JP7617439B2 - 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 Unexamined Patent Publication 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 if hydraulic oil is leaking from a hydraulic cylinder.

The hydraulic unit of the present disclosure comprises:
A hydraulic pump for supplying hydraulic oil to the hydraulic cylinder;
A motor that drives the hydraulic pump;
a rotation speed sensor for detecting a rotation speed of the motor;
a pressure sensor for detecting a pressure of the hydraulic oil discharged by the hydraulic pump;
a control unit that receives an operation start signal that starts a process involving the operation of the hydraulic cylinder and controls the motor;
The control unit is
measuring a total number of rotations of the motor detected by the rotation speed sensor during a period from input of the operation start signal to completion of the process;
When pressure is maintained by the hydraulic cylinder before the end of the period, the rotation speed sensor measures the number of rotations per unit time of the motor during the pressure maintenance, and the pressure sensor measures the pressure of the hydraulic oil during the pressure maintenance,
When the sum of the rotation speeds of the motors is equal to or greater than a predetermined total rotation speed, or when the rotation speed per unit time of the motors during pressure maintenance is equal to or greater than a predetermined first rotation speed, it is determined that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinder.

This disclosure makes it possible to determine if hydraulic oil is leaking from a hydraulic cylinder.

In addition, in a hydraulic unit according to one aspect of the present disclosure,
The control unit is
estimating a next measured sum of the motor rotation speeds using a trend of change in the sum of the motor rotation speeds when the above steps are repeated;
When the estimated sum of the rotation speeds of the motors is equal to or greater than the predetermined total rotation speed, it is determined that leakage of hydraulic oil exceeding a predetermined amount will occur in the hydraulic cylinder in the next process.

According to the present disclosure, by estimating the sum of the motor rotation speeds to be measured next, measures can be taken before the leakage of hydraulic oil from the hydraulic cylinder becomes serious.

In addition, in a hydraulic unit according to one aspect of the present disclosure,
The control unit is
estimating a next measured number of rotations per unit time of the motor using a trend of change in the number of rotations per unit time of the motor during the pressure holding period when the above process is repeated;
When the estimated number of rotations per unit time of the motor is equal to or greater than the first predetermined number of rotations, it is determined that leakage of hydraulic oil exceeding a predetermined amount will occur in the hydraulic cylinder in the next process.

According to the present disclosure, by estimating the next measured motor rotation speed per unit time, measures can be taken before hydraulic oil leakage in the hydraulic cylinder becomes serious.

In addition, in a hydraulic unit according to one aspect of the present disclosure,
The control unit is
When the number of rotations per unit time of the motor during the pressure holding is equal to or greater than the predetermined first number of rotations and the pressure of the hydraulic oil during the pressure holding reaches a predetermined pressure, the degree of leakage of the hydraulic oil from the hydraulic cylinder is determined to be relatively slight,
When the number of rotations per unit time of the motor during the pressure holding period is equal to or greater than the predetermined first number of rotations and the pressure of the hydraulic oil during the pressure holding period is less than the predetermined pressure, the degree of leakage of the hydraulic oil in the hydraulic cylinder is determined to be relatively severe.

According to the present disclosure, it is possible to easily determine whether the degree of hydraulic oil leakage in a hydraulic cylinder is relatively minor or relatively major, and the most appropriate measures can be taken based on the results of this determination.

In addition, in a hydraulic unit according to one aspect of the present disclosure,
The predetermined pressure 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 present disclosure, a load is applied when the hydraulic cylinder is driven either in the forward direction or in the reverse direction, so hydraulic oil leakage can be accurately determined.

In addition, in a hydraulic unit according to one aspect of the present disclosure,
The control unit is
Measure the time period,
When the sum of the rotation speeds of the motors is equal to or greater than the predetermined total rotation speed and the time period is less than a predetermined time, the degree of leakage of hydraulic oil from the hydraulic cylinder is determined to be relatively slight,
When the sum of the rotation speeds of the motors is equal to or greater than the predetermined total rotation speed and the duration of the period is equal to or greater than a predetermined time, it is determined that the degree of leakage of hydraulic oil from the hydraulic cylinder is relatively severe.

According to the present disclosure, it is possible to easily determine whether the degree of hydraulic oil leakage in a hydraulic cylinder is relatively minor or relatively major, and the most appropriate measures can be taken based on the results of this determination.

In addition, in a hydraulic unit according to one aspect of the present disclosure,
The predetermined time 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 present disclosure, the predetermined time 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 in both cases when the hydraulic cylinder is driven in the forward direction and when it is driven in the reverse direction.

In addition, in a hydraulic unit according to one aspect of the present disclosure,
The predetermined total number of rotations 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 present disclosure, the specified total rotation speed 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.

In addition, in a hydraulic unit according to one aspect of the present disclosure,
The predetermined first rotation speed 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 present disclosure, the predetermined first rotation speed 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.

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. 1 is an example of a graph of pressure and flow rate in a process without pressure maintenance of the hydraulic unit. 13 is an example of a graph of pressure and flow rate in a process with pressure maintenance of the hydraulic unit. 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 a diagnostic process during pressure maintenance of the hydraulic unit. 4 is a flowchart for explaining an abnormality registration process of the hydraulic unit. 4 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. 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 an embodiment of the present disclosure.

In this embodiment, 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 and three directional control valves 4A, 4B, 4C. 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. The hydraulic unit 1 supplies hydraulic oil to the hydraulic cylinders 3A, 3B, 3C to drive the hydraulic cylinders 3A, 3B, 3C.

In this embodiment, the hydraulic cylinders 3A, 3B, and 3C are double-acting single-rod cylinders. The hydraulic cylinders 3A, 3B, and 3C have 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 drive, in which the piston 32 together with the rod 33 is pushed from the cap side to the rod side, and reverse drive, 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 the embodiment, there are cases where there is no need to distinguish between the hydraulic cylinders 3A, 3B, and 3C, and where the hydraulic cylinders 3A, 3B, and 3C are simply referred to as hydraulic cylinders 3. Similarly, there are cases where there is no need to distinguish between the directional control valves 4A, 4B, and 4C, and where the directional control valves 4A, 4B, and 4C are 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. The directional control valve 4 is an electromagnetic control valve, and if it is designed to output a monitor signal that indicates the operating state of the directional control valve 4, it becomes possible to detect the state of the directional control valve 4 more reliably.

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 the first switching position, the cap side port 31a of the hydraulic cylinder 3 is connected to the discharge side of the hydraulic unit 1. In addition, 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 the second switching position, the rod side port 31b of the hydraulic cylinder 3 is in communication with 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 in communication with the oil tank 11.

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

The main engine 2 also includes a main engine control device 5. The 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 indicating the operating state is input from the directional control valve 4 to the main engine control device 5.

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

The hydraulic unit 1 includes a hydraulic circuit 10 that is fluidly connected to the hydraulic cylinder 3, and a unit control device 20 that controls the hydraulic circuit 10. The unit control device 20 is an example of a control unit according to the present disclosure.

<Hydraulic circuit>
The hydraulic circuit 10 includes an oil tank 11 that stores hydraulic oil, a hydraulic pump 12 that supplies the hydraulic oil from 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 represents 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 via the directional control valve 4A. Similarly, the discharge flow passage 14 is fluidly connected to the hydraulic cylinder 3B via the directional control valve 4B. The discharge flow passage 14 is fluidly connected to the hydraulic cylinder 3C via the directional control valve 4C.

The pressure sensor 15 detects the pressure of the hydraulic oil in the discharge passage 14 and outputs a pressure signal. In other words, the pressure sensor 15 detects the discharge pressure of the hydraulic pump 12 and outputs a pressure signal.

<Unit control device>
The unit control device 20 is composed of a CPU (Central Processing Unit), an input/output circuit, and the like, 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. The unit control device 20 receives a pressure command signal, a flow command signal, and an operation start signal indicating the start of a process involving an operation in any one of the hydraulic cylinders 3A, 3B, and 3C from the main machine control device 5. Here, the operation start signal includes cylinder information that can identify which of the hydraulic cylinders 3A, 3B, and 3C is to start operating. The unit control device 20 performs a diagnosis process for each hydraulic cylinder based on the cylinder information included in the operation start signal. Note that an identification signal for identifying the hydraulic cylinders 3A, 3B, and 3C may be input from the main machine control device 5 to the unit control device 20 separately from the operation start signal.

The pressure signal detected by the pressure sensor 15 is input to the PQ control unit 21. The PQ control unit 21 outputs a speed command signal to the speed control unit 23 based on the input pressure signal, pressure command signal, flow command signal, 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 that indicates the number of rotations per unit time.

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 input speed command signal and the speed signal, and outputs a current command signal 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 input from the speed control unit 23.

In this embodiment, the PQ control unit 21, the speed control unit 23, and the inverter 24 autonomously 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 of operating the hydraulic cylinder 3 that is executed 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 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 input discharge pressure and the discharge flow rate of the hydraulic pump 12 obtained from the input 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 an example of a pressure/flow rate graph for a process without pressure retention in hydraulic unit 1. In Figure 3, the horizontal axis represents time [arbitrary scale], and the vertical axis represents pressure [arbitrary scale] and flow rate [arbitrary scale] (number of rotations per unit time of motor 13).

In Figure 3, during the period T (time t) from when the operation start signal is input to when the process ends, the piston 32 of the hydraulic cylinder 3 moves to the target position by flow control, completing one process. At this time, the shaded area during period T represents the sum of the rotation speeds of the motor 13, ΣR (∝ total flow rate).

Figure 4 is an example of a pressure/flow rate graph for a process with pressure retention for hydraulic unit 1. In Figure 4, the horizontal axis represents time [arbitrary scale], and the vertical axis represents pressure [arbitrary scale] and flow rate [arbitrary scale] (number of rotations per unit time of motor 13).

In FIG. 4, the piston 32 of the hydraulic cylinder 3 is moved to the target position by flow control, and then pressure control is used to maintain pressure, completing one process. At the end of this process (when the operation start signal is turned off), the rotation speed and pressure of the motor 13 are measured. Here, the pressure is the pressure of the hydraulic oil in the discharge flow passage 14 detected by the pressure sensor 15.

It is advisable to measure the rotation speed and pressure of the motor 13 not only at the end of the process (when the operation start signal is off), but also at a point where the rotation speed and pressure of the motor 13 are stable while maintaining pressure through pressure control.

<Hydraulic cylinder abnormality diagnosis control>
Next, an explanation will be given of the abnormality diagnosis control of the hydraulic cylinder 3 by the unit control device 20. Figures 5 to 12 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 above-mentioned normal operation refers to, for example, an 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 from a standby state to an operating state.

Figure 5 is the main flowchart for abnormality diagnosis control.

First, the process proceeds to step S1 shown in FIG. 5. If it is determined that an operation start signal has been input, the process proceeds to step S2, where an abnormality diagnosis process is performed for the hydraulic cylinder 3 corresponding to the operation start signal.

Next, proceed to step S3. If it is determined that the diagnosis of all hydraulic cylinders 3 has been completed, proceed to step S4 and perform a priority determination process to determine the priority of abnormalities in each hydraulic cylinder 3.

Next, the process proceeds to step S5, and the result of the determination based on the priority determination process in step S4 is reported to the main unit 2.

This abnormality diagnosis control process is repeated to diagnose all hydraulic cylinders 3.

<Abnormality Diagnosis Processing>
Fig. 6 is a flow chart for explaining the abnormality diagnosis process in step S2 in Fig. 5. In the abnormality diagnosis process, diagnosis processes are performed for each hydraulic cylinder 3 when it is driven in the forward direction and when it is driven in the reverse direction.

In this abnormality diagnosis process, the process proceeds to step S11 shown in Fig. 6, where the operation of the hydraulic cylinder 3 is started. Next, the process proceeds to step S12, where the timer is counted up.
Next, the process proceeds to step S13, where the number of revolutions of the motor 13 is integrated. More specifically, the pulse signals from the pulse generator 16 are counted to obtain an integrated value ΣR of the number of revolutions of the motor 13 (the sum of the number of revolutions).

Next, the process proceeds to step S14, where it is determined whether the target pressure Pa has been reached. If it is determined that the target pressure Pa has been reached, the process proceeds to step S15. If it is determined that the target pressure Pa has not been reached, the process proceeds to step S18.

If it is determined in step S18 that the limit SW is on, the process proceeds to step S15, whereas if it is determined that the limit SW is not on, the process returns to step S11. Here, the limit SW is turned on when the piston 32 of the hydraulic cylinder 3 reaches the target position.

Whether the piston 32 of the hydraulic cylinder 3 has reached the target position may be determined by a position sensor or the like.

Next, in step S15, the operation diagnosis process is performed.

Next, the process proceeds to step S16. If it is determined that there is pressure retention, the process proceeds to step S17. If it is determined that there is no pressure retention, the process ends.

Here, the determination of whether or not pressure is maintained may be made based on a pressure command signal and a flow rate command signal from the main engine control device 5, or the unit control device 20 may receive a separate pressure maintaining signal from the main engine control device 5.

Next, in step S17, the pressure-holding diagnosis process is performed, and the diagnosis process ends.

<Diagnosis process during operation>
FIG. 7 is a flowchart for explaining the diagnostic process during operation of the hydraulic unit 1.

In this operational diagnostic process, the process proceeds to step S21 shown in FIG. 7, and the integrated rotation speed value ΣR (total rotation speed) is recorded.

Next, proceed to step S22 and record the timer value t (time t of section T).

Next, proceed to step S23. If it is determined that the first and second thresholds ΣRx,tx have been registered, proceed to step S24. If it is determined that the first and second thresholds ΣRx,tx have not been registered, proceed to step S28.

In step S28, a specified multiple (e.g., 1.1 times) of the first integrated rotation speed value ΣR is recorded as a first threshold value ΣRx (predetermined total rotation speed), 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 a second threshold value tx (predetermined time), and this operational diagnosis process ends. Here, the specified multiples of the integrated rotation speed value ΣR and the timer value t are set separately.

The first threshold value ΣRx and the second threshold value tx 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.

In this embodiment, the first rotation speed integrated value ΣR and the timer value t are used as reference values to set the first threshold value ΣRx and the second threshold value tx, but the first threshold value ΣRx and the second threshold value tx may be set in advance through simulation, experiment, etc.

In addition, in step S24, if it is determined that the rotation speed integrated value ΣR is equal to or greater than the first threshold value ΣRx, the process proceeds to step S25, whereas if it is determined that the rotation speed integrated value ΣR is less than the first threshold value ΣRx, the process proceeds to step S30.

If it is determined in step S25 that the timer value t is equal to or greater than the second threshold value tx, the process proceeds to step S26, where an abnormality registration process is performed, and the operational 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 tx, the process proceeds to step S27, where a warning registration process is performed and the operational diagnosis process is terminated.

In step S30, the rate of change of the current integrated value ΣR of the number of revolutions relative to the previous integrated value ΣR of the number of revolutions is calculated and recorded. Here, the rate of change is the percentage of the change of the current integrated value ΣR of the number of revolutions relative to the previous integrated value ΣR of the number of revolutions, as shown in the following formula.
Rate of change = (current accumulated RPM value - previous accumulated RPM value) / previous accumulated RPM value x 100

Next, proceed to step S31, and estimate the next rotation speed integrated value ΣR from the rate of change calculated in step S30.

In this embodiment, the rate of change of the integrated rotation speed value ΣR is used to estimate the next integrated rotation speed value ΣR, but the total rotation speed ΣR of the motor 13 in the next process may be estimated using an approximation curve or the like as the tendency of change in the total rotation speed ΣR of the motor 13 when the in-operation diagnostic process is performed multiple times.

Next, the process proceeds to step S32. If it is determined that the next rotation speed integrated value ΣR estimated in step S31 is equal to or greater than the first threshold value ΣRx, the process proceeds to step S27. On the other hand, if it is determined that the next rotation speed integrated value ΣR is less than the first threshold value ΣRx, the operation diagnostic process is terminated.

<Diagnosis process during pressure retention>
FIG. 8 is a flowchart for explaining the pressure maintaining diagnostic process of the hydraulic unit 1.

In this pressure-holding diagnostic process, the process proceeds to step S31 shown in FIG. 8. If it is determined that the operation start signal is off, the process proceeds to step S32. If it is determined that the operation start signal is not off, the process repeats step S31.

Next, proceed to step S32 and record the rotation speed Rh during pressure maintenance, and then proceed to step S33 and record the pressure value Ph (pressure Ph of the hydraulic oil during pressure maintenance).

Next, the process proceeds to step S34. If it is determined that the third threshold value Rhx (predetermined first rotation speed) has been registered, the process proceeds to step S35. If it is determined that the third threshold value Rhx has not been registered, the process proceeds to step S39.

In step S39, a specified multiple (e.g., 1.1 times) of the first pressure-holding rotation speed Rh is recorded as the third threshold value Rhx, and the pressure-holding diagnosis process is terminated.

The third threshold value Rhx is recorded in the second threshold table for each hydraulic cylinder 3, the value when the hydraulic cylinder 3 is driven in the forward direction and the value when the hydraulic cylinder 3 is driven in the reverse direction.

In this embodiment, the first pressure-holding rotation speed Rh is used as the reference value to set the third threshold value Rhx, but the third threshold value Rhx may be set in advance through simulation, experiment, etc.

In addition, in step S35, if it is determined that the rotational speed Rh during pressure maintenance is equal to or greater than the third threshold value Rhx, the process proceeds to step S36, whereas if it is determined that the rotational speed Rh during pressure maintenance is less than the third threshold value Rhx, the process proceeds to step S40.

If it is determined in step S36 that the pressure value Ph is less than the target pressure Pa (predetermined pressure), the process proceeds to step S37, where an abnormality registration process is performed, and the pressure-maintaining diagnosis process is terminated.

On the other hand, if it is determined in step S36 that the pressure value Ph is equal to or greater than the target pressure Pa, the process proceeds to step S38, where a warning registration process is performed and the pressure-maintaining diagnostic process is terminated.

In step S40, the rate of change of the current rotation speed Rh during pressure holding relative to the previous rotation speed Rh during pressure holding is calculated and recorded. Here, the rate of change is the percentage of the change of the current rotation speed Rh during pressure holding relative to the previous rotation speed Rh during pressure holding, as shown in the following formula.
Rate of change = (current rotation speed during pressure holding Rh - previous rotation speed during pressure holding Rh) / previous rotation speed during pressure holding Rh x 100

Next, proceed to step S41, and estimate the next pressure-holding rotation speed Rh from the rate of change calculated in step 430.

Next, the process proceeds to step S42. If it is determined that the next rotation speed Rh during pressure holding estimated in step S41 is equal to or greater than the third threshold value Rhx, the process proceeds to step S38. On the other hand, if it is determined that the next rotation speed Rh during pressure holding is less than the third threshold value Rhx, the process terminates.

<Abnormal registration process>
Fig. 9 is a flow chart for explaining the abnormality registration process of the hydraulic unit 1. In this abnormality registration process, the process proceeds to step S51 shown in Fig. 9, where it is determined that the packing has deteriorated, and then to step S52, where an abnormality is registered for the hydraulic cylinder, and then this abnormality registration process is terminated.

<Warning registration process>
Fig. 10 is a flowchart for explaining the warning registration process of the hydraulic unit 1. In this warning registration process, the process proceeds to step S61 shown in Fig. 10, 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, and then this warning registration process is terminated.

<Priority determination process>
11 and 12 are flow charts for explaining the priority order determination process of the hydraulic unit 1. In FIG.

In this priority determination process, the process proceeds to step S71 shown in FIG. 11. If it is determined that the rotation speed Rh during pressure retention is recorded, the process proceeds to step S72. However, if it is determined that the rotation speed Rh during pressure retention is not recorded, the process proceeds to step S81 shown in FIG. 12.

In step S72, it is determined whether the current rotation speed Rh during pressure maintenance is equal to or greater than the third threshold value Rhx (predetermined first rotation speed). If it is determined that the current rotation speed Rh during pressure maintenance is equal to or greater than the third threshold value Rhx, the process proceeds to step S73. However, if it is determined that the current rotation speed Rh during pressure maintenance is less than the third threshold value Rhx, step S73 is skipped.

In step S73, the abnormality rankings (in descending order of severity) of the hydraulic cylinders 3A, 3B, and 3C are sorted in descending order of the deviation ΔR1 between the current pressure-holding rotation speed Rh and the third threshold value Rhx. That is, the deviation ΔR1 is calculated using the following formula, and the abnormality rankings of the hydraulic cylinders 3A, 3B, and 3C are rearranged in descending order of the deviation ΔR1.
△R1 = current pressure-holding rotation speed Rh - third threshold Rhx

Next, the process proceeds to step S74. If it is determined that the next rotation speed Rh during pressure maintenance determined in the pressure maintenance diagnosis process (step S41 in FIG. 8) is equal to or greater than the third threshold value Rhx, the process proceeds to step S75. On the other hand, if it is determined that the next rotation speed Rh during pressure maintenance is less than the third threshold value Rhx, the process proceeds to step S78.

In step S75, the warning priority (highest level of warning) of the hydraulic cylinders 3A, 3B, 3C is sorted in descending order of the deviation ΔR2 between the next pressure-holding rotation speed Rh and the third threshold value Rhx. That is, the deviation ΔR2 is calculated using the following formula, and the warning priority of the hydraulic cylinders 3A, 3B, 3C is rearranged in descending order of the deviation ΔR2.
△R2 = Next pressure-holding rotation speed Rh - Third threshold Rhx

Next, proceed to step S76, and if it is determined that the pressure values Ph during pressure maintenance are different for each of the hydraulic cylinders 3A, 3B, and 3C, proceed to step S77, and sort the abnormality and warning ranks in ascending order of pressure value Ph. In other words, the abnormality and warning ranks of the hydraulic cylinders 3A, 3B, and 3C are rearranged in ascending order of pressure value Ph during pressure maintenance.

Next, when it is determined in step S78 that diagnosis of all hydraulic cylinders 3A, 3B, and 3C has been completed, this priority determination process ends.

Note that if the increase in leakage on the low pressure side of the pressure value Ph during pressure holding is not important, steps S76 and S77 may be omitted.

In addition, in step S81, if it is determined that the current integrated value of the rotation speed ΣR is equal to or greater than the first threshold value ΣRx, the process proceeds to step S82, and if it is determined that the current integrated value of the rotation speed ΣR is less than the first threshold value ΣRx, step S82 is skipped.

Then, in step S82, the abnormalities are sorted in descending order of the deviation between the current integrated rotation speed value ΣR and the first threshold value ΣRx.

Next, the process proceeds to step S83. If it is determined that the next integrated rotation speed value ΣR is equal to or greater than the first threshold value ΣRx, the process proceeds to step S84. If it is determined that the next integrated rotation speed value ΣR is less than the first threshold value ΣRx, the process skips step S84.

Then, in step S84, the warning priority is sorted in descending order of the deviation between the next rotation speed integrated value ΣR and the first threshold value ΣRx.

In the hydraulic unit 1 configured as above, the unit control device 20 measures the sum ΣR of the number of rotations of the motor 13 detected by the pulse generator 16 for each hydraulic cylinder 3 during the period T from the input of the operation start signal to the end of the process, and when pressure is maintained by the hydraulic cylinder 3 before the end of the period T, the pulse generator 16 measures the number of rotations Rh of the motor 13 per unit time during pressure maintenance, and the pressure sensor 15 measures the pressure Ph of the hydraulic oil during pressure maintenance. Then, when the sum ΣR of the number of rotations of the motor 13 during the period T from the input of the operation start signal to the end of the process is equal to or greater than the first threshold ΣRx (predetermined total number of rotations), it is determined that hydraulic oil is leaking from the hydraulic cylinder 3. Alternatively, when the number of rotations Rh of the motor 13 per unit time during pressure maintenance is equal to or greater than the third threshold Rhx (predetermined first number of rotations), it is determined that hydraulic oil is leaking from the hydraulic cylinder 3 in excess of a predetermined amount.

In this way, hydraulic oil leakage can be determined for each hydraulic cylinder 3A, 3B, and 3C based on the operation start signal.

According to the hydraulic unit 1, the pressure and flow rate of the hydraulic oil discharged by the hydraulic pump 12 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 cylinders 3A, 3B, and 3C 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 sum ΣR of the motor 13 rotation speeds for each hydraulic cylinder 3 using the tendency of change in the sum ΣR of the motor 13 rotation speeds when the process is repeated, and when the estimated sum ΣR of the motor 13 rotation speeds is equal to or greater than a first threshold ΣRx (predetermined total rotation speed), determines that a leakage of hydraulic oil exceeding a predetermined amount will occur in the next process in the hydraulic cylinders 3A, 3B, and 3C.

In this way, by estimating the sum ΣR of the rotation speeds of the motors 13 that will be measured next, measures can be taken before the leakage of hydraulic oil from the hydraulic cylinders 3 becomes serious.

The unit control device 20 also estimates the next measured rotation speed Rh of the motor 13 per unit time using the tendency of change in the rotation speed Rh of the motor 13 per unit time during pressure holding when the process is repeated, and when the estimated rotation speed Rh of the motor 13 per unit time is equal to or greater than a third threshold value Rhx (predetermined first rotation speed), determines that a leakage of hydraulic oil exceeding a predetermined amount will occur in the hydraulic cylinders 3A, 3B, and 3C in the next process.

In this way, by estimating the next measured rotation speed Rh of the motor 13 per unit time, measures can be taken before the hydraulic oil leak in the hydraulic cylinder 3 becomes serious.

Furthermore, when the number of rotations Rh per unit time of the motor 13 during pressure maintenance is equal to or greater than the third threshold value Rhx (predetermined first rotation speed) and the hydraulic oil pressure Ph during pressure maintenance has reached the target pressure Pa (predetermined pressure), the unit control device 20 determines that the degree of hydraulic oil leakage in the hydraulic cylinders 3A, 3B, and 3C is relatively minor. If the degree of hydraulic oil leakage is relatively minor, a warning is sent to the main engine 2.

On the other hand, when the number of rotations Rh per unit time of the motor 13 during pressure maintenance is equal to or greater than the third threshold value Rhx (predetermined first rotation speed) and the hydraulic oil pressure Ph during pressure maintenance is less than the target pressure Pa (predetermined pressure), 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.

In addition, the target pressure Pa (predetermined pressure) 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, so that a load is applied at least when the hydraulic cylinder 3 is driven in the forward direction or when it is driven in the reverse direction, making it possible to accurately determine whether the hydraulic oil is leaking.

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 unit control device 20 also measures the time t of the period T, and when the sum ΣR of the rotation speeds of the motors 13 is equal to or greater than a first threshold ΣRx (a predetermined total rotation speed) and the time t of the period T is less than a second threshold tx (a predetermined time), 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 notifies the main engine 2 of a warning.

On the other hand, when the sum ΣR of the rotation speeds of the motors 13 is equal to or greater than the first threshold ΣRx (a predetermined total rotation speed) and the time t of the period T is equal to or greater than the second threshold tx (a predetermined time), it is determined that the degree of hydraulic oil leakage in the hydraulic cylinders 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.

In addition, the second threshold value tx (predetermined time) 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, so that 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 addition, the first threshold value ΣRx (predetermined total rotation speed) 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, so that leakage of hydraulic oil can be accurately determined when the hydraulic cylinder 3 is driven in both the forward direction and the reverse direction.

The third threshold value Rhx (predetermined first rotation speed) 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, so that 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 total rotation speed ΣR 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 in the total rotation speed ΣR 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 the large rate of change in the total number of rotations ΣR 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.

Furthermore, if the rate of change in the sum ΣR of the rotation speeds during pressure holding when all hydraulic cylinders 3A, 3B, and 3C are stopped is large, this is likely due to internal wear of the hydraulic pump 12, so replace the hydraulic pump 12.

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.

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 (9)

A hydraulic pump (12) for supplying hydraulic oil to the hydraulic cylinders (3A, 3B, 3C);
A motor (13) that drives the hydraulic pump (12);
A rotation speed sensor (16) for detecting the rotation speed of the motor (13);
a pressure sensor (15) for detecting the pressure of the hydraulic oil discharged by the hydraulic pump (12);
a control unit (20) for controlling the motor (13) upon receiving an operation start signal for starting a process involving the operation of the hydraulic cylinders (3A, 3B, 3C);
The control unit (20)
During the period (T) from the input of the operation start signal to the end of the process, the sum (ΣR) of the number of rotations of the motor (13) detected by the number of rotations sensor (16) is measured ,
When the sum (ΣR) of the rotation speeds of the motors (13) is equal to or greater than a predetermined total rotation speed (ΣRx) , it is determined that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinders (3A, 3B, 3C) ,
determining whether or not to perform pressure retention by the hydraulic cylinders (3A, 3B, 3C) before the end of the period (T);
when it is determined that pressure maintenance should be performed by the hydraulic cylinders (3A, 3B, 3C) before the end of the period (T), the rotation speed sensor (16) measures the number of rotations (Rh) per unit time of the motor (13) during the pressure maintenance, and the pressure sensor (15) measures the pressure (Ph) of the hydraulic oil during the pressure maintenance;
When the number of rotations (Rh) per unit time of the motor (13) during the pressure maintenance is equal to or greater than a predetermined first number of rotations (Rhx), it is determined that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinder (3A, 3B, 3C) . A hydraulic pump (12) for supplying hydraulic oil to the hydraulic cylinders (3A, 3B, 3C);
A motor (13) that drives the hydraulic pump (12);
A rotation speed sensor (16) for detecting the rotation speed of the motor (13);
a pressure sensor (15) for detecting the pressure of the hydraulic oil discharged by the hydraulic pump (12);
a control unit (20) for controlling the motor (13) upon receiving an operation start signal for starting a process involving the operation of the hydraulic cylinders (3A, 3B, 3C);
The control unit (20)
During the period (T) from the input of the operation start signal to the end of the process, the sum (ΣR) of the number of rotations of the motor (13) detected by the number of rotations sensor (16) is measured ,
When the sum (ΣR) of the rotation speeds of the motors (13) is equal to or greater than a predetermined total rotation speed (ΣRx) , it is determined that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinders (3A, 3B, 3C),
determining whether or not to perform pressure retention by the hydraulic cylinders (3A, 3B, 3C) before the end of the period (T);
when it is determined that pressure maintenance should be performed by the hydraulic cylinders (3A, 3B, 3C) before the end of the period (T), the rotation speed sensor (16) measures the number of rotations (Rh) per unit time of the motor (13) during the pressure maintenance, and the pressure sensor (15) measures the pressure (Ph) of the hydraulic oil during the pressure maintenance;
When the number of rotations (Rh) per unit time of the motor (13) during the pressure maintenance is equal to or greater than a predetermined first number of rotations (Rhx), it is determined that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinder (3A, 3B, 3C),
The control unit (20)
Using the tendency of change in the sum (ΣR) of the number of revolutions of the motor (13) when the above steps are repeated, the sum (ΣR) of the number of revolutions of the motor (13) to be measured next is estimated;
When the estimated sum (ΣR) of the rotation speeds of the motors (13) is equal to or greater than the predetermined total rotation speed (ΣRx), it is determined that a leakage of hydraulic oil exceeding a predetermined amount will occur in the hydraulic cylinders (3A, 3B, 3C) in the next process. A hydraulic pump (12) for supplying hydraulic oil to the hydraulic cylinders (3A, 3B, 3C);
A motor (13) that drives the hydraulic pump (12);
A rotation speed sensor (16) for detecting the rotation speed of the motor (13);
a pressure sensor (15) for detecting the pressure of the hydraulic oil discharged by the hydraulic pump (12);
a control unit (20) for controlling the motor (13) upon receiving an operation start signal for starting a process involving the operation of the hydraulic cylinders (3A, 3B, 3C);
The control unit (20)
During the period (T) from the input of the operation start signal to the end of the process, the sum (ΣR) of the number of rotations of the motor (13) detected by the number of rotations sensor (16) is measured ,
When the sum (ΣR) of the rotation speeds of the motors (13) is equal to or greater than a predetermined total rotation speed (ΣRx) , it is determined that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinders (3A, 3B, 3C),
determining whether or not to perform pressure retention by the hydraulic cylinders (3A, 3B, 3C) before the end of the period (T);
when it is determined that pressure maintenance should be performed by the hydraulic cylinders (3A, 3B, 3C) before the end of the period (T), the rotation speed sensor (16) measures the number of rotations (Rh) per unit time of the motor (13) during the pressure maintenance, and the pressure sensor (15) measures the pressure (Ph) of the hydraulic oil during the pressure maintenance;
When the number of rotations (Rh) per unit time of the motor (13) during the pressure maintenance is equal to or greater than a predetermined first number of rotations (Rhx), it is determined that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinder (3A, 3B, 3C),
The control unit (20)
Using the tendency of change in the number of rotations (Rh) per unit time of the motor (13) during the pressure holding period when the above process is repeated, the number of rotations (Rh) per unit time of the motor (13) to be measured next is estimated;
When the estimated rotation speed (Rh) per unit time of the motor (13) is equal to or greater than the predetermined first rotation speed (Rhx), it is determined that a leakage of hydraulic oil exceeding a predetermined amount will occur in the hydraulic cylinder (3A, 3B, 3C) in the next process. 4. The hydraulic unit according to claim 3,
The control unit (20)
When the number of rotations (Rh) per unit time of the motor (13) during the pressure maintenance is equal to or greater than the predetermined first number of rotations (Rhx) and the pressure (Ph) of the hydraulic oil during the pressure maintenance reaches a predetermined pressure (Pa), the degree of leakage of the hydraulic oil from the hydraulic cylinders (3A, 3B, 3C) is determined to be relatively slight,
a hydraulic unit that determines that the degree of hydraulic oil leakage in the hydraulic cylinders (3A, 3B, 3C) is relatively severe when the rotation speed (Rh) per unit time of the motor (13) during the pressure maintenance is equal to or greater than the specified first rotation speed (Rhx) and the pressure of the hydraulic oil (Ph) during the pressure maintenance is less than the specified pressure (Pa). 5. The hydraulic unit according to claim 3,
The predetermined pressure (Pa) is set to a different value when the hydraulic cylinders (3A, 3B, 3C) are driven in the forward direction and when they are driven in the reverse direction, a hydraulic unit. A hydraulic pump (12) for supplying hydraulic oil to the hydraulic cylinders (3A, 3B, 3C);
A motor (13) that drives the hydraulic pump (12);
A rotation speed sensor (16) for detecting the rotation speed of the motor (13);
a pressure sensor (15) for detecting the pressure of the hydraulic oil discharged by the hydraulic pump (12);
a control unit (20) for controlling the motor (13) upon receiving an operation start signal for starting a process involving the operation of the hydraulic cylinders (3A, 3B, 3C);
The control unit (20)
During the period (T) from the input of the operation start signal to the end of the process, the sum (ΣR) of the number of rotations of the motor (13) detected by the number of rotations sensor (16) is measured ,
When the sum (ΣR) of the rotation speeds of the motors (13) is equal to or greater than a predetermined total rotation speed (ΣRx) , it is determined that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinders (3A, 3B, 3C),
determining whether or not to perform pressure retention by the hydraulic cylinders (3A, 3B, 3C) before the end of the period (T);
when it is determined that pressure maintenance should be performed by the hydraulic cylinders (3A, 3B, 3C) before the end of the period (T), the rotation speed sensor (16) measures the number of rotations (Rh) per unit time of the motor (13) during the pressure maintenance, and the pressure sensor (15) measures the pressure (Ph) of the hydraulic oil during the pressure maintenance;
When the number of rotations (Rh) per unit time of the motor (13) during the pressure maintenance is equal to or greater than a predetermined first number of rotations (Rhx), it is determined that a leakage of hydraulic oil exceeding a predetermined amount is occurring in the hydraulic cylinder (3A, 3B, 3C),
The control unit (20)
Measure the time (t) of the period (T),
When the sum (ΣR) of the rotation speeds of the motors is equal to or greater than the predetermined total rotation speed (ΣRx) and the time (t) of the period (T) is less than a predetermined time (tx), the degree of leakage of hydraulic oil from the hydraulic cylinders (3A, 3B, 3C) is determined to be relatively slight,
A hydraulic unit that determines that the degree of hydraulic oil leakage in the hydraulic cylinders (3A, 3B, 3C) is relatively severe when the sum (ΣR) of the rotation speeds of the motors is equal to or greater than the specified total rotation speed (ΣRx) and the time (t) of the period (T) is equal to or greater than a specified time (tx). 7. The hydraulic unit according to claim 6,
The predetermined time (tx) is set to a different value when the hydraulic cylinders (3A, 3B, 3C) are driven in the forward direction and when they are driven in the reverse direction, a hydraulic unit. A hydraulic unit according to any one of claims 1 to 7,
The predetermined total rotation speed (ΣRx) is set to a different value when the hydraulic cylinders (3A, 3B, 3C) are driven in the forward direction and when they are driven in the reverse direction, a hydraulic unit. A hydraulic unit according to any one of claims 1 to 8,
The predetermined first rotation speed (Rhx) is set to a different value when the hydraulic cylinders (3A, 3B, 3C) are driven in the forward direction and when they are driven in the reverse direction.

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