JPH0232482B2 - - Google Patents

Description

[Detailed Description of the Invention] Conventional fixed-displacement drum-driving hydraulic motors for truck cranes have a constant load during lifting or lowering loads. When supplying pressure oil from a type pump, it is not possible to set the speed control lever of the all-speed governor at a fixed position and adjust the pump discharge amount while lifting or lowering a load. This is because the variable displacement pump's tilting angle adjustment device adjusts the total displacement per revolution according to the load or pump discharge pressure, regardless of whether the variable displacement pump operated by the engine increases or decreases. The total pump rotational torque, which is proportional to the product of the total displacement and the pump discharge oil pressure, is kept approximately constant, so that the engine output is approximately constant, and the total pump discharge amount is adjusted according to the pump discharge pressure. This is because it is maintained approximately constant.

Therefore, in order to quickly adjust the lifting and lowering speed of the suspended load (hoisting drum speed) during cargo handling operations, the opening degree of the switching valve that controls the hoisting drum drive hydraulic motor is adjusted to reduce the amount of oil pressurized by the pump. This is done by returning the water directly to the tank through the switching valve.

In order to increase the speed of the winding drum, the discharge ports of the first and second variable displacement pumps, which are driven by an engine with an all-speed governor, are fixed displacement pumps that can be connected in parallel via switching valves. A first cylinder chamber provided with a winding drum drive hydraulic motor (actuator) and first and second operating cylinder chambers with equal pressure receiving areas capable of operating in opposite directions the parent and child pistons that are constantly biased by a spring in the direction of increasing the discharge amount. , a piston cylinder device for adjusting the discharge amount common to the second pump, and a hydraulic circuit in which the discharge opening of the first pump and the first working cylinder chamber are connected by a pilot passage. The two switching valves are connected to each other by a pilot passage, and both switching valves are controlled by one operating lever so that the oil discharged from the first and second pumps is combined and supplied to the drum drive hydraulic motor. Synchronous control is also known (see, for example, Japanese Patent Publication No. 116932/1982 and Japanese Utility Model Application No. 89803/1983).

However, with this configuration, when constructing a steel frame for a high-rise building, it is difficult to lift the steel frame and other construction materials through the narrow space formed between the steel frames at high places, and to assemble the lifted steel frame to the frame. When the lifting and lowering speed of a suspended load must be adjusted to an extremely low speed, as in the case of Since the (head loss of the valve) increases with acceleration, it is not only difficult to adjust the winding drum speed to an extremely low speed, but also because both switching valves return excess pump discharge oil directly to the tank, energy loss is reduced. There will be more.

In order to avoid this, instead of the synchronous control of the two switching valves by the operating lever, the two switching valves are sequentially controlled by one operating lever.
There is a state in which the winding cylinder is driven by a pump and the pilot hydraulic pressure is applied only to the first working cylinder chamber, and a state in which the winding drum is simultaneously driven by the first and second pumps and the pilot oil pressure is applied to the first and second working cylinder chambers, respectively. The pump tilting angle is significantly different from the state in which hydraulic pressure is applied, even though the suspended load is the same, so when switching between these two states, the pump tilting angle is about to change suddenly, causing a large impact on the engine. By applying load fluctuations, the discharge flow rate of both pumps increases or decreases rapidly, making the operation of the winding drum unstable, which is truly dangerous.

The present invention sequentially controls both switching valves with one operating lever, and prevents the pump discharge pressure from rising or falling suddenly when switching between drum drive by a single pump and drum drive by two pumps. The purpose is to

In order to achieve this object, the present invention provides that, in the hydraulic circuit, among the discharge hydraulic pressures of the first and second pumps,
A one-way valve is connected between the discharge ports of both pumps and the second working cylinder chamber so as to supply pilot oil pressure on the high pressure side to the second working cylinder chamber, thereby controlling the oil discharged from the first pump. After the switching valve is fully opened, the speed increasing switching valve that controls the discharge oil of the second pump starts to open, and after the speed increasing switching valve is fully closed, the switching valve for controlling the discharge oil of the first pump starts to close. The operating mechanisms of both switching valves are linked together.

FIG. 1 shows an embodiment of the present invention applied to a truck crane, in which a variable displacement first pump 1 and a second pump 2 are equivalent axial piston pumps simultaneously driven by an engine 3 equipped with an all-speed governor. The discharge port of the first pump 1 is connected to a constant displacement type drum drive hydraulic motor (actuator) 5 via a switching valve 4, and the discharge port of the second pump 2 is connected to a derrick cylinder for lifting the telescopic boom. 6 and a boom telescopic cylinder 7 are connected in parallel via switching valves 8 and 9, respectively. In the case shown, the second pump 2
A flow control valve 10 is inserted between the switching valves 8 and 9, which is controlled by the pressure difference before and after the switching valve 8 and preferentially supplies pressure oil to the derrick cylinder side. Reference numeral 11 controls the pilot pressure on the outlet side of the switching valve 8 to the flow rate control valve 1.
This is a shuttle valve that transmits to 0.

The tilting angle adjusting device for the first and second pumps 1 and 2 is
During normal operation, the discharge rate control rod 13 common to both pumps is constantly forced to slide to the left in the figure to the maximum discharge position by the elasticity of the compression spring 12, and is fixed to the left end of the discharge rate control rod 13. A piston-cylinder device for adjusting a discharge amount is provided, in which a parent-child piston 14 is fitted into a parent-child cylinder 15 to form a first working cylinder chamber 16 and a second working cylinder chamber 17. The tilting discs of both pumps 1 and 2 are connected. First and second working cylinder chambers 1
The pressure receiving areas of 6 and 17 are equal.

18 is a flow control valve 10 at the discharge port of the second pump 2.
The speed increasing switching valve 18 is connected in parallel with the switching valve 9 via a pipe to supply pressure oil to the winding drum drive actuator 5, and the switching valve 18 is connected to the winding drum drive actuator 5 in parallel with the switching valve 9. The lever mechanisms are interlocked 19 so that the speed increasing switching valve 18 starts to open after the switching valve 4 is fully opened, and the switching valve 4 starts closing after the speed increasing switching valve 18 is fully closed.

20 is a pilot passage which constantly connects the discharge port of the first pump 1 to the first working cylinder chamber 16;
Reference numeral 1 designates a one-way valve (shuttle valve) for taking out the pilot hydraulic pressure on the high pressure side of the pilot passage 22 connected to the pilot passage 20 and the discharge port of the second pump 2, and the shuttle valve 21 is connected to the pilot passage 23. Pilot hydraulic pressure is supplied to the second working cylinder chamber 17 via the hydraulic pressure.

In the figure, 24, 25, 26 are actuators 5,
Counter balance valves 6 and 7 are inserted into the operating circuits, 27 and 28 are relief valves 29, 30, and 31 connected to the discharge ports of the first and second pumps 1 and 2, respectively.
T is a check valve inserted into the pressure port side of each switching valve 4, 18, 9, respectively, and T is a tank.

Since the present invention has the above configuration, when the actuator 5 is driven independently by the pump 1, the pump discharge pressure corresponding to the load is supplied from the oil passage 20 to the first cylinder chamber 16, and at the same time the shuttle valve 21 is Also, when the actuator 5 is driven by the pumps 1 and 2, the pump discharge pressure is simultaneously supplied to the cylinder chambers 16 and 17. The total amount of displacement is always approximately constant depending on the suspended load, regardless of the number of pump operations.

Therefore, by rotating the speed control lever of the all-speed governor to the maximum speed position or a position close to this, the engine will move to the shaft output curve P shown in Figure 3.
After achieving the performance of the shaft torque curve T, when only the switching valve 4 is switched to the hoisting side, pilot oil pressure corresponding to the suspended load at that time is supplied to the cylinder chambers 16 and 17, and the pump Since the tilting angle of the pump is adjusted and the rotational torque of the pump is determined, the engine 3 rotates with an output A corresponding to the torque t, producing a pump discharge amount corresponding to the engine output, and the actuator 5 at low speed.
Subsequently, when the speed increasing switching valve 18 is switched to the hoisting side, the pump 2 becomes operational and the total rotational torque of the pumps 1 and 2 is doubled, so the output B corresponding to the torque 2t is The engine 3 rotates, produces a total pump discharge amount corresponding to the output, and drives the actuator 5 at high speed.

FIG. 4 is an experimental diagram showing the flow rate change of the motor (actuator) 5 with respect to the valve spool displacement in this case, where S1 is the spool stroke of the switching valve 4, S2 is the spool stroke of the switching valve 18, and C
is the valve opening variation range of each switching valve, D is the valve fully open range,
F1 indicates the total discharge amount of the pump 1, F2 indicates the total discharge amount of the pump 2, and the flow rate increase inclination angle θ, which is proportional to the valve opening degree, decreases as the load oil pressure or the pump discharge oil pressure decreases. As is clear from the figure, there is a substantially horizontal step between the low-speed drive by the pump 1 and the high-speed drive by the pumps 1 and 2, allowing the speed of the motor 5 to be changed quickly and reliably.

When the actuator 6 or 7 is driven by the pump 2, the load oil pressure is supplied from the passage 22 to the cylinder chamber 17 via the shuttle valve 21, and the pump tilting angle is adjusted according to the load. It is clear from the figure.

FIG. 2 shows another embodiment of the present invention, in which members given the same reference numerals as those in the embodiment of FIG. 1 are corresponding members. In the case of FIG. 2, between the neutral position and the winding and lowering positions of the switching valve 4, an intermediate opening position is provided in which the throttle is half-open, and the actuator 5 is controlled by the differential pressure before and after the switching valve 4. In the case of FIG. 1, a flow control valve 32 for preferentially supplying pressure oil to is inserted between the first pump 1 and the switching valve 4, and the actuator 5 and another actuator can be driven by the first pump. It's just different.

According to the present invention, the following effects are achieved.

(a) The switching valves for controlling the oil discharged from the first and second pumps are sequentially controlled by operating levers, and when the winding drum is driven at low speed, the drive hydraulic motor is controlled only for the oil discharged from the first pump. Since the winding drum is driven at extremely low speed, the opening degree of the discharge oil control switching valve increases to about twice that of the conventional one, reducing pressure loss and making it possible to drive the winding drum at an extremely low speed. The speed can be easily adjusted to low speeds, and energy loss due to excess pump discharge oil is reduced.

(b) Moreover, a one-way valve is provided to supply the pilot hydraulic pressure on the high pressure side of the discharge pressures of the first and second pumps to the second working cylinder chamber, so that the winding drum can be driven by a single pump and the winding drum by two pumps. Since the pump tilt angle does not fluctuate when switching between the drive state and the drive state, there is no risk that the pump discharge flow rate will suddenly increase or decrease due to sudden changes in the load on the engine during the switch. Can be switched.

(c) Also, by providing the one-way valve, an actuator other than the drum drive hydraulic motor can be connected to the discharge port of the second pump via a switching valve, and the second pump can supply pressure oil according to the load. can be supplied to the actuator.

[Brief explanation of drawings]

Fig. 1 is a hydraulic circuit diagram of one embodiment of the present invention, Fig. 2 is a hydraulic circuit diagram of another embodiment, Fig. 3 is an engine performance curve diagram, and Fig. 4 is a diagram of a switching valve and a speed increasing switching valve. FIG. 3 is a motor flow rate diagram with respect to spool displacement. 1...first pump, 2...second pump, 3...
Engine, 4...Switching valve, 5, 6, 7...Actuator, 12...Compression spring, 13...Discharge amount control rod, 16...First operating cylinder chamber, 17...
Second operating cylinder chamber, 18...Speed-up switching valve, 2
1...One-way valve.

Claims (1)

[Claims] 1. A constant displacement drum drive hydraulic motor in which the discharge ports of variable displacement first and second pumps 1 and 2, which are driven by an engine with an all-speed governor, can be connected in parallel via switching valves 4 and 18, respectively. 5, and a parent and child piston 1 that is constantly pressed by a spring in the direction of increasing the discharge amount.
4 with equal pressure receiving areas that can be operated in opposite directions.
The first and second cylinders are provided with working cylinder chambers 16 and 17.
In a hydraulic circuit of a truck crane or the like, which is equipped with a common piston cylinder device for adjusting the discharge amount of the pump, and in which the discharge port of the first pump 1 and the first working cylinder chamber 16 are connected by a pilot passage, Among the discharge hydraulic pressure of the pump, the pilot hydraulic pressure on the high pressure side is supplied to the second working cylinder chamber 17.
A one-way valve 21 is connected between the discharge ports of both pumps and the second operating cylinder chamber to control the oil discharged from the second pump after the switching valve 4, which controls the oil discharged from the first pump, is fully opened. The operation mechanisms of both switching valves are linked so that the speed switching valve 18 starts to open and the switching valve 4 for controlling the discharge oil of the first pump starts to close after the speed increasing switching valve 18 is fully closed. Features a gearbox for the hydraulic motor that drives the winding drum.