The present invention relates generally to the field of vehicle hydraulic systems. The present invention relates more specifically to a load sensing system for vehicle hydraulic system including multiple hydraulic pumps and multiple actuators.
Hydraulic systems typically include a pressure source (e.g., a hydraulic pump), a hydraulic circuit through which the pressurized fluid is transported, and one or more devices (e.g., hydraulic cylinders, hydraulic motors, etc.) in which the pressure is used to do work. Flow of hydraulic fluid to the device may be controlled with a valve in the hydraulic circuit. The hydraulic pump may be a fixed displacement hydraulic pump that provides a fixed flow rate of hydraulic fluid. Because the hydraulic system may include several devices and more than one of the devices may be operated simultaneously using the pressurized hydraulic fluid, the pump is typically sized to provide a flow rate and pressure that is sufficient to run all or a number of the devices simultaneously. However, if only one device is operated with the hydraulic pump providing an excessive flow rate and pressure, excess pressure accumulates in the hydraulic circuit. To prevent damage to the components of the hydraulic system, a high pressure relief valve may be provided in the hydraulic circuit which allows excess hydraulic fluid to pass through the system (e.g., to a fluid reservoir). However, the hydraulic pump consumes excessive energy to provide a high fluid flow rate, the excess energy being converted to heat that can shorten the system life and jeopardize system function.
In current refuse industry vehicles, the hydraulic systems may include multiple hydraulic pumps working together to provide the pressure and flow rate required by several devices such as hydraulic actuators, with the flow to each of the devices controlled through valves in the hydraulic circuit. The hydraulic source used may be variable displacement hydraulic pumps with a pressure compensating load sensing system to regulate the output of the source and provide hydraulic fluid at a desired flow rate and pressure to match the varying demand of the multiple devices. The load sensing signals, the flow, or both are typically combined before the control valves.
When performing refuse collection functions, the working load faced by one valve from the associated actuator will likely affect both pumps. If a high load is sensed at one valve, the pressure in the system is increased to compensate and the other valves operate under unnecessarily high pressures, reducing the energy efficiency of the hydraulic system and potentially causing undesired, erratic movement of the actuators. In some cases, the unnecessarily high pressure can prevent normal performance of the system or contribute to the premature failure of components of the hydraulic system. When the load sense and flow are combined between pumps and the valves, one pump may become saturated before the other pump begins operating. One pump may work constantly while another pump only works intermittently. Flow limiters may be added to prevent one pump from operating excessively, but this adds cost and complexity to the hydraulic system. Further, the combined load sensing typically may amplify the load shocks and pressure spikes in the hydraulic system. This amplification can cause erratic or jerky movement of the actuators and accelerate premature failure of the components of the hydraulic system.
One embodiment of the invention relates to a hydraulic system for a vehicle, the hydraulic system including a first hydraulic circuit, a second hydraulic circuit, and a main actuator. The first hydraulic circuit includes a first pump having a flow outlet; a first pressure line having a pump end coupled to the flow outlet of the first pump; and a first load sensing line having a pump end coupled to the first pump and a pressure end coupled to the first pressure line. The second hydraulic circuit includes a second pump having a flow outlet; a second pressure line having a pump end coupled to the flow outlet of the second pump; and a second load sensing line having a pump end coupled to the second pump and a pressure end coupled to the second pressure line. The main actuator is coupled to the first pressure line and the second pressure line and is configured to oppose a load force. The first load sensing line is separate from the second load sensing line such that the first pump and the second pump respond independently to the load force.
Another embodiment of the invention relates to a hydraulic system for a vehicle, the hydraulic system including a plurality of pumps configured to provide a pressurized fluid including a first pump and a second pump. The hydraulic system further includes a plurality of pressure lines including a first pressure line coupled to the first pump and defining a first flow path and a second pressure line coupled to the second pump and defining a second flow path. The hydraulic system further includes a plurality of load sensing lines including a first load sensing line and a second load sensing line; a main actuator in fluid communication with the first pressure line and the second pressure line; a plurality of control valves including a first control valve disposed along the first flow path and a second control valve disposed along the second flow path; and a union coupling the first pressure line to the second pressure line. The union is positioned along the first flow path and the second flow path between the plurality of control valves and the main actuator thereby reducing hydraulic competition between the first pump and the second pump.
Yet another embodiment of the invention relates to a vehicle including a chassis; a driver coupled to the chassis, a first hydraulic circuit coupled to the chassis, a second hydraulic circuit coupled to the chassis, and a main actuator. The first hydraulic circuit includes a first pump coupled to the driver and having a flow outlet; a first pressure line having a pump end coupled to the flow outlet of the first pump; and a first load sensing line having a pump end coupled to the first pump and a pressure end coupled to the first pressure line. The second hydraulic circuit includes a second pump coupled to the driver and having a flow outlet; a second pressure line having a pump end coupled to the flow outlet of the second pump; and a second load sensing line having a pump end coupled to the second pump and a pressure end coupled to the second pressure line. The main actuator is coupled to the first pressure line and the second pressure line and configured to oppose a load force. The first load sensing line is separate from the second load sensing line such that the first pump and the second pump respond independently to the load force.
The invention is capable of other embodiments and of being carried out in various ways. Alternative exemplary embodiments relate to other features and combinations of features as may be recited in the claims.
The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements, in which:
Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the present application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting.
Referring to
The refuse truck 10 is configured to collect and transport refuse, such as from waste receptacles (e.g., cans, bins, containers) from a collection area, such as on the side of the road or in an alley. The body 14 includes sidewalls 22 defining a collection chamber, shown as a compartment 20 (e.g., hopper) in the rear of the refuse truck 10. Refuse may be deposited in the compartment 20 for transport to a waste disposal site such as a landfill or recycling facility.
Referring to
Referring to
Referring to
According to an exemplary embodiment shown in
According to an exemplary embodiment, the portion of the body 14 forming the compartment 20 may be rotated or tipped to empty refuse from the compartment 20 into another receptacle or collection area. According to an exemplary embodiment, the body 14 is tipped backwards (e.g., towards the tailgate 32 with a hydraulic actuator (e.g., lift cylinders, dump cylinders, raise cylinders, etc.). The tailgate 32 may simultaneously be rotated to open the rear of the body with an actuator, shown in
Referring now to
The flow outlet 65 of the first hydraulic pump 64 is coupled to one or more devices, shown as actuators 70a-70c, via a first pressure line 72 (e.g., high pressure line). A first valve block 74 includes a multitude of valves 76a-76c configured to control the flow of pressurized fluid to the actuators 70a-70c from the pressure line 72 and from the actuators 70a-70c to the reservoir 81 via a first return line 78 (e.g., low pressure line). According to an exemplary embodiment, the actuators 70a-c operate at between 500-1500 psi. According to a preferred exemplary embodiment, the actuators 70a-c operate at approximately 1000 psi.
The flow outlet 69 of the second hydraulic pump 68 is coupled to one or more devices, shown as actuators 80a-80b, via a second pressure line 82 (e.g., high pressure line). A second valve block 84 includes a multitude of valves 86a-86b configured to control the flow of pressurized fluid to the actuators 80a-80b from the pressure line 82 and from the actuators 80a-80b to the reservoir 81 via a second return line 88 (e.g., low pressure line). According to an exemplary embodiment, the actuators 80a-b operate at between 1500-2500 psi. According to a preferred exemplary embodiment, the actuators 80a-b operate at approximately 2000 psi.
According to an exemplary embodiment, the actuators 70a-70c and 80a-80b may be smaller capacity actuators, such as the hydraulic cylinders 26 for the front arms 24, the hydraulic cylinders 46 for the tailgate 32, the hydraulic cylinder for the top door 30, the hydraulic cylinders 37 for the side load arm 36, or the actuators for the grabber 34.
According to an exemplary embodiment, the hydraulic system 60 further includes a main actuator, shown as an actuator 90, that is coupled to both the first hydraulic circuit 62 and the second hydraulic circuit 66. The actuator 90 is coupled to the first hydraulic circuit 62 (e.g., the first pressure line 72) via a first valve 92 and is coupled to the second hydraulic circuit 66 (e.g., the second pressure line 82) via a second valve 94. According to an exemplary embodiment, the first valve 92 is provided as a part of the first valve block 74 and the second valve 94 is provided as part of the second valve block 84. The actuator 90 may be configured to oppose a load force that exceeds the maximum output capabilities (e.g., maximum pressure, maximum flow rate, etc.) of either the first hydraulic pump 64 or the second hydraulic pump 68. For example, the actuator 90 may be a high volume actuator such as the hydraulic cylinder 44 for the packer 40, where the actuator 90 opposes the load force of the refuse to be compacted.
The hydraulic system 60 further includes a load sensing system to monitor the load on the hydraulic system and provide a feedback independently to the first hydraulic pump 64 and the second hydraulic pump 68. A first load sensing line 96 is coupled between the first pressure line 72 and the first hydraulic pump 64. A second load sensing line 98 is coupled between the second pressure line 82 and the second hydraulic pump 68. The first load sensing line 96 and the second load sensing line 98 provide a feedback passage from the high pressure line back to the first hydraulic pump 64 and the second hydraulic pump 68, respectively. The first load sensing line 96 is coupled to control valves 97 (e.g., flow compensator, pressure compensator) that are coupled to the first hydraulic pump 64 and control the output of the first hydraulic pump 64 (e.g., by varying the angle of the camplate). The second load sensing line 98 is coupled to control valves 99 (e.g., flow compensator, pressure compensator) that are coupled to the first hydraulic pump 64 and control the output of the first hydraulic pump 64 (e.g., by varying the angle of the camplate). If an increased load is experienced in the high pressure line, it is sensed by the respective hydraulic pump via the load sensing line. The hydraulic pump output is then increased to compensate for the increased load.
According to an exemplary embodiment, the first load sensing line 96 is coupled to the branches 73 of the first pressure line 72 downstream from each of the control valves 76. The second load sensing line 98 is likewise coupled to the branches 83 of the second pressure line 82 downstream from each of the control valves 86.
The first hydraulic pump 64 and the second hydraulic pump 68 are generally isolated from each other. A fluctuation in the load on any of the actuators 70a-c as is sensed by the first load sensing line 96 to vary the output of the first hydraulic pump 64. A fluctuation in the load on any of the actuators 80a-b as is sensed by the second load sensing line 98 to vary the output of the second hydraulic pump 68. In either scenario, the first hydraulic pump 64 and the second hydraulic pump 68 are free to operate independent of each other. For example, if one of the actuators 80a-b encounters an elevated load and requires additional energy at a high pressure (e.g., approximately 2000 psi), only the output of the second hydraulic pump 68 is increased. The first hydraulic pump 64 is free to operate with an output tuned to the requirements of the actuators 70a-c of the first hydraulic circuit 62 at a lower pressure (e.g. approximately 1000 psi) without trying to match the output of the second hydraulic pump 68, the resulting difference in power which would be converted into waste heat.
The majority of the hydraulic functions of the hydraulic system 60, including those of the actuators 70a-c and the actuators 80a-b, are powered by just one of the hydraulic pumps 64 and 68. During a large majority of the operation of the refuse truck 10, only one of the actuators in each of the first hydraulic circuit 62 and the second hydraulic circuit 66 are operated at a time. The first hydraulic pump 64 may be configured to have a maximum output that is sufficient to operate each of the actuators 70a-c in the first hydraulic circuit 62 simultaneously and the second hydraulic pump may be configured to have a maximum output that is sufficient to operate each of the actuators 80a-b in the second hydraulic circuit 66 simultaneously.
The main actuator 90 may require a flow rate that exceeds the maximum flow rate of both the first hydraulic pump 64 on its own and the second hydraulic pump 68 on its own. According to an exemplary embodiment, the actuators 70a-c and the actuators 80a-b may have a maximum travel of approximately 6 feet, while the main actuator 90 may have a maximum travel of approximately 30-35 feet. The outputs of the pumps 64 and 68 may therefore be joined to provide a sufficient flow rate to the main actuator 90. According to an exemplary embodiment, the main actuator 90 is coupled to the first hydraulic circuit 62 via branches 91 and to the second hydraulic circuit 66 via branches 93. Unions 100 are provided between the valves 92 and 94 and the main actuator 90, with each union 100 having an inlet for one of the branches 91 of the first pressure line 72 and one of the branches 93 of the second pressure line 82. The unions 100 are each include an outlet coupled to the main actuator 90 via a common pressure line 102.
Referring now to
The load from the actuator 90 in the first pressure line 72 is sensed by the first load sensing line 96 independently compared to the load from the actuator 90 in the second pressure line 82 sensed by the second load sensing line 98. By joining the first pressure line 72 and the second pressure line 82 at unions 100 downstream of the valves 92 and 94 and downstream of the respective load sensing lines 96 and 98, the first pressure line 72 and the second pressure line 82 (and the loads as detected by the respective load sensing lines 96 and 98) are isolated from each other. The load from the main actuator 90 on the first hydraulic circuit 62 and the second hydraulic circuit 66 is therefore sensed independently for the first hydraulic pump 64 and the second hydraulic pump 68, minimizing cross-talk between the hydraulic pumps 64 and 68. The change in output of either the first hydraulic pump 64 or the second hydraulic pump 68 will not result in a change in output of the other pump as would be the case for two pumps attempting to compensate for the varying output in a shared pressure line as sensed by a shared load sensing line.
The construction and arrangements of the hydraulic system, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process, logical algorithm, or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.
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