JP4911127B2 - Internal combustion engine warm-up control system - Google Patents

Description

  The present invention relates to an internal combustion engine warm-up control system including an exhaust heat recovery device that recovers exhaust heat.

  Conventionally, in order to complete the warm-up operation of the internal combustion engine at an early stage, the following two means are disclosed in Patent Documents 1 and 2 and the like.

That is, in Patent Document 1, the pump that circulates the coolant (engine coolant) of the internal combustion engine is an electric type, and the operation of the electric pump is stopped during the warm-up operation so that the heat exchange with the internal combustion engine (water jacket) ) Engine coolant is stopped to promote a temperature rise, thereby achieving early completion of warm-up operation. Patent Document 2 discloses an exhaust heat recovery device that recovers exhaust heat by exchanging heat between exhaust discharged from an internal combustion engine and engine cooling water. If the engine coolant is heated by the exhaust heat recovery device, the warm-up operation can be completed early.
JP 2004-360509 A JP 2007-24424 A

  Here, the present inventors considered further early completion of the warm-up operation by providing the means for stopping the electric pump during the warm-up operation described above, the means for recovering the exhaust heat, and both means. As a result of the examination, it has been found that the following problems occur when these two means are provided.

  That is, if the electric pump is stopped during the warm-up operation, the circulation of the engine cooling water in the exhaust heat recovery device is also stopped, so that the heat transfer from the high-temperature exhaust to the engine cooling water is delayed. . Then, the exhaust heat recovery device may be damaged by the heat of the high-temperature exhaust.

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a warm-up control system for an internal combustion engine that achieves early completion of warm-up operation while reducing thermal damage of the exhaust heat recovery device. Is to provide.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  In the invention of claim 1, a pump for circulating the coolant of the internal combustion engine, an exhaust heat recovery device for recovering exhaust heat by exchanging heat between the exhaust discharged from the internal combustion engine and the coolant, and Pump control means for controlling the discharge flow rate of the pump. The pump control means is configured such that the coolant temperature (Tw) is lower than a first predetermined value (Tw <T1) and the exhaust gas temperature (Tg) is lower than a second predetermined value (Tg <T2). In this case, the discharge flow rate is limited to a predetermined amount or less. Note that “restricting the discharge flow rate to a predetermined amount or less” includes limiting the discharge flow rate to zero as described in claim 2.

  According to this, when Tw <T1 and Tg <T2, the discharge flow rate is limited to a predetermined amount or less (hereinafter, referred to as warm-up control by pump restriction), so that Tw <T1 and warm-up operation is required. Even in this case, unless the condition of Tg <T2 is satisfied, the warm-up control by the pump restriction is not executed, so that the risk of the exhaust heat recovery device being damaged by the heat of the high-temperature exhaust during the pump-limited warm-up control is reduced. it can.

  Even when the discharge restriction is canceled without satisfying the condition of Tg <T2, the coolant is heated by the exhaust heat recovery device, so that the effect of promoting warm-up by the exhaust heat recovery device is exhibited. The Moreover, since the coolant inside the exhaust heat recovery device is heated by the exhaust even during the pump limit warm-up control, the low-temperature coolant enters the internal combustion engine (for example, inside the water jacket) immediately after the pump is operated. Inflow can be suppressed. Therefore, it helps to promote warm-up operation.

  The above effect will be described more specifically. For example, when the internal combustion engine is started in a state where the outside air temperature is low and Tw <T1 and Tg <T2, the pump discharge flow rate is limited and the internal combustion engine (for example, water The warm-up is promoted by promoting the temperature rise of the coolant staying in the jacket. After that, when the warm-up operation is not completed (Tw <T1) but the exhaust temperature rises and Tg ≧ T2, the pump restriction is released. Thereby, while avoiding that an exhaust heat recovery device is damaged by high temperature exhaust heat, warming-up promotion is aimed at by heating a cooling fluid with an exhaust heat recovery device.

  In the case where Tw <T1 and Tg <T2, the temperature of the internal combustion engine (for example, inside the water jacket) is stopped and the temperature is higher than that of circulating the coolant and heating the coolant with the exhaust heat recovery device. The promotion of the rise can raise the temperature of the internal combustion engine earlier. In view of this point, in the first aspect of the present invention, when Tw <T1 and Tg <T2, pump limited warm-up control is selected instead of coolant heating by the exhaust heat recovery device.

Further , the exhaust heat recovery device forms a refrigerant passage in which the refrigerant circulates inside, an exhaust / refrigerant heat exchanging section that exchanges heat between the exhaust and the refrigerant, and exchanges heat between the refrigerant and the coolant. And a refrigerant / coolant heat exchange section, wherein the refrigerant circulates through the refrigerant passage by convection.

Here, when the exhaust heat recovery unit has the above-described structure in which the heat exchange between the coolant and the exhaust is performed via the refrigerant, the refrigerant temperature increases due to the heat of the high-temperature exhaust during the pump limit warm-up control, and the pressure increases There is a concern that the refrigerant passage may be damaged by the pressure of the high-pressure refrigerant. Therefore, when applied to warm-up control system including an exhaust heat recovery unit having such a structure, the concern is suitably eliminated.

Further, a pressure value of the refrigerant, the pressure value when in a high pressure enough to damage the exhaust heat recovery unit and the pressure limit value, said second predetermined value, the pressure of the refrigerant is the pressure The exhaust gas temperature is set to be a limit value.

By the way, since the vapor | steam of the refrigerant | coolant at the time of becoming a pressure limit value is in a saturated state, it can be said that the refrigerant | coolant pressure at that time is equal to a saturated vapor pressure. Since the saturated vapor pressure is specified by the refrigerant temperature, it can be said that the exhaust temperature considered to be substantially equal to the refrigerant temperature has a correlation with the refrigerant pressure. Above Symbol onset bright in view of this point, the second predetermined value as the execution condition of the pump limited warm-up control (T2), since the set to be the exhaust temperature at which a pressure limit value, It can be easily realized to set the second predetermined value so that the refrigerant passage portion is not damaged by the increased pressure of the refrigerant.
Furthermore, the invention according to claim 2 is characterized in that the pump control means implements the restriction so that the discharge flow rate becomes zero. According to this, since the degree of retention of the coolant in the internal combustion engine (water jacket) can be improved when the pump restriction control is performed, the temperature rise of the coolant can be improved, and further warm-up can be promoted. it can.

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

  FIG. 1 is a diagram showing a circulation path of an engine coolant (hereinafter simply referred to as cooling water) that cools the engine 10 for an engine 10 (internal combustion engine) that is mounted on a vehicle and serves as a travel drive source. 1A shows a state in which the cooling water is circulated by arrows, and FIG. 1B shows a state in which the circulation of the cooling water is stopped.

  An electric W / P 11 driven by an electric motor is used for a water pump 11 (hereinafter referred to as W / P) that circulates engine cooling water, and an electric W / P 11 driven by an electric control unit (hereinafter referred to as ECU 12). The operation of / P11 is duty controlled.

  When the electric W / P 11 is operated, the cooling water inside the water jacket 13 attached to the engine 10 is connected to the circulation path J1 leading to the radiator 14 (cooling heat exchanger) and the circulation path J2 leading to the exhaust heat recovery unit 30. Branch and flow.

  The cooling water flowing through the circulation path J1 flows through the radiator 14 and the thermostat 15 in this order, and returns to the electric W / P11. Outside air is blown to the radiator 14 by a cooling fan (not shown), whereby the cooling water heated by the engine 10 in the water jacket 13 is cooled by exchanging heat with the outside air. The thermostat 15 controls the circulation opening degree of the circulation path J1 according to the temperature of the cooling water. The higher the cooling water temperature is, the larger the circulation opening degree is, and the circulation flow rate of the cooling water is increased. Increase the degree.

  The cooling water flowing through the circulation path J2 flows through the exhaust heat recovery device 30, the heater core 41, and the thermostat 15 described later in detail, and returns to the electric W / P11. A part of the cooling water flowing through the circulation path J2 is branched and distributed to the throttle valve 16 that controls the intake flow rate to the combustion chamber. According to this, even if the condensed water adhering to the throttle valve 16 is frozen when the engine 10 is stopped, it can be thawed early by the heat of the cooling water flowing to the throttle valve 16. Therefore, the malfunction due to the freezing of the throttle valve 16 can be eliminated at an early stage.

  Next, the structure of the exhaust heat recovery device 30 will be described with reference to FIG. FIG. 2 is a schematic view showing a single unit of the exhaust heat recovery device 30 as seen from the upstream side in the exhaust flow direction.

  The exhaust heat recovery device 30 forms therein a refrigerant passage (a portion with a halftone dot in FIG. 2) through which the refrigerant circulates, and an evaporator 31 (exhaust gas) that exchanges heat between the exhaust discharged from the engine 10 and the refrigerant. / Refrigerant heat exchanging part) and a condensing part 32 (refrigerant / coolant liquid heat exchanging part) for exchanging heat between the refrigerant and the coolant, and the refrigerant is configured to circulate through the refrigerant passage by convection. .

  The evaporating unit 31 is provided in a first housing 33 disposed in the exhaust pipe 17 of the engine 10, and is configured to exchange heat between the exhaust and the refrigerant to evaporate the refrigerant. . Incidentally, reference numeral 18 in FIG. 1 denotes a catalyst device for purifying exhaust gas, and the first housing 33 is arranged in the exhaust pipe 17 on the downstream side of the exhaust gas flow of the catalyst device 18.

  The condensing unit 32 is provided outside the exhaust pipe 17 and is provided in the second casing 34 disposed in the cooling water circulation path J2. And the condensation part 32 is comprised so that a refrigerant | coolant may be condensed by performing heat exchange between the refrigerant | coolant evaporated in the evaporation part 31, and engine cooling water. The second casing 34 is provided with an inlet 34a through which the cooling water flowing out from the water jacket 13 flows into the internal space 34c of the housing 34, and an outlet 34b through which cooling water flows out from the internal space 34c of the housing 34. It has been.

  Next, a specific configuration of the evaporation unit 31 will be described. The evaporation unit 31 includes a plurality of evaporation side heat pipes 31a and corrugated fins 31b joined to the outer surface of the evaporation side heat pipe 31a. A plurality of the evaporation side heat pipes 31a are arranged in parallel (stacked arrangement) in a direction perpendicular to the flow direction of the exhaust gas (perpendicular to the plane of FIG. 2). Evaporation side heat pipes 31a are respectively provided with evaporation side headers 31c communicating with all the evaporation side heat pipes 31a at both ends in the longitudinal direction.

  Next, a specific configuration of the condensing unit 32 will be described. The condensing unit 32 includes a plurality of condensing side heat pipes 32a and straight fins 32b joined to the outer surface of the condensing side heat pipe 32a. A plurality of condensing-side heat pipes 32a are arranged in parallel (stacked arrangement) in a direction perpendicular to the flow direction of the exhaust gas. Condensation side headers 32c communicating with all the condensation side heat pipes 32a are provided at both ends in the longitudinal direction of the evaporation side heat pipe 31a.

  The evaporation side header 31c and the condensation side header 32c are connected in a communicating state. A closed loop is formed by the evaporation side and condensation side heat pipes 31a and 32a and the evaporation side and condensation side headers 31c and 32c, and a refrigerant capable of evaporating and condensing such as water and alcohol is enclosed in these. Yes.

  In addition, you may make it arrange | position the valve mechanism 35 shown by the dashed-dotted line in FIG. 2 to the condensation side header 32c. The valve mechanism 35 is a diaphragm type opening / closing means that opens and closes the flow path according to the internal pressure (refrigerant pressure) of the evaporation side heat pipe 31a. Specifically, the valve mechanism 35 closes when the internal pressure rises at a predetermined cooling water temperature and exceeds a first predetermined pressure from a normal valve opening state, and conversely the internal pressure decreases and the first predetermined pressure decreases. When the pressure falls below the lower second predetermined pressure, the valve is opened again. As a result, the exhaust heat recovery amount can be reduced in order to avoid an overheating state of the cooling water due to excessive heating of the cooling water with the exhaust heat during a high engine load in summer.

  Next, the configuration of the air conditioning unit 40 provided with the heater core 41 will be described with reference to FIG.

  The air conditioning unit 40 air-conditions the vehicle interior by blowing warm air or cold air into the vehicle interior, and is disposed outside the engine room (for example, inside the instrument panel). The air conditioning unit 40 includes an air conditioning case 42 that forms an air passage therein. A heater core 41 (heating heat exchanger) and an evaporator 43 (cooling heat exchanger) are disposed in the air conditioning case 42. Then, the air blown into the air passage by the blower 44 passes through the evaporator 43 and the heater core 41 and is subjected to heat exchange so as to reach a desired temperature, and then blown out as conditioned air toward the vehicle interior.

  Therefore, even when the air conditioning unit 40 is required to perform the heating operation, if the temperature of the cooling water flowing through the heater core 41 is not equal to or higher than the predetermined temperature, the conditioned air at a temperature lower than the desired temperature is generated. In order to avoid blowing out into the passenger compartment, the operation of the blower 44 is prohibited.

  Next, the control content of the electric W / P 11 by the ECU 12 will be described.

  The ECU 12 includes a detection signal output from an exhaust temperature sensor 19 that detects the temperature of exhaust gas (hereinafter referred to as exhaust temperature Tg), and a cooling water temperature sensor that detects the temperature of cooling water (hereinafter referred to as cooling water temperature Tw). The detection signal output from 20 is input. The exhaust temperature sensor 19 is disposed in a portion of the exhaust pipe 17 downstream of the evaporator 31 and detects the temperature of the exhaust gas after heat exchange with the refrigerant in the exhaust heat recovery device 30. The cooling water temperature sensor 20 is disposed at the outlet of the cooling water in the water jacket 13 and detects the temperature of the cooling water after being heated by the engine 10. Note that the exhaust temperature sensor 19 may be disposed so as to detect the exhaust temperature before heat exchange in the exhaust heat recovery unit 30.

  A microcomputer (not shown) provided in the ECU 12 (hereinafter referred to as a microcomputer) performs duty control on the operation of the electric W / P 11 based on detection signals from the exhaust temperature sensor 19 and the cooling water temperature sensor 20. The ECU 12 that controls the discharge flow rate of the electric W / P 11 in this way corresponds to “pump control means” recited in the claims. FIG. 3 is a flowchart showing a processing procedure that is repeatedly executed by the CPU of the microcomputer of the ECU 12, and the processing execution is started when an ignition switch (not shown) is turned on.

  First, in step S10, detection signals from the exhaust temperature sensor 19 and the coolant temperature sensor 20 are read as parameters representing the operating state of the engine 10. That is, the coolant temperature Tw at the outlet portion of the engine 10 and the exhaust gas temperature Tg in the downstream portion of the exhaust heat recovery device 30 are acquired.

  Next, in step S20, it is determined whether or not the acquired cooling water temperature Tw is lower than a preset first predetermined value T1. The determination in step S20 is for determining whether or not the engine 10 requires a warm-up operation. Therefore, the first predetermined value T1 is set to about 95 ° C., for example.

  If it is determined that Tw <T1 (S20: YES), it is assumed that warm-up operation is required, and the process proceeds to step S30. If an affirmative determination is made in step S30, which will be described in detail later, electric W / Duty control is performed to stop the operation of P11. Incidentally, in the present embodiment employing on-duty control, the operation of the electric W / P 11 is stopped by setting the duty ratio to 0%. On the other hand, if it is determined that Tw ≧ T1 (S20: NO), it is determined that the warm-up operation is unnecessary, and the process proceeds to step S50, and duty control is performed so as to operate the electric W / P11.

  By the way, when it is determined in step S20 that the warm-up operation is required (Tw <T1), it is effective to stop the cooling water in the water jacket 13 by stopping the operation of the electric W / P11. is there. According to this, since the temperature rise of the cooling water in the water jacket 13 can be promoted, the temperature rise of the engine 10 can be promoted, and as a result, the warm-up operation of the engine 10 can be completed early.

  However, when the operation of the electric W / P 11 is stopped, the circulation of the cooling water in the condensing part 32 of the exhaust heat recovery device 30 is also stopped. Then, the heat transfer from the refrigerant heated by the high-temperature exhaust to the cooling water is delayed. As a result, the refrigerant temperature rises to increase the pressure, and there is a concern that the portion forming the refrigerant passage may be damaged by the increased pressure of the refrigerant.

  Step S30 is for determining whether or not the exhaust gas temperature Tg has risen to such an extent that such a risk of damage occurs, and the exhaust gas temperature Tg acquired in step S10 is a second predetermined value set in advance. It is determined whether it is lower than T2. If it is determined that Tg <T2, it is considered that the risk of damage is low, and the process proceeds to step S40 as the pump stop control means. That is, execution of warm-up promotion by the stop control of the electric W / P 11 is permitted.

  On the other hand, if it is determined that Tg ≧ T2, it is considered that the risk of damage is low, and the process proceeds to step S50 as the pump drive control means. That is, execution of warm-up promotion by the stop control of the electric W / P 11 is prohibited. If the electric W / P 11 is driven in this way, warm-up promotion by stop control cannot be achieved, but the heat transfer from the refrigerant to the cooling water in the exhaust heat recovery device 30 increases, so that the cooling water by the exhaust heat is increased. Heating is promoted, and warm-up can be promoted by exhaust heat recovery.

  In short, if both the first condition Tw <T1 and the second condition Tg <T2 are satisfied (S20: YES AND S30: YES), the operation of the electric W / P 11 is stopped. On the other hand, if at least one of the first and second conditions is not satisfied (S20: NO AND / OR S30: NO), the electric W / P 11 is driven.

  Next, the second predetermined value T2 will be described. In the case where the pressure value of the refrigerant in the exhaust heat recovery device 30 is a pressure limit value when the pressure value is high enough to damage the portion with the lowest pressure resistance among the refrigerant passage forming portions, The second predetermined value T2 is set to be the exhaust temperature (or higher temperature) when the refrigerant pressure reaches the pressure limit value. Therefore, the second predetermined value T2 is set to about 130 ° C., for example, and is higher than the first predetermined value T1 set to about 95 ° C.

  Next, the effect by this embodiment provided with the said structure and control is demonstrated using FIG.

  FIG. 4 is a time chart showing one mode when the control of FIG. 3 is performed, and the cooling water temperature Tw at the cooling water outlet portion (engine outlet portion) of the water jacket 13 and the exhaust heat recovery device 30 downstream. It is a figure which shows each change about the exhaust gas temperature Tg and the duty ratio at the time of carrying out duty control of electric W / P11.

  First, when the engine 10 is started at time t1 in FIG. 4, the cooling water temperature Tw and the exhaust gas temperature Tg gradually increase. At this time, Tw <95 ° C. and Tg <130 ° C., and it is determined in step S20 that the warm-up operation is required, and in step S30, it is determined that the risk of damage due to the high pressure of the refrigerant is low. Therefore, the duty ratio of the electric W / P11 is set to 0%, and the cooling water circulation to the circulation paths J1 and J2 is stopped.

  Thereafter, the cooling water temperature Tw and the exhaust gas temperature Tg gradually increase, and Tg ≧ 130 ° C. at time t2. Then, when it is determined in step S30 that there is a high risk of damage, the duty ratio of the electric W / P 11 is set to 100%, and the cooling water is circulated through the circulation paths J1 and J2. Then, since the cooling water inside the water jacket 13 whose temperature has been raised by the stop control flows out to the outside, the temperature Tw of the cooling water at the engine outlet portion temporarily falls. However, at this point in time, Tw <95 ° C. still rises, reaches 95 ° C. at time t3, and the warm-up operation ends. Further, when the electric W / P 11 is driven at the time t2, the heat transfer from the refrigerant to the cooling water in the exhaust heat recovery device 30 increases, so the rate of increase in the exhaust temperature Tg decreases.

  As described above, the electric W / P 11 is stopped during the period M1 from the time point t1 to the time point t2 in a situation where the cooling water temperature Tw is lower than 95 ° C. (first predetermined temperature) and the engine 10 needs to be warmed up. Warm-up promotion by control is achieved. When the exhaust temperature Tg reaches 130 ° C. (second predetermined value), the electric W / P 11 is driven to avoid damage due to the increased pressure of the refrigerant, and until the time t3 when the warm-up operation ends. In the period M2, warm-up is promoted by exhaust heat recovery in the exhaust heat recovery unit 30. In particular, when there is a heating request to the air conditioning unit 40 in the period M2, the effect of promoting the rise of the cooling water temperature by exhaust heat recovery is suitably exhibited.

(Other embodiments)
The present invention is not limited to the description of the above-described embodiments, and the characteristic configurations of the respective embodiments may be arbitrarily combined. In addition, each of the above embodiments may be modified as follows.

  In the above embodiment, the drive of the electric W / P11 is stopped when Tw <T1 and Tg <T2, but instead of such stop control, the electric W / P11 is satisfied when Tw <T1 and Tg <T2. The discharge flow rate may be controlled to be limited to a predetermined amount or less. In this case, for example, the duty ratio of power supplied to the electric W / P 11 may be limited to a predetermined value or less.

  In the above embodiment, the electrically driven W / P 11 is used for the pump according to the present invention. However, even when a pump driven by an engine output shaft (crankshaft) is used, for example, from the output shaft If a clutch mechanism is provided in the power transmission path to the pump, the discharge amount of the pump can be made zero (controllable) regardless of the operating state of the engine 10. Therefore, a pump with a clutch mechanism may be adopted instead of the electric W / P11. In this case, the clutch mechanism corresponds to “pump control means” described in the claims.

  In the above embodiment, when determining Tg <T2 in step S30 of FIG. 3, the exhaust temperature sensor 19 detects the exhaust temperature Tg and determines Tg <T2 based on the detected value. A physical quantity having a high correlation with Tg (for example, the refrigerant temperature, the refrigerant pressure, the temperature of the evaporation side header 31c, etc.) may be detected by another sensor (not shown), and Tg <T2 may be determined based on the detected value.

  In the above embodiment, when Tw <T1 is determined in step S20 of FIG. 3, the cooling water temperature Tw is detected by the cooling water temperature sensor 20, and Tw <T1 is determined based on the detected value. A physical quantity highly correlated with the water temperature Tw (for example, the temperature of the cylinder head or cylinder block of the engine 10 or the temperature of the lubricating oil of the engine 10) is detected by another sensor (not shown), and Tw <T1 is determined based on the detected value. You may make it do.

  In the above embodiment, the duty ratio of the power supplied to the electric W / P 11 is controlled, but on / off control that switches between energization and interruption of the electric W / P 11 may be used.

  In the above embodiment, the first and second predetermined values T1 and T2 are fixed, but at least one of the two predetermined values T1 and T2 is variably set depending on, for example, the presence or absence of a heating request to the air conditioning unit 40 You may do it.

The figure which shows the circulation path of the cooling water of the engine to which the warm-up control system concerning one Embodiment of this invention is applied. The figure which shows the exhaust heat recovery device of FIG. The flowchart which shows the process sequence performed by ECU of FIG. The time chart which shows the one aspect | mode at the time of implementing control of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 11 ... Electric W / P (electric pump), 12 ... ECU (pump control means), 30 ... Exhaust heat recovery device, 31 ... Evaporation part (exhaust / refrigerant heat exchange part), 32 ... Condensing part (refrigerant / coolant heat exchange part).

Claims (2)

A pump for circulating the coolant of the internal combustion engine;
An exhaust heat recovery unit that recovers exhaust heat by exchanging heat between the exhaust discharged from the internal combustion engine and the coolant;
Pump control means for controlling the discharge flow rate of the pump;
With
The pump control means limits the discharge flow rate to a predetermined amount or less when the temperature of the coolant is lower than a first predetermined value and the temperature of the exhaust gas is lower than a second predetermined value ,
The exhaust heat recovery unit includes a refrigerant passage in which a refrigerant circulates, an exhaust / refrigerant heat exchange unit that exchanges heat between the exhaust and the refrigerant, and a refrigerant / refrigerant that exchanges heat between the refrigerant and the coolant. A coolant heat exchange section, and the refrigerant is configured to circulate through the refrigerant passage by convection,
The pressure value of the refrigerant, which is a pressure value when the pressure is high enough to damage the exhaust heat recovery device,
The warm-up control system for an internal combustion engine, wherein the second predetermined value is set to be the temperature of the exhaust gas when the pressure of the refrigerant reaches the pressure limit value . 2. The warm-up control system for an internal combustion engine according to claim 1, wherein the pump control unit performs the restriction so that the discharge flow rate becomes zero.

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