JPH0436248B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention collects particulate contained in the exhaust gas of a diesel engine in a filter, heats and burns the collected particulate with a heat source, and releases it into the atmosphere. The present invention relates to an improvement in an exhaust gas purification device for an engine that purifies exhaust gas.

As is well known, the exhaust gas from diesel engines contains a large amount of particulates (carbon particles), which significantly pollutes the atmosphere and has become a social problem.

This invention was made in view of the above points, and includes collecting particulates generated from the engine with a filter, determining the amount of particulates adhering to the filter by detecting the pressure loss of the filter, In this method, when a predetermined pressure loss is reached, a heat source is driven to heat the particulate and forcibly burn it, and the pressure sensor that detects the pressure loss and the piping route are cleaned of contaminants such as particulate, moisture, oil mist, etc. It is an object of the present invention to provide an exhaust gas purification device in which the amount of adhesion is significantly reduced and the reliability of the device is improved.

Embodiments of the exhaust gas purification device of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of one embodiment of the present invention, where 1 is an engine and 2 is an exhaust pipe for discharging exhaust gas after combustion. A filter 3 is provided in the path of this exhaust pipe 2. This filter 3 is designed to collect particulates in the exhaust gas.

On the other hand, 4 is a solenoid valve connected from the upstream pressure outlet of the filter 3 via piping 6, and 5 is a solenoid valve connected from the downstream pressure outlet of the filter 3 via piping 7. It is a valve.

A pressure sensor 9 is connected to these electromagnetic valves 4 and 5 via pipes 8 and 18. The control device 10 performs predetermined calculations based on the signal from the pressure sensor 9, the signal from the opening sensor 14 that indicates the opening degree of the accelerator pedal 13, and the signal from the rotational speed detector 15 that detects the rotational speed of the engine 1. The control device 10 drives a burner 11, and the burner 11 is ignited by an ignition device 12.

Note that the burner 11 includes fuel 11a and air 11.
The mixed gas b is supplied.

Next, the operation of the engine exhaust gas purification device of the present invention configured as described above will be explained. Particulate matter contained in the exhaust gas discharged from the engine 1 is collected by the filter 3, and as shown in FIG. The resulting pressure loss, that is, the pressure difference between the upstream side and the downstream side of the filter 3 becomes large.

Since an increase in pressure loss means an increase in exhaust loss, the output of the engine 1 will decrease, and furthermore, if a large amount of particulate is collected in the filter 3 and is then combusted, the filter 3 will become hot. There is a problem with damage.

In order to solve this problem, filter 3
When the pressure loss in reaches a predetermined amount, the ignition device 1
2, it is necessary to ignite the burner 11 and burn the particulate collected in the filter 3 by the amount of heat generated by the burner 11.

FIG. 3 shows the method of detecting the pressure loss of the filter 3 and the control of the burner 11 using a time chart. FIG. 3a shows the amount of particulate collected, FIG. 3b shows the operating state of the solenoid valve 4, FIG. 3c shows the operating state of the solenoid valve 5, and FIG.
Figure d shows the output signal of the pressure sensor 9, and Figure 3e
3 shows the calculation result of the pressure difference, and FIG. 3f shows the burner operating state.

As shown in Figure 3b and Figure 3c, for a predetermined time
For each To, the solenoid valve 4 and the solenoid valve 5 are sequentially opened for a fixed short time width τo, and the pressure on the upstream side of the filter 3 is passed through the piping 6, the solenoid valve 4, and the piping 8, and then to the filter 3. The pressure on the downstream side is introduced into the pressure sensor 9 via the piping 7, the solenoid valve 5, the piping 18, the solenoid valve 4, and the piping 8, and the pressure is detected (FIG. 3d).

For a very short time after the solenoid valves 4 and 5 were opened, the output of the pressure sensor 9 did not show the true value due to the pressure transmission delay due to the piping route, so the solenoid valves 4 and 5 were operated in the open direction. After that, after a short period of time, the output of the pressure sensor 9 is transferred to the control device 1.
0 reads.

The pressure difference detected in this way between the upstream side and the downstream side of the filter 3 is calculated by the control device 10, and if the result is less than a predetermined value Ps, the burner 11 is deactivated, and when the pressure difference is more than the predetermined value Ps. When you reach
The igniter 12 and burner 11 are activated to heat the filter 3 to a high temperature, so the particulates collected on the filter 3 are combusted and the filter 3 is regenerated.

The time width τo for opening the solenoid valves 4 and 5 is set to a value that allows some margin for the time during which pressure is transmitted to the pressure sensor 9 through the piping route, but normally
A short time of about 0.5 seconds is sufficient.

The exhaust loss in the filter 3 changes depending on the engine speed and load (high load a, low load b) as shown in FIG. It is desirable to make this variable in accordance with the rotational speed and fuel injection amount, which represent the amount of displacement in the filter 3, so that the correlation between the pressure loss of the filter 3 and the amount of particulate collected becomes more accurate.

The amount of particulate collected varies greatly depending on the engine load and rotation speed, so filter 3
The time it takes for the pressure loss to reach a predetermined value varies depending on the operating conditions, but under normal operating conditions it takes about 2 hours.
The time during which exhaust gas is introduced into the pressure sensor 9 can be made a very small proportion of the total.

Cycle To according to the operating condition with the highest displacement
By setting , the pressure difference between the upstream and downstream sides of the filter 3 can always be detected early, but if the period To is shortened, the frequency at which the upstream and downstream sides of the filter 3 communicate with the pressure sensor 9 is increased. increases, and the cumulative value of the time that the pressure sensor 9 is exposed to the exhaust gas increases, so the pressure sensor 9, the piping route, and the solenoid valves 4 and 5 are exposed to particulate matter, moisture contained in the exhaust gas, oil mist, etc. This increases the possibility of causing blockages and malfunctions.

In order to eliminate such problems, an integral value of the fuel injection amount supplied to the engine 1 or an equivalent product of the output signal of the opening sensor 14 and the engine rotation speed obtained from the rotation speed detector 15 is used. By opening the solenoid valves 4 and 5 every time the value corresponding to the value reaches a predetermined amount, the frequency of introducing exhaust gas to the pressure sensor 9, and therefore the cumulative time, can be reduced to a minimum. Furthermore, since the solenoid valve 5 is provided with an air inlet 5a, when the solenoid valves 4 and 5 are closed (which occupies most of the operating time), outside air flows from the air inlet 5a to the solenoid valve 5 to the piping. 18 → Solenoid valve 4 → Introduced to pressure sensor 9 through piping 8, so pressure sensor 9, solenoid valves 4 and 5,
Pipes 8 and 18 are filled with clean air. Therefore, the degree to which the pressure sensor 9, the electromagnetic valves 4 and 5, and the pipes 8 and 18 are contaminated by particulates, oil mist, moisture, etc. in the exhaust gas can be significantly reduced.

As described above, according to the engine exhaust gas purification device of the present invention, the amount of particulate collected in the filter is determined based on the pressure loss of the filter, and when the value reaches a predetermined value, the burner is activated. The particulate is combusted by evaporating the particulate in the exhaust gas, and the pressure is introduced into the pressure sensor by the switching valve for the minimum necessary time through the pressure introduction paths upstream and downstream of the filter. Atmospheric air is introduced into the pressure sensor and switching valve path during non-detection periods, significantly reducing contaminants such as particulates, moisture, and oil mist that adhere to the pressure sensor, electromagnetic switching valve, piping, etc. be able to. Therefore, there is an effect that the reliability of the device is improved without causing any trouble in pressure detection even during long-time operation.

[Brief explanation of drawings]

FIG. 1 is a partially cross-sectional configuration diagram of an embodiment of the engine exhaust gas purification device of the present invention, and FIG.
The figures are characteristic diagrams showing the relationship between the operating time of the filter and the amount of particulate collected in the engine exhaust gas purification device of the present invention.
FIG. It is a characteristic diagram. In the figure, 1... Engine, 2... Exhaust pipe, 3... Filter, 4, 5... Solenoid valve, 9... Pressure sensor, 10...
Control device, 11... Burner, 12... Ignition device, 14
...Load sensor, 15... Rotation speed detector. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A filter installed in the exhaust pipe path of the engine to collect particulate, a heat source installed around this filter to burn the particulate, exhaust pressure on the upstream side of the filter, and exhaust pressure on the downstream side of the filter. A pressure sensor for selectively detecting exhaust pressure, disposed in a piping route that connects the pressure sensor to the upstream pressure outlet and downstream pressure outlet of the filter, and detecting the pressure upstream or downstream of the filter. and a switching valve that selectively introduces pressure to the pressure sensor, and the switching valve introduces and detects the upstream pressure and downstream pressure of the filter to the pressure sensor for a short time at predetermined time intervals. In the exhaust gas purification device that controls the heat source based on the pressure difference between the filters, atmospheric air is introduced into the pressure sensor during a time period when neither the upstream pressure nor the downstream pressure of the filter is detected. An exhaust gas purification device for an engine, characterized in that the switching valve described above is configured as follows.