JP4952649B2 - Engine cooling system - Google Patents

Description

  The present invention relates to an engine cooling apparatus for cooling an engine by circulating cooling water between an engine and a radiator of a vehicle.

  The engine cooling device is provided with a passage through which cooling water circulated between the engine and the radiator (radiator) flows. The thermostat starts to open when the temperature exceeds a predetermined temperature, and closes when the temperature is lower than that temperature. Is provided.

  Such an engine cooling system thermostat system (thermostat system) includes an outlet thermostat system in which the coolant engine outlet temperature is controlled to be constant and an inlet thermostat system in which the engine inlet temperature is controlled to be constant.

  In the case of gasoline passenger cars, the outlet thermostat system has been switched from the 100% outlet thermostat system to the inlet thermostat system over the past 10 years, but the outlet thermostat system is still the mainstream in diesel engines, particularly commercial vehicle diesel engines.

  The inlet thermostat system has become popular in passenger cars that place emphasis on fuel efficiency (the fuel efficiency regulations are enforced) because of the advantages that the cooling water temperature rises quickly and the engine warms up quickly, and the water temperature hunting is low.

  For example, there is an engine cooling device 61a shown in FIG. 6A as a conventional engine outlet side control method (outlet thermo method), and FIG. 6B as a conventional engine inlet side control method (inlet thermo method). There is a conventional engine cooling device 61b shown in FIG.

  The engine cooling device 61a in FIG. 6A connects the engine 62 and the radiator 63 by an upper hose 64 and a lower hose (bottom hose) 65 through which cooling water flows, and further bypasses between the upper hose 64 and the lower hose 65. A thermostat 67 is provided at a connection portion between the bypass hose 66 and the upper hose 64. A water pump 68 that pumps cooling water from the radiator 63 into the engine 62 is provided at the downstream end of the lower hose 65 (cooling water inlet portion of the engine 62).

In this engine cooling device 61a,
Advantages: Engine outlet water temperature is constant regardless of load Disadvantages: Long warm-up time and water temperature hunting.

Also, in the engine cooling device 61b of FIG. 6B, unlike the engine cooling device 61a described in FIG. 6A, a thermostat 67 is provided at the connection portion of the bypass hose 66 and the lower hose 65.
Advantages: Short warm-up time, no water temperature hunting Disadvantages: The engine outlet water temperature rises at high loads.

  The prior art document information related to the invention of this application includes the following.

Japanese Patent Laid-Open No. 5-33648 JP-A-6-33762

  In the inlet thermostat system, the temperature of the cooling water engine inlet is controlled to be constant, so the temperature rise of the cooling water corresponding to the cooling water loss from when the cooling water enters the engine until it leaves the engine is set by design. The valve opening temperature of the inlet side thermostat is set so that there is no problem in durability reliability due to overheating of the cylinder head and thermal load on the cylinder head.

  In a passenger car, since the engine load (load factor) during general driving is small, the temperature rise width of the cooling water is within a designed range, and there is no problem in the heater performance.

  However, in commercial vehicles, under full load and uphill driving conditions, the engine outlet water temperature tends to rise because it runs under a high load condition with the accelerator fully open. Therefore, in the case of the inlet thermostat method, the engine outlet water temperature becomes a temperature that is designed by design under the accelerator fully open condition, and therefore it is necessary to set the valve opening temperature of the thermostat lower.

  On the other hand, during normal driving, if the thermostat valve opening temperature is set low, the cooling water temperature does not increase, and heater performance deteriorates. In extreme cases, there is a possibility that fuel efficiency deteriorates.

  This difference in the way passenger cars and commercial vehicles are used is a major factor that prevents the introduction of the inlet thermostat system, which has many advantages, in commercial vehicles.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an engine cooling apparatus that can adopt an inlet thermostat system even in a large vehicle such as a commercial vehicle.

  In order to achieve the above object, the present invention provides a first passage through which cooling water flows from the engine to the radiator, and a second passage through which cooling water flows from the radiator to the engine. A second thermostat is provided, the first passage communicates with the first thermostat, and a first bypass passage that bypasses the flow of cooling water to the radiator, and a third thermostat is provided. A second bypass passage that bypasses the first thermostat, and a second thermostat and a third thermostat that communicate with one end and the other end of the second passage. A third bypass passage that bypasses the first thermostat, and the first thermostat is set with respect to a set temperature of the first thermostat. One set temperature of the thermostat is high, the set temperature of the said relative set temperature of the first thermostat third thermostat is a cooling device for low engine.

  In addition, a water pump that pumps cooling water from the radiator to the engine is provided at the downstream end of the second passage, and the engine outlet temperature is a design value by the water pump and the first to third thermostats. If it is within the range, the cooling water is circulated through the engine, the first passage, the radiator, and the second passage, and the cooling water is allowed to flow through the first bypass passage so that the engine outlet temperature is designed. When it becomes higher than the value, it is preferable to flow cooling water through the second bypass passage and the third bypass passage.

  The first to third thermostats may be bottom bypass type thermostats.

  According to the present invention, it is possible to adopt an inlet thermostat system even in a large vehicle such as a commercial vehicle.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic view of an engine cooling apparatus showing a preferred embodiment of the present invention.

  As shown in FIG. 1, an engine cooling device 1 according to this embodiment includes an engine 2 of a large vehicle such as a truck and other commercial vehicles, a railway vehicle, and a cooling water w flowing into the engine 2. It is provided between the radiator 3 for keeping the coolant water temperature at a predetermined temperature. The basic configuration of the engine cooling device 1 is the same as the conventional engine cooling device 61b of FIG. 6B.

  That is, the engine cooling device 1 includes a first passage (flow path) 4A that connects the engine 2 and the upper portion of the radiator 3 and the cooling water w flows from the engine 2 to the radiator 3, and the engine 2 and the radiator 3. Between the first passage 4B and the second passage 4B, and the coolant flowing into the radiator 3 is connected to the lower portion of the first passage 4B. A first bypass passage bA (bypass A) is provided that partially flows the water w through the second passage 4B and bypasses the flow of the cooling water w to the radiator 3.

  The connecting portion between the first bypass passage bA and the second passage 4B starts to open when the temperature exceeds a predetermined temperature (set temperature or valve opening temperature) Ta, and closes at a temperature lower than the temperature Ta. 1 thermostat 5A (Thermo A) is provided. A water pump (cooling water pump) 6 that pumps the cooling water w from the radiator 3 into the engine 2 is provided at the downstream end of the second passage 4B.

  The engine cooling device 1 further communicates one end (the end on the radiator side) and the other end (the end on the engine side) of the second passage 4B with the first thermostat from the radiator 3 side. A part of the cooling water w flowing into 5A flows to connect the second bypass passage bB (bypass B) bypassing the first thermostat 5A, and between the first bypass bA and the second bypass passage bB; A part of the cooling water w flowing into the first thermostat 5A from the first bypass passage bA side flows to have a third bypass passage bC (bypass C) that bypasses the first thermostat 5A.

  A connecting portion between the first bypass passage bA and the third bypass passage bC has a second thermostat 5B (ThermoB) that starts to open when the temperature exceeds a predetermined temperature Tb and closes at a temperature lower than the temperature Tb. Provided. A connection portion between the second bypass passage bB and the third bypass passage bC has a third thermostat 5C (ThermoC) that starts to open when the temperature exceeds a predetermined temperature Tc and closes at a temperature lower than the temperature Tc. Provided.

  In the present embodiment, an upper hose through which the cooling water w heated by the engine 2 flows is used as the first passage 4A, and a lower hose through which the cooling water w cooled by the radiator 3 flows as the second passage 4B. A bypass hose was used.

  A bottom bypass thermostat is used for each of the first to third thermostats 5A to 5C. The bottom bypass type thermostat is accommodated in the valve housing 7. The valve housing 7 is formed with three ports to which the inlet end or outlet end of any of the passages described above is connected. The three ports include an up port up, a bottom port bp formed opposite to the up port up, and a side port sp formed on the side of the bottom port bp.

  The thermostat is provided with a needle in the center, and an up valve that opens and closes the up port up and a bottom valve that opens and closes the bottom port bp are provided above and below, and a thermostat temperature sensing part (wax pellet) is accommodated between these valves. And a coil spring that urges the bottom valve in the valve closing direction is provided around the case.

  In the bottom bypass type thermostat, below the predetermined temperature, the side port sp and the bottom port bp are always open, the up port up is closed, and the cooling water w flows from the side port sp to the bottom port bp (state X). Also, in the bottom bypass type thermostat, when the temperature reaches a predetermined temperature, the wax pellet whose temperature is the melting point melts and thermally expands, and when the needle is pushed down, the up valve starts to open and the bottom valve closes. At the same time, the cooling water w flows from the side port sp to the bottom port bp and the cooling water w flows from the side port sp to the bottom port bp (state Y). Further, in the bottom bypass type thermostat, when the fully open temperature is reached, the up valve is fully opened, the bottom valve is fully closed, and the cooling water w flows from the side port sp to the up port up (state Z).

  In the following description, state X is the thermostat fully closed state (Close), state Y is the thermostat valve open state (Open), and state Z is the thermostat fully open state. The thermo-characteristic of this bottom bypass type thermostat is general as shown in FIG.

  Returning to FIG. 1, in more detail, in the first thermostat 5A, the upstream end of the second passage 4B is connected to the up port up, and the downstream end of the second passage 4B is connected to the bottom port bp. The inlet end is connected, and the outlet end on the downstream side of the first bypass passage bA is connected to the side port sp.

  In the second thermostat 5B, an outlet end on the upstream side of the first bypass passage bA is connected to the side port sp, an inlet end on the downstream side of the first bypass passage bA is connected to the bottom port bp, and the up port up Is connected to the inlet end of the third bypass passage bC.

  In the third thermostat 5C, the upstream end of the second bypass passage bB is connected to the up port up, the downstream end of the second bypass passage bB is connected to the bottom port bp, and the side port sp Is connected to the outlet end of the third bypass passage bC.

  Therefore, in the engine cooling apparatus 1, the first thermostat 5B and the first thermostat 5A communicate with each other by the second thermostat 5B and the first bypass path bA, and the third thermostat 5B and the second bypass path bB. Thus, one end and the other end of the second passage 4B communicate with each other, and the second thermostat 5B and the third thermostat 5C communicate with each other through the third bypass passage bC.

  In addition, as the first thermostat 5A and the second thermostat 5B, a jiggle valve for extracting air mixed in when the cooling water w flows in or a general bottom bypass thermostat having a leak hole is used. As the second thermostat 5B, in order to maintain a complete valve closing state until the valve opening temperature reaches Tb, a general bottom bypass thermostat having no jiggle valve or a leak hole is used.

  In the engine cooling device 1, the set temperature Tb of the second thermostat 5B is higher than the set temperature Ta of the first thermostat 5A, while the set temperature of the third thermostat 5C is set with respect to the set temperature Ta of the first thermostat 5A. Although Tc is low and changes depending on the engine required water temperature characteristic, Tc <Ta <Tb regardless of the displacement of the engine 2.

  In the present embodiment, as will be described later, the difference between the engine outlet temperature and the engine inlet temperature (engine thermal load) ΔT is about 10 ° C. during general traveling, and the engine thermal load ΔT is about 20 under high load conditions. Since it is necessary to further cool the engine 2 under high load conditions at T.degree. C., Tc was set at 60.degree. C., Ta was set at 80.degree. C., and Tb was set at 100.degree. The cooling capacity of the radiator 3 is such that at least 100 ° C. cooling water w flowing into the radiator 3 is set to 60 ° C. or less and flows out of the radiator 3.

  Next, the operation of this embodiment will be described together with the operation of the engine cooling device 1 with reference to FIGS. However, in FIG. 2A and FIG. 2B, the second passage 4B and the bypass passages A to C are shown as simplified examples in order to make the passage through which the cooling water w flows easier to understand.

The set temperatures of the thermostats 5A to 5C need to satisfy the relationship of Tc <Ta <Tb. In order to facilitate the explanation of the functions, the engine thermal load ΔT, the set temperatures of the thermostats 5A to 5C, Engine inlet water temperature and engine outlet design water temperature are as follows: General travel: ΔT = 10 ° C, high load travel: ΔT = 20 ° C
Each thermostat set temperature: Ta = 80 ° C., Tb = 100 ° C., Tc = 60 ° C.
Engine inlet water temperature during general driving = 80 ° C
Engine outlet design water temperature = 90 ° C
Assume that

(1) When the engine outlet design water temperature is within the design value (during general travel) (FIG. 2 (a))
In this case, the operation of the engine cooling device 1 is basically the same as the operation of the conventional engine cooling device 61b described with reference to FIG.

  That is, when the engine outlet temperature is less than 80 ° C., when the engine 2 is operated, the water pump 6 is driven by the power. The cooling water w of 80 ° C. does not operate when Thermo B is Tb = 100 ° C. and Thermo A is fully closed, and flows into Thermo A through the engine 2, the first passage 4 A and the bypass A. Thereby, the cooling water w flows into the engine 2 again through the engine 2, the first passage 4 </ b> A, the bypass A, and ThermoA.

  Further, when the engine outlet temperature is from 80 ° C. to the engine outlet design water temperature of 90 ° C., Thermo A is Ta = 80 ° C., so the valve is opened by the cooling water w at 90 ° C. When ThermoA is opened, the low-temperature cooling water w from the radiator 3 flows into ThermoA and is mixed with the 90 ° C cooling water w from the bypass A, so that the temperature of the thermostat temperature sensing part of ThermoA is lower than 90 ° C. Become. Since Thermo B is fully closed, Thermo C remains fully closed, and the cooling water w from Thermo B does not flow into Thermo C.

  At this time, when the temperature of the mixed cooling water w is higher than the valve opening temperature of Thermo A, Thermo A maintains the valve lift amount to further lower the cooling water temperature, and the water temperature of the cooling water w flowing into the water pump 6 Is saturated to 80 ° C., the valve opening temperature of Thermo A.

  As a result, the cooling water w mainly flows into the engine 2 again through the engine 2, the first passage 4A, the radiator 3, the second passage 4B, and ThermoA and circulates, and the engine 2 and the first passage 4A. , It again flows into the engine 2 through the bypass A and Thermo A. Accordingly, the cooling water w does not flow through the bypasses B and C.

  (2) When the engine outlet water temperature is higher than the design value (high load condition) (FIG. 2 (b)) As shown in FIG. 2 (b), the engine cooling device 1 is in the state (1). When the engine 2 is operated continuously under a high load condition, in particular, the cooling water temperature rise ΔT in the engine 2 increases from 10 ° C. to 20 ° C. in FIG. As an example, the temperature rises to 100 ° C.

  At this time, Thermo B installed in the bypass A is opened, and 100 ° C. cooling water w flows from the bypass A to the bypass C, and 100 ° C. cooling water w is supplied to Thermo C. Furthermore, ThermoC is Tc = 60 ° C., so it is opened by 100 ° C. cooling water w. When ThermoC opens, low-temperature cooling water w from the radiator 3 flows into ThermoC.

  Since ThermoC is set to Tc = 60 ° C., the outlet temperature of ThermoC is controlled to 60 ° C. In addition, since the engine inlet temperature (water pump inlet temperature) is Thermo A, the 80 ° C. cooling water w from Thermo A and the 60 ° C. cooling water w from Thermo C are in the second passage 4B and bypass C. Are joined and mixed, and the temperature drops to 70 ° C.

  As a result, ΔT = 20 ° C. is absorbed by the cooling device 1 of the engine, and the engine outlet temperature does not exceed the designed value of 90 ° C.

  Thus, in the engine cooling device 1, the engine inlet water temperature during general traveling is controlled to 80 ° C. (thermal load ΔT = 10 ° C.), and 70 ° C. (thermal load ΔT = 20 ° C.) under high load conditions. The outlet water temperature does not last even if a state exceeding the design value of 90 ° C. occurs during general driving and high load conditions.

  In addition to the configuration of the engine cooling device 61b described in FIG. 6B, the engine cooling device 1 forms a third bypass passage bC by connecting the second thermostat 5B to the first bypass passage bA. A second bypass passage bB that bypasses the first thermostat 5A is formed in the second passage 4B, and a third thermostat is connected to the second bypass passage bB.

  Furthermore, in the engine cooling device 1, since the set temperatures of the thermostats 5A to 5C are set to Tc <Ta <Tb, the route (the first thermostat 5A) indicated by the large arrow in FIG. And a route passing through the first bypass passage bA), and in a high load condition such as full loading of the vehicle and traveling uphill, the route indicated by a large arrow in FIG. 2B (a route passing through all thermostats). Let

  That is, the engine cooling device 1 has a path that functions during normal driving of the vehicle, and a path for controlling the water pump inlet water temperature to a temperature lower than the set temperature Ta of the first thermostat 5A under the high load condition described above. The water pump inlet water temperature can be set in two stages according to the heat load condition of the engine 2, which is a so-called engine cooling water temperature two-stage setting type thermostat device (inlet thermostat device).

  The engine cooling device 1 maintains the design set temperature of the cooling water w during normal travel of a large vehicle, and opens the second thermostat 5B when the cooling water temperature rises when the engine is heavily loaded. By using this as a switch of the third thermostat 5C, the two paths described above are appropriately switched so as to further reduce the temperature of the cooling water w.

  Therefore, according to the engine cooling device 1, even in a large vehicle such as a commercial vehicle, the inlet thermostat method can be adopted as the engine cooling system thermostat method, the engine warm-up performance can be improved, and the practical fuel consumption can be improved. Can be improved.

  Here, the reason why the engine warm-up time is short in the engine inlet system will be briefly described.

  In the engine outlet method, a jiggle valve or leak hole is provided in the thermostat in order to remove air mixed in when cooling water is injected, and even if the thermostat is not open when the engine is started, the air is passed through the jiggle valve or leak hole. It is configured to release air from the radiator to the radiator. With engine cooling water, the water temperature rises and the pressure rises as the engine starts, but with the engine outlet system, cooling water flows out from this jiggle valve to the radiator side, and the cooling water that is cold by that amount. It will flow into the engine.

  On the other hand, in the engine inlet method, a thermostat with a jiggle valve is also installed in front of the water pump. Due to the suction negative pressure of the water pump, the jiggle valve works in the closing direction, and cold cooling water flows from the jiggle valve. Never do. As a result, the engine warm-up time is short in the engine inlet system.

  In addition, since the engine cooling device 1 can adopt the inlet thermostat method even in a large vehicle, it can prevent hunting of the coolant temperature of the engine cooling water during traveling, and engine control (fuel injection amount, EGR (exhaust gas recirculation)) The fluctuation of the control etc.) can also be prevented, and the practical fuel consumption can be improved from this point.

  Here, the reason why there is no water temperature hunting in the engine inlet system will be briefly described.

  When the engine warm-up is finished and the thermostat is opened, in the engine outlet system, the cold cooling water from the radiator flows into the engine as it is, and goes around the engine and reaches the thermostat. At this time, since the thermostat starts to close for the first time, the water temperature decreases due to a response delay, and this repetition continues for several cycles.

  On the other hand, in the engine inlet method, even if the cold water from the radiator reaches the inlet thermostat, it merges with the warm water from the bypass passage, and the cooling water at the thermostat set temperature flows into the engine, so water temperature hunting does not occur .

  Further, the engine cooling device 1 has an advantage that the system can be simplified by mechanically controlling the path through which the cooling water w flows using only the existing thermostat and hose.

  In order to operate the engine cooling device 1, the water temperature of the cooling water w flowing into the third thermostat 5C needs to be equal to or lower than the valve opening temperature of the third thermostat 5C (60 ° C. in the above example).

  Further, as the cooling water temperature flowing into the third thermostat 5C becomes closer to the valve opening temperature of the third thermostat 5C (there is no sufficient cooling capacity), the diameter of each passage through which the cooling water w flows (outside the hose) It is necessary to change the (diameter) ratio. Since the engine cooling system is established by the balance between engine heat generation and radiator heat dissipation, the actual setting specifications vary depending on the capacity margin.

  Furthermore, the outer diameter of the hose is based on the premise that an engine cooling system is established (a cooling system that does not overheat), but there is no particular restriction on the diameter of the passage through which the cooling water w flows. Generally, the upper hose diameter and the bottom hose diameter of the radiator are about 2.5 times the diameter of the bypass hose at the maximum, so that it is established within the range of such a hose outer diameter ratio.

  Considering the above points, a more detailed example of the engine cooling device 1 will be described as an embodiment.

(1) Prerequisites Maximum cooling capacity of the radiator system: The maximum cooling capacity of the radiator system (radiator + cooling fan or electric fan) satisfies the engine cooling limit performance in the conventional system described in FIG. It is premised on not to overheat (engine inlet water temperature 95 ° C. or higher). Therefore, the engine cooling device 1 is obtained by adding a device capable of setting the water pump inlet temperature in two stages to the conventional system of FIG. 6B. Secured.

(2) Setting of thermostat set temperature and cooling water flow path area In order to establish a two-stage setting of the water pump inlet temperature, i) setting order of thermostat valve opening temperature, ii) area of each cooling water flow path is important . Since i) has been described above, ii) will be described.

  4 and Table 1 show an example of the flow area of each passage corresponding to the outer diameter φ of the hose used in each passage in a large vehicle having an engine 2 displacement of 3 to 10 L class. In order to adapt the engine cooling device 1 to the engine 2 having a different displacement, the prescribed values of the displacement of the engine 2 and the flow passage area corresponding to φ of the hose are equivalent to φ of the displacement 3L and 10L shown in FIG. X and Y were connected by a straight line and defined to be ± 30% corresponding to the area.

  FIG. 5 shows an engine cooling device 51 in consideration of i) and ii) for a large vehicle having an engine displacement of 3 L class. It has been confirmed that the above-described effects can be obtained by the engine cooling device 51.

It is the schematic of the cooling device of the engine which shows suitable embodiment of this invention. 2A is a schematic diagram for explaining the operation when the engine outlet temperature is within the design value in the engine cooling device shown in FIG. 1, and FIG. 2B is a diagram illustrating the engine outlet temperature from the design value. It is the schematic explaining the operation | movement when it becomes high. It is a figure which shows the thermo characteristic of each thermostat used with the cooling device of the engine shown in FIG. It is a figure which shows the relationship between the flow area of each channel | path used for the setting of the cooling water flow path area of the cooling device of the engine shown in FIG. It is the schematic which shows an example of the cooling device of the engine set based on FIG. FIG. 6A is a schematic diagram of a conventional engine cooling apparatus using an outlet thermostat system, and FIG. 6B is a schematic diagram of a conventional engine cooling apparatus using an inlet thermostat system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine cooling device 2 Engine 3 Radiator 4A 1st channel | path 4B 2nd channel | path 4C 3rd channel | path 5A 1st thermostat 5B 2nd thermostat 5C 3rd thermostat Ta 1st thermostat setting temperature Tb 2nd Set temperature Tc of the third thermostat set temperature of the third thermostat

Claims (3)

A first passage through which cooling water flows from the engine to the radiator;
A first thermostat, a second passage through which cooling water flows from the radiator to the engine;
A second thermostat is provided, and communicates the first passage with the first thermostat, and a first bypass passage that bypasses the flow of cooling water to the radiator;
A third thermostat is provided, communicates one end and the other end of the second passage, and bypasses the first thermostat; a second bypass passage;
The second thermostat and the third thermostat communicate with each other, and a third bypass passage that bypasses the first thermostat,
The engine cooling is characterized in that the set temperature of the second thermostat is higher than the set temperature of the first thermostat, whereas the set temperature of the third thermostat is lower than the set temperature of the first thermostat. apparatus. A water pump that pumps cooling water from the radiator to the engine is provided at the downstream end of the second passage, and the engine outlet temperature is within a design value by the water pump and the first to third thermostats. In some cases, cooling water is circulated through the engine, the first passage, the radiator, and the second passage, and the cooling water is allowed to flow through the first bypass passage.
The engine cooling device according to claim 1, wherein when the engine outlet temperature becomes higher than a design value, cooling water is further allowed to flow through the second bypass passage and the third bypass passage.   The engine cooling apparatus according to claim 1 or 2, wherein the first to third thermostats are bottom bypass type thermostats.

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