Variable flow rate pump

A water pump (30) includes an impeller chamber (32) formed in a housing (31), a swirl chamber (40) formed in the housing (31) to communicate with a coolant passage (8) and the impeller chamber (32), and an impeller (33) that is supported to be free to rotate in the impeller chamber (32) and rotates in conjunction with an engine (2) so as to take in a coolant and discharge the coolant into the coolant passage (8) via the swirl chamber (40). The swirl chamber (40) is formed to be divided into a first swirl chamber (41) that communicates with the coolant passage (8) at all times, and a second swirl chamber (42) and a third swirl chamber (43) respectively connected to the coolant passage (8) via thermostats (S1, S2) respectively having switch valves that can be opened and closed. The thermostats (S1, S2) are operated to open and close, thereby connecting and cutting off the swirl chambers (42, 43) and the coolant passage (8), in accordance with a temperature of the coolant.

TECHNICAL FIELD

The present invention relates to a variable flow rate pump represented by a water pump or the like, for example, that circulates a coolant through an engine.

TECHNICAL BACKGROUND

A water pump is used conventionally in a cooling device for a water-cooled engine installed in a vehicle or the like, and a cooling performance of the engine is closely related to a flow rate of a coolant circulated by the water pump. This type of cooling device is constituted by a coolant passage including a water jacket, which is provided in an engine main body, and a radiator, a thermostat, the aforesaid water pump, and so on, which are connected to the coolant passage. In this type of cooling device, the water pump is operated when the engine is driven to circulate the coolant through the coolant passage. As the coolant flows through the water jacket, heat exchange is performed with an engine main body, and as a result, the engine is cooled (see Patent Document 1, for example).

PRIOR ARTS LIST

Patent Document

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

Incidentally, in an engine cooling device, the engine must be cooled when warm using the coolant circulated by the water pump in order to suppress burning, friction, and so on in the engine. During engine startup from a cold condition, on the other hand, the engine must be warmed quickly from the cold condition, in which thermal efficiency is poor. In a conventional water pump that operates in conjunction with driving of the engine, when a pump rotation speed is maintained at a fixed speed at this time, the coolant is discharged at a fixed flow rate corresponding to a volume of a pump swirl chamber or the like, regardless of a temperature of the circulating coolant. Therefore, during an engine warm-up operation, a discharge flow rate of the water pump increases gradually as the pump rotation speed of the water pump rises in conjunction with the engine such that when the pump rotation speed is maintained at a fixed speed thereafter, the coolant supplied to the engine is likewise discharged at a fixed flow rate (a maximum flow rate) corresponding to a pump capacity, regardless of variation in the temperature of the coolant. As a result, the engine may be cooled, leading to friction and so on in the engine interior and an increase in an amount of CO2discharged in exhaust gas due to a reduction in thermal efficiency.

The present invention has been designed in consideration of this problem, and an object thereof is to provide a variable flow rate pump with which an improvement in a warm-up performance of an engine can be achieved.

Means to Solve the Problems

To solve the problem described above, a variable flow rate pump (a water pump30according to an embodiment, for example) according to the present invention is provided in a coolant circulation passage to take in a coolant from a suction passage (a coolant passage7according to an embodiment, for example) of the circulation passage and supply the coolant to a discharge passage (a coolant passage8according to an embodiment, for example), and includes: a housing; an impeller chamber formed in the housing to communicate with the suction passage; a swirl chamber formed in the housing to communicate with the discharge passage and the impeller chamber; an impeller supported to be free to rotate in the impeller chamber so as to take in the coolant from the suction passage and discharge the coolant into the discharge passage via the swirl chamber while rotating; and driving means (an engine2according to an embodiment, for example) for rotating the impeller. The swirl chamber is formed to be divided into a main swirl chamber (a first swirl chamber41according to an embodiment, for example) that communicates with the discharge passage at all times and a secondary swirl chamber (a second swirl chamber42according to an embodiment, for example) that is connected to the discharge passage via a thermostat having a switch valve that can be opened and closed. The thermostat is operated to open and close, thereby connecting and cutting off the secondary swirl chamber and the discharge passage, in accordance with a temperature of coolant delivered from the secondary swirl chamber.

In the variable flow rate pump configured as described above, the secondary swirl chamber is preferably further divided to form a plurality of divided swirl chambers (the second swirl chamber42and a third swirl chamber43according to an embodiment, for example), a plurality of thermostats respectively having switch valves that can be opened and closed to connect and cut off the plurality of divided swirl chambers and the discharge passage in accordance with the temperature of the coolant are preferably disposed between the plurality of divided swirl chambers and the discharge passage, and sensitive temperatures of the plurality of thermostats for connecting and cutting off the plurality of divided swirl chambers and the discharge passage are preferably set at respectively different temperatures.

Further, a volume of the main swirl chamber is preferably formed to be smaller than a volume of each of the divided swirl chambers.

Advantageous Effects of the Invention

With the variable flow rate pump according to the present invention, when the engine is started from a cold condition, coolant is supplied to the engine at a small flow rate only from the main swirl chamber that communicates with the engine at all times, and therefore warm-up of the engine can be promoted while suppressing a thermal load such that the engine can be warmed quickly. When the engine is warm, on the other hand, the thermostat connects the secondary swirl chamber and the discharge passage by a valve opening corresponding to the temperature of the circulating coolant such that coolant is supplied to the engine from the secondary swirl chamber in addition to the coolant from the constantly communicative main swirl chamber. As a result, a sufficient engine cooling effect can be exhibited by the coolant having the increased flow rate, leading to a reduction in friction in the engine interior and a corresponding improvement in fuel efficiency. Moreover, an improvement in the thermal efficiency of the engine can be achieved, enabling a reduction in the amount of CO2discharged from the engine in the exhaust gas.

In the inventions described above, by further dividing the secondary swirl chamber into the plurality of divided swirl chambers and setting the sensitive temperatures of the plurality of thermostats for connecting and cutting off the plurality of divided swirl chambers and the discharge passage at respectively different temperatures, a pump discharge flow rate can be controlled more finely in response to variation in the temperature of the coolant. Further, by adjusting the discharge flow rate in steps in accordance with variation in the temperature of the coolant, coolant discharge at a flow rate exceeding a required flow rate of the engine can be prevented. As a result, a workload of the water pump can be prevented from becoming excessive, and energy loss can be reduced.

Furthermore, in the inventions described above, by forming the volume of the main swirl chamber to be smaller than the volume of the divided swirl chambers, the coolant can be supplied to the engine at a small flow rate when the engine is started from a cold condition, and therefore an engine warm-up time can be reduced even further. When the engine is warm, on the other hand, the coolant can be supplied to the engine at a larger flow rate, and therefore the engine cooling effect can be improved even further such that overheating and the like can be prevented.

DESCRIPTION OF THE EMBODIMENTS

A preferred embodiment of the present invention will be described below with reference to the drawings. In this embodiment, a variable flow rate pump is disposed on a coolant circulation path of an engine, but before describing the variable flow rate pump according to this embodiment, an engine cooling device to which the variable flow rate pump is applied will be described usingFIG. 1.

An engine cooling device1is constituted mainly by an engine2formed from a water-cooled internal combustion engine, a radiator10for cooling a coolant serving as an engine cooling medium when the coolant is discharged from the engine2, a thermostat20for controlling circulation of the coolant in accordance with a temperature of the coolant, and a variable flow rate pump (to be referred to in the following description as a “water pump”)30for forcibly circulating the coolant. The engine cooling device1cools the engine2by circulating the coolant through coolant passages5(5a,5b),6,7,8connecting the components described above. Note that inFIG. 1, a flow of the coolant flowing through the coolant passages5to8is indicated by solid line arrows.

The engine2is a water-cooled gasoline engine, for example, and a water jacket (not shown) is provided in the interior thereof as a space formed to cover a cylinder (not shown). The coolant is caused to flow into the water jacket through a coolant introduction port3, performs heat exchange with the cylinder and so on while passing through the water jacket, and is then discharged from a coolant discharge port4.

The radiator10is connected to the coolant discharge port4of the engine2via the coolant passage5(5a), and is configured to cool the coolant passing through the interior thereof by blowing air from an electric fan, not shown in the drawing, such that heat is released to the outside. Hence, a temperature of the coolant, which was raised in the water jacket of the engine2, is lowered by heat radiation as the coolant passes through the radiator10.

The thermostat20is connected to the radiator10via the coolant passage6and connected to the coolant passage5b, which is formed as a bypass passage that bifurcates from the coolant passage5so as to bypass the radiator10. The thermostat20is constituted by a coolant-sensitive switch valve that opens and closes in accordance with the temperature of the coolant. Accordingly, when the temperature of the coolant is equal to or lower than a predetermined temperature, the coolant passage (the bypass passage)5bcommunicates with the coolant passage7, and when the temperature of the coolant exceeds the predetermined temperature, the coolant passage6communicates with the coolant passage7.

The water pump30is connected to the thermostat20via the coolant passage7, and a pump rotary shaft thereof is drive-coupled to a crankshaft (not shown) of the engine2via a pulley, a belt, and so on. Thus, the water pump30operates in conjunction with driving of the engine2. The coolant passage8is connected to a discharge port of the water pump30such that the coolant discharged from the water pump30is supplied to the water jacket from the coolant introduction port3of the engine2through the coolant passage8.

In the engine cooling device thus configured, the coolant discharged from the water pump30flows into the water jacket formed in the interior of the engine2, cools the engine2, and is then discharged to the outside. The discharged coolant is either cooled by the radiator10or caused to flow into the thermostat20via the bypass passage5bwithout passing through the radiator10, and then returned to the water pump30to be circulated.

In the engine cooling device1described above, the engine2must be cooled when warm to suppress burning, friction, and so on in the engine2. When the engine2is started up from a cold condition, on the other hand, the engine2must be warmed quickly from the cold condition, in which thermal efficiency is poor. In a conventional water pump, however, a discharge flow rate increases as a pump rotation speed rises, and when the pump rotation speed is maintained at a fixed speed, the coolant is discharged at a fixed flow rate corresponding to a volume of a swirl chamber or the like, regardless of variation in the temperature of the coolant. Therefore, when an engine rotation speed increases during a warm-up operation in the engine2, the rotation speed of the pump rotary shaft (an impeller) of the water pump30, which operates in conjunction with the engine2via the crankshaft and so on, also increases, leading to an increase in the flow rate of the coolant supplied to the engine2. When the pump rotation speed is maintained at a fixed speed, the coolant supplied to the engine is discharged at a fixed flow rate (a maximum flow rate) corresponding to a pump capacity, regardless of variation in the temperature of the coolant, and as a result, the engine2is cooled, thereby impairing the warm-up operation.

Hence, in the water pump30according to this embodiment, the discharge flow rate of the coolant supplied to the engine2is controlled variably in accordance with the temperature of the circulating coolant. The constitution of the water pump30will now be described with additional reference toFIGS. 2 and 3. Note thatFIG. 2is a sectional view showing the main parts of the water pump30, andFIG. 3is a pattern diagram showing operation conditions of the water pump30corresponding to variation in the temperature of the coolant.

As shown inFIG. 2, the water pump30is mainly constituted by an impeller chamber32formed in a housing31, a swirl chamber40formed in the housing31on an outer peripheral side of the impeller chamber32and divided into three chambers, and an impeller33attached to the impeller chamber32to be free to rotate.

The impeller33includes a base plate portion34formed in an annular plate shape, and a plurality of vanes35formed to project at equal intervals on one side face of the base plate portion34, and is configured to be capable of rotating in a rotation direction F (a clockwise direction) about a pump rotary shaft36, which is drive-coupled to the crankshaft (not shown) of the engine2via a pulley, a belt, and so on.

A suction passage (not shown) that communicates with the coolant passage7is connected to a central portion of the impeller chamber32, and the impeller chamber32receives a centrifugal force generated when the impeller33rotates such that the coolant flowing through the coolant passage7is suctioned therein through the suction passage.

The swirl chamber40is constituted by three swirl chambers, namely a first swirl chamber41, a second swirl chamber42, and a third swirl chamber43, which are disposed at intervals in a circumferential direction on the outer peripheral side of the impeller chamber32. In other words, rather than being formed in an integral ring shape around the entire circumference of the outer peripheral side of the impeller chamber32, as in the related art, the swirl chamber40is divided into three chambers on the outer peripheral side of the impeller chamber32in the circumferential direction in respective ranges of angles θ1, θ2, θ3.

The first swirl chamber41opens onto the outer peripheral side of the impeller chamber32on an inner peripheral side thereof such that coolant delivered outwardly in a radial direction from the impeller33can flow therein over a circumferential direction range of the angle θ1, and a first discharge port51serving as an outlet for the inflowing coolant is provided in a terminal end portion thereof so as to communicate with the coolant passage8at all times. Hence, the coolant that is delivered into the first swirl chamber41is discharged from the first discharge port51of the first swirl chamber41constantly as the impeller33rotates.

The second swirl chamber42opens onto the outer peripheral side of the impeller chamber32on an inner peripheral side thereof such that the coolant delivered outwardly in the radial direction from the impeller33can flow therein over a circumferential direction range of the angle θ2(θ2>θ1), and a second discharge port52serving as an outlet for the inflowing coolant is provided in a terminal end portion thereof so as to communicate with the coolant passage8.

Further, a thermostat S1that connects and cuts off the second discharge port52and the coolant passage8is connected between the second discharge port52and the coolant passage8. The thermostat S1is constituted by a coolant-sensitive switch valve that opens and closes in accordance with the temperature of the coolant discharged from the second discharge port52. When the temperature of the coolant is equal to or lower than a predetermined first temperature T1(60° C., for example), the thermostat S1closes, thereby completely cutting off the second discharge port52from the coolant passage8, and when the coolant temperature exceeds the first temperature T1, the thermostat S1begins to open such that the second discharge port52communicates with the coolant passage8and the coolant introduced into the second swirl chamber41is discharged from the second discharge port52at a flow rate corresponding to a valve opening. When the temperature of the coolant reaches a predetermined second temperature T2(70° C., for example), the thermostat S1enters a fully open condition.

The third swirl chamber43opens onto the outer peripheral side of the impeller chamber32on an inner peripheral side thereof such that the coolant delivered outwardly in the radial direction from the impeller33can flow therein over a circumferential direction range of the angle θ3(θ3>θ1), and a third discharge port53serving as an outlet for the inflowing coolant is provided in a terminal end portion thereof so as to communicate with the coolant passage8.

Further, a thermostat S2that connects and cuts off the third discharge port53and the coolant passage8is connected between the third discharge port53and the coolant passage8. The thermostat S2is constituted by a coolant-sensitive switch valve that opens and closes in accordance with the temperature of the coolant discharged from the third discharge port53. When the temperature of the coolant is equal to or lower than a predetermined third temperature T3(75° C., for example), the thermostat S2closes, thereby completely cutting off the third discharge port53from the coolant passage8, and when the coolant temperature exceeds the third temperature T3, the thermostat S2begins to open such that the third discharge port53communicates with the coolant passage8and the coolant introduced into the third swirl chamber43is discharged from the third discharge port53at a flow rate corresponding to the valve opening. When the temperature of the coolant reaches a predetermined fourth temperature T4(85° C., for example), the thermostat S2enters a fully open condition, and at this point, the flow rate of the coolant discharged from the respective discharge ports51,52,53of the water pump30reaches a maximum.

The water pump30configured as described above introduces the coolant delivered into the respective swirl chambers41,42,43by the centrifugal force generated when the impeller33rotates into the engine2at a discharge flow rate corresponding to the temperature of the coolant. In other words, the water pump30varies a volume by which the swirl chamber communicates with the coolant passage8by switching between a condition in which the coolant passage8communicates with the first swirl chamber41, a condition in which the coolant passage8communicates with the first and second swirl chambers41,42, and a condition in which the coolant passage8communicates with the respective swirl chambers41,42,43in accordance with the temperature of the coolant at a fixed pump rotation speed. Thus, the water pump30variably controls the discharge flow rate of the coolant supplied to the engine2.

Next, an operation of the water pump30having the above constitution will be described with additional reference toFIG. 4.FIG. 4is a graph comparing the water pump30according to this embodiment with a conventional water pump (a normal pump) in terms of a relationship of the coolant temperature to the pump discharge flow rate and a pump workload (a consumed horsepower) at a fixed pump rotation speed (2000 rpm). Note that in the drawing, solid lines indicate the discharge flow rate relative to the coolant temperature, while dotted lines indicate the consumed horsepower relative to the coolant temperature. Further, here, the fourth temperature T4(85° C.) is set as an appropriate cooling temperature of the engine2.

When the pump rotation speed is maintained at the fixed speed (2000 rpm) in the conventional water pump at this time, the discharge flow rate and the workload are held at fixed levels at all times, regardless of variation in the temperature of the coolant. As a result, the warm-up performed while the engine is cold, as described above, is impaired, and even when an engine load is small such that a heat balance is maintained, the coolant may be supplied at a greater flow rate than necessary such that an excessive workload (engine driving force) is used. In the water pump30, on the other hand, as shown inFIG. 4, the discharge flow rate and the workload are adjusted in accordance with variation in the temperature of the coolant, even when the pump rotation speed is maintained at the fixed speed (2000 rpm). This operation will now be described more specifically.

When the engine2is started in a vehicle, for example, the impeller33of the water pump30rotates in the rotation direction F (the clockwise direction) about the pump rotary shaft36drive-coupled to the crankshaft (not shown) of the engine2via a pulley, a belt, and so on. When the engine2is started up from a cold condition at this time, the coolant temperature is low, and therefore the thermostats S1, S2are both closed, as shown inFIG. 3A, such that only the first discharge port51communicates with the coolant passage8for introducing the coolant into the engine2while the second and third discharge ports52,53are cut off from the coolant passage8. Accordingly, the coolant that is suctioned into the impeller chamber32from the suction passage by the centrifugal force generated as the impeller33rotates is delivered into the respective swirl chambers41,42,43by the impeller33, whereupon only the coolant delivered into the first swirl chamber41is discharged through the first discharge port51at a flow rate corresponding to the volume of the swirl chamber and supplied to the engine2through the coolant passage8.

Hence, when the engine2is started up from a cold condition, coolant is supplied to the engine2at a small flow rate only from the first swirl chamber41having a small volume, and therefore an engine cooling effect is suppressed (warm-up of the engine2is promoted). Hence, in comparison with a conventional water pump configured such that coolant is discharged from a swirl chamber formed integrally around the entire outer periphery (360°) of the impeller chamber in an amount corresponding to the volume of the swirl chamber, a warm-up time of the engine2can be reduced, enabling quick warm-up, under an identical pump rotation speed (engine rotation speed) condition.

As warm-up of the engine2progresses in this condition, the flow rate at which the coolant is supplied to the engine2may become insufficient, causing a partial temperature increase in the engine2, and as a result, burning or an increase in friction may occur. Therefore, at a prior stage (T1to T2: 60° C. to 70° C.) before the coolant rises to the appropriate coolant temperature (T4: 85° C.) for the engine2, coolant is supplied to the engine2from the second swirl chamber42in addition to the coolant from the first swirl chamber41. More specifically, when the engine2is driven such that the temperature of the coolant circulating through the coolant passage increases gradually so as to exceed the predetermined first temperature T1(60° C.), the thermostat S1begins to open, as shown inFIG. 3B, whereby the second discharge port52communicates with the coolant passage8. As the temperature of the coolant transitions from the first temperature T1(60° C.) to the second temperature T2(70° C.), the valve opening of the thermostat S1increases substantially proportionately with the coolant temperature, leading to an increase in the flow rate of the coolant from the second swirl chamber42. As a result, the coolant from the second discharge port52, the flow rate of which increases in accordance with the valve opening of the thermostat S1, and the coolant that is discharged from the first discharge port51at all times at a fixed flow rate are delivered into the coolant passage8and supplied to the engine2. In an environment where a heat balance is maintained in the engine2at the flow rate of the coolant from the first swirl chamber41and the second swirl chamber42(i.e. below a maximum capacity of the water pump30), for example, the engine2can be cooled efficiently using a smaller pump workload than that of the related art.

When a heat balance is not maintained in the engine2and the temperature of the coolant rises further so as to exceed the third temperature T3(75° C.), on the other hand, the other thermostat S2begins to open such that the third discharge port53communicates with the coolant passage8, and as a result, the coolant passage8communicates with all of the first to third discharge ports51,52,53. As the temperature of the coolant transitions from the third temperature T3(75° C.) to the fourth temperature T4(85° C.), the valve opening of the thermostat S2increases substantially proportionately with the coolant temperature, leading to an increase in the flow rate of the coolant from the third swirl chamber43. As a result, the coolant from the third discharge port53, the flow rate of which increases in accordance with the valve opening of the thermostat S2, and the coolant that is discharged from the first and second discharge ports51,52at a fixed flow rate are delivered into the coolant passage8and supplied to the engine2. Therefore, the engine2can be cooled even more effectively by the action of the coolant having the even higher flow rate.

When the temperature of the coolant reaches the fourth temperature T4(85° C.), the valve opening of the thermostat S2reaches a maximum, and after exceeding the appropriate coolant temperature, the coolant is discharged from the respective discharge ports51,52,53and supplied to the engine2at the maximum discharge flow rate of the water pump30. In other words, an equal discharge flow rate to that of the conventional water pump is realized in this condition.

According to the water pump30configured as described above, when the engine2is started up from a cold condition, the coolant is supplied to the engine2at a small flow rate only from the first swirl chamber41that communicates with the engine2via the coolant passage8at all times, and therefore warm-up of the engine2can be promoted while suppressing a thermal load of the engine2such that the engine2can be warmed quickly. When the engine2is warm, on the other hand, the thermostats S1, S2are opened to a valve opening corresponding to the temperature of the circulating coolant such that the coolant is supplied to the engine2from the second and third swirl chambers42,43at a flow rate corresponding to the valve opening in addition to the coolant from the first swirl chamber41. As a result, a sufficient engine cooling effect can be exhibited, leading to a reduction in friction in the engine2and a corresponding improvement in fuel efficiency, and an improvement in the thermal efficiency can be achieved, enabling a reduction in an amount of CO2discharged from the engine in exhaust gas. Further, by adjusting the discharge flow rate in steps in accordance with variation in the temperature of the coolant, coolant discharge at a flow rate exceeding the required flow rate of the engine2can be prevented. As a result, the workload of the water pump can be prevented from becoming excessive, and energy loss can be reduced.

A preferred embodiment of the present invention was described above, but the scope of the present invention is not limited to the above embodiment. For example, in the above embodiment, the swirl chamber40of the water pump30is divided into the first, second, and third swirl chambers, but the present invention is not limited thereto, and the swirl chamber40may be further divided into fourth and fifth swirl chambers. In so doing, the discharge flow rate of the water pump can be varied in more steps, enabling finer control of the flow rate.

Further, in the above embodiment, the predetermined temperatures (sensitive temperatures) at which the thermostats S1, S2open and close are set at the first temperature T1, i.e. 60° C., and the third temperature T3, i.e. 75° C., respectively, but the present invention is not limited thereto, and the sensitive temperatures may be modified appropriately in accordance with a required cooling performance of the engine.

EXPLANATION OF NUMERALS AND CHARACTERS

1engine cooling device