WO2019050064A1

WO2019050064A1 - Hydraulic machine

Info

Publication number: WO2019050064A1
Application number: PCT/KR2017/009816
Authority: WO
Inventors: Hungju SHIN
Original assignee: Volvo Construction Equipment Ab
Priority date: 2017-09-07
Filing date: 2017-09-07
Publication date: 2019-03-14

Abstract

A hydraulic machine may include an engine; a working fluid source driven by the engine to supply working fluid; an actuator; a flow control valve fluidly communicating with the working fluid source, wherein when signal pressure is applied to the flow control valve, the flow control valve shifts, by an amount corresponding to the signal pressure, from a first position to a second position in which the flow control valve directs working fluid from the working fluid source to the actuator; an operator input device, by which an operator input an input; and a control device configured to regulate the signal pressure as a function of the input and a speed of the engine to control the flow control valve.

Description

HYDRAULIC MACHINE

The present disclosure relates to a hydraulic machine and, more particularly, to a hydraulic machine having improved responsiveness by compensating for low engine speed.

In a negative control hydraulic machine, an orifice is generally disposed on a return line through which fluid returns to a hydraulic tank to control a displacement of a pump using a pressure of fluid within the return line as signal pressure. When the flow rate is decreased due to reduced engine speed, the pressure within the return line is automatically reduced, so that feedback control to increase the displacement of the pump is performed. This can compensate for reduced engine speed to a certain extent, thereby improving initial responsiveness.

An electronic positive control hydraulic machine does not have the above-described control mechanism but has functions of detecting a speed of an engine and increasing a displacement of a pump, based on the engine speed at an early stage.

In a load sensing hydraulic machine, a flow rate thereof is adjusted depending on a degree of opening of a flow control valve, so that the same level of initial responsiveness can be obtained.

However, all of the above-described three control methods compensate for low speed of an engine by changing a displacement of the pump and are not employable when a fixed displacement pump is used.

FIG. 1 is a graph illustrating a relationship between an input, input via an operator input device, and signal pressure in a hydraulic machine of the related art, while FIG. 2 is a graph illustrating a relationship between the input and a working speed of a working device in the hydraulic machine as described with relation to FIG. 1.

As illustrated in FIG. 1, signal pressure applied to a flow control valve is generally determined depending on an input, input via an operator input device, regardless of a speed of the engine. Thus, as illustrated in FIG. 2, a flow rate and a pressure of working fluid are low during low engine speed, thereby causing a delay time during which a working device does not start moving, even after the operator input device is operated, and the flow control valve is opened thereby. That is, the lower the engine speed is, the greater the input required to move the working device is.

Accordingly, the present disclosure has been made in consideration of the above-described problems occurring in the related art, and the present disclosure is intended to provide improved responsiveness by compensating for low engine speed.

According to an aspect of the present disclosure, A hydraulic machine may include an engine; a working fluid source driven by the engine to supply working fluid; an actuator; a flow control valve fluidly communicating with the working fluid source, wherein when signal pressure is applied to the flow control valve, the flow control valve shifts, by an amount corresponding to the signal pressure, from a first position to a second position in which the flow control valve directs working fluid from the working fluid source to the actuator; an operator input device, by which an operator input an input; and a control device configured to regulate the signal pressure as a function of the input and a speed of the engine to control the flow control valve.

FIG. 1 is a graph illustrating a relationship between an input, input via an operator input device, and signal pressure in a hydraulic machine of the related art;

FIG. 2 is a graph illustrating a relationship between the input and a working speed of a working device in the hydraulic machine of the related art;

FIG. 3 is a circuit diagram schematically illustrating the configuration of a hydraulic machine according to exemplary embodiments;

FIG. 4 is a circuit diagram schematically illustrating the configuration of a hydraulic machine according to exemplary embodiments;

FIG. 5 is a flowchart sequentially illustrating a control process performed in a hydraulic machine according to exemplary embodiments;

FIG. 6 is a graph illustrating a relationship between an input, input via an operator input device, and signal pressure in a hydraulic machine according to exemplary embodiments;

FIG. 7 is a graph illustrating a relationship between an input, input via an operator input device, and a working speed of a working device in a hydraulic machine according to exemplary embodiments; and

FIG. 8 is a graph illustrating a relationship between an input, input via an operator input device, and a working speed of a working device in a hydraulic machine according to exemplary embodiments.

Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

Hydraulic machines according to the present disclosure include machines in which pressurized fluid is supplied to an actuator 130, which in turn actuates a working device using the pressurized fluid supplied thereto. Such hydraulic machines are used in a wide range of technical fields. In particular, construction machines, such as an excavator, industrial machines, and the like, are included in hydraulic machines according to the present disclosure.

FIG. 3 is a circuit diagram schematically illustrating the configuration of a hydraulic machine according to exemplary embodiments.

In some embodiments, as illustrated in FIG. 3, a hydraulic machine includes an engine 110, a working fluid source 120, an actuator 130, a flow control valve 140, an operator input device 150, and a control device 160.

The working fluid source 120 is driven by the engine 110. The working fluid source 120 can draw working fluid from a tank 180 and then discharge the working fluid toward the flow control valve 140. The working fluid source 120 may be a hydraulic pump. The hydraulic pump may be a fixed displacement pump that pumps a fixed amount of fluid per revolution of a driving shaft 105 (i.e. per revolution of the engine 110). The hydraulic machine may include a plurality of working fluid sources.

The actuator 130 may be operated by working fluid supplied by the working fluid source 120. A working device, a swing device, a travel device, and the like may be connected to the actuator 130, so that the working device, the swing device, the travel device, and the like can be actuated by the operation of the actuator 130. The actuator 130 may be a hydraulic cylinder or a hydraulic motor. The working device may be a boom, an arm, a bucket, or the like.

The flow control valve 140 may communicate with the working fluid source 120. When signal pressure is applied, the flow control valve 140 can shift a first position to a second position by an amount corresponding to the signal pressure. The first position may be a neutral position in which the flow control valve 140 may direct working fluid from the working fluid source 120 to the tank 180. When the flow control valve 140 is in the second position, the flow control valve 140 may direct working fluid from the working fluid source 120 to the actuator 130. The second position may include a third position and a fourth position, and a flow of working fluid, when the flow control valve 140 is in the third position, and a flow of working fluid, when the flow control valve 140 is in the fourth position, may be in opposite directions. The hydraulic machine may include a plurality of flow control valves. The plurality of flow control valves may be arranged in series on a central bypass passage extending from the working fluid source 120 to the tank 180, while being connected to the working fluid source 120, in parallel, via parallel passages.

The operator input device 150, by which an operator can input an input, may generate a first electrical signal corresponding to the input, and transmit the first electrical signal to an electronic control unit (ECU) 161, that will be described later. The operator input device 150 may include an operating member, such as a lever (for example, a joystick), a pedal, or a steering wheel, and an electrical signal generator generating the first electrical signal.

The control device 160 may control signal pressure as a function of the input and a speed of the engine 110.

FIG. 4 is a circuit diagram schematically illustrating the configuration of a hydraulic machine according to exemplary embodiments.

The control device 160 may include an ECU 161. The ECU 161 may include a central processing unit (CPU), a memory, and the like. The ECU 161 may generate a second electrical signal corresponding to an input, input via the operator input device 150, and a speed of the engine 110 using a pre-determined function. The control device 160 may include an electro-proportional pressure reducing valve 163. The electro-proportional pressure reducing valve 163 may, in an opened position, allow pilot fluid to flow from a pilot fluid source 170 to a flow control valve 140, and may, in a closed position, block a flow of pilot fluid from the pilot fluid source 170 to the flow control valve 140. When the ECU 161 applies a second electrical signal to the electro-proportional pressure reducing valve 163, the electro-proportional pressure reducing valve 163 can shift to an opened position by an amount corresponding to the second electrical signal, so that an amount of pilot pressure corresponding to the second electrical signal is applied to the flow control valve 140. That is, the electro-proportional pressure reducing valve 163 can operate the flow control valve 140 by applying an amount of signal pressure corresponding to the second electrical signal to the flow control valve 140. When the electro-proportional pressure reducing valve 163 applies signal pressure to the left of the flow control valve 140 in the drawing, the flow control valve 140 can shift to the third position, and when the electro-proportional pressure reducing valve 163 applies signal pressure to the right of the flow control valve 140 in the drawing, the flow control valve 140 can shift to the fourth position.

The hydraulic machine may include an engine control module (not shown). The engine control module may receive a control signal from the ECU 161 and regulate an amount of fuel injected into the engine 110, based on the control signal. The engine control module may include a speed sensor detecting a speed of the engine 110. The engine control module may transmit the value of the detected speed of the engine to the ECU 161

The hydraulic machine may include an engine speed control switch (not shown). The hydraulic machine may include a mode selection switch (not shown). When an operator operates at least one of the engine speed control switch and the mode selection switch, an operation signal may be transmitted to the ECU 161. The ECU 161 may transmit a signal corresponding to the operation signal to the engine control module, which in turn regulates an amount of fuel injected into the engine 110, based on the received signal,

FIG. 5 is a flowchart sequentially illustrating a control process performed in a hydraulic machine according to exemplary embodiments.

The control device 160 collects data of a speed of the engine 110 and an input, input via the operator input device 150. As described above or similarly to the above, the control device 160 is connected to a speed sensor to receive an electrical signal from the speed sensor so as to collect data of a speed of the engine 110. In addition, the control device 160 is connected to the operator input device 150 to receive a first electrical signal from the operator input device 150 so as to collect data of an input, input via the operator input device 150.

Afterwards, the ECU 161 calculates a second electrical signal corresponding to the collected data of the speed of the engine 110 and the collected value of the input using a pre-determined (previously stored) function and applies the calculated second electrical signal to the electro-proportional pressure reducing valve 163. The electro-proportional pressure reducing valve 163 is moved to an opened position by an amount corresponding to the second electrical signal, and thereby generates signal pressure corresponding to the second electrical signal (see FIG. 6).

Then, the control device 160, i.e. the electro-proportional pressure reducing valve 163, applies the generated signal pressure to the flow control valve 140.

In response thereto, the flow control valve 140 shifts by a calibrated amount.

Consequently, working fluid can be supplied at a calibrated flow rate to the actuator 130 (see FIG. 7).

FIG. 6 is a graph illustrating a relationship between an input, input via an operator input device 150 and signal pressure in a hydraulic machine according to exemplary embodiments. Reference symbols p1, p2, p3, p4, e1, e2, e3, e4, e5, m1, m2, m3, and m4 to be mentioned hereinafter are random values.

The hydraulic machine may generate different levels of signal pressure depending on a speed of the engine, even if the same input is input. That is, the lower the engine speed is, the higher the signal pressure may be.

The control device 160 may regulate signal pressure to be p1, when an input is m1 and a speed of the engine 110 is e1, and the control device 160 may regulate signal pressure to be p2, higher than p1, when an input is m1 and a speed of the engine 110 is e2, slower than e1.

The control device 160 may control signal pressure to be p3, higher than p1, when an input 150 is m3, higher than m1, and a speed of the engine 110 is e1.

The control device 160 may control signal pressure to be higher than p2, when an input is m3, higher than m1, and a speed of the engine 110 is e2.

The control device 160 may control signal pressure to be p3, higher than p2, when an input is higher than m1 and lower than m3, and a speed of the engine 110 is e2.

The control device 160 may control signal pressure to be p4, higher than p3, when an input is m4, higher than m3, and a speed of the engine 110 is e1, and the control device 160 may control signal pressure to be p4, when an input is m4 and a speed of the engine 110 is e2.

The control device 160 may control signal pressure to be 0, when an input is lower than m1.

The control device 160 may control signal pressure to be inversely proportional to a speed of the engine 110, when an input is m1.

FIG. 7 is a graph illustrating a relationship between an input, input via an operator input device 150, and a working speed of a working device in a hydraulic machine according to exemplary embodiments, and FIG. 8 is a graph illustrating a relationship between an input, input via an operator input device 150, and a working speed of a working device in a hydraulic machine, according to exemplary embodiments.

In some embodiments, as illustrated in FIG. 7, although speeds of the engine 110 are different, triggering inputs to trigger the working device may be the same (m1). That is, when the same input m1 is input via the operator input device 150, operations of the working device may be initiated regardless of whether a speed of the engine 110 is high or low. Thus, the operator can precisely operate the hydraulic machine with the same feeling of operation, so that the responsiveness of the hydraulic machine can be improved.

However, in some alternative embodiments, inputs to trigger the working device may be different, depending on a speed of the engine 110. In some of such embodiments, the standard deviation of the triggering inputs, as illustrated in FIG. 8, may be smaller than the standard deviation of triggering inputs in the hydraulic machine of the related art as described with reference to FIG. 2.

[Explanation of Reference numerals]

105: driving shaft 110: Engine

120: Working fluid source 130: Actuator

140: Flow control valve 150: Operator input device

160: Control device 161: Electronic control unit

163: Electro-proportional pressure reducing valve

170: Pilot fluid source 180: Tank

Claims

A hydraulic machine comprising:

an engine;

a working fluid source driven by the engine to supply working fluid;

an actuator;

a flow control valve fluidly communicating with the working fluid source, wherein when signal pressure is applied to the flow control valve, the flow control valve shifts, by an amount corresponding to the signal pressure, from a first position to a second position in which the flow control valve directs working fluid from the working fluid source to the actuator;

an operator input device, by which an operator inputs an input; and

a control device configured to regulate the signal pressure as a function of the input and a speed of the engine to control the flow control valve.
The hydraulic machine of claim 1, wherein

when the input is m1 and the speed of the engine is e1, the control device regulates the signal pressure to be p1, and

when the input is m1 and the speed of the engine is e2, the control device regulates the signal pressure to be p2,

where e1>e2, and p1<p2.
The hydraulic machine of claim 2, wherein

when the input is m3 and the speed of the engine is e1, the control device regulates the signal pressure to be p3,

where m1<m3, and p1<p3.
The hydraulic machine of claim 3, wherein

when the input is m4 and the speed of the engine is e1, the control device regulates the signal pressure to be p4, and

when the input is m4 and the speed of the engine is e2, the control device regulates the signal pressure to be p4,

where m3<m4, and p3<p4.
The hydraulic machine of claim 2, wherein

when the input is lower than m1, the control device regulates the signal pressure to be 0.
The hydraulic machine of claim 5, wherein

when the input is m1, the control device regulates the signal pressure to be inversely proportional to the speed of the engine.
The hydraulic machine of claim 1, wherein the control device comprises an electronic control unit and an electro-proportional pressure reducing valve, and

wherein the operator input device generates a first electrical signal corresponding to the input and transmits the first electrical signal to the electronic control unit,

the electronic control unit generates a second electrical signal corresponding to the input and the speed of the engine using a preset function and applies the second electrical signal to the electro-proportional pressure reducing valve, and

the electro-proportional pressure reducing valve shifts the flow control valve by applying the signal pressure corresponding to the second electrical signal to the flow control valve.
The hydraulic machine of claim 1, wherein the working fluid source comprises a fixed displacement hydraulic pump.
The hydraulic machine of claim 1, further comprising a tank,

wherein when the flow control valve is in the first position, the flow control valve directs working fluid from the working fluid source to the tank.