JP2012102628A - Internal combustion engine cooling system - Google Patents

Abstract

The present invention optimizes the opening and closing conditions of a thermostat.
In a cooling system for an internal combustion engine (1) in which cooling water having a specific heat larger at a plurality of predetermined temperatures than in a temperature other than the predetermined temperature is circulated through the cooling water passage (12), a radiator (13) and a bypass for bypassing the radiator (13) A passage 14, a thermostat 15, and a control device 30 that opens the thermostat 15 at any of a plurality of predetermined temperatures and changes the temperature at which the thermostat 15 is opened according to the operating state of the internal combustion engine 1.
[Selection] Figure 1

Description

  The present invention relates to a cooling system for an internal combustion engine.

  A technique is known in which the cooling water temperature is set so that the internal combustion engine does not overheat, and the electronic thermostat is controlled so as to be the set cooling water temperature (see, for example, Patent Document 1). In addition, cooling water whose specific heat changes at a predetermined temperature is known (for example, see Patent Document 2). This cooling water is configured by dispersing capsules in which a substance causing a phase transition is enclosed in a liquid.

  Here, in the system that controls the electronic thermostat so that the set cooling water temperature is reached, when the cooling water whose specific heat is changed at a predetermined temperature is used, the electronic thermostat is controlled as in the conventional case. It cannot be said that the characteristic that the specific heat of water changes is fully utilized.

JP 2004-353602 A JP 2010-168538 A

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a technique for optimizing the opening / closing conditions of a thermostat.

In order to achieve the above object, a cooling system for an internal combustion engine according to the present invention comprises:
In a cooling system for an internal combustion engine that circulates cooling water having a specific heat at a plurality of predetermined temperatures higher than that at a temperature other than the predetermined temperature in the cooling water passage,
A radiator provided in the cooling water passage to remove heat from the cooling water;
A bypass passage for bypassing the radiator;
A thermostat that shuts off the flow of cooling water to the radiator when closed and distributes the cooling water to the bypass passage, and opens the cooling water to at least the radiator when opened;
A control device that opens the thermostat at any of the plurality of predetermined temperatures, and changes a temperature at which the thermostat is opened according to an operating state of the internal combustion engine;
Is provided.

  The predetermined temperature can be, for example, a temperature at which a structural phase transition occurs in a substance contained in cooling water. That is, since heat is released or absorbed by the structural phase transition, the specific heat of the cooling water increases at a temperature at which the structural phase transition occurs. For this reason, at the predetermined temperature, the temperature of the cooling water is substantially constant even if there is some heat in and out. By including a plurality of types of substances with different temperatures at which the structural phase transition occurs in the cooling water, the specific heat becomes larger at a plurality of predetermined temperatures than at a temperature other than the predetermined temperature.

And if a thermostat is opened at any predetermined temperature, cooling water will distribute | circulate to a radiator. At this time, since the cooling water is at a predetermined temperature, the specific heat is large, so that the temperature of the cooling water is prevented from fluctuating.

  Here, since the cooling capacity required for the cooling system differs depending on the operating state of the internal combustion engine, if the temperature at which the thermostat opens is changed according to the operating state of the internal combustion engine, the temperature of the cooling water corresponding to the required cooling capacity Control becomes possible. And since the fluctuation | variation of the cooling water temperature at that time is suppressed, the temperature of an internal combustion engine can be maintained at a suitable temperature.

  In the present invention, the controller can increase the temperature at which the thermostat is opened as the rotational speed or load of the internal combustion engine increases.

  Here, when the rotation speed or load of the internal combustion engine increases, the temperature of the cooling water increases and the internal combustion engine may overheat. As described above, the temperature of the cooling water rises when at least one of the rotational speed or the load of the internal combustion engine increases. At this time, the temperature at which the thermostat opens is set as a predetermined temperature on the high temperature side. Thereby, when the cooling water temperature reaches a predetermined temperature on the high temperature side, the specific heat increases and the temperature rise is suppressed. On the other hand, when the rotational speed or load of the internal combustion engine is lowered, the temperature of the cooling water is lowered and the fuel consumption may be deteriorated. As described above, when at least one of the rotational speed and the load of the internal combustion engine becomes small, the temperature of the cooling water decreases. At this time, the temperature at which the thermostat opens is set to a predetermined temperature on the low temperature side. As a result, the specific heat increases when the cooling water temperature reaches a predetermined temperature on the low temperature side, and a decrease in temperature is suppressed. That is, if the temperature at which the thermostat opens is selected according to the rotational speed or load of the internal combustion engine, the temperature of the cooling water can be suppressed from becoming excessively high or low. Engine overheating can be suppressed.

  In the present invention, the control device can open the thermostat based on the temperature of the cooling water flowing into the internal combustion engine from the cooling water passage.

  Here, the cooling water flowing into the internal combustion engine from the cooling water passage is the cooling water just before receiving heat from the internal combustion engine. And the cooling water which flowed into the internal combustion engine from the cooling water passage receives heat from the internal combustion engine. For this reason, if it sets so that a thermostat may open when the temperature of the cooling water which flows in into an internal combustion engine from a cooling water channel | path is predetermined temperature, it can suppress that the temperature of a cooling water changes inside an internal combustion engine. That is, since the temperature of the cooling water inside the internal combustion engine can be maintained at an appropriate temperature, deterioration of fuel consumption and overheating of the internal combustion engine can be suppressed.

  Note that when the cooling water temperature becomes lower than the lowest temperature among the plurality of predetermined temperatures, the thermostat may be kept closed. Further, when the cooling water temperature becomes higher than the highest temperature among the plurality of predetermined temperatures, the thermostat may be kept open.

  According to the present invention, the opening / closing conditions of the thermostat can be optimized.

It is a figure which shows schematic structure of the cooling system of the internal combustion engine which concerns on an Example. It is the figure which showed the relationship between cooling water temperature and the specific heat of cooling water. It is the flowchart which showed the control flow of the thermostat concerning an Example.

  Hereinafter, specific embodiments of a cooling system for an internal combustion engine according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of a cooling system for an internal combustion engine according to the present embodiment. An internal combustion engine 1 shown in FIG. 1 is a water-cooled internal combustion engine.

  A water jacket 2 for circulating cooling water is formed inside the internal combustion engine 1. The internal combustion engine 1 is connected to a first cooling water passage 11 and a second cooling water passage 12. A radiator 13 and a bypass passage 14 are connected to the first cooling water passage 11 and the second cooling water passage 12.

  The first cooling water passage 11 connects the outlet side of the water jacket 2 and the inlet side of the radiator 13. That is, the first cooling water passage 11 is a passage for discharging cooling water from the water jacket 2. The second cooling water passage 12 connects the outlet side of the radiator 13 and the inlet side of the water jacket 2. That is, the second cooling water passage 12 is a passage for supplying cooling water to the water jacket 2.

  Further, a water pump 3 that discharges cooling water from the second cooling water passage 12 side to the water jacket 2 side is provided at a connection portion between the second cooling water passage 12 and the water jacket 2.

  The bypass passage 14 bypasses the radiator 13 by connecting the first cooling water passage 11 and the second cooling water passage 12.

  Further, an electronically controlled thermostat 15 is provided in the second cooling water passage 12 closer to the radiator 13 than the connecting portion between the second cooling water passage 12 and the bypass passage 14. The opening degree of the thermostat 15 is adjusted according to a signal from the ECU 30 described later. The amount of cooling water supplied to the radiator 13 is adjusted by controlling the opening degree of the thermostat 15.

  When the thermostat 15 is closed, the cooling water flowing out from the water jacket 2 to the first cooling water passage 11 is sent to the water jacket 2 again via the bypass passage 14. By such cooling water circulation, the cooling water is gradually warmed, and warming up of the internal combustion engine 1 is promoted.

  Further, when the thermostat 15 is open, the cooling water is circulated through the radiator 13 and the bypass passage 14. Regardless of the state of the thermostat 15, the cooling water circulates in parts other than the radiator 13 and the bypass passage 14, but these parts are omitted in FIG.

  Further, in the second cooling water passage 12 between the connection portion of the water jacket 2 and the connection portion of the bypass passage 14, the temperature of the cooling water flowing into the water jacket 2 (hereinafter also referred to as inlet side temperature) is measured. An inlet side temperature sensor 32 is attached.

  The internal combustion engine 1 configured as described above is provided with an ECU 30 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 30 controls the internal combustion engine 1 in accordance with the operating conditions of the internal combustion engine 1 and the driver's request.

In addition to the above sensors, the ECU 30 includes an accelerator opening sensor 33 that outputs an electric signal corresponding to the accelerator opening to detect the engine load, and a crank position sensor 34 that detects the engine speed via electric wiring. Connected. The output signals of these sensors are E
Input to CU30. On the other hand, the thermostat 15 is connected to the ECU 30 via electric wiring, and the ECU 30 controls the thermostat 15.

  Here, the specific heat of the cooling water according to the present embodiment changes at a predetermined temperature. For example, it includes a substance that undergoes a phase transition from a solid to a liquid or from a liquid to a solid at a predetermined temperature. That is, when the temperature of the cooling water reaches a predetermined temperature, the substance contained in the cooling water changes from a solid to a liquid, and at this time, heat is absorbed from the surroundings. On the other hand, when the temperature of the cooling water reaches a predetermined temperature, the substance contained in the cooling water changes from a liquid to a solid, and at this time, heat is released around. As described above, the specific heat of the cooling water changes when the phase transition occurs between the liquid and the solid. In addition, by including a plurality of substances that undergo phase transition at different temperatures in the cooling water, it is possible to set a plurality of temperatures at which the specific heat increases.

  Here, FIG. 2 is a diagram showing the relationship between the cooling water temperature and the specific heat of the cooling water. As shown in FIG. 2, the specific heat is higher at the temperatures indicated by A and B than at the other temperatures. That is, the cooling water contains two substances that undergo phase transition at different temperatures. Hereinafter, A is referred to as a low temperature side predetermined temperature, and B is referred to as a high temperature side predetermined temperature. At the low temperature side predetermined temperature A and the high temperature side predetermined temperature B, the low temperature side predetermined temperature A or the high temperature side predetermined temperature B once becomes constant even when the cooling water temperature is in the middle of rising or falling.

  In this embodiment, the temperature at which the thermostat 15 is opened is the low temperature side predetermined temperature A when the cooling water temperature can be low, and the high temperature side predetermined temperature B when the cooling water temperature is high. And The operating state in which the coolant temperature can be low is, for example, a case where the engine speed and the engine load are relatively low. This may be during low rotation, low load, steady operation, or deceleration operation. In addition, the operating state in which the coolant temperature can be high is, for example, a case where at least one of the engine speed and the engine load is relatively high. This may be during high rotation and high load or during acceleration operation. Which predetermined temperature is selected may be mapped in advance.

  If the thermostat 15 is set to open when the inlet side temperature is the low temperature side predetermined temperature A or the high temperature side predetermined temperature B, the characteristic that the specific heat of the cooling water increases, that is, the characteristic that the cooling water temperature becomes constant is utilized. Can do. That is, when the cooling water temperature is rising, the temperature rise can be suppressed by removing heat. Further, when the cooling water temperature is decreasing, the temperature decrease can be suppressed by applying heat. In this way, the temperature when the cooling water passes through the water jacket 2 can be kept constant. Thereby, since it can control that the temperature of cooling water goes up too much, overheating of internal-combustion engine 1 can be controlled. Moreover, since it can suppress that the temperature of a cooling water falls too much, the deterioration of a fuel consumption can be suppressed.

  In this embodiment, the thermostat 15 is opened based on the inlet side water temperature.

  Here, the cooling water flowing into the internal combustion engine 1 from the second cooling water passage 12 is the cooling water immediately before receiving heat from the internal combustion engine 1. The cooling water flowing into the internal combustion engine 1 from the second cooling water passage 12 receives heat from the internal combustion engine 1. For this reason, if the thermostat 15 is set to open when the temperature of the cooling water flowing into the internal combustion engine 1 from the second cooling water passage 12 is the low temperature side predetermined temperature A or the high temperature side predetermined temperature B, the inside of the internal combustion engine 1 The temperature of the cooling water becomes constant at the low temperature side predetermined temperature A or the high temperature side predetermined temperature B. That is, the cooling water temperature inside the internal combustion engine 1 can be maintained at an appropriate temperature.

FIG. 3 is a flowchart showing a control flow of the thermostat 15 according to the present embodiment. This routine is executed every predetermined time. In this embodiment, the ECU 30 that processes the flow shown in FIG. 3 corresponds to the control device in the present invention.

  In step S101, it is determined whether or not the operation state is such that the coolant temperature can be high. For example, it is determined whether or not the internal combustion engine 1 is operating at a high speed or a high load. The relationship between the engine speed, the engine load, and the operating state where the coolant temperature becomes high may be mapped in advance. In this step, it is determined whether or not the valve opening temperature of the thermostat 15 is set to the high temperature side predetermined temperature B.

  If an affirmative determination is made in step S101, the process proceeds to step S102, and if a negative determination is made, the process proceeds to step S103.

  In step S102, the temperature at which the thermostat 15 opens is set to the high temperature side predetermined temperature B. When the inlet side temperature reaches the high temperature side predetermined temperature B, the thermostat 15 is opened.

  In step S103, the temperature at which the thermostat 15 opens is set to the low temperature side predetermined temperature A. When the inlet side temperature reaches the low temperature side predetermined temperature A, the thermostat 15 is opened.

  The low temperature side predetermined temperature A and the high temperature side predetermined temperature B are obtained in advance by experiments or the like as temperatures for suppressing deterioration of fuel consumption and temperatures for suppressing overheating of the internal combustion engine 1. When the coolant temperature is lower than the low temperature side predetermined temperature A, the thermostat 15 is closed. The thermostat 15 is also closed when the cooling water temperature is higher than the low temperature side predetermined temperature A and lower than the high temperature side predetermined temperature B. When the coolant temperature is higher than the high temperature side predetermined temperature B, the thermostat 15 is opened.

  As described above, according to this embodiment, the temperature at which the thermostat 15 opens according to the operating state of the internal combustion engine 1 is selected from a plurality of predetermined temperatures, thereby suppressing fluctuations in the internal temperature of the internal combustion engine 1. Therefore, deterioration of fuel consumption and overheating of the internal combustion engine 1 can be suppressed.

1 Internal combustion engine 2 Water jacket 3 Water pump 11 First cooling water passage 12 Second cooling water passage 13 Radiator 14 Bypass passage 15 Thermostat 30 ECU
32 Inlet side temperature sensor 33 Accelerator opening sensor 34 Crank position sensor

Claims (3)

In a cooling system for an internal combustion engine that circulates cooling water having a specific heat at a plurality of predetermined temperatures higher than that at a temperature other than the predetermined temperature in the cooling water passage,
A radiator provided in the cooling water passage to remove heat from the cooling water;
A bypass passage for bypassing the radiator;
A thermostat that shuts off the flow of cooling water to the radiator when closed and distributes the cooling water to the bypass passage, and opens the cooling water to at least the radiator when opened;
A control device that opens the thermostat at any of the plurality of predetermined temperatures, and changes a temperature at which the thermostat is opened according to an operating state of the internal combustion engine;
An internal combustion engine cooling system comprising:   2. The cooling system for an internal combustion engine according to claim 1, wherein the control device increases a temperature at which the thermostat is opened as at least one of a rotational speed and a load of the internal combustion engine is increased.   The cooling system for an internal combustion engine according to claim 1 or 2, wherein the control device opens the thermostat based on a temperature of cooling water flowing into the internal combustion engine from the cooling water passage.

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