KR102666906B1 - Pump units and hydraulic systems - Google Patents

Abstract

The pump unit 1 is a positive displacement rotary pump, and includes a plurality of hydraulic pumps 12a and 12b that discharge a fixed capacity of hydraulic oil, and a main flow path 13 where the hydraulic oil discharged by the plurality of hydraulic pumps 12a and 12b joins. ) and a plurality of hydraulic pumps 12a, 12b are provided in correspondence with each other, and the corresponding hydraulic pumps 12a, 12b are placed in an on-load state for load operation or an unload state for no-load operation, and the corresponding hydraulic pumps 12a, 12b are provided in correspondence with each other. When the pump is in an on-load state, a plurality of switching units (20a, 20b) that return some of the hydraulic oil discharged by the corresponding hydraulic pumps (12a, 12b) to the tank (10) when a pressure higher than the preset relief pressure is applied. and a control unit 19 that maintains the pressure of the main flow path 13 at the target pressure by controlling the switching parts 20a and 20b based on the detected value of the pressure of the main flow path 13.

Description

Pump units and hydraulic systems

The present disclosure relates to low noise pump units and hydraulic systems.

Hydraulic systems transmit power using pressurized hydraulic oil as a medium and can convert small forces into large forces or torques, so they are widely used in fields such as ships, aircraft, automobiles, and machine tools. The hydraulic system is composed of a hydraulic pump that applies pressure to the hydraulic oil to produce pressurized hydraulic oil, and a hydraulic actuator that converts the fluid energy of the hydraulic oil supplied from the hydraulic pump into physical motion.

Among hydraulic pumps, a positive displacement pump is a pump that applies energy to the hydraulic oil in the pump and delivers the fluid by reciprocating or rotating a moving body such as a piston or gear. A positive displacement pump that delivers liquid by reciprocating motion is called a reciprocating pump, and a positive displacement pump that delivers liquid by rotating motion is called a rotary pump. In addition, hydraulic pumps are classified into fixed capacity pumps in which the discharge amount of hydraulic oil per unit time is fixed, and variable displacement pumps in which the discharge amount of hydraulic oil per unit time is variable.

When supplying hydraulic oil to multiple hydraulic actuators, a parallel circuit may be used. The parallel circuit connects the hydraulic pump and hydraulic actuators by branching a flow path from one flow path through which the hydraulic oil discharged by the hydraulic pump flows toward each of a plurality of hydraulic actuators, and is also called a central circuit or ring main circuit. In this case, the required amount of hydraulic oil in the hydraulic circuit changes depending on the usage situation of the hydraulic actuator. For this reason, as disclosed in Non-Patent Document 1, a variable displacement pump is usually used in the central circuit, and the supply amount of hydraulic oil is changed according to the required amount of hydraulic oil, and the circuit pressure is controlled to become the target pressure.

Non-patent Document 1: Kawasaki Heavy Industries Co., Ltd., “Kawasaki Hydraulic Deck Machinery”,［online］,［Retrieved June 17, 2021］, Internet＜URL：https://www.khi.co.jp/industrial_equipment/hydraulic/ others/pdf/deckmachinery_catalog_J_1902.pdf＞

However, in the hydraulic circuit disclosed in Non-Patent Document 1, since a reciprocating pump such as a piston pump is used, there is a problem of large noise. In order to reduce noise, it is conceivable to use a rotary pump with a significantly smaller noise level than a reciprocating pump. However, since the rotary pump is only a fixed displacement pump and does not have a variable displacement pump, the pump alone does not have a mechanism for maintaining the circuit pressure at the target pressure, so it cannot be used in the central circuit.

The present invention has been made in view of the above, and its object is to provide a pump unit capable of maintaining the circuit pressure at the target pressure and reducing noise by using a rotary pump, which is a fixed capacity pump, in a parallel circuit. Do this.

In order to solve the above-mentioned problem and achieve the purpose, the pump unit according to the present invention is a positive displacement rotary pump, which includes a plurality of hydraulic pumps that discharge a fixed capacity of hydraulic oil, and the hydraulic oil discharged by the plurality of hydraulic pumps joins. It is provided corresponding to the main flow path and each of the plurality of hydraulic pumps, and puts the corresponding hydraulic pump in an on-load state for load operation or an unload state for no-load operation, and when the corresponding hydraulic pump is in an on-load state, in advance When a pressure higher than the set relief pressure is applied, a plurality of switching units return some of the hydraulic oil discharged by the corresponding hydraulic pump to the tank, and by controlling the switching units based on the detected value of the pressure in the main flow path, the pressure in the main flow path is adjusted. It is provided with a control unit that maintains the target pressure, and the control unit switches the hydraulic pump to the on-load state in order from the side with the higher relief pressure set in the corresponding switching section, and switches the hydraulic pump to the unload state in order from the side with the lower relief pressure. It is characterized by conversion.

The pump unit according to the present invention achieves the effect of reducing noise.

1 is a diagram showing the configuration of a hydraulic system according to Embodiment 1 of the present invention.
FIG. 2 is a diagram showing an example of the relief pressure and threshold value used in the pump unit shown in FIG. 1.
FIG. 3 is a flowchart for explaining the operation of the control unit of the pump unit shown in FIG. 1.
Figure 4 is a diagram showing the configuration of a hydraulic system according to Embodiment 2.
FIG. 5 is a diagram showing a first example of relief pressure and threshold values used by the pump unit shown in FIG. 4.
FIG. 6 is a flowchart for explaining the operation of the pump unit shown in FIG. 4.
FIG. 7 is a diagram showing a second example of relief pressure and threshold values used by the pump unit shown in FIG. 4.
Figure 8 is a graph showing the difference in noise value depending on the type of pump used.
Figure 9 is a graph showing the difference in pulsation rate depending on the type of pump used.

Below, the configuration of a pump unit and a hydraulic system according to an embodiment of the present invention will be described in detail based on the drawings. In the drawings and the following description, each of a plurality of components having similar functions may be distinguished by assigning a different alphabet after the same symbol. However, if there is no need to specifically distinguish between a plurality of similar components, only the same symbol is assigned.

Embodiment 1.

1 is a diagram showing the configuration of a hydraulic system 100 according to Embodiment 1 of the present invention. The hydraulic system 100 is a hydraulic circuit having a pump unit 1 and a plurality of hydraulic actuators 2. The hydraulic actuator 2 is, for example, a hydraulic motor mounted on a driven device such as a winch. The flow path between the pump unit 1 and the hydraulic actuator 2 branches off from one flow path on the discharge side of the pump unit 1 into a plurality of flow paths and is connected to each of the plurality of hydraulic actuators 2. Multiple hydraulic actuators 2 can be used simultaneously. For this reason, in the hydraulic system 100, the required amount of hydraulic oil supplied by the pump unit 1 changes depending on the usage situation of the hydraulic actuator 2, for example, the number of operating units and the operating speed.

The pump unit 1 includes a tank 10 for storing hydraulic oil, an electric motor 11, and a plurality of hydraulic pumps 12 driven by the electric motor 11, specifically, a first hydraulic pump 12a and a second hydraulic pump 12a. 2 It has a hydraulic pump (12b). Hereinafter, when there is no need to specifically distinguish between the first hydraulic pump 12a and the second hydraulic pump 12b, they are simply referred to as the hydraulic pump 12. The same goes for other components.

The pump unit 1 further has a main flow path 13 where the hydraulic oil discharged from each of the plurality of hydraulic pumps 12 joins. In the main flow path 13, the hydraulic oil discharged by the first hydraulic pump 12a and the hydraulic oil discharged by the second hydraulic pump 12b merge. In addition, although it is omitted in FIG. 1 for simplicity, a flow path for the hydraulic oil to rotate is actually connected to each of the plurality of hydraulic actuators 2. Additionally, a hydraulic valve such as a control valve is connected between the pump unit 1 and each hydraulic actuator 2 as necessary.

The plurality of hydraulic pumps 12 and the main flow path 13 are connected by a pump flow path 14. Specifically, between the first hydraulic pump 12a and the main flow path 13 is connected by a first pump flow path 14a, and between the second hydraulic pump 12b and the main flow path 13, It is connected to the second pump flow path 14b. The first pump flow path 14a and the second pump flow path 14b are connected to the main flow path 13 at the confluence point P. A check valve 15 is provided in the pump passage 14. Specifically, the first check valve 15a is provided in the first pump passage 14a, and the second check valve 15b is provided in the second pump passage 14b.

The pump unit 1 has a plurality of switching units 20 provided corresponding to each of the plurality of hydraulic pumps 12. Specifically, the pump unit 1 includes a first switching unit 20a provided corresponding to the first hydraulic pump 12a, and a second switching unit 20b provided corresponding to the second hydraulic pump 12b. has The switching unit 20 further includes a relief valve 16 and an electromagnetic valve 17. Specifically, the first switching unit 20a has a first relief valve 16a and a first solenoid valve 17a, and the second switching unit 20b has a second relief valve 16b and a second electromagnetic valve 17a. It has a solenoid valve (17b). The first relief valve 16a of the first switching section 20a is connected to a connection point Pa upstream of the first check valve 15a of the first pump passage 14a. The 2nd relief valve 16b of the 2nd switching part 20b is connected to the connection point Pb upstream of the 2nd check valve 15b of the 2nd pump flow path 14b. The pump unit 1 includes a pressure sensor 18 that measures the pressure of the main flow path 13, a first solenoid valve 17a of the first switching unit 20a, and a second electromagnetic valve 17a of the second switching unit 20b. It further has a control unit 19 that controls the valve 17b.

The electric motor 11 drives the first hydraulic pump 12a and the second hydraulic pump 12b. The first hydraulic pump 12a and the second hydraulic pump 12b each suck hydraulic oil from the tank 10, apply pressure to the hydraulic oil, and discharge the pressurized hydraulic oil. The first hydraulic pump 12a and the second hydraulic pump 12b are positive displacement rotary pumps, and are fixed displacement pumps whose discharge amount of hydraulic oil per unit time is fixed. In addition, the rotary pump here is a general term for pumps, such as gear pumps, vane pumps, and screw pumps, that apply energy to hydraulic fluid and transmit the liquid through the rotational movement of the moving body. As a concept corresponding to a rotary pump, there are reciprocating pumps such as piston pumps, diaphragm pumps, and plunger pumps that apply energy to hydraulic fluid and transmit fluid through the reciprocating motion of a moving body. Rotary pumps have the characteristic of significantly lower noise levels during operation than reciprocating pumps. The second hydraulic pump 12b has a larger capacity than the first hydraulic pump 12a. In addition, here, capacity refers to the discharge amount of hydraulic oil per unit time.

The first check valve 15a prevents reverse flow of hydraulic oil from the first hydraulic pump 12a toward the main flow path 13, and the second check valve 15b prevents the backflow of hydraulic oil from the second hydraulic pump 12b to the main flow path ( It prevents reverse flow of hydraulic oil towards 13).

The switching unit 20 sets the corresponding hydraulic pump 12 to an on-load state for load operation or an unload state for no-load operation, and also provides a preset relief when the corresponding hydraulic pump 12 is in an on-load state. When a pressure higher than the pressure is applied, part of the hydraulic oil discharged by the corresponding hydraulic pump 12 is returned to the tank 10. Hereinafter, the functions of the relief valve 16 and the electromagnetic valve 17 of each of the plurality of switching units 20 will be described.

The first relief valve 16a opens and closes a passage that returns the hydraulic oil discharged by the first hydraulic pump 12a to the tank 10. The second relief valve 16b opens and closes a passage that returns the hydraulic oil discharged by the second hydraulic pump 12b to the tank 10. Relief pressure is provided in each of the first relief valve 16a and the second relief valve 16b, the relief pressure of the first relief valve 16a is referred to as the first relief pressure, and the relief pressure of the second relief valve 16b is referred to as the first relief pressure. The relief pressure is called the second relief pressure. When the pressure at the connection point Pa exceeds the first relief pressure, the first relief valve 16a returns a part of the hydraulic oil discharged by the first hydraulic pump 12a to the tank 10, and returns the pressure at the connection point Pa is maintained as the first relief pressure. When the pressure at the connection point Pb exceeds the second relief pressure, the second relief valve 16b returns a part of the hydraulic oil discharged by the second hydraulic pump 12b to the tank 10, thereby reducing the pressure at the connection point Pb. is maintained as the second relief pressure.

The electromagnetic valve 17 controls the relief valve 16 to switch the state of the hydraulic pump 12 corresponding to the control target relief valve 16 to the on-load state or the unload state. The unloaded state is a state in which the hydraulic pump 12 is operating without load, and the relief valve 16 returns the entire amount of hydraulic oil discharged by the hydraulic pump 12 to the tank 10. The on-load state is a state in which the hydraulic pump 12 is operating under load, and the relief valve 16 is closed, or part of the hydraulic oil discharged by the hydraulic pump 12 is returned to the tank 10 at the connection point (Pa, The pressure of Pb) is maintained as a relief pressure.

When the first hydraulic pump 12a is in an on-load state, at least a portion of the hydraulic oil discharged by the first hydraulic pump 12a passes through the first pump flow path 14a and the first check valve 15a to the main flow path ( 13) and is supplied to the hydraulic actuator (2). Specifically, when the pressure at the connection point Pa is less than the first relief pressure, all of the hydraulic oil discharged by the first hydraulic pump 12a flows to the main through the first pump passage 14a and the first check valve 15a. It flows towards the flow path (13). When the pressure at the connection point Pa reaches the first relief pressure, some of the hydraulic oil discharged by the first hydraulic pump 12a is returned to the tank 10 through the first relief valve 16a, and the remaining hydraulic oil is returned to the first relief valve 16a. It flows toward the main flow path 13 through the pump flow path 14a and the first check valve 15a. When the first hydraulic pump 12a is in an unloaded state, the entire amount of hydraulic oil discharged by the first hydraulic pump 12a is returned to the tank 10 from the connection point Pa through the first relief valve 16a.

When the second hydraulic pump 12b is in the on-load state, at least a portion of the hydraulic oil discharged by the second hydraulic pump 12b passes through the second pump flow path 14b and the second check valve 15b to the main flow path ( 13) and is supplied to the hydraulic actuator (2). Specifically, when the pressure at the connection point Pb is less than the second relief pressure, all of the hydraulic oil discharged by the second hydraulic pump 12b flows into the main through the second pump passage 14b and the second check valve 15b. It flows towards the flow path (13). When the pressure at the connection point Pb reaches the second relief pressure, some of the hydraulic oil discharged by the second hydraulic pump 12b is returned to the tank 10 through the second relief valve 16b, and the remaining hydraulic oil is returned to the second relief valve 16b. It flows toward the main flow path 13 through the pump flow path 14b and the second check valve 15b. When the second hydraulic pump 12b is in an unloaded state, the entire amount of hydraulic oil discharged by the second hydraulic pump 12b is returned to the tank 10 from the connection point Pb through the second relief valve 16b.

The control unit 19 controls the electromagnetic valve 17 of the switching unit 20 based on the detected value of the pressure of the main passage 13 to change the state of the relief valve 16, thereby changing the state of the hydraulic pump 12. It is a processing circuit that switches to the on-load state or unload state. The processing circuit may be realized by dedicated hardware, or may be a control circuit using a CPU (Central Processing Unit). Moreover, in FIG. 1, the control unit 19 is separate from the pressure sensor 18, but the control unit 19 may be integrated with the pressure sensor 18. The control unit 19 can maintain the pressure of the main passage 13 at the target pressure by switching the state of the hydraulic pump 12. When increasing the hydraulic pump 12 in the on-load state, the control unit 19 switches the hydraulic pump 12 to the on-load state in order from the higher relief pressure set in the corresponding switching unit 20. Additionally, when reducing the hydraulic pump 12 in the on-load state, the control unit 19 switches the hydraulic pump 12 to the unloaded state in order from the lower relief pressure set in the corresponding switching unit 20. Specifically, when the pump unit 1 is started, the control unit 19 places the hydraulic pump 12 with the highest relief pressure of the corresponding switching unit 20 in an on-load state, and sets the remaining hydraulic pumps 12 to an on-load state. Put in unloaded state. Thereafter, the control unit 19 controls the switching unit 20 based on the detected value of the pressure sensor 18 to switch the state of the remaining hydraulic pump 12 to the unloaded state or the on-loaded state. The control unit 19 switches the state of each of the remaining hydraulic pumps 12 using a threshold value provided corresponding to each of the remaining hydraulic pumps 12. The threshold value is higher than the relief pressure of the switching unit 20 corresponding to the hydraulic pump 12 as the switching target, and in the order in which the relief pressure is higher, it is higher than the switching unit 20 corresponding to the hydraulic pump 12 as the switching target. It is set lower than the relief pressure of one quick switching unit 20. In addition, the relief pressure of the switching unit 20 corresponding to the hydraulic pump 12 with the smallest capacity among the plurality of hydraulic pumps 12 is among the relief pressures of the plurality of switching parts 20 of the pump unit 1. You can set it to the highest.

FIG. 2 is a diagram showing an example of the relief pressure and threshold value used in the pump unit 1 shown in FIG. 1. In the example of FIG. 2, the first relief pressure is 20.6 MPa and the second relief pressure is 19.6 MPa. In this case, the order in which the control unit 19 switches to the on-load state is the order of the first hydraulic pump 12a and the second hydraulic pump 12b. Specifically, at the time of startup, the control unit 19 places the first hydraulic pump 12a, which has the highest relief pressure of the corresponding switching unit 20, in an on-load state, and sets the second hydraulic pump 12, which is the remaining hydraulic pump 12, to an on-load state. The hydraulic pump 12b is placed in an unloaded state. Thereafter, the control unit 19 controls the second switching unit 20b based on the detected value of the pressure sensor 18, thereby switching the state of the second hydraulic pump 12b to the unloaded state or the on-loaded state. . At this time, a threshold value is predetermined for each hydraulic pump 12 to be controlled, and the threshold value determined for the second hydraulic pump 12b is called the first threshold value. The control unit 19 switches the state of the second hydraulic pump 12b based on the magnitude relationship between the first threshold value and the detection value. As described above, the threshold value is higher than the relief pressure of the switching unit 20 corresponding to the hydraulic pump 12 as the switching target, and in the order of higher relief pressure, the switching unit 20 corresponding to the hydraulic pump 12 as the switching target ) is set lower than the relief pressure of the switching unit 20, which is one order earlier than ). Accordingly, the first threshold value is set higher than the second relief pressure of the second switching unit 20b corresponding to the second hydraulic pump 12b and lower than the first relief pressure of the first switching unit 20a. Specifically, the first threshold is 20.1 MPa, which is higher than 19.6 MPa and lower than 20.6 MPa.

The target pressure varies depending on the number of hydraulic pumps 12 that are on load. The target pressure is determined by the relief pressure of the relief valve 16 with the corresponding hydraulic pump 12 in the on-load state, among the plurality of relief valves 16 in the pump unit 1, and the hydraulic pump in the on-load state. It becomes the smallest among the relief pressures of the switching section 20 corresponding to (12). Specifically, when the first hydraulic pump 12a is in an on-load state and the second hydraulic pump 12b is in an unloaded state, the target pressure becomes the first relief pressure. When both the first hydraulic pump 12a and the second hydraulic pump 12b are in the on-load state, the target pressure becomes the second relief pressure. For this reason, the relief pressure is set so that the lowest of the relief pressures is equal to or higher than the circuit pressure required by the hydraulic system 100.

FIG. 3 is a flow chart for explaining the operation of the control unit 19 of the pump unit 1 shown in FIG. 1. When the pump unit 1 is started, the control unit 19 places the first hydraulic pump 12a, which has the highest relief pressure of the corresponding switching unit 20, in an on-load state, and sets the second hydraulic pump 12, which is the remaining hydraulic pump 12, to an on-load state. The hydraulic pump 12b is placed in an unloaded state (step S100). During standby after the pump unit 1 is started and before the start of operation of the winch equipped with the hydraulic actuator 2, the pressure in the main flow passage 13 is 20.6 MPa due to the operation of the first relief valve 16a. is maintained.

Next, the control unit 19 switches the status of the remaining hydraulic pumps 12 based on the detected value. The control unit 19 determines whether the detection value of the pressure sensor 18 is below the first threshold (step S101). When the detection value is below the first threshold (step S101: Yes), the control unit 19 places the second hydraulic pump 12b in an on-load state (step S102). For example, if the use situation of the winch changes, such as an increase in the number of winches in operation, and the flow rate of hydraulic oil is insufficient only through the first hydraulic pump 12a, the detection value of the pressure sensor 18 decreases. When the detection value reaches 20.1 MPa, which is the first threshold, the second hydraulic pump 12b is switched to the on-load state, and at this time, the pressure in the main flow path 13 is increased by the operation of the second relief valve 16b. is maintained at 19.6MPa.

When the detection value is not below the first threshold (step S101: No), the control unit 19 places the second hydraulic pump 12b in an unloaded state (step S103). For example, when there is no change in the winch's usage status and the pressure in the main flow path 13 is maintained at 20.6 MPa, the second hydraulic pump 12b continues to be in an unloaded state. In addition, once the second hydraulic pump 12b is switched to the on-road state, if the use situation of the winch changes, such as a decrease in the number of winches in operation, and the flow rate of hydraulic oil becomes excessive, the pressure in the main flow path 13 rises. When the detection value of the pressure sensor 18 exceeds the first threshold value of 20.1 MPa, the second hydraulic pump 12b is switched to the unloaded state, and at this time, by operating the first relief valve 16a, the main The pressure in the flow path 13 is maintained at 20.6 MPa.

After step S102 or step S103, the control unit 19 repeats the process from step S101. While the pump unit 1 is operating, the control unit 19 repeats the processing from step S101 to step S103 to switch the state of the second hydraulic pump 12b according to the use situation of the winch.

As described above, the pump unit 1 uses the detected value of the pressure of the main flow path 13 to control the switching unit 20 to switch the state of the hydraulic pump 12 to the on-load state or the unload state. You can. As a result, even if the hydraulic pump 12 itself is a fixed capacity pump, it becomes possible to adjust the amount of hydraulic oil discharged by the pump unit 1, making it possible to maintain the pressure in the main flow passage 13 at the target pressure. I do it. Therefore, in the central circuit, a fixed displacement pump, such as a positive displacement rotary pump, such as a gear pump, vane pump, or screw pump, can be used, and compared to the case of using a reciprocating pump such as a piston pump, the hydraulic system It becomes possible to significantly reduce the noise of (100).

The control unit 19 switches the hydraulic pump to the on-load state in order, starting from the side with the higher relief pressure set in the corresponding switching part 20, and switches the hydraulic pump to the on-load state in order from the side with the lower relief pressure set in the corresponding switching part 20. Switch pump (12) to unloaded state. When switching the second hydraulic pump 12b from the unloaded state to the on-loaded state, the flow rate is insufficient, and the detected value of the pressure sensor 18 is falling from the state maintained at 20.6 MPa, which is the first relief pressure. . When the detection value becomes 20.1 MPa or less, which is the first threshold, the second hydraulic pump 12b switches to the on-load state, and the supply of hydraulic oil from the second pump flow path 14b to the main flow path 13 begins. do. For this reason, the speed of drop of the pressure in the main flow path 13 decreases from the point where it reaches 20.1 MPa, and the second relief pressure, which is the target pressure, is maintained at 19.6 MPa. In this way, by including the plurality of switching units 20 with different relief pressures, the pressure in the main passage 13 is maintained at a different target pressure for each number of hydraulic pumps 12 in the on-load state. In addition, by switching the hydraulic pump 12 to the on-load state in order from the one with the highest relief pressure set in the corresponding switching unit 20, an upper limit of the supply pressure from the hydraulic pump 12 is established, and the hydraulic oil is excessive. When this happens, the pressure in the main flow path 13 increases, making it possible to adjust the supply amount according to the required amount of hydraulic oil.

Additionally, the first threshold value is set higher than the second relief pressure and lower than the first relief pressure. When the use situation of the winch does not change and the required amount of hydraulic oil does not change, the pressure in the main passage 13 is maintained at the first relief pressure or the second relief pressure. For this reason, by setting the first threshold value higher than the second relief pressure and lower than the first relief pressure, it is possible to detect changes in the use situation of the winch, and it is also possible to prevent hunting and realize stable operation. . Additionally, by setting the difference between the first relief pressure and the first threshold to the same level as the difference between the second relief pressure and the first threshold, hunting can be prevented more reliably.

Moreover, among the plurality of hydraulic pumps 12 included in the pump unit 1, the relief pressure of the first switching unit 20a corresponding to the first hydraulic pump 12a with the smallest capacity is the highest. As a result, at the time of startup, the first hydraulic pump 12a with the smallest capacity is in an on-load state, and the second hydraulic pump 12b, which is the remaining hydraulic pump 12, is in an unloaded state. Therefore, the amount of hydraulic oil supplied during standby can be reduced, making it possible to further reduce the noise of the pump unit 1. In addition, the capacity of each of the plurality of hydraulic pumps 12 of the pump unit 1 is determined based on the required amount of hydraulic oil in the hydraulic system 100. The capacity of each hydraulic pump 12 is set so that the maximum amount of hydraulic oil discharged by the pump unit 1 is greater than the maximum amount of hydraulic oil required when all hydraulic actuators 2 of the hydraulic system 100 are in operation. It is decided.

Embodiment 2.

FIG. 4 is a diagram showing the configuration of a hydraulic system 200 according to Embodiment 2. Hereinafter, parts that are different from the hydraulic system 100 shown in FIG. 1 will be mainly described, and description of parts that are the same as the hydraulic system 100 will be omitted.

The hydraulic system 200 has a pump unit 1-1 and a plurality of hydraulic actuators 2. While the pump unit 1 has two hydraulic pumps 12, the pump unit 1-1 has three hydraulic pumps 12. Specifically, in addition to the configuration of the pump unit 1, the pump unit 1-1 includes a third hydraulic pump 12c, a third pump passage 14c, a third check valve 15c, and a third hydraulic pump 12c. 3 It further has a switching section 20c. The third switching unit 20c has a third relief valve 16c and a third solenoid valve 17c.

The third hydraulic pump 12c is driven by an electric motor 11. The third pump flow path 14c connects the third hydraulic pump 12c and the main flow path 13. The third check valve 15c is provided in the third pump flow path 14c, and the third check valve 15c prevents reverse flow of hydraulic oil from the third hydraulic pump 12c toward the main flow path 13. The third relief valve 16c is connected to a connection point Pc upstream of the third check valve 15c of the third pump passage 14c. The third electromagnetic valve 17c is provided to correspond to the third relief valve 16c, and controls the third relief valve 16c to switch the state of the third hydraulic pump 12c to the unloaded state or the on-loaded state. do.

FIG. 5 is a table showing a first example of relief pressure and threshold values used by the pump unit 1-1 shown in FIG. 4. In the first example shown in Fig. 5, the first relief pressure is 20.6 MPa, the second relief pressure is 19.6 MPa, and the third relief pressure is 18.6 MPa. In this case, the order in which the control unit 19 switches to the on-load state is the order of the first hydraulic pump 12a, the second hydraulic pump 12b, and the third hydraulic pump 12c. Specifically, at the time of startup, the control unit 19 places the first hydraulic pump 12a, which has the highest relief pressure of the corresponding switching unit 20, in an on-load state, and sets the second hydraulic pump 12, which is the remaining hydraulic pump 12, to an on-load state. The pump 12b and the third hydraulic pump 12c are placed in an unloaded state. Thereafter, the control unit 19 controls each of the second switching unit 20b and the third switching unit 20c based on the detection value of the pressure sensor 18, thereby controlling the second hydraulic pump 12b and the third switching unit 20c. Each state of the hydraulic pump 12c is converted to an unloaded state or an on-loaded state. The threshold value determined for the third hydraulic pump 12c is referred to as the second threshold value. As described above, the threshold value is higher than the relief pressure of the switching unit 20 corresponding to the hydraulic pump 12 as the switching target, and in the order of higher relief pressure, the switching unit 20 corresponding to the hydraulic pump 12 as the switching target ) is set lower than the relief pressure of the switching unit 20, which is one order earlier than ). Therefore, the first threshold value is set higher than the relief pressure of the second switching unit 20b corresponding to the second hydraulic pump 12b and lower than the relief pressure of the first switching unit 20a. Specifically, the first threshold is 20.1 MPa, which is higher than 19.6 MPa and lower than 20.6 MPa. The second threshold value is set higher than the third relief pressure corresponding to the third hydraulic pump 12c and lower than the second relief pressure of the second switching unit 20b. Specifically, the second threshold is 19.1 MPa, which is higher than 18.6 MPa and lower than 19.6 MPa.

FIG. 6 is a flowchart for explaining the operation of the pump unit 1-1 shown in FIG. 4. When the pump unit 1-1 is started, the control unit 19 places the first hydraulic pump 12a, which has the highest relief pressure of the corresponding switching unit 20 among the plurality of hydraulic pumps 12, into an on-load state. , the second hydraulic pump 12b and the third hydraulic pump 12c, which are the remaining hydraulic pumps 12, are placed in an unloaded state (step S200). During standby after the pump unit 1-1 is started and before the start of operation of the winch equipped with the hydraulic actuator 2, the pressure in the main flow passage 13 is 20.6 by the operation of the first relief valve 16a. It is maintained at MPa.

Next, the control unit 19 determines whether the detection value of the pressure sensor 18 is less than or equal to the first threshold value (step S201). When the detection value is below the first threshold (step S201: Yes), the control unit 19 places the second hydraulic pump 12b in an on-load state (step S202). For example, if the use situation of the winch changes, such as an increase in the number of winches in operation, and the flow rate of hydraulic oil is insufficient only through the first hydraulic pump 12a, the detection value of the pressure sensor 18 decreases. When the detection value reaches the first threshold of 20.1 MPa, the second hydraulic pump 12b switches to the on-load state, and at this time, the hydraulic oil supplied by the first hydraulic pump 12a and the second hydraulic pump 12b When the furnace flow rate is sufficient, the pressure in the main passage 13 is maintained at 19.6 MPa by the operation of the second relief valve 16b.

When the detection value is not below the first threshold (step S201: No), the control unit 19 places the second hydraulic pump 12b in an unloaded state (step S203). For example, when there is no change in the use situation of the winch and the pressure of the main flow path 13 is maintained at 20.6 MPa, the second hydraulic pump 12b continues to be in an unloaded state. In addition, once the second hydraulic pump 12b is switched to the on-road state, if the use situation of the winch changes, such as a decrease in the number of winches in operation, and the flow rate of hydraulic oil becomes excessive, the pressure in the main flow path 13 rises. When the detection value of the pressure sensor 18 exceeds the first threshold value of 20.1 MPa, the second hydraulic pump 12b is switched to the unloaded state, and at this time, by operating the first relief valve 16a, the main The pressure of the flow path 13 is maintained at 20.6 MPa.

Next, the control unit 19 determines whether the detection value of the pressure sensor 18 is less than or equal to the second threshold (step S204). When the detection value is below the second threshold (step S204: Yes), the control unit 19 places the third hydraulic pump 12c in an on-load state (step S205). For example, if the use situation of the winch changes, such as an increase in the number of winches in operation, and the flow rate of hydraulic oil becomes insufficient, the detection value of the pressure sensor 18 decreases. When the detection value reaches 19.1 MPa, which is the second threshold, the third hydraulic pump 12c is switched to the on-load state, and at this time, the pressure of the main flow path 13 is increased by the operation of the third relief valve 16c. is maintained at 18.6 MPa.

When the detection value is not below the second threshold (step S204: No), the control unit 19 places the third hydraulic pump 12c in an unloaded state (step S206). For example, when there is no change in the use situation of the winch and the pressure of the main flow path 13 is maintained at 20.6 MPa or 19.6 MPa, the third hydraulic pump 12c continues to be in an unloaded state. In addition, once the third hydraulic pump 12c is switched to the on-road state, if the use situation of the winch changes, such as a decrease in the number of winches in operation, and the flow rate of hydraulic oil becomes excessive, the pressure in the main flow path 13 rises. When the detection value of the pressure sensor 18 exceeds the second threshold of 19.1 MPa, the third hydraulic pump 12c is switched to the unloaded state, and at this time, the main pressure is released by operation of the second relief valve 16b. The pressure in the flow path 13 is maintained at 19.6 MPa.

After step S205 or step S206, the control unit 19 repeats the process from step S201. While the pump unit 1-1 is operating, the control unit 19 repeats the processing from step S201 to step S206 to adjust the second hydraulic pump 12b and the third hydraulic pump 12c according to the use situation of the winch. changes the state of

As explained above, the pump unit 1-1 controls the switching unit 20 using the detected value of the pressure of the main flow passage 13, thereby changing the state of the hydraulic pump 12 to the on-load state or the unload state. You can switch. As a result, even if the hydraulic pump 12 itself is a fixed capacity pump, it becomes possible to adjust the amount of hydraulic oil discharged by the pump unit 1, making it possible to maintain the pressure in the main flow passage 13 at the target pressure. I do it. Therefore, in the central circuit, a fixed displacement pump, such as a positive displacement rotary pump, such as a gear pump, vane pump, or screw pump, can be used, and compared to the case of using a reciprocating pump such as a piston pump, the hydraulic system It becomes possible to significantly reduce the noise of (100).

The control unit 19 switches to the on-load state in the order that the relief pressure set in the corresponding switching unit 20 is high, and switches to the unload state in the order that the relief pressure is low. When switching the third hydraulic pump 12c from the unloaded state to the on-loaded state, the flow rate is insufficient, and the detected value of the pressure sensor 18 is falling from the state maintained at 19.6 MPa, which is the second relief pressure. . When the detection value becomes 19.1 MPa or less, which is the second threshold, the third hydraulic pump 12c switches to the on-load state, and the supply of hydraulic oil from the third pump flow path 14c to the main flow path 13 begins. do. For this reason, the pressure of the main flow path 13 decreases at a lowering speed from the point where it reaches 19.1 MPa, and is maintained at the third relief pressure of 18.6 MPa, which is the target pressure. In this way, by including the plurality of switching units 20 with different relief pressures, the pressure in the main passage 13 is maintained at a different target pressure for each number of hydraulic pumps 12 in the on-load state. In addition, the hydraulic pump 12 is switched to the on-load state in the order in which the relief pressure of the corresponding switching part 20 is high, and the hydraulic pump 12 is unloaded in the order of the relief pressure of the corresponding switching part 20 being low. By switching to this state, while setting an upper limit on the supply pressure from the hydraulic pump 12, when the hydraulic oil becomes excessive, the pressure in the main flow path 13 increases, making it possible to adjust the supply amount according to the required amount of hydraulic oil. do.

In addition, the threshold value used when switching the state of the hydraulic pump 12 is higher than the relief pressure of the switching unit 20 corresponding to the hydraulic pump 12 as the switching target, and in the order of the relief pressure being higher, the It is lower than the relief pressure of the switching unit 20, which is one order earlier than the switching unit 20 corresponding to the hydraulic pump 12. Specifically, the first threshold value is set higher than the second relief pressure and lower than the first relief pressure, and the second threshold value is set higher than the third relief pressure and lower than the second relief pressure. When the use situation of the winch does not change and the required amount of hydraulic oil does not change, the pressure in the main passage 13 is maintained at the first relief pressure, the second relief pressure, or the third relief pressure. For this reason, by setting the first threshold value higher than the second relief pressure and lower than the first relief pressure, and setting the second threshold value higher than the third relief pressure and lower than the second relief pressure, changes in the use situation of the winch can be prevented. In addition to being able to detect, it is possible to prevent hunting and realize stable operation.

In addition, among the plurality of hydraulic pumps 12 included in the pump unit 1, the relief pressure of the first switching unit 20a corresponding to the first hydraulic pump 12a with the smallest capacity is determined by the plurality of switching units 20. ) is the highest among them. As a result, at the time of startup, the first hydraulic pump 12a with the smallest capacity is in the on-load state, and the remaining hydraulic pumps 12, the second hydraulic pump 12b and the third hydraulic pump 12c, are in the unloaded state. It becomes. Therefore, the amount of hydraulic oil supplied during standby can be reduced, making it possible to further reduce the noise of the pump unit 1.

In addition, in the example shown in FIG. 5, the relief pressures of the plurality of relief valves 16 are set to different values, but the same values can also be used. FIG. 7 is a table showing a second example of relief pressure and threshold values used by the pump unit 1-1 shown in FIG. 4. In the second example shown in FIG. 7, the first relief pressure is 20.6 MPa, and the second relief pressure and the third relief pressure are 19.6 MPa. In this case, by equalizing the threshold values provided for each of the plurality of hydraulic pumps 12 where the relief pressure of the corresponding switching unit 20 is the same, the control unit 19 determines that the relief pressure of the corresponding switching unit 20 The order of switching the same plurality of hydraulic pumps 12 to the on-load state can be the same. Specifically, the first threshold and the second threshold are 20.1 MPa. By setting the threshold value in this way, the order in which the control unit 19 switches to the on-load state is set to “1” for the first hydraulic pump 12a, “1” for the second hydraulic pump 12b, and “1” for the third hydraulic pump 12c. It becomes “2”.

When the values of the second example shown in FIG. 7 are used, the timing at which the states of the second hydraulic pump 12b and the third hydraulic pump 12c are switched to the on-load state or the unload state are simultaneous, so in FIG. 5 By using the values of the first example shown, it is possible to control the flow rate of hydraulic oil in detail. However, depending on the requirements of the system, a plurality of relief valves 16 with the same relief pressure may be used as shown in FIG. 7, and the threshold value used when switching the state of each hydraulic pump 12 may be the same. .

Next, the effect of the present invention will be explained using data. Figure 8 is a graph showing the difference in noise value depending on the type of pump used. The horizontal axis represents the number of rotations, and the vertical axis represents the noise value. As the rotation speed increases, the noise value also increases, but it can be seen that the noise value of the internal gear pump is lower than that of the piston pump at the same rotation speed across the entire rotation speed shown in FIG. 8. For example, in order to reduce noise in hydraulic pumps, motors with a rotation speed as low as 1,200 revolutions/min are sometimes used, but the noise value of internal gear pumps is higher than the piston even when a motor with 1,800 revolutions/min is used. It can be seen that the noise value is lower than when the pump uses an electric motor running at 1200 times/min.

Figure 9 is a graph showing the difference in pulsation rate depending on the type of pump used. The horizontal axis represents the rotation speed, and the vertical axis represents the pulsation rate. For internal gear pumps, the pulsation rate decreases as the rotation speed increases, and for piston pumps, the pulsation rate increases as the rotation speed increases. It can be seen that at the commonly used speed of 1200-1800 times/min, the pulsation rate is lower for the internal gear pump. When the pulsation rate is low, the freedom of arrangement of the pump unit 1 increases. For example, when the pulsation rate is low, since vibration during operation is small, the hydraulic pump 12 of the pump unit 1 may be arranged to overlap the tank 10. For this reason, there is an advantage that the installation area of the pump unit 1 can be reduced.

The configuration shown in the above embodiments represents an example of the content of the present invention, and can be combined with other known techniques, and it is also possible to omit or change some of the configuration without departing from the gist of the present invention. do.

For example, in Embodiment 1 above, the pump unit 1 has two hydraulic pumps 12, and in Embodiment 2, the pump unit 1-1 has three hydraulic pumps 12. However, the present invention is not limited to this example. For example, the pump unit 1 may have four or more hydraulic pumps 12. As the number of hydraulic pumps 12 included in the pump unit 1 increases and the number of stages of relief pressure used increases, it becomes possible to finely control the supply amount according to the required amount of hydraulic oil, thereby reducing waste of hydraulic oil.

In addition, in Embodiment 1 above, a twin pump in which two hydraulic pumps 12 are driven by one electric motor 11 is shown, and in Embodiment 2, three hydraulic pumps 12 are driven by one electric motor. Although a three-stage pump driven by (11) is shown, the present invention is not limited to this example. Each of the plurality of hydraulic pumps 12 may be driven by a different electric motor 11. When driving a plurality of hydraulic pumps 12 with one electric motor 11, the number of electric motors 11 used can be reduced, making it possible to reduce the cost of the pump unit 1.

In addition, in Embodiment 1 and Embodiment 2 above, the hydraulic systems 100 and 200 are assumed to have three hydraulic actuators 2, but the present invention is not limited to this example. The number of hydraulic actuators 2 included in the hydraulic systems 100 and 200 may be two or four or more.

In addition, in Embodiment 1 and Embodiment 2 above, the pressure sensor 18 is installed in the housing of the pump unit 1, but the present invention is not limited to this example. For example, the pressure sensor 18 may be installed outside the housing of the pump unit 1 as long as it is in a position where it is possible to detect the circuit pressure of the flow path where the hydraulic oil discharged by the plurality of hydraulic pumps 12 joins.

In addition, in the above-described embodiments 1 and 2, the function of the switching unit 20 is to control the relief valve 16 and the relief valve 16, which has a function of putting the corresponding hydraulic pump 12 in an unloaded state. Although this is realized using the solenoid valve 17, the present invention is not limited to this example. The switching unit 20 may be realized using an electromagnetic relief valve or an electromagnetic proportional relief valve in which the relief valve 16 and the electromagnetic valve 17 are integrated. Alternatively, the function of the switching unit 20 may be realized using a flow control valve such as an electromagnetic proportional flow control valve.

1, 1-1: Pump unit 2: Hydraulic actuator
10: tank 11: electric motor
12: hydraulic pump 12a: first hydraulic pump
12b: second hydraulic pump 12c: third hydraulic pump
13: Main flow path 14: Pump flow path
14a: first pump flow path 14b: second pump flow path
14c: Third pump flow path 15: Check valve
15a: first check valve 15b: second check valve
15c: third check valve 16: relief valve
16a: first relief valve 16b: second relief valve
16c: third relief valve 17: electromagnetic valve
17a: first solenoid valve 17b: second solenoid valve
17c: third solenoid valve 18: pressure sensor
19: control unit 20: switching unit
20a: first transition section 20b: second transition section
20c: third transition section 100, 200: hydraulic system
P: junction point Pa, Pb, Pc: junction point

Claims (13)

A plurality of hydraulic pumps that discharge a fixed capacity of hydraulic oil as positive displacement rotary pumps;
a main flow path where hydraulic oil discharged from the plurality of hydraulic pumps merges;
It is provided corresponding to each of the plurality of hydraulic pumps, and puts the corresponding hydraulic pump in an on-load state for load operation or an unload state for no-load operation, and when the corresponding hydraulic pump is in an on-load state, a preset relief is provided. a plurality of switching units that return a portion of the hydraulic oil discharged by the corresponding hydraulic pump to the tank when a pressure higher than the pressure is applied;
A control unit that maintains the pressure of the main flow path at a target pressure by controlling the switching unit based on the detected value of the pressure of the main flow path,
The control unit switches the hydraulic pump to the on-load state in order from the side where the relief pressure set in the corresponding switching unit is high, and switches the hydraulic pump to the unload state in order from the side where the relief pressure is low. pump unit. In claim 1,
At the time of startup, the control unit places the hydraulic pump with the highest relief pressure of the corresponding switching unit among the plurality of hydraulic pumps in an on-load state and puts the remaining hydraulic pumps in an unload state, and determines the status of the remaining hydraulic pumps based on the detection value. A pump unit characterized in that control. In claim 2,
The control unit switches the states of the remaining hydraulic pumps based on whether the detection value is less than or equal to a threshold value provided for each of the remaining hydraulic pumps,
The threshold value is higher than the relief pressure of the switching section corresponding to the hydraulic pump to be switched, and is lower than the relief pressure of the switching section one order earlier than the switching section corresponding to the hydraulic pump to be switched in the order of higher relief pressure. pump unit. In claim 3,
The plurality of hydraulic pumps include a plurality of hydraulic pumps having the same relief pressure of the corresponding switching portion,
A pump unit, wherein the plurality of threshold values provided in response to each of the plurality of hydraulic pumps having the same relief pressure of the corresponding switching unit are the same. In claim 1,
A pump unit, wherein the relief pressure of the switching section corresponding to the hydraulic pump with the smallest capacity among the plurality of hydraulic pumps is the highest among the relief pressures of the plurality of switching sections. In claim 1,
A pump unit, wherein the control unit controls the switching unit to change the state of each of the plurality of hydraulic pumps, thereby changing the target pressure. In claim 1,
The target pressure changes depending on the number of the hydraulic pumps in the on-load state and becomes the smallest value among the relief pressures of the switching portion corresponding to the hydraulic pump in the on-load state. In claim 1,
A pump unit, characterized in that the hydraulic pump is a gear pump. In claim 1,
A pump unit, characterized in that the hydraulic pump is a vane pump. In claim 1,
A pump unit, characterized in that the hydraulic pump is a screw pump. In claim 1,
The pump unit, wherein the switching unit includes a relief valve that has a function of putting the corresponding hydraulic pump into an unloaded state, and an electromagnetic valve, an electromagnetic relief valve, or an electromagnetic proportional relief valve that controls the relief valve. The pump unit according to any one of claims 1 to 11,
A hydraulic system comprising a plurality of hydraulic actuators connected to flow paths branching from the main flow path of the pump unit.
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