JPS6030410Y2 - 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.
More 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 remove clogging that occurs in the filter member due to the accumulation of particulate components. It is well known to detect this and operate the heating device to burn off particulate components and combustible components, thereby eliminating clogging of the filter member.

By the way, as a 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 type uses 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.

In addition, to prevent this, it is necessary to detect clogging of the filter member by comparing a preset exhaust pressure map according to the operating state with the actual exhaust pressure detected above, and to detect clogging of the filter member. The disadvantage is that the configuration is extremely complicated.

Therefore, in order to eliminate such conventional drawbacks and directly and reliably detect clogging of the filter member with a simple configuration, the present applicant previously developed a diesel engine as shown in FIG. We are proposing an engine exhaust purification device (
Specification and drawings of Utility Application No. 56-83631 (Utility Application No. 1983)
7-19621)).

That is, in FIG. 1, 1 is the exhaust passage of the engine;
Reference numeral 2 denotes a filter member disposed in the middle of the exhaust passage 1, and the filter member 2 alternately connects the upstream and downstream ports of the pores of the honeycomb-shaped body made of non-conductive porous material. It is closed with a blind plug and collects particulate components such as carbon particles in the exhaust gas flowing through the exhaust passage 1.

On the other hand, numeral 3 denotes a burner device as a clogging eliminating heating device disposed in the exhaust passage 1 on the upstream side of the filter member 2, and the burner device 3 pumps the fuel supplied from the fuel pump 4 into the air The ignition heater 3a ignites and burns the air supplied from the ignition heater 3a to generate high-temperature combustion gas, and the combustion gas heats and burns the particulate components deposited on the filter member 2. This is to eliminate clogging.

Further, 6 and 7 are respectively 1 of the filter member 2.
The electrodes are inserted into two holes facing each other from the upstream and downstream ports, and are arranged at a predetermined interval, and of the two electrodes 6 and 7, the downstream electrode 7 is It is grounded, and the upstream electrode 6 is connected to the positive terminal of a battery 9 via a resistor 8.

Both ends of the resistor 8 are connected to a resistance value detection circuit 10, and the resistance value detection circuit 10 detects the electrical resistance value between the electrodes 6 and 7 due to the accumulation of carbon particles on the filter member 2. It is configured to detect the voltage value between both ends.

Further, the output of the resistance value detection circuit 10 is inputted to a control circuit 12 that controls three components: a switch 11 that turns on and off the ignition heater 3a of the burner device 3, the fuel pump 4, and the air pump 5. , the output signal from the resistance value detection circuit 10 is compared with a reference level signal to determine the clogging state of the filter member 2, and if it is smaller than the reference level signal, it is determined that the filter member 2 is clogged, and the burner device 3 It is designed to operate.

In addition, 13 is a rotation speed sensor that detects the engine rotation speed;
Reference numeral 4 denotes a load sensor for detecting the load condition of the engine, and both of these sensors 13 and 14 are inputted to the control circuit 12. After the filter member 2 becomes clogged,
Both sensors 13 and 14 detect the operating state of the engine, and if the engine is idling, the burner device 3 is activated.

However, in this proposal, since the electrodes 6 and 7 are fitted separately into the filter member 2, the spacing between the electrodes 6 and 7 is not constant, and the electrodes 6 and 7 may be damaged due to engine vibration or the like.
There was a fear that the resistance value between 7 and 7 would change, making it difficult to stably detect clogging, leading to deterioration of detection accuracy.

In addition, if a break occurs in the middle of the circuit, a signal indicating that the resistance value between the electrodes 6 and 7 is infinite, that is, the same signal as the signal indicating that the filter member 2 is not clogged, is input to the control circuit 12. Therefore, there was a problem that circuit breakage could not be detected.

The present invention was developed in view of these points, and by connecting the above-mentioned electrodes with a fixed resistor and providing an initial resistance between the electrodes (in the circuit), the distance between the electrodes is maintained constant. In addition to preventing resistance value changes due to external vibrations, the signal input to the control circuit is made different between when the circuit is disconnected and when the circuit is not clogged, thereby improving the accuracy of detecting clogging of the filter member and making it easier to detect disconnections. It is an object of the present invention to provide an exhaust purification device for a diesel engine that can achieve both

That is, in the present invention, 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 the filter member is unclogged in the exhaust passage upstream of the filter member. A diesel engine exhaust purification device including a heating device such as a burner device for eliminating clogging includes two electrodes spaced apart from each other within the filter member and a fixed resistor connected between the electrodes. a resistance value detection circuit that generates an output according to a change in electrical resistance between the body and the electrodes due to the accumulation of carbon particles on the filter member, and a clogging state of the filter member according to the output of the resistance value detection circuit. The heating device is characterized by comprising a control circuit that determines the heating device and controls the operation of the heating device.

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

Incidentally, since the overall structure of the exhaust purification device for a diesel engine has been explained with reference to FIG. 1, the same parts as in FIG. 1 are given the same reference numerals and detailed explanation thereof will be omitted.

FIG. 2 shows a first embodiment of the present invention, in which a honeycomb-shaped filter member 2 is disposed in the middle of an exhaust passage 1, and two electrodes 6 and 7 are arranged at a predetermined interval within the filter member 2. Of the two electrodes 6.7, the upstream electrode 6 is grounded, and the downstream electrode 7 is connected to the positive terminal of the battery 9 via a resistor 8.

Further, both ends of the resistor 8 are connected to a resistance value detection circuit 10.

The tips of the electrodes 6 and 7 are connected to each other by a fixed resistor 15 having a predetermined resistance value.
is configured in a closed circuit with an initial resistance.

Therefore, in the first embodiment, when the amount of carbon particles deposited on the filter member 2 is small and the filter member 2 is not clogged, the electrodes 6, 7
The resistance value between is almost only the resistance value of the fixed resistor 15,
An output signal corresponding to the resistance value is output from the resistance value detection circuit 10, and therefore, the control circuit 12 determines that there is no clogging.

On the other hand, when the amount of deposited carbon particles increases and the filter member 2 becomes clogged, the resistance value between the electrodes 6 and 7 is influenced by the resistance value between the electrodes 6 and 7 via the carbon particles. , the resistance value of the fixed resistor 15 alone changes, and an output signal corresponding to this change is sent to the resistance value detection circuit 10.
Therefore, the control circuit 12 determines that there is a clogging state.

In that case, since the electrodes 6 and 7 are connected by the fixed resistor 15, the distance between the electrodes 6 and 7 can always be maintained at a constant distance, and external vibrations such as engine vibration can cause the electrodes 6 and 7 to Even if it vibrates, the resistance value between them will not change,
Therefore, deterioration of the clogging detection accuracy can be prevented.

Furthermore, as described above, when the filter member 2 is not clogged, the signal input to the resistance value detection circuit 10 is almost a signal corresponding to the resistance value of the fixed resistor 15 alone. It is possible to clearly distinguish between a blockage and a break in the circuit 16 when the resistance value input to the resistance value detection circuit 10 becomes infinite, and therefore a break in the circuit 16 can be easily detected.

Furthermore, among the two electrodes 6 and 7, the filter member 2
Since the downstream electrode 7 located in a portion where the amount of deposited carbon particles is relatively small is connected to the positive terminal of the battery 9, the upstream electrode 6 is connected to the positive terminal of the battery 9 as shown in FIG. Compared to the case where the electrode 7 is connected to The current and the current flowing through the resistor 8 (current corresponding to the input voltage value to the resistance value detection circuit 10) can be made to match well, so that the accuracy in detecting clogging of the filter member 2 can be further improved.

In addition, FIG. 3 shows a second embodiment of the present invention, and the same parts as in FIGS. It is designed to be detectable by operation.

That is, in FIG. 3, the electrodes 6' and 7' are embedded from the outside of the exhaust passage 1 through the passage wall (exhaust pipe) and into the filter member 2 in a direction perpendicular to its axial direction. .

Further, in the circuit 16, a normally closed relay switch 17 is interposed between the downstream electrode 7' and the resistor 8.
A relay coil 17a of the relay switch 17 is connected to the battery 9 via a disconnection detection switch 18.

Furthermore, one end of the fixed resistor 15' is connected between the relay switch 17 of the circuit 16 and the resistor 8, and the other end is grounded together with the upstream electrode 6'.

In addition, in the control circuit 12, 19 is a temperature correction circuit, and 20 is a temperature correction circuit.
21 is a clogging determination circuit, 21 is a reference signal generation circuit, 22 is a burner control circuit, and the temperature correction circuit 19 adjusts the output signal of the resistance value detection circuit 10 to a predetermined temperature based on the output signal from the temperature sensor 23. The temperature correction is applied to the signal at .

Further, the clogging determination circuit 20 compares the correction signal from the temperature correction circuit 19 with the reference signal from the reference signal generation circuit 21 to determine the clogging state of the filter member 2.

Further, the burner control circuit 22 receives the clogging signal from the clogging determination circuit 20, and the rotation speed sensor 13
Based on the detection signal of the load sensor 14, the burner device 3 is operated when the engine is idling.

Further, in FIG. 3, 24 is a cover that protects the fixed resistor 15' and the relay switch 17.

Therefore, in the second embodiment, when the disconnection detection switch 18 is closed, the relay switch 17 is opened and the circuit 16 is opened.

At that time, regardless of whether or not the filter member 2 is clogged, if there is no disconnection in the circuit 16a including the battery 9, the resistor 8, and the fixed resistor 15', the signal input to the resistance value detection circuit 10 will be While the signal is based on the resistance value of the fixed resistor 15', if a disconnection occurs, a signal with an infinite resistance value is input to the resistance value detection circuit 10.

Therefore, a circuit break can be easily detected by simply operating the break detection switch 18.

In addition, since the fixed resistor 15' is disposed outside the exhaust passage 1, the fixed resistor 15' is not exposed to the exhaust gas at a temperature of 1000m and is not corroded. This has the advantage that the clogging detection accuracy of the filter member 2 can be stably maintained over a long period of time.

As described above, according to the present invention, two opposing electrodes are disposed on a filter member that collects particulate components in exhaust gas, and the change in electrical resistance due to the accumulation of carbon particles between the electrodes causes the filter member to Since the electrodes of the diesel engine exhaust purification system designed to detect clogging are connected with a fixed resistor, the gap between the electrodes can be maintained constant and the filter member can be cleaned without being affected by external vibrations. It is possible to stably and accurately detect clogging, improve clogging detection accuracy, and provide a predetermined initial resistance between the electrodes, making it easy to detect circuit breaks. It is possible.

[Brief explanation of drawings]

Fig. 1 is an overall schematic configuration diagram of a conventional example, Figs. 2 and 3 illustrate an embodiment of the present invention, Fig. 2 is an enlarged view of the main part of the first embodiment, and Fig. 3 is a diagram of the second embodiment. It is a partial schematic block diagram of an example. 1... Exhaust passage, 2... Filter member, 3... Burner device (heating device), 6.6',
7.7'... Electrode, 10... Resistance value detection circuit, 12... Control circuit, 15.15'...
...Fixed resistor.

Claims (1)

[Scope of utility model registration request] A filter member is installed in the exhaust passage of the engine to collect particulate components such as carbon particles in the exhaust gas, and
In the exhaust gas purification device for a diesel engine, the exhaust passage for a diesel engine is provided with a clogging eliminating heating device for eliminating clogging of the filter member in the exhaust passage on the upstream side of the filter member. a fixed resistor connected between the electrodes, a resistance value detection circuit that generates an output according to a change in electrical resistance between the electrodes due to deposition of carbon particles on the filter member, and the resistance value detection circuit. 1. An exhaust gas purification device for a diesel engine, comprising a control circuit that determines a clogging state of a filter member according to an output of the circuit and controls the operation of a heating device.