EGR device

Abstract

To inhibit generation of corrosion of an aluminum adapter without providing a cooling structure in an EGR valve.SOLUTION: An EGR device recirculates a part of exhaust gas discharged from an engine to an intake passage. The EGR device includes: an EGR valve for controlling a flow rate of the part of the exhaust gas to the intake passage; and an aluminum adapter abutting on a cylinder head to take out the part of the exhaust gas from at least one cylinder provided in the cylinder head of the engine and supply the taken-out part of the exhaust gas to the EGR valve.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an EGR device. [Background technology]

[0002] There is a known technology in which an intake passage and an exhaust passage provided in an engine are connected by a gas passage, and a part of the exhaust gas is recirculated to the intake passage as EGR (Exhaust Gas Recirculation) gas through the gas passage. An EGR valve for adjusting the amount of recirculated EGR gas is provided in the gas passage. Some EGR valves are integrally formed with a valve heat exchanger for exchanging heat between the EGR gas and cooling water (see, for example, Patent Document 1).

[0003] Also known is a pipe connection member (hereinafter referred to as an adapter) made of an aluminum alloy that has a cooling water flow passage and passes the EGR gas to cool it. The adapter is attached to the cylinder head of the engine and discharges the cooled EGR gas to the EGR valve. By cooling the EGR gas, it is possible to prevent a decrease in intake charging efficiency, etc. (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-002787 A [Patent Document 2] JP 2010-084581 A Summary of the Invention [Problem to be solved by the invention]

[0005] Here, when a cooling structure such as a valve heat exchanger is provided in the EGR valve, there is a problem that the EGR valve (specifically, the valve housing) becomes structurally complex. On the other hand, when EGR gas is discharged from the adapter to the EGR valve, high-temperature EGR gas flows from the cylinder head into the adapter upstream of the EGR valve. When the engine is warmed up, the cooling water is not circulated from the viewpoint of early warming of the engine, and the cooling water remaining in the cooling water flow passage of the adapter may boil. If the adapter is made of aluminum containing an aluminum alloy, the adapter may corrode due to the boiling of the cooling water.

[0006] Therefore, an object of the present invention is to suppress the occurrence of corrosion of the aluminum adapter without providing a cooling structure to the EGR valve. [Means for solving the problem]

[0007] The EGR device according to the present invention is an EGR device that recirculates a portion of exhaust gas discharged from an engine to an intake passage, the EGR device comprising: an EGR valve that adjusts a flow rate of the portion of the exhaust gas into the intake passage; a flow rate control valve for controlling a flow rate of a coolant that cools a portion of the exhaust gas; A part of the exhaust gas is extracted from at least one cylinder provided inside a cylinder head of the engine, and the extracted part of the exhaust gas is A portion of the exhaust gas after heat exchange between the exhaust gas and the refrigerant an aluminum adapter that abuts against the cylinder head and supplies the EGR valve with a control unit that controls the flow rate control valve to be fully closed when the engine is warmed up; has.

[0008] In the above configuration, the adapter may be configured to take out a portion of the exhaust gas from any one of the cylinders.

[0009] In the above configuration, Cooling The engine may further include an EGR cooler having a first refrigerant passage through which a refrigerant flows, the adapter having a second refrigerant passage through which the refrigerant flows, and the refrigerant may flow from the second refrigerant passage into the first refrigerant passage without passing through the EGR valve. Effect of the Invention

[0010] According to the present invention, it is possible to suppress the occurrence of corrosion of the aluminum adapter without providing a cooling structure to the EGR valve. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing a general configuration of a vehicle. [Diagram 2] FIG. 2 is a schematic diagram showing the internal configuration of the cylinder head. [Diagram 3] FIG. 3 is a graph illustrating the operation of the EGR device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] As shown in FIG. 1, a vehicle 100 is equipped with an engine 10 and an automatic transmission 30. The engine 10 may be a gasoline engine or a diesel engine. An intake passage 11 that sends air into the combustion chamber of a cylinder, and an exhaust passage 12 that discharges combustion gas combusted in the combustion chamber as exhaust gas are connected to the engine 10. A water jacket 20 through which cooling water flows is provided on a cylinder head 70 of the engine 10. Note that in FIG. 1 and FIG. 2 described later, the flow of exhaust and intake air is indicated by solid arrows, and the flow of cooling water is indicated by dashed arrows.

[0014] 2, a plurality of cylinder groups, such as a first cylinder 71, a second cylinder 72, a third cylinder 73, and a fourth cylinder 74, and an exhaust port 75 are provided inside the cylinder head 70. Although not shown, the engine 10 is provided with a valve mechanism in which each cylinder has two intake valves and two exhaust valves. Note that in this embodiment, an in-line four-cylinder engine in which the first cylinder 71, the second cylinder 72, the third cylinder 73, and the fourth cylinder 74 are arranged in a row will be described as an example, but other types of engines having different numbers of cylinders or cylinder arrangements may also be used.

[0015] The exhaust port 75 includes a first port portion 75A, a second port portion 75B, a third port portion 75C, a fourth port portion 75D, and an EGR port portion 75E. The first port portion 75A, the second port portion 75B, the third port portion 75C, the fourth port portion 75D, and the EGR port portion 75E each have an inlet through which the exhaust gas flows and an outlet through which the exhaust gas flows out. For example, the combustion chamber of the fourth cylinder 74 is connected to the inlet of the fourth port portion 75D. Therefore, the exhaust gas discharged from the combustion chamber of the fourth cylinder 74 flows into the fourth port portion 75D. The first cylinder 71, the second cylinder 72, and the third cylinder 73 are similar to the fourth cylinder 74, so their explanations will be omitted.

[0016] On the other hand, the fourth port portion 75D has two outlets, one of which is connected to the junction port of the first port portion 75A. The other outlet, which is closer to the fourth cylinder 74 than the one outlet, is connected to the inlet of the EGR port portion 75E. Therefore, a part of the exhaust gas flowing through the fourth port portion 75D flows into the EGR port portion 75E as EGR gas, and the remaining part of the exhaust gas flows into the first port portion 75A. In the first port portion 75A, the exhaust gases of the first cylinder 71 and the fourth cylinder 74 merge, so the amount of exhaust gas increases and the temperature of the exhaust gas rises. In other words, the exhaust gas from the fourth cylinder 74 alone flows through the fourth port portion 75D, and a part of this exhaust gas is used as EGR gas, so the amount of exhaust gas is smaller than the amount after the exhaust gases are merged, and the temperature of the exhaust gas is lower than the amount after the exhaust gases are merged. Such EGR gas flows through the EGR port portion 75E.

[0017] The outlet of the second port portion 75B is connected to the junction port of the third port portion 75C. The outlet of the third port portion 75C may be connected to the junction port of the second port portion 75B. The outlet of the first port portion 75A is connected to the junction port of the second port portion 75B or the third port portion 75C. When the outlet of the first port portion 75A is connected to the junction port of the second port portion 75B, the outlet of the second port portion 75B is connected to the exhaust passage 12. When the outlet of the first port portion 75A is connected to the junction port of the third port portion 75C, the outlet of the third port portion 75C is connected to the exhaust passage 12. Therefore, not only the remaining part of the exhaust discharged from the combustion chamber of the fourth cylinder 74 but also the exhaust gas discharged from each combustion chamber of the first cylinder 71 to the third cylinder 73 flows into the exhaust passage 12.

[0018] In this manner, this embodiment employs exhaust port 75 that connects first port portion 75A and fourth port portion 75D, connects second port portion 75B and third port portion 75C, and further connects the two connected ports. This type of connection configuration is sometimes called a dual type.

[0019] Furthermore, in this embodiment, a manifold exhaust passage 12 that is separate from the cylinder head 70 is not used, but a manifold exhaust port 75 that is integrated with the cylinder head 70 inside the cylinder head 70 is used. Therefore, the exhaust gas flowing into the exhaust passage 12 is greater in volume and has a higher temperature than the EGR gas flowing into the EGR port 75E. In other words, the EGR gas flowing into the EGR port 75E is smaller in volume and has a lower temperature than the exhaust gas flowing into the exhaust passage 12.

[0020] As shown in Figs. 1 and 2, the cylinder head 70 is provided with an aluminum adapter 13A as a part of the EGR device. By making the adapter 13A from aluminum, the cost of the adapter 13A can be reduced while ensuring heat resistance equivalent to or close to that of cast iron. As shown in Figs. 1 and 2, the adapter 13A is provided with a refrigerant passage 13X and a gas passage (not shown) independent of the refrigerant passage 13X inside. As shown in Fig. 2, the outlet of the EGR port 75E is connected to this gas passage of the adapter 13A. Therefore, the EGR gas flowing through the EGR port 75E flows into the gas passage of the adapter 13A. The adapter 13A is configured to exchange heat between the EGR gas flowing through the gas passage of the adapter 13A and the cooling water flowing through the refrigerant passage 13X.

[0021] 1 and 2, the adapter 13A is attached in contact with the cylinder head 70. Therefore, even if EGR gas flows from the cylinder head 70 to the adapter 13A when the engine 10 is warmed up, heat from the adapter 13A is transferred to the cylinder head 70 via the contact surface between the adapter 13A and the cylinder head 70. When the engine 10 is warmed up, it is assumed that the cylinder head 70 is cooler than the adapter 13A into which the EGR gas has flowed. This allows the heat of the adapter 13A to be released.

[0022] In particular, because the EGR gas from only the fourth cylinder 74 flows from the cylinder head 70 into the adapter 13A, the EGR gas flowing into the adapter 13A is at a lower temperature than the EGR gas from all of the first cylinder 71 to the fourth cylinder 74. Because the heat of the low-temperature EGR gas is transferred from the adapter 13A to the cylinder head 70, the temperature of the adapter 13A hardly rises or the rise in temperature is limited. This makes it possible to prevent the cooling water remaining in the coolant passage 13X from boiling even if the cooling water is not circulating when the engine 10 is warmed up, and as a result, it is possible to prevent the occurrence of corrosion even if the adapter 13A is made of aluminum.

[0023] For example, if the exhaust passage 12 has multiple branches (a so-called exhaust manifold), it is also possible to attach the adapter 13A to the exhaust passage 12 at the portion through which the exhaust from the fourth cylinder 74 flows. In this case, however, it is assumed that the amount of heat absorbed by the exhaust passage 12 is less than that of the cylinder head 70, and the heat dissipation effect of the adapter 13A is low. It is also assumed that it is easier to attach the adapter 13A to the cylinder head 70 than to the exhaust passage 12.

[0024] 1, an EGR passage 13 for returning the EGR gas flowing out from the adapter 13A to the intake passage 11 is connected to the adapter 13A and the intake passage 11. In addition, an EGR valve 14 for adjusting the flow rate of the EGR gas to the intake passage 11 is provided in the EGR passage 13 as a part of the EGR device. The EGR valve 14 is supplied with the EGR gas from the adapter 13A.

[0025] A stainless steel EGR cooler 17 is provided downstream of the EGR valve 14 as part of the EGR device. A coolant passage 17X and a gas passage (not shown) independent of the coolant passage 17X are provided inside the EGR cooler 17. In the EGR cooler 17, heat is exchanged between the EGR gas flowing through the gas passage of the EGR cooler 17 and the cooling water flowing through the coolant passage 17X. This cooling water flows from the coolant passage 13X of the adapter 13A into the coolant passage 17X without passing through the EGR valve 14, passes through it, and flows out of the EGR cooler 17. That is, the EGR valve 14 does not have a cooling structure, and as a result, the EGR valve 14 can be prevented from becoming complicated. Since the cooling water does not circulate during warm-up of the engine 10, the cooling water remaining in the coolant passage 17X may boil, but since the EGR cooler 17 is made of stainless steel, the EGR cooler 17 does not corrode or the corrosion is extremely limited.

[0026] As shown in Fig. 1, vehicle 100 is provided with an oil cooler 25 in which engine oil, used as a lubricant or hydraulic fluid for various parts of engine 10, exchanges heat with cooling water. An oil passage 26 through which engine oil flows is connected to oil cooler 25. The engine oil is introduced into oil cooler 25 through oil passage 26 and is returned to various lubricated parts of engine 10 after exchanging heat with the cooling water.

[0027] The automatic transmission 30 is connected to the engine 10 via a torque converter 31. The automatic transmission 30 contains hydraulic fluid for operating the automatic transmission 30, i.e., automatic transmission fluid (hereinafter referred to as ATF). The vehicle 100 is provided with an ATF warmer 35 where the ATF exchanges heat with the coolant. The ATF warmer 35 is connected to an ATF passage 37 through which the ATF in the automatic transmission 30 flows. The ATF is introduced into the ATF warmer 35 through the ATF passage 37, and after exchanging heat with the coolant, is returned to the automatic transmission 30 through the ATF passage 37.

[0028] The vehicle 100 is equipped with a coolant circuit 40 through which coolant circulates. In the coolant circuit 40, a downstream end of an inlet-side passage 41 is connected to a water jacket inlet 21, which is the inlet of the water jacket 20 described above. A water pump 45 is connected to the middle of the inlet-side passage 41. The water pump 45 is driven in accordance with the rotation of the crankshaft, which is the output shaft of the engine 10. In addition, a water jacket outlet 22, which is the outlet of the water jacket 20, is connected to an inlet 47 of a flow rate control valve 46 via an outlet-side passage 42.

[0029] The flow rate control valve 46 includes the inlet 47, the first outlet 48A, the second outlet 48B, and the third outlet 48C. The inlet 47, the first outlet 48A, the second outlet 48B, and the third outlet 48C all communicate with the internal space of the flow rate control valve 46. A valve body is accommodated in the internal space of the flow rate control valve 46. By controlling the valve body, the open and closed states of the inlet 47 and the first outlet 48A can be adjusted. Similarly, by controlling the valve body, the open and closed states of the inlet 47 and the second outlet 48B, and the open and closed states of the inlet 47 and the third outlet 48C can also be adjusted.

[0030] The upstream end of the first heat exchange passage 50 is connected to the first outlet 48A of the flow rate adjustment valve 46. The upstream end of the second heat exchange passage 51 is connected to the second outlet 48B of the flow rate adjustment valve 46. The downstream end of the first heat exchange passage 50 and the downstream end of the second heat exchange passage 51 join together and are connected to the upstream end of the inlet side passage 41. A parallel passage 50b in which the oil cooler 25 and the ATF warmer 35 are connected in parallel is connected to the first heat exchange passage 50. A radiator 55 is connected midway through the second heat exchange passage 51.

[0031] The upstream end of the third heat exchange passage 52 is connected to the third outlet 48C of the flow rate control valve 46. The downstream end of the third heat exchange passage 52 is connected to the inlet of the refrigerant passage 13X of the adapter 13A. The upstream end of the fourth heat exchange passage 53 is connected to the outlet of the refrigerant passage 13X of the adapter 13A. The downstream end of the fourth heat exchange passage 53 is connected to the refrigerant passage 17X of the EGR cooler 17. The upstream end of the fifth heat exchange passage 54 is connected to the outlet of the refrigerant passage 17X of the EGR cooler 17. The downstream end of the fifth heat exchange passage 54 merges with the outlet-side passage 42.

[0032] The vehicle 100 is provided with an ECU (Electronic Control Unit) 60 for controlling the flow state and temperature of the coolant in the coolant circuit 40. The ECU 60 is mainly composed of a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory) in which various programs and maps are stored in advance, a RAM (Random Access Memory) in which the results of CPU calculations and the like are temporarily stored, an input interface, an output interface, and the like.

[0033] The ECU 60 adjusts the temperature, flow state, and cut-off state of the coolant flowing through the coolant circuit 40 by receiving signals from various sensors provided in the vehicle 100. Examples of the various sensors include an air flow meter 61 that detects the amount of intake air, and a rotation speed sensor 62 that detects the engine rotation speed, which is the rotation speed of the crankshaft. Other examples of the various sensors include an accelerator sensor 63 that detects the accelerator operation amount, which is the amount of depression of the accelerator pedal, and a vehicle speed sensor 64 that detects the vehicle speed. Other examples of the various sensors include a water temperature sensor 65 that detects or estimates the temperature of the coolant flowing out of the water jacket outlet 22 and flowing through the outlet-side passage 42. The ECU 60 adjusts the temperature, flow state, and cut-off state of the coolant flowing through the coolant circuit 40 by controlling the flow rate adjustment valve 46 and the EGR valve 14 based on the detection signals from these various sensors.

[0034] The operation of this embodiment will be described with reference to Fig. 3. First, when the engine 10 is warmed up, the ECU 60 controls the EGR valve 14 and the flow rate control valve 46 to be fully closed. As a result, the EGR gas passes through a gas passage provided inside the adapter 13A and flows into the EGR valve 14, and is retained inside the EGR valve 14.

[0035] Also, since the flow rate control valve 46 is controlled to be fully closed, the coolant does not circulate through the coolant circuit 40. Therefore, the coolant in the refrigerant passage 13X provided inside the adapter 13A cannot exchange heat with the EGR gas passing through the adapter 13A. Therefore, when the EGR gas flows into the gas passage of the adapter 13A, the adapter gas temperature, which is the temperature of the gas in the gas passage, gradually rises. This gas may be EGR gas or a mixture of EGR gas and air.

[0036] However, even if the adapter gas temperature rises, because the adapter 13A is in contact with the cylinder head 70, the heat of the adapter 13A is transferred to the cylinder head 70. Therefore, the temperature rise of the cooling water in the refrigerant passage 13X is suppressed to a state not reaching the boiling point, compared to the comparative example in which the temperature rise exceeds the boiling point of the cooling water. This makes it possible to suppress corrosion of the adapter 13A.

[0037] Since the EGR valve 14 is controlled to be fully closed, no EGR gas flows into the EGR cooler 17 disposed downstream of the EGR valve 14. Therefore, the temperature of the air in the gas passage provided inside the EGR cooler 17 is maintained as the cooler gas temperature.

[0038] Furthermore, since EGR gas remains in the EGR valve 14, the temperature of the valve wall of the EGR valve 14 rises. Since the heat of the EGR valve 14 is conducted to the EGR cooler 17 via the EGR passage 13, the temperature of the fins provided in the EGR cooler 17 also rises. After time has passed and the ECU 60 determines that the engine 10 has been warmed up, it controls the EGR valve 14 and the flow rate control valve 46 to be fully open at different timings. Note that the ECU 60 may control the opening degrees of the EGR valve 14 and the flow rate control valve 46 to several tens of percent (for example, 10% or 70%) based on the detection results of various sensors.

[0039] Although the preferred embodiment of the present invention has been described above in detail, the present invention is not limited to the specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. For example, in the above embodiment, cooling water is described as an example of the refrigerant, but the refrigerant may be antifreeze liquid.

[0040] In the above embodiment, the inlet of the EGR port 75E is connected to the other outlet of the fourth port 75D, but this is not particularly limited to the fourth port 75D. For example, instead of the fourth port 75D, a new outlet may be provided in any one of the first port 75A, the second port 75B, and the third port 75C, and the inlet of the EGR port 75E may be connected to this new outlet. Also, new outlets may be provided in at least two of the first port 75A, the second port 75B, and the third port 75C, and the inlet of the EGR port 75E may be connected to these outlets.

[0041] Furthermore, the above-mentioned engine 10 may be equipped with a turbocharger. In this case, air is sent to the combustion chamber through a compressor of the turbocharger and an intake passage 11 in that order, and exhaust gas discharged from an exhaust passage 12 is sent to the turbine of the turbocharger. [Explanation of symbols]

[0042] 10 Engine 11 Intake passage 12 Exhaust passage 13 EGR passage 13A adapter (part of EGR device) 13X Coolant path (second coolant path) 14 EGR valve (part of the EGR system) 17 EGR cooler (part of the EGR device) 17X Refrigerant path (1st refrigerant path) 70 Cylinder head 71,72,73,74 1st cylinder, 2nd cylinder, 3rd cylinder, 4th cylinder 75 Exhaust port 75D 4th port section 75E EGR port

Claims

1. An EGR device that recirculates a portion of exhaust gas discharged from an engine to an intake passage, an EGR valve that adjusts a flow rate of a portion of the exhaust gas into the intake passage; a flow rate control valve for controlling a flow rate of a coolant that cools a portion of the exhaust gas; an aluminum adapter that abuts against the cylinder head and extracts a portion of the exhaust gas from at least one cylinder provided inside a cylinder head of the engine, and supplies the portion of the exhaust gas after heat exchange between the extracted portion of the exhaust gas and the refrigerant inside the adapter to the EGR valve; a control unit that controls the flow rate control valve to be fully closed when the engine is warmed up; An EGR device having:

2. The adapter extracts a portion of the exhaust gas from any one of the cylinders.

2. The EGR device according to claim 1 .

3. The engine further includes an EGR cooler having a first coolant passage through which the coolant flows, the adapter includes a second coolant passage through which the coolant flows; The refrigerant flows from the second refrigerant passage into the first refrigerant passage without passing through the EGR valve.

3. The EGR device according to claim 1 or 2.

Images