RIDE CONTROL FOR WORK MACHINES

A hydraulic system can include a hydraulic actuator including a piston rod slidably disposed within a housing having a base-side port and a rod-side port, a hydraulic pump, a hydraulic reservoir, an accumulator, a first control valve operable to selectively control flow from the pump to the base-side port and from the base-side port to the reservoir, a second control valve operable to selectively control flow from the pump to the rod-side port and from the rod-side port to the reservoir, a third control valve operable to selectively allow flow between the base-side port and the accumulator, and a controller for operating the hydraulic system and including a ride control mode in which damping is provided to the hydraulic actuator by operation of the first, second, and third control valves.

BACKGROUND

Work machines, such as fork lifts, wheel loaders, track loaders, excavators, backhoes, bull dozers, fire trucks and telehandlers are known. Work machines can be used to move material, such as pallets, dirt, and/or debris. The work machines typically include a work implement (e.g., a fork) connected to the work machine. The work implements attached to the work machines are typically powered by a hydraulic system. The hydraulic system can include a hydraulic pump that is powered by a prime mover, such as a diesel engine. The hydraulic system typically includes a number of work sections for operating actuators via control valve assemblies. Many work machines are provided without independent suspension systems. Accordingly, when work machines are carrying a load via the work implement while moving in a forward or reverse direction, significant oscillations of the work machine induced by bouncing of the load can occur. Without compensating for this circumstance, an operator generally must reduce the speed of the work machine in order to maintain acceptable control of the work machine. Ride control systems for such work machines are known in which the hydraulic fluid of the hydraulic system is used to dampen the oscillations. Frequently, such systems require the addition of numerous control components, such as control valves. While these systems are beneficial in increasing performance, they introduce additional cost and complexity. Improvements are desired.

SUMMARY

A hydraulic system can include a hydraulic actuator including a first port and a second port, a hydraulic pump, a hydraulic reservoir, an accumulator, a first control valve operable to selectively control flow from the pump to the first port and from the first port to the reservoir, a second control valve operable to selectively control flow from the pump to the second port and from the second port to the reservoir, a third control valve operable to selectively allow flow between the first port and the accumulator, and a controller for operating the hydraulic system and including a ride control mode in which damping is provided to the hydraulic actuator by operation of the first, second, and third control valves. In some examples, the hydraulic actuator is a linear type actuator having a piston rod slidably disposed within a housing and wherein the first port is a base-side port and the second port is a rod-side port.

A hydraulic system can include a hydraulic actuator including a piston rod slidably disposed within a housing having a base-side port and a rod-side port, a hydraulic pump, a hydraulic reservoir, an accumulator, a first control valve operable to selectively control flow from the pump to the base-side port and from the base-side port to the reservoir, a second control valve operable to selectively control flow from the pump to the rod-side port and from the rod-side port to the reservoir, a third control valve operable to selectively allow flow between the base-side port and the accumulator, and a controller for operating the hydraulic system and including a ride control mode in which damping is provided to the hydraulic actuator by operation of the first, second, and third control valves.

In some examples, the ride control mode includes a passive bounce-down dampening control in which: the first control valve is operated to isolate the base-side port from both the pump and the reservoir, the second control valve is operated to place the rod-side port in fluid communication with the reservoir, and the third control valve is operated to place the accumulator in fluid communication with the base-side port.

In some examples, the system further includes a pressure sensor in fluid communication with the rod-side port, wherein the ride control mode includes an active bounce-up dampening control in which: the first control valve is operated to isolate the base-side port from both the pump and the reservoir, the second control valve is operated to place the rod-side port in fluid communication with the reservoir and modulated to meet a meter-out pressure set point value at the pressure sensor, and the third control valve is operated to place the accumulator in fluid communication with the base-side port.

In some examples, the third control valve is a two-position solenoid valve.

In some examples, the system further includes a first pressure sensor in fluid communication with the base-side port, wherein the ride control mode includes an active bounce-down dampening control in which: the first control valve is operated to isolate the base-side port from both the pump and the reservoir, the second control valve is operated to place the rod-side port in fluid communication with the reservoir, and the third control valve is operated to place the accumulator in fluid communication with the base-side port and modulated to meet a pressure set point value at the first pressure sensor.

In some examples, the system further includes a second pressure sensor in fluid communication with the rod-side port, wherein the ride control mode includes an active bounce-up dampening control wherein: the first control valve is operated to isolate the base-side port from both the pump and the reservoir, the second control valve is operated to place the rod-side port in fluid communication with the reservoir and modulated to meet a meter-out pressure set point value at the second pressure sensor, and the third control valve is operated to place the accumulator in fluid communication with the base-side port and modulated to meet a pressure set point value at the first pressure sensor.

In some examples, the system further includes a fourth control valve disposed between the base-side port and the first control valve, wherein the fourth control valve is operable between open and closed positions, and is placed in the closed position when the ride control mode is active.

In some examples, the system further includes a relief valve in fluid communication with the base-side port and the first control valve, wherein the first control valve has a neutral position including an orifice placing the reservoir in fluid communication with the base-side port via an orifice within the first control valve, wherein, when the ride control mode is active, the first control valve is in the neutral position such that when hydraulic fluid flows through the relief valve, the hydraulic fluid flows through the orifice to the reservoir.

In some examples, the system further includes a relief valve piloted by fluid from the rod-side port.

In some examples, the hydraulic actuator is a linear hydraulic actuator.

In some examples, the first and second control valves are disposed in a common valve assembly.

In some examples, the first, second, and third control valves are disposed in a common valve assembly.

DETAILED DESCRIPTION

General Description

As depicted atFIGS.1and2, a work machine1and hydraulic system10are shown. The work machine1may be any type of work machine, for example a telehandler, fork lift, wheel loader, track loader, excavator, backhoe, bull dozer, or fire truck. As depicted, work machine1includes a work attachment2for performing a variety of lifting tasks associated with a load3. In one embodiment, the work machine1is a telehandler having a telescoping boom4that supports the work attachment2. In one embodiment, the work attachment2includes a pair of forks. However, one skilled in the art will appreciate that the work attachment may be any hydraulically powered work implement.

Work machine1is also shown as including at least one drive wheel5and at least one steer wheel6. In certain embodiments, one or more drive wheels5may be combined with one or more steer wheels6. The drive wheels5are powered by an engine7. Engine7is also configured to power a hydraulic system10including various work circuits11. As illustrated atFIG.2, example work circuits11are a tilt work circuit11a,an extension work circuit11b,and a lift work circuit11c.The work circuits11can be powered by a hydraulic pump12and placed in fluid communication with a common reservoir14. In some examples, the work machine1includes hydraulic actuators and valves for effectuating steering and propulsion, stabilizing, and for lifting, extending, tilting, and sideways motions of the work attachment2. In one embodiment, the pump12is powered indirectly by the engine7. In one embodiment, the pump12is mechanically coupled to the engine7, such as by an output shaft or a power take-off9. In operation, the work circuit11actuates the work attachment2by operation of the pump12in cooperation with a number of hydraulic actuators102and control valves110,120. As shown, the pump12is a variable displacement axial pump provided with a conventional load-sense control arrangement to control the displacement of the pump12such that an appropriate flow can be delivered to the work circuits11. In one aspect, the load-sense arrangement can include a load-sense spool, a maximum pressure cut-off spool, and an actuator for adjusting a swash plate angle of the pump12. Although three work circuits are shown, additional work circuits can be provided in the hydraulic system without departing from the concepts presented herein. Although an example work machine1is shown and described, the disclosure is not limited to any particular work machine and is broadly applicable to any hydraulic system including actuators operated via control valves and a pump. In the example shown, the actuator102is associated with a lift function of a boom and is configured as a linear actuator. Other types of actuators may be used in various applications. For example, a rotary type hydraulic actuator may be used in a winch application.

Referring toFIG.3, an example work circuit11for operating an actuator102is presented for use in a hydraulic system100which may in turn form part of hydraulic system10. In the example shown, the actuator102is associated with a lift function of a boom. Although a single actuator102is shown, it should be understood that the depicted work circuit could include multiple actuators102operated by the same control valves110,120as is shown, for example, atFIG.2.

In one aspect, the actuator102has a housing104with a base-side port104aand a rod-side port104band piston rod106slidably disposed within the housing104. As fluid enters the base-side port104aand exits the rod-side port104b,the piston rod106extends. Likewise, as fluid enters the rod-side port104band exits the base-side port104a,the piston rod106contracts.

As shown, the work circuit11includes a first control valve110and a second control valve120for controlling the position and function of the actuator(s)102. Each of the control valves110,120is configured as a three-position, three-way valve with ports110a,110b,110cand120a,120b,120c,respectively. The control valves110,120are also operable between positions A, B, and C. Each control valve110,120is also shown as being provided with oppositely acting centering springs112,114and122,124for biasing the control valves110,120into the position C. Oppositely acting actuators214,216are provided for moving the control valve into either position B or C via a control system50. The actuators214,216can be any type of actuators for selectively controlling the position of the control valves110,120, for example, the actuators214,216can be electric, hydraulic, electro-hydraulic, mechanical, and/or any other type of actuator capable of performing the operations described herein. Position sensors211,212, which may be configured as LVDT (Linear Variable Differential Transformer) sensors, are also shown as being provided with each control valve110,120. The work circuit11is also shown as being provided with pressure sensors202,204,206, and208, with counterbalance valves170,172, and oppositely acting check valves174,176. The check valves174and/or176may be utilized where the reservoir is pressurized to avoid cavitation, for example during a load bounce-down, depending on the system.

As configured, the first control valve110is in fluid communication with the base-side port104avia port110cwhile the second control valve120is in fluid communication with the rod-side port104bvia port120c.When the first control valve110is in the first position A and the second control valve120is in the second position B, the port104ais placed in fluid communication with the reservoir14via ports110a,110cand the port104bis placed in fluid communication with the pump12via ports120b,120csuch that the piston rod106contracts. When the first control valve110is in the second position B and the second control valve120is in the first position A, the port104ais placed in fluid communication with the pump12via ports110b,110cand the port104bis placed in fluid communication with the reservoir14via ports120a,120csuch that the piston rod106extends. Generally, when either or both of the control valves110,120are in the third position C, at least one of the ports104a,104bis blocked such that fluid flow via the pump12and/or reservoir14is blocked through the actuator102.

The work circuit11is also shown as including an accumulator arrangement including an accumulator140and a control valve130. In one aspect, the accumulator140has a port140awhile a control valve130has ports130a,130b,wherein the ports140a,130aare in fluid communication with each other and the port130bis in fluid communication with the base-side port104a.As configured, the control valve130is a two-position, two-port control valve movable between first and second positions A, B.

The control valve130is provided with a biasing spring132that biases the control valve130towards the position B and an actuator222for actuating the control valve130towards the position A. The actuator222can be any type of actuator for selectively controlling the position of the control valve130, for example, the actuator222can be electric, hydraulic, electro-hydraulic, mechanical, and/or any other type of actuator capable of performing the operations described herein. In the position A, the ports130aand130bare placed in fluid communication such that the accumulator port140bis placed in fluid communication with the actuator base-side port104a.In the position B, the ports130aand130bare isolated from each other such that fluid flow into or out of the accumulator140is blocked.

With reference toFIG.4, the work circuit11is shown as further including an arrangement180having a load- holding valve150, shown herein as a poppet valve. As configured, the load-holding valve150is a two-position, two-port control valve with ports150a,150band is movable between first and second positions A, B. As shown, the port150ais in fluid communication with the base-side port104aand with the port130aof the valve130. The port150bis in fluid communication with the port110cof the valve110. The control valve150is provided with a biasing spring152that biases the control valve150towards the position B and with an actuator224for actuating the control valve150towards the position A. The actuator224can be any type of actuator for selectively controlling the position of the control valve150. For example, the actuator224can be electric, hydraulic, electro-hydraulic, mechanical, and/or any other type of actuator capable of performing the operations described herein. In the position A, the ports150aand110bare placed in fluid communication such that fluid can flow between the valve110and the base-side port104a.In the position B, the ports150aand150bare isolated from each other such that fluid flow between the valve110and the base-side port104ais blocked. Accordingly, the valve150can act as a load-holding valve to prevent retraction of the actuator102when the valve150is in the second position B. With such a configuration, the control valve110can be provided with a spring offset or software control to functionally form an orifice to allow fluid flow to achieve equilibrium with the reservoir14. Accordingly, when a ride control mode is active and the control valve is in the position C and hydraulic fluid is flowing through the below-described relief valve160, the hydraulic fluid can flow through the control valve110to the reservoir14.

With reference toFIGS.5to7, the work circuit11and arrangement180are further shown as including a counterbalance/relief valve160with ports160a,160bthat provides a flow path around the load-holding valve150and is piloted by fluid from the rod-side port104band/or the control valve120. The counterbalance valve is biased in a closed position by a spring162such that the ports160a,160bare normally isolated from each other. The valve160can also be provided with a port160cfor receiving a pilot fluid. When sufficient pressure exists, for example when thermal relief is required, fluid flow is allowed to pass through ports160a,160band around valve150. It is noted that the any of the actuators associated with operating the control valves of the present disclosure may be configured as proportional actuators.

Ride Control Mode for Configurations of FIGS.3to7

In general, the configurations shown atFIGS.3to7may be referred to as cylinder-side ride-control configurations as the accumulator140is in fluid communication with at least one of the actuator ports104a,104b.Through the use of the control system50, described in more detail below, the above-described control valves and sensors can be used in conjunction to effectuate a ride-control mode in bounce-up and bounce-down control phases. By use of the term ride-control mode, it is meant to include a control mode or configuration effectuated by the control valves that minimizes the bouncing of a load supported by the work attachment when the associated vehicle or work machine is moving in a direction, for example a forward direction via drive wheels5. By use of the term bounce-up control, it is meant to include a ride control mode phase that minimizes the bouncing of the load in an upward direction against gravity. By use of the term bounce-down control, it is meant to include a ride control mode phase that minimizes the bouncing of the load in a downward direction with gravity. In general terms, the ride control mode of the configurations shown inFIGS.3to7can be effectuated through the operation of the control valves110,120, and130. As the valves110,120are already present in the system for control of the actuator102, the disclosed ride control modes can be accomplished with a minimum of additional components, as compared to prior art approaches.

In one example, the ride control mode can include a passive bounce-down dampening control phase in which the control valve110is operated to the position C to isolate the base-side port104afrom both the pump12and the reservoir14, the control valve120is operated to the position A to place the rod-side port104bin fluid communication with the reservoir14, and the control valve130is operated to the position A to place the accumulator in fluid communication with the base-side port104a. With such a configuration, the accumulator can absorb the fluid pushed out of the base-side port104adue to a bounce-down condition in which a load is causing the actuator102to retract, thereby dampening the bouncing of the load.

In one example, the ride control mode can include an active bounce-up dampening control phase in which the control valve110is operated to the position C to isolate the base-side port104afrom both the pump12and the reservoir14, the control valve120is operated between positions A and C in a metering or modulating state to place the rod-side port104bin fluid communication with the reservoir14and to meet a meter-out pressure set point value at the pressure sensor208, and the control valve130is operated to the position A place the accumulator140in fluid communication with the base-side port104a.With such a configuration, the control valve120can act as a dampening orifice and the reservoir can absorb the fluid pushed out of the rod-side port104bdue to a bounce-up condition in which a load is causing the actuator102to extend, thereby dampening the bouncing of the load. In some examples, the control valve130is actively modulated with reference to the pressure sensor206to control flow out of the accumulator and into the base-side port104aduring the bounce-up control phase.

In one example, the ride control mode can include an active bounce-down dampening control phase in which the control valve110is operated to the position C to isolate the base-side port104afrom both the pump12and the reservoir14, the control valve120is operated between positions A and C in a metering or modulating state to place the rod-side port104bin fluid communication with the reservoir14and to meet a meter-out pressure set point value at the pressure sensor208, and the control valve130is15operated to the position A place the accumulator140in fluid communication with the base-side port104b.In some examples, the control valve control valve130is actively modulated with reference to the pressure sensor206to control flow into the accumulator and out of the base-side port104aduring the bounce-down control phase.

Where a load-holding valve150is provided, the load-holding valve can be placed in the closed position B when the ride control mode is active.

The hydraulic system configurations shown atFIGS.8to17are generally similar to those shown atFIGS.3to7with respect to the configurations of the pump12, reservoir14, and the valves110,120,150,160,170to176. Accordingly, the descriptions for these components need not be repeated here. Rather the differences between the systems will be discussed. The primary difference between the systems is that the accumulator140in the configurations shown atFIGS.8to17is placed in fluid communication with the pump12and reservoir14via valves130and135. As configured, the valve130controls fluid flow between the accumulator140and the reservoir-side components (e.g. the reservoir14, port110aof valve110, and port120aof valve120) and the valve135controls fluid between the accumulator140and the pump-side components (e.g. the pump12, port110bof valve110, and port120bof valve120). A check valve178is also shown such that fluid flow can occur between the ports110b,120band the accumulator140via valve130without requiring involvement of the pump12or causing fluid to flow in a reverse direction through the pump12. Also, as the accumulator140is no longer in direct fluid communication with the actuator port104a,a pressure sensor210can be provided to provide an input for the accumulator pressure. Also, as illustrated atFIGS.10to17, valves150and160can also be provided in the system, as is described previously for the systems shown atFIGS.5-7. It is noted that the any of the actuators associated with operating the control valves of the present disclosure may be configured as proportional actuators.

Ride Control Modes for Configurations of FIGS.8-17

In general, the configurations shown atFIGS.8to17may be referred to as pump-side ride-control configurations as the accumulator140is in fluid communication with the pump12via valve135rather than being directly connected to at least one of the actuator ports104a,104b.Through the use of the control system50, described in more detail below, the above-described control valves and sensors can be used in conjunction to effectuate a ride-control mode in bounce-up and bounce-down control phases. In general terms, the ride control mode of the configurations shown inFIGS.8to17can be effectuated through the operation of the control valves110,120,130, and135. As the valves110,120are already present in the system for control of the actuator102, the disclosed ride control modes can be accomplished with a minimum of additional components, as compared to prior art approaches.

With reference toFIGS.8and15, the hydraulic system100can be placed in a charge or pre-charge mode in which the accumulator140pressure is charged with fluidized pressure from the pump12. In one aspect, boom pressure is read by the control system at pressure sensor206and the accumulator140is charged by sending load-sense pressure from a load-sense arrangement18to the pump12until the pressure sensor210indicates the accumulator140is at the desired pressure. Any overshoot may be drained using orifice131and control valve130. Similarly, the accumulator140can be drained by de-energizing the control valve130such that fluid can flow from the accumulator140to the reservoir14. The check valve178may be included to ensure the pump12does not go over center from accumulator or load induced pressure.

With continued reference toFIGS.8and12, the system can be placed in a ride control mode with a bounce-down control in which control valves130and135are energized to block flow from the accumulator140to the reservoir14and open flow from the accumulator to the pump-side components. Prior to engaging this mode, the control system50can verify via sensor210that the accumulator140is at sufficient pressure to absorb and rebound hydraulic oil coming from actuator102. During bounce down, the oil is metered through the valve130into the accumulator140at a desired dampening rate which is accomplished by reading pressure sensors204,206, and210, and by using a closed loop control of valve110with spool position feedback from position sensor211. Actuator rod-side make up oil to port104bmay be provided from reservoir14through the check valve174, which for example may be set at 0.3 bar, and fed through the fully open valve120and anti-cavitation function in a work port of valve172.

With reference toFIGS.9and12, the system100can be placed in a bounce-up control by activating the control valves130,135, by fully opening valve110, and by metering valve120. During bounce-up of the load, the rod-side port104boil is metered through control valve120and through check valve176, which for example may be set at 5 bar. The desired dampening rate may be accomplished by reading the pressure sensors, for example pressure sensors202and208, and by using a closed loop control of control valve120along with spool position feedback from position sensor212. Actuator base-side make up oil at port104acan be provided from the accumulator140through the control valve135and the fully open control valve110.

With reference toFIG.10, it is noted that the system is placed in a load-holding mode in which the control valve150is closed and the control valves110,120are placed in position C such that flow to the actuator102is cut off from the pump12and reservoir. As with other examples, any flow through the relief valve160can pass through the internal orifice of the valve110and to the reservoir14. The valve160allows for manual override for lowering and also provides for thermal relief. In some instances, the control system50can override the position of the valve110such that flow is not permitted through the valve110.

With reference toFIG.13, the system100is placed in a boom gravity-lower mode in which the control valve120is fully open to the reservoir14in position A and the valve150is energized to the open position. In this mode, the control valve110is metering in position A to allow fluid flow to pass from the base-side port104ato the reservoir in a controlled manner to allow the boom4to lower by gravity at a desired rate. During lowering, fluid flows from the reservoir14to the rod-side port104bvia the valve120.

With reference toFIG.14, the system100is placed in a counterbalance valve down mode in which both of the valves110,120are metering in the position B to direct flow to the reservoir14via the counterbalance valves170,172.

With reference toFIG.16, it is illustrated that the actuator102can be actuated by the accumulator140, for example when the engine is off and/or the pump12is deactivated or unavailable. In such a configuration, the valve135is energized into the open position, the valve110is metered in the position B, and the valve120is metered in the position A to lift the boom via actuation of the actuator102. In one aspect, feedback from the actuator can be used to accomplish unpowered drift compensation.

With reference toFIG.17, the system100can be operated in a warm-up cycle to raise the temperature of the hydraulic oil in the system. In such a mode, the valves110,120are placed in a closed position C, the valve135is energized to the open position, and the valve130is metered in the open position such that oil flowing from the pump12is directed through the valves130,135in a controlled manner. The pressure drop associated with the fluid flowing through these components operates to elevate the temperature of the oil. In such an operation, the pump12can be commanded to meet a pressure set point, for example as defined at sensor210. The oil temperature can be monitored by a temperature sensor associated with the system100such that the warm-up cycle can be terminated once a desired oil temperature is achieved.

Electronic Control System50

In one aspect, the above-described pump, control valves, pressure sensors, position sensors, and other related components can be operated by an electronic control system50with any desired number of inputs and outputs to achieve the above-described methods of operation. The electronic control system50can include multiple controllers. For example, the control system50can include a system-level HFX programmable controller manufactured by Eaton Corporation of Cleveland, Ohio, USA; and an Eaton VSM controller which serves as an interface module and acts as a standard vehicle CAN bus (controller area network) gateway, a DC to DC power supply, and a supervisory controller for the hydraulic valve system. In one aspect, the control system50can also include valve assemblies, for example valve assemblies110,120, that are configured within an Eaton CMA valve which includes a CAN-Enabled electrohydraulic sectional mobile valve that utilizes pressure and position sensors, on board electronics, and advanced software control algorithms.

The control system50can include a processor and a non-transient storage medium or memory, such as RAM, flash drive or a hard drive. Memory is for storing executable code, the operating parameters, and the input from the operator user interface while processor is for executing the code. The control system50can also include transmitting/receiving ports, such as a CAN bus connection or an Ethernet port for two-way communication with a WAN/LAN related to an automation system and to interrelated controllers. A user interface may be provided to activate and deactivate the system, allow a user to manipulate certain settings or inputs to the control system50, and to view information about the system operation.