JPS6131414B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a misfire sensor for an internal combustion engine that can quickly and reliably detect misfire conditions and misfire cycles in various operating conditions of a positive displacement internal combustion engine.

Conventionally used misfire detection devices include:
There are various types, but all of them have the drawback of poor responsiveness.

For example, there is a device that detects a misfire by detecting a drop in exhaust gas temperature at the time of a misfire by detecting the concentration of the exhaust gas discharged from the combustion chamber of an internal combustion engine during the exhaust process using a temperature sensor such as a thermocouple. . However, the time required for one engine cycle is approximately 200 msec or less even in the case of a 4-cycle engine, and when considering practical use, the response speed of this type of temperature sensor is generally slow at several 100 msec or more, so the temperature that follows the misfire cycle is Detection was extremely difficult. In addition, the exhaust temperature changes greatly due to changes in operating conditions (load, rotational speed), and the difference between the exhaust temperature during normal combustion and the exhaust temperature at the time of misfire is small, so the S/N ratio is small and the misfire condition can be quickly corrected. Moreover, it was difficult to detect with high accuracy.

Another method is to analyze the exhaust gas emitted from the combustion chamber of an internal combustion engine. In other words, when the engine misfires, carbon monoxide CO decreases and hydrocarbon HC increases. There is a device that detects a misfire by detecting the content in exhaust gas, but the response is slow, i.e., the response of an analyzer is generally 1 to 3 seconds, and it depends on the displacement and type of internal combustion engine, the load, and the air/fuel consumption used. Since the absolute values of the contents of carbon monoxide and hydrocarbons in the exhaust gas differ depending on the engine, it has been difficult to detect a misfire with good response and accuracy.

There is also a device that measures the gas pressure in the combustion chamber of an internal combustion engine and analyzes this pressure waveform to detect the number of misfires, but doing this electrically requires a very complex electronic circuit. Moreover, it took a lot of effort for the experimenter to judge each waveform, and there were problems that made it difficult to put it into practical use when it was considered for automotive use.

The present inventors arrived at the present invention in the process of researching and developing a misfire detection device for an internal combustion engine that eliminates the drawbacks of the above-mentioned conventional devices. The present invention solves the problems of the conventional devices described above, has a very simple configuration, and is applicable to all types of positive displacement internal combustion engines.
It is almost unaffected by various operating conditions such as load and air-fuel ratio, and makes it possible to detect engine misfires with high precision and responsiveness.It also has excellent durability and is highly durable. The purpose is to enable it to be mounted on a vehicle as a sensor for various control devices that need to be detected.

The intake and exhaust gas flows in the intake and exhaust pipes of positive displacement internal combustion engines form more or less pulsating flows, and exhibit complex pressure changes over time and location. It is expected that the pattern of change will change. Therefore, the inventors of the present invention attempted to measure the static pressure in the intake pipe or exhaust pipe, but found that there were no major fluctuations due to engine misfire, and that there were no significant fluctuations due to engine misfire, and that there were no significant changes under various operating conditions such as engine speed, load, and air-fuel ratio used. The misfire device is easily affected by this, and when summarized as a misfire device, the S/N ratio is poor.Moreover, in the case of multiple cylinders, it is strongly influenced by other cylinders. The present inventors further added this knowledge to the above-mentioned problems to be solved, and as a result of their investigation, they reached the following conclusion.

No matter what kind of combustion (normal combustion, abnormal combustion such as pre-burning, after-burning, etc.) occurs in the combustion chamber of a positive displacement internal combustion engine due to the influence of rotation speed, load, air-fuel ratio, etc., during combustion, there will be an explosion, The high temperature, high pressure, and expanded exhaust gas due to combustion is discharged from the exhaust hole into the exhaust passage at high speed at the same time as the exhaust valve in the exhaust stroke opens.
There is no significant difference in the speed and flow conditions.
However, if the engine misfires for some reason,
Since there is no explosion or combustion as mentioned above,
Since the unburned gas is simply discharged from the combustion chamber into the exhaust passage by the pumping action of the piston member during the exhaust stroke, its velocity is very small compared to the exhaust gas velocity during combustion. Therefore, the static pressure and dynamic pressure of the exhaust gas in the exhaust passage immediately after the exhaust valve opens are temporarily lower than those during combustion.

Therefore, the present inventors focused on the fact that engine misfire can be detected by detecting changes in the static pressure and dynamic pressure of the exhaust gas flow flowing in the exhaust passage downstream of the exhaust hole. A beat pipe is installed in the passageway to detect pressure fluctuations in response to speed fluctuations in the exhaust gas flow as a change in total pressure, and as shown in Figure 2, the total pressure is temporarily lower during misfire exhaust compared to during combustion exhaust. The present inventors have devised a misfire sensor of the present invention that reliably and quickly detects engine misfires.

In addition, the present inventors have further reached the following conclusion in order to solve the above-mentioned problems. As described above, a misfire state in the engine can be detected reliably and quickly because the total pressure in the exhaust passage downstream of the exhaust valve is temporarily lower than that during combustion. However, the problem is how to measure this total pressure change.

In other words, the fall in the total exhaust pressure during a misfire compared to the total exhaust pressure during normal combustion is usually a minute pressure change of several tens of millimeters of water column, and since it is a high-speed phenomenon within a few milliseconds, it is necessary to measure this high-speed and minute pressure. is generally very difficult.

For example, a semiconductor strain conversion element is a powerful measurement means that can convert and detect the aforementioned high-speed, minute pressure changes into voltage changes with good response, and can distinguish between normal combustion and misfire conditions from the measured voltage signal. It is not difficult to output it.

However, considering the temperature resistance of the exhaust gas, which is a high-temperature gas that reaches approximately 200 degrees Celsius, and the effects of electrical noise emitted from a running engine, there are issues with durability, reliability, and in-vehicle use. Many problems are expected to be overcome for practical application.

Therefore, the present inventors focused on fluid logic elements as a measurement means that can detect fast and minute pressure changes in high-temperature atmospheres and environments that generate electrical noise with good response, and can also perform signal processing. devised a misfire detection sensor that uses a fluid logic element to perform the entire process from detecting changes in the total exhaust pressure to determining misfire or normal combustion and outputting the output.

In other words, in general, in an internal combustion engine, the exhaust flow rate per unit time varies greatly depending on the operating state of the engine, so the speed of the exhaust gas flow in the exhaust pipe and the overall level of the pressure pulsating flow (indicated by Pd in Figure 2) DC component) fluctuates. For this reason, the inventors
In order to accurately detect a misfire condition in an internal combustion engine without being affected by this level fluctuation, it is not always sufficient to directly introduce the pressure to be detected into the input port of the fluid logic element and compare it with the reference pressure. It has been found that it is preferable to detect the total exhaust pressure and its difference (relative amount) with respect to the DC component using a fluid logic element. In order to achieve this, both input ports are connected to the other opening of the exhaust gas introduction pipe, and the piping that communicates with one input port is equipped with an appropriate restriction and linked to an appropriate capacity. We have arrived at the present invention.

The present invention is formed into a communicating tubular shape having openings at both ends, and one opening is inserted into an exhaust passage communicating with a combustion chamber of a positive displacement internal combustion engine via an exhaust hole to introduce exhaust gas from the opening. and an exhaust gas introduction pipe disposed outside the exhaust passage of the positive displacement internal combustion engine at the other opening, and one input port communicating with the other opening of the exhaust gas introduction pipe from the combustion chamber. The other input port communicates with the other opening of the exhaust gas introduction pipe through a piping provided with a restriction, and communicates with the volume through the piping to control the exhaust gas flow. It cuts out the high frequency components of the total exhaust pressure and derives a DC component corresponding to the overall level, which reduces the total pressure of the exhaust gas flow being directed to one input port and the exhaust gas being supplied to the other input port. If the difference is within the set value, the supply air flow supplied from the supply port is discharged from one output port, and the exhaust gas guided to one input port is compared with the DC component of the total exhaust pressure. When the pressure of the gas flow temporarily decreases due to a misfire in the internal combustion engine and the difference between it and the DC component of the exhaust total pressure supplied to the other input port becomes larger than the set value, the gas is supplied from the supply port. It consists of a fluid logic element that switches the port that discharges the air flow and discharges the air flow from the other output port.

The present invention configured as described above introduces the exhaust gas exhausted by the combustion chamber as pressure through the exhaust gas introduction pipe arranged in the exhaust passage, and guides it to one input port of the fluid logic element. The pressure of the exhaust gas flow led to one input port based on a misfire is compared with the DC component of the total exhaust pressure supplied to the other input port, and the difference is greater than the set value. When the internal combustion engine misfires, the supply air flow that was previously supplied from the supply port to one output port is switched by the air flow supplied to the other input port and discharged from the other output port. It has the function of detecting.

According to the present invention, which has the above-described structure and function, when an internal combustion engine misfires, the total exhaust pressure of the exhaust gas flow from the combustion chamber rapidly decreases, and the throttle and capacity equivalently reduce the low-pass filter in the electric circuit. Since the difference between the DC component of the exhaust total pressure supplied to the other input port connected to the constituting piping system is greater than the set value, the supply air flow is adjusted by the amount of air supplied to the other input port. By immediately switching the output port from one output port to the other, a misfire condition in an internal combustion engine can be detected more responsively and quickly than the above-mentioned conventional technology, and in particular, it is possible to detect a misfire condition in an internal combustion engine more quickly than the above-mentioned conventional technology. This has the effect of being able to accurately detect the total pressure without being affected by the direct current component.

Further, as is clear from the above-mentioned structure, the present invention has the advantage of being simple and compact, and has the advantage of being inexpensive and having high durability.

Below, in order to explain the fluctuations in the exhaust gas pressure of the internal combustion engine detected by the internal combustion engine misfire sensor of the present invention,
A reference example will be explained in detail.

The reference example misfire sensor for an internal combustion engine consists of an exhaust gas introduction pipe and a fluid logic element.
This will be explained using the diagram and FIG.

The reference example consists of an inlet pipe 2 as an exhaust gas inlet pipe for detecting the total exhaust pressure, and a signal processing circuit 3 composed of a Schmitt circuit using an OR/NOR element as a logic element.

In the reference example, in order to install the inlet pipe 2 at a predetermined position in the exhaust passage in order to detect the total pressure fluctuation corresponding to the total pressure fluctuation corresponding to the speed fluctuation of the exhaust gas flow downstream of the exhaust hole, the internal combustion engine 1 A connecting pipe 7 is inserted between the side wall of the cylinder block 17 and the exhaust pipe 11, and the combustion chamber and the exhaust pipe 11 are communicated through the exhaust valve 12 and the exhaust passage 14 of the cylinder block 17.

A hole 72 having approximately the same diameter as the outside diameter of the introduction pipe 2 is bored in the side wall 71 of the connecting pipe 7, and the introduction pipe 2 is inserted into the cylinder block 17 downstream of the exhaust valve 12 of the internal combustion engine through the hole 72. inserted into the exhaust passage 14 and the side wall 71
Then, it is fixed to the connecting pipe by welding means.

As shown in the figure, the introduction pipe 2 is bent into a substantially L-shape and is constructed of a stainless steel pipe with an inner diameter of 6 mm (6φ) and an outer diameter of 8 mm (8φ). The reason why we chose the one with an inner diameter of 6φ was to take into account unburned components contained in the exhaust gas. This passage having an inner diameter of 6φ constitutes a communication passage 26 that communicates the openings at both ends.

One opening 21 of the introduction pipe 2 has a sharp tip in order to minimize disturbance in the flow of exhaust gas, and has a tip approximately 10 to 20 mm away from the exhaust valve 12 of the exhaust passage 14.
It is installed at a position centimeter downstream from the side wall of the exhaust passage 14 and approximately at the center.

That is, these installation conditions were determined in consideration of the reproducibility of the change in the exhaust total pressure in response to the change in the flow velocity of the exhaust gas flow during normal combustion and misfire.

The other end of the introduction pipe 2 is connected to a pipe 91 of the signal processing circuit 3 constituted by a fluidic logic element.

The signal processing circuit 3 is constituted by a Schmitt circuit using an OR/NO element 5 as a logic element.

In the OR/NOR element 5, one input port (set port) 51 communicates with the introduction pipe 2 via a pipe 91, and the other input port (bias port) 52 communicates with the introduction pipe 2 via a pipe 92. air pressure source
Communicates with AS.

The piping 92 is equipped with a throttle having a predetermined diameter in relation to the air pressure source AS in order to set the working pressure to the input port, that is, the reference pressure (Pr in Fig. 2) for detecting a misfire state of the internal combustion engine. 921 is inserted.

The supply port 50 of the or-no-no element 5 introduces an air flow with a constant pressure of 0.5 Kg/cm ² from an air pressure source, and this supply air flow is such that the pressure of the exhaust gas flow acting on one input port 51 is equal to the pressure of the exhaust gas flow acting on the other input port 51. When the pressure of the exhaust gas flow acting on the port 52 is lower than the reference pressure, it is always output from one output port 53, and the pressure of the exhaust gas flow acting on one input port 51 is lower than the reference pressure of the other input port 5.
If the pressure is greater than the reference pressure acting on the second output port 54, the output is output from the other output port 54. When the pressure of the exhaust gas flow at the input port 51 again decreases from the reference pressure at the input port 52, the supply air flow is again switched to the output port 53 and output.

Next, the operation of the reference example misfire sensor constructed as described above will be explained below.

When the single-cylinder spark-ignition internal combustion engine 1 is in a combustion state (including normal combustion and abnormal combustion such as pre-burning and after-burning), at the start of the exhaust stroke, the exhaust valve 12 flows into the exhaust passage 14. Exhaust gas with a high static pressure and high speed (compared to when a misfire occurs) is discharged, and the static pressure and dynamic pressure in the exhaust passage 14, that is, the total pressure, temporarily increases. Then, until the exhaust valve closes and the next exhaust stroke begins, the exhaust passage 14 is not filled with exhaust gas, so the total pressure that temporarily increased continues to decrease. Become. Then, when the next exhaust stroke is started, it will increase again.

In other words, in the combustion state, the total exhaust pressure is the DC component (Pd in Figure 2) of the total exhaust pressure, which is determined by the operating conditions (engine speed, load), and the fluctuating pressure component that has a fluctuation period for each cycle. This is shown by A and B in FIG. 2, where a pressure fluctuation state is obtained. As long as the combustion state continues, the fluctuation amplitude of the fluctuating pressure component remains approximately constant.

However, if the engine 1 misfires for some reason, during its exhaust stroke, exhaust gas with low static pressure and low velocity (compared to combustion) is discharged into the exhaust passage 14, and the total amount of exhaust gas in the exhaust passage 14 is The pressure will drop temporarily. It is indicated by C in FIG. That is, at the time of misfire, the fall value of the fluctuating pressure component with respect to the DC component value of the total exhaust pressure becomes larger than that at the time of combustion. Moreover, the magnitude of the falling value of the fluctuating pressure relative to the DC component value during a misfire is usually at least twice as large as that during combustion.

Therefore, if a pressure value that is smaller than the falling value of the fluctuating pressure during combustion with respect to the DC component of the total exhaust pressure and larger than that of the fluctuating pressure at the time of misfire is set as the "threshold value", the fluctuating pressure with respect to the DC component of the total exhaust pressure can be set as a "threshold value". If the falling value exceeds the "threshold", it is a misfire, and if it does not, it is combustion. Both states can be distinguished, and the fluid logic element circuit described below can distinguish between these two states. This is what is being done.

That is, the total exhaust pressure is detected by the introduction pipe 2 installed in the exhaust passage 14 downstream of the exhaust valve 12 of the engine 1, and is led to one input port 51 of the or-no-no element 5 by the pipe 91. I'm scared. An air flow having a reference pressure Pr set to the above-mentioned threshold value is guided to the other input port 52 of one of the OR/NO elements. That is, the reference pressure is set to be smaller than the total pressure of exhaust gas during combustion and larger than the total pressure of exhaust gas during misfire.

Therefore, during combustion, one input port 51
The exhaust gas pressure acting on the other input port 5
2, the air flow being supplied from the supply port 50 of the or-no-no element 5 is always outputted to the other output port 54 due to the Coanda effect ("Yes"... …
"1"), and the output pressure of one output port 53 is the same ("no"..."0").

In case of misfire, one input port 51
Since the pressure of the exhaust gas acting on the other input port 52 is temporarily lower than the pressure Pr acting on the other input port 52, the air flow being supplied from the supply port 50 of the or-no-no element 5 is not output during combustion. The other output port 54 is switched to one output port 58, and the air flow is output from the one output port 58.

The fluctuating total pressure, which temporarily dropped significantly at the time of a misfire, will return again (rise) at the next moment, but in that transient state, the exhaust gas acting on one input port 51 The gas pressure becomes higher than the reference pressure Pr acting on the other input port 52, and the or-no-no element 5 returns the gas from the one output port 53 to the other output port 54.

Therefore, if the engine 1 misfires, the output of the output port 54 ("present"...
“1”) will be emitted in an impulse manner.

A fluid logic element has no mechanically moving parts between its input and output, and the exhaust flow (or exhaust pressure)
It switches the direction of the supply air flow,
The response speed between input and output is on the order of several milliseconds or more, and has the great effect of being much faster than conventional devices, which have response times on the order of seconds or hundreds of milliseconds.

Furthermore, since fluid logic elements do not have mechanically moving parts, reliability is important and durability is semi-permanent. And if ceramic material is used as the element material, it can withstand high temperature conditions of 1000℃.
Considering that it is not affected by electrical noise, is small, and can be manufactured at low cost, it can be said that it is extremely practical.

In the reference example, the misfire condition was detected as a pneumatic pressure signal, but this pressure signal can be converted into an electrical signal using a pressure converter, or converted into hydraulic and mechanical quantities using other conversion means, and these Depending on the conversion amount, other members can be driven and controlled, and the misfire state can be displayed on a display device.

Next, embodiments of the present invention will be described.

The misfire sensor of the first embodiment consists of an exhaust gas introduction pipe 1 and a fluid logic element a, and will be explained using FIGS. 3 and 4. The exhaust gas introduction pipe is
It has the same configuration as the exhaust gas introduction pipe of the reference example described above, and the same reference numerals are given in the drawings, and the explanation thereof will be omitted. The fluid logic element a has a logic configuration different from that of the reference example described above, and has a signal processing system consisting of an addition circuit using a newly added proportional element and a Schmitt circuit using an OR/NO element similar to the first embodiment. circuit 3
The same parts are denoted by the same reference numerals and their explanation will be omitted.

The signal processing circuit 3a is connected to the introduction pipe 2 of the exhaust gas introduction pipe via a pipe 81. The addition circuit of the signal processing circuit includes a pipe 82 connected to a pipe 81, a throttle 831 and a capacity 8 branched from the pipe 81.
32 and a proportional element 4, the circuit proportionally converts the magnitude of the fluctuation component with respect to the DC component of the total exhaust pressure introduced through the introduction pipe 2 using air pressure. It is.

That is, the piping 81 is branched into two paths, a piping 82 and a piping 83, the piping 82 is connected to the input port 41 of the proportional element 4, and the piping 83 is connected to the proportional element 4 after inserting the throttle 831 and the capacity 832. It is connected to the input port 42 of.

Therefore, the fluctuating state of the exhaust gas total pressure detected by the inlet pipe 2 is directly guided to the input port 41 of the proportional element without being attenuated, while the other input port 42 is connected to the exhaust gas total pressure. A state in which the fluctuating component of the total pressure is attenuated and removed by the throttle and the capacitance, that is, a DC component of the exhaust total pressure is introduced.

An air flow having a constant pressure (for example, 0.5 Kg/cm ² ) is guided to the supply port 40 of the proportional element from an air pressure supply source (not shown), and this supply air flow is as follows:
It operates so that the output is output from the output ports 43 and 44 at a rate proportional to the pressure difference between the input ports 41 and 42.

For example, if the value of the total exhaust pressure acting on the input port 41 is smaller than the total exhaust pressure (DC component) acting on the input port 42, the output air pressure of the output port 43 increases in proportion to the differential pressure. Therefore, the output air pressure of the output port 44 becomes smaller in proportion to the differential pressure.

Next, a pipe 91 introducing the output pressure of the output port 43 of the proportional element, a pipe 92 introducing an air flow set to a predetermined pressure from an air pressure source, and an or/noor element (OR/NOR) element 5 are connected. This circuit is a Schmitt circuit in which the output of the OR/NO element 5 is switched when the output pressure of the output port 43 of the proportional element exceeds a certain predetermined pressure.

That is, the output port 43 of the proportional element 4 and the input port 51 (set port) of the OR/NO element
is connected to the other input port 52 by piping 91.
(Reset or bias port) is connected to a pipe 92 from an air pressure source.

A throttle 921 is inserted into the pipe 92 to set the working pressure on the input port 52 to a predetermined pressure.

An air flow having a constant pressure (for example, 0.5 kg/cm ² ) is guided from an air pressure source to the supply port 50 of the or-no-no element 5, and this air flow is caused by the pressure acting on the input port 51 Whenever the pressure acting on port 52 is lower than the predetermined pressure, output port 53
If the working pressure of the input port 51 becomes higher than the predetermined pressure of the input port 52, the output port 54
It operates to produce more output. Then, when the working pressure of the input port 51 becomes lower than the predetermined pressure of the input port 52 again, the supply air flow is switched to the output port 53 again.

Next, the effects of the misfire sensor of the first embodiment having the above-described structure will be explained below.

Exhaust passage 14 downstream of exhaust valve 12 of internal combustion engine 1
The total exhaust pressure is detected by the introduction pipe 2 installed inside.

This detected total exhaust pressure is introduced into the input port 41 of the proportional element 4 via the piping 82 and the input port of the proportional element 4 via the piping 83. 42 pressure.

The pressure introduced into the input port 41 is
The pressure led to the input port 42 is the exhaust total pressure itself detected by the exhaust system, whereas the pressure led to the input port 42 is the exhaust pressure after the fluctuating components of the exhaust total pressure are attenuated and removed by the throttle 831 and the capacity 832. The DC component of the total pressure will be derived.

Therefore, at the output port 43 of the proportional element 4, an air pressure proportional to the differential pressure between the pressure acting on the input port 41 and the pressure acting on the input port 42 is obtained. Moreover, the output pressure of the output port 43 is
Due to the pressure acting on input port 42, input port 4
The polarity is high when the pressure acting on 1 is small.

That is, the output port 43 of the proportional element obtains an air pressure output proportional to the magnitude of the fall of the fluctuating component of the exhaust total pressure with respect to the DC component of the exhaust total pressure.

Next, the output pressure of this proportional element 4 is led to the input port 51 of the or-no-element element 5 through a pipe 91. On the other hand, air pressure set to a predetermined pressure is introduced from the OR/NO element 5 to another input port 52. The predetermined pressure is greater than the maximum output pressure of the proportional element output port 43 during combustion,
It is set smaller than the maximum output pressure of the proportional element output port 43 at the time of misfire.

Therefore, during combustion, the pressure acting on the input port 52 exceeds the pressure acting on the input port 51, so the air flow supplied to the or-no-no element is always output to the output port 53, and the output The output pressure of the port 54 is zero..."0".

In the case of a misfire, the pressure acting on the input port 51 temporarily overcomes the pressure acting on the input port 52, so during that time, the output pressure of the or-no-element is switched from the output port 53 to the output port 54. As a result, the output port 54 obtains an output state of "1".

In the event of a misfire, the fluctuating total pressure that temporarily drops significantly will return (rise) again at the next moment, but in that transient state, the pressure acting on the input port 51 is 52, the output pressure of the or-no element is again changed from the output port 54 to the set pressure 52.
Returned to 3.

That is, in the misfire sensor of the first embodiment, as described above, when the engine 1 is in a combustion state, the output of the output port 54 of the or-nore element 5 constituting the Schmitt trigger circuit is "no"..."0". In this state, if the engine 1 misfires, the output of the output port 54 (impulse "present"...
A misfire can be measured and detected by emitting a signal “1”.

Furthermore, the misfire sensor of the second embodiment has a very simple configuration consisting of an inlet pipe, a signal processing circuit consisting of one proportional element, and one or-no element,
It is possible to output a misfire state with a good S/N ratio without being affected by engine operating conditions.

The misfire sensor of the first embodiment, like the reference example, has no mechanically moving parts, so it has excellent responsiveness and durability.

Further, according to the misfire sensor of the first embodiment, the output signal indicating the misfire state is output as a pressure pulse of about 0.1 to 0.2 Kg/cm ² when the air pressure supplied to the or-no-no element is 0.5 Kg/cm ² . Therefore, this pressure signal can be transmitted to a semiconductor strain element, wire strain element, or air.
It is very easy to convert this into an electrical signal using an electrical conversion type pressure switch or the like, and to use this electrical signal as a trigger to drive a control device or the like. In addition, the output pressure pulses can be used to directly drive mechanical members such as diaphragm valves, bellows phragm valves, actuator spools, and pistons without converting them into electrical signals, so they function as sensors and actuators. You will also have the great advantage of having .
One of the major advantages of fluid logic elements is that "signal values" can be used immediately for "work."

For example, FIGS. 4a, 4b, and 4c show an application example in which a misfire state of the internal combustion engine 1 is observed using an oscilloscope using the sensor of the second embodiment.

That is, as shown in FIGS. 4a, b, and c, the output pressure state at the output port 54 of the or-no-no element 5 is detected by an acupressure meter 100 equipped with a semiconductor strain element, and the acupressure output voltage Vp is detected by an oscilloscope. 200
The purpose is to observe the voltage waveform imaged on the cathode ray tube 201.

The acupressure gauge 100 is composed of, for example, a pick-up 101 and an amplifier 102, and the pick-up 101 is as shown in the detailed drawing, and is attached to the output port 54 as shown in the enlarged view of FIG. 4b. I'm letting you do it.

In this configuration, if a misfire occurs in engine 1,
A misfire condition can be observed because the voltage changes in an impulse manner on an oscilloscope.

FIG. 5 shows a misfire sensor according to a second embodiment of the present invention. The misfire sensor of the second embodiment has a signal processing circuit 3b comprising an inlet pipe 2 for introducing the total exhaust pressure, an addition circuit including a proportional element 4, and a Schmitt circuit including a flip-flop (Flip-FLop) element 6. The difference from the first embodiment is that the Schmitt circuit 302 is flip-flopped.
It is characterized in that it is constructed using a flop (Flip-FLop) element (the first embodiment is constructed using an or-no-element element).

Hereinafter, the present embodiment will be explained focusing on the differences from the first embodiment, and the same parts will be given the same reference numerals and the explanation thereof will be omitted.

The Schmitt circuit 302 includes a pipe 91 to introduce the output air pressure of the output port 43 of the proportional element 4;
It is comprised of a pipe 92 and a flip-flop element 6 for introducing an air flow set at a predetermined pressure from an air pressure source. That is, the output port 43 of the proportional element 4 and the input port 61 of the flip-flop element are connected by a pipe 91, and the other input port 62 is connected to a pipe 92 from an air pressure source.

A restrictor 921 is inserted into the pipe 92 to set the working pressure to the input port 62 at a predetermined pressure.

The supply port 60 of the flip-flop element 6 is supplied with a constant pressure (for example, 0.5 kg/cm ² ) from an air pressure source.
This air flow is always output from the output port 63 when the pressure acting on the input port 61 is lower than the predetermined pressure acting on the input port 62; When the operating pressure becomes higher than the predetermined pressure of the input port 62, the output is output from the output port 64. Then, the working pressure of the input port 61 becomes the input port 6 again.
When the pressure decreases below the predetermined pressure of 2, the supply air flow is switched to the output port 63 side again.

The above operation is exactly the same as that of the first embodiment using an or-no element. Therefore, the effects of the misfire sensor of this embodiment having the above-described configuration are exactly the same as those of the first embodiment.

FIG. 6 shows a misfire sensor according to a third embodiment of the present invention.

This third embodiment includes an inlet pipe 2 for introducing the total exhaust pressure, an addition circuit with a proportional element 4, and a Schmitt circuit 30 with an OR/NOR element 5'.
The feature of this embodiment lies in the configuration of the Schmitt circuit 303 using an OR/NO element 5', and its "threshold" is set to the external input signal 3C. As in the example and the second example), instead of
The point is that it utilizes the unique "switching resistance value" that exists inside the OR/NO element.

Hereinafter, the differences between the third embodiment and the previously described embodiments will be mainly explained, and the same parts will be given the same reference numerals and the explanation thereof will be omitted.

The Schmitt circuit 303 is connected to a pipe 91 to introduce the output air pressure of the output port 43 of the proportional element 4;
The piping 91 connects the output port 43 of the proportional element and the set side input port 52' of the OR/NO element, and the supply port 50 of the OR/NO element is connected to a predetermined air pressure source. An air flow of pressure (for example, 0.5 kg/cm ² ) is introduced, and the reset side input port 51' of the or-no-no element is opened to the atmosphere. Also, the OR side output port for the set input is 53', and the NOR side output port is 53'.
4'. That is, in this configuration circuit, when the signal to the set port 52' is "0" (the working pressure is atmospheric pressure), the supply air flow from the supply port 50' is emitted to the Noah side output port 54', and the set port 52'
If the signal to 1' is "1" (the working pressure is higher than the required switching pressure), the output is from the or side output port 53'.
This circuit is designed to perform monostable operation of the OR/NO element itself, which is assumed to emit light.

However, in this embodiment, the pressure applied to the set port 52' is not given as logical signals, that is, "0" and "1", but as a signal level "0".
It is characterized in that it applies a working pressure that continuously changes between , OR side output port 5
3' becomes "0" (no output), and when the working pressure on the set port 52' is higher than the required switching pressure (signal level is "1" or higher), the OR side output port 53' becomes "1" ( The Schmitt circuit is configured to operate using the required switching pressure as the "threshold value" when the output is present.

The magnitude of this required switching pressure, or "threshold value", is determined by the flow path shape of the element (mainstream nozzle width, control nozzle width,
offset amount, set pack amount, side wall inclination angle, etc.)
Although it varies depending on the supply air pressure and supply air pressure, commercially available elements have a range of 100 to 200
It is usually about a millimeter of water column.

Therefore, if we use an or-no-no element with a water column of 100 mm of pressure required for switching,
When the engine 1 is in a combustion state, the output pressure of the adder circuit (the output pressure of the output port 43 of the proportional element 4) is less than 100 mm water column, and when the engine 1 misfires, the adder circuit output pressure is more than 100 mm water column. By adjusting the additive output gain (for example, by adjusting the magnitude of the supply pressure of the proportional element), misfire can be detected as described below.

The total exhaust pressure downstream of the exhaust valve of the engine 1 is detected by the inlet pipe 2. The total pressure sensed by the inlet tube 2 is divided into the total pressure and the DC component of the total pressure. The proportional element 4 emits an output pressure to the output port 43 that increases as the fall of the fluctuating component of the total pressure with respect to the DC component of the total pressure increases. This adder circuit output pressure is guided to the set port 52' of the OR/NOR element 5'.

Assuming that the required pressure for switching the OR/NO element, that is, the "threshold value" is Po, during combustion, the output pressure of the adder circuit is smaller than Po, so the OR side output port 53' of the OR/NO element is “0”
(no output), and if there is a misfire, the output pressure will temporarily become higher than Po, so the OR side output port 53' will temporarily become "1" (with output) and become "0" again. Return.

In other words, in the event of a misfire, the OR side output port 5
Since the output pressure is obtained in a pulsed manner at 3', a misfire can be detected and measured.

Therefore, this embodiment has the same effects as the above-mentioned embodiments.

In the first and second embodiments, the threshold value of the Schmitt circuit was set to a predetermined value using a pneumatic pressure source, but in the third embodiment, this pressure was set to a predetermined value by a pneumatic source. The feature is that it uses the required pressure value for switching. In the first embodiment and its second embodiment, it is necessary to pay attention to fluctuations in the threshold value due to pressure fluctuations in the air pressure source, foreign matter contamination at the throttle 921, etc. in setting this threshold value.
The embodiment has the advantage that these effects are absent.

FIG. 7 shows a misfire sensor according to a fourth embodiment of the present invention. In this embodiment, the introduction pipe 2 that introduces the exhaust total pressure is
and a signal processing circuit 3d consisting of an addition circuit using a proportional element 4 and a Schmitt circuit 304 using a flip-flop (Flip-FLop) element 6'. It is in the configuration of the Schmitt circuit.

That is, in the fourth embodiment, the switching resistance value of the OR/NO element was used as the threshold value of the Schmitt circuit, but in this embodiment, the switching resistance value of the flip-flop element was used as the threshold value. Furthermore, it also works as a one shot multi. Hereinafter, the explanation will focus on the differences from the previous example, and the same parts will be given the same reference numerals and the explanation thereof will be omitted.

The Schmitt circuit 304 includes a flip-flop element 6', a pipe 91 connecting the input port 62' and the output port 43 of the proportional element 4, and a pipe 93 leading to the output pressure of the output port 63' of the flip-flop element. Branching from the piping 93, the input port 6
1', and a feedback tube 92. Note that 60' is a supply port to which supply air pressure is introduced from an air pressure source, and 64' is an output port open to the atmosphere.

Next, the operation of the misfire sensor of the fourth embodiment having the above configuration will be described. A flip-flop element is originally a bistable element, but as shown in the figure, if the output flow from the output port 63' is fed back (single feed back) to the input port 61', it becomes simple. Performs stable operation, ie, or-nor operation. In this case, the input port 62' becomes the set input port, the output port 63' becomes the OR side output, and the output port 64' becomes the NOR side output port, which is exactly the same as in the third embodiment described above.

Moreover, in the flip-flop element 6', there is a switching resistance (necessary switching pressure) of 100 to 200 mm of water column, similar to the above-mentioned or-nor element. A Schmitt operation can be performed using a threshold value.

That is, when the engine 1 is in combustion mode, the output of the adder circuit, that is, the working pressure on the input port 62' is below the threshold value, so no output is obtained at the OR output terminal 93 of the Schmitt circuit... However, in the event of a misfire, the working pressure on the input port 62' temporarily exceeds the threshold value, and "1" is generated at the OR output terminal 93 of the Schmitt circuit.

The state in which "1" is issued to the OR output end 93 means the time it takes for the output pressure issued to the OR side output to be transmitted to the input port 61 via the feed back piping 92, that is, the sound velocity of the air. If a is the pipe length of the feed back piping, then it is maintained for the time expressed by L/a, and then becomes "0" again.
It will return to the state of. In other words, the misfire detection output is obtained as a one-shot multi-shot having a constant pulse width of L/a.
This embodiment is effective when it is desired to set the output pulse width at the time of misfire to an arbitrary value.

In addition to the above, this embodiment has the same effects as the above-mentioned embodiments.

FIG. 8 shows a misfire sensor according to a fifth embodiment of the present invention. In the first to fourth embodiments, the adder circuit was composed of a proportional element, and the Schmitt circuit was composed of an OR-NO element and a flip-flop element. This is an embodiment with the simplest configuration in which a misfire in a four-cylinder internal combustion engine is detected by a signal processing circuit 3e consisting only of a Schmitt circuit according to No. 7. Hereinafter, differences from the previous example will be mainly explained, and the same parts will be given the same reference numerals and the explanation thereof will be omitted.

A variable throttle 811 inserted into the pipe 81 is installed to adjust the magnitude of the total exhaust pressure introduced by the introduction pipe 2.

In the OR/NOR element 7,
70 is a supply port, 72 is a set side port, 71 is a reset side port, 73 is an OR side output port, and 74 is a NOR side output port.

A pipe 82 that directly leads the exhaust total pressure is connected to the reset port 71, and a pipe 83 that leads the direct current component of the exhaust total pressure is connected to the set port 72. In this configuration, whether the airflow supplied to the supply port 70 is output to the OR side output 73 depends on the magnitude of the total exhaust pressure acting on the reset side port 71 and the amount of exhaust pressure acting on the set side port 72. It is determined by the difference between the total exhaust pressure (DC component) and the magnitude of the exhaust gas pressure (DC component). Then, "1" is issued to the OR side output when the following relationship holds between the working pressure P 72 to the set side port ₇₂ and the working pressure P ₇₁ to the reset side port 71.

P ₇₂ - P ₇₁ ≧PS>0 Here, PS is the aforementioned switching resistance (required switching pressure), and generally has a value of 100 to 200 mm water column.

Therefore, if an or-no-no element with a PS of 200 mm of water column is used, the fall of the total exhaust pressure relative to the DC component at the time of a misfire will be more than PS, that is, 200 mm of water column, and during combustion, it will be less than 200 mm of water column. If the variable aperture 811 can be adjusted to a sufficiently small value, the corresponding
A Schmitt operation is performed using PS as a threshold, and a misfire can be detected.

That is, when the engine 1 is in combustion mode, as mentioned above, P ₇₂ - P ₇₁ < PS (200 mm water column), so the OR side output port 73 is always "0".
It is in a state of If engine 1 now misfires, the total exhaust pressure will temporarily drop significantly relative to its DC component. As a result, since P ₇₂ −P ₇₁ >PS, the OR side output port 73 outputs a “1” state during that time. Then, when the total pressure, which has temporarily fallen, returns to its original state again, and P ₇₂ -P ₇₁ <PS, the OR side output port 73 becomes "0" again.

That is, in the event of a misfire, the OR side output port 73
By emitting “1” in a pulsed manner,
Misfires can be detected.

Therefore, this embodiment also exhibits the same effects as the above-mentioned embodiments.

In summary, the present invention uses a simple sensor using a fluid disk to accurately and responsively detect a misfire condition in an internal combustion engine, is inexpensive, and has sufficient durability against high-temperature exhaust gas. It is.

The present invention can be modified in many ways other than the embodiments described above.

In other words, in the embodiments other than the first embodiment, a misfire condition is detected as a pneumatic pressure signal, but this pressure signal is converted into an electrical signal using a pressure transducer, or is converted into an electrical signal by other converting means to a hydraulic machine or other quantity. These conversion amounts can be used to drive and control other members, and to display misfire conditions on a display device.

Although each of the above-mentioned embodiments describes an example in which the inlet pipe is arranged near the exhaust hole of the combustion chamber, the present invention is not limited to this, and the present invention may detect it at any position in the exhaust system, for example, it may be arranged downstream of the muffler. Even if it is set, the same effect as each embodiment is achieved.

In any of the embodiments other than the fourth embodiment, if it is desired to obtain the output pulse for misfire detection as a one-shot/multiple shot, the output pulse may be used as a trigger and a ninth
All that is required is to drive the one-shot multi-element shown in the figure.

Further, the misfire sensor of the present invention can detect not only a misfire in a single-cylinder spark-ignition internal combustion engine, but also a misfire in a multi-cylinder spark-ignition internal combustion engine such as a four-cylinder engine to which the misfire sensor of the fifth embodiment is applied. be.

Furthermore, this misfire sensor can detect a misfire well even when the inlet pipe 2 introduces only exhaust static pressure and dynamic pressure instead of the total exhaust pressure.

In addition, regarding the essential constituent elements of the present invention, it is possible to use other elements that exhibit similar effects other than those shown in the embodiments.

In addition, the present invention may be modified in numerous additions and designs without departing from the spirit of the claims.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a misfire sensor of an internal combustion engine as a reference example for explaining the present invention, Fig. 2 is a diagram showing total pressure fluctuations of exhaust gas flow of the internal combustion engine, and Fig. 3 is a diagram showing the misfire sensor of an internal combustion engine as a reference example for explaining the present invention. FIG. 4 is a diagram showing an application example of the first embodiment, and FIG. 5 is a diagram showing a misfire sensor for an internal combustion engine according to the second embodiment of the present invention. 6 is a diagram showing a misfire sensor for an internal combustion engine according to a third embodiment of the present invention, FIG. 7 is a diagram showing a misfire sensor for an internal combustion engine according to a fourth embodiment of the present invention, and FIG. 9 shows a diagram showing a misfire sensor for an internal combustion engine according to a fifth embodiment of the present invention, and FIG. 9 shows a diagram showing an application example of the present invention. In the figure, 1... internal combustion engine, 2... introduction pipe,
...Logic element, 3 ... Signal processing circuit, 4 ... Proportional element, 5 ... Or-Noah element, 6 ... Flip
It is a flop element.

Claims (1)

[Scope of Claims] 1. An exhaust gas formed into a communicating tube shape having openings at both ends, one opening communicating with the combustion chamber of a positive displacement internal combustion engine via an exhaust hole to introduce exhaust gas through the opening. an exhaust gas introduction pipe disposed within the passage and having the other opening disposed outside the exhaust passage of the positive displacement internal combustion engine; and one input port communicating with the other opening of the exhaust gas introduction pipe. The total exhaust pressure of the exhaust gas flow from the combustion chamber is guided, and the other input port communicates with the other opening of the exhaust gas introduction pipe via a piping provided with a throttle, and communicates with the volume via the piping. to derive the DC component of the total exhaust pressure of the exhaust gas flow, and compare the total exhaust pressure of the exhaust gas flow led to one input port with the DC component of the total exhaust pressure supplied to the other input port. When the difference is within the set value, the supply air flow supplied from the supply port is discharged from one output port, and the pressure of the exhaust gas flow led to one input port is increased due to a misfire in the internal combustion engine. When the difference between the DC component of the exhaust total pressure supplied to the other input port temporarily decreases and becomes larger than the set value, the port that discharges the supply air flow supplied from the supply port is switched, and the and a fluid logic element that discharges air from the output port, and is characterized by detecting a misfire state of the internal combustion engine by discharging the supply air flow supplied from the supply port from the other output port only when the internal combustion engine misfires. Internal combustion engine misfire sensor.