching valve 210 is driven by a diaphragm 203 connected to the vacuum pump 12 via a link mechanism. A solenoid valve 204 is provided between the diaphragm 203 and the vacuum pump 12. Same solenoid valve 2
04 is the valve body 205, coil 206 and spring 2
07, when current flows through the coil 206, the valve body 205 is pulled by the coil 206, and the solenoid valve 2
04 is released. Then, the negative pressure of the vacuum pump 12 acts on the diaphragm 203, and the exhaust switching valve 21
0 moves from position a to position b to close the exhaust passage 3. As a result, the exhaust gas discharged from the engine 1 passes through the exhaust bypass passage 202 and is guided to the muffler 200, so that the exhaust gas discharged from the engine 1 is directed to the burner device 200.
It is designed so that it does not affect the combustion conditions of 0.

Note that 17 is a fuel adjustment valve, 18 is a pressure adjustment valve, 15 is a controller that controls the ignition coil 6, air pumps 7, 9, solenoid valve 14, and fuel adjustment valve 17.
6 indicates an atmospheric pressure sensor.

If excessive particulate matter adheres to the filter 5 of the engine 1, the controller 1
5 starts re-combustion, for example, by detecting with the pressure sensor 19 that the exhaust passage pressure on the upstream side of the filter 5 has exceeded a set value. in this case,
When the atmospheric pressure is low at a high altitude, the controller 15 outputs an input signal from the atmospheric pressure sensor 16 to the solenoid valve 14, and controls the flow area of the secondary air to increase by a certain amount from the reference value.

This makes it possible to prevent a decrease in the weight flow rate due to a decrease in air density 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 11 that receives a constant negative pressure has the disadvantage that the precision of the flow rate of the secondary air is low due to variations in the type 2 air pump itself.

SUMMARY OF THE INVENTION An object of the present invention is to provide a burner air control device for a diesel particulate filter that can accurately control the flow rate of secondary air with a simple configuration.

The burner air control device for a diesel particulate filter according to the present invention includes an exhaust bypass passage that bypasses the filter, an air supply passage to the burner, a flow control valve that changes the flow area of the air supply passage, and a flow control valve before and after the flow control valve. The configuration includes a relief valve that operates to keep the differential pressure constant, and a control section that operates the valve opening/closing amount of the flow control valve. It has a configuration with two chambers.

The present invention will be described below with reference to the accompanying drawings.

FIG. 5 shows a burner air control device (hereinafter simply referred to as burner air control device) for a diesel particulate filter as an embodiment of the present invention. This burner air control device includes the same members as the conventional device shown in FIG. 4, and the same members will be given the same reference numerals to avoid confusion hereafter, and their repeated explanation will be omitted. A burner 20 that supplies hot air with a predetermined high temperature and a predetermined excess air ratio to the filter 5 of the exhaust path 3 is a secondary air flow path (hereinafter simply referred to as a secondary flow path).
Secondary air is received from a secondary air pump (hereinafter simply referred to as secondary pump) 9 via 21. Secondary pump 9
Air flows into the secondary flow path 21 through the air filter 22, and is supplied to the burner 20 through a flow control valve 28 that increases or decreases the flow area of the secondary flow path. 2
The next flow path 21 includes an air filter 22 and a secondary pump 9.
An atmospheric temperature sensor 25 is provided between the flow control valve 2 and the flow control valve 2.
A pressure sensor 26 is provided on the upstream side of 8 to detect the pressure.
Equipped with. These two sensors are connected to transmit their output signals to a fuel control device 27 that controls the flow rate of secondary air.

The valve drive device 23 integrally connects the flow control valve 28 with a diaphragm 29 , which has a negative pressure chamber 3 equipped with an atmosphere opening chamber 30 and a compression spring 47 .
1 is facing. The valve-to-flow control valve 28 is attached to the secondary air flow path 21 so as to vary the flow path area S thereof. The negative pressure chamber 31 is connected to the vacuum pump 12, which is a negative pressure source, via a duty solenoid valve (hereinafter simply referred to as duty valve) 32. The duty valve 32 turns the valve body on and off at a frequency of 10Hz to 20Hz to control switching between communicating the negative pressure chamber 31 with the vacuum pump 12 or guiding the atmosphere to the negative pressure chamber 31, and controls the ON time period of the valve body. The pulse width is variably controlled by the output signal of the combustion control device 27, thereby changing the negative pressure value of the negative pressure chamber 31, and moving the flow control valve 28 to a position where this value, the compression spring, and the atmospheric pressure are in balance. The flow path area S is variably controlled. Note that the flow rate control valve 28 is displaced from the fully open position to the fully closed position, and this displacement is detected by the position sensor 33 as an output signal corresponding to the variable electrical resistance value.
This is fed back to the fuel control device 27.

A relief valve 51 is installed in the secondary flow path 21 between the flow rate control valve 28 and the secondary pump 9 to release air to the atmosphere. This relief valve 51 has a rear chamber 53 equipped with a compression spring 52 that presses in the valve closing direction C.
The front chamber 54, which receives the pressure between the flow rate control valve 28 and the secondary pump 9, applies air pressure to the diaphragm 55. That is, when the pressing force due to the pressure difference between the front and rear pressures exceeds the pressing force of the compression spring 52, the relief valve 51 moves in the valve opening direction P, and when it becomes a check, the relief valve 51 moves in the valve closing direction C. The main part of the combustion control device 27 is formed by a microcomputer. The combustion control device 27 includes a pressure sensor 26 on the upstream side of the flow rate control valve 23, an atmospheric temperature sensor 25, and a position sensor 33.
It receives output signals from the burner exhaust gas temperature sensor 46 and increases or decreases the volumetric flow rate of the secondary air by an appropriate amount according to the upstream pressure of the flow control valve and the atmospheric temperature, and also adjusts the fuel flow rate according to the burner exhaust gas temperature. It has the property of increasing or decreasing the amount to an appropriate amount.

To explain in more detail, the weight flow rate Ga of the secondary air is Ga=SC√2, where S: flow path cross-sectional area, Δρ: differential pressure across the flow control valve 28, ρ: air density on the upstream side of the flow control valve 28. However, in this example, Δρ is always kept constant and C is a flow rate coefficient that takes an almost constant value, so by correcting the flow passage cross-sectional area by the change in air density, the weight of the secondary air can be adjusted. The flow rate can be kept constant.

Furthermore, the equation can be modified as follows, taking into account the air temperature and pressure.

In other words, if the formula is the weight flow rate when the air temperature is T and the air pressure is P, then the air density ρ is ρ=C ₁ ×273.16/(273.16+t)×P/760 From T=273.16+t Here, if we set C ₂ = 273.1/760 If Ca=constant, P=constant You can leave it as

Therefore, S=K√ Where, T: Air temperature upstream of the flow control valve, P: Air pressure upstream of the flow control valve, K: Proportionality constant In other words, as the air temperature rises, increase the cross-sectional area of the flow path, and increase the air pressure. In response to a rise, the weight flow rate can be kept constant by controlling the cross-sectional area of the flow path to be reduced. Note that since the cross-sectional area of the flow path has a one-to-one correspondence with the lift amount of the flow control valve, the weight flow rate can be kept constant by indicating the required lift amount for T and P using a map or the like.

Here, p is the air pressure on the upstream side of the flow rate control valve 28, but it may be any pressure in the flow path near the flow rate control valve 28, and can also be the air pressure on the downstream side of the flow rate control valve 28.

In addition, as shown in Figure 6, in order to keep the burner exhaust gas temperature constant, it is compared with the reference value T ₀ , and while the reference value is below the set value Δt, the reference fuel amount is
The fuel injection amount q is controlled by the combustion control device 27 so that a small fuel amount q ₂ is injected while q ₀ exceeds the reference value by a set value Δt or more.
The operation of the burner air control device shown in FIG. 5 will be explained.

The combustion control device 27 detects the exhaust pressure on the upstream side of the filter 5 with the pressure detection device 19, and when the exhaust pressure exceeds a set value, starts re-combustion processing. First, combustion control device 2
7 issues a signal to turn on each of the primary and secondary air pumps 7 and 9, the fuel pump 8, and the ignition coil 6. At the same time, the burner exhaust gas temperature sensor 46
Based on the output signal of , if this is lower than the reference temperature T ₀ , an output signal is given to the fuel regulating valve 17 to meter the fuel flow value from q ₀ to q ₁ and vice versa to q ₂ . By the way, the relief valve 51 is controlled to always maintain the secondary flow path 21 at the differential pressure value set in the compression spring 52. That is, when the pressing force due to the differential pressure between the front and rear exceeds the pressing force of the compression spring 52, the relief valve 51 moves in the third valve opening direction P and becomes a check;
moves in the valve closing direction C. The differential pressure across the flow rate control valve 28 is maintained constant only by this so-called pneumatic operation.

On the other hand, negative pressure is applied to the negative pressure chamber 31 of the valve drive device 23 via the duty valve 32. In this case, the combustion control device 27 uses a map stored in advance to determine the lift position of the flow control valve 28 that can obtain a predetermined weight flow rate Ga based on the upstream pressure of the flow control valve 28 and the atmospheric temperature. . Then, the combustion control device 27 performs feedback control by varying the duty ratio of the duty valve 32 so that the signal corresponding to the determined lift position of the valve body 28 and the output signal generated by the position sensor 33 match. It should be noted that each of the above-mentioned maps is inputted in advance after setting the proportionality constant K etc. through experiments based on the above-mentioned theoretical formulas. This allows the secondary air to flow through the secondary flow path 2.
1, the weight flow rate is always adjusted to be constant and supplied to the burner 20.

From the above, the burner air control device shown in FIG. Relief valve drive device 3 that automatically operates the differential pressure between the front and rear
By controlling the operation of the duty valve 32 so that the flow area S is always kept constant at 4, etc., and the flow path area S is corrected to a predetermined value by the control unit 27 to cancel fluctuations in the pressure on the upstream side of the flow rate control valve 28 and the atmospheric temperature. The flow rate control of the secondary air is performed with high precision, and the combustion control device 27 does not need to control variations in the discharge amount of the secondary pump 9 itself, resulting in an effect of being simplified accordingly.

The burner air control device shown in FIG. 5 operates the valve drive device 23 using the combustion control device 27, the upstream pressure sensor 26 of the flow rate control valve 28, and the atmospheric temperature sensor 25, but instead of this, FIG. The flow rate control valve 61 may be controlled only at atmospheric pressure as shown in FIG. A diaphragm 6 integrated with this flow control valve 61
2 is sandwiched between an atmosphere open chamber 63 and a constant pressure chamber 65 equipped with a compression spring 64 that generates a pressing force in the valve opening direction P. The constant pressure chamber 65 is connected to a constant pressure source 66 that generates a constant pressure with respect to absolute pressure.

The constant pressure source 66 has the configuration shown in FIG. 9, for example, and includes a constant pressure chamber 301 sealed by a housing 300, a vacuum diaphragm 302 provided in the identified pressure chamber 301, a vacuum pump 12, and the constant pressure chamber 301. While communicating, there is a constriction part 303a in the middle.
It is composed of a negative pressure pipe 303 provided with a negative pressure pipe 303, an air release pipe 306 whose one end is open to the atmosphere and has a spring 304 and a sphere 305 incorporated therein as shown in FIG. 9, and a communication pipe 307 which supplies a constant pressure.
When the pressure in the constant pressure chamber 301 decreases, the vacuum diaphragm 302 expands and presses the sphere 305 in the atmosphere opening tube 306, causing the atmosphere to flow into the constant pressure chamber 301 through the opening tube 306. When the atmosphere flows into the constant pressure chamber 301, the pressure inside the constant pressure chamber 301 increases, the vacuum diaphragm 302 contracts, and the sphere 305 closes the atmosphere opening pipe 306. By repeating these steps, the pressure in the constant pressure chamber becomes approximately constant.

The control section consisting of such a pneumatic system operates as follows. When the atmospheric pressure decreases (for example, when reaching a high altitude), the flow control valve 61 opens in the valve opening direction P.
The flow path area S is increased to increase the volumetric flow rate. Conversely, when atmospheric pressure rises, the flow control valve 6
1 moves in the closing direction C, narrowing the flow path area S and lowering the volumetric flow rate. By such an operation, the weight flow rate of the secondary air can be maintained substantially constant. In this case, the control section is simplified and there is an effect of reducing parts.

Furthermore, as shown in FIG. 8, the above-mentioned flow rate control device 6
The flow rate control device 102 may use an aneroid bellows 100 whose interior is vacuum-sealed instead of the bellows 100 to directly open and close the flow rate control valve 28. The flow rate control device 102 includes a bellows 100 whose interior is vacuum-sealed, and a casing 104 surrounding the bellows 100 and having an opening 103 open to the atmosphere.
and a spring 105 provided within the bellows, and the bellows 100 and the flow control valve 28 are connected.

According to the above configuration, when the atmospheric pressure becomes low, the bellows 100 expands due to the balance between the surrounding atmospheric pressure and the biasing force of the spring 105, and the flow control valve 28
decreases, and the flow path area S increases. Also,
When the atmospheric pressure increases, the bellows 100 contracts,
The flow control valve 28 narrows the upward flow area S.

Therefore, according to the configuration of this embodiment, the flow area S can be controlled in accordance with atmospheric pressure with an extremely simple configuration.

Furthermore, the control unit 27 shown in FIG. 5 controls the flow path area S based on the upstream pressure of the flow control valve and the atmospheric temperature, but it can also be controlled depending on either the outflow side pressure of the flow control valve or the atmospheric temperature. It may be controlled or other factors such as engine speed and load may be added.

[Brief explanation of drawings]

Figure 1 is a discharge pressure-volume flow diagram of a positive displacement air pump, Figure 2 is a diagram explaining changes in weight flow rate due to differences in altitude, Figure 3 is a diagram explaining variations in weight flow rate of the air pump itself, FIG. 4 is a schematic diagram of a conventional burner air control device, FIGS. 5, 7, and 8 are schematic diagrams of burner air control devices as different embodiments of the present invention, and FIG. 6 is a diagram of burner exhaust gas temperature. The fuel quantity characteristic diagram and FIG. 9 each show a sectional view showing an embodiment of the constant pressure source. 3... Exhaust path, 5... Filter, 9... Secondary pump, 20... Burner, 21... Secondary flow path, 23
...Flow control device, 27...Combustion control device, 28
...flow control valve, 34 ... relief valve, 66 ... constant pressure source, a ... negative pressure adjustment path, 102 ... bellows, 2
02...Exhaust bypass path.

Claims (1)

[Claims] 1. A particulate filter that is provided in the exhaust passage of a diesel engine and collects particulate matter in the exhaust gas, an exhaust bypass passage that bypasses the particulate filter, and an upstream side of the particulate filter. The burner device is provided with a burner device to which fuel and air are supplied, and the exhaust gas is passed through the exhaust bypass passage in a state where a set amount or more of particulate matter is collected in the particulate matter filter, and the particulate matter is combusted by the burner. A filter regeneration device that supplies air to the burner device via an air supply device, a flow rate control valve that is provided in the supply path and variably controls a flow path area of the supply path, and the flow rate control valve. a flow rate control device that increases the opening degree as atmospheric pressure decreases, a relief valve that is provided in the supply path and releases a part of the air in the supply path to the outside, and the relief valve. A relief valve control device that controls opening and closing, and a combustion control device that detects the regeneration timing of the filter and causes the exhaust gas to flow into the exhaust bypass path and causes the burner device to perform combustion operation, further comprising: a relief valve control device that controls opening and closing; a first chamber to which the downstream pressure of the flow control valve is guided, a second chamber to which the upstream pressure is guided, and a relief valve that partitions the first and second chambers and is linked to the relief valve. It consists of a diaphragm connected to the diaphragm and a spring that applies a biasing force to the diaphragm, and when the pressure on the upstream side of the flow control valve is higher than the set value compared to the pressure on the downstream side, the relief valve is opened. 1. A regeneration device for a diesel particulate filter, characterized in that the pressure difference between upstream and downstream sides is constant. 2. The flow control device includes an atmospheric pressure chamber to which atmospheric pressure is introduced, a constant pressure chamber to which a predetermined constant pressure is introduced, a diaphragm that partitions the two chambers and is connected to the flow control valve, and applies an urging force to the diaphragm. 2. The diesel particulate filter regeneration device according to claim 1, characterized in that it is constituted by a pressure responsive device comprising a spring for applying pressure. 3. The flow control device is constituted by a pressure responsive device consisting of a bellows connected to the flow control valve and a casing surrounding the bellows and having an opening to the atmosphere, and the bellows is configured to expand when atmospheric pressure decreases. A diesel particulate filter regeneration device according to claim 1, characterized in that: 4. A particulate filter installed in the exhaust passage of a diesel engine to collect particulate matter in the exhaust gas, an exhaust bypass path that bypasses the particulate filter, and a particulate filter provided upstream of the particulate filter to collect particulate matter from the exhaust gas. In a filter regeneration device, the filter regeneration device is equipped with a burner device supplied with the particulate matter, and causes the exhaust gas to pass through the exhaust bypass passage in a state where a set amount or more of particulate matter is collected in the particulate matter filter, and burns the particulate matter by the burner, a control device that detects the regeneration timing of the filter and causes the exhaust gas to flow through the exhaust bypass path and causes a filter regeneration device including the burner device to perform a combustion operation; a supply path that supplies air to the burner device; a flow rate control valve provided in the supply path for variably controlling the flow area of the supply path; a pressure detection means provided in the vicinity of the flow rate control valve in the supply path; and a temperature sensor for detecting the air temperature in the supply path. means, a calculation section provided in the control device for calculating an optimum lift amount of the flow control valve based on the pressure and temperature, and a flow control section connected to the flow control valve based on the lift amount calculated by the calculation section. a flow control device comprising a valve drive device for driving a valve; a relief valve provided in the supply path for releasing a part of the air in the supply path to the outside; and a relief valve control device for controlling opening and closing of the relief valve. Further, the relief valve control device includes a first chamber to which the downstream pressure of the flow control valve is guided, and a second chamber to which the upstream pressure is guided.
It consists of a diaphragm that partitions the first chamber and the second chamber and is connected to the relief valve so as to operate in conjunction with the relief valve, and a spring that applies a biasing force to the diaphragm, and the pressure on the upstream side of the flow rate control valve is Regeneration of a diesel particulate filter characterized in that the relief valve is opened when the pressure on the downstream side is greater than a set value compared to the pressure on the downstream side, and the pressure difference between the upstream and downstream sides of the flow rate control valve is kept constant. Device. 5. The valve driving device partitions a negative pressure chamber communicated with a negative pressure source, an atmospheric pressure chamber open to the atmosphere, and the atmospheric pressure chamber and the negative pressure chamber, and operates in conjunction with the flow rate control valve. a diaphragm connected to the flow rate control valve, a spring that applies a biasing force to the diaphragm, and a spring provided between the negative pressure chamber and the negative pressure source to open the negative pressure chamber to the atmosphere or to The claim is characterized in that the flow rate control valve is set to a target value by controlling the switching valve based on a value calculated by the calculation unit, the switching valve being switched to communicate with a pressure source. A regeneration device for a diesel particulate filter according to item 4. 6. The diesel particulate filter according to claim 5, wherein the switching valve is duty-controlled by a signal from the calculation section to set the valve lift amount of the flow rate control valve to a target value. playback device. 7. The diesel particulate filter according to claim 5, wherein the switching valve is controlled on and off by a signal from the calculation section to set the valve lift amount of the flow rate control valve to a target value. playback device. 8. It has a lift position detector that detects the valve lift position of the flow control valve, and inputs the value detected by the lift position detector to the calculation section, and sets the valve lift amount of the flow control valve to a target by feedback control. 6. The diesel particulate filter regeneration device according to claim 5, wherein the regeneration device is set to a value of 0.