JP2011017315A - Warmup promoting device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an exhaust characteristic by early completing warmup after starting in an internal combustion engine including an EGR (Exhaust Gas Recirculation) cooler capable of cooling EGR gas by a cooling system independent from a cooling system of the internal combustion engine.SOLUTION: This warmup promoting device is the internal combustion engine 1 including an EGR device for recirculating a part of exhaust as the EGR gas to a combustion chamber 5 via an EGR passage 101. The warmup promoting device includes the EGR cooler 102 performing heat exchange between the EGR gas in the EGR passage 101 and a heat medium of the cooling system of the internal combustion engine 1 and a low temperature EGR cooler 103 performing heat exchange between the EGR gas in the EGR passage 101 and a heat medium of a low temperature EGR cooling system independent from the cooling system of the internal combustion engine 1. During a cold operation, at least a part of the EGR gas passing the EGR cooler 102 and the low temperature EGR cooler 103 is returned to an exhaust passage 6, and the heat medium is shared by connecting the low temperature EGR cooling system and the cooling system of the internal combustion engine.

Description

  The present invention relates to a warm-up promoting device for an internal combustion engine provided with an EGR (exhaust gas recirculation) device that recirculates a part of exhaust gas from a combustion device into a combustion chamber and reburns it.

  Purifying the exhaust from the internal combustion engine to suppress the expansion of air pollution is an important issue, but as one of the systems (devices) for this purpose, a part of the exhaust from the combustion device is returned to the combustion chamber. A so-called EGR (Exhaust Gas Recirculation) system is known for reducing the concentration (exhaust amount) of nitrogen oxides (hereinafter referred to as NOx) in exhaust gas by reducing the combustion temperature by recombusting the exhaust gas. ing.

  In such an EGR system, for example, when the internal combustion engine is cold at a predetermined temperature or lower, the EGR gas amount (exhaust gas recirculation amount) recirculated into the combustion chamber is controlled to a predetermined amount in order to make the NOx emission amount desired. When the operation is performed, the combustion in the combustion chamber is remarkably deteriorated, leading to misfires, and white smoke and unburned fuel may be discharged into the atmosphere.

  For this reason, it is conceivable to limit the amount of EGR gas to a small amount or to stop EGR when cold, but with such a method, it becomes impossible to reduce the NOx emission amount as desired.

  For this reason, exhausting NOx as a whole until a predetermined time elapses after cold start by promoting warm-up and completing warm-up early after start-up (reducing the cold time) A method for reducing the amount has been proposed.

  For example, in Patent Document 1, as shown in FIG. 1 of Patent Document 1, a cold EGR cooler (see reference numeral 14 in the figure) used for cooling normal EGR gas after warm-up is cold. At times, by introducing the exhaust gas by switching the flow path of the EGR valve (see reference numeral 15 in the figure) composed of a three-way valve, and heating the cooling water (shared with the cooling water of the internal combustion engine) with the heat of the exhaust gas, A system is described that facilitates warm-up of an internal combustion engine.

JP 2006-57460 A

  By the way, in order to further reduce the NOx emission amount, as shown in FIG. 5, a cooling system independent of the refrigerant (cooling medium, for example, cooling water) of the internal combustion engine 1 on the downstream side of the EGR gas flow of the EGR cooler. A low temperature EGR cooler that makes it possible to effectively cool the EGR gas by using the low temperature EGR cooler, and the EGR gas temperature is further effectively lowered after the engine is warmed up by the low temperature EGR cooler, thereby reducing the EGR rate (EGR gas amount / (new A system has also been proposed in which the amount of NOx emissions can be further reduced by increasing the air volume + the amount of EGR gas) × 100 (%)).

  However, the above-described system is intended to increase the EGR rate by effectively cooling the EGR gas during normal operation by using a cooling system independent from the cooling system of the internal combustion engine. It did not contribute to the promotion of NOx reduction.

  The present invention has been made in view of such circumstances, and in an internal combustion engine having an EGR cooler capable of cooling EGR gas by a cooling system independent of the cooling system of the internal combustion engine while having a simple and inexpensive configuration. Therefore, it is intended to improve exhaust characteristics by enabling warm-up to be completed early after starting.

For this reason, the warm-up promoting device for an internal combustion engine according to the present invention is
An internal combustion engine including an EGR device that recirculates a part of exhaust gas as EGR gas to a combustion chamber through an EGR passage,
An EGR cooler that exchanges heat between the EGR gas in the EGR passage and the heat medium of the cooling system of the internal combustion engine;
A low-temperature EGR cooler that exchanges heat between the EGR gas in the EGR passage and the heat medium of the low-temperature EGR cooling system independent of the cooling system of the internal combustion engine;
With
During the cold operation of the internal combustion engine, at least a part of the EGR gas that has passed through the EGR cooler and the low temperature EGR cooler is returned to the exhaust passage, and the low temperature EGR cooling system and the internal combustion engine cooling system are connected to It is characterized by sharing.

  In the present invention, during the cold operation of the internal combustion engine, a low-temperature EGR cooler, a heat exchanger that exchanges heat between a heat medium of the low-temperature EGR cooling system and a cooling medium (for example, outside air or other refrigerant), Between the low-temperature EGR cooler and the heat exchanger in the circulation passage for circulating the heat medium between them is supplied with the heat medium from the cooling system of the internal combustion engine and The heat medium can be returned to the engine cooling system.

  In the present invention, in the cold operation of the internal combustion engine, the flow of the heat medium into the heat exchanger is restricted.

  According to the present invention, in an internal combustion engine equipped with an EGR cooler that can cool EGR gas by a cooling system independent of the cooling system of the internal combustion engine with a simple and inexpensive configuration, the engine warms up earlier after the start than in the past. Since the machine can be completed, the exhaust characteristics can be improved.

1 is a schematic overall configuration diagram schematically showing a configuration example of an internal combustion engine including an EGR device according to an embodiment of the present invention. It is a figure for demonstrating the mode of an action | operation at the time of the cold operation of the EGR gas cooling system which concerns on embodiment same as the above. It is a figure for demonstrating the mode of an operation | movement after the warm-up operation completion of the EGR gas cooling system which concerns on embodiment same as the above. It is a schematic whole block diagram which shows roughly the other structural example of the EGR gas cooling system which concerns on embodiment same as the above. It is a figure which shows an example of the internal combustion engine provided with the conventional EGR apparatus.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

  As shown in FIG. 1, in the internal combustion engine 1 according to the present embodiment, outside air (fresh air) is sucked through an air cleaner (not shown) or the like, and the fresh air is supercharged through an intake passage 2. Then, the air is guided to the compressor (impeller) 3 and compressed to a predetermined level, and then cooled to a predetermined temperature via an intercooler 4 interposed in the intake passage 2 and guided into a combustion chamber (cylinder) 5.

  The combusted gas discharged from the combustion chamber 5 is guided to an exhaust passage (exhaust manifold portion) 6 through an exhaust port (not shown) opened facing the combustion chamber 5, and then the supercharger 3. After the rotational energy of the exhaust turbine is supplied, the exhaust gas is purified by receiving predetermined processing in an exhaust processing device (not shown) (oxidation catalyst, NOx reduction catalyst, diesel particulate filter, etc.) disposed downstream of the exhaust passage 6. Discharged into the atmosphere.

  Here, in the present embodiment, a part of the gas after combustion (that is, the exhaust gas) is led again to the combustion chamber 5 together with the intake air (fresh air), thereby reducing the combustion temperature and reducing NOx. An EGR device 100 is provided.

  The EGR device 100 according to the present embodiment includes an EGR passage (exhaust gas recirculation passage) 101 that communicates with an exhaust passage (exhaust manifold portion) 6, and the EGR passage 101 includes exhaust gas that flows through the EGR passage 101. An EGR cooler 102 for intercooling (EGR gas: recirculation exhaust gas) is provided.

  Further, in the present embodiment, a low temperature EGR cooler 103 for further cooling the EGR gas cooled by the EGR cooler 102 is interposed on the EGR passage 101 at the downstream side of the EGR gas flow of the EGR cooler 102.

  An EGR valve 110 is interposed in the vicinity of the connection portion between the EGR passage 101 and the intake passage 2, and in a predetermined operation state, a part of the exhaust flowing through the exhaust passage 6 is opened by a predetermined valve. The gas is led to the intake passage 2 of the internal combustion engine 1 while being cooled by the EGR cooler 102 and the low temperature EGR cooler 103.

  Further, in the present embodiment, a branch passage 111 in which an on-off valve 112 is interposed is provided, and one end of the branch passage 111 is connected to the EGR passage 101 between the EGR valve 110 and the low temperature EGR cooler 103. The other end is connected to the exhaust passage 6 on the downstream side of the exhaust turbine of the supercharger 3.

  Here, the EGR cooler 102 is configured such that the heat medium (for example, cooling water) of the cooling system of the internal combustion engine 1 is used as the heat medium. That is, the EGR cooler 102 includes a supply passage 102A for supplying the EGR cooler 102 with cooling water of the internal combustion engine 1, a return passage 102B for returning the cooling water from the EGR cooler 102 to the internal combustion engine 1, Are connected to each other, and the cooling water of the internal combustion engine 1 is fed to the EGR cooler 102 by a water pump or the like (not shown).

The low temperature EGR cooler 103 is connected to a circulation passage 105 for circulating a heat medium to and from the heat exchanger 104. For example, the heat medium can be fed by an electric pump (not shown). The heat exchanger 104 is configured to perform heat exchange between the heat medium and a cooling medium such as outside air or other gas or liquid.
An on-off valve 106 is interposed in the circulation passage 105 (corresponding to one of the portions between the low temperature EGR cooler 103 and the heat exchanger 104) near the outlet of the heat exchanger 104, and beyond that The circulation passage 105 is connected to a passage 103A branched from the supply passage 102A. Note that an on-off valve 107 is interposed in the passage 103A.

  On the other hand, a circulation passage 105 near the inlet of the heat exchanger 104 (corresponding to the other of the portions between the low temperature EGR cooler 103 and the heat exchanger 104) has a passage 103B joined to the supply passage 102A. It is connected. An opening / closing valve 108 is interposed in the passage 103B.

  Further, in the present embodiment, an on-off valve 109 is interposed in the supply passage 102A between the connection portion 103a between the passage 103A and the supply passage 102A and the connection portion 103b between the passage 103B and the supply passage 102A. ing.

The internal combustion engine 1 according to the present embodiment having such a configuration is controlled as follows via an engine control unit (not shown) or the like.
<When the internal combustion engine 1 is cold>
When the temperature of the internal combustion engine 1 is cold (being cold), the EGR gas is not recirculated to the intake passage 2 in the same manner as in the past in order to suppress the occurrence of misfire and the amount of white smoke discharged, or The EGR valve 110 is closed or controlled to a predetermined minute opening so as to limit the recirculation amount to a predetermined value.
As a result, EGR gas does not flow through the EGR passage 101, EGR cooler 102, and low-temperature EGR cooler 103, or only a small amount of EGR gas flows, but in this embodiment, the EGR valve 110 is closed. In the cold state (or controlled to a predetermined minute opening), control is performed to open the on-off valve 112, and the amount of EGR gas passing through the branch passage 111, the EGR cooler 102, and the low temperature EGR cooler 103 is increased.

  At this time, in this embodiment, as shown in FIG. 2, the on-off valve 107 and the on-off valve 108 are opened, and the on-off valve 106 and the on-off valve 109 are controlled to close. As a result, the EGR cooler 102 and the low-temperature EGR cooler 103 share the cooling water of the internal combustion engine 1 as a heat medium. Therefore, the EGR cooler 102 and the low-temperature EGR cooler 103 have relatively high EGR gas Heat exchange is efficiently performed with the cooling water of the internal combustion engine 1 at a low temperature, and the temperature rise of the cooling water of the internal combustion engine 1, that is, warm-up is promoted.

  In order to perform heat exchange efficiently in the low-temperature EGR cooler 103, it is preferable that the on-off valve 106 and the on-off valve 109 are completely closed. However, although the degree of warm-up promotion is inferior, the valve is opened on demand. The state may be maintained, or the opening degree may be reduced so as to limit the flow rate of the heat medium passing through the on-off valve 106 and on-off valve 109 without completely closing the valve.

  Thus, in the present embodiment, during the cold operation of the internal combustion engine 1, high-temperature EGR gas (a part of the exhaust gas) passes through the EGR cooler 102 and the low-temperature EGR cooler 103 in a large amount. Since the on-off valve 112 is controlled and the on-off valves 106 to 109 are controlled to switch the circulation path of the heat medium circulating through the EGR cooler 102 and the low-temperature EGR cooler 103. The temperature of the cooling water of the internal combustion engine 1 can be raised at an early stage, so that warming up of the internal combustion engine 1 can be promoted.

  Therefore, in the present embodiment, since a relatively large amount of EGR gas can be recirculated to the internal combustion engine 1 at an early stage after the start compared to the conventional case, the EGR is not sufficiently applied in the cold state, and the NOx emission amount is reduced. Even if it cannot be reduced as desired, the total amount of NOx emission can be reduced, and the exhaust characteristics can be improved.

<After warming up the internal combustion engine 1>
After the internal combustion engine 1 is warmed up to a predetermined level (for example, after the cooling water temperature of the internal combustion engine 1 becomes equal to or higher than a predetermined temperature), a relatively large amount of EGR gas is less likely to be misfired. In this embodiment, the EGR valve 110 is opened as predetermined as shown in FIG. 3 while the on-off valve can be recirculated to the one combustion chamber. 112 is controlled to close, and the state where the EGR gas flows out to the exhaust passage 6 via the branch passage 111 is stopped.

  As for the cooling circuit (heat medium circulation circuit) of the EGR cooler 102 and the low temperature EGR cooler 103, as shown in FIG. 3, the on-off valve 107 and the on-off valve 108 are closed, and the on-off valve 106 and on-off valve 109 is opened.

  As a result, the EGR cooler 102 uses the cooling water sent from the internal combustion engine 1 as a heat medium, and cools the EGR gas by removing heat from the relatively high temperature EGR gas flowing through the EGR passage 101. In particular, the EGR rate can be increased and the NOx reduction effect can be increased.

  Further, with respect to the low temperature EGR cooler 103, by closing the on-off valve 107 and the on-off valve 108, a cooling system independent of the cooling system of the internal combustion engine 1 is provided by the low temperature EGR cooler 103, the heat exchanger 104, and the circulation passage 105. As a result of the construction, the EGR gas cooled by the EGR cooler 102 can be further cooled, and the EGR rate can be further effectively increased to increase the NOx reduction effect.

  As described above, according to the present embodiment, during the cold operation of the internal combustion engine 1, even if the cooling circuit through which the heat medium circulates is independent, the plurality of EGR coolers are used to promote the warm-up of the internal combustion engine 1. Since the configuration can be used, the internal combustion engine 1 can be raised in temperature early after starting, and the warm-up characteristic of the internal combustion engine 1 can be improved. Since the cold operation time during which EGR cannot be sufficiently applied can be shortened, exhaust characteristics can be improved as a whole.

  In the present embodiment, if the on-off valves 106 to 109 can perform the functions described above, it is not necessary to configure each of them separately. For the purpose of reducing the size and weight of the system, for example, The on-off valve 106 and the on-off valve 107 are disposed in the connection portion 103a as a common valve (for example, a three-way valve), or the connection portion 103b is provided as a common valve (for example, a three-way valve) of the on-off valve 108 and the on-off valve 109. It is also possible to arrange them.

  Further, in the present embodiment, in order to promote warm-up of the internal combustion engine 1, the rotational speed of the internal combustion engine 1 is increased as in the prior art, or an exhaust brake (not shown) is operated to increase the exhaust resistance. Therefore, there is an advantage that it is not necessary to cause a decrease in drivability or a deterioration in fuel consumption due to a decrease in output.

  By the way, the present embodiment can be applied to a configuration in which the EGR cooler 102 is omitted as shown in FIG. 4, and the internal combustion engine 1 is warmed up as described in FIGS. In the state, as shown by the solid line arrows in FIG. 4, the on-off valves 106 to 108 are controlled to circulate the heat medium between the low temperature EGR cooler 103 and the heat exchanger 104, while the internal combustion engine 1 of the heat medium. In the cold operation, the on-off valve 112 is controlled so that high-temperature EGR gas passes through the low-temperature EGR cooler 103 in large quantities, and as shown by the two-dot chain line arrow in FIG. By controlling 106 to 108 and switching the circulation path of the heat medium that circulates through the low-temperature EGR cooler 103, the temperature of the cooling water of the internal combustion engine 1 is raised earlier after the cold start than in the past. The internal combustion engine 1 In which it is possible to enhance the warming-up.

  The direction in which the cooling water flows is not limited to the direction illustrated in FIGS. 2, 3, and 4, but EGR in a heat exchanger such as the EGR cooler 102, the low-temperature EGR cooler 103, and the heat exchanger 104. With respect to the gas flow direction, the direction in which the cooling water (heat medium) flows can be set to the opposite direction (counter direction) or the forward direction according to various circumstances and requirements.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake passage 6 Exhaust passage 100 EGR apparatus 101 EGR passage 102 EGR cooler 103 Low temperature EGR cooler 104 Heat exchanger 105 Circulation passage 106-109 Open / close valve 110 EGR valve 111 Branch passage 111
112 On-off valve

Claims (3)

An internal combustion engine including an EGR device that recirculates a part of exhaust gas as EGR gas to a combustion chamber through an EGR passage,
An EGR cooler that exchanges heat between the EGR gas in the EGR passage and the heat medium of the cooling system of the internal combustion engine;
A low-temperature EGR cooler that exchanges heat between the EGR gas in the EGR passage and the heat medium of the low-temperature EGR cooling system independent of the cooling system of the internal combustion engine;
With
During the cold operation of the internal combustion engine, at least a part of the EGR gas that has passed through the EGR cooler and the low temperature EGR cooler is returned to the exhaust passage, and the low temperature EGR cooling system and the internal combustion engine cooling system are connected to A warm-up promoting device for an internal combustion engine characterized by being shared.   In a cold operation of the internal combustion engine, a low-temperature EGR cooler and a circulation passage that circulates the heat medium between the heat medium that exchanges heat between the heat medium and the cooling medium of the low-temperature EGR cooling system, One of the portions between the low-temperature EGR cooler and the heat exchanger is supplied with a heat medium from the cooling system of the internal combustion engine, and the heat medium is returned to the cooling system of the internal combustion engine from the other of the intermediate portions. The warm-up promoting device for an internal combustion engine according to claim 1.   The warm-up promoting device for an internal combustion engine according to claim 2, wherein inflow of the heat medium into the heat exchanger is restricted during cold operation of the internal combustion engine.

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