JP2001271644A - Method and device for adjusting engine oil temperature - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make oil temperature adjustment by heat exchanging between the cooling water flowing in the cooling water system of an engine and the oil in the engine further effective. SOLUTION: The cooling water system of a water cooled engine 10 is roughly constituted with cooling water circulating between a water jacket 11 and a radiator 12. To the oil cooler 16 is provided in the cooling water system, through a cooling water passage f, cooling water flows from the side downstream of the engine 10, and through a cooling water passage g, cooling water flows from the side downstream of the engine 10. A three-way valve 17 switches the passage of the water to be made to flow to the oil cooler 16, by selectively cutting-off either the cooling water passage f or g according to the operation control by an electronic controller 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for adjusting an oil temperature of an engine.

[0002]

2. Description of the Related Art A water-cooled engine is provided with a cooling water system that circulates between a water jacket provided inside the engine and a radiator that radiates heat of the cooling water to the atmosphere. For example, as shown in Japanese Utility Model Application Laid-Open No. 2-61125, an oil cooler, which is a type of an oil heat exchanger, is provided in the cooling water system, and oil for engine lubrication is supplied by cooling water flowing through the oil cooler. Cooling oil temperature control devices are known.

In this oil temperature controller, when the cooling water is at a low temperature, the connection of the radiator and the oil cooler to the cooling water system is cut off by a thermostat. Therefore, when the temperature of the cooling water is low, such as during warm-up, the cooling water does not flow through the radiator and the oil cooler. As a result, the temperature rise of the cooling water is promoted to the extent that the heat of the cooling water is no longer radiated to the atmosphere or oil in the radiator or the oil cooler.

[0004]

As described above, if the supply of the cooling water to the oil cooler is cut off before the warm-up is completed, the temperature rise of the cooling water is accelerated by the amount of heat taken by the oil, Although the warm-up property of the cooling water affecting the heater in the vehicle and the like is improved, the temperature rise of the oil itself is delayed. As a result, the elimination of friction between the related components of the engine due to the low oil temperature is delayed, and it becomes impossible to improve the fuel efficiency.

[0005] Further, not only those described in the above-mentioned publications, but also conventional oil temperature control devices in which an oil cooler is simply arranged in the middle of a cooling water system, or as described in the above-mentioned publications, Since only the means for shutting off the supply of cooling water to the oil is further provided, there is naturally a limit in improving the efficiency of oil temperature control. In particular, when the engine is warmed up, it has been difficult to efficiently raise the temperature of both the cooling water and the oil.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an oil temperature adjusting method and an oil temperature adjusting device for an engine capable of adjusting oil temperature more efficiently. Is to do.

[0007]

The means for achieving the above object and the effects thereof will be described below. The invention according to claim 1 is a method for adjusting the temperature of oil by heat exchange with cooling water flowing through a cooling water system of an engine, wherein the cooling water exchanged with oil is cooled by the engine in the cooling water system. The cooling water flowing on the downstream side and the cooling water flowing on the upstream side of the engine are switched according to the operating state of the engine.

[0008] The cooling water flowing on the downstream side of the engine is heated in the engine, and thus has a higher temperature than the cooling water flowing on the upstream side of the engine. Therefore, according to the above method, depending on the operating state of the engine, the oil and heat are transferred between the cooling water downstream of the higher temperature engine and the cooling water upstream of the relatively low temperature engine. The exchanged cooling water can be switched according to the operating state of the engine. For this reason, heat exchange with oil is promoted by using cooling water flowing on the upstream side of the cooler engine to promote oil cooling, and using cooling water flowing on the downstream side of the hotter engine to promote oil temperature rise. The cooling water to be switched can be appropriately switched between two cooling waters having different temperatures according to the operation state of the engine. Therefore, the temperature of the oil can be more efficiently adjusted.

The invention described in claim 2 is the first invention.
In the method for adjusting the oil temperature of an engine according to the above, the temperature of the oil is used as an operating state of the engine.

According to this method, the cooling water exchanged with the oil can be switched according to the temperature of the oil. Therefore, more appropriate temperature adjustment according to the oil temperature state can be performed.

[0011] The invention according to claim 3 is based on claim 1.
Alternatively, in the oil temperature adjusting method for an engine described in 2, the cooling water is switched to use the cooling water flowing upstream of the engine when the engine is warmed up.

According to the above method, when the engine is warmed up, the temperature is lower than the cooling water flowing downstream of the engine.
The cooling water flowing upstream of the engine having a small temperature difference from the oil is used for heat exchange with the oil. As a result, the amount of heat deprived of the oil by heat exchange with the oil is suppressed, so that the temperature of the cooling water can be raised earlier when the engine is warmed up. If the temperature of the cooling water is raised early in this way, subsequently, the temperature of the oil is increased by the sufficiently raised cooling water. Therefore, it is possible to more efficiently raise the temperatures of the cooling water and the oil when the engine is warmed up.

In the above method, after the engine is warmed up, if the heat exchange with the oil is performed by using the cooling water on the downstream side of the engine, the temperature becomes further higher by passing through the engine. The temperature of the oil is raised by the cooling water, and the efficiency of raising the temperature of the oil can be further improved.

The invention according to claim 4 is applied to a water-cooled engine provided with a cooling water system passing through the inside of the engine, wherein an oil heat exchanger is provided in the cooling water system, and the oil heat exchanger is provided in the oil heat exchanger. An oil temperature adjusting device for an engine that adjusts the temperature of oil by heat exchange with cooling water passing therethrough, wherein cooling water downstream of the engine in the cooling water system is provided to pass through the oil heat exchanger. A first cooling water passage, a second cooling water passage provided so that cooling water upstream of the engine in the cooling water system passes through the oil heat exchanger, and a first cooling water passage. And a blocking means for selectively blocking either of them.

According to the above configuration, the cooling water that has passed through the engine and has become higher in temperature through the first cooling water channel, and has the lower temperature before passing through the engine through the second cooling water channel. Of cooling water respectively pass through the oil heat exchanger. Then, by selectively blocking either of the first and second cooling water passages by the blocking means, it becomes possible to selectively allow cooling water having different temperatures to pass through the oil heat exchanger. For example, when it is desired to raise the temperature of the oil, the second cooling water passage can be shut off by the shut-off means, and relatively high-temperature cooling water can be sent to the oil heat exchanger through the first cooling water passage. When it is desired to cool the oil, the first cooling water passage can be shut off by the shut-off means, and relatively low-temperature cooling water can be sent to the oil heat exchanger through the second cooling water passage. Therefore, it is possible to more efficiently adjust the temperature of the oil by properly using the two cooling water passages through which the cooling waters having different temperatures pass.

The invention described in claim 5 is the same as the invention in claim 4.
The oil temperature adjusting device for an engine according to claim 1, further comprising: a switching control unit that switches a cooling water passage, which is shut off by the shut-off unit, from the first and second cooling water passages in accordance with an operation state of the engine. It is.

According to the above configuration, the cooling water passage cut off by the cut-off means is appropriately selected according to the operating state of the engine. Therefore, efficient oil temperature adjustment can be performed according to the operating state of the engine.

The invention described in claim 6 is the same as the invention in claim 5
In the oil temperature adjusting device for an engine described in (1), the switching control means switches a cooling water passage to be shut off by the shutoff means according to the temperature of the oil.

According to the above configuration, the cooling water sent to the oil heat exchanger can be appropriately switched according to the temperature of the oil. Therefore, it is possible to more efficiently adjust the oil temperature in accordance with the oil temperature state.

The invention described in claim 7 is the same as the invention in claim 5
Or in the oil temperature adjusting device for an engine according to 6, wherein the switching control means comprises:
The cooling water passage blocked by the blocking means is switched to the second cooling water passage.

According to the above configuration, when the engine is warmed up, the second cooling water passage is shut off, and the cooling water flows to the oil heat exchanger through the first cooling water passage. That is, the cooling water on the downstream side of the engine, which has a lower temperature than the cooling water on the upstream side of the engine and has a small temperature difference from the oil, is sent to the oil exchanger. Therefore, the amount of heat of the cooling water taken by the oil in the oil heat exchanger is suppressed, so that the temperature of the cooling water can be raised more quickly when the engine is warmed up. If the temperature of the cooling water is raised early in this way, subsequently, the temperature of the oil is increased by the sufficiently raised cooling water. Therefore, it is possible to more efficiently raise the temperatures of the cooling water and the oil when the engine is warmed up.

In the above configuration, after the engine is warmed up, if the first cooling water passage is shut off and the cooling water flows through the second cooling water passage to the oil heat exchanger, the temperature can be sufficiently increased. In addition, the temperature of the oil is raised by the cooling water that has become hotter as it passes through the engine, so that the temperature of the oil can be raised more efficiently.

[0023]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a method and an apparatus for adjusting an oil temperature of an engine according to the present invention.

FIG. 1 schematically shows the overall configuration of a cooling water system of a water-cooled engine 10 to which the present embodiment is applied. As shown in FIG. 1, the cooling water system of the water-cooled engine 10 is roughly divided into a water jacket 11 and a radiator 1.
2. The cooling water is circulated so as to sequentially go around the water pump 13.

The water jacket 11 is connected to the engine 10
The engine 10 is cooled by cooling water flowing through the water jacket 11 in the cylinder head and the cylinder block. The radiator 12 is a heat exchanger that radiates heat of the cooling water to the atmosphere.
The cooling water that has passed through 0 and has become high temperature is cooled. Further, the water pump 13 circulates the cooling water through the cooling water system by sucking the cooling water from the suction port and discharging the compressed water from the discharge port.

Water jacket 11 in engine 10
The cooling water outlet side and the radiator 12 are connected by a cooling water passage A. Further, the downstream side of the radiator 12 is connected to the thermostat 14 through the cooling water passage B, and further downstream thereof is connected to the suction port of the water pump 13 through the cooling water passage C. And further, water pump 1
The discharge port 3 and the cooling water inlet side of the water jacket 11 are connected by a cooling water passage D. In this way, a cooling water circulation path is formed between the water pump 13, the water jacket 11, and the radiator 12 through the cooling water paths A → B → C → D.

The cooling water system bypasses the radiator 12 and the water jacket 11 and the water pump 13.
A cooling water passage (bypass water passage) E for circulating the cooling water between the cooling water passage and the cooling water passage is provided. This bypass channel E
Is branched from the middle of a cooling water passage A connecting the water jacket 11 and the radiator 12 and is connected to a thermostat 14. The thermostat 14 automatically operates in response to the temperature of the cooling water flowing through the thermostat 14, and selectively shuts off the connection to the cooling water passage C between the cooling water passage B and the bypass water passage E connected to the radiator 12. ing.

That is, when the cooling water is at a high temperature, such as after completion of warming up of the engine 10, the thermostat 14
The connection between the bypass water passage E and the cooling water passage C is cut off, and the cooling water flows to the cooling water passage C only from the cooling water passage B connected to the radiator 12. The cooling water at this time circulates between the water pump 13, the water jacket 11, and the radiator 12 through the cooling water passages A, B, C, and D as described above. And water jacket 1
The cooling water, which has passed through 1 and has cooled the engine 10 and has become high temperature, is radiated by the radiator 12, cooled, and then sent to the water jacket 11 again by the water pump 13.

On the other hand, when the temperature of the cooling water is low, such as when the engine 10 is warmed up, the thermostat 14 cuts off the connection between the cooling water passage B connected to the radiator 12 and the cooling water passage C connected to the water pump 13. And bypass waterway E
The cooling water flows to the cooling water passage C only from the outlet. The cooling water at this time circulates only between the water jacket 11 and the water pump 13, bypassing the radiator 12 through the cooling water passages A → E → C → D. This prevents the heat of the cooling water from being dissipated by the radiator 12,
The temperature rise of the cooling water is promoted.

A heater 15 is connected to the cooling water system for heating the interior of the vehicle cabin by utilizing the heat of the cooling water. Here, the heater 15 is connected to a water passage A on the downstream side of the engine 10 and a water passage C on the downstream side of the thermostat 14, respectively. Therefore, thermostat 1
Regardless of the operation state of 4, the cooling water downstream of the engine 10 that has been heated by flowing through the water jacket 11 always flows to the heater 15.

In this embodiment, an oil heat exchanger (oil cooler) 16 is further connected to the cooling water system, and the oil cooler 16 controls the temperature of engine oil for lubricating the engine 10. .
The oil cooler 16 controls the temperature of the engine oil through heat exchange between the cooling water flowing through the cooling water system and the engine oil.

In the cooling water system, one of the oil coolers 16 has a cooling water passage A on the downstream side of the engine 10.
The other is connected to the three-way valve 17, respectively. Further, the three-way valve 17 is connected to the water pump 13 through the cooling water passage F.
Are connected to the cooling water passage C on the suction port side of the pump 13 and to the cooling water passage D on the discharge port side of the pump 13 through the cooling water passage G, respectively.

The three-way valve 17 is configured as an electromagnetic valve that is operated and controlled by an electronic control unit (ECU) 18 that performs various controls of the engine 10, and based on a command signal from the ECU 18, a cooling water passage F to the oil cooler 16 and a three-way valve 17. One of the connections of the cooling water passage G is selectively cut off.

Here, the oil cooler 1 is controlled by the three-way valve 17.
When the cooling water 6 is connected to the cooling water passage F connected to the cooling water passage C on the suction port side of the oil pump 13, the cooling water flows from the cooling water passage A to the cooling water passage F. Therefore, the cooling water flows from the downstream side of the engine 10 heated by passing through the water jacket 11 to the oil cooler 16 at this time (see FIG. 2).

On the other hand, the three-way valve 17 controls the oil cooler 1
6 is connected to the cooling water passage G connected to the cooling water passage D on the discharge port side of the water pump 13 so that the cooling water flows from the cooling water passage G toward the cooling water passage A this time. Become. Therefore, the cooling water flows into the oil cooler 16 at this time from a relatively low temperature upstream side of the engine 10 before passing through the water jacket 11 (see FIG. 3).

Here, the cooling water passage from the passage through the engine 10 to the release of heat by the radiator 12 is referred to as the downstream side of the engine 10 in the cooling water system. The cooling water passage leading to the jacket 11) is connected to the cooling water engine 1
0 upstream.

As described above, in the present embodiment, the path of the cooling water flowing to the oil cooler 16 is switched according to the operation of the three-way valve 17, and from the downstream side of the engine 10 through the cooling water path F and from the downstream side of the engine 10 through the cooling water path G. The cooling water flows from the upstream side of the engine 10. Therefore, in the present embodiment, the cooling water passage F corresponds to the “first cooling water passage”, and the cooling water passage G corresponds to the “second cooling water passage”. Further, in the present embodiment, the three-way valve 17 is used to set the “first / second cooling water channel”.
One of the cooling water channel F and the cooling water channel G is selectively shut off. Therefore, in the present embodiment, the three-way valve 17 corresponds to the above-mentioned “shut-off means”.

Therefore, in the present embodiment, one of the cooling water downstream of the engine 10 having a relatively high temperature and the cooling water relatively low in the upstream of the engine 10 is selected.
This allows the oil to flow to the oil cooler 16. Then, depending on the operating state of the engine 10, the oil cooler 1
By switching the cooling water flowing into the cooling water 6 between the two cooling waters having different temperatures, it is possible to more efficiently adjust the temperature of the engine oil.

Next, an example of the switching control of the cooling water by the three-way valve 17 in the above-described embodiment will be described. In this example, the operation of the three-way valve 17 is appropriately controlled in accordance with the temperature of the engine oil, so that the temperature of the engine oil is efficiently adjusted. Here, the ECU 18 is provided with an oil temperature sensor 1 provided in the oil passage.
Based on the output signal of No. 9, the temperature state of the engine oil is grasped (see FIG. 1).

When the engine oil is at a low temperature, such as when the engine 10 is warmed up, the ECU 18 controls the three-way valve 17 so as to shut off the cooling water passage G and connect the oil cooler 16 to the cooling water passage F. . At this time, as shown in FIG. 2, cooling water flows from the downstream side of the engine 10, which has a higher temperature than the upstream side of the engine 10, to the oil cooler 16. Will be promoted.

Incidentally, if the engine 10 is warming up and the cooling water is not sufficiently heated, the radiator 12 is turned on by the thermostat 14 as shown in FIG.
The cooling water passage B connected to the oil pump 13
Is connected to the cooling water passage C on the suction port side and the bypass water passage E. Therefore, the cooling water is circulated around the radiator 12. When the warming-up is completed and the temperature of the cooling water is sufficiently increased, the bypass water passage E is shut off by the thermostat 14, and the cooling water passage C and the cooling water passage B are connected. Therefore, the cooling water is radiator 1
2 and the water jacket 11 are circulated.

Then, when the engine oil becomes hot,
When the need for cooling occurs, the ECU 18 controls the three-way valve 17 to shut off the cooling water passage F and connect the oil cooler 16 to the cooling water passage G. At this time, as shown in FIG. 3, the cooling water flows from the upstream side of the engine 10, which has a lower temperature than the downstream side of the engine 10, to promote cooling of the engine oil. Become so.

As described above, the cooling water flowing to the oil cooler 16 in accordance with the temperature of the engine oil is switched between the cooling water flowing on the downstream side of the engine and the cooling water flowing on the upstream side of the engine. Thus, the temperature of the engine oil can be adjusted.

According to the oil temperature adjusting device and the oil temperature adjusting method for an engine of the present embodiment described above, the following effects can be obtained. (1) In the present embodiment, the oil cooler 16 is cooled through the two cooling water passages, the cooling water passage F through which the cooling water downstream of the engine 10 flows, and the cooling water passage G through which the cooling water upstream of the engine 10 flows. The cooling water system is configured so that water flows and one of the two cooling water passages F and G is selectively shut off by the three-way valve 17. for that reason,
The cooling water flowing through the oil cooler 16 can be selectively switched between the cooling water heated by passing through the engine 10 and the cooling water before passing through the engine 10 which is lower in temperature than the cooling water. . Accordingly, the temperature of the engine oil can be more efficiently adjusted.

(2) In the present embodiment, the operation of the three-way valve 17 is controlled by the ECU 18 according to the temperature of the engine oil, so that the cooling water flowing to the oil cooler 16 is switched. Therefore, the temperature of the engine oil can be appropriately adjusted according to the temperature state of the engine oil.

(3) In this embodiment, when the engine oil is at a low temperature, the cooling water passage G is shut off by the three-way valve 17 and the cooling water passage F is connected to the oil cooler 16. Therefore, the oil cooler 16 at that time
The cooling water flows from the downstream side of the engine 10 which has a higher temperature than the upstream side of the engine 10, and the temperature rise of the engine oil is promoted.

(4) In this embodiment, when the engine oil is at a high temperature, the three-way valve 17 controls the cooling water passage F
And the cooling water passage G is connected to the oil cooler 16. Therefore, the oil cooler 16 at that time
The cooling water flows from the upstream side of the engine 10 at a lower temperature than the downstream side of the engine 10 so that the cooling of the engine oil is promoted.

If the configuration of the cooling water system described above is used, the cooling water flowing to the oil cooler 16 is appropriately switched in accordance with the operation state of the engine 10, so that the present invention is not limited to the above-described example, but may be applied to other control modes. Accordingly, the temperature of the engine oil can be efficiently adjusted. Hereinafter, other examples of control aspects related to the temperature adjustment of the engine oil will be described. In this example, the operation of the three-way valve 17 is controlled so that the temperatures of the cooling water and the engine oil when the engine 10 is warmed up are more efficiently increased.

That is, here, when the engine 10 is warmed up, in which both the cooling water and the engine oil have not been sufficiently heated, the ECU 18 connects the cooling water passage G to the oil cooler 16.
The three-way valve 17 is controlled to connect to the oil cooler 1
The cooling water is supplied to the engine 6 from the upstream side of the engine 10.

At this time, the cooling water flowing on the upstream side of the engine 10 has a lower temperature than the cooling water flowing on the downstream side of the engine 10, and the temperature difference from the engine oil is smaller. Therefore, as compared with the case where the cooling water flows from the downstream side of the engine 10, the amount of heat taken by the oil in the oil cooler 16 is suppressed, and the temperature rise of the cooling water is promoted. The temperature can be raised early by giving priority to the cooling water.

After the temperature of the cooling water is sufficiently raised, the ECU 18 controls the three-way valve 17 so as to connect the cooling water passage F to the oil cooler 16, and from the downstream side of the engine 10 to the oil cooler 16. Cooling water is allowed to flow.
At this time, the cooling water flowing on the downstream side of the engine 10 has been sufficiently heated, and has a higher temperature as it passes through the water jacket 11. Therefore, the temperature of the engine oil can be raised early.

As described above, in this case, when the engine 10 is warmed up, the cooling water is first raised at an early stage in preference to the temperature rise of the engine oil. Then, the temperature of the engine oil is raised by the sufficiently raised cooling water. As a result, both the cooling water and the engine oil can be efficiently heated.

The engine oil temperature adjusting device and oil temperature adjusting method of the present embodiment described above can be modified as follows. In the former of the two control examples described in the above embodiment, that is, in the control example in which the cooling water is switched according to the temperature of the engine oil, the oil temperature sensor 19 detects the temperature of the engine oil. However, the temperature state of the engine oil can be grasped indirectly, depending on the temperature of the cooling water and the operating state of the engine 10 such as during warm-up or after warm-up. Even if the switching control of the cooling water is performed based on the temperature of the engine oil thus grasped, the temperature of the engine oil can be efficiently adjusted.

In the above description, two control modes for switching the cooling water flowing through the oil cooler 16 are illustrated, but the control mode for switching the cooling water may be arbitrarily changed. In short, the operation of the three-way valve 17 is controlled in accordance with the operation state of the engine 10 and the like,
If the cooling water flowing through the oil cooler 16 is appropriately switched between the upstream side and the downstream side, the temperature of the engine oil can be efficiently adjusted.

In the above embodiment, the cooling water flowing to the oil cooler 16 is switched by the three-way valve 17 configured as an electromagnetic valve whose operation is controlled by the ECU 18. Even if one of the cooling water passages F and G is selectively shut off by means other than the three-way valve 17, the temperature of the engine oil can be efficiently adjusted. For example, a thermostat may be provided in place of the three-way valve 17 so that the cooling water path to be shut off can be switched according to the temperature of the cooling water. In this case, the engine oil temperature can be efficiently adjusted with a simpler configuration.

In the above embodiment, the temperature of the engine oil used for lubricating the engine 10 is adjusted by the oil cooler 16.
Even if the temperature of any oil such as transmission oil (mission oil) is adjusted by using the above, the same effects as in the above embodiment can be obtained.

The configuration of the cooling water system is not limited to the configuration described in the above embodiment, but may be appropriately changed. In short, as a cooling water passage for flowing the cooling water to the oil cooler 16, a first cooling water passage for flowing the cooling water from the downstream side of the engine 10 to the oil cooler 16, and a cooling water for the oil cooler 16 from the upstream side of the engine 10. If two cooling water passages with the flowing second cooling water passage are provided, and the cooling water system is configured to selectively shut off either of them, the oil temperature can be efficiently adjusted. .

Even if the above two cooling water passages (first and second cooling water passages) are not provided, the cooling water system is switched by means such as switching the flow direction of the cooling water in the oil cooler 16. If the cooling water flowing to the oil cooler 16 is switched between the cooling water on the upstream side of the engine 10 and the cooling water on the downstream side of the engine 10 in the same cooling water system, efficient oil temperature adjustment It can be performed.

The method and apparatus for adjusting oil temperature of an engine according to the present invention
The present invention can also be applied to a water-cooled engine having a cooling water system of an open loop structure, which is not provided with a circulation structure between the inside (water jacket 11) and the radiator 12.

[Brief description of the drawings]

FIG. 1 shows an engine 10 to which an embodiment of the present invention is applied.
FIG. 2 is a schematic diagram schematically showing a cooling water system of FIG.

FIG. 2 is an exemplary diagram showing an example of a control mode according to the embodiment;

FIG. 3 is an exemplary diagram showing an example of a control mode according to the embodiment;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Engine, 11 ... Water jacket, 12 ... Radiator, 13 ... Water pump, 14 ... Thermostat, 15 ... Heater, 16 ... Oil cooler, 17 ... Three-way valve ("cut-off means"), 18 ... Electronic control unit (ECU: "Switching control means"), 19 ... oil temperature sensors, A to G ... cooling channels (cooling channel F: "first cooling channel", cooling channel G: "second cooling channel").

Claims (7)

[Claims] 1. A method for adjusting the temperature of oil by heat exchange with cooling water flowing through a cooling water system of an engine, wherein the cooling water exchanged with oil flows downstream of the engine in the cooling water system. An oil temperature adjusting method for an engine, characterized in that switching is performed between cooling water and cooling water flowing upstream of the engine in accordance with an operation state of the engine. 2. The method according to claim 1, wherein the operating state of the engine is a temperature of the oil. 3. The engine oil temperature adjusting method according to claim 1, wherein when the engine is warmed up, the cooling water is switched to use the cooling water flowing upstream of the engine. 4. The present invention is applied to a water-cooled engine having a cooling water system passing through an engine, wherein an oil heat exchanger is disposed in the cooling water system, and heat exchange with cooling water passing through the oil heat exchanger is performed. An oil temperature adjusting device for an engine that adjusts an oil temperature by using a first cooling water passage provided so that cooling water downstream of the engine passes through the oil heat exchanger in the cooling water system; A second cooling water passage provided so that cooling water on the upstream side of the engine passes through the oil heat exchanger in a water system; and a shutoff for selectively shutting off one of the first and second cooling water passages. Means for adjusting the oil temperature of the engine. 5. The oil temperature control device for an engine according to claim 4, wherein a cooling water passage, which is cut off by said shut-off means, of said first and second cooling water passages is changed according to an operation state of said engine. An oil temperature adjusting device for an engine, further comprising switching control means for switching. 6. An oil temperature adjusting device for an engine according to claim 5, wherein said switching control means switches a cooling water passage which is shut off by said shut-off means according to a temperature of said oil. 7. The engine oil according to claim 5, wherein said switching control means switches the cooling water passage cut off by said shut-off means to said second cooling water passage when said engine is warmed up. Temperature control device.