Patent Application
20130276439
This invention relates generally to the hydraulic system field, and more specifically to an improved hydraulic system with a low pressure accumulator in the hydraulic main pump field.
Typical hydraulic pump systems include a hydraulic pump that pumps and/or cycles fluid to a hydraulic device to do work (for example, to drive a hydraulic motor of a vehicle or to drive a hydraulic suspension system of a vehicle). In the operation of hydraulic pumps, a substantially continuous supply of fluid to the hydraulic pump is desired to minimize or prevent cavitation (i.e., interruptions of fluid supply to the hydraulic pump) within the hydraulic pump, which may damage or decrease the efficiency of the hydraulic pump. Hydraulic systems also typically lose fluid due to evaporation, leaks, and/or inefficiencies that further increases the risk of an interruption of fluid supply to the hydraulic pump. To overcome these issues, hydraulic systems typically include a fluid reservoir with additional fluid that compensates for fluid loss within the system. However, drawing fluid from a reservoir may not be sufficient to supply uninterrupted fluid supply for hydraulic pumps, in particular, for high speed hydraulic pumps that may be used in hydraulic vehicles or hydraulic suspension systems that require substantially fast response time of the hydraulic circuit. Additionally, some hydraulic pumps may operate better when the fluid entering the hydraulic pump is at a pressure that is higher than atmospheric. To provide a substantially continuous supply of pressurized fluid to a hydraulic pump also serves as a challenge. Some hydraulic systems in the field utilize low pressure supercharge pumps to increase the pressure/aid the flow of fluid to the hydraulic pump. However, such supercharge pumps may not be fast enough to provide enough fluid at the desired pressure under high speed conditions. Alternatively, large supercharge pumps may be utilized, but such large supercharge pumps may be expensive and costly to operate. In other hydraulic systems, a low pressure accumulator may be used to “store” fluid at an increased pressure that is readily available to the hydraulic pump when necessary. However, hydraulic systems that utilize such low pressure accumulators must maintain a certain volume of pressurized fluid within the low pressure accumulator and may include a system dedicated to maintaining the low pressure accumulator, which may be substantially costly, complicated to manage and maintain, and consume a substantially large amount of energy. In systems that aim to utilize hydraulic power as a means to replace fossil fuels, using such methods to main low pressure accumulators may not be an attractive option.
Thus, there is a need in the hydraulic pump field to create an improved hydraulic system with a low pressure accumulator that provides a substantially continuous supply of fluid for a hydraulic pump.
a, 2b, and 2c are a schematic representation of the method for managing fluid in a fluid system with a hydraulic pump that displaces fluid, in the run mode, fluid compensation, and charge mode, respectively.
The following description of the invention is not intended to limit the invention to these preferred embodiments, but rather to enable any person skilled in the art to make and use this invention.
As shown in
As shown in
As mentioned above, typical hydraulic systems that utilize low pressure accumulators include substantially complex, expensive, and high energy use systems that maintain the low pressure accumulator. For example, in the hydraulic system, there may be a low pressure accumulator fluid maintenance system that operates substantially separately from the hydraulic main pump fluid system. Additionally, hydraulic main pumps may operate better with a certain quality of fluid, for example, hydraulic main pumps may become damaged when unwanted sediment or contaminants (such as particulates or entrained gas such as air) are contained within the fluid going through the hydraulic main pump. Furthermore, hydraulic main pumps may operate better with fluid at a certain temperature. Thus, fluid systems typically also include a fluid preparation system that prepares fluid prior to the inlet to the hydraulic main pump.
Typical hydraulic systems also include a secondary pump that functions to direct fluid through the fluid preparation system. This allows the hydraulic main pump to function to pump fluid to a load without the hindrance of also driving fluid through the fluid preparation system. As a result, typical fluid systems with hydraulic main pumps may be relatively complicated and costly. As shown in
The system 100 and method S100 for managing fluid in a fluid system with a hydraulic main pump 110 is preferably used to maintain a substantially continuous supply of fluid 112 to the hydraulic main pump no. The hydraulic main pump no is preferably used to power a load 114, as shown in
In the variation where the hydraulic main pump no functions to pump fluid to a the hydraulic suspension strut of U.S. Pat. No. 5,988,599, the fluid 112 is preferably a compressible fluid and cooperates to supply the suspending spring force hydraulic suspension strut. The fluid 112 is preferably a silicone fluid that compresses about 1.5% volume at 2,000 psi, about 3% volume at 5,000 psi, and about 6% volume at 10,000 psi. Above 2,000 psi, the compressible fluid has a larger compressibility than conventional hydraulic oil. The compressible fluid, however, may alternatively be any suitable fluid, with or without a silicon component that provides a larger compressibility above 2,000 psi than conventional hydraulic oil. In the variation where the hydraulic main pump 110 functions to pump fluid to a hydraulic motor that drives a vehicle, the fluid 112 is preferably also a compressible fluid because the hydraulic main pump 110 may function to displace the fluid 112 in packets of fluid, and not in a continuous stream of fluid flow. This may cause the hydraulic motor to not run as smoothly as when supplied with a continuous stream of fluid flow. The compressibility of the fluid 112 in this variation cooperates with the hydraulic main pump 110 to decrease the impact of a non-continuous stream of fluid flow to the performance of the hydraulic main pump no. Additionally, in the variation where the load 114 is a hydraulic motor that drives a vehicle, because the hydraulic motor may experience, through backdrive, the irregularities of the road that the vehicle may encounter, for example, bumps or change in friction. Such irregularities in the road may cause the hydraulic motor to stall or increase speed, thus disrupting the flow of fluid 112 through the fluid system. The compressibility of the fluid 112 may function to dampen the effect of the disruption to the flow of the fluid 112 through the hydraulic system 100. For example, if the hydraulic motor stalls for a substantially short period of time, the flow of the fluid 112 is temporarily halted while the hydraulic main pump 110 continues to pump fluid through the system. If an incompressible fluid is used, the increase in flow pressure is directly transmitted to the hydraulic main pump no. If a compressible fluid is used, the increase of pressure is dampened through the compressibility of the fluid 112 and is not directly transmitted to the hydraulic main pump 110. However, any other suitable type of fluid may be used in the fluid system.
The reservoir 120 functions to store a portion of the fluid 112 at a first pressure. The first pressure is preferably of atmospheric pressure, decreasing the need for a pressure system that manages the reservoir 120, but may alternatively be of any other suitable pressure. The reservoir pressure is preferably equilibrated with the ambient environment through a vent or opening. Alternatively, the reservoir can be substantially sealed, or configured to hold a pressure seal. The reservoir 120 is preferably coupled to the fluid system and preferably supplies the fluid system with fluid 112. More preferably, the reservoir 120 is fluidly coupled to the fluid system through the valve system, but can be otherwise coupled to the system. The reservoir 120 is preferably of a material that is substantially chemically inert when in contact with the fluid 112. Alternatively, the reservoir 120 may include material that is chemically reactive when in contact with the fluid 112, where the chemically reactive material may function as a temporal indicator. The temporal indicator may inform the user or maintenance personnel of the age of the fluid 112 contained within the reservoir 120 and/or may instruct the user or the maintenance personnel of the need to replace the fluid 112. However, the reservoir 120 may be constructed of any other suitable material. The reservoir 120 is preferably of a shape that is substantially similar to a rectangular prism, but may alternatively be of any suitable shape that contains a suitable volume of fluid 112. The reservoir 120 preferably includes an orifice that is selectively opened and closed that allows for the fluid 112 to be removed and/or added to the reservoir 120. The orifice may also be selectively opened to remove contaminants in the fluid 112. The orifice can additionally include a particulate filter to prevent particulate egress into the fluid system. Alternatively, the reservoir 120 may include an orifice for the removal of the fluid 112 and/or contaminants and another orifice for the addition of the fluid 112. The reservoir 120 may also include a fluid level sensor to determine the amount of fluid within the reservoir 120. However, the reservoir 120 may be of any other suitable type, material, shape, or volume.
The accumulator 130 functions to store another portion of the fluid 112 at a second pressure that is higher than the first pressure. When there is a need for additional fluid 112 to the hydraulic main pump no (for example, when fluid is lost due to inefficiencies in the fluid system), the accumulator 130 functions to provide the additional fluid 112 to the hydraulic main pump no. Similarly, as shown in
The accumulator 130 preferably also includes a fluid level sensor that functions to determine the level of fluid 112 contained within the accumulator. The fluid sensor may be a sensor contained within the accumulator 130 that senses the level of the fluid 112, for example, an ultrasonic sensor or a wave sensor that detects wave changes that result from propagation through a fluid. In the variation of the accumulator 130 with a sprung wall that moves with the level of fluid, the location of the sprung wall may also be detected. In the variation of the accumulator 130 with pressurized gas, the pressure of the gas may be detected to determine the actual volume that the gas is occupying and assuming that the remainder of the volume is taken up by the fluid. In this variation, the temperature of the gas is also used to determine the volume of the gas. To determine the initial amount of gas within the accumulator 130, or to calibrate the sensor, the accumulator 130 may be “purged” using the third mode of the secondary pump 150 (in other words, substantially all of the fluid 112 is removed from the accumulator 130. However, any other suitable type of fluid level sensor may be used.
The system 100 is configured to operate in one of at least two modes: a first mode to displace fluid 112 from the outlet of the hydraulic main pump 110 through the fluid preparation system 140 to the inlet of the hydraulic main pump no (to “run” the fluid system) and a second mode to displace fluid 112 from the reservoir 120 to the accumulator 130 (to “charge” the accumulator 130. The system 100 may also be configured to operate in a third mode to displace fluid from at least one of the outlet of the hydraulic main pump no and the accumulator 130 back to the reservoir 120 (to “purge” the accumulator 130 and/or the fluid system). Because the pressure within the fluid system is higher than that of the reservoir 120, the secondary pump 150 in the third mode may be configured to be off to allow the pressure difference to drive fluid from the fluid system into the reservoir 120 to “purge” the accumulator 130 and/or the fluid system. Alternatively, the secondary pump 150 in the third mode may be configured to drive fluid within the fluid system towards the reservoir 120. However, any other suitable operation of the secondary pump 120 in the third mode may be used. The system 100 preferably operates in one mode at a time, but may alternatively operate in more than one mode concurrently, for example, the system 100 may operate in both the “run” mode and the “charge” mode concurrently to both displace fluid between the inlet and outlet of the hydraulic main pump 110 and charge the accumulator 130. The system 100 preferably additionally includes a controller configured to control the valve system (e.g., valves A and B), the secondary pump 150, and/or the valve of the hydraulic pump inlet to achieve the aforementioned modes. The secondary pump 150 may be substantially similar to the hydraulic main pump 110 or a pump within the hydraulic main pump 110, but may alternatively be different. Alternatively, the secondary pump 150 can be the hydraulic main pump 110, be a pump within the hydraulic main pump no, or be any other suitable pump. The secondary pump 150 is preferably packaged within the same package as the hydraulic main pump no, but can alternatively be packaged in a separate housing. The secondary pump 150 is preferably driven by the same shaft or power source as the hydraulic main pump no, but can alternatively be driven by a different shaft or power source from the hydraulic main pump no. In the variation where the pressure necessary to displace fluid 112 through the fluid preparation system 140 is lower than the second pressure of the accumulator 130, the secondary pump 150 is preferably of a pump that increases the pressure of the fluid 112 to at least the second pressure of the fluid 112 in the accumulator 130. The secondary pump 150 may also increase the pressure of the fluid 112 to above the second pressure of the accumulator 130 to compensate for any pressure loss between the fluid preparation system 140 and the travel distance of the fluid 112 to the accumulator 130. The variation where the pressure necessary to displace the fluid 112 through the fluid preparation system 140 is higher than the second pressure of the accumulator 130, the secondary pump 150 preferably increases the pressure of the fluid 112 to at least the pressure necessary to displace fluid through the fluid preparation system 140. In the second mode of the secondary pump 150, the secondary pump 150 may also function to displace fluid through the fluid preparation system 140 to the accumulator 130, as shown in
As described above, once the level of fluid within the accumulator 130 is determined to be below a certain “low fluid level” threshold (for example, a volume of the fluid 112 has been supplied to the hydraulic main pump no), the secondary pump 150 functions to “charge” the accumulator 130 from the reservoir 120. The secondary pump 150 preferably charges the accumulator 130 using fluid proximal the bottom of the reservoir 120 (e.g., wherein the bottom is a location within the reservoir furthest along a gravity vector) to prevent intake of fluid that may contain contaminants (for example, particulates or entrained gases such as air) that may enter the reservoir 120 and float to the top of the reservoir 120. The fluid is preferably drawn from a sidewall of the reservoir 120 adjacent the reservoir bottom, but can alternatively be drawn from the reservoir bottom or from any other portion of the reservoir 120. During “charge,” the secondary pump 150 may displace a volume of fluid into the accumulator 130 until a “high fluid level” threshold (second threshold), which is preferably higher than the “low fluid level” threshold, is reached. This provides the accumulator 130 with a buffer of fluid volume between the “low fluid level” threshold and the “high fluid level” threshold where the accumulator 130 may operate without substantial maintenance, which may decrease the number of times that the secondary pump 150 switches between the first mode and second mode of operation. Similar to the “low fluid level” threshold, the “high fluid level” threshold may be a predetermined threshold, but may alternatively be a dynamic threshold that actively changes to compensate for changes in the ambient temperature, fluid temperature, total fluid volume in the fluid system, and/or changing load requirements. Alternatively, during “charge,” the secondary pump 150 may function to displace a volume of fluid into the accumulator 130 until the fluid level is no longer below the “low fluid level” threshold. However, the secondary pump 150 may function to displace any suitable volume of fluid into the accumulator 130 to any suitable threshold. As shown in
The valve system 160 is configured to direct fluid 112 in one of at least two paths: a first path from the outlet of the hydraulic main pump no to the secondary pump 150 (as shown in
In a first variation, as shown in
As mentioned above, the system 100 may also include piping 170 that functions to allow fluid to flow within the system 100. The piping 170 may each be of any suitable length or geometry. This allows for the components of the fluid system to be placed in any suitable location relative to the load 114. The piping 170 is preferably composed of material that is substantially chemically inert to the fluid 112 and that is capable of withstanding the fluid pressure used in the fluid system. However, any other suitable type of piping may be used.
As a person skilled in the art will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claims.
This application claims the benefit of U.S. Provisional Application No. 61/636,854 filed 23 Apr. 2012, which is incorporated in its entirety by this reference.
| Number | Date | Country | |
|---|---|---|---|
| 61636854 | Apr 2012 | US | |
| 61636854 | Apr 2012 | US |
