Electrode fabrication method and electrode fabrication apparatus

Abstract

To obtain an electrode shape suitable for the gas flow in the combustion chamber. [Solution] The electrode fabrication method includes a voltage application step in which a discharge is generated between the center electrode and the outer electrode of a spark plug, while an engine equipped with a spark plug is motorized by an electric motor and metal powder is supplied to the combustion chamber of the engine. In the voltage application step, the metal powder is sprayed onto at least one of the center electrode and the outer electrode of the spark plug by generating a discharge between them.

Description

Technical Field

[0001] The present disclosure relates to an electrode shaping method and an electrode shaping apparatus.

Background Art

[0002] Engines that use fuels such as gasoline have spark plugs provided with a center electrode and an outer electrode (see Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in order to stabilize the lean combustion of an engine, it is often necessary to generate gas flow such as tumble flow in the combustion chamber. However, the gas flow generated in the combustion chamber is a factor that complicates the arc behavior of the spark plug and affects the shape design of the center electrode and the outer electrode. Therefore, when designing the electrode shape of the spark plug, it is required to consider the gas flow in the combustion chamber.

Means for Solving the Problems

[0005] According to this disclosure, the electrode fabrication method includes a voltage application step in which a discharge is generated between the center electrode and the outer electrode of a spark plug, while an engine equipped with a spark plug is motorized by an electric motor and metal powder is supplied to the combustion chamber of the engine. In the voltage application step, the metal powder is sprayed onto at least one of the center electrode and the outer electrode of the spark plug by generating a discharge between them.

[0006] According to this disclosure, the electrode molding apparatus includes an electric motor connected to the output shaft of an engine, a powder supply unit containing metal powder, and a voltage application unit that generates a discharge between the center electrode and the outer electrode of a spark plug. The voltage application unit generates a discharge between the center electrode and the outer electrode while the engine is being motorized by the electric motor and the metal powder is being supplied to the combustion chamber of the engine by the powder supply unit, thereby spraying the metal powder onto at least one of the center electrode and the outer electrode. [Effects of the Invention]

[0007] According to this disclosure, while the engine is motoring, metal powder is sprayed onto at least one of the central electrode and the outer electrode. This makes it possible to obtain an electrode shape suitable for the gas flow in the combustion chamber. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows an electrode fabrication apparatus that is one embodiment of the present disclosure. [Figure 2] Figure 2 is an enlarged view showing the combustion chamber and its vicinity. [Figure 3] Figure 3 is a magnified view showing the spark plug and its vicinity. [Figure 4] Figure 4 is a flowchart showing the procedure for executing an electrode fabrication method according to one embodiment of the present disclosure. [Figure 5]Figure 5 shows an example of the execution status of the voltage application step. [Figure 6] Figure 6 shows the outer electrode after the electrode fabrication method has been performed. [Figure 7] Figure 7 shows a part of an electrode fabrication apparatus, which is another embodiment of the present disclosure. [Figure 8] Figure 8 is a flowchart showing the execution procedure of an electrode fabrication method, which is another embodiment of the present disclosure. [Figure 9] Figure 9 is a flowchart showing the execution procedure of an electrode fabrication method, which is another embodiment of the present disclosure. [Figure 10A] Figure 10A shows the outer electrode and central electrode during the electrode fabrication process. [Figure 10B] Figure 10B shows the outer electrode and central electrode after the electrode fabrication method has been performed. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described in detail below with reference to the drawings. In the following description, identical or substantially identical components and elements will be denoted by the same reference numerals, and repeated descriptions will be omitted.

[0010] <Electrode shaping device> Figure 1 shows an electrode molding apparatus 10, which is one embodiment of the present disclosure. As shown in Figure 1, the electrode molding apparatus 10 includes a workbench 11 on which an engine 40 is installed, a motor unit 12 connected to the crankshaft 41 of the engine 40, and a control system 13 for controlling the engine 40 and the motor unit 12. The electrode molding apparatus 10 also includes a powder supply unit 14 attached to the intake system 60 of the engine 40, and a voltage application unit 15 electrically connected to the spark plug 80 of the engine 40. The engine 40 installed on the workbench 11 has specifications equivalent to those of a mass-produced engine mounted in a vehicle such as an automobile. That is, the engine 40 has an engine body 42 equivalent to that of a mass-produced engine. The engine 40 also has an intake system 60 equivalent to that of a mass-produced engine, and an exhaust system 70 equivalent to that of a mass-produced engine.

[0011] The motor unit 12 of the electrode molding apparatus 10 includes an electric motor 16 connected to a crankshaft (output shaft) 41 and a motor drive circuit 17 that controls the energization state of the electric motor 16. The powder supply unit 14 of the electrode molding apparatus 10 includes a powder tank 19 connected to the intake system 60 via a branch pipe 18 and a flow control valve 20 provided on the branch pipe 18. The powder tank 19 of the powder supply unit 14 contains metal powder P made of a metal material such as an iron alloy. Furthermore, the voltage application unit 15 of the electrode molding apparatus 10 includes an ignition coil 21 and an igniter 22.

[0012] The control system 13 of the electrode shaping device 10 has a computer device 26 composed of a microcontroller 25 or the like. The microcontroller 25 includes a processor 23 and a main memory 24 that are communicably connected to each other. By executing a predetermined control program, the computer device 26 drives the electric motor 16 to rotate the crankshaft 41 and controls a throttle valve 63, variable valve mechanisms 53 and 54, etc., which will be described later. A motor rotation sensor 27 for detecting the rotation speed of the electric motor 16, a crank angle sensor 28 for detecting the rotation angle of the crankshaft 41 (hereinafter referred to as the crank angle), and a cam angle sensor 29 for detecting the rotation angle of a camshaft (hereinafter referred to as the cam angle), which will be described later, are connected to the computer device 26. Further, an air flow sensor 30 for detecting the intake air flow rate and a throttle opening sensor 31 for detecting the opening degree of the throttle valve 63 are connected to the computer device 26.

[0013] <Engine> The engine 40 has an engine body 42 composed of a cylinder block 43 and a cylinder head 44. A piston 45 is reciprocally accommodated in the cylinder block 43 of the engine body 42. Further, a crankshaft 41 connected to the piston 45 is rotatably supported in the cylinder block 43. The cylinder head 44 of the engine body 42 has an intake port 47 communicating with the combustion chamber 46 and an intake valve 48 for opening and closing the intake port 47. Similarly, the cylinder head 44 has an exhaust port 49 communicating with the combustion chamber 46 and an exhaust valve 50 for opening and closing the exhaust port 49. Further, the cylinder head 44 has an intake camshaft 51 for driving the intake valve 48 and an exhaust camshaft 52 for driving the exhaust valve 50. Furthermore, the cylinder head 44 has a variable valve mechanism 53 for controlling the opening and closing timing of the intake camshaft 51 and a variable valve mechanism 54 for controlling the opening and closing timing of the exhaust camshaft 52.

[0014] The engine 40 has an intake system 60 connected to the intake port 47 of the cylinder head 44 and an exhaust system 70 connected to the exhaust port 49 of the cylinder head 44. The intake system 60 is composed of an air cleaner box 61, an intake pipe 62, a throttle valve 63, an intake pipe 64, a surge tank 65, and an intake manifold 66. The powder supply unit 14 of the electrode shaping device 10 described above is connected to the intake pipe 62 located upstream of the throttle valve 63. Further, the exhaust system 70 is composed of an exhaust manifold 71, a catalytic converter 72, an exhaust pipe 73, and a muffler 74.

[0015] Figure 2 is an enlarged view showing the combustion chamber 46 and its vicinity, and Figure 3 is an enlarged view showing the ignition plug 80 and its vicinity. As shown in Figures 2 and 3, an ignition plug 80 having electrodes 81, 85 exposed to the combustion chamber 46 is attached to the cylinder head 44 of the engine 40. As shown in Figure 3, the ignition plug 80 has a center electrode 81 disposed at the center, a cylindrical insulator 82 disposed radially outside the center electrode 81, and a cylindrical housing 83 disposed radially outside the insulator 82. Further, the housing 83 of the ignition plug 80 has a male screw portion 84 fastened to the plug hole 55 of the cylinder head 44 and an outer electrode 85 joined to the tip surface of the male screw portion 84. Note that the outer electrode 85 is sometimes referred to as a ground electrode.

[0016] <Voltage application unit> As shown in Figure 3, the voltage application unit 15 includes an ignition coil 21 equipped with a primary coil 32 and a secondary coil 33, and an igniter 22 equipped with a transistor 34. One end of the primary coil 32 is connected to a power supply 36 via an ignition switch 35, and the other end of the primary coil 32 is connected to the transistor 34 of the igniter 22. Similarly, one end of the secondary coil 33 is connected to the power supply 36 via an ignition switch 35, and the other end of the secondary coil 33 is connected to the center electrode 81 of the spark plug 80 via a current-carrying shaft 86. The computer device 26 controls the transistor 34 of the igniter 22 to rapidly switch the current of the primary coil 32 on and off, and applies the induced voltage of the secondary coil 33 to the center electrode 81 of the spark plug 80. The computer device 26 also generates an ignition signal consisting of ignition timing and energizing time based on signals from the crank angle sensor 28, cam angle sensor 29, and airflow sensor 30, and transmits it to the igniter 22. Furthermore, the computer device 26 can switch the ignition switch 35 between the ON and OFF states.

[0017] <Gas flow and arc discharge> As shown in Figure 2, the shapes of the intake port 47, combustion chamber 46, and piston 45 are designed to generate gas flow FL, such as tumble flow, within the combustion chamber 46, from the viewpoint of stabilizing lean combustion of the engine 40. Furthermore, as shown in Figure 3, gas flow FL is also generated between the central electrode 81 and the outer electrode 85, so the discharge path between the central electrode 81 and the outer electrode 85 (hereinafter referred to as arc discharge path α) is affected by the gas flow FL and deviates from the shortest path between the central electrode 81 and the outer electrode 85. Note that the arc discharge path α shown is just one example, and the arc discharge path α is constantly changing depending on the conditions of the combustion chamber 46.

[0018] <Electrode forming method> As mentioned above, the arc discharge path α of the spark plug 80 is affected by the gas flow FL. Therefore, when designing the shape of the central electrode 81 and the outer electrode 85 of the spark plug 80, it is important to consider the gas flow FL of the combustion chamber 46. Accordingly, as will be described later, in the technology of this disclosure, metal powder P is sprayed onto the outer electrode 85 by utilizing arc discharge to obtain a shape of the outer electrode 85 that is suitable for the gas flow FL of the combustion chamber 46. Here, Figure 4 is a flowchart showing the execution procedure of an electrode fabrication method according to one embodiment of this disclosure. Each step of the electrode fabrication method shown in Figure 4 is a step executed by the processor 23 of the computer device 26.

[0019] As shown in Figure 4, the computer device 26 proceeds to step S10 and reads the engine operating mode set by the operator. Here, the engine operating mode is the operating pattern of the engine 40 that is executed when forming the outer electrode 85. This engine operating mode is set to include the engine speed, throttle opening, ignition timing, and opening / closing timing. The computer device 26 proceeds to step S11 and controls the electric motor 16 based on the engine operating mode, as well as the throttle valve 63 and variable valve mechanisms 53, 54 based on the engine operating mode. As a result, the engine 40 is motorized and the throttle valve 63, etc. are controlled, so that air can flow from the intake system 60 through the combustion chamber 46 to the exhaust system 70, just as when a mass-produced engine is running. The situation in which the engine 40 is motorized is when the crankshaft 41 of the engine 40 is rotated by the electric motor 16. Note that no fuel is injected from the injector 56 in step S11.

[0020] The computer device 26 proceeds to step S12, where it adjusts the flow control valve 20 based on the intake air flow rate to control the amount of metal powder P supplied to the intake air. The computer device 26 increases the amount of metal powder P supplied by opening the flow control valve 20 as the intake air flow rate increases. Furthermore, in this embodiment, the particle size of the metal powder P is adjusted to several μm to several tens of μm in order to properly disperse the metal powder P in the intake air. The computer device 26 then proceeds to step S13, where it controls the voltage application unit 15 based on the crank angle and cam angle to perform ignition control of the spark plug 80 according to the engine operating mode described above. Specifically, in step S13, the voltage application unit 15 applies a dielectric breakdown voltage to the center electrode 81, causing a discharge (hereinafter referred to as arc discharge) between the center electrode 81 and the outer electrode 85 of the spark plug 80.

[0021] Next, the computer device 26 proceeds to step S14 and determines whether a predetermined set time has elapsed. If the computer device 26 determines in step S14 that the set time has not elapsed, it returns to step S11 and continues the operation of the engine 40 according to the engine operation mode, and proceeds to steps S12 and S13 to continue the supply of metal powder and ignition control. On the other hand, if the computer device 26 determines in step S14 that the set time has elapsed, it proceeds to step S15 and stops the engine operation, stops the supply of metal powder, and stops the ignition control.

[0022] As described above, in step (voltage application step) S13, with the engine 40 being motored by the electric motor 16 and metal powder P supplied to the combustion chamber 46 of the engine 40, an arc discharge is generated between the center electrode 81 and the outer electrode 85 of the spark plug 80. Here, Figure 5 is a diagram showing an example of the execution of the voltage application step. As shown in the enlarged portion of Figure 5, when an arc discharge is generated between the center electrode 81 and the outer electrode 85 with the metal powder P dispersed in the intake air, the intake air containing the metal powder P is ionized into plasma, and the positively charged metal powder P is sprayed onto the outer electrode 85, which is the negative electrode. That is, as shown by the arrow Ts in the enlarged portion of Figure 5, the molten metal powder P moves along the arc discharge path α, and the metal powder P is sprayed onto the outer electrode 85. Then, a metal layer 87 consisting of the sprayed metal powder P is formed on the surface of the outer electrode 85. Furthermore, in order to suppress the influence of the initial shape of the outer electrode 85 on the arc discharge path α, it is desirable that the initial shape of the outer electrode 85 be a curved surface or a flat surface without edges.

[0023] Figure 6 shows the outer electrode 85 after the electrode fabrication method has been executed. As described above, since the metal powder P is sprayed onto the outer electrode 85 for a predetermined set time, a laminate 88 extending along the arc discharge path α is formed on the outer electrode 85, as shown in Figure 6. Since this laminate 88, consisting of a metal layer 87, takes shape along the arc discharge path α, a shape of the outer electrode 85 suitable for the gas flow FL of the combustion chamber 46 can be obtained. In other words, since the arc discharge path α changes under the influence of the gas flow FL, by extending the laminate 88 from the outer electrode 85 in accordance with this arc discharge path α, an outer electrode 85 suitable for the gas flow FL of the combustion chamber 46 can be fabricated.

[0024] Thus, the outer electrode 85 fabricated by the electrode fabrication method of this disclosure can be used as a template when designing the electrode shape of the spark plug 80. Furthermore, a spark plug 80 equipped with an outer electrode 85 fabricated by the electrode fabrication method of this disclosure can be attached to an engine mounted in a vehicle or the like and used. In addition, in the above description, the outer electrode 85 of the spark plug 80 is the negative electrode and is fabricated by thermal spraying of metal powder P, but this is not the only method. That is, by setting the center electrode 81 of the spark plug 80 as the negative electrode, the center electrode 81 may also be fabricated by thermal spraying of metal powder P.

[0025] Furthermore, the engine operating mode when executing the electrode fabrication method may be one in which the engine speed and throttle opening are kept constant, or it may be one in which the engine speed and throttle opening are actively changed. For example, when the target is an engine installed in a hybrid vehicle, the engine's operating range is limited, so it is possible to adopt an engine operating mode that keeps the engine speed and throttle opening constant. On the other hand, when the target is an engine used in a wide operating range, it is possible to adopt an engine operating mode that actively changes the engine speed and throttle opening.

[0026] <Other embodiments> In the above description, metal powder P is sprayed onto the outer electrode 85 or the central electrode 81, but this is not the only option; metal powder P may be sprayed onto both the outer electrode 85 and the central electrode 81. The following description will focus on the differences from the electrode fabrication apparatus 10 and electrode fabrication method described above.

[0027] Figure 7 shows a part of an electrode fabrication apparatus 90, which is another embodiment of the present disclosure. As shown in Figure 7, the cylinder head 91 of the engine 40 has a current-carrying sleeve 92 with a plug hole 55 and an insulating sleeve 93 positioned outside the current-carrying sleeve 92. The current-carrying sleeve 92 is formed from a metal material, and the insulating sleeve 93 is formed from an insulating material.

[0028] The electrode molding apparatus 90 has a voltage application unit 94 that is electrically connected to the spark plug 80 of the engine 40. The voltage application unit 94 has an ignition coil 21 with a primary coil 32 and a secondary coil 33, an igniter 22 with a transistor 34, and a switch circuit 95 that switches the polarity of the center electrode 81 and the outer electrode 85. The switch circuit 95 has a first positive contact 96a and a second positive contact 97a connected to the secondary coil 33, and a first negative contact 96b and a second negative contact 97b that are grounded. The switch circuit 95 also has a central movable contact 96 connected to the center electrode 81 via a current-carrying shaft 86, and an outer movable contact 97 connected to the outer electrode 85 via a current-carrying sleeve 92.

[0029] The switch circuit 95 can be switched between an external grounding state, in which the outer electrode 85 of the spark plug 80 is grounded, and a central grounding state, in which the central electrode 81 of the spark plug 80 is grounded. In the external grounding state of the switch circuit 95, the central movable contact 96 is connected to the first positive contact 96a, and the external movable contact 97 is connected to the second negative contact 97b. In the central grounding state of the switch circuit 95, the central movable contact 96 is connected to the first negative contact 96b, and the external movable contact 97 is connected to the second positive contact 97a. The switch circuit 95 can also be switched between the external grounding state and the central grounding state based on a control signal from the computer device 26.

[0030] Figures 8 and 9 are flowcharts showing the execution procedure of an electrode fabrication method according to another embodiment of this disclosure. The flowcharts shown in Figures 8 and 9 are connected to each other at the points indicated by reference numeral A. Each step of the electrode fabrication method shown in Figures 8 and 9 is executed by the processor 23 of the computer device 26.

[0031] As shown in Figure 4, the computer device 26 proceeds to step S20, reads the engine operating mode set by the operator, and proceeds to step S21, controlling the switch circuit 95 to an external ground state. As a result, the center electrode 81 of the spark plug 80 is connected to the secondary coil 33, and the outer electrode 85 of the spark plug 80 is grounded. Next, the computer device 26 proceeds to step S22, controls the electric motor 16 based on the engine operating mode, and also controls the throttle valve 63 and variable valve mechanisms 53, 54 based on the engine operating mode. Note that no fuel is injected from the injector 56 in step S22.

[0032] The computer device 26 proceeds to step S23, where it adjusts the flow control valve 20 based on the intake air flow rate to control the amount of metal powder P supplied to the intake air. The computer device 26 then proceeds to step S24, where it controls the voltage application unit 94 based on the crank angle and cam angle to perform ignition control of the spark plug 80 according to the engine operating mode. In other words, in step S24, an dielectric breakdown voltage is applied from the secondary coil 33 of the voltage application unit 94 to the center electrode 81, causing an arc discharge between the center electrode 81 and the outer electrode 85 of the spark plug 80. In this way, by causing an arc discharge while metal powder P is supplied to the combustion chamber 46, the metal powder P is sprayed onto the outer electrode 85 of the spark plug 80.

[0033] The computer device 26 proceeds to step S25 to determine whether a predetermined first set time has elapsed. If the computer device 26 determines in step S25 that the first set time has not elapsed, it returns to step S22 and continues the operation of the engine 40 according to the engine operation mode, and proceeds to steps S23 and S24 to continue the supply of metal powder and ignition control. On the other hand, if the computer device 26 determines in step S25 that the first set time has elapsed, it proceeds to step S26, as shown in Figure 9, and controls the switch circuit 95 to a center ground state. As a result, the center electrode 81 of the spark plug 80 is grounded, and the outer electrode 85 of the spark plug 80 is connected to the secondary coil 33. Subsequently, the computer device 26 proceeds to step S27 to control the electric motor 16 based on the engine operation mode, and also controls the throttle valve 63 and variable valve mechanisms 53 and 54 based on the engine operation mode. Note that no fuel is injected from the injector 56 in step S27.

[0034] The computer device 26 proceeds to step S28, where it adjusts the flow control valve 20 based on the intake air flow rate to control the amount of metal powder P supplied to the intake air. The computer device 26 then proceeds to step S29, where it controls the voltage application unit 94 based on the crank angle and cam angle to perform ignition control of the spark plug 80 according to the engine operating mode. In other words, in step S29, an dielectric breakdown voltage is applied from the secondary coil 33 of the voltage application unit 94 to the outer electrode 85, causing an arc discharge between the center electrode 81 and the outer electrode 85 of the spark plug 80. In this way, by causing an arc discharge while metal powder P is supplied to the combustion chamber 46, the metal powder P is sprayed onto the center electrode 81 of the spark plug 80.

[0035] The computer device 26 proceeds to step S30 and determines whether a predetermined second set time has elapsed. If the computer device 26 determines in step S30 that the second set time has not elapsed, it returns to step S27 and continues the operation of the engine 40 according to the engine operation mode, and proceeds to steps S28 and S29 to continue the supply of metal powder and ignition control. On the other hand, if the computer device 26 determines in step S30 that the second set time has elapsed, it proceeds to step S31 and stops the engine operation, stops the supply of metal powder, and stops the ignition control.

[0036] As described above, in step (voltage application step, first step) S24, with the engine 40 being motored by the electric motor 16 and metal powder P supplied to the combustion chamber 46 of the engine 40, an arc discharge is generated between the center electrode 81 and the outer electrode 85 of the spark plug 80. As shown in the enlarged portion of Figure 7, when an arc discharge is generated between the center electrode 81 and the outer electrode 85 with the metal powder P dispersed in the intake air, the intake air containing the metal powder P is ionized into plasma, and the positively charged metal powder P is sprayed onto the outer electrode 85, which is the negative electrode.

[0037] In other words, as shown by arrow Ts1 in the enlarged portion of Figure 7, the molten metal powder P moves along the arc discharge path α, and the metal powder P is sprayed onto the outer electrode 85. A metal layer 100 consisting of the sprayed metal powder P is then formed on the surface of the outer electrode 85. In order to suppress the influence of the initial shape of the outer electrode 85 on the arc discharge path α, it is desirable that the initial shape of the outer electrode 85 be a curved surface or a flat surface without edges.

[0038] Furthermore, in step (voltage application step, second step) S29, with the engine 40 being motored by the electric motor 16 and metal powder P supplied to the combustion chamber 46 of the engine 40, an arc discharge is generated between the center electrode 81 and the outer electrode 85 of the spark plug 80. As shown in the enlarged portion of Figure 7, when an arc discharge is generated between the center electrode 81 and the outer electrode 85 with the metal powder P dispersed in the intake air, the intake air containing the metal powder P is ionized into plasma, and the positively charged metal powder P is sprayed onto the center electrode 81, which is the negative electrode.

[0039] In other words, as shown by the arrow Ts2 in the enlarged portion of Figure 7, the molten metal powder P moves along the arc discharge path α, and the metal powder P is sprayed onto the central electrode 81. A metal layer 101 made of the sprayed metal powder P is then formed on the surface of the central electrode 81. In order to suppress the influence of the initial shape of the central electrode 81 on the arc discharge path α, it is desirable that the initial shape of the central electrode 81 be a curved surface or a flat surface without edges.

[0040] As explained above, the electrode fabrication method includes a first step S24 in which a discharge is generated between the central electrode 81 and the outer electrode 85 as a voltage application step, thereby spraying metal powder P onto the outer electrode 85, which is either the central electrode 81 or the outer electrode 85. The electrode fabrication method also includes a second step S29 in which the polarity of the central electrode 81 and the outer electrode 85 is switched to generate a discharge between the central electrode 81 and the outer electrode 85, thereby spraying metal powder P onto the other central electrode 81, which is either the central electrode 81 or the outer electrode 85. Thus, in the electrode fabrication method shown in Figures 8 and 9, metal powder P is sprayed onto the outer electrode 85 first, and then onto the central electrode 81. Here, Figure 10A shows the outer electrode 85 and the central electrode 81 during the execution of the electrode fabrication method, and Figure 10B shows the outer electrode 85 and the central electrode 81 after the execution of the electrode fabrication method.

[0041] As described above, since the metal powder P is sprayed onto the outer electrode 85 for a predetermined first set time, a laminate 102 extending along the arc discharge path α is formed on the outer electrode 85, as shown in Figure 10A. Since this laminate 102, made of metal layer 100, takes shape along the arc discharge path α, a shape of the outer electrode 85 suitable for the gas flow FL of the combustion chamber 46 can be obtained. In other words, since the arc discharge path α changes in response to the gas flow FL, by extending the laminate 102 from the outer electrode 85 in accordance with this arc discharge path α, an outer electrode 85 suitable for the gas flow FL of the combustion chamber 46 can be fabricated.

[0042] Furthermore, as mentioned above, since the metal powder P is sprayed onto the central electrode 81 for a predetermined second set time, a laminate 103 extending along the arc discharge path α is formed on the central electrode 81, as shown in Figure 10B. Since this laminate 103 made of metal layer 101 takes shape along the arc discharge path α, a shape of the central electrode 81 suitable for the gas flow FL of the combustion chamber 46 can be obtained. In other words, since the arc discharge path α changes under the influence of the gas flow FL, by extending the laminate 103 from the central electrode 81 in accordance with this arc discharge path α, a central electrode 81 suitable for the gas flow FL of the combustion chamber 46 can be fabricated.

[0043] Thus, the outer electrode 85 and the center electrode 81 fabricated by the electrode fabrication method of this disclosure can be used as templates when designing the electrode shape of the spark plug 80. Furthermore, the spark plug 80 equipped with the outer electrode 85 and the center electrode 81 fabricated by the electrode fabrication method of this disclosure can be attached to and used in an engine mounted in a vehicle or the like.

[0044] <Variation> This disclosure is not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the gist of the disclosure. In the above description, a metal powder P made of an iron alloy is used, but it is not limited thereto. For example, a metal powder made of a copper alloy may be used, a metal powder made of a nickel alloy may be used, a metal powder made of an iridium alloy may be used, or a metal powder made of a platinum alloy may be used. Also, in the above description, the particle size of the metal powder P is adjusted to several micrometers to several tens of micrometers, but it is not limited thereto. For example, the particle size of the metal powder P may be smaller than several micrometers, or larger than several tens of micrometers. Also, in the above description, air is taken into the combustion chamber 46, but it is not limited thereto, and an inert gas such as argon gas may be taken into the combustion chamber 46.

[0045] In the flowcharts shown in Figures 8 and 9, the outer electrode 85 is fabricated first, followed by the center electrode 81. However, the order is not limited to this. For example, the center electrode 81 may be fabricated first, followed by the outer electrode 85. Alternatively, the fabrication of the center electrode 81 and the outer electrode 85 may be repeated alternately. Furthermore, in the flowcharts shown in Figures 4, 8, and 9, the motoring of the engine 40 is started, the supply of metal powder P is started, and then the ignition control of the spark plug 80 is started. However, the order is not limited to this. For example, the supply of metal powder P may be started after the ignition control of the spark plug 80 is started. Alternatively, the motoring of the engine 40 may be started after the supply of metal powder P is started.

[0046] In the illustrated example, the powder supply unit 14 is connected to the intake pipe 62 located upstream of the throttle valve 63, but this is not the only option. For example, the powder supply unit 14 may be connected to the surge tank 65, or to the intake port 47. Furthermore, the illustrated intake system 60 and exhaust system 70 are just examples, and other intake and exhaust systems with different configurations may be used. The engine 40 may be a multi-cylinder engine or a single-cylinder engine. [Explanation of symbols]

[0047] 10…Electrode molding device, 14…Powder supply unit, 15…Voltage application unit, 16…Electric motor, 40…Engine, 41…Crankshaft (output shaft), 46…Combustion chamber, 80…Spark plug, 81…Center electrode, 85…Outer electrode, 90…Electrode molding device, 94…Voltage application unit, 95…Switch circuit, P…Metal powder, S13…Step (Voltage application step), S24…Step (Voltage application step, 1st step), S29…Step (Voltage application step, 2nd step)

Claims

1. The invention includes a step of applying a voltage to generate a discharge between the center electrode and the outer electrode of a spark plug, while an engine equipped with a spark plug is being motorized by an electric motor and metal powder is being supplied to the combustion chamber of the engine. In the voltage application step, a discharge is generated between the central electrode and the outer electrode of the spark plug, thereby causing the metal powder to be sprayed onto at least one of the central electrode and the outer electrode. Electrode shaping method.

2. In the electrode fabrication method according to claim 1, The voltage application step is, The first step involves generating a discharge between the central electrode and the outer electrode, thereby spraying the metal powder onto either the central electrode or the outer electrode. A second step involves switching the polarity of the central electrode and the outer electrode to generate a discharge between the central electrode and the outer electrode, thereby spraying the metal powder onto the other of the central electrode or the outer electrode. Includes, Electrode shaping method.

3. In the electrode fabrication method according to claim 1, The metal powder is supplied from the intake system of the engine to the combustion chamber. Electrode shaping method.

4. An electric motor connected to the engine's output shaft, A powder supply unit attached to the aforementioned engine, which contains metal powder, A voltage application unit connected to the spark plug of the engine, which generates a discharge between the center electrode and the outer electrode of the spark plug, It has, The voltage application unit is With the engine being motorized by the electric motor and the metal powder being supplied to the combustion chamber of the engine by the powder supply unit, a discharge is generated between the central electrode and the outer electrode, thereby causing the metal powder to be sprayed onto at least one of the central electrode and the outer electrode. Electrode shaping device.

5. In the electrode fabrication apparatus according to claim 4, The voltage application unit includes a switch circuit that switches the polarity between the central electrode and the outer electrode. Electrode shaping device.

Images