JP7464860B2 - hydraulic unit - Google Patents

Description

This disclosure relates to a hydraulic unit.

Conventionally, hydraulic units that drive hydraulic cylinders detect oil leaks based on the difference between the hydraulic pressure on the cap side and the hydraulic pressure on the rod side of the hydraulic cylinder, detected by a pressure detector (see, for example, JP 61-55405 A (Patent Document 1)).

Japanese Patent Application Laid-Open No. 61-55405

In the conventional hydraulic units described above, in order to diagnose oil leaks in the hydraulic cylinders, two pressure detectors must be installed for each hydraulic cylinder, which creates the problem that the configuration of the hydraulic unit becomes more complex as the number of hydraulic cylinders increases.

This disclosure proposes a hydraulic unit that can determine hydraulic oil leakage in a hydraulic cylinder.

A hydraulic unit according to one aspect of the present disclosure includes:
A hydraulic pump for supplying hydraulic oil to the hydraulic cylinder;
A motor that drives the hydraulic pump;
a pressure sensor for detecting a pressure of the hydraulic oil discharged by the hydraulic pump;
a control unit for controlling the motor during a process involving the operation of the hydraulic cylinder;
The control unit is
Calculating an integrated value of the product of the pressure of the hydraulic oil discharged by the hydraulic pump and the flow rate of the hydraulic oil discharged by the hydraulic pump from the start of the process to the end of the process;
When the integrated value is equal to or greater than a predetermined threshold value, it is determined that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinder.

According to the above configuration, when the integrated value is equal to or greater than a predetermined threshold, the control unit determines that a hydraulic oil leak exceeding a predetermined amount is occurring in the hydraulic cylinder. Therefore, the hydraulic unit can determine whether or not there is a hydraulic oil leak in the hydraulic cylinder.

In one aspect of the present disclosure, a hydraulic unit includes:
The control unit is
Using a trend of change in the integrated value when the process is repeated, the integrated value to be measured in the next process is estimated;
When the estimated integrated value is equal to or greater than the predetermined threshold value, it is determined that a leakage of hydraulic oil exceeding a predetermined amount will occur in the hydraulic cylinder in the next process.

According to the above aspect, when the integrated value estimated to be measured in the next process is equal to or greater than a predetermined threshold, the control unit determines that a hydraulic oil leak exceeding a predetermined amount will occur in the hydraulic cylinder in the next process. Therefore, measures can be taken before the hydraulic oil leak in the hydraulic cylinder becomes serious.

In one aspect of the present disclosure, a hydraulic unit includes:
The control unit is
When the integrated value is equal to or greater than the predetermined threshold value and the time from when it is determined that the process has started to when it is determined that the process has ended is less than a predetermined time, the degree of leakage of the hydraulic oil from the hydraulic cylinder is determined to be relatively slight,
When the integrated value is equal to or greater than the predetermined threshold value and the time from when it is determined that the process has started to when it is determined that the process has ended is equal to or greater than the predetermined time, the degree of hydraulic oil leakage in the hydraulic cylinder is determined to be relatively severe.

According to the above aspect, when determining whether or not a leakage of hydraulic oil in excess of a predetermined amount has occurred in the hydraulic cylinder, the time from the start determination to the end determination of the process is used, thereby improving the reliability of the determination of the degree of leakage of hydraulic oil in the hydraulic cylinder.

In one aspect of the present disclosure, a hydraulic unit includes:
The predetermined threshold value is set to a different value when the hydraulic cylinder is driven in the forward direction and when the hydraulic cylinder is driven in the reverse direction.

According to the above aspect, the above-mentioned predetermined threshold value is set to a different value when the hydraulic cylinder is driven in the forward direction and when it is driven in the reverse direction, so that leakage of hydraulic oil can be accurately determined when the hydraulic cylinder is driven in both the forward direction and the reverse direction.

A hydraulic unit according to one aspect of the present disclosure includes:
A hydraulic pump for supplying hydraulic oil to the hydraulic cylinder;
A motor that drives the hydraulic pump;
a pressure sensor for detecting a pressure of the hydraulic oil discharged by the hydraulic pump;
a rotation speed sensor for detecting the rotation speed of the motor;
a control unit for controlling the motor during a process involving the operation of the hydraulic cylinder;
The control unit is
Calculating an integrated value of the product of the pressure of the hydraulic oil discharged by the hydraulic pump and the rotation speed of the motor detected by the rotation speed sensor from the start of the process to the end of the process;
When the integrated value is equal to or greater than a predetermined threshold value, it is determined that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinder.

Here, an example of the rotation speed sensor is a pulse generator connected to a motor. This pulse generator outputs a pulse signal that represents the number of rotations per unit time of the motor.

According to the above configuration, when the integrated value is equal to or greater than a predetermined threshold, the control unit determines that a hydraulic oil leak exceeding a predetermined amount is occurring in the hydraulic cylinder. Therefore, the hydraulic unit can determine whether or not there is a hydraulic oil leak in the hydraulic cylinder.

FIG. 1 is a schematic block diagram of a hydraulic system using a hydraulic unit according to an embodiment of the present disclosure. FIG. 4 is a diagram showing the discharge pressure-discharge flow rate characteristics of the hydraulic unit. 5 is a graph showing an example of a relationship between a plurality of steps of the hydraulic unit and a pressure command signal and a rotation speed command signal. 4 is a main flowchart for explaining abnormality diagnosis control of the hydraulic unit. 4 is a flowchart for explaining a diagnostic process for the hydraulic unit. 4 is a flowchart for explaining a diagnostic process during operation of the hydraulic unit. 4 is a flowchart for explaining an abnormality registration process of the hydraulic unit. 5 is a flowchart for explaining a warning registration process of the hydraulic unit. 5 is a flowchart for explaining a priority order determination process for the hydraulic units.

The following describes an embodiment of a hydraulic unit according to the present disclosure.

Figure 1 is a schematic block diagram of a hydraulic system using a hydraulic unit 1 according to one embodiment of the present disclosure.

The hydraulic unit 1 is fluidly connected to a main machine 2, such as an industrial machine (e.g., an injection molding machine or a press machine).

The main engine 2 is equipped with three hydraulic cylinders 3A, 3B, 3C, three directional control valves 4A, 4B, 4C, and a main engine control device 5. The hydraulic circuit 10 of the hydraulic unit 1 is fluidly connected to the hydraulic cylinders 3A, 3B, 3C via the directional control valves 4A, 4B, 4C. This makes it possible to supply hydraulic oil from the hydraulic unit 1 to the hydraulic cylinders 3A, 3B, 3C to drive the hydraulic cylinders 3A, 3B, 3C. Note that although the main engine 2 is equipped with three hydraulic cylinders 3, it may be equipped with one, two, or four or more hydraulic cylinders, or one, two, or four or more directional control valves.

In this embodiment, the hydraulic cylinders 3A, 3B, and 3C are double-acting single-rod cylinders. Each of the hydraulic cylinders 3A, 3B, and 3C has a cylinder tube 31, a piston 32 that reciprocates within the cylinder tube 31, and a rod 33 with one end fixed to the piston 32. In the hydraulic cylinders 3A, 3B, and 3C, the side where the rod 33 protrudes from the cylinder tube 31 is the rod side, and the side where the rod 33 does not protrude from the cylinder tube 31 is the cap side. The piston 32 reciprocates within the cylinder tube 31 by forward driving, in which the piston 32 together with the rod 33 is pushed from the cap side to the rod side, and reverse driving, in which the piston 32 together with the rod 33 is pushed back from the rod side to the cap side.

In the following description of this embodiment, when there is no need to distinguish each of the hydraulic cylinders 3A, 3B, and 3C from the other hydraulic cylinders, the hydraulic cylinders 3A, 3B, and 3C may be simply referred to as hydraulic cylinders 3. Similarly, when there is no need to distinguish each of the directional control valves 4A, 4B, and 4C from the other directional control valves 4A, 4B, and 4C, the directional control valves 4A, 4B, and 4C may be simply referred to as directional control valves 4.

The directional control valve 4 controls the start, stop and direction of movement of the hydraulic cylinder 3. If the directional control valve 4 is, for example, an electromagnetic control valve, and is designed to output a monitor signal indicating the operating state of the directional control valve 4 to the main engine control device 5, it becomes possible to detect the state of the directional control valve 4 more reliably.

To explain in more detail, when the first solenoid 4a is energized and the second solenoid 4b is de-energized, the directional control valve 4 is in the first switching position on the left side in FIG. 1. In this first switching position, the cap side port 31a of the hydraulic cylinder 3 is connected to the discharge side of the hydraulic unit 1. Also, in the first switching position, the rod side port 31b of the hydraulic cylinder 3 is connected to the oil tank 11.

On the other hand, when the first solenoid 4a is de-energized and the second solenoid 4b is energized, the directional control valve 4 is in the second switching position on the right side in FIG. 1. In this second switching position, the rod side port 31b of the hydraulic cylinder 3 is connected to the discharge side of the hydraulic unit 1. In addition, in the second switching position, the cap side port 31a of the hydraulic cylinder 3 is connected to the oil tank 11.

When both the first solenoid 4a and the second solenoid 4b are de-energized, the directional control valve 4 is in a neutral position. In this neutral position, all ports of the directional control valve 4 are closed.

The main engine 2 also includes a main engine control device 5. This main engine control device 5 outputs an excitation signal for exciting the first solenoid 4a and an excitation signal for exciting the second solenoid 4b to each of the directional control valves 4. As a result, the main engine control device 5 switches the switching position of the directional control valve 4. At the same time, a monitor signal is input from the directional control valve 4 to the main engine control device 5.

In addition, when the main machine 2 is performing normal operation (e.g., injection molding or press processing), the main machine control device 5 operates the hydraulic cylinders 3 according to the specified process.

The hydraulic unit 1 includes a hydraulic circuit 10 that is fluidly connected to the hydraulic cylinder 3 via a directional control valve 4, and a unit control device 20 that controls the hydraulic circuit 10. The unit control device 20 is an example of a control unit.

<Hydraulic circuit>
The hydraulic circuit 10 includes an oil tank 11 that stores hydraulic oil, a hydraulic pump 12 that supplies the hydraulic oil in the oil tank 11 to the hydraulic cylinder 3, and a motor 13 that drives the hydraulic pump 12. The hydraulic circuit 10 also includes a discharge flow path 14 that fluidly connects the discharge side of the hydraulic pump 12 to the hydraulic cylinder 3. The hydraulic circuit 10 also includes a pressure sensor 15 that detects the pressure of the hydraulic oil in the discharge flow path 14. The hydraulic pump 12 is a fixed displacement pump that draws in and discharges hydraulic oil in the oil tank 11.

The motor 13 is a variable speed motor that is mechanically connected to the hydraulic pump 12 and drives the hydraulic pump 12. The motor 13 is an interior permanent magnet synchronous (IPM) motor. A pulse generator 16 is connected to the motor 13. The pulse generator 16 outputs a pulse signal that indicates the number of rotations per unit time of the motor 13. The pulse generator 16 is an example of a rotation speed sensor according to the present disclosure.

The discharge flow passage 14 is fluidly connected to the hydraulic cylinder 3A and the directional control valve 4A. The discharge flow passage 14 is also fluidly connected to the hydraulic cylinders 3B and 3C and the directional control valves 4B and 4C.

The pressure sensor 15 detects the pressure of the hydraulic oil in the discharge passage 14 and outputs a pressure signal indicating this pressure. In other words, the pressure sensor 15 detects the discharge pressure of the hydraulic pump 12 and outputs a pressure signal to the unit control device 20.

<Unit control device>
The unit control device 20 is composed of a CPU (Central Processing Unit), an input/output circuit, etc., and includes a PQ control unit 21, a speed detection unit 22, a speed control unit 23, an inverter 24, and an abnormality determination unit 25. A pressure command signal, a flow command signal, and an operation start signal are input to this unit control device 20 from the main machine control device 5. The unit control device 20 also performs diagnosis processing for each hydraulic cylinder based on an input signal (e.g., an operation start signal) from the main machine control device 5.

The operation start signal indicates that a process involving the operation of the hydraulic cylinder 3 has started, and is turned on from the start to the end of the process. In addition, at least one of the operation start signal, pressure command signal, flow command signal, and process number includes cylinder information for identifying which of the hydraulic cylinders 3A, 3B, and 3C is to start operating. In other words, at least one of the operation start signal, pressure command signal, flow command signal, and process number is configured to enable the unit control device 20 to identify which of the hydraulic cylinders 3A, 3B, and 3C is in operation. Note that a signal indicating information similar to the cylinder information may be input from the main machine control device 5 to the unit control device 20 separately from the operation start signal.

The PQ control unit 21 receives a pressure signal from the pressure sensor 15. This PQ control unit 21 outputs a speed command signal to the speed control unit 23 based on the pressure signal from the pressure sensor 15, the pressure command signal and the flow command signal from the main engine control device 5, and the discharge pressure-discharge flow rate characteristic shown in FIG. 2.

A pulse signal is input to the speed detection unit 22 from the pulse generator 16. The speed detection unit 22 measures the input interval of the pulse signal to detect the number of rotations per unit time (rotational speed) of the motor 13, and outputs a speed signal indicating this number of rotations.

The speed control unit 23 receives a speed command signal from the PQ control unit 21 and a speed signal from the speed detection unit 22. The speed control unit 23 performs a speed control calculation using the speed command signal from the PQ control unit 21 and the speed signal from the speed detection unit 22. The current command signal generated by this speed control calculation is output from the speed control unit 23 to the inverter 24.

The inverter 24 controls the number of rotations per unit time of the motor 13 by outputting a drive signal to the motor 13 based on the current command signal from the speed control unit 23.

In this embodiment, the PQ control unit 21, the speed control unit 23, and the inverter 24 switch between flow control and pressure control of the hydraulic pump 12 based on the discharge pressure-discharge flow rate characteristics shown in Figure 2 during the process in which the hydraulic cylinder 3 operates when the main engine 2 is in normal operation.

In the hydraulic cylinder 3, there are cases where one process is completed by performing flow control until the piston 32 of the hydraulic cylinder 3 is moved to the target position, and cases where one process is completed by performing pressure control to hold pressure after the piston 32 has moved to the target position by flow control. In other words, in a process that includes holding pressure in the hydraulic cylinder 3, after the flow control is performed, pressure control is performed following the flow control. Note that the flow control and pressure control are not performed simultaneously.

In flow control, as shown in FIG. 2, the rotation speed per unit time of the motor 13 (the rotation speed per unit time of the hydraulic pump 12) is controlled so that the discharge flow rate of the hydraulic pump 12 becomes the flow rate setting value Qa. In this embodiment, since the hydraulic pump 12 is a fixed displacement pump, the discharge flow rate of the hydraulic pump 12 is calculated by multiplying the pump capacity (discharge flow rate per revolution) by the rotation speed per unit time of the motor 13. The target flow rate Qa is determined by a flow rate command signal input from the main engine control device 5.

In flow rate control, the rotation speed per unit time of the motor 13 (the rotation speed per unit time of the hydraulic pump) is set so that the discharge flow rate of the hydraulic pump 12 becomes the target flow rate Qa at each discharge pressure, and the rotation speed per unit time of the motor 13 is controlled to become the set rotation speed Na.

The increase in hydraulic oil pressure during flow control (the transition from point A to point B in Figure 2) may be due to, for example, deterioration of the packing provided between the piston 32 of the hydraulic cylinder 3 and the casing that houses the piston 32. When the packing deteriorates, frictional resistance increases when the piston 32 moves, and the pressure detected by the pressure sensor 15 may increase.

In pressure control, the number of rotations per unit time of the motor 13 (the number of rotations per unit time of the hydraulic pump 12) is controlled so that the discharge pressure of the hydraulic pump 12 becomes the target pressure Pa. The target pressure Pa is determined by a pressure command signal input from the main engine control device 5.

An increase in the hydraulic oil discharge flow rate of the hydraulic pump 12 during pressure control (for example, a transition from point C to point D in Figure 2) may be due to an increase in the amount of hydraulic oil leaking inside the hydraulic cylinder 3. When the amount of hydraulic oil leaking inside the hydraulic cylinder 3 increases, the pressure of the hydraulic oil in the discharge passage 14 decreases and falls below the target pressure Pa. As a result, the discharge flow rate of the hydraulic pump 12 increases in order to maintain the discharge pressure of the hydraulic pump 12 at the target pressure Pa.

The abnormality determination unit 25 also receives a pressure signal (a signal indicating the discharge pressure of the hydraulic pump 12) from the pressure sensor 15 and a speed signal (a signal indicating the number of rotations per unit time of the motor 13) from the speed detection unit 22. The abnormality determination unit 25 determines the state of the hydraulic cylinder 3 based on the discharge pressure of the hydraulic pump 12 and the discharge flow rate of the hydraulic pump 12 obtained from the number of rotations per unit time of the motor 13. The abnormality determination unit 25 outputs the determination result of the state of the hydraulic cylinder 3 to the main machine control device 5.

Figure 3 is a graph showing an example of the relationship between multiple processes 1, 2, ... executed by the hydraulic unit 1 and the main engine 2 and the pressure command signal and the rotation speed command signal output from the main engine control device 5 to the unit control device 20.

Steps 1, 2, ... start sequentially in this order. In each of steps 1, 2, ..., it is predetermined which of the hydraulic cylinders 3A, 3B, 3C will operate. Furthermore, steps 1, 2, ... are configured so that when one of the hydraulic cylinders 3A, 3B, 3C operates, the other two of the hydraulic cylinders 3A, 3B, 3C do not operate. For example, in step 1, when the hydraulic cylinder 3A operates, the hydraulic cylinders 3B and 3C do not operate.

In short, the unit control device 20 is able to determine which of the hydraulic cylinders 3A, 3B, and 3C is operating by determining which of the processes 1, 2, and so on is being executed.

In addition, when a process involving the operation of the hydraulic cylinder 3 (e.g., process 1) among processes 1, 2, etc., starts, an operation start signal corresponding to this process is output from the main machine control device 5 to the unit control device 20.

<Hydraulic cylinder abnormality diagnosis control>
The abnormality diagnosis control of the hydraulic cylinder 3 by the unit control device 20 will be described below.

Figures 4 to 9 are flowcharts of the abnormality diagnosis control of the hydraulic cylinder 3 by the unit control device 20. This abnormality diagnosis control is executed simultaneously when the main machine 2 is performing normal operation. Here, the normal operation refers to, for example, operation for machining a workpiece using the hydraulic cylinder 3 if the main machine 2 is a press machine.

The unit control device 20 starts abnormality diagnosis control of the hydraulic cylinder 3 when the hydraulic unit 1 changes, for example, from a standby state to an operating state.

Figure 4 is the main flowchart of the abnormality diagnosis control.

When the abnormality diagnosis control starts, the process proceeds to step S1 shown in FIG. 4. If it is determined that an operation start signal for step 1 (shown in FIG. 3) has been input, for example, the process proceeds to step S2, where abnormality diagnosis processing is performed for the hydraulic cylinder 3 corresponding to the operation start signal. Note that step S1 is repeated until it is determined that the operation start signal has been input.

Next, the process proceeds to step S3, where it is determined whether the operation start signal has been turned off. If it is determined in step S3 that the operation start signal corresponding to the final process of process 1, 2, ... has been turned off, the process proceeds to step S4, where a priority determination process is performed to determine the priority of the abnormality of each hydraulic cylinder 3. On the other hand, if it is not determined in step S3 that the operation start signal has been turned off, the process returns to step S1.

Next, the process proceeds to step S5, where the result of the judgment based on the abnormality diagnosis process in step S2 and the result of the judgment based on the priority judgment process in step S4 are reported to the main unit 2.

Next, proceed to step S6 and reset the process number. This erases the stored data of the judgment results based on the abnormality diagnosis process in step S2 and the stored data of the judgment results based on the priority judgment process in step S4, and ends the abnormality diagnosis control. Note that in step S6, the process numbers linked to these stored data are also deleted.

This abnormality diagnosis control process diagnoses all hydraulic cylinders 3.

<Abnormality Diagnosis Processing>
Fig. 5 is a flow chart for explaining the abnormality diagnosis process in step S2 in Fig. 4. In this abnormality diagnosis process, diagnosis processes are performed on each of the hydraulic cylinders 3A, 3B, 3C when they are driven in the forward and reverse directions.

When the abnormality diagnosis process starts, the process first proceeds to step S11 shown in FIG. 5, where the operation of the hydraulic cylinder 3 begins.

Next, proceed to step S12 and start counting up the timer.

Next, proceed to step S13, and integrate the product of the discharge pressure P of the hydraulic pump 12 and the discharge flow rate Q of the hydraulic pump 12. To explain in more detail, the discharge pressure P of the hydraulic pump 12 indicated by the pressure signal from the pressure sensor 15 is multiplied by the discharge flow rate Q of the hydraulic pump 12 calculated using the speed signal from the speed detection unit 22 to obtain a value, and this value is integrated to obtain the PQ integrated value Σ (P x Q). Here, the PQ integrated value Σ (P x Q) corresponds to the amount of work in the process. Note that the rotation speed R of the motor 13 may be used instead of the discharge flow rate Q of the hydraulic pump 12.

Next, the process proceeds to step S14, where it is determined whether the pressure command signal or the flow command signal has changed. If it is determined in step S14 that the pressure command signal or the flow command signal has changed, the process proceeds to step S15, whereas if it is determined that the pressure command signal or the flow command signal has not changed, the process returns to step S11.

If the process proceeds from step S14 to step S15, in-operation diagnosis processing is performed.

Next, the process proceeds to step S16, where the process number is counted up, and the diagnostic result data based on the operational diagnosis in step S15 is stored, and the diagnostic process ends. Note that in step S16, the process number linked to the diagnostic result data is also stored.

<Diagnosis process during operation>
FIG. 6 is a flowchart for explaining the diagnostic process during operation of the hydraulic unit 1.

When the above-mentioned operational diagnostic process starts, the process proceeds to step S21 shown in FIG. 6, and the PQ integrated value Σ(P×Q) is recorded.

Next, proceed to step S22 and record the timer value t (the time that the operation start signal is on). The timer value t corresponds to the time required from the start of one process to the end of said process.

Next, the process proceeds to step S23. If it is determined that the first and second thresholds X1 and X2 have been registered, the process proceeds to step S24. If it is determined that the first and second thresholds X1 and X2 have not been registered, the process proceeds to step S28.

When proceeding from step S23 to step S28, a specified multiple (e.g., 1.1 times) of the first PQ accumulated value Σ (P×Q) is recorded as the first threshold value X1 (predetermined threshold), and then the process proceeds to step S29, where a specified multiple (e.g., 1.1 times) of the first timer value t is recorded as the second threshold value X2 (predetermined time), and this operational diagnosis process ends. Here, the specified multiples of the PQ accumulated value Σ (P×Q) and the timer value t are set separately.

The first threshold value X1 and the second threshold value X2 are recorded in the first threshold value table for each hydraulic cylinder 3, as values when the hydraulic cylinder 3 is driven in the forward direction and values when the hydraulic cylinder 3 is driven in the reverse direction. Note that the first threshold value X1 and the second threshold value X2 may be recorded in a threshold value table for each process number.

In this embodiment, the first PQ accumulated value Σ(P×Q) and the timer value t are used as reference values to set the first threshold value X1 and the second threshold value X2, but the first threshold value X1 and the second threshold value X2 may be set in advance by simulation, experiment, or the like.

When proceeding from step S23 to step S24, it is determined whether the PQ accumulated value Σ(P×Q) is equal to or greater than a preregistered first threshold value X1 (predetermined threshold value). In this step S24, if it is determined that the PQ accumulated value Σ(P×Q) is equal to or greater than the first threshold value X1, it proceeds to step S25, whereas if it is determined that the PQ accumulated value Σ(P×Q) is less than the first threshold value X1, it proceeds to step S30.

When the process proceeds from step S24 to step S30, the rate of change of the PQ integrated value Σ(P×Q) is calculated and recorded. Here, the rate of change is the percentage of the ratio of the change in the previous PQ integrated value Σ(P×Q) to the current PQ integrated value Σ(P×Q), as shown in the following formula.

Next, proceed to step S31 and estimate the next PQ integrated value Σ(P×Q) from the rate of change calculated in step S30.

Next, the process proceeds to step S32. If it is determined that the next PQ accumulated value Σ(P×Q) estimated in step S31 is equal to or greater than the first threshold value X1, the process proceeds to step S27. On the other hand, if it is determined that the next PQ accumulated value Σ(P×Q) is less than the first threshold value X1, the process ends the in-operation diagnostic process.

When the process proceeds from step S24 to step S25, it is determined whether the timer value t is equal to or greater than the second threshold value X2 (predetermined time) registered in advance. If it is determined in step S25 that the timer value t is equal to or greater than the second threshold value X2, the process proceeds to step S26, where an abnormality registration process is performed, and the operation-time diagnosis process is terminated. On the other hand, if it is determined in step S25 that the timer value t is less than the second threshold value X2, the process proceeds to step S27, where a warning registration process is performed, and the operation-time diagnosis process is terminated.

<Abnormal registration process>
FIG. 7 is a flowchart for explaining the abnormality registration process of the hydraulic unit 1.

When the abnormality registration process starts, the process proceeds to step S51 shown in FIG. 7, where it is determined that the packing has deteriorated, and then to step S52, where an abnormality is registered for the hydraulic cylinder, after which the abnormality registration process ends.

<Warning registration process>
FIG. 8 is a flowchart for explaining the warning registration process of the hydraulic unit 1.

When the warning registration process starts, the process proceeds to step S61 shown in FIG. 8, where it is determined that there is a sign of packing deterioration, and then to step S62, where a warning is registered for the hydraulic cylinder, after which the warning registration process ends.

<Priority determination process>
FIG. 9 is a flowchart for explaining the priority order determination process of the hydraulic unit 1.

When the priority order determination process starts, the process proceeds to step S71 shown in FIG. 9, where it is determined whether the current PQ accumulated value Σ(P×Q) is equal to or greater than the first threshold value X1 that has been registered in advance. If it is determined in step S71 that the current PQ accumulated value Σ(P×Q) is equal to or greater than the first threshold value X1, the process proceeds to step S72. However, if it is determined that the current PQ accumulated value Σ(P×Q) is less than the first threshold value X1, step S72 is skipped and the process proceeds to step S73.

When proceeding from step S71 to step S72, the abnormality rankings (order of severity of abnormality) of processes 1, 2, ... are sorted in descending order of the deviation ΔR1 between the current PQ integrated value Σ(P×Q) and the first threshold value X1. In other words, the deviation ΔR1 is calculated using the following formula, and the abnormality rankings of processes 1, 2, ... are rearranged in descending order of the deviation ΔR1.

ΔR1=current PQ integrated value Σ(P×Q)−first threshold value X1
When proceeding from step S71 or S72 to step S73, it is determined whether the next PQ accumulated value Σ(P×Q) is equal to or greater than the first threshold value X1. If it is determined in step S73 that the next PQ accumulated value Σ(P×Q) is equal to or greater than the first threshold value X1, the process proceeds to step S74. If it is determined that the next PQ accumulated value Σ(P×Q) is less than the first threshold value X1, the process skips step S74 and proceeds to step S75.

If the process proceeds to step S74, the warning rankings (in descending order of severity) of processes 1, 2, ... are sorted in descending order of the deviation ΔR2 between the next PQ integrated value Σ (P × Q) and the first threshold value X1. In other words, the deviation ΔR2 is calculated using the following formula, and the abnormality rankings of processes 1, 2, ... are rearranged in descending order of the deviation ΔR2.

ΔR1 = next PQ integrated value Σ(P×Q)h - first threshold value X1
Next, when it is determined in step S75 that the diagnosis of all the processes has been completed, the priority order determination process ends.

In the hydraulic unit 1 configured as above, when a process involving the operation of the hydraulic cylinder 3 (hereinafter, the diagnosis target process) among processes 1, 2, ... starts, the unit control device 20 obtains a PQ integrated value Σ (P x Q) based on the discharge pressure P of the hydraulic pump 12 detected by the pressure sensor 15 and the discharge flow rate Q of the hydraulic pump 12 calculated using the speed signal from the speed detection unit 22 while this process is being performed. Then, when the PQ integrated value Σ (P x Q) is equal to or greater than the first threshold value X1, it is determined that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinder 3. At this time, the unit control device 20 also determines which of the hydraulic cylinders 3A, 3B, 3C is operating based on at least one of the operation start signal, the pressure command signal, the flow command signal, and the process number.

In this way, hydraulic oil leakage can be determined for each of the hydraulic cylinders 3A, 3B, and 3C based on at least one of the operation start signal, pressure command signal, flow command signal, and process number.

In addition, the pressure sensor 15 and the speed detection unit 22 are used to diagnose abnormalities in the hydraulic cylinder 3. This eliminates the need to provide separate equipment for diagnosing abnormalities in each of the hydraulic cylinders 3A, 3B, and 3C. As a result, the configuration for diagnosing abnormalities in the hydraulic cylinder 3 can be simplified.

In addition, before problems caused by oil leakage from hydraulic cylinders 3A, 3B, and 3C on the main engine 2 side become serious, measures such as part replacement can be taken in the order of priority.

The unit control device 20 also estimates the next measured PQ accumulated value Σ(P×Q) for each hydraulic cylinder 3 using the tendency of change in the PQ accumulated value Σ(P×Q) when steps 1, 2, ... are repeated, and when the estimated PQ accumulated value Σ(P×Q) is equal to or greater than the first threshold value X1, it determines that a leakage of hydraulic oil exceeding a predetermined amount will occur in the next step in the hydraulic cylinders 3A, 3B, 3C.

In this way, by estimating the next measured PQ integrated value Σ(P×Q), measures can be taken before the hydraulic oil leak in the hydraulic cylinder 3 becomes serious.

The unit control device 20 also measures the times of steps 1, 2, ..., and when the PQ integrated value Σ(P×Q) is equal to or greater than the first threshold value X1 and the times of steps 1, 2, ... are less than the second threshold value X2, it determines that the degree of hydraulic oil leakage in the hydraulic cylinder 3 is relatively minor. If the degree of hydraulic oil leakage is relatively minor, it issues a warning to the main engine 2.

On the other hand, when the PQ integrated value Σ(P×Q) is equal to or greater than the first threshold value X1 and the time for steps 1, 2, ... is equal to or greater than the second threshold value X2, it is determined that the degree of hydraulic oil leakage in the hydraulic cylinder 3 is relatively severe. If the degree of hydraulic oil leakage is relatively severe, the main engine 2 is notified of the abnormality.

This makes it easy to determine whether the degree of hydraulic oil leakage in the hydraulic cylinder 3 is relatively minor or relatively major, and the most appropriate measures can be taken based on the results of this determination.

The first threshold value X1 is set to a different value when the hydraulic cylinder 3 is driven in the forward direction and when it is driven in the reverse direction. Therefore, if an operation that applies a load is performed when the hydraulic cylinder 3 is driven in at least one of the forward direction and reverse direction, leakage of hydraulic oil can be accurately determined when the hydraulic cylinder 3 is driven in either the forward direction or reverse direction.

Here, the forward direction of the hydraulic cylinder 3 is the direction in which the piston 32 moves to the side where the rod 33 of the hydraulic cylinder 3 protrudes. The reverse direction of the hydraulic cylinder 3 is the direction in which the piston 32 moves to the side where the rod 33 of the hydraulic cylinder 3 retracts.

The second threshold value X2 is set to a different value when the hydraulic cylinder 3 is driven in the forward direction and when it is driven in the reverse direction. Therefore, leakage of hydraulic oil can be accurately determined when the hydraulic cylinder 3 is driven in both the forward direction and the reverse direction.

In this embodiment, the hydraulic pump 12 may be provided with a capacity detection unit 12a (see FIG. 1) that detects the capacity of the hydraulic pump 12. In this case, a variable capacity pump may be used as the hydraulic pump 12, and a constant speed motor may be used as the motor 13. Even when a variable capacity pump is used as the hydraulic pump 12, the discharge flow rate of the hydraulic pump 12 is calculated by the product of the pump capacity detected by the capacity detection unit 12a and the number of rotations per unit time of the motor 13.

<Replacing packing according to the operating direction of the hydraulic cylinder>
In the hydraulic cylinders 3A, 3B, and 3C, the piston 32 reciprocates when driven in a forward direction, that is, when the piston 32 is pushed from the cap side to the rod side, and when driven in a reverse direction, that is when the piston 32 is returned from the rod side to the cap side.

If the rate of change of the Q integrated value Σ(P×Q) is large only when pressure is applied in the forward direction, pushing the piston 32 toward the rod, and an abnormality is reported from the hydraulic unit 1, replace the piston packing that seals the cylinder tube 31 and the piston 32.

On the other hand, if the rate of change of the Q integrated value Σ(P×Q) is large only when pressure is applied in the reverse direction, pushing the piston 32 back toward the cap, and an abnormality is reported from the hydraulic unit 1, replace the rod packing that seals the cylinder tube 31 and the rod 33.

If an abnormality is reported from hydraulic unit 1 due to a large rate of change in the Q integrated value Σ (P x Q) both when pressure is applied in the reverse direction back to the cap side and when pressure is applied in the forward direction pushing out towards the rod side, replace the piston packing and rod packing.

In the above embodiment, abnormality diagnosis of the hydraulic unit 1 is performed simultaneously while the main engine 2 is operating normally, but abnormality diagnosis may also be performed by operating the main engine 2 in a dedicated abnormality diagnosis mode.

In the above embodiment, a hydraulic unit 1 that drives three hydraulic cylinders 3A, 3B, and 3C has been described, but the number of hydraulic cylinders is not limited to this, and the present disclosure may be applied to a hydraulic unit that drives one, two, or four or more hydraulic cylinders.

In the above embodiment, a flow rate sensor was not provided in the discharge flow path 14, but a flow rate sensor may be provided in the discharge flow path 14. In this case, the discharge flow rate of the hydraulic pump 12 can be detected by the flow rate sensor without having to calculate the discharge flow rate of the hydraulic pump 12 by the product of the pump capacity and the number of rotations per unit time of the motor 13.

In the above embodiment, one hydraulic cylinder 3 operates in each of steps 1, 2, ..., but multiple hydraulic cylinders 3 may operate in each of steps 1, 2, .... In this case, too, an operation start signal configured to identify the hydraulic cylinder 3 operating in each of steps 1, 2, ... may be input from the main machine control device 5 to the unit control device 20.

In the above embodiment, the unit control device 20 determines the start of process 1 based on an operation start signal corresponding to process 1, but it may also be configured to determine the start of process 1 based on an excitation signal to the directional control valve 4, or to determine the start of process 1 based on a monitor signal from the directional control valve 4.

In the above embodiment, the unit control device 20 determined the start of process 1, process 2, ... based on the operation start signals corresponding to process 1, process 2, ..., but it may also be configured to determine the start of process 2, process 3, ... based on a change in at least one of the pressure command signal and the rotation speed command signal.

In the above embodiment, in step S1, when it is determined that the operation start signal has been input, the process proceeds to step S2. However, it may also proceed to step S2 when it is determined that an excitation signal has been sent to the directional control valve 4. In this case, for example, a signal indicating that an excitation signal has been output to the directional control valve 4 is output from the main machine control device 5 to the unit control device 20.

In the above embodiment, in step S1, when it is determined that the operation start signal has been input, the process proceeds to step S2. However, it may also proceed to step S2 when it is determined that the monitor signal output from the directional control valve 4 has changed. In this case, for example, a signal indicating that the monitor signal output from the directional control valve 4 has changed is output from the main machine control device 5 to the unit control device 20.

In the above embodiment, it was determined whether the PQ accumulated value Σ(P×Q) was equal to or greater than the first threshold value X1 registered in advance, but it may be determined whether the value obtained by subtracting a predetermined initial value from the PQ accumulated value Σ(P×Q) is equal to or greater than the first threshold value X1 registered in advance. In other words, in step S24, the "difference between the PQ accumulated value Σ(P×Q) and a predetermined initial value" may be used instead of the "PQ accumulated value Σ(P×Q)". In this case, the same changes as those in step S24 may also be made in steps S32, S71, and S73.

In the above embodiment, the next PQ accumulated value Σ(P×Q) was estimated using the rate of change of the current PQ accumulated value Σ(P×Q) relative to the previous PQ accumulated value Σ(P×Q). However, when the in-operation diagnostic process is performed multiple times, the next PQ accumulated value Σ(P×Q) may be estimated using an approximation curve or the like as the trend of change in the PQ accumulated value Σ(P×Q).

In the above embodiment, when it is determined in step S24 that the PQ accumulated value Σ(P×Q) is equal to or greater than the first threshold value X1, the process proceeds to step S26 or S27 via step S25. However, when it is determined in step S24 that the PQ accumulated value Σ(P×Q) is equal to or greater than the first threshold value X1, the process may proceed to step S26 without passing through step S25. In short, the flowchart in FIG. 6 may be modified so as to eliminate step S25.

In the above embodiment, when the rotation speed R of the motor 13 is used instead of the discharge flow rate Q of the hydraulic pump 12, the product of the discharge pressure P of the hydraulic pump 12 and the rotation speed R of the motor 13 is integrated to obtain a PR integrated value Σ (P × R), and when this PR integrated value Σ (P × R) is equal to or greater than a predetermined threshold, it may be determined that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinder 3.

Specific embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above embodiments and can be modified and implemented in various ways within the scope of the present disclosure.

REFERENCE SIGNS LIST 1 Hydraulic unit 2 Main engine 3, 3A, 3B, 3C Hydraulic cylinder 4, 4A, 4B, 4C Directional control valve 5 Main engine control device 11 Oil tank 12 Hydraulic pump 12a Capacity detection unit 13 Motor 14 Discharge flow path 15 Pressure sensor 16 Pulse generator (rotation speed sensor)
20 Unit control device (control unit)
21 PQ control section 22 Speed detection section 23 Speed control section 24 Inverter 25 Abnormality determination section 31 Cylinder tube 32 Piston 33 Rod

Claims (4)

A hydraulic pump (12) for supplying hydraulic oil to the hydraulic cylinders (3A, 3B, 3C);
A motor (13) for driving the hydraulic pump (12);
a pressure sensor (15) for detecting a pressure (P) of hydraulic oil discharged by the hydraulic pump (12);
a control unit (20) for controlling the motor (13) during a process involving the operation of the hydraulic cylinders (3A, 3B, 3C);
The control unit (20)
Calculating an integrated value (Σ(P×Q)) of the product of the pressure (P) of the hydraulic oil discharged by the hydraulic pump (12) and the flow rate (Q) of the hydraulic oil discharged by the hydraulic pump (12) from the start of the process to the end of the process;
When the integrated value (Σ(P×Q)) is equal to or greater than a predetermined threshold value (X1), the hydraulic unit determines that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinder (3A, 3B, 3C). 2. The hydraulic unit according to claim 1,
The control unit (20)
Using a tendency of change in the integrated value (Σ(P×Q)) when the process is repeated, the integrated value (Σ(P×Q)) to be measured in the next process is estimated;
When this estimated integrated value (Σ(P×Q)) is equal to or greater than the predetermined threshold value (X1), the hydraulic unit determines that a leakage of hydraulic oil exceeding a predetermined amount will occur in the hydraulic cylinder (3A, 3B, 3C) in the next process. 3. The hydraulic unit according to claim 1,
The control unit (20)
When the integrated value (Σ(P×Q)) is equal to or greater than the predetermined threshold value (X1) and the time from when it is determined that the process has started to when it is determined that the process has ended is less than a predetermined time (X2), the degree of leakage of hydraulic oil from the hydraulic cylinders (3A, 3B, 3C) is determined to be relatively light,
When the integrated value (Σ(P×Q)) is equal to or greater than the predetermined threshold value (X1) and the time from when it is determined that the process has started to when it is determined that the process has ended is equal to or greater than the predetermined time (X2), the degree of leakage of hydraulic oil in the hydraulic cylinders (3A, 3B, 3C) is determined to be relatively severe. Infringement detection level B (determined at the time of basic application consultation)
A hydraulic unit according to any one of claims 1 to 3,
A hydraulic unit, wherein the predetermined threshold value (X1) is set to a different value when the hydraulic cylinders (3A, 3B, 3C) are driven in a forward direction and when the hydraulic cylinders (3A, 3B, 3C) are driven in a reverse direction.

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