JP2018135870A - Structure of cooling water system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make compatible both the activation of a catalyst at a cold start of an internal combustion engine in an initial stage, and the prevention of thermal damage.SOLUTION: In a cooling water system of an internal combustion engine 0, after shunting cooling water flowing in the internal combustion engine 0 into a plurality of flows L1, L2, one flow L1 is supplied to a heat exchanger 3 for cooling exhaust emission progressing toward an exhaust emission purification catalyst which is discharged from a cylinder, and the other flow L2 is guided to the outside of the internal combustion engine 0 not via the heat exchanger 3. A throttle 73 whose cross section area is smaller than a region in which a cross section area of a flow passage becomes the smallest out of the flow passage in which the cooling water L1 supplied to the heat exchanger 3 flows is arranged on a flow passage in which the cooling water L2 guided to the outside of the internal combustion engine 0 not via the heat exchanger 3 flows.SELECTED DRAWING: Figure 1

Description

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

  Generally, a three-way catalyst for oxidizing and reducing harmful substances contained in exhaust discharged from a cylinder is attached to an exhaust passage of an internal combustion engine.

  When the internal combustion engine is operated in a high rotational speed region, a large amount of high-temperature exhaust gas flows into the catalyst, and the exhaust purification catalyst may be excessively heated to suffer from heat damage (melting damage). As one means for preventing such heat damage, a heat exchanger (exhaust cooling adapter) is attached to surround the exhaust port or exhaust manifold of the cylinder, and the cooling water of the internal combustion engine is attached to this heat exchanger. By circulating the gas, heat exchange is performed between the exhaust gas discharged from the cylinder and the cooling water, and the exhaust gas is cooled and allowed to flow into the catalyst (for example, refer to the following patent document). .

JP 2011-236850 A

  On the other hand, the three-way catalyst is not activated unless the temperature becomes higher than a certain level, and sufficient purification performance cannot be exhibited. If the entire amount of cooling water for the internal combustion engine is always allowed to flow into the heat exchanger for cooling the exhaust gas, there is a concern that the temperature rise of the catalyst is delayed after the cold start, and the emission is deteriorated.

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

  The cooling water system for an internal combustion engine according to the present invention divides the cooling water flowing through the internal combustion engine into a plurality of flows, and then discharges one of the flows from the cylinder toward the exhaust purification catalyst. Cooling water supplied to the heat exchanger for cooling and having the other flow guided outside the internal combustion engine without going through the heat exchanger, and led outside the internal combustion engine without going through the heat exchanger In the flow path through which the cooling water supplied to the heat exchanger flows, the throttle having a smaller cross-sectional area than the portion where the cross-sectional area is minimum is provided.

  When the cooling water of the internal combustion engine is also used in another heat exchanger different from the heat exchanger for exhaust cooling, a part of the cooling water led outside the internal combustion engine without passing through the heat exchanger or It is preferable that all and a part or all of the cooling water supplied to the heat exchanger are merged and then flowed into another heat exchanger that exchanges heat with the cooling water.

  ADVANTAGE OF THE INVENTION According to this invention, coexistence with the early activation of the catalyst at the time of the cold start of an internal combustion engine and prevention of heat damage can be aimed at.

The figure which shows typically the circuit structure of the cooling water system | strain of one Embodiment of this invention. The perspective view which shows the structure of the principal part of the cooling water system | strain of the internal combustion engine of the embodiment. In the cooling water system of the same embodiment, the shape of the junction part of the flow path through which the cooling water guided outside the internal combustion engine without passing through the heat exchanger and the flow path through which the cooling water supplied to the heat exchanger flows FIG. The figure which shows the relationship between engine rotation speed, the rotation speed of a cooling water pump, and the flow volume of cooling water.

  An embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 3, the cooling water system of the internal combustion engine 0 of the present embodiment has a plurality of cooling waters flowing through the internal combustion engine 0 and cooling various portions of the internal combustion engine 0 inside the internal combustion engine 0. A plurality of outlets 21 and 22 for branching into the flows L1 and L2 and flowing out the cooling water L1 and L2 to the outside of the internal combustion engine 0 are opened, and one of the flows L1 is exhausted from the first outlet 21 While flowing into the water-cooled adapter 3 that is a heat exchanger for cooling, the other flow L2 is led out of the internal combustion engine 0 from the second outlet 22 to bypass the water-cooled adapter 3. In the figure, the flow of cooling water is indicated by arrows.

  The cooling water of the internal combustion engine 0 is pumped by the cooling water pump 11, and the cylinder head which forms the ceiling part and the intake / exhaust port of the combustion chamber of these cylinders from the inside of the cylinder block 1 containing a 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 transmission of rotational driving force from the crankshaft of the internal combustion engine 0 or may be an electric pump that is driven by an electric motor. As the rotational speed increases, the cooling water discharge amount and discharge pressure increase. The mechanical coolant pump 11 is driven by the crankshaft of the internal combustion engine 0, and the rotation speed is proportional to the engine rotation speed.

  The cooling water reaching the inside of the cylinder head 2 is divided in the cylinder head 2, and one of the flows L 1 flows out from the first outlet 21 that opens at the front side surface of the cylinder head 2, and the water cooling adapter 3. Flows into. 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 exhausted from the exhaust port of each cylinder flows. The cooling water L1 flowing into the water cooling adapter 3 exchanges heat with the exhaust flowing through the exhaust passage 4, and lowers the temperature of the exhaust toward the exhaust purification three-way catalyst (not shown). Thereafter, the cooling water L1 flowing out from the water-cooled adapter 3 flows into the flow pipe 5 connected to the outlet of the water-cooled adapter 3, and travels 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 the air by exchanging heat with air in the vehicle interior, or recirculates 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 by exchanging heat with the working fluid (transmission fluid) of the automatic transmission mounted on the vehicle Or

  The other flow L2 divided in the cylinder head 2 flows out from the second outlet 22 opened on the 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. The bypass pipe 6 is substantially orthogonal to a portion extending straight in the flow pipe 5 routed from the first outlet 21 and is connected to and communicates therewith. That is, the two cooling water flows L <b> 1 and L <b> 2 branched in the cylinder head 2 merge at the connection 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 described above, and in the heat exchanger 9, other fluids, specifically, air in the vehicle interior, EGR gas, or working fluid of the transmission And heat exchange. Thereafter, the cooling water L1 and L2 are sucked into the cooling water pump 11 again.

  Cooling water that has reached a high temperature inside the internal combustion engine 0 is forcibly cooled by the radiator 8. In the illustrated example, an introduction pipe 81 connected to the inlet of the radiator 8 is connected to the cylinder head 2, and a lead-out 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, the thermostat 12 that opens and closes the flow path (particularly, the outlet pipe 82) connected to the radiator 8 is opened. 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 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, the second flow established in the cylinder head 2 is on the flow path through which the cooling water L2 that bypasses without passing through the water cooling adapter 3 flows. By providing a throttle 73 at a required position (from the outlet 22 to a place 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 is The ratio with the flow rate of the other flow L2 that flows out of the cylinder head 2 but bypasses the water-cooled 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 (that is, the first flow path of the cooling water L1 supplied to the water cooling adapter 3). From the outlet 21 to the flow pipe 5 through the water-cooled adapter 3 and to the place where the flow pipe 5 and the bypass pipe 6 communicate with each other, the flow path cross-sectional area (in other words, the flow of cooling water L1) , 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 flow path is minimum. 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 throttle 73 can pass is set smaller than the cross-sectional area of the flow paths.

  As shown in FIG. 3, in this embodiment, the flow pipe 5 and the bypass pipe 6 are connected via a joint 7 having a T shape in plan view. The joint 7 has a shape in which a cylindrical main pipe portion 71 extending along the extending direction of the flow pipe 5 is abutted with a cylindrical sub 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, by making 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, the inside of the sub pipe portion 72 is communicated with the inside of the main pipe portion 71. As a result, the bypass pipe 6 communicates with the flow pipe 5. In addition, the peripheral wall of the main pipe portion 71 remaining at the periphery of the through hole 70 is used as a throttle 73 for the flow L2 of the cooling water that bypasses without passing through the water cooling adapter 3. The restrictor 73 is located at the end of the bypass pipe 6, and the area (inner diameter or inner dimension) of the through hole 70 becomes the opening cross-sectional area (inner diameter or inner dimension) of the restrictor 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 the inner dimension of the sub pipe portion 72) through which the cooling water L2 of the sub pipe portion 72 can flow. It becomes smaller than the channel cross-sectional area.

The flow rate of the cooling water L1 flowing out from the first outlet 21 of the cylinder head 2 and flowing through the water cooling adapter 3 and the flow pipe 5 and the flow rate of the cooling water L2 flowing out from the second outlet 22 and flowing through the bypass pipe 6 are supplemented. 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 a circular cross-section is shown as follows:
Q = − (πa ⁴ / 8η) · (ΔP / l)
And given. Here, a is the radius of the pipe cross section, η is the viscosity coefficient of the fluid, and ΔP is the differential pressure across the length l pipe. The average flow velocity v in the tube is
v = Q / πa ² = (a ² / 8η) · (ΔP / l)
It becomes. That is, the average flow velocity v of the incompressible viscous fluid flowing through the straight pipe is proportional to the differential pressure ΔP.

On the other hand, a loss occurs in the flow energy in a rapidly reducing pipe whose flow path cross-sectional area rapidly decreases in a stepwise manner or a rapidly expanding pipe whose flow path cross-sectional area rapidly increases in a stepwise manner. The differential pressure (P ₁ −P ₂ ) between the upstream pressure P ₁ and the downstream pressure P ₂ of the sudden reduction part or the sudden expansion part, that is, the pressure drop due to reduction loss or enlargement loss is:
_{(P 1 -P 2) = ζ} · (ρw 2/2)
It becomes. Here, ζ is an experimentally determined loss coefficient, and ρ is a fluid density. w is the average flow velocity upstream of the sudden contraction site or the rapid expansion site,
w = √ {(2 / ζρ) · (P ₁ −P ₂ )}
It becomes. That is, the average flow velocity w of the incompressible viscous fluid flowing through the sudden contraction tube or the rapid expansion tube is proportional to the 1/2 power of the differential pressure (P ₁ −P ₂ ).

  In a region where the engine speed is low and the cooling water pump 11 and the discharge pressure are low, the upstream side pressure and the downstream side pressure of the throttle 73 on the flow path through which the cooling water L2 that bypasses without passing through the water cooling adapter 3 flows. The differential pressure from the pressure is small. However, if 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 regarded as a sudden reduction pipe and a sudden 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 that flows through the bypass pipe 6 can be roughly described. 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 flow velocity w.

  On the other hand, no restriction is provided in the flow pipe 5 through which the cooling water L1 through the water cooling adapter 3 flows, and the cooling water flowing through the flow pipe 5 does not cause a loss due to the restriction. Therefore, the flow rate of the cooling water L1 flowing through the flow pipe 5 has a tendency to increase following the increase in the discharge pressure of the cooling water pump 11 which is roughly close to the flow velocity v described above. 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. As the value increases, the ratio decreases. In the figure, the flow rate of the cooling water L1 flowing through the flow pipe 5 is indicated by hatching, and the flow rate of the cooling water L2 flowing through the bypass pipe 6 is indicated by halftone dots.

  That is, the cooling water L2 flows through the bypass pipe 6 relatively much in the low rotation range, and the amount of the cooling water L1 flowing into the water cooling adapter 3 is suppressed accordingly, but the cooling water flowing through the bypass pipe 6 in the high rotation range. The flow rate of L2 becomes relatively small, and the flow rate of the cooling water L1 flowing into the water cooling adapter 3 is remarkably increased. 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-cooled adapter 3 is suppressed, and higher temperature exhaust gas can flow into the three-way catalyst. Rapid temperature rise is promoted. In turn, during operation in a high rotation range where a large amount of exhaust is discharged from the cylinder, the water cooling performance of the exhaust 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 then one of the flows L1 is discharged from the cylinder and used for exhaust purification. Supplying to the heat exchanger (water cooling adapter) 3 for cooling the exhaust gas which goes to a catalyst, it has the structure which guides the other flow L2 out of the internal combustion engine 0 without passing through the said heat exchanger 3, The part where the cross-sectional area is the smallest in the flow path through which the cooling water L1 supplied to the heat exchanger 3 flows on the flow path through which the cooling water L2 guided outside the internal combustion engine 0 without passing through the heat exchanger 3 A diaphragm 73 having a smaller sectional area is provided.

  According to this embodiment, the temperature of the catalyst is kept high so that the cooling water does not flow so much in the heat exchanger 3 for cooling the exhaust in the low rotation range, and a large amount is added to the heat exchanger 3 in the high rotation range. It becomes possible to suppress the temperature of the exhaust gas flowing into the catalyst by supplying the cooling water. In order to realize the control of the amount of cooling water flowing into the heat exchanger 3 as described above, it is not always necessary to install an electromagnetic solenoid valve or the like on the flow path, and the cost is not increased. However, it does not prevent the installation of an electromagnetic solenoid valve or the like for the purpose of adjusting the amount of cooling water flowing into the heat exchanger 3.

  When water is injected into the internal combustion engine 0 that is shipped to the market after manufacture, the internal combustion engine 0 and the cooling water pump 11 are operated to circulate the cooling water, and air is supplied from the cooling water passage inside the cylinder head 2. Need to be driven out. According to the present embodiment, the air inside the cylinder head 2 can be directly taken out via the bypass pipe 6, and is used for venting the connection portion 7 between the flow pipe 5 and the bypass pipe 6 or downstream thereof. The air can be easily discharged from the hole 91.

  The cooling water L2 guided outside the internal combustion engine 0 without passing through the heat exchanger 3 for cooling the exhaust and the cooling water L1 supplied to the heat exchanger 3 are merged, and then the cooling water L1, L2 It flows into another heat exchanger 9 that exchanges heat. Thereby, 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 embodiment described in detail above. For example, in the above embodiment, the flow L1 of the cooling water toward the heat exchanger 3 for cooling the exhaust and the flow L2 of the cooling water that bypasses the heat exchanger 3 are generated inside the cylinder head 2 of the internal combustion engine 0. Although the flow is branched, the flow may be branched outside the internal combustion engine.

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

  In the above embodiment, the entire cooling water L1 supplied to the heat exchanger 3 for exhaust cooling and the entire cooling water L2 bypassing the heat exchanger 3 are merged, and then another heat exchanger 9 is combined. 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 can also be said.

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

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

DESCRIPTION OF SYMBOLS 0 ... Internal combustion engine 3 ... Heat exchanger for exhaust cooling 73 ... Throttling 9 ... Another heat exchanger L1 ... Flow of the cooling water supplied to a heat exchanger L2 ... Outside an internal combustion engine without passing through a heat exchanger Cooling water flow led

Claims (2)

After the cooling water flowing through the internal combustion engine is divided into a plurality of flows, one of the flows is supplied to a heat exchanger for cooling the exhaust discharged from the cylinder and going to the exhaust purification catalyst, In which the flow of the engine is guided out of the internal combustion engine without passing through the heat exchanger,
The cross-sectional area is smaller than the portion where the cross-sectional area of the flow path through which the cooling water supplied to the heat exchanger flows on the flow path through which the cooling water guided outside the internal combustion engine without passing through the heat exchanger is smaller. The structure of the cooling water system of the internal combustion engine provided with a small throttle. After combining a part or all of the cooling water guided outside 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 and heat The structure of a cooling water system for an internal combustion engine according to claim 1, wherein the cooling water system is caused to flow into another heat exchanger to be replaced.

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