CONTROL UNIT FOR UPPER SWIVEL BODY OF HYDRAULIC EXCAVATOR

Abstract

 This invention relates to a control unit for an upper swivel body of a hydraulic excavator which is used in order to prevent an abrupt pressure rise in a hydraulic line and to make a smooth swivel control when the upper swivel body equipped with a driver's cabin and a working machine and having a large inertia is accelerated or decelerated. To this end, pressure control valves (10), (11) controlled together with proportional solenoid valves (8), (8a) by a controller (7) are connected to a discharge line and return line of a hydraulic pump (1) so as to control an input pressure and an output pressure of an upper swivel body driving motor (3) when the motor rotates. Particularly, one of the pressure control valves (10) controls and increases the driving pressure of the driving motor (3) in accordance with a speed increase signal outputted from the controller (7) and the other pressure control valve (11) controls and decrease the braking pressure of the driving motor (3) in accordance with a speed decrease signal outputted from the controller (7).

Description

TECHNICAL FILED

[0001] This invention relates to a hydraulic drive unit for an upper swivel body equipped with a driver's cabin and working machine of a hydraulic excavator, and more specifically, to a control unit for an upper swivel body of a hydraulic excavator by which an abrupt pressure rise in a hydraulic line is prevented when the upper swivel body having a large inertia is accelerated or decelerated.

BACKGROUND ART

[0002] As shown in Figure 3, a control unit for an upper swivel body of this kind of a hydraulic excavator is arranged such that a port of an upper swivel body driving motor 3 is connected to the discharge line of a hydraulic pump 1 through a meter-in-poppet valve 2 and the other port of the driving motor 3 is connected to the return line to a tank 5 through a meter-out-poppet valve 4. Further, the other port of the driving motor 3 is connected to the discharge line of the hydraulic pump 1 through a meter-in-poppet valve 12 and the one port of the driving motor 3 is connected to the return line to the tank 5 through a meter-out-poppet valve 15. The pilot line of the meter-in-poppet valve 2 is formed from the upstream side to the downstream side thereof through an orifice 6 and a proportional solenoid valve 8 controlled by a controller 7, and the pilot line of the meter-out-poppet valve 4 is formed from the upstream side to the downstream side thereof through an orifice 9 and a proportional solenoid valve 8a controlled by the controller 7. On the other hand, the pilot line of the meter-in-poppet valve 12 is formed from the upstream to the downstream thereof through an orifice 13 and a proportional solenoid valve 14 controlled by the controller 7, and the pilot line of the meter-out-poppet valve 15 is formed from the upstream side to the downstream side thereof through an orifice 16 and a proportional solenoid valve 14a controlled by the controller 7.

[0003] When the upper swivel body arranged as described above is to be swung to the right, a swinging speed signal is output to the solenoid A of the proportional solenoid valves 8, 8a from the controller 7 in accordance with an actuated amount of an electric lever 17, so that a pilot flow of fluid having an amount corresponding to the signal is produced from the upstream side to the downstream side of the meter-in-poppet valve 2. Accordingly, a pressure difference corresponding to the above pilot flow is produced between the upstream and the downstream of the meter-in-poppet valve 2 by the orifice 6, whereby a degree of opening of the meter-in-poppet valve 2 is determined. An amount of fluid passing through the meter-in-poppet valve 2 is determined in accordance with the degree of opening. Further, a pilot flow of fluid having an amount corresponding to the above signal is produced between the upstream and the downstream of the meter-out-poppet valve 4. Accordingly, a pressure difference corresponding to the above pilot flow is produced between the upstream and the downstream of the meter-out-poppet valve 4 by the orifice 9, whereby a degree of opening of the meter-out-poppet valve 4 is determined. An amount of fluid passing through the meter-out-poppet valve 4 is determined in accordance with the degree of opening. A swinging speed of the driving motor 3 to the right is determined by the amount of fluid passing through the meter-in-poppet valve 2 and the amount of fluid passing through the meter-out-poppet valve 4.

[0004] When the upper swivel body is to be swung to the left, a swinging speed signal is output to the solenoid B of the proportional solenoid valves 14, 14a from the controller 7 in accordance with an actuated amount of the electric lever 17, so that a pilot flow of fluid having an amount corresponding to the signal is produced from the upstream side to the downstream side of the meter-in-poppet valve 12 and between the upstream and the downstream of the meter-out-poppet valve 15. Accordingly, a swinging speed of the upper swivel body driving motor 3 to the left is determined in the same manner as that of the above swinging to the right. On the other hand, since signals corresponding to the signals output to the solenoids A and B are also output to the discharge amount control unit 1a of the hydraulic pump 1 from the controller 7, the hydraulic pump 1 is controlled to discharge fluid the amount of which corresponds to the amount of fluid passing thorough the meter-in-poppet valves 2, 12 and the meter-out-poppet valves 4, 15.

[0005] Since, however, the upper swivel body has a large inertial, a driving hydraulic pressure or braking hydraulic fluid pressure is abruptly risen when the upper swivel body driving motor 3 is accelerated or decelerated regardless of that the upper swivel body swings to the right or to the left, operating fluid returns to the tank through maximum hydraulic pressure regulating valves 18, 19, and thus the speed of the driving motor 3 is decreased by the amount of the returned operating fluid. Therefore, when an operator controls the driving motor 3, the operator must actuate the electric lever additionally, taking into consideration the amount of the operating fluid returning to the tank through the maximum hydraulic pressure regulating valves 18, 19. Since the amount of the electric lever to be additionally actuated is not uniform depending upon a speed of the upper swivel body and the like, the operator needs considerable practice. Further, there is a problem in that since the driving hydraulic pressure or braking hydraulic pressure cannot be controlled, it is abruptly risen when the upper swivel body is accelerated or decelerated so that smooth acceleration or deceleration cannot be obtained, and thus swinging controllability is deteriorated. Taking the above into consideration, an object of this invention is to provide a control unit for an upper swivel body of a hydraulic excavator by which the upper swivel body driving motor 3 can be smoothly controlled in acceleration and deceleration, an operator is not required to have considerable practice, and swinging can be easily controlled.

DISCLOSURE OF THE INVENTION

[0006] A control unit for an upper swivel body of a hydraulic excavator according to this invention comprises an electro-hydraulic circuit formed by connecting the discharge line of a hydraulic pump to the inlet of an upper swivel body driving motor through a meter-in-poppet valve the degree of opening of which is controlled by a proportional solenoid valve controlled by a controller and connecting the outlet of the driving motor to the return line to a tank through a meter-out-poppet valve the degree of opening of which is controlled by a proportional solenoid valve controlled by the controller, wherein a pair of pressure control valves controlled together with the proportional solenoid valves by the controller are connected to the discharge line and the return line, respectively so as to control an input pressure and an output pressure of the driving motor when the driving motor rotates to the right. In particular, one of the pressure control valves controls and increases the driving pressure of the upper swivel body driving motor in accordance with a speed increase signal of the driving motor output from the controller, and the other pressure control valve controls and decreases the braking pressure of the driving motor in accordance with a speed decrease signal of the driving motor output from the controller.

[0007] Further, in a control unit for an upper swivel body of a hydraulic excavator comprising an electro-hydraulic circuit formed by connecting the discharge line of a hydraulic pump to the outlet of an upper swivel body driving motor through a meter-in-poppet valve the degree of opening of which is controlled by a proportional solenoid valve controlled by a controller and connecting the inlet of the driving motor to the return line to a tank through a meter-out-poppet valve the degree of opening of which is controlled by a proportional solenoid valve controlled by the controller, a pair of pressure control valves controlled together with the proportional solenoid valves by the controller are connected to the discharge line and the return line, respectively so as to control an input pressure and an output pressure of the driving motor when the driving motor rotates to the left (reversely).

[0008] When the upper swivel body driving motor is swung to the right or to the left in response to a signal from the controller and accelerated or decelerated, the driving pressure or the braking pressure in the driving line of the driving motor is risen, but since the value thereof is controlled by the pressure control valves, an abrupt rise of the pressure can be prevented, whereby the upper swivel body driving motor can be smoothly controlled. Further, since the driving pressure or the braking pressure of the upper swivel body is controlled in accordance with the amount of acceleration or deceleration thereof, the amount of operation carried out to the upper swivel body by an operator is made uniform and thus the operator need not to have considerable practice.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] 

Figure 1 is an electro-hydraulic circuit diagram showing an embodiment of this invention;

Figure 2 is a diagram showing the relationship between a degree of opening of a poppet valve and a driving pressure or braking pressure in Figure 1; and

Figure 3 is an electro-hydraulic circuit diagram showing a prior art.

BEST MODE OF CARRYING OUT THE INVENTION

[0010] An embodiment of this invention will be described in detail with reference to Figures 1 and 2. Figure 1 is an electro-hydraulic circuit diagram showing the embodiment of this invention, wherein the same numerals as used in Figure 3 showing the conventional electro-hydraulic circuit are used to designate components similar to those used in Figure 3 and they are not described further. In Figure 1, the high pressure port of a pressure control valve 11 is connected between an orifice 9 equipped with the pilot line of a meter-out-poppet valve 4 and the proportional solenoid valve 8a of a meter-in-poppet valve 2, and the low pressure port of the pressure control valve 11 is connected to the return line to a tank 5. On the other hand, the high pressure port of a pressure control valve 10 is connected between an orifice 16 equipped with the pilot line of a meter-out-poppet valve 15 and the proportional solenoid valve 14a of a meter-in-poppet valve 12, and the low pressure port of the pressure control valve 10 is connected to the return line to the tank 5.

[0011] When an upper swivel body driving motor 3 is to be swung to the right and accelerated, an acceleration signal corresponding to a desired swinging speed of the driving motor 3 is output from a controller 7 to the solenoid A for the proportional solenoid valve 8 of the meter-in-poppet valve 2 and a signal is output to the solenoid C of the pressure control valve 10 to provide a set pressure corresponding to a degree of opening signal of the poppet valve shown in Figure 2. Although the driving pressure of the driving motor 3 is risen by the inertia of the upper swivel body at this time, the hydraulic pressure thereof is set to be gradually increased in accordance with the degree of opening of the meter-in-poppet valve 2 as shown in Figure 2, and thus an abrupt rise of the driving pressure of the driving motor 3 can be prevented. On the other hand, when the driving motor 3 is to be decelerated, a deceleration signal corresponding to a desired swinging speed in the driving motor 3 is output from the controller 7 to the solenoid A for the proportional solenoid valve 8a of the meter-out-poppet valve 9 and a signal is output to the solenoid D of the pressure control valve 11 to provide a set pressure corresponding to a degree of opening signal of the poppet valve shown in Figure 2. Although the braking pressure of the driving motor 3 is risen by the inertia of the upper swivel body at this time, the hydraulic pressure thereof is set to be gradually increased in accordance with the degree of opening of the meter-out-poppet valve 9 as shown in Figure 2, and thus an abrupt rise of the braking pressure of the driving motor 3 can be prevented. Further, since an amount to actuate the upper swivel body is made uniform, an operator can easily perform a swinging operation.

[0012] When the driving motor 3 is be swung to the left (reversely) and accelerated or decelerated, prescribed signals are output to the meter-in-poppet valve 12, the meter-out-poppet valve 15, the solenoid B for the proportional solenoid valves 14, 14a, the solenoids C, D for the pressure control valves 10, 11 to thereby control an abrupt rise of the driving pressure or braking pressure of the driving motor 3, as in the acceleration or deceleration when the upper swivel body is swung to the right. Further, since an amount to operate the upper swivel body is made uniform, an operator can easily perform an swinging operation.

[0013] Because of the above description, shock conventionally caused to a hydraulic excavator when it swings can be decreased and an operator is not required to have considerable practice to perform a swinging operation.

INDUSTRIAL APPLICABILITY

[0014] This invention is applied to a hydraulic drive unit for an upper swivel body equipped with a driver's cabin and working machine of a hydraulic excavator, and particularly useful as a control unit to prevent an abrupt pressure rise in a hydraulic line which is caused when the upper swivel body is accelerated or decelerated.

Claims

1. A control unit for an upper swivel body of a hydraulic excavator, comprising an electro-hydraulic circuit formed by connecting the discharge line of a hydraulic pump (1) to the inlet of an upper swivel body driving motor (3) through a meter-in-poppet valve (2) the degree of opening of which is controlled by a proportional solenoid valve (8) controlled by a controller (7) and connecting the outlet of said driving motor (3) to the return line to a tank (5) through a meter-out-poppet valve (4) the degree of opening of which is controlled by a proportional solenoid valve (8a) controlled by the controller (7), wherein pressure control valves (10), (11) controlled together with said proportional solenoid valves (8), (8a) by said controller (7) are connected to said discharge line and said return line, respectively so as to control an input pressure and an output pressure of said driving motor (3) when said driving motor (3) rotates to the right.

2. A control unit for an upper swivel body of a hydraulic excavator according to claim 1, wherein one of said pressure control valves (10) controls and increases the driving pressure of said upper swivel body driving motor (3) in accordance with a speed increase signal of said driving motor (3) output from said controller (7), and the other pressure control valve (11) controls and decreases the braking pressure of said driving motor (3) in accordance with a speed decrease signal of said driving motor (3) output from said controller (7).

3. A control unit for an upper swivel body of a hydraulic excavator, comprising an electro-hydraulic circuit formed by connecting the discharge line of a hydraulic pump (1) to the outlet of an upper swivel body driving motor (3) through a meter-in-poppet valve (12) the degree of opening of which is controlled by a proportional solenoid valve (14) controlled by a controller (7) and connecting the inlet of said driving motor (3) to the return line to a tank (5) through a meter-out-poppet valve (15) the degree of opening of which is controlled by a proportional solenoid valve (14a) controlled by the controller (7), wherein pressure control valves (10), (11) controlled together with said proportional solenoid valves (14), (14a) by said controller (7) are connected to said return line and said discharge line, respectively so as to control an input pressure and an output pressure of said driving motor (3) when said driving motor (3) rotates to the left (reversely).

4. A control unit for an upper swivel body of a hydraulic excavator according to claim 3, wherein one of said pressure control valves (11) controls and increases the driving pressure of said upper swivel body driving motor (3) in accordance with a speed increase signal of said driving motor (3) output from saidcontroller (7), and the other pressure control valve (10) controls and decreases the braking pressure of said driving motor (3) in accordance with a speed decrease signal of said driving motor (3) output from said controller (7).

Drawing