Patent Description:
A hydraulic machine is an apparatus configured to carry out work by supplying high pressure fluid to (an actuator of) a working device. To improve the fuel efficiency of the hydraulic machine, a technology of recovering energy contained in fluid discharged from an actuator of the working device has been proposed. Such a technology may reduce the consumption of fuel by recovering energy.

Various aspects of the present invention provide a hybrid hydraulic machine to recover energy from fluid discharged from a boom actuator so as to reduce fuel consumption and at the same time, improve the responsiveness of a jack-up motion.

According to the present invention, a hydraulic machine includes: a boom actuator including a large chamber and a small chamber, wherein the large chamber and the small chamber is are defined by a piston movable within the actuator, the piston being connected to a piston rod that extends through the small chamber, wherein when fluid is received pressurized by the boom actuator and discharged from the boom actuator, an area on which fluid inside the small chamber is in contact with the piston is smaller than an area on which fluid inside the large chamber is in contact with the piston; a recovery unit configured to receive fluid discharged from the large chamber and then recover energy; a recovery line connecting the large chamber and the recovery unit; an accumulator connected to the recovery line; a jack-up assist line connecting the accumulator and the small chamber; a jack-up assist valve disposed on the jack-up assist line to block flow of fluid from the accumulator to the small chamber in a first position and allow the flow of fluid from the accumulator to the small chamber in a second position; and a controller configured to control movement of the jack-up assist valve.

The controller determines whether or not the hydraulic machine is in a jack-up condition, and when the hydraulic machine is determined to be in the jack-up condition, moves the jack-up assist valve to the second position. The controller is configured to determine that the hydraulic machine is in the jack-up condition when a load pressure applied to the large chamber by a load is equal to or less than a threshold value.

In some embodiments, the hydraulic machine may further include a first sensor configured to measure a pressure in the accumulator. The controller may control movement of the jack-up assist to the second position such that, the greater a value obtained by subtracting a pressure in the small chamber from the pressure in the accumulator measured by the first sensor is, the smaller the amount of the movement of the jack-up assist valve to the second position is.

In some embodiments, the hydraulic machine may further include a first operator input device by which an operator-desired operating speed of the boom actuator is input. The controller may control movement of the jack-up assist valve to the second position such that, the higher the operator-desired operating speed of the boom actuator, the greater the amount of the movement of the jack-up assist valve to the second position is.

In some embodiments, the threshold value may be in the range of <NUM> to <NUM> bars.

In some embodiments, the hydraulic machine may comprise a second sensor and a third sensor and the load pressure may be Pa - Pb/(Aa/Ab), where Pa is pressure in the large chamber measured by the second sensor, Pb is pressure in the small chamber measured by the third sensor, Aa is an area of the large chamber on which the fluid inside the large chamber is in contact with the piston, and Ab is an area of the small chamber on which the fluid inside the small chamber is in contact with the piston.

According to embodiments of the present disclosure, the hybrid hydraulic machine can recover energy from fluid discharged from a boom actuator so as to reduce fuel consumption and at the same time, improve the responsiveness of a jack-up motion.

Within the scope of the present invention as defined by the appended claims, other features and advantages will be apparent from or which are set forth in greater detail in the accompanying drawings, the description of which are incorporated herein, and in the following Detailed Description, which together serve to explain certain principles of the present invention.

<FIG> is a schematic diagram illustrating an external appearance of a hydraulic machine according to some embodiments.

A hydraulic machine may carry out work by actuating a working device <NUM> using hydraulic pressure. In some embodiments, the hydraulic machine may be a construction machine.

In some embodiments, the hydraulic machine may be an excavator as illustrated in <FIG>. The hydraulic machine includes an upper structure <NUM>, an under structure <NUM>, and the working device <NUM>.

The under structure <NUM> includes a travel actuator allowing the hydraulic machine to travel. The travel actuator may be a hydraulic motor.

The upper structure <NUM> may include a working fluid tank, a pump, a power source, a control valve, and the like. In addition, the upper structure <NUM> may include a swing actuator allowing the upper structure <NUM> to rotate with respect to the under structure <NUM>. The swing actuator may be a hydraulic motor.

The working device <NUM> allows the excavator to carry out work. The working device <NUM> includes a boom <NUM>, an arm <NUM>, and a bucket <NUM>, as well as a boom actuator <NUM>, an arm actuator <NUM>, and a bucket actuator <NUM> actuating the boom <NUM>, the arm <NUM>, and the bucket <NUM>, respectively. The boom actuator <NUM>, the arm actuator <NUM>, and the bucket actuator <NUM> are hydraulic cylinders, respectively.

<FIG> illustrates a hydraulic circuit of a hydraulic machine according to some embodiments.

The hydraulic machine includes the boom actuator <NUM>, an energy recovery circuit <NUM>, a tank <NUM>, and a controller <NUM>. The energy recovery circuit <NUM> is provided between the boom actuator <NUM> and the tank <NUM>. The energy recovery circuit <NUM> is connected to the boom actuator <NUM> to recover energy in fluid discharged from the boom actuator <NUM>. The energy recovery circuit <NUM> includes a return valve <NUM>, a regeneration valve <NUM>, a charging valve <NUM>, and a recovery unit <NUM>.

In some embodiments, the hydraulic machine may include an energy consumption circuit <NUM>. The energy consumption circuit <NUM> may be provided between the tank <NUM> and the boom actuator <NUM>. The energy consumption circuit <NUM> is a circuit connected to the boom actuator <NUM> to supply high pressure fluid to the boom actuator <NUM> or to return fluid discharged from the boom actuator <NUM> to the tank <NUM>. In some embodiments, the energy consumption circuit <NUM> may include a power source <NUM>, a main pump <NUM>, and a control valve <NUM>. The main pump <NUM> may direct pressurized fluid to the boom actuator <NUM>. The power source <NUM> may drive the main pump <NUM>. In some embodiments, the power source <NUM> may include an engine.

In some embodiments, the hydraulic machine may be configured to actuate the working device using the energy consumption circuit <NUM> at normal time and to recover energy using the energy recovery circuit <NUM> when a hybrid function is intended to be performed.

In some embodiments, the power source <NUM> may drive the main pump <NUM> by supplying power to the main pump <NUM> through a main shaft <NUM>. The main pump <NUM> may pressurize fluid and direct the pressurized fluid to the boom actuator <NUM>. The boom actuator <NUM> may receive the pressurized fluid from the main pump <NUM> and return fluid toward the tank <NUM>. The boom actuator <NUM> may actuate the boom by providing the boom with the force by the pressurized fluid received from the main pump <NUM>.

The boom actuator <NUM> is a hydraulic cylinder, and includes a large chamber 313a and a small chamber 313b. Since a piston rod connected to the boom extends through the small chamber 313b, an area Ab on which the fluid inside the small chamber 313b is in contact with the piston is smaller than an area Aa on which the fluid inside the large chamber 313a is in contact with the piston, due to the area occupied by the piston rod. Referring to <FIG>, in a boom down operation in which the boom is lowered, the piston rod is also lowered. Consequently, fluid enters the small chamber 313b, while fluid is discharged from the large chamber 313a.

The control valve <NUM> may control the directions of flows of fluid between the main pump <NUM>, the tank <NUM>, and the boom actuator <NUM> by connecting the main pump <NUM>, the tank <NUM>, and the boom actuator <NUM>. In some embodiments, the control valve <NUM> may be in a neutral position, a first non-neutral position, or a second non-neutral position. When the control valve <NUM> is in the neutral position, the control valve <NUM> may not be in fluid communication with the boom actuator <NUM> and return the fluid that has flowed from the main pump <NUM> to the tank <NUM> through a central bypass path. When the control valve <NUM> is in the first non-neutral position, the control valve <NUM> may prevent the fluid that has flowed from the main pump <NUM> from returning to the tank <NUM> through the central bypass path, direct the fluid that has flowed from the main pump <NUM> to the small chamber 313b, and direct the fluid that has flowed from the large chamber 313a to the tank <NUM>, thereby allowing the boom to move down. When the control valve <NUM> is in the second non-neutral position, the control valve <NUM> may prevent the fluid that has flowed from the main pump <NUM> from returning to the tank <NUM> through the central bypass path, direct the fluid that has flowed from the main pump <NUM> to the large chamber 313a, and direct the fluid that has flowed from the small chamber 313b to the tank <NUM>, thereby allowing the boom to move up.

In some embodiments, the hydraulic machine may include a first operator input device <NUM> to move the control valve <NUM>. An operator may indicate his/her desire to raise or lower the boom by operating the first operator input device <NUM>. In some embodiments, the first operator input device <NUM> may be a lever, but the present invention is not limited thereto.

In some embodiments, the first operator input device <NUM> may be an electrical input device, and may generate an electrical signal indicative of the operator's desire and transmit the electrical signal to the controller <NUM>. In some embodiments, the hydraulic machine may include a pilot pump <NUM> and an electronic proportional pressure reducing valve <NUM>. When an electrical signal is received from the first operator input device <NUM>, the controller <NUM> may responsively operate the electronic proportional pressure reducing valve <NUM> by transmitting a control signal to the electronic proportional pressure reducing valve <NUM>. When the electronic proportional pressure reducing valve <NUM> is in a first position, the electronic proportional pressure reducing valve <NUM> may allow the control valve <NUM> to move by directing pilot fluid that has flowed from the pilot pump <NUM> to the control valve <NUM>. When the electronic proportional pressure reducing valve <NUM> is in a second position, the electronic proportional pressure reducing valve may block flow of the pilot fluid from the pilot pump <NUM> to the control valve <NUM> and allow the pilot fluid which has been provided to the control valve <NUM> to drain.

The return valve <NUM> may be provided between the large chamber 313a and the tank <NUM> to allow or block flow of fluid from the large chamber 313a to the tank <NUM>. The regeneration valve <NUM> may connect the large chamber 313a and the small chamber 313b to allow or block flow of fluid from the large chamber 313a to the small chamber 313b. The charging valve <NUM> may be provided between the large chamber 313a and the recovery unit <NUM> to allow or block flow of fluid from the large chamber 313a to the recovery unit <NUM>.

The recovery unit <NUM> is a power recovering component. In some embodiments, the recovery unit <NUM> may be a hydraulic motor (e.g., an assist motor). The assist motor may assist the power source <NUM> by providing the recovered power for the power source <NUM>. In this regard, in some embodiments, the hydraulic machine may include a power transmission. The power transmission may be connected to the power source <NUM> and the assist motor to transmit power therebetween. In some embodiments, the power transmission may include the main shaft <NUM> connecting the power source <NUM> and the main pump <NUM>, an assist shaft <NUM> connected to the assist motor, and a power transmission part <NUM>. In some embodiments, the power transmission part <NUM> may include a gear train as illustrated in <FIG>. Within the scope of the appended claims, the present invention is not limited thereto, and a variety of other embodiments are possible.

In some embodiments, the hydraulic machine may include a second operator input device <NUM> movable to indicate an operator's desire to select or deselect a hybrid mode. When the desire to select the hybrid mode is input to the second operator input device <NUM> and a desire for a boom down movement is input to the first operator input device <NUM>, the controller <NUM> may control the electronic proportional pressure reducing valve <NUM> such that the pilot fluid is not supplied to the control valve <NUM>, thereby moving the control valve <NUM> to the neutral position. In this manner, the controller <NUM> may block flow of fluid between the boom actuator <NUM> and the energy consumption circuit <NUM>. Thus, in a situation in which the hybrid mode is activated, the boom down operation may only be induced by the weight thereof without the supply of the pressurized fluid by the main pump <NUM>. When a desire to deselect the hybrid mode is input to the second operator input device <NUM> or no boom down desire is input to the first operator input device <NUM> even in the case that the desire to deselect the hybrid mode is input to the second operator input device <NUM>, the controller <NUM> may move the return valve <NUM>, the regeneration valve <NUM>, and the charging valve <NUM> to block flow of fluid between the boom actuator <NUM> and the energy recovery circuit <NUM>.

In some embodiments, in the boom down operation in which the boom is lowered, the return valve <NUM> may be moved to block flow of fluid from the large chamber 313a to the tank <NUM>. In the boom down operation, the regeneration valve <NUM> may be moved to allow flow of fluid from the large chamber 313a to the small chamber 313b. In the boom down operation, the charging valve <NUM> may be moved to allow flow of fluid from the large chamber 313a to the recovery unit <NUM>.

The energy recovery circuit <NUM> includes a recovery line <NUM> connecting the large chamber 313a and the recovery unit <NUM>. In some embodiments, the charging valve <NUM> may be provided on the recovery line <NUM>. In some embodiments, the energy recovery circuit <NUM> may include a discharge valve <NUM> provided on the recovery line <NUM>. The energy recovery circuit <NUM> includes an accumulator <NUM> connected to the recovery line <NUM> between the charging valve <NUM> and the discharge valve <NUM>. The charging valve <NUM> may allow or block flow of fluid from the large chamber 313a to the accumulator <NUM> through the recovery line <NUM>. The discharge valve <NUM> may allow or block flow of fluid from the accumulator <NUM> to the recovery unit <NUM>. In the boom down operation, the discharge valve <NUM> may be moved to allow flow of fluid to the recovery unit <NUM>.

In some embodiments, in the boom down operation, the controller <NUM> may control the regeneration valve <NUM> and the charging valve <NUM> such that about half of a flow rate of high pressure fluid discharged from the large chamber 313a flows through the regeneration valve <NUM> to be regenerated and the remaining flow rate flows through the charging valve <NUM> to be stored in the accumulator <NUM>. The stored flow rate is supplied to the recovery unit <NUM> through the discharge valve <NUM>. Here, how much boom down energy is to be lost is determined depending on how much of areas of the regeneration valve <NUM>, the charging valve <NUM>, and the discharge valve <NUM> are controlled to be opened. In some embodiments, in the boom down operation (i.e., when receiving a boom down operation desire input by the operator using the first operator input device <NUM>), the controller <NUM> may open the regeneration valve <NUM> and the charging valve <NUM> to the maximum extent and close the return valve <NUM> so as to minimize pressure loss.

In some embodiments, the hydraulic machine may include a first sensor <NUM> measuring pressure in the accumulator <NUM>. In addition, the hydraulic machine may include a second sensor <NUM> measuring pressure in the large chamber 313a and a third sensor <NUM> measuring pressure in the small chamber 313b.

The hydraulic machine includes a jack-up assist line <NUM> connecting the accumulator <NUM> and the small chamber 313b and a jack-up assist valve <NUM> disposed on the jack-up assist line <NUM>. The jack-up assist valve <NUM> blocks flow of fluid from the accumulator <NUM> to the small chamber 313b in a first position and allows flow of fluid from the accumulator <NUM> to the small chamber 313b in a second position. The controller <NUM> controls the jack-up assist valve <NUM> to move to the first position or the second position.

In some alternative embodiments, the first operator input device <NUM> may be a hydraulic input device including a built-in pressure reducing valve (not shown), and the hydraulic machine may include an auxiliary valve 117a. In these embodiments, the pilot pump <NUM> may be connected to the pressure reducing valve of the first operator input device <NUM>, and the pressure reducing valve may transmit a hydraulic signal indicative of an operator's desire input using the first operator input device <NUM>, to the auxiliary valve 117a. In some embodiments, the hydraulic machine may include a sensor measuring the pressure of the hydraulic signal transmitted to the auxiliary valve 117a by the pressure reducing valve. The sensor may generate an electrical signal corresponding to the hydraulic signal and provide the electrical signal to the controller <NUM>. Thus, although the controller <NUM> is not directly connected to the first operator input device <NUM>, the controller <NUM> may determine what desire has been input by the operator, i.e., whether a boom down operation desire is input or a boom up operation desire is input. When a desire to deselect the hybrid mode is input through the second operator input device <NUM>, a hydraulic signal generated by the first operator input device <NUM> may be transmitted to the control valve <NUM> through the auxiliary valve 117a. However, when a desire to select the hybrid mode is input to the second operator input device <NUM>, even in the case that the boom down desire is input to the first operator input device <NUM>, the controller <NUM> may control the auxiliary valve 117a such that the pilot fluid is not supplied to the control valve <NUM>, thereby moving the control valve <NUM> to the neutral position. In this manner, the controller <NUM> may block flow of fluid between the boom actuator <NUM> and the energy consumption circuit <NUM>.

<FIG> is a flowchart schematically illustrating a jack-up assist method according to some embodiments.

First, the controller <NUM> calculates a load pressure applied to the large chamber 313a by a load. In some embodiments, the load pressure may be calculated as follows:
<MAT>.

Here, Pa is a pressure in the large chamber 313a measured by the second sensor <NUM>, Pb is a pressure in the small chamber 313b measured by the third sensor <NUM>, Aa is an area of the large chamber 313a, and Ab is an area of the small chamber 313b.

Afterwards, the controller <NUM> determines whether or not the hydraulic machine is in a jack-up condition. The controller <NUM> determines that the hydraulic machine is in the jack-up condition when the load pressure is equal to or less than a preset threshold value. In some embodiments, the threshold value may be in the range of <NUM> to <NUM> bars.

Subsequently, when the hydraulic machine is determined to be in the jack-up condition, the controller <NUM> controls the jack-up assist valve <NUM> to move the jack-up assist valve to the second position in which the flow of fluid from the accumulator to the small chamber is allowed. When the hydraulic machine is determined to be in the jack-up condition, the controller <NUM> may control the jack-up assist valve <NUM> to move according to a value obtained by subtracting the pressure in the small chamber 313b from the pressure in the accumulator <NUM> measured by the first sensor <NUM>. The controller <NUM> may control the movement of the jack-up assist valve <NUM> so that, the greater the value obtained by subtracting the pressure in the small chamber 313b from the pressure in the accumulator <NUM> measured by the first sensor <NUM> is, the smaller the amount of the movement of the jack-up assist valve <NUM> to the second position (i.e., the opened area of the jack-up assist valve <NUM>) is. (That is, the controller <NUM> may control the movement of the jack-up assist valve <NUM> so that, the smaller the value obtained by subtracting the pressure in the small chamber 313b from the pressure in the accumulator <NUM> measured by the first sensor <NUM> is, the greater the amount of the movement of the jack-up assist valve <NUM> to the second position (i.e., the opened area of the jack-up assist valve <NUM>) is. Even in the case that the opened area of the jack-up assist valve <NUM> is the same, a higher flow rate of fluid is supplied to the small chamber 313b when the value obtained by subtracting the pressure in the small chamber 313b from the pressure in the accumulator <NUM> is greater. Thus, in order to supply an optimal flow rate of fluid to the small chamber 313b during the jack-up assist, the controller <NUM> may control the movement of the jack-up assist valve <NUM> so that, the greater the value obtained by subtracting the pressure in the small chamber 313b from the pressure in the accumulator <NUM>, the smaller the opened area of the jack-up assist valve <NUM> is. When the hydraulic machine is determined to be in the jack-up condition, pressurized fluid stored in the accumulator <NUM> is supplied to the small chamber 313b by moving the jack-up assist valve <NUM> to the second position, thereby improving the responsiveness of a jack-up motion.

In some embodiments, the controller <NUM> may control the movement of the jack-up assist valve <NUM> so that, the higher a desired movement speed of the boom actuator <NUM> input to the first operator input device <NUM>, the greater the amount of the movement of the jack-up assist valve <NUM> to the second position is. (That is, the controller <NUM> may control the movement of the jack-up assist valve <NUM> so that, the lower the desired movement speed of the boom actuator <NUM> input to the first operator input device <NUM>, the smaller the amount of the movement of the jack-up assist valve <NUM> to the second position is. ) When the operator desires a high speed jack-up operation by increasing the amount of the movement of the first operator input device <NUM>, a faster response characteristic may be obtained by responsively increasing a jack-up assist flow rate. In contrast, when the operator desires a quiet jack-up operation by reducing the amount of the movement of the first operator input device <NUM>, rapid movement of the boom may be prevented by reducing the jack-up assist flow rate.

In some embodiments, the controller <NUM> may simultaneously perform the above-described control operations, i.e., the operation of controlling the amount of the movement of the jack-up assist valve <NUM> to the second position according to the value obtained by subtracting the pressure in the small chamber 313b from the pressure in the accumulator <NUM> and the operation of controlling the amount of the movement of the jack-up assist valve <NUM> to the second position according to the desired movement speed of the boom actuator <NUM> input to the first operator input device <NUM>. That is, the controller <NUM> may control the amount of the movement of the jack-up assist valve <NUM> to the second position according to the value obtained by subtracting the pressure in the small chamber 313b from the pressure in the accumulator <NUM> and the desired movement speed of the boom actuator <NUM> input to the first operator input device <NUM>.

Claim 1:
A hydraulic machine comprising:
a boom actuator (<NUM>) comprising a large chamber (313a) and a small chamber (313b), wherein the large chamber (313a)and the small chamber (313b) are
defined by a piston movable within the actuator (<NUM>), the piston being connected to a piston rod that extends through the small chamber (313b), wherein when fluid is received pressurized by the boom actuator and discharged from the boom actuator,
an area on which fluid inside the small chamber (313b) is in contact with the piston is smaller than an area on which fluid inside the large chamber (313a) is in contact with the piston;
a recovery unit (<NUM>) configured to receive fluid discharged from the large chamber (313a) and then recover energy;
a recovery line (<NUM>) connecting the large chamber (313a) and the recovery unit (<NUM>);
an accumulator (<NUM>) connected to the recovery line (<NUM>);
a jack-up assist line (<NUM>) connecting the accumulator (<NUM>) and the small chamber (313b);
a jack-up assist valve (<NUM>) disposed on the jack-up assist line (<NUM>) to block flow of fluid from the accumulator (<NUM>) to the small chamber (313b) in a first position and allow the flow of fluid from the accumulator (<NUM>) to the small chamber (313b) in a second position; and
a controller (<NUM>) configured to control movement of the jack-up assist valve (<NUM>),
wherein the controller (<NUM>) is configured to:
determine whether or not the hydraulic machine is in a jack-up condition; and
when the hydraulic machine is determined to be in the jack-up condition, move the jack-up assist valve (<NUM>) to the second position,
characterized in that the controller (<NUM>) is configured to determine that the hydraulic machine is in the jack-up condition when a load pressure applied to the large chamber (313a) by a load is equal to or less than a threshold value.