Method for operating a hydraulic actuation power system experiencing pressure sensor faults

The present invention relates to a hydraulic drive system, and more specifically to an operation mode for a hydraulic drive system used in a machine having a pressure sensor failure.

A hydraulic drive system used to operate with a lift arm in a transshipment device, such as a construction machine, generally has a pressure source such as a pump, a fluid tank, and at least one fluid to control the lift arm of the target machine. Includes cylinder.

Utilization of a pressure sensor to control the operation of such a hydraulic drive system is known in the art. Pressure sensors are commonly used in the control of valves that control the flow rate between a fluid cylinder and a pressure source and fluid tank based on load. However, such pressure sensors may malfunction and render the system inoperable.

Methods for operating the hydraulic drive system during pressure sensor malfunction are disclosed. The hydraulic drive system includes a pressure source such as a pump arranged to supply the flow rate according to the required flow rate, a reservoir arranged to accommodate the fluid, and first and second work ports. The pressure source communicates fluid with the reservoir and the first and second workports.

The hydraulic drive system further includes a valve system capable of controlling the flow rate. The valve system has a first orifice located between the pressure source and the first pressure chamber, a second orifice located between the pressure source and the second pressure chamber, and between the first pressure chamber and the reservoir. It has an arranged third orifice and a fourth orifice arranged between the second pressure chamber and the reservoir.

The hydraulic drive system determines the pressure of the fluid supplied by the pressure source (Ps), the pressure of the fluid supplied to the first pressure chamber (Pa), and the pressure of the fluid supplied to the second pressure chamber (Pb). It also includes a sensitive pressure sensor system. In addition, the hydraulic drive system adjusts the pressure source and valve system based on the required flow rate and the (pressure) difference determined between Ps, Pa, Pb and the pressure (Pt) of the fluid returned to the reservoir. Includes the deployed controller.

This method detects anomalies in a single sensor placed to detect Pa, closes the second and third orifices, and adjusts the pressure source to generate a flow rate corresponding to the maximum Ps. Including doing. In addition, the method involves assigning a value for the difference between Ps and Pa that corresponds to a value within the feasible range for the difference between the two pressures. It also includes adjusting the first and fourth orifices according to the required flow rate, and the system continues to operate despite anomalies in the sensors arranged to sense Pa.

According to this method, adjusting the 4th control valve is accomplished by generating a flow rate through the 4th orifice that corresponds to the required flow rate increased by the area ratio of the 1st and 2nd workports. be able to. Further, the abnormality signal is generated in response to detecting the abnormality of the sensor arranged to detect Pa described above.

This method detects anomalies in a single sensor arranged to detect Pb, closes the second and third orifices, and manages the pressure source to generate a flow rate equivalent to Ps> Pa. Moreover, it further includes assigning the value of the difference between Pb and Pt corresponding to the maximum value substantially feasible. In such cases, the method also includes adjusting the first orifice according to the required flow rate and adjusting the fourth orifice to generate the Pb, and the system is arranged to sense the Pb. It continues to operate despite the malfunction of the sensor. Further, adjusting the fourth orifice is accomplished by keeping Pa below the maximum value. This method also includes generating an anomaly signal in response to detecting an anomaly in a sensor arranged to detect the Pb described above.

If the reservoir used in the hydraulic drive system operates above a known minimum pressure, the pressure sensor system may further include a pressure sensor capable of sensing the pressure Pt.

The above method can be applied to machines operated by hydraulic drive systems. The hydraulic drive system of the machine uses actuators with opposing first and second pressure chambers arranged to operate the arms of the machine in response to the flow rate controlled above.

The features and advantages described above, as well as other features and advantages of the invention, will be readily apparent from the detailed description of the best embodiments below in connection with the accompanying drawings.

<figref num="1">FIG. 1 is a circuit diagram illustrating a hydraulic drive system using a valve with a pressure sensor to control the functioning of the system.</figref>

<figref num="2">FIG. 2 is a flowchart of a method for controlling a hydraulic drive system having a second pressure sensor failure, and</figref>

<figref num="3">FIG. 3 is a flowchart of a method for controlling a hydraulic drive system causing a third pressure sensor failure.</figref>

With reference to the drawings, similar reference numbers correspond to similar or similar components across the diagrams, with FIG. 1 showing the hydraulic drive system 10 with a valve system and pressure sensor to control the functioning of the system. The circuit diagram to be illustrated is shown. The hydraulic drive system 10 is commonly used in civil or construction machinery (not shown) that raises and / or lowers the arm of the machine to move the load.

The hydraulic drive system 10 includes a fluid reservoir 12 that communicates fluid with a pressure source such as a fluid pump 14 via a fluid passage 13. The pressure source 14 communicates fluid with the first pressure sensor 18 via the fluid passage 16. The sensor 18 is arranged to sense the pressure Ps of the fluid supplied by the pressure source 14. The sensor 18 communicates fluid with the orifice 22 via the fluid passage 20. The orifice 22 communicates fluidly with the second pressure sensor 24. The pressure sensor 24 is arranged to sense the pressure Pa of the fluid supplied to the hydraulic actuator 28 via the fluid passage 26.

The hydraulic actuator 28 includes a movable piston 30 including a piston head 30a and a piston rod 30b. The piston 30 partitions the hydraulic actuator into a first work port or pressure chamber 32 on the piston head 30a side and a second work port or pressure chamber 34 on the piston rod 30b side. Specifically, the pressure Pa sensed by the pressure sensor 24 corresponds to the pressure of the fluid inside the first pressure chamber 32.

The sensor 18 further communicates fluid with the orifice 38 via the fluid passage 36. The orifice 38 communicates with the third pressure sensor 40. The pressure sensor 40 is arranged to detect the pressure Pb of the fluid supplied to the hydraulic actuator 28 via the fluid passage 42. Specifically, the pressure Pb sensed by the pressure sensor 40 corresponds to the pressure of the fluid inside the second pressure chamber 34.

The sensor 24 also communicates fluid with the orifice 46 via the fluid passage 44. The orifice 46 communicates with the fourth pressure sensor 48. The pressure sensor 48 is arranged to detect the pressure Pt of the fluid returned to the reservoir 12 via the fluid passage 50. Orifice 22 and Orifice 46 may be separate control valves configured to regulate the flow rate between the pressure source 14, reservoir 12 and first pressure chamber 32, or in combination with a single control valve mechanism. be able to.

The sensor 40 also communicates fluid with the orifice 54 via the fluid passage 52. The orifice 54 communicates fluid with the pressure sensor 48. Orifice 38 and orifice 54 may be separate control valves configured to regulate the flow rate between the pressure source 14, reservoir 12 and second pressure chamber 34, or combined with a single control valve mechanism. be able to.

Orifices 22, 38, 46 and 54 combine to form a valve system for controlling flow through the hydraulic drive system 10. A controller 56, such as an electronic control unit (ECU), is programmed to adjust the pressure source 14 and orifices 22, 38, 46, 54. As will be appreciated by those skilled in the art, the controller 56 follows the required flow rate, as well as the pressure source 14 and orifice 22, based on the pressure difference between the pressures Ps, Pa, Pb, and Pt calculated by the controller. Adjust 38, 46, 54. The required flow rate is generally set, for example, to increase or decrease a particular load, as requested by the operator of the construction machine.

The pressure data sensed and transmitted to the controller 56 is further used to determine which of the two chambers 32 and 34 of the actuator 28 receives the load. To increase the load, the hydraulic drive system 10 is adjusted to supply fluid to chamber 32 so that the pressure generated inside chamber 32 exceeds the pressure found in chamber 34. As is known to those skilled in the art, the rate at which the load is raised is controlled by the pressure difference between Pa, Pb, Ps and Pt. When raising a particular load, the chamber 32 is required to operate against gravity to move that load, that is, the load is "passive" and thus coupled to the pressure source 14. It is further understood to operate upstream workports. In such a situation, the chamber 34 acts as a downstream workport that connects to the fluid flow to the reservoir 12. On the other hand, when lowering the load, gravity assists the movement of chamber 32, that is, the load "overruns", thus the chamber 32 acts as a downstream workport, while the chamber 34 is upstream. Acts as a workport.

At least one of the pressure sensors 18, 24, 40, and 48 preferably includes a temperature sensor (not shown) to detect the temperature of the pressurized fluid and feed this data to the controller 56. Having such temperature data allows the controller 56 to calculate the viscosity of the fluid. As will be appreciated by those skilled in the art, the fluid viscosity and the known position of each particular orifice and the pressure drop between each particular orifice can be used to calculate the flow rate between each orifice. The calculated flow rate between each particular orifice in combination with the transmitted required flow rate is used by the controller 56 to regulate the flow rate, thus the pressure Ps is supplied by the pressure source 14. The operation of the hydraulic drive system 10 depends on the capacity or performance of the maximum flow rate of the pressure source 14. Therefore, like the flow rate to other actuators in the extended system, the flow rate to the actuator 28 is reduced to ensure that it does not exceed the maximum capacitance of the pressure source, a machine for moving a particular load. The operator's requirements are met.

2 and 3 show methods 100 and 200, respectively, for operating the hydraulic drive system 10 in the event that either the pressure sensor 24 or 40 fails. The loss of data from one of the sensors 24 and 40 results in the deactivation of the hydraulic drive system 10, typically due to the loss of control of the flow rate associated with the control loss due to pressure regulation as well. In addition, it recognizes whether the load is passive or overrun, which is the ability to determine the amount of pressure Ps required to overcome and move this load with the loss of this data. Performance is lost as well. Methods 100 and 200, on the other hand, put both chambers 32 and 34 into flow control mode, which means that the flow to both chambers is minimized and actively controlled to complete the work in progress by the machine operator. Make it possible.

Method 100, shown in FIG. 2, begins at frame 102, where an anomaly in sensor 24 is detected. Anomalies in sensor 24 are detected by controller 56 by recording the loss of pressure signals that would otherwise be continuously transmitted to the controller, or by recording signals that are outside the expected range. Following the frame 102, this method proceeds to the frame 104 in which the orifices 38 and 46 are closed. Subsequently, after closing the orifices 38 and 46, the method proceeds to frame 106, where the pressure source 14 is adjusted to produce a flow rate corresponding to the maximum value Ps. The maximum value Ps is the maximum pressure that the pressure source 14 can supply.

From frame 106, this method sets the difference between Ps and Pa, or (Ps-Pa), to a value that corresponds to a value within the feasible range for the difference between the two pressures. Proceed to frame 108. This (Ps-Pa) setting is assumed and assigned in place of the (Ps-Pa) unknown for use by the controller 56. This (Ps-Pa) setting is probably not the actual value of (Ps-Pa), but the selected value is based on the recognition that allows the controller 56 to continue adjusting the hydraulic drive system 10. Be selected. This (PsPa) value can be set as a default value to an average value or an intermediate value in a feasible range for this pressure difference. Following frame 108, this method proceeds to frame 110.

In the frame 110, the orifice 22 is adjusted by the controller 56 according to the required flow rate as instructed by the machine operator. After the frame 110, this method is adjusted by the controller 56 so that the orifice 54 passes through the fourth orifice and produces a flow rate corresponding to the required flow rate offset due to the area ratio of the first chamber 32 and the second chamber 34. Proceed to frame 112. In other words, the flow rate at the orifice 54 is set to the required flow rate increased by the area ratio of the first chamber 32 and the second chamber 34. The area ratio of chambers 32 and 34 is a known quantification. As a result of the execution of Method 100, despite the anomaly of the sensor 24, the hydraulic drive system 10 operates the actuator 28 and is controlled to support the load or extend the arm of the construction machine.

Method 200, shown in FIG. 3, begins at frame 202, where anomalies in sensor 40 are detected. Similar to the sensor 24 anomaly above, the sensor 40 anomaly is a signal that would otherwise be through continuously recording the loss of the pressure signal transmitted to the controller or out of the expected range. Is detected by the controller 56 after recording. Following frame 202, this method proceeds to frame 204, where orifices 38 and 46 are closed. After closing the orifices 38 and 46, this method proceeds to frame 206.

In frame 206, the pressure source 14 is adjusted so that the fluid pressure generated by the pressure source 14 is greater than the pressure seen in the sensor 24, i.e., to generate a flow rate corresponding to Ps&gt; Pa. Setting the pressure of the pressure source 14 above the pressure seen by the sensor 24 ensures that the pressure generated by the pressure source 14 is sufficient to support the load in the first pressure chamber 32. To enable. From frame 206, this method proceeds to frame 208.

In frame 208, the value for the difference between Pb and Pt, i.e. (Pb-Pt), is set to the maximum feasible value for this pressure difference. The maximum value of (Pb-Pt) is assumed and programmed in controller 56. Probably not the actual value of (Pb-Pt), but the selected value is the maximum value of (Pb-Pt) selected based on the recognition that allows the controller 56 to continue adjusting the hydraulic drive system 10. Will be done. Following frame 208, this method proceeds to frame 210.

In the frame 210, the orifice 22 is adjusted by the controller 56 according to the required flow rate as instructed by the construction machinery operator. After the frame 210, this method proceeds to the frame 212, which is adjusted by the controller 56 to keep Pa at or below the maximum pressure value that the orifice 54 can tolerate. Thus, Method 200 uses this pressure Pa control to regulate the pressure in chamber 34, which is called "cross-shaft" control. As a result of the execution of method 200, as in method 100 above, despite the anomaly of sensor 40, the hydraulic drive system 10 operates actuator 28 to support the load or extend the arm of the construction machine. Be controlled.

Methods 100 and 200 allow control of the hydraulic drive system 10 by assigning assumed pressure differences, so the respective pressures generated in pressure chambers 32 and 34 exactly match the load being handled. do not. As a result of using the hypothetical values to control the operation of the hydraulic drive system 10, the momentum of the piston 30 inside the actuator 28 and the speed at which the piston moves differ somewhat from the expected results. Such a loss of accuracy generally results in poor operating efficiency of the hydraulic drive system. Operation with reduced efficiency nevertheless maintains the functionality of the construction machine and allows the machine to complete a given task despite having a pressure sensor anomaly. ..

Despite the anomaly of either the pressure sensor 24 or the pressure sensor 40, both methods 100 and 200 can provide the machine operator with an anomaly signal generation while maintaining the operation of the hydraulic drive system 10. Such anomalous signals can preferably be displayed as visual and / or audio alerts on the instrument panel of the subject machine.

The best mode for carrying out the present invention has been described in detail so far, but if the person is familiar with the technology related to the present invention, various methods for carrying out the present invention within the scope of the appended claims have been described. You will recognize alternative designs and embodiments.