A composite sensor and an internal combustion engine equipped with the composite sensor

Abstract

The present invention provides a composite sensor that facilitates the correlation between heat transport and flame behavior, and an internal combustion engine equipped with the composite sensor. [Solution] The composite sensor comprises a substrate, an insulating layer 14, sensor wiring 16a, 16b, 16c, 16d, a resistor 18, ion probes 20a, 20b, and a protective layer. The substrate can be bonded to an adapter and placed in the combustion chamber of an internal combustion engine. The resistance value of the resistor 18 can be determined and used to evaluate heat transfer. The ion current can be determined using the ion probes 20a and 20b, and the determined ion current can be used to understand flame behavior. The resistor 18 and the ion probes 20a and 20b are integrally formed, making it easier to correlate heat transport and flame behavior.

Description

Technical Field

[0001] The present invention relates to a composite sensor for evaluating combustion heat transfer.

Background Art

[0002] In internal combustion engines such as automobile engines, in order to evaluate the heat transfer that occurs between a flame and a combustion chamber wall surface, a heat flux sensor such as that of Patent Document 1 has been used. Further, in order to grasp the flame behavior in the combustion chamber, an ion current sensor such as that of Patent Document 2 has been used.

[0003] However, in the above conventional technologies, since each is only measured individually, there is a problem that heat transport and flame behavior cannot be associated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a composite sensor that easily associates heat transport and flame behavior, and an internal combustion engine equipped with the composite sensor.

Means for Solving the Problems

[0006] The composite sensor of the present invention comprises a substrate, an insulating layer formed on the substrate, a plurality of sensor wirings having a first terminal and a second terminal formed on the insulating layer, a resistor connected to the first terminal of some of the plurality of sensor wirings, an ion probe connected to the first terminal of the remaining sensor wirings, and a protective layer formed to cover the insulating layer, the sensor wirings and the resistor. The internal combustion engine of the present invention is equipped with the composite sensor of the present invention. [Effects of the Invention]

[0007] According to the present invention, the resistor and the ion probe are integrally formed, making it easier to correlate heat transport and flame behavior. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the composite sensor of the present invention. [Figure 2] This is a plan view showing the sensor wiring, resistor, and ion probe. [Figure 3] This is a cross-sectional view showing the vicinity of the sensor wiring, resistor, and ion probe. [Figure 4] This is a cross-sectional view showing the area between the first and second surfaces of the substrate. [Figure 5] This is a cross-sectional view showing the area near the connection point between the through-wiring and the ion probe. [Figure 6] This is a magnified plan view of the area around the resistor and ion probe. [Figure 7] This is a circuit diagram showing the configuration for measuring ion current. [Figure 8] This is a cross-sectional view showing an ion probe formed on a protective layer. [Figure 9] This is a cross-sectional view showing a resistor with ion probes formed on both sides. [Figure 10] This is a cross-sectional view showing multiple ion probes arranged side by side. [Figure 11] This figure shows a combustion vessel for testing the characteristics of the composite sensor of the present invention. [Figure 12]The graph shows the heat flux and ion current when tested in a combustion vessel. [[ID=II]] [Figure 13] It is a graph showing the relationship between the ion current and the flame-wall distance when tested in a combustion vessel.

Embodiments of the Invention

[0009] The composite sensor of the present invention and the internal combustion engine equipped with the composite sensor will be described with reference to the drawings.

[0010] [Embodiment 1] The composite sensor 10 of the present invention shown in FIGS. 1 to 3 includes a substrate 12, an insulating layer 14, sensor wirings 16a, 16b, 16c, 16d, a resistor 18, ion probes 20a, 20b, and a protective layer 22.

[0011] The substrate 12 is a plate body, a cylinder, a cube, etc. having a first surface 24 and a second surface 26. The first surface 24 and the second surface 26 are flat and parallel. For example, the shapes of the first surface 24 and the second surface 26 are circular. The shapes of the first surface 24 and the second surface 26 are not limited as long as they can be joined to the adapter 28 described later and arranged in the combustion chamber of the internal combustion engine.

[0012] The substrate 12 is formed of metal or alloy, etc. For example, the substrate 12 is formed of stainless steel or aluminum alloy, etc. If it is stainless steel, it is excellent in corrosion resistance, heat resistance, and strength, so sensor production becomes easy. If it is an aluminum alloy, since it is the same as the component of the internal combustion engine, it is less likely to become a thermal singularity.

[0013] A first through hole 30 is formed in the substrate 12 (FIGS. 4 and 5). The first through hole 30 is a hole penetrating from the first surface 24 to the second surface 26. A through wiring 32 is passed through the first through hole 30. The first terminal 34 of the through wiring 32 is connected to the sensor wirings 16a, 16b, 16c, 16d. In order to prevent the inner wall of the first through hole 30 and the through wiring 32 from short-circuiting, the space between them may be filled with an insulating adhesive 36.

[0014] An insulating layer 14 is formed on the first surface 24 of the substrate 12. The insulating layer 14 is a layer for insulating the substrate 12 from the sensor wirings 16a, 16b, 16c, 16d, etc. Examples of the insulating layer 14 include epoxy resin, phenol resin, styrene resin, acrylic resin, silicon oxide, silicon nitride, alumina, etc. For example, the insulating layer 14 may be formed of a photoresist containing epoxy resin. When a liquid photoresist is dropped onto the first surface 24 and spin-coated to form the insulating layer 14, it is easy to smooth the surface of the insulating layer 14 during formation.

[0015] The portion of the first surface 24 of the substrate 12 where the first through-hole 30 is formed does not have the insulating layer 14 formed thereon. After forming the insulating layer 14 on the first surface 24, the insulating layer 14 above the first through-hole 30 is removed. If the insulating layer 14 is formed of a photoresist, the insulating layer 14 can be removed by exposure and development. The sensor wirings 16a, 16b, 16c, 16d are connected to the through-wiring 32 through this removed portion.

[0016] A first adhesive layer may be formed on the insulating layer 14. The first adhesive layer is a thin layer composed of silicon oxide or the like. The first adhesive layer can improve the adhesion between the insulating layer 14 and the sensor wirings 16a, 16b, 16c, 16d, the resistor 18, and the ion probes 20a, 20b.

[0017] The sensor wirings 16a, 16b, 16c, 16d are formed on the insulating layer 14 or the first adhesive layer. The sensor wirings 16a, 16b, 16c, 16d are formed of a metal such as platinum, nickel, copper, etc. The sensor wirings 16a, 16b, 16c, 16d have a first terminal 38 and a second terminal 40. The first terminal 38 is connected to the resistor 18 or the ion probes 20a, 20b, and the second terminal 40 is connected to the through-wiring 32.

[0018] A second adhesive layer may be formed under the sensor wirings 16a, 16b, 16c, 16d. The second adhesive layer is a thin layer formed of titanium or the like. The second adhesive layer can improve the adhesion between the insulating layer 14 or the first adhesive layer and the sensor wirings 16a, 16b, 16c, 16d.

[0019] The resistor 18 is a thin film formed from a metal such as platinum, nickel, or copper. It utilizes the property that the electrical resistance of a metal increases with increasing temperature. While platinum is preferred for its stability and precision, this invention is not limited to platinum. The desired resistance is achieved by adjusting the length and cross-sectional area of ​​the metal used in the resistor 18. As shown in Figure 6, the resistor 18 may be serpentine to achieve the desired resistance value. Using the same material for the sensor wiring 16a, 16b and the resistor 18 prevents an increase in the number of manufacturing steps for the composite sensor 10.

[0020] The resistor 18 is equipped with a first terminal 42 and a second terminal 44. The first terminal 42 and the second terminal 44 are connected to the first terminal 38 of different sensor wires 16a and 16b, respectively. Each terminal 42 and 44 of the resistor 18 is connected to the two sensor wires 16a and 16b. The four-terminal method is used to measure the resistance value of the resistor 18. Alternatively, the two-terminal method may be used by using only one of the two sensor wires 16a and 16b.

[0021] The second adhesive layer may be formed beneath the resistor 18. The second adhesive layer can improve the adhesion between the resistor 18 and the insulating layer 14 or the first adhesive layer.

[0022] Ion probes 20a and 20b are linear in shape and have a first terminal 54 and an open end 56. The first terminal 54 is connected to the first terminal 38 of the sensor wiring 16c and 16d. The open end 56 of ion probes 20a and 20b is not connected to anything.

[0023] The first ion probe 20a and the second ion probe 20b have one positive electrode and the other negative electrode, forming a set of positive and negative electrodes. Each ion probe 20a and 20b is linear. The two ion probes 20a and 20b are parallel to each other. An ionic current flows between the two ion probes 20a and 20b. Conventionally, spark plugs were used as ion probes, but in this invention, the ion probes 20a and 20b are formed on the same substrate 12 as the resistor 18.

[0024] An example of an ion current measurement circuit is shown in Figure 7. The first ion probe 20a is connected to a power supply 58, and the second ion probe 20b is connected to a resistor 60 and a voltmeter 62 that measures the voltage drop across the resistor 60. The ion current is calculated by measuring the voltage drop across the resistor 58. The power supply 60 may apply either a positive voltage or a negative voltage to the first ion probe 20a, or it may apply a positive voltage and a negative voltage in sequence. The obtained ion current can be used to understand flame behavior.

[0025] Multiple sets of ion probes 20a and 20b are provided. The spacing between the ion probes 20a and 20b in each set may be different. For example, as shown in Figure 6, the spacing d1 and d2 between the two sets of ion probes 20a and 20b are different. The flame detection distance changes, and multiple data can be obtained for the same flame.

[0026] The ion probes 20a and 20b, like the sensor wiring 16a, 16b, 16c, 16d and the resistor 18, are made of a metal such as platinum, nickel, or copper. The second adhesive layer may be formed beneath the ion probes 20a and 20b to improve adhesion to the insulating layer 14 or the first adhesive layer.

[0027] It is desirable that the resistor 18 and ion probes 20a and 20b have a spatial scale equivalent to or smaller than the turbulence of the flame being measured. In the case of an automotive internal combustion engine, the integral length scale is from millimeters to sub-millimeters. By using a spatial scale equivalent to or smaller than the turbulence of the flame, the measurements can be considered as being taken on the same flame, making it possible to correlate heat transport with flame behavior.

[0028] The protective layer 22 is formed to cover the sensor wiring 16a, 16b, 16c, 16d and the resistor 16. The protective layer 22 is an insulator and is made of, for example, silicon oxide. The protective layer 22 protects the sensor wiring 16a, 16b, 16c, 16d and the resistor 16 from flames. The ion probes 20a and 20b are not covered by the protective layer 22. This is to allow the ion current generated by the flame to flow between the two ion probes 20a and 20b. It is preferable that the insulating layer 14 be covered by the protective layer 22, but the area between the ion probes 20a and 20b and their periphery may not be covered. For example, the area 64 shown by the dotted line in Figure 6 may not be covered by the protective layer 22.

[0029] The present invention may include a metal adapter 28 that is attached to the combustion chamber of an internal combustion engine. The second surface 26 of the base plate 12 is attached to the adapter 28. The adapter 28 is cylindrical in shape. Screw threads 66 may be provided on part or all of the outer circumference of the adapter 28. The adapter 28 is made capable of being attached to the combustion chamber of an internal combustion engine.

[0030] The upper surface of the composite sensor 10 should be flush with the inner wall surface of the combustion chamber. The influence of the composite sensor 10 on the combustion occurring in the combustion chamber should be minimized. However, if the height from the first surface 24 of the substrate 12 to the surface of the protective layer 22 is low, the first surface 24 of the substrate 12 may be flush with the inner wall of the combustion chamber, or other layers may be flush with the inner wall surface of the combustion chamber. It is preferable to mount the composite sensor 10 in a way that does not affect the combustion occurring in the combustion chamber.

[0031] A second through-hole 68 is provided inside the adapter 28. The first through-hole 30 and the second through-hole 68 are connected to form a single through-hole. The through-wiring 32 described above is passed through the second through-hole 68. The space between the inner wall of the second through-hole 68 and the through-wiring 32 is filled with an insulator. This prevents a short circuit between the through-wiring 32 and the adapter 28.

[0032] The second terminal of the through-wiring 32 is connected to a desired measuring instrument. The measuring instrument may include the power supply 58, resistor 60, voltmeter 62, etc. A computer may be provided for analyzing the values ​​measured by the measuring instrument. The analyzed data may be used to control the drive of the internal combustion engine.

[0033] Next, the manufacturing method of the composite sensor 10 will be described. (1) Prepare a substrate 12 having a first surface 24 and a second surface 26. The substrate 22 is made of a metal or alloy such as stainless steel.

[0034] (2) A first through-hole 30 is formed by drilling or the like, penetrating from the first surface 24 to the second surface 26. The number of first through-holes 30 is the same as the number of sensor wirings 16a, 16b, 16c, and 16d. Through-wirings 32 are passed through the first through-holes 30, and insulating adhesive 36 is placed in the first through-holes 30 to prevent short circuits between the substrate 12 and the through-wirings 32. The through-wirings 32 and adhesive 36 that protrude beyond the first surface 24 are scraped off and removed, and the first surface 24 is cleaned with alcohol or the like.

[0035] (3) An insulating layer 14 is formed on the first surface 24. The insulating layer 14 is formed of a permanent film photoresist. Liquid photoresist is dropped onto the first surface 24, spin-coated, and pre-baked. Then, exposure, post-exposure bake, development, and hard bake are performed to remove the photoresist only over the through-wiring 32. At this time, the photoresist over the first through-hole 30 may also be removed. The insulating layer 14 may also be formed of a resin other than photoresist, such as silicon oxide, silicon nitride, or alumina. In that case, the pattern is made using photoresist, and the unwanted parts are removed by the lift-off method or etching method.

[0036] A first adhesive layer made of silicon oxide may be laminated on the insulating layer 14 by sputtering or the like. The first adhesive layer on the through-wiring 32 is removed by lift-off or the like.

[0037] (4) Sensor wiring 16a, 16b, 16c, 16d, resistor 18, and ion probe 20a, 20b are formed on the insulating layer 14 or adhesive layer. A photoresist is laminated on the insulating layer 14 or adhesive layer, and patterns of the desired shapes of sensor wiring 16a, 16b, 16c, 16d, resistor 18, and ion probe 20a, 20b are formed by pre-baking, exposure, post-exposure baking, and development. A metal layer such as platinum is formed on top of this by sputtering or the like. Then, the unwanted parts of the metal layer are removed by the lift-off method. The removal of the unwanted parts may also be performed by etching.

[0038] A second adhesive layer, such as titanium, may be formed before laminating the metal layers. The second adhesive layer enhances the adhesive strength of the metal layers. The second adhesive layer is formed by sputtering or the like. The second adhesive layer may also be formed at the same time as the sensor wiring 16a, 16b, 16c, 16d, resistor 18, and ion probes 20a, 20b are formed.

[0039] (5) A protective layer 22 is formed on the insulating layer 14, the sensor wiring 16a, 16b, 16c, 16d and the resistor 18. An insulator such as silicon dioxide is formed by sputtering, and the insulator on the ion probes 20a and 20b is removed by the lift-off method.

[0040] (6) The second surface 26 of the substrate 14 is joined to the adapter 28. The through-wiring 32 is passed through the second through-hole 66 formed in the adapter 28. The through-wiring 32 is connected to a measuring instrument.

[0041] (7) The adapter 28 is attached to the combustion chamber of the internal combustion engine. A hole is made in the combustion chamber that penetrates from the outside to the inside, and the adapter 28 is attached to this hole. The adapter 28 has screw threads 66 and a screw hole is made in the combustion chamber. The adapter 28 is attached to the combustion chamber by screw connection. At this time, the first surface 24 of the substrate 12 or the layer from the first surface 24 to the protective layer 22 is made flush with the inner wall of the combustion chamber.

[0042] As described above, the composite sensor 10 of the present invention has the resistor 18 and the ion probes 20a and 20b integrally formed, making it easier to correlate heat transport and flame behavior.

[0043] [Embodiment 2] The number of ion probes 20a and 20b is not limited to two sets. There may be one set or multiple sets of ion probes 20a and 20b.

[0044] As shown in Figure 8, the resistor 18 may be covered with a protective layer 22, and then the ion probes 20a and 20b may be formed on top of it. This allows for miniaturization of the composite sensor 10. Sensor wirings 16c and 16d connected to the ion probes 20a and 20b are also formed on top of the protective layer 22, and the sensor wirings 16c and 16d are covered with the protective layer 22.

[0045] As shown in Figure 9, two ion probes 20a and 20b may be arranged so as to sandwich the resistor 18. This allows for the measurement of both resistance and ion current for the same flame.

[0046] The number of ion probes 20a and 20b is not limited. Multiple ion probes 20a and 20b may be arranged in a row as shown in Figure 10. The first ion probe 20a is placed at the very end and there is only one of them. The other ion probes are designated as second ion probes 20b. The second ion probe 20b to be driven is appropriately selected and the ion current is measured. A switch for selecting the second ion probe 20b may be provided. The first ion probe 20a is not limited to one, nor is it limited to being placed at the very end. Multiple first ion probes 20a may be provided, and a switch for selecting them may be provided. The first ion probe 20a and the second ion probe 20b may be swapped.

[0047] The shapes of the ion probes 20a and 20b are not particularly limited, nor is the position of the first terminal 54.

[0048] [Examples] A stainless steel substrate 12 with a diameter of 7 mm and a thickness of 4 mm was prepared. A first through-hole 30 with a diameter of 1 mm was drilled in the substrate 12. A through-wire 32 and sealant 36 were inserted into the first through-hole 30 and fixed in place, insulating the substrate 12 from the through-wire 32. The substrate 12 was polished so that the through-wire 32 and the adhesive 36 were flush with the first surface 24, and the surface was cleaned.

[0049] An insulating layer 14 was formed on the first surface 24 of the substrate 12 by dropping a liquid negative photoresist, SU-8, spin coating, pre-baking, and exposure. The thickness of the insulating layer 14 was 10 μm. The portion of the insulating layer 14 above the through-wiring 32 was removed by development, and then stabilized by hard baking. A thin film of silicon oxide was deposited on the insulating layer 12 by sputtering. The thickness of the silicon oxide layer was 0.2 μm. The lift-off method was used to remove the silicon oxide above the through-wiring 32.

[0050] Photoresist was deposited on silicon oxide, pre-baked, exposed, post-exposure baked, and developed, and only the photoresist in the sensor wiring 16a, 16b, 16c, 16d, resistor 18, and ion probes 20a, 20b was removed. On top of that, titanium was deposited as the second adhesive layer. The titanium was deposited by sputtering, and its layer thickness was 0.02 μm. Platinum was deposited on top of the titanium. The platinum was deposited by sputtering, and its layer thickness was 0.2 μm.

[0051] By the lift-off method, unwanted portions of the stacked titanium and platinum were removed to form sensor wiring 16a, 16b, 16c, 16d, resistor 18, and ion probes 20a, 20b. The resistor 18 had a side length of 330 μm. The electrode distance d1 of the ion probes 20a and 20b on the left side of Figure 6 was 150 μm, and the electrode distance d2 of the ion probes 20a and 20b on the right side was 100 μm. The distance between the resistor 18 and the first ion probe 20a was 250 μm.

[0052] A layer of silicon oxide was formed on the insulating layer 14, sensor wiring 16a, 16b, 16c, 16d, resistor 18, and ion probes 20a, 20b. The silicon oxide was formed by sputtering. The thickness of the silicon oxide layer was 0.2 μm. A lift-off method was used to remove the silicon oxide from the ion probes 20a, 20b and their periphery. The remaining silicon oxide formed a protective layer 22 covering the sensor wiring 16a, 16b, 16c, 16d and resistor 18.

[0053] After manufacturing the composite sensor 10 using the above process, the second surface 26 of the substrate 12 was joined to the adapter 28. During joining, the through-wiring 32 was passed through the second through-hole 66 formed in the adapter 28.

[0054] The completed composite sensor 10 was tested. The combustion container 70 used in the experiment was shown in Figure 11. The volume of the chamber 72 of the combustion container 70 was 0.24 liters. The composite sensor 10 was mechanically joined by screwing the threads 66 of the adapter 28 into the screw holes of the sensor mounting hole 76 provided in the bottom 74 of the combustion container 70.

[0055] A heater 78 is placed inside the chamber 72 of the combustion container 70, allowing the walls of the chamber 72 to be heated to any desired temperature. The wall temperature was set to approximately 70°C to prevent condensation of moisture generated by combustion on the walls.

[0056] Butane gas was used as the fuel. A premix was formed by measuring the amount to an equivalent ratio of 1 and injecting it through the fuel inlet 80. Ignition was performed by the ignition electrode 82, and the propagation of the flame and its impact on the wall was observed through the observation window 84.

[0057] The graph in Figure 12 shows the heat flux and ion current measured by the composite sensor 10 when the flame collides with the wall. The solid line represents the ion current, and the dotted line represents the heat flux. A voltage of 30V was applied to the ion probe 20a, and the rise time of the ion current was set to time 0ms. The ion current rises slightly faster than the heat flux, and the timing of its peak value is also slightly earlier than that of the heat flux. After reaching its peak value, the ion current falls rapidly, while the heat flux decays relatively slowly. When the flame at this time was photographed with a high-speed camera, the peak time of the ion current was almost simultaneous with the time the flame went out, i.e., the timing of flame extinguishing.

[0058] Figure 13 shows the relationship between ion current and the distance between the flame and the wall. The distance between the flame and the wall was determined from flame images captured by a high-speed camera. When the flame approached the composite sensor to within approximately 500 μm, the ion current rose, and the ion current increased as the flame approached. When the distance between the flame and the wall shortened to approximately 280 μm, the flame extinguished and was no longer visible, and at that point the ion current showed its peak value.

[0059] It was found that by calibrating the ion current and the flame-wall distance, it is possible to determine the flame-wall distance from the measured ion current, even in systems where visualization observation is not possible. Furthermore, since the heat flux can be measured simultaneously with the ion current at the same location, it is possible to investigate the relationship between heat transport and flame behavior from the measured values ​​of both.

[0060] Furthermore, the present invention can be implemented in various forms with improvements, modifications, and changes based on the knowledge of those skilled in the art, without departing from its spirit. [Explanation of Symbols]

[0061] 10: Combined Sensor 12: Circuit board 14: Insulating layer 16a, 16b, 16c, 16d: Sensor wiring 18: Resistor 20a, 20b: Ion probes 22:Protective layer 24: First side of the circuit board 26: Second side of the circuit board 28: Adapter 30: First through hole 32: Through-hole wiring 34: Terminals for through-wiring 36: Adhesive 38: First terminal of sensor wiring 40: Second terminal of sensor wiring 42: First terminal of the resistor 44: Second terminal of the resistor 54: First terminal of the ion probe 56: Open end of ion probe 58: Power supply 60: Resistor 62: Voltmeter 64: Areas not covered by the protective layer 66: Screw thread 68: Second through hole 70: Combustion container 72: Inside the combustion chamber 74: Bottom of the combustion container 76: Sensor mounting hole 78: Heater 80: Fuel inlet 82:Ignition electrode 84: Observation window

Claims

1. circuit board and An insulating layer formed on the substrate, A plurality of sensor wirings having first terminals and second terminals formed on the insulating layer, A resistor with terminals connected to the first terminals of some of the sensor wirings among the plurality of sensor wirings, An ion probe, to which a terminal is connected to the first terminal of the remaining sensor wiring among the plurality of sensor wirings, A protective layer formed to cover the sensor wiring and resistor, A composite sensor equipped with [specific features / features].

2. The composite sensor according to claim 1, wherein the ion probes each consist of a positive and negative electrode, and a plurality of such ion probes are provided.

3. The composite sensor according to claim 2, wherein in the plurality of sets of ion probes, the spacing between one set of ion probes is different from the spacing between the other sets of ion probes.

4. A first through-hole penetrating the substrate, A through-hole is placed inside the first through-hole and connected to the second terminal of the sensor wiring, A composite sensor according to claim 1, comprising:

5. The adapter on which the aforementioned circuit board is attached, The adapter has a second through-hole formed therein, which is connected to the first through-hole and through which the through-wiring passes, A composite sensor according to claim 4, comprising:

6. The composite sensor according to claim 5, further comprising a screw thread for attaching the adapter to an internal combustion engine.

7. The composite sensor according to claim 1, comprising at least one of the sensor wiring, resistor and ion probe, a second adhesive layer formed beneath them, or a first adhesive layer formed on top of the insulating layer.

8. An internal combustion engine equipped with the composite sensor of claim 1.

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