JP6799480B2 - Hydraulic system - Google Patents

Description

The present invention relates to an electric positive control type hydraulic system.

Conventionally, electric positive control type hydraulic systems have been adopted in construction machinery and industrial machinery. For example, Patent Document 1 discloses a hydraulic system 100 for construction machinery as shown in FIG.

In this hydraulic system 100, hydraulic oil is supplied from the variable displacement pump 110 to each hydraulic actuator 130 via the control valve 120. The control valve 120 increases the opening area of the passage for supplying the hydraulic oil to the hydraulic actuator 130 as the amount of operation with respect to the operation unit (operation lever in FIG. 6) of the corresponding operation device 140 increases.

The tilt angle of the pump 110 is adjusted by the regulator 111. The regulator 111 is connected to the first electromagnetic proportional valve 112. The first electromagnetic proportional valve 112 outputs a higher secondary pressure as the amount of operation with respect to the operating portion of the operating device 140 increases. As a result, the discharge flow rate of the pump 110 increases as the amount of operation of the operating device 140 with respect to the operating portion increases.

The flood control system 100 is provided with an unload valve 150 for letting the hydraulic oil discharged from the pump 110 escape to the tank during standby (a state in which all the operating devices 140 are not operated). The unload valve 150 has a pilot port, and is configured so that the opening area decreases from the fully open state to the fully closed state as the pilot pressure guided to the pilot port increases. The pilot port of the unload valve 150 is connected to the second electromagnetic proportional valve 160. The second electromagnetic proportional valve 160 outputs a higher secondary pressure as the amount of operation on the operating portion of the operating device 140 increases.

Japanese Unexamined Patent Publication No. 10-61604

However, in the hydraulic system 100 shown in FIG. 6, when the second electromagnetic proportional valve 160 fails, the secondary pressure of the second electromagnetic proportional valve 160 becomes zero or becomes equal to the primary pressure. When the secondary pressure of the second electromagnetic proportional valve 160 becomes zero, the unload valve 150 is fully opened. Therefore, even if the operation unit of the operation device 140 is operated, the discharge pressure of the pump 110 does not increase and the hydraulic actuator cannot be operated. On the other hand, when the secondary pressure of the second electromagnetic proportional valve 160 becomes equal to the primary pressure, the unload valve 150 is fully closed. Therefore, the discharge pressure of the pump 110 becomes excessive (equal to the relief pressure) during standby.

Therefore, an object of the present invention is to enable the hydraulic actuator to be operated even when the electromagnetic proportional valve for the unload valve fails and the secondary pressure of the electromagnetic proportional valve becomes zero.

In order to solve the above problems, the present invention operates on an operation device that outputs an operation signal according to the amount of operation on the operation unit from one side surface, and on the hydraulic actuator as the operation signal output from the operation device increases. A control valve that increases the opening area of the passage for supplying oil, a variable displacement pump that is connected to the control valve by a supply line, and a secondary pressure that increases as the operation signal output from the operation device increases. The first electromagnetic proportional valve, the regulator that increases the tilt angle of the pump as the secondary pressure output from the first electromagnetic proportional valve increases, and the unload line branching from the supply line are provided. An unload valve having a pilot port, the unload valve whose opening area decreases from the fully open state to the fully closed state as the pilot pressure guided to the pilot port increases, and an operation signal output from the operating device. A second electromagnetic proportional valve that outputs a higher secondary pressure as the value increases, and the secondary pressure of the second electromagnetic proportional valve is set higher than the secondary pressure of the first proportional valve for the same operation signal. The pilot of the unload valve is selected from the second electromagnetic proportional valve, the secondary pressure output from the first electromagnetic proportional valve, and the secondary pressure output from the second electromagnetic proportional valve, whichever is higher. A hydraulic system is provided with a high pressure selection valve leading to a port.

According to the above configuration, when the second electromagnetic proportional valve is normal, the secondary pressure of the second electromagnetic proportional valve is guided to the pilot port of the unload valve, so that the unload valve is operated by the second electromagnetic proportional valve. The opening area of the can be controlled. On the other hand, when the second electromagnetic proportional valve fails and the secondary pressure of the second electromagnetic proportional valve becomes zero, the secondary pressure of the first electromagnetic proportional valve is guided to the pilot port of the unload valve. Therefore, the opening area of the unload valve decreases as the operation signal increases. As a result, the discharge pressure of the pump increases according to the amount of operation of the operating device with respect to the operating portion, and the hydraulic actuator can be operated.

In the unload valve, when the pilot pressure rises from zero to the first set value, the opening area decreases from the maximum value to the intermediate value with the first inclination, and the pilot pressure decreases from the first set value to the second. The opening area may be configured to decrease from the intermediate value to zero with a second inclination that is gentler than the first inclination when rising to the set value. Alternatively, in the unload valve, when the pilot pressure rises from zero to the first set value, the opening area decreases from the maximum value to the intermediate value with the first inclination, and the pilot pressure decreases from the first set value. When rising to the second set value, the opening area decreases from the intermediate value to zero along a curve that is convex upward with respect to a straight line having a second slope that is gentler than the first slope. It may be configured. According to this configuration, the opening area in standby is secured without sacrificing the control gain in the range required for controlling the unload valve and without significantly increasing the stroke of the spool of the unload valve. it can. As a result, the power of the engine that drives the pump can be reduced during the standby of the hydraulic system.

Further, according to the present invention, from another side, an operation device that outputs an operation signal according to the amount of operation to the operation unit, and a passage that supplies hydraulic oil to the hydraulic actuator as the operation signal output from the operation device becomes larger. A control valve that increases the opening area, a variable displacement pump that is connected to the control valve by a supply line, and a first electromagnetic proportional valve that outputs a higher secondary pressure as the operation signal output from the operation device increases. An unload having a regulator that increases the tilt angle of the pump as the secondary pressure output from the first electromagnetic proportional valve increases, and a pilot port provided on the unload line branching from the supply line. The unload valve includes a valve and a second electromagnetic proportional valve that outputs a secondary pressure that increases as the operation signal output from the operating device increases to the pilot port of the unload valve, and the unload valve has the second electromagnetic wave. When the secondary pressure output from the proportional valve changes between the first set value and the second set value larger than the first set value, the opening area is continuous between the fully open state and the fully closed state. When the secondary pressure is equal to or less than the third set value smaller than the first set value and greater than or equal to the fourth set value larger than the second set value, the opening area is fully open and fully closed. Provided is a hydraulic system configured to be an intermediate value between.

According to the above configuration, when the second electromagnetic proportional valve fails and the secondary pressure of the second electromagnetic proportional valve becomes zero, the opening area of the unload valve becomes an intermediate value and the unload valve becomes Functions as an aperture. As a result, the discharge pressure of the pump increases to some extent even when the operating device is not operated, and when the operating device is operated, the discharge pressure of the pump increases according to the amount of operation, so that the hydraulic actuator can be operated.

Further, in the above configuration, even when the second electromagnetic proportional valve fails and the secondary pressure of the second electromagnetic proportional valve becomes equal to the primary pressure, the opening area of the unload valve becomes an intermediate value. As a result, it is possible to prevent the discharge pressure of the pump from becoming excessive without increasing to the relief pressure during standby.

According to the present invention, the hydraulic actuator can be operated even when the electromagnetic proportional valve for the unload valve fails and the secondary pressure of the electromagnetic proportional valve becomes zero.

It is a schematic block diagram of the hydraulic system which concerns on 1st Embodiment of this invention. It is a graph which shows the relationship between the operation amount with respect to the operation part of the operation apparatus, and the secondary pressure of the 1st electromagnetic proportional valve and the 2nd electromagnetic proportional valve. (A) is a graph showing the relationship between the pilot pressure of the unload valve and the opening area in the first embodiment, and (b) is a graph showing the relationship between the pilot pressure of the unload valve and the opening area in the modified example. It is a schematic block diagram of the hydraulic system which concerns on 2nd Embodiment of this invention. It is a graph which shows the relationship between the pilot pressure of an unload valve and an opening area. It is a schematic block diagram of the hydraulic system of the conventional construction machine.

(First Embodiment)
FIG. 1 shows the hydraulic system 1A according to the first embodiment of the present invention. The hydraulic system 1A is mounted on a construction machine such as a hydraulic excavator or a hydraulic crane, a civil engineering machine, an agricultural machine or an industrial machine.

Specifically, the hydraulic system 1A includes a hydraulic actuator 24 and a main pump 21 that supplies hydraulic oil to the hydraulic actuator 24 via a control valve 3. In the illustrated example, the hydraulic actuator 24 and the control valve 3 are set in one set, but a plurality of sets of the hydraulic actuator 24 and the control valve 3 may be provided.

The main pump 21 is a variable displacement type pump whose tilt angle can be changed. The main pump 21 may be a swash plate pump or a swash shaft pump. The tilt angle of the main pump 21 is adjusted by the regulator 22.

The main pump 21 is connected to the control valve 3 by a supply line 11. The discharge pressure of the main pump 21 is kept below the relief pressure by the relief valve 12.

In the present embodiment, the hydraulic actuator 24 is a double-acting cylinder, and the control valve 3 is connected to the hydraulic actuator 24 by a pair of supply / discharge lines 31. However, the hydraulic actuator 24 may be a single-acting cylinder, and the control valve 3 may be connected to the hydraulic actuator 24 by a single supply / discharge line 31. Alternatively, the hydraulic actuator 24 may be a hydraulic motor.

The control valve 3 is moved from the neutral position to the first position (the position where the hydraulic actuator 24 is operated in one direction) or the second position (the position where the hydraulic actuator 24 is operated in the opposite direction) when the operating device 4 is operated. Can be switched. In this embodiment, the control valve 3 is a hydraulic pilot type and has a pair of pilot ports. However, the control valve 3 may be an electromagnetic pilot type.

The operation device 4 has an operation unit 41 and outputs an operation signal according to the amount of operation for the operation unit 41. That is, the operation signal output from the operation device 4 increases as the operation amount increases. The operation unit 41 is, for example, an operation lever, but may be a foot pedal or the like.

In the present embodiment, the operation device 4 is a pilot operation valve that outputs a pilot pressure as an operation signal. Therefore, the operating device 4 is connected to the pilot port of the control valve 3 by a pair of pilot lines 42. Then, as the pilot pressure (operation signal) output from the operation device 4 increases, the opening area of the passage through which the control valve 3 supplies the hydraulic oil to the hydraulic actuator 24 increases. However, the operation device 4 may be an electric joystick that outputs an electric signal as an operation signal. In this case, each pilot port of the control valve 3 is connected to the secondary pressure port of the electromagnetic proportional valve.

The regulator 22 described above is connected to the secondary pressure port of the first electromagnetic proportional valve 6 by a secondary pressure line 62. The primary pressure port of the first electromagnetic proportional valve 6 is connected to the auxiliary pump 23 by the primary pressure line 61. The discharge pressure of the auxiliary pump 23 is maintained at the set pressure by the relief valve 15.

The first electromagnetic proportional valve 6 is a direct proportional type that outputs a higher secondary pressure as the command current increases. The regulator 22 increases the tilt angle of the main pump 21 as the secondary pressure output from the first electromagnetic proportional valve 6 increases.

The first electromagnetic proportional valve 6 is controlled by the control device 9. For example, the control device 9 has a memory such as a ROM or RAM and a CPU, and the program stored in the ROM is executed by the CPU.

The control device 9 is electrically connected to the pressure sensors 91 provided in each of the pair of pilot lines 42 described above. However, in FIG. 1, only some signal lines are drawn for the sake of simplification of the drawing.

The pressure sensor 91 detects the pilot pressure output from the operating device 4. Then, the control device 9 increases the command current supplied to the first electromagnetic proportional valve 6 as the pilot pressure output from the operating device 4 increases. That is, the first electromagnetic proportional valve 6 outputs a higher secondary pressure as the pilot pressure output from the operating device 4 increases. As a result, the discharge flow rate of the main pump 21 increases as the amount of operation of the operating device 4 with respect to the operating unit 41 increases.

The unload line 13 is branched from the supply line 11 described above. The unload line 13 is connected to the tank. The unload line 13 is provided with an unload valve 5A.

The unload valve 5A is pilot type and has a pilot port 5c. The unload valve 5A is configured such that the opening area between the pump port 5a and the tank port 5b decreases from the fully open state to the fully closed state as the pilot pressure guided to the pilot port 5c increases. .. That is, when the unload valve 5A is in the neutral state, the opening area is maximized.

In the present embodiment, as shown in FIG. 3A, the unload valve 5A has a first inclination S1 from the maximum value to the intermediate value when the pilot pressure rises from zero to the first set value α. And when the pilot pressure rises from the first set value α to the second set value β, the opening area decreases from the intermediate value to zero at the second slope S2, which is gentler than the first slope S1. It is configured to do. In other words, the absolute value of the first slope S1 is larger than the absolute value of the second slope S2. For example, the first set value α is 20% to 80% of the second set value β. However, the opening area of the unload valve 5A does not necessarily have to decrease linearly between the first set value α and the second set value β, and as shown in FIG. 3B, the second set value It may decrease along a curve that is convex upward with respect to the straight line of the slope S2 of.

Returning to FIG. 1, the pilot port 5c of the unload valve 5A is connected to the secondary pressure port of the second electromagnetic proportional valve 7 via the high pressure selection valve 8. The primary pressure port of the second electromagnetic proportional valve 7 is connected to the auxiliary pump 23 by the primary pressure line 71.

More specifically, the high pressure selection valve 8 has two input ports and one output port, and the pilot port 5c of the unload valve 5A is connected to the output port of the high pressure selection valve 8 by an output line 83, and the high pressure selection valve 8 is connected. One input port of 8 is connected to the secondary pressure port of the second electromagnetic proportional valve 7 by the first input line 81. Further, another input port of the high pressure selection valve 8 is connected by a second input line 82 to a secondary pressure line 62 extending from the secondary pressure port of the first electromagnetic proportional valve 6. That is, the high-pressure selective valve 8 selects the higher of the secondary pressure output from the first electromagnetic proportional valve 6 and the secondary pressure output from the second electromagnetic proportional valve 7, and selects the pilot port of the unload valve 5A. Lead to 5c.

The second electromagnetic proportional valve 7 is a direct proportional type that outputs a higher secondary pressure as the command current increases. The second electromagnetic proportional valve 7 is controlled by the control device 9.

Similar to the first electromagnetic proportional valve 6, the control device 9 increases the command current supplied to the second electromagnetic proportional valve 7 as the pilot pressure output from the operating device 4 increases. That is, the second electromagnetic proportional valve 7 outputs a higher secondary pressure as the pilot pressure output from the operating device 4 increases. However, as shown in FIG. 2, the secondary pressure of the second electromagnetic proportional valve 7 is higher than the secondary pressure of the first electromagnetic proportional valve 6 with respect to the same pilot pressure (operation signal) output from the operating device 4. It is set high.

Therefore, when the second electromagnetic proportional valve 7 is normal, the secondary pressure of the second electromagnetic proportional valve 7 is guided to the pilot port 5c of the unload valve 5, so that the second electromagnetic proportional valve 7 unloads. The opening area of the valve 5A can be controlled. On the other hand, when the second electromagnetic proportional valve 7 fails and the secondary pressure of the second electromagnetic proportional valve 7 becomes zero, the secondary pressure of the first electromagnetic proportional valve 6 is connected to the pilot port 5c of the unload valve 5A. Is guided. Therefore, the opening area of the unload valve 5A decreases as the operation signal increases. As a result, the discharge pressure of the main pump 21 increases according to the amount of operation of the operating device 4 with respect to the operating unit 41, and the hydraulic actuator 24 can be operated.

Further, in the present embodiment, as shown in FIG. 3A, the opening area of the unload valve 5A decreases sharply at first and gradually decreases in the middle. Therefore, the unload valve 5A does not sacrifice the control gain in the range required for control of the unload valve 5A (the pilot pressure is in the range between the first set value α and the second set value β). It is possible to secure the opening area at the time of standby without making the stroke of the spool too long. As a result, the power of the engine (not shown) that drives the pump 21 can be reduced during the standby of the hydraulic system 1A. This effect can be obtained even in the case shown in FIG. 3 (b). However, the pump 21 may be driven by an electric motor.

(Second Embodiment)
FIG. 4 shows the hydraulic system 1B according to the second embodiment of the present invention. In the present embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and duplicate description will be omitted.

In the first embodiment, the unload valve 5A which is a two-position valve is adopted, but in the present embodiment, the unload valve 5B which is a four-position valve is adopted. Further, in the present embodiment, the pilot port 5c of the unload valve 5B is connected to the secondary pressure port of the second electromagnetic proportional valve 7 by the secondary pressure line 72, and the second electromagnetic proportional valve 7 is the unload valve 5B. The secondary pressure is output to the pilot port 5c of.

In the present embodiment, even if the secondary pressure of the second electromagnetic proportional valve 7 is equal to the secondary pressure of the first electromagnetic proportional valve 6 with respect to the same pilot pressure (operation signal) output from the operating device 4. It may be lower, lower, or higher as in the first embodiment.

As shown in FIG. 5, the unload valve 5B has a second set value P2 in which the secondary pressure (pilot pressure) output from the second electromagnetic proportional valve 7 is larger than the first set value P1 and the first set value P1. When changing between, the opening area between the pump port 5a and the tank port 5b is configured to continuously change between the fully open state and the fully closed state. In the present embodiment, the opening area of the unload valve 5B decreases from the maximum value to zero as the secondary pressure of the second electromagnetic proportional valve 7 increases from the first set value P1 to the second set value P2.

Further, the unload valve 5B has a second set value P4 or more when the secondary pressure of the second electromagnetic proportional valve 7 is smaller than the first set value P1 and less than the third set value P3 and larger than the second set value P2. In the case of, the opening area is configured to be an intermediate value between the fully open state and the fully closed state. For example, the median value is 0.5 to 50% of the maximum value of the opening area. The intermediate value of the opening area when the secondary pressure of the second electromagnetic proportional valve 7 is the third set value P3 or less is the opening when the secondary pressure of the second electromagnetic proportional valve 7 is the fourth set value P4 or more. It may be equal to or different from the median value of the area.

When the pilot pressure guided to the pilot port 5c of the unload valve 5B rises from zero to the third set value P3, the spool of the unload valve 5B moves slightly while the opening area of the unload valve 5B is maintained at an intermediate value. To do. When the pilot pressure rises from the third set value P3 to the first set value P1, the spool of the unload valve 5B moves so that the opening area of the unload valve 5B increases from the intermediate value to the maximum value. When the pilot pressure rises from the first set value P1 to the second set value P2, the spool of the unload valve 5B moves so that the opening area of the unload valve 5B decreases from the maximum value to zero. When the pilot pressure rises from the second set value P2 to the fourth set value P4, the spool of the unload valve 5B moves slightly while the opening area of the unload valve 5B is maintained at zero. When the pilot pressure becomes the fourth set value P4 or more, the tank port 5b communicates with the pump port 5a again by the movement of the spool of the unload valve 5B, and the opening area of the unload valve 5B is maintained at an intermediate value.

In the hydraulic system 1B of the present embodiment, when the second electromagnetic proportional valve 7 fails and the secondary pressure of the second electromagnetic proportional valve 7 becomes zero, the opening area of the unload valve 5B becomes an intermediate value. , The unload valve 5B functions as a throttle. As a result, the discharge pressure of the main pump 21 increases to some extent even when the operating device 4 is not operated, and when the operating device 4 is operated, the discharge pressure of the main pump 21 increases according to the amount of operation, and the hydraulic actuator 24 is operated. Can be activated.

Further, in the present embodiment, even when the second electromagnetic proportional valve 7 fails and the secondary pressure of the second electromagnetic proportional valve 7 becomes equal to the primary pressure, the opening area of the unload valve 5B becomes an intermediate value. As a result, it is possible to prevent the discharge pressure of the main pump 21 from becoming excessive without increasing to the relief pressure during standby. Then, when the operating device 4 is operated, the discharge pressure of the main pump 21 rises according to the amount of operation, and the hydraulic actuator 24 can be operated.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

1A, 1B Hydraulic system 11 Supply line 21 Main pump 22 Regulator 24 Hydraulic actuator 3 Control valve 4 Operating device 41 Operation unit 5A, 5B Unload valve 5c Pilot port 6 1st electromagnetic proportional valve 7 2nd electromagnetic proportional valve 8 High pressure selection valve

Claims (4)

An operation device that outputs an operation signal according to the amount of operation on the operation unit,
A control valve that increases the opening area of the passage that supplies hydraulic oil to the hydraulic actuator as the operation signal output from the operation device increases.
A variable displacement pump connected to the control valve by a supply line,
A first electromagnetic proportional valve that outputs a higher secondary pressure as the operating signal output from the operating device becomes larger,
A regulator that increases the tilt angle of the pump as the secondary pressure output from the first electromagnetic proportional valve increases.
An unload valve having a pilot port provided on an unload line branching from the supply line, and the opening area decreases from a fully open state to a fully closed state as the pilot pressure guided to the pilot port increases. Unload valve and
A second proportional solenoid valve which outputs a higher secondary pressure operation signal output from the operating device is increased, for the same operation signal of the second solenoid proportional valve secondary pressure is the first electromagnetic A second electromagnetic proportional valve set higher than the secondary pressure of the proportional valve,
A high-pressure selective valve that selects the higher of the secondary pressure output from the first electromagnetic proportional valve and the secondary pressure output from the second electromagnetic proportional valve and guides it to the pilot port of the unload valve.
A hydraulic system.
In the unload valve, when the pilot pressure rises from zero to the first set value, the opening area decreases from the maximum value to the intermediate value with the first inclination, and the pilot pressure decreases from the first set value to the second. The hydraulic system according to claim 1, wherein the opening area decreases from the intermediate value to zero with a second inclination gentler than the first inclination when rising to a set value. In the unload valve, when the pilot pressure rises from zero to the first set value, the opening area decreases from the maximum value to the intermediate value with the first inclination, and the pilot pressure decreases from the first set value to the second. When rising to the set value, the opening area is configured to decrease from the intermediate value to zero along a curve that is convex upward with respect to a straight line having a second slope that is gentler than the first slope. The hydraulic system according to claim 1. An operation device that outputs an operation signal according to the amount of operation on the operation unit,
A control valve that increases the opening area of the passage that supplies hydraulic oil to the hydraulic actuator as the operation signal output from the operation device increases.
A variable displacement pump connected to the control valve by a supply line,
A first electromagnetic proportional valve that outputs a higher secondary pressure as the operating signal output from the operating device becomes larger,
A regulator that increases the tilt angle of the pump as the secondary pressure output from the first electromagnetic proportional valve increases.
An unload valve having a pilot port provided on the unload line branching from the supply line,
A second electromagnetic proportional valve that outputs a higher secondary pressure to the pilot port of the unload valve as the operation signal output from the operation device becomes larger is provided.
The unload valve has a fully open opening area when the secondary pressure output from the second electromagnetic proportional valve changes between the first set value and the second set value larger than the first set value. When the secondary pressure continuously changes between the first set value and the fully closed state, and the secondary pressure is equal to or less than the third set value smaller than the first set value and greater than or equal to the fourth set value larger than the second set value. Is a hydraulic system in which the opening area is configured to be an intermediate value between the fully open and fully closed states.

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