JP6940992B2 - A hydraulic drive system and a hydraulic drive system including the hydraulic drive system. - Google Patents

Description

The present invention relates to a hydraulic drive device for driving a hydraulic actuator by flowing hydraulic oil from a main pump to a hydraulic actuator, and a hydraulic drive system including the hydraulic drive system.

The hydraulic actuator is driven by hydraulic oil from the main pump, and the main pump constitutes a hydraulic drive circuit together with a multi-control valve. In the hydraulic drive circuit, the direction and flow rate of the hydraulic oil flowing from the main pump to the hydraulic actuator are controlled by the multi-control valve, and the movement of the hydraulic actuator is controlled by this. As an example of a hydraulic drive circuit having such a function, for example, a hydraulic drive circuit as described in Patent Document 1 is known.

In the hydraulic drive circuit of Patent Document 1, the pilot pressure input to the multi-control valve is controlled by the electromagnetic proportional control valve. That is, the operation amount of the operation lever is input to the control device, and the control device controls the movement of the electromagnetic proportional control valve so as to apply the pilot pressure according to the input operation amount to the spool of the multi-control valve. As a result, the hydraulic oil of the flow rate corresponding to the manipulated variable is guided to the hydraulic actuator, and the hydraulic actuator can be moved at the speed corresponding to the manipulated variable.

Japanese Unexamined Patent Publication No. 64-6501

The electromagnetic proportional control valve may have the following failures. That is, a failure may occur in the wiring path such that the signal line connecting the electromagnetic proportional control valve and the control device is disconnected. In this case, even if the operating lever is operated, the passage on the primary pressure side and the passage on the secondary pressure (output) side of the electromagnetic proportional control valve continue to be cut off, and the output pressure from the electromagnetic proportional control valve remains zero. It becomes. In addition, a failure may occur in which the valve body of the electromagnetic proportional control valve sticks while blocking the passage on the primary pressure side and the passage on the secondary pressure side of the electromagnetic proportional control valve, and in this case as well, a failure occurs in the wiring path. The output pressure from the electromagnetic proportional control valve remains zero as if it had occurred. Therefore, in any case, the spool of the multi-control valve is maintained in the neutral position even if the operating lever is operated, so that the hydraulic actuator does not react even if the operating lever is operated. However, it is desired that the hydraulic actuator can be operated even when such a failure occurs.

Therefore, the present invention is a hydraulic drive device capable of operating a hydraulic actuator in response to an operation of the operating device even if a failure occurs in which the output pressure from the electromagnetic proportional control valve is maintained at zero, and a hydraulic driving device thereof. It is an object of the present invention to provide a hydraulic drive system equipped with.

In the hydraulic drive device of the present invention, two pilot pressures are input in directions opposite to each other, and the operation is such that the two pilot pressures move in one direction and the other in a predetermined direction according to the differential pressure of the two pilot pressures and flow from the main pump to the hydraulic actuator. Pressure oil supplied from a flow control valve having a spool that switches the direction of oil and controls the opening degree between the main pump and the hydraulic actuator, and a pressure source that supplies pressure oil maintained at a constant set pressure. Is a direct proportional type electromagnetic proportional control valve having A direct proportional first electromagnetic proportional control valve that outputs the pilot pressure to the flow control valve to move the spool in one of the predetermined directions, and a direct proportional type that uses the pressure oil supplied from the pressure source as the primary pressure. An electromagnetic proportional control valve, which is a direct proportional type second electromagnetic proportional control valve that is controlled to reduce the pressure to a second output pressure according to an input current and outputs, a set pressure supplied from the pressure source, and the second. Any one of the second output pressures output from the electromagnetic proportional control valve is output to the flow control valve as the second pilot pressure which is the other of the two pilot pressures, and the spool is sent to the other in the predetermined direction. The switching valve to be moved and the oil passage branching from the passage between the first electromagnetic proportional control valve and the flow control valve and connected to the switching valve can be operated in different first and second directions. When the operating device, the first electromagnetic proportional control valve, and the second electromagnetic proportional control valve are operating normally, and the operating device is operated in the first direction, the operation amount in the first direction is adjusted. Control that the corresponding current is passed through the first electromagnetic proportional control valve, and when the operating device is operated in the second direction, the current corresponding to the amount of operation in the second direction is passed through the second electromagnetic proportional control valve. The switching valve includes a unit, and the first pilot pressure and the second output pressure are input so as to oppose each other, and the difference obtained by subtracting the second output pressure from the first pilot pressure is predetermined. When the pressure is equal to or higher than the predetermined pressure, the set pressure is output to the flow control valve as the second pilot pressure, and when the difference is less than the predetermined pressure, the second output pressure is the second pilot pressure. In the control unit, a failure occurs in the second electromagnetic proportional control valve or its wiring path so that the second output pressure is maintained at zero even when the operating device is operated in the second direction. If it is determined that the pressure is high, the first electromagnetic ratio is Example: The control valve is energized, and the first output pressure that is equal to or higher than the predetermined pressure and that corresponds to the amount of operation in the second direction of the operating device is used as the first pilot pressure. The output is output to the switching valve.

According to the present invention, when the operating device is operated in the second direction in a state where there is no failure in the second electromagnetic proportional control valve or its wiring path, a second output pressure corresponding to the operating amount of the operating device is output. NS. On the other hand, if there is no output from the first electromagnetic proportional control valve, the difference obtained by subtracting the second output pressure from the first pilot pressure is equal to or less than the predetermined pressure, and the second output pressure is set as the second pilot pressure, and the flow control valve from the switching valve. Is output to. As a result, the spool of the flow control valve moves to the other side in the predetermined direction and to the position corresponding to the second output pressure, and the opening degree between the main pump and the hydraulic actuator becomes the opening degree corresponding to the second output pressure. Become. That is, the hydraulic oil of the flow rate corresponding to the operation amount of the operating device can be flowed to the hydraulic actuator, and the hydraulic actuator can be moved at the speed corresponding to the operating amount of the operating device.

On the other hand, for example, when the operating device is operated in the second direction in a state where the wiring path of the second electromagnetic proportional control valve has a failure, the control unit controls the first electromagnetic proportional control instead of the second electromagnetic proportional control valve. The valve is energized to output a first output pressure equal to or higher than a predetermined pressure from the first electromagnetic proportional control valve. As a result, the first pilot pressure becomes equal to or higher than the predetermined pressure, and the set pressure is output from the switching valve to the flow control valve as the second pilot pressure. That is, two pilot pressures that oppose each other act on the spool. Here, the first pilot pressure is controlled to be equal to or lower than the set pressure, and the second pilot pressure is the same as the set pressure. Therefore, when the two pilot pressures act on the spool, the spool moves in the other direction in a predetermined direction and in a position corresponding to the difference between the two pilot pressures. Therefore, the difference between the two pilot pressures can be adjusted by adjusting the first output pressure according to the amount of operation of the operating device, and the spool can be operated even if a failure occurs in the wiring path of the second electromagnetic proportional control valve. It can be moved to a position according to the amount of operation in the second direction of the device. That is, a failure occurred in the second electromagnetic proportional control valve such that the output pressure from the second electromagnetic proportional control valve was maintained at zero, as in the case where a failure occurred in the wiring path of the electromagnetic proportional control valve. In this case, the hydraulic oil at a flow rate corresponding to the amount of operation in the second direction of the operating device can be flowed to the hydraulic actuator, and the hydraulic actuator can be moved at a speed corresponding to the amount of operation in the second direction of the operating device.

When the operating device is operated in the first direction, the control unit applies a current according to the operating amount of the operating device to the first electromagnetic wave regardless of whether or not there is a failure in the second electromagnetic proportional control valve or its wiring path. Output to the proportional control valve. Then, the first output pressure of the pressure corresponding to the operation amount of the operating device is output from the first electromagnetic proportional control valve to the flow rate control valve as the first pilot pressure, and is in the first direction in which the operating device is operated. The spool moves to a position according to the amount of operation. As a result, the hydraulic oil at a flow rate corresponding to the first-direction operation amount of the operating device can be flowed to the hydraulic actuator, and the hydraulic actuator can be moved at a speed corresponding to the first-direction operation amount of the operating device.

In the above invention, when the first pilot pressure is larger than the second pilot pressure and the differential pressure between the two pilot pressures reaches a predetermined predetermined pressure, the spool strokes in one of the predetermined directions. The switching valve may be configured so that the amount is maximized and the predetermined pressure is larger than the specified pressure.

According to the above configuration, the specified pressure is set lower than the predetermined pressure, so even if the first pilot pressure is boosted to the specified pressure in a state where the second electromagnetic proportional control valve or its wiring path is out of order. The set pressure is not output as the second pilot pressure. Therefore, even when the second electromagnetic proportional control valve or its wiring path is out of order, the spool can be stroked in one of the predetermined directions up to the maximum stroke amount. That is, in a state where the second electromagnetic proportional control valve or its wiring path is out of order, it is possible to prevent the function of the hydraulic drive device from deteriorating when the spool is moved in one direction in a predetermined direction by the first pilot pressure.

In the above invention, the flow control valve uses either one of the first output pressure output from the first electromagnetic proportional control valve and the set pressure kept constant by the pressure source as the first pilot pressure. A first switching valve for outputting is further provided, and the first switching valve is input so that the second pilot pressure and the first output pressure oppose each other, and the first output pressure is changed from the second pilot pressure. When the first difference obtained by subtracting is equal to or higher than the first predetermined pressure, the set pressure is output as the first pilot pressure, and when the first difference is less than the first predetermined pressure, the first output is obtained. The pressure is output as the first pilot pressure, and the second switching valve, which is the switching valve, is input so that the first pilot pressure and the second output pressure oppose each other, and the first pilot pressure is used as the first pilot pressure. When the second difference, which is the difference obtained by subtracting the second output pressure, is equal to or higher than the second predetermined pressure, which is the predetermined pressure, the set pressure is output to the flow control valve as the second pilot pressure, and the second difference is obtained. Is less than the second predetermined pressure, the second output pressure is output to the flow control valve as the second pilot pressure, and the control unit is operated even when the operating device is operated in the first direction. When it is determined that a failure such that the first output pressure is maintained at zero occurs in the first electromagnetic proportional control valve or its wiring path, the second electromagnetic proportional control valve is energized and the first electromagnetic proportional control valve is energized. The second output pressure, which is equal to or higher than a predetermined pressure and corresponds to the amount of operation in the first direction of the operating device, is output as the second pilot pressure from the second electromagnetic proportional control valve to the flow control valve and the second switching valve. You may.

According to the above configuration, even when the first electromagnetic proportional control valve or its wiring path is out of order, the operation amount of the operating device can be adjusted regardless of whether the operation is performed in the first direction or the second direction with respect to the operating device. The flow rate of hydraulic oil can be flowed through the hydraulic actuator, and the hydraulic actuator can be moved at a speed corresponding to the amount of operation of the operating device.

In the above invention, the spool moves in one of the predetermined directions when the first pilot pressure is larger than the second pilot pressure and the differential pressure between the two pilot pressures reaches a predetermined first specified pressure. When the stroke amount becomes maximum, the second pilot pressure is larger than the first pilot pressure, and the differential pressure between the two pilot pressures reaches a predetermined second specified pressure, the stroke amount in the predetermined direction and the other direction. The first switching valve is configured so that the first predetermined pressure is larger than the first specified pressure, and the second switching valve has the second predetermined pressure as the first predetermined pressure. 2 It may be configured to be larger than the specified pressure.

According to the above configuration, since the first specified pressure is set lower than the first predetermined pressure, it is set even if the second pilot pressure is boosted to the specified pressure while the first electromagnetic proportional control valve cannot be energized. The pressure is not output as the first pilot pressure. Therefore, even in a state where the first electromagnetic proportional control valve or its wiring path is out of order, the spool can be stroked up to the maximum stroke amount in the other direction in a predetermined direction. That is, in a state where the first electromagnetic proportional control valve or its wiring path is out of order, it is possible to prevent the function of the hydraulic drive system from deteriorating when the spool is moved to the other in a predetermined direction.

Similarly, since the second specified pressure is set lower than the second predetermined pressure, the spool is directed to the other in the predetermined direction even when the second electromagnetic proportional control valve or its wiring path is out of order. It is possible to make a stroke up to the maximum stroke amount. That is, it is possible to prevent the function of the hydraulic drive system from deteriorating when the spool is moved in one direction in a predetermined direction.

In the above invention, the spool may be positioned at a neutral position that cuts off between the main pump and the hydraulic actuator when the differential pressure between the two pilot pressures is zero.

According to the above configuration, when the second electromagnetic proportional control valve sticks in a state where the secondary pressure port communicates with the primary pressure port and becomes uncontrollable, the pressure is the same as the set pressure from the second electromagnetic proportional control valve. The second output pressure will be output. Then, the second output pressure, which is the same as the set pressure, is output from the second switching valve to the flow control valve as the second pilot pressure. On the other hand, in the first switching valve, the second output pressure, which is the same as the set pressure, is input as the second pilot pressure, so that the first switching valve outputs the set pressure as the first pilot pressure to the flow control valve. Will be. As a result, the first pilot pressure and the second pilot pressure of the same pressure act on the spool of the flow control valve so as to oppose each other, and the spool is held in the neutral position. As a result, it is possible to prevent the hydraulic oil from being guided by the hydraulic actuator and making undesired movements, and fail-safe can be achieved.

The hydraulic drive system of the present invention includes the above-mentioned hydraulic drive device, a main pump for discharging hydraulic oil to be supplied to the hydraulic actuator, and a sub-pump constituting the pressure source.

According to the above configuration, a hydraulic drive system having the above-mentioned functions can be realized.

According to the present invention, the hydraulic actuator can be operated according to the operation of the operating device even if a failure occurs in which the output pressure from the electromagnetic proportional control valve is maintained at zero.

It is a circuit diagram which shows the structure of the hydraulic drive system of this embodiment. It is a graph which shows the relationship between the pilot pressure acting on the spool of the flow control valve provided in the hydraulic drive system of FIG. 1 and the stroke amount of the spool. It is a graph which shows the relationship between the pressure output from the 1st electromagnetic proportional control valve and the pilot pressure acting on a spool when the 2nd electromagnetic proportional control valve provided in the hydraulic drive system of FIG. 1 breaks down.

Hereinafter, the hydraulic drive system 1 of the embodiment according to the present invention will be described with reference to the drawings. The concept of the direction used in the following description is used for convenience in the explanation, and does not limit the direction of the configuration of the invention to that direction. Further, the hydraulic drive system 1 described below is only one embodiment of the present invention. Therefore, the present invention is not limited to the embodiment, and can be added, deleted, or changed without departing from the spirit of the invention.

Construction machinery is equipped with various attachments, which are driven by a hydraulic actuator 2 such as a hydraulic cylinder or a hydraulic motor. Further, the construction machine is provided with a hydraulic drive system 1 for moving the hydraulic actuator 2. The hydraulic drive system 1 supplies hydraulic oil to the hydraulic actuator 2 (hydraulic cylinder in the present embodiment) to drive the hydraulic actuator 2. In the present embodiment, for convenience of explanation, only one hydraulic actuator 2 is connected to the hydraulic drive system 1, but two or more hydraulic actuators may be connected to the hydraulic drive system 1. Hereinafter, the configuration of the hydraulic drive system 1 will be described in more detail.

[Flood drive system]
The hydraulic drive system 1 includes a main pump 11, a tank 12, an engine E, a sub pump 13, and a hydraulic drive device 14. The main pump 11 is a variable displacement swash plate pump, in which the tank 12 is connected to the suction port 11a and the hydraulic drive device 14 is connected to the discharge port 11b. Further, the main pump 11 is connected to the engine E, and the engine E rotates the rotation shaft 11c of the main pump 11 at an arbitrary predetermined rotation speed. Further, the main pump 11 has a swash plate 11d whose tilt angle can be changed, and the discharge capacity of the main pump 11 can be adjusted by changing the tilt angle of the swash plate 11d. Further, a regulator 15 is provided on the swash plate 11d of the main pump 11, and the tilt angle of the swash plate 11d can be changed by the regulator 15.

In the main pump 11 configured in this way, the hydraulic oil is discharged by the engine E rotating the rotating shaft 11c, and the flow rate of the discharged hydraulic oil (that is, the discharge flow rate) is oblique. The flow rate corresponds to the tilt angle of the plate 11d and the rotation speed of the engine E. The rotating shaft 11c of the main pump 11 having such a function is further adapted so that the rotating shaft 13a of the sub pump 13 rotates integrally with the rotating shaft 11c. In the present embodiment, the sub-pump 13 is connected in series with the main pump 11, but may be connected in parallel, or is connected to the engine E on the opposite side of the main pump 11. May be good.

The sub-pump 13 connected in this way is a fixed-capacity pump, the tank 12 is connected to the suction port 13b, and the sub-passage 20 of the hydraulic drive device 14 is connected to the discharge port 13c. Further, the rotation shaft 13a of the sub pump 13 is connected to the engine E via the rotation shaft 11c, and rotates at a rotation speed corresponding to the rotation speed of the engine E. Further, the sub-pump 13 is designed to discharge pressure oil to the sub-passage 20 by rotating, and the sub-passage 20 is provided with a relief valve 28 in order to keep the pressure of the pressure oil constant.

The relief valve 28 is arranged so as to communicate the sub-passage 20 and the tank 12. When the oil pressure of the sub-passage 20 exceeds a predetermined set pressure, the relief valve 28 discharges the hydraulic oil flowing through the sub-passage 20 and maintains the sub-pump discharge pressure pp of the sub-pump 13 at a set pressure (that is, a constant pressure). .. In this way, the hydraulic drive system 14 is supplied with pressure oil at a constant pressure.

[Flood drive system]
The hydraulic drive device 14 operates by utilizing the sub-pump discharge pressure pp from the sub-pump 13, and also switches which passage of the hydraulic actuator 2 the hydraulic oil discharged from the main pump 11 is guided to, and adjusts the flow rate. By doing so, the movement of the hydraulic actuator 2 is controlled. More specifically, the hydraulic drive system 14 includes a flow rate control valve 21, a first electromagnetic proportional control valve 22R, a second electromagnetic proportional control valve 22L, a first switching valve 24R, a second switching valve 24L, and the like. It includes a control unit 26 and an operating device 27.

The flow rate control valve 21 is connected to the main pump 11 and the hydraulic actuator 2, and controls the direction and flow rate of the hydraulic oil flowing from the main pump 11 to the hydraulic actuator 2. More specifically, the hydraulic actuator 2 has two ports 2a and 2b, and the flow control valve 21 is connected to the two ports 2a and 2b. Further, the flow rate control valve 21 is connected to the discharge port 11b and the tank 12 of the main pump 11, and has a spool 21a for switching the connection state between them. That is, the flow rate control valve 21 can adjust the direction in which the hydraulic oil flows and the opening degree of the flow rate control valve 21 by moving the spool 21a.

More specifically, the spool 21a can move from one and the other in a predetermined direction, that is, from the neutral position M0 to the first offset position M1 and the second offset position M2, respectively, and at the neutral position M0, the main pump 11 And the hydraulic actuator 2 and the hydraulic actuator 2 and the tank 12 are cut off from each other so that the hydraulic oil does not flow between them. When the spool 21a is located at the first offset position M1, the discharge port 11b of the main pump 11 and the first port (head side port in this embodiment) 2a of the hydraulic actuator 2 are connected, and the second port of the hydraulic actuator 2 is connected. (In this embodiment, the rod side port) 2b and the tank 12 are connected. At this time, the discharge port 11b and the first port 2a are connected with an opening degree corresponding to the position of the spool 21a, and the hydraulic oil of the flow rate corresponding to the position (stroke amount) of the spool 21a is guided to the first port 2a. .. As a result, the hydraulic actuator 2 extends at a speed corresponding to the position of the spool 21a. On the other hand, when the spool 21a is located at the second offset position M2, the discharge port 11b of the main pump 11 and the second port 2b of the hydraulic actuator 2 are connected, and the first port 2a of the hydraulic actuator 2 and the tank 12 are connected. Will be done. At this time, the discharge port 11b and the second port 2b are connected with an opening degree corresponding to the position of the spool 21a, and the hydraulic oil of the flow rate corresponding to the position of the spool 21a is guided to the second port 2b. As a result, the hydraulic actuator 2 contracts at a speed corresponding to the position of the spool 21a.

The flow control valve 21 configured in this way further has two springs 31L and 31R, and the two springs 31L and 31R urge the spool 21a so as to oppose each other and position the spool 21a in the neutral position. It is maintained at M0. Further, the flow control valve 21 has two pilot ports 21R and 21L, and pilot pressures piR and piL are input to each of the two pilot ports 21R and 21L. The first pilot port 21R is formed so that the first pilot pressure piR input therein acts on the spool 21a so as to oppose the first spring 31L, and the spool 21a is formed by the first pilot pressure piR. It is pressed toward the first offset position M1. Further, the second pilot port 21L is formed so that the second pilot pressure piL input therein acts on the spool 21a so as to oppose the second spring 31R, and the spool 21a is formed with the second pilot pressure. It is pushed toward the second offset position M2 by the piL. Therefore, the spool 21a moves to a position corresponding to the differential pressure of the two pilot pressures piR and piL acting on the spool 21a, and the hydraulic oil in the direction and the flow rate corresponding to the position flows to the hydraulic actuator 2. ing. The two pilot pressures piR and piL input in this way are generated from the sub-pump discharge pressure pp discharged from the sub-pump 13, and the sub-passage 20 is provided in the sub-pump 13 to generate the two pilot pressures piR and piL. Two electromagnetic proportional control valves 22R and 22L are connected in parallel via the two electromagnetic proportional control valves 22R and 22L.

In the first electromagnetic proportional control valve 22R, which is one of the two electromagnetic proportional control valves 22R and 22L, the primary pressure port is selectively connected to either the sub pump 13 or the tank 12, and the secondary pressure port is the first. It is connected to the switching valve 24R. Further, the first electromagnetic proportional control valve 22R is capable of passing a current through its solenoid section 22Ra (that is, inputting a first command signal), and opens according to the current flowing through the solenoid section 22Ra. The degree is switched. That is, the first electromagnetic proportional control valve 22R is a direct proportional type electromagnetic proportional control valve, and the sub pump 13 and the secondary pressure port are connected by passing a current through the solenoid unit 22Ra, and the sub pump 13 and the secondary pressure port are connected. The space is opened with an opening degree corresponding to the current flowing through the solenoid unit 22Ra. On the other hand, when the current flowing through the solenoid portion 22Ra is stopped, the space between the sub pump 13 and the valve secondary pressure port is cut off, and the valve secondary pressure port is connected to the tank 12. The first electromagnetic proportional control valve 22R configured in this way controls the subpump discharge pressure pp to a pressure corresponding to the current flowing through the solenoid unit 22Ra (first output pressure psR) and outputs the subpump discharge pressure pp to the secondary pressure port. do.

The second electromagnetic proportional control valve 22L, which is the other of the two electromagnetic proportional control valves 22R and 22L, has the same structure as the first electromagnetic proportional control valve 22R, and the primary pressure port is the sub pump 13 and the tank 12. The secondary pressure port is selectively connected to any of the above, and is connected to the second switching valve 24L. That is, the second electromagnetic proportional control valve 22L is a direct proportional type electromagnetic proportional control valve, and the sub pump 13 and the secondary pressure port are connected by passing a current through the solenoid unit 22La, and the sub pump 13 and the secondary pressure port are connected. The space is opened with an opening degree corresponding to the current flowing through the solenoid portion 22La. On the other hand, when the current flowing through the solenoid portion 22La is stopped, the space between the sub pump 13 and the secondary pressure port valve is cut off, and the secondary pressure port valve is connected to the tank 12. The second electromagnetic proportional control valve 22L configured in this way controls the subpump discharge pressure pp to a pressure corresponding to the current flowing through the solenoid unit 22La (that is, the second output pressure psL) to control the secondary pressure port. Output to.

The two electromagnetic proportional control valves 22R and 22L having such a configuration have the following functions. That is, the output pressures psR and psL output from the two electromagnetic proportional control valves 22R and 22L are input to each of the two switching valves 24R and 24L. Further, in addition to the secondary pressure port of the first electromagnetic proportional control valve 22R, the sub pump 13 and the first pilot port 21R of the flow rate control valve 21 are connected to the first switching valve 24R, and the second switching valve 24L is connected to the second switching valve 24L. In addition to the secondary pressure port of the second electromagnetic proportional control valve 22L, the sub pump 13 and the second pilot port 21L of the flow rate control valve 21 are connected. The first switching valve 24R and the second switching valve 24L connected in this way are configured as follows.

The first switching valve 24R is connected to the first pilot port 21R of the flow rate control valve 21 via the first pilot passage 23R, and switches the first pilot pressure piR input to the flow rate control valve 21. That is, the first switching valve 24R has a spool 24Ra that can move between the first position M1R and the second position M2R, and the first electromagnetic proportional control is performed in a state where the spool 24Ra is located at the first position M1R. The secondary port of the valve 22R and the first pilot port 21R are connected. As a result, the first output pressure psR, which is the secondary pressure of the first electromagnetic proportional control valve 22R, is output to the flow control valve 21 as the first pilot pressure piR. On the other hand, in the state where the spool 24Ra is located at the second position M2R, the sub pump 13 and the first pilot port 21R are connected, and the sub pump discharge pressure pp of the sub pump 13 is output to the flow control valve 21 as the first pilot pressure piR. ..

Further, the second switching valve 24L is connected to the second pilot port 21L of the flow rate control valve 21 via the second pilot passage 23L, and switches the second pilot pressure piL input to the flow rate control valve 21. There is. That is, the second switching valve 24L has a spool 24La that can be switched between the first position M1L and the second position M2L, and the second electromagnetic proportional control is performed in a state where the spool 24La is located at the first position M1L. The second output pressure psl of the valve 22L and the second pilot port 21L are connected. As a result, the second output pressure psL of the second electromagnetic proportional control valve 22L is output to the flow rate control valve 21 as the first pilot pressure piL. On the other hand, in the state where the spool 24La is located at the second position M2L, the sub pump 13 and the second pilot port 21L are connected, and the sub pump discharge pressure pp is output to the flow control valve 21 as the second pilot pressure piL.

Further, the first pilot passage 23R is connected to the first oil passage 25R so as to branch in the middle thereof, and the first oil passage 25R is connected to the second switching valve 24L. The first oil passage 25R applies the first pilot pressure piR to the spool 24La of the second switching valve 24L. Further, a second output pressure psL output from the second electromagnetic proportional control valve 22L acts on the spool 24La of the second switching valve 24L in a direction against the first pilot pressure piR. Therefore, the spool 24La of the second switching valve 24L moves according to the differential pressure between the second output pressure psL and the first pilot pressure piR, and switches its position. Further, the spool 24La of the second switching valve 24L is provided with a spring 24Lb that gives an urging force in a direction that opposes the first pilot pressure piR. Therefore, the spool 24La is located at the first position M1L when the differential pressure obtained by subtracting the second output pressure psL from the first pilot pressure piR is less than the second predetermined pressure ps2, and the second output pressure psL. Is output to the flow control valve 21 as the second pilot pressure piL. On the other hand, when the difference is the second predetermined pressure ps2 or more, the spool 24La is located at the second position M2L. As a result, the sub-pump discharge pressure pp is output to the flow control valve 21 as the second pilot pressure piL.

The second predetermined pressure ps2 is a pressure determined according to the urging force of the spring 24Lb that urges the spool 24La, and is set as follows. That is, the second predetermined pressure ps2 is set to a pressure larger than the pressure pm1 required to cause the first pilot pressure piR to act on the spool 21a to stroke the spool 21a to the maximum stroke amount and smaller than the sub pump discharge pressure pp. There is. In the present embodiment, the second predetermined pressure ps2 is set to the same pressure as the first predetermined pressure ps1.

Further, the second pilot passage 23L is connected to the second oil passage 25L so as to branch in the middle, and the second oil passage 25L is connected to the first switching valve 24R. The second oil passage 25L applies a second pilot pressure piL to the spool 24Ra of the first switching valve 24R. Further, a first output pressure psR output from the first electromagnetic proportional control valve 22R acts on the spool 24Ra of the first switching valve 24R in a direction against the second pilot pressure piL. Therefore, the spool 24Ra of the first switching valve 24R moves according to the differential pressure between the first output pressure psR and the second pilot pressure piL, and switches its position. Further, the spool 24Ra of the first switching valve 24R is provided with a spring 24Rb that gives an urging force in a direction that opposes the second pilot pressure piL. Therefore, the spool 24Ra is located at the first position M1R when the differential pressure obtained by subtracting the first output pressure psR from the second pilot pressure piL is less than the first predetermined pressure ps1, and the first output pressure psR is set. It is output to the flow control valve 21 as the first pilot pressure piR. On the other hand, when the difference is equal to or higher than the first predetermined pressure, the spool 24Ra is located at the second position M2R. As a result, the sub-pump discharge pressure pp is output to the flow control valve 21 as the first pilot pressure piR.

The first predetermined pressure ps1 is a pressure determined according to the urging force of the spring 24Rb that urges the spool 24Ra, and is set as follows. That is, the first predetermined pressure ps1 is set to a pressure larger than the pressure pm2 required to act the second pilot pressure piL on the spool 21a to stroke the spool 21a to the maximum stroke amount and smaller than the discharge pressure pp of the sub pump 13. (See the graph in FIG. 2). In the graph of FIG. 2, the horizontal axis shows the pilot pressures piR and piL, and the vertical axis shows the stroke amount of the spool 24Ra.

As described above, the hydraulic drive system 14 configured in this way is capable of passing an electric current through the two electromagnetic proportional control valves 22R and 22L, and by passing the electric current, the spool of the flow rate control valve 21 The position of 21a is controlled. A control unit 26 is electrically connected to the two electromagnetic proportional control valves 22R and 22L configured in this way in order to pass an electric current through them to control their movements, and the control unit 26 is connected to an operating device. 27 are electrically connected. The operating device 27 has an operating lever 27a, and the operating lever 27a is configured to be operable (more specifically, tiltable) in the first direction A1 and the second direction A2, which are opposite to each other. Further, the operation device 27 outputs an operation command according to the operation direction and the operation amount (that is, the tilt amount) of the operation lever 27a to the control unit 26.

The control unit 26 is electrically connected to the first electromagnetic proportional control valve 22R, the second electromagnetic proportional control valve 22L, and the regulator 15, and controls their movements in response to an operation command from the operating device 27. ing. That is, the control unit 26 operates the regulator 15 and adjusts the tilt angle of the swash plate 11d to the tilt angle according to the operation amount of the operation lever 27a. Further, the control unit 26 controls one of the two electromagnetic proportional control valves 22R and 22L according to the operation direction of the operation lever 27a, and the flow rate in the direction according to the operation direction of the operation lever 27a and according to the operation amount. The hydraulic oil of the above is supplied to the hydraulic actuator 2.

Further, the control unit 26 operates as follows in order to detect a failure of the first electromagnetic proportional control valve 22R and the second electromagnetic proportional control valve 22L. That is, the control unit 26 detects the value of the current flowing through the first electromagnetic proportional control valve 22R and the second electromagnetic proportional control valve 22L, and the wiring paths of the electromagnetic proportional control valves 22R and 22L (that is, the first and second solenoids). For each of the proportional control valves 22R and 22L, the energized state of the harness, the connecting portion, and the solenoid portion 22Ra, 22La) connected to the control unit 26 is detected, and the energization failure in each wiring path (that is, the disconnection in the wiring path and the disconnection in the wiring path) are detected. Occurrence of short circuit) is detected. Further, the control unit 26 detects the discharge pressure p of the main pump 11 using a pressure sensor (not shown), and from the relationship between the detected discharge pressure p and the operation amount of the operation lever 27a, the first electromagnetic proportional control valve 22R and the first electromagnetic proportional control valve 22R. 2 It is possible to detect whether or not the valve body of the electromagnetic proportional control valve 22L is operating according to the supplied current value (that is, whether or not a stick is generated).

[Operation of hydraulic drive system]
The hydraulic drive system 1 configured as described above can supply the hydraulic oil in the direction and flow rate according to the operation amount of the operating lever 27a to the hydraulic actuator 2. That is, the hydraulic actuator 2 can be driven in a direction and at a speed corresponding to the amount of operation of the operating lever 27a. For example, when the operation lever 27a is operated in the second direction, an operation command corresponding to the operation direction and the operation amount of the operation lever 27a is output from the operation device 27 to the control unit 26. The control unit 26 causes a current corresponding to this operation command to flow through the solenoid unit 22La of the second electromagnetic proportional control valve 22L. As a result, the second output pressure psL corresponding to the operation amount of the operating lever 27a is output from the second electromagnetic proportional control valve 22L to the second switching valve 24L.

In the second switching valve 24L, the spool 24Ra changes its position according to the differential pressure between the first output pressure psR and the second pilot pressure piL. The first pilot pressure piR fluctuates according to the positions of the first output pressure psR of the first electromagnetic proportional control valve 22R and the spool 24Ra of the first switching valve 24R. When the operating lever 27a is operated in the second direction, the first output pressure psR is basically the tank pressure, and the position of the spool 24Ra of the first switching valve 24R is such that the second pilot pressure piL is the first predetermined position. It depends on whether the pressure is ps1 or more. As described above, the spool 21a of the flow control valve 21 is adapted to stroke up to the maximum stroke amount when the second pilot pressure piL reaches the pressure pm2. Therefore, the control unit 26 is controlled so that the second output pressure psL is within the range of 0 ≦ psL ≦ pm2, except in the case described later (that is, the failure of the second electromagnetic proportional control valve 22L). As a result, the second pilot pressure piL is controlled within the range of 0 ≦ piL ≦ pm2. That is, the second pilot pressure piL is basically less than the first predetermined pressure ps1, the spool 24Ra of the first switching valve 24R is located at the first position M1R, and the first pilot pressure piR is at the tank pressure. It is maintained.

By maintaining the first pilot pressure piR at the tank pressure, the differential pressure obtained by subtracting the second output pressure psL from the first pilot pressure piR becomes less than the second predetermined pressure ps2, and the spool 24La of the second switching valve 24L also becomes. It is located at the first position M1L. As a result, the second output pressure psL is output from the second switching valve 24L to the flow rate control valve 21 as the second pilot pressure piL, and the spool 21a of the flow rate control valve 21 is positioned according to the second pilot pressure piL, that is, the operating lever. It moves to a position according to the operation amount of 27a. By moving, the hydraulic oil of the flow rate corresponding to the operation amount of the operation lever 27a is guided to the direction in which the operation lever 27a is operated, that is, the second port 2b of the hydraulic actuator 2. As a result, the hydraulic actuator 2 can be contracted at a speed corresponding to the operation amount of the operation lever 27a.

The case where the operation lever 27a is operated in the first direction is the same as the case where the operation lever 27a is operated in the second direction. An operation command is output from 27 to the control unit 26. The control unit 26 causes a current corresponding to this operation command to flow through the solenoid unit 22Ra of the first electromagnetic proportional control valve 22R. Then, the first output pressure psR is output to the flow rate control valve 21 via the first switching valve 24R, that is, the first output pressure psR is input to the flow rate control valve 21 as the first pilot pressure piR. As a result, when the operating lever 27a is operated in the first direction, the hydraulic oil in a flow rate corresponding to the operating amount of the operating lever 27a is guided to the first port 2a of the hydraulic actuator 2. As a result, the hydraulic actuator 2 can be extended at a speed corresponding to the operation amount of the operation lever 27a.

[Operation at the time of failure]
The hydraulic drive system 1 that operates in this way operates as follows when either the first electromagnetic proportional control valve 22R or the second electromagnetic proportional control valve 22L fails. Here, as a failure, the second output pressure psL of the second electromagnetic proportional control valve 22L (or the first output pressure psR of the first electromagnetic proportional control valve 22R) is maintained at zero due to poor energization and the stick of the valve body. The second output pressure psL of the second electromagnetic proportional control valve 22L (or the first output pressure psR of the first electromagnetic proportional control valve 22R) becomes the sub-pump discharge pressure pp due to such a failure and the stick of the valve body. A failure that can be maintained is assumed. In the following, the failure is such that the second output pressure psL of the second electromagnetic proportional control valve 22L (or the first output pressure psR of the first electromagnetic proportional control valve 22R) is maintained at zero, and the second electromagnetic proportional control is controlled. An example is a case where the second electromagnetic proportional control valve 22L (or the first electromagnetic proportional control valve 22R) cannot be energized due to a failure (that is, disconnection and short circuit) in the wiring path of the valve 22L (or the first electromagnetic proportional control valve 22R). I will explain.

In the hydraulic drive system 1, even if one of the first electromagnetic proportional control valve 22R and the second electromagnetic proportional control valve 22L has a failure in the wiring path, the other one in which the failure has not occurred is operated to operate the flood control. The actuator 2 is driven. Therefore, the case where the wiring path of the second electromagnetic proportional control valve 22L cannot be energized due to a failure will be described below, and the case where the wiring path of the first electromagnetic proportional control valve 22R is failed and cannot be energized will be omitted. do.

The control unit 26 detects the value of the current when the second electromagnetic proportional control valve 22L is energized. Therefore, the command current corresponding to the operation command (that is, the current value instructed by the control unit) and the actually detected current value (that is, the current value actually flowing through the second electromagnetic proportional control valve) are different. If they are different, for example, if the current value is not detected even though the second electromagnetic proportional control valve 22L is being energized, the control unit 26 determines that the wiring path in the second electromagnetic proportional control valve 22L has a failure. .. When a failure occurs in the wiring path, the second solenoid proportional control valve 22L is a direct proportional type solenoid valve, so that the second switching valve 24L and the tank 12 are in communication with each other regardless of the operation of the operating lever 27a. It is maintained. On the other hand, when the first electromagnetic proportional control valve 22R operates normally, the first output pressure psR can be controlled within the range of 0 ≦ psR ≦ pm 1, so that the spool 24La of the second switching valve 24L is the first. It can be fastened at position M1L. That is, the second pilot pressure piL is maintained at the tank pressure. Therefore, when the operating lever 27a is operated in the first direction, the control unit 26 is within the range of 0 ≦ psR ≦ pm1 as in the case where the wiring path in the second electromagnetic proportional control valve 22L has not failed. The first electromagnetic proportional control valve 22R can be controlled and the hydraulic actuator 2 can be extended at a speed corresponding to the operation amount of the operating lever 27a (see the effective pilot range (0 ≦ psR ≦ pm1) in the graph of FIG. 3). ). In FIG. 3, the horizontal axis shows the output pressure psR, the upper side of the vertical axis shows the first pilot pressure piR, and the lower side of the vertical axis shows the second pilot pressure piL.

On the other hand, when the operating lever 27a is operated in the second direction, the second electromagnetic proportional control valve 22L cannot be energized. Therefore, the control unit 26 uses the first electromagnetic proportional control valve 22R as described below. 2 is contracted. That is, the control unit 26 is a first electromagnetic proportional control valve so that when the operation lever 27a is operated in the second direction and an operation signal is received from the operation device 27, the first output pressure psR becomes the second predetermined pressure ps2 or more. Controls the operation of 22R. As a result, the first output pressure psR having a second predetermined pressure ps2 or more is output from the first switching valve 24R as the first pilot pressure pir, and the first pilot pressure piR becomes the second predetermined pressure ps2 or more. Further, when the first pilot pressure piR becomes the second predetermined pressure ps2 or more, the spool 24La of the second switching valve 24L moves to the second position M2L, and the second switching valve 24L causes the sub pump 13 and the flow rate control valve 21 to move. It is connected to the second pilot port 21L. That is, the sub pump discharge pressure pp of the sub pump 13 is output from the second switching valve 24L as the second pilot pressure piL. As a result, the spool 21a of the flow control valve 21 can be made to act on the spool 21a of the flow control valve 21 so as to have a second pilot pressure piL larger than the first pilot pressure piR against the first pilot pressure piR, and the spool 21a is based on the differential pressure. Can be moved towards the second offset position M2. That is, the cylinder can be contracted by flowing hydraulic oil through the second port 2b of the hydraulic actuator 2 in response to the operation of the operating lever 27a in the second direction.

Further, as shown in the graph of FIG. 3, the control unit 26 controls the output pressure psR according to the operation amount of the operation lever 27a, and the hydraulic oil of the flow rate corresponding to the operation amount of the operation lever 27a flows to the hydraulic actuator 2. The position of the spool 21a is adjusted so as to. That is, the spool 21a moves to a position corresponding to the differential pressure of the two pilot pressures piR and piL, and the differential pressure Δp of the two pilot pressures piR and piL is adjusted by adjusting the first output pressure psR. (The two-dot chain line in FIG. 3) is adjusted to move the spool 21a toward the position corresponding to the operation amount of the operation lever 27a, that is, the second offset position M2.

For example, in the hydraulic drive system 1, when the second electromagnetic proportional control valve 22L operates normally, the output pressure psL of the pressure value px is output from the second electromagnetic proportional control valve 22L with respect to the operation amount of the operating lever 27a. And. The control unit 26 moves the spool 21a by the same stroke amount with respect to the above-mentioned operation amount even when the second electromagnetic proportional control valve 22L fails, so that the differential pressure between the two pilot pressures piL and piR (more detailed). The output pressure psR adjusted so that the pressure value px (differential pressure obtained by subtracting the first pilot pressure piR from the second pilot pressure piL) is output from the first electromagnetic proportional control valve 22R. That is, the control unit 26 adjusts the output pressure psR so that the difference from the sub-pump discharge pressure pp is the pressure value px. As a result, even if the second electromagnetic proportional control valve 22L fails, the hydraulic actuator 2 can be contracted at a speed corresponding to the operating amount of the operating lever 27a.

As can be seen from the two-dot chain line (difference described above) in FIG. 3, when the second electromagnetic proportional control valve 22L becomes poorly energized, the operating lever 27a is operated in the second direction (that is, ps2). ≤psR≤pp), the relationship between the first output pressure psR and the position of the spool 21a has an inversely proportional relationship. That is, the spool 21a is in the neutral position when the control unit 26 energizes the first electromagnetic proportional control valve 22R to maximize the opening degree (that is, the first output pressure psR becomes the same pressure as the sub pump discharge pressure pp). Located in. Further, from that state, the current flowing through the first electromagnetic proportional control valve 22R by the control unit 26 is reduced to reduce the opening degree, so that the stroke amount of the spool 21a in the direction to the second offset position M2 is increased. The stroke amount becomes maximum when the first output pressure psR becomes the same pressure as the second predetermined pressure ps2.

Further, since the hydraulic drive system 1 of the present embodiment has the above-mentioned function as a fail-safe function, it is configured as follows. That is, in the hydraulic drive system 1 of the present embodiment, when the second electromagnetic proportional control valve 22L becomes poorly energized, the second pilot pressure piL can be changed in the range of 0 ≦ piL ≦ pp-ps2. be. Therefore, the sub-pump discharge pressure pp and the second predetermined pressure ps2 are set so that the value obtained by subtracting the second predetermined pressure ps2 from the sub-pump discharge pressure pp is smaller than the above-mentioned pressure pm2. As a result, when the second electromagnetic proportional control valve 22L fails, the maximum stroke amount of the spool 21a can be limited, and when the operating amount of the operating lever 27a exceeds a predetermined amount, the speed with respect to the operating amount is increased. Can be limited to a constant speed without being proportional. Further, in this way, it is possible to notify the driver of the failure of the proportional valve without adding any parts. The value obtained by subtracting the second predetermined pressure ps2 from the sub-pump discharge pressure pp may be larger than the pressure pm2. 1 can be configured.

As described above, in the hydraulic drive system 1, the first output pressure psR of the first specified pressure pm1 or more, which is not effectively used even if the first electromagnetic proportional control valve 22R is output in a normal state without failure, is output. As a result, even if a failure occurs in the wiring path of the second electromagnetic proportional control valve 22L, the first electromagnetic proportional control valve 22R makes it possible to not only extend the hydraulic actuator 2 but also contract it. Therefore, in the hydraulic drive system 1, fail-safe can be achieved even when a failure occurs in the wiring path of the second electromagnetic proportional control valve 22L, and the hydraulic drive system 1 with high reliability can be realized. Further, since the configuration is such that only the switching valves 24R and 24L are added, it is possible to suppress the cost increase of the hydraulic drive system 1 while achieving fail-safe.

Further, in the hydraulic drive system 1, by setting the first specified pressure pm1 to be smaller than the second predetermined pressure ps2, the first pilot pressure piR is set to the first specified in the state where the second electromagnetic proportional control valve 22L is poorly energized. Even if the pressure is increased to pm1, the sub pump discharge pressure pp is not output as the second pilot pressure piL. Therefore, even in a state where the second electromagnetic proportional control valve 22L is poorly energized, the spool 21a can be stroked toward the first offset position M1 up to the maximum stroke amount. That is, in a state where the second electromagnetic proportional control valve 22L is poorly energized, it is possible to prevent the function of the hydraulic drive device 14 from deteriorating when the spool 21a is moved to the first offset position M1.

Next, as a failure in which the second output pressure psL of the second electromagnetic proportional control valve 22L (or the first output pressure psR of the first electromagnetic proportional control valve 22R) is maintained at zero, the output side and the tank 12 The case where the valve body of the second electromagnetic proportional control valve 22L (or the first electromagnetic proportional control valve 22R) sticks while the two electromagnetic proportional control valves 22L (or the first electromagnetic proportional control valve 22R) are in communication with each other will be described. In this case as well, the hydraulic actuator 2 can be contracted according to the amount of operation of the operating lever 27a by executing the same control as in the case where the second electromagnetic proportional control valve 22L cannot be energized as described above. .. Whether or not the valve body sticks with the first electromagnetic proportional control valve 22R and the second electromagnetic proportional control valve 22L in a state where the output side and the tank 12 communicate with each other is determined by the first electromagnetic proportional control valve 22R and the second electromagnetic proportional control valve 22L. While detecting the energized state of the second electromagnetic proportional control valve 22L, it can be detected from the relationship between the operating amount of the operating lever 27a and the discharge pressure p of the main pump 11.

Finally, in the hydraulic drive system 1, one of the valve bodies of the first electromagnetic proportional control valve 22R and the second electromagnetic proportional control valve 22L sticks with the output side and the sub-passage 20 communicating with each other. The case will be described. Regardless of which of the first electromagnetic proportional control valve 22R and the second electromagnetic proportional control valve 22L sticks, fail-safe can be achieved by the other non-stick. Therefore, as in the description of the failure of the wiring path, only the case where the valve body of the second electromagnetic proportional control valve 22L sticks with the output side and the sub-passage 20 communicating with each other will be described.

In the second electromagnetic proportional control valve 22L, when the valve body sticks in a state where the output side thereof and the sub-passage 20 that gives the primary pressure thereof are communicated with each other, the second output pressure psL of the second electromagnetic proportional control valve 22L is discharged from the sub pump. It becomes equal to the pressure pp. Therefore, the spool 24La of the second switching valve 24L is located at the first position M1L regardless of the magnitude of the first pilot pressure piR, and the second output pressure psL equal to the sub pump discharge pressure pp is the flow rate as the second pilot pressure piL. It is output to the control valve 21. On the other hand, in the spool 24Ra of the first switching valve 24R, the second output pressure psL equal to the sub pump discharge pressure pp is output as the second pilot pressure piL in a state where the first electromagnetic proportional control valve 22R is not energized. Move to 2 position M2R. As a result, the sub-pump discharge pressure pp is output to the flow control valve 21 as the first pilot pressure piR. By doing so, the first pilot pressure piR and the second pilot pressure piL of the same pressure act on the spool 21a of the flow control valve 21 so as to oppose each other, and the spool 21a is held at the neutral position M0. As a result, it is possible to prevent the hydraulic oil from being guided by the hydraulic actuator 2 and making an undesired movement, and fail-safe can be achieved.

[Other Embodiments]
The hydraulic drive system 1 of the present embodiment is connected to only one hydraulic actuator 2, but the number of connected hydraulic actuators is not limited to one as described above. For example, the hydraulic drive system 1 may be connected to two or more hydraulic actuators, and may have a plurality of flow control valves 21 accordingly. In this case, the plurality of flow control valves 21 are connected in parallel to, for example, the main pump 11, and the first electromagnetic proportional control valve 22R, the second electromagnetic proportional control valve 22L, and the second electromagnetic proportional control valve 22L are connected to each of the flow control valves 21. A switching valve 24R and a second switching valve 24L are provided, respectively. As a result, the flood control drive system including the plurality of flow rate control valves 21 also achieves the same function as described above. Further, in the hydraulic drive system 1, switching valves 24R and 24L are provided in any of the ports 21R and 21L of the flow control valve 21, but it is not always necessary to provide both of them, and even if only one of them is provided. good.

Further, in the hydraulic drive system 1 of the present embodiment, the pressure source for supplying a constant set pressure is composed of the sub pump 13 and the relief valve 28, but such a configuration is not always necessary. For example, the pressure source may be composed of the main pump 11 and the pressure reducing valve, and a constant set pressure may be supplied from the main passage connecting the main pump 11 and the flow control valve 21 to the sub passage 20 via the pressure reducing valve. ..

Further, in the hydraulic drive system 1 of the present embodiment, the maximum speed of the hydraulic actuator 2 is limited after a failure occurs in the electromagnetic proportional control valves 22R and 22L, and the operating amount of the operating lever 27a and the hydraulic actuator 2 before and after the failure occurs. The control unit 26 is configured so that the relationship with the speed of the above does not change. However, the control unit 26 does not necessarily have to be configured in this way. That is, when the operating amount of the operating lever 27a is maximized even after the failure occurs, the operating amount of the operating lever 27a and the speed of the hydraulic actuator 2 are adjusted so that the hydraulic actuator 2 can be driven at the same maximum speed as before the failure occurred. The correspondence may be changed. In this case, the sub-pump discharge pressure pp needs to be the higher of the pressure obtained by adding the second specified pressure pm2 to the first predetermined pressure ps1 and the pressure obtained by adding the first specified pressure pm1 to the second predetermined pressure ps2.

Further, in the hydraulic drive system 1 of the present embodiment, a hydraulic cylinder is adopted as the hydraulic actuator 2, but the hydraulic cylinder is not necessarily limited to the hydraulic cylinder. That is, the hydraulic actuator 2 may be a hydraulic motor, and may be an actuator that operates by supplying hydraulic oil such as hydraulic oil.

1 Hydraulic drive system 2 Hydraulic actuator 11 Main pump 13 Sub pump 14 Hydraulic drive device 21 Flow control valve 21a Spool 21R 1st pilot port 21L 2nd pilot port 22R 1st electromagnetic proportional control valve 22L 2nd electromagnetic proportional control valve 23R 1st pilot Passage 23L 2nd pilot passage 24R 1st switching valve 24L 2nd switching valve 25R 1st oil passage 25L 2nd oil passage 26 Control unit 27 Operating device

Claims (6)

Two pilot pressures are input in directions that oppose each other, and according to the differential pressure between the two pilot pressures, they move in one direction and one in the other direction to switch the direction of the hydraulic oil flowing from the main pump to the hydraulic actuator, and the main A flow control valve having a spool that controls the opening degree between the pump and the hydraulic actuator,
A direct proportional electromagnetic control valve that uses the pressure oil supplied from a pressure source that supplies pressure oil maintained at a constant set pressure as the primary pressure, and reduces the pressure to the first output pressure according to the input current. A direct proportional first electromagnetic proportionality that controls and outputs the first output pressure to the flow control valve as the first pilot pressure which is one of the two pilot pressures to move the spool in one of the predetermined directions. Control valve and
It is a direct proportional type electromagnetic proportional control valve that uses the pressure oil supplied from the pressure source as the primary pressure, and is a direct proportional type second electromagnetic that outputs by reducing the pressure to the second output pressure according to the input current. Proportional control valve and
The flow rate control is performed by using either the set pressure supplied from the pressure source or the second output pressure output from the second electromagnetic proportional control valve as the second pilot pressure which is the other of the two pilot pressures. A switching valve that outputs to the valve and moves the spool to the other in the predetermined direction,
One end is connected to a passage provided between the first electromagnetic proportional control valve and the flow rate control valve to apply the first pilot pressure to the flow control valve so as to apply the first pilot pressure. An oil passage whose other end is connected to the switching valve,
Operating devices that can be operated in different first and second directions,
When the first electromagnetic proportional control valve and the second electromagnetic proportional control valve are operating normally and the operating device is operated in the first direction, a current corresponding to the amount of operation in the first direction is applied. A control unit that flows through the first electromagnetic proportional control valve, and when the operating device is operated in the second direction, causes a current corresponding to the amount of operation in the second direction to flow through the second electromagnetic proportional control valve. Prepare,
In the switching valve, the first pilot pressure and the second output pressure are input so as to oppose each other, and the difference obtained by subtracting the second output pressure from the first pilot pressure is equal to or higher than a predetermined predetermined pressure. If there is, the set pressure is output to the flow control valve as the second pilot pressure, and if the difference is less than the predetermined pressure, the second output pressure is output as the second pilot pressure.
The control unit has determined that a failure has occurred in the second electromagnetic proportional control valve or its wiring path so that the second output pressure is maintained at zero even when the operating device is operated in the second direction. In the case, the first electromagnetic proportional control is performed by energizing the first electromagnetic proportional control valve and using the first output pressure that is equal to or higher than the predetermined pressure and corresponding to the amount of operation in the second direction of the operating device as the first pilot pressure. A hydraulic drive device that outputs from a valve to the flow control valve and the switching valve. When the first pilot pressure is larger than the second pilot pressure and the differential pressure between the two pilot pressures reaches a predetermined predetermined pressure, the stroke amount in one of the predetermined directions becomes maximum. Is configured as
The hydraulic drive device according to claim 1, wherein the switching valve is configured such that the predetermined pressure becomes larger than the specified pressure. The first output pressure output from the first electromagnetic proportional control valve and one of the set pressures kept constant by the pressure source are output to the flow control valve as the first pilot pressure. Further equipped with a switching valve,
In the first switching valve, the second pilot pressure and the first output pressure are input so as to oppose each other, and the first difference obtained by subtracting the first output pressure from the second pilot pressure is the first predetermined pressure. In the case of the above, the set pressure is output as the first pilot pressure, and when the first difference is less than the first predetermined pressure, the first output pressure is output as the first pilot pressure.
The second switching valve, which is the switching valve, is a difference obtained by subtracting the second output pressure from the first pilot pressure when the first pilot pressure and the second output pressure are input so as to oppose each other. When the two differences are equal to or greater than the second predetermined pressure, which is a predetermined pressure, the set pressure is output to the flow control valve as the second pilot pressure, and when the second difference is less than the second predetermined pressure, the pressure is output to the flow control valve. , The second output pressure is output to the flow control valve as the second pilot pressure.
The control unit determines that a failure has occurred in the first electromagnetic proportional control valve or its wiring path so that the first output pressure is maintained at zero even when the operating device is operated in the first direction. If so, the second electromagnetic proportional control valve is energized and the second output pressure equal to or higher than the first predetermined pressure and corresponding to the amount of operation in the first direction of the operating device is used as the second pilot pressure. The hydraulic drive device according to claim 1, wherein the electromagnetic proportional control valve outputs the output to the flow control valve and the second switching valve. The spool has a larger first pilot pressure than the second pilot pressure, and when the differential pressure between the two pilot pressures reaches a predetermined first specified pressure, the stroke amount in one of the predetermined directions is maximum. When the second pilot pressure is larger than the first pilot pressure and the differential pressure between the two pilot pressures reaches a predetermined second specified pressure, the stroke amount in the predetermined direction and the other is maximized. Is configured as
The first switching valve is configured such that the first predetermined pressure is larger than the first specified pressure.
The hydraulic drive system according to claim 3, wherein the second switching valve is configured such that the second predetermined pressure becomes larger than the second specified pressure. The spool according to any one of claims 1 to 4, wherein the spool is located at a neutral position that cuts off between the main pump and the hydraulic actuator when the differential pressure between the two pilot pressures is zero. Hydraulic drive. The hydraulic drive device according to any one of claims 1 to 5.
The main pump that discharges the hydraulic oil supplied to the hydraulic actuator,
A hydraulic drive system including a sub-pump constituting the pressure source.

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