Hydraulic system, reservoir and pump suction enhancer for motor vehicle

A hydraulic system for a motor vehicle is provided with a pump suction enhancer includes a body section defining a small chamber, a venturi tube passage exposed to the small chamber at an inner end thereof and connected to the suction port of the oil pump, and a nozzle protruding into the small chamber to face the inner end of the venturi tube passage with a space relative to the venturi tube passage in axial alignment with the same. The flow divider divides the operating oil discharged from the oil pump into a return flow to the pump suction enhancer and a supply flow which passes through a power steering device to return to an oil reservoir. The pump suction enhancer may be integrally formed with the oil reservoir or provided as a discrete component separated from the oil reservoir, oil pump and the flow divider.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydraulic system for a motor vehicle incorporating a pump suction enhancer therein for boosting operating oil flow into a suction port of an oil pump, and also relates to an oil reservoir provided bodily with the pump suction enhancer. It further relates to the pump suction enhancer for use in the hydraulic system or in combination with the oil reservoir.

2. Discussion of the Related Art

In a hydraulic system or circuit device for a motor vehicle, the oil flow discharged from a power steering oil pump tends to become larger with increase in number of function components or accessories such as a radiator cooling fan device, suspension control actuators and the like in addition to a power steering device. With the large discharge flow from the oil pump, it has been required to improve the suction of a large return oil flow into the oil pump in order to prevent cavitation from occurring at the suction passage to the oil pump.

In a hydraulic system of this kind, as described in U.S. Pat. No. 5,802,848 to McClendon et al., a power steering pump draws operating oil from a reservoir and supplies a constant volume of the operating oil to a fluid motor for a radiator cooling fan device through a main conduit. At the downstream of the radiator cooling fan device, the main conduit is divided by a flow divider into a low flow conduit leading to the reservoir through a steering assist fluid motor (i.e., power steering device) and a high flow conduit bypassing the steering assist fluid motor to lead to the reservoir. Thus, a large volume of the operating oil is returned to the reservoir after the use for driving the radiator cooling fan device, while a small volume of the operating oil is used for driving the steering assist motor before being returned to the reservoir. Further, means for boosting the suction of the operating oil into a suction port of the power steering pump is incorporated in an internal chamber of the reservoir and is submerged in the operating oil in the chamber. The means for boosting the suction includes a venturi tube passage and a nozzle which are arranged so that the large volume of the operating oil returned from the high flow conduit is ejected from the nozzle into the venturi tube passage thereby to boost the suction of the operating oil to a passage connected to the suction port of the power steering pump.

However, in the known hydraulic system, the means for boosting the suction is incorporated submerged in the reservoir, and the reservoir itself is provided bodily with the power steering pump. Thus, a problem arises in that substantial restraint is imposed on the place where the pump and reservoir combination is arranged. That is, the place where the pump and reservoir combination can be arranged is determined in dependence on the arrangement in an engine room of mechanical units and components such as an engine, a power steering device, a brake booster device, a battery, a radiator, etc. In some cases, the pump and reservoir combination may be arranged close to the power steering device but may be too far from the radiator cooling fan device to use a conduit of an adequate length which is designed against vibration, pulsation and other adverse causes. In this case, an oil pump and an oil reservoir may not be used in integration and may rather be arranged at respective places separated from, and independently of, each other. This problem becomes more serious in the case that the number of accessories such as radiator cooling fan device, suspension control actuators and the like increases.

Another known hydraulic system of this kind is described in U.S. Pat. No. 5,943,861 to Davison et al., wherein an oil reservoir is provided separated from a power steering pump and wherein means for boosting the suction of the operating oil into a suction port of the power steering pump is incorporated in the reservoir to extend across an internal chamber of the same. The means for boosting the suction is composed of a venturi tube passage and a nozzle which are arranged in the internal chamber of the reservoir to extend diametrically of the same in alignment. Therefore, the venturi tube passage and the nozzle have to be assembled inside of the reservoir. This disadvantageously makes the assembling work for the oil reservoir complicated and troublesome and also makes the maintenance or check of the boosting means substantially impossible.

SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to provide an improved hydraulic system for a motor vehicle wherein means for boosting pump suction does not impose any substantial restraint on the place where an oil pump is arranged.

Another object of the present invention is to provide an improved oil reservoir with a pump suction enhancer for use in a hydraulic system for a motor vehicle.

A further object of the present invention is to provide an improved pump suction enhancer which is capable of boosting the suction of a large return flow into an oil pump and which does not impose any substantial restraint on the places where the oil pump and an oil reservoir therefor are arranged.

Briefly, in one aspect of the present invention, there is provided a hydraulic system for a motor vehicle, which comprises an oil pump driven by a prime mover for discharging operating oil from a discharge port thereof, function component means hydraulically operated by permitting the operating oil discharged form the oil pump to pass therethrough, and flow divider means provided between the oil pump and the function component means for dividing the operating oil discharged from the oil pump into a part thereof directed toward the function component means and the remaining part thereof. The hydraulic system further comprises an oil reservoir provided independently of the oil pump and fluidly connected to the function component means through conduit means for receiving the operating oil returned from the function component means and a pump suction enhancer provided bodily with the oil reservoir outside the same for boosting the suction of the operating oil into the oil pump. The pump suction enhancer includes a body section provided on an external portion of the oil reservoir for defining a side chamber opening to a reservoir chamber defined in the oil reservoir, a venturi tube passage exposed at one end thereof to the side chamber and fluidly connected to the suction port of the oil pump through a second conduit for enabling the operating oil to be drawn into a suction port of the oil pump, and a nozzle fluidly connected to the flow divider means for receiving the remaining part of the operating fluid returned from the flow divider means and protruding into the side chamber to face an inner end of the venturi tube passage with a space relative to the venturi tube passage for ejecting a jet stream of the operating oil into the venturi tube passage thereby to draw and plunge the operating oil from the side chamber into the venturi tube passage.

With this construction, the pump suction enhancer is provided bodily with the oil reservoir which is separated from the oil pump. Thus, the pump suction enhancer can be arranged together with the oil reservoir at a desired place which is different from the place where the oil pump is arranged. Thus, the location of the pump suction enhancer in an engine room of the motor vehicle can get rid of being restrained to the location of the oil pump in the engine room, so that freedom can be gained in designing the arrangement of hydraulic components such as the oil pump, the oil reservoir, the function components and the like in the engine room. Further, since the pump suction enhancer is provided outside, or on an external surface, of the oil reservoir, it can be easily assembled with the oil reservoir, so that the assembling work for the oil reservoir can be simplified. In addition, the maintenance or check of the boosting means becomes easier to carry out from the outside of the oil reservoir.

In another aspect of the present invention, an oil reservoir incorporated in a hydraulic system for a motor vehicle is provided, wherein flow divider means is provided for dividing operating oil discharged from an oil pump into a first stream directed toward function component means which is hydraulically operated by permitting the operating oil discharged form the oil pump to pass therethrough, and into a second stream. The oil reservoir comprises a reservoir body defining therein a reservoir chamber for containing the operating oil to be supplied to a suction port of the oil pump and provided with return port means for leading the operating oil returned from the function component means to the reservoir chamber and a pump suction enhancer provided bodily with the oil reservoir outside the same for boosting the suction of the operating oil into the oil pump. The pump suction enhancer includes a body section provided on an external portion of the reservoir body for defining a side chamber opening to the reservoir chamber defined in the reservoir body, a venturi tube passage exposed at an inner end thereof to the side chamber and fluidly connected to the suction port of the oil pump through a conduit for supplying the operating oil to the oil pump, and a nozzle fluidly connected to the flow divider means for receiving the remaining part of the operating fluid returned from the flow divider means and protruding into the side chamber to face the inner end of the venturi tube passage with a space relative to the venturi tube passage for ejecting a jet stream of the operating oil into the venturi tube passage to plunge the operating oil from the side chamber into the venturi tube passage.

With this construction, the pump suction enhancer is provided bodily with the oil reservoir which is separated from the oil pump, on an external portion of the reservoir body. Thus, the same advantages and effects as attained by the aforementioned hydraulic system can also attained by the oil reservoir according to the present invention in this aspect.

In a further aspect of the present invention, there is provided a pump suction enhancer for use in a hydraulic system for a motor vehicle, wherein flow divider means divides operating oil discharged from an oil pump into a first stream to pass through function component means hydraulically operated by the operating oil therethrough and a second stream to be returned to the pump suction enhancer. The pump suction enhancer is provided independently of, and separated from, the oil pump and the oil reservoir and comprises a body section formed with a chamber connectable to receive the operating oil from the oil reservoir. The pump suction enhancer further comprises a venturi tube passage formed in the body section to open to the chamber at an inner end thereof and connectable to charge the operating oil into a suction port of the oil pump and a nozzle formed in the body section in axial alignment with the venturi tube passage and protruding into the chamber to face the inner end of the venturi tube passage with a space relative thereto for ejecting the operating oil, returned from the flow divider means, as a jet stream into the venturi tube passage to plunge the operating oil from the chamber into the venturi tube passage.

With this construction, the pump suction enhancer is constituted as a discrete component separated from the oil pump, the oil reservoir and other function components hydraulically operated by the operating oil discharged from the oil pump. Therefore, it can be realized to arrange the pump suction enhancer at any desirable place which is suitable for connections with other components, so that the pump suction enhancer does not impose any substantial restraint on the arrangement of the oil pump, the oil reservoir and other function components hydraulically operated by the operating oil discharged from the oil pump. In addition, by the appropriate arrangement of the oil pump, the oil reservoir and those function components in the engine room, conduits for fluidly connecting the components may be made as those having adequate lengths, so that the performance of the hydraulic system can also be improved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

A hydraulic system for a motor vehicle in a first embodiment according to the present invention will be described hereinafter with reference toFIGS. 1 through 4. The hydraulic system comprises an oil reservoir10and an oil pump22which constitute an operating oil supply and further comprises a radiator cooling fan device23, a power steering device24, and a suspension control mechanism25which constitute hydraulically operated function accessories or components for a motor vehicle (not shown).

The oil pump22constituted by, e.g., a vane pump, which is connected to be driven by a crankshaft of a combustion engine (both not shown) of the motor vehicle. The oil pump22incorporates a flow control mechanism and a relief valve mechanism (both not shown) therein. The relief valve mechanism operates in an abnormal state to protect the oil pump22from damage. The flow control mechanism controls the flow volume discharged from a discharge port22ato increase in proportion to an increase in the rotational speed of the crankshaft or a pump rotor (not shown) until the rotational speed reaches a predetermined rotational speed and maintains the discharge flow volume substantially constant (i.e., a predetermined maximum flow volume Qmax) irrespective of a further increase in the rotation speed after the same reaches the predetermined rotational speed. The predetermined maximum flow volume Qmax discharged from the discharged port22ais designed to be equal to or somewhat larger than the sum of the maximum flow volumes (i.e., first to third predetermined maximum flow volumes Q1-Q3) which the radiator cooling fan device23, the power steering device24, and the suspension mechanism25respectively demand when exercising their full capabilities or performances.

The operating oil discharged from the discharge port22ais supplied to a first flow divider31, which is controllable by an electromagnetic control valve31aincorporated therein, That is, the electromagnetic control valve31ais operated in response to a command signal from an ECU (Electronic Control Unit)38of the motor vehicle and controls the ratio between the flow volume of the operating oil directed to the radiator cooling fan device23and the flow volume of the operating oil directed to a second flow divider32. Thus, a part of the operating oil passes through a cooling fan drive motor23a, so that the operation of the cooling fan device23, i.e., the rotational motion and speed of the cooling fan device23can be controlled by the ECU38. The cooling fan drive device23is of a known type, wherein a cooling fan23bcan be rotated by the cooling fan drive motor23aconstituted by a hydraulic motor such as, e.g., a vane type motor. The first flow divider31is constituted by, for example, a conventional flow control mechanism of the same construction as that incorporated in the oil pump22. However, the first flow divider31is different from the flow control mechanism incorporated in the oil pump22in that it can be controllable by the electromagnetic control valve31aso that the ratio between the flow volumes branched toward the radiator cooling fan device23and the second flow divider32can be adjusted as instructed by the command signal from the ECU38.

The operating oil directly supplied from the first flow divider31and the operating oil discharged from the fan drive motor23aare joined and supplied to the second flow divider32. The second flow divider32directs the operating oil as a supply flow or stream through a filter33to a third flow divider34until the flow volume toward the same reaches the sum of the second and third predetermined maximum flow volumes Q2, Q3which the power steering device24and the suspension mechanism25respectively demand when exercising their full performances or capabilities. When having a larger flow volume than the sum of the second and third predetermined maximum flow volumes Q2, Q3flown thereinto, the second flow divider32directs toward a pump suction enhancer40as referred to later in detail the superfluous or surplus flow volume which is the remaining part of such a large flow volume after directing the sum of the second and third predetermined maximum flow volumes Q2, Q3toward the third flow divider34. That is, the second flow divider32directs the operating oil exclusively toward the third flow divider34until the flow volume directed toward the third flow divider34reaches the sum of the second and third predetermined maximum flow volumes Q2, Q3, but directs the surplus flow volume beyond the sum toward the pump suction enhancer40. The second flow divider32is constituted by, for example, a conventional flow control mechanism (not shown) of the same construction as that incorporated in the oil pump22. The second flow divider32also incorporates therein a relief valve mechanism (not shown) so that the passages which connect the second flow divider32to the power steering gear24and the suspension mechanism25through the filter33and the third flow divider34can be prevented from increasing in pressure beyond a predetermined relief pressure.

The third flow divider34divides the operating oil discharged from the second flow divider32into two streams for use by the power steering device24and the suspension mechanism25. More specifically, the third flow divider34directs the operating oil exclusively toward the power steering device24until the flow volume toward the same reaches the second predetermined maximum flow volume Q2which the power steering device24demands when exercising the full performance or capability thereof. When having a larger flow volume than the second predetermined maximum flow volume Q2flown thereinto, the third flow divider34directs for use by the suspension mechanism25the superfluous or surplus flow volume which is the remaining part of such a large flow volume after directing the second predetermined maximum flow volume Q2toward the power steering device24.

That is, the third flow divider34directs the operating oil exclusively toward the power steering device24until the flow volume directed toward the same reaches the second predetermined maximum flow volume Q2, but directs the surplus flow volume which exceeds the second predetermined maximum flow volume Q2, for use by the suspension mechanism25. Thus, the third flow divider34is constituted by, for example, a conventional flow control mechanism and an orifice (both not shown) which is connected in series with a drain port of the flow control mechanism. More specifically, the flow control mechanism incorporated in the third flow divider34directs the operating oil supplied thereto exclusively toward the power steering device24until the flow volume toward the same reaches the second predetermined maximum flow volume Q2and discharges the surplus flow volume over the same Q2from the drain port toward the orifice. A passage branches from between the drain port of the flow control mechanism and the orifice at the downstream thereof and is connected to hydraulic cylinders25a,25bof the suspension mechanism25so that a controlled pressure is applied to the hydraulic cylinders25a,25b. The downstream of the orifice is connected to a second return port10bof the oil reservoir10for returning the operating oil from the third flow divider34to the oil reservoir10.

The power steering device24is a known type, which is composed of a power cylinder24aand a center-open servo valve24b. The power cylinder.24ahas a pair of cylinder chambers partitioned by a movable piston (not shown) which is connected to right and left front wheels (not shown) of the vehicle through a pair of right and left link mechanisms24r,24l. The servo valve24bis connected to be operated by a steering handle37. When the steering handle37is at the neutral position, the servo valve24bis at the center position and directs the operating oil flown from an inlet port P, to an outlet port T therethrough without developing substantial resistance or impedance. As is well-known in the art, when the steering handle37is turned in either one direction, the servo valve24bcontrols the supply of the operating oil to one of the cylinder chambers and simultaneously controls the discharge of the operating oil from the other cylinder chamber in dependence on the turning angle of the steering handle37, so that the operation of the power cylinder24aand hence, the orientation of the front wheels can be controlled to follow the turning motion of the steering handle27. The operating oil discharged from the outlet port T of the servo valve24bis returned to a first return port10aof the oil reservoir10through an oil cooler36. The oil cooler36is constituted by a conventional heat exchanger of a self-cooling type or a compulsory cooling type.

The oil reservoir10includes a body section12and a top cap11. The pump suction enhancer40is provided bodily on the body section12for boosting the suction of operating oil into a suction port22bof the oil pump22. The pump suction enhancer40is connected at an inlet port42to the second flow divider32to be charged with the superfluous oil flow returned toward the oil reservoir10and is also connected at an outlet port46to the suction port22bof the oil pump22.

Specifically, as shown inFIGS. 2 through 4, the body section12is composed of first and second members12a,12bwhich are made of a resin and which are fabricated by Injection Molding. The first member12awith a mounting hook12ctakes a vertically elongated, generally box-like shape, while the second member12btakes a vertically elongated, generally plate-like shape closing the lateral opening of the first member12a. These members12a,12bare joined along a vertical plane to close the lateral opening, so that a reservoir chamber14is defined inside the body section12. The first return port10afor returning the operating oil from the power steering device24opens into a lower part of the reservoir chamber14, and the second return port10bfor returning the operating oil from the third flow divider34opens into a middle part of the reservoir chamber14. In the lower part of the reservoir chamber14, there is provided a magnet holder15, by which a permanent magnet piece16is held for magnetically attracting iron powder flowing in the operating oil. Also in the lower part of the reservoir chamber14, there is provided a deflector17in position to face the first return port10a, so that the operating oil returned into the reservoir chamber14from the power steering device24is deflected toward the boundary between the body section12and the pump suction enhancer40.

As best shown inFIG. 3, the pump suction enhancer40is integrally provided at the lower part of the second member12bof the pump body section12. The pump suction enhancer40defines a side chamber40atherein, which opens to the reservoir chamber14. A mesh filter element18is arranged at the boundary between the reservoir chamber14and the side chamber40a. The deflector17directs the return oil flow toward the mesh filter element18, so that the operating oil returned from the power steering device24is caused by the deflector17to flow into the side chamber40a.

Specifically, the pump suction enhancer40is composed of an inlet section41and an outlet section44which is seated on, and bodily joined with, a top round edge portion of the inlet section41for defining the side chamber40a. The inlet section41integrally protrudes the inlet port42downward and also integrally protrudes a nozzle43upward inside the side chamber40a. The inlet port42and the nozzle43are connected to constitute a single tapered hole decreasing in diameter toward the nozzle43. The tapered hole ensures that the return oil flows from the inlet port42to the nozzle43smoothly not to make any turbulent flow. The outlet section44is spaced at its inner end from the upper end of the nozzle43and is formed with a venturi tube passage45which includes a chamfer portion45a, a throat portion45b, a diffusion portion45cand an outlet port46in turn from the inner end toward the upper end thereof in axial alignment with the nozzle43. Thus, when the operating oil from the second flow divider32is ejected from the nozzle43into the venturi tube passage45, the operating oil inside the side chamber40ais drawn and plunged into the venturi tube passage45by way of the space between the nozzle43and the inner end of the venturi tube passage45.

The operation of the hydraulic system as constructed above will be described hereafter. First of all, let it be assumed that during the full performance operations, the radiator cooling fan device23, the power steering device24and the suspension mechanism25demand their maximum flow volumes Q1-Q3of, e.g., 37 liters per minute, 10 liters per minute and 5 liters per minute, respectively, and that the oil pump22discharges the flow volume as high as 52 liters per minute or somewhat larger than the same in its full performance operation. However, it is to be noted the flow volume discharged from the oil pump22depends on the pump rotor (i.e., engine) rotational speed and ranges from 8 liters per minute to 52 liters per minute as the engine rotational speed increases from 800 rpm (idling) to 4,000 rpm.

Assuming now that the engine is rotating at 4,000 rpm, the oil pump discharges 52 liters per minute to the first flow divider31. In dependence upon the command signal from the ECU38, the electromagnetic control valve31ais operated to make a part of the discharged operating oil pass through the cooling fan drive motor23aand the remaining part thereof go directly to the second flow divider32. The ratio between these streams of the operating oil is controlled by the electromagnetic control. valve31awhich operates in response to the command signal from the ECU38. Thus, the radiator cooling fan device23is operated under the control of the ECU38to maintain the radiator temperature less than a predetermined value, for example, The second flow divider32directs the operating oil flown thereinto exclusively toward the third flow divider34until the flow volume toward the same reaches the sum of the second and third predetermined maximum flow volumes Q2, Q3(i.e., 10 liters per minute and 5 liters per minute) which are respectively demanded by the power steering device24and the suspension mechanism25during their full performance operations. The second flow divider32can return the superfluous flow volume exceeding the sum (i.e., 15 liters per minute), to the inlet port42of the pump suction enhancer40provided integrally with the oil reservoir10.

The operating oil discharged from the second flow divider32is supplied through the filter33to the third flow divider34. The third flow divider34takes a priority over directing the operating oil toward the power steering device24rather than directing it toward the suspension mechanism25. Thus, the third flow divider34operates to direct the operating oil exclusively toward the power steering device24until the flow volume to the same reaches the predetermined maximum flow volume Q2(i.e., 10 liters per minute) demanded by the power steering device24, and thereafter, to direct the superfluous flow volume exceeding the maximum flow volume Q2, for use in pressure control of the suspension mechanism25. The operating oil supplied to the power steering device24and discharged therefrom is returned through the oil cooler36to the first return port10aof the oil reservoir10and is further returned into the reservoir chamber14. The operating oil returned inside the reservoir chamber14is deflected by the deflector17toward the side chamber40aof the pump suction enhancer40.

On the other hand, the operating oil directed by the third flow divider34toward the suspension mechanism25is throttled by the orifice provided at the downstream of the flow control mechanism also incorporated therein, so that a pressure is generated between the drain port of the flow control mechanism and the orifice to operate the cylinder devices25a,25bof the suspension mechanism25. The operating oil past the orifice is returned to the reservoir chamber14through the second return port10b.

Accordingly, when the oil pump discharges its maximum flow volume Qmax (e.g., 72 liters per minute) at 4,000 rpm of the engine speed, the first maximum flow volume Q1(e.g., 37 liters per minute) demanded by the radiator cooling fan device23is returned from the second flow divider32to the pump suction enhancer40and is ejected from the nozzle43to make a jet stream boosted into the venturi tube passage45. The flow of the operating oil ejected from the nozzle43into the venturi tube passage45acts to draw the operating oil in the side chamber40a. Since the operating oil ejected from the nozzle43into the venturi tube passage45is sufficiently larger in flow volume than that drawn from the side chamber40ainto the venturi tube passage45, the operating oil to be replenished from the side chamber40ainto the venturi tube passage45is carried by the jet stream and is boosted to be plunged into the venturi tube passage45. That is, the jet stream ejected from the nozzle43draws and plunges the operating oil from the side chamber40ainto the venturi tube passage45. The velocity energy of the jet steam is converted into the pressure energy as it passes through the venturi tube passage45, and the pressure of the operating oil charged into to the suction port22bof the oil pump22is increased. Consequently, the pump suction efficiency can be improved, and the cavitation which would otherwise be caused by the insufficient charge of the operating oil into the suction port22bof the oil pump22can be suppressed or prevented from being generated.

In the foregoing first embodiment, the pump suction enhancer40is constituted to be integral with the oil reservoir10, but separated from the oil pump22. Therefore, the freedom in choosing the places where to mount the oil reservoir10and the oil pump22can be heightened. That is, in designing the arrangement of function components in an engine room of a motor vehicle, it has been often required that an oil pump and an oil reservoir as an oil supply be located at different places. Further, it is a recent trend that the number of hydraulically operated function accessories or components like the power steering device24, the radiator cooling fan drive23, the suspension mechanism25and so on increases for easier maneuver as well as for more comfortable and luxurious feeling. These requirements can be satisfied by the hydraulic system in the first embodiment, wherein the oil reservoir10can be located at a desirable place which is suitable for connections not only with the oil pump22but also with other hydraulically operated function components like the power steering device24, the radiator cooling fan device23and the suspension mechanism25. Thus, in the hydraulic system or circuit device in the first embodiment, the pump suction enhance40hardly imposes any substantial restraint on the arrangement of the hydraulically operated function components in the engine room. In addition, by the appropriate arrangement of those function components in the engine room, the conduits for fluidly connecting the components may be made as those having adequate lengths, so that the performance of the hydraulic system can also be improved.

Although the pump suction enhancer40is provided integrally with the oil reservoir10, it may be fabricated as a discrete component and may be attached by suitable fixing means such as bolts, rivets or the like onto the oil reservoir10. Further, the pump suction enhancer40is provided on a lateral surface of the pump body section12, it may be provided on another lateral surface or a bottom surface of the pump body section12. Moreover, although the pump suction enhancer40is provided with the nozzle43and the venturi tube passage45extending vertically in axial alignment, the nozzle43and the venturi tube passage45may be provided to extend horizontally or on an oblique line.

Second Embodiment

Next, a hydraulic system or circuit device in a second embodiment according to the present invention will be described with reference toFIGS. 5 and 6. Referring now toFIG. 5, a pump suction enhancer140is illustrated as being a discrete component separated from the oil reservoir10. Thus, the oil reservoir10is provided with a suction outlet port19to open to the lower part of the reservoir chamber14. As shown inFIG. 6, the pump suction enhancer140in the second embodiment includes a body member147of a generally block-like shape, which is formed with a through hole148and a blind hole149. The blind hole149intersects with the through hole148to define an intersection chamber140a. An inlet section141and an outlet section144are fixedly screwed respectively into opposite open end portions of the through hole148, and a reservoir port section150is fixedly screwed into an open end portion of the blind hole149.

The inlet section141is provided with an inlet port142outside and a nozzle143inside, while the outlet section144is provided with an outlet port146outside and a Venturi tube passage145inside. The venturi tube passage145includes a chamfer portion145a, a throat portion145band a diffusion portion145cwhich are arranged connected in turn from the inner end toward the outer end thereof. The inner ends of the inlet and outlet sections141,144are inserted into a cross hole which is formed in a tubular member151to pass through lateral sides thereof. The reservoir port section150is provided with a reservoir connection port152outside and a passage153inside to open to the through hole151aof the tubular member151. The tubular member151is supported inside the intersection chamber140ain axial alignment with the reservoir port section150.

In operation, the operating oil returned from the second flow divider32is flown into the inlet port142and is ejected from the nozzle143to make a jet stream toward the venturi tube passage145. The operating oil in the oil reservoir10flows into the reservoir connection port152and reaches the intersection chamber140aand the inside of the tubular member151through the passage153. Thus, the jet stream ejected from the nozzle143draws and plunges the operating oil from the tubular member151and the intersection chamber140ainto the venturi tube passage145. The velocity energy of the jet steam is converted into the pressure energy as the jet stream passes through the venturi tube passage145, and the pressure of the operating oil charged into the suction port22bof the oil pump22is increased. Consequently, the pump suction efficiency can be improved, and the cavitation which would otherwise be caused by the insufficient pressure in the operating oil charged into the suction port22bof the oil pump22can be suppressed or prevented from being generated.

In the foregoing second embodiment, the pump suction enhancer140is constituted as a discrete component which is separated from other components in the hydraulic system such as the oil pump22, the oil reservoir10, the power steering device24, the radiator cooling fan device23and the suspension mechanism25which suffer substantial restraint on the places where they are arranged in the engine room. Therefore, it can be realized to arrange the pump suction enhancer140at any desirable place which is suitable for connections with other components, so that the pump suction enhancer140does not impose any substantial restraint on the arrangement of the oil pump22, the reservoir10, the power steering device24, the radiator cooling fan device23and the like. In addition, by the appropriate arrangement of those components in the engine room, the conduits for fluidly connecting the components may be made as those having adequate lengths, so that the performance of the hydraulic system can also be improved.

In the foregoing first and second embodiments, the components such as the oil reservoir10, the oil pump22, the power steering device24, the radiator cooling fan drive23, the suspension mechanism25and the like are fluidly connected to one another through conduits which are indicated by solid lines inFIGS. 1 and 5. Some or all of these conduits used in the embodiments may be flexible hoses like rubber hoses or may be metallic pipes or may be hybrid conduits each constituted by a center metallic pipe and a pair of flexible hoses connected to the opposite ends of the metallic pipe.

Further, a prime mover for rotationally driving the oil pump22is not only constituted by the engine as in the foregoing embodiments, but may also be constituted by other means such as, for example, an electric motor. Where the electric motor is used, the flow control mechanism incorporated in the oil pump22may be omitted, instead of which a control function may be added for controlling the rotational speed of the oil pump22thereby to control the discharge volume therefrom. Further, pumps of various kinds such as piston pump, gear pump, plunger pump and so on can be used as the oil pump22in substitution for the vane pump which is exemplified as a preferred form of such oil pump in the foregoing embodiments.

Third Embodiment

A third embodiment of the present invention will be described hereafter with reference toFIGS. 5,7and8. In the third embodiment, another pump suction enhancer240shown inFIGS. 7 and 8is employed in substitution for the pump suction enhancer140which is arranged in the hydraulic system shown inFIG. 5. Like the pump suction enhancer140in the second embodiment, the pump suction enhancer240in the third embodiment is provided as a discrete component which is separated from the oil pump22and the oil reservoir10. As best shown inFIG. 8, the pump suction enhancer240is constituted by joining two parts; i.e., an inlet section241and an outlet section244. The inlet section241and the outlet section244are joined with each other thereby to constitute a body section247. The pump suction enhancer240defines an annular chamber240atherein to which a reservoir connection port252opens, so that the operating oil is drawn from the reservoir10to the annular chamber240a.

Specifically, the outlet section244is seated on, and bodily joined with, a top round edge portion of the inlet section241for defining the annular chamber240a. The inlet section241integrally protrudes the inlet port242downward and also integrally protrudes a nozzle243upward thereby to define the annular chamber240aaround the nozzle243. That is, the annular chamber240ais defined at a juncture portion between the inlet section241and the outlet section244and around a nozzle243, so that it becomes easier to define the chamber240aas desired in shape as well as in dimension. The inlet port242and the nozzle243are connected to constitute a single tapered hole decreasing in diameter toward the nozzle243. The tapered hole ensures that the return oil flows from the inlet port242to the nozzle243smoothly not to make any turbulent flow.

The outlet section244is spaced at its inner end from the upper end of the nozzle243and is formed with a venturi tube passage245which includes a chamfer portion245a, a throat portion245b, a diffusion portion245cand an outlet port246in turn from the inner end toward the upper end thereof in axial alignment with the nozzle243. Thus, when the operating oil from the second flow divider32(FIG. 5) is ejected as a jet stream from the nozzle243into the venturi tube passage245, the operating oil inside the annular chamber240ais drawn and plunged into the venturi tube passage245by way of the space between the nozzle243and the inner end of the venturi tube passage245. The velocity energy of the jet steam is converted into the pressure energy as the jet stream passes through the venturi tube passage245, and the pressure of the operating oil charged into the suction port22bof the oil pump22is increased. Consequently, substantially the same effects as in the foregoing second embodiment can be attained in the third embodiment.

Finally, various features and many of the attendant advantages in the foregoing embodiments will be summarized as follows:

In the foregoing first embodiment typically shown inFIGS. 1 and 3for example, the pump suction enhancer40is provided integrally with the oil reservoir10which is separated from the oil pump22Thus, the pump suction enhancer40can be arranged together with the oil reservoir10at a desired place which is different from the place where the oil pump22is arranged. Thus, the location of the pump suction enhancer40in the engine room of the motor vehicle can get rid of being restrained to the location of the oil pump22in the engine room, so that freedom can be gained in designing the arrangement of hydraulic components such as the oil pump22, the oil reservoir10, the function components24,25and the like in the engine room. Further, since the pump suction enhancer40is provided outside, or on an external surface, of the oil reservoir10, it can be easily assembled with the oil reservoir10, so that the assembling work for the oil reservoir10can be simplified. In addition, the maintenance or check of the pump suction enhancer40becomes easier to carry out from the outside of the oil reservoir10.

Also in the foregoing first embodiment typically shown inFIG. 1, plural flow dividers31,32,34are used, at least one of which is provided to direct the operating oil discharged from the oil pump22exclusively toward the power steering device24until the flow of the operating oil toward the power steering device24reaches that which the power steering device24demands during the operation of its full capability. Thus, the power steering device24is given the priority in being supplied with the operating oil from the oil pump22, so that the power steering device24can be operated reliably even while the oil pump22is operated at a low rotational speed.

Also in the foregoing first embodiment typically shown inFIG. 1, first to third flow dividers31,32,34are provided. The first flow divider31makes a part of the operating oil pass through the radiator cooling fan device23. The second flow divider32divides the operating oil discharged from the oil pump22through the first flow divider31into a supply flow toward the third flow divider34and a return flow to the pump suction enhancer40. The third flow divider34divides the operating oil directed by the second flow divider32into a part and the remaining part thereof, which are used to operate the power steering device24and the suspension mechanism25respectively before being returned to the oil reservoir10. Since the second flow divider32and the third flow divider34first supply the power steering device24with the maximum flow volume Q2demanded thereby, then supplies the suspension mechanism25with the maximum flow volume Q3demanded thereby and finally return the superfluous flow volume to the pump suction enhancer40. Accordingly, it can be obviated that the power steering device24falls into failure due to lack of the operating oil supplied thereto even during the low rotational speed operation of the oil pump22.

Further, in the foregoing first embodiment typically shown inFIG. 1, since the first flow divider31is provided with an electromagnetic control valve31a, the operating oil flow passing through the radiator cooling fan device23is controlled in dependence on the electrical command signal applied to the electromagnetic control valve31a, so that the operation of the radiator cooling fan device23can be controlled in dependence on various conditions during the vehicle traveling.

Further, when the power steering device24is kept at either of its operation ends, it may occur that the pressure on a circuit passage line from the second flow divider32to the power steering device24exceeds a predetermined relief pressure. However, in the foregoing first embodiment typically shown inFIG. 1, since the second flow divider32is given a relief function for escaping the operating oil therefrom to the pump suction enhancer40, the hydraulic system can be prevented from being damaged.

Yet in the foregoing first embodiment typically shown inFIGS. 2 and 3, the pump suction enhancer40is provided integrally with the oil reservoir10which is separated from the oil pump10. Thus, the same advantages and effects as attained by the aforementioned hydraulic system can also attained by the oil reservoir10in this embodiment.

Yet in the foregoing first embodiment typically shown inFIG. 3, the lid member12bwhich closes the lateral opening of the box-like body member12aof the oil reservoir10, is provided integrally with the pump suction enhancer40so that the side chamber40aopens to a lower part of the reservoir chamber14. That is, the pump suction enhancer40is provided on an external surface of the oil reservoir10. Thus, the access to the pump suction enhancer40becomes easier, and the inspection thereof can be done easily.

Also in the foregoing first embodiment typically shown inFIG. 3, the operating oil flown into the reservoir chamber14from the first return port10ais deflected by the deflector17to be directed toward the side chamber40aof the pump suction enhancer40. Thus, the supply of the operating oil to the side chamber40acan be facilitated, so that plunging the operating oil from the side chamber40ainto the venturi tube passage45can be done highly efficiently.

Also in the foregoing first embodiment typically shown inFIG. 1, the nozzle43of the pump suction enhancer40ejects a larger flow volume than that returned into the reservoir chamber14. That is, in the pump suction enhancer40, the larger flow volume ejected as a jet stream from the nozzle43draws and plunges the smaller flow volume to be replenished, into the venturi tube passage45, so that the charge of the operating oil into the suction port22bof the oil pump22can be boosted highly efficiently.

Furthermore, in the foregoing second embodiment shown inFIGS. 5 and 6, the pump suction enhancer140is constituted as a discrete component separated from the oil pump22, the oil reservoir10and other function components23-25hydraulically operated by the operating oil discharged from the oil pump22. Therefore, it can be realized to arrange the pump suction enhancer140at any desirable place which is suitable for connections with other components10,22and32, so that the pump suction enhancer140does not impose any substantial restraint on the arrangement of the oil pump22, the oil reservoir10and those function components23-25. In addition, by the appropriate arrangement of the oil pump22, the oil reservoir10and those function components23-25in the engine room, the conduits for fluidly connecting the components10,22,32and others may be made as those having adequate lengths, so that the performance of the hydraulic system can also be improved.

In addition, in the foregoing third embodiment typically shown inFIG. 8, the body section247of the pump suction enhancer240is constituted by joining two parts including the inlet section241formed with the nozzle243and the outlet section244formed with the venturi tube passage245. Thus, the number of parts which constitute the pump suction enhancer240can be reduced, so that the assembling work for the pump suction enhancer240can be simplified, thereby resulting in a substantial reduction in the manufacturing cost.

Also in the foregoing third embodiment typically shown inFIG. 8, since the chamber240aprovided in the body section247is defined at a juncture portion between the inlet section241and the outlet section244and around the nozzle243, it becomes easier to define the chamber240aas desired in shape as well as in dimension.