Internal combustion engine

Abstract

To provide an internal combustion engine capable of improving exhaust emissions at cold start of the internal combustion engine.SOLUTION: An internal combustion engine includes a combustion chamber, an intake passage, an exhaust passage, an exhaust gas recirculation passage, one or more first injectors and a second injector. The intake passage and the exhaust passage are connected to the combustion chamber. The exhaust gas recirculation passage is connected to the intake passage and the exhaust passage. The one or more first injectors inject fuel to the intake passage. The second injector injects fuel to the exhaust gas recirculation passage. The exhaust gas recirculation passage includes no catalyst.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] As a conventional invention related to an internal combustion engine, for example, the internal combustion engine described in Patent Document 1 is known. The internal combustion engine described in Patent Document 1 is equipped with a first fuel injection valve with a large spray particle size and a second fuel injection valve with a small spray particle size. According to the internal combustion engine described in Patent Document 1, deterioration of exhaust emissions is prevented when the internal combustion engine is started at low temperatures. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-262174 A Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, various internal combustion engines have been proposed for improving exhaust emissions during cold start of the internal combustion engine.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an internal combustion engine capable of improving exhaust emissions during cold start of the internal combustion engine. [Means for solving the problem]

[0006] The first aspect of the present invention is The internal combustion engine includes a combustion chamber, an intake path, an exhaust path, an exhaust gas recirculation path, one or more first injectors, and a second injector; the intake path and the exhaust path are connected to the combustion chamber, the exhaust gas recirculation path is connected to the intake path and the exhaust path, The one or more first injectors inject fuel into the intake path; The second injector injects fuel into the exhaust gas recirculation path, The exhaust gas recirculation path is not provided with a catalyst. It is an internal combustion engine.

[0007] A second aspect of the present invention is The internal combustion engine includes a combustion chamber, an intake path, an exhaust path, an exhaust gas recirculation path, an exhaust cooler, a bypass path, one or more first injectors, and a second injector; the intake path and the exhaust path are connected to the combustion chamber, the exhaust gas recirculation path is connected to the intake path and the exhaust path, The exhaust cooler is provided in the exhaust gas recirculation path and reduces a temperature of the exhaust gas flowing through the exhaust gas recirculation path. the bypass path connects a first portion of the exhaust gas recirculation path and a second portion of the exhaust gas recirculation path, The first portion is located upstream of the exhaust cooler in the exhaust gas recirculation path, The second portion is located downstream of the exhaust cooler in the exhaust gas recirculation path, The one or more first injectors inject fuel into the intake path; The second injector injects fuel into a third portion of the exhaust gas recirculation path, The third portion is located downstream of the second portion in the exhaust gas recirculation path. It is an internal combustion engine.

[0008] A third aspect of the present invention is The internal combustion engine further includes a switching valve and a control device, The switching valve adjusts the flow rate of the exhaust gas flowing through the bypass path, The control device controls the switching valve to an open state during a period in which the second injector injects fuel. 2. The internal combustion engine according to claim 1 .

[0009] A fourth aspect of the present invention is The internal combustion engine further includes an exhaust temperature sensor. the exhaust temperature sensor generating a first temperature signal indicative of a temperature of the exhaust; When the temperature indicated by the first temperature signal is lower than a first temperature, the controller causes the one or more first injectors to inject fuel and causes the second injector not to inject fuel; When the temperature indicated by the first temperature signal is greater than the first temperature, the controller causes the second injector to inject fuel. 3. The internal combustion engine according to claim 2 .

[0010] A fifth aspect of the present invention is The internal combustion engine further includes a water temperature sensor or an oil temperature sensor and a control device, the water temperature sensor generates a second temperature signal indicative of a temperature of a coolant for the internal combustion engine; the oil temperature sensor generates a third temperature signal indicative of a temperature of lubricating oil in the internal combustion engine; When the temperature indicated by the second temperature signal is lower than a second temperature or when the temperature indicated by the third temperature signal is lower than a third temperature, the control device causes the second injector to inject fuel; When the temperature indicated by the second temperature signal is higher than the second temperature or when the temperature indicated by the third temperature signal is higher than the third temperature, the control device does not cause the second injector to inject fuel. The internal combustion engine according to the third or fourth aspect.

[0011] A sixth aspect of the present invention is when the temperature indicated by the second temperature signal is lower than a fourth temperature or when the temperature indicated by the third temperature signal is lower than a fifth temperature, the control device controls the one or more first injectors and the second injector so that an amount of fuel injected by the second injector per unit time is greater than a sum of amounts of fuel injected by the one or more first injectors per unit time; the fourth temperature is lower than the second temperature; The fifth temperature is lower than the third temperature. 5. An internal combustion engine according to claim 1 .

[0012] A seventh aspect of the present invention is the control device controls the second injector so that an amount of fuel injected per unit time by the second injector decreases as the temperature indicated by the second temperature signal increases to approach the fourth temperature or as the temperature indicated by the third temperature signal increases to approach the fifth temperature. 6. An internal combustion engine according to claim 1 .

[0013] An eighth aspect of the present invention is When the temperature indicated by the second temperature signal is higher than the fourth temperature or when the temperature indicated by the third temperature signal is higher than the fifth temperature, the control device controls the one or more first injectors and the second injector so that a total amount of fuel injected by the one or more first injectors per unit time is greater than an amount of fuel injected by the second injector per unit time. The internal combustion engine according to the sixth or seventh aspect.

[0014] A ninth aspect of the present invention is When the temperature indicated by the second temperature signal is lower than the second temperature or when the temperature indicated by the third temperature signal is lower than the third temperature, the control device controls the switching valve to an open state; When the temperature indicated by the second temperature signal is higher than the second temperature or when the temperature indicated by the third temperature signal is higher than the third temperature, the control device controls the switching valve to a closed state. 5. An internal combustion engine according to claim 1 . Effect of the Invention

[0015] According to the present invention, exhaust emissions during cold start of an internal combustion engine can be improved. [Brief description of the drawings]

[0016] [Figure 1]FIG. 1 is a schematic diagram of an internal combustion engine 10 . [Diagram 2] FIG. 2 is a top view of the internal combustion engine 10. [Diagram 3] FIG. 3 is a flowchart executed by the control device 100. [Figure 4] FIG. 4 is a schematic diagram of an internal combustion engine 10a. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] (Embodiment) [Structure of an internal combustion engine] Hereinafter, the structure of an internal combustion engine 10 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of the internal combustion engine 10. FIG. 2 is a top view of the internal combustion engine 10. In FIG. 1 and FIG. 2, the directions in which the pistons 18a to 18d move are defined as upward and downward directions. However, the upward and downward directions in this specification are directions defined for the convenience of explanation, and do not necessarily match the upward and downward directions when the internal combustion engine 10 is actually used.

[0018] The internal combustion engine 10 is used, for example, as a power source for an automobile. The internal combustion engine 10 is, for example, a four-stroke gasoline engine. Therefore, the fuel is gasoline. The internal combustion engine 10 of Figs. 1 and 2 is, for example, an engine having four cylinders. The internal combustion engine 10 includes an engine body 12, a crankshaft 14, connecting rods 16a to 16d (connecting rods 16b to 16d are not shown), pistons 18a to 18d (pistons 18b to 18d are not shown), intake valves 20a to 20d (intake valves 20b to 20d are not shown), exhaust valves 22a to 22d (exhaust valves 22b to 22d are not shown), spark plugs 24a to 24d (spark plugs 24b to 24d are not shown), and ignition coils 26a to 26d (ignition coils 26b to 26d are not shown).

[0019] The engine body 12 includes a cylinder block 12a, a cylinder head 12b, and a crankcase 12c. The cylinder block 12a is provided with cylinders Sya to Syd (cylinders Syb to Syd are not shown). The cylinders Sya to Syd have a cylindrical shape with a central axis extending along the vertical axis.

[0020] The cylinder head 12b is located above the cylinder block 12a. The cylinder head 12b is fixed to the cylinder block 12a. The cylinder head 12b is provided with combustion chambers Spa to Spd (combustion chambers Spb to Spd are shown in FIG. 2). The combustion chambers Spa to Spd are located above the cylinders Sya to Syd, respectively. The combustion chambers Spa to Spd are connected to the cylinders Sya to Syd, respectively.

[0021] The cylinder head 12b is provided with intake ports P1a to P1d (intake ports P1b to P1d are not shown) and exhaust ports P2a to P2d (exhaust ports P2b to P2d are not shown). The intake port P1a is connected to the combustion chamber Spa. The intake port P1a is a part of the intake path R1a. Therefore, the intake path R1a is connected to the combustion chamber Spa. The intake path R1a is a path through which air or a mixture of fuel and air passes.

[0022] The exhaust port P2a is connected to the combustion chamber Spa. The exhaust port P2a is a part of the exhaust path R2a. The exhaust path R2a is connected to the combustion chamber Spa. The exhaust path R2a is a path through which exhaust gas passes. Note that the structures of the intake paths R1b to R1d and the exhaust paths R2b to R2d are the same as the structures of the intake path R1a and the exhaust path R2a, and therefore description thereof will be omitted.

[0023] 2, the upstream ends of the intake paths R1a-R1d are connected to the intake path R1. The downstream ends of the exhaust paths R2a-R2d are connected to the exhaust path R2. As described above, the internal combustion engine 10 includes the combustion chambers Spa-Spd, the intake paths R1a-R1d, R1, and the exhaust paths R2a-R2d, R2. In this specification, the combustion chambers, the intake paths, and the exhaust paths refer to spaces and members for forming the spaces.

[0024] The crankcase 12c is located below the cylinder block 12a. The crankcase 12c is fixed to the cylinder block 12a. The engine body 12 as described above is made of cast iron.

[0025] The crankshaft 14 is supported by the cylinder block 12a and the crankcase 12c and can rotate about a rotation axis that is perpendicular to the vertical axis.

[0026] The piston 18a is located in the cylinder Sya. The piston 18a has a cylindrical shape. The piston 18a can move upward and downward.

[0027] The connecting rod 16a connects the crankshaft 14 and the piston 18a. As a result, the piston 18a moves up and down when the crankshaft 14 rotates. The combustion chamber Spa described above is a space surrounded by the piston 18a and the cylinder head 12b when the piston 18a is located at top dead center (TDC).

[0028] The intake valve 20a is supported by the cylinder head 12b. The intake valve 20a is located downstream of a first injector 29a (described later) in the intake path R1a. The intake valve 20a opens and closes the intake path R1a. When the intake valve 20a opens the intake path R1a, a mixture of fuel and air flows from the intake path R1a into the combustion chamber Spa. The exhaust valve 22a is supported by the cylinder head 12b. The exhaust valve 22a opens and closes the exhaust path R2. When the exhaust valve 22a opens the exhaust path R2a, exhaust flows from Spa to the exhaust path R2a. The intake valve 20a and the exhaust valve 22a as described above are driven by a valve mechanism (not shown).

[0029] The spark plug 24a is fixed to the cylinder head 12b. The spark plug 24a includes a center electrode and a ground electrode. The center electrode and the ground electrode are exposed to the combustion chamber Spa.

[0030] The ignition coil 26a applies a high voltage between the center electrode and the ground electrode of the ignition plug 24a based on an ignition signal from the control device 100, which will be described later. This generates a spark between the center electrode and the ground electrode of the ignition plug 24a, igniting the fuel in the combustion chamber Spa.

[0031] The structures of connecting rods 16b-16d, pistons 18b-18d, intake valves 20b-20d, exhaust valves 22b-22d, spark plugs 24b-24d, and ignition coils 26b-26d are the same as the structures of connecting rod 16a, pistons 18a, intake valves 20a, exhaust valve 22a, spark plugs 24a, and ignition coils 26a, so descriptions thereof will be omitted.

[0032] The internal combustion engine 10 further includes an exhaust gas recirculation path R3, a bypass path R4, an exhaust cooler 50, a switching valve 52, and a second injector 54. The exhaust gas recirculation path R3 is connected to the intake paths R1a to R1d and the exhaust path R2. In the exhaust gas recirculation path R3, exhaust gas flows from the exhaust path R2 to the intake paths R1a to R1d. No catalyst is provided in the exhaust gas recirculation path R3. The catalyst removes, for example, NOx, unburned HC, carbon monoxide, and the like in the exhaust gas.

[0033] The exhaust cooler 50 is provided in the exhaust gas recirculation path R3. The exhaust gas cooler 50 reduces the temperature of the exhaust gas flowing through the exhaust gas recirculation path R3.

[0034] The bypass path R4 connects the first portion P1 of the exhaust gas recirculation path R3 and the second portion P2 of the exhaust gas recirculation path R3. The first portion P1 is located upstream of the exhaust cooler 50 in the exhaust gas recirculation path R3. That is, the path length from the first portion P1 to the exhaust path R2 is shorter than the path length from the exhaust cooler 50 to the exhaust path R2. Therefore, the first portion P1 is located between the exhaust cooler 50 and the exhaust path R2 in the exhaust gas recirculation path R3. Moreover, the second portion P2 is located downstream of the exhaust cooler 50 in the exhaust gas recirculation path R3. That is, the path length from the second portion P2 to the intake path R1a is shorter than the path length from the exhaust cooler 50 to the intake path R1a. Therefore, the second portion P2 is located between the exhaust cooler 50 and the intake path R1a in the exhaust gas recirculation path R3. Exhaust gas flows through the bypass path R4.

[0035] The switching valve 52 is provided in the bypass route R4. The switching valve 52 adjusts the flow rate of the exhaust gas flowing through the bypass route R4. The switching valve 52 is, for example, an electromagnetic valve.

[0036] The second injector 54 is fixed to the exhaust gas recirculation path R3. In this embodiment, the second injector 54 is located downstream of the second portion P2 in the exhaust gas recirculation path R3. The second injector 54 injects fuel into the third portion P3 of the exhaust gas recirculation path R3. The third portion P3 is located downstream of the second portion P2 in the exhaust gas recirculation path R3. That is, the path length from the third portion P3 to the intake path R1a is shorter than the path length from the second portion P2 to the intake path R1a. Therefore, the third portion P3 is located between the second portion P2 and the intake path R1a in the exhaust gas recirculation path R3.

[0037] The internal combustion engine 10 further includes first injectors 29a to 29d (first injectors 29b to 29d are not shown), a throttle valve 32, a throttle position sensor 34, an air flow meter 36, a water temperature sensor 38, and an exhaust temperature sensor 40.

[0038] The first injector 29a is fixed to the cylinder head 12b. The first injector 29a injects fuel into the intake path R1a. The structures of the first injectors 29b to 29d are the same as that of the first injector 29a, and therefore a description thereof will be omitted.

[0039] 1, the throttle valve 32 is located upstream of the first injectors 29a to 29d in the intake path R1. The throttle valve 32 opens and closes the intake path R1 in response to the driver's operation of the accelerator pedal. In this way, the throttle valve 32 adjusts the amount of air supplied to the combustion chambers Spa to Spd. The throttle position sensor 34 detects the open / closed state of the throttle valve 32.

[0040] The air flow meter 36 is located in the intake path R1 upstream of the throttle valve 32. The air flow meter 36 detects the amount of air passing through the intake path R1.

[0041] The water temperature sensor is provided in the engine body 12. The water temperature sensor generates a second temperature signal Sig2 that indicates the temperature of the cooling water of the internal combustion engine 10 (hereinafter, water temperature T).

[0042] The exhaust temperature sensor 40 is provided in the exhaust path R2a. The exhaust temperature sensor 40 generates a first temperature signal Sig1 that indicates the temperature of the exhaust gas (hereinafter, referred to as the exhaust temperature t).

[0043] The internal combustion engine 10 further includes a control device 100. The control device 100 is an ECU (Engine Control Unit). The control device 100 controls the operation of the internal combustion engine 10 based on a signal from the throttle position sensor 34, a signal from the air flow meter 36, a second temperature signal Sig2 from the water temperature sensor 38, and a first temperature signal Sig1 from the exhaust temperature sensor 40. Specifically, the control device 100 controls the timing of fuel injection by the first injectors 29a to 29d and the second injector 54, and the timing of ignition by the spark plugs 24a to 24d.

[0044] [Operation of the internal combustion engine 10] Next, the operation of the internal combustion engine 10 will be described with reference to the drawings. Fig. 3 is a flowchart executed by the control device 100. The control device 100 executes the flowchart of Fig. 3 by reading a program stored in a storage device (not shown).

[0045] This process is started when the driver starts the starter of the vehicle equipped with the internal combustion engine 10. As a result, the control device 100 starts the operation of the first injectors 29a-29d (step S1). The first injectors 29a-29d inject fuel into the intake paths R1a-R1d, respectively. At this time, the control device 100 applies a high voltage to the ignition plugs 24a-24d through the ignition coils 26a-26d, respectively. As a result, the fuel in the combustion chambers Spa-Spd is ignited. This starts the internal combustion engine 10.

[0046] Next, the control device 100 controls the switching valve 52 to an open state (step S2), so that the exhaust gas flows through the bypass route R4.

[0047] Next, the control device 100 judges whether the exhaust temperature t is higher than the first temperature T1 (step S3). In this process, the control device 100 judges whether the exhaust temperature t has risen sufficiently. The first temperature T1 is, for example, 100° C. The first temperature T1 is set to a temperature at which the fuel injected by the second injector 54 is sufficiently vaporized. If the exhaust temperature t indicated by the first temperature signal Sig1 is equal to or lower than the first temperature T1, this process returns to step S3. That is, if the exhaust temperature t indicated by the first temperature signal Sig1 is equal to or lower than the first temperature T1, the control device 100 causes the first injectors 29a to 29d to inject fuel and does not cause the second injector 54 to inject fuel. On the other hand, if the exhaust temperature t indicated by the first temperature signal Sig1 is higher than the first temperature T1, this process proceeds to step S4.

[0048] When the exhaust temperature t indicated by the first temperature signal Sig1 is higher than the first temperature T1, the control device 100 causes the second injector 54 to inject fuel (step S4). At this time, the control device 100 controls the first injectors 29a to 29d and the second injector 54 so that the amount of fuel injected by the second injector 54 per unit time (hereinafter, injection amount I2) is greater than the total amount of fuel injected by the first injectors 29a to 29d per unit time (hereinafter, injection amount I1) (step S5). Since the exhaust temperature t is sufficiently high, the fuel injected by the second injector 54 vaporizes. As a result, the mixture of fuel and exhaust flows through the exhaust gas recirculation path R3. Then, the mixture of fuel and exhaust flows into the intake paths R1a to R1d.

[0049] Next, the control device 100 determines whether the water temperature T indicated by the second temperature signal Sig2 is rising (step S6). If the water temperature T indicated by the second temperature signal Sig2 is not rising, the process returns to step S6. If the water temperature T indicated by the second temperature signal Sig2 is rising, the process proceeds to step S7.

[0050] When the water temperature T indicated by the second temperature signal Sig2 is rising, the control device 100 controls the second injector 54 so that the amount of fuel injected by the second injector 54 per unit time (hereinafter, injection amount I2) decreases (step S7).

[0051] Next, the control device 100 determines whether the water temperature T indicated by the second temperature signal Sig2 is higher than the fourth temperature T4 (step S8). In step S8, the control device 100 determines whether the warm-up of the internal combustion engine 10 is complete. If the water temperature T indicated by the second temperature signal Sig2 is equal to or lower than the fourth temperature T4, the process returns to step S6. If the water temperature T indicated by the second temperature signal Sig2 is higher than the fourth temperature T4, the process proceeds to step S9.

[0052] When the water temperature T indicated by the second temperature signal Sig2 is higher than the fourth temperature T4, the control device 100 controls the first injectors 29a-29d and the second injector 54 so that the total amount of fuel injected by the first injectors 29a-29d per unit time (injection amount I1) is greater than the amount of fuel injected by the second injector 54 per unit time (injection amount I2) (step S9). As shown in steps S5 to S9, when the water temperature T indicated by the second temperature signal Sig2 is lower than the fourth temperature T4 (i.e., before warm-up is completed), the control device 100 controls the first injectors 29a-29d and the second injector 54 so that the amount of fuel injected by the second injector 54 per unit time (injection amount I2) is greater than the total amount of fuel injected by the first injectors 29a-29d per unit time (injection amount I1). However, as the water temperature T indicated by the second temperature signal Sig2 rises closer to the fourth temperature T4 (i.e., as the warm-up approaches completion), the control device 100 controls the second injector 54 so that the amount of fuel injected by the second injector 54 per unit time (injection amount I1) decreases. Then, when the warm-up is completed, the control device 100 controls the first injectors 29a-29d and the second injector 54 so that the injection amount I1 is greater than the injection amount I2.

[0053] Next, the control device 100 judges whether the water temperature T indicated by the second temperature signal Sig2 is higher than the second temperature T2 (step S10). The second temperature T2 is higher than the fourth temperature T4. That is, the fourth temperature T4 is lower than the second temperature T2. The second temperature T2 is the water temperature T when the warm-up is "completely" completed. In step S10, the control device 100 judges whether the warm-up of the internal combustion engine 10 is "completely" completed. The warm-up being completed completely means that the water temperature T has stabilized because a sufficient amount of time has passed since the warm-up was completed. If the water temperature T indicated by the second temperature signal Sig2 is equal to or lower than the second temperature T2, the process returns to step S10. Therefore, if the water temperature T indicated by the second temperature signal Sig2 is equal to or lower than the second temperature T2, the control device 100 controls the second injector 54 to inject fuel and controls the switching valve 52 to be in an open state. In this way, the control device 100 controls the switching valve 52 to be open during the period in which the second injector 54 injects fuel. If the water temperature T indicated by the second temperature signal Sig2 is higher than the second temperature T2, the process proceeds to step S11.

[0054] When the water temperature T indicated by the second temperature signal Sig2 is higher than the second temperature T2, the control device 100 does not allow the second injector 54 to inject fuel (step S11) and controls the switching valve 52 to a closed state (step S12). This ends the process. After the process ends, the internal combustion engine 10 performs normal operation.

[0055] [effect] According to the internal combustion engine 10, it is possible to improve exhaust emissions during cold start of the internal combustion engine 10. More specifically, during cold start, fuel is difficult to vaporize. Therefore, in a conventional general internal combustion engine, the amount of fuel injected is increased so that the internal combustion engine can be easily started.

[0056] However, in a port injection type internal combustion engine, fuel adheres to the inner surface of the port and the valve. Because the inner surface of the port is away from the combustion chamber, the temperature of the inner surface of the port does not increase easily. Therefore, the fuel adhering to the port may flow into the combustion chamber in a large amount in a liquid state. In this case, the liquid fuel adheres to the inner surface of the cylinder. Some of this liquid fuel is not burned during the expansion stroke and exhaust stroke, but vaporizes and flows out into the exhaust port. This increases unburned HC and worsens exhaust emissions. This tendency is particularly noticeable when starting the internal combustion engine in a low temperature state.

[0057] Incidentally, an internal combustion engine described in Patent Document 1 is known. The internal combustion engine described in Patent Document 1 is equipped with a first fuel injection valve with a large spray particle size and a second fuel injection valve with a small spray particle size. During cold start, fuel is injected by the second fuel injection valve. The internal combustion engine described in Patent Document 1 as described above can prevent fuel from adhering to the intake port.

[0058] However, in the internal combustion engine described in Patent Document 1, the fuel injection amount is increased during cold start, so a large amount of fuel adheres to the vicinity of the intake valve before the intake valve opens. Therefore, there is still room for improvement in exhaust emissions in the internal combustion engine described in Patent Document 1.

[0059] Therefore, in the internal combustion engine 10, the second injector 54 injects fuel into the exhaust gas recirculation path R3. High-temperature exhaust gas flows through the exhaust gas recirculation path R3. Therefore, the fuel injected by the second injector 54 is vaporized in the exhaust gas recirculation path R3. As a result, a mixture of fuel and exhaust gas flows through the exhaust gas recirculation path R3. Then, the mixture of fuel and exhaust gas flows into the intake paths R1a to R1d. As a result, even during a cold start, the vaporized fuel flows into the combustion chambers Spa to Spd, so that unburned HC is reduced. As a result, exhaust emissions during a cold start of the internal combustion engine 10 can be improved.

[0060] According to the internal combustion engine 10, exhaust emissions during cold start of the internal combustion engine 10 can also be improved for the following reason. More specifically, during cold start of the internal combustion engine 10, the exhaust temperature t is low. Therefore, when the exhaust gas passes through the exhaust cooler 50, the exhaust gas is cooled by the exhaust cooler 50, and the exhaust temperature t decreases. As a result, there is a possibility that the fuel injected by the second injector 54 cannot be sufficiently vaporized in the exhaust gas recirculation route R3.

[0061] Therefore, the bypass route R4 connects the first portion P1 of the exhaust gas recirculation route R3 to the second portion P2 of the exhaust gas recirculation route R3. The route length from the first portion P1 to the exhaust route R2 is shorter than the route length from the exhaust cooler 50 to the exhaust route R2. The route length from the second portion P2 to the intake route R1a is shorter than the route length from the exhaust cooler 50 to the intake route R1a. Such a bypass route R4 is a route that bypasses the exhaust gas cooler 50. As a result, the exhaust gas can pass through the bypass route R4 during a cold start of the internal combustion engine 10. As a result, the exhaust gas is not cooled by the exhaust cooler 50, and the exhaust gas temperature t is less likely to decrease. Therefore, the fuel injected by the second injector 54 is sufficiently vaporized in the exhaust gas recirculation route R3. As a result, the exhaust emission during a cold start of the internal combustion engine 10 can be improved.

[0062] According to the internal combustion engine 10, exhaust emissions during cold start of the internal combustion engine 10 can also be improved for the following reasons. More specifically, the control device 100 controls the switching valve 52 to an open state during the period in which the second injector 54 injects fuel. This causes the second injector 54 to inject fuel into the high-temperature exhaust gas that has passed through the bypass route R4. This makes it easier for the fuel injected by the second injector 54 to vaporize. As a result, exhaust emissions during cold start of the internal combustion engine 10 can be improved.

[0063] According to the internal combustion engine 10, the fuel injected by the second injector 54 can be appropriately vaporized. More specifically, when the exhaust temperature t indicated by the first temperature signal Sig1 is equal to or lower than the first temperature T1, the fuel injected by the second injector 54 may not be sufficiently vaporized. In this case, the control device 100 causes the first injectors 29a to 29d to inject fuel, and does not cause the second injector 54 to inject fuel. On the other hand, when the exhaust temperature t indicated by the first temperature signal Sig1 is higher than the first temperature T1, the fuel injected by the second injector 54 is sufficiently vaporized. In this case, the control device 100 causes the second injector 54 to inject fuel. As a result, according to the internal combustion engine 10, the fuel injected by the second injector 54 can be appropriately vaporized.

[0064] According to the internal combustion engine 10, exhaust emissions during cold start of the internal combustion engine 10 can also be improved for the following reasons. More specifically, when the water temperature T indicated by the second temperature signal Sig2 is lower than the fourth temperature T4, the warm-up of the internal combustion engine 10 is not complete. In this case, the temperature of the intake ports P1a-P1d of the internal combustion engine 10 has not risen sufficiently. Therefore, the fuel injected by the first injectors 29a-29d is not sufficiently vaporized and may adhere to the intake ports P1a-P1d. On the other hand, the fuel injected by the second injector 54 is vaporized by the high-temperature exhaust gas.

[0065] Therefore, before the internal combustion engine 10 is completely warmed up, the control device 100 controls the first injectors 29a-29d and the second injector 54 so that the amount of fuel injected by the second injector 54 per unit time (injection amount I2) is greater than the total amount of fuel injected by the first injectors 29a-29d per unit time (injection amount I1). This reduces the amount of fuel that easily adheres to the intake ports P1a-P1d and increases the amount of fuel that easily vaporizes. As a result, exhaust emissions during cold start of the internal combustion engine 10 can be improved.

[0066] In the internal combustion engine 10, as the warm-up of the internal combustion engine 10 approaches completion, the temperature of the intake ports P1a to P1d rises, so that the fuel injected by the first injectors 29a to 29d is more likely to vaporize. Therefore, the control device 100 controls the second injector 54 so that the amount of fuel injected by the second injector 54 per unit time (injection amount I2) decreases as the temperature indicated by the second temperature signal Sig2 rises to approach the fourth temperature T4. This increases the ratio of fuel injected by the first injectors 29a to 29d as the warm-up of the internal combustion engine 10 approaches completion. Therefore, the amount of fuel that easily adheres to the intake ports decreases, and exhaust emissions during cold start of the internal combustion engine 10 can be improved.

[0067] (Modification) An internal combustion engine 10a according to a modified example will be described below with reference to the drawings. Fig. 4 is a schematic diagram of the internal combustion engine 10a.

[0068] The internal combustion engine 10a further includes a surge tank 56. The surge tank 56 is provided in the intake path R1. That is, the surge tank 56 is a part of the intake path R1. The exhaust gas recirculation path R3 is connected to the surge tank 56. The internal combustion engine 10a described above can achieve the same effects as the internal combustion engine 10.

[0069] (Other embodiments) The internal combustion engine according to the present invention is not limited to the internal combustion engines 10 and 10a, and can be modified within the scope of the invention.

[0070] The fuel may be a fuel other than gasoline. The fuel may be a hydrocarbon fuel other than gasoline, or may be an alcohol fuel such as bioethanol fuel.

[0071] In step S12, the control device 100 controls the switching valve 52 to the closed state. However, before step S11, if the exhaust temperature t becomes sufficiently high, the control device 100 may close the switching valve 52. In this case, the second injector 54 injects fuel into the exhaust gas that has passed through the exhaust cooler 50.

[0072] When the internal combustion engine 10, 10a is equipped with the exhaust cooler 50 and the bypass route R4, a catalyst may be provided in the exhaust gas recirculation route R3.

[0073] The internal combustion engines 10, 10a may include an oil temperature sensor instead of the water temperature sensor 38. The oil temperature sensor generates a third temperature signal Sig3 indicating the temperature of the lubricating oil (oil sound TT) of the internal combustion engines 10, 10a. In this case, the control device 100 may perform the following operations (1) to (5).

[0074] (1) When the oil sound TT indicated by the third temperature signal Sig3 is lower than the third temperature T3, the control device 100 causes the second injector 54 to inject fuel. When the oil sound TT indicated by the third temperature signal Sig3 is higher than the third temperature T3, the control device 100 does not cause the second injector 54 to inject fuel.

[0075] (2) When the oil sound TT indicated by the third temperature signal Sig3 is lower than a fifth temperature T5, the control device 100 controls the first injectors 29a-29d and the second injector 54 so that the amount of fuel injected per unit time by the second injector 54 is greater than the sum of the amounts of fuel injected per unit time by the first injectors 29a-29d. The fifth temperature T5 is lower than the third temperature T3.

[0076] (3) The control device 100 controls the second injector 54 so that the amount of fuel injected per unit time by the second injector 54 decreases as the oil sound TT indicated by the third temperature signal Sig3 rises and approaches the fifth temperature T5.

[0077] (4) When the temperature indicated by the third temperature signal Sig3 is higher than the fifth temperature T5, the control device 100 controls the first injectors 29a-29d and the second injector 54 so that the total amount of fuel injected per unit time by the first injectors 29a-29d is greater than the amount injected per unit time by the second injector 54.

[0078] (5) When the oil sound TT indicated by the third temperature signal Sig3 is lower than the third temperature T3, the control device 100 controls the switching valve 52 to an open state. When the oil sound TT indicated by the third temperature signal Sig3 is higher than the third temperature T3, the control device 100 controls the switching valve 52 to a closed state.

[0079] When the exhaust temperature t indicated by the first temperature signal Sig1 is lower than the first temperature T1, the control device 100 may cause the first injectors 29a-29d to inject fuel, and may not cause the second injector 54 to inject fuel. In this case, when the exhaust temperature t indicated by the first temperature signal Sig1 is equal to or higher than the first temperature T1, the control device 100 causes the second injector 54 to inject fuel.

[0080] Note that, when the water temperature T indicated by the second temperature signal Sig2 is lower than the second temperature T2 or when the oil sound TT indicated by the third temperature signal Sig3 is lower than the third temperature T3, the control device 100 may cause the second injector 54 to inject fuel. In this case, when the water temperature T indicated by the second temperature signal Sig2 is higher than the second temperature T2 or when the oil sound TT indicated by the third temperature signal Sig3 is higher than the third temperature T3, the control device 100 does not cause the second injector 54 to inject fuel.

[0081] In addition, when the water temperature T indicated by the second temperature signal Sig2 is equal to or lower than the fourth temperature T4, or when the oil sound TT indicated by the third temperature signal Sig3 is equal to or lower than the fifth temperature T5, the control device 100 may control the first injectors 29a-29d and the second injectors 54 so that the amount of fuel injected per unit time by the second injector 54 is greater than the amount injected per unit time by the first injectors 29a-29d.

[0082] In addition, when the water temperature T indicated by the second temperature signal Sig2 is equal to or higher than the fourth temperature T4, or when the temperature indicated by the third temperature signal Sig3 is equal to or higher than the fifth temperature T5, the control device 100 may control the first injectors 29a-29d and the second injector 54 so that the amount of fuel injected per unit time by the first injectors 29a-29d is greater than the amount injected per unit time by the second injector 54.

[0083] When the water temperature T indicated by the second temperature signal Sig2 is lower than the second temperature T2 or when the oil sound TT indicated by the third temperature signal Sig3 is lower than the third temperature T3, the control device 100 may control the switching valve 52 to an open state. In this case, when the water temperature T indicated by the second temperature signal Sig2 is equal to or higher than the second temperature T2 or when the oil sound TT indicated by the third temperature signal Sig3 is equal to or higher than the third temperature T3, the control device 100 controls the switching valve 52 to a closed state.

[0084] The automobile may be a four-wheeled automobile, a three-wheeled automobile, or a two-wheeled automobile. A two-wheeled automobile is a leaning vehicle in which the body leans in the same direction as the direction of travel around the corner. A three-wheeled automobile may be a leaning vehicle, or may be a vehicle that rolls in the opposite direction to the direction of travel around the corner.

[0085] The internal combustion engine 10 may be used as a power source for vehicles other than automobiles. Also, the internal combustion engine 10 may be used as a generator for generating electric power for an EV (Electric Vehicle).

[0086] The number of the first injectors may be one or more.

[0087] The control device 100 may perform control based on temperatures related to the internal combustion engines 10, 10a detected by sensors other than the water temperature sensor and the oil sound sensor. [Explanation of symbols]

[0088] 10, 10a: Internal combustion engine 29a to 29d: First injector 38: Water temperature sensor 40: Exhaust temperature sensor 50: Exhaust cooler 52: Switching valve 54: Second injector 100: Control device P1: 1st part P2: 2nd part P3: 3rd part R1, R1a, R1b: Intake path R2, R2a, R2b: Exhaust route R3: Exhaust gas recirculation path R4: Bypass route

Claims

1. The internal combustion engine includes a combustion chamber, an intake path, an exhaust path, an exhaust gas recirculation path, one or more first injectors, and a second injector; the intake path and the exhaust path are connected to the combustion chamber, the exhaust gas recirculation path is connected to the intake path and the exhaust path, The one or more first injectors inject fuel into the intake path; The second injector injects fuel into the exhaust gas recirculation path, The exhaust gas recirculation path is not provided with a catalyst. Internal combustion engine.

2. The internal combustion engine includes a combustion chamber, an intake path, an exhaust path, an exhaust gas recirculation path, an exhaust gas cooler, a bypass path, one or more first injectors, and a second injector; the intake path and the exhaust path are connected to the combustion chamber, the exhaust gas recirculation path is connected to the intake path and the exhaust path, The exhaust cooler is provided in the exhaust gas recirculation path and reduces a temperature of the exhaust gas flowing through the exhaust gas recirculation path. the bypass path connects a first portion of the exhaust gas recirculation path and a second portion of the exhaust gas recirculation path, The first portion is located upstream of the exhaust cooler in the exhaust gas recirculation path, The second portion is located downstream of the exhaust cooler in the exhaust gas recirculation path, The one or more first injectors inject fuel into the intake path; The second injector injects fuel into a third portion of the exhaust gas recirculation path, The third portion is located downstream of the second portion in the exhaust gas recirculation path. Internal combustion engine.

3. The internal combustion engine further includes a switching valve and a control device, The switching valve adjusts the flow rate of the exhaust gas flowing through the bypass path, The control device controls the switching valve to an open state during a period in which the second injector injects fuel.

3. The internal combustion engine according to claim 2.

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