Ignition device for internal combustion engine and internal combustion engine

Abstract

To provide a technology that can perform proper ignition operation in an internal combustion engine using a fuel that is mixed with a plurality of types of gaseous fuel.SOLUTION: An ignition device for an internal combustion engine 1 includes: an ignition plug 43 disposed in a combustion chamber 21 of the internal combustion engine 1; an ignition circuit 40 for providing a high-discharge voltage to the ignition plug; and an ion current detection circuit 50 including a detection probe 51 disposed in the combustion chamber 21. The ignition circuit 40 adjusts a discharge condition on the basis of an ion current value in the combustion chamber 21 which is detected by the ion current detection circuit 50.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ignition device for an internal combustion engine. [Background technology]

[0002] In an internal combustion engine known as a four-stroke (or four-cycle) reciprocating engine, the exhaust stroke, intake stroke, compression stroke, and expansion stroke are repeated by opening and closing the exhaust and intake valves, introducing fuel, and igniting the engine in accordance with the reciprocating motion of the pistons.

[0003] A conventional internal combustion engine is described, for example, in Patent Document 1. Conventionally, gasoline, diesel, propane gas, alcohol, and the like have been used as fuel for internal combustion engines. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-82193 A Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, ammonia gas has been attracting attention as a carbon-free fuel. However, ammonia burns slower and is harder to ignite than conventional fuels such as gasoline, making it difficult to stably operate a reciprocating engine using ammonia alone. For this reason, ammonia is generally used as a mixed fuel with added fuel additives such as hydrogen.

[0006] When ammonia gas and hydrogen gas are mixed in a mixer and used as fuel, a complex mechanism is required to strictly control the mixture ratio. On the other hand, since the ease of ignition varies depending on the mixture ratio of ammonia gas and hydrogen gas, it is preferable to adjust the discharge timing and discharge voltage value of the spark plug according to the mixture ratio.

[0007] An object of the present invention is to provide a technique capable of performing an appropriate ignition operation in an internal combustion engine that uses a fuel that is a mixture of multiple types of gaseous fuel. [Means for solving the problem]

[0008] In order to solve the above problems, the first invention of the present application is an ignition device for an internal combustion engine that uses multiple types of gaseous fuel, the ignition device comprising: an ignition plug that is arranged in a combustion chamber of the internal combustion engine and performs ignition operations; an ignition circuit that supplies a high discharge voltage to the ignition plug; and an ion current detection circuit that detects an ion current flowing through a detection probe arranged in the combustion chamber, the ignition circuit adjusting discharge conditions based on the ion current value in the combustion chamber detected by the ion current detection circuit.

[0009] A second aspect of the present invention is the ignition device of the first aspect, wherein the ignition circuit adjusts the discharge condition based on a peak value of the ion current value.

[0010] A third aspect of the present invention is the ignition device of the first aspect, wherein the ignition circuit adjusts the supply timing of the discharge voltage based on a peak value of the ion current value.

[0011] A fourth aspect of the present invention is the ignition device of the first aspect, wherein the ignition circuit adjusts a voltage value of the discharge voltage based on a peak value of the ion current value.

[0012] A fifth aspect of the present invention is the ignition device of the second aspect, wherein the gaseous fuel contains hydrogen gas and ammonia gas, and the ignition circuit reduces the voltage value of the discharge voltage as the peak value of the ion current value increases.

[0013] A sixth aspect of the present invention is an ignition device according to the second aspect of the present invention, wherein the gaseous fuel includes hydrogen gas and ammonia gas, and the ignition circuit retards the supply timing of the discharge voltage as the peak value of the ion current value becomes larger.

[0014] The seventh invention of the present application is an internal combustion engine that uses multiple types of gaseous fuel as fuel, and has an ignition device of any one of the first to sixth inventions, a mixer that mixes the first gaseous fuel and the second gaseous fuel to produce a mixed fuel, and a fuel supply unit that supplies the mixed fuel into the combustion chamber, and the mixer adjusts the mixing ratio of the first gaseous fuel to the second gaseous fuel based on the ion current value detected by the ion current detection circuit. Effect of the Invention

[0015] According to the first to seventh aspects of the present application, appropriate discharge conditions can be determined from the peak value of the ion current, and appropriate ignition operation can be performed. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic view of a main part of an internal combustion engine according to a first embodiment. [Diagram 2] 1 is a circuit diagram of an ignition device for an internal combustion engine according to a first embodiment. [Diagram 3] 4 is a flowchart showing a flow of power supply control. [Figure 4] FIG. 4 is a schematic diagram of voltage values ​​corresponding to ion current values ​​for each gas fuel mix-combustion ratio. [Diagram 5] FIG. 4 is a schematic diagram of a map showing peak values ​​of voltage values ​​corresponding to ion current values ​​and a mixed-fuel ratio. [Figure 6] FIG. 2 is a schematic diagram of a three-dimensional map showing discharge conditions corresponding to the rotation speed, intake pressure, and fuel mix ratio. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings.

[0018] <1. Configuration of an ignition device for an internal combustion engine> The configuration of an internal combustion engine according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a schematic diagram of a main part of an internal combustion engine 1. Fig. 2 is a simplified circuit diagram of an ignition circuit 40, which is an ignition device for an internal combustion engine according to the first embodiment, and an ion current detection circuit 50.

[0019] The internal combustion engine 1 of this embodiment is a device mounted on the body of a vehicle such as an automobile, and generates driving force for the vehicle. The internal combustion engine 1 is, for example, a four-cylinder internal combustion engine. The internal combustion engine 1 has an ECU 10, four cylinders 20 each having a combustion chamber 21, a fuel supply unit 30, an ignition circuit 40, and an ion current detection circuit 50. Only a portion related to one combustion chamber 21 is shown in FIG. 1.

[0020] The ECU 10 is an electronic control unit (Engine Control Unit) that controls the operation of each part of the internal combustion engine 1. The ECU 10 is a computer that comprehensively controls the transmission of the vehicle body, the operation of the airbag, etc. The outputs of various sensors provided in the internal combustion engine 1 are input to the ECU 10. The ECU 10 controls the operation of the fuel supply unit 30, the ignition circuit 40, the ion current detection circuit 50, and each part of the internal combustion engine 1 based on these input signals.

[0021] Each combustion chamber 21 has a space for combusting fuel supplied from a fuel supply unit 30. When the fuel is burned and exploded in the combustion chamber 21, a piston (not shown) moves up and down, thereby generating a driving force.

[0022] The fuel supply unit 30 has a first gas fuel tank 31, a second gas fuel tank 32, a mixer 33, and four injectors .

[0023] The first gas fuel tank 31 is a storage unit that stores ammonia gas, which is the first gas fuel. The ammonia gas in the first gas fuel tank 31 is supplied to the mixer 33 via a first supply pipe 311.

[0024] The second gas fuel tank 32 is a storage unit that supplies hydrogen gas, which is the second gas fuel. The hydrogen gas in the second gas fuel tank 32 is supplied to the mixer 33 via a second supply pipe 321.

[0025] The mixer 33 has a mixing chamber 330, a first fuel valve 331, and a second fuel valve 332. The mixing chamber 330 has a space for mixing the ammonia gas supplied from the first gas fuel tank 31 and the hydrogen gas supplied from the second gas fuel tank 32. A downstream end of the first supply pipe 311 and a downstream end of the second supply pipe 321 are connected to the mixing chamber 330.

[0026] The first fuel valve 331 is a flow rate adjustment valve that is inserted at the downstream end of the first supply pipe 311. The first fuel valve 331 adjusts the flow rate of the ammonia gas supplied from the first gas fuel tank 31 to the mixing chamber 330.

[0027] The second fuel valve 332 is a flow rate adjustment valve that is interposed at the downstream end of the second supply pipe 321. The second fuel valve 332 adjusts the flow rate of the ammonia gas supplied from the second gas fuel tank 32 to the mixing chamber 330.

[0028] The mixed fuel obtained by mixing ammonia gas and hydrogen gas in the mixing chamber 330 is supplied to each of the four injectors 34 via mixed fuel supply pipes 333. An opening / closing valve 334 and a pump 335 for generating a gas flow from the mixing chamber 330 to the injectors 34 are inserted in the mixed fuel supply pipes 333.

[0029] The injector 34 supplies the mixed fuel to each cylinder. The internal combustion engine 1 is a so-called direct injection engine of the cylinder injection type, and injects the mixed fuel directly into the combustion chamber 21. For this reason, the injection port of the injector 34 is disposed in the combustion chamber 21. However, the present invention is not limited to this, and the internal combustion engine 1 may be a port injection type engine in which the injection port of the injector 34 is disposed in an intake port.

[0030] The ignition circuit 40 is a device that applies a high voltage to generate a spark discharge to an ignition plug 43 disposed in each cylinder 20 of the internal combustion engine 1. As shown in FIG.

[0031] The transformer 41 has a primary coil L1 and a secondary coil L2 that are electromagnetically coupled. The secondary coil L2 has a larger number of turns than the primary coil L1. The secondary coil L2 has a high voltage side terminal 411 and a low voltage side terminal 412 at both ends thereof.

[0032] The current control unit 42 controls the current flow to the primary coil L1. The current control unit 42 includes a battery 421 and an igniter 422.

[0033] The battery 421 is a power supply device (storage battery) capable of charging and discharging DC power. In this embodiment, the battery 421 is electrically connected to the primary coil L1 of the transformer 41 and the igniter 422. The battery 421 supplies a DC voltage to the primary coil L1 of the transformer 41 and the igniter 422.

[0034] The igniter 422 controls the energization of the primary coil L1. The igniter 422 is a switching element such as an IGBT (Insulated Gate Bipolar Transistor). The igniter 422 turns on / off in response to an ignition signal supplied from the ECU 10 to control the energization of the primary coil L1.

[0035] The spark plug 43 is disposed inside the combustion chamber 21 and is a device for realizing an ignition operation in the combustion chamber 21. The spark plug 43 is electrically connected between the high-voltage side terminal 411 of the secondary coil L2 of the transformer 41 and the ground. That is, one end of the spark plug 43 is connected to the high-voltage side terminal 411, and the other end of the spark plug 43 is grounded. When a high voltage is induced in the high-voltage side terminal 411 of the secondary coil L2, a discharge occurs in the gap of the spark plug 43, generating a spark. This ignites the fuel filled in the combustion chamber 21.

[0036] The ion current detection circuit 50 is a device for detecting an ion current flowing through a detection probe disposed in the combustion chamber 21. In this embodiment, the ignition plug 43 is used as the detection probe for detecting the ion current. However, the ion current detection circuit 50 may have a detection probe other than the ignition plug 43. The ion current detection circuit 50 has a capacitor 51, a Zener diode 52, a diode 53, an operational amplifier 54, a first resistor 55, and a second resistor 56.

[0037] A cathode of a Zener diode 52 is connected to a low-voltage side terminal 412 of the secondary coil L2. An anode of a diode 53 is connected to an anode of the Zener diode 52. A cathode of the diode 53 is grounded. A capacitor 51 is connected in parallel to the Zener diode 52. A bias voltage is generated by the capacitor 51.

[0038] The inverting input terminal of the operational amplifier 54 is connected to the connection point between the anode of the Zener diode 52 and the capacitor 51 via a first resistor 55. The non-inverting input terminal of the operational amplifier 54 is grounded. The inverting input terminal and the output terminal of the operational amplifier 54 are connected to each other via a second resistor 56. As a result, a potential with a voltage value Vi proportional to the current value of the ion current flowing through the gap of the spark plug 43 is generated from the output terminal of the operational amplifier 54. The output terminal of the operational amplifier 54 is connected to the ECU 10. That is, the voltage value Vi proportional to the current value of the ion current is input to the ECU 10 from the ion current detection circuit 50.

[0039] As described above, in this embodiment, the ECU 10, the ignition circuit 40, and the ion current detection circuit 50 configure an ignition device for the internal combustion engine 1.

[0040] <2. Current control using ion current measurements> Next, the energization control in the igniter 422 using the voltage value Vi detected in the ion current detection circuit 50 will be described.

[0041] When using a mixed fuel of ammonia gas and hydrogen gas as in this embodiment, it is preferable to appropriately adjust the discharge timing and discharge energy for discharging the spark plug 43 according to the mixture ratio of the fuel. For example, when the ratio of ammonia gas increases, the ignitability of the mixed fuel decreases, so it is preferable to advance the discharge timing and increase the discharge energy. On the other hand, when the ratio of hydrogen gas increases, the ignitability of the mixed fuel increases, so it is preferable to retard the discharge timing and decrease the discharge energy.

[0042] On the other hand, in the mixer 33, although the flow rate of ammonia gas supplied from the first gas fuel tank 31 and the flow rate of hydrogen gas supplied from the second gas fuel tank 32 can be adjusted to some extent by the first fuel valve 331 and the second fuel valve 332, it is difficult to strictly adjust the mixing ratio.

[0043] Therefore, the ECU 10 estimates the mixture ratio of ammonia gas and hydrogen gas in the mixed fuel using the voltage value Vi detected by the ion current detection circuit 50, and adjusts the discharge voltage value and discharge timing of the ignition plug 43 based on the estimated mixture ratio.

[0044] As shown in FIG. 3, the ECU 10 first estimates the mixture ratio of the mixed fuel from the opening degree of the first fuel valve 331 and the opening degree of the second fuel valve 332, and determines the discharge conditions (discharge timing and discharge energy) based on the estimated mixture ratio (step S1).

[0045] After that, the ECU 10 controls the fuel supply unit 30 to inject the mixed fuel from the injector 34 into the combustion chamber 21 (step S2).

[0046] Meanwhile, the ECU 10 turns on / off the igniter 422 of the ignition circuit 40 to store electric energy by energizing and to induce a high voltage by cutting off the energization, thereby causing discharge in the spark plug 43 (step S3). This ignites and burns the mixed fuel in the combustion chamber 21.

[0047] Specifically, in step S3, the ECU 10 turns on the igniter 422 before the discharge timing to start energizing the primary coil L1. This forms a magnetic flux in the transformer 41. After that, when the ECU 10 turns off the igniter 422 to cut off the power supply to the primary coil L1, a high voltage is generated across the secondary coil L2 by electromagnetic induction. This applies a high voltage to the spark plug 43, and a discharge occurs in the gap of the spark plug 43. This timing at which the discharge starts is called the discharge timing.

[0048] Among the discharge conditions, the discharge energy can be adjusted by the time for which the primary coil L1 is energized and the voltage value supplied to the primary coil L1. Therefore, the ECU 10 energizes the primary coil L1 for a time that corresponds to the set discharge energy. Furthermore, when the voltage supplied from the battery 421 to the primary coil L1 is variable, the ECU 10 energizes the primary coil L1 at a voltage value that corresponds to the set discharge energy. Furthermore, among the discharge conditions, the discharge timing is determined by the timing for cutting off the power supply to the primary coil L1. Therefore, the ECU 10 determines the power cut-off time that corresponds to the set discharge timing and the power start time going back from that time.

[0049] In this way, the energization of the primary coil L1 starts before the discharge is performed. Therefore, the energization of the primary coil L1 for the discharge in step S3 may start before the injection of the mixed fuel in step S2.

[0050] After the discharge, the ECU 10 acquires a peak value of the voltage value Vi based on the voltage value Vi input from the ion current detection circuit 50 (step S4). Then, the ECU 10 calculates the mixture ratio of ammonia gas and hydrogen gas in the mixed fuel based on the acquired peak value (step S5). Note that, hereinafter, the ratio of ammonia gas in the mixed fuel is referred to as the "mixed combustion ratio."

[0051] Here, the relationship between the peak value of the voltage value Vi and the mixture ratio of ammonia gas and hydrogen gas in the mixed fuel will be described with reference to Fig. 4. Fig. 4 is a schematic diagram of the voltage value Vi corresponding to the ion current value for each type of gaseous fuel. Fig. 4 shows the change over time of the voltage value Vi for three types of gaseous fuel: mixed gas fuel G1 with 50% ammonia gas and 50% hydrogen gas (mixture ratio 50%), mixed gas fuel G2 with 25% ammonia gas and 75% hydrogen gas (mixture ratio 25%), and gaseous fuel G3 with 100% hydrogen gas (mixture ratio 0%).

[0052] As shown in FIG. 4, as the co-combustion ratio (ammonia gas mixture ratio) decreases from 50%, to 25%, to 0%, the peak value of the voltage value Vi increases in that order. That is, in a mixed fuel of ammonia gas and hydrogen gas, as the ratio of hydrogen gas increases, the voltage value Vi corresponding to the ion current increases. By utilizing this relationship, the mixture ratio of ammonia gas and hydrogen gas in the mixed fuel can be estimated from the peak value of the voltage value Vi. Note that in FIG. 4, the discharge timing is different for each of the co-combustion ratios of 50%, 25%, and 0%, so the timing of the peak of the voltage value Vi is different.

[0053] Using this relationship, in step S5, the ECU 10 uses a map M1 as shown in Fig. 5 to calculate the fuel-mix ratio based on the peak value of the voltage value Vi input from the ion current detection circuit 50. Fig. 5 is a schematic diagram of the map M1 showing the peak value of the voltage value Vi and the fuel-mix ratio.

[0054] When fuel containing hydrocarbons such as gasoline is used, a very large and unstable ion current is generated compared to when fuels not containing hydrocarbons such as ammonia gas or hydrogen gas are used. In addition, when fuel containing hydrocarbons such as gasoline is used, two peaks are generated: an ion current peak due to chemical ions generated in the reaction process of hydrocarbons, and an ion current peak due to thermal ions generated in the subsequent reaction process of nitrogen. In contrast, when fuel not containing hydrocarbons such as ammonia gas or hydrogen gas is used, one relatively small and stable ion current peak can be detected. Therefore, the waveform of the ion current (voltage value Vi) for each combustion ratio as shown in Figure 4 is stable and highly reproducible. Therefore, the combustion ratio estimated from the voltage value Vi is highly reliable.

[0055] Following step S5, the ECU 10 determines the discharge conditions (discharge timing and discharge energy) using a three-dimensional map M2 as shown in Fig. 6 (step S6). Fig. 6 is a diagram showing an example of the three-dimensional map M2. In the three-dimensional map M2, the discharge conditions are determined in advance for each of three conditions, namely, the rotation speed of the internal combustion engine 1, the intake pressure, and the fuel-mix ratio. This allows the ECU 10 to determine the optimal discharge conditions in step S6 according to the rotation speed, the intake pressure, and the fuel-mix ratio.

[0056] The discharge conditions defined in the three-dimensional map M2 are such that, when the rotation speed and intake pressure are the same, the higher the fuel-mix ratio (mixture ratio of ammonia gas), the more the discharge timing is advanced and the discharge energy is increased. That is, the smaller the peak value of the ion current value (voltage value Vi), the more the supply timing of the discharge voltage is advanced and the voltage value of the discharge voltage is increased. As a result, as the proportion of ammonia gas increases and the ignition ability decreases, the discharge timing is advanced and the voltage value of the discharge voltage is increased to make ignition easier.

[0057] In other words, the discharge conditions defined in the three-dimensional map M2, when the rotation speed and intake pressure are the same, the smaller the fuel-mix ratio (mixture ratio of ammonia gas), the more the discharge timing is retarded and the discharge energy is reduced. That is, the larger the peak value of the ion current value (voltage value Vi), the more the supply timing of the discharge voltage is retarded and the voltage value of the discharge voltage is reduced. As a result, as the proportion of hydrogen gas increases and the ignition ability improves, the discharge timing is retarded and the voltage value of the discharge voltage is reduced within the range necessary for ignition at a crank angle closer to the top dead center to perform ignition.

[0058] Then, the ECU 10 determines whether the new discharge conditions determined in step S6 match the current discharge conditions (step S7). If it is determined that the new discharge conditions match the current discharge conditions (step S7: Yes), the ECU 10 returns to step S2 and performs fuel injection and discharge.

[0059] On the other hand, if it is determined that the new discharge condition does not match the current discharge condition (step S7: Yes), the ECU 10 updates the discharge condition to the new discharge condition (step S8). After that, the ECU 10 returns to step S2 and performs fuel injection and discharge.

[0060] In this way, the fuel mixture ratio (mixture ratio of ammonia gas and hydrogen gas) can be estimated by detecting the voltage value Vi corresponding to the ion current. Then, by determining appropriate discharge conditions (discharge timing and discharge energy) using the estimated mixture ratio, appropriate ignition operation can be performed even when a fuel containing a mixture of multiple types of gaseous fuels is used.

[0061] <3. Modifications> Although the exemplary embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0062] In the above embodiment, the mixed fuel is a mixture of ammonia gas and hydrogen gas. However, the mixed fuel is not limited to this. For example, the mixed fuel may contain oxygen gas as a combustion improver in addition to ammonia gas and hydrogen gas.

[0063] In the above embodiment, the supply sources of the first gaseous fuel and the second gaseous fuel are both tanks (gas cylinders). However, the supply sources of the first gaseous fuel and the second gaseous fuel are not necessarily limited to such gaseous fuel storage units. The supply source of the gaseous fuel may be, for example, a device that generates the gaseous fuel. Specifically, the supply source of the gaseous fuel may be, for example, a device that vaporizes ammonia from ammonia water to generate ammonia gas, or a device that electrolyzes water to generate hydrogen gas and oxygen gas. When using such a device, it is difficult to strictly control the amount of gaseous fuel generated. For this reason, the technology of the present application for estimating the mixture ratio of multiple gaseous fuels is particularly useful.

[0064] The internal combustion engine ignition device of the present invention may be installed not only in vehicles such as automobiles, but also in various devices such as generators and industrial machinery, and may be used to generate an electric spark in the spark plug of an internal combustion engine to ignite fuel.

[0065] The detailed shape and structure of the above-mentioned internal combustion engine ignition device may be appropriately modified without departing from the spirit and scope of the present invention. Furthermore, the elements appearing in the above-mentioned embodiment and modified examples may be appropriately combined without causing any contradiction. [Explanation of symbols]

[0066] 1. Internal combustion engine 10 ECU 20 cylinders 21 Combustion chamber 30 Fuel supply section 31 No. 1 gas fuel tank 32 No. 2 gas fuel tank 33 Mixer 34 Injector 40 Ignition circuit 43 Spark plug 50 Ion current detection circuit M1 Map M2 3D Map Vi voltage value

Claims

1. An ignition device for an internal combustion engine fueled by multiple types of gaseous fuel, a spark plug disposed in a combustion chamber of the internal combustion engine and performing an ignition operation; an ignition circuit that supplies a high discharge voltage to the spark plug; an ion current detection circuit for detecting an ion current flowing through a detection probe disposed in the combustion chamber; and The ignition circuit adjusts discharge conditions based on the ion current value in the combustion chamber detected by the ion current detection circuit.

2. 10. The ignition device according to claim 1, The ignition circuit adjusts discharge conditions based on the peak value of the ion current value.

3. 10. The ignition device according to claim 1, The ignition circuit adjusts discharge timing based on the peak value of the ion current value.

4. 10. The ignition device according to claim 1, The ignition circuit adjusts discharge energy based on the peak value of the ion current value.

5. 3. The ignition device according to claim 2, the gaseous fuel includes hydrogen gas and ammonia gas; The ignition device, wherein the ignition circuit reduces discharge energy as the peak value of the ion current increases.

6. 3. The ignition device according to claim 2, the gaseous fuel includes hydrogen gas and ammonia gas; The ignition circuit delays the discharge timing as the peak value of the ion current increases.

7. An internal combustion engine fueled by multiple types of gaseous fuel, The ignition device according to any one of claims 1 to 6, a mixer that mixes the first gaseous fuel and the second gaseous fuel to form a mixed fuel; a fuel supply unit that supplies the mixed fuel into the combustion chamber; and The mixer adjusts a mixing ratio of the first gaseous fuel and the second gaseous fuel based on the ion current value detected by the ion current detection circuit.

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