JP5543127B2 - Hydraulic circuit control system for forklift - Google Patents

Description

  The present invention relates to a hydraulic circuit control system for a forklift.

In general, a forklift lifts a load by an operation of an actuator such as a hydraulic cylinder, and transports the load to a large transport machine such as a truck or a ship or a warehouse.
For example, there are those that are transported by a fork connected to an actuator and those that are transported by a spreader that holds a load in a suspended form (see Patent Document 1).

Japanese Patent No. 3141616

  However, in these forklifts, when the load held in the load holding part such as a fork or spreader is raised during traveling, the forklift falls due to the sudden change in the center of gravity and the interaction between inertial force and centrifugal force due to traveling. There was a problem that.

  Accordingly, an object of the present invention is to provide a hydraulic circuit control system for a forklift that prevents the overturn by adjusting the operating speed of an actuator according to the state of the forklift.

In order to achieve the above object, a hydraulic circuit control system for a forklift according to the present invention includes a first pump and a second pump that supply hydraulic oil to a lift actuator, and the first pump and the actuator are provided between the first pump and the actuator. A main valve interposed, an adjustment valve interposed between the second pump and the actuator, and a control valve for switching a pilot pressure of the adjustment valve. A load detection means for detecting whether or not the forklift is running, a load detection means for detecting whether the forklift is running, a load signal from the load detection means, and a drive signal from the travel detection means based anda control unit for operating the control valve, the control unit, when the forklift is not holding the luggage, traveling Regardless of whether or not, the control valve is switched so as to supply hydraulic oil from the second pump to the actuator, the control unit, when the forklift is holding a load and is not running, The control valve is switched so that hydraulic oil from the second pump is supplied to the actuator, and the control unit is configured to supply hydraulic oil from the second pump when the forklift is traveling while holding a load. the Ru shall der switching the control valve so as not to supply to the actuator.

According to the hydraulic circuit control system for a forklift according to the present invention, the supply amount of hydraulic oil per hour to the actuator is adjusted according to the state of the forklift such as whether the load is held or whether the vehicle is traveling. The operating speed can be adjusted. This prevents sudden changes in the center of gravity while driving, makes it easy to determine the balance between the forklift and the load, and prevents falls. Safety can be improved without reducing work efficiency. Further, the number of pumps to which supply load is applied can be adjusted according to the state of the forklift, and it is not necessary to use a large prime mover that requires a large torque, and the prime mover can be miniaturized.

It is a side view which shows embodiment of this invention. It is a circuit diagram which shows embodiment of this invention. It is a flowchart figure explaining a control process.

Hereinafter, the present invention will be described in detail based on the illustrated embodiment.
As shown in FIGS. 1 and 2, the forklift hydraulic circuit control system according to the present invention includes a first pump P1 and a second pump P2 that supply hydraulic oil to an actuator 4 composed of a hydraulic cylinder for raising and lowering a load. Is provided. The first and second pumps P1 and P2 are driven by a prime mover 29 such as an engine or a motor that drives the forklift 20. Further, the forklift 20 has a luggage holding portion 21 composed of a spreader that moves up and down with the operation of the actuator 4.

  A tank 5 that stores hydraulic oil pumped up by the first pump P1 and the second pump P2, a first supply path 11 that supplies hydraulic oil from the first pump P1 to the actuator 4 via the main valve V1, And a second supply path 12 for supplying hydraulic oil from the pump P2 to the actuator 4 via the adjustment valve V2. The first supply path 11 and the second supply path 12 join at a supply junction 13 provided between the main valve V1 and the adjustment valve V2 and the actuator 4.

  Further, a first return path 15 for returning the hydraulic oil to the tank 5 in response to the switching of the main valve V1, and a second return path 16 for returning the hydraulic oil to the oil storage tank 5 in response to the switching of the adjustment valve V2. I have. The first return path 15 and the second return path 16 merge at a return junction 17 provided between the main valve V1 and the adjustment valve V2 and the oil storage tank 5.

In addition, a lift lever valve LV is provided that causes pilot pressure generated by a third pump (not shown) to act on the main valve V1 and the adjustment valve V2 via the transmission path 30.
When receiving the pilot pressure from the lift lever valve LV, the main valve V1 is provided so as to supply hydraulic oil from the first pump P1 to the actuator 4. The adjustment valve V2 is provided so as to supply hydraulic oil from the second pump P2 to the actuator 4. The lift lever valve LV applies a pilot pressure corresponding to the operation lever 27 for raising and lowering the load holding portion 21.

The transmission path 30 is divided into a first transmission path 31 connected to the pilot pressure receiving section of the main valve V1 and a second transmission path 32 connected to the pilot pressure receiving section of the adjusting valve V2 at the branch portion 30A. Branched.
A control valve SV for switching the pilot pressure acting on the adjustment valve V2 is provided in the second transmission path 32. The control valve SV is a solenoid valve that switches the pilot valve to switch between “supply hydraulic oil to the actuator 4” and “do not supply (return to the tank 5)” by switching the pilot pressure. .

Furthermore, the control part 3 which controls the control valve SV with the control signal F is provided.
The control unit 3 detects the load signal N from the load detection means 1 for detecting whether or not the forklift 20 is holding a load, and whether or not the forklift 20 (the vehicle part thereof) is traveling. A control signal F is transmitted to the control valve SV based on the travel signal R from the travel detection means 2. The control unit 3 can be a relay circuit, a sequencer, a computer having a RAM, a ROM, a CPU, or the like.

The control unit 3 holds the package based on the package signal N1 indicating that the package is held and the package signal N2 indicating that the package is not held (receiving either). It is determined whether or not. It is determined whether or not a load from the load is applied to the actuator 4.
In addition, based on the travel signal R1 of the travel signal R and the travel signal R2 that the vehicle is not traveling (stopped), it is determined whether or not the vehicle is traveling. .

The control unit 3 starts a control process (step) as shown in FIG. First, the package signal N is received, and it is determined whether or not the package is held in step S1.
If not, the process proceeds to step S11, where it is determined that there is no load on the actuator 4 due to the load, and in the next step S12, the control signal F1 for applying the pilot pressure to the adjustment valve V2 is sent to the control valve. Send to SV.
If the load is held, the process proceeds to step S2, and it is determined that there is a load on the actuator 4 due to the load. Thereafter, the process proceeds to step S3, and it is determined whether or not the vehicle is traveling by receiving the traveling signal R.
If the vehicle is not traveling, the process proceeds to step S12 as in the case where the vehicle is not held.
When the vehicle is running, the process proceeds to step S4, and a control signal F2 that does not cause the pilot pressure to act on the adjustment valve V2 is transmitted to the control valve SV.
That is, the process proceeds to step S4 upon simultaneous reception of the luggage signal N1 indicating that the luggage is being held and the signal R1 indicating that the luggage is being traveled (when both are received).

Here, the baggage detection means 1 and the travel detection means 2 will be described more specifically.
In FIG. 1, a forklift 20 is a lift bracket 24 that can be moved up and down by an actuator 4 and a spreader that is a load holding portion 21. A proximity switch that confirms that the twist lock pin 22 of the spreader has rotated and locked the load (container) is used as the load detection means 1.
In addition, the auto mission controller of the speed reducer 28 connected to the prime mover 29 is used as the travel detection means 2. A traveling signal R1 indicating that the vehicle is traveling is transmitted to the control unit 3 when the traveling speed is 0.1 km / h or higher. The absence of the travel signal R1 indicating that the vehicle is traveling is used as the travel signal R2 that the vehicle is not traveling (stopped). That is, when not traveling (stopped), it is defined as a case where the traveling speed is less than 0.1 km / h.

  The present invention can be modified in design. For example, the actuator 4 is a single hydraulic cylinder, but it may be two or more. Further, the load holding unit 21 of the forklift 20 may be a fork, a crane arm, a clamp arm or the like as long as it can carry the load. Further, the luggage detection means 1 may be provided at a location where it can be detected whether or not the luggage is being held, and may be any sensor such as a proximity sensor, a photoelectric sensor, or a pressure sensor, or a limit switch. Further, the rotation sensor provided in the vicinity of the rotation member for traveling such as the speed reducer 28, the axle, the wheel or the like is used as the traveling detection means 2, and the control unit 3 calculates the traveling signal R from the rotation sensor. It may be determined that the vehicle is stopping when the vehicle speed is less than 1 km / h and that the vehicle is traveling when the traveling speed is 0.1 km / h or more. In this case, the traveling signal R that is the basis of the calculation result that the vehicle is traveling is the traveling signal R1 that the vehicle is traveling. In addition, the travel signal R that is the basis of the calculation result that the vehicle is stopped is the travel signal R2 that the vehicle is stopped. Further, at 0 km / h from the auto mission controller, a traveling signal R2 indicating that the vehicle is stopped is transmitted to the control unit 3, and it is determined that the vehicle is stopped when the vehicle is completely stopped. The absence of R2 may be the running signal R1 indicating that the vehicle is running.

The use method (action) of the hydraulic circuit control system for a forklift of the present invention described above will be described.
When the operation lever 27 is operated, the pilot pressure from the lift lever valve LV is always applied to the main valve V1. The main valve V1 supplies hydraulic oil from the first pump P1 to the actuator 4.

Further, in accordance with the operation of the operation lever 27, the processing of the control unit 3 is started.
When the forklift 20 does not hold a load, the control unit 3 transmits a control signal F1 for applying a pilot pressure regardless of whether or not the vehicle is traveling by the above-described processing. The control valve SV causes the pilot pressure to act on the adjustment valve V2. The adjustment valve V2 supplies hydraulic oil from the second pump P2 to the actuator 4. Actuator oil is supplied to the actuator 4 from both the first and second pumps P1 and P2 to operate. The luggage rises together with the luggage holding unit 21.
When the vehicle is stopped, it is the same as when no load is held, and hydraulic oil is supplied to the actuator 4 from the first pump P1 and the second pump P2.

  When the operation lever 27 is operated while traveling while holding a load, a control signal F2 that does not cause the pilot pressure to act is transmitted from the control unit 3 to the control valve SV. The control valve SV does not apply a pilot pressure to the adjustment valve V2. The adjusting valve V2 returns the hydraulic oil from the second pump P2 to the tank 5 without supplying it to the actuator 4. The supply of the hydraulic oil to the actuator 4 is only from the main valve V1 (the supply amount of hydraulic oil per hour is reduced), and the operating speed of the actuator 4 (the lifting speed of the load) is reduced more than in other cases. The

When the load is raised, the center of gravity of the whole (the load and the forklift 20) becomes considerably higher than the case where only the load holding portion 21 is raised. In addition, inertial force and centrifugal force are applied during traveling. In other words, the rising of the load during traveling may cause a fall if the driver does not observe and manipulate the change in the center of gravity acting on the forklift 20 and the inertial force and centrifugal force.
However, according to the present invention, when a load is raised during traveling, the load is raised at a slower speed than when the vehicle is stopped, and therefore, a sudden change in the center of gravity during traveling is prevented, thereby preventing a fall.

  That is, the control unit 3 adjusts the adjusting valve V2 via the control valve SV so as to adjust the operating speed of the actuator 4 in accordance with the state of the forklift 20 such as whether the baggage is held or whether the vehicle is traveling. Is controlling. In other words, it can be said that it is determined whether or not the operating speed of the actuator 4 should be made slower than when the vehicle is stopped or when no load is held. In other words, it can be said that it is determined whether the actuator 4 is safe by operating the actuator 4 at the operating speed when the vehicle is stopped or when no luggage is held.

  Further, when raising the load during traveling, the hydraulic oil from the second pump P2 is not supplied to the actuator 4 (returned to the tank 5), so the load generated to supply the hydraulic oil is reduced, Most of the load on the prime mover 29 is the supply load of the first pump P1 and the load due to traveling. When the two operations of running and baggage raising are performed simultaneously, the load on the prime mover 29 is reduced and engine stall is prevented. Alternatively, the problem of lowering the traveling speed or preventing the traveling speed from increasing by assigning the force for operating the second pump P2 used to supply the hydraulic oil to the actuator 4 to the traveling is prevented. That is, the control unit 3 controls the adjustment valve V2 via the control valve SV so that the prime mover 29 is not overloaded according to the state of the forklift 20.

As described above, the first pump P1 supplies hydraulic oil to the actuator 4 for lifts provided a second pump P2, a main valve V1 which is interposed between the first pump P1 and the actuator 4, the 2 An adjustment valve V2 interposed between the pump P2 and the actuator 4 and a control valve SV for switching the pilot pressure of the adjustment valve V2, and further detecting whether or not the forklift 20 holds a load. Based on the load detection means 1 for detecting the load, the travel detection means 2 for detecting whether or not the forklift 20 is traveling, the load signal N from the load detection means 1 and the travel signal R from the travel detection means 2. And a control unit 3 for operating the control valve SV, so that the amount of hydraulic oil supplied to the actuator 4 is adjusted in accordance with the state of the forklift 20, and the appropriate actuator 4 It is possible to obtain a dynamic rate. A sudden change in the center of gravity during travel can be prevented, preventing falls. This makes it easier for the driver to determine the balance between the forklift 20 and the load lift while driving. Safety can be improved without reducing work efficiency. Further, the number of pumps to which a supply load is applied can be adjusted according to the state of the forklift 20, so that it is not necessary to use a large engine or the like, and the prime mover 29 can be downsized.

  In addition, the control unit 3 simultaneously receives the luggage signal N1 indicating that the luggage is held from the luggage detection means 1 and the traveling signal R1 indicating that the luggage is traveling from the traveling detection means 2, and receives the signal from the second pump P2. Since the control valve SV is operated so that the hydraulic oil is not supplied to the actuator 4, a fall due to a sudden change in the center of gravity during traveling can be prevented. When the two operations of traveling and baggage raising are performed simultaneously, the load on the prime mover 29 can be reduced and engine stall can be prevented. Alternatively, it is possible to prevent problems such as a decrease in travel speed and an increase in travel speed by assigning a force for operating the second pump P2 to travel. That is, the prime mover 29 can be prevented from being overloaded.

DESCRIPTION OF SYMBOLS 1 Baggage detection means 2 Travel detection means 3 Control part 4 Actuator
20 Forklift N Luggage signal N1 Luggage signal indicating that a load is being held P1 1st pump P2 2nd pump R Travel signal R1 Travel signal that travel is in progress SV Control valve V1 Main valve V2 Adjustment valve

Claims (1)

A first pump (P1) and a second pump (P2) for supplying hydraulic oil to the lift actuator (4);
A main valve (V1) interposed between the first pump (P1) and the actuator (4), and an adjustment valve (between the second pump (P2) and the actuator (4) ( V2) and a control valve (SV) for switching the pilot pressure of the adjustment valve (V2),
Further, a load detection means (1) for detecting whether or not the forklift (20) holds a load, and a travel detection means (2) for detecting whether or not the forklift (20) is traveling. And a control unit (3) for operating the control valve (SV) based on the load signal (N) from the load detection means (1) and the travel signal (R) from the travel detection means (2); , comprising a,
When the forklift (20) is not holding a load, the control unit (3) sends hydraulic oil from the second pump (P2) to the actuator (4) regardless of whether or not the vehicle is traveling. Switch the control valve (SV) to supply,
The control unit (3) supplies hydraulic oil from the second pump (P2) to the actuator (4) when the forklift (20) holds a load and is not traveling. Switching the control valve (SV)
When the forklift (20) is traveling while holding a load, the control unit (3) performs the control so as not to supply hydraulic oil from the second pump (P2) to the actuator (4). hydraulic circuit control system for a forklift according to claim Rukoto switching valve (SV).

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