Control method and control device for a rotary piston engine

Abstract

In systems including rotary piston engines, the catalytic converter is rapidly heated. [Solution] The control method for the rotary piston engine 2 involves the first injector 51 injecting fuel into the working chamber of the first housing 23 of the first rotor 21 so that an air-fuel ratio distribution in the direction of rotor rotation is created, and the second injector 52 injecting fuel into the working chamber of the second housing 24 of the second rotor 22 so that an air-fuel ratio distribution in the direction of rotor rotation is created, causing the air-fuel ratio of the exhaust discharged from the first housing to periodically fluctuate between rich and lean, and the air-fuel ratio of the exhaust discharged from the second housing to periodically fluctuate between rich and lean in the opposite phase to the exhaust from the first housing, and the turbine 32 of the turbocharger 3 mixes the exhaust discharged from the first housing and the exhaust discharged from the second housing, and the exhaust, which has become hot due to the oxidation reaction after mixing, heats up the catalytic converter 39.

Description

Technical Field

[0001] The technology disclosed herein relates to a control method for a rotary piston engine and a control device for a rotary piston engine.

Background Art

[0002] Patent Document 1 describes a conventional rotary piston engine. This rotary piston engine includes two rotors. The exhaust gas discharged from the housings of the two rotors rotates the turbine of a turbocharger and is then purified by a catalytic device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in general internal combustion engines including rotary piston engines, when the catalytic converter is inactive, a warm-up operation of the catalytic converter is performed. During the warm-up operation, generally, the ignition timing is retarded so that the temperature of the exhaust gas discharged from the internal combustion engine becomes high. However, in a rotary piston engine, an operating chamber moves around an eccentric shaft as the rotor rotates, and an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke are performed. The spark plug is located near the short axis of the housing so that forced ignition can be performed on the air-fuel mixture in the operating chamber during the compression stroke or the expansion stroke. There is a limit to the retardation of the ignition timing due to the structure of the rotary piston engine. In a rotary piston engine, it is difficult to significantly increase the temperature of the exhaust gas discharged from the housing by retarding the ignition timing.

[0005] Furthermore, the exhaust gas discharged from the rotary piston engine housing cools down as it passes through the turbine. The temperature of the exhaust gas supplied to the catalytic converter cools down even further. This decrease in exhaust temperature is detrimental to the warm-up of the catalytic converter.

[0006] The technology disclosed herein rapidly raises the temperature of a catalytic converter in a system including a rotary piston engine. [Means for solving the problem]

[0007] The technology disclosed herein relates to a method for controlling a rotary piston engine. The method for controlling a rotary piston engine includes the following steps: During the warm-up period of the catalytic converter, the first injector injects fuel into the working chamber of the first housing of the first rotor so that an air-fuel ratio distribution is created in the direction of rotor rotation. During the warm-up operation, the second injector injects fuel into the working chamber of the second housing of the second rotor, which is in a different phase from the first rotor, so that an air-fuel ratio distribution in the direction of rotor rotation is created. The air-fuel ratio of the exhaust gas discharged from the first housing fluctuates periodically between rich and lean due to the air-fuel ratio distribution in the operating chamber, and the air-fuel ratio of the exhaust gas discharged from the second housing fluctuates periodically between rich and lean in the opposite phase to that of the exhaust gas from the first housing due to the air-fuel ratio distribution in the operating chamber. The turbine of the turbocharger mixes the exhaust gas discharged from the first housing with the exhaust gas discharged from the second housing. The exhaust gas, which becomes hot due to the oxidation reaction after mixing, raises the temperature of the catalytic converter located downstream of the turbine.

[0008] During the warm-up period of the catalytic converter, fuel is injected into the working chambers of both the first and second housings so that an air-fuel ratio distribution is created in each. This air-fuel ratio distribution refers to the presence of regions within the working chamber with relatively high fuel concentrations and regions with relatively low fuel concentrations. The air-fuel ratio distribution is in the direction of rotor rotation. Because the working chamber of a rotary piston engine has an elongated shape in the direction of rotor rotation, an air-fuel ratio distribution in the direction of rotor rotation is relatively easy to form. Furthermore, because the air-fuel ratio distribution is in the direction of rotor rotation, the air-fuel ratio of the exhaust gas discharged from the first housing fluctuates periodically between rich and lean as the rotor rotates. In other words, exhaust gas with a relatively high proportion of unburned fuel and exhaust gas with a relatively high proportion of air are alternately discharged from the first housing.

[0009] Similarly, exhaust gases with a relatively high proportion of unburned fuel and exhaust gases with a relatively high proportion of air are discharged alternately from the second housing. Here, because the first rotor and the second rotor are in different phases, the exhaust gas discharged from the second housing fluctuates periodically between rich and lean in the opposite phase to the exhaust gas from the first housing.

[0010] The turbine of a turbocharger mixes exhaust gases discharged from the first housing with exhaust gases discharged from the second housing. As mentioned above, the air-fuel ratio of the exhaust gases discharged from the first housing and the air-fuel ratio of the exhaust gases discharged from the second housing fluctuate periodically between rich and lean in opposite phases. At one point, the exhaust gases discharged from the first housing, which contain a relatively large amount of unburned fuel, are mixed with the exhaust gases discharged from the second housing, which contain a relatively large amount of air. At another point, the exhaust gases discharged from the first housing, which contain a relatively large amount of air, are mixed with the exhaust gases discharged from the second housing, which contain a relatively large amount of unburned fuel. When unburned fuel and air are mixed in a relatively high-temperature environment, an oxidation reaction of the fuel occurs, further increasing the temperature of the exhaust gases.

[0011] The even hotter exhaust gas is supplied to the catalytic converter downstream of the turbine. The temperature of the catalytic converter rises rapidly. The catalytic converter activates quickly. The exhaust emission performance of the system, including the rotary piston engine, is improved.

[0012] According to this rotary piston engine control method, unburned fuel is oxidized between the rotary piston engine and the catalytic converter, increasing the exhaust temperature. Even if the exhaust temperature discharged from the rotary piston engine housing is not very high, a high-temperature exhaust can be supplied to the catalytic converter.

[0013] Furthermore, the exhaust gas discharged from the first housing and the exhaust gas discharged from the second housing are mixed in the turbine, causing the exhaust gas to become hotter, which suppresses the transfer of heat energy to the turbine. Because the temperature drop of the exhaust gas is suppressed, a hotter exhaust gas can be supplied to the catalytic converter.

[0014] As a result, in systems including rotary piston engines, the catalytic converter heats up rapidly.

[0015] The first injector injects fuel so that the overall air-fuel ratio in the operating chamber becomes the stoichiometric air-fuel ratio. The second injector may inject fuel such that the overall air-fuel ratio in the operating chamber becomes the stoichiometric air-fuel ratio.

[0016] Although air-fuel ratio distributions occur in both the first and second housings, the overall air-fuel ratio in the working chamber is the stoichiometric air-fuel ratio. The air-fuel ratio after the exhaust gases discharged from the first and second housings are mixed is the stoichiometric air-fuel ratio. Having a stoichiometric air-fuel ratio in the exhaust is advantageous for exhaust gas purification by catalytic converters, such as those containing a three-way catalytic converter.

[0017] During the warm-up operation, the first injector injects fuel such that the air-fuel ratio on the advancing angle side in the rotor rotation direction becomes relatively rich and the air-fuel ratio on the retarding angle side in the rotor rotation direction becomes relatively lean. During the warm-up operation, the second injector may inject fuel such that the air-fuel ratio on the advancing angle side in the rotor rotation direction becomes relatively rich and the air-fuel ratio on the retarding angle side in the rotor rotation direction becomes relatively lean.

[0018] In the working chamber, with the rotation of the rotor, a flow from the retarding angle side to the advancing angle side occurs. The fuel injected into the working chamber rides on the flow in the working chamber and is likely to move from the retarding angle side to the advancing angle side. In a rotary piston engine, an air-fuel ratio distribution in which the air-fuel ratio on the advancing angle side in the rotor rotation direction becomes relatively rich and the air-fuel ratio on the retarding angle side in the rotor rotation direction becomes relatively lean is relatively easily formed. <000007​​​​​​​​​​​​​​​​​​​​​ The first injector injects fuel into the working chamber in the intake stroke or the compression stroke, on the advanced angle side in the rotor rotation direction with respect to the major axis of the first housing. The second injector may inject fuel into the working chamber in the intake stroke or the compression stroke, on the advanced angle side in the rotor rotation direction with respect to the major axis of the second housing.

[0024] Injecting fuel into the working chamber in the intake stroke or the compression stroke, on the advanced angle side in the rotor rotation direction, is advantageous for forming an air-fuel ratio distribution in which the air-fuel ratio on the advanced angle side in the rotor rotation direction becomes relatively rich and the air-fuel ratio on the retarded angle side in the rotor rotation direction becomes relatively lean.

[0025] The injection holes of the first injector are located on the advanced angle side in the rotor rotation direction with respect to the major axis of the first housing. The injection holes of the second injector may be located on the advanced angle side in the rotor rotation direction with respect to the major axis of the second housing.

[0026] When the injection holes of the injector are located on the advanced angle side in the rotor rotation direction with respect to the major axis of the housing, the timing at which the apex seal of the rotor passes through the injection holes of the injector is relatively late. The period during which the injector can inject fuel into the working chamber is extended. The extension of the injection possible period increases the degree of freedom in setting the injection timing of the injector, which is advantageous for forming the air-fuel ratio distribution in the rotor rotation direction.

[0027] During the warm-up operation, the first spark plug forcibly ignites the air-fuel mixture in the working chamber at a timing after the timing when the working chamber of the first housing is at the compression top dead center. <id= During the warm-up operation, the second spark plug may forcibly ignite the air-fuel mixture in the working chamber at a timing after the timing when the working chamber of the second housing is at the compression top dead center.

[0028] Because the ignition timing of the first and second spark plugs is delayed, the time from ignition to the start of exhaust is short. The temperature of the exhaust gases discharged from the first and second housings increases. Furthermore, retarding the ignition timing increases the amount of unburned fuel discharged from the first and second housings. The increase in unburned fuel promotes the oxidation reaction of the exhaust gases after they have been mixed by the turbine, and also favors the temperature rise of the exhaust gases associated with the oxidation reaction.

[0029] The first spark plug, during normal operation of the engine without warm-up, forcibly ignites the air-fuel mixture in the working chamber of the first housing at a timing earlier than when the working chamber is at top dead center of compression. The second spark plug may, during normal operation, forcibly ignite the air-fuel mixture in the working chamber of the second housing at a timing earlier than when the working chamber is at top dead center of compression.

[0030] During normal engine operation without warming up the catalytic converter, the first and second spark plugs ignite the air-fuel mixture at a relatively earlier timing. This relatively earlier ignition timing is advantageous for improving the output or fuel efficiency of a rotary piston engine during normal operation.

[0031] During the warm-up operation, the throttle valve may be opened to a greater degree than required during normal operation of the engine without the warm-up operation.

[0032] During warm-up, the throttle valve is opened relatively wide, increasing the amount of air introduced into the operating chamber. This accelerates the oxidation reaction of the exhaust gas after it has been mixed by the turbine. The wide throttle valve opening is also advantageous for rapid temperature rise of the catalytic converter.

[0033] The warm-up operation may be performed if the coolant temperature of the rotary piston engine is between a first predetermined temperature and a second predetermined temperature, and the estimated temperature of the catalytic converter is below a third predetermined temperature.

[0034] If the coolant temperature of the rotary piston engine is below the first predetermined temperature, the rotary piston engine is cold, and the mixture distribution formed in the working chamber may worsen combustion stability. If the coolant temperature exceeds the second predetermined temperature, the rotary piston engine is warmed up, and it can be assumed that the temperature of the catalytic converter is also high. Performing warm-up operation with a high catalytic converter temperature may damage the catalytic converter.

[0035] The warm-up of the catalytic converter can be properly performed based on the coolant temperature of the rotary piston engine and the estimated temperature of the catalytic converter.

[0036] The control device for the rotary piston engine disclosed herein is A rotary piston engine having a first housing for a first rotor and a second housing for a second rotor having a different phase from the first rotor, A first injector that injects fuel into the working chamber of the first housing, A second injector that injects fuel into the working chamber of the second housing, A turbocharger comprising a first exhaust passage connected to the first housing and a second exhaust passage connected to the second housing, each connected to a turbine that rotates due to the exhaust flow discharged from the first housing and the second housing, A catalytic converter connected to the turbine via a third exhaust passage and for purifying the exhaust gas that has passed through the turbine, The system includes a controller that outputs control signals to the first injector and the second injector, The controller controls the first injector so that an air-fuel ratio distribution in the rotor rotation direction is generated in the working chamber of the first housing while the rotary piston engine is warming up the catalytic converter, and controls the second injector so that an air-fuel ratio distribution in the rotor rotation direction is generated in the working chamber of the second housing. During the warm-up operation, the air-fuel ratio of the exhaust discharged from the first housing fluctuates periodically between rich and lean due to the air-fuel ratio distribution in the operating chamber, and the air-fuel ratio of the exhaust discharged from the second housing fluctuates periodically between rich and lean in the opposite phase to that of the exhaust from the first housing due to the air-fuel ratio distribution in the operating chamber.

[0037] This control device generates an air-fuel ratio distribution in the rotor rotation direction within the working chambers of the first and second housings during the warm-up of the catalytic converter. The air-fuel ratio of the exhaust gases discharged from the first and second housings periodically fluctuates between rich and lean, causing the exhaust gases mixed by the turbine to undergo an oxidation reaction, and the resulting high-temperature exhaust gases can be supplied to the catalytic converter. The rotary piston engine control device allows the catalytic converter to be heated rapidly. [Effects of the Invention]

[0038] The aforementioned control method and control device for the rotary piston engine can rapidly raise the temperature of the catalytic converter. [Brief explanation of the drawing]

[0039] [Figure 1] Figure 1 shows an engine system including a rotary piston engine. [Figure 2] Figure 2 is a cross-sectional view of a rotary piston engine. [Figure 3] Figure 3 shows the boost map for a turbocharger. [Figure 4] Figure 4 is a functional block diagram related to the control system of a rotary piston engine. [Figure 5] Figure 5 shows the control map related to the warm-up operation of the catalytic converter. [Figure 6] Figure 6 is a time chart illustrating the fluctuations in the exhaust air-fuel ratio during the warm-up period of the catalytic converter. [Figure 7] Figure 7 is a flowchart showing the control procedure related to the warm-up operation of the catalytic converter. [Figure 8] Figure 8 is a cross-sectional view of a modified rotary piston engine. [Modes for carrying out the invention]

[0040] The following describes embodiments of a control method and control device for a rotary piston engine with reference to the drawings. The control method and control device for a rotary piston engine described herein are illustrative examples.

[0041] (Overall configuration of the engine system) Figure 1 shows engine system 1. Engine system 1 is mounted on a four-wheeled vehicle. Engine system 1 generates driving force for the four-wheeled vehicle or driving force for power generation. Engine system 1 includes a control device for the rotary piston engine 2.

[0042] The engine system 1 includes a rotary piston engine 2. The rotary piston engine 2 has two rotors, a first rotor 21 and a second rotor 22. The first rotor 21 and the second rotor 22 have different rotational phases. The first rotor 21 is housed in a first housing 23, and the second rotor 22 is housed in a second housing 24. Details of the structure of the rotary piston engine 2 will be described later.

[0043] The engine system 1 includes an intake passage 11. The intake passage 11 is connected to a rotary piston engine 2. The intake passage 11 supplies intake air to the rotary piston engine 2.

[0044] The compressor 31 of the turbocharger 3 is located in the middle of the intake passage 11. The compressor 31 compresses the intake air.

[0045] The intercooler 12 is located downstream of the compressor 31 in the intake passage 11. The intercooler 12 cools the intake air compressed by the compressor 31.

[0046] The throttle valve 13 is located downstream of the intercooler 12 in the intake passage 11. The throttle valve 13 adjusts the amount of intake air supplied to the rotary piston engine 2.

[0047] Downstream of the throttle valve 13, the intake passage 11 has a first intake pipe 14 and a second intake pipe 15. The first intake pipe 14 and the second intake pipe 15 are each connected to the throttle valve 13 and are independent of each other. The first intake pipe 14 is connected to a primary intake port 41, which will be described later. The rotary piston engine 2 has two primary intake ports 41: one corresponding to the first rotor 21 and another corresponding to the second rotor 22. The first intake pipe 14 branches into two midway and is connected to each of the two primary intake ports 41.

[0048] The second intake pipe 15 is connected to the secondary intake port 42, which will be described later. The rotary piston engine 2 has two secondary intake ports 42: one corresponding to the first rotor 21 and another corresponding to the second rotor 22. The second intake pipe 15 branches into two midway and is connected to each of the two secondary intake ports 42.

[0049] An on / off valve 16 is installed in the middle of the second intake pipe 15. The on / off valve 16 opens and closes the second intake pipe 15. The on / off valve 16 closes, for example, when the engine speed is low and the engine load is high, and opens in other cases.

[0050] The engine system 1 includes an exhaust passage 17. The exhaust passage 17 is connected to the rotary piston engine 2. The exhaust passage 17 discharges exhaust from the rotary piston engine 2. The rotary piston engine 2 has a side exhaust port 43 and a peripheral exhaust port 44, as will be described later. The exhaust passage 17 includes an exhaust pipe 18 connected to the side exhaust port 43 and an exhaust pipe 19 connected to the peripheral exhaust port 44.

[0051] The rotary piston engine 2 has two side exhaust ports 43: one corresponding to the first rotor 21 and another corresponding to the second rotor 22. The exhaust pipe 18 includes two independent exhaust pipes 18 connected to each of the two side exhaust ports 43. Of the two exhaust pipes 18, the exhaust pipe 18 on the first rotor 21 side corresponds to a first exhaust passage connecting the first housing 23 and the turbine 32, and the exhaust pipe 18 on the second rotor 22 side corresponds to a second exhaust passage connecting the second housing 24 and the turbine 32.

[0052] The rotary piston engine 2 has two peripheral exhaust ports 44: one corresponding to the first rotor 21 and another corresponding to the second rotor 22. The exhaust pipe 19 is connected to each of the two peripheral exhaust ports 44 and merges into one along the way.

[0053] The turbine 32 of the turbocharger 3 is located in the middle of the exhaust passage 17. Two exhaust pipes 18 are connected to the turbine 32. The turbine 32 is a so-called twin-scroll turbine. The turbine housing is divided into two spaces. The two exhaust pipes 18 are connected to each of the two spaces of the turbine housing. The exhaust pipe 19 bypasses the turbine 32.

[0054] The turbocharger 3 has a bypass passage 37. The bypass passage 37 is connected to each of the two exhaust pipes 18 and is a passage that bypasses the turbine 32. The turbocharger 3 also has a wastegate valve 35. The wastegate valve 35 opens and closes the bypass passage 37. A valve actuator 36 opens and closes the wastegate valve 35.

[0055] The catalytic converter 39 is located downstream of the turbine 32 in the exhaust passage 17. The catalytic converter 39 purifies the exhaust gas. The catalytic converter 39 may include, for example, a three-way catalyst. The three-way catalyst oxidizes hydrocarbons and carbon monoxide in the exhaust gas to carbon dioxide and reduces nitrogen oxides to nitrogen. The exhaust passage 17 corresponds to a third exhaust passage connecting the turbine 32 and the catalytic converter 39.

[0056] The GPF (Gasoline Particulate Filter) 40 is located downstream of the catalytic converter 39 in the exhaust passage 17. The GPF 40 captures particulate matter (PM) in the exhaust.

[0057] The rotary piston engine 2 has a first injector 51 and a second injector 52. The first injector 51 injects fuel into the first housing 23. The second injector 52 injects fuel into the second housing 24.

[0058] The rotary piston engine 2 has a first spark plug 53 and a second spark plug 54. The first spark plug 53 forces ignition of the fuel-air mixture in the first housing 23. The second spark plug 54 forces ignition of the fuel-air mixture in the second housing 24.

[0059] The engine system 1 includes an ECU (Engine Continuous Unit) 10. The ECU 10 is an example of a controller. The ECU 10 has a Central Processing Unit (CPU) 101, a memory 102, and an I / F circuit 103. The CPU 101 is a controller based on a well-known microcomputer and executes programs. The memory 102 is configured, for example, as RAM (Random Access Memory) and / or ROM (Read Only Memory) and stores programs and data. The I / F circuit 103 performs input and output of electrical signals.

[0060] The engine system 1 has various sensors. In detail, the engine system 1 has an airflow sensor 61. The airflow sensor 61 is located in the intake passage 11. The airflow sensor 61 outputs an electrical signal to the ECU 10 that corresponds to the flow rate of intake air flowing through the intake passage 11.

[0061] The engine system 1 has an accelerator pedal position sensor 62. The accelerator pedal position sensor 62 is attached to the accelerator pedal. The accelerator pedal position sensor 62 outputs an electrical signal to the ECU 10 that corresponds to the driver's accelerator pedal operation.

[0062] The engine system 1 has a boost pressure sensor 63. The boost pressure sensor 63 is located in the intake passage 11. The boost pressure sensor 63 outputs an electrical signal to the ECU 10 that corresponds to the pressure of the intake air boosted by the turbocharger 3.

[0063] The engine system 1 has an eccentric angle sensor 64. The eccentric angle sensor 64 is attached to the rotary piston engine 2. The eccentric angle sensor 64 outputs an electrical signal corresponding to the rotation angle of the eccentric shaft 25 (described later) of the rotary piston engine 2 to the ECU 10. The eccentric shaft 25 is the output shaft of the rotary piston engine 2.

[0064] The engine system 1 has a water temperature sensor 65. The water temperature sensor 65 is attached to the rotary piston engine 2. The water temperature sensor 65 outputs an electrical signal corresponding to the temperature of the coolant in the rotary piston engine 2 to the ECU 10.

[0065] The engine system 1 has an outside temperature sensor 66. The outside temperature sensor 66 outputs an electrical signal corresponding to the outside air temperature to the ECU 10.

[0066] The ECU 10 determines the operating state of the rotary piston engine 2 based on signals from these sensors 61 to 66. Depending on the operating state of the rotary piston engine 2, the ECU 10 outputs control signals to the throttle valve 13, the on / off valve 16, the first injector 51, the second injector 52, the first spark plug 53, the second spark plug 54, and / or the valve actuator 36 (see the dashed arrows in Figure 1).

[0067] (Structure of a rotary piston engine) Figure 2 shows the structure of the rotary piston engine 2. Figure 2 shows the first rotor 21 and the first housing 23 that houses the first rotor 21. The structure of the second rotor 22 and the second housing 24 that houses the second rotor 22 is the same as the structure of the first rotor 21 and the first housing 23.

[0068] The first housing 23 has a trochoidal inner surface 231. The first rotor 21 is generally triangular in shape. The first rotor 21 is supported to rotate planetarily relative to the eccentric shaft 25. The first rotor 21 rotates around the eccentric shaft 25 such that its three vertices move along the trochoidal inner surface 231. Apex seals 214 attached to the three vertices of the first rotor 21 maintain airtightness between adjacent working chambers. The interior of the first housing 23 is divided by the first rotor 21 into three working chambers: the first chamber 211, the second chamber 212, and the third chamber 213.

[0069] As the first rotor 21, indicated by the arrow in Figure 2, rotates, the first chamber 211, the second chamber 212, and the third chamber 213 shift around the eccentric shaft 25. The intake stroke, compression stroke, expansion stroke, and exhaust stroke are performed sequentially in each of the first chamber 211, the second chamber 212, and the third chamber 213.

[0070] More specifically, the first rotor 21 rotates clockwise in Figure 2. The first housing 23 is divided into upper left, upper right, lower right, and lower left regions by a major axis Y and a minor axis Z passing through the rotation center X. The working chamber performs roughly the intake stroke in the upper left region, roughly the compression stroke in the upper right region, roughly the expansion stroke in the lower right region, and roughly the exhaust stroke in the lower left region.

[0071] The first injector 51 is mounted in the first housing 23. The first injector 51 is mounted in the first housing 23 near the top where it intersects the long axis Y. More specifically, the injection hole 511 of the first injector 51 is located on the trochoidal inner surface 231 on the advance side of the rotor rotation direction relative to the long axis Y, that is, to the right of the long axis Y in Figure 2. The first injector 51 is mounted in the first housing 23 with its injection shaft oriented along the long axis Y. The injection direction of the first injector 51 is along the long axis Y. The first injector 51 injects fuel into the working chamber during the intake stroke or the compression stroke.

[0072] The first spark plug 53 is mounted on the right side wall of the first housing 23. The first spark plug 53 is positioned on the advance side in the rotor rotation direction relative to the minor axis Z, that is, below the minor axis Z in Figure 2. The first spark plug 53 forcibly ignites the air-fuel mixture in the working chamber during the compression stroke or expansion stroke. The rotary piston engine 2 may have two spark plugs, one in the first housing 23 and one in the second housing 24.

[0073] The primary intake port 41 and the secondary intake port 42 each open into the first housing 23. The openings of the primary intake port 41 and the secondary intake port 42 open and close in accordance with the rotation of the first rotor 21. The openings of the primary intake port 41 and the secondary intake port 42 are located in the upper left region of the first housing 23. The primary intake port 41 and the secondary intake port 42 communicate with the working chamber during the intake stroke.

[0074] The side exhaust port 43 opens into the first housing 23. The opening of the side exhaust port 43 opens and closes in accordance with the rotation of the first rotor 21. The opening of the side exhaust port 43 is located in the lower left region of the first housing 23. The side exhaust port 43 communicates with the working chamber during the exhaust stroke.

[0075] The peripheral exhaust port 44 opens into the inner circumferential surface 231 of the trochoid of the first housing 23. The opening of the peripheral exhaust port 44 opens and closes in accordance with the rotation of the first rotor 21. The opening of the peripheral exhaust port 44 is located in the lower left region of the first housing 23. The peripheral exhaust port 44 communicates with the working chamber during the exhaust stroke. The timing of the opening of the peripheral exhaust port 44 is later than the timing of the opening of the side exhaust port 43.

[0076] In the rotary piston engine 2, one stroke of one working chamber corresponds to a period of 270 degrees of rotation of the eccentric shaft 25. One cycle of one working chamber, including the intake stroke, compression stroke, expansion stroke, and exhaust stroke, corresponds to a period of 1080 degrees of rotation of the eccentric shaft 25. Furthermore, the second chamber 212 lags the first chamber 211 by 360 degrees in phase. The third chamber 213 lags the second chamber 212 by 360 degrees in phase. Also, the second rotor 22 lags the first rotor 21 by 180 degrees in phase.

[0077] (Warm-up of the catalytic converter) After the rotary piston engine 2 starts, if the catalytic converter 39 is inactive due to low temperature, it is necessary to activate the catalytic converter 39 early to prevent a decrease in the exhaust emission performance of the engine system 1. If the catalytic converter 39 is inactive, the engine system 1 performs a warm-up operation of the catalytic converter 39. Figure 3 illustrates the supercharging map 300 of the engine system 1. The supercharging map 300 is defined by the rotational speed of the rotary piston engine 2 and the torque of the rotary piston engine 2. The region where the torque of the rotary piston engine 2 is relatively low is the non-supercharging region, and the region where the torque is relatively high is the supercharging region. The AWS (Accelerated Warm-up System) region 301, where the warm-up operation of the catalytic converter 39 is performed, is within the non-supercharging region with low rotational speed and low torque.

[0078] The engine system 1 increases the temperature of the exhaust gas supplied to the catalytic converter 39 during the warm-up period of the catalytic converter 39. To this end, the engine system 1 induces an oxidation reaction in the exhaust gas between the turbine 32 and the catalytic converter 39. The engine system 1 increases the amount of unburned fuel and air in the exhaust gas discharged from the first housing 23 and the second housing 24 to promote the oxidation reaction. The control of the engine system 1 during the warm-up period of the catalytic converter 39 will be described below.

[0079] Figure 4 illustrates a functional block for controlling the warm-up operation of the catalytic converter 39. The ECU 10 has a first calculation unit 104 and a second calculation unit 105 as functional blocks for the warm-up operation of the catalytic converter 39. The first calculation unit 104 determines whether or not the catalytic converter 39 needs to be warmed up based on the estimated catalyst temperature 106 and the coolant temperature 107 of the rotary piston engine 2. Figure 5 is a control map 500 for the warm-up operation of the catalytic converter 39. The control map 500 is defined by the water temperature and the estimated catalyst temperature. The water temperature is based on a signal from the water temperature sensor 65. The estimated catalyst temperature is based on calculations by the second calculation unit 105, which will be described later.

[0080] The ECU 10 determines to warm up the catalytic converter 39 when the water temperature is between a first predetermined temperature Te1 and a second predetermined temperature Te2, and the estimated catalyst temperature is below a third predetermined temperature Tc. If the water temperature is below the first predetermined temperature Te1, the rotary piston engine 2 is in an extremely cold state, which reduces the combustion stability of the rotary piston engine 2. Therefore, the catalytic converter 39 is not warmed up. If the water temperature exceeds the second predetermined temperature Te2, the temperature of the rotary piston engine 2 is sufficiently high, and therefore the temperature of the catalytic converter 39 is also expected to be high. The estimated catalyst temperature estimated by the second calculation unit 105 may have reduced accuracy due to, for example, the loss of stored data due to battery replacement. Therefore, if the temperature of the rotary piston engine 2 is sufficiently high, the temperature of the catalytic converter 39 is also estimated to be high, and the catalytic converter 39 is not warmed up. Avoiding warm-up based on the coolant temperature suppresses damage to the catalytic converter 39.

[0081] The warm-up operation of the catalytic converter 39, described later, ends when the estimated catalyst temperature exceeds the third predetermined temperature Tc.

[0082] Returning to Figure 4, the second calculation unit 105 calculates the estimated catalyst temperature 106 from the water temperature 107, engine speed 108, ambient temperature 109, engine load 110, ignition timing 111, and engine stop time 112. The engine stop time 112 is the elapsed time from when the rotary piston engine 2 stops until it starts. The longer the engine stop time 112, the lower the estimated catalyst temperature 106. Alternatively, the engine system 1 may have a catalyst temperature sensor that measures the temperature of the catalytic converter 39 instead of calculating the estimated catalyst temperature 106.

[0083] The first calculation unit 104 also sets the throttle valve 13 opening degree 113, the fuel injection mode 114, and the ignition timing 111, respectively, based on the engine speed 108 of the rotary piston engine 2 when performing a warm-up operation of the catalytic converter 39.

[0084] During warm-up, the ECU 10 increases the opening degree 113 of the throttle valve 13 to a greater degree than required during normal operation without warm-up. In this case, normal operation corresponds to the idle operation of the rotary piston engine 2. If the opening degree of the throttle valve 13 is relatively large during warm-up, the amount of air introduced into the operating chamber of the rotary piston engine 2 increases. As will be described later, this increase in air volume is advantageous for the rapid temperature rise of the catalytic converter 39.

[0085] The ECU 10 changes the fuel injection pattern 114 from the injection pattern used during normal operation without warm-up. Specifically, during warm-up, the ECU 10 injects fuel into the working chamber all at once into the first injector 51 and the second injector 52 during one cycle. This all-at-once fuel injection creates an air-fuel ratio distribution in the working chamber in the direction of rotor rotation. More specifically, the air-fuel ratio distribution formed in the second chamber 212 in Figure 2, as shown by the shading, results in a relatively fuel-rich air-fuel ratio on the advance side of the rotor rotation direction in the working chamber, and a relatively fuel-lean air-fuel ratio on the retard side of the rotor rotation direction. Note that in Figure 2, an intermediate air-fuel ratio mixture is shown in the middle of the rotor rotation direction, but the air-fuel ratio distribution in the working chamber is not limited to three stages; it may be two stages, or the air-fuel ratio distribution may be continuous in the direction of rotor rotation.

[0086] The ECU 10 also injects fuel into the first injector 51 or the second injector 52 so that the overall air-fuel ratio in the working chamber is the stoichiometric air-fuel ratio, while forming an air-fuel ratio distribution in the direction of rotor rotation within the working chamber. By maintaining the stoichiometric air-fuel ratio, the catalytic converter 39, including the three-way catalyst, can purify the exhaust gas.

[0087] Figure 6 is a time chart illustrating the fluctuation of the exhaust air-fuel ratio during the warm-up of the catalytic converter 39. The horizontal axis in Figure 6 represents the rotation angle of the eccentric shaft 25, and when the rotational speed of the rotary piston engine 2 is constant, the horizontal axis in Figure 6 corresponds to the progression of time. As shown in 601 of Figure 6, the intake stroke (I), compression stroke (C), expansion stroke (E), and exhaust stroke (X) are performed sequentially in the first chamber 211, second chamber 212, and third chamber 213 of the first rotor 21. Similarly, as shown in 602 of Figure 6, the intake stroke (I), compression stroke (C), expansion stroke (E), and exhaust stroke (X) are performed sequentially in the first, second, and third chambers of the second rotor 22. The phase of the second rotor 22 is shifted by 180 degrees relative to the first rotor 21.

[0088] Figure 6 also illustrates the injection timing 71 (see 605) of the first injector 51 and the injection timing 72 (see 606) of the second injector 52. During warm-up, the first injector 51 or the second injector 52 injects fuel in a single burst toward the advanced region of the working chamber during the intake stroke or compression stroke. As shown in Figure 2, the nozzle 511 of the first injector 51 is located on the advanced side in the rotor rotation direction relative to the long axis Y of the first housing 23. The timing at which the apex seal 214 passes through the nozzle 511 of the first injector 51 is delayed compared to when the nozzle 511 of the first injector 51 is located in a position that coincides with the long axis Y. As shown in Figure 6, the period 73 during which the first injector 51 can inject fuel into the working chamber during warm-up is from the late intake stroke to the middle of the compression stroke. Note that the middle and late stages of the stroke refer to the middle and late stages when one stroke is divided into three equal parts: initial, middle, and late. If the injection period is 73, as shown in Figure 2, the distance between the injection hole 511 of the first injector 51 and the surface of the first rotor 21 having the recess 210 is wide. This allows for the formation of an air-fuel ratio distribution in the rotor rotation direction within the working chamber while suppressing the adhesion of fuel injected from the first injector 51 to the surface of the first rotor 21.

[0089] If the injection hole 511 of the first injector 51 is located in a position that coincides with the long axis Y, the timing at which the apex seal 214 passes through the injection hole 511 of the first injector 51 is relatively early. As illustrated in Figure 6, the injectable period 74 during which an air-fuel ratio distribution in the rotor rotation direction can be formed while suppressing fuel adhesion to the surface of the first rotor 21 is limited to a significantly shorter period during the intake stroke. Extending the injectable period 73 by offsetting the first injector 51 increases the degree of freedom in setting the injection timing, which is advantageous for forming an air-fuel ratio distribution in the rotor rotation direction. In the example in Figure 6, the injection timing of the first injector 51 is set to a relatively early timing within the injectable period 73, but the injection timing of the first injector 51 can be arbitrarily set within the injectable period 73.

[0090] Furthermore, the fuel injection pattern of the second injector 52 is the same as that of the first injector 51.

[0091] As will be described later, the air-fuel ratio distribution formed in the rotor rotation direction within the working chamber is advantageous for the rapid temperature rise of the catalytic converter 39.

[0092] Furthermore, during normal operation without warm-up, the ECU 10 causes the first injector 51 and the second injector 52 to perform split injection, injecting fuel into the working chamber multiple times during one cycle. The first injector 51 and the second injector 52 inject fuel multiple times during the intake stroke and / or compression stroke. Split fuel injection forms a homogeneous fuel mixture in the working chamber. The formation of a homogeneous fuel mixture is advantageous for improving the combustion stability of the rotary piston engine 2 and reducing exhaust emissions during normal operation.

[0093] Returning to Figure 4, the ECU 10 delays the ignition timing 111 compared to the ignition timing during normal operation without warm-up. Figures 605 and 606 also illustrate the ignition timing 75 for the first spark plug 53 and the ignition timing 76 for the second spark plug 54. Both ignition timings 75 and 76 are retarded after the compression top dead center (TDC). Retarding the ignition timing 111 increases exhaust losses, thus raising the temperature of the exhaust gas discharged from the rotary piston engine 2. Furthermore, retarding the ignition timing 111 shortens the time from ignition to the start of exhaust, thus increasing the amount of unburned fuel discharged from the rotary piston engine 2. The increase in exhaust temperature and the increase in unburned fuel are advantageous for the rapid temperature rise of the catalytic converter 39, as will be described later.

[0094] Furthermore, during normal operation without warm-up, the ECU 10 sets the ignition timing of the first spark plug 53 and the second spark plug 54 to an earlier timing than the compression top dead center (TDC). A relatively earlier ignition timing is advantageous for improving the output of the rotary piston engine 2 during normal operation.

[0095] By forcibly igniting the fuel-air mixture, the mixture burns in the working chamber during the expansion stroke, and then exhaust gas is discharged from the first housing 23 and the second housing 24. Figure 603 shows the variation in the air-fuel ratio of the exhaust gas discharged from the side exhaust port 43 of the first housing 23, and 604 shows the variation in the air-fuel ratio of the exhaust gas discharged from the side exhaust port 43 of the second housing 24.

[0096] As mentioned above, the air-fuel mixture in the working chamber has an air-fuel ratio distribution in the direction of rotor rotation. The air-fuel ratio of the exhaust gas discharged from the first housing 23 fluctuates periodically between rich and lean. Similarly, the air-fuel ratio of the exhaust gas discharged from the second housing 24 also fluctuates periodically between rich and lean. Because the first rotor 21 and the second rotor 22 are in different phases, the phase of the air-fuel ratio fluctuation of the exhaust gas discharged from the first housing 23 and the phase of the air-fuel ratio fluctuation of the exhaust gas discharged from the second housing 24 are inverse, as shown in Figure 6.

[0097] Here, when the exhaust air-fuel ratio is rich, there is a relatively large amount of unburned fuel in the exhaust, and when the exhaust air-fuel ratio is lean, there is a relatively large amount of air in the exhaust.

[0098] As shown in Figure 1, exhaust gas discharged from the first housing 23 through the side exhaust port 43 reaches the turbine 32 of the turbocharger 3 through the exhaust pipe 18. Similarly, exhaust gas discharged from the second housing 24 through the side exhaust port 43 also reaches the turbine 32 through the exhaust pipe 18. The exhaust gas discharged from the first housing 23 and the exhaust gas discharged from the second housing 24 are mixed by the turbine 32.

[0099] The air-fuel ratio of the exhaust gas discharged from the first housing 23 and the air-fuel ratio of the exhaust gas discharged from the second housing 24 fluctuate periodically between rich and lean in opposite phases. As can be seen from Figure 6, at a certain time, the exhaust gas discharged from the first housing 23, which contains a relatively large amount of unburned fuel, is mixed with the exhaust gas discharged from the second housing 24, which contains a relatively large amount of air. At another time, the exhaust gas discharged from the first housing 23, which contains a relatively large amount of air, is mixed with the exhaust gas discharged from the second housing 24, which contains a relatively large amount of unburned fuel. When unburned fuel and air are mixed in a relatively high-temperature environment, an oxidation reaction occurs, further increasing the temperature of the exhaust gas.

[0100] The exhaust gas, whose temperature has risen further between the turbine 32 and the catalytic converter 39, is supplied to the catalytic converter 39. This causes the temperature of the catalytic converter 39 to rise rapidly. Through this warm-up operation, the catalytic converter 39 is quickly activated.

[0101] According to this control method for the rotary piston engine 2, unburned fuel is oxidized between the rotary piston engine 2 and the catalytic converter 39, thereby increasing the exhaust temperature. Even if the temperature of the exhaust discharged from the first housing 23 or the second housing 24 of the rotary piston engine 2 is not very high, high-temperature exhaust can be supplied to the catalytic converter 39. Due to its structure, the rotary piston engine 2 has a limit on ignition timing retardation, making it difficult to increase the exhaust temperature by increasing exhaust losses. The aforementioned warm-up operation is particularly suitable for the engine system 1 including the rotary piston engine 2.

[0102] Furthermore, the exhaust gas discharged from the first housing 23 and the exhaust gas discharged from the second housing 24 are mixed in the turbine 32, causing the exhaust gas to become hot, which reduces the amount of heat energy lost to the turbine 32. Because the temperature drop of the exhaust gas is suppressed, a hotter exhaust gas can be supplied to the catalytic converter 39.

[0103] As a result, the engine system 1, including the rotary piston engine 2, can rapidly raise the temperature of the catalytic converter 39.

[0104] As mentioned above, the increased air volume due to the wide opening of the throttle valve 13 increases the amount of exhaust air, thus promoting the oxidation reaction of the exhaust. Furthermore, the increase in unburned fuel due to retarding the ignition timing also promotes the oxidation reaction of the exhaust. Because the temperature of the exhaust supplied to the catalytic converter 39 increases, the catalytic converter 39 activates earlier. The warm-up period is shortened.

[0105] Furthermore, in both the first housing 23 and the second housing 24, the overall air-fuel ratio in the working chamber is the stoichiometric air-fuel ratio. The air-fuel ratio of the exhaust gas, which is mixed in the turbine 32 and then supplied to the catalytic converter 39, is the stoichiometric air-fuel ratio. The engine system 1 can suppress a decrease in exhaust emission performance. By maintaining the exhaust air-fuel ratio at the stoichiometric air-fuel ratio, the engine system 1 suppresses a decrease in exhaust emission performance, while simultaneously generating an oxidation reaction of unburned fuel just before the catalytic converter 39, thereby rapidly raising the temperature of the catalytic converter 39.

[0106] Figure 7 shows the control procedure for warming up the catalytic converter 39, which is performed by the ECU 10. Note that in the flowchart of Figure 7, it is possible to rearrange the steps, omit some steps, or add new steps to the extent possible.

[0107] First, in the starting step S71, the ECU 10 starts the rotary piston engine 2. In the following step S72, the ECU 10 determines whether the coolant temperature is within a predetermined range, that is, between a first predetermined temperature Te1 and a second predetermined temperature Te2 (see Figure 5). If the determination in step S72 is No, the process in Figure 7 proceeds to step S710. In other words, the warm-up operation of the catalytic converter 39 is not performed.

[0108] If the determination in step S72 is Yes, the ECU 10 determines in step S73 whether the estimated catalyst temperature is below a predetermined temperature, i.e., below the third predetermined temperature Tc (see Figure 5). If the determination in step S73 is No, the process in Figure 7 proceeds to step S710. In other words, the warm-up operation of the catalytic converter 39 is not performed.

[0109] If the decision in step S73 is Yes, the ECU 10 decides in step S74 to perform a warm-up of the catalytic converter 39. In step S75, following step S74, the ECU 10 sets the throttle valve 13 opening to a large value, sets fuel injection to a single injection in step S76, and sets the ignition timing to retarded in step S77. Then, it operates the rotary piston engine 2. As described above, an air-fuel ratio distribution is formed in the operating chamber, and an exhaust oxidation reaction occurs just before the catalytic converter 39, which promotes the temperature rise of the catalytic converter 39.

[0110] In step S78, the ECU10 estimates the catalyst temperature, and in the following step S79, it determines whether the estimated catalyst temperature has exceeded a predetermined temperature, i.e., the third predetermined temperature Tc. If the determination in step S79 is No, the process in Figure 7 returns to step S74 and continues the warm-up operation.

[0111] If the decision in step S79 is Yes, the ECU 10 terminates the warm-up operation and performs normal operation in step S710. In other words, the ECU 10 sets the opening of the throttle valve 13 to an opening corresponding to the required torque of the rotary piston engine 2, sets the fuel injection mode to split injection, and sets the ignition timing to an earlier timing than top dead center of compression.

[0112] (modified version) Figure 8 shows a modified rotary piston engine 2. The first injector 51 is not limited to being located on the advance side in the rotor rotation direction relative to the long axis Y. The first injector 51 may be mounted on the first housing 23 such that the injection hole 511 is located near the long axis Y and the injection shaft is tilted with respect to the long axis Y. In the rotary piston engine 2 of Figure 8, the first injector 51 can inject fuel into the working chamber during the intake stroke or compression stroke on the advance side in the rotor rotation direction. If the first injector 51 injects fuel all at once at a predetermined timing, an air-fuel ratio distribution is formed in the working chamber in which the air-fuel ratio on the advance side in the rotor rotation direction is relatively rich and the air-fuel ratio on the retard side in the rotor rotation direction is relatively lean.

[0113] In the example described above, the air-fuel ratio distribution formed in the working chamber is such that the air-fuel ratio on the advance side in the rotor rotation direction is relatively rich, and the air-fuel ratio on the retard side in the rotor rotation direction is relatively lean, as shown in Figure 2. Conversely, the air-fuel ratio distribution may be formed such that the air-fuel ratio on the advance side in the rotor rotation direction is relatively lean, and the air-fuel ratio on the retard side in the rotor rotation direction is relatively rich. In this case as well, the air-fuel ratio of the exhaust gas discharged from the first housing 23 fluctuates periodically between rich and lean due to the air-fuel ratio distribution in the working chamber. Also, the air-fuel ratio of the exhaust gas discharged from the second housing 24 fluctuates periodically between rich and lean in the opposite phase to the exhaust gas from the first housing 23 due to the air-fuel ratio distribution in the working chamber. However, in the working chamber, a flow occurs from the retard side to the advance side as the rotor rotates. Fuel injected into the working chamber tends to move from the retard side to the advance side by riding on the flow in the working chamber. In rotary piston engine 2, an air-fuel ratio distribution is more likely to be formed in which the air-fuel ratio on the advance side of the rotor rotation direction is relatively rich in fuel, and the air-fuel ratio on the retard side of the rotor rotation direction is relatively lean in fuel. [Explanation of Symbols]

[0114] 1. Engine system (control device for rotary piston engine) 13 Throttle valve 17. Exhaust passage (3rd exhaust passage) 18. Exhaust pipe (first exhaust passage, second exhaust passage) 2 Rotary Piston Engine 21. Rotor 1 22. Second Rotor 23 Housing 1 24 Second Housing 3. Turbocharger 32 Turbines 39 Catalytic converter 51 First Injector 511 nozzles 52 Second Injector 53. First spark plug 54. Second spark plug Y long axis

Claims

1. During the warm-up period of the catalytic converter, the first injector injects fuel into the working chamber of the first housing of the first rotor so that an air-fuel ratio distribution is created in the direction of rotor rotation. During the warm-up operation, the second injector injects fuel into the working chamber of the second housing of the second rotor, which is in a different phase from the first rotor, so that an air-fuel ratio distribution in the direction of rotor rotation is created. The air-fuel ratio of the exhaust gas discharged from the first housing fluctuates periodically between rich and lean due to the air-fuel ratio distribution in the operating chamber, and the air-fuel ratio of the exhaust gas discharged from the second housing fluctuates periodically between rich and lean in the opposite phase to that of the exhaust gas from the first housing due to the air-fuel ratio distribution in the operating chamber. The turbine of the turbocharger mixes the exhaust gas discharged from the first housing with the exhaust gas discharged from the second housing. The exhaust gas, which has become hot due to the oxidation reaction after mixing, raises the temperature of the catalytic converter located downstream of the turbine. Control methods for rotary piston engines.

2. In the control method for a rotary piston engine according to claim 1, The first injector injects fuel so that the overall air-fuel ratio in the operating chamber becomes the stoichiometric air-fuel ratio. The second injector injects fuel so that the overall air-fuel ratio in the operating chamber becomes the stoichiometric air-fuel ratio. Control methods for rotary piston engines.

3. In the control method for a rotary piston engine according to claim 1, During the warm-up operation, the first injector injects fuel such that the air-fuel ratio on the advance side in the rotor rotation direction becomes relatively rich, and the air-fuel ratio on the retard side in the rotor rotation direction becomes relatively lean. During the warm-up operation, the second injector injects fuel such that the air-fuel ratio on the advance side in the rotor rotation direction becomes relatively rich, and the air-fuel ratio on the retard side in the rotor rotation direction becomes relatively lean. Control methods for rotary piston engines.

4. In the control method for a rotary piston engine according to claim 3, The first injector injects fuel into the operating chamber all at once during one cycle. The second injector injects fuel into the operating chamber all at once during one cycle. Control methods for rotary piston engines.

5. In the control method for a rotary piston engine according to claim 4, The first injector, during normal operation of the engine without warm-up, injects fuel into the operating chamber in multiple portions during one cycle. The second injector, during normal operation, injects fuel into the operating chamber in multiple portions during one cycle. Control methods for rotary piston engines.

6. A control method for a rotary piston engine according to any one of claims 3 to 5, The first injector injects fuel into the operating chamber during the intake stroke or compression stroke, on the side of the rotor rotation direction that is advanced relative to the long axis of the first housing. The second injector injects fuel into the operating chamber during the intake stroke or compression stroke, on the side of the rotor rotation direction that is advanced relative to the long axis of the second housing. Control methods for rotary piston engines.

7. In the control method for a rotary piston engine according to claim 6, The nozzle of the first injector is located on the advance side in the rotor rotation direction relative to the long axis of the first housing, The nozzle of the second injector is located on the advance side in the rotor rotation direction relative to the long axis of the second housing. Control methods for rotary piston engines.

8. In the control method for a rotary piston engine according to claim 1, During the warm-up operation, the first spark plug forcibly ignites the air-fuel mixture in the working chamber of the first housing at a timing after the working chamber is at top dead center of compression. During the warm-up operation, the second spark plug forcibly ignites the air-fuel mixture in the working chamber of the second housing at a timing after the working chamber is at top dead center of compression. Control methods for rotary piston engines.

9. In the control method for a rotary piston engine according to claim 8, The first spark plug, during normal operation of the engine without warm-up, forcibly ignites the air-fuel mixture in the working chamber of the first housing at a timing earlier than when the working chamber is at top dead center of compression. The second spark plug, during normal operation, forcibly ignites the air-fuel mixture in the working chamber of the second housing at a timing earlier than when the working chamber is at top dead center of compression. Control methods for rotary piston engines.

10. In the control method for a rotary piston engine according to claim 1, During the warm-up period, the throttle valve opens to a greater degree than required during normal operation of the engine without the warm-up period. Control methods for rotary piston engines.

11. In the control method for a rotary piston engine according to claim 1, When the coolant temperature of the rotary piston engine is between a first predetermined temperature and a second predetermined temperature, and the estimated temperature of the catalytic converter is below a third predetermined temperature, the warm-up operation is performed. Control methods for rotary piston engines.

12. A rotary piston engine having a first housing for a first rotor and a second housing for a second rotor having a different phase from the first rotor, A first injector that injects fuel into the working chamber of the first housing, A second injector that injects fuel into the working chamber of the second housing, A turbocharger comprising a first exhaust passage connected to the first housing and a second exhaust passage connected to the second housing, each connected to a turbine that rotates due to the exhaust flow discharged from the first housing and the second housing, A catalytic converter connected to the turbine via a third exhaust passage and for purifying the exhaust gas that has passed through the turbine, The system includes a controller that outputs control signals to the first injector and the second injector, The controller controls the first injector so that an air-fuel ratio distribution in the rotor rotation direction is generated in the working chamber of the first housing while the rotary piston engine is warming up the catalytic converter, and also controls the second injector so that an air-fuel ratio distribution in the rotor rotation direction is generated in the working chamber of the second housing. During the warm-up operation, the air-fuel ratio of the exhaust discharged from the first housing fluctuates periodically between rich and lean due to the air-fuel ratio distribution in the operating chamber, and the air-fuel ratio of the exhaust discharged from the second housing fluctuates periodically between rich and lean in the opposite phase to that of the exhaust from the first housing due to the air-fuel ratio distribution in the operating chamber. Control device for a rotary piston engine.

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