JP2013007308A - Device and method for controlling cooling water of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for preventing overheating of an internal combustion engine by using cooling water having a specific heat change band in at least one temperature region.SOLUTION: This device of controlling cooling water of an internal combustion engine using the cooling water having a specific heat change band while the specific heat changes in at least one temperature region comprises: a thermostat subject to opening and closing control for adjusting a temperature of the cooling water and having variable opening and closing control timing; a remaining latent heat amount estimation means for estimating a remaining latent heat not contributing to temperature rise of the cooling water obtained by the cooling water having the specific heat change band; and a control means opening the thermostat when the remaining latent heat amount estimated by the remaining latent heat amount estimation means becomes equal to or lower than a predetermined value being a threshold as to whether it is the timing for opening the thermostat.

Description

  The present invention relates to an internal combustion engine coolant control apparatus and an internal combustion engine coolant control method.

  As cooling water for cooling an internal combustion engine, a technique is disclosed that uses cooling water whose specific heat is variable by including particles that change the specific heat of the medium by changing the phase between a solid phase state and a liquid phase state. (For example, refer to Patent Document 1). Thereby, heat can be efficiently transported by the heat storage effect of the particles, and the circulation amount of the cooling water by the pump can be reduced by that much, and the cooling efficiency of the heat source to be cooled can be improved.

JP 2009-044896 A

  When the cooling water disclosed in Patent Document 1 has variable specific heat, a cooling water medium having a low specific heat is used as the cooling water medium (solvent) containing the particles. When a cooling water medium having a low specific heat is used, the temperature changes drastically in a temperature range other than the specific heat changing zone where the specific heat is increased by the particles contained in the cooling water. Then, when the temperature of the cooling water rises beyond the specific heat change zone, the cooling is not in time, which may cause overheating of the internal combustion engine.

  An object of the present invention is to provide a technique for suppressing overheating of an internal combustion engine by using cooling water having a specific heat change zone in at least one temperature region.

In the present invention, the following configuration is adopted. That is, the present invention
A cooling water control device for an internal combustion engine that uses cooling water having a specific heat change zone in which the specific heat is changing in at least one temperature range,
A thermostat that is controlled to be opened and closed to adjust the temperature of the cooling water, and whose opening and closing control timing is variable,
A residual latent heat amount estimating means for estimating a residual latent heat amount that does not contribute to the temperature rise of the cooling water obtained by the cooling water having a specific heat change zone;
Control means for opening the thermostat when the residual latent heat amount estimated by the residual latent heat amount estimation means is equal to or less than a predetermined amount which is a threshold value indicating whether or not the timing for opening the thermostat;
A cooling water control device for an internal combustion engine, comprising:

  Here, the specific heat change zone is a temperature zone in which the specific heat of the cooling water is changing. In this specific heat change zone, even if a change occurs in the amount of heat applied to the cooling water, the specific heat changes and cooling is performed. The temperature of water becomes difficult to change. The residual latent heat amount is a latent heat amount that is obtained when the cooling water has a specific heat change zone, and is a latent heat amount that does not contribute to an increase in the temperature of the cooling water because the specific heat of the cooling water changes in the specific heat change zone. is there. In addition, the predetermined amount is an amount that becomes a timing for opening the thermostat when the residual latent heat amount becomes less than that, and is a threshold value indicating whether or not it is a timing for opening the thermostat.

According to the present invention, when the residual latent heat amount becomes a predetermined amount or less, the thermostat is opened to reduce the temperature of the cooling water. That is, the timing for opening the thermostat can be changed according to the residual latent heat amount and the predetermined amount. For this reason, the overheating of the internal combustion engine is suppressed by setting the timing at which the residual latent heat amount that lowers the temperature of the cooling water by opening the thermostat to a predetermined amount or less is set to a timing before the internal combustion engine overheats. Can do. Therefore, it is possible to suppress overheating of the internal combustion engine by using cooling water having a specific heat change zone in at least one temperature range.

  The predetermined amount serving as a threshold value indicating whether or not the timing for opening the thermostat is preferably changed according to the operating state of the internal combustion engine.

  According to the present invention, the predetermined amount for determining the timing for opening the thermostat can be changed according to the operating state of the internal combustion engine. For this reason, it is possible to set the timing at which the amount of residual latent heat that lowers the temperature of the cooling water by opening the thermostat to a predetermined amount or less is set to a timing before the internal combustion engine overheats in consideration of the operating state of the internal combustion engine. And overheating of the internal combustion engine can be suppressed.

  The timing when the control means opens the thermostat may be a timing when the temperature of the cooling water is within the specific heat change zone and the amount of residual latent heat changes.

  According to the present invention, the thermostat can be opened at the timing when the temperature of the cooling water does not change and the residual latent heat amount changes. Therefore, it is possible to avoid opening the thermostat at a timing when the temperature of the cooling water varies such that the remaining latent heat amount does not change and the temperature of the cooling water changes. Stabilization can be suppressed.

The cooling water has specific heat change bands in a plurality of temperature ranges,
The timing at which the control means opens the thermostat may be a timing at which the residual latent heat amount changes in the specific heat change zone in the temperature range where the temperature of the cooling water is highest.

  According to the present invention, the specific heat change zone in the highest temperature range can be used for adjusting the valve opening timing of the thermostat, and the specific heat change zone in other temperature ranges can be used for temperature control of the cooling water. .

  The cooling water preferably has a specific heat change zone in a plurality of temperature ranges by including many kinds of particles that change the specific heat of the medium by phase change.

  According to the present invention, when various types of particles undergo a phase change in different temperature ranges, the temperature range in which each type of particles undergoes a phase change becomes a specific heat change zone.

In the present invention, the following configuration is adopted. That is, the present invention
A cooling water control method for an internal combustion engine using cooling water having a specific heat change zone in a state where specific heat is changing in at least one temperature range,
Estimating the amount of residual latent heat that does not contribute to the temperature rise of the cooling water obtained by the cooling water having a specific heat change zone,
The estimated residual latent heat amount is a thermostat that is controlled to open and close in order to adjust the temperature of the cooling water, and is less than or equal to a predetermined amount that is a threshold value for determining whether or not to open the thermostat with variable open / close control timing. In this case, the cooling water control method for an internal combustion engine is characterized in that the thermostat is opened.

  According to the present invention, the overheat of the internal combustion engine can be suppressed by using the cooling water having the specific heat change zone in at least one temperature range.

  According to the present invention, it is possible to suppress overheating of an internal combustion engine by using cooling water having a specific heat change zone in at least one temperature range.

1 is a diagram illustrating a schematic configuration of an internal combustion engine according to Embodiment 1 of the present invention. It is a figure which shows the model of the cooling water which concerns on Example 1. FIG. It is a figure which shows the relationship between the temperature of the cooling water which concerns on Example 1, and specific heat. It is a figure which shows the characteristic curve of the residual latent-heat amount change and the temperature change of a cooling water with respect to the elapsed time at the time of the temperature rise of the cooling water from which the specific heat which concerns on Example 1 changes. It is a figure which shows the map which calculates | requires the predetermined amount which concerns on Example 1 from the thermal radiation amount per engine load (engine rotational speed). 4 is a flowchart illustrating a valve opening timing determination routine of the electronic thermostat according to the first embodiment.

Specific examples of the present invention will be described below.
<Example 1>
FIG. 1 is a diagram illustrating a schematic configuration of an internal combustion engine to which an internal combustion engine cooling apparatus according to a first embodiment of the present invention is applied. In the internal combustion engine 1 shown in FIG. 1, cooling water circulates through the cooling water passage 2 in order to cool the cylinder block and the cylinder head. The cooling water passage 2 includes a passage 2a through which the cooling water flows through the radiator 3, a passage 2b through which the cooling water flows through the oil cooler 4, a passage 2c through which the cooling water flows through the throttle valve 5a and the EGR valve 5b, and the cooling water as a reservoir. A passage 2d through which the tank 6 flows, a passage 2e through which the cooling water flows through the heater core 7, a passage 2f through which the cooling water flows through the EGR cooler 8, and a bypass passage 2g through which the cooling water flows as it is are provided.

  The radiator 3 cools the cooling water by exchanging heat between the cooling water and outside air. The oil cooler 4 is a water-cooled oil cooler, and cools the oil by exchanging heat between the oil supplied to the internal combustion engine 1 and the cooling water. The throttle valve 5a is a valve that controls the intake air amount in the internal combustion engine 1, and is cooled by cooling water. The EGR valve 5b is a valve that controls the amount of EGR gas that is part of the exhaust gas recirculated to the internal combustion engine 1, and is cooled by cooling water. The reservoir tank 6 temporarily stores cooling water. The heater core 7 warms the air supplied to the room with warmed cooling water. The EGR cooler 8 is a water-cooled EGR cooler, and cools the EGR gas by exchanging heat between the EGR gas recirculated to the internal combustion engine 1 and the cooling water.

  The passage 2 a through which the cooling water flows through the radiator 3 joins the passage 2 b through which the cooling water from the cylinder block flows through the oil cooler 4. The passage 2a through which the cooling water flows through the radiator 3 branches into a passage 2c through which the cooling water flows through the throttle valve 5a and the EGR valve 5b, and a passage 2d through which the cooling water flows through the reservoir tank 6. The passage 2 f through which the cooling water communicated from the cylinder block flows through the EGR cooler 8 joins the passage 2 e through which the cooling water flows through the heater core 7.

An electronic thermostat 9 is disposed at a portion where the passage 2a through which the cooling water flows through the radiator 3 and the bypass passage 2g merge. The electronic thermostat 9 is a control valve that is controlled to open and close in response to a command in order to adjust the temperature of the cooling water, and the open / close control timing is variable. By opening the electronic thermostat 9, the temperature of the cooling water can be lowered by changing the flow path and flow rate of the cooling water so that the cooling water flows through the radiator 3. When the valve is opened, the circulation amount of the cooling water is reduced in the bypass passage 2g. On the contrary, by closing the electronic thermostat 9, it is possible to change the flow path and flow rate of the cooling water so that the cooling water does not easily flow through the radiator 3, thereby making it difficult to lower the temperature of the cooling water. When the valve is closed, the circulation amount of the cooling water increases in the bypass passage 2g. Cooling water is fed into the water pump 10 downstream of the electronic thermostat 9. The water pump 10 pumps up cooling water and supplies it to the cylinder block of the internal combustion engine 1. Further, a water temperature sensor 11 is disposed at a portion where the cooling water passage 2 is connected to the outlet of the internal combustion engine 1, and the temperature of the cooling water flowing out from the internal combustion engine 1 is detected by the water temperature sensor 11.

  Here, the cooling water flowing through the cooling water passage 2 is a cooling water whose specific heat is variable, and is a cooling water having specific heat change zones C1 and C2 in a state where the specific heat changes in two temperature ranges. That is, the cooling water has two types of particles that change the specific heat of the medium by changing the phase between the solid phase and the liquid phase, or changing between the liquid phase and the gas phase. It is a cooling water with a variable specific heat. As the particles, not only particles that change between a solid phase and a liquid phase but also particles that change between a liquid phase and a gas phase can be used. The particles are configured by, for example, putting a substance that can store heat by latent heat or the like and change phase in a capsule. Further, the cooling water is not limited to one having a specific heat change band in two temperature ranges, but may be one having a specific heat change band in one or three or more temperature ranges. As shown in FIG. 2, the cooling water is composed of two particles P1 and P2 encapsulating substances whose phase changes from a solid to a liquid when the temperature rises above a certain level. It is mixed. FIG. 2 is a diagram illustrating a cooling water model according to the present embodiment. FIG. 2 illustrates a case where the particle P1 undergoes a phase change.

  FIG. 3 is a diagram illustrating the relationship between the temperature of the cooling water and the specific heat according to the present embodiment. As shown in FIG. 2, two types of particles P1 and P2 in the cooling water undergo a phase change between the solid phase state and the liquid phase state, whereby the two types of particles P1 and P2 undergo a phase change and the cooling water. The specific heat change zones C1 and C2 in which the specific heat changes are generated (see FIG. 3). These specific heat change zones C1 and C2 are phase change temperature zones in which the phase of the particles changes and the specific heat of the cooling water is changed even if heat is applied to the cooling water (see FIG. 4). That is, the specific heat change zone is a temperature zone in which the specific heat of the cooling water is changing. In this specific heat change zone, even if the amount of heat applied to the cooling water changes, the specific heat changes and the cooling water changes. The temperature is difficult to change. Here, as shown in FIG. 3, of the two specific heat change zones C1 and C2, the allowable heat receiving amount allowable by the specific heat change in the specific heat change zone C2 in the highest temperature range is changed to the other specific heat change. More than the allowable heat receiving amount in the band C1. Here, the allowable heat receiving amount is a heat receiving amount that can be allowed without changing the temperature of the cooling water due to a change in the specific heat of the cooling water, and when the allowable heat receiving amount is exceeded, the temperature of the cooling water changes in the specific heat. It will deviate from the belt. In other words, as shown in FIG. 3, the specific heat change amount in the specific heat change zone C2 in the highest temperature range is made larger than the specific heat change amount in the other specific heat change zone C1. In order to vary the allowable heat receiving amount in this way, the amount of the particles P2 forming the specific heat change zone C2 is made larger than the amount of the particles P1 forming the specific heat change zone C1.

  FIG. 4 is a diagram illustrating a characteristic curve of a change in residual latent heat amount and a change in temperature of the cooling water with respect to an elapsed time when the temperature of the cooling water in which specific heat changes according to the present embodiment. As shown in FIG. 4, when the temperature of the cooling water rises, two specific heat change zones C1 and C2 pass. Here, the timing at which the electronic thermostat 9 of the internal combustion engine 1 opens is included in the specific heat change zone C2 in the highest temperature range, as shown in FIG. Thereby, when the electronic thermostat 9 of the internal combustion engine 1 is opened, different amounts of heat can be received in the specific heat change zone C2 in the highest temperature range. As a result, the specific heat change zone C2 in the highest temperature range where the allowable heat receiving amount is increased is effectively used. By using such cooling water, the warm-up process of the internal combustion engine 1 can be improved in the warm-up process of the internal combustion engine 1 by lowering the specific heat of the coolant than before, so that the warm-up property of the internal combustion engine 1 can be improved and the fuel consumption can be improved. Since the specific heat increases in a certain temperature range (phase change temperature range), the allowable range of the amount of heat received can be increased to avoid overheating and the like.

The internal combustion engine 1 is provided with an ECU (electronic control unit) 12. ECU12
In addition, various sensors such as a water temperature sensor 11, a crank position sensor 13, and an accelerator position sensor 14 are connected via electric wiring, and output signals of these various sensors are input to the ECU 12. On the other hand, a throttle valve 5a, an EGR valve 5b, a heater core 7, an electronic thermostat 9, a water pump 10, and the like are connected to the ECU 12 through electric wiring, and these devices are controlled by the ECU 12.

(Cooling water control)
Conventionally, it has been considered to use cooling water with variable specific heat. In order to increase the specific heat change and to improve the warm-up property, the cooling water medium having a variable specific heat is used to use a cooling water medium having a low specific heat as a cooling water medium (solvent) containing particles. Become. When a cooling water medium having a low specific heat is used, the temperature changes drastically in a temperature range other than the specific heat changing zone where the specific heat is increased by the particles contained in the cooling water. Then, when the temperature of the cooling water rises beyond the specific heat change zone, the cooling is not in time, which may cause overheating of the internal combustion engine.

  Therefore, in this embodiment, the residual latent heat amount QL is estimated, and the electronic thermostat 9 is opened when the residual latent heat amount QL in the specific heat change zone C2 in the highest temperature range becomes equal to or less than a predetermined amount QT. did. Here, the residual latent heat amount QL is a latent heat amount obtained when the cooling water has a specific heat change zone, and the latent heat that does not contribute to the temperature rise of the cooling water by changing the specific heat of the cooling water in the specific heat change zone. Amount. Further, the predetermined amount QT is an amount that becomes a timing for opening the electronic thermostat 9 when the residual latent heat amount QL becomes less than that, and is a threshold value for determining whether or not the timing for opening the electronic thermostat 9 is reached.

  Specifically, in the present embodiment, the residual latent heat amount QL is estimated by subtracting the heat radiation amount to the cooling water from the total latent heat amount determined in advance by the characteristics of the cooling water. Here, the amount of heat released to the cooling water is derived based on the temperature of the cooling water detected by the water temperature sensor 11 and the operating history determined from the operating state detected by the crank position sensor 13 and the accelerator position sensor 14. The ECU 12 that estimates the residual latent heat amount QL corresponds to the residual latent heat amount estimation means of the present invention.

  When the residual latent heat amount QL is estimated, a predetermined amount QT is determined. FIG. 5 is a diagram showing a map for obtaining the predetermined amount QT from the engine load. The engine load can be obtained from the operating state detected by the crank position sensor 13 and the accelerator position sensor 14, and a predetermined amount QT corresponding to the operating state of the internal combustion engine 1 can be determined based on the map shown in FIG. Thus, the predetermined amount QT is changed according to the operating state of the internal combustion engine 1 so that the electronic thermostat 9 is opened before the internal combustion engine 1 is overheated.

  Then, the estimated remaining latent heat amount QL is compared with a predetermined amount QT, and when the remaining latent heat amount QL becomes equal to or less than the predetermined amount QT, the electronic thermostat 9 is opened. The ECU 12 that opens the electronic thermostat 9 when the residual latent heat amount QL becomes equal to or less than the predetermined amount QT corresponds to the control means of the present invention.

  According to this embodiment, when the residual latent heat amount QL becomes equal to or less than the predetermined amount QT, the electronic thermostat 9 is opened to lower the temperature of the cooling water. That is, the timing for opening the electronic thermostat 9 can be changed according to the residual latent heat amount QL and the predetermined amount QT. For this reason, by setting the timing at which the residual latent heat amount QL, which lowers the temperature of the cooling water by opening the electronic thermostat 9, to be equal to or less than the predetermined amount QT, is set to a timing before the internal combustion engine 1 overheats, Overheating can be suppressed. Therefore, it is possible to suppress overheating of the internal combustion engine 1 by using the cooling water having the specific heat change zones C1 and C2 in the two temperature ranges.

  Further, according to the present embodiment, the timing for opening the electronic thermostat 9 is the timing at which the residual latent heat amount changes in the specific heat change zone C2 in the temperature range where the temperature of the cooling water is the highest. Thereby, the electronic thermostat 9 can be opened at the timing when the temperature of the cooling water does not change and the residual latent heat amount QL changes. Therefore, it is possible to avoid opening the electronic thermostat 9 at the timing when the temperature of the cooling water varies such that the residual latent heat amount QL does not change and the temperature of the cooling water changes. Control instability can be suppressed. Further, the specific heat change zone C2 in the highest temperature range can be used for adjusting the valve opening timing of the electronic thermostat 9, and the specific heat change zone C1 in other temperature ranges can be used for temperature control of the cooling water. it can.

  Further, the predetermined amount QT, which is a threshold value indicating whether or not the timing for opening the electronic thermostat 9 is changed according to the operating state of the internal combustion engine 1. For this reason, the timing at which the residual latent heat quantity QL, which opens the electronic thermostat 9 and lowers the temperature of the cooling water, becomes equal to or less than the predetermined quantity QT, before the internal combustion engine 1 overheats in consideration of the operating state of the internal combustion engine 1. The timing can be set, and overheating of the internal combustion engine 1 can be suppressed.

(Valve opening timing determination routine of the electronic thermostat 9)
A routine for determining the valve opening timing of the electronic thermostat 9 executed by the ECU 12 will be described with reference to the flowchart shown in FIG. FIG. 6 is a flowchart showing a valve opening timing determination routine of the electronic thermostat according to the present embodiment. This routine is repeatedly executed by the ECU 12 every predetermined time.

In S100, it is determined whether or not the cooling water temperature is in the specific heat change zone C2. If an affirmative determination is made, the process proceeds to S101, and if a negative determination is made, the routine is exited.
In S101, the residual latent heat amount QL is estimated. It is estimated from the expression “residual latent heat amount QL = latent heat total amount−heat radiation amount to cooling water”. The ECU 12 that executes S101 corresponds to the residual latent heat amount estimating means of the present invention. In S102, a predetermined amount QT is determined. The amount of heat released per engine load (engine speed) is determined by taking it into the map shown in FIG. In S103, it is determined whether or not the residual latent heat amount QL is equal to or less than a predetermined amount QT. If a positive determination is made in S103, the process proceeds to S104. If a negative determination is made in S103, this routine is once terminated. In S104, the electronic thermostat 9 is opened. ECU12 which performs S103 and S104 respond | corresponds to the control means of this invention. After the processing of S104, this routine is temporarily terminated.

  According to the above routine, since the valve opening timing of the electronic thermostat 9 is determined by the residual latent heat amount QL and the predetermined amount QT, the valve opening timing of the electronic thermostat 9 is before the overheating of the internal combustion engine, and the overheating of the internal combustion engine can be suppressed. .

<Others>
The cooling water control apparatus for an internal combustion engine according to the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention. Moreover, the said Example is also an Example of the cooling water control method of an internal combustion engine.

In the above embodiment, when the cooling water temperature is in the specific heat change zone C2, the remaining latent heat of the cooling water in the specific heat change zone C2 is estimated, and the thermostat is opened based on a comparison with a predetermined amount determined according to the operating conditions. Although the example which controls a valve was explained, in the case of an internal combustion engine using cooling water with a plurality of specific heat change zones, the same thermostat control may be performed in each specific heat change zone. Since the purpose of control varies depending on the specific heat change zone, the relationship between the operating condition and the predetermined amount varies depending on the specific heat change zone. For example, the specific heat change zone C2 is varied by a predetermined amount depending on whether or not the operating condition is desired to prevent overheating. However, in the specific heat change zone C1 in the low temperature range, the specific heat change zone C2 from the viewpoint of, for example, fuel consumption characteristics. It is preferable to define the relationship between the operating condition and the predetermined amount separately.

  In the present invention, the specific heat is at a temperature other than the predetermined temperature range in a predetermined at least one temperature range (the temperature or the temperature range is collectively expressed as a temperature range) (referred to as a specific heat change zone in the above description). An object of the present invention is to more reliably suppress overheating of an internal combustion engine in a cooling device for an internal combustion engine that uses a cooling water (heat medium) having a value larger than a specific heat. A radiator that takes heat from the cooling water, a bypass passage that bypasses the radiator, and a cooling water flow to the radiator when closed, A thermostat that distributes cooling water to at least the radiator when it is circulated and opened, and a control that controls opening and closing of the thermostat And the control means determines the remaining latent heat amount of the cooling water in the predetermined temperature range according to the operating state of the internal combustion engine when the temperature of the cooling water is in the predetermined temperature range. The thermostat is opened when a predetermined threshold value (predetermined amount) or less is reached. When using the cooling water having a plurality of the predetermined temperature ranges, the control means cools the highest temperature range when the temperature of the cooling water is in the highest temperature range among the plurality of temperature ranges. The thermostat may be opened when the residual latent heat amount of water becomes equal to or less than a threshold value.

  The predetermined temperature range may be a temperature at which a phase transition occurs in a substance contained in the cooling water. Since heat is released or absorbed by the phase transition, the specific heat of the cooling water increases at the temperature at which the phase transition occurs. For this reason, in the predetermined temperature range, even if heat enters and exits, the temperature of the cooling water becomes substantially constant. By including a plurality of types of substances having different temperatures at which phase transition occurs in the cooling water, the specific heat becomes larger at a plurality of predetermined temperature ranges than at a temperature outside the predetermined temperature range.

  The case where the particles are capsule particles in the above description will be described in detail. The cooling water is a liquid containing capsule particles enclosing therein a latent heat storage material that undergoes a phase transition in a predetermined temperature range within the temperature range that the cooling water can take. Plural types of capsule particles having different phase transition temperatures of the enclosed latent heat storage material may be mixed. The total amount of latent heat of the latent heat storage material with the highest phase transition temperature contained in the cooling water may be larger than the total amount of latent heat of the latent heat storage material with any other phase transition temperature contained in the cooling water. . The total amount of latent heat of a latent heat storage material contained in the cooling water is the sum of all the latent heats of the latent heat storage material contained in the cooling water. For example, the number of capsule particles enclosing the latent heat storage material having the highest phase transition temperature is set to be larger than the number of particles in other capsules. In the temperature range determined by the phase transition temperature of the latent heat storage material enclosed in the capsule particles or the temperature at which the phase transition starts and the temperature at which the phase transition ends, heat transfer to the cooling water is expended for the phase transition of the latent heat storage material. For this reason, the temperature of the cooling water is substantially constant. That is, the apparent specific heat of the cooling water is larger in this temperature range than the specific heat in other temperature ranges. This temperature range is the specific heat change zone. By using the cooling water in which the predetermined temperature range is set in a temperature range lower than the temperature at which the internal combustion engine overheats, the temperature of the cooling water is less likely to change with respect to heat input and output in the temperature range lower than the overheating temperature. Therefore, the overheat resistance is improved. The remaining latent heat amount of the cooling water in a certain temperature range is a heat amount obtained by subtracting the amount of heat already absorbed from the total amount of latent heat of the latent heat storage material included in the cooling water and having a phase transition temperature in the temperature range.

In FIG. 3, the cooling water is cooling water in which the specific heat in two predetermined temperature ranges C1, C2 (referred to as specific heat change zones in the above description) is larger than the specific heat in other than the temperature ranges C1, C2. . That is, this cooling water is composed of capsule particles encapsulating a predetermined substance (latent heat storage material) whose phase range is the temperature range C1 from the phase transition temperature or the phase transition start temperature to the end temperature, and the phase transition temperature or phase transition. Capsule particles encapsulating a predetermined substance (latent heat storage material) whose temperature range from the start temperature to the end temperature is the temperature range C2, and in the temperature ranges C1 and C2, heat entering and exiting the cooling water Because it is used for the phase transition of the latent heat storage material (solid phase and liquid phase, liquid phase and gas phase, solid phase and gas phase, etc.), the temperature of the cooling water becomes substantially constant in these temperature ranges and cooling This is a multistage variable specific heat cooling water in which the specific heat of water is apparently larger than the specific heat outside the temperature ranges C1 and C2. The cooling water includes three or more types of latent heat storage materials having different phase transition temperatures enclosed in a capsule and included (mixed) in the cooling water, so that the specific heat in three or more predetermined temperature ranges is within the predetermined temperature range. Cooling water having a value larger than the specific heat in the other case may be used.
In general, the specific heat of a substance is temperature-dependent, and the specific heat may change as the temperature changes, but the specific heat in the predetermined temperature range described above is larger than the specific heat in a temperature other than the predetermined temperature range. The temperature change of the specific heat is due to the phase transition of the latent heat storage material contained in the cooling water, and is different from the general temperature change of the specific heat which is not due to the phase transition of the contained material.

  Moreover, as shown in FIG. 3, in this embodiment, the specific heat of the solvent of the cooling water is smaller than the specific heat of the cooling water of the prior art. As described above, the relationship between the temperature and the specific heat is such that the specific heat is smaller than that of the conventional cooling water except in the predetermined temperature range, and the specific heat is higher than that of the conventional cooling water in the predetermined temperature range. When the temperature is outside the temperature range, the temperature of the cooling water rapidly changes with the entry and exit of heat, while when the temperature of the cooling water is within the predetermined temperature range, the temperature change of the cooling water with respect to the entry and exit of heat. Become slow. For this reason, by setting the temperature of the cooling water to a temperature other than the predetermined temperature range during warm-up, the temperature of the cooling water can be quickly increased to improve fuel efficiency, and large heat transfer can be performed in the predetermined temperature range. Even if it exists, since it becomes possible to maintain the temperature of cooling water, the improvement of overheat tolerance and the improvement of temperature controllability are possible.

  Further, as shown in FIG. 3, in the present embodiment, the thermostat valve opening temperature is in the predetermined temperature range C2. That is, the control means opens the thermostat when the temperature of the cooling water is in the predetermined temperature range C2 and the remaining latent heat amount of the cooling water in the predetermined temperature range C2 is equal to or less than the threshold value. When the temperature of the cooling water is in the predetermined temperature range C2, the heat entering and exiting the cooling water is spent on the phase transition of the latent heat storage material having the phase transition temperature in the predetermined temperature range C2, and the temperature of the cooling water is within the predetermined temperature range. Maintained at C2. The latent heat of the cooling water in the predetermined temperature range C2 is reduced by the amount of the latent heat storage material that has already undergone phase transition due to the heat that has entered and exited. The control means estimates the remaining amount of latent heat (residual latent heat amount) obtained by subtracting the amount of heat already spent for the phase transition of the latent heat storage material from the total amount of latent heat of the cooling water in the predetermined temperature range C2, and the remaining amount of latent heat. When is below a predetermined threshold, the thermostat is opened. Until the remaining amount of latent heat reaches zero, the temperature of the cooling water is maintained in the predetermined temperature range C2 even if heat enters and exits. Therefore, the residual latent heat amount is such that the cooling water deviates from the predetermined temperature range C2. It can be said that the amount of heat that can be received (or radiated).

  As shown in FIG. 3, in the present embodiment, the specific heat in the highest temperature range C2 of the cooling water in the two predetermined temperature ranges C1 and C2 is larger than the specific heat in the predetermined temperature range C1. In other words, the difference (specific heat change amount, specific heat change width) of the specific heat in the predetermined temperature region C2 with respect to the specific heat in the temperature region other than the predetermined temperature region C1, C2 is the predetermined temperature for the specific heat in the temperature region other than the predetermined temperature region C1, C2. It is larger than the difference in specific heat in the area C1. Therefore, the amount of capsule particles P2 enclosing the latent heat storage material having a phase transition temperature in the predetermined temperature region C2 is set to be larger than the amount of capsule particles P1 enclosing the latent heat storage material having the phase transition temperature in the predetermined temperature region C1. There are many.

  FIG. 4 shows the relationship between the amount of heat given to the cooling water, the temperature of the cooling water and the residual latent heat amount of the cooling water, and the horizontal axis can also be regarded as the amount of heat given to the cooling water.

In FIG. 5, the predetermined amount QT is determined according to the operating state of the internal combustion engine. For example, in conditions where you want to prevent overheating (high load operation, low vehicle speed (low heat dissipation from the radiator), or high outside air temperature (intake air temperature)), the predetermined amount QT is set to a large value, Under other conditions, the predetermined amount QT is set to a small value. Thus, under conditions where it is desired to prevent overheating, the electronic thermostat is opened in a state where the latent heat of the cooling water in the specific heat change zone C2 remains to some extent (a state where the residual latent heat amount is relatively large), while in other conditions The electronic thermostat is not opened until the latent heat of the cooling water in the specific heat change zone C2 becomes relatively small. Thus, even if the temperature of the cooling water is in the same specific heat change zone C2, the electronic thermostat It is possible to vary the valve opening timing, and it is possible to improve the controllability of the cooling water temperature as well as improving the overheat resistance. FIG. 5 shows an example of a map or calculation for obtaining the predetermined amount QT from the engine load. The higher the load (the right side of the horizontal axis), the larger the predetermined amount QT. The value of the predetermined amount QT according to the load is determined according to the amount of heat radiated to the cooling water per rotation in the operating state at the load, in other words, the latent heat amount of the cooling water consumed per rotation. In FIG. 5, the predetermined amount QT becomes a constant value with respect to a certain load or more, indicating that the predetermined amount QT does not exceed the total latent heat amount of the cooling water in the specific heat change zone C2. When heat exceeding the total latent heat amount of the cooling water in the specific heat change zone C2 is given to the cooling water, the amount exceeding the total latent heat amount causes sensible heat to increase the temperature of the cooling water. FIG. 5 is an example of a map for determining the predetermined amount QT according to the engine load, but the predetermined amount QT may be determined based on a map for determining the predetermined amount QT according to the intake air temperature or the vehicle speed. For example, the higher the intake air temperature and the lower the vehicle speed, the easier it is to overheat, so the predetermined amount QT is set to a large value.

1 Internal combustion engine 2 Cooling water passages 2a to 2g Passage 3 Radiator 4 Oil cooler 5a Throttle valve 5b EGR valve 6 Reservoir tank 7 Heater core 8 Cooler 9 Electronic thermostat 10 Water pump 11 Water temperature sensor 12 ECU
13 Crank position sensor 14 Accelerator position sensor C1, C2 Specific heat change zone P1, P2 Particles

Claims (6)

A cooling water control device for an internal combustion engine that uses cooling water having a specific heat change zone in which the specific heat is changing in at least one temperature range,
A thermostat that is controlled to be opened and closed to adjust the temperature of the cooling water, and whose opening and closing control timing is variable,
A residual latent heat amount estimating means for estimating a residual latent heat amount that does not contribute to the temperature rise of the cooling water obtained by the cooling water having a specific heat change zone;
Control means for opening the thermostat when the residual latent heat amount estimated by the residual latent heat amount estimation means is equal to or less than a predetermined amount which is a threshold value indicating whether or not the timing for opening the thermostat;
A cooling water control device for an internal combustion engine, comprising:   The cooling water control device for an internal combustion engine according to claim 1, wherein the predetermined amount serving as a threshold value indicating whether or not the timing for opening the thermostat is changed according to an operating state of the internal combustion engine.   3. The internal combustion engine according to claim 1, wherein the timing at which the control means opens the thermostat is a timing at which the temperature of the cooling water is within a specific heat change zone and the amount of residual latent heat changes. Cooling water control device. The cooling water has specific heat change bands in a plurality of temperature ranges,
The timing at which the control means opens the thermostat is a timing at which the amount of residual latent heat changes in the specific heat change zone in the temperature range where the temperature of the cooling water is highest. Cooling water control device for internal combustion engine.   5. The cooling water for an internal combustion engine according to claim 4, wherein the cooling water includes a plurality of types of particles that change the specific heat of the medium by phase change, thereby having specific heat change zones in a plurality of temperature ranges. Control device. A cooling water control method for an internal combustion engine using cooling water having a specific heat change zone in a state where specific heat is changing in at least one temperature range,
Estimating the amount of residual latent heat that does not contribute to the temperature rise of the cooling water obtained by the cooling water having a specific heat change zone,
The estimated residual latent heat amount is a thermostat that is controlled to open and close in order to adjust the temperature of the cooling water, and is less than or equal to a predetermined amount that is a threshold value for determining whether or not to open the thermostat with variable open / close control timing. In this case, the cooling water control method for an internal combustion engine, wherein the thermostat is opened.

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