JP4682863B2 - Engine cooling system - Google Patents

Engine cooling system Download PDF

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JP4682863B2
JP4682863B2 JP2006037058A JP2006037058A JP4682863B2 JP 4682863 B2 JP4682863 B2 JP 4682863B2 JP 2006037058 A JP2006037058 A JP 2006037058A JP 2006037058 A JP2006037058 A JP 2006037058A JP 4682863 B2 JP4682863 B2 JP 4682863B2
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cooling water
temperature
engine
water
cooling
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JP2007218115A (en
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裕典 中尾
和男 市川
明 栗原
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マツダ株式会社
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  The present invention relates to an engine cooling device that changes the flow state of cooling water in accordance with the state of the engine.

  In general, in a cooling system for a water-cooled engine, a water pump is mechanically driven by a crankshaft to distribute cooling water to a water jacket (cooling water passage in the engine body) of a cylinder block or a cylinder head. , It is circulated with the radiator. In addition, a thermostat is disposed in the cooling water flow path between the engine body and the radiator, and when the engine is cooled after the engine is started, the flow of the cooling water between the engine body and the radiator is interrupted. It is designed to promote warm-up.

  In such a combination of a mechanical pump and a thermostat, the water pump operates with the rotation of the crankshaft while the engine is running. For example, in the case of a vehicle, cooling with a heater core for heating the passenger compartment, etc. The water circulates, and the amount of heat released from the engine increases accordingly, so that the warm-up is delayed, and there is a problem that the deterioration of fuel consumption and emission during cold cooling cannot be sufficiently suppressed.

  Therefore, it has been proposed to use an electric water pump instead of a mechanical pump or a thermostat so that the circulation state of the cooling water in the water jacket can be changed regardless of the operating state of the engine (for example, patents). Reference 1). In this proposal, an electric pump is disposed between the engine main body and the radiator, and when the engine is cold, the pump is not operated to stop the circulation of the cooling water between the radiator and the cooling water in the water jacket. The distribution itself is also stopped.

  However, if the water jacket cooling water flow is stopped when the engine is cold as in the above proposal, the water temperature locally rises in a part of the periphery of the cylinder, resulting in abnormal noise due to partial boiling of the cooling water. There is a risk that it may occur or reliability may be lowered due to an excessive temperature rise in a specific part.

  In order to prevent the occurrence of such problems, the electric pump must be operated so that the cooling water flows before the temperature of the cooling water becomes too high. In the end, however, it could not be said that the engine warm-up could be sufficiently promoted, and there was room for improvement in fuel efficiency and emissions when the engine was cold.

  In this regard, the applicant of the present application is able to increase the local temperature around the cylinder while facilitating warm-up in the same manner as stopping it by circulating cooling water intermittently when the engine is cold. We have developed a product that has been suppressed, and filed a patent application first (for example, Japanese Patent Application No. 2005-024958).

That is, if the water jacket cooling water does not move continuously from the inlet to the outlet, for example, by intermittent operation of the electric pump, it is possible to repeat the movement and stop for a very short time. The entire cooling water of the jacket is shaken and agitated slightly, thereby suppressing the local temperature rise and thus reducing the time for the cooling water to move, thereby stopping its circulation. In the same way as this, the amount of heat radiation can be reduced to sufficiently promote the warm-up of the engine.
JP 2002-161748 A

  However, if the cooling water is circulated intermittently when the engine is cold, as in the previous application, the cooling water circulating from the water jacket to the thermostat via the bypass circuit becomes very small. Even if the cooling water temperature becomes considerably high, the thermostat will not open sufficiently. On the other hand, even if the thermostat is opened and low-temperature cooling water flows from the radiator and the cooling water temperature of the water jacket is lowered, the thermostat is not immediately closed.

  In other words, since the thermostat opening / closing operation is greatly delayed with respect to the change in the cooling water temperature in the water jacket in the engine body, the engine water temperature fluctuates greatly despite the warm-up, and is performed accordingly. An error occurs in the control of the air-fuel ratio and ignition timing, resulting in worsening of combustion, and as a result, the flow of low-temperature cooling water from the radiator increases, resulting in a delay in warm-up. The improvement effect is diminished, and in the case of a vehicle, an unfavorable influence also appears on the heating performance of the passenger compartment.

  The present invention has been made in view of such a point, and an object of the present invention is to delay the operation of a thermostat when coolant is circulated intermittently to promote engine warm-up. In order to prevent erroneous control due to fluctuations in engine water temperature and further promote warm-up, the fuel consumption, emission, and heating performance are further improved.

  In order to achieve the above object, according to the present invention, the coolant is intermittently circulated while the engine is warmed up, and the circulation amount of the coolant is increased before the thermostat starts to open in response to the temperature rise. The cooling water temperature difference from the cooling water passage in the body to the vicinity of the thermostat was reduced.

That is, according to the first aspect of the present invention, the flow variable means capable of changing the flow state of the cooling water in the cooling water passage in the engine body, and the cooling water intermittently at the first predetermined flow rate in the cooling water passage during engine warm-up. manner while the operating the flow varying means so that the first circulatory state circulating, after warm-up is continuously circulated in a second predetermined flow amount more flow cooling water in excess of the first predetermined flow rate It is assumed that the engine cooling device includes control means for operating the flow variable means so as to be in the second flow state .

A thermostat that mechanically opens and closes according to a change in the temperature of the cooling water is disposed in the communication path that connects the cooling water path and the passage in the radiator, and the control means cools the engine during warming up of the engine. before the thermostat starts to open in response to an increase in water temperature, the intermediate distribution state which cooling water intermittently circulated in the first predetermined flow rate greater than and less than the second predetermined flow rate a flow rate in the cooling water passage Thus, the distribution variable means is operated.

  With the above configuration, during the warm-up of the engine, first, the flow variable means is controlled by the control means so that the cooling water intermittently flows in the cooling water passage in the main body. Here, intermittent circulation means that the cooling water does not continuously move from the inlet to the outlet of the cooling water passage, but repeatedly moves and stops for a short time in the cooling water passage. In other words, it means a minute flow state in which the entire cooling water in the cooling water passage is shaken and slightly stirred.

  In this way, the engine is the same as when the movement of the cooling water was stopped while suppressing the local temperature rise around the cylinder by shaking the cooling water in the cooling water passage in the engine body and slightly stirring it. The amount of heat released can be reduced and the warm-up can be promoted sufficiently.

  Thus, before the temperature of the cooling water rises and thereby the thermostat starts to open, the control of the flow variable means by the control means is changed so that the cooling water is warmed up to the intermittent flow state in the cooling water passage. It becomes a distribution state intermediate between the continuous distribution state after the machine. That is, the amount of cooling water flowing in the cooling water passage in the engine body increases, and the amount of cooling water circulated from there to the thermostat increases, so that the temperature difference between the cooling water from the cooling water passage to the periphery of the thermostat decreases.

  This reduces the operating delay of the thermostat with respect to changes in the cooling water temperature in the cooling water passage in the engine body, thereby reducing fluctuations in the engine water temperature during warming-up, and erroneous control of the air-fuel ratio and ignition timing. In addition to being prevented, there is no excessive flow of low-temperature cooling water from the radiator, so there is no delay in warm-up due to this, and fuel consumption, emission and heating performance can be further improved than before. .

Preferably, a water temperature sensor is arranged facing the cooling water passage in the engine body, and the control means receives a signal from the water temperature sensor, and the detected value of the cooling water temperature starts opening the thermostat. when it becomes the first temperature or the temperature is that cooling water is assumed to operate the flow varying means so that the intermediate distribution state (the invention of claim 2).

  That is, when the cooling water flows intermittently, the cooling water temperature in the cooling water passage in the engine body is higher than that around the thermostat, so the cooling water temperature in the cooling water passage is the valve opening start temperature (first temperature) of the thermostat. ), The temperature difference of the cooling water is reduced to reduce the temperature difference of the cooling water, so that the opening of the thermostat can be accelerated to prevent an excessive increase in the cooling water temperature in the engine body.

As a result, if the detected value of the cooling water temperature falls below the first temperature, the flow variable means may be operated by the control means so that the cooling water again enters the first flow state. (Invention of Claim 3). In other words, once the flow rate of cooling water is increased and the temperature difference between the cooling water passage and the vicinity of the thermostat is reduced, the flow rate is minimized again to sufficiently warm up the engine. Can be promoted.

Then, after the detected value of the cooling water temperature has changed a predetermined number of times or more between the high temperature side and the low temperature side with the first temperature interposed therebetween, the cooling water is in the first circulation state even if it exceeds the first temperature. The flow variable means may be operated by the control means so as to remain (the invention of claim 4). In other words, after the cooling water increase control is performed a predetermined number of times determined by the capacity of the cooling water passage, the temperature difference between the cooling water passage and the vicinity of the thermostat is almost eliminated and the warm-up is almost complete. Therefore, after that, even if the detected value by the water temperature sensor exceeds the first temperature, the engine warm-up is sufficiently promoted until completion without being brought into the intermediate flow state.

Then, when the engine warm-up is completed and the detected value of the cooling water temperature by the water temperature sensor reaches the second temperature, which is the fully open temperature of the thermostat, the cooling water then becomes the second circulation state. Thus, the flow variable means may be operated by the control means (invention of claim 5).

  On the other hand, when the detected value of the coolant temperature by the water temperature sensor is less than the first temperature immediately after the cold start of the engine, the control means causes the coolant to stop flowing in the coolant passage in the engine body for a predetermined period. It is preferable to control the distribution variable means (invention of claim 6). That is, for example, for a predetermined time immediately after the cold start, the flow variable means can be operated so that the flow of the cooling water in the cooling water passage in the engine body stops and thereafter the cooling water flows intermittently. That's fine.

  In this way, in a situation where the cooling water temperature is low and local excessive temperature rise cannot occur, the heat dissipation of the engine can be minimized by stopping the circulation of the cooling water, thereby maximizing the warm-up. Can promote.

  Here, the water temperature sensor is preferably arranged in association with any one of the cylinders other than the cylinder located at the end in the cylinder row direction in the water jacket on the exhaust side of the cylinder block. ). That is, when the circulation of the cooling water is very small as in the intermittent circulation state described above, generally, the intake side water jacket of the cylinder block in the engine main body becomes low temperature, while the exhaust side water jacket of the cylinder head becomes high temperature. The exhaust water jacket of the cylinder block is in an average temperature state.

  In the case of a multi-cylinder engine, the cooling water generally flows in the direction of the cylinder row. Therefore, when the cooling water flows continuously, the temperature of the cooling water in the portion near the center in the direction of the cylinder row is more stable than both ends. To do. Therefore, an average coolant temperature in the engine body can be detected by a water temperature sensor disposed at a position closer to the center in the cylinder row direction in the exhaust side water jacket of the cylinder block. However, the fluctuation of the detection value by the sensor is reduced, and erroneous control of the air-fuel ratio and ignition timing is prevented.

  More preferably, a recess is formed on the wall surface of the water jacket facing the tip of the water temperature sensor so as to enlarge the cross-sectional area of the water jacket (invention of claim 8). By doing so, the movement of the cooling water by convection is likely to occur near the tip of the water temperature sensor, so that the influence of the local increase in water temperature around the cylinder can be reduced and the average cooling water temperature can be detected.

Further, as the flow variable means, for example, an electric pump for circulating cooling water may be provided, and in this case, the control means is configured to flow cooling water in the first flow state. It is preferable that the electric pump is intermittently operated so that the operation time thereof is shorter than the non-operation time (invention of claim 9). In this way, the flow variable means can be easily configured by taking advantage of the electric pump that can be controlled regardless of the operating state of the engine.

  Further, in this case, if the control means can control the amount of electric power supplied to the electric pump, the operating state of the electric pump can be controlled finely and with high accuracy. It is possible to minimize the heat dissipation amount of the engine while more surely suppressing the local temperature rise.

As described above, according to the engine cooling device of the present invention, for example, when the engine is cold after cold start, a minute amount of cooling water is circulated intermittently in the cooling water passage in the main body (first flow). As in the case of stopping the flow of the cooling water, it is possible to suppress a local temperature rise around the cylinder and the like while reducing the amount of heat released from the engine. To improve fuel efficiency and emissions.

Then, before the thermostat starts to open in response to an increase in coolant temperature, the intermittent flow conditions in the flow state of the cooling water the small flow quantity (first circulation condition), a lot of circulation amount than this intermittent By changing to a general distribution state ( intermediate distribution state ) , the temperature difference of the cooling water from the cooling water passage in the engine body to the periphery of the thermostat can be reduced, and the operation delay of the thermostat can be reduced. Control of air-fuel ratio and ignition timing can be improved by suppressing fluctuations in water temperature, and warm-up can be further promoted.

  At that time, first, when the detected value of the cooling water temperature by the water temperature sensor becomes equal to or higher than the valve opening start temperature (first temperature) of the thermostat, the cooling water is changed to the intermediate flow state (the invention of claim 2). ), The valve opening of the thermostat can be accelerated, and an excessive increase in the cooling water temperature in the engine body can be prevented.

As a result, if the detected value of the cooling water temperature falls below the first temperature, the cooling water is again brought into the intermittent flow state (first flow state) with a minute flow rate (the invention of claim 3). ), Engine warm-up can be promoted sufficiently.

In addition, after the detected value of the cooling water temperature has changed more than a predetermined number of times between the first temperature and the high temperature side and the low temperature side, the cooling water is intermittently distributed even if it exceeds the first temperature. By keeping the state (first distribution state) (invention of claim 4 ) , it is possible to sufficiently promote engine warm-up until completion.

  Further, by stopping the flow of the cooling water for a predetermined period after the engine is started (invention of claim 5), it is possible to minimize heat dissipation from the engine and promote warm-up as much as possible.

Furthermore, if the water temperature sensor is disposed in association with any one cylinder other than the cylinder located at the end in the cylinder row direction in the water jacket on the exhaust side of the cylinder block (invention of claim 7), Even when the circulation of the cooling water is very small as in the intermittent flow state (first flow state) of the minute flow rate, the average temperature state of the water jacket can be detected.

  Further, if a concave portion is formed on the wall surface of the water jacket facing the tip of the water temperature sensor so as to increase the cross-sectional area of the water jacket (invention of claim 8), cooling water by convection near the tip of the water temperature sensor. Since the movement is likely to occur, the influence of the local water temperature rise around the cylinder can be reduced, and the average cooling water temperature can be detected.

  Further, if an electric pump is used as the flow variable means (invention of claim 9), the flow variable means can be easily constructed taking advantage of the feature of the electric pump that can be controlled regardless of the operating state of the engine.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

  FIG. 1 schematically shows a configuration of an engine cooling device A according to an embodiment of the present invention. The cooling device A includes water jackets 4 and 5 as cooling water passages formed in a cylinder block 2 and a cylinder head 3 constituting the main body 1 of the engine, and a front portion of the vehicle for cooling the cooling water by outside air. A radiator 6 arranged in the upper and lower sides, upper and lower hoses 7 and 8 constituting a flow path for circulating cooling water between the radiator 6 and the engine main body 1, and a water jacket 4 of the cylinder block 2. And an electric water pump (hereinafter, simply referred to as an electric pump) 9 for supplying cooling water.

  In the illustrated example, the water jacket 4 of the cylinder block 2 surrounds the outer circumferences of the four cylinders s1 to s4 over the entire longitudinal direction of the cylinder block 2 (the cylinder row direction, hereinafter also referred to as the engine longitudinal direction). And communicates with the discharge side of the electric pump 9 through an introduction path 4a that opens to the intake side (the lower side in the figure) of the front end. Further, a bypass passage 10 for returning the cooling water to the suction side of the electric pump 9 is opened in the vicinity of the opening of the introduction path 4a, and the first cylinder s1 to the cylinder block 2 are adjacent to the opening. A partition wall 4b is formed up to the side wall.

  Therefore, the cooling water discharged from the electric pump 9 and flowing into the front end portion of the water jacket 4 from the introduction path 4a is formed in the water jacket 4 as shown by an arrow in the figure if the bypass passage 10 is closed. After flowing on the exhaust side (upper side in the figure) toward the rear of the engine and turning back at the rear end, this time, the air flows on the intake side toward the front of the engine. On the other hand, if the bypass passage 10 is opened, the cooling water mainly flows into the bypass passage 10 and is returned to the suction side of the electric pump 9.

  The water jacket 4 of the cylinder block 2 is connected to the cylinder block 2 through a plurality of holes formed in the top deck of the cylinder block 2 and a plurality of holes formed in the bottom deck of the cylinder head 3. The cooling water flowing through the water jacket 4 of the cylinder block 2 as described above is sequentially communicated with the water jacket 5 of the cylinder head 3 as shown by the arrows in the drawing. It comes to circulate.

  The water jacket 5 of the cylinder head 3 is formed over the entire longitudinal direction of the cylinder head 3 so as to wrap around the outer periphery of the intake / exhaust ports and plug holes (not shown) of the cylinders s1 to s4. It communicates with the flow path in the upper hose 7 via a lead-out path 5a that opens to the section. In addition, a flow path in the heater hose 12 that circulates the cooling water between the lead-out path 5a and the heater core 11 of the vehicle air conditioner is also communicated. As a result, the relatively high-temperature cooling water that has circulated through the water jacket 5 of the cylinder head 3 flows out from the outlet path 5a to the flow paths in the upper hose 7 and the heater hose 12.

  The downstream end of the upper hose 7 is connected to the upper tank of the radiator 6, and the relatively high-temperature cooling water flowing through the upper hose 7 as described above is cooled by heat exchange with the outside air in the radiator 6. Afterwards, it flows out into the flow path in the lower hose 8 connected to the lower tank of the radiator 6, flows through the lower hose 8, and returns to the suction side of the electric pump 9. Similarly, the relatively high-temperature cooling water flowing through the heater hose 12 is returned to the suction side of the electric pump 9 after exchanging heat with air-conditioning air in the heater core 11.

  More specifically, in this embodiment, the housing 13a of the thermostat 13 is provided on the side wall of the cylinder block 2 adjacent to the suction side of the electric pump 9, and the lower hose 8 and the heater hose 12 are provided in the housing 13a. Each downstream end is connected to each other. The flow path in the lower hose 8 communicates with the suction port of the electric pump 9 via the valve body 13b of the thermostat 13 so as to be openable and closable, while the flow path in the heater hose 12 connects the valve body 13b of the thermostat 13 to the suction port. Instead, it communicates directly with the suction port of the electric pump 9 through a space (valve chamber) in the housing 13a that accommodates it.

  Further, the bypass passage 10 is opened facing the valve chamber of the thermostat 13, and the bypass passage 10 communicates with the suction port of the electric pump 9 through the valve chamber. In conjunction with the valve body 13b of the thermostat 13, a throttle valve 15 (hereinafter referred to as a bypass flow rate adjustment valve) that adjusts the amount of cooling water flowing from the bypass passage 10 into the valve chamber of the thermostat 13 is provided. Thereby, the bypass passage 10 is opened and closed in conjunction with opening and closing of the thermostat 13.

  That is, when the thermostat 13 is fully closed as shown in the figure, the bypass flow rate adjusting valve 15 opens the bypass passage 10 fully. On the other hand, when the thermostat 13 starts to open and the valve body 13b moves to the lower side of the drawing, The flow rate adjustment valve 15 is also moved downward to restrict the flow of the cooling water from the bypass passage 10 and when the thermostat 13 is fully opened, the bypass passage 10 is fully closed.

  The electric pump 9 is, for example, a well-known centrifugal type that sends cooling water by rotating the impeller, and the operation of the electric motor connected to the shaft of the impeller is controlled by an engine control unit 20 (hereinafter referred to as a control means). ECU). In other words, the electric pump 9 is controlled by the ECU 20 so as to constitute a flow variable means capable of changing the flow state of the cooling water in the water jackets 4 and 5 in the engine body 1.

  As is well known, the ECU 20 includes a CPU, a memory, an I / O interface circuit, a driver circuit, and the like, and performs fuel injection control and ignition timing control for each cylinder s1 to s4 for engine operation control. In addition to this, in this embodiment, the operation of the electric pump 9 is controlled mainly in accordance with the temperature and load state of the engine, the rotational speed, or the like.

  That is, in this embodiment, the ECU 20 includes at least a signal from a sensor 16 (for example, an accelerator opening sensor or an airflow sensor of a vehicle, hereinafter referred to as a load state sensor) for detecting a load state of the engine. The signal from the engine speed sensor 17 and the signal from the water temperature sensor 18 disposed facing the water jacket 4 on the exhaust side of the cylinder block 2 are input to determine the state of the engine. Accordingly, the output voltage to the electric pump 9 is controlled.

  In this embodiment, the water temperature sensor 18 is located at a portion corresponding to the second cylinder s2 in the water jacket 4 on the exhaust side of the cylinder block 2 (that is, the first and fourth cylinders s1 located at the end in the cylinder row direction). , S4 in association with any one of the cylinders), so that the circulation of the cooling water is very small as in the short pulse control mode described later, and the cooling water in the water jacket 4 is disposed. Even when the temperature difference becomes considerably large, the average temperature can be detected.

  That is, as will be described later, for example, when the electric pump 9 is stopped immediately after the cold start so as to promote warm-up of the engine or when it is operated in the short pulse control mode, the circulation of the cooling water in the water jacket 4 is almost stopped. The temperature difference between the parts of the cylinder block 2 and the cylinder head 3 is directly reflected in the cooling water temperature. At this time, the cooling water temperature is highest on the exhaust side of the cylinder head 3. On the other hand, the temperature becomes lowest on the intake side of the cylinder block 2 and becomes an average temperature state on the exhaust side of the cylinder block 2.

  Further, when the cooling water flows through the water jackets 4 and 5 in the cylinder row direction as in the long pulse control mode and the normal control mode, the cooling water temperature in the portion near the center in this direction is more stable than at both ends. Therefore, if the water temperature sensor 18 is disposed in the water jacket 4 on the exhaust side of the cylinder block 2 in association with either the second or third cylinder s2, s3 located near the center in the cylinder row direction as described above. The water temperature sensor 18 can detect the average cooling water temperature in the engine body.

  Further, in this embodiment, as shown in an enlarged cross-sectional view in FIG. 2, the recesses 2 a and 2 a are formed on both side walls of the water jacket 4 where the tip of the water temperature sensor 18 faces, and in the vicinity of the water temperature sensor 18. The cross section of the water jacket 4 is enlarged. As a result, even if the cooling water temperature around the cylinders s1 to s4 rises locally in the short pulse control mode, convection of the cooling water is likely to occur due to this temperature change, and the influence of the local water temperature rise is affected. Since it can be reduced, the water temperature sensor 18 is advantageous for detecting the average cooling water temperature.

  The overall flow of the cooling water in the engine cooling apparatus A configured as described above is schematically shown in FIG. FIG. 2A shows the flow when the thermostat 13 is closed by an arrow, and a part of the cooling water sent to the water jacket 4 of the cylinder block 2 by the electric pump 9 is driven by the bypass passage 10. 9 is returned to the suction side, and part of the cooling water also flows into the water jacket 5 of the cylinder head 3, flows through the flow path in the heater hose 12, and is returned to the suction side of the electric pump 9. At this time, since the thermostat 13 is closed, the cooling water does not flow between the radiator 6 and the radiator 6.

  On the other hand, when the thermostat 13 is fully open, the bypass passage 10 is closed by the bypass flow rate adjusting valve 15, so that the coolant from the electric pump 9 flows into the cylinder block as shown by the arrow in FIG. After flowing through the water jackets 4 and 5 of the cylinder head 3 and the cylinder head 3, they flow out into the flow paths in the upper hose 7 and the heater hose 12, and then return to the suction side of the electric pump 9. Of course, if the electric pump 9 does not operate, the flow of the cooling water as described above does not occur, and the cooling water substantially stops except for the flow by convection.

(Operation control of electric pump)
Next, operation control of the electric pump 9 by the ECU 20 will be described. The control of the output voltage to the electric pump 9 is so-called duty control in which the magnitude of the output voltage is adjusted by changing the duty ratio. By changing the control duty ratio in the range of 0 to 100%, the output voltage is controlled. For example, the rotational speed of the electric pump 9 can be finely controlled with high accuracy by changing it to substantially linear within a predetermined range of about 0.5 to 12V.

  Further, as a characteristic part of the present invention, the ECU 20 switches the control duty ratio at a preset time interval and supplies the electric pump 9 with a pulsed voltage, thereby intermittently driving the electric pump 9 at a constant cycle. It can be operated. And it switches to the pulse control mode which operates the electric pump 9 in that way, and the normal control mode which changes the rotation speed according to the state of the engine while operating the electric pump 9 continuously as mentioned above. Thus, the operating state of the electric pump 9 is controlled.

  More specifically, in the normal control mode, the rotational speed of the electric pump 9 is controlled based on a control map as shown in FIG. This control map is a three-dimensional map in which the basic control rotation speed of the electric pump 9 is preset according to the engine load and rotation speed, and the pump rotation speed is relatively high on a relatively high load or high rotation side. Thus, while ensuring the flow rate of cooling water corresponding to the large amount of heat generated by the engine, the pump speed is lowered on the relatively low load or low rotation side to prevent overcooling of the engine, thereby reducing fuel consumption. It comes to reduce.

  On the other hand, the pulse control mode is performed mainly when the engine is cold, such as after a cold start of the engine, and by operating the electric pump 9 intermittently, the water jackets 4 and 5 in the engine main body 1 are operated. The circulation amount of the cooling water is made smaller than that in the normal control mode.

  That is, the pulse control mode includes a short pulse control mode in which the electric pump 9 is intermittently operated at a relatively low frequency and a long pulse control mode in which the electric pump 9 is intermittently operated at a relatively high frequency. In the mode, the electric pump 9 is intermittently operated so that the operation time is shorter than the non-operation time. As a result, the circulation of the cooling water in the water jackets 4 and 5 in the engine main body 1 is almost almost stopped, and warm-up is promoted. The entire cooling water in the jackets 4 and 5 is shaken and slightly agitated, whereby a local temperature rise around the cylinders s1 to s4 can be suppressed.

  On the other hand, in the long pulse control mode, the electric pump 9 is intermittently operated at an average higher frequency than the short pulse control mode (for example, the operation time is longer than the non-operation time). As a result, the cooling water flows through the water jackets 4 and 5 in the engine main body 1 in a slight amount continuously, but the flow rate is continuously operated by the electric pump 9 in the normal control mode. Less than the minimum flow rate. In other words, in the long pulse control mode, the circulation state of the cooling water in the water jackets 4 and 5 is intermediate between the short pulse control mode and the normal control mode.

  FIGS. 5 (a) and 5 (b) show an engine having the same configuration as that of the present embodiment, for example, a temperature sensor disposed in a cylinder liner of the third cylinder s3 and a predetermined portion of the water jacket 5 in the vicinity thereof to cool the engine. The experimental result which measured the temperature rise after a long start is shown. A graph indicated by a broken line in the figure shows an increase in the water temperature when the electric pump 9 is operated at a rotational speed proportional to the engine rotational speed as in the case of a conventional mechanical pump. The solid line graph shows the state when the electric pump 9 is intermittently operated in the short pulse control mode.

  As shown in FIG. 6A, the temperature rise of the cylinder liner is the fastest when the electric pump 9 is stopped and the slowest when the electric pump 9 is operated in the same manner as the conventional mechanical pump. When the electric pump 9 is intermittently operated in the mode, the temperature of the cylinder liner rises as early as when the electric pump 9 is stopped, and it can be seen that the engine can be quickly warmed up.

  On the other hand, as shown in FIG. 5B, when the electric pump 9 is stopped, the water temperature at the predetermined location of the water jacket 5 is rapidly increased and decreased, and the partial boiling due to the cooling water being stopped. Is considered to have occurred. On the other hand, when the electric pump 9 is operated in the same manner as a conventional mechanical pump and continuously circulated, the water temperature of the above-mentioned is not only when intermittently operated in the short pulse control mode. Abrupt fluctuations are not observed, and it can be seen from this that local temperature rise can be suppressed by intermittently circulating cooling water as described above.

-Control procedure when engine is cold-
Hereinafter, a specific control procedure of the electric pump 9 performed by the ECU 20 after the engine is started will be described with reference to FIGS. 7 to 10 mainly based on the flowchart of FIG. First, in the flow of FIG. 6 started in response to the engine start, in step S1, the electric pump 9 is stopped, and in the subsequent step S2, it is determined whether or not it is a cold start from the engine water temperature th at the time of start detected by the water temperature sensor 18. To do.

  If the determination is NO and the engine is warm start, the process proceeds to step S11 described later, and the electric pump 9 is operated in the normal control mode. If the determination is YES and the engine is cold start, the process proceeds to step S3 and the engine is started. It is determined whether or not a set time t1 until the operation of the electric pump 9 is started later. For this set time t1, an appropriate value corresponding to the engine water temperature at the time of starting is determined in advance by experiment or the like, and set in a table as schematically shown in FIG. 7, for example, and read from this table. Good. In the example of the figure, it is estimated that it takes longer to warm up the engine as the engine water temperature at the time of starting is lower, and the set time t1 is made longer.

  If the determination in step S3 is NO, that is, if the set time t1 has not elapsed, the electric pump 9 is maintained in a stopped state while waiting for the elapse of time. Thereby, circulation of the cooling water in the water jackets 4 and 5 in the engine main body 1 can be stopped and the warm-up can be promoted to the maximum. If the set time t1 has elapsed since the cold start (YES in step S3), the process proceeds to step S4, and the electric pump 9 is operated in the short pulse control mode.

  That is, first, the intermittent operation cycle of the electric pump 9 in the short pulse control mode and the control duty ratio during the operation are read from preset tables. In this table, for example, as schematically shown in FIG. 8, the operating period of the electric pump 9 and the appropriate value of the duty ratio are determined based on the experiment according to the engine water temperature. The higher the water temperature, the shorter the operation cycle, while the duty ratio is set so that it does not change much, but instead or in addition to this, the higher the engine water temperature, the higher the duty ratio is set. May be.

  Then, an output voltage is applied in a pulsed manner to the motor of the electric pump 9 by a control signal corresponding to the operation cycle and the duty ratio, and this is operated intermittently. When the electric pump 9 is intermittently operated at a relatively low frequency, the cooling water in the water jackets 4 and 5 of the cylinder block 2 and the cylinder head 3 enters the inlet as in the continuous operation of the electric pump 9. Instead of continuously moving from the side toward the outlet side, it stops repeatedly immediately after moving small by instantaneous pump operation.

  In other words, in the short pulse control mode, due to the intermittent operation of the electric pump 9, the entire cooling water of the water jackets 4 and 5 is periodically swayed and circulated intermittently so as to be slightly stirred. As a result, local temperature rise around the cylinders s1 to s4 of the engine is suppressed and the amount of heat released from the engine is reduced in the same manner as when the cooling water is stopped. It will be fully promoted.

  Here, when the relationship between the operating state of the electric pump 9 after the cold start as described above and the increase in the engine water temperature (the outlet water temperature in the vicinity of the outlet path 5a at the rear end of the cylinder head) is shown in the time chart of FIG. First, until the set time t1 elapses after the cold start (t = 0 to t1), the control duty ratio of the electric pump 9 is set to 0%, and the pump is maintained in a stopped state (waiting in step S3). This minimizes heat dissipation from the engine. At this time, as shown by the solid line in the figure, the rise in the engine outlet water temperature is apparently delayed because the electric pump 9 is stopped and the cooling water in the water jackets 4 and 5 hardly moves. This is because the warmed cooling water around s1 to s4 does not reach the outlet of the water jacket 5.

  Then, when the cooling water heated as described above reaches the outlet of the water jacket 5 by convection, the water temperature rises as shown in the figure, and in the case of a conventional general mechanical water pump (shown in phantom lines). However, when the set time t1 has elapsed from the start (time t1), the operation in the short pulse control mode is started (step S4), and the electric pump 9 operates intermittently as described above. The intermittent operation of the electric pump 9 causes the cooling water in the water jackets 4 and 5 to circulate intermittently, which is slightly agitated, so that the local temperature rise around each cylinder s1 to s4, etc. Is suppressed.

  Even if the engine outlet water temperature, that is, the cooling water temperature of the water jackets 4 and 5 rises, in the short pulse control mode, the amount of cooling water circulating to the vicinity of the thermostat 13 via the heater hose 12 or the like is very small. The cooling water temperature around the thermostat 13 does not rise so much. Therefore, even if the engine outlet water temperature exceeds the valve opening start temperature th1 (for example, 87 ° C.), the thermostat 13 does not open, and the water temperature rapidly rises to about 100 ° C. as shown in the figure (time t2).

  Thus, after the cooling water temperature of the water jackets 4 and 5 rises, the cooling water temperature around the thermostat 13 rises with a delay, and when the valve opening start temperature th1 or higher is reached, the thermostat 13 is opened for the first time, and the temperature of the radiator 6 decreases. However, even if the cooling water temperature of the water jackets 4 and 5 is lowered due to the inflow of this cooling water, the cooling water temperature around the thermostat 13 is not immediately lowered. Closes late, the amount of inflow of cooling water from the radiator 6 increases, and the water temperature rapidly decreases (time t3).

  That is, in the short pulse control mode, as a result that the opening / closing operation of the thermostat 13 is greatly delayed with respect to the change of the coolant temperature in the water jackets 4 and 5, as shown in FIG. The engine outlet water temperature, that is, the cooling water temperature in the water jackets 4 and 5 fluctuates greatly, and the control of the air-fuel ratio and the ignition timing performed accordingly may cause an error, leading to deterioration of combustion. .

  Further, as described above, the operation delay of the thermostat 13 is increased and the flow of low-temperature cooling water from the radiator 6 is increased. As a result, as shown in the figure, the engine outlet water temperature easily converges to the full opening temperature th2 or more of the thermostat 13. No longer. That is, the engine warm-up is delayed, and the effect of improving the fuel consumption and emission by pulse control is diminished, and the temperature of the cooling water supplied to the heater core 11 is not stable, so that a bad influence appears on the heating performance of the passenger compartment. Become.

  Therefore, in this embodiment, when the cooling water temperature th detected by the water temperature sensor 18 is equal to or higher than the valve opening start temperature th1 of the thermostat 13, the operation of the electric pump 9 is switched to the long pulse control mode to flow the cooling water. The amount is increased so as to reduce the temperature difference of the cooling water from the water jackets 4 and 5 to the periphery of the thermostat 13.

  That is, subsequent to step S4 of the flow shown in FIG. 6, in step S5, the detected value th of the cooling water temperature by the water temperature sensor 18 is equal to or higher than the first set temperature th1 (in this example, the thermostat valve opening start temperature). Judge whether. If this determination is NO, the process returns to step S4 and the operation in the short pulse control mode is continued. If the determination is YES and the detected water temperature th ≧ th1, the process proceeds to step S6.

  In step S6, it is determined whether or not the detected water temperature th is equal to or higher than a second set temperature th2 (in this example, the fully open temperature of the thermostat) higher than the first set temperature th1. On the other hand, if the determination is NO and th <th2, the process proceeds to step S7, and the electric pump 9 is operated in the long pulse control mode. That is, the electric pump 9 is operated intermittently by controlling the intermittent operation cycle and the duty ratio of the electric pump 9 as in the short pulse control mode.

  In this long pulse control mode, as described above, the water jackets 4 and 5 continue to flow even if a small amount of cooling water, and the amount of cooling water circulated from there to the thermostat 13 increases so that the thermostat 13 The cooling water temperature difference between the periphery and the water jackets 4 and 5 is reduced. That is, the cooling water temperature around the thermostat 13 increases and approaches the valve opening start temperature th1, while the cooling water temperature of the water jackets 4 and 5 decreases.

  Therefore, in the subsequent step S8, it is determined whether or not the detected value th of the cooling water temperature by the water temperature sensor 18 is equal to or higher than the first set temperature th1, and if this determination is YES, then in the subsequent step S9, whether or not it is now equal to or higher than the second set temperature th2. judge. If this determination is YES and th ≧ th2, the process proceeds to step S11 to be described later. On the other hand, if the determination is NO and lower than the second set temperature th2, the process returns to step S7 to continue the operation in the long pulse control mode. To do.

  Then, when the cooling water temperature of the water jackets 4 and 5 is further lowered by the operation in the long pulse control mode and becomes lower than the first set temperature th1, it is determined NO in the step S8, and the process returns to the step S4. The electric pump 9 is operated again in the short pulse control mode. As a result, the cooling water in the water jackets 4 and 5 again circulates again and the temperature rise is accelerated to the maximum. As a result, the detected water temperature th by the water temperature sensor 18 is again equal to or higher than the first set temperature th1. Thus, the long pulse control mode is resumed (steps S5 to S7).

  Thus, when the engine warm-up progresses and the cooling water temperature increases as a whole while the temperature difference between the water jackets 4 and 5 and the thermostat 13 is suppressed by the operation in the long pulse control mode, for example, the accelerator pedal When the fuel injection amount is rapidly increased in response to the depression, the heat dissipation amount temporarily increases, and the water temperature th detected by the water temperature sensor 18 may be equal to or higher than the second set temperature th2.

  At this time, YES is determined in step S6, and the process proceeds to step S10, in which it is determined whether or not the cumulative number of executions of the long pulse control mode after engine startup is equal to or greater than a predetermined number (for example, twice) set in advance. If it is less than the predetermined number of times and YES, it is considered that it takes time until the warm-up is completed. Therefore, the process proceeds to step S7 to set the long pulse control mode, whereby the detected water temperature th becomes less than the first set temperature th1. If so, the electric pump 9 is again operated in the short pulse control mode (steps S8 → S4).

  Even if the electric pump 9 is operated in the long pulse control mode, if the detected water temperature th does not decrease and remains at the second set temperature th2 or more (YES in step S9), the process proceeds to step S11 to enter the normal control mode. The electric pump 9 is continuously operated so that the flow rate of the cooling water is sufficiently increased so that the cooling water temperature does not become too high.

  As described above, the detected value th of the cooling water temperature by the water temperature sensor 18 changes a plurality of times across the first set temperature th1, and the operation in the short pulse control mode and the long pulse control mode is alternately repeated accordingly. After that, if it is determined NO in step S10 that the number of executions of the long pulse control mode exceeds the predetermined number, this time, even if the water temperature is equal to or higher than the first set temperature th1, the long pulse control mode is not switched. Returning to step S4, the operation in the short pulse control mode is continued.

  This is because if the cumulative number of executions of the long pulse control mode exceeds a predetermined number, the cooling water temperature from the water jackets 4 and 5 to the vicinity of the thermostat 13 is considered to be close to the warm-up completion temperature as a whole. At this time, the operation of the electric pump 9 is maintained in the short pulse control mode, and warm-up is sufficiently promoted until completion. Then, if the cooling water temperature becomes higher as a whole and the detection value th detected by the water temperature sensor 18 exceeds the second set temperature th2, YES is determined in step S9, that is, warm-up is completed, and the electric pump 9 is turned on in step S11. By switching to the normal control mode, the control at the time of cooling is completed (end).

  Therefore, according to the engine cooling apparatus A according to the above-described embodiment, first, the set time t1 after the cold start of the engine is caused by stopping the electric pump 9 as shown by the solid line graph in FIG. By stopping the flow of the cooling water in the water jackets 4 and 5 in the cylinder block 2 and the cylinder head 3, the heat dissipation from the engine can be minimized and the warm-up can be promoted to the maximum.

  Further, after the set time t1 has elapsed, the electric pump 9 is operated in the short pulse control mode, and the cooling water is circulated intermittently in the water jackets 4 and 5, thereby greatly reducing heat dissipation from the engine. The local temperature rise around the cylinders s1 to s4 can be suppressed, and the engine warm-up can be sufficiently promoted.

  When the engine warms up and the engine outlet water temperature exceeds 80 ° C. for a while as shown by the solid line graph in FIG. 10, the detection value th by the water temperature sensor 18 provided in the water jacket 4 on the exhaust side becomes If the temperature is equal to or higher than the first set temperature th1, the operation of the electric pump 9 is switched to the long pulse control mode (time t2), and the flow rate of the cooling water circulating from the water jackets 4 and 5 to the periphery of the thermostat 13 is increased. To do.

  This cooling water circulation lowers the cooling water temperature of the water jackets 4, 5, while the cooling water temperature around the thermostat 13 is increased, the valve opening starts earlier, and low temperature cooling water flows from the radiator 6. By starting, the cooling water temperature of the water jackets 4 and 5 is further lowered. Therefore, as shown after time t2 in FIG. 10, an excessive increase in the engine outlet water temperature is suppressed.

  On the other hand, if the cooling water temperature of the water jackets 4 and 5 decreases due to the inflow of low-temperature cooling water from the radiator 6, the cooling water temperature around the thermostat 13 also decreases without much delay. By closing the valve, the inflow of cooling water from the radiator 6 is blocked. For this reason, the engine outlet water temperature is relatively stable at times t3 to t5 in the figure, and the water temperature does not drop significantly as in the case of only the short pulse control mode (indicated by a virtual line).

  Then, once the detected value th of the cooling water temperature by the water temperature sensor 18 becomes less than the first set temperature th1, the electric pump 9 is operated in the short pulse control mode to sufficiently promote engine warm-up (time t3). ~ T4). As a result, when the detected water temperature th again becomes equal to or higher than the first set temperature th1, the operation in the long pulse control mode is performed again (time t4 to t5).

  If the cumulative number of executions of the long pulse control mode becomes 2 or more, then the operation in the short pulse control mode is not performed even if the water temperature becomes equal to or higher than the first set temperature th1. By continuing, as shown after time t5 in the figure, the engine outlet water temperature rapidly rises, converges to the full opening temperature th2 or more of the thermostat 13, and when the detected water temperature th ≧ th2, the electric pump 9 switches to the normal control mode. (Time t6), the warm-up is completed.

  In this way, warm-up is completed much faster than when the operation is continued in the short pulse control mode (the phantom line graph), and the fuel consumption and emission improvement effect by the pulse control is further enhanced and supplied to the heater core 11. The cooling water temperature is stabilized and the heating performance of the passenger compartment is improved.

  That is, in this embodiment, in order to promote engine warm-up after the cold start, the electric pump 9 is basically operated in the short pulse control mode, and the local temperature rise is suppressed while the pump is stopped. In the same manner as described above, the heat radiation from the engine is extremely reduced, and the water jackets 4 and 5 and the thermostat 13 of the engine main body 1 are increased by switching to the operation in the long pulse control mode and increasing the circulation amount of the cooling water. The temperature difference between the cooling water and the surroundings is reduced so that the response delay of the thermostat 13 does not increase. Thereby, fluctuations in the engine water temperature can be suppressed, controllability of the air-fuel ratio and ignition timing can be improved, and warm-up can be further promoted.

  Further, in this embodiment, the water temperature sensor 18 is disposed near the center of the water jacket 4 on the exhaust side of the cylinder block 2 for detecting the engine water temperature used for the operation control of the electric pump 9 and the engine operation control as described above. Thus, since the average cooling water temperature of the water jackets 4 and 5 can be detected, the controllability is high, and the above-described effects can be sufficiently obtained.

(Other embodiments)
In the above embodiment, the flow of the cooling water in the water jackets 4 and 5 is stopped for a predetermined period (set time t1) immediately after the cold start of the engine. You may make it distribute | circulate a cooling water intermittently.

  Moreover, in the said embodiment, when the detected value th of the cooling water temperature by the water temperature sensor 18 is equal to or higher than the valve opening start temperature (first set temperature) th1 of the thermostat 13, the electric pump 9 is operated in the long pulse control mode. However, the present invention is not limited to this, and the first set temperature is set according to the moving amount of the cooling water in the short pulse control mode, the capacity of the water jackets 4, 5, etc. In short, the thermostat 13 It is only necessary to switch to the long pulse control mode before starting to open.

  In the above embodiment, the electric pump 9 may be operated in the pulse control mode according to the operation state even after the engine is warmed up. That is, since the electric pump 9 is required to secure a maximum flow rate corresponding to a large amount of heat generated during high load operation of the engine, no matter how low the rotation is performed, for example, low load operation of the engine However, when the heat generation amount is small and the outside air temperature is low and the temperature of the cooling water tends to decrease, the engine temperature is relatively low and the heat loss increases, and the fuel consumption may deteriorate.

  Therefore, for example, when the engine is in a relatively low load and low speed operation range and the value detected by the water temperature sensor 18 falls below a predetermined temperature (eg, 93 ° C.), the electric pump 9 is set in the short pulse control mode. You may make it drive. If it carries out like this, the cooling water of the water jackets 4 and 5 will come to circulate intermittently temporarily, the temperature rises rapidly, and it returns to normal control mode again. Therefore, the engine water temperature after warm-up can be maintained at a higher temperature state (eg, 93 ° C. or higher) than before, increasing the thermal efficiency and reducing the fuel consumption.

  Furthermore, in the embodiment, as shown in FIG. 2, the recesses 2a and 2a are formed on the both side walls of the water jacket 4 where the tip of the water temperature sensor 18 faces, but the present invention is not limited to this. As shown, the recess 2a may be formed only on the side wall portion on the cylinder s2 side, or may be formed only on the opposite side wall portion as shown in FIG.

  As described above, the engine cooling device A according to the present invention is characterized by the flow control of the cooling water during cooling, and suppresses local temperature rise and partial boiling of the cooling water in the water jacket. However, the engine warm-up can be promoted as much as possible to improve the fuel economy and emission during cold operation, and therefore, it is particularly suitable for an automobile engine or the like that is frequently driven and stopped.

It is a mimetic diagram showing a schematic structure of an engine cooling device concerning an embodiment of the present invention. It is an expanded sectional view which shows the arrangement structure of the water temperature sensor which faces a water jacket. It is a schematic diagram which shows the flow of the cooling water in embodiment. It is a schematic diagram which shows an example of the control map of the normal operation mode of an electric pump. It is a graph which shows a mode that water temperature etc. rise at the time of intermittent operation | movement of an electric pump compared with the time of a pump's continuous operation | movement and a stop. It is a flowchart figure which shows the control procedure of the electric pump after a cold start. It is the schematic diagram of the table which set the time which stops an electric pump after cold start corresponding to the water temperature at the time of start. It is a schematic diagram of the table which set the operation cycle and duty ratio of the electric pump in short pulse control mode according to engine water temperature. It is a time chart which shows a mode that engine water temperature rises by the driving | operation in the short pulse control mode of the electric pump after cold start. FIG. 10 is an enlarged view corresponding to FIG. 9 illustrating an enlarged change in engine water temperature when the long pulse control mode is added to the short pulse control mode. FIG. 3 is a view corresponding to FIG. 2 according to another embodiment. FIG. 3 is a view corresponding to FIG. 2 according to another embodiment.

A Engine cooling device s1 to s4 Cylinder 1 Engine body 2 Cylinder block 2a Recess 4,5 Water jacket (cooling water passage)
7 Upper hose (communication path)
8 Lower hose (communication passage)
9 Electric pump (distribution variable means)
13 Thermostat 18 Water temperature sensor 20 Engine control unit (ECU: Control means)

Claims (9)

  1. And changeable distribution changing means the flow state of cooling water in the cooling water passage in the engine body, a first circulatory state in which the cooling water in the cooling water passage in an engine warm-up intermittently distributed in the first predetermined flow rate while operating the flow varying means so that, after the warm-up is such that a second circulatory state in which cooling water is continuously circulated in the first second predetermined flow amount or more of a flow rate that is greater than a predetermined flow rate An engine cooling device comprising control means for operating the flow variable means,
    A thermostat that mechanically opens and closes according to a change in the temperature of the cooling water is disposed in the communication path that connects the cooling water path and the passage in the radiator.
    The control means is configured so that the cooling water in the cooling water passage exceeds the first predetermined flow rate and is less than the second predetermined flow rate before the thermostat starts to open in response to an increase in the cooling water temperature during engine warm-up. The engine cooling apparatus is characterized in that the distribution variable means is operated so as to be in an intermediate distribution state in which the distribution is intermittently performed.
  2. The cooling device according to claim 1, wherein
    A water temperature sensor is arranged facing the cooling water passage in the engine body,
    Control means receives a signal from the water temperature sensor, when the detection value of the cooling water temperature is equal to or higher than the first temperature is a valve opening start temperature of the thermostat, distribution as cooling water becomes said intermediate fluid communication An engine cooling apparatus for operating a variable means.
  3. The cooling device according to claim 2, wherein
    The control means operates the flow variable means so that the cooling water enters the first flow state again when the detected value of the cooling water temperature becomes equal to or higher than the first temperature and then returns to a temperature lower than this temperature. An engine cooling system characterized by that.
  4. The cooling device according to claim 3, wherein
    After the detected value of the cooling water temperature changes more than a predetermined number of times on the high temperature side and the low temperature side across the first temperature, the control means allows the cooling water to flow through the first circulation even if it exceeds the first temperature. A cooling device for an engine, wherein the flow variable means is operated so as to remain in a state.
  5. The cooling device according to claim 2, wherein
    The control means operates the flow variable means so that the cooling water enters the second flow state after the detected value of the cooling water temperature by the water temperature sensor reaches the second temperature, which is the fully open temperature of the thermostat. An engine cooling system characterized by that.
  6. The cooling device according to claim 2, wherein
    The control means controls the flow variable means so that the flow of the cooling water stops in the cooling water passage in the engine body for a predetermined period when the detected value of the cooling water temperature by the water temperature sensor is lower than the first temperature. An engine cooling device.
  7. In the cooling device according to any one of claims 2 to 6,
    An engine cooling device, wherein the water temperature sensor is arranged in association with any one of the cylinders other than the cylinders located at the end in the cylinder row direction in the water jacket on the exhaust side of the cylinder block.
  8. The cooling device according to claim 7, wherein
    A cooling device for an engine, wherein a recess is formed in a wall surface of a water jacket facing a tip of a water temperature sensor.
  9. In the cooling device according to any one of claims 1 to 8,
    The distribution variable means includes an electric pump for circulating cooling water,
    The control means is configured to intermittently operate the electric pump so that the operation time is shorter than the non-operation time when the cooling water is circulated in the first distribution state. .
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