JP4271105B2 - Industrial machinery control circuits - Google Patents

Description

  The present invention relates to an industrial machine control circuit used in an industrial machine such as a forklift.

As this type of control circuit, a control circuit described in Patent Document 1 is conventionally known. In this conventional control circuit, a priority valve is connected to a constant discharge type pump, a control flow port of the priority valve is connected to a steering system circuit, and an excess flow port is connected to a work machine system circuit.
A constant flow rate, that is, a control flow rate, is supplied preferentially to the steering system circuit through the control flow port among the flow rates discharged from the constant discharge type pump, and the control flow rate from the discharge capacity of the constant discharge type pump. The surplus flow amount obtained by subtracting is always supplied to the work machine system circuit.

The work machine system circuit as described above is provided with a plurality of work machine system switching valves, and when these work machine system switching valves are maintained in a neutral position, in other words, the work machine connected to these switch valves is operated. If not, all of the surplus flow is returned to the tank via the neutral flow path of all work implement system switching valves.
JP 2000-007300 A

In the above conventional control circuit, when all the work machine switching valves provided in the work machine system circuit are held in the neutral position, in other words, when any work machine is not operating, the total amount of the excess flow rate. Is returned to the tank. There was a problem that the greater the flow rate recirculated to this tank, the greater the energy loss.
In addition, when an energy loss occurs as described above, the heat generation amount naturally increases. However, if the heat generation amount increases, a device for cooling the heat generation device is required, which increases the manufacturing cost of the circuit. There was also a problem of doing.

Furthermore, since the above-mentioned conventional control circuit uses a constant discharge type pump, the supply flow rate could not be adjusted according to the working machine to be operated, for example.
An object of the present invention is to provide a control circuit for an industrial machine that is capable of supplying a necessary flow rate to a required working machine while having an extremely small energy loss.

  The first invention is a constant discharge pump, a priority valve connected to the constant discharge pump, a steering system circuit connected to a control flow port of the priority valve, and an excess flow port of the priority valve. In addition, a work machine system circuit provided with a plurality of work machine system switching valves, and the work machine system circuit provided at a position upstream of the plurality of work machine system switch valves and according to the pressure in the pilot chamber A flow rate setting valve that can be switched to a fully open position that is a first switching position, a throttling position that is a second switching position, or a drain position that is a normal position; a pilot passage communicating with the pilot chamber of the flow rate setting valve; A flow rate control valve provided in the passage and for supplying a preset flow rate to the pilot passage, and provided on the downstream side of the flow rate control valve, and the pressure of the set pressure control unit A pilot pressure control means capable of controlling the set pressure in two steps of high and low, and a pilot control valve for communicating the pilot passage with the set pressure control section of the pilot pressure control means or blocking the communication. When the pilot passage communicates with the set pressure control unit of the pilot pressure control means, the set pressure of the pilot pressure control means is set to a pressure necessary for the flow rate setting valve to switch to the fully open position which is the first switching position. When the communication between the pilot passage and the set pressure control unit of the pilot pressure control means is interrupted, the set pressure of the pilot pressure control means is necessary for switching the flow rate setting valve to the throttle position which is the second switching position. It is characterized in that it is configured to be set to pressure.

According to the first invention, when the work implement connected to the work implement system circuit is not operated, the flow rate setting valve is switched to the drain position, so that the surplus flow rate does not directly pass through the work implement switch valve. It will be returned to the tank. Thus, energy loss is reduced by not passing through the work machine system switching valve, and the amount of heat generation is reduced by the amount of energy loss, thereby eliminating the need for a cooling device and the like, and reducing the manufacturing cost of the circuit. .
And according to 1st invention, the flow volume required for a specific working machine can be supplied appropriately.

  FIG. 1 shows a first embodiment when the industrial machine control circuit of the present invention is used in a forklift, and is provided with a constant discharge amount type pump P. FIG. The constant discharge amount type pump P is connected to a supply passage 1, and the supply passage 1 communicates with the inflow port 3 of the priority valve 2. The priority valve 2 configured as described above has the control flow port 4 connected to the steering system circuit 5 and the surplus flow port 6 connected to the work machine system circuit 7.

  The priority valve 2 preferentially supplies the control flow rate Q1 to the steering system circuit 5 and supplies the surplus flow rate Q2 higher than the control flow rate Q1 to the work machine system circuit 7. The control flow rate Q1 is controlled by the control orifice 8 And the spring 9. That is, the priority valve 2 is configured to guide the pressure upstream of the control orifice 8 to one pilot chamber 2a and guide the pressure downstream of the control orifice 8 to the other pilot chamber 2b. A spring 9 is provided in the pilot chamber 2b.

The priority valve 2 thus configured operates so that the differential pressure across the control orifice 8 becomes equal to the spring force of the spring 9. In other words, the control pressure Q1 supplied to the steering system circuit 5 is always kept constant by keeping the pressure difference across the control orifice 8 constant. When the surplus flow Q2 equal to or higher than the control flow Q1 flows into the inflow port 3, the surplus flow Q2 flows out from the surplus flow port 6.
In the figure, reference numerals 10 and 11 denote damper orifices.

  Further, the pilot passage 12 is branched from the supply passage 1 on the upstream side of the priority valve 2, and a flow rate control valve 13 is connected to the pilot passage 12, and the downstream side of the flow rate control valve 13 A pressure reducing valve 14 is connected as pilot pressure control means of the invention. The flow rate control valve 13 guides the minimum flow rate required for generating the pilot pressure in the pilot passage 12 among the flow rates supplied to the supply passage 1 to the pilot passage 12 as a pilot flow rate Q3. The maximum discharge amount of the constant discharge pump P is the sum of the control flow Q1, the surplus flow Q2, which is the total flow required by a plurality of work machines, and the pilot flow Q3. Yes.

  On the other hand, the pressure reducing valve 14 is provided with a spring 14a on one side thereof, and a control piston 14b for adjusting the spring force of the spring 14a is provided in the piston chamber 14c. When the pressure is applied to the control piston 14b, the spring 14a is bent to increase the spring force. On the other hand, when no pressure is applied to the control piston 14b, the spring 14a is maintained in an extended state and its spring force is weakened.

Further, if the spring force is strong, the set pressure of the pressure reducing valve 14 becomes high, and if the spring force is weak, the set pressure becomes low.
The spring 14a, the piston 14b, and the piston chamber 14c constitute the set pressure control unit of the present invention.

  Further, the work machine system circuit 7 connected to the surplus flow port 6 of the priority valve 2 includes a first work machine system switching valve 16 for controlling the lift cylinder 15 and a second work machine system switching valve for controlling the tilt cylinder 17. 18 and a third work machine system switching valve 19 for controlling an attachment actuator (not shown). Each of the first, second, and third work machine system switching valves 16, 18, and 19 is a center open type, and when they are in the illustrated neutral position, the working fluid that has flowed out of the excess flow port 6 is circulated to the tank T. Let

The first work machine system switching valve 16 is provided with a pilot port 20. This pilot port 20 communicates with the tank T when the switching valve 16 is in a neutral position and a lowered position where the lift cylinder 15 is lowered. The pilot port 20 is closed when a full stroke is made at the raised position where the lift cylinder 15 is raised.
The pilot port 20 communicates with the piston chamber 14 c of the pressure reducing valve 14 through a control passage 21. Further, the control passage 21 is connected to a pilot control valve 22, and the configuration of the pilot control valve 22 is as follows.

The pilot control valve 22 has a first port 22 a communicating with the pilot passage 12, a second port 22 b communicating with the control passage 21, and a pilot port 23 of the second work machine system switching valve 18 via the pilot passage 24. And a third port 22c communicating with each other. Pilot chambers 22d and 22e are provided at both ends of the pilot control valve 22, and a centering spring 25 is provided in each of the pilot chambers 22d and 22e.
Further, the pressure in the control passage 21 is guided to the one pilot chamber 22d, and the pressure of the pilot passage 24 leading to the second work machine system switching valve 18 is guided to the other pilot chamber 22e. .

  When the pilot control valve 22 is in the normal position shown in the figure by the action of the centering spring 25, the first to third ports 22a to 22c are opened, and the pilot passage 12, the control passage 21, the pilot passage 12, The pilot passage 24 is communicated. Further, when the pilot control valve 22 is switched to the right position in the drawing by the pressure action of one pilot chamber 22d, the first port 22a and the second port 22b are opened, and the pilot passage 12 and the control passage 21 are communicated with each other. At the same time, the third port 22c is closed to block communication between the pilot passages 12 and 24.

  On the contrary, when the pilot control valve 22 is switched to the left position in the drawing by the pressure action of the other pilot chamber 22e, the first port 22a and the third port 22c are opened, and the pilot passages 12 and 24 are communicated with each other. At the same time, the second port 22b is closed to block communication between the pilot passage 12 and the control passage 21.

  The pilot port 23 of the second work machine system switching valve 18 is opened when the switch valve 18 is in the neutral position shown in the figure, and communicates with the pilot port 26 of the third work machine system switching valve 19. . The pilot port 23 is configured to be closed when the second work machine system switching valve 18 is switched from the neutral position shown in the drawing to either the left or right control position.

Further, the pilot port 26 of the third work machine system switching valve 19 is also opened when the switching valve 19 is in the neutral position shown in the figure, and this port 26 is communicated with the tank T. The pilot port 26 is closed when the third work machine system switching valve 19 is switched from the neutral position shown in the figure to either the left or right control position.
In the figure, reference numeral 27 is a main relief valve, and 28 is a relief valve of the steering system circuit 5.

  A flow rate setting valve 29 is provided between the priority valve 2 and the first work machine system switching valve 16. The flow rate setting valve 29 is provided with a pilot chamber 29a communicating with the pilot passage 12, and a spring force of a spring 29b is applied to the side opposite to the pilot chamber 29a. The chamber provided with the spring 29b communicates with the tank.

  The flow rate setting valve 29 configured as described above can be switched to three positions, and when the pilot pressure is not acting on the pilot chamber 29a, the illustrated normal position, that is, the drain position is held by the spring force of the spring 29b. In this drain position, the inflow port 29c communicates with the tank port 29d in the fully opened state, and the communication port 29e communicated with the first, second and third work machine system switching valves 16, 18, 19 is closed.

  Further, when the two-stage pilot pressure is applied to the pilot chamber 29a, the flow rate setting valve 29 can be switched between the first switching position (a) and the second switching position (b). The pilot pressure corresponds to the high pressure setting and the low pressure setting of the pressure reducing valve 14. When a pressure corresponding to the low pressure setting of the pressure reducing valve 14 is applied to the pilot chamber 29a, the flow rate setting valve 29 is switched to the second switching position (b). In the second switching position (b), the inflow port 29c and the communication port 29e, and the inflow port 29c and the tank port 29d communicate with each other through a throttle.

  However, the throttle in the communication process between the inflow port 29c and the communication port 29e is configured to have a larger opening than the throttle in the communication process between the inflow port 29c and the tank port 29d. Therefore, a part of the surplus flow Q2 that has passed through the priority valve 2 is returned to the tank from the tank port 29d via the throttle, but the flow obtained by subtracting the recirculation flow from the surplus flow Q2 to the tank is the communication port. It flows out of 29e.

Further, when a pressure corresponding to the high pressure setting of the pressure reducing valve 14 acts on the pilot chamber 29a, the flow rate setting valve 29 is switched to the first switching position (a). In the first switching position (a), the inflow port 29c and the communication port 29e communicate with each other in a fully opened state, and the communication between the inflow port 29c and the tank port 29d is blocked. Therefore, the entire surplus flow rate Q2 flows out from the communication port 29e.
That is, in the first embodiment, the flow rate flowing out from the communication port 29e is changed in two steps depending on whether the flow rate setting valve 29 is switched to the first switching position (a) or the second switching position (b). Can be controlled.

Next, the operation of the first embodiment will be described.
Now, with the first, second and third work machine system switching valves 16, 18, 19 of the work machine system circuit 7 kept in the neutral position, the lift cylinder 15, the tilt cylinder 17 and the attachment actuator (not shown) are operated. When not, each of the pilot ports 20, 23 and 26 of the switching valves 16, 18, and 19 communicates with the tank T.

  As described above, if each of the pilot ports 20, 23, and 26 communicates with the tank T, no pressure is generated in the pilot chambers 22d and 22e of the pilot control valve 22. The first to third ports 22a to 22c are opened while maintaining the position. Therefore, the pilot passage 12 also communicates with the tank T. Since the pilot passage 12 is guided to the tank T in this way, the inside of the pilot passage 12 is kept at the tank pressure.

  If the tank pressure is maintained in the pilot passage 12, the pilot chamber 29a of the flow rate setting valve 29 also becomes the tank pressure, so that the flow rate setting valve 29 maintains the drain position shown in the figure. If the flow rate setting valve 29 maintains the illustrated drain position, the entire surplus flow rate Q2 is directly returned to the tank T via the inflow port 29c and the fully open tank port 29d.

  In this way, the entire surplus flow rate Q2 is returned directly from the inflow port 29c to the tank T via the tank port 29d in the fully opened state. The pressure loss is extremely less than when returned to the tank T through 16, 18, and 19. In other words, the energy loss is reduced.

  From the above state, for example, when the first work machine system switching valve 16 is fully stroked to the lift lift position on the right side of the drawing while keeping the second and third work machine system switching valves 18 and 19 in the neutral position, the pilot Port 20 is closed. When the pilot port 20 is closed in this way, the control passage 21 has the same pressure as the pilot passage 12.

  On the other hand, the pilot passage 24 side circulates to the tank T via the pilot ports 23 and 26. In other words, pressure loss due to fluid flow occurs in the flow process between the first port 22a and the third port 22c, so the pressure on the pilot passage 12 side becomes higher than the pressure on the pilot passage 24 side. Therefore, the pressure on the control passage 21 side, which is the same pressure as the pilot passage 12 side, is relatively higher than the pressure on the pilot passage 24 side.

  Thus, since the pressure on the control passage 21 side becomes high, the pressure on the pilot chamber 22d side of the pilot control valve 22 also becomes relatively high. Therefore, the pilot control valve 22 switches to the right side position in the drawing, communicates the first and second ports 22a and 22b, and closes the third port 22c. As a result, the pressure in the pilot passage 12 is guided to the piston chamber 14 c of the pressure reducing valve 14 through the first port 22 a → the second port 22 b → the control passage 21.

As described above, when the pressure guided to the piston chamber 14c acts on the piston 14b, the piston 14b moves and deflects the spring 14a, strengthening the spring force, and setting the pressure of the pressure reducing valve 14. Set to high pressure. If the set pressure of the pressure reducing valve 14 is set to a high pressure, the pilot pressure acting on the pilot chamber 29a of the flow rate setting valve 29 is also increased, so that the flow rate setting valve 29 is switched to the first switching position (a).
When the flow rate setting valve 29 is switched to the first switching position (a), the inflow port 29c and the communication port 29e communicate with each other in the fully opened state, so that the entire surplus flow rate Q2 passes through the first work machine system switching valve 16. To the lift cylinder 15.

  When the first work machine system switching valve 16 is switched to the lowered position, which is the left position in the drawing, the lift cylinder 15 communicates with the tank T, so that the lift cylinder 15 is lowered by its own weight, and at this time, the pilot port 20 Communicates with tank T. Since the pilot passage 12 communicates with the tank T via the pilot port 20 in this way, the flow rate setting valve 29 maintains the illustrated normal position, and the total discharge flow amount of the constant discharge type pump P is from the tank port 29d. It is returned directly to the tank T. Therefore, the energy loss at this time can be kept to a minimum.

  On the other hand, when the second or third work machine system switching valve 18 or 19 is fully stroked while the first work machine system switching valve 16 is kept at the neutral position, the pilot port 23 or 26 is closed. When the pilot port 23 or 26 is thus closed, the pilot passage 24 has the same pressure as the pilot passage 12. On the other hand, the control passage 21 side circulates to the tank T via the pilot port 20. In other words, pressure loss due to fluid flow occurs in the flow process between the first port 22a and the second port 22b, so that the pressure on the pilot passage 12 side becomes higher than the pressure on the control passage 21 side. Therefore, the pressure on the pilot passage 24 side, which is the same pressure as the pilot passage 12 side, is relatively higher than the pressure on the control passage 21 side.

  As described above, since the pressure on the pilot passage 24 side becomes high, the pressure on the pilot chamber 22e side of the pilot control valve 22 also becomes relatively high. Accordingly, the pilot control valve 22 is switched to the left position in the drawing, communicates with the first and third ports 22a and 22c, and closes the second port 22b. Since the second port 22b is closed in this way, no pressure acts on the piston chamber 14c. Therefore, the pressure reducing valve 14 sets the set pressure to a low pressure without bending the spring 14a.

  If the pressure reducing valve 14 is set to a low pressure as described above, the pilot pressure acting on the pilot chamber 29a of the flow rate setting valve 29 becomes a pressure corresponding to the low pressure setting, so that the flow rate setting valve 29 is in the second switching position ( Switch to b). When the flow rate setting valve 29 is switched to the second switching position (b), each of the inflow port 29c and the communication port 29e and the inflow port 29c and the tank port 29d communicate with each other through the restriction, so that of the surplus flow rate Q2, A part thereof is returned to the tank from the tank port 29d via the throttle, but a flow rate obtained by subtracting the flow rate circulating to the tank from the surplus flow rate Q2 flows out from the communication port 29e. In other words, a smaller flow rate is supplied to the tilt cylinder 17 or the actuator for attachment than when the first work machine system switching valve 16 is fully stroked to the right position.

As described above, according to the first embodiment, the supply flow rate can be varied according to the actuator to be operated while using the constant discharge pump. In addition, when the work implement connected to the work implement system circuit is not used, the tank T is connected to the surplus flow rate Q2 through the flow setting valve 29 in the fully open state without passing through each work implement switch valve. Therefore, the pressure loss is small and the energy loss is reduced accordingly.
The pressure reducing valve 14 constitutes a pilot pressure control means of the present invention, and this pilot pressure control means has the greatest feature that the pilot pressure for the flow rate setting valve 29 can be controlled in two stages.

  FIG. 2 shows a second embodiment when the industrial machine control circuit of the present invention is used for a forklift. Particularly, the pilot pressure control means is different from the first embodiment, and the others are the first embodiment. The form is the same. Therefore, in the description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description of the same components is omitted.

  The pilot pressure control means in the second embodiment includes a flow control valve 13 and a pilot control relief valve 30. The flow rate control valve 13 is connected to the pilot passage 12 at the outflow port side, and the pilot control relief valve 30 is connected to the communication process between the flow rate control valve 13 and the pilot passage 12. The relief valve 30 communicates with the tank T on the outflow port side.

  The pilot control relief valve 30 as described above is provided with a spring 30a on one side thereof, and a control piston 30b for adjusting the spring force of the spring 30a is provided in the piston chamber 30c. When the pressure acts on the control piston 30b, the spring 30a is bent to increase the spring force.

  On the other hand, when no pressure is applied to the control piston 30b, the spring force is weakened while keeping the spring 30a extended. If the spring force is strong, the set pressure of the pilot control relief valve 30 is high, and if the spring force is weak, the set pressure is low. The piston chamber 30c communicates with the same control passage 21 as in the second embodiment. The spring 30a, the piston 30b, and the piston chamber 30c constitute the set pressure control unit of the present invention.

  Therefore, when the first work machine system switching valve 16 is fully stroked, the pressure of the pilot passage 12 is changed from the first port 22a → the second port 22b → the control passage 21 to the piston chamber via the pilot control relief valve 30b. It is guided to 30c and acts on the control piston 30b. When the pilot pressure acts on the control piston 30b in this manner, the spring 30a is deflected, and the set pressure of the pilot control relief valve 30 is increased. Therefore, this high pressure is applied to the pilot chamber 29a of the flow rate setting valve 29 to switch the flow rate setting valve 29 to the first switching position (a).

On the other hand, when the second working machine system switching valve 18 or the third working machine system switching valve 19 is full stroke, the communication between the pilot passage 12 and the control passage 21 is cut off as in the first embodiment. No pressure acts on 30c. Therefore, the relief valve 30 is maintained at a relatively low set pressure without deflecting the spring 30a.
Therefore, this relatively low pressure acts on the pilot chamber 29a of the flow rate setting valve 29 to switch the flow rate setting valve 29 to the second switching position (b). Other configurations and operations are the same as those in the first embodiment.

1 is a circuit diagram of a first embodiment of the present invention. It is a circuit diagram of a 2nd embodiment of this invention.

Explanation of symbols

P Constant discharge type pump 2 Priority valve 4 Control flow port 5 Steering system circuit 6 Surplus flow port 7 Work machine system circuit 12 Pilot passage 13 Flow rate control valve 14 Pressure reducing valve 14a as pilot pressure control means A set pressure control unit is configured Spring 14b Control piston 14c constituting the set pressure control unit Piston chamber 16 constituting the set pressure control unit First work machine system switching valve 18 Second work machine system switching valve 19 Third work machine system switching valve 22 Pilot control valve 29 Flow rate setting valve 29a Pilot chamber 30 Relief valve 30a which is a pilot pressure control means Spring 30b which constitutes the set pressure control unit Control piston 30c which constitutes the set pressure control unit Piston chamber which constitutes the set pressure control unit T tank

Claims (3)

  A constant discharge pump, a priority valve connected to the constant discharge pump, a steering system circuit connected to the control flow port of the priority valve, and a surplus flow port of the priority valve and a plurality of work machines A work machine system circuit provided with a system switching valve, and the work machine system circuit provided at a position upstream of the plurality of work machine system switching valves and at the first switching position according to the pressure of the pilot chamber A flow rate setting valve that can be switched to the fully open position, the throttle position or the drain position that is the second switching position, a pilot passage that communicates with the pilot chamber of the flow rate setting valve, and a preset flow rate that is provided in the pilot passage A flow rate control valve for supplying to the pilot passage, and provided downstream of these flow rate control valves, the set pressure can be controlled in two steps according to the pressure of the set pressure control unit. And a pilot control valve for communicating the pilot passage with the set pressure control unit of the pilot pressure control means or blocking the communication. The pilot passage is a set pressure of the pilot pressure control means. When communicating with the control unit, the set pressure of the pilot pressure control means is set to a pressure necessary for the flow rate setting valve to switch to the fully open position which is the first switching position, and the set pressure of the pilot passage and the pilot pressure control means is set. Industrial machine control configured to set the set pressure of the pilot pressure control means to a pressure required for the flow rate setting valve to switch to the throttle position which is the second switching position when communication with the control unit is interrupted circuit.   2. The work machine control circuit according to claim 1, wherein the pilot pressure control means comprises a pressure reducing valve provided in the pilot passage.   2. The work machine control circuit according to claim 1, wherein the pilot pressure control means comprises a flow rate control valve provided in the pilot passage and a pilot control relief valve provided downstream thereof.

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