JP3552735B2 - Hydraulic circuit of construction machinery - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a hydraulic circuit optimal for use in a power shovel, for example, a construction vehicle.
[0002]
[Prior art]
The conventional hydraulic circuit shown in FIG. 4 is used for a power shovel, and among a plurality of actuators, actuators a ₁ and a ₂ shown in the figure include a cylinder a ₁ for raising and lowering a boom of the power shovel, and a swing. a swing motor a ₂ for causing movement. The required flow rate to each of the actuators a ₁ and a ₂ is determined by the opening of each spool valve 1. The switching of the spool valve 1 and the adjustment of the opening are performed through manual operation means. A pressure compensating valve 2 is provided in the circuit to the spool valve 1 to prevent the flow rate to the actuators from fluctuating even when the load on each of the actuators a ₁ and a ₂ changes. The flow rate in which this fluctuation is prevented is proportional to the opening of the throttle 3 of the main valve. The switching of the pressure compensating valve 2 and the control of the regulator 4 are performed by the higher pressure in the circuit to the spool valve 1. That is, if the pressure is high, the regulator 4 changes the discharge amount of the variable pump 5 so as not to generate useless power (load sensing circuit). If an excessively high pressure is generated, the relief valve opens to release a part of the hydraulic pressure.
In particular, this circuit is called an after orifice type depending on the position of the throttle valve 3, and when the sum of the required flow rates of the actuators a ₁ and a ₂ exceeds the pump discharge flow capacity, the circuit decreases in proportion to the opening of the throttle 3. It has an anti-saturation function that the flow rate is automatically distributed to the actuators a ₁ and a ₂ .
[0003]
[Problems to be solved by the invention]
For example, FIG. 5 shows the flow rate when the turning operation is performed during the operation of raising the boom of the power shovel. That is, as in FIG. 5, with respect to the boom required flow L ₁ for the operation to raise the boom with cylinder a _1, there is sufficient pump discharge flow capacity L ₂ when not performed yet a pivot. However, start turning operation, the sum of the turning request flow L ₃ and the boom required flow L ₁ because more than pump discharge flow capacity, the flow rate in proportion to the opening degree of the throttle 3 is allocated. Therefore pump discharge flow capacity L _21, L _22, which is distributed to the boom is reduced, this reduction is the shock (boom actual flow rate L ₄₎ in the cylinder a ₁ for happen rapidly.
Further, since the swirling start pressure is high, the overall pump discharge flow capacity (L ₂₁ + L ₂₂ ) is further reduced by the pump horsepower control performed by the equal horsepower curve as shown in FIG. Thus, the shock increases. Moreover, the oil for transmitting the hydraulic pressure to the swivel startup Kirazu through the aperture 3, a portion of the oil for the high-pressure swivel activation pressure is opened to the relief valve 6 to flow the tank T, a sufficient flow rate to flow yet the turning motor a ₂ Absent. Thus the rise of the pivot actual flow rate and L ₅ becomes gentle, so-called relief loss l arises. Because of this relief loss 1, the boom shock is greater. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. When a part of a plurality of actuators is operated and another is started, the relief loss of the actuator that starts the operation is reduced. Accordingly, an object of the present invention is to provide a hydraulic circuit of a construction machine that can prevent the occurrence of a shock of an actuator that has already operated.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a plurality of actuators, each spool valve that determines a required flow rate to the actuator by an opening, an operation procedure for switching the spool valve and adjusting the opening, and A control valve for controlling the degree of opening of a throttle provided in the circuit, a pump for generating hydraulic pressure provided in a circuit to the control valve, a required flow rate detecting means for detecting a required flow rate to the spool valve, and a control valve A first pressure sensor for detecting the pressure on the upstream side of the control valve, a second pressure sensor for detecting the pressure on the downstream side of the control valve, an opening degree sensor for detecting the opening degree of the control valve, and detection signals from the sensors. And a controller that outputs a flow command value that determines the throttle opening of each control valve when the total of the required flow rates of the actuators exceeds the pump discharge flow capacity. , Output a flow command value to decrease the flow rate of each control valve by the excess rate, and when the result is that the flow rate actually passing through the control valve is small, redistribute the small amount as surplus flow to other control valves. It is characterized in that each flow rate command value is corrected as much as possible.
[0005]
[Action]
The controller sums the required flow rates to the respective spool valves detected by the required flow rate detecting means, and calculates the pump discharge flow capacity at that time based on the pressure on the downstream side of the pump detected by the first pressure sensor or the like. When the sum of the required flow rates exceeds the discharge flow capacity of the pump, a flow command value for reducing the flow rate of each control valve by the ratio exceeding the output rate is output, and the throttle opening of each control valve is determined. If the result of passing the oil through the control valve in this way is that the flow rate that actually passes through the control valve is smaller than the flow rate according to the flow rate command value, each of the small quantities is redistributed as an excess flow rate to each control valve as an excess flow rate. Correct the flow command value. By this correction, the flow rate which has conventionally been the relief loss can be redistributed to other control valves as an excess flow rate, and the shock of the actuator during another operation at the start of the operation of the actuator can be eliminated.
[0006]
【Example】
An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a hydraulic circuit according to the present embodiment, which is used for a power shovel. The figure shows two actuators a ₁ and a ₂ , a cylinder a ₁ for vertically moving the boom and a turning motor a ₂ for performing the turning operation. Although other actuators actually exist, they are not shown.
A main valve m of an actuator circuit for supplying hydraulic pressure to each of the actuators a ₁ and a ₂ is provided with a spool valve 12 and a control valve 11 which is a pressure compensating valve.
The spool valve 12 has pilot chambers 12a and 12b provided on both sides thereof connected to a pilot operation valve 20, and is switched and its opening is adjusted according to a pressure signal from the pilot operation valve 20. I have. In addition, centering springs 12c and 12d are provided in the two pilot chambers 12a and 12b, respectively, so that a neutral position shown in the drawing is normally maintained. A meter-out restrictor 12e is provided in the return passage of the spool valve 12 in this manner. Then, the higher one of the pilot chambers 12 a and 12 b is selected by the shuttle valve 21, and the selected pressure is electrically detected by the third pressure sensor 22 and input to the main controller 14.
[0007]
Further, the spool valve 12 is provided with a bleed-off throttle 12f for maximizing the opening at the illustrated neutral position. The brief-off aperture 12f communicates with the main passage m via the parallel passage 23. The main passage m is provided with a load check valve 24 that allows only the flow from the main passage m to the actuator. When the spool valve 12 is at the neutral position, the bleed-off restrictor 12f maintains the opening at the maximum and returns the fluid that has passed through the parallel passage 23 to the tank T.
The control valve 11 has a servo valve mechanism, a spring 15 acting on one side thereof, and an electromagnetic control section 11a on the other side. The electromagnetic controller 11a controls the opening of the control valve 11 by operating the control valve 11 against the spring 15 in proportion to the output signal from the valve controller 16. However, the opening of the control valve 11 is maximized when the control valve 11 is at the normal position shown in the figure. Further, a stroke sensor 17, a first pressure sensor 18, and a second pressure sensor 19 are connected to the valve controller 16.
The stroke sensor 17 detects the stroke of the control valve 11, and substantially detects the opening of the control valve 11 based on the stroke. Further, the first pressure sensor 18 detects the pressure on the upstream side of the control valve 11. Similarly, the second pressure sensor 19 detects the pressure on the downstream side.
As described above, the valve controller 16 receiving the signals from the sensors 17 to 19 controls the opening of the control valve 11 as described above, and transmits the signal from each sensor to the main controller 14 as well.
[0008]
Next, the operation of this embodiment will be described with reference to the flowchart of FIG.
The spool valve 12 is switched by the pressure signal of the pilot operation valve 20 and the opening is adjusted. This pressure signal is input to the main controller 14 via the shuttle valve 21 and the third pressure sensor 22. As described above, the magnitude of this pressure signal is proportional to the opening of the spool valve 12, that is, the required flow rate of the actuators a ₁ and a _2. Therefore, the main controller 14 determines the value of each actuator based on the input pressure signal. The required flow rate can be known, and the sum of these required flow rates is S ₁ . S ₃ and the required flow rate sum, whether or not exceed pump discharge flow capacity at that time is determined. S ₂ pump delivery rate capability, which is calculated by the equal horsepower curve (see FIG. 6) by the pressure or the like on the downstream side of the detected variable pump P for example by the first pressure sensor 18. If beyond the pump discharge flow rate capability the required flow rate sum S _3, for each actuator a _1, a _2, a control valve 11, to create a flow rate command value of the required flow rate itself S _4, the flow rate command value outputs S ₅ that controls the control valve 11 via a valve controller 16.
[0009]
If the total required flow rate exceeds the pump discharge flow capacity, S ₃ , each actuator a ₁ , a ₂
Then, a flow command value is generated for the control valve 11 by multiplying the required flow rate by the correction value in S ₆ . This correction value is determined by pump discharge flow capacity / total required flow rate. This flow rate command value is output and the control valve 11 is controlled via the valve controller 16 in S _7.
. As a result, even when the pump discharge flow capacity is exceeded, the flow rate proportional to the degree of opening of the throttle of the control valve 11 is maintained at each actuator a ₁ , a ₂
Automatically distributed to perform the so-called anti-saturation function.
Next, the pressure on the upstream side of the control valve 11 detected by the first pressure sensor 18, the pressure on the downstream side similarly detected by the second pressure sensor 19, and the pressure detected by the stroke sensor 17 which is an opening degree sensor. S ₈ based on the opening degree of the control valve 11, the main controller 14 for calculating the flow rate that actually passes through the control valve 11. Then, a difference obtained by multiplying the required flow rate by the correction value is obtained by subtracting the actual flow rate at S _9.
. That is, when the swing motor as the actuator a ₂ starts the turning operation, to convey the turning start pressure (high pressure) to the swing motor oil is not flowed yet to swing motor, predetermined to flow take time. During this time, there is a possibility that the oil flows to the relief valve 6 (not shown) and returns to the tank T because the turning start pressure is high. However, according to the present embodiment, the swing motor a ₂
When the oil is about to flow into the oil, the difference is calculated and is regarded as an excess flow rate. S ₉ actuator when starting a plurality overlap in time, the these differences are summed by the surplus flow rate to such an operation start
.
[0010]
Excess flow rate, the actuator in the other operation, in the present embodiment is redistributed into the cylinder a _1, etc. that the operation to raise the boom. This redistribution is performed at the ratio of the flow rate command values already created. The by redistribution, it is output plus been modified S ₁₀ flow rate command value, the control valve 11 via a valve controller 16 is controlled.
Thus, as shown in FIG. 3, when the operation starts of the swing motor as the actuator a ₂ conventionally has been a relief loss l flow as surplus, is performed an operation to raise the other actuator a ₁ That boom Redistributed to cylinders. Thus the flow rate to the cylinder a ₁ Conventional (Fig. 5) rapidly without decrease as the shock is reduced (boom actual flow rate L _4).
[0011]
Although the stroke sensor 17 is used as the opening sensor for detecting the opening of the control valve 11 in the above embodiments, other sensors may be used in other embodiments.
As the required flow rate detecting means, a means for detecting the pressure signal of the pilot operated valve 20 via the shuttle valve 21 and the third pressure sensor 22 is used. In other embodiments, an electric signal is used instead of the pilot operated valve 20. The required flow rate may be directly detected by an electric signal using a simple operating device.
In the above embodiments, the actuators a ₁ and a ₂ are a cylinder and a swing motor. However, in other embodiments, other actuators may be provided. Is also possible. That is, if a relief loss occurs at the start of operation even if the motor is not a swing motor, a shock is applied to another actuator, and the present invention is effectively implemented to prevent the shock.
[0012]
【The invention's effect】
As described above, according to the hydraulic circuit for a construction machine of the present invention, when the operation of the actuator is started, the excess flow, which has conventionally been a relief loss, is redistributed to another operating actuator. The shock caused by the decrease in the flow rate of the actuator during the operation can be eliminated.
[Brief description of the drawings]
FIG. 1 is an overall view of a hydraulic circuit according to one embodiment of the present invention.
FIG. 2 is a flowchart illustrating control of the hydraulic circuit of FIG. 1;
FIG. 3 is a diagram for explaining that a shock caused by a relief loss can be prevented by the control of FIG. 2;
FIG. 4 is a conventional hydraulic circuit diagram.
FIG. 5 is a diagram illustrating a shock caused by a relief loss, which is a problem of the hydraulic circuit of FIG. 4;
FIG. 6 is a diagram showing an equal horsepower curve of the motor of FIG. 4;
[Explanation of symbols]
a ₁ actuator a ₂ actuator 11 control valve 11 a electromagnetic control unit 12 spool valve 12 a pilot chamber 12 b pilot chamber 12 f bleed-off throttle 14 main controller 15 spring 16 valve controller 17 stroke sensor 18 first pressure sensor 19 second pressure sensor 20 pilot operation Valve 12c Centering spring 12d Centering spring 12e Meter-out throttle 21 Shuttle valve 22 Third pressure sensor 23 Parallel passage m Main passage 24 Load check valve T Tank

Claims (1)

A plurality of actuators, each spool valve that determines a required flow rate to the actuator by an opening degree, operating means for switching the spool valve and adjusting the opening degree, and controlling an opening degree of a throttle provided in a circuit to the spool valve. A control valve, a pump provided in a circuit to the control valve to generate hydraulic pressure, a required flow rate detecting means for detecting a required flow rate to the spool valve, and a first pressure sensor for detecting a pressure on an upstream side of the control valve. A second pressure sensor for detecting a pressure on the downstream side of the control valve, an opening sensor for detecting an opening of the control valve, and a detection signal from each of the sensors being inputted to determine a throttle opening of each control valve. A controller that outputs a flow command value, and when the total required flow of each actuator exceeds the pump discharge flow capacity, the controller reduces the flow rate of each control valve by an excess ratio. The flow command value to be output is output, and when the result is that the flow rate actually passing through the control valve is small, each flow rate command value is corrected so as to redistribute the small amount as surplus flow to other control valves. And the hydraulic circuit of construction machinery.

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