Ignition device

Abstract

To solve a problem that a circuit for detecting secondary voltage of an ignition coil requires high voltage resistance and high safety and circuit cost is increased as a result.SOLUTION: An ignition device includes: a switch section 3 configured to conduct and shut off a primary current flowing from a primary coil 21 of an ignition coil 2 comprising the primary coil 21 and a secondary coil 22 connected to an ignition plug 7 in a cylinder to a ground side on the basis of an ignition signal input from a control device 70; and primary side detection sections 10, 11 (8, 12, 13) for detecting a value related to the primary voltage in time sequence of the ignition coil 2. The primary side detection sections 10, 11 (8, 12, 13) output a value related to the primary voltage to the control device 70 in order to estimate cylinder internal pressure on the basis of relation between a value related to the primary voltage of the ignition coil 2 and the cylinder internal pressure in the control device 70.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an ignition device that ignites an air-fuel mixture in a combustion chamber of an internal combustion engine. [Background technology]

[0002] In recent years, regulations on fuel consumption (fuel economy) and harmful components in exhaust gases for automobiles and other vehicles have been strengthened, and these regulations are likely to become even stronger in the future. In particular, regulations on fuel economy are an issue of great concern due to issues such as rising fuel prices, the impact on global warming, and the depletion of energy resources.

[0003] Under such circumstances, a technology is known in which a control device estimates the combustion state based on the engine's in-cylinder pressure (the pressure of the mixture in the combustion chamber) and controls the engine. The control device generates an ignition signal according to the current combustion state and appropriately controls the ignition timing, the gas composition in the combustion chamber, and other factors, thereby improving the engine's thermal efficiency. A combustion pressure sensor using a piezoelectric element is typically used to detect the in-cylinder pressure. However, this method has issues such as increased costs and the need for space for installing the sensor. Therefore, a technology is known that estimates the in-cylinder pressure from the voltage value of the ignition coil. By using an existing ignition coil as a combustion pressure sensor, the installation of a dedicated combustion pressure sensor is unnecessary, which is considered to be effective in addressing the above issues. An example of such an in-cylinder pressure estimation technology is disclosed in, for example, Patent Document 1.

[0004] Patent document 1 describes that the combustion pressure is estimated based on the maximum voltage value when the spark plug is controlled, detected by a voltage detection circuit that detects the voltage between the secondary coil and the spark plug (hereinafter also referred to as "coil secondary voltage"). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-200280 Summary of the Invention [Problem to be solved by the invention]

[0006] In order for a spark plug to produce a spark discharge, a potential difference greater than the breakdown voltage of the high-pressure in-cylinder gas must be generated across the spark plug's discharge gap. As a result, the coil secondary voltage can reach a high voltage of over 10,000 volts. Therefore, the circuit that detects the coil secondary voltage must have high voltage resistance and high safety, which creates the issue of high circuit costs.

[0007] In view of the above circumstances, there has been a demand for a method that enables estimation of the in-cylinder pressure of an internal combustion engine at low cost based on the voltage or current of the ignition coil. [Means for solving the problem]

[0008] In order to solve the above problem, an ignition device in a first aspect of the present invention includes a switch unit configured to conduct and cut off a primary current flowing from the primary coil of an ignition coil composed of a primary coil and a secondary coil connected to an ignition plug in a cylinder to the ground side based on an ignition signal input from a control device, and a primary side detection unit that detects a value related to the time-series primary voltage of the ignition coil, and the primary side detection unit outputs the value related to the primary voltage to the control device so that the control device can estimate the in-cylinder pressure based on the correlation between the value related to the primary voltage of the ignition coil and the pressure in the cylinder. The primary side detection unit may be configured to detect extreme values of values related to the time series primary voltage of the ignition coil and output the extreme values of values related to the primary voltage to the control device.

[0009] In a second aspect of the present invention, the ignition device includes, as the primary side detection unit, a primary current detection unit that detects a primary current of the ignition coil, and a minimum value detection unit that detects a minimum value of the primary current of the ignition coil detected by the primary current detection unit. The minimum value detection unit outputs the first minimum value of the primary current to the control device so that the control device can estimate the in-cylinder pressure based on a correlation between a first minimum value, which is the first minimum value of the primary current of the ignition coil after the start of ignition, and the pressure in the cylinder.

[0010] In addition, an ignition device according to a third aspect of the present invention includes, as the primary side detection unit, a primary voltage detection unit that detects a primary voltage of the ignition coil, a primary current detection unit that detects a primary current of the ignition coil, and a primary power detection unit that detects a primary power of the ignition coil from a first maximum value of the primary voltage detected by the primary voltage detection unit after the start of ignition and a first minimum value of the primary current detected by the primary current detection unit after the start of ignition. The primary power detection unit outputs the value of the primary power to the control device so that the control device can estimate the in-cylinder pressure based on the correlation between the value of the primary power of the ignition coil and the pressure in the cylinder.

[0011] In addition, an ignition device according to a fourth aspect of the present invention includes, as the primary-side detection unit, a primary voltage detection unit that detects a primary voltage of the ignition coil, and a primary voltage averaging processing unit that calculates an average value of the primary voltage of the ignition coil detected by the primary voltage detection unit over a predetermined period during discharge. The primary voltage averaging processing unit outputs the average value of the primary voltage to the control device so that the control device can estimate the in-cylinder pressure based on the correlation between the average value of the primary voltage of the ignition coil and the pressure in the cylinder.

[0012] In addition, an ignition device according to a fifth aspect of the present invention includes a switch unit configured to conduct and cut off a primary current flowing from the primary coil of an ignition coil, which is composed of a primary coil and a secondary coil connected to an ignition plug in a cylinder, to a ground side based on an ignition signal input from a control device, a secondary current detection unit that detects the secondary current of the ignition coil, and a secondary current averaging processor that calculates an average value of the secondary current of the ignition coil detected by the secondary current detection unit over a predetermined period during discharge. The secondary current averaging processor outputs the average value of the secondary current to the control device so that the control device can estimate the in-cylinder pressure based on the correlation between the average value of the secondary current of the ignition coil and the pressure in the cylinder. [Effects of the Invention]

[0013] According to at least one aspect of the present invention, it is possible to estimate the in-cylinder pressure of an internal combustion engine based on the voltage or current of the ignition coil, without relying on the secondary voltage of the ignition coil, which is a high voltage. This makes it possible to detect the combustion state in the cylinder using an ignition device with low circuit cost. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is an explanatory diagram showing a schematic configuration of an internal combustion engine system equipped with an ignition device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram illustrating an example of a hardware configuration of an ECU. [Figure 3] 1 is a schematic circuit diagram showing an example of the configuration of an ignition device according to a first embodiment of the present invention. [Figure 4] FIG. 3 is a waveform diagram showing an example of the operation of the ignition device according to the first embodiment of the present invention. [Figure 5] FIG. 4 is a characteristic diagram showing the correlation between the first maximum value of the primary voltage of the ignition coil and the in-cylinder pressure. [Figure 6] FIG. 6 is an explanatory diagram showing a schematic configuration of an internal combustion engine system equipped with an ignition device according to a second embodiment of the present invention. [Figure 7]FIG. 5 is a schematic circuit diagram showing an example of the configuration of an ignition device according to a second embodiment of the present invention. [Figure 8] FIG. 4 is a characteristic diagram showing the correlation between the first minimum value of the primary current of the ignition coil and the in-cylinder pressure. [Figure 9] FIG. 10 is an explanatory diagram showing a schematic configuration of an internal combustion engine system equipped with an ignition device according to a third embodiment of the present invention. [Figure 10] FIG. 10 is a schematic circuit diagram showing an example of the configuration of an ignition device according to a third embodiment of the present invention. [Figure 11] FIG. 4 is a characteristic diagram showing the correlation between the primary power of the ignition coil and the pressure inside the cylinder. [Figure 12] 10 is a graph showing an example of measurement results of correlation coefficients between the first maximum value of the primary voltage, the first minimum value of the primary current, and the primary power value of the ignition coil and the in-cylinder pressure at the ignition start time. [Figure 13] FIG. 10 is an explanatory diagram showing a schematic configuration of an internal combustion engine system equipped with an ignition device according to a fourth embodiment of the present invention. [Figure 14] FIG. 10 is a schematic circuit diagram showing an example of the configuration of an ignition device according to a fourth embodiment of the present invention. [Figure 15] FIG. 10 is a waveform diagram showing an example of the operation of the ignition device according to the fourth embodiment of the present invention. [Figure 16] FIG. 4 is a characteristic diagram showing the correlation between the average value of the primary voltage of the ignition coil and the in-cylinder pressure. [Figure 17] FIG. 10 is an explanatory diagram showing a schematic configuration of an internal combustion engine system equipped with an ignition device according to a fifth embodiment of the present invention. [Figure 18] FIG. 10 is a schematic circuit diagram showing an example of the configuration of an ignition device according to a fifth embodiment of the present invention. [Figure 19] FIG. 10 is a waveform diagram showing an example of the operation of the ignition device according to the fifth embodiment of the present invention. [Figure 20] FIG. 4 is a characteristic diagram showing the correlation between the average value of the secondary current of the ignition coil and the in-cylinder pressure. [Figure 21] FIG. 2 is a schematic circuit diagram showing a configuration example of a switch section in the first to fifth embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, examples of embodiments of the present invention will be described with reference to the accompanying drawings. In this specification and the accompanying drawings, components having substantially the same functions or configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0016] First Embodiment First, a first embodiment of the present invention will be described. This embodiment is configured to estimate the in-cylinder pressure based on the maximum value of the primary voltage of the ignition coil 2 in a predetermined section.

[0017] [Schematic configuration of internal combustion engine system] Fig. 1 shows a schematic configuration of an internal combustion engine system equipped with an ignition device according to a first embodiment of the present invention. The internal combustion engine system shown in the figure is composed of a spark-ignition engine 60, an ignition device 50, and an electronic control unit (ECU) 70. The spark-ignition engine 60 is, for example, a multi-cylinder reciprocating gasoline engine. A multi-cylinder reciprocating gasoline engine ignites a compressed air-fuel mixture using a spark plug provided in each combustion chamber (cylinder), and generates power through the explosion that accompanies the combustion.

[0018] The ignition device 50 supplies electrical energy required for ignition (hereinafter referred to as "ignition energy") to the spark plug 7 at a predetermined timing based on an ignition signal output from the ECU 70. The ignition device 50 also detects a first maximum value V1max of a primary voltage V1 (see FIG. 4) of the ignition coil 2 shown in FIG. 3, which will be described later, and sends the voltage value to the ECU 70.

[0019] The ECU 70 estimates the in-cylinder pressure of the engine 60 based on the first maximum value V1max of the primary voltage V1 of the ignition coil 2, and controls the engine 60 based on the estimated in-cylinder pressure. That is, the ECU 70 includes an estimation unit 71 that estimates the state of the engine 60, such as the in-cylinder pressure, and a control unit 72 that determines the operation amount of the engine 60 based on the estimated state of the engine 60 to control the engine 60, and to which the control amount of the engine 60 is fed back.

[0020] For example, in the ECU 70, the estimation unit 71 estimates the in-cylinder pressure based on the first maximum value V1max of the primary voltage V1 of the ignition coil 2, and further estimates the combustion center position (MFB50) from the cylinder pressure. Then, the control unit 72 controls the ignition timing of the spark plug 7 so that the combustion center position provides the maximum thermal efficiency.

[0021] In the ECU 70, for example, an estimation unit 71 estimates the in-cylinder pressure and further estimates the magnitude of cycle fluctuations in combustion torque from the in-cylinder pressure. Then, a control unit 72 controls the ignition timing, the amount of ignition energy, the amount of exhaust gas recirculation (EGR), the air-fuel ratio, etc. so that the magnitude of cycle fluctuations in combustion torque is equal to or less than a predetermined value.

[0022] In the ECU 70, for example, an estimation unit 71 estimates the in-cylinder pressure and further estimates the presence or absence of misfire or the misfire rate from the in-cylinder pressure. Then, a control unit 72 controls the ignition timing, the amount of ignition energy, the amount of exhaust gas recirculation (EGR), the air-fuel ratio, etc. depending on the presence or absence of misfire or the misfire rate.

[0023] In the ECU 70, for example, an estimation unit 71 estimates the in-cylinder pressure and further estimates the presence or absence of knocking or pre-ignition (hereinafter abbreviated as "plague") from the in-cylinder pressure. Then, a control unit 72 controls the ignition timing depending on the presence or absence of knocking or pre-ignition.

[0024] [ECU hardware configuration] FIG. 2 is a block diagram showing an example of the hardware configuration of the ECU 70. The ECU 70 includes an input circuit 191, an A / D conversion unit 192, a CPU (Central Processing Unit) 193, which is a central processing unit, a ROM (Read Only Memory) 194, a RAM (Random Access Memory) 195, and an output circuit 196. The ECU 70 also includes a communication circuit 199. The ECU 70 is configured by, for example, a microcontroller (MCU: Micro-Control Unit).

[0025] The CPU 193 loads a program stored in a ROM 194 (an example of a storage unit) into a RAM 195 and executes the program, thereby realizing the functions of the estimation unit 71 and the control unit 72 of the ECU 70. The ECU 70 is an example of a control device.

[0026] The input circuit 191 receives signals output from sensors 200 as input signals 190. The sensors 200 include, for example, a throttle sensor, a water temperature sensor, a crank angle sensor, an intake cam angle sensor, an exhaust cam angle sensor, and the like (not shown). The sensors 200 also include the various detection units of the ignition device 50 shown in FIG. 3. When the input signal 190 is an analog signal (for example, a signal from a water temperature sensor, a throttle sensor, etc.), the input circuit 191 removes noise components from the input signal 190 and outputs the noise-removed signal to an A / D conversion unit 192.

[0027] The A / D conversion unit 192 converts the analog signal into a digital signal and outputs it to the CPU 193. The CPU 193 takes in the digital signal output from the A / D conversion unit 192 and executes a control logic (program) stored in a storage medium such as a ROM 194, thereby performing a wide variety of calculations, diagnoses, controls, and the like.

[0028] The calculation results of the CPU 193 and the conversion results of the A / D conversion unit 192 are temporarily stored in the RAM 195. The ROM 194 may be a non-volatile memory such as an EEPROM (Electrically Erasable and Programmable Read Only Memory) whose contents can be rewritten. For example, a program in which an algorithm for realizing control of the ignition device 50 according to the first embodiment of the present invention is written is stored in the ROM 194 or an auxiliary storage device (not shown).

[0029] The calculation result of CPU 193 is output as control signal 197 from output circuit 196 and is used to control controlled object 210, which is made up of an actuator for driving engine 60 and the like. Controlled object 210 is, for example, an intake valve driving device, an exhaust valve driving device, a fuel injection valve, an ignition device 50 (spark plug 7), etc. (not shown). Controlled object 210 also includes ignition device 50 (spark plug 7).

[0030] When the input signal 190 is a digital signal, the input signal 190 is sent directly from the input circuit 191 to the CPU 193 via a signal line 198, and the CPU 193 executes the necessary calculations and controls.

[0031] The communication circuit 199 is a communication interface configured to be able to send and receive data to and from a communication device (not shown) outside the ECU 70 or other ECUs.

[0032] [Ignition device configuration] Next, the configuration of the ignition device 50 according to the first embodiment will be described. 3 is a schematic circuit diagram showing an example configuration of an ignition device 50. The illustrated ignition device 50 includes a power source 1, an ignition coil 2 composed of a primary coil 21 and a secondary coil 22, a switch unit 3, a primary voltage detection unit 8, and a maximum value detection unit 9. The number of turns of the secondary coil 22 is, for example, about 100 times the number of turns of the primary coil 21. The ignition coil 2 is configured to have a voltage boosting effect from the primary side to the secondary side.

[0033] The illustrated ignition device 50 is configured such that one end of the spark plug 7 is connected to one end of the secondary coil 22, and the anode of the high-voltage diode 6 is connected to the other end of the secondary coil 22. The other end of the spark plug 7 and the cathode of the high-voltage diode 6 are connected to a ground conductor.

[0034] The power source 1 is, for example, a battery mounted on a vehicle, and supplies a DC voltage. The power source 1 has a high-potential electrode connected to one end of the primary coil 21.

[0035] The other end of the primary coil 21 is connected to one end of the open / close contact of a switch unit 3, which is made up of a semiconductor switch such as an IGBT (Insulated Gate Bipolar Transistor), and to an input end of a primary voltage detection unit 8. The other end of the switch unit 3 and the other end of the primary voltage detection unit 8 are connected to a ground conductor. A signal output end of the primary voltage detection unit 8 is connected to an input end of a maximum value detection unit 9. An ignition signal sent from the ECU 70 is input to the other input end of the maximum value detection unit 9.

[0036] The switch unit 3 is configured to conduct or cut off the primary current flowing from the primary coil 21 to the grounding conductor based on an ignition signal sent from the ECU 70. The circuit configuration of the switch unit 3 is shown in Figure 21. The switch unit 3 includes an IGBT that functions as a switching element, a clamp diode D that protects the IGBT from overvoltage, and a GC ,D GE , and resistor R G ,R GE Clamp diode D GC is connected between the gate and collector of the IGBT, and the clamp diode D GE is connected between the gate and emitter of the IGBT. Also, the resistor R G is connected to the gate of the IGBT, and the resistor R GE is connected between the gate and emitter of the IGBT.

[0037] The circuit configuration of the switch unit 3 is an example and is not limited to this example. The semiconductor switch is not limited to an IGBT, and may be configured using other semiconductor switches such as a MOSFET or a transistor.

[0038] Returning to the description of the ignition device 50 in Fig. 3, the primary voltage detection unit 8 detects the potential difference between one end of the primary coil 21 and the grounding conductor as the primary voltage V1 of the ignition coil 2, and outputs the detection results (primary voltage values) to the maximum value detection unit 9 in chronological order.

[0039] The maximum value detection unit 9 detects a first maximum value V1max within a predetermined section of the primary voltage V1 of the ignition coil 2 detected in time series by the primary voltage detection unit 8, and outputs the detection result (first maximum value V1max) to the ECU 70 disposed outside the ignition device 50. The maximum value detection unit 9 is configured by devices such as a microcontroller (hereinafter abbreviated as "microcomputer") and a memory.

[0040] [Ignition device operation] Next, the operation of the ignition device 50 according to the first embodiment will be described. 4 is a waveform diagram showing an example of the operation of the ignition device 50. This diagram is a timing chart showing the ignition operation within one combustion stroke in a single cylinder. In the diagram, the top line shows the ignition signal input from the ECU 70, the line below that shows the primary current I1 flowing through the primary coil 21, the line below that shows the primary voltage V1 of the primary coil 21 detected by the primary voltage detection unit 8, the line below that shows the secondary current I2 output and discharged from the secondary coil 22, and the line below that shows the secondary voltage V2 applied across the discharge gap of the spark plug 7 over time.

[0041] When the ignition signal input from the ECU 70 transitions from low level to high level, the switch unit 3 closes the open / close contacts to pass a primary current I1 through the primary coil 21. While the switch unit 3 is closed, the primary current I1 flowing through the primary coil 21 increases over time.

[0042] Thereafter, when the ignition signal transitions from high level to low level, the switch unit 3 changes the on-off contact to an open state, cutting off the primary current I1. When the primary current I1 is cut off, a high voltage is induced in the secondary coil 22. This causes a high voltage to be applied from the secondary coil 22 to the spark plug 7, generating a discharge spark in the spark plug 7 and causing a secondary current I2 to flow through the secondary coil 22. As the spark plug 7 releases discharge energy, the absolute value of the secondary current I2 decreases and eventually reaches zero, ending the discharge. In other words, the period from when the secondary current I2 falls until it reaches zero is the discharge period T of the ignition coil 2.

[0043] The absolute value of secondary voltage V2 increases to near the breakdown voltage in the discharge gap of spark plug 7 immediately before the discharge, and then rapidly decreases as the discharge starts. Therefore, secondary voltage V2 appears at a first minimum value near the start of the discharge. After that, the length of the discharge path (arc) increases due to the gas flow in the discharge gap of spark plug 7, so the absolute value of secondary voltage V2 increases again and appears at a second minimum value near the end of discharge period T. The first and second minimum values of secondary voltage V2 are generally high voltages of around -10,000V.

[0044] Furthermore, a change in the current in the secondary coil 22 generates a back electromotive force in the primary coil 21. This back electromotive force causes a first maximum value (V1max) and a second maximum value to appear in the primary voltage V1 in synchronization with the occurrence of the first minimum value and the second minimum value of the secondary voltage V2. Because the ignition coil 2 performs a voltage step-down operation from the secondary coil 22 to the primary coil 21, the first maximum value V1max and the second maximum value of the primary voltage V1 are lower voltage values (several hundred volts) than the first maximum value and the second maximum value of the secondary voltage V2.

[0045] In addition, the clamp diode D of the switch section 3 is turned on by the counter electromotive force generated in the primary coil 21. GC ,D GE , and resistor R G ,R GE A current flows through the primary coil 21. Then, in synchronization with the occurrence of the first and second minimum values of the secondary voltage V2, a first minimum value (I1min) and a second minimum value appear in the primary current I1, respectively.

[0046] The maximum value detection unit 9 detects a first maximum value V1max of the primary voltage V1. Specifically, the maximum value detection unit 9 reads values of the primary voltage V1 from time t0 when the ignition signal transitions from high level to low level (hereinafter referred to as the "ignition start time") until an inspection time Δt has elapsed, and determines the maximum voltage value as the first maximum value V1max from the values read. Here, the inspection time Δt is determined so as to be longer than the time from the ignition start time t0 until the first maximum value V1max of the primary voltage V1 appears, but sufficiently shorter than the discharge period T of the secondary coil 22. A specific value of the inspection time Δt is, for example, 0.1 ms. Alternatively, the length of the inspection time Δt may be defined as a ratio to the discharge period T, for example, by setting the inspection time Δt to 10% of the discharge period T. The inspection time Δt is determined in advance by experiment or the like and stored in a memory (not shown) provided in the maximum value detection unit 9.

[0047] The first maximum value V1max of the primary voltage V1 is sent from the ignition device 50 to the ECU 70, and the ECU 70 estimates the in-cylinder pressure using the first maximum value V1max of the primary voltage V1.

[0048] [Correlation between the first maximum value of the primary voltage and the in-cylinder pressure] Fig. 5 is a characteristic diagram showing the correlation between the first maximum value V1max of the primary voltage V1 of the ignition coil 2 and the in-cylinder pressure. Fig. 5 shows the results of measurements of the first maximum value V1max of the primary voltage V1 and the in-cylinder pressure at the ignition start time t0 using a spark-ignition engine 60. In the diagram, the horizontal axis represents the in-cylinder pressure [Pa], and the vertical axis represents the first maximum value V1max [V].

[0049] It is known that the breakdown voltage of a spark discharge depends on the gas pressure in the discharge gap of the spark plug, and that the higher the gas pressure, the greater the breakdown voltage. Because the first minimum value of the secondary voltage V2 of the ignition coil 2 is approximately equal to the breakdown voltage, the first minimum value of the secondary voltage V2 is strongly correlated with the in-cylinder pressure at the ignition timing. Furthermore, because the first maximum value V1max of the primary voltage V1 generated by the back electromotive force is substantially proportional to the first minimum value of the secondary voltage V2, the first maximum value V1max also has a strong correlation with the in-cylinder pressure. As shown in FIG. 5, the in-cylinder pressure is substantially proportional to the first maximum value V1max. Therefore, the ECU 70 can estimate the in-cylinder pressure of the engine 60 based on the first maximum value V1max of the primary voltage V1 sent from the ignition device 50.

[0050] The ECU 70 stores in the ROM 194 the correlation between the first maximum value V1max of the primary voltage V1 and the in-cylinder pressure, which is previously determined by calibration or the like, as a correlation formula or table data. The pressure sensor is used to measure the in-cylinder pressure during calibration, etc. The ECU 70 obtains the in-cylinder pressure from the first maximum value V1max of the primary voltage V1 by referring to this correlation formula or table.

[0051] In this embodiment, the in-cylinder pressure is calculated based on the voltage on the primary side of the ignition coil 2, which has a relatively low voltage value, so the pressure resistance of the circuit can be reduced compared to when the in-cylinder pressure is calculated based on the secondary voltage V2 of the ignition coil 2. Therefore, the ignition device 50 according to this embodiment can keep the cost of the circuit used to estimate the in-cylinder pressure low.

[0052] The second minimum value of the secondary voltage V2 and the second maximum value of the primary voltage V1 have a low correlation with the in-cylinder pressure for the following reason.

[0053] The second minimum value of the secondary voltage V2 and the second maximum value of the primary voltage V1 occur when the discharge path formed in the discharge gap of the spark plug 7 is elongated by the gas flow, increasing the electrical resistance of the discharge path. That is, the second minimum value of the secondary voltage V2 and the second maximum value of the primary voltage V1 are affected by the gas flow in addition to the in-cylinder pressure. Therefore, if the in-cylinder pressure is estimated using the second minimum value of the secondary voltage V2 or the second maximum value of the primary voltage V1, a large error may occur in the estimation result.

[0054] If the discharge path is greatly elongated, the second maximum value of the primary voltage V1 may reach a level equivalent to the first maximum value V1max of the primary voltage V1. Therefore, the maximum value detection unit 9 must take care not to erroneously detect the second maximum value of the primary voltage V1 as the first maximum value V1max. For this reason, in this embodiment, as described above, the inspection time Δt ( FIG. 4 ) is determined to be longer than the time from the ignition start time t0 until the first maximum value V1max of the primary voltage V1 appears, and sufficiently shorter than the discharge period T. The maximum value detection unit 9 then obtains the maximum value of the primary voltage V1 within the inspection time Δt from the ignition start time t0, thereby preventing erroneous detection of the first maximum value V1max of the primary voltage V1. This allows the ECU 70 according to this embodiment to maintain high reliability in the estimation result of the in-cylinder pressure.

[0055] As described above, the ignition device (ignition device 50) according to the first embodiment includes a switch unit (switch unit 3) configured to conduct and interrupt a primary current (primary current I1) flowing from the primary coil of an ignition coil (ignition coil 2) that includes a primary coil and a secondary coil connected to an ignition plug (ignition plug 7) in a cylinder to ground based on an ignition signal input from a control device (ECU 70), a primary voltage detection unit (primary voltage detection unit 8) that detects a primary voltage (primary voltage V1) of the ignition coil, and a maximum value detection unit (maximum value detection unit 9) that detects a maximum value of the primary voltage of the ignition coil detected by the primary voltage detection unit. The maximum value detection unit is configured to output a first maximum value (first maximum value V1max), which is the first maximum value of the primary voltage of the ignition coil after the start of ignition, to the control device.

[0056] <Second embodiment> An ignition device according to a second embodiment of the present invention will be described below. This embodiment is configured to estimate the in-cylinder pressure based on the minimum value of the primary current I1 of the ignition coil 2 in a predetermined section.

[0057] [Schematic configuration of internal combustion engine system] 6 shows a schematic configuration of an internal combustion engine system equipped with an ignition device according to a second embodiment of the present invention. The internal combustion engine system shown in the figure is composed of a spark-ignition engine 60, an ignition device 50A, and an electronic control unit (ECU) 70A.

[0058] The ignition device 50A supplies ignition energy to the spark plug 7 at a predetermined timing based on an ignition signal input from the ECU 70A. The ignition device 50A also detects a first minimum value I1min of the primary current I1 of the ignition coil 2, which will be described later, and sends the current value to the ECU 70A.

[0059] The ECU 70A estimates the in-cylinder pressure of the engine 60 based on the first minimum value I1min of the primary current I1 of the ignition coil 2, and controls the engine 60 based on the estimated in-cylinder pressure. Although not shown, the ECU 70A includes an estimation unit 71 and a control unit 72, similar to the ECU 70 in the first embodiment. In the ECU 70A, the estimation unit 71 estimates the state of the engine 60, including at least the in-cylinder pressure, based on the first minimum value I1min of the primary current I1 of the ignition coil 2, and the control unit 72 controls the engine 60 based on the estimated state of the engine 60.

[0060] [Ignition device configuration] Next, the configuration of an ignition device 50A according to a second embodiment will be described. 7 is a schematic circuit diagram showing an example configuration of an ignition device 50A. Similar to the ignition device 50 in the first embodiment, the illustrated ignition device 50A includes a power supply 1 that supplies DC voltage, an ignition coil 2 that is configured by a primary coil 21 and a secondary coil 22, a high-voltage diode 6, and a switch unit 3. Furthermore, the ignition device 50A includes a primary current detection unit 10 and a minimum value detection unit 11.

[0061] The primary current detection unit 10 is provided between the high potential side of the power supply 1 and the primary coil 21. A signal output terminal of the primary current detection unit 10 is connected to an input terminal of the minimum value detection unit 11. An ignition signal sent from the ECU 70A is input to the other input terminal of the minimum value detection unit 11.

[0062] The primary current detection unit 10 detects the current value of the primary current I1 flowing through the primary coil 21, and outputs the detection results (primary current values) to the minimum value detection unit 11 in chronological order.

[0063] The minimum value detection unit 11 detects a first minimum value I1min (FIG. 4) within a predetermined section of the primary current I1 of the ignition coil 2 detected in time series by the primary current detection unit 10, and outputs the detection result (first minimum value I1min) to the ECU 70A disposed outside the ignition device 50A. The minimum value detection unit 11 is configured by devices such as a microcomputer and a memory.

[0064] [Ignition device operation] Next, the operation of the ignition device 50A according to the second embodiment will be described. The behavior of the secondary voltage V2 and secondary current I2 of the secondary coil 22 of the ignition device 50A, and the primary voltage V1 and primary current I1 of the primary coil 21 is similar to the behavior shown in Figure 4 in the first embodiment, so duplicated explanations will be omitted here.

[0065] The minimum value detection unit 11 detects a first minimum value I1min of the primary current I1 of the primary coil 21. Specifically, the minimum value detection unit 11 reads current values of the primary current I1 of the primary coil 21 from the ignition start time t0 until the elapse of the inspection time Δt, and selects the smallest current value from the read current values as the first minimum value I1min of the primary current I1. Here, the inspection time Δt is determined so as to be longer than the time from the ignition start time t0 until the first minimum value I1min of the primary current I1 appears, but is sufficiently shorter than the discharge period T of the secondary coil 22. A specific value of the inspection time Δt is, for example, 0.1 ms. Note that the length of the inspection time Δt may be defined as a ratio to the discharge period T, for example, by setting the inspection time Δt to 10% of the discharge period T. The inspection time Δt is determined in advance by experiment or the like and stored in a memory (not shown) provided in the minimum value detection unit 11.

[0066] The first minimum value I1min of the primary current I1 is sent from the ignition device 50A to the ECU 70A disposed outside the ignition device 50A. The ECU 70A estimates the in-cylinder pressure using the first minimum value I1min of the primary current I1.

[0067] [Correlation between the first minimum value of primary current and in-cylinder pressure] Fig. 8 is a characteristic diagram showing the correlation between the first minimum value I1min of the primary current I1 of the ignition coil 2 and the in-cylinder pressure. Fig. 8 shows the results of measurements taken using a spark ignition engine 60, measuring the first minimum value of the primary current I1 and the in-cylinder pressure at the ignition start time t0 (Fig. 4). In the figure, the horizontal axis represents the in-cylinder pressure [Pa], and the vertical axis represents the first minimum value I1min [A].

[0068] According to the new findings of the inventors of the present application, a strong correlation is obtained between the in-cylinder pressure at the ignition start time t0 and the first minimum value I1min of the primary current I1, as shown in Fig. 8. Therefore, the ECU 70A can estimate the in-cylinder pressure of the engine 60 based on the first minimum value I1min of the primary current I1 sent from the ignition device 50A.

[0069] The ECU 70A stores the correlation between the first minimum value I1min of the primary current I1 of the ignition coil 2 and the in-cylinder pressure, which has been obtained in advance by calibration or the like, as a correlation formula or table data in the ROM 194. The ECU 70A obtains the in-cylinder pressure from the first minimum value I1min of the primary current I1 by referring to this correlation formula or table.

[0070] In this embodiment, the in-cylinder pressure is calculated based on the current on the primary side of the ignition coil 2, which has a relatively low voltage value, so the pressure resistance of the circuit can be reduced compared to when the in-cylinder pressure is calculated based on the secondary voltage V2 of the ignition coil 2. Therefore, the ignition device 50A according to this embodiment can keep the cost of the circuit used to estimate the in-cylinder pressure low.

[0071] Note that, like the second maximum value of the primary voltage V1 in the first embodiment, the second minimum value of the primary current I1 is affected by not only the in-cylinder pressure but also the gas flow. Therefore, the correlation between the second minimum value of the primary current I1 and the in-cylinder pressure is low. Therefore, if the in-cylinder pressure is estimated using the second minimum value of the primary current I1, a large error may occur in the estimation result.

[0072] If the discharge path is elongated significantly, the second minimum value of the primary current I1 may reach a level equivalent to the first minimum value I1min of the primary current I1. Therefore, the minimum value detection unit 11 must take care not to erroneously detect the second minimum value of the primary current I1 as the first minimum value I1min of the primary current I1. For this reason, as described above, in this embodiment, the inspection time Δt ( FIG. 4 ) is determined to be longer than the time from the ignition start time t0 until the first minimum value I1min of the primary current I1 appears, but sufficiently shorter than the discharge period T. The minimum value detection unit 11 then determines the minimum value of the primary current I1 within the inspection time Δt from the ignition start time t0, thereby preventing erroneous detection of the first minimum value I1min of the primary current I1. This allows the ECU 70A according to this embodiment to maintain high reliability in the in-cylinder pressure estimation result.

[0073] As described above, the ignition device (ignition device 50A) according to the second embodiment includes a switch unit (switch unit 3) configured to conduct and interrupt a primary current (primary current I1) flowing from the primary coil of an ignition coil (ignition coil 2) composed of a primary coil and a secondary coil connected to an ignition plug (ignition plug 7) in a cylinder to ground based on an ignition signal input from a control device (ECU 70A), a primary current detection unit (primary current detection unit 10) that detects the primary current of the ignition coil, and a minimum value detection unit (minimum value detection unit 11) that detects the minimum value of the primary current of the ignition coil detected by the primary current detection unit. The minimum value detection unit is configured to output a first minimum value (first minimum value I1min), which is the first minimum value of the primary current of the ignition coil after the start of ignition, to the control device.

[0074] <Third embodiment> An ignition device according to a third embodiment of the present invention will be described below. This embodiment is configured to estimate the in-cylinder pressure based on the primary power of the ignition coil 2.

[0075] [Schematic configuration of internal combustion engine system] 9 shows a schematic configuration of an internal combustion engine system equipped with an ignition device according to a third embodiment of the present invention. The internal combustion engine system shown in the figure is composed of a spark ignition engine 60, an ignition device 50B, and an electronic control unit (ECU) 70B.

[0076] The ignition device 50B supplies ignition energy to the spark plug 7 at a predetermined timing based on an ignition signal input from the ECU 70B. The ignition device 50B also detects a primary power Pw1 (also referred to as a "primary power value Pw1") of the ignition coil 2, which will be described later, and sends the power value to the ECU 70B.

[0077] The ECU 70B estimates the in-cylinder pressure of the engine 60 based on the primary power Pw1 of the ignition coil 2, and controls the engine 60 based on the estimated in-cylinder pressure. Although not shown, the ECU 70B includes an estimation unit 71 and a control unit 72, similar to the ECU 70 in the first embodiment. In the ECU 70B, the estimation unit 71 estimates the state of the engine 60, including at least the in-cylinder pressure, based on the primary power Pw1 of the ignition coil 2, and the control unit 72 controls the engine 60 based on the estimated state of the engine 60.

[0078] [Ignition device configuration] Next, the configuration of an ignition device 50B according to a third embodiment will be described. 10 is a schematic circuit diagram showing an example configuration of an ignition device 50B. Similar to the ignition device 50 in the first embodiment, the illustrated ignition device 50B includes a power supply 1 that supplies DC voltage, an ignition coil 2 that is configured by a primary coil 21 and a secondary coil 22, a high-voltage diode 6, and a switch unit 3. Furthermore, the ignition device 50B includes a primary voltage detection unit 8, a primary current detection unit 10, and a primary power detection unit 12.

[0079] A signal output terminal of the primary voltage detection unit 8 is connected to an input terminal of the primary power detection unit 12. A signal output terminal of the primary current detection unit 10 is connected to another input terminal of the primary power detection unit 12. Furthermore, an ignition signal sent from the ECU 70B is input to the other input terminal of the primary power detection unit 12.

[0080] The primary power detection unit 12 is configured to determine the primary power Pw1 from the time-series voltage value of the primary voltage V1 and the current value of the primary current I1 input from the primary voltage detection unit 8 and the primary current detection unit 10, and to output this power value to the ECU 70B. The primary power detection unit 12 is configured from devices such as a microcomputer and a memory.

[0081] [Ignition device operation] Next, the operation of the ignition device 50B according to the third embodiment will be described. The behavior of the secondary voltage V2 and secondary current I2 of the secondary coil 22 of the ignition device 50B, and the primary voltage V1 and primary current I1 of the primary coil 21 is similar to the behavior shown in Figure 4 in the first embodiment, so duplicated explanations will be omitted here.

[0082] The primary power detection unit 12 detects a first minimum value I1min of the primary current I1 of the primary coil 21. Specifically, the primary power detection unit 12 reads the current values of the primary current I1 of the primary coil 21 from the ignition start time t0 until the inspection time Δt has elapsed, and selects the smallest current value from among the current values as the first minimum value I1min of the primary current I1.

[0083] Furthermore, the primary power detection unit 12 detects a first maximum value V1max of the primary voltage V1 of the primary coil 21. Specifically, the primary power detection unit 12 reads the voltage values of the primary voltage V1 of the primary coil 21 from the ignition start time t0 until the inspection time Δt has elapsed, and selects the maximum voltage value from among the voltage values as the first maximum value V1max of the primary voltage V1.

[0084] The primary power detection unit 12 then outputs the absolute value of the product of the first minimum value I1min of the primary current I1 and the first maximum value V1max of the primary voltage V1 as the primary power Pw1. The inspection time Δt is determined so as to be longer than the time from the ignition start time t0 until the first minimum value I1min of the primary current I1 and the first maximum value V1max of the primary voltage V1 appear, but sufficiently shorter than the discharge period T of the secondary coil 22. A specific value of the inspection time Δt is, for example, 0.1 ms. As in the first and second embodiments, the inspection time Δt may be defined as a ratio to the discharge period T, such as by setting the inspection time Δt to 10% of the discharge period T. The inspection time Δt is determined in advance by experiment or the like and stored in a memory (not shown) provided in the primary power detection unit 12.

[0085] The primary electric power Pw1 is sent from the ignition device 50B to the ECU 70B arranged outside the ignition device 50B. The ECU 70B estimates the in-cylinder pressure using the primary electric power Pw1.

[0086] [Correlation between primary power and in-cylinder pressure] Fig. 11 is a characteristic diagram showing the correlation between the primary power Pw1 of the ignition coil 2 and the in-cylinder pressure. Fig. 11 shows the results of measurements of the primary power Pw1 and the in-cylinder pressure at the ignition start time t0 (Fig. 4) using a spark ignition engine 60. In the diagram, the horizontal axis represents the in-cylinder pressure [Pa], and the vertical axis represents the primary power Pw1 [W].

[0087] According to new findings by the inventors of the present application, a strong correlation is obtained between the in-cylinder pressure at the ignition start time t0 and the primary electric power Pw1, as shown in Fig. 11. Therefore, the ECU 70B can estimate the in-cylinder pressure of the engine 60 based on the primary electric power Pw1 sent from the ignition device 50B.

[0088] The ECU 70B stores the correlation between the primary electric power Pw1 and the in-cylinder pressure, which is determined in advance by calibration or the like, as a correlation formula or table data in the ROM 194. The ECU 70B determines the in-cylinder pressure from the primary electric power Pw1 by referring to this correlation formula or table.

[0089] In this embodiment, the in-cylinder pressure is calculated based on the power on the primary side of the ignition coil 2, which has a relatively low voltage value, so the pressure resistance of the circuit can be reduced compared to when the in-cylinder pressure is calculated based on the secondary voltage V2 of the ignition coil 2. Therefore, the ignition device 50B according to this embodiment can keep the cost of the circuit used to estimate the in-cylinder pressure low.

[0090] Furthermore, according to new findings by the inventors of the present application, it has become clear that the correlation between the primary power Pw1 of the ignition coil 2 and the in-cylinder pressure is higher than the correlation between the first maximum value V1max of the primary voltage V1 and the in-cylinder pressure in the first embodiment described above, and the correlation between the first minimum value I1min of the primary current I1 and the in-cylinder pressure in the second embodiment described above.

[0091] [Correlation between the first maximum value of the primary voltage, the first minimum value of the primary current, the primary power value, and the in-cylinder pressure] FIG. 12 shows an example of the measurement results of the correlation coefficient R between the first maximum value V1max of the primary voltage V1 of the ignition coil 2, the first minimum value I1min of the primary current I1, and the primary power value Pw1, and the in-cylinder pressure at the ignition start time t0.

[0092] 12, the correlation coefficient between the primary power value Pw1 and the in-cylinder pressure is close to 1, followed by the correlation coefficient between the first maximum value V1max of the primary voltage V1 and the in-cylinder pressure, and the correlation coefficient between the first minimum value I1min of the primary current I1 and the in-cylinder pressure, in that order. In other words, the correlation coefficient between the primary power value Pw1 and the in-cylinder pressure is higher than the correlation coefficient between the first maximum value V1max of the primary voltage V1 and the in-cylinder pressure and the correlation coefficient between the first minimum value I1min of the primary current I1 and the in-cylinder pressure. Therefore, when the primary power value Pw1 is used, the in-cylinder pressure can be estimated with higher accuracy than when the first maximum value V1max of the primary voltage V1 and the first minimum value I1min of the primary current I1 are used.

[0093] As described above, the ignition device (ignition device 50B) according to the third embodiment includes a switch unit (switch unit 3) configured to conduct and cut off the primary current (primary current I1) flowing from the primary coil of the ignition coil (ignition coil 2) that is composed of a primary coil and a secondary coil connected to the ignition plug (ignition plug 7) in the cylinder to the ground side, based on an ignition signal input from the control device (ECU 70B), and a primary voltage detection unit (primary voltage detection unit 8) that detects the primary voltage (primary voltage V1) of the ignition coil. ), a primary current detection unit (primary current detection unit 10) that detects the primary current of the ignition coil, and a primary power detection unit (primary power detection unit 12) that detects the primary power of the ignition coil (primary power Pw1) from the first maximum value (first maximum value V1max) of the primary voltage after the start of ignition detected by the primary voltage detection unit and the first minimum value (first minimum value I1min) of the primary current after the start of ignition detected by the primary current detection unit, and outputs the value of the primary power of the ignition coil to the control device.

[0094] <Fourth embodiment> An ignition device according to a fourth embodiment of the present invention will be described below. This embodiment is configured to estimate the in-cylinder pressure based on the average value of the primary voltage of the ignition coil 2.

[0095] [Schematic configuration of internal combustion engine system] 13 shows a schematic configuration of an internal combustion engine system equipped with an ignition device according to a fourth embodiment of the present invention. The internal combustion engine system shown in the figure is composed of a spark ignition engine 60, an ignition device 50C, and an electronic control unit (ECU) 70C.

[0096] The ignition device 50C supplies ignition energy to the spark plug 7 at a predetermined timing based on an ignition signal input from the ECU 70C. The ignition device 50C also detects an average value V1mean of a primary voltage V1 of the ignition coil 2, which will be described later, and sends the voltage value to the ECU 70C.

[0097] The ECU 70C estimates the in-cylinder pressure of the engine 60 based on the average value V1mean of the primary voltage V1 of the ignition coil 2, and controls the engine 60 based on the estimated in-cylinder pressure. Although not shown, the ECU 70C, like the ECU 70 in the first embodiment, includes an estimation unit 71 and a control unit 72. In the ECU 70C, the estimation unit 71 estimates the state of the engine 60, including at least the in-cylinder pressure, based on the average value V1mean of the primary voltage V1 of the ignition coil 2, and the control unit 72 controls the engine 60 based on the estimated state of the engine 60.

[0098] [Ignition device configuration] Next, the configuration of an ignition device 50C according to a fourth embodiment will be described. 14 is a schematic circuit diagram showing an example configuration of an ignition device 50C. Similar to the ignition device 50 in the first embodiment, the illustrated ignition device 50C includes a power supply 1 that supplies DC voltage, an ignition coil 2 that is configured by a primary coil 21 and a secondary coil 22, a high-voltage diode 6, and a switch unit 3. Furthermore, the ignition device 50C includes a primary voltage detection unit 8 and a primary voltage averaging processing unit 13.

[0099] A signal output terminal of the primary voltage detection unit 8 is connected to an input terminal of a primary voltage averaging processing unit 13. An ignition signal sent from the ECU 70C is input to the other input terminal of the primary voltage averaging processing unit 13.

[0100] The primary voltage averaging processing unit 13 is configured to calculate an average value V1mean of the primary voltage V1 input from the primary voltage detection unit 8 over a predetermined period, and output the average value V1mean to the ECU 70C. The predetermined period is a time period after the vibration amplitude of the primary voltage V1 becomes equal to or less than a predetermined value, and is shorter than a predetermined time period within the discharge period T of the ignition coil 2. The primary voltage averaging processing unit 13 is configured from devices such as a microcomputer and a memory.

[0101] [Ignition device operation] Next, the operation of the ignition device 50C according to the fourth embodiment will be described. 15 is a waveform diagram showing an example of the operation of the ignition device 50C, and shows a timing chart of the ignition signal input from the ECU 70C and the primary voltage V1 of the primary coil 21 detected by the primary voltage detection unit 8. Note that this figure is an enlarged view of the vicinity of the time when the first maximum value V1max occurs in the timing chart of the ignition signal and the primary voltage V1 shown in FIG. 4 in the first embodiment.

[0102] The primary voltage averaging processor 13 reads the value of the primary voltage V1 of the primary coil 21 from the primary voltage detector 8 during the period from time t1 after the ignition start time t0 until time t2 (t2>t1). The primary voltage averaging processor 13 then calculates the average value V1mean of the primary voltage V1 during the period from time t1 to time t2 using equation (1). In equation (1), "dt" is the sampling period of the primary voltage V1.

[0103]

number

[0104] 15, immediately after the first maximum value V1max occurs, high-amplitude vibration occurs in the primary voltage V1 of the primary coil 21 due to resonance between the reactance component L and the capacitance component C included in the primary side of the ignition coil 2 of the ignition device 50C. This vibration may increase the error in the calculation result of the average value of the primary voltage V1 by the primary voltage averaging processor 13. Therefore, it is desirable that the time (t1-t0) from the ignition start time t0 to the start of averaging the primary voltage V1 of the ignition coil 2 be a time when the vibration amplitude of the primary voltage V1 of the ignition coil 2 becomes sufficiently small (below a predetermined specified value). The specified value for a sufficiently small vibration amplitude may be set to, for example, one-tenth of the maximum amplitude.

[0105] Furthermore, during the discharge period T of the ignition coil 2, the primary voltage V1 of the ignition coil 2 increases over time due to the extension of the discharge path caused by gas flow. Because this voltage increase has a low correlation with the in-cylinder pressure, when the in-cylinder pressure is estimated using the primary voltage V1, the extension of the discharge path increases the error in the in-cylinder pressure estimation. Therefore, to reduce the influence of the extension of the discharge path caused by the gas flow in the cylinder, it is desirable that the averaging period (t2-t1) be sufficiently short with respect to the discharge period T (FIG. 4). That is, the averaging period (t2-t1) is set to a time after time t1 that is shorter than the specified time that satisfies the above-described condition within the discharge period T. The specified time is determined in advance by experiment or the like and stored in a memory (not shown) provided in the primary voltage averaging processor 13.

[0106] From the above perspective, preferable values for the time (t1 - t0) from the ignition start time t0 to the start of averaging of the primary voltage V1 and the time (t2 - t0) from the ignition start time t0 to the end of averaging of the primary voltage V1 are calculated as t1 = 0.2 ms and t2 = 0.3 ms, respectively, when the ignition start time t0 is set as the starting point (0 ms). However, t1 and t2 are not limited to these values, and various optimum values are determined depending on the discharge period of the ignition coil 2, the gas flow strength, the sampling period of the coil voltage, etc. The length of the averaging period may be specified as a ratio to the discharge period T, for example, by setting the averaging period (t2 - t1) to 10% of the discharge period T.

[0107] The average value V1mean of the primary voltage V1 calculated by the primary voltage averaging processing unit 13 is sent from the ignition device 50C to the ECU 70C. The ECU 70C estimates the in-cylinder pressure using the average value V1mean of the primary voltage V1 of the ignition coil 2.

[0108] [Correlation between average primary voltage and in-cylinder pressure] Fig. 16 is a characteristic diagram showing the correlation between the average value V1mean of the primary voltage V1 of the ignition coil 2 and the in-cylinder pressure. Fig. 16 shows the results of measurements taken using a spark ignition engine 60, measuring the average value V1mean of the primary voltage V1 and the in-cylinder pressure at the ignition start time t0 (Fig. 4).

[0109] According to the new findings of the inventors of the present application, a strong correlation is obtained between the in-cylinder pressure after the ignition start time t0 and the average value V1mean of the primary voltage V1, as shown in Fig. 16. Therefore, the ECU 70C can estimate the in-cylinder pressure of the engine 60 based on the average value V1mean of the primary voltage V1 sent from the ignition device 50C.

[0110] The ECU 70C stores in the ROM 194 a correlation between the average value V1mean of the primary voltage V1, which is obtained in advance by calibration or the like, and the in-cylinder pressure, as a correlation formula or table data. The ECU 70C obtains the in-cylinder pressure from the average value V1mean of the primary voltage V1 by referring to this correlation formula or table.

[0111] In this embodiment, the in-cylinder pressure is calculated based on the voltage on the primary side of the ignition coil 2, which has a relatively low voltage value, so the pressure resistance of the circuit can be reduced compared to when the in-cylinder pressure is calculated based on the secondary voltage V2 of the ignition coil 2. Therefore, the ignition device 50C according to this embodiment can keep the cost of the circuit used to estimate the in-cylinder pressure low.

[0112] Furthermore, calculating the in-cylinder pressure using the average value V1mean of the primary voltage V1 of the ignition coil 2 has the following advantages over the method of calculating the in-cylinder pressure using the first maximum value V1max of the primary voltage V1 (first embodiment), the first minimum value I1min of the primary current I1 (second embodiment), and the primary power Pw1 (third embodiment).

[0113] The maximum value of the primary voltage V1 or the minimum value of the primary current I1 that appears immediately after the discharge of the ignition coil 2 generally occurs in an extremely short period of time, on the order of microseconds. Therefore, to accurately capture this maximum or minimum value, it is necessary to sample the voltage or current of the primary coil 21 at a high speed, on the order of megahertz. This may increase the computational load and cost of the circuit.

[0114] On the other hand, the primary voltage V1 fluctuates at a relatively low frequency and amplitude a predetermined time after the occurrence of the maximum value (first maximum value V1max) of the primary voltage V1 that appears immediately after the discharge of the ignition coil 2. Therefore, the average value V1mean of the primary voltage V1 can be calculated with high accuracy even at a relatively slow sampling rate on the order of kilohertz. Therefore, the ignition device 50C according to this embodiment can reduce the computational load and cost of the circuit.

[0115] As described above, the ignition device (ignition device 50C) of the fourth embodiment is configured to conduct and cut off the primary current (primary current I1) flowing from the primary coil of the ignition coil (ignition coil 2) composed of a primary coil and a secondary coil connected to an ignition plug (ignition plug 7) in the cylinder to the ground side based on an ignition signal input from the control device (ECU 70C), a primary voltage detection device (primary voltage detection device 8) that detects the primary voltage (primary voltage V1) of the ignition coil, and a primary voltage averaging processing device (primary voltage averaging processing device 13) that calculates the average value (V1mean) of the primary voltage of the ignition coil detected by the primary voltage detection device within a predetermined period (t2-t1) during discharge and outputs the average value of the primary voltage to the control device.

[0116] <Fifth embodiment> An ignition device according to a fifth embodiment of the present invention will be described below. This embodiment is configured to estimate the in-cylinder pressure based on the average value of the secondary current I2 of the ignition coil 2.

[0117] [Schematic configuration of internal combustion engine system] 17 shows a schematic configuration of an internal combustion engine system equipped with an ignition device according to a fifth embodiment of the present invention. The internal combustion engine system shown in the figure is composed of a spark-ignition engine 60, an ignition device 50D, and an electronic control unit (ECU) 70D.

[0118] The ignition device 50D supplies ignition energy to the spark plug 7 at a predetermined timing based on an ignition signal input from the ECU 70D. The ignition device 50D also detects an average value I2mean of a secondary current I2 of the ignition coil 2, which will be described later, and sends the average value to the ECU 70D.

[0119] The ECU 70D estimates the in-cylinder pressure of the engine 60 based on the average value I2mean of the secondary current I2 of the ignition coil 2, and controls the engine 60 based on the estimated in-cylinder pressure. Although not shown, the ECU 70B, like the ECU 70 in the first embodiment, includes an estimation unit 71 and a control unit 72. In the ECU 70D, the estimation unit 71 estimates the state of the engine 60, including at least the in-cylinder pressure, based on the average value I2mean of the secondary current I2 of the ignition coil 2, and the control unit 72 controls the engine 60 based on the estimated state of the engine 60.

[0120] [Ignition device configuration] Next, the configuration of an ignition device 50D according to a fifth embodiment will be described. 18 is a schematic circuit diagram showing an example configuration of an ignition device 50D according to a fifth embodiment. Similar to the ignition device 50 according to the first embodiment, the illustrated ignition device 50D includes a power supply 1 that supplies a DC voltage, an ignition coil 2 that is configured by a primary coil 21 and a secondary coil 22, a high-voltage diode 6, and a switch unit 3 that turns on and off the primary current I1 that flows through the primary coil 21. Furthermore, the ignition device 50D includes a secondary current detection unit 5 and a secondary current averaging processing unit 14.

[0121] The secondary current detection unit 5 is provided between the cathode of the high-voltage diode 6 and the ground conductor. A signal output terminal of the secondary current detection unit 5 is connected to an input terminal of a secondary current averaging processing unit 14. An ignition signal sent from the ECU 70D is input to the other input terminal of the secondary current averaging processing unit 14.

[0122] The secondary current detection unit 5 detects the current value of the secondary current I2 flowing through the secondary coil 22, and outputs the detection results (secondary current values) to the secondary current averaging processing unit 14 in time series.

[0123] The secondary current averaging processing unit 14 is configured to calculate an average value I2mean of the secondary current I2 input from the secondary current detection unit 5 over a predetermined period, and output the average value I2mean to the ECU 70D. The predetermined period is within the discharge period of the ignition coil 2 and is a fixed time from the start of discharge. The secondary current averaging processing unit 14 is configured from devices such as a microcomputer and a memory.

[0124] [Ignition device operation] Next, the operation of the ignition device 50D according to the fifth embodiment will be described. 19 is a waveform diagram showing an example of the operation of the ignition device 50D, and shows a timing chart of the ignition signal input from the ECU 70D and the secondary current I2 of the secondary coil 22 detected by the secondary current detection unit 5. This figure shows an enlarged view of the discharge period T in the timing chart of the ignition signal and the secondary current I2 shown in FIG. 4 in the first embodiment.

[0125] The secondary current averaging processor 14 reads the value of the secondary current I2 of the secondary coil 22 from the secondary current detection unit 5 during the period from ignition start time t0 to time t3 (t3>t0). Then, the secondary current averaging processor 14 calculates the average value I2mean of the secondary current I2 during the period from time t0 to time t3 using equation (2). In equation (2), "dt" is the sampling period of the secondary current I2.

[0126]

number

[0127] Furthermore, it is desirable to determine the time t3 at which the period (averaging period) for calculating the average value I2mean of the secondary current I2 ends so that the averaging period (t3-t0) of the secondary current I2 is a predetermined specified proportion of the discharge period T of the ignition coil 2. For example, in this embodiment, the specified proportion is set to about 10%.

[0128] If the averaging period (t3-t0) of the secondary current I2 is significantly shorter than 10% of the discharge period T, the range of change in the average value I2mean of the secondary current I2 associated with changes in the in-cylinder pressure becomes smaller, resulting in a decrease in the S / N ratio. Also, if the averaging period (t3-t0) of the secondary current I2 is significantly longer than 10% of the discharge period T, the correlation between the average value I2mean of the secondary current I2 and the in-cylinder pressure decreases due to the influence of the discharge path extension associated with the gas flow in the cylinder.

[0129] Therefore, the secondary current averaging processor 14 calculates the discharge period T from the difference between the time when the absolute value of the moving average value of the secondary current I2 becomes equal to or less than a predetermined value and the ignition start time t0, and determines the time t3 so that the averaging period of the secondary current I2 is approximately 10% of the discharge period T. The number of samples of the secondary current I2 used to calculate the moving average value of the secondary current I2 is set in advance. Furthermore, the time t3 calculated for each engine operating condition (torque, rotational speed, ignition timing, etc.) by calibration is stored as table data in a memory (not shown) included in the secondary current averaging processor 14. The secondary current averaging processor 14 may then refer to the table to determine the time t3 that defines the averaging period (t3-t0). In this way, the averaging period (t3-t0) is set to a fixed time from the start of discharge within the discharge period T. The fixed time is calculated in advance by experiment or the like and stored in a memory (not shown) included in the secondary current averaging processor 14.

[0130] The average value I2mean of the secondary current I2 calculated by the secondary current averaging processor 14 is sent from the ignition device 50D to the ECU 70D. The ECU 70D estimates the in-cylinder pressure using the average value I2mean of the secondary current I2 of the ignition coil 2.

[0131] [Correlation between average secondary current and in-cylinder pressure] Fig. 20 is a characteristic diagram showing the correlation between the average value I2mean of the secondary current I2 of the ignition coil 2 and the in-cylinder pressure. Fig. 20 shows the results of measurements taken using a spark ignition engine 60, measuring the average value I2mean of the secondary current I2 and the in-cylinder pressure at the ignition start time t0 (Fig. 4).

[0132] According to new findings by the inventors of the present application, it has been found that the rate at which the absolute value of the secondary current I2 immediately after the start of ignition decreases depends on the in-cylinder pressure, and that the higher the in-cylinder pressure, the faster the absolute value of the secondary current I2 immediately after the start of ignition decreases. Therefore, as shown in FIG. 20, a strong correlation is obtained between the in-cylinder pressure after the ignition start time t0 and the average value I2mean of the secondary current I2. Therefore, the ECU 70D can estimate the in-cylinder pressure of the engine 60 based on the average value I2mean of the secondary current I2 sent from the ignition device 50D.

[0133] The ECU 70D stores the correlation between the average value I2mean of the secondary current I2 of the ignition coil 2, which is determined in advance by calibration or the like, and the in-cylinder pressure as a correlation formula or table data in the ROM 194. The ECU 70D determines the in-cylinder pressure from the average value I2mean of the secondary current I2 by referring to this correlation formula or table.

[0134] In this embodiment, the voltage applied to the secondary current detection unit 5 is low, so the voltage resistance of the circuit can be lowered compared to when the in-cylinder pressure is determined based on the secondary voltage V2 of the ignition coil 2. Therefore, the ignition device 50D according to this embodiment can keep the cost of the circuit used to estimate the in-cylinder pressure low.

[0135] Furthermore, the secondary current I2 immediately after discharge of the ignition coil 2 fluctuates with a relatively low frequency and low amplitude. Therefore, the average value I2mean of the secondary current I2 can be accurately calculated even with relatively slow sampling on the order of kilohertz. Therefore, the ignition device 50 according to this embodiment can reduce the computational load and cost of the circuit. Furthermore, this embodiment directly detects the discharge current on the secondary side without using the back electromotive force acting from the secondary side of the ignition coil 2 to the primary side, which has the advantage of being less susceptible to the effects of noise generated inside the ignition device 50D and signal attenuation.

[0136] As described above, the ignition device (ignition device 50D) of the fifth embodiment is configured to include a switch unit (switch unit 3) configured to conduct and cut off the primary current (primary current I1) flowing from the primary coil of the ignition coil (ignition coil 2) composed of a primary coil and a secondary coil connected to an ignition plug (ignition plug 7) in the cylinder to the ground side based on an ignition signal input from the control device (ECU 70D), a secondary current detection unit (secondary current detection unit 5) that detects the secondary current (secondary current I2) of the ignition coil, and a secondary current averaging processing unit (secondary current averaging processing unit 14) that calculates the average value (I2mean) of the secondary current of the ignition coil detected by the secondary current detection unit within a predetermined period (t3-t0) during discharge and outputs the average value of the secondary current to the control device.

[0137] <Modification> Furthermore, the present invention is not limited to the above-described embodiments, and it goes without saying that various other applications and modifications are possible as long as they do not deviate from the gist of the present invention as set forth in the claims. For example, the above-described embodiments have described the configuration of an ignition device in detail and specifically in order to clearly explain the present invention, and are not necessarily limited to those including all of the components described. Furthermore, it is possible to replace a portion of the configuration of one embodiment with a component of another embodiment. It is also possible to add a component of another embodiment to the configuration of one embodiment. It is also possible to add, replace, or delete other components from a portion of the configuration of each embodiment.

[0138] In addition, although the ignition coil 2 is disposed inside the ignition device in each of the above-described embodiments, the ignition coil 2 may be disposed outside the ignition device. In addition, although the local maximum value detection unit 9, the local minimum value detection unit 11, the primary power detection unit 12, the primary voltage averaging processing unit 13, the secondary current detection unit 5, and the secondary current averaging processing unit 14 are disposed inside the ignition device in each of the above-described embodiments, they may be disposed inside the ECU.

[0139] Furthermore, the ignition device of each of the above-described embodiments is not limited to an engine (internal combustion engine) having one ignition coil and one ignition plug for each cylinder, but can also be applied to an engine having multiple ignition coils or multiple ignition plugs for each cylinder.

[0140] Furthermore, the above-described configurations, functions, processing units, etc. may be partially or entirely realized in hardware, for example, by designing them as integrated circuits, etc. As the hardware, a broad processor device such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit) may be used. [Explanation of symbols]

[0141] 1...power supply, 2...ignition coil, 3...switch section, 5...secondary current detection section, 7...spark plug, 8...primary voltage detection section, 9...maximum value detection section, 10...primary current detection section, 11...minimum value detection section, 12...primary power detection section, 13...primary voltage averaging processing section, 14...secondary current averaging processing section, 21...primary coil, 22...secondary coil, 50, 50A, 50B, 50C, 50D...ignition device, 60...engine, 70, 70A, 70B, 70C, 70D...electronic control unit (ECU), V1...primary voltage, V1max...first maximum value, V1mean...mean value, V2...secondary voltage, I1...primary current, I1min...first minimum value, I2...secondary current, I2mean...mean value, Pw1...primary power, T...discharge period

Claims

1. a switch unit configured to conduct and cut off a primary current flowing from the primary coil to a ground side of an ignition coil composed of a primary coil and a secondary coil connected to an ignition plug in a cylinder, based on an ignition signal input from a control device; a primary side detection unit that detects a value related to a time series primary voltage of the ignition coil, The primary side detection unit outputs a value related to the primary voltage to the control device so that the control device can estimate an in-cylinder pressure based on a correlation between a value related to the primary voltage of the ignition coil and the pressure in the cylinder. Ignition device.

2. The primary side detection unit detects an extreme value of a value related to a time series primary voltage of the ignition coil, and outputs the extreme value of the value related to the primary voltage to the control device.

10. The ignition device of claim 1.

3. As the primary side detection unit, a primary current detection unit that detects a primary current of the ignition coil; a minimum value detection unit that detects a minimum value of the primary current of the ignition coil detected by the primary current detection unit, The minimum value detection unit outputs a first minimum value of the primary current to the control device in order to estimate an in-cylinder pressure based on a correlation between a first minimum value, which is the first minimum value of the primary current of the ignition coil after ignition starts, and the pressure in the cylinder in the control device.

3. The ignition device according to claim 2.

4. As the primary side detection unit, a primary voltage detection unit that detects a primary voltage of the ignition coil; a primary current detection unit that detects a primary current of the ignition coil; a primary power detection unit that detects primary power of the ignition coil from a first maximum value of the primary voltage detected by the primary voltage detection unit after the start of ignition and a first minimum value of the primary current detected by the primary current detection unit after the start of ignition, The primary power detection unit outputs the value of the primary power to the control device so that the control device can estimate an in-cylinder pressure based on a correlation between the value of the primary power of the ignition coil and the pressure in the cylinder.

3. The ignition device according to claim 2.

5. As the primary side detection unit, a primary voltage detection unit that detects a primary voltage of the ignition coil; a primary voltage averaging processing unit that calculates an average value of the primary voltage of the ignition coil detected by the primary voltage detection unit over a predetermined period during discharge, The primary voltage averaging processing unit outputs the average value of the primary voltage to the control device so that the control device can estimate an in-cylinder pressure based on a correlation between the average value of the primary voltage of the ignition coil and the pressure in the cylinder.

10. The ignition device of claim 1.

6. a switch unit configured to conduct and cut off a primary current flowing from the primary coil to a ground side of an ignition coil composed of a primary coil and a secondary coil connected to an ignition plug in a cylinder, based on an ignition signal input from a control device; a secondary current detection unit that detects a secondary current of the ignition coil; a secondary current averaging processing unit that calculates an average value of the secondary current of the ignition coil detected by the secondary current detection unit during a predetermined period of discharge, The secondary current averaging processing unit outputs the average value of the secondary current to the control device so that the control device can estimate an in-cylinder pressure based on a correlation between the average value of the secondary current of the ignition coil and the pressure in the cylinder. Ignition device.

7. The period during which the minimum value detection unit detects the first minimum value of the primary current is set to be longer than the time from the start of ignition until the first minimum value of the primary current appears, and shorter than the discharge period of the secondary coil.

4. The ignition device according to claim 3.

8. The period during which the primary power detection unit detects the primary power is set to be longer than the time from the start of ignition until the first maximum value of the primary voltage after the start of ignition and the first minimum value of the primary current after the start of ignition appear, and shorter than the discharge period of the secondary coil.

5. The ignition device according to claim 4.

9. The predetermined period during which the primary voltage detection unit calculates the average value of the primary voltage is a period after the vibration amplitude of the primary voltage becomes equal to or less than a specified value and is shorter than a specified time within a discharge period of the ignition coil.

6. The ignition device according to claim 5.

10. The predetermined period during which the secondary current detection unit calculates the average value of the secondary current is a fixed period of time from the start of discharge of the ignition coil.

7. The ignition device according to claim 6.

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