JPH0441268Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a device for controlling the total horsepower of three variable displacement pumps mounted on a construction machine such as a power shovel to a constant value.

(Prior Art) In general, a power shovel, as shown in FIG. 1 or 2, has a bucket a attached to a rotating body d via an arm b and a boom c, and the arm b and boom c are respectively swung by hydraulic cylinders. The revolving body d is rotated by a hydraulic motor, and excavated materials dug by a bucket truck a are loaded onto, for example, a dump truck e. In this case, to ensure independent operation of each hydraulic cylinder and hydraulic motor, fluid is supplied to each hydraulic cylinder and hydraulic motor from three first to third variable displacement pumps driven by one prime mover of the power shovel. However, when the first variable displacement pump that drives the hydraulic motor is under no load, the second and third variable displacement pumps that drive each hydraulic cylinder are
The horsepower setting of the variable displacement pump is increased as shown in curve A shown in the third diagram, and the horsepower setting of the second and third variable displacement pumps is increased when the first variable displacement pump is operated at a horsepower setting as shown in curve B. As shown in curve C, the total horsepower of each pump is always controlled to be constant.

An example of the control device, as shown in FIG. A control cylinder k into which the higher of the discharge pressures is introduced, and a servo valve m which is operated by the control pressure introduced from the pilot pump j through the throttle l to control the operation of the control cylinder k. A regulator n is provided, and when the first variable displacement pump g is not loaded, the second and third regulators
It is constructed by providing a control valve O that controls the control pressure acting on each servo valve m of each regulator n of variable displacement pumps h and i to be low, and controls the control pressure to be high when the pump g is loaded.

(Problems to be Solved by the Invention) With the conventional control device described above, it is not possible to change the horsepower setting of the first variable displacement pump g, so it may not be possible to speed up the work of the construction machine. For example, in the case shown in Figure 1, when loading excavated material taken by bucket truck a onto dump truck e, rotating body d
Since it is necessary to raise arm b and boom c higher while turning 180 degrees, the second and third variable displacement pumps h that drive arm b and boom c are used more than the first variable displacement pump g that drives rotating structure d. , i must perform a large work, but in the case shown in the second diagram, while the rotating body d rotates 180°, the arm b
Also, if the turning speed of the rotating body d can be increased without the need to raise the boom c too high, work efficiency will be increased. However, in the device shown in the fourth diagram, when the first variable displacement pump g is not loaded, the set horsepower of the other pumps can be increased, and the working efficiency in the case shown in the first diagram can be improved. Since the set horsepower cannot be changed, the work efficiency cannot be increased in the case shown in the second diagram.

The object of the present invention is to provide a constant horsepower control device for construction machinery in which the total horsepower of the first to third variable displacement pumps is constant, and which can be applied to various types of work by arbitrarily changing the setting horsepower of these pumps. shall be.

(Means for solving the problem) In the present invention, construction machinery is provided with three variable displacement pumps, first to third, which are driven by a single prime mover, and the pump capacity of each variable displacement pump is adjusted independently. A control cylinder into which the higher of the discharge pressure and the discharge pressure of the pilot pump is introduced, and a servo valve which is actuated by the control pressure introduced from the pilot pump via a throttle to control the operation of the control cylinder. In the regulator having a variable displacement pump, the first variable displacement pump is provided with a first regulating valve for regulating the control pressure introduced into the regulator, and the first regulating valve is provided with a first regulating valve for adjusting the control pressure. As the adjustment pressure, the total force of the pilot pressure obtained by controlling the pressure from the pilot pump with an electromagnetic proportional valve and the force due to the self-discharge pressure of the first variable displacement pump balances the force due to the adjustment pressure. A first shift valve that operates to introduce a pressure that controls the self-discharge pressure, and a second shift valve that adjusts the control pressure that is introduced to each regulator of the second and third variable displacement pumps.
A regulating valve is provided, and first and second regulating pressures are introduced into the second regulating valve as regulating pressures for the regulating operation,
Both adjustment pressures are the higher of the discharge pressures of the second or third variable displacement pump, and the force due to both discharge pressures and the force due to the first adjustment pressure and the pilot pressure acting in opposition thereto. The second
The pilot pressure is controlled by a shift valve, and is actuated by an increase in the discharge pressure of the first variable displacement pump to guide the pilot pressure to the second shift valve.
The above-mentioned problem was solved by providing the regulating valve with a hydro switching valve for introducing the second regulating pressure.

(Function) When the first variable displacement pump is operating under load and there is no electric signal input to the electromagnetic proportional valve, the pilot pressure acting on the first shift valve becomes zero, and the first shift valve changes to the first regulating valve. Control the applied regulating pressure to a low pressure. As a result, the first regulating valve controls the control pressure acting on the servo valve of the first variable displacement pump to a high pressure, and the regulator of the pump maximizes the set horsepower of the pump as shown by curve D in FIG. Set. At this time, the discharge pressure of the first variable displacement pump acts on the hydro switching valve, and the second regulating valve is switched to apply the first and second regulating pressures controlled by the second shift valve.

The second shift valve controls the first and second adjusted pressure to a pressure obtained by subtracting the pressure corresponding to the pilot pressure of the electromagnetic proportional valve from the average discharge pressure of the first and second variable displacement pumps, and controls the first and second adjusted pressure When the second regulating valve receives the action of 2. 3rd
The set horsepower of the variable displacement pump is variably controlled, but when the pilot pressure is zero as described above, the first and second adjustment pressures are high, and the second adjustment valve is connected to the servo valves of the second and third variable displacement pumps. Since the control pressure of
The set horsepower of both pumps becomes smaller as shown by curve E in FIG.

When the first variable displacement pump is operating under load, if an electric signal is input to the electromagnetic proportional valve, a pilot pressure corresponding to the magnitude of the signal is generated, and the first shift valve acts on the first regulating valve. The adjustment pressure to be used is controlled to a high pressure. As a result, the set horsepower of the first variable displacement pump becomes smaller as shown by curve F in FIG. The pilot pressure generated at the same time acts on the second shift valve, which operates to control the first and second regulating pressures low, and the second regulating valve acts on each servo valve of the second and third variable displacement pumps. Since the control pressure is increased, the set horsepower of both the second and third variable displacement pumps can be increased as shown by curve G in FIG.

Note that when the first variable displacement pump enters no-load operation, the hydro switching valve stops introducing the pilot pressure to the second shift valve and the second regulating pressure to the second regulating valve. The valve performs a regulating operation based on the first regulating pressure, and the control pressure acting on the servo valve of the second and third variable displacement pump increases, thereby increasing the set horsepower thereof.

Therefore, by controlling the electromagnetic proportional valve with an electric signal, the set horsepower of each pump can be changed without changing the total horsepower of all the first to third pumps, and the first variable displacement pump can be used for example as shown in FIG. Second
By driving the illustrated rotating body d, the efficiency of the work shown in the second figure, which mainly involves turning work, can be improved.

(Embodiment) To explain the case where the embodiment of the present invention is applied to a power shovel, in FIG. The three variable displacement pumps 5 are constant displacement pilot pumps driven by the prime mover 1.

The variable displacement pump 2 has its discharge circuit connected to a hydraulic motor that drives the revolving structure of the power shovel, and the second and third variable displacement pumps 3 and 4 are each connected to a hydraulic cylinder that drives the arm and boom of the power shovel. .

The pump capacity of each variable displacement piston 2, 3, 4 is determined by the control cylinder 7 into which the higher of the self-discharge pressure of each pump extracted by the shuttle valve 6 and the discharge pressure of the pilot pump 5 is introduced; a regulator 10 having a servo valve 9 which is actuated by control pressure introduced from a pilot pump 5 through a throttle 8 to control the operation of the control cylinder 7;
is variably controlled. This regulator 10 is similar to the conventional one, and when the control pressure acting on the servo valve 9 is increased, the control cylinder 7 comes to control the pump displacement even when the pressure from the shuttle valve 6 increases, and the pump discharge pressure By increasing the setting of the pump horsepower expressed as the product of the pump capacity and the pump capacity, and by lowering the control pressure acting on the servo valve 9, the pump horsepower setting becomes smaller.

The total set horsepower of each pump 2, 3, and 4 is set to be smaller than the horsepower of the prime mover 1 to prevent the prime mover 1 from being overloaded, but the set horsepower of each pump 2, 3, and 4 is If it can be changed arbitrarily, the workability of the construction machine can be improved.

Therefore, in the present invention, a first regulating valve 11 configured with a relief valve that regulates the control pressure introduced into the regulator 10a of the first variable displacement pump 2 is provided, and the regulating operation of the first regulating valve 11 is controlled. As the adjustment pressure introduced into the regulator 11a provided for The pressure controlled by the self-discharge pressure is introduced by the first shift valve 13, which operates so that the total force balances the force due to the regulated pressure.

Furthermore, a second regulating valve 14 is provided, which is composed of one relief valve that adjusts the control pressure introduced into each regulator 10b, 10c of the FIG. 2 and third variable displacement pumps 3, 4. First and second regulating pressures are introduced as regulating pressures introduced into the regulator 14a provided for regulating operation, and both regulating pressures are extracted by the shuttle valve 15 from the second or third variable displacement pumps 3, 4. The higher of the two discharge pressures,
The force due to both discharge pressures and the first force acting in opposition to this
The second shift valve 16 operates so that the forces caused by the adjustment pressure and the pilot pressure are balanced.

Furthermore, a hydro switching system is operated by an increase in the discharge pressure of the first variable displacement pump 2 to guide the pilot pressure to the second shift valve 16 and to guide a third regulating pressure to the regulator 14a of the second regulating valve 14. A valve 17 is provided.

The electromagnetic proportional valve 12 controls the pilot pressure to zero when no electric signal is input thereto, and controls the pilot pressure to gradually increase when the input increases.

The first shift valve 13 is constituted by a spool-type proportional valve, and has two stages of areas A and C on which the discharge pressure P1 of the first variable displacement pump ₂ and the pilot pressure _Pp act on one end of the spool. A piston 13a having a pressure receiving surface is provided, and a first regulating valve 11 is provided on the other end side.
The piston 13b has a pressure-receiving surface with an area B on which the adjustment pressure P _s acts, and the relationship between the pilot pressure and each pressure-receiving surface is P _p ×C + P ₁ ×A = P _s ×B, that is, P _s = A/ The pressure of P _s was controlled so that the relationship of B×P ₁ +C/B×P _p always held, and the pressure worked as the regulating pressure of the first regulating valve 11. Therefore, when the pilot pressure P _p is zero, the regulating pressure P _s becomes small, so the first regulating valve 11 is controlled by the regulator 1.
By controlling the control pressure applied to the servo valve 9 of 0a to a high pressure, the set horsepower of the first variable displacement pump 2 increases as shown by curve D in Fig. 5, and when the pilot pressure P _p is increased, the set horsepower increases. On the contrary, it becomes smaller as shown by curve F in FIG.

The second shift valve 16 is also composed of a spool-type proportional valve, and one end of the spool has a discharge pressure P ₂ of the second variable displacement pump 3 and a discharge pressure of the third variable displacement pump 4.
The piston 16a has two stages of pressure receiving surfaces each having an area D on which P ₃ acts, and a pressure receiving surface on the other end having an area 2D on which the first regulating pressure P _t of the second regulating valve 14 acts. and a pressure receiving surface with an area E on which the pilot pressure P _p acts, and the relationship of P ₂ × D + P ₃ × D = 2D × P _t + E × P _p , that is, P _t = (P ₂ + P ₃ )/2−(E/2D)×P _p The pressure of P _t was controlled so that the relationship: )/2−(E/2D)×P p was established, and this pressure acted on the second regulating valve 14 as the first regulating pressure. The second adjustment pressure is the hydro switching valve 17
When the pressure is switched, it acts on the second regulating valve 14, and its magnitude is the same as the first regulating pressure. At this time, if the pilot pressure P _p is zero, the first regulating pressure and the second regulating pressure P _t become high, and therefore the second regulating valve 14 regulates the control pressure acting on the servo valves 10b and 10c low. Therefore, the set horsepower of the second and third variable displacement pumps 3 and 4 is set small as shown by curve E in FIG. Furthermore, as the pilot pressure P _p increases, the first and second adjustment pressures P _t decrease, so the second adjustment valve 14 adjusts the control pressures of the servo valves 10b and 10c to a higher level, thereby increasing the set horsepower of both pumps 3 and 4. It is set high as shown by curve G in FIG.

Furthermore, when the first variable displacement pump 2 becomes unloaded and its discharge pressure decreases, the hydro switching valve 17
stops the conduction between the pilot pressure P _p and the second adjustment pressure P _t ,
Since only the first regulating pressure P _t acts on the second regulating valve 14, the control pressure to the servo valves 10b and 10c is adjusted to a high level, and the second and third variable capacitances are controlled regardless of whether the pilot pressure P _p is generated. The horsepower of pumps 3 and 4 can be set higher.

Therefore, when performing the work shown in the first diagram, an appropriate electrical signal is input to the electromagnetic proportional valve 12,
When performing the work shown in the second diagram, the horsepower setting of the first variable displacement pump 2 is lowered, and the horsepower setting of the second and third variable displacement pumps 3, 4 is simultaneously increased while keeping the total horsepower of all pumps constant. By making the electrical signal input to the electromagnetic proportional valve 12 weak or zero, the set horsepower of the first variable displacement pump 2 is increased, and at the same time the set horsepower of the other pumps 3 and 4 is lowered, thereby reducing the turning power of the rotating body. This makes it possible to increase the productivity and improve work efficiency.

(Effect of the invention) As described above, in the invention, the pilot pressure controlled by the electromagnetic proportional valve is applied to the first shift valve that controls the adjustment pressure to the first adjustment valve, and the first variable displacement pump Since it is made to act on the second shift valve that controls the adjustment pressure to the second adjustment valve via the hydro switching valve which is switched depending on the discharge pressure of
By controlling the input to the electromagnetic proportional valve, the horsepower settings of the first to third variable displacement pumps of the construction machine can be arbitrarily changed, and the workability thereof can be improved.

[Brief explanation of the drawing]

Figures 1 and 2 are side views showing the working status of the construction machine, Figure 3 is a control characteristic diagram of a conventional constant horsepower control device for construction machinery, Figure 4 is a diagram of the conventional device, and Figure 5 is a diagram of the conventional constant horsepower control device. 6 and 6 are horsepower control characteristic diagrams of a variable displacement pump according to the device of the present invention, and FIG. 7 is a diagram of an embodiment of the present invention. 1... Prime mover, 2... First variable displacement pump, 3
... Second variable displacement pump, 4 ... Third variable displacement pump, 5 ... Pilot pump, 7 ... Control cylinder, 8 ... Throttle, 9 ... Servo valve, 10 ... Regulator, 11 ... First Regulating valve, 12... Solenoid proportional valve, 13... First shift valve, 14... Second regulating valve, 16... Second shift valve, 17... Hydro switching valve.

Claims (1)

[Scope of utility model registration request] The construction machine is equipped with three variable displacement pumps, first to third, driven by one prime mover, and the pump capacity of each variable displacement pump is set to the higher of the self-discharge pressure and the pilot pump discharge pressure. In a regulator that has a control cylinder into which pressure is introduced and a servo valve that is operated by the control pressure introduced from the pilot pump through a throttle to control the operation of the control cylinder,
The first variable displacement pump is provided with a first regulating valve that adjusts the control pressure introduced into the regulator thereof, and the first regulating valve has a regulating pressure for its regulating operation.
The force due to the pilot pressure obtained by controlling the pressure from the pilot pump with a solenoid proportional valve and the first
introducing a pressure that controls the self-discharge pressure with a first shift valve that operates so that the total force of the self-discharge pressure of the variable displacement pump balances the force due to the adjusted pressure;
A second regulating valve is provided for regulating the control pressure introduced into each regulator of the second and third variable displacement pumps,
First and second regulating pressures are introduced into the second regulating valve as regulating pressures for its regulating operation, and both regulating pressures are equal to the second regulating pressure.
Alternatively, the higher discharge pressure of the third variable displacement pump is operated so that the force due to both discharge pressures and the force due to the first adjustment pressure and the pilot pressure acting opposite thereto are balanced. The pilot pressure is controlled by a second shift valve to be controlled by a second shift valve, and further actuated by an increase in the discharge pressure of the first variable displacement pump to guide the pilot pressure to the second shift valve and to supply a second regulating pressure to the second regulating valve. A constant horsepower control device for three variable displacement pumps installed on construction machinery, characterized by being equipped with a hydro switching valve that guides the flow of water.