HYDRAULICALLY POWERED FAN AND POWER STEERING IN A VEHICLE

Abstract: A hydraulic system for an automotive vehicle. A source of hydraulic pressure operates in two modes. In one mode (which is the normal operating mode), it feeds a radiator cooling fan (12) and a power steering system (3) in parallel. In another mode, a priority flow divider (81) feeds only the power steering system (3) when the hydraulic flow falls below a minimum which generally corresponds to the flow required by the steering system (3).

Description: HYDRAULICAL Y POWERED FAN AND POWER STEERING IN VEHICLE Cross-Reference to Related Application This application is a continuation- in-part of application serial no. 08/680,482 filed July 15, 1996, which is a continuation of application serial no. 08/400,927 filed March 9, 1995, now issued as U.S. Patent No. 5,535,845. Background of the Invention 1. Field of the Invention The invention concerns a hydraulically powered fan for a motor vehicle which shares a hydraulic power source with a power steering system. 2. Description of Related Art In automotive vehicles, a fan commonly removes heat from liquid coolant, by pumping air over a heat exchanger, or radiator, through which the coolant flows. The fan is commonly driven directly by the engine through a power-transmission belt. However, one problem with such direct -drive of the fan is that fan speed is linked to engine speed: as engine speed increases, the fan speed also increases. However, as engine speed increases, vehicle speed also generally increases. Increased vehicle speed increases the ram air flow through the radiator, which also cools the coolant, thereby reducing the need for fan cooling. Thus, at high engine speed, in many cases, the fan runs at a high speed, but is not needed. Some fans are equipped with a clutch, which dis-engages them from the engine, at high engine speeds, to solve this problem. However, even when this fan problem is solved, other factors exist which are undesirable. One is that fans, at excessive speeds, are noisy. Each fan blade, as it passes an observer, delivers a small pressure pulse to the observer. As fan speed increases, the number of blade-passes occurring per second also increases, thereby increasing the number of pulses per second. That is, pulse frequency increases as fan speed increases. In addition, the magnitude of the pulses also increases as speed increases. Thus, a high-speed fan acts as a loud, high-frequency, noise source. Another problem which arises is not so much attributable to the fan, as to automotive design principles. In a transversely mounted engine, the crankshaft is perpendicular to the direction of travel . However, the cooling face of the radiator is preferably perpendicular to the ram air stream, which is parallel to the direction of travel. If the disc representing the fan blades is parallel to the cooling surface of the radiator, then the fan's rotational axis is perpendicular to the crankshaft, causing complexity in transferring power from the crankshaft to the fan. Summary of the Invention An object of the invention is to provide an improved cooling system in an automotive vehicle. Another object of the invention is to provide a cooling system for an automotive vehicle in which power extracted from the engine to power a cooling fan is independent of engine speed. In one form of the invention, a hydraulic power source in an automotive vehicle supplies power to both a cooling fan and a power steering system, either in parallel or in series, as conditions require. In one aspect, this invention comprises a hydraulic system for use in a vehicle comprising a source of hydraulic pressure, a power steering system, a hydraulic fan system for cooling engine coolant and a switching system for selectively delivering hydraulic pressure to the power steering system and blocking hydraulic pressure from the fan system and delivering hydraulic pressure to both the power steering system and the fan system. In another aspect, this invention comprises a method of delivering hydraulic fluid to components in a vehicle, comprising the following steps delivering flow to a power steering system while delivering no flow to a radiator cooling system during a first flow condition and delivering flow to both the power steering system and the radiator cooling system during a non-first flow condition. Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings, and the appended claims. Brief Description of the Drawings Figure 1 illustrates an overview of operation of one form of the invention; Figure 2 illustrates one type of hydraulic circuitry which accomplishes the operation shown in Figure 1 ; Figure 3 illustrates how the hydraulic circuitry of Figure 2 provides hydraulic power exclusively to the power steering system shown in Figure 1 ; Figure 4 illustrates how the hydraulic circuitry of Figure 2 provides hydraulic power to both the power steering system and the fan system shown in Figure 1; and Figure 5 illustrates logic implemented by one form of the invention. Detailed Description of the Invention Figure 1 illustrates a simplified overview of one form of the invention which is used in a motor vehicle. The invention switches between the two modes of operation shown in Figure 1. The left side of Figure 1 shows hydraulic power being delivered to a power steering system 3, by a pump 6, as indicated by the dotted path 9. No power is delivered to a fan system 12. The right side of Figure 1 shows hydraulic power being delivered, in parallel, to both the power steering system 3 , and the fan system 12 as indicated by the pair of dotted paths 9 and 15. In the embodiment being described, the pump 6 provides sufficient output 10 to satisfy both systems 3 and 12 at low rpms, such as less than 1500 or 2000 rpms A priority flow divide 81 described later herein provides the priority function by making sure that the power steering system's 3 flow requirements are met before delivering excess flow to fan system 12. Thus, the right side of Figure 1 is a normal operation, and the left side represents an operating mode that occurs if there is a reduction of flow, such as below the flow requirements of the steering system 3. Figure 2 illustrates one type of hydraulic circuitry which accomplishes the implementation shown in Figure 1. The group of components 18 correspond to the pump 6 of Figure 1. Components 18 include a fixed displacement pump 21, a relief valve 24, a pressure sensor 27, and an adjustable throttling valve 30. "Fixed displacement" means, speaking generally, that every revolution of the rotor (not shown) of the pump 21 produces a given volume of output. That is, the amount of fluid which the pump "displaces" per revolution is fixed. Thus, at higher speeds, the pump produces a greater volume of output due to a greater number of rotations per second. To accommodate the increasing fluid flow which occurs at higher speeds, sensor 27 directs the fluid flow through a venturi (not shown) . The pressure sensed by the sensor 27, corresponds to the flow rate through the venturi. This pressure is fed to the variable throttling valve 30, which opens and closes, according to a schedule (not shown), based on the pressure sensed by sensor 27. For example, when sensor 27 senses a low pressure, as at engine idle, the schedule may cause adjustable valve 30 to remain closed, causing all of the output of the pump 21 to be delivered to line 42. At a higher speed, as at 2,000 rpm, the schedule may cause the adjustable valve 30 to open a significant amount, thus dumping some amount of flow into the reservoir 10. The relief valve 24 acts as protection in the event that the output pressure, in line 42, becomes excessive. The overall operation of components 18 is well- known and includes: adjustable valve 30 opens and closes as output of the pump 21 changes in order to provide the proper flow rate in line 42. As an alternate to the group of components 18, a variable displacement pump (not shown) can be used. Such a pump maintains a constant volumetric flow, irrespective of engine speed. The fan system 12 of Figure 1 can be viewed as including three components shown in Figure 2, namely: a fan motor 51, a fan speed control valve 48, and a relief valve 45. The relief valve 45 acts as protection in the event that the input pressure to the fan motor 51, in line 54, becomes excessive. The fan speed control valve 48 controls speed of the fan motor 51 by causing fluid to bypass the fan motor 51. When the valve 48 is fully open, the system 12 is designed such that all fluid entering line 54 bypasses the fan motor 51. When the valve 48 is fully closed, all fluid entering line 54 enters the fan motor 51. At intermediate positions of valve 48, intermediate amounts of fluid reach the fan motor 51. Thus, assuming the relief valve 45 to be closed, as is the case in normal operation, the amount by which valve 48 is open controls the speed of the fan motor 51. The power steering system 3 of Figure 1 can be viewed as including three components of Figure 2, namely: a steering valve 60, a steering assembly 63, and a relief valve 66. The relief valve 66 serves as protection in case the pressure to the input of the steering valve 60, in line 57, becomes too great. Ordinarily, the relief valve 66 is closed. The steering valve 60 is a valve which selectively directs pressure to lines 72 and 75, to a steering assembly 63 to assist a driver of the vehicle in operating the steering wheels. Figure 3 illustrates how the hydraulic circuitry of Figure 2 accomplishes the parallel operation of Figure 1. A priority flow divider 81 allows flow indicated by the dashed path 100. Flowpath 100 is directed through steering valve 60, through line 57. After exiting the steering valve 60, the flow reaches line 115, which joins line 109 at junction 121, en route to the reservoir 10. The priority flow divider 81 is a conventional divider which partially or completely blocks flow through its first outlet 81A while measuring a flow parameter at its second outlet 8IB, such as flow rate. When that flow parameter reaches a threshold, such as a minimum flow rate, then the priority flow divider 81 opens flow to its first outlet 81A. (Of course, if the initial flow rate through the second outlet 81B already exceeded the threshold, then flow through the second outlet 81A would never have been blocked.) Figure 4 illustrates how the hydraulic circuitry of Figure 2 accomplishes the parallel operation mode shown at the right side of Figure 1. It should be appreciated that this is the normal operating state. If, however, the flow in the hydraulic systems 3 and 12 fall below a predetermined minimum, then divider 81 will deliver all output of pump 6 to the steering system 12. This has the advantage of causing steering system 12 and fan system 3 to operate in parallel during high engine rpms (such as in excess of, for example, 2000 rpms) . The flow parameter through the second outlet 81B has exceeded the threshold, so the priority flow divider 81 opens its first outlet 81A, creating the flowpath indicated by dotted line 103. From line 54, the flow reaches the fan motor 51, and, upon exiting the fan motor 51, reaches outlet line 109, which connects with the reservoir 10. Substantially, simultaneously therewith, the flow 10 directed to steering system 3 as in Figure 3 because flow divider 81 permits flow through second outlet 8IB. One form of the invention can be viewed as a control system for switching a hydraulic system between the two modes shown in Figure 1. The preceding discussion has presumed that all signals were hydraulic signals, and that these signals induced hydraulic switches, such as valve 81, to change state. However, the invention is not limited to a purely hydraulic control system. Electronic pressure sensors can be used, for example, to detect when flow in second outlet 81B is sufficient to trigger opening of the first outlet 81A. Note that the required size of pump 4 at engine idle speed is dictated by the fixed flow rate at outlet 81B which feeds the steering system 3. Conventional approaches of addressing increased flow rate needs in a hydraulic system is, for example, to provide a larger pump or increase engine speed. In contrast, it is envisioned that features of the present invention may be used with conventional variable effort and speed sensitive steering systems (not shown) so that the outlet 8IB may be provided such that it provides a flow which is responsive to, for example, electrical inputs from the variable effort or speed sensitive steering systems. This, in turn, will permit the flow directed to outlet 81A to be variable and available a greater percentage of the time, such as at low engine speeds. Consequently, the features of this invention provide means for eliminating or reducing the needs for a larger pump 21 or change in engine speed. Irrespective of whether a purely hydraulic control system is used, or a combined electronic- hydraulic control system is used, Figure 5 illustrates logic which the invention implements. In the case of a combined electronic-hydraulic control system, the ignition computer of the vehicle (also called the "onboard computer") can be used to perform the logic. At decision block 200, it is determined whether flow is sufficient for parallel operation (i.e., whether flow is sufficient to supply the fan system and the power steering system in parallel) . If so, then the logic reaches block 205, indicating that parallel flow is provided, as by the hydraulic circuit of Figure 3. If not, the logic reaches block 210, indicating that flow exclusively to the power steering system 3 is provided, as by the hydraulic circuit of Figure 3. The logic then returns to block 200, and repeats. Advantageously, this system and method provide means for dividing and/or prioritizing flow among a plurality of hydraulic components using a single flow divider. While the methods herein described, and the forms of apparatus for carrying these methods into effect, constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus, and that changes may be made in either without departing from the scope of the invention, which is defined in the appended claims . What is claimed is:

Claims: Claims 1. A hydraulic system for use in a vehicle comprising: a source of hydraulic pressure; a power steering system; a hydraulic fan system for cooling engine coolant ; a switching system for selectively i) delivering hydraulic pressure to the power steering system and blocking hydraulic pressure from the fan system; and ii) delivering hydraulic pressure to both the power steering system and the fan system. 2. A method of delivering hydraulic fluid to components in a vehicle, comprising the following steps: delivering flow to a power steering system while delivering no flow to a radiator cooling system during a first flow condition; and delivering flow to both the power steering system and the radiator cooling system during a non- first flow condition. 3. A hydraulic circuit for an automotive vehicle, comprising : a first line; a reservoir; a pump for drawing fluid from said reservoir and feeding fluid to said first line; a flow divider, which receives fluid from said first line, and selectively, i) delivers flow exclusively to a first low flow valve having first and second outlets; or ii) delivers flow both to the first low flow valve and to an excess flow port; a second line, which i) connects to said excess flow port, through a check valve which blocks flow from the second line into the excess flow port ; and ii) connects directly to a first outlet of the first low flow valve; a third line, which connects to the second outlet of the first low flow valve; a second relief valve connecting between the second line and the reservoir; a fan speed control valve, connecting between the second line and the reservoir; a fan motor, connecting between the second line and an inlet of a second low flow valve, having first and second outlets, i) the first outlet of which connects to the third line; and ii) the second outlet of which connects to the reservoir; a third relief valve, connecting between the third line and the reservoir; a power steering selector gear, connecting between the third line and the reservoir; wherein, in one mode of operation fluid flows in parallel from the flow divider, to the fan motor and the power steering selector gear; and in another mode of operation, fluid flows in series from the flow divider, to the fan motor, and thence to the power steering valve. 4. The hydraulic system as recited in claim 1 wherein said switching comprises a priority flow divider. 5. The hydraulic system as recited in claim 1 wherein said switching system comprises a priority flow divider coupled to both said power steering system and said hydraulic fan system; said system comprising a plurality of conduits coupled to said priority flow divider, said power steering system and said fan system such that when said priority flow divider delivers hydraulic pressure to both said power steering system and said fan system, said fan system and said power steering systems operate in parallel . 6. The hydraulic system as recited in claim 1 wherein said switching system comprises a priority flow divider coupled to both said power steering system and said hydraulic fan system; said system comprising a plurality of conduits coupled to said priority flow divider, said power steering system and said fan system such that hydraulic fluid is directed in parallel to said fan system and said power steering systems operate in parallel when said flow exceeds a predetermined flow rate. 7. The hydraulic system as recited in claim 1 wherein said switching system comprises a priority flow divider coupled to both said power steering system and said hydraulic system; said system comprising a plurality of conduits coupled to said priority flow divider, said power steering system and said fan system such that hydraulic fluid is directed in parallel to said fan system and said power steering systems except that when hydraulic fluid flow falls below a predetermined minimum level, said priority flow divider delivers fluid only to said steering system. 8. The method as recited in claim 2 wherein said method further comprises the step of : using a priority flow divider which selectively delivers fluid to either a first outlet or a second outlet in order to deliver flow to said steering system or said fan system, respectively. 9. The method as recited in claim 2 wherein said method further comprises the step of: coupling a single priority flow divider to said fan system and said steering system such that it divides flow between said fan system and said steering system they operate in parallel. 10. The method as recited in claim 2 wherein said method further comprises the step of: coupling a single priority flow divider to said fan system and said steering system such that it prioritizes said steering system over said fan system when hydraulic flow falls below a minimum level . 11. The method as recited in claim 2 wherein said method further comprises the step of: varying the delivery of flow to said power steering system or said radiator cooling system in response to a speed sensitive steering system signal from a speed sensitive steering system, said speed sensitive steering signal being generated in response to an operator actuating a steering wheel.

Inventors: BUSCHUR JEFFREY J, MACHESNEY KERRY A, BUSCHUR, JEFFREY, J., MACHESNEY, KERRY, A.
Applicants: ITT AUTOMOTIVE ELECTRICAL SYST, ITT AUTOMOTIVE ELECTRICAL SYSTEMS, INC.
Application year: 1997
Main classification: B62D5
IPC codes: B62D5, F01P7