Engine device

Abstract

To provide an engine device that can be operated by avoiding abnormal combustion when inputting gaseous fuel and liquid fuel.SOLUTION: In an engine device 1 that is driven by inputting at least one of gaseous fuel and liquid fuel to a combustion chamber 12a of an engine 2, a dangerous region in which abnormal combustion is predicted relative to a mixed combustion ratio of the gaseous fuel included in fuel to be input to the combustion chamber 12a is preset, and the dangerous region is avoided during an operation of the engine 2. For example, in the case where the engine 2 is operated while the mixed combustion ratio is changed, the engine device 1 performs avoidance control for avoiding the dangerous region. For example, in the relation between an engine load and the mixed combustion ratio of the gaseous fuel, the engine device 1 presets the dangerous region.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an engine device that is driven by injecting at least one of gaseous fuel and liquid fuel into a combustion chamber. [Background technology]

[0002] 2. Description of the Related Art Conventionally, some engine devices are driven by feeding at least one of a gaseous fuel such as hydrogen and a liquid fuel such as light oil or heavy oil into a combustion chamber in a cylinder. For example, some engine devices operate in either a gas mode in which gas fuel is injected into the combustion chamber, or a diesel mode in which liquid fuel is injected into the combustion chamber. In such engine devices, when switching between the gas mode and the diesel mode, the mixed combustion ratio of the gas fuel contained in the fuel injected into the combustion chamber changes. Some engine devices operate in a dual-fuel mode as another operating mode in which both gaseous fuel and liquid fuel are fed into the combustion chamber.

[0003] For example, in the engine device disclosed in Patent Document 1, when switching the operating mode from one of the gas mode and the diesel mode to the other, the supply amount of the first fuel to be input in the operating mode after the switch is increased to a switching threshold value by an increase control that monotonically increases the amount, and then the amount is controlled by a governor control based on the engine speed.

[0004] Moreover, the operation control device for an internal combustion engine disclosed in Patent Document 2 includes a fuel property estimation unit that estimates the component ratio of the fuel supplied to the internal combustion engine, and an operation limiting unit that determines an operating region in which abnormal combustion may occur in the internal combustion engine based on the component ratio of the fuel estimated by the fuel property estimation unit, and limits the operation of the internal combustion engine in the operating region in which abnormal combustion may occur in the internal combustion engine. Here, the component ratio of the fuel is the ratio of butane and propane contained in liquefied petroleum gas. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6594714 [Patent Document 2] JP 2008-057500 A Summary of the Invention [Problem to be solved by the invention]

[0006] In an engine device that can be driven by injecting gaseous fuel and liquid fuel into the combustion chamber, when switching between gas and diesel modes or when operating in a mixed combustion mode, the mixed combustion ratio of the gaseous fuel contained in the fuel injected into the combustion chamber is changed to a predetermined target mixed combustion ratio. Depending on the mixed combustion ratio, abnormal combustion such as pre-ignition or knocking may occur locally in a certain region of the engine. However, with conventional technology, it is difficult to avoid such abnormal combustion.

[0007] An object of the present invention is to provide an engine device that can be operated while avoiding abnormal combustion when gaseous fuel and liquid fuel are input. [Means for solving the problem]

[0008] In order to solve the above problems, the engine device of the present invention is an engine device that is driven by injecting at least one of gaseous fuel and liquid fuel into a combustion chamber, and is characterized in that a danger zone in which abnormal combustion is predicted for the mixed combustion ratio of the gaseous fuel contained in the fuel injected into the combustion chamber is set in advance, and the danger zone is avoided when the engine is operating. Effect of the Invention

[0009] According to the present invention, there is provided an engine device that can be operated while avoiding abnormal combustion when gaseous fuel and liquid fuel are input. [Brief description of the drawings]

[0010] [Figure 1] 1 is a left side view showing an engine device according to an embodiment of the present invention. FIG. [Diagram 2] 1 is a graph showing the relationship between the mixed combustion ratio of gaseous fuel and the maximum pressure of a combustion chamber in an engine device. [Diagram 3] 1 is a graph showing the relationship between the mixed combustion ratio of gaseous fuel and the frequency of pre-ignition in an engine device. [Figure 4] FIG. 2 is a top view showing a danger area map indicating a danger area with respect to a relationship between a mixed combustion ratio of gaseous fuel and an engine load in an engine device according to an embodiment of the present invention. [Diagram 5] FIG. 11 is a top view showing a danger area map indicating a danger area with respect to the relationship between the mixed combustion ratio of gaseous fuel and the engine load in the engine device according to the first modified example of the present invention. [Figure 6] 1 is a graph showing the relationship between the mixed combustion ratio of gaseous fuel and the maximum temperature of the combustion chamber and the excess air ratio of the gaseous fuel in an engine system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An engine device 1 according to an embodiment of the present invention will be described with reference to the drawings. As shown in Fig. 1, the engine device 1 includes an engine 2, an intake passage 3, an exhaust passage 4, a turbocharger 5, an intercooler 6, a first recirculation device 7, a second recirculation device 8, and a control unit 9.

[0012] Particularly in this embodiment, the engine device 1 is configured to be capable of being driven by feeding gas fuel such as hydrogen and liquid fuel such as light oil or heavy oil into the combustion chamber 12a of the engine 2, and includes a gas fuel injection unit 16 for feeding the gas fuel and a liquid fuel injection unit 17 for feeding the liquid fuel. The engine device 1 is configured to operate by switching between an operation mode of a gas mode in which gas fuel is fed into the combustion chamber 12a for driving, and a diesel mode in which liquid fuel is fed into the combustion chamber 12a for driving.

[0013] The engine 2 is configured with a cylinder block 11 and multiple cylinders 12, but Fig. 1 shows only one cylinder 12. As shown in Fig. 1, each cylinder 12 is configured with a cylinder 13, a piston 14, and a cylinder head 15. A gas fuel injection unit 16 and a liquid fuel injection unit 17 are provided for each cylinder 12.

[0014] The cylinder 13 is formed, for example, in a cylindrical shape within the cylinder block 11, and the piston 14 is slidably housed within the cylinder 13. The cylinder head 15 is attached to the upper side of the cylinder 13, and the cylinder 13 and the cylinder head 15 form a combustion chamber 12a therein.

[0015] Below the cylinder 13, a crankshaft 19 is connected to the piston 14 via a connecting rod 18, and the reciprocating motion of the piston 14 is converted into the rotational motion of the crankshaft 19 via the connecting rod 18.

[0016] The cylinder 13 is provided with a rotation speed sensor 20 such as an encoder that detects the rotation speed of the crankshaft 19, i.e., the rotation speed of the engine 2, and the rotation speed sensor 20 transmits the detection result to the control unit 9. The cylinder 13 is provided with a torque sensor 21 near the crankshaft 19 that detects the engine load (engine torque) of the engine 2, and the torque sensor 21 transmits the detection result to the control unit 9.

[0017] The cylinder head 15 also has an intake port 22 and an exhaust port 23 that communicate with the combustion chamber 12a of the cylinder 13, and is equipped with an intake valve 24 and an exhaust valve 25 that respectively open and close the intake port 22 and the exhaust port 23 to the combustion chamber 12a.

[0018] The intake port 22 is connected to the intake passage 3 and introduces air supplied from the intake passage 3 into the combustion chamber 12a, while the exhaust port 23 is connected to the exhaust passage 4 and discharges exhaust gas generated in the combustion chamber 12a into the exhaust passage 4. By opening the intake valve 24, a mixture of fuel gas and air can be taken into the combustion chamber 12a via the intake port 22, while by opening the exhaust valve 25, exhaust gas generated in the combustion chamber 12a can be exhausted via the exhaust port 23.

[0019] 1 shows an example in which the intake passage 3 and the intake port 22 are directly connected, but in order to connect the intake passage 3 to each of the intake ports 22 of the multiple cylinders 12, an intake manifold having branch passages branching from the intake passage 3 to the multiple cylinders 12 may be provided between the intake passage 3 and the engine 2. Also, in FIG. 1 shows an example in which the exhaust passage 4 and the exhaust port 23 are directly connected, but in the case of connecting the exhaust passage 4 to each of the exhaust ports 23 of the multiple cylinders 12, an exhaust manifold having branch passages branching from the exhaust passage 4 to the multiple cylinders 12 may be provided between the exhaust passage 4 and the engine 2.

[0020] In each cylinder 12, the gaseous fuel injection unit 16 is provided in an intake port 22 and is controlled by the control unit 9 to inject gaseous fuel supplied from a gaseous fuel tank (not shown) into the intake port 22. A mixture of air supplied from the intake passage 3 and gaseous fuel supplied from the gaseous fuel tank (not shown) is supplied from the intake port 22 to the combustion chamber 12a. The gaseous fuel injection unit 16 is composed of, for example, a gas admission valve, a gas injector, etc. The gaseous fuel injection unit 16 is controlled by the control unit 9 in terms of injection pressure, injection timing, etc. of the gaseous fuel.

[0021] In each cylinder 12, a liquid fuel injection unit 17 is provided in the cylinder head 15 and is controlled by the control unit 9 to inject liquid fuel supplied from a liquid fuel tank (not shown) into the combustion chamber 12a below the cylinder head 15. The liquid fuel injection unit 17 is composed of an injector and the like. The liquid fuel injection unit 17 is controlled by the control unit 9 with respect to the injection pressure, injection timing, number of injections, etc. of the liquid fuel.

[0022] Ignition in the combustion chamber 12a of each cylinder 12 may be performed using a micro-pilot method in which a small amount of liquid fuel is injected from the liquid fuel injection unit 17, or may be performed using a spark ignition method in which each cylinder 12 is provided with an ignition plug.

[0023] The intake passage 3 is connected to intake ports 22 of the cylinders 12 of the engine 2, and supplies compressed and cooled air to each cylinder 12 via the intake ports 22. A turbocharger 5 and an intercooler 6 are provided in the intake passage 3, in this order from the upstream side in the intake direction. An air filter (not shown) that purifies and introduces fresh air may be provided at the upstream end of the intake passage 3 in the intake direction.

[0024] The exhaust passage 4 is connected to an exhaust port 23 of each cylinder 12 of the engine 2, and exhaust gas generated in each cylinder 12 is discharged through the exhaust port 23. An exhaust bypass flow path 4a is provided in the exhaust passage 4, which communicates between the upstream side and downstream side of the turbocharger 5 in the exhaust direction, and an exhaust bypass valve 4b is provided in the exhaust bypass flow path 4a for adjusting the flow rate of the exhaust gas.

[0025] The exhaust bypass valve 4b has its opening adjusted by being controlled by the control unit 9, and the amount of air compressed by the turbocharger 5 can be adjusted by adjusting the flow rate of exhaust gas flowing into the turbocharger 5 according to the opening rate of the exhaust bypass valve 4b. That is, by adjusting the opening rate of the exhaust bypass valve 4b, the flow rate of air supplied from the intake passage 3 to the intake port 22 can be adjusted.

[0026] The turbocharger 5 compresses the air flowing through the intake passage 3 and sends it downstream in the intake direction, and the intercooler 6 cools the air compressed by the turbocharger 5. The turbocharger 5 has a turbine 5a and a compressor 5b. The turbine 5a is disposed in the exhaust passage 4, and the compressor 5b is disposed in the intake passage 3. The turbine 5a is rotated by the exhaust gas flowing through the exhaust passage 4, and the compressor 5b is driven by the rotational force of the turbine 5a, thereby compressing the air flowing through the intake passage 3.

[0027] The first recirculation device 7 recirculates exhaust gas flowing through the exhaust passage 4 and supplies it to the intake passage 3. The first recirculation device 7 is connected to the exhaust passage 4 downstream of the turbocharger 5 (turbine 5a) in the exhaust direction, and is connected to the intake passage 3 upstream of the turbocharger 5 (compressor 5b) in the intake direction.

[0028] The first recirculation device 7 is configured to include, for example, a first recirculation cooler 7a and a first recirculation valve 7b. The first recirculation device 7 cools the exhaust gas flowing through the exhaust passage 4 downstream of the turbocharger 5 in the exhaust direction by the first recirculation cooler 7a, recirculates the exhaust gas, and supplies the exhaust gas to the intake passage 3 upstream of the turbocharger 5 in the intake direction. The first recirculation valve 7b is controlled by the control unit 9 to adjust its opening, and the amount of oxygen in the air flowing through the intake passage 3 can be adjusted by adjusting the flow rate of the recirculated exhaust gas flowing into the intake passage 3 according to the opening of the first recirculation valve 7b.

[0029] The second recirculation device 8 recirculates exhaust gas flowing through the exhaust passage 4 and supplies it to the intake passage 3. The second recirculation device 8 is connected to the exhaust passage 4 upstream of the turbocharger 5 (turbine 5a) in the exhaust direction, and is connected to the intake passage 3 downstream of the intercooler 6 in the intake direction.

[0030] The second recirculation device 8 is configured to include, for example, a second recirculation cooler 8a and a second recirculation valve 8b. The second recirculation device 8 cools and recirculates exhaust gas flowing through the exhaust passage 4 upstream of the turbocharger 5 in the exhaust direction by the second recirculation cooler 8a, and supplies the exhaust gas to the intake passage 3 downstream of the intercooler 6 in the intake direction. The second recirculation valve 8b is controlled by the control unit 9 to adjust its opening, and the amount of oxygen in the air flowing through the intake passage 3 can be adjusted by adjusting the flow rate of the recirculated exhaust gas flowing into the intake passage 3 according to the opening of the second recirculation valve 8b.

[0031] The control unit 9 is a computer such as an ECU (Engine Control Unit) that controls the operation of the engine 2, and includes a CPU, ROM, RAM, etc., and is configured to control each part of the engine 2. The control unit 9 may store various programs for controlling the engine 2, and control the engine 2 by reading and executing the programs.

[0032] Incidentally, the engine device 1 can be operated by switching between an operation mode of a gas mode in which gas fuel is injected into the combustion chamber 12a and a diesel mode in which liquid fuel is injected into the combustion chamber 12a. The control unit 9 switches the operation mode automatically in response to the load of the engine 2, etc., or in response to an operation by a user.

[0033] In the gas mode, the fuel injected into the combustion chamber 12a is gaseous fuel injected by the gaseous fuel injection unit 16, but also contains a very small amount of liquid fuel as an ignition agent by the liquid fuel injection unit 17, i.e., the mixed combustion rate of the gaseous fuel contained in the fuel injected into the combustion chamber 12a is approximately 100%. In the diesel mode, the fuel injected into the combustion chamber 12a is liquid fuel injected by the liquid fuel injection unit 17, i.e., the mixed combustion rate of the gaseous fuel contained in the fuel injected into the combustion chamber 12a is 0%.

[0034] At this time, from the start of switching the operating mode from diesel mode to gas mode until the operating mode is completely switched, the control unit 9 controls the ratio of liquid fuel in the fuel injected into the combustion chamber 12a to gradually decrease from 100% to 0% and the ratio of gas fuel to gradually increase from 0% to 100%, i.e., controls the mixed combustion ratio of gas fuel.

[0035] In addition, from the time when the operation mode starts to be switched from gas mode to diesel mode until the operation mode is completely switched, the control unit 9 controls the ratio of liquid fuel in the fuel injected into the combustion chamber 12a to gradually increase from 0% to 100% and the ratio of gas fuel to gradually decrease from 100% to 0%, i.e., controls the mixed combustion ratio of gas fuel.

[0036] That is, during switching between the gas mode and the diesel mode, the fuel injected into the combustion chamber 12a is a mixture of gas fuel and liquid fuel.

[0037] Fig. 2 is a graph showing the maximum pressure of the combustion chamber 12a measured when the mixed-fuel ratio of gaseous fuel is changed at a constant engine load, and Fig. 3 is a graph showing the frequency of pre-ignition detected when the mixed-fuel ratio of gaseous fuel is changed at a constant engine load. According to these graphs, when the mixed-fuel ratio is in a predetermined range, the maximum pressure of the combustion chamber 12a tends to be higher than the allowable pressure and the frequency of pre-ignition tends to be relatively high. Therefore, such a range can be set as a danger range where abnormal combustion such as pre-ignition or knocking of the engine 2 is predicted.

[0038] Therefore, when the engine 2 is operated at a constant engine load while changing the mixed combustion ratio of the gaseous fuel, for example, when switching the operation mode, the control unit 9 executes avoidance control to avoid the danger area.

[0039] In the engine system 1, danger zones where abnormal combustion is predicted with respect to such changes in the mixed combustion ratio of gaseous fuel are set in advance and stored in the control unit 9. For example, as shown in Fig. 4, a danger zone map showing danger zones where abnormal combustion is predicted when the mixed combustion ratio of gaseous fuel is changed at a constant engine load is set in advance and stored in the control unit 9. Note that the control unit 9 may store danger zone maps in advance for various operating environments such as the temperature of air taken into the engine 2 (ambient temperature of the engine system 1) and the oxygen excess rate (proportion of oxygen in the air according to the environmental altitude of the engine system 1, such as lowlands or highlands).

[0040] As an avoidance control for avoiding the danger area described above, the control unit 9, when changing the mixed-fuel ratio of the gaseous fuel, limits the change in the mixed-fuel ratio so as not to enter the danger area based on the danger area map. For example, when switching the operation mode at a predetermined engine load, the control unit 9 refers to the danger area map to determine whether or not there is a danger area of ​​the mixed-fuel ratio of the gaseous fuel corresponding to the engine load. At this time, the control unit 9 detects the engine load by the torque sensor 21. In addition, the control unit 9 detects the operating environment such as the air temperature and the oxygen excess rate, and acquires and refers to the danger area map corresponding to the operating environment as a result of the detection.

[0041] If it is determined that no dangerous area exists as a result of the above determination, the control unit 9 may completely switch the operation mode without executing avoidance control. On the other hand, if it is determined that a dangerous area exists, the control unit 9 performs avoidance control by setting an upper or lower limit for the change in the mixed combustion ratio of the gas fuel based on the dangerous area, and controlling the injection amount of the gas fuel by the gas fuel injection unit 16 and the injection amount of the liquid fuel by the liquid fuel injection unit 17.

[0042] For example, as shown in Fig. 4, when operating at a given engine load T1, if the gaseous fuel mixing ratio is gradually increased by switching from the diesel mode to the gaseous mode, the danger zone will be reached at the mixing ratio R1, so the control unit 9 sets the upper limit of the change in the gaseous fuel mixing ratio to be equal to or lower than the mixing ratio R1. Also, if the gaseous fuel mixing ratio is gradually decreased by switching from the gaseous mode to the diesel mode, the danger zone will be reached at the mixing ratio R2, so the control unit 9 sets the lower limit of the change in the gaseous fuel mixing ratio to be equal to or higher than the mixing ratio R2.

[0043] As described above, according to this embodiment, the engine device 1 is an engine device 1 that is driven by feeding at least one of gaseous fuel and liquid fuel into the combustion chamber 12a of the engine 2, and a danger zone in which abnormal combustion is predicted for the mixed-fuel ratio of the gaseous fuel contained in the fuel fed into the combustion chamber 12a is set in advance, and when the engine 2 is operated while changing the mixed-fuel ratio at a constant engine load, avoidance control is executed to avoid the danger zone.

[0044] As a result, when gaseous fuel and liquid fuel are fed into the combustion chamber 12a, the engine device 1 can operate while avoiding abnormal combustion in the engine 2 caused by the mixed combustion ratio of the gaseous fuel.

[0045] Furthermore, according to this embodiment, the engine device 1 preliminarily sets a danger region in the relationship between the engine load and the mixed combustion ratio of the gaseous fuel.

[0046] As a result, when the engine device 1 is operated at a specified engine load, it is possible to grasp the gas fuel combustion ratio corresponding to that engine load, and by avoiding a gas fuel combustion ratio that is in a dangerous range, it is possible to operate the engine 2 while avoiding abnormal combustion.

[0047] Further, according to the present embodiment, the engine device 1 performs avoidance control by restricting the change in the mixed combustion ratio of the gaseous fuel to the danger area.

[0048] As a result, when the engine device 1 is operated at a specified engine load, it is possible to more reliably prevent the mixed combustion ratio of the gaseous fuel from entering the danger range, thereby enabling the engine 2 to be operated while avoiding abnormal combustion.

[0049] In the above embodiment, an example has been described in which, in the engine device 1, the control unit 9, as an avoidance control for avoiding a danger area, limits the change in the mixed-combustion ratio of the gaseous fuel based on the danger area map when changing the mixed-combustion ratio so as not to enter the danger area. However, the present invention is not limited to this example.

[0050] As a first modification, the control unit 9 may perform avoidance control to change the operating conditions so as to eliminate or alleviate the danger area that limits the mixed combustion ratio of gaseous fuel. In other words, the control unit 9 performs control to reduce the danger area by changing the operating conditions, and for example, the control unit 9 can change the danger area map shown in Fig. 4 to a danger area map with a reduced danger area as shown in Fig. 5 by changing the operating conditions.

[0051] In the engine device 1, when the engine 2 is operated at a constant engine load while changing the mixed combustion ratio of the gaseous fuel, for example, when switching the operation mode, the maximum temperature (combustion temperature) of the combustion chamber 12a and the excess air ratio of the gaseous fuel (the ratio of air to gaseous fuel in the mixture) change. In the engine 2, abnormal combustion is likely to occur when the maximum temperature of the combustion chamber 12a becomes abnormally high, and when the excess air ratio of the gaseous fuel becomes low and the gaseous fuel becomes rich, the mixture is likely to ignite, so abnormal combustion is likely to occur.

[0052] For example, Fig. 6 is a graph showing the measured maximum temperature of the combustion chamber 12a with a square symbol and the calculated excess air ratio of the gaseous fuel with a triangle symbol when the mixed combustion ratio of the gaseous fuel is changed at a constant engine load. According to this graph, in the stable operation region A1 where the mixed combustion ratio of the gaseous fuel is relatively low (for example, 60% or less), the temperature of the combustion chamber 12a increases due to the combustion of the liquid fuel because the amount of the liquid fuel input is large, but abnormal combustion tends not to occur because the amount of the gaseous fuel input is small and lean. In addition, in the dangerous operation region A2 where the mixed combustion ratio of the gaseous fuel is higher than the stable operation region A1 (for example, 60% to 90%), the gaseous fuel may play a role as a combustion aid, so the temperature of the combustion chamber 12a increases sharply due to the combustion of the liquid fuel, and furthermore, because the amount of the gaseous fuel input is large and rich, the mixture is easily ignited, so abnormal combustion tends to occur easily. In addition, in the stable operation region A3 where the gas fuel mixing ratio is higher than that in the dangerous operation region A2 (for example, 90% or more), the amount of gas fuel input is large and rich, making the mixture easier to ignite, but the amount of liquid fuel input is small, so the combustion of the liquid fuel is slow and the temperature of the combustion chamber 12a does not become relatively high, and therefore abnormal combustion tends not to occur.

[0053] Therefore, when switching the operating mode at a specified engine load, the control unit 9 refers to the danger area map, and if it determines that a danger area of ​​the gas fuel mixing ratio corresponding to that engine load exists, it is preferable to eliminate or alleviate the danger area that limits the gas fuel mixing ratio by changing the operating conditions to increase the maximum temperature of the combustion chamber 12a and / or the excess air ratio of the gas fuel.

[0054] For example, the control unit 9 can control the internal temperature of the combustion chamber 12a to be lowered by controlling the injection pressure, injection timing, number of injections, etc. of the liquid fuel by the liquid fuel injection unit 17 as the operating conditions. Also, the control unit 9 can control the internal temperature of the combustion chamber 12a to be lowered by controlling the injection pressure, injection timing, etc. of the gas fuel by the gas fuel injection unit 16 as the operating conditions. Also, the control unit 9 can detect the rotation speed of the engine 2 by the rotation speed sensor 20 and calculate the engine output based on the rotation speed of the engine 2, and can control the internal temperature of the combustion chamber 12a and the excess air ratio of the gas fuel to be increased by feedback control of the engine output.

[0055] The control unit 9 may change at least one of the injection pressure of the liquid fuel, the injection timing of the liquid fuel, the number of injections of the liquid fuel, the injection pressure of the gas fuel, the injection timing of the gas fuel, and the engine output, or may change a combination of two or more of them.

[0056] Furthermore, the control unit 9 controls the turbocharger 5, the intercooler 6, the first recirculation device 7, the second recirculation device 8, the exhaust bypass valve 4b, the intake valve 24, etc., to control the internal temperature of the combustion chamber 12a and the excess air ratio of the gaseous fuel to be increased by lowering the intake air temperature in the combustion chamber 12a, raising the intake air pressure, increasing the intake air amount, or raising the specific heat of the intake air, as operating conditions.

[0057] In addition, the control unit 9 may change at least one of the intake air temperature of the combustion chamber 12a, the intake air pressure of the combustion chamber 12a, the intake air volume of the combustion chamber 12a, and the specific heat of the intake air of the combustion chamber 12a, or may change a combination of two or more of them.

[0058] For example, the control unit 9 can directly lower the internal temperature of the combustion chamber 12a by lowering the temperature of the air supplied to the combustion chamber 12a from the intake passage 3 and the intake port 22 through control of the flow rate of air passing through the intercooler 6, control of the opening and closing timing of the intake valve 24, or control of the amount of cooling water or lubricating oil, thereby slowing down the combustion in the combustion chamber 12a and suppressing abnormal combustion.

[0059] In addition, the control unit 9 controls the exhaust bypass valve 4b and the compressor 5b of the turbocharger 5 to increase the density of the air supplied to the combustion chamber 12a from the intake passage 3 and the intake port 22, thereby reducing the ratio of gaseous fuel injected into the combustion chamber 12a, thereby suppressing abnormal combustion.

[0060] In addition, the control unit 9 increases the amount of air supplied to the combustion chamber 12a from the intake passage 3 and the intake port 22 by controlling the flow rate of air passing through the intercooler 6, controlling the opening and closing timing of the intake valve 24, and controlling the exhaust bypass valve 4b and the compressor 5b of the turbocharger 5, thereby reducing the ratio of gaseous fuel injected into the combustion chamber 12a and suppressing abnormal combustion.

[0061] In addition, the control unit 9 increases the specific heat of the air supplied to the combustion chamber 12a from the intake passage 3 and the intake port 22 by controlling the first recirculation device 7 and the second recirculation device 8, or by adjusting the humidity by water injection, etc., thereby making the air contain a lot of carbon dioxide or water vapor, for example, and thereby lowering the internal temperature of the combustion chamber 12a during compression, thereby suppressing abnormal combustion.

[0062] As described above, according to the first modification, the engine device 1 can increase the maximum temperature of the combustion chamber 12a and / or the excess air ratio of the gaseous fuel by performing avoidance control to change at least one of the operating conditions, which are the injection pressure of the liquid fuel, the injection timing of the liquid fuel, the number of injections of the liquid fuel, the injection pressure of the gaseous fuel, the injection timing of the gaseous fuel, and the engine output. In addition, the engine device 1 can increase the maximum temperature of the combustion chamber 12a and / or the excess air ratio of the gaseous fuel by performing avoidance control to change at least one of the operating conditions, which are the intake air temperature of the combustion chamber 12a, the intake air pressure of the combustion chamber 12a, the intake air amount of the combustion chamber 12a, and the specific heat of the intake air of the combustion chamber 12a. Therefore, the danger area that limits the mixed combustion ratio of the gaseous fuel can be abolished or relaxed, and the danger area in the danger area map can be made smaller, so that the range in which the mixed combustion ratio can be changed can be made larger even when the change in the mixed combustion ratio of the gaseous fuel is limited so as not to enter the danger area.

[0063] As a second modification, when a danger zone exists between the current and target combustion ratios when changing the combustion ratio of the gaseous fuel, the control unit 9 may perform avoidance control to change the combustion ratio of the gaseous fuel so as to avoid (jump) the combustion ratio within the danger zone. In this case, in order to change the combustion ratio of the gaseous fuel while avoiding the danger zone, the control unit 9 may calculate the total input heat amount of the liquid fuel and the gaseous fuel at the current combustion ratio and convert it into the input heat amount of the liquid fuel and the gaseous fuel at the target combustion ratio.

[0064] For example, as shown in Fig. 4, when operating at a certain engine load T1, if the control unit 9 switches from diesel mode to gas mode and gradually increases the gaseous fuel mixing ratio, the target mixing ratio is 100%, but the danger zone is reached at mixing ratio R1 and continues up to mixing ratio R2. In this case, when the gaseous fuel mixing ratio reaches or approaches mixing ratio R1, the control unit 9 jumps over the danger zone and sets the gaseous fuel mixing ratio to R2 or higher, thereby avoiding the mixing ratio in the danger zone and changing the mixing ratio.

[0065] Furthermore, when the control unit 9 switches from the gas mode to the diesel mode and gradually lowers the gaseous fuel mixing ratio, the target mixing ratio is 0%, but the danger zone is reached at mixing ratio R2 and the danger zone continues up to mixing ratio R1. In this case, when the gaseous fuel mixing ratio reaches or approaches mixing ratio R2, the control unit 9 jumps over the danger zone and sets the gaseous fuel mixing ratio to be equal to or lower than mixing ratio R1, thereby changing the mixing ratio and avoiding the mixing ratio in the danger zone.

[0066] As described above, according to the second modification, the engine device 1 performs avoidance control to change the gaseous fuel combustion ratio beyond the danger zone, and therefore, by more reliably preventing the gaseous fuel combustion ratio from entering the danger zone, it is possible to operate the engine 2 while avoiding abnormal combustion. In addition, since the gaseous fuel combustion ratio can be changed to the target combustion ratio, the operation mode can be completely switched.

[0067] In the above embodiment, the engine device 1 is configured to switch between an operation mode of a gas mode in which gas fuel is injected into the combustion chamber 12a and a diesel mode in which liquid fuel is injected into the combustion chamber 12a, but the present invention is not limited to this example. In another example, the engine device 1 may be configured to operate in a multi-combustion mode in which both gas fuel and liquid fuel are injected into the combustion chamber 12a as another operation mode.

[0068] In addition, the present invention can be modified as appropriate within the scope that does not contradict the gist or concept of the invention that can be read from the claims and the entire specification, and engine devices involving such modifications are also included in the technical concept of the present invention.

[0069] [Appendix to the invention] The following will provide an overview of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0070] <Appendix 1> An engine device that is driven by injecting at least one of gas fuel and liquid fuel into a combustion chamber, A danger zone in which abnormal combustion is predicted for a mixed combustion ratio of the gaseous fuel contained in the fuel charged into the combustion chamber is set in advance; An engine device characterized in that the danger area is avoided when the engine is operated.

[0071] <Appendix 2> 2. The engine device according to claim 1, wherein when the engine is operated while changing the mixed-fuel ratio, avoidance control is executed to avoid the danger area.

[0072] <Appendix 3> 3. The engine device according to claim 1, wherein the danger area is preset in relation to an engine load and the mixed combustion ratio.

[0073] <Appendix 4> 4. The engine device according to claim 1, wherein the avoidance control includes limiting a change in the mixed-fuel ratio with respect to the danger area.

[0074] <Appendix 5> The engine device according to any one of appendices 1 to 4, characterized in that as the avoidance control, at least one of the injection pressure of the liquid fuel, the injection timing of the liquid fuel, the number of injections of the liquid fuel, the injection pressure of the gas fuel, the injection timing of the gas fuel, and the engine output is changed.

[0075] <Appendix 6> The engine device according to any one of appendixes 1 to 5, characterized in that, as the avoidance control, at least one of an intake air temperature of the combustion chamber, an intake air pressure of the combustion chamber, an intake air amount of the combustion chamber, and a specific heat of the intake air of the combustion chamber is changed.

[0076] <Appendix 7> The engine device according to any one of appendices 1 to 6, wherein, as the avoidance control, when the danger area exists between the current fuel-mixture ratio and a target fuel-mixture ratio when the fuel-mixture ratio is changed, the fuel-mixture ratio is changed while avoiding the fuel-mixture ratio in the danger area.

[0077] <Appendix 7> 8. The engine device according to claim 1, wherein the gaseous fuel is hydrogen. [Explanation of symbols]

[0078] 1 Engine unit 2 Engine 3 Intake passage 4 Exhaust passage 4a Exhaust bypass passage 4b Exhaust bypass valve 5. Turbocharger 5a Turbine 5b Compressor 6 Intercooler 7 1st recirculation device 7a First recirculation cooler 7b First recirculation valve 8 Second recirculation device 8a Second recirculation cooler 8b Second recirculation valve 9. Control Unit 11 Cylinder block 12 cylinders 12a Combustion chamber 13 Cylinder 14 Piston 15 Cylinder head 16 Gas fuel injection section 17 Liquid fuel injection part 18 Connecting rod 19 Crankshaft 20 Rotational speed sensor 21 Torque sensor 22 Intake port 23 Exhaust port 24 Intake valve 25 Exhaust valve

Claims

1. An engine device that is driven by injecting at least one of gas fuel and liquid fuel into a combustion chamber, A danger zone in which abnormal combustion is predicted for a mixed combustion ratio of the gaseous fuel contained in the fuel charged into the combustion chamber is set in advance; An engine device characterized in that the danger area is avoided when the engine is operated.

2. 2. The engine device according to claim 1, wherein, when the engine is operated while changing the mixed combustion ratio, an avoidance control is executed to avoid the danger area.

3. 2. The engine device according to claim 1, wherein the danger area is preset in relation to the engine load and the mixed combustion ratio.

4. The engine device according to claim 2 , wherein the avoidance control is to limit a change in the mixed combustion ratio with respect to the danger area.

5. 3. The engine device according to claim 2, wherein the avoidance control is performed by changing at least one of the injection pressure of the liquid fuel, the injection timing of the liquid fuel, the number of injections of the liquid fuel, the injection pressure of the gas fuel, the injection timing of the gas fuel, and the engine output.

6. 3. The engine device according to claim 2, wherein the avoidance control is performed by changing at least one of an intake air temperature of the combustion chamber, an intake air pressure of the combustion chamber, an intake air amount of the combustion chamber, and a specific heat of the intake air of the combustion chamber.

7. 3. The engine apparatus according to claim 2, wherein, as the avoidance control, when the danger area exists between the current fuel-fuel ratio and the target fuel-fuel ratio when the fuel-fuel ratio is changed, the fuel-fuel ratio is changed while avoiding the fuel-fuel ratio in the danger area.

8. 2. The engine system according to claim 1, wherein the gaseous fuel is hydrogen.

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