JPS6042332B2 - Diesel engine exhaust purification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust purification device for a diesel engine,
Specifically, the present invention relates to an improvement in which clogging of a filter member disposed in an exhaust passage for collecting particulate components such as carbon particles in exhaust gas is detected based on changes in electrical resistance due to accumulation of carbon particles.

Conventionally, as an exhaust purification device for a diesel engine, a filter member for collecting particulate components such as carbon particles in the exhaust gas is disposed in the exhaust passage of the engine, and a filter member is installed in the exhaust passage upstream of the filter member to prevent clogging of the filter member. A heating device such as a burner device for eliminating clogging is provided to purify the exhaust gas by the collection action of the particulate components of the filter member, and to prevent clogging when the filter member is clogged due to the accumulation of particulate components. It is well known that the filter member is unclogged by detecting this and operating the burner device to burn and remove particulate components.

By the way, as means for detecting clogging of the filter member, conventionally, for example, the magnitude of the exhaust pressure in the exhaust passage on the upstream side of the filter member is detected, and the clogging state is determined based on the presence or absence of an increase in the exhaust pressure. There is something I did.

However, since this method utilizes exhaust pressure, there is a problem in that clogging cannot be detected accurately if the exhaust pressure changes depending on engine operating conditions such as engine speed and load.

Additionally, in order to prevent this, it is necessary to detect clogging of the filter member by comparing the exhaust pressure map set in advance according to the operating condition with the actual exhaust pressure detected above. The drawback was that the circuit configuration was complicated.・
Therefore, in order to overcome these conventional drawbacks and directly and reliably detect clogging of the filter member with a simple configuration, the applicant previously proposed a method in which two electrodes were disposed on the filter member. At the same time, a detection circuit detects a change in electrical resistance between the two electrodes, which changes depending on the amount of carphone particles (main component of fine particle components) deposited on the filter member, by applying a predetermined voltage between the two electrodes. proposed a diesel engine exhaust purification device in which clogging of the filter member is detected based on the output signal of the detection circuit (Utility Application No. 56-83631 (Utility Model Application No. 57-1)).
9621? ) See specification and drawings).

However, in this proposal, the electrical resistance between both electrodes changes greatly depending on the temperature factor, so even if the clogging state is the same, the exhaust temperature is low, e.g. about 90°C.
There is a difference in the output signal of the detection circuit between idling operation and high-load operation when the exhaust temperature is high, e.g. 800°C, and as a result, it is still not possible to accurately and stably detect clogging. . Therefore, in view of these points, the present invention has been made by taking the above-mentioned proposal one step further, and corrects the output of the detection circuit for detecting the change in electrical resistance between the electrodes according to the exhaust temperature. By doing this, if the filter member is in the same clogged state, a constant detection signal is always obtained regardless of the exhaust temperature, and therefore, clogging of the filter member is detected by the change in electrical resistance between the electrodes. The present invention aims to improve the clogging detection accuracy of the exhaust purification device for a diesel engine.

That is, the present invention provides exhaust gas to the exhaust passage of the engine. A filter member is disposed to collect particulate components such as carbon particles in the air, and a heating device such as a clogging burner device to unclog the filter member is provided in the exhaust passage upstream of the filter member. Diesel engine exhaust that is installed! In the purification device, a resistance value detection circuit that generates an output according to a change in electrical resistance between two electrodes arranged on the filter member due to the accumulation of carbon particles on the filter member; a control circuit that determines the clogging state of the filter member and controls the operation of the four heating devices; a temperature sensor that detects the temperature of the exhaust gas near the filter member; and a temperature sensor that detects the resistance value in accordance with the output of the temperature sensor. The present invention is characterized in that it includes a temperature correction circuit that corrects the output of the circuit.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

In FIG. 1, reference numeral 1 denotes an exhaust passage for discharging exhaust gas from a diesel engine, and a honeycomb-shaped filter member 2 made of non-conductive porous material is disposed in the middle of the exhaust passage 1.
The filter holes of the filter member 2 are reversed at the upstream and downstream ports, and every other filter hole is closed. It is designed to collect.

Further, in the exhaust passage 1 on the upstream side of the filter member 2 (on the left side in the figure), there is a heating device for eliminating clogging of the filter member 2. -na device 3 is provided.

That is, the burner device 3 includes a torch section 3a, an air supply chamber 3b formed to surround the torch section 3a, and an ignition heater 3c.The torch section 3a is connected to a fuel tank via a fuel pump 4. 5, and the air supply chamber 3b is connected to an air pump 6, and the holes 3d, 3d, . . . are connected to the outer circumference of the torch portion 3a.
The ignition heater 3c is placed in communication with the inside of the torch section 3a through the ignition heater 3c, and the ignition heater 3c is arranged with its tip facing inside the torch section 3a. Then, the fuel is combusted in the torch section 3a to generate high-temperature combustion gas, and the particulate components deposited on the filter member 2 are heated and burned by the high-temperature combustion gas to eliminate clogging thereof. It is something to do. Two electrodes 7 and 8 are embedded in the filter member 2 in parallel to the inside of the filter member 2 with their respective tips penetrating the passage wall (exhaust pipe) of the exhaust passage 1, and are perpendicular to the axial direction of the filter member 2. Of the electrodes 7 and 8, the upstream electrode 7 is grounded, and the downstream electrode 8 is connected to a battery 10 via a fixed resistor 9.

Further, both ends of the resistor 9 are connected to a resistance value detection circuit 11, and when the amount of carbon particles in the particulate component deposited on the filter member 2 is small, the resistance value between the electrodes 7 and 8 is fixed at a large value. Since the voltage drop across the resistor 9 is small, the resistance value detection circuit 11 outputs a large resistance value signal, while when the amount of carbon particles deposited on the filter member 2 is large, the resistance value between the electrodes 7 and 8 is Since the voltage drop across the fixed resistor 9 is small and the voltage drop across the fixed resistor 9 is large, the resistance value detection circuit 11 outputs a small resistance value signal. It is designed to generate an output signal R in response to changes in electrical resistance due to particle deposition. has been completed. Further, the output of the resistance value detection circuit 11 is input to a control circuit 12.

As shown in FIG. 2, the control circuit 12 generates a reference level signal R when the filter member 2 is clogged. and a reference level signal R from the reference level generating circuit 13. and an output signal R'' from the resistance value detection circuit 11 via a temperature correction circuit 17 (described later) to determine the clogging state of the filter member 2; and a burner control circuit 15 for controlling the operation of the burner device 3 by controlling the operation of the ignition heater 3C1, the fuel pump 4, and the air pump 6 of the burner device 3 in response to the output of the resistance value detection circuit 11. Filter member-2 according to the output of
The burner device 3 is controlled to operate for a predetermined period of time when the filter member 2 is clogged. Furthermore, the filter member 2
A temperature sensor 1 is installed at the upstream side of the upstream electrode 7.
Like the electrodes 7 and 8, electrodes 6 are disposed with their tips buried in the filter member 2 from the passage wall of the exhaust passage 1, and the temperature sensor 16 detects the exhaust temperature near the filter member 2. The temperature signal T is output using the temperature signal T.

The output of the temperature sensor 16 is input to a temperature correction circuit 17 interposed between the clogging determination circuit 14 and the resistance value detection circuit 11 of the control circuit 12, as shown in FIG. The temperature correction circuit 17 is configured to correct the output from the resistance value detection circuit 11 according to the output signal T of the temperature sensor 16.

That is, the output signal R of the resistance value detection circuit 11 is determined according to the exhaust temperature, that is, the output signal T from the temperature sensor 16, as shown in FIG. α is a coefficient), which has the characteristic of changing exponentially.

Therefore, in order to obtain the resistance value signal R'' at a predetermined temperature from the above relational expression (a), the temperature correction circuit 17 logarithmically transforms the output signal R (=R''e−αT) from the resistance value detection circuit 11. logarithmic conversion circuit 18 and the temperature sensor 16
an amplifier circuit 19 that amplifies the output signal T from the above by the coefficient α; and an adder circuit 20 that receives the output signals of both the logarithmic conversion circuit 18 and the amplifier circuit 19 and adds the two signals.
and an anti-logarithmic conversion circuit 21 for anti-logarithmically changing (exponentially converting) the output signal of the adding circuit 20, and the output of the anti-logarithmic converting circuit 21 is input to the clogging determination circuit 14. As shown in FIG. 4, the logarithmic conversion circuit 1
At step 8, the above relational expression (a) is converted into the relational expression t, and at the adding circuit 20, the output signal αT from the amplifier circuit 19 is added to both sides of this relational expression (gate) to convert it into a relational expression. The inverse logarithmic conversion circuit 21 is configured to derive the above conversion equation (c) or I:), and input the relational equation into the clogging determination circuit 14.

In addition, 22 is a rotational speed sensor that detects the engine rotational speed;
Reference numeral 3 denotes a load sensor for detecting the load state of the engine, and both sensors 22 and 23 are input to the burner control circuit 15 of the control circuit 12, and the burner control circuit 15 is connected to the clogging determination circuit 14. After receiving the clogging signal, that is, after it is determined that the filter member 2 is in the clogging state, the engine enters an idling state based on the detection signals from both the rotation speed sensor 22 and the load sensor 23. When the transition occurs, the burner control circuit 15 is activated to operate the burner device 3. Next, to explain the operation of the above embodiment, the resistance between the two electrodes 7 and 8 of the filter member 2 is
is detected as the voltage value across the fixed resistor 9, and a resistance value signal R (=R″e−αT) corresponding to this resistance is outputted from the resistance value detection circuit 11 and inputted to the control circuit 12. The resistance value signal R input to this control circuit 12
As shown in the flowchart in FIG.
10gR=10gR''-αT), and then in the adding circuit 20, the temperature signal (αT) detected by the temperature sensor 16 and amplified by the amplifier circuit 19 is added (10gR+αT=
10gR''), which is further subjected to antilogarithmic conversion in the antilogarithmic conversion circuit 21 (R''=Re=R''EaT), and then input to the clogging determination circuit 14 and compared with the reference level signal R from the reference level generation circuit 13. When the amount of particulate components (carbon particles) deposited on the filter member 2 is small and the filter member 2 is not clogged, the electrical resistance between the electrodes 7 and 8 is large, so the temperature correction is performed. circuit 1
Correction signal R'' input from 7 to the clogging determination circuit 14
The voltage value of (=ReαT) exceeds the reference level signal RO (R≧RO), and as a result, no activation signal is output from the clogging determination circuit 14 to the burner control circuit 15, and therefore the burner device 3 is activated. do not. On the other hand, when the amount of particulate components deposited on the filter member 2 increases with engine operation and the filter member 2 becomes clogged, the electrical resistance between the electrodes 7 and 8 decreases. The voltage value of the correction signal R'' input to the clogging determination circuit 14 is the reference level signal R.

becomes smaller (R″<RO), and as a result, a clogging state is determined, and an activation signal is output from the clogging determination circuit 14 to the burner control circuit 15.Then, in the burner control circuit 15, the rotation speed sensor The operating state of the engine is determined based on the engine rotational speed signal from 22 and the load signal from load sensor 23, and if the engine is not in an idling state, the burner device 3 is kept in a standby state; The burner device 3 operates for a predetermined period of time, and the combustion gas burns off the particulate components deposited on the filter member 2, thereby eliminating clogging of the filter member 2. Therefore, the resistance value The resistance value signal R output from the detection circuit 11 is sent to the control circuit 12, temperature corrected by the temperature correction circuit 17, and then input to the clogging determination circuit 14.
The clogging determination circuit 14 can determine the presence or absence of clogging regardless of the exhaust temperature, and can therefore stably and accurately detect the clogging of the filter member 2 from engine idling to high-load operation. It is possible to improve the detection accuracy.

Note that a microcomputer may be used as the control circuit 12 including the temperature correction circuit 17 in the above embodiment, and the microcomputer may perform temperature correction, clogging determination, and control of the burner device all at once.

It is also possible to use a thermocouple in place of the thermistor (which is normally used as the temperature sensor 16), and to approximately correct the temperature of the output of the resistance value detection circuit using the output current of the thermocouple. Further, in the above embodiment, the two electrodes 7 and 8 were inserted from the passage wall (exhaust pipe) of the exhaust passage 1 into the filter member 2 so as to be orthogonal to the axial direction of the filter member 2. may be inserted into the same filter hole of the filter member from its upstream and downstream ports facing each other, and the same effects as in the above embodiment can be obtained.

As explained above, according to the diesel engine exhaust purification device of the present invention, the electric resistance change between the two electrodes disposed on the filter member that collects particulate components such as carbon particles in the exhaust gas is adjusted to the exhaust temperature. Since the clogging of the filter member is detected by correcting the temperature accordingly, the clogging of the filter member can be detected stably and accurately regardless of the engine operating conditions, and the clogging detection accuracy can be improved. This is something that can be improved.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the present invention, and FIG. 1 is an overall system diagram, FIG. 2 is a block diagram of the control circuit, FIG. 3 is a flowchart showing the operation of the control circuit, and FIG. 4 is a temperature correction diagram. An explanatory diagram showing the calculation process of the circuit, and FIG. 5 is a graph showing the output characteristics of the resistance value detection circuit. 1... Exhaust passage, 2... Filter member, 3... Burner device (heating device), 7, 8...
...Electrode, 11...Resistance value detection circuit, 12...
・Control circuit, 16...Temperature sensor, 17...
...Temperature correction circuit.

Claims (1)

[Claims] 1 A filter member for collecting particulate components such as carbon particles in the exhaust gas is disposed in the exhaust passage of the engine, and a clogging eliminating heating device is provided in the exhaust passage upstream of the filter member to unclog the filter member. In a diesel engine exhaust purification device including a device,
A resistance value detection circuit detects the electrical resistance of carbon particles deposited on the filter member using a pair of electrodes arranged on the filter member, and a clogging state of the filter member is determined according to the output of the resistance value detection circuit. a control circuit that controls the operation of the heating device; a temperature sensor that detects exhaust temperature near the filter member; and a temperature correction circuit that corrects the output of the resistance value detection circuit according to the output of the temperature sensor. An exhaust purification device for a diesel engine, characterized in that it is provided with.