JP2016132988A - Fail-safe hydraulic drive system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fail-safe hydraulic drive system that comprises a plurality of hydraulic pumps and has a simple structure.SOLUTION: A fail-safe hydraulic drive system comprises: first and second hydraulic pumps; a first regulator including a first horsepower control piston and a first flow control piston; a second regulator including a second horsepower control piston and a second flow control piston; first and second proportional solenoid valves that output secondary pressures depending on supplied command currents, as flow control pressures; a primary line that leads a primary pressure to the first and second proportional solenoid valves; and a switching valve that shuts off the supply of the primary pressure from the primary pressure line to the first and second horsepower control pistons at a normal time and leads the primary pressure from the primary pressure line to the first and second horsepower control pistons at the time of a failure. The first flow control pistons make discharge flow rates of the first and second hydraulic pumps lower as the command currents supplied to the first and second proportional solenoid valves become higher.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydraulic drive system that electrically controls the flow rate of a working fluid discharged from a hydraulic pump, and relates to a fail-safe hydraulic drive system that can function safely in the event of a failure due to disconnection of an electrical system. .

  2. Description of the Related Art Conventionally, a hydraulic drive system that electrically controls the flow rate of a working fluid discharged from a hydraulic pump using an electromagnetic proportional valve is known. As shown in FIG. 6A, the hydraulic drive system is generally a positive type in which the command current to the electromagnetic proportional valve and the discharge flow rate have a positive correlation. In such a hydraulic drive system, measures are taken when the electromagnetic proportional valve stops operating during a failure. For example, Patent Literature 1 discloses a fail-safe hydraulic drive system 100 as shown in FIG.

  Specifically, the hydraulic drive system 100 includes a variable displacement hydraulic pump 110, a regulator 120 that adjusts the tilt angle of the hydraulic pump 110, an electromagnetic proportional valve 130, and a switching valve 140. The regulator 120 includes a servo piston 121 connected to the swash plate of the hydraulic pump 110, a spool 122 that drives the servo piston 121, a horsepower control piston 124 that operates the spool 122, and a flow rate control piston 123. Further, the regulator 120 includes two pressure receiving chambers 126 and 127 for the horsepower control piston 124 and a pressure receiving chamber 125 for the flow rate control piston 123.

  The discharge pressure Pd of the hydraulic pump 110 is guided to one pressure receiving chamber 126 for the horsepower control piston 124, and the horsepower control piston 124 moves the spool 122 in the flow rate reduction direction when the discharge pressure Pd increases. The other pressure receiving chamber 127 communicates with the tank in normal times.

  A flow rate control pressure is guided to the pressure receiving chamber 125 for the flow rate control piston 123, and the flow rate control piston 123 moves the spool 122 in the direction of increasing the flow rate when the flow rate control pressure increases. The electromagnetic proportional valve 130 receives the primary pressure Psv and outputs a secondary pressure as the flow control pressure. The horsepower control piston 124 and the flow rate control piston 123 are configured to move the spool 122 with priority given to control of the discharge flow rate to be small.

  During normal operation, a relatively large secondary pressure is output from the electromagnetic proportional valve 130, so that the switching valve 140 is maintained in the state on the left side in FIG. 5 and the secondary pressure from the electromagnetic proportional valve 130 is used for the flow control piston 123. The pressure receiving chamber 125 is guided. On the other hand, at the time of failure, the secondary pressure from the electromagnetic proportional valve 130 becomes substantially zero, so that the switching valve 140 is switched to the state on the right side in FIG. As a result, the pilot pressure Pp is guided to the pressure receiving chamber 125 for the flow control piston 123 and the primary pressure Psv is guided to the pressure receiving chamber 127 for the horsepower control piston 124. When the primary pressure Psv is guided to the pressure receiving chamber 127, the horsepower control characteristic is shifted from the line A to the line B as shown in FIG. 6B, and the upper limit of the discharge flow rate Q at each discharge pressure Pd is kept low.

JP 2005-146969 A

  By the way, many construction machines, industrial vehicles, and the like are equipped with a plurality of hydraulic actuators to perform various operations, and these hydraulic drive systems supply working fluid to the plurality of hydraulic actuators. For this purpose, a plurality of hydraulic pumps (for example, a double pump hydraulic pump) are provided. When the above-described hydraulic drive system with fail-safe 100 is applied to such a hydraulic drive system having a plurality of hydraulic pumps, a switching valve 140 for fail-safe is required for each hydraulic pump, and the configuration is complicated. Lead to higher manufacturing costs. Therefore, a hydraulic drive system with a fail safe having a simpler configuration is desired.

  Further, in the above-described hydraulic drive system with fail safe 100, the switching valve 140 is switched at the time of failure, and another pressure source for supplying the pilot pressure Pp to the pressure receiving chamber 125 for the flow rate control piston 123 is required. Without this pressure source, the flow rate control piston 123 operates so as to minimize the discharge flow rate, so that the function is given priority over the horsepower control piston 124, and the fail safe does not function. Such a separately provided pressure source leads to a complicated configuration and an increase in manufacturing cost.

  Accordingly, an object of the present invention is to provide a fail-safe hydraulic drive system having a simple configuration and having a plurality of hydraulic pumps.

  In order to solve the above-mentioned problems, the inventors of the present invention have used a negative correlation instead of a positive drive system in which the command current to the electromagnetic proportional valve and the discharge flow rate that are conventionally used have a positive correlation. I came up with the idea that the configuration could be simplified by adopting a negative drive system. The present invention has been made from such a viewpoint.

  That is, the fail-safe hydraulic drive system of the present invention is a variable displacement first hydraulic pump and a second hydraulic pump, and a first regulator that adjusts the discharge amount of the first hydraulic pump, A first horsepower control piston that regulates a maximum discharge flow rate of the first hydraulic pump according to the discharge pressure of the first hydraulic pump, and a discharge flow rate of the first hydraulic pump according to the flow control pressure A first regulator that includes a first flow rate control piston, and a second regulator that adjusts a discharge amount of the second hydraulic pump, wherein the second liquid according to a discharge pressure of the second hydraulic pump A second regulator including a second horsepower control piston that regulates the maximum discharge flow rate of the pressure pump, and a second flow rate control piston that controls the discharge flow rate of the second hydraulic pump according to the flow rate control pressure; The command current supplied The first proportional solenoid valve for outputting the secondary pressure as the flow control pressure of the first flow control piston, and the secondary pressure corresponding to the commanded current supplied to the flow control of the second flow control piston. A second electromagnetic proportional valve that outputs pressure, a primary pressure line that guides the primary pressure to the first electromagnetic proportional valve and the second electromagnetic proportional valve, and pressure reception for the first horsepower control piston from the primary pressure line during normal operation The primary pressure supply to the chamber and the pressure receiving chamber for the second horsepower control piston is shut off, and the pressure receiving chamber for the first horsepower control piston and the pressure receiving pressure for the second horsepower control piston from the primary pressure line at the time of failure A switching valve for guiding the primary pressure to the chamber, and the first flow rate control piston decreases the discharge flow rate of the first hydraulic pump as the command current supplied to the first electromagnetic proportional valve increases. The second flow rate control Stone is as command current to be fed to the second solenoid proportional valve becomes high, and decreases the discharge flow rate of the second hydraulic pump.

  According to the above configuration, since the supply of the primary pressure from the primary pressure line to the pressure receiving chambers for the first and second horsepower control pistons is normally shut off by the switching valve, the first and second horsepower control pistons are normally used. The primary pressure is not guided to any of the pressure receiving chambers. Further, since the secondary pressure from the electromagnetic proportional valve is led to each of the pressure receiving chambers for the first and second flow control pistons, it is possible to perform electrical flow control according to the command current to the electromagnetic proportional valve. it can.

  On the other hand, at the time of failure, the primary pressure is guided to each of the pressure receiving chambers for the first and second horsepower control pistons through the switching valve. For this reason, the maximum discharge flow rate of the hydraulic pump can be kept low. In addition, the flow rate control piston decreases the discharge flow rate of the hydraulic pump as the command current supplied to the solenoid proportional valve increases.Therefore, when the command current becomes zero, the horsepower control piston is not the flow rate control piston. Prioritize and function. Thus, during a failure, the hydraulic pump is controlled to discharge at a maximum discharge flow rate that is kept low by the horsepower control piston. Therefore, even during a failure, the hydraulic actuator can be driven with a certain amount of horsepower. it can.

  Further, since the switching valve for fail-safe for a plurality of hydraulic pumps is made into one common switching valve, it is not necessary to provide a switching valve for each hydraulic pump, and the configuration is complicated and the manufacturing cost is increased. Can be avoided.

  In the above hydraulic drive system with fail-safe, the first electromagnetic proportional valve and the second electromagnetic proportional valve are direct proportional valves that increase the secondary pressure to be output as the supplied command current increases. The first flow rate control piston decreases the discharge flow rate of the first hydraulic pump when the flow rate control pressure increases, and the second flow rate control piston decreases the second flow rate control piston when the flow rate control pressure increases. The discharge flow rate of the hydraulic pump may be reduced.

  In the hydraulic drive system with failsafe, the first electromagnetic proportional valve and the second electromagnetic proportional valve are inverse proportional valves that decrease the output secondary pressure as the supplied command current increases. The first flow rate control piston decreases the discharge flow rate of the first hydraulic pump when the flow rate control pressure decreases, and the second flow rate control piston decreases when the flow rate control pressure decreases. The discharge flow rate of the second hydraulic pump may be reduced.

  The above hydraulic drive system with fail-safe further includes a control device that supplies a command current to each of the first electromagnetic proportional valve and the second electromagnetic proportional valve, and the switching valve transmits a switching current from the control device. An electromagnetic switching valve to be supplied, maintained by a spring at a communication position for guiding the primary pressure from the primary pressure line to the pressure receiving chamber for the first horsepower control piston and the pressure receiving chamber for the second horsepower control piston; The pressure receiving chamber for the first horsepower control piston and the pressure reception for the second horsepower control piston from the primary pressure line from the communication position against the biasing force of the spring when current is supplied from the control device. You may move to the interruption | blocking position which interrupts | blocks supply of the said primary pressure to a chamber. According to this configuration, when the electric system of the control device fails and current supply from the control device is not performed, the switching valve automatically switches from the shut-off position to the communication position, and the primary pressure line The primary pressure is automatically led from the pressure receiving chambers for the first and second horsepower control pistons.

  ADVANTAGE OF THE INVENTION According to this invention, it has a several hydraulic pump and can provide the hydraulic drive system with a fail safe of a simple structure.

1 is a hydraulic circuit diagram of a fail-safe hydraulic drive system according to a first embodiment of the present invention. (A) is a graph showing the relationship between the command current to the electromagnetic proportional valve and the secondary pressure from the electromagnetic proportional valve in the hydraulic drive system shown in FIG. 1, and (b) is a graph showing the relationship between the secondary pressure and the discharge flow rate. (C) is a graph which shows the relationship (input / output characteristic) of command electric current and discharge flow volume. It is a hydraulic-pressure circuit diagram of the hydraulic drive system with a fail safe which concerns on 2nd Embodiment of this invention. (A) is a graph showing the relationship between the command current to the electromagnetic proportional valve and the secondary pressure from the electromagnetic proportional valve in the hydraulic drive system shown in FIG. 3, and (b) is a graph showing the relationship between the secondary pressure and the discharge flow rate. (C) is a graph which shows the relationship (input / output characteristic) of command electric current and discharge flow volume. It is a hydraulic-pressure circuit diagram of the conventional hydraulic drive system with a fail safe. (A) is a graph which shows the input-output characteristic of a general conventional hydraulic drive system, (b) is a graph which shows the horsepower characteristic of the hydraulic drive system shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Below, the same code | symbol is attached | subjected to the element which is the same or it corresponds through all the drawings, and the overlapping description is abbreviate | omitted.

(First embodiment)
FIG. 1 shows a hydraulic drive system 1A with a fail safe according to the first embodiment of the present invention. The hydraulic drive system 1A is mounted on, for example, a construction machine such as a hydraulic excavator having a plurality of hydraulic actuators (not shown), an industrial vehicle, or the like in order to execute various operations. The hydraulic drive system 1A supplies a working fluid to each hydraulic actuator.

Specifically, the hydraulic drive system 1A includes a variable displacement first hydraulic pump 21 and a second hydraulic pump 22, a first regulator 31 that adjusts the discharge amount of the first hydraulic pump 21, and a second And a second regulator 32 that adjusts the discharge amount of the hydraulic pump 22. The hydraulic pressure drive system 1 </ b> A includes a first electromagnetic proportional valve 51, a second electromagnetic proportional valve 52, and a switching valve 8. The hydraulic drive system 1A includes a control device 9 that supplies command currents I ₁ and I ₂ to the first electromagnetic proportional valve 51 and the second electromagnetic proportional valve 52, respectively.

  The first hydraulic pump 21 and the second hydraulic pump 22 discharge a working fluid having a flow rate corresponding to the tilt angle. In the present embodiment, swash plate pumps whose tilt angles are defined by the angles of the swash plate 23 and the swash plate 24 are employed as the first hydraulic pump 21 and the second hydraulic pump 22. However, the first hydraulic pump 21 and the second hydraulic pump 22 may be an oblique axis pump in which the tilt angle is defined by the angle of the oblique axis.

  The first regulator 31 includes a servo piston 33 that changes the tilt angle of the first hydraulic pump 21, a spool 35a that adjusts the driving pressure for driving the servo piston 33, and a sleeve 35b that houses the spool 35a. . The servo piston 33 is connected to the swash plate 23 of the first hydraulic pump 21. The second regulator 32 includes a servo piston 34 that changes the tilt angle of the second hydraulic pump 22, a spool 36a that adjusts the driving pressure for driving the servo piston 34, and a sleeve 36b that houses the spool 36a. including. The servo piston 34 is connected to the swash plate 24 of the second hydraulic pump 22. The spool 35a and the sleeve 35b constitute a pressure adjustment valve 37 for the servo piston 33, and the spool 35a and the sleeve 35b constitute a pressure adjustment valve 38 for the servo piston 34.

The operation of the first regulator 31 shown on the right side of FIG. 1 will be described in more detail. When the spool 35a moves in the flow rate reduction direction (leftward in FIG. 1) (when switched to the right side position), the first hydraulic pressure is increased. The servo piston 33 is driven so that the tilt angle of the pump 21 is reduced, and the first hydraulic pump 21 is moved when it is moved in the direction of increasing the flow rate (to the right in FIG. 1) (when switched to the left position). The servo piston 33 is driven so that the tilt angle becomes large. The sleeve 35b is the feedback lever 33a is coupled to the servo piston 33, together with the pump discharge pressure Pd ₁ is the small diameter side of the servo piston 33 acts, regulated by a pressure regulating valve 37 in the large diameter side of the servo piston 33 The driven driving pressure acts. The pressure adjustment valve 37 adjusts the drive pressure so that the force (pressure × servo piston pressure receiving area) acting from both sides of the servo piston 33 is balanced. In this way, the pressure adjusting valve 37 operates so that the relative position (metering characteristic) between the spool 35a and the sleeve 35b is constant. In this way, the sleeve 35b moves following the movement of the spool 35a. The second regulator 32 shown on the left side of FIG. 1 so as to be reversed left and right with respect to the first regulator 31 operates in the same manner as the first regulator 31.

  The first regulator 31 includes a first horsepower control piston 41 and a first flow control piston 43 that operate the spool 35a. The first horsepower control piston 41 and the first flow control piston 43 are connected to the spool 35a via a first horsepower control lever 41c and a first flow control lever 43b, respectively. Similarly, the second regulator 32 includes a second horsepower control piston 42 and a second flow rate control piston 44 that operate the spool 36a. The second horsepower control piston 42 and the second flow rate control piston 44 are connected to the spool 36a via a second horsepower control lever 42c and a second flow rate control lever 44b, respectively.

Further, the first regulator 31 includes two pressure receiving chambers 41a and 41b for the first horsepower control piston 41 and a pressure receiving chamber 43a for the first flow rate control piston 43. The second regulator 32 includes the second horsepower control piston. Two pressure receiving chambers 42 a and 42 b for 42 and a pressure receiving chamber 44 a for the second flow rate control piston 44 are included. The first horsepower control piston 41 defines the maximum discharge flow rate of the first hydraulic pump 21 according to the discharge pressure Pd ₁ of the first hydraulic pump 21. Further, the second horsepower control piston 42 defines the maximum discharge flow rate of the second hydraulic pump 22 according to the discharge pressure Pd ₂ of the second hydraulic pump 22.

The discharge pressure Pd ₁ of the first hydraulic pump 21 is guided to _one pressure receiving chamber 41 a for the first horsepower control piston 41. The first power control piston 41, the spool 35a is moved to the flow reduction direction when the discharge pressure Pd ₁ rises, the discharge pressure Pd ₁ moves the spool 35a in the flow rate increasing direction when lowered. Similarly, one of the pressure receiving chamber 42a for the second power control piston 42, the discharge pressure Pd ₂ of the second hydraulic pump 22 is introduced. The second power control piston 42 moves the spool 36a in the flow reduction direction when the discharge pressure Pd ₂ rises, the discharge pressure Pd ₂ moves the spool 36a in the flow rate increasing direction when lowered.

In the other pressure receiving chamber 41b for the first horsepower control piston 41, the primary pressure line 61 through the first horsepower control line 64 is primary depending on whether the switching valve 8 is located at a communication position or a shut-off position described later. or pressure P ₁ is led, or not guided. Similarly, in the other pressure receiving chamber 42b for the second horsepower control piston 42, the second horsepower control line 65 is connected from the primary pressure line 61 to the other pressure receiving chamber 42b depending on whether the switching valve 8 is located at a communication position or a shut-off position described later. or the primary pressure P ₁ is led through, or not guided.

A flow control pressure is guided to the pressure receiving chamber 43a for the first flow control piston 43 and the pressure receiving chamber 44a for the second flow control piston 44, and the first hydraulic pump 21 and the second liquid according to the flow control pressure. The discharge flow rate of the pressure pump 22 is controlled. In the present embodiment, the first regulator 31 and the second regulator 32 both perform negative flow rate control in which the discharge flow rates Q ₁ and Q ₂ decrease as the flow rate control pressure increases. That is, the first flow rate control piston 43 moves the spool 35a in the flow rate decreasing direction when the flow rate control pressure increases, and moves the spool 35a in the flow rate increasing direction when the flow rate control pressure decreases. The second flow rate control piston 44 moves the spool 36a in the flow rate decreasing direction when the flow rate control pressure increases, and moves the spool 36a in the flow rate increasing direction when the flow rate control pressure decreases. Thus, the first flow rate control piston 43 and the second flow rate control piston 44 have the first hydraulic pressure pump 21 and the second hydraulic pressure pump 22 when the flow rate control pressure led to the respective pressure receiving chambers 43a and 44a increases. Each of the discharge flow rates is reduced.

The first horsepower control piston 41 and the first flow rate control piston 43 are configured to move the spool 35a with priority given to the _one that restricts the discharge flow rate Q1 (that is, the direction that commands a small flow rate). the second power control piston 42 and the second flow control piston 44 is configured to move the spool 36a in preference is better to restrict the discharge flow rate Q ₂ of them.

The pressure receiving chamber 43a for the first flow control piston 43 is connected to the first electromagnetic proportional valve 51 by the first flow control line 66, and the pressure receiving chamber 44a for the second flow control piston 44 is connected to the second flow control line. 67 is connected to the second electromagnetic proportional valve 52. A primary pressure P ₁ is led from the primary pressure line 61 to the first electromagnetic proportional valve 51 and the second electromagnetic proportional valve 52.

The first electromagnetic proportional valve 51 outputs the secondary pressure P ₂₁ corresponding to the command current I ₁ supplied from the control device 9 as the flow control pressure of the first flow control piston 43, and the second electromagnetic proportional valve 52. Outputs the secondary pressure P ₂₂ corresponding to the command current I ₂ supplied from the control device 9 as the flow rate control pressure of the second flow rate control piston 44. The secondary pressure P ₂₁ of the first electromagnetic proportional valve 51 is directly and constantly guided from the first electromagnetic proportional valve 51 to the pressure receiving chamber 43 a by the first flow rate control line 66, and the secondary pressure P _{22 of} the second electromagnetic proportional valve 52. Is directly and constantly guided from the second electromagnetic proportional valve 52 to the pressure receiving chamber 44a by the second flow rate control line 67.

In the present embodiment, the first electromagnetic proportional valve 51 and the second electromagnetic proportional valve 52 output the higher the command currents I ₁ and I ₂ supplied from the control device 9 as shown in FIG. This is a direct proportional valve that raises the secondary pressures P ₂₁ and P ₂₂ . Further, as described above, in the present embodiment, since the first regulator 31 and the second regulator 32 both perform negative flow control, the secondary pressures P ₂₁ and P ₂₂ as flow control pressures increase. As a result, the discharge flow rates Q ₁ and Q ₂ decrease. For this reason, the relationship between the secondary pressures P ₂₁ and P ₂₂ and the discharge flow rates Q ₁ and Q ₂ is as shown in FIG. 2B, and the command currents I ₁ and I ₂ and the discharge flow rates Q ₁ and Q ₂ are The relationship is as shown in FIG. As shown in FIG. 2C, in the hydraulic drive system 1A, the command currents I ₁ and I ₂ and the discharge flow rates Q ₁ and Q _{2 to} the first electromagnetic proportional valve 51 and the second electromagnetic proportional valve 52 are negative. It is a negative type showing the correlation.

  Returning to FIG. 1, the primary pressure line 61 is connected to the switching valve 8 by an upstream line 62, and the switching valve 8 is connected to the first horsepower control line 64 and the second horsepower control line by the downstream line 63. 65 is connected.

The switching valve 8 is an electromagnetic switching valve to which a switching current Is is supplied from the control device 9. Further, the switching valve 8, the shut-off position to shut off the supply of the primary pressure P ₁ from the primary pressure line 61 to the first pressure receiving chamber 41b for power control piston 41 and the second power control piston 42 for the pressure-receiving chamber 42b, It is switched between the primary pressure line 61 to the communicating position for guiding the primary pressure P ₁ in the first power control pressure bearing chamber 41b of the piston 41 and the pressure receiving chamber 42b for the second power control piston 42. In the present embodiment, the tank line 68 is also connected to the switching valve 8, and the downstream line 63 is communicated with the tank line 68 when the switching valve 8 is located at the shut-off position.

  More specifically, the switching valve 8 has a spring 81 for maintaining the switching valve 8 in the communicating position. When the switching current Is is not supplied from the control device 9, the switching valve 8 communicates with the spring 81. Maintained in position. When the switching current Is is supplied from the control device 9, the switching valve 8 moves from the communication position to the blocking position against the biasing force of the spring 81. In normal times, the switching valve 8 is supplied with the switching current Is from the control device 9 and is maintained at the cutoff position. At the time of failure, the switching current Is is not supplied from the control device 9 and is moved to the communication position by the spring 81 and maintained.

Since the switching valve 8 is an electromagnetic switching valve, for example, when the electrical system of the control device 9 breaks down and the switching current Is is not supplied from the control device 9, the switching valve 8 is automatically turned on. It switched to the communication position from the cutoff position, the primary pressure from the line 61 for the first and second power control piston 41 pressure chamber 41b, the primary pressure P ₁ to 42b is automatically guided. However, the switching valve 8 may be a manual switching valve that is manually switched from the shut-off position to the communication position during a failure.

  Next, the operation of the hydraulic drive system 1A will be described.

Normal state, since the pressure receiving chamber 41b from the primary pressure line 61 for the first and second power control piston 41, the supply of the primary pressure P ₁ to 42b is blocked by the switching valve 8, the first and second receiving chamber 41b for power control piston 41, the primary pressure _{P 1} in either 42b is not guided, the pressure bearing chamber 41b, the pressure of 42b is substantially zero. Thus, only the discharge pressures Pd ₁ and Pd ₂ guided to the pressure receiving chambers 41a and 42a act on the first and second horsepower control pistons 41 and 42, respectively, and the horsepower control based only on the discharge pressures Pd ₁ and Pd ₂ is performed. Done. Since the horsepower control by the first and second horsepower control pistons 41 and 42 is set to a very high horsepower similarly to the line A in FIG. 6B, the discharge flow rate Q is not normally limited. . That is, at the normal time, the discharge flow rate Q is controlled only by the action of the first and second flow rate control pistons 43 and 44. Since the secondary pressures P ₂₁ and P ₂₂ are led from the first and second electromagnetic proportional valves 51 and 52 to the pressure receiving chambers 43 a and 44 a for the first and second flow control pistons 43 and 44, respectively. Electrical flow control according to the command currents I ₁ and I ₂ to the first and second electromagnetic proportional valves 51 and 52 can be performed.

On the other hand, when failure is first and the pressure receiving chamber 41b for the second power control piston 41 through the switching valve 8, the primary pressure _{P 1} is introduced into each of 42b. Therefore, the first power control piston 41 primary pressure _{P 1} between the discharge pressure Pd ₁ is applied, the primary pressure _{P 1} and the Pd ₂ is applied to the second power control piston 42. As a result, the maximum discharge flow rates of the first and second hydraulic pumps 21 and 22 are kept low as in the case of shifting from the line A to the line B in FIG. Further, the hydraulic drive system 1A is a negative type in which the command currents I ₁ and I ₂ to the first and second electromagnetic proportional valves 51 and 52 and the discharge flow rates Q ₁ and Q ₂ are negatively correlated. At the time of failure when the command currents I ₁ and I ₂ are zero, the first and second horsepower control pistons 41 and 42 function in preference to the first and second flow rate control pistons 43 and 44, respectively. Thus, at the time of failure, the first and second hydraulic pumps 21 and 22 are controlled so as to be discharged at the maximum discharge flow rate suppressed by the first and second horsepower control pistons 41 and 42. Even so, a hydraulic actuator (not shown) can be driven with a certain amount of horsepower.

  Furthermore, since the switching valve for fail-safe for the first and second hydraulic pumps 21 and 22 is one common switching valve 8, there is no need to provide a switching valve for each hydraulic pump. It is possible to avoid complications and an increase in manufacturing costs. In this embodiment, another pressure source for supplying pilot pressure to the pressure receiving chambers 43a, 44a for the first and second flow control pistons 43, 44 at the time of failure is not necessary, and the number of ports as the switching valve 8 is not required. Since it is possible to use a valve having a small amount, a simple configuration can be realized.

(Second Embodiment)
Next, with reference to FIG. 3, the hydraulic drive system 1B with a fail safe which concerns on 2nd Embodiment of this invention is demonstrated.

In the present embodiment, as the first electromagnetic proportional valve 53 and the second electromagnetic proportional valve 54 that output the secondary pressure as the flow control pressure, the higher the command currents I ₁ and I _{2 that} are supplied, the higher the output secondary pressure. An inverse proportional valve that reduces the pressures P ₂₁ and P ₂₂ is employed.

In the present embodiment, the first and second regulators 31 and 32 have first flow rate control levers 43d and 44d, respectively, which are different from those in the above embodiment, and as the flow rate control pressure increases. Thus, the positive flow rate control in which the discharge flow rates Q ₁ and Q ₂ are increased is performed. That is, the first flow rate control piston 43 moves the spool 35a in the flow rate increasing direction when the flow rate control pressure increases, and moves the spool 35a in the flow rate decreasing direction when the flow rate control pressure decreases. The second flow rate control piston 44 moves the spool 36a in the flow rate increasing direction when the flow rate control pressure increases, and moves the spool 36a in the flow rate decreasing direction when the flow rate control pressure decreases. Thus, the first flow rate control piston 43 and the second flow rate control piston 44 have the first hydraulic pressure pump 21 and the second hydraulic pressure pump 22 when the flow rate control pressure led to the respective pressure receiving chambers 43a and 44a decreases. The respective discharge flow rates are reduced.

In the present embodiment, as described above, since both the first electromagnetic proportional valve 53 and the second electromagnetic proportional valve 54 are inverse proportional valves, they are fed from the control device 9 as shown in FIG. As the command currents I ₁ and I ₂ become higher, the output secondary pressures P ₂₁ and P ₂₂ are lowered. As described above, since both the first regulator 31 and the second regulator 32 perform the positive flow rate control, the discharge flow rate Q ₁ is reduced as the secondary pressures P ₂₁ and P ₂₂ as the flow rate control pressure are reduced. , Q ₂ decreases. For this reason, the relationship between the secondary pressures P ₂₁ and P ₂₂ and the discharge flow rates Q ₁ and Q ₂ is as shown in FIG. 4B, and the command currents I ₁ and I ₂ and the discharge flow rates Q ₁ and Q ₂ are The relationship is as shown in FIG.

As shown in FIG. 4C, the hydraulic drive system 1B of the present embodiment is also instructed to the first electromagnetic proportional valve 53 and the second electromagnetic proportional valve 54, similarly to the hydraulic drive system 1A of the first embodiment. It is a negative type in which the currents I ₁ and I ₂ and the discharge flow rates Q ₁ and Q ₂ have a negative correlation. For this reason, also in this embodiment, the same effect as the first embodiment can be obtained.

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

  In the above embodiment, the first electromagnetic proportional valve and the second electromagnetic proportional valve are the same type of proportional valve, and the first regulator and the second regulator employ the same flow rate control method, but the present invention is not limited to this. . For example, the first electromagnetic proportional valve is a direct proportional valve, the first regulator adopts a negative flow control method, the second electromagnetic proportional valve is an inverse proportional valve, and the second regulator adopts a positive flow control method. There may be. Moreover, in the said embodiment, although the pump was two units | sets, you may be comprised by three or more.

1A, 1B Hydraulic drive system with fail safe 21 First hydraulic pump 22 Second hydraulic pump 31 First regulator 32 Second regulator 41 First horsepower control piston 42 Second horsepower control piston 43 First flow control piston 44 First 2 flow control pistons 41b, 42b pressure receiving chamber 51 first electromagnetic proportional valve 52 second electromagnetic proportional valve 61 primary pressure line 8 switching valve 81 spring 9 controller

Claims (4)

A variable displacement first hydraulic pump and a second hydraulic pump;
A first regulator for adjusting a discharge amount of the first hydraulic pump, wherein the first horsepower control piston defines a maximum discharge flow rate of the first hydraulic pump according to a discharge pressure of the first hydraulic pump; And a first regulator that includes a first flow control piston that controls a discharge flow rate of the first hydraulic pump in accordance with a flow control pressure;
A second regulator for adjusting a discharge amount of the second hydraulic pump, a second horsepower control piston for defining a maximum discharge flow rate of the second hydraulic pump according to a discharge pressure of the second hydraulic pump; And a second regulator including a second flow rate control piston for controlling a discharge flow rate of the second hydraulic pump according to a flow rate control pressure,
A first electromagnetic proportional valve that outputs a secondary pressure corresponding to a command current to be supplied as a flow control pressure of the first flow control piston;
A second electromagnetic proportional valve that outputs a secondary pressure corresponding to a command current to be supplied as a flow control pressure of the second flow control piston;
A primary pressure line for guiding a primary pressure to the first electromagnetic proportional valve and the second electromagnetic proportional valve;
During the normal time, the supply of the primary pressure from the primary pressure line to the pressure receiving chamber for the first horsepower control piston and the pressure receiving chamber for the second horsepower control piston is shut off, and during the failure, the first horsepower is supplied from the primary pressure line. A pressure receiving chamber for the control piston and a switching valve for guiding the primary pressure to the pressure receiving chamber for the second horsepower control piston,
The first flow rate control piston decreases the discharge flow rate of the first hydraulic pump as the command current supplied to the first electromagnetic proportional valve increases, and the second flow rate control piston decreases the second electromagnetic rate control piston. A hydraulic drive system with a fail safe that reduces the discharge flow rate of the second hydraulic pump as the command current supplied to the proportional valve increases. The first electromagnetic proportional valve and the second electromagnetic proportional valve are direct proportional valves that increase the secondary pressure to be output as the command current supplied increases.
The first flow rate control piston decreases the discharge flow rate of the first hydraulic pump when the flow rate control pressure increases, and the second flow rate control piston decreases the second flow rate control piston when the flow rate control pressure increases. The hydraulic drive system with a fail safe according to claim 1, wherein the discharge flow rate of the hydraulic pump is reduced. The first electromagnetic proportional valve and the second electromagnetic proportional valve are inverse proportional valves that reduce the secondary pressure to be output as the command current supplied increases.
The first flow rate control piston decreases the discharge flow rate of the first hydraulic pump when the flow rate control pressure decreases, and the second flow rate control piston decreases the second flow rate control piston when the flow rate control pressure decreases. The hydraulic drive system with a fail safe according to claim 1, wherein the discharge flow rate of the hydraulic pump is reduced. A control device for supplying a command current to each of the first electromagnetic proportional valve and the second electromagnetic proportional valve;
The switching valve is an electromagnetic switching valve to which a switching current is supplied from the control device, and a pressure receiving chamber for the first horsepower control piston and a pressure receiving pressure for the second horsepower control piston from the primary pressure line by a spring. The first horsepower from the primary pressure line from the primary pressure line is maintained against the urging force of the spring when the current is supplied from the control device and maintained in the primary position to guide the primary pressure to the chamber. The liquid with fail-safe according to any one of claims 1 to 3, which moves to a shut-off position that shuts off the supply of the primary pressure to the pressure receiving chamber for the control piston and the pressure receiving chamber for the second horsepower control piston. Pressure drive system.

Images