JP2007211594A - Engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine in which environmental performance is further improved by more appropriately controlling a state of multistage fuel injection according to an engine operating condition. <P>SOLUTION: A cooling water circulating system 170 for circulating cooling water of an engine 100 switches between a supply state of cooling water to a cylinder head 110 and a supply state of cooling water to a cylinder block 120 according to an operating state. A signal corresponding to the cooling state of the cylinder head 110 due to the cooling water circulating system 170 is outputted from a cylinder head side cooling water temperature sensor 186. On the basis of the signal, the control part 190 controls the timing/quantity of pilot injection and main injection, a cooling water supply state to an EGR cooler 162 and an execution state of EGR by controlling the operation of a combustion chamber injector 156, EGR passage opening/closing control valve 163 and EGR cooling control valve 179c. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an engine configured to inject fuel in a fuel mixture introduction path including an intake passage, a cylinder, and a combustion chamber.

  Conventionally, various types of fuel injection engines of this type are known. For example, Japanese Patent Laid-Open No. 4-1436 (Patent Document 1) discloses a configuration in which an engine cooling system is divided into a cylinder block cooling system and a cylinder head cooling system. In an engine having such a configuration, the cylinder head and the cylinder block can be set to different temperatures.

For example, the temperature of the cylinder block can be relatively high. Thereby, the sliding resistance of movable members, such as a piston, becomes small, and a fuel consumption improves. Further, the temperature of the cylinder head may be relatively lowered. Thereby, generation | occurrence | production of knocking in a gasoline engine and generation | occurrence | production of NOx in a diesel engine are suppressed.
JP-A-4-1436

  Today, there is an increasing demand for engine environmental measures such as exhaust gas purification and fuel efficiency improvement. As a countermeasure for this environment, fuel injection may be performed in multiple stages in this type of fuel injection engine. That is, prior to main injection, pre-injection in which a smaller amount of fuel than the main injection is injected may be performed. This multistage fuel injection is mainly performed in a diesel engine. This pre-injection may be further divided into multiple stages.

  By this pre-injection, before combustion (referred to as main combustion after compression top dead center and main injection; the same applies hereinafter), the temperature of the fuel mixture in the combustion chamber rises in advance and the fuel and air are mixed. Can be promoted. Therefore, combustion efficiency is improved and fuel efficiency is improved. Furthermore, a rapid pressure increase in the cylinder is suppressed. Therefore, generation of noise and NOx is suppressed.

  However, if the state of multi-stage fuel injection, such as the amount, ratio, and injection timing of main injection and pre-injection, is not properly controlled according to the operating state of the engine, the environmental performance improvement effect of multi-stage fuel injection is reduced. It can be done.

Means for Solving the Problems and Effects of the Invention

  The present invention has been made to solve the above-described problems. Therefore, an object of the present invention is to provide an engine having further improved environmental performance by more appropriately controlling the state of multistage fuel injection according to the operating state of the engine.

  (1) The engine of the present invention includes a cylinder head, a cylinder block, a cooling medium circulation system, and a cylinder head side cooling medium temperature sensor. This engine is configured such that fuel is injected in a fuel mixture introduction path including an intake passage, a cylinder, and a combustion chamber.

  The cylinder head and the cylinder block are configured to be cooled by a cooling medium. The cylinder block and the cylinder head are joined to each other. The cooling medium circulation system is configured to change the supply state of the cooling medium to the cylinder head and the cylinder block in accordance with the operating state. That is, this cooling medium circulation system makes the cooling medium supply state to the cylinder head different from the supply state of the cooling medium to the cylinder block according to the operating state. The cooling state of the cylinder head and the cooling state of the cylinder block can be made different. The cylinder head side cooling medium temperature sensor is configured to output a signal corresponding to the temperature of the cooling medium on the cylinder head side.

  A feature of the present invention is that the engine further includes a fuel injection control unit having a characteristic configuration. The fuel injection control unit is configured to control the state of fuel injection in the main injection and the pre-injection according to the output of the cylinder head side coolant temperature sensor.

  In the engine of the present invention having such a configuration, the supply state of the cooling medium to the cylinder head and the cylinder block is appropriately set by the cooling medium circulation system according to the operating state. For example, during the warm-up operation after the cold start, the supply of the cooling medium to the cylinder block is restricted while the supply of the cooling medium to the cylinder head is secured. Thereby, the temperature rise of the cylinder block is promoted while the cylinder head is cooled well. On the other hand, after the warm-up operation ends, the restriction on the supply of the cooling medium to the cylinder block is relaxed or released.

  As described above, while the supply state of the cooling medium to the cylinder head and the cylinder block is appropriately set by the cooling medium circulation system, the cylinder head side cooling medium temperature sensor is connected to the cylinder head side. A signal corresponding to the temperature of the cooling medium is output. Here, the cylinder head is a member close to the fuel injection position and the combustion chamber, and has a smaller heat capacity than the cylinder block. Therefore, the temperature change of the cooling medium on the cylinder head side and the change of the gas temperature in the fuel injection position and the combustion chamber at the time of fuel injection can correspond with a relatively small delay.

  Therefore, the fuel injection control unit controls the state of fuel injection in the main injection and the pre-injection according to the output of the cylinder head side coolant temperature sensor. Thereby, the state of fuel injection in the main injection and the pre-injection can be appropriately controlled in accordance with changes in the fuel injection position and the gas temperature in the combustion chamber.

  That is, the pre-injection has a temperature rising side in the cylinder prior to the main injection and a pre-mixing side prior to combustion. The fuel injection states (main injection amount, main injection timing, pre-injection amount, pre-injection timing) in the main injection and the pre-injection are appropriately controlled according to the output of the cylinder head side coolant temperature sensor. The Accordingly, the temperature rise and premixing by the pre-injection and the combustion for generating power are performed in a more appropriate manner in accordance with the cooling state of the cylinder head appropriately set by the cooling medium circulation system. obtain.

  As described above, according to the engine of the present invention having such a configuration, the state of multistage fuel injection is more appropriately controlled according to the operating state. Therefore, the environmental performance of the engine can be further improved.

  (2) The fuel injection control unit may be configured to control the pre-injection amount in accordance with an output of the cylinder head side coolant temperature sensor.

  For example, the pre-injection amount is increased when the temperature of the cooling medium on the cylinder head side is relatively low.

  When the temperature of the cylinder head is relatively low, a certain amount of fuel is injected at the time of the pre-injection, so that a part of the fuel of the pre-injection amount is reduced before the combustion. It is used for raising the gas temperature in the cylinder, and the remainder of the fuel is well mixed with the gas in the cylinder.

  Due to the gas temperature increase in the cylinder before combustion, the ignition delay time during the main injection is shortened. And by shortening this ignition delay time, the rapid pressure rise in the said cylinder is suppressed, and generation | occurrence | production of noise and NOx is suppressed. Further, the remaining portion of the pre-injected fuel that has not been used for the gas temperature rise in the cylinder before combustion remains in the cylinder prior to the main injection. This remaining fuel is well mixed with the gas in the cylinder. Thereby, combustion efficiency improves. Therefore, an increase in output during high-load operation and an improvement in fuel efficiency (by suppressing the amount of the main injection following the pre-injection) can be achieved.

  Furthermore, the amount of generated heat related to the pre-injection increases as the pre-injection amount increases. Thereby, even if the main injection timing is retarded in order to warm the catalyst device by raising the exhaust gas temperature, the occurrence of misfire during combustion can be suppressed.

  On the other hand, when the temperature of the cooling medium on the cylinder head side is low, if the pre-injection amount is too small, the increase in gas temperature in the cylinder during the main injection and combustion is insufficient. Further, the amount of unignited fuel remaining in the cylinder prior to the main injection is insufficient. Therefore, the effect of suppressing the generation of noise and NOx during combustion and the effect of improving combustion efficiency by the pre-injection are reduced.

  On the other hand, when the temperature of the cooling medium on the cylinder head side is high and the pre-injection amount is large, the amount of fuel that is ignited before the main injection and combustion without being used for generating power increases. Resulting in. Therefore, fuel consumption will deteriorate. Therefore, in this case, the pre-injection is limited. That is, the pre-injection is cut or the pre-injection amount is reduced. Thereby, the said pre-injection can be implemented by the minimum level which can show | play a predetermined effect.

  (3) The fuel injection control unit may be configured to control the pre-injection timing according to an output of the cylinder head side coolant temperature sensor.

  For example, the pre-injection timing is advanced when the temperature of the cooling medium on the cylinder head side is relatively low. In this case, since the fuel related to the pre-injection is injected while the temperature and pressure in the cylinder are low, sufficient premixing is performed by the pre-injection. Further, the ignition delay of the previous injection is compensated by the advance angle of the previous injection timing.

  Therefore, the ignition stability and the combustion efficiency after the main injection are improved by the advance angle of the pre-injection timing. Furthermore, the generation of noise and NOx is suppressed.

  On the other hand, when the temperature of the cooling medium on the cylinder head side is extremely low, such as during warm-up operation, the pre-injection timing is retarded. In this case, since the fuel is injected after the temperature and pressure in the cylinder are increased, a relatively large amount of heat is generated by the pre-injection. Thereby, the occurrence of misfire can be prevented during the combustion after the main injection.

  (4) The fuel injection control unit may be configured to control the main injection amount in accordance with an output of the cylinder head side coolant temperature sensor.

  For example, when the temperature of the cooling medium on the cylinder head side is relatively low, the main injection amount is decreased while the pre-injection amount is increased. Thereby, fuel consumption improves.

  (5) The fuel injection control unit may be configured to control an injection timing of the main injection in accordance with an output of the cylinder head side coolant temperature sensor.

  For example, when the cylinder head is well cooled by the cooling medium circulation system and the temperature of the cooling medium on the cylinder head side is relatively low, the main injection timing is advanced. That is, the main injection timing, which is normally delayed to some extent from the compression top dead center, approaches the compression top dead center. Thereby, combustion efficiency is improved. At this time, since the cylinder head is well cooled by the cooling medium circulation system, an excessive increase in the combustion temperature is not caused. Therefore, the fuel efficiency is improved while the generation of NOx is suppressed.

  Further, the main injection timing is advanced when the temperature of the cooling medium on the cylinder head side is relatively low and the previous injection timing is advanced. Thereby, extension of the interval between the pre-injection and the main injection is suppressed. Thus, the amount of heat generated by the pre-injection can be maintained during the main injection and combustion. Therefore, the occurrence of misfire is prevented during combustion after the main injection.

  (6) The cooling medium circulation system includes a cooling medium delivery section, an inter-block passage, a cylinder head discharge passage, a cylinder block discharge passage, a radiator, a radiator inflow passage, a radiator discharge passage, and a bypass passage. A first control valve and a second control valve may be provided.

  The cooling medium delivery unit is configured to deliver the cooling medium toward the cylinder head.

  The inter-block flow path is provided so as to connect a cylinder-head cooling medium passage formed in the cylinder head and a cylinder-block cooling medium passage formed in the cylinder block. The cooling medium is supplied from the cylinder head cooling medium passage to the cylinder block cooling medium passage through the inter-block flow path.

  The cylinder head discharge passage is a passage of the cooling medium for discharging the cooling medium in the cylinder medium cooling medium passage from the cylinder head.

  The cylinder block discharge passage is a passage of the cooling medium for discharging the cooling medium in the cylinder medium cooling medium passage from the cylinder block.

  The radiator is configured to cool the cooling medium that has passed through the cylinder head and the cylinder block by heat exchange with outside air.

  The radiator inflow passage is a passage of the cooling medium configured to connect the cylinder head discharge passage, the cylinder block discharge passage, and the radiator. The cooling medium passing through the cylinder head cooling medium passage and the cylinder block cooling medium passage can flow into the radiator via the radiator inflow passage.

  The radiator discharge passage is a passage of the cooling medium configured to connect the radiator and the cooling medium delivery unit. The cooling medium cooled by the radiator and discharged from the radiator is sent to the cooling medium delivery section through the radiator discharge passage.

  The bypass passage is a passage of the cooling medium configured to connect the cylinder head discharge passage and the radiator discharge passage. That is, the bypass passage is configured to allow the cooling medium discharged from the cylinder head cooling medium passage through the cylinder head discharge passage to be returned to the cooling medium delivery section by bypassing the radiator. ing.

  The first control valve is configured to control a communication state between the bypass passage, the radiator discharge passage, and the cooling medium delivery unit. That is, the first control valve is configured to selectively communicate the cooling medium delivery part with either the bypass passage or the radiator discharge passage.

  The second control valve is configured to control a communication state between the cylinder block discharge passage and the radiator inflow passage.

  In this configuration, the coolant passage that bypasses the radiator is formed by communicating the bypass passage and the coolant supply section by the first control valve. That is, the coolant circulation such that the coolant returns to the coolant supply portion again through the cylinder head coolant passage, the cylinder block discharge passage, and the bypass passage from the coolant supply portion. A passage is formed.

  On the other hand, the radiator discharge passage and the cooling medium delivery section are communicated with each other by the first control valve, and the communication between the bypass passage and the cooling medium delivery section is released (closed). The circulation path of the cooling medium that bypasses is eliminated. On the other hand, a circulation path for the cooling medium passing through the radiator is formed. That is, from the cooling medium delivery section, the cooling medium delivery section is again passed through the cylinder head cooling medium passage, the cylinder block discharge passage, the radiator inflow passage, the radiator, and the radiator discharge passage. A circulation path for the cooling medium is formed so as to recirculate.

  Further, the radiator discharge passage and the cooling medium delivery section are communicated with each other by the first control valve, and the cylinder block discharge passage and the radiator inflow passage are communicated with each other by the second control valve. A circulation path of the cooling medium is formed such that the cooling medium discharged from the head and the cylinder block reaches the cooling medium delivery section through the radiator.

  In such a configuration, whether or not the cooling medium discharged from the cylinder head is cooled by the radiator is set according to the operating state of the first control valve. Further, whether or not the cooling medium discharged from the cylinder block is cooled by the radiator is set according to the operating states of the first control valve and the second control valve. That is, the cooling state of the cylinder head by the cooling medium and the cooling state of the cylinder block by the cooling medium can be individually set according to the operating states of the first control valve and the second control valve. .

  According to such a configuration, the cylinder head can be satisfactorily cooled by intensively supplying the cooling medium to the cylinder head. In particular, the cooling medium cooled by heat exchange with the outside air through the radiator is supplied to the cylinder head by the cooling medium delivery unit, so that the temperature rise of the cylinder head can be effectively suppressed. And, as described above, the state of the multistage fuel injection is more appropriately controlled according to the temperature of the cylinder head that has been cooled well in this way. Therefore, the environmental performance of the engine can be further improved.

  (7) The cooling medium circulation system may further include a cylinder head supply passage, an EGR cooler, an EGR cooler supply passage, and an EGR cooling control valve. Here, EGR (exhaust gas recirculation) is a method in which a part of the burned gas is recirculated to the intake air as EGR gas in order to reduce the amount of NOx emission in the exhaust gas. This is a technique for suppressing NOx generation by keeping the temperature low.

  The cylinder head supply passage forms a passage of the cooling medium that connects the cooling medium delivery section and the cylinder head.

  The EGR cooler is interposed in an EGR passage configured to be able to introduce the EGR gas from an exhaust passage to the intake passage. The EGR cooler is configured to cool the EGR gas by heat exchange between the EGR gas and the cooling medium.

  The EGR cooler supply passage constitutes a passage of the cooling medium for branching from the cylinder head supply passage and supplying the cooling medium to the EGR cooler.

  The EGR cooling control valve is interposed in the EGR cooler supply passage. The EGR cooling control valve is configured to control the supply state of the cooling medium to the EGR cooler.

  According to such a configuration, the state of multistage fuel injection is more appropriately controlled while the EGR gas having an appropriate temperature is introduced into the intake passage. Therefore, the environmental performance of the engine can be further improved.

  (8) The engine may further include an EGR gas amount control valve and an EGR control unit.

  The EGR gas amount control valve is interposed in the EGR passage. The EGR gas amount control valve is configured to control the flow rate of the burned gas in the EGR passage.

  The EGR control unit is configured to control an opening degree of the EGR gas amount control valve according to an output of the cylinder head side coolant temperature sensor.

  According to such a configuration, the implementation status of EGR is appropriately controlled as necessary, and the state of multistage fuel injection is more appropriately controlled. Therefore, the environmental performance of the engine can be further improved.

  Hereinafter, embodiments of the present invention (embodiments that the applicant considers best at the time of filing of the present application) will be described with reference to the drawings.

<Schematic configuration of engine>
FIG. 1 is a schematic configuration diagram of an engine 100 according to an embodiment of the present invention. The engine 100 is a diesel engine, and includes a cylinder head 110, a cylinder block 120, an intake system 130, an exhaust system 140, a common rail fuel injection system 150, an EGR system 160, a cooling water circulation system 170, And a control unit 190.

<< Engine block configuration >>
Initially, the structure of the cylinder head 110 and the cylinder block 120 which comprise the engine block which is a main-body part of the engine 100 which concerns on this embodiment is demonstrated.

  The cylinder head main body 111 constituting the main part of the cylinder head 110 is made of a metal block. The cylinder head main body 111 is formed with a water jacket 111a in the cylinder head which is a cooling water passage. The cylinder head 110 is configured to be cooled by heat exchange between the cooling water and the cylinder head 110 when the cooling water passes through the water jacket 111a in the cylinder head.

  The cylinder head body 111 is formed with an intake port 111b and an exhaust port 111c. Intake port 111 b is a cavity that forms an intake passage of engine 100. The end portion of the intake port 111b (the end on the downstream side in the flow direction of intake air) is opened and closed by the intake valve 112. Exhaust port 111 c is a cavity that constitutes an exhaust passage of engine 100. A start end portion (upstream end portion in the flow direction of the burned gas) of the exhaust port 111c is opened and closed by an exhaust valve 113.

  The cylinder block main body 121 constituting the main part of the cylinder block 120 is made of a metal block. The cylinder block body 121 is formed with a cylinder bore 121a which is a cylindrical space. A cylinder block water jacket 121b, which is a cooling water passage, is formed in the cylinder block main body 121 so as to surround the cylinder bore 121a. The cylinder block 120 is configured to be cooled by heat exchange between the cooling water and the cylinder block 120 when the cooling water passes through the water jacket 121b in the cylinder block.

  A piston 122 is accommodated in the cylinder bore 121a so as to be capable of reciprocating in the vertical direction in the figure. At the top of the piston 122, a cavity 122a, which is a recess that forms the main part of the combustion chamber, is formed.

<< Configuration of intake and exhaust systems >>
Next, the configuration of the intake system 130 and the exhaust system 140 will be described.

  An intake pipe 131 is connected to the start end of the intake port 111b (the upstream end in the flow direction of intake air). A surge tank 132 is interposed in the intake pipe 131. The surge tank 132 is formed as a space having a predetermined volume so as to suppress intake air interference between the cylinders and to suppress intake air pulsation.

  A throttle valve 133 is interposed upstream of the surge tank 132 in the flow direction of the intake air. The throttle valve 133 is configured such that the opening degree can be changed by a throttle valve actuator 133a formed of a DC motor.

  An exhaust pipe 141 is connected to the end portion of the exhaust port 111c (the end on the downstream side in the flow direction of the burned gas). A turbocharger 142 is interposed in the intake pipe 131 and the exhaust pipe 141.

  A catalyst device 143 is interposed in the exhaust pipe 141 downstream of the turbocharger 142 in the flow direction of the burned gas. The catalyst device 143 accommodates a DPF catalyst 143a. Here, DPF is an abbreviation for Diesel Particulate Filter. The DPF catalyst 143a is configured to function as a particulate filter that collects particulates (particulates) in the exhaust gas and to function as a catalyst that can simultaneously process NOx.

  That is, when the air-fuel ratio of the burned gas (exhaust gas) reaching the catalyst device 143 is lean, the DPF catalyst 143a stores NOx by changing it to nitrate, and the active oxygen released at this time and The particulates can be oxidized by oxygen in the exhaust gas. Further, when the air-fuel ratio of the exhaust gas is rich, the DPF catalyst 143a releases the stored NOx as NO, and particulates due to the active oxygen generated when the released NO is reduced by HC and CO. It can be oxidized.

<< Configuration of Common Rail Fuel Injection System >>
The common rail fuel injection system 150 includes a fuel tank 151, a fuel intake pipe 152, a fuel supply pump 153, a common rail 154, a fuel supply pipe 155, a combustion chamber injector 156, a fuel supply branch pipe 157, and an exhaust port. And an injector 158.

  The fuel tank 151 is configured to store diesel fuel. One end of a fuel intake pipe 152 is inserted into the fuel tank 151. A fuel supply pump 153 is interposed in the fuel suction pipe 152. The fuel supply pump 153 is configured to supply (send out) fuel at a high pressure toward the common rail 154 connected to the other end of the fuel suction pipe 152. The common rail 154 has a pressure accumulation chamber with a constant volume inside. And the common rail 154 is comprised so that the fuel supplied in the high pressure state by the fuel supply pump 153 can be stored in the said pressure accumulation chamber.

  The fuel supply pipe 155 is provided so as to extend from the common rail 154 toward the cylinder head 110. A combustion chamber injector 156 accommodated in the cylinder head body 111 is connected to the tip of the fuel supply pipe 155. Combustion chamber injector 156 is arranged so that fuel can be injected into the combustion chamber, the main part of which is constituted by a cavity 122 a formed at the top of piston 122.

  In other words, the common rail fuel injection system 150 accumulates the fuel boosted by the fuel supply pump 153 in the common rail 154 and equalizes the fuel, and then supplies the fuel to the combustion chamber injector 156 in each cylinder. In contrast, the fuel injection can be performed with high accuracy.

  A fuel supply branch pipe 157 is provided so as to branch from the fuel supply pipe 155. An exhaust port injector 158 is connected to the tip of the fuel supply branch pipe 157. The exhaust port injector 158 is attached to the exhaust pipe 141. The exhaust port injector 158 is configured to inject fuel into the exhaust gas discharged from the combustion chamber via the exhaust port 111c.

<< Configuration of EGR system >>
The EGR (exhaust gas recirculation) system 160 is configured so that a part of the burned gas can be recirculated to the intake gas as EGR gas in order to suppress the combustion temperature and suppress the generation of NOx. ing. The EGR system 160 includes an EGR passage 161, an EGR cooler 162, and an EGR passage opening / closing control valve 163.

  The EGR passage 161 is provided as a gas passage that connects a position upstream of the exhaust port injector 158 in the exhaust pipe 141 and the surge tank 132. The EGR passage 161 is configured so that a part of the burned gas discharged from the combustion chamber via the exhaust port 111c can be introduced into the intake pipe 131 via the surge tank 132.

  The EGR cooler 162 is interposed in the EGR passage 161. The EGR cooler 162 is configured to cool the EGR gas passing through the EGR passage 161.

  An EGR passage opening / closing control valve 163 is interposed in the EGR passage 161. The EGR passage opening / closing control valve 163 includes an electromagnetic valve mechanism. The EGR execution status can be controlled by the open / close state of the EGR passage open / close control valve 163.

<< Configuration of cooling water circulation system >>
The cooling water circulation system 170 is configured to change the supply state of the cooling water to the cylinder head 110 and the cylinder block 120 by changing the circulation state of the cooling water according to the operation state. That is, the cooling water circulation system 170 includes a so-called “two-system cooling structure” or “separated cooling structure”. Specifically, the cooling water circulation system 170 is configured as follows.

  A cooling water delivery pump 171 is mounted on the outer wall portion on the side and below the cylinder block 120. The cooling water delivery pump 171 sends the cooling water toward the water jacket 111a in the cylinder head formed in the cylinder head body 111, so that the cooling water circulation flow can be generated in the cooling water circulation system 170. It is configured.

  The radiator 172 is configured to cool the cooling water that has passed through the cylinder head 110 and the cylinder block 120 by exchanging heat with the outside air.

  A pump delivery pipe 173 a is connected to a coolant delivery outlet in the coolant delivery pump 171. The cooling water delivery pump 171 is connected to a water jacket 111a in the cylinder head formed on the cylinder head 110 via the pump delivery pipe 173a. Further, a pump suction pipe 173 b is connected to the cooling water suction port of the cooling water delivery pump 171.

  An inter-block communication path 174 is provided at the joint between the cylinder head 110 and the cylinder block 120. The inter-block communication path 174 is formed so as to connect the cylinder head water jacket 111a and the cylinder block water jacket 121b.

  That is, in the cooling water circulation system 170 in the present embodiment, the cooling water is supplied to the water jacket 111 a in the cylinder head by the cooling water delivery pump 171, and the inside of the cylinder block from the water jacket 111 a in the cylinder head via the inter-block communication path 174. The cooling water can be supplied to the water jacket 121b.

  A cylinder head discharge pipe 175a is connected to the water jacket 111a in the cylinder head. The cylinder head discharge pipe 175a is a member that constitutes a cooling water passage that is discharged from the cylinder head 110 (the water jacket 111a in the cylinder head) and travels toward the radiator 172. A cylinder block discharge pipe 175b is connected to the water jacket 121b in the cylinder block. The cylinder block discharge pipe 175b is a member that constitutes a cooling water passage that is discharged from the cylinder block 120 (the water jacket 121b in the cylinder block) and travels toward the radiator 172.

  One end of a radiator inflow pipe 176 a is connected to the cooling water inlet of the radiator 172. The other end of the radiator inflow pipe 176a is connected to the cylinder head discharge pipe 175a and the cylinder block discharge pipe 175b. The radiator inflow pipe 176a is configured to allow cooling water that has passed through the water jacket 111a in the cylinder head and the water jacket 121b in the cylinder block to flow into the radiator 172.

  One end of a radiator discharge pipe 176 b is connected to the cooling water discharge port of the radiator 172. The other end of the radiator discharge pipe 176b is connected to the pump suction pipe 173b. That is, the radiator discharge pipe 176b is provided so as to connect the radiator 172 and the cooling water delivery pump 171. Further, the radiator discharge pipe 176b is configured to be able to send the cooling water cooled by the radiator 172 and discharged from the radiator 172 to the cooling water delivery pump 171.

  One end of a bypass pipe 177 is connected to the upstream side in the flow direction of the cooling water with respect to the connecting part between the cylinder head discharge pipe 175a and the radiator inflow pipe 176a. The other end of the bypass pipe 177 is connected to the pump suction pipe 173b. That is, the bypass pipe 177 is a member that connects the cylinder head discharge pipe 175a and the pump suction pipe 173b so as to bypass the radiator 172.

  An EGR cooler supply pipe 178a is provided so as to branch from the pump delivery pipe 173a. The EGR cooler supply pipe 178 a is connected to the cooling water inlet of the EGR cooler 162. The EGR cooler supply pipe 178a is configured to supply cooling water to the EGR cooler 162. One end of an EGR cooler discharge pipe 178b is connected to the cooling water discharge port of the EGR cooler 162. The other end of the EGR cooler discharge pipe 178b is connected to a portion of the pump suction pipe 173b that is downstream of the joining position of the radiator discharge pipe 176b and the bypass pipe 177.

  A first control valve 179a is interposed at a joining position of the radiator discharge pipe 176b and the bypass pipe 177 in the pump suction pipe 173b. The first control valve 179a is a two-way switching valve that operates electromagnetically, and is configured to control the communication state of the bypass pipe 177 and the radiator discharge pipe 176b with the cooling water delivery pump 171. That is, the first control valve 179a is configured to selectively communicate the cooling water suction port of the cooling water delivery pump 171 with the radiator 172 or the bypass pipe 177.

  Specifically, in the first state, the first control valve 179a blocks communication between the radiator 172 (radiator discharge pipe 176b) and the cooling water delivery pump 171, and the bypass pipe 177 and the cooling water delivery pump 171. Are configured to communicate with each other. In the second state, the first control valve 179a allows the radiator 172 (the radiator discharge pipe 176b) and the cooling water delivery pump 171 to communicate with each other, and prevents the bypass pipe 177 and the cooling water delivery pump 171 from communicating with each other. Is configured to do.

  A second control valve 179b is interposed at the joining position of the cylinder head discharge pipe 175a and the cylinder block discharge pipe 175b and the radiator inflow pipe 176a. The second control valve 179b is configured to control the communication state between the cylinder block discharge pipe 175b and the radiator inflow pipe 176a.

  In other words, in the present embodiment, the second control valve 179b is opened to allow the cylinder block 120 (cylinder block discharge pipe 175b) and the radiator 172 (radiator inflow pipe 176a) to communicate with each other and close the valve. The communication between the cylinder block 120 and the radiator 172 is cut off. In the present embodiment, the cylinder head discharge pipe 175a and the radiator 172 (the radiator inflow pipe 176a) are always in communication regardless of the operating state of the second control valve 179b.

  An EGR cooling control valve 179c composed of an electromagnetic valve is interposed in the EGR cooler supply pipe 178a. The EGR cooling control valve 179c is configured to control the supply state of the cooling water to the EGR cooler 162.

<< Control system configuration >>
The engine 100 according to the present embodiment controls various operations based on signals from various sensors 181 to 186 configured to generate signals based on driving conditions, and the sensors 181 to 186 and the like. And a configured control unit 190.

  A throttle position sensor 181 is interposed at a position corresponding to the throttle valve 133 in the intake pipe 131. The throttle position sensor 181 is configured to output a signal corresponding to the opening of the throttle valve 133 (throttle valve opening TA).

  An air flow meter 182 is interposed upstream of the throttle valve 133 in the flow direction of the intake air. The air flow meter 182 is a known hot-wire air flow meter, and is configured to generate an output corresponding to a mass flow rate per unit time of intake air flowing in the intake pipe 131.

  An upstream air-fuel ratio sensor 183a and a downstream air-fuel ratio sensor 183b are interposed in the exhaust pipe 141. The upstream air-fuel ratio sensor 183a is interposed at a position upstream of the catalyst device 143 in the flow direction of the exhaust gas. On the other hand, the downstream air-fuel ratio sensor 183b is interposed at a position downstream of the catalyst device 143 in the flow direction of the exhaust gas. These air-fuel ratio sensors 183a and 183b are configured to generate an output corresponding to the air-fuel ratio of the exhaust gas.

  The catalyst device 143 is provided with a catalyst bed temperature sensor 184 configured to generate an output corresponding to the bed temperature of the DPF catalyst 143a.

  A fuel pressure sensor 185 configured to generate an output corresponding to the pressure of the fuel in the pressure accumulating chamber is attached to the common rail 154.

  A cylinder head side cooling water temperature sensor 186 is interposed on the cylinder head 110 side in the cooling water circulation system 170. The cylinder head side cooling water temperature sensor 186 is configured to generate an output signal corresponding to the cooling water temperature on the cylinder head 110 (inside cylinder head water jacket 111a) side. That is, the cylinder head side coolant temperature sensor 186 generates an output signal corresponding to the coolant temperature in the cylinder head water jacket 111a or in the cylinder block discharge pipe 175b immediately after being discharged from the cylinder head water jacket 111a. Is configured to do.

  The control unit 190 includes various actuators such as a throttle valve actuator 133a, a combustion chamber injector 156, an exhaust port injector 158, an EGR passage opening / closing control valve 163, a first control valve 179a, a second control valve 179b, and an EGR cooling control valve 179c. It is comprised so that operation | movement can be controlled. Specifically, the control unit 190 includes a CPU 191, a ROM 192, a RAM 193, a backup RAM 194, and an interface 195. These are connected to each other by a bus 196.

  The CPU 191 receives signals from the above-described sensors 181 to 186 via the interface 195, performs various calculations based on the signals, and controls various actuators such as the combustion chamber injector 156 based on the calculation results. A command signal for operation is generated.

  The ROM 192 stores in advance a routine (program) that is executed when the CPU 191 performs the calculation, a table (look-up table, map) that is referred to when the routine is executed, and the like. The RAM 193 and the backup RAM 194 are configured to temporarily store data as necessary when the CPU 191 executes a routine. The backup RAM 194 is configured so that data is stored with the power turned on, and the stored data can be retained even after the power is shut off.

  The interface 195 is electrically connected to various actuators such as the throttle valve actuator 133a and various sensors such as the throttle position sensor 181. The interface 195 is configured to supply signals received from the various sensors described above to the CPU 191 and to transmit command signals received from the CPU 191 to the various actuators described above.

  The control unit 190 according to the present embodiment uses the combustion chamber injector 156 and the exhaust port injector 158 to generate fuel based on signals from the upstream air-fuel ratio sensor 183a, the downstream air-fuel ratio sensor 183b, the cylinder head-side cooling water temperature sensor 186, and the like. The injection timing and the injection amount can be controlled. In particular, the control unit 190 of the present embodiment is configured to control the timing and amount of main injection and pilot injection to the combustion chamber by the combustion chamber injector 156 based on a signal from the cylinder head side coolant temperature sensor 186. ing.

  Here, “main injection” is fuel injection performed near the compression top dead center. The “pilot injection” is a relatively small amount of fuel injection that is performed prior to the main injection. The pilot injection is performed before the compression top dead center, and the main injection is performed after a slight interval from the pilot injection. Details of control of main injection and pilot injection based on the output signal of the cylinder head side coolant temperature sensor 186 will be described later.

  Further, the control unit 190 of the present embodiment controls the operating states of the first control valve 179a, the second control valve 179b, and the EGR cooling control valve 179c based on signals from the cylinder head side cooling water temperature sensor 186 and the like. Thus, the circulating state of the cooling water can be controlled.

  Specifically, the control unit 190 opens the first control valve 179a when the cooling water temperature is equal to or higher than a predetermined first reference temperature (70 ° C.), whereby the radiator 172 (radiator discharge pipe 176b). And the coolant feed pump 171 are communicated with each other, and the communication between the bypass pipe 177 and the coolant feed pump 171 is blocked. On the other hand, the control unit 190 opens the second control valve 179b when the cooling water temperature is equal to or higher than a predetermined second reference temperature (80 ° C.), and the cylinder block 120 (cylinder block discharge pipe 175b) The radiator 172 (radiator inflow pipe 176a) is configured to communicate with each other.

  That is, the control unit 190 controls the operation states of the first control valve 179a and the second control valve 179b in accordance with a signal from the cylinder head side coolant temperature sensor 186, as will be described in detail in the following operation description. The cooling water circulation state is changed according to the operation state, and the cooling water supply state to the cylinder head 110 and the cylinder block 120 can be changed.

  Further, the control unit 190 can increase or decrease the amount of EGR gas by controlling the valve opening state of the EGR passage opening / closing control valve 163 according to the operating state of the engine 100, that is, the cooling water temperature on the cylinder head 110 side. It is configured.

  Furthermore, the control unit 190 is configured to control the supply state of the cooling water to the EGR cooler 162 by controlling the open / closed state of the EGR cooling control valve 179c according to the operating state of the engine 100. .

  For example, the control unit 190 closes the EGR cooling control valve 179c during the warming-up operation in which the cooling water temperature has not reached a predetermined temperature (the second reference temperature) after the start, so that the cooling water during the warming-up operation is closed. The supply to the EGR cooler 162 is cut off. Further, the control unit 190 is configured to permit the supply of the cooling water to the EGR cooler 162 by opening the EGR cooling control valve 179c after the warm-up operation is completed. Furthermore, the control unit 190 is configured to open the EGR cooling control valve 179c as necessary even when the engine load is high even during the warm-up operation.

<Description of Operation of Engine of Embodiment>
Next, the operation of the engine 100 of the present embodiment having the above-described configuration will be described.

<< Operation of cooling water circulation system >>
FIGS. 2 to 4 are schematic diagrams for illustrating the flow state of the cooling water in the engine 100 of the present embodiment shown in FIG.

  (A) First, when the engine is warming up and the coolant temperature is lower than the first reference temperature, the first control valve 179a is set to the first state, and the second control valve 179b is closed. . Thereby, a bypass flow path reaching the cooling water delivery pump 171 is formed from the cylinder head discharge pipe 175a via the bypass pipe 177 (bypassing the radiator 172). Further, the communication between the cylinder block discharge pipe 175b and the radiator inflow pipe 176a is blocked. Therefore, a flow of cooling water is formed as indicated by arrows in FIG.

  That is, the cooling water is sent from the cooling water delivery pump 171 toward the pump delivery pipe 173a. The cooling water delivered toward the pump delivery pipe 173a flows into the cylinder head 110 (in-cylinder head water jacket 111a in FIG. 1). The cooling water flowing into the cylinder head 110 cools the cylinder head 110 and is then discharged to the cylinder head discharge pipe 175a.

  At this time, since the second control valve 179b is closed, the bypass pipe 177 and the cooling water delivery pump 171 communicate with each other, but the communication between the radiator discharge pipe 176b and the cooling water delivery pump 171 is blocked. Therefore, the cooling water discharged from the cylinder head 110 to the cylinder head discharge pipe 175a is not passed through the radiator inflow pipe 176a, the radiator 172, and the radiator discharge pipe 176b, but through the bypass flow path passing through the bypass pipe 177. Then, the refrigerant returns to the cooling water delivery pump 171.

  Further, since the second control valve 179b is closed, the flow of the cooling water in the cylinder block discharge pipe 175b, that is, the flow of the cooling water discharged from the cylinder block 120 is blocked. Therefore, the cooling water stays in the cylinder block 120 (inside the cylinder block water jacket 121b in FIG. 1). Thereby, rapid temperature increase in the cylinder block 120 is achieved. That is, rapid warm-up operation is achieved. Therefore, the friction in the cylinder block 120 is reduced early.

  At the cooling water temperature, normally, the EGR cooling control valve 179c is closed. Therefore, in this case, the supply of the cooling water to the EGR cooler 162 is stopped. However, when the engine load is high, etc., the EGR cooling control valve 179c is opened as necessary, so that the cooling water is exchanged between the EGR cooler 162 and the cylinder head 110 (drawn by a broken line in the figure). See the arrow).

  (B) Next, when the coolant temperature is equal to or higher than the first reference temperature and lower than the second reference temperature, the first control valve 179a is set to the second state. Thereby, the bypass flow path which makes the bypass pipe 177 and the cooling water delivery pump 171 communicate is interrupted | blocked. Therefore, a flow of cooling water is formed as indicated by arrows in FIG.

  That is, the cooling water discharged from the cylinder head 110 to the cylinder head discharge pipe 175a returns to the cooling water delivery pump 171 through a flow path passing through the radiator inflow pipe 176a, the radiator 172, and the radiator discharge pipe 176b. Thereby, the cooling water cooled by the heat exchange with the outside air by the radiator 172 is supplied to the cooling water delivery pump 171.

  Here, as in the case of (A) described above, since the warm-up operation is also performed at the cooling water temperature, normally, the EGR cooling control valve 179c is closed, and if necessary, the EGR cooling control valve 179c is It is opened (see the arrow drawn with a broken line in the figure).

  (C) Next, when the coolant temperature is equal to or higher than the second reference temperature, the second control valve 179b is opened (end of warm-up operation). Thereby, the cylinder block discharge pipe 175b and the radiator inflow pipe 176a are communicated with each other, and a flow of cooling water as shown by an arrow in FIG. 4 is formed.

  That is, the cooling water that has flowed into the cylinder head 110 from the cooling water delivery pump 171 via the pump delivery pipe 173a cools the cylinder head 110, and a part thereof passes through the inter-block communication path 174 (see FIG. 1). And flows into the cylinder block 120. The remaining portion of the cooling water flowing into the cylinder head 110 that flows into the cylinder block 120 is discharged to the cylinder head discharge pipe 175a, cooled by the radiator 172, and then returned to the cooling water feed pump 171.

  The cooling water that has flowed into the cylinder block 120 cools the cylinder block 120, is discharged to the cylinder block discharge pipe 175 b, is cooled by the radiator 172, and then returns to the cooling water feed pump 171.

  Here, at the cooling water temperature, the EGR cooling control valve 179c is opened. Therefore, in this case, the cooling water is supplied to the EGR cooler 162. Thereby, the EGR cooler 162 is cooled.

  (D) Note that, even under the conditions (A) and (B) described above, when the engine load suddenly increases, the first control valve 179a is the second control valve as in the above (C). And the second control valve 179b is opened. Thereby, the cooling water in the cylinder head 110 and the cylinder block 120 is introduced into the radiator 172 (see FIG. 4).

  (E) Further, even under the condition (B) described above, the cooling water temperature is set to the second reference temperature when the engine is cold started and particularly when the outside air temperature at the start is extremely low. Until reaching, the first control valve 179a is in the first state and the second control valve 179b is closed (see FIG. 2), as in (A) above. Thereby, warm-up is further promoted.

  (F) Further, even when the DPF regeneration process is performed in the engine 100 under the above-described condition (C), that is, even after the warm-up operation is finished, the first control valve 179a is set to the first state. . In this case, similarly to the case of (A) described above, the cooling water that has passed through the cylinder head 110 returns to the cooling water delivery pump 171 without being cooled by the radiator 172. As a result, the temperature of the cylinder head 110 is raised, so that the temperature of the exhaust gas rises and the regeneration process of the DPF catalyst 143a is efficiently performed.

  In this case, when the EGR cooling control valve 179c is opened, the introduction of the cooling water to the EGR cooler 162 is continued. In this case, heat exchange occurs between the heated EGR gas introduced into the EGR passage 161 and the cooling water introduced into the EGR cooler 162. As a result, the EGR gas is sufficiently cooled to such an extent that the NOx reduction effect can be sufficiently achieved. Further, the temperature of the cylinder head 110 is promoted by further increasing the temperature of the cooling water by heat transfer from the EGR gas to the cooling water in the EGR cooler 162. Therefore, the regeneration process (DPF regeneration process) of the DPF catalyst 143a can be efficiently performed while exhaust gas recirculation (EGR) for NOx reduction is performed without any inconvenience.

  (G) Furthermore, under the condition (C) described above, that is, even after the warm-up operation is completed, the low-load operation, the fuel cut operation, and the like are continued for a long time, so that the cylinder head side cooling is performed. The water temperature may be near the second reference temperature or below the second reference temperature. In such a case, the EGR cooling control valve 179c is closed in order to prevent excessive cooling of the EGR gas. Thereby, generation | occurrence | production of HC etc. by EGR gas being cooled excessively can be suppressed.

<< Control of EGR gas amount >>
In the present embodiment, the EGR passage opening / closing control valve 163 is closed during the catalyst warm-up in which the exhaust gas temperature is raised and the catalyst device 143 is warmed up. That is, EGR is cut.

  Further, during the EGR, the open state of the EGR passage opening / closing control valve 163 is controlled based on the map or arithmetic expression stored in advance in the ROM 192 and the parameters based on the engine operating state described above.

  That is, in this embodiment, when the coolant temperature on the cylinder head 110 side becomes high, the EGR amount is increased. As a result, a relatively large amount of EGR gas cooled well by the EGR cooler 162 is introduced into the combustion chamber. Therefore, the combustion temperature is lowered in combination with an increase in the heat capacity of the fuel mixture and a decrease in the oxygen concentration, which are the effects of the introduction of EGR gas. Therefore, NOx is reduced.

  On the other hand, when the cylinder head 110 is cooled well and the cooling water temperature on the cylinder head 110 side becomes low, the generation amount of NOx can be sufficiently reduced even if the EGR amount is not so large. Therefore, in this case, the EGR amount is reduced. Thereby, generation | occurrence | production of misfire, HC, etc. can be suppressed.

<< Operation of fuel injection system >>
Referring to FIG. 1 again, the control unit 190 controls the supply state of the cooling water to the cylinder head 110 and the cylinder block 120 as described above according to the signal from the cylinder head side cooling water temperature sensor 186, while the combustion chamber injector. The operations of 156 and the exhaust port injector 158 are controlled as follows.

<<< Calculation of target fuel injection amount >>>
First, the CPU 191 is based on the engine speed NE, the intake air flow rate Ga obtained based on the output of the air flow meter 182, the opening degree of the EGR passage opening / closing control valve 163, and the table stored in the ROM 192. Thus, the in-cylinder intake air amount that is the current intake air amount of the cylinder that reaches the intake stroke is obtained.

  Next, the CPU 191 determines various parameters based on the engine operating state, such as the engine speed NE and the throttle valve opening degree TA obtained based on the output of the throttle position sensor 181, and the in-cylinder intake air previously obtained. The basic fuel injection amount Qb is calculated based on the amount. The calculation of the basic fuel injection amount Qb is performed based on a map or an arithmetic expression showing the relationship among the engine speed NE, the throttle valve opening degree TA, and the basic fuel injection amount Qb. This map or arithmetic expression is created based on experiments or simulations performed in advance, and is stored in the ROM 192 in advance.

  Feedback correction based on the outputs of the upstream air-fuel ratio sensor 183a and the downstream air-fuel ratio sensor 183b is performed on the basic fuel injection amount Qb. Thereby, the target fuel injection amount Qt, which is the fuel amount required in the current stroke, is calculated.

<<< Determination of main injection timing / pilot injection timing >>>
Subsequently, the CPU 191 determines a main injection timing Tmain and a pilot injection timing Tpilot. Here, the main injection timing Tmain is the start timing of the main injection, more precisely, the timing at which the CPU 191 issues a fuel injection command signal to the combustion chamber injector 156. The same applies to the pilot injection timing Tpilot.

  By this pilot injection, temperature rise and premixing in the combustion chamber are performed prior to main injection and combustion. That is, a part of the injected fuel related to the pilot injection is used for increasing the gas temperature in the combustion chamber before combustion, and the remaining portion of the fuel is well mixed with the gas in the combustion chamber.

  Due to the gas temperature rise in the combustion chamber before combustion by this pilot injection, the ignition delay time at the time of main injection is shortened. And by shortening this ignition delay time, rapid pressure rise in the combustion chamber is suppressed, and generation of noise and NOx is suppressed. Further, the remaining part of the fuel related to the pilot injection that has not been used for the gas temperature rise in the combustion chamber before combustion remains in the combustion chamber prior to the main injection. This remaining fuel is well mixed with the gas in the combustion chamber.

  The main injection timing Tmain is determined mainly based on the outputs of the catalyst bed temperature sensor 184 and the cylinder head side coolant temperature sensor 186. The main injection timing Tmain is usually performed at a time delayed from the compression top dead center (TDC) in order to suppress the generation of NOx due to the high combustion temperature. In the present embodiment, the main injection timing Tmain during normal operation is set in the vicinity of the crank angle (ATDC 5 ° CA) when it is retarded by about 5 ° from the compression top dead center (TDC). Depending on the fuel injection amount, the main injection during normal operation ends when the crank angle is approximately 10 ° (ATDC 10 ° CA) after compression top dead center.

  When the warm-up operation is being performed and the bed temperature of the DPF catalyst 143a is low, the main injection timing Tmain is retarded by about 5 ° for catalyst warm-up. As a result, the exhaust temperature rises and the catalyst is warmed up quickly. When the catalyst warm-up is completed, the main injection timing Tmain is returned to that during normal operation.

  On the other hand, when the cylinder head 110 is well cooled after the warm-up operation is finished and the coolant temperature on the cylinder head 110 side is lower than a predetermined reference temperature, the main injection timing Tmain is advanced. Is done. In this case, the main injection is performed at a point closer to the compression top dead center. In this embodiment, the main injection timing Tmain in this case is set in the vicinity of 2 ° before compression top dead center (BTDC 2 ° CA). Thereby, combustion efficiency is improved. At this time, since the cylinder head 110 is cooled well, an excessive increase in the combustion temperature is not caused. Therefore, the fuel efficiency is improved while the generation of NOx is suppressed.

  The pilot injection is usually performed prior to the main injection by a predetermined crank angle (20 ° CA in the present embodiment). That is, the interval Tint between the pilot injection and the main injection is about 20 ° CA. Therefore, the normal pilot injection timing Tpilot is in the vicinity of BTDC 15 ° CA in the present embodiment.

  Here, at the initial stage of the warm-up operation and during the catalyst warm-up, the pilot injection timing Tpilot is retarded by about 5 °. Thereby, the interval Tint between the pilot injection and the main injection can be maintained. Therefore, it is possible to prevent misfire due to the interval Tint becoming too long.

  Further, when the warm-up operation is being performed and the above-described catalyst warm-up is not performed, the pilot injection timing Tpilot is advanced by about 5 °. Thereby, the ignition delay of the pilot injection itself is compensated by the advance angle. Therefore, when the main injection timing Tmain arrives, the temperature in the combustion chamber is appropriately raised. Therefore, combustion during warm-up operation where the engine temperature is low is stabilized.

  Further, when the cylinder head 110 is cooled well after the warm-up operation is finished and the coolant temperature on the cylinder head 110 side is lower than a predetermined reference temperature, the pilot injection timing Tpilot is advanced. Is done. In this case, fuel is injected by pilot injection while the temperature and pressure in the combustion chamber are low. Thereby, sufficient premixing and temperature rise of the combustion chamber are performed. Therefore, the ignition stability and the combustion efficiency after the main injection are improved by the advance angle of the pilot injection timing Tpilot after the warm-up operation ends. Furthermore, the generation of noise and NOx is suppressed.

<<< Determination of main injection quantity / pilot injection quantity >>>
Further, the CPU 191 calculates the main injection amount Qmain and the pilot injection amount Qpilot from the target fuel injection amount Qt and the interval Tint between the pilot injection and the main injection.

  That is, the amount of ignition before combustion by pilot injection does not contribute to the generation of power during combustion, while the amount of premixing by pilot injection (the amount of non-ignition before combustion) contributes to the generation of power during combustion.

  Here, when the interval Tint is long, if the amount of ignition before combustion by pilot injection is not increased, the temperature rise in the combustion chamber at the time of main injection and combustion is insufficient. In this case, the pilot injection amount Qpilot is increased. However, since most of the increase in the pilot injection amount Qpilot does not contribute to the generation of power during combustion, the main injection amount Qmain cannot be reduced corresponding to the increase in the pilot injection amount Qpilot.

  On the other hand, when the interval Tint is short, or after the warm-up operation is finished and the cylinder head 110 is well cooled and the coolant temperature on the cylinder head 110 side is lower than a predetermined reference temperature, the pilot The proportion of premixing by injection increases. In these cases, the main injection amount Qmain is decreased corresponding to the premixed amount. Thereby, combustion efficiency is improved by sufficient premixing, and fuel efficiency is improved.

  The CPU 191 calls a table created in consideration of these matters from the ROM 192, calculates the main injection amount Qmain and the pilot injection amount Qpilot based on the above-described parameters, and calculates the calculated values to the cylinder head side. According to the output of the cooling water temperature sensor 186, the correction is made as follows.

  For example, when the coolant temperature on the cylinder head 110 side is relatively low, the pilot injection amount Qpilot is increased.

  When the temperature of the cylinder head 110 is relatively low, a certain amount of fuel is injected to a certain extent at the time of pilot injection, so that a part of the fuel related to the pilot injection is before combustion. This is used to raise the gas temperature in the combustion chamber, so that the temperature of the combustion chamber is raised satisfactorily, and a sufficient amount of ignition remaining fuel remains in the combustion chamber. The remaining fuel is well mixed with the gas in the combustion chamber, so that the combustion efficiency is improved.

  Further, the amount of generated heat related to the pilot injection is increased by increasing the pilot injection amount Qpilot. Thereby, even if the main injection timing Tmain is retarded in order to warm the exhaust gas temperature and warm up the catalyst device 143, the occurrence of misfire during combustion can be suppressed.

  On the other hand, when the coolant temperature on the cylinder head 110 side is high and the pilot injection amount Qpilot is large, the amount of fuel that is ignited before main injection and combustion without being used for generating power increases. Therefore, fuel consumption will deteriorate. Therefore, in this case, pilot injection is limited. That is, the pilot injection is cut or the pilot injection amount Qpilot is reduced. As a result, pilot injection can be performed at a minimum level at which a predetermined effect can be achieved.

  Furthermore, when the coolant temperature on the cylinder head 110 side is relatively low, the pilot injection amount Qpilot is increased, but the main injection amount Qmain can be decreased. Thereby, fuel consumption improves.

<<< Injection control to exhaust port >>>
Further, when the DPF regeneration process is performed, fuel is appropriately injected from the exhaust port injector 158. As a result, the exhaust temperature rises, and the regeneration process of the DPF catalyst 143a is performed efficiently.

<< Example of Combustion Chamber Fuel Injection Control by Control Section >>
Next, with respect to the embodiment of the fuel injection control process to the combustion chamber executed by the control unit 190 shown in FIG. 1, the flow chart of FIG. Will be described.

  FIG. 5 is a combustion chamber fuel injection control routine. In this embodiment, it is activated and executed every predetermined time (for example, every time the crank angle becomes BTDC 30 ° CA).

  When the fuel injection control routine 500 in FIG. 5 is started, first, at step 505, the elapsed time t from the engine start, the engine speed NE, the accelerator opening ACCP, the throttle valve opening TA, the cylinder head side cooling water temperature. Parameters such as THW and catalyst bed temperature THC are read.

  Next, at step 510, the basic fuel injection amount Qb is calculated based on the above-described map or arithmetic expression stored in advance in the ROM 192 and the parameters read in advance. By correcting the calculated basic fuel injection amount Qb as appropriate in step 515, the target fuel injection amount Qt is calculated.

  Subsequently, in step 520, based on the map or arithmetic expression stored in advance in the ROM 192 and the parameters read in advance, the pilot injection amount Qpilot, the main injection amount Qmain, the main injection timing Tmain, and the pilot injection timing Tpilot Is determined.

  Thereafter, in step 525, it is determined whether the current operating state is a warm-up operation. That is, it is determined whether the elapsed time t from the engine start is before the predetermined time t1 has elapsed and the cylinder head side cooling water temperature THW is lower than the predetermined water temperature THW1 (the second reference temperature, that is, 80 ° C.). The

  When the current operation state is the warm-up operation (step 525 = Yes), it is subsequently determined whether or not the current operation state is the catalyst warm-up. That is, it is determined whether or not the catalyst bed temperature THC is lower than the predetermined temperature THC1.

  If the current operating state is the catalyst warming up (step 530 = Yes), the main injection timing Tmain is retarded by a predetermined time ΔTmain at step 540 and the pilot injection amount Qpilot at step 545. Is increased by a predetermined amount ΔQpilot. These ΔTmain and ΔQpilot are determined based on a map or arithmetic expression stored in advance in the ROM 192 and the parameters read in advance.

  On the other hand, if the current operation state is not warming the catalyst (step 530 = No), the pilot injection timing Tpilot is advanced by a predetermined time ΔTpilot in step 550, and the pilot injection amount Qpilot is determined in step 555. The amount is increased by a fixed amount ΔQpilot. These ΔTpilot and ΔQpilot are determined based on a map or arithmetic expression stored in advance in the ROM 192 and the parameters read in advance.

  If the current operation state is after the end of the warm-up operation (step 525 = No), then, in step 560, the current cylinder head side cooling water temperature THW is a predetermined water temperature higher than the above-mentioned predetermined water temperature THW1. It is determined whether the temperature is lower than THW2.

  If the current cylinder head-side cooling water temperature THW is lower than the predetermined water temperature THW2 (step 560 = Yes), the cylinder head 110 is cooled well, so the main injection timing Tmain is made closer to the compression top dead center. However, the generation of NOx due to an increase in the combustion temperature can be suppressed, and the combustion efficiency can be increased. Therefore, in this case, at step 570, the main injection timing Tmain is advanced by a predetermined time ΔTmain. This ΔTmain is determined on the basis of a map or arithmetic expression stored in advance in the ROM 192 and the parameters read earlier.

  In step 575, the pilot injection timing Tpilot is advanced by a predetermined time ΔTpilot corresponding to the advance angle of the main injection timing Tmain. This ΔTpilot is determined based on a map or arithmetic expression stored in advance in the ROM 192 and the parameters read earlier.

  Further, at step 580, the pilot injection amount Qpilot is increased by a predetermined amount ΔQpilot. In step 585, the main injection amount Qmain is decreased by a predetermined amount ΔQmain in response to the increase in the pilot injection amount Qpilot. These ΔQmain and ΔQpilot are determined based on a map or arithmetic expression stored in advance in the ROM 192 and the parameters read earlier.

  If the current cylinder head-side cooling water temperature THW is not lower than the predetermined water temperature THW2 (step 560 = No), the temperature of the cylinder head 110 is relatively high, so the pilot injection amount Qpilot calculated in step 520, the main injection The quantity Qmain, the main injection timing Tmain, and the pilot injection timing Tpilot are maintained. That is, fuel injection is performed under normal fuel injection conditions.

  In this manner, after the final pilot injection amount Qpilot, main injection amount Qmain, main injection timing Tmain, and pilot injection timing Tpilot are determined, the process proceeds to step 590. In step 590, the final pilot injection amount Qpilot, the main injection amount Qmain, the main injection timing Tmain, the pilot injection timing Tpilot, and the output of the fuel pressure sensor 185 (common rail internal pressure) are determined. Thus, the combustion chamber injector 156 is operated for a predetermined time. That is, pilot injection and main injection of the determined predetermined timing and predetermined amount (predetermined injection time) are performed on the combustion chamber. Thereafter, the process proceeds to step 595, and this routine is temporarily terminated.

<Effects of Embodiment and Examples>
Hereinafter, operations and effects of the configuration of the present embodiment will be described with reference to the drawings.

  Referring to FIG. 1, the cooling water circulation system 170 of this embodiment includes a so-called “two-system cooling structure” or “separated cooling structure”. In particular, in the cooling water circulation system 170 of the present embodiment, the relatively low-temperature cooling water immediately after being sent from the cooling water delivery pump 171 (cooled by the radiator 172) is supplied to the cylinder head 110. Then, according to the coolant temperature on the cylinder head 110 side, the execution status of pilot injection, main injection, and EGR is controlled by the control unit 190.

  Therefore, according to the configuration of the present embodiment, when the cylinder head 110 is well cooled as in the above-described example, the pilot injection amount Qpilot is increased to increase the temperature in the combustion chamber before combustion. Premixing is performed appropriately. Thereby, combustion efficiency improves.

  In particular, in this case, the amount of fuel of the premixed amount (remaining ignition amount) that contributes to the generation of power during combustion without contributing to the temperature rise is secured among the fuel of the pilot injection amount Qpilot. Therefore, the fuel efficiency is improved by reducing the main injection amount Qmain corresponding to the premixed amount.

  In this case, even if the main injection timing Tmain is advanced and the main injection is performed at a timing closer to the compression top dead center, the amount of NOx generated can be suppressed. That is, it is possible to set the main injection timing Tmain so that the combustion efficiency is higher than that of the conventional one while suppressing the generation of NOx.

  Further, in this case, the pilot injection timing Tpilot is advanced. Thereby, sufficient premixing is performed by the pilot injection. Further, the ignition delay of the pilot injection is compensated by the advance angle. Therefore, when the main injection timing Tmain arrives, the temperature in the combustion chamber is appropriately raised. Therefore, the ignition stability and the combustion efficiency after the main injection are improved by the advance angle of the pilot injection timing Tpilot. Furthermore, the generation of noise and NOx is suppressed more favorably.

  According to the above-described embodiment, the pilot injection timing Tpilot is advanced when the temperature of the cylinder head 110 is low, such as during warm-up operation. Therefore, combustion at a low temperature is stabilized.

  According to the above-described embodiment, the main injection timing Tmain and the pilot injection timing Tpilot are retarded by about 5 ° during catalyst warm-up. Therefore, the catalyst warm-up is performed quickly while suppressing the occurrence of misfire during combustion.

  According to the configuration of the present embodiment, the relatively low-temperature cooling water immediately after being sent from the cooling water delivery pump 171 (cooled by the radiator 172) is supplied to the EGR cooler 162. Thereby, cooling of EGR gas is performed more efficiently. Therefore, combined with the fuel injection control described above, generation of NOx can be further suppressed.

  The opening degree of the EGR passage opening / closing control valve 163 of the present embodiment is controlled by the control unit 190 according to the output of the cylinder head side cooling water temperature sensor 186. The controller 190 appropriately controls the EGR implementation status as necessary, and more appropriately controls the above-described pilot injection and main injection states. Therefore, the environmental performance of the engine can be further improved.

<Suggestion of modification>
It should be noted that the above-described embodiments and examples are merely examples of typical embodiments and examples of the present invention that the applicant has considered to be the best at the time of filing the application as described above. Absent. Therefore, the present invention is not limited to the above-described embodiments and the like, and various modifications can be made to the above-described embodiments and examples without departing from the essential part of the present invention. Is natural.

  In the following, some modifications are illustrated to the extent that they can be added when filing an application of the present application under the prior application principle, but it goes without saying that the modifications are not limited to these. Limiting and interpreting the present invention based on the description of the above-described embodiments and examples and the following modifications unfairly harms the interests of applicants who rush to filing applications under the prior application principle, but unfairly imitators. Contrary to the purpose of patent law for the protection and use of the invention, it is not allowed.

  In addition, it goes without saying that a plurality of the following modifications can be appropriately combined within a technically consistent range.

  (I) The configuration of the present invention can be applied to engines other than diesel engines such as gasoline engines. Moreover, the use of the engine can be applied to a generator as well as an automobile.

  (Ii) The combustion chamber injector 156 may be arranged to inject fuel into the intake port 111b. Alternatively, in addition to the combustion chamber injector 156 that injects fuel into the combustion chamber, another injector that injects fuel into the intake port 111b may be provided.

  (Iii) As for the advance / retard angle and the increase / decrease pattern of the main injection / pilot injection, an appropriate pattern can be selected in addition to those mentioned in the above-described embodiments and examples.

  For example, in the above-described embodiment, only one of the advance / retard angle of main injection / pilot injection and the increase / decrease may be performed. Further, more detailed condition classification may be performed.

  Further, the pilot injection timing Tpilot may be retarded so as to correspond to the retardation of the main injection timing Tmain at the time of catalyst warm-up.

  In addition, the pilot injection timing Tpilot may be retarded when the coolant temperature on the cylinder head 110 side is extremely low, such as during a warm-up operation after a cryogenic start. As a result, pilot injection is performed after the temperature and pressure in the combustion chamber have increased, so that a relatively large amount of heat is generated by the pilot injection. Therefore, the occurrence of misfire can be prevented during the combustion after the main injection.

  Further, in the above-described embodiment, after the warm-up operation ends, when the cylinder head 110 is cooled well, and the coolant temperature on the cylinder head 110 side is lower than a predetermined reference temperature, The main injection timing Tmain and the pilot injection timing Tpilot are advanced, and the main injection amount Qmain is decreased corresponding to the increase in the pilot injection amount Qpilot. However, when the main injection timing Tmain is advanced, the combustion efficiency is improved, so that only the main injection amount Qmain may be decreased without increasing the pilot injection amount Qpilot. Thereby, fuel consumption is further improved.

  Further, an EGR control process (a process for controlling the operation of the EGR passage opening / closing control valve 163 and the EGR cooling control valve 179c) is incorporated in the control routine of the main injection / pilot injection as in the above-described embodiment. Also good.

  Furthermore, in the above-described embodiment, processing for setting the main injection timing Tmain and the pilot injection timing Tpilot has been performed. However, instead of this, by setting either one of the main injection timing Tmain and the pilot injection timing Tpilot and the interval Tint, the other one different from the one of the main injection timing Tmain and the pilot injection timing Tpilot As a result, processing may be performed. That is, by changing the interval Tint, the other advance / retard of the main injection timing Tmain and the pilot injection timing Tpilot may be performed.

  (Iv) The cooling water delivery pump 171 may be configured to adjust the amount of cooling water delivered according to the operating state. In this case, the cooling water delivery pump 171 can be composed of an electrically driven pump or a so-called variable water pump whose delivery flow rate is variable.

  According to such a configuration, for example, the cooling performance of the cylinder head 110 and the EGR cooler 162 can be improved by increasing the delivery flow rate according to the operating state. Further, the cooling water delivery pump 171 may be stopped under the control of the control unit 190 during the regeneration process of the DPF catalyst 143a (DPF regeneration process). Thereby, the temperature of the exhaust gas is effectively increased, and the DPF regeneration process is efficiently performed.

  (V) In place of the first control valve 179a, a valve that is interposed in the radiator discharge pipe 176b and controls the communication state between the radiator 172 and the coolant feed pump 171 and a bypass pipe 177 Two valves, that is, a valve for controlling the communication state between the bypass pipe 177 and the cooling water delivery pump 171 may be used.

  (Vi) The second control valve 179b may be interposed in the cylinder block discharge pipe 175b.

  (Vii) The second control valve 179b allows the cylinder head discharge pipe 175a and the radiator inflow pipe 176a to communicate with each other at the first reference temperature or higher, and the cylinder head discharge pipe 175a and the radiator at a temperature lower than the first reference temperature. The communication with the inflow pipe 176a may be blocked.

  (Viii) As the first control valve 179a and the second control valve 179b, in addition to the electromagnetic valve, a thermostat valve or a so-called electronic thermostat valve can be used. This electronic thermostat valve is a combination of the above-described thermostat valve and a heater. Such an electronic thermostat valve is configured such that the thermostat valve can be forcibly opened by the heat from the heater by causing a current to flow through the heater to generate heat.

  (Xi) The cooling water circulation system 170 of the above-described embodiment uses the first control valve 179a and the second control valve 179b, and (a) the cooling water not cooled by the radiator 172 is not supplied to the cylinder block 120. A state in which the cylinder head 110 is intensively supplied; and (b) a state in which the cooling water cooled by the radiator 172 is intensively supplied to the cylinder head 110 without being supplied to the cylinder block 120; The cooling water circulation state is controlled in three states: a state in which the cooling water cooled by the radiator 172 is also supplied to the cylinder block.

  However, the present invention is not limited to the cooling water circulation system 170 configured as described above. That is, the present invention can employ a cooling water circulation system having any configuration other than the configuration of the above-described embodiment as long as it can be referred to as a so-called “two-system cooling structure” or “separated cooling structure”.

  For example, a configuration in which the cooling state of the cylinder head 110 and the cooling state of the cylinder block 120 can be controlled completely independently can be used in place of the cooling water circulation system 170 of the above-described embodiment. Specifically, for example, a cylinder head cooling system including a cooling water delivery pump and a radiator for the cylinder head 110, and a cylinder block cooling system including a cooling water delivery pump and a radiator for the cylinder block 120, A configuration that exists and operates independently can be used (in this sense, the cooling water circulation system 170 of this embodiment can also be referred to as a “pseudo two-system cooling structure” or a “pseudo separated cooling structure”).

  (X) Other modifications not specifically mentioned are naturally included in the scope of the present invention as long as they do not change the essential part of the present invention. For example, in the description of each embodiment described above, the integrally formed components may be integrally formed without joints, or a plurality of separate parts may be joined by bonding, welding, screwing, or the like. Of course, it may be formed by.

  (Xi) In addition, in each element constituting the means for solving the problems of the present invention, the elements expressed in terms of operation and function are the specific structures disclosed in the above-described embodiments and modifications. In addition, any structure capable of realizing the action / function is included.

1 is a schematic configuration diagram of an engine according to an embodiment of the present invention. It is the schematic for showing the flow state of the cooling water in the engine of this embodiment shown by FIG. It is the schematic for showing the flow state of the cooling water in the engine of this embodiment shown by FIG. It is the schematic for showing the flow state of the cooling water in the engine of this embodiment shown by FIG. It is a flowchart which shows the Example of the fuel-injection control process to a combustion chamber performed by the control part shown by FIG.

Explanation of symbols

100 ... Engine, 110 ... Cylinder head,
111a ... Water jacket in the cylinder head, 111b ... Intake port,
111c ... exhaust port, 120 ... cylinder block,
121b ... Water jacket in the cylinder block, 122a ... Cavity,
131 ... Intake pipe, 141 ... Exhaust pipe,
150 ... Common rail fuel injection system, 156 ... Combustion chamber injector,
161 ... EGR passage, 162 ... EGR cooler,
163 ... EGR passage opening / closing control valve, 170 ... Cooling water circulation system,
171 ... Cooling water delivery pump, 172 ... Radiator,
173a ... pump delivery pipe (cylinder head supply passage), 173b ... pump suction pipe,
174 ... Communication path between blocks, 175a ... Cylinder head discharge pipe,
175b ... Cylinder block discharge pipe, 176a ... Radiator inflow pipe,
176b ... Radiator discharge pipe, 177 ... Bypass pipe,
178a ... EGR cooler supply pipe, 178b ... EGR cooler discharge pipe,
179a ... first control valve, 179b ... second control valve,
179c ... EGR cooling control valve, 186 ... Cylinder head side cooling water temperature sensor,
190 ... control unit, 191 ... CPU,
192 ... ROM

Claims (8)

In an engine configured to inject fuel in a fuel mixture introduction path including an intake passage, a cylinder, and a combustion chamber,
A cylinder head configured to be cooled by a cooling medium;
A cylinder block joined to the cylinder head and configured to be cooled by the cooling medium;
A cooling medium circulation system configured to change the supply state of the cooling medium to the cylinder head and the cylinder block in accordance with an operation state;
A cylinder head-side coolant temperature sensor configured to output a signal corresponding to the temperature of the coolant on the cylinder head side;
A fuel injection control unit configured to control a state of fuel injection in main injection and pre-injection prior to the main injection in accordance with an output of the cylinder head side coolant temperature sensor;
An engine characterized by comprising The engine according to claim 1,
The engine, wherein the fuel injection control unit is configured to control a fuel injection amount in the pre-injection according to an output of the cylinder head side coolant temperature sensor. The engine according to claim 1 or 2,
The engine, wherein the fuel injection control unit is configured to control an injection timing of the pre-injection according to an output of the cylinder head side coolant temperature sensor. An engine according to any one of claims 1 to 3,
The engine, wherein the fuel injection control unit is configured to control a fuel injection amount in the main injection according to an output of the cylinder head side coolant temperature sensor. An engine according to any one of claims 1 to 4,
The engine, wherein the fuel injection control unit is configured to control an injection timing of the main injection in accordance with an output of the cylinder head side coolant temperature sensor. An engine according to any one of claims 1 to 5,
The cooling medium circulation system is
A cooling medium delivery section configured to deliver the cooling medium toward the cylinder head;
The cylinder head cooling medium passage and the cylinder head cooling medium passage so that the cooling medium can be supplied from the cylinder head cooling medium passage formed in the cylinder head to the cylinder block cooling medium passage formed in the cylinder block. A flow path between blocks connecting the coolant passage in the cylinder block;
A cylinder head discharge passage constituting a passage of the cooling medium for discharging the cooling medium in the cylinder medium cooling medium passage from the cylinder head;
A cylinder block discharge passage constituting a passage of the cooling medium for discharging the cooling medium in the cylinder medium cooling medium passage from the cylinder block;
A radiator configured to cool the cooling medium that has passed through the cylinder head and the cylinder block by heat exchange with outside air;
A radiator inflow that connects the cylinder head discharge passage, the cylinder block discharge passage and the radiator so that the cooling medium that has passed through the cylinder head cooling medium passage and the cylinder block cooling medium passage can flow into the radiator. A passage,
A radiator discharge passage connecting the radiator and the cooling medium delivery section so that the cooling medium cooled by the radiator and discharged from the radiator can be sent to the cooling medium delivery section;
A bypass passage connecting the cylinder head discharge passage and the radiator discharge passage;
A first control valve configured to control communication between the bypass passage and the radiator discharge passage and the cooling medium delivery unit;
A second control valve configured to control the communication state between the cylinder block discharge passage and the radiator inflow passage;
An engine characterized by comprising The engine according to claim 6,
The cooling medium circulation system is
A cylinder head supply passage that constitutes a passage of the cooling medium that connects the cooling medium delivery section and the cylinder head;
It is interposed in an EGR passage configured to be able to introduce a burned gas from an exhaust passage to the intake passage so that the burned gas can be cooled by heat exchange between the burned gas and the cooling medium. An EGR cooler configured in
An EGR cooler supply passage that branches from the cylinder head supply passage and constitutes a passage of the cooling medium for supplying the cooling medium to the EGR cooler;
An EGR cooling control valve that is interposed in the EGR cooler supply passage and configured to control a supply state of the cooling medium to the EGR cooler;
An engine characterized by further comprising: The engine according to claim 7,
An EGR gas amount control valve interposed in the EGR passage and configured to control a flow rate of the burned gas in the EGR passage;
An EGR controller configured to control an opening of the EGR gas amount control valve according to an output of the cylinder head side coolant temperature sensor;
An engine characterized by further comprising:

Images