Pilot Pressure Control Device

Abstract

To provide a pilot pressure control device capable of securing pilot pressure with an inexpensive configuration. The device is equipped with a controller (26) that controls to narrow the opening of a spool (8) that is causing the drop in pump pressure when the pump pressure drops below a predetermined pressure due to the drive of a fluid pressure actuator (4). The device can hold pump pressure with an inexpensive configuration without increasing the size of an accumulator (22) for accumulating pressure, and can secure pilot pressure from this pump pressure by a pilot circuit (17).

Description

[Technical Field]

[0001] The present invention relates to a pilot pressure control device for controlling a pilot pressure of a fluid pressure circuit. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there is a hydraulic circuit that generates pilot pressure without requiring a pilot pump by reducing a portion of the oil discharged from a main pump to a set pressure using a pressure reducing valve.

[0003] In such a configuration, there is a concern that if the pressure of the oil discharged from the main pump drops, it may become impossible to maintain the required pilot pressure.

[0004] Therefore, it is known that by installing an accumulator, even if the pressure of the main pump drops below the required pilot pressure, the required pilot pressure can be maintained for a short period of time using the pressure stored in the accumulator (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-20903 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the case of the above-described configuration, in order to extend the time for which the pilot pressure is held, it is necessary to increase the size of the accumulator, which leads to an increase in the size of the system and an increase in costs.

[0007] The present invention has been made in view of the above points, and has as its object to provide a pilot pressure control device that can ensure pilot pressure with an inexpensive configuration. [Means for solving the problem]

[0008] The invention described in claim 1 is a control valve Displacement of each spool The working fluid discharged from the pump is controlled by each A pilot pressure control device controls the pilot pressure of a fluid pressure circuit that includes a main circuit that drives a fluid pressure actuator and a pilot circuit that supplies a pressure obtained by reducing and controlling the pressure of a portion of the working fluid discharged from a pump as a pilot pressure source. When the pump pressure drops below a predetermined pressure due to the driving of the fluid pressure actuator, the pilot pressure control device controls the pilot pressure of the fluid pressure circuit. Control valve This is a pilot pressure control device equipped with a controller that controls the spool opening to narrow.

[0009] The invention of claim 2 is characterized in that the controller in the pilot pressure control device of claim 1 detects the cause of the drop in pump pressure when the pump pressure is below a predetermined pressure due to the driving of the fluid pressure actuator and continues for a predetermined time or more. Control valve This is a pilot pressure control device that controls the spool opening to narrow it.

[0010] The invention of claim 3 is a pilot pressure control device according to claim 1 or 2, further comprising a pressure sensor that detects the fluid pressure of the fluid pressure actuator, and the controller identifies the spool that is causing the drop in pump pressure based on the pressure detected by the pressure sensor. [Effects of the Invention]

[0011] According to the invention of claim 1, the pump pressure can be maintained with an inexpensive configuration without increasing the size of the accumulator for accumulating pressure, and the pilot pressure can be secured from this pump pressure by the pilot circuit.

[0012] According to the invention of claim 2, it is possible to prevent the controller from frequently throttling the opening of the spool in response to instantaneous changes in pump pressure.

[0013] According to the invention as set forth in claim 3, it is possible to control the pump pressure and the pilot pressure with high precision. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a circuit diagram showing an embodiment of a pilot pressure control device according to the present invention. [Figure 2] FIG. 2 is a control block diagram of the pilot pressure control device. [Figure 3] 4 is a flowchart showing a control method performed by the pilot pressure control device. [Figure 4] 1A is a graph showing an example of changes in pump pressure and actuator fluid pressure in a fluid pressure circuit equipped with the same pilot pressure control device, and FIG. 1B is a graph showing an example of a lever operation that causes the pressure change in FIG. 1A. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described in detail below based on an embodiment shown in FIGS.

[0016] In FIG. 1, reference numeral 1 denotes a fluid pressure circuit. The fluid pressure circuit 1 includes a pump 2. The pump 2 is operated by a prime mover 3 such as an engine or a motor, and is a main pump that supplies working fluid to the fluid pressure circuit 1. In other words, the pump 2 converts mechanical power into fluid pressure power. The fluid pressure power converted by the pump 2 is converted back into mechanical power by a fluid pressure actuator 4. Any number of fluid pressure actuators 4 may be used. In FIG. 1, the fluid pressure actuators 4 are shown as examples of a fluid pressure motor 4a and a fluid pressure cylinder 4b. The working fluid supplied by the pump 2 to the fluid pressure circuit 1 is stored in a tank (not shown). The tank receives return fluid from the fluid pressure circuit 1.

[0017] The fluid pressure circuit 1 includes a main circuit 6 that operates the fluid pressure actuator 4 to obtain power by controlling the flow rate and direction of the working fluid discharged from a pump 2 operated by a prime mover 3 and supplied to the fluid pressure actuator 4 using a control valve 5 in response to the operation of an operating body such as a lever or pedal by an operator.

[0018] The control valve 5 includes a pump line 7, which is a discharge line of the pump 2. The pump 2 is connected to a tank via the pump line 7. A number of spools 8 corresponding to the number of fluid pressure actuators 4 are arranged in the pump line 7. The spools 8 and the fluid pressure actuators 4 are connected by a pair of connecting passages 9, 10, and the direction and flow rate of the working fluid supplied to the fluid pressure actuators 4 are controlled according to the direction and amount of displacement of the spool 8.

[0019] The spool 8 has its displacement direction and displacement amount, i.e., its opening (valve opening), controlled in response to pilot pressure supplied in response to the operation of an operator's operating body. This pilot pressure is supplied from a pilot circuit 17. The pilot circuit 17 branches off from the pump line 7 and supplies a portion of the working fluid discharged from the pump 2, which is operated by the prime mover 3, after reducing and controlling the pressure. As an example, the pilot circuit 17 includes a pressure-reducing valve 20 that reduces the pressure of the working fluid discharged from the pump 2 to generate pilot primary pressure, a check valve 21 that maintains the pilot primary pressure, an accumulator 22 that smooths the pilot primary pressure, and a solenoid valve (solenoid proportional valve) 23 that controls the pilot pressure (pilot secondary pressure) acting on the spool 8. The pressure-reducing valve 20, check valve 21, and accumulator 22 are sequentially arranged in a pilot line 24 that branches off from the pump line 7, and the pilot line 24 branches off to solenoid valves 23 that are arranged at one end and the other end of each spool 8. That is, the hydraulic oil discharged from the pump 2 is decompressed by the pressure reducing valve 20 and distributed to each solenoid valve 23 that controls the stroke of each spool 8.

[0020] The pilot pressure set by this pilot circuit 17 is set via a controller (ECM) 26. The controller 26 is electrically connected to the solenoid of the solenoid valve 23. In response to an operation by an operator or the like, the controller 26 outputs a control signal, which is an electric signal, to the solenoid of the solenoid valve 23, and the amount of displacement of the spool 8 is controlled to increase or decrease in response to an increase or decrease in the amount of electricity (current) supplied to the solenoid of the solenoid valve 23 by this control signal.

[0021] As shown in FIGS. 1 and 2, the controller 26 is electrically connected to a pump pressure sensor 28 that detects the pump pressure, and a pressure sensor 29 that detects the fluid pressure of the fluid pressure actuator 4.

[0022] The pressure sensor 29 detects the load pressure when the fluid pressure motor 4a rotates in one direction and the other direction (forward and reverse rotation), as well as the rod pressure and head pressure of the fluid pressure cylinder 4b.

[0023] When the pump pressure drops below a predetermined pressure due to the driving of the fluid pressure actuator 4, the controller 26 controls the solenoid valve 23 to narrow the opening of the spool 8, which is causing the drop in pump pressure. The controller 26, pump pressure sensor 28, pressure sensor 29, and solenoid valve 23 together make up a pilot pressure control device 30.

[0024] In this embodiment, the fluid pressure circuit 1 is a hydraulic circuit used in a work machine such as a hydraulic excavator. In this case, the fluid pressure actuator 4 has a fluid pressure motor 4a used for driving and rotating the work machine, and a fluid pressure cylinder 4b used for operating the work equipment including a boom, arm (stick), bucket, etc.

[0025] Next, the control of the pilot pressure in the illustrated embodiment will be described in detail with reference to the control block diagram shown in FIG. 2 and the flowchart shown in FIG.

[0026] In summary, the controller 26 monitors the pump pressure and actuator pressure using the pump pressure sensor 28 and pressure sensor 29, respectively, and when the pump pressure drops below the required pilot pressure due to the operation of the fluid pressure actuator 4, it identifies the spool 8 that controls the direction and flow rate of the working fluid to the fluid pressure actuator 4, which is the cause or main factor of the drop in pump pressure, and generates a control signal to narrow the opening of that spool 8 and outputs it to the solenoid of the solenoid valve 23 corresponding to that spool 8, thereby suppressing the drop in pump pressure and maintaining the pilot pressure.

[0027] More specifically, first, the controller 26 checks the pump pressure based on the output of the pump pressure sensor 28 as shown in FIG. 2, and determines the pump pressure state.

[0028] Specifically, in step S1 shown in FIG. 3, the controller 26 determines whether the pump pressure is equal to or lower than a predetermined pressure. The predetermined pressure is a predetermined required pilot pressure, such as 4 MPa. If the controller 26 determines in step S1 that the pump pressure is equal to or lower than the predetermined pressure (YES in the flowchart), the controller 26 determines in step S2 whether a predetermined time has elapsed. The predetermined time is set based on the discharge time of the accumulator 22. If the controller 26 determines in step S2 that the predetermined time has elapsed (YES in the flowchart), that is, if the controller 26 determines that the pump pressure has remained equal to or lower than the predetermined pressure for a predetermined time or longer, the controller 26 proceeds to step S3. On the other hand, if the controller 26 determines in step S1 that the pump pressure is not equal to or lower than the predetermined pressure (NO in the flowchart), or if the controller 26 determines in step S2 that the predetermined time has not elapsed (NO in the flowchart), the controller 26 returns to step S1.

[0029] Next, as shown in Fig. 2, the controller 26 checks the fluid pressure (load pressure), i.e., the actuator pressure, of the fluid pressure actuators 4 based on the output of the pressure sensor 29, and determines the actuator pressure state. Specifically, in step S3 shown in Fig. 3, the controller 26 detects the fluid pressure (load pressure) of each fluid pressure actuator 4 from the output of the pressure sensor 29, and determines whether or not each fluid pressure is equal to or lower than a predetermined threshold pressure set in advance.

[0030] As shown in FIG. 2, the controller 26 controls the actuator based on the pump pressure state and the actuator pressure state.

[0031] Specifically, based on the actuator pressure confirmed in step S3 shown in FIG. 3, in step S4, the controller 26 identifies the target spool for controlling the direction and flow rate of the working fluid to the fluid pressure actuator 4 that is the cause or main factor of the drop in pump pressure.

[0032] Subsequently, in step S5, the controller 26 changes the command value, i.e., the control signal, sent to the solenoid of the solenoid valve 23 of the target spool 8 identified in step S4, thereby throttling the opening of the target spool 8 and increasing the actuator pressure of the fluid pressure actuator 4. At this time, the spool 8 is throttled smoothly to ensure smooth operation. For example, the controller 26 sets the command value sent to the solenoid of the solenoid valve 23 so that the spool 8 is throttled over a predetermined time period that does not cause a sudden change in pressure, so that the operation of the target fluid pressure actuator 4 does not suddenly fluctuate. At this time, although the throttle operation of the spool 8 results in some speed sacrifice for the target fluid pressure actuator 4, the controller 26 limits the speed reduction to a level that does not cause discomfort or stress to the operator.

[0033] Thereafter, the controller 26 checks the pump pressure based on the output of the pump pressure sensor 28 and determines the pump pressure state.

[0034] Specifically, in step S6, the controller 26 determines whether the pump pressure is equal to or greater than a predetermined pressure. The predetermined pressure is a predetermined required pilot pressure, e.g., 4 MPa. This predetermined pressure may be the same as or different from the predetermined pressure used in the determination in step S1. If the controller 26 determines in step S6 that the pump pressure is equal to or greater than the predetermined pressure (YES in the flowchart), the controller 26 determines in step S7 whether a predetermined time has elapsed. The predetermined time is set according to the time it takes for pressure to be re-accumulated in the accumulator 22 and may be the same as or different from the predetermined time used in the determination in step S2. If the controller 26 determines in step S7 that the predetermined time has elapsed (YES in the flowchart), that is, if the controller 26 determines that the pump pressure has remained equal to or greater than the predetermined pressure for a predetermined time or longer, the controller 26 terminates control. On the other hand, if the controller 26 determines in step S6 that the pump pressure is not equal to or greater than the predetermined pressure (NO in the flowchart) or if the controller 26 determines in step S7 that the predetermined time has not elapsed (NO in the flowchart), the controller 26 returns to step S6.

[0035] 4(a) and 4(b), when a work machine is traveling due to operation inputs OP1 and OP2 from the left and right travel pedals (when not zero in the diagram), if full operation input OP3 for arm-out (stick-out) of the work machine is input, the rod pressure PA and pump pressure PP of the fluid pressure actuator 4 suddenly drop significantly and fall below a predetermined pressure PTH. In this embodiment, when the duration T of this state exceeds a predetermined time, the rod pressure PA and pump pressure PP of the fluid pressure actuator 4 are restored to above the predetermined pressure PTH by narrowing the opening of the spool 8 that is causing this, in this example, the spool 8 that controls the direction and flow rate of the working fluid supplied to the arm-operating fluid pressure actuator 4.

[0036] That is, according to one embodiment, when the pump pressure drops below a predetermined pressure due to the driving of the fluid pressure actuator 4, the controller 26 controls the opening of the spool 8, which is the cause of the drop in pump pressure, to narrow. This makes it possible to maintain the pump pressure without increasing the size of the accumulator 22 for accumulating pressure, i.e., with an inexpensive configuration, and the pilot pressure can be secured from this pump pressure by the pilot circuit 17.

[0037] At this time, when the driving of the fluid pressure actuator 4 causes the pump pressure to remain below a predetermined pressure for a predetermined period of time or more, the controller 26 controls the opening of the spool 8, which is causing the drop in pump pressure, to be narrowed, thereby preventing the controller 26 from frequently narrowing the opening of the spool 8 in response to instantaneous changes in pump pressure.

[0038] Furthermore, when narrowing the opening of the spool 8, narrowing it smoothly makes the operation of the fluid pressure actuator 4 smoother and prevents the operator from feeling uncomfortable with the operation of the fluid pressure actuator 4.

[0039] The controller 26 identifies the spool 8 that is causing the drop in pump pressure based on the fluid pressure of the fluid pressure actuator 4 detected by the pressure sensor 29, making it possible to control the pump pressure and pilot pressure with high accuracy. In addition, the spool 8 to be controlled can be easily detected by monitoring the pump pressure and the fluid pressure of the fluid pressure actuator 4, simplifying the adjustment of control parameters.

[0040] Furthermore, even if the pump pressure exceeds the predetermined pressure, control continues until the pressure is again accumulated in the accumulator 22, so that the pump pressure can be prevented from dropping below the predetermined pressure again immediately after it has exceeded the predetermined pressure.

[0041] In the above embodiment, the controller 26 controls the opening of the spool 8, which is the main cause of the pump pressure dropping below a predetermined pressure, to be narrowed. However, if the drive of a plurality of fluid pressure actuators 4 is causing the drop in pump pressure, the controller 26 is not limited to controlling the opening of the single spool 8 that is the main cause to be narrowed, and may control the opening of at least one of the plurality of spools 8 to be narrowed.

[0042] Furthermore, a solenoid valve 23 is provided to control the opening amount of the spool 8, and the controller 26 generates a control signal for the solenoid valve 23, thereby making it possible to adjust the opening amount of the spool 8. However, this is not limiting, and the spool 8 itself may be an electromagnetic proportional valve, and the controller 26 may generate a control signal for the spool 8, thereby making it possible to directly adjust the opening amount of the spool 8. [Industrial Applicability]

[0043] The present invention has industrial applicability to businesses involved in the manufacturing and sales of fluid pressure circuits and work machines equipped with such circuits.

Claims

1. A pilot pressure control device for controlling a pilot pressure of a fluid pressure circuit including: a main circuit that controls the working fluid discharged from the pump by displacing each spool of a control valve to drive each fluid pressure actuator; and a pilot circuit that supplies a pressure obtained by reducing and controlling a portion of the working fluid discharged from the pump as a pilot pressure source, When the pump pressure drops below a predetermined pressure due to the drive of the fluid pressure actuator, the controller controls the spool opening of the control valve that is causing the drop in pump pressure to narrow. A pilot pressure control device characterized by:

2. When the pump pressure remains below a predetermined pressure for a predetermined period of time due to the drive of the fluid pressure actuator, the controller controls the spool opening of the control valve that is causing the drop in pump pressure to narrow.

2. The pilot pressure control device according to claim 1.

3. a pressure sensor for detecting a fluid pressure of the fluid pressure actuator; The controller identifies the spool that is causing the drop in pump pressure based on the pressure detected by the pressure sensor.

3. The pilot pressure control device according to claim 1 or 2.

Images