JP6875881B2 - Structure of cooling water system of internal combustion engine - Google Patents

Description

The present invention relates to the structure of a cooling water system in which cooling water of an internal combustion engine circulates.

Generally, the exhaust passage of an internal combustion engine is equipped with a three-way catalyst for oxidizing / reducing and purifying harmful substances contained in the exhaust gas discharged from the cylinder.

When the internal combustion engine is operated in a high rotation speed region, a large amount of high-temperature exhaust gas flows into the catalyst, and the catalyst for exhaust gas purification may be excessively heated to cause heat damage (melting damage). As one of the means for preventing such heat damage, a heat exchanger (exhaust cooling adapter) is attached so as to surround the exhaust port or the exhaust manifold of the cylinder, and the cooling water of the internal combustion engine is attached to this heat exchanger. Heat exchange is performed between the exhaust discharged from the cylinder and the cooling water, and the exhaust is cooled before flowing into the catalyst (see, for example, the following patent documents). ..

Japanese Unexamined Patent Publication No. 2011-236850

On the other hand, the three-way catalyst does not activate and cannot exhibit sufficient purification performance unless the temperature rises above a certain level. If the entire amount of cooling water of the internal combustion engine is constantly flowed into the heat exchanger for exhaust cooling, the temperature rise of the catalyst is delayed after the cold start, which may lead to deterioration of emissions.

An object of the present invention is to achieve both early activation of a catalyst during a cold start of an internal combustion engine and prevention of heat damage.

The cooling water system of the internal combustion engine according to the present invention divides the cooling water flowing inside the internal combustion engine into a plurality of streams, and then discharges one of the streams from the cylinder to the catalyst for exhaust purification. Cooling water that is supplied to a heat exchanger for cooling and the other flow is guided to the outside of the internal combustion engine without passing through the heat exchanger, and is guided to the outside of the internal combustion engine without passing through the heat exchanger. On the flow path through which the cooling water flows, a throttle having a smaller cross-sectional area than the portion of the flow path through which the cooling water supplied to the heat exchanger has the minimum cross-sectional area is provided. It is not necessary to install a solenoid valve for controlling the amount of cooling water flowing into the heat exchanger that cools the exhaust gas.

When the cooling water of the internal combustion engine is used in another heat exchanger different from the heat exchanger for exhaust cooling, a part of the cooling water guided to the outside of the internal combustion engine without passing through the heat exchanger or Of at least the heater core, EGR cooler, ATF warmer, and CVT warmer that use the cooling water to exchange heat with the cooling water after merging all of the cooling water supplied to the heat exchanger. It is preferable to allow the heat to flow into any one of the other heat exchangers.

According to the present invention, it is possible to achieve both early activation of the catalyst at the time of cold start of the internal combustion engine and prevention of heat damage.

The figure which shows typically the circuit structure of the cooling water system of one Embodiment of this invention. The perspective view which shows the structure of the main part of the cooling water system of the internal combustion engine of the same embodiment. In the cooling water system of the same embodiment, the shape of the confluence of the flow path through which the cooling water guided to the outside of the internal combustion engine flows without passing through the heat exchanger and the flow path through which the cooling water supplied to the heat exchanger flows. A perspective view and a cross-sectional view showing. The figure which shows the relationship between the engine speed and the rotation speed of a cooling water pump, and the flow rate of cooling water.

An embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 3, in the cooling water system of the internal combustion engine 0 of the present embodiment, a plurality of cooling waters that circulate inside the internal combustion engine 0 and cool various parts of the internal combustion engine 0 are provided inside the internal combustion engine 0. A plurality of outlets 21 and 22 are opened so as to branch into the flows L1 and L2 and allow the cooling waters L1 and L2 to flow out to the outside of the internal combustion engine 0, and one flow L1 is exhausted from the first outlet 21. It is configured so that the other flow L2 is guided from the second outlet 22 to the outside of the internal combustion engine 0 while flowing into the water cooling adapter 3 which is a heat exchanger for cooling, and bypasses the water cooling adapter 3. In the figure, the flow of cooling water is indicated by an arrow.

The cooling water of the internal combustion engine 0 is pumped by the cooling water pump 11, and the cylinder head forming the ceiling of the combustion chamber of those cylinders and the intake / exhaust port from the inside of the cylinder block 1 containing the plurality of cylinders of the internal combustion engine 0. It rises toward the inside of 2. The cooling water pump 11 may be a mechanical pump that receives rotational driving force from the crankshaft of the internal combustion engine 0, or may be an electric pump driven by an electric motor, but basically it is an engine. The higher the number of revolutions, the higher the discharge amount and discharge pressure of the cooling water. The mechanical cooling water pump 11 is driven by the crankshaft of the internal combustion engine 0, and its rotation speed is proportional to the engine rotation speed.

The cooling water that has reached the inside of the cylinder head 2 is diverted in the cylinder head 2, and one of the flows L1 flows out from the first outlet 21 that opens on the front side surface of the cylinder head 2, and the water cooling adapter 3 Inflow to. The water cooling adapter 3 is outside the cylinder head 2 and has a shape surrounding an exhaust passage (which may be an exhaust manifold) 4 through which exhaust gas discharged from the exhaust port of each cylinder flows. The cooling water L1 flowing into the water cooling adapter 3 exchanges heat with the exhaust gas flowing through the exhaust passage 4, and lowers the temperature of the exhaust gas toward the three-way catalyst (not shown) for exhaust gas purification. After that, the cooling water L1 flowing out of the water cooling adapter 3 flows into the flow pipe 5 connected to the outlet of the water cooling adapter 3, and goes to another heat exchanger 9 outside the internal combustion engine 0 through the flow pipe 5. The heat exchanger 9 is a heater core of an air conditioner that heats and exchanges heat with the air in the vehicle interior to warm the air, or returns from the exhaust passage 4 to the intake passage by an EGR (Exhaust Gas Recirculation) device attached to the internal combustion engine 0. An EGR cooler that cools the EGR gas by exchanging heat with the EGR gas, or an ATF warmer or CVT warmer that heats the working fluid (transmission fluid) of the automatic transmission mounted on the vehicle to warm the working fluid. Or something like that.

The other flow L2 divided in the cylinder head 2 flows out from the second outlet 22 that opens on the lateral side surface of the cylinder head 2 and flows into the bypass pipe 6 connected to the second outlet 22. .. The bypass pipe 6 extends straight from the second outlet 22. Then, the bypass pipe 6 is substantially orthogonal to the straight portion of the flow pipe 5 drawn from the first outlet 21, and is connected to and communicates with the portion. That is, the two streams L1 and L2 of the cooling water branched in the cylinder head 2 merge at the connecting portion 7 between the flow pipe 5 and the bypass pipe 6. The combined cooling waters L1 and L2 flow into another heat exchanger 9 already described, and in the heat exchanger 9, another fluid, specifically air in the vehicle interior, EGR gas, or a working fluid of the transmission is used. And heat exchange. After that, the cooling waters L1 and L2 are sucked into the cooling water pump 11 again.

The cooling water that has become hot inside the internal combustion engine 0 is forcibly air-cooled in the radiator 8. In the illustrated example, the introduction pipe 81 connected to the inlet of the radiator 8 is connected to the cylinder head 2, and the outlet pipe 82 connected to the outlet of the radiator 8 is connected to the cylinder block 1. When the temperature of the cooling water rises above a predetermined threshold value, the thermostat 12 that opens and closes the distribution path (particularly, the outlet pipe 82) connected to the radiator 8 opens. As a result, the cooling water flowing in the cylinder head 2 flows into the radiator 8 through the introduction pipe 81. The cooling water air-cooled by the radiator 8 returns to the cylinder block 1 through the outlet pipe 82.

Thus, in the present embodiment, as shown in FIGS. 1 and 3, a second flow opened in the cylinder head 2 flows on the flow path through which the cooling water L2 bypassing without passing through the water cooling adapter 3 flows (that is, the second flow). By providing the throttle 73 at a required position (between the outlet 22 and the point where the bypass pipe 6 and the flow pipe 5 communicate with each other), the flow rate of one flow L1 flowing out from the cylinder head 2 and reaching the water cooling adapter 3 , The ratio with the flow rate of the other flow L2 that flows out from the cylinder head 2 but bypasses the water cooling adapter 3 is adjusted.

The cross-sectional area of the flow path through which the cooling water L2 of the bypass pipe 6 can flow (in other words, the inner diameter or the inner dimension of the bypass pipe 6) is the flow path through which the cooling water L1 supplied to the water cooling adapter 3 flows (that is, the first). (In other words, the cross-sectional area of the flow path through which the cooling water L1 can flow (in other words, between the outlet 21 of the water), the flow pipe 5 via the water cooling adapter 3 and the point where the flow pipe 5 and the bypass pipe 6 communicate with each other). , The inner diameter or inner dimension of the flow path) is substantially equal to the flow path cross-sectional area of the portion where the minimum is achieved. Then, the size of the cross-sectional area (in other words, the inner diameter or the inner dimension of the throttle 73) through which the cooling water L2 of the diaphragm 73 can pass is set smaller than the cross-sectional area of the flow path thereof.

As shown in FIG. 3, in the present embodiment, the distribution pipe 5 and the bypass pipe 6 are connected via a joint 7 having a T-shape in a plan view. The joint 7 has a shape in which a tubular main pipe portion 71 extending along the extending direction of the flow pipe 5 is abutted against a tubular auxiliary pipe portion 72 extending along the extending direction of the bypass pipe 6. The tip of the peripheral wall of the sub-pipe portion 72 is joined to the peripheral wall of the main pipe portion 71 from the side, and the inside of the sub-pipe portion 72 surrounded by the peripheral wall faces the peripheral wall of the main pipe portion. Then, the inside of the sub-pipe portion 72 is communicated with the inside of the main pipe portion 71 by forming a through hole 70 having a diameter smaller than the inner diameter of the sub-pipe portion 72 in the peripheral wall of the main pipe portion 71 facing the inside of the sub-pipe portion 72. As a result, the bypass pipe 6 is communicated with the distribution pipe 5. Moreover, the peripheral wall of the main pipe portion 71 remaining on the peripheral edge of the through hole 70 is a throttle 73 with respect to the flow L2 of the cooling water that bypasses without passing through the water cooling adapter 3. The throttle 73 is located at the end of the bypass pipe 6, and the area (inner diameter or inner dimension) of the through hole 70 is the opening cross-sectional area (inner diameter or inner dimension) of the throttle 73. The opening cross-sectional area of the throttle 73 is smaller than the flow path cross-sectional area (in other words, the inner diameter or inner dimension of the sub-pipe portion 72) through which the cooling water L2 of the sub-pipe portion 72 can flow, and the bypass pipe 6 It is smaller than the cross-sectional area of the flow path.

Supplementary information regarding the flow rate of the cooling water L1 that flows out from the first outlet 21 of the cylinder head 2 and flows through the water cooling adapter 3 and the flow pipe 5, and the flow rate of the cooling water L2 that flows out from the second outlet 22 and flows through the bypass pipe 6. To do. According to the Hagen-Poiseuille flow equation, the volumetric flow rate Q of an incompressible steady flow of a straight pipe with a constant cross-sectional area and horizontally placed and a circular cross-section of the flow path is
Q =-(πa ⁴ /8η) ・ (ΔP / l)
Is given. Here, a is the radius of the cross section of the pipeline, η is the viscosity coefficient of the fluid, and ΔP is the differential pressure at both ends of the pipe having a length l. The average flow velocity v in the pipe is
v = Q / πa ² = (a ² /8η) ・ (ΔP / l)
Will be. That is, the average flow velocity v of the uncompressed viscous fluid flowing through the straight pipe is proportional to the differential pressure ΔP.

On the other hand, in a rapid reduction pipe in which the cross-sectional area of the flow path is rapidly reduced in steps and a rapid expansion pipe in which the cross-sectional area of the flow path is rapidly expanded in steps, a loss occurs in the energy of the flow. The differential pressure (P _{1 −} P _{2 ) between the pressure P 1} on the upstream side and the pressure P ₂ on the downstream side of the sudden contraction site or the rapid expansion site, that is, the pressure drop due to the contraction loss or the expansion loss is
_{(P 1 -P 2) = ζ} · (ρw 2/2)
Will be. Here, ζ is the experimentally obtained loss coefficient, and ρ is the fluid density. w is the average flow velocity upstream of the rapidly contracting site or the rapidly expanding site.
w = √ {(2 / ζρ) ・ (P ₁ −P ₂ )}
Will be. That is, the average flow velocity w of the uncompressed viscous fluid flowing through the rapidly reducing pipe or the rapidly expanding pipe is proportional to the 1/2 power of the _{differential pressure (P 1 −} P _2).

In the region where the engine rotation speed is low and the rotation speed and discharge pressure of the cooling water pump 11 are low, the pressure on the upstream side and the downstream side of the throttle 73 on the flow path through which the cooling water L2 bypassing without passing through the water cooling adapter 3 flows. The differential pressure from the pressure is small. However, as the engine speed increases and the rotation speed and discharge pressure of the cooling water pump 11 increase, the differential pressure between the upstream side and the downstream side of the throttle 73 on the same flow path increases. Since the throttle 73 can be seen as a rapid reduction pipe and a rapid expansion pipe, the flow rate of the cooling water L2 that bypasses without passing through the water cooling adapter 3, that is, the flow rate of the cooling water L2 flowing through the bypass pipe 6 is roughly speaking. It tends to increase in proportion to the 1/2 power of the differential pressure between the upstream side and the downstream side of the throttle 73, which is close to the above-mentioned flow velocity w.

On the other hand, the flow pipe 5 through which the cooling water L1 passing through the water cooling adapter 3 flows is not provided with a throttle, and the cooling water flowing through the flow pipe 5 does not have a loss due to the throttle. Therefore, the flow rate of the cooling water L1 flowing through the flow pipe 5 tends to increase following an increase in the discharge pressure of the cooling water pump 11, which is roughly close to the above-mentioned flow velocity v. Therefore, as shown in FIG. 4, when the engine speed is low, the ratio of the flow rate of the cooling water L2 flowing through the bypass pipe 6 to the flow rate of the cooling water L1 flowing through the flow pipe 5 is larger than a certain level, but the engine speed is large. The higher the value, the smaller the ratio. In the figure, the flow rate of the cooling water L1 flowing through the flow pipe 5 is represented by hatching, and the flow rate of the cooling water L2 flowing through the bypass pipe 6 is represented by halftone dots.

That is, in the low rotation range, the cooling water L2 flows through the bypass pipe 6 in a relatively large amount, and the amount of the cooling water L1 flowing into the water cooling adapter 3 is suppressed by that amount, but in the high rotation range, the cooling water flowing through the bypass pipe 6 is suppressed. The flow rate of L2 becomes relatively small, and the flow rate of the cooling water L1 flowing into the water cooling adapter 3 increases remarkably. Therefore, during the warm-up operation immediately after the cold start of the internal combustion engine 0, the cooling performance of the exhaust gas by the water cooling adapter 3 is suppressed, and the exhaust gas having a higher temperature can flow into the three-way catalyst. Rapid temperature rise is promoted. On the other hand, during operation in a high rotation range where a large amount of exhaust gas is discharged from the cylinder, the water cooling performance of the exhaust gas by the water cooling adapter 3 is enhanced, and the catalyst can be appropriately prevented from being damaged by heat.

In the cooling water system of the internal combustion engine 0 in the present embodiment, the cooling water flowing inside the internal combustion engine 0 is divided into a plurality of flows L1 and L2, and one of the flows L1 is discharged from the cylinder for exhaust purification. It has a structure of supplying to a heat exchanger (water cooling adapter) 3 for cooling the exhaust toward the catalyst and guiding the other flow L2 to the outside of the internal combustion engine 0 without passing through the heat exchanger 3. The portion of the flow path through which the cooling water L1 supplied to the heat exchanger 3 has the smallest cross-sectional area on the flow path through which the cooling water L2 guided to the outside of the internal combustion engine 0 does not pass through the heat exchanger 3. A throttle 73 having a smaller cross-sectional area than that of the throttle 73 is provided.

According to the present embodiment, the temperature of the catalyst is kept high by not allowing much cooling water to flow through the heat exchanger 3 for exhaust cooling in the low rotation range, and a large amount of heat exchanger 3 is used in the high rotation range. It is possible to supply cooling water and suppress the temperature of the exhaust that flows into the catalyst. In order to control the amount of cooling water flowing into the heat exchanger 3, it is not always necessary to install a solenoid valve or the like on the flow path, which does not lead to an increase in cost. However, it does not prevent the installation of a solenoid valve or the like for the purpose of adjusting the amount of cooling water flowing into the heat exchanger 3.

When injecting cooling water into the internal combustion engine 0 shipped to the market after production, the internal combustion engine 0 and the cooling water pump 11 are operated to circulate the cooling water, and air is discharged from the cooling water passage inside the cylinder head 2. I need to get rid of it. According to this embodiment, the air inside the cylinder head 2 can be taken out directly through the bypass pipe 6, and the air is evacuated at the connection portion 7 between the flow pipe 5 and the bypass pipe 6 or downstream thereof. Air can be easily discharged from the hole 91 of.

The cooling water L2 guided to the outside of the internal combustion engine 0 without passing through the heat exchanger 3 for exhaust cooling and the cooling water L1 supplied to the heat exchanger 3 merge with the cooling waters L1 and L2. It flows into another heat exchanger 9 that exchanges heat with. As a result, a necessary and sufficient amount of cooling water can be supplied to the heat exchanger (particularly, the heater core) 9, and the heat exchanger 9 can exhibit sufficient performance.

The present invention is not limited to the embodiments described in detail above. For example, in the above embodiment, the flow L1 of the cooling water toward the heat exchanger 3 for exhaust cooling and the flow L2 of the cooling water bypassing the heat exchanger 3 are provided inside the cylinder head 2 of the internal combustion engine 0. Although it was branched, the flow may be branched outside the internal combustion engine.

Further, in the above embodiment, the heat exchanger 3 for exhaust cooling is attached to the outside of the cylinder head 2 in the form of an adapter, but the heat exchanger is installed inside the cylinder head (exhaust port formed in the cylinder head). Alternatively, it may be built (surrounding the exhaust manifold).

In the above embodiment, all of the cooling water L1 supplied to the heat exchanger 3 for exhaust cooling and all of the cooling water L2 bypassing the heat exchanger 3 are merged, and then another heat exchanger 9 is used. However, a part of the cooling water supplied to the heat exchanger for exhaust cooling and / or a part of the cooling water bypassing the heat exchanger is not allowed to flow into another heat exchanger. It is possible that.

In addition, the specific configuration of each part can be variously modified without departing from the spirit of the present invention.

The present invention can be applied to an internal combustion engine mounted on a vehicle or the like.

0 ... Internal combustion engine 3 ... Heat exchanger for exhaust cooling 73 ... Squeeze 9 ... Another heat exchanger L1 ... Flow of cooling water supplied to the heat exchanger L2 ... Outside the internal combustion engine without going through the heat exchanger Guided flow of cooling water

Claims (2)

After dividing the cooling water flowing inside the internal combustion engine into multiple flows, one of the streams is discharged from the cylinder and supplied to the heat exchanger for cooling the exhaust toward the catalyst for exhaust gas purification, and the other. It is a structure that guides the flow of air to the outside of the internal combustion engine without going through the heat exchanger.
On the flow path through which the cooling water guided to the outside of the internal combustion engine flows without passing through the heat exchanger, the cross-sectional area of the flow path through which the cooling water supplied to the heat exchanger flows is smaller than the portion where the cross-sectional area is the minimum. Is provided with a small aperture,
After merging a part or all of the cooling water guided to the outside of the internal combustion engine without passing through the heat exchanger and a part or all of the cooling water supplied to the heat exchanger, the cooling water is used. The structure of the cooling water system of the internal combustion engine that flows into at least one of the heater core, the EGR cooler, the ATF warmer, and the CVT warmer, which exchanges heat with the cooling water. The structure of a cooling water system for an internal combustion engine according to claim 1, wherein an electromagnetic solenoid valve for controlling the amount of cooling water flowing into the heat exchanger that cools the exhaust is not installed.

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