JP4571897B2 - EGR cooler cooling water circuit - Google Patents

Description

  The present invention relates to a cooling water circuit of an EGR cooler.

  Conventionally, a part of the exhaust gas is recirculated to the intake side through the exhaust gas recirculation flow path, so that the supply air containing the exhaust gas is supplied to the engine to reduce NOx (outside air gas). Recirculation) devices are known. Such an EGR device may be provided with an EGR cooler that cools a part of exhaust gas (hereinafter referred to as EGR gas) that is recirculated to the supply side.

  The EGR cooler is a kind of heat exchanger, and is configured such that heat exchange is performed between engine cooling water and EGR gas. In the EGR cooler, when the engine cooling water is at a low temperature just after the engine is started, the degree of cooling of the EGR gas by the engine cooling water increases, and a lot of condensed water may be generated. If this condensed water stays in the EGR cooler or in the vicinity of gas discharge, it causes corrosion, which is not preferable.

  Therefore, proposals have been made to suppress the generation of condensed water. As an example of this proposal, a cooling water adjustment valve is provided on the cooling water circuit for circulating the engine cooling water between the engine and the EGR cooler, a temperature sensor is provided on the cooling water discharge side of the EGR cooler, and detection by this temperature sensor is performed. There is one provided with an EGR control device that controls opening and closing of the cooling water regulating valve based on the result (for example, Patent Document 1).

  In the proposal using this EGR control device, when the engine coolant is at a low temperature equal to or lower than a predetermined temperature, the EGR control device controls the coolant adjustment valve to close so that the engine coolant is supplied from the coolant engine side to the EGR cooler. In order not to flow, the EGR gas in the EGR cooler is prevented from lowering the temperature more than necessary, and the generation of condensed water is suppressed. When the engine cooling water exceeds a predetermined temperature, the EGR control device controls to open the cooling water adjustment valve so that the EGR gas is cooled by the EGR cooler.

Japanese Patent Laid-Open No. 11-351073

  However, according to the proposal of Patent Document 1, a plurality of expensive parts such as a high-accuracy temperature sensor and a solenoid-type cooling water regulating valve that operates by a control signal from the EGR control device are required, and the configuration There is a problem that becomes complicated.

  An object of the present invention is to provide a cooling water circuit for an EGR cooler that can reliably prevent generation of condensed water in the EGR cooler with an inexpensive and simple configuration.

According to a first aspect of the present invention, there is provided an EGR apparatus including: an EGR passage that recirculates a part of exhaust gas by communicating an exhaust side and an intake side of an engine; and an EGR cooler provided in the EGR passage. in the cooling water circuit of the EGR cooler, the downstream of the cooling water circuit of the EGR cooler, and provided upstream from the merging portion of the discharge flow path from the outlet side cooling water passage and the engine of the EGR cooler, the exit side A thermostat that opens and closes the cooling water flow path, and a temperature sensitive side branch flow that branches from between the cooling water chamber of the EGR cooler and the thermostat in the outlet side cooling water flow path and constantly flows cooling water to the temperature sensitive greenhouse of the thermostat And the thermostat shuts off the outlet-side cooling water flow path when the cooling water flowing into the temperature-sensitive room is below a predetermined temperature and exceeds the predetermined temperature. Wherein the valve member for communicating the outlet side cooling water passage to is provided.

  The invention according to claim 2 is the cooling water circuit of the EGR cooler according to claim 1, wherein the cooling water is engine cooling water.

  In the above, according to the first aspect of the present invention, when the cooling water is below the predetermined temperature, the cooling water flowing into the EGR cooler is sensed because the valve member in the thermostat blocks the outlet side cooling water flow path of the EGR cooler. It becomes a slight flow rate through the branch channel on the greenhouse side, and is heated by the EGR gas in the EGR cooler. Therefore, the temperature of the cooling water rises in a short time, and it becomes difficult for condensed water to be generated from the EGR gas. Also, if the temperature of the cooling water exceeds a predetermined temperature, the outlet side cooling water flow path is communicated by the valve member in the thermostat, so that a large amount of cooling water flows into the EGR cooler, effectively cooling the EGR gas. To do. In addition, since the cooling water circuit having such a configuration does not use an expensive temperature sensor or a cooling water regulating valve as in the prior art, the configuration is simple and inexpensive.

  According to the invention of claim 2, since the cooling water is engine cooling water, the cooling water circuit according to the present invention can be easily applied to a vehicle or the like on which the engine is mounted.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 schematically shows a configuration around the engine 1 in which the cooling water circuit 20 according to the present embodiment is employed.

  The engine 1 is, for example, a diesel engine or a gasoline engine provided with a turbocharger (not shown). An air supply line 2 is connected to the compressor side outlet of the turbocharger, and an air supply manifold 3 for distributing the air supply to each cylinder is provided between the air supply line 2 and the engine 1. Further, an exhaust pipe 4 is connected to the turbine side inlet of the turbocharger, and an exhaust manifold 5 that collects and exhausts exhaust gases from each cylinder is provided between the exhaust pipe 4 and the engine 1. Is provided. Further, the engine 1 in the present embodiment is provided with an EGR device 10 that recirculates a part of the exhaust gas to the supply side as EGR gas (see arrow).

  The EGR device 10 includes an EGR passage 11 that connects the exhaust pipe 4 and the air supply pipe 2 (which becomes an intake pipe in the case of non-supercharging), and an EGR valve 12 that is provided in the middle of the EGR passage 11. The EGR cooler 13 provided downstream of the EGR valve 12 and an EGR control device (not shown) that controls opening and closing of the EGR valve 12 according to the rotational speed and load (fuel injection amount) of the engine 1 are provided. . In a state where the EGR device 10 is operating, the EGR valve 12 is opened, and the EGR gas is recirculated from the exhaust side to the supply side through the EGR passage 11. At this time, the EGR gas passes through the EGR cooler 13 and exchanges heat with the engine coolant.

  The cooling water circuit 20 for circulating the engine cooling water includes a discharge flow path 22 that connects the cooling water outlet 1A of the engine 1 and the cooling water inlet 21A of the radiator 21, the cooling water outlet 21B of the radiator 21, and the cooling of the engine 1. A return channel 23 for communicating the water inlet 1B and a bypass channel 24 for communicating the channels 22, 23 are provided. Further, in the discharge channel 22, a known first wax-type thermostat 25, for example, is provided at a branch portion of the bypass channel 24. In the return channel 23, a known water pump 26 is also provided on the downstream side of the joining portion of the bypass channel 24.

  Here, the first thermostat 25 switches the flow of the engine cooling water to the bypass flow path 24 side when the engine cooling water discharged from the engine 1 has a low temperature equal to or lower than the predetermined temperature T1, and exceeds the predetermined temperature T1. It functions to switch to the radiator 21 side. This switching is for quickly raising the engine cooling water after the engine 1 is started to the predetermined temperature T1, preventing white smoke in the exhaust gas, reducing wear loss, and condensate water in the cylinder block. The purpose is to prevent outbreaks.

  In addition, the cooling water circuit 20 in the present embodiment is also a circuit for heat exchange in the EGR cooler 13 and has the following configuration. That is, in the return flow path 23, a branch portion 23 </ b> A is provided on the downstream side of the water pump 26, and the branch portion 23 </ b> A and the cooling water inlet 13 </ b> A of the EGR cooler 13 communicate with each other through the cooler side branch flow path 27. Further, in the discharge flow path 22, a merging portion 22 </ b> A is provided upstream of the first thermostat 25, and the merging portion 22 </ b> A and the cooling water outlet 13 </ b> B provided in the cooling water chamber of the EGR cooler 13 are connected to the outlet side cooling water flow path. 28. Therefore, in this embodiment, the cooler circulation channel 29 is formed including the discharge channel 22, the return channel 23, the cooler side branch channel 27, and the outlet side cooling water channel 28. Engine cooling water passing through the EGR cooler 13 is circulated through the cooler circulation passage 29.

  At this time, the outlet side cooling water flow path 28 includes an upstream flow path 28A and a downstream flow path 28B, and the upstream flow path 28A is further branched into two. That is, the temperature sensitive side branch flow path 28D provided with an orifice 28C in the middle and the main flow path 28E provided with no orifice, and the temperature sensitive side branch flow path 28D has a flow resistance higher than that of the main flow path 28E. Is getting bigger. A wax-type second thermostat 30 is provided between the upper and lower flow paths 28A and 28B, for example.

  The second thermostat 30 includes a temperature sensing greenhouse 31 into which engine cooling water after heat exchange in the EGR cooler 13 flows in through the temperature sensing side branching channel 28D, a main inflow chamber 32 into which the engine cooling water flows in through the main channel 28E, and a downstream channel. A discharge chamber 33 communicating with 28B is provided. A temperature sensing unit 34 is provided in the temperature sensing chamber 31 to be in contact with the flowing engine cooling water. The temperature sensing part 34 is provided with a cylindrical guide part 35 projecting into the main inflow chamber 32, and a rod 36 is disposed in the guide part 35 so as to be able to protrude and retract. The valve member 37 that moves is fixed.

  That is, the rod 36 appears and disappears in accordance with the temperature of the engine coolant that has contacted the temperature sensing portion 34. When the engine coolant is at a low temperature equal to or lower than the predetermined temperature T2, the compression spring that biases the valve member 37. It is returned to the temperature sensing unit 34 side by 38 and is in a closed state. In this state, the valve member 37 abuts on a valve seat 37A provided in a partition portion between the main inflow chamber 32 and the discharge chamber 33, and closes the communication opening 37B of each chamber 32, 33 (one-dot chain line in the figure). On the other hand, when the engine coolant exceeds the predetermined temperature T2, the rod 36 protrudes along with the volume change due to the expansion of the wax in the temperature sensing portion 34 according to the temperature, so that the valve member 37 is a spring of the compression spring 38. The valve seat 37A is left against the force and the communication opening 37B is opened (solid line in the figure). As a result, the main inflow chamber 32 communicates with the discharge chamber 33, and thus the downstream side of the second thermostat 30.

  The sensitive room 31 and the discharge chamber 33 communicate with each other via a communication channel 39. Therefore, even when the main inflow chamber 32 and the discharge chamber 33 are closed by the valve member 37, the sensitive greenhouse 31 is always in communication with the discharge chamber 33 and thus the downstream side of the second thermostat 30. In the chamber 33, engine cooling water branched from the downstream side of the radiator 21 to the EGR cooler 13 side (the flow rate is small because it passes through the temperature-sensitive greenhouse side branch flow path 28 </ b> D) enters the discharge chamber 33 via the temperature-sensitive room 31. It flows in and returns to the discharge flow path 22 on the engine 1 side through the outlet-side cooling water flow path 28.

  The predetermined temperature T2 related to the operation of the second thermostat 30 is a temperature set so as to prevent a slight amount of engine coolant flowing into the EGR cooler 13 from becoming excessively high. The first thermostat 25 It may be different from the predetermined temperature T1.

  Below, the flow when the temperature of the engine coolant is low will be described based on FIG. 2, and the flow when the temperature is high will be described based on FIG.

  In FIG. 2, when the engine cooling water is equal to or lower than the predetermined temperature T1 immediately after the engine is started, the first thermostat 25 blocks the discharge flow path 22 on the radiator 21 side from the first thermostat 25 (in the figure). dotted line). For this reason, the engine coolant discharged from the engine 1 flows through the bypass flow path 24 without passing through the radiator 21, and most of it flows through the return flow path 23 as it is and returns to the engine 1.

  Further, when the engine cooling water is at a low temperature and is equal to or lower than the predetermined temperature T2, the second thermostat 30 is closed, so that it flows only through the temperature-sensitive greenhouse side branch flow path 28D. For this reason, the engine coolant having a slight flow rate regulated by the outlet-side coolant channel 28 flows into the EGR cooler 13 and returns to the junction 22A of the discharge channel 22 through the second thermostat. Accordingly, since a large amount of low-temperature engine coolant does not flow into the EGR cooler 13, the EGR cooler 13, which is a refrigerant of the EGR cooler 13, flows from the EGR gas through the cooler-side branch passage 27 and then the outlet-side coolant passage 28. Since the heat inflow per unit flow rate of the cooling water flowing into the engine cooling water is increased, it can be raised within an appropriate temperature range in a short time, and the EGR cooler 13 is unlikely to generate condensed water from the EGR gas. it can. Moreover, since the engine coolant flowing into the EGR cooler 13 does not pass through the radiator 21 at this stage, the temperature can be increased efficiently.

  Further, when the engine 1 continues to operate and the temperature of the engine cooling water rises, a slight amount of engine cooling water flowing into the EGR cooler 13 becomes even higher due to heating by the EGR gas, and the EGR cooler 13 and the second thermostat 30 are adversely affected. There is a possibility of receiving. However, in the present embodiment, when the engine cooling water after heat exchange in the EGR cooler 13 exceeds the predetermined temperature T2, the second thermostat 30 is opened as shown in FIG. Will return through. By doing so, the flow rate of the engine cooling water flowing from the EGR cooler 13 to the outlet side cooling water flow path 28 is increased, and the temperature of the engine cooling water passing through the EGR cooler 13 and the second thermostat 30 is lowered to an appropriate temperature range. For this reason, the influence on the EGR cooler 13 and the second thermostat 30 can be eliminated, and the EGR gas can be reliably cooled at an appropriate temperature in the EGR cooler 13.

  In FIG. 3, when the engine coolant temperature rises due to continuous operation of the engine 1 and exceeds a predetermined temperature T1, the flow to the bypass passage 24 side is reduced or completely blocked by the switching operation of the first thermostat 25. The engine coolant discharged from the engine 1 flows through the radiator 21 (dotted line in the figure). Therefore, the temperature of the engine coolant flowing into the EGR cooler 13 is properly maintained, and the EGR gas is subsequently cooled at an appropriate temperature. Depending on the setting of the predetermined temperatures T1 and T2 at the first and second thermostats 25 and 30, the first thermostat 25 may be switched before the second thermostat 30 is opened, and the engine 21 is connected to the radiator 21 side. It is also possible to flow cooling water.

  As described above, the cooling water circuit 20 in the present embodiment does not use expensive parts corresponding to conventional temperature sensors or solenoid type cooling water regulating valves, and has a configuration. The EGR gas can be reliably cooled while being simple and inexpensive and preventing the generation of condensed water in the EGR cooler 13.

In addition, this invention is not limited to the said embodiment, Other structures etc. which can achieve the objective of this invention are included, The deformation | transformation etc. which are shown below are also contained in this invention.
For example, in the above embodiment, the engine 1 with a turbocharger has been described. However, the engine may be a non-supercharged type in which a turbocharger or the like is not provided.

  In the above embodiment, the cooler circulation passage 29 for circulating the engine cooling water is formed including the discharge passage 22 toward the radiator 21 and the return passage 23 returning from the radiator 21 to the engine 1. Alternatively, a dedicated cooler circulation channel provided separately may be used.

  In the above-described embodiment, the orifice 28C is used to increase the flow resistance of the temperature sensitive side branching flow path 28D. For example, the diameter of the temperature sensitive side branching flow path 28D with respect to the main flow path 28E is used. The channel resistance may be increased by significantly reducing

  Furthermore, in the said embodiment, although the EGR cooler 13 was cooled with engine cooling water, when applying this invention to a stationary power generation device etc., cooling water is an external cooling water source such as a cooling tower or tap water. You may lead from.

In addition, the best configuration, method, and the like for carrying out the present invention have been disclosed above, but the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of quantity, other details, and the like.
Therefore, the description limited to the shape, quantity and the like disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

  INDUSTRIAL APPLICABILITY The present invention can be applied as a cooling water circuit of an engine with an EGR device regardless of the presence or absence of a turbocharger, and a construction machine, a transport truck, a construction dump truck, a private car, and a power generation equipped with such an engine. It can be used for devices.

The schematic diagram which shows the structure around the engine by which the cooling water circuit which concerns on one Embodiment of this invention was employ | adopted. The schematic diagram for demonstrating the case where engine cooling water is below predetermined temperature. The schematic diagram for demonstrating the case where engine cooling water exceeds predetermined temperature.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 10 ... EGR apparatus, 11 ... EGR passage, 13 ... EGR cooler, 20 ... Cooling water circuit, 28 ... Outlet side cooling water channel, 28D ... Sensitive greenhouse side branch channel, 28E ... Main channel, 29 ... Cooler Circulating flow path 30... Second thermostat as thermostat 31. Sensitive greenhouse 32. Main inflow chamber 37 Valve member 39 Communication path.

Claims (2)

In the cooling water circuit of the EGR cooler in the EGR device comprising an EGR passage for recirculating a part of the exhaust gas by communicating the exhaust side and the intake side of the engine, and an EGR cooler provided in the EGR passage,
Wherein downstream of the cooling water circuit of the EGR cooler, and provided upstream from the merging portion of the discharge flow path from the outlet side cooling water passage and the engine of the EGR cooler, a thermostat for opening and closing the exit-side cooling water passage ,
A temperature-sensing greenhouse-side branch flow channel that branches from between the cooling water chamber of the EGR cooler and the thermostat in the outlet-side cooling water flow channel and constantly flows cooling water to the temperature-sensitive greenhouse of the thermostat,
The thermostat has a valve member that shuts off the outlet side cooling water flow path when the cooling water flowing into the temperature-sensitive room is equal to or lower than a predetermined temperature and communicates the outlet side cooling water flow path when the temperature exceeds a predetermined temperature. A cooling water circuit for an EGR cooler, which is provided. In the cooling water circuit of the EGR cooler according to claim 1,
The cooling water circuit of an EGR cooler, wherein the cooling water is engine cooling water.

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