Relief pressure control device

Abstract

Provided is a relief pressure control device that can easily set the relief pressure and that reduces power consumption. The relief pressure control device (8) includes a relief valve (5) whose set pressure is varied according to the amount of electricity supplied thereto, and a controller (7) that sets at least one relief pressure of the fluid pressure circuit (1) by controlling the amount of electricity supplied to the relief valve (5). The controller (7) supplies electricity to the relief valve (5) when the pump pressure exceeds a predetermined threshold pressure that is lower than the set pressure of the relief valve (5) in a non-energized state.

Description

[Technical field]

[0001] The present invention relates to a relief pressure control device that controls the relief pressure of a fluid pressure circuit. [Background technology]

[0002] 2. Description of the Related Art Conventionally, in a hydraulic circuit system, which is a fluid pressure circuit used in a work machine or the like, a main relief valve is provided in a control valve to limit an excessive pressure rise in the system.

[0003] It may be useful to have multiple relief pressure settings for the hydraulic system depending on the application. For example, it is useful to be able to set different relief pressures for travel and work equipment operation, or for normal mode and lifting mode (heavy lift mode).

[0004] To address this issue, it is possible to use a relief valve that can switch the set pressure in two stages. Generally, a two-stage adjustable main relief valve or an on-off valve is used.

[0005] However, when these valves are used, there are problems in that the adjustment becomes complicated, for example, pressure adjustment work needs to be performed multiple times, and the component configuration and system configuration also become complicated.

[0006] In this regard, there is known a system that uses an electromagnetic relief valve whose set pressure can be set according to the amount of current flow, and makes it possible to adjust the set pressure of the electromagnetic relief valve according to a signal from a controller, thereby making it possible to switch between multiple relief pressures (see, for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 2732922 [Patent Document 2] Patent No. 4458083 [Patent Document 3] Patent No. 6347936 [Patent Document 4] Japanese Patent Application Publication No. 7-36548 Summary of the Invention [Problem to be solved by the invention]

[0008] In a hydraulic circuit system using an electromagnetic relief valve as described above, it is desirable to reduce power consumption.

[0009] The present invention has been made in consideration of the above points, and has an object to provide a relief pressure control device that can easily set the relief pressure and suppresses power consumption. [Means for solving the problem]

[0010] The invention described in claim 1 is a relief pressure control device for controlling the relief pressure of a fluid pressure circuit, comprising an electromagnetic relief valve in which a set pressure is set to be higher as the amount of current flow is larger, and a controller for setting at least one relief pressure of the fluid pressure circuit by controlling the amount of current flow to the electromagnetic relief valve, and the controller is configured to set at least one relief pressure of the fluid pressure circuit when the pump pressure is lower than the set pressure of the electromagnetic relief valve in a non-energized state. 1. When a certain threshold pressure is exceeded, the electromagnetic relief valve The amount of current supplied to the electromagnetic relief valve is set to a first predetermined value, and when the pump pressure is smaller than the first predetermined threshold pressure and exceeds a second predetermined threshold pressure set according to the pressure at which forward leakage occurs in the electromagnetic relief valve in a non-energized state, the amount of current supplied to the electromagnetic relief valve is set to a second predetermined value larger than the first predetermined value. It is something 。 Effect of the Invention

[0011] According to the invention described in claim 1, the relief pressure can be easily set according to the amount of current supplied from the controller, and the electromagnetic relief valve is de-energized under normal conditions, and current is supplied from the controller to the electromagnetic relief valve only when the pump pressure becomes high, thereby reducing power consumption. Furthermore, the relief pressure can be easily set with a minimum amount of current while preventing forward leakage by setting the set pressure high until just before the pump pressure reaches the first predetermined threshold pressure. [Brief description of the drawings]

[0012] [Figure 1] 1 is a circuit diagram showing a related art of a relief pressure control device according to the present invention. [Diagram 2] 4 is a graph showing an example of the energization amount-set pressure characteristic of the electromagnetic relief valve of the relief pressure control device. [Diagram 3] 5 is a graph illustrating a method for calibrating the amount of current supplied to the electromagnetic relief valve of the relief pressure control device. [Figure 4] 4A is a graph showing an example of a change in pump pressure over time when the relief pressure control device is in operation, and FIG. 4B is a graph showing an example of control of the amount of current supplied to an electromagnetic relief valve in accordance with FIG. [Diagram 5] 4 is a graph showing an example of characteristics of an electromagnetic relief valve of an embodiment of the relief pressure control device according to the present invention. [Figure 6] 5 is a graph illustrating a method for calibrating the amount of current supplied to the electromagnetic relief valve of the relief pressure control device. [Figure 7] 1A is a graph showing an example of the change in pump pressure over time when the relief pressure control device is operating, FIG. 1B is a graph showing an example of control of the amount of current flowing through the electromagnetic relief valve according to FIG. 1A, and FIG. 1C is a graph showing the change in flow rate of the electromagnetic relief valve according to FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will now be described with reference to the accompanying drawings, in which: Related Technology , and the structures shown in Figs. one A detailed description will be given based on an embodiment.

[0014] first, Related Technology This article explains:

[0015] In FIG. 1, 1 denotes a fluid pressure circuit. The fluid pressure circuit 1 includes a pump 2. The pump 2 is operated by a prime mover such as an engine or a motor, and supplies a working fluid to the fluid pressure circuit 1. That is, 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 3. Any number of fluid pressure actuators may be used as the fluid pressure actuators 3. In FIG. 1, one fluid pressure cylinder is shown as an example of the fluid pressure actuator 3. The working fluid supplied to the fluid pressure circuit 1 by the pump 2 is stored in a tank 4. The tank 4 receives the return fluid of the fluid pressure circuit 1.

[0016] The fluid pressure circuit 1 is configured to operate the fluid pressure actuator 3 to obtain power by controlling the flow rate and direction of working fluid supplied to the fluid pressure actuator 3 from the pump 2 operated by a prime mover using a control valve (not shown) in response to an operator's lever operation, etc.

[0017] Books Related Technology In the above, 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 3 is used for driving and rotating the work machine, or for operating a work implement including a boom, arm, bucket, etc.

[0018] The upper limit of the pump pressure, which is the circuit pressure of the fluid pressure circuit 1, i.e., the relief pressure, is set by a relief valve 5. The relief valve 5 is connected to the discharge passage of the pump 2 and is set to release a part of the working fluid to the tank 4. Related Technology In the present embodiment, the relief valve 5 is an electromagnetic relief valve whose set pressure is variable according to the amount of current flowing through it, i.e., an electromagnetically variable relief valve. The relief valve 5 is configured such that the set pressure increases as the amount of current flowing through it increases. Related TechnologyIn the above, the relief valve 5 is a proportional solenoid relief valve whose set pressure changes in proportion to the amount of current flowing to the solenoid (input current). An example of the amount of current flowing (input current) vs. set pressure characteristics of the relief valve 5 is shown in Fig. 2. In the example shown, the set pressure of the relief valve 5 (Fig. 1) increases linearly or approximately linearly from a set pressure P0 in a non-energized state to a maximum set pressure P1 as the amount of current flowing increases.

[0019] 1, the amount of electricity supplied to the relief valve 5 is electronically controlled by a controller (ECM) 7 according to the output of a pressure sensor 6 that detects the pump pressure. The controller 7 is electrically connected to the pressure sensor 6 and the solenoid of the relief valve 5. The controller 7 outputs a control signal that controls the amount of electricity supplied to the relief valve 5, and uses the set pressure of the relief valve 5 that is set according to the amount of electricity supplied to the relief valve 5 to set at least one upper limit (system pressure) of the circuit pressure, which is the relief pressure of the fluid pressure circuit 1. The controller 7 and the relief valve 5 constitute a relief pressure control device 8.

[0020] It should be noted that detailed configurations of other valves, filters, sensors, etc. of the fluid pressure circuit 1 are omitted for clarity of explanation.

[0021] Next, the illustrated Related Technology The action of will be explained.

[0022] Books Related Technology In this case, by utilizing a relief valve 5 that has a certain degree of set pressure even when de-energized, the relief valve 5 is de-energized under normal circumstances, and only when the pump pressure rises is electricity applied from the controller 7 to the relief valve 5 to release the pump pressure.

[0023] When the relief pressure, which is the upper limit (system pressure) of the circuit pressure of the fluid pressure circuit 1, is set according to the amount of electricity supplied to the relief valve 5, the amount of electricity required to supply electricity to the relief valve 5 differs depending on the performance of the actual relief valve 5 and individual differences in the work machine, etc., and therefore is calibrated in advance.

[0024] During this calibration, the engine horsepower is set to the maximum output, the fluid pressure actuator 3 is placed in a maximum load state by the lever, and the amount of electricity supplied to the solenoid of the relief valve 5 by the controller 7 is set to a predetermined amount of electricity. For example, a boom cylinder is used as the fluid pressure actuator 3, and the lever is maintained at a position where the boom is raised to the maximum operating limit, i.e., where the boom cylinder is fully extended, i.e., the boom-raising stall state.

[0025] In this state, as shown in an example in Figure 3, the controller 7 (Figure 1) gradually increases (sweeps) the amount of current i of the relief valve 5 (Figure 1) from a predetermined amount of current i0, and records the amount of current i when the pump pressure detected by the pressure sensor 6 (Figure 1) at a predetermined set flow rate Q of the relief valve 5 (Figure 1) becomes a target pressure PR. The predetermined amount of current i0 may be an arbitrarily small amount of current, but may be set to 0, for example. The predetermined set flow rate Q is the maximum flow rate that the pump 2 can discharge at the pressure PR, and is a value that is determined according to the horsepower curve of the work machine or the like, and varies from machine to machine.

[0026] Thereafter, the controller 7 again sets the energization amount i of the relief valve 5 to the predetermined energization amount i0, and gradually increases the energization amount i of the relief valve 5 from the controller 7, and records the energization amount i when the pump pressure detected by the pressure sensor 6 at the predetermined set flow rate Q of the relief valve 5 becomes the target pressure PR. This operation is repeated a predetermined number of times, and the average of the recorded energization amounts i is registered in the controller 7 as a predetermined value ia corresponding to the relief pressure.

[0027] By carrying out the above calibration before shipping of a work machine or the like, it becomes possible to set the amount of current flow in advance according to the variations between individual machines.

[0028] For example, when the pump pressure changes over time as shown in Fig. 4(a), the controller 7 does not basically energize the relief valve 5, and only while the pump pressure exceeds a predetermined threshold pressure PTH, the controller 7 sets the amount of electricity supplied to the relief valve 5 to a predetermined value ia as shown in Fig. 4(b) and energizes the relief valve 5. This causes the relief valve 5 to open and release a portion of the working fluid into the tank 4, limiting the system pressure of the fluid pressure circuit 1 to a predetermined pressure PR and suppressing an excessive rise in the system pressure.

[0029] In this way, Related Technology According to this, the relief pressure can be easily set by the controller 7 energizing the relief valve 5 when the pump pressure exceeds a predetermined threshold pressure that is lower than the set pressure of the relief valve 5 in a non-energized state. In other words, when the relief pressure is set mechanically using a general relief valve, as the set pressure increases through pressure adjustment, the set flow rate decreases according to the set pressure-flow rate characteristics (PQ curve) which differ depending on the model (horsepower) of the work machine, etc., and the set pressure-flow rate characteristics also vary greatly depending on the machine, making manual adjustments cumbersome. Related Technology In this case, by supplying electricity from the controller 7 to the relief valve 5 with an amount of electricity that can be easily set for each aircraft by calibration, it is possible to easily and accurately set the relief pressure without the need for pressure adjustment work or variations occurring depending on the aircraft.

[0030] Furthermore, since the relief valve 5 can be de-energized during normal operation and energized only when the pump pressure becomes high, power consumption can be reduced.

[0031] In particular, when a work machine or the like is in operation, a pressure at the relief pressure level is rarely required, so by appropriately setting the specified threshold pressure, the actual energizing time of the relief valve 5 can be significantly reduced.

[0032] In addition, since the set pressure of the relief valve 5 can be set by switching between energized and de-energized, no manual work is required to adjust the set pressure of the relief valve 5, and there is no need to consider differences and variations in the set flow rate of the relief valve 5 for each machine by calibration. Furthermore, since it is possible to set the relief pressure according to different work modes by selecting the relief valve 5 and setting the amount of electricity energized to the relief valve 5 without changing the configuration according to differences in the specifications of work machines, etc., having different work modes, there is no need for circuit components according to specifications, and the number of circuit components can be reduced, making it possible to configure at low cost, eliminating differences in configuration due to differences in the use of work machines, etc., and reducing the risk of leakage of the working fluid.

[0033] In addition, Related Technology Although one predetermined threshold pressure is set in the above, the present invention is not limited to this, and multiple predetermined threshold pressures different from each other may be set. Related Technology Similarly, by performing calibration for each threshold pressure, it becomes possible to set the amount of energization of the relief valve 5 corresponding to each of a plurality of predetermined threshold pressures.

[0034] For example, the configuration shown in FIGS. one As in the embodiment, the predetermined threshold pressure may be set according to the pressure at which forward leakage occurs in the relief valve 5 in the non-energized state.

[0035] child Fruit In the embodiment, Related Technology Similarly, when the pump pressure rises, the controller 7 energizes the relief valve 5 to release the pump pressure. In addition, the set pressure of the relief valve 5 is set by energizing the relief valve 5 from the controller 7 so that no forward leakage occurs at the pump pressure immediately before energizing the relief valve 5.

[0036] 5, in general, the relief valve 5 gradually starts to let out the working fluid from a pressure immediately before the circuit pressure (system pressure) of the fluid pressure circuit 1 reaches a predetermined set pressure (front leakage). In this embodiment, the amount of electricity supplied to set the set pressure of the relief valve 5 is set so as to prevent energy loss due to such front leakage.

[0037] At this time, the set pressure of the relief valve 5 may be set arbitrarily as long as it is equal to or higher than the pressure at which no forward leakage occurs. However, when the current flow (input current)-set pressure characteristic of the relief valve 5 is as shown in FIG. 2, for example, the set pressure is set to be lower than the maximum set pressure P1.

[0038] When calibrating the set pressure, Related Technology Similarly, the engine horsepower is set to the maximum output, the fluid pressure actuator 3 is placed in a maximum load state by the lever, and the amount of electricity supplied to the solenoid of the relief valve 5 by the controller 7 is set to a predetermined first amount of electricity. For example, a boom cylinder is used as the fluid pressure actuator 3, and the lever is maintained at a position where the boom is raised to the maximum operating limit, i.e., where the boom cylinder is fully extended, i.e., a boom-raising stall state is set.

[0039] 6, the controller 7 gradually increases the amount of current i1 to the relief valve 5 from a predetermined first amount of current i01, and records the amount of current i1 when the pump pressure detected by the pressure sensor 6 at a predetermined first set flow rate Q1 of the relief valve 5 reaches a target first pressure PR1. The predetermined first amount of current i01 may be an arbitrarily small amount of current, but may be set to 0, for example.

[0040] After that, the energization amount i1 of the relief valve 5 from the controller 7 is set to a predetermined first energization amount i01 again, the energization amount i1 of the relief valve 5 from the controller 7 is gradually increased, and the pump pressure detected by the pressure sensor 6 at a predetermined first set flow rate Q1 of the relief valve 5 is the target first pressure PR1. The energization amount i1 at this time is recorded. This operation is repeated a predetermined number of times, and the average value of the recorded energization amounts i1 is registered in the controller 7 as a first predetermined value ia1 (Fig. 7(b)) corresponding to the relief pressure.

[0041] The predetermined first set flow rate Q1 is the maximum flow rate that the pump 2 can discharge at the first pressure PR1, is a value determined according to the horsepower curve of the work machine or the like, and is a value that varies from machine to machine.

[0042] Similarly, as shown in an example in Fig. 6, the energization amount i2 of the relief valve 5 from the controller 7 is gradually increased from a predetermined second energization amount i02, and the pump pressure detected by the pressure sensor 6 at a predetermined second set flow rate Q2 of the relief valve 5 is the target second pressure PR2. The energization amount i2 at this time is recorded. The predetermined second energization amount i02 may be the same as or different from the predetermined first energization amount i0. However, in this embodiment, since the second pressure PR2 is greater than the first pressure PR1, the energization amount i2 when the second pressure PR2 is reached is assumed to be greater than the energization amount i1 when the first pressure PR1 is reached (i1 < i2). Therefore, by setting the predetermined second energization amount i02 to be greater than the predetermined first energization amount i01 or the first predetermined value ia1 (Fig. 7(b)), it is possible to shorten the time required for calibration.

[0043] After that, the energization amount i2 of the relief valve 5 from the controller 7 is set to a predetermined second energization amount i02 again, the energization amount i2 of the relief valve 5 from the controller 7 is gradually increased, and the pump pressure detected by the pressure sensor 6 at a predetermined second set flow rate Q2 of the relief valve 5 is the target second pressure PR2. The energization amount i2 at this time is recorded. This operation is repeated a predetermined number of times, and the average value of the recorded energization amounts i2 is registered in the controller 7 as a second predetermined value ia2 (Fig. 7(b)).

[0044] In this embodiment, the second predetermined value ia2 is set to be greater than the first predetermined value ia1. Either the first predetermined value ia1 or the second predetermined value ia2 may be registered first.

[0045] The above calibration is carried out before the work machine or the like is shipped.

[0046] Then, for example, when the pump pressure changes over time as shown in Fig. 7(a), the controller 7 basically does not energize the relief valve 5, and while the pump pressure exceeds a predetermined threshold pressure PTH2, sets the amount of energization of the relief valve 5 to a second predetermined value ia2 as shown in Fig. 7(b). This prevents the occurrence of forward leakage as shown by the two-dot chain line in Fig. 7(c) before the relief valve 5 opens to release part of the working fluid into the tank 4 to protect the fluid pressure circuit 1.

[0047] When the pump pressure further increases and exceeds a first predetermined threshold pressure PTH1 as shown in Fig. 7(a), the amount of current flowing through the relief valve 5 is set to a first predetermined value ia1 as shown in Fig. 7(b). This causes the relief valve 5 to open and release a portion of the working fluid into the tank 4, limiting the system pressure of the fluid pressure circuit 1 to a predetermined first pressure PR1 and suppressing an excessive increase in the system pressure.

[0048] In this manner, in this embodiment, when the pump pressure exceeds a predetermined threshold pressure that is lower than the set pressure of the relief valve 5 in a non-energized state, the relief valve 5 is energized, so that the relief pressure can be easily set. Furthermore, since the relief valve 5 is de-energized under normal conditions and energized only when the pump pressure becomes high, power consumption can be reduced. Related Technology The same effect can be achieved.

[0049] In addition, by setting the specified threshold pressure according to the pressure at which forward leakage occurs in the relief valve 5 when it is not energized, it is possible to suppress energy loss caused by forward leakage and to prevent the relief pressure from becoming lower than desired due to forward leakage.

[0050] In this embodiment, when the pump pressure exceeds a first predetermined threshold pressure that is lower than the set pressure of the relief valve 5 in an unenergized state, the controller 7 sets the amount of current flowing through the relief valve 5 to a first predetermined value, and when the pump pressure exceeds a second predetermined threshold pressure that is lower than the first predetermined threshold pressure and is set according to the pressure at which forward leakage occurs through the relief valve 5 in an unenergized state, the controller 7 sets the amount of current flowing through the relief valve 5 to a second predetermined value that is greater than the first predetermined value.This makes it possible to easily set the relief pressure with a minimum amount of current flowing while preventing forward leakage by setting the set pressure high until just before the pump pressure reaches the first predetermined threshold pressure.

[0051] In particular, when setting the set pressure mechanically using a two-stage adjustable relief valve, the adjustments are cumbersome, the configuration is complex, and pressure adjustment work needs to be performed multiple times, whereas in the present embodiment, complicated adjustments are not necessary and the configuration is simple, resulting in a configuration that is inexpensive and less likely to cause leakage of the working fluid.

[0052] In addition, Related Technology and In the embodiment, the set pressure of the relief valve 5 in the non-energized state may be set mechanically.

[0053] Furthermore, three or more predetermined threshold pressures of the pump pressure for energizing the relief valve 5 from the controller 7 may be set. Even when multiple threshold pressures are set, it is only necessary to control the amount of electricity supplied from the controller 7 to the relief valve 5, and different relief pressures can be easily set according to the operation or mode of the work machine, etc. [Industrial Applicability]

[0054] The present invention has industrial applicability to businesses involved in the manufacture, sale, etc. of fluid pressure circuits and working machines and the like equipped with the same.

Claims

[Claim 1] A relief pressure control device that controls a relief pressure of a fluid pressure circuit, an electromagnetic relief valve in which the set pressure is set to a larger value as the amount of current flow increases; and a controller that sets at least one relief pressure of the fluid pressure circuit by controlling the amount of current supplied to the electromagnetic relief valve. The controller sets the amount of current supplied to the electromagnetic relief valve to a first predetermined value when the pump pressure exceeds a first predetermined threshold pressure that is lower than the set pressure of the electromagnetic relief valve in a non-energized state, and sets the amount of current supplied to the electromagnetic relief valve to a second predetermined value that is larger than the first predetermined value when the pump pressure exceeds a second predetermined threshold pressure that is lower than the first predetermined threshold pressure and is set according to the pressure at which forward leakage occurs through the electromagnetic relief valve in a non-energized state. A relief pressure control device comprising:

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