Hydraulic pump performance degradation detection system

Abstract

To provide a performance deterioration detecting system of a hydraulic pump capable of detecting deterioration of the performance of a hydraulic pump without using a flowmeter.SOLUTION: A hydraulic pump deterioration detecting system 1A in one embodiment comprises a hydraulic pump 3 supplying working fluid to a hydraulic actuator 5 and actuating the hydraulic actuator 5 and driven by a primer mover 2, a selector valve 65 provided on a flow path 64 in which the working fluid emitted from the hydraulic pump 3 flows, and capable of being switched between an open position and a closed position, and a control device 7 capable of changing a rotation number of the prime mover 2. The control device 7 determines whether a performance of the hydraulic pump 3 is deteriorated based on the rotation number of the prime mover 2 and discharge pressure of the hydraulic pump 3 measured by a pressure sensor 72, while the selector valve 65 is switched to the closed position, when the hydraulic actuator 5 is not operated.SELECTED DRAWING: Figure 1

Description

Technical Field

[0004]

[0001] The present disclosure relates to a system for detecting a performance degradation of a hydraulic pump.

Background Art

[0002] Conventionally, a hydraulic circuit that supplies hydraulic fluid from a hydraulic pump to a hydraulic actuator has been known. In such a hydraulic circuit, it is desirable to detect a performance degradation of the hydraulic pump.

[0003] For example, Patent Document 1 discloses a device that measures a drain flow rate from a hydraulic pump with a flow meter and determines whether the hydraulic pump is worn based on the drain flow rate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the drain flow rate is small, the measured value of the flow meter is easily affected by the measurement accuracy. Therefore, it is difficult to detect a performance degradation of the hydraulic pump, such as a slight decrease in the discharge flow rate due to wear of the sliding portion of the hydraulic pump, based on the drain flow rate measured by the flow meter.

[0006] Therefore, an object of the present disclosure is to provide a hydraulic pump performance degradation detection system that can detect a performance degradation of a hydraulic pump without using a flow meter.

Means for Solving the Problems

[0007] This disclosure provides a hydraulic pump performance degradation detection system comprising: a hydraulic pump driven by a prime mover that supplies working fluid to a hydraulic actuator to operate the hydraulic actuator; a switching valve provided in a passage through which the working fluid discharged from the hydraulic pump flows, which can be switched between an open position that opens the passage and a closed position that closes the passage; a control device that can change the rotational speed of the prime mover; and a pressure sensor that measures the discharge pressure of the hydraulic pump upstream of the switching valve, wherein the control device determines whether the performance of the hydraulic pump has deteriorated based on the rotational speed of the prime mover and the discharge pressure of the hydraulic pump measured by the pressure sensor when the hydraulic actuator is not operating and the switching valve is switched to the closed position.

[0008] This disclosure provides a hydraulic pump performance degradation detection system comprising: a hydraulic pump driven by a prime mover that supplies working fluid to a hydraulic actuator to operate the hydraulic actuator; a switching valve provided in a flow path through which the working fluid discharged from the hydraulic pump flows, which can be switched between an open position that opens the flow path and a specific throttle position with an opening degree in the range of 1 to 70%; a control device that can change the rotational speed of the prime mover; and a pressure sensor that measures the discharge pressure of the hydraulic pump upstream of the switching valve, wherein the control device determines whether the performance of the hydraulic pump has deteriorated based on the rotational speed of the prime mover and the discharge pressure of the hydraulic pump measured by the pressure sensor when the hydraulic actuator is not operating and the switching valve is switched to the specific throttle position. [Effects of the Invention]

[0009] According to this disclosure, a decrease in the performance of a hydraulic pump can be detected without using a flow meter. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of the hydraulic pump performance degradation detection system according to the first embodiment. [Figure 2]This graph shows the relationship between the rotational speed of the prime mover and the discharge pressure of the hydraulic pump. [Figure 3] This is a schematic diagram showing a modified example of the first embodiment. [Figure 4] This is a schematic diagram showing another modified example of the first embodiment. [Figure 5] This is a schematic diagram of the hydraulic pump performance degradation detection system according to the second embodiment. [Modes for carrying out the invention]

[0011] (First Embodiment) Figure 1 shows a hydraulic pump performance degradation detection system 1A according to the first embodiment. This embodiment is configured to allow the detection of performance degradation of the hydraulic pump 3 to be performed, for example, in the hydraulic circuit of a construction machine. Examples of construction machines include hydraulic excavators and hydraulic cranes.

[0012] The hydraulic pump 3 is driven by the prime mover 2. In this embodiment, the prime mover 2 is an engine. However, the prime mover 2 may be an electric motor. Also, in this embodiment, the hydraulic pump 3 is an axial piston pump (swashplate pump or swash shaft pump). However, the hydraulic pump 3 may be other types of pumps such as a vane pump, gear pump, or screw pump.

[0013] Furthermore, in this embodiment, the hydraulic pump 3 is a variable displacement pump. The capacity (discharge volume per revolution) of the hydraulic pump 3 is changed by the regulator 31. The capacity of the hydraulic pump 3 can be arbitrarily changed between the minimum capacity and the maximum capacity. In this embodiment, the minimum capacity of the hydraulic pump 3 is set to be greater than zero. However, the minimum capacity of the hydraulic pump 3 may be zero. The regulator 31 is operated by an electrical signal.

[0014] For example, if the hydraulic pump 3 is a swashplate pump, the regulator 31 may electrically change the hydraulic pressure acting on a servo piston connected to the swashplate of the hydraulic pump 3, or it may be an electric actuator connected to the swashplate of the hydraulic pump 3.

[0015] The hydraulic pump 3 supplies working fluid to multiple hydraulic actuators 5 via multiple control valves 4 to operate those hydraulic actuators 5. In the illustrated example, there are two hydraulic actuators 5, but there may be one hydraulic actuator 5 (in which case there is also one control valve 4), or three or more.

[0016] The hydraulic pump 3 is connected to the control valve 4 by a supply channel 61. In other words, the supply channel 61 includes a common channel extending from the hydraulic pump 3 and multiple branch channels that branch off from the common channel and connect to the control valve 4. The control valve 4 is connected to the tank by a tank channel 62. A relief channel branches off from the common channel of the supply channel 61, and a relief valve is provided in this relief channel.

[0017] In this embodiment, the hydraulic actuator 5 is a double-acting cylinder or hydraulic motor that operates in both directions. Therefore, each control valve 4 is connected to the corresponding hydraulic actuator 5 by a pair of supply and discharge passages 63.

[0018] Each control valve 4 is, for example, a spool valve with a built-in spool. Each control valve 4 is switchable between a neutral position, a first operating position, and a second operating position. In the neutral position, each control valve 4 closes all of the supply passage 61, the tank passage 62, and the pair of supply and discharge passages 63. In the first operating position or the second operating position, each control valve 4 connects the supply passage 61 to one of the supply and discharge passages 63, and connects the other supply and discharge passage 63 to the tank passage 62.

[0019] Each control valve 4 operates according to the operation amount of an operating device for operating the corresponding hydraulic actuator 5. In the present embodiment, each control valve 4 has a pair of pilot ports. When the operating device is an electric joystick, a pair of electromagnetic proportional valves are respectively connected to the pair of pilot ports of each control valve 4. Each control valve 4 is controlled by a control device 7 via those electromagnetic proportional valves.

[0020] The control device 7 increases the operation amount (i.e., the opening area) of the corresponding control valve 4 as the operation amount of the operating device increases. Further, the control device 7 controls the regulator 31 so that the capacity of the hydraulic pump 3 increases as the operation amount of the operating device increases.

[0021] When the operating device is a pilot-operated valve that outputs a pilot pressure according to the operation amount, the pair of pilot ports of each control valve 4 are connected to the pilot-operated valve. Alternatively, each control valve 4 may be a solenoid valve directly controlled by the control device 7.

[0022] Regarding the control device 7, the functions of the elements disclosed in this specification can be executed using a circuit or a processing circuit including a general-purpose processor, a dedicated processor, an integrated circuit, an ASIC (Application Specific Integrated Circuits), a conventional circuit, and / or a combination thereof configured or programmed to execute the disclosed functions. Since the processor includes transistors and other circuits, it is regarded as a processing circuit or a circuit. In the present disclosure, a circuit, a unit, or a means is hardware that executes the listed functions or hardware programmed to execute the listed functions. The hardware may be the hardware disclosed in this specification or other known hardware programmed or configured to execute the listed functions. When the hardware is a processor considered to be a type of circuit, the circuit, the means, or the unit is a combination of hardware and software, and the software is used for the configuration of the hardware and / or the processor.

[0023] An unloading channel 64 branches off from the common supply channel 61, and this unloading channel 64 extends to the tank. In this embodiment, the unloading channel 64 also serves as a center bypass channel that passes through all the control valves 4.

[0024] Each control valve 4 opens the unload passage 64 in the neutral position (opening 100%), and as the amount of operation from the neutral position increases, the opening of the valve to the unload passage 64 decreases, closing the unload passage 64 at least when the amount of operation is at its maximum (opening 0%). In other words, unless any of the control valves 4 closes the unload passage 64 or the unload valve 65 (described later) closes the unload passage 64, the working fluid discharged from the hydraulic pump 3 flows through the unload passage 64.

[0025] An unload valve 65 is provided downstream of all control valves 4 in the unload passage 64. The unload valve 65 can be switched between an open position (opening degree 100%) that opens the unload passage 64 and a closed position (opening degree 0%) that closes the unload passage. The opening degree of the unload valve 65 can be arbitrarily changed between the open position and the closed position. In this embodiment, the open position is the neutral position, but the closed position may also be the neutral position.

[0026] In this embodiment, the unload valve 65 is a spool valve that incorporates a spool. That is, the open position, which is the neutral position, is one stroke end of the spool, and the closed position is the other stroke end of the spool. In other words, in the neutral position, the spool is pressed against the stopper by a spring, and in the closed position, the spool is furthest away from the stopper (full stroke).

[0027] In this embodiment, the unload valve 65 is an electromagnetic valve including a solenoid and is controlled by the control device 7. That is, the neutral position described above is the de-energized state of the solenoid. The control device 7 decreases the opening degree of the unload valve 65 as the amount of operation of the operating device described above increases. Alternatively, the unload valve 65 may include a pilot port instead of a solenoid, and this pilot port may be connected to an electromagnetic valve provided separately from the unload valve. In this case, the unload valve 65 is controlled by the control device 7 via the electromagnetic valve.

[0028] Furthermore, the control device 7 is capable of changing the rotational speed of the prime mover 2. In this embodiment, since the prime mover 2 is an engine, the control device 7 controls the fuel injection amount. The control device 7 may be divided into an engine control device that controls the fuel injection amount and a pump control device that controls the regulator 31.

[0029] The control device 7 is electrically connected to a tachometer 71 installed on the prime mover 2 and a pressure sensor 72 installed in the common path of the supply flow path 61. The tachometer 71 measures the rotational speed of the prime mover 2, and the pressure sensor 72 measures the discharge pressure of the hydraulic pump 3. As described above, since the unload flow path 64 branches off from the common path of the supply flow path 61, the pressure sensor 72 measures the discharge pressure of the hydraulic pump 3 upstream of the unload valve 65.

[0030] The control device 7 performs a performance check on the hydraulic pump 3 when the hydraulic actuator 5 is not operating, that is, when the hydraulic pump 3 is not supplying hydraulic fluid to the hydraulic actuator 5.

[0031] More specifically, the control device 7 first controls the regulator 31 so that the capacity of the hydraulic pump 3 is minimized. Normally, when the hydraulic actuator 5 is not operating, the capacity of the hydraulic pump 3 is kept at its minimum, so the control device 7 does not instruct the regulator 31 to perform any new operations.

[0032] Next, the control device 7 sets the rotational speed of the prime mover 2 to a predetermined value Ns that is somewhat low. For example, if the rotational speed of the prime mover 2 is normally kept constant within the range of 1000 to 2500 rpm, the predetermined value Ns may be lower than the rotational speed of the prime mover 2 under normal conditions (for example, 900 to 1800 rpm).

[0033] Subsequently, the control device 7 switches the unload valve 65 to the closed position. As a result, the discharge of working fluid from the hydraulic pump 3 is shut off as long as the discharge pressure of the hydraulic pump 3 does not exceed the set pressure (relief pressure) of the relief valve.

[0034] When the discharge of working fluid from the hydraulic pump 3 is shut off, and the rotational speed of the prime mover 2 is relatively low, such as a predetermined value Ns, the discharge pressure of the hydraulic pump 3 does not become very high due to internal leaks in the hydraulic pump 3 (in this embodiment, there are also leaks in the control valve 4).

[0035] In this state, the control device 7 determines whether the performance of the hydraulic pump 3 has deteriorated based on the rotational speed of the prime mover 2 measured by the tachometer 71 and the discharge pressure of the hydraulic pump 3 measured by the pressure sensor 72. This determination is made while the regulator 31 is controlled to minimize the capacity of the hydraulic pump 3, as described above.

[0036] More specifically, as shown in Figure 2, the control device 7 increases the rotational speed of the prime mover 2 from a predetermined value Ns, and stores the rotational speed when the discharge pressure of the hydraulic pump 3, measured by the pressure sensor 72, reaches a threshold Pt, or in other words, when the discharge pressure of the hydraulic pump 3 rises to the threshold Pt, as the determination rotational speed N1.

[0037] The control device 7 stores a reference rotational speed N0 in advance. The reference rotational speed N0 is the rotational speed when the discharge pressure of the hydraulic pump 3 reaches the threshold value Pt in the case where there is no abnormality in the hydraulic pump 3 (for example, before factory shipment after a short-time operation after the hydraulic drive device including the hydraulic pump 3 is attached to the machine, or during a short period of operation immediately after factory shipment after the machine is completed). As the reference rotational speed N0, the rotational speed when the discharge pressure of the hydraulic pump 3 reaches the threshold value Pt, which can be obtained more simply by performance confirmation of the pump alone, may be used.

[0038] The control device 7 compares the stored determination rotational speed N1 with the reference rotational speed N0. When the determination rotational speed N1 is greater than or equal to the set value V more than the reference rotational speed N0 (N1 - N0 ≧ V), it is determined that the performance of the hydraulic pump 3 has deteriorated. On the other hand, when the determination rotational speed N1 is not greater than or equal to the set value V more than the reference rotational speed N0 (N1 - N0 < V), the control device 7 determines that the performance of the hydraulic pump 3 has not deteriorated.

[0039] When the rotational speed of the prime mover 2 is increased from a predetermined value Ns that is somewhat low, depending on the degree of abnormality of the hydraulic pump 3 (for example, when the hydraulic pump 3 is a swash plate pump, wear of the shoe that slides on the swash plate provided at the tip of the piston, or wear of the sliding surface between the valve plate and the cylinder block), the rotational speed when the discharge pressure of the hydraulic pump 3 reaches the threshold value Pt changes. Therefore, by using the rotational speed of the prime mover 2 and the discharge pressure of the hydraulic pump 3 as in this embodiment, it is possible to detect a decrease in the performance of the hydraulic pump 3 without using a flow meter. Moreover, it is possible to detect a decrease in the performance of the hydraulic pump 3 with higher accuracy than measuring the drain flow rate.

[0040] Furthermore, since hydraulic circuits for construction machinery often include an unloading passage 64 equipped with an unloading valve 65 and a pressure sensor 72 for measuring the discharge pressure of the hydraulic pump 3, such hydraulic circuits can detect a decrease in the performance of the hydraulic pump 3 without adding any additional equipment. In addition, measurements can be taken including even slight leaks other than those from the pump included in the hydraulic drive system. In other words, instead of focusing only on internal leaks in the pump itself, the effects of control valves 4 and other components in the hydraulic circuit can be included, making it possible to precisely determine the deterioration of pump performance without being affected by individual machine variations.

[0041] Furthermore, in this embodiment, since the rotational speed of the prime mover 2 is increased from a predetermined value Ns after the capacity of the hydraulic pump 3 is set to its minimum, the difference between the rotational speed N1 used for determining when the performance of the hydraulic pump 3 has deteriorated and the reference rotational speed N0 becomes larger. Therefore, the accuracy of detecting the deterioration in the performance of the hydraulic pump 3 can be improved.

[0042] <Variation> In the above embodiment, when the rotational speed at which the discharge pressure of the hydraulic pump 3 reaches a threshold Pt is stored as the determination rotational speed N1, the control device 7 increased the rotational speed of the prime mover 2 from a predetermined value Ns that was relatively low. Conversely, the control device 7 may decrease the rotational speed of the prime mover 2 from a predetermined value that was relatively high, and store the rotational speed at which the discharge pressure of the hydraulic pump 3, measured by the pressure sensor 72, drops to the threshold Pt as the determination rotational speed N1. Even when the rotational speed of the prime mover 2 is decreased from a predetermined value that was relatively high, the rotational speed at which the discharge pressure of the hydraulic pump 3 reaches the threshold Pt changes depending on the degree of abnormality of the hydraulic pump 3. Therefore, even in this case, by using the rotational speed of the prime mover 2 and the discharge pressure of the hydraulic pump 3, it is possible to detect a decrease in the performance of the hydraulic pump 3 without using a flow meter. Furthermore, even when the rotational speed of the prime mover 2 is reduced from a predetermined value that is somewhat high, if the rotational speed of the prime mover 2 is reduced from the predetermined value after the capacity of the hydraulic pump 3 has been set to its minimum, the difference between the rotational speed N1 used for determining when the performance of the hydraulic pump 3 has deteriorated and the reference rotational speed N0 will increase, thereby improving the accuracy of detecting the deterioration in the performance of the hydraulic pump 3.

[0043] Furthermore, as shown in the modified performance degradation detection system 1B in Figure 3, the unload valve 65 may be switchable between an open position, a closed position, and a specific throttling position. The specific throttling position is a position where the opening degree is set to a predetermined value within the range of 1 to 70%. The opening degree of the unload valve 65 can be arbitrarily changed between the open position and the adjacent closed position.

[0044] In Figure 3, the specific aperture position is the neutral position, and the open position is located on the opposite side of the closed position from the specific aperture position. That is, the specific aperture position, which is the neutral position, is one stroke end of the spool, and the open position is the other stroke end of the spool. However, the open position may be between the specific aperture position and the closed position, and both the specific aperture position and the closed position may be stroke ends. Alternatively, either the open position or the closed position of the unload valve 65 may be the neutral position, which is one stroke end, and the specific aperture position may be the other stroke end. In this way, if the specific aperture position is a stroke end, the reproducibility of the opening degree at the specific aperture position can be guaranteed.

[0045] As shown in Figure 3, even when the unload valve 65 can be switched to a specific throttle position, the prime mover 2 may be an engine or an electric motor.

[0046] In the performance degradation detection system 1B, when the control device 7 checks the performance of the hydraulic pump 3, it sets the rotational speed of the prime mover 2 to a predetermined value Ns, and then switches the unload valve 65 to a specific throttle position. This restricts the discharge of working fluid from the hydraulic pump 3. In this state, the control device 7 increases the rotational speed of the prime mover 2 from the predetermined value Ns. The subsequent processing performed by the control device 7 is the same as in the embodiment described above.

[0047] Even when the discharge of working fluid from the hydraulic pump 3 is restricted, as in the above embodiment, when the rotational speed of the prime mover 2 is relatively low, such as a predetermined value Ns, the discharge pressure of the hydraulic pump 3 does not become very high due to internal leakage of the hydraulic pump 3, etc. On the other hand, when the rotational speed of the prime mover 2 is increased from a relatively low predetermined value Ns, the rotational speed at which the discharge pressure of the hydraulic pump 3 reaches a threshold Pt changes depending on the degree of abnormality of the hydraulic pump 3. Therefore, even with the performance degradation detection system 1B, the performance degradation of the hydraulic pump 3 can be detected without using a flow meter by using the rotational speed of the prime mover 2 and the discharge pressure of the hydraulic pump 3. Moreover, the performance degradation of the hydraulic pump 3 can be detected with higher accuracy than by measuring the drain flow rate.

[0048] In the modified example shown in Figure 3, in order to accurately reproduce the performance verification of the hydraulic pump 3, measures are desired such that the opening area of ​​the unload valve 65 remains constant at a specific throttling position. In contrast, if the unload valve 65 is switched to the closed position when the performance verification of the hydraulic pump 3 is performed, as in the embodiment described above, the performance verification of the hydraulic pump 3 can be reproduced with high accuracy without the need for such measures.

[0049] In addition, even in the modified configuration shown in Figure 3, the control device 7 may reduce the rotational speed of the prime mover 2 from a predetermined value that is somewhat high, and store the rotational speed at which the discharge pressure of the hydraulic pump 3, measured by the pressure sensor 72, drops to the threshold Pt as the rotational speed N1 for determination. Even when reducing the rotational speed of the prime mover 2 from a predetermined value that is somewhat high, the rotational speed at which the discharge pressure of the hydraulic pump 3 reaches the threshold Pt will change depending on the degree of abnormality of the hydraulic pump 3.

[0050] In the modified example shown in Figure 3, the unload valve 65 may only be switchable between an open position and a specific throttling position, and the unload passage 64 may not be blocked by the unload valve 65. In this case, the control valve 4 also does not block the unload passage 64, which also serves as the center bypass passage, and the unload passage 64 may not always be blocked.

[0051] Furthermore, as shown in Figure 4, in the performance degradation detection system 1C of another modified example, the unload passage 64 may not also serve as a center bypass passage that passes through all the control valves 4, but may extend to the tank without passing through the control valves 4.

[0052] (Second Embodiment) Figure 5 shows the hydraulic pump performance degradation detection system 1D according to the second embodiment. In this embodiment, the same reference numerals are used for components identical to those in the first embodiment, and redundant explanations are omitted.

[0053] This embodiment is configured to allow detection of performance degradation of the hydraulic pump 3 to be performed, for example, by the hydraulic circuit of an industrial machine. Examples of industrial machines include press machines.

[0054] The hydraulic pump 3 supplies working fluid to the hydraulic actuator 5 to operate the hydraulic actuator 5. In this embodiment, the prime mover 2 that drives the hydraulic pump 3 is an electric motor (for example, a servo motor). Similar to the first embodiment, the rotational speed of the prime mover 2 is measured by a tachometer 71 and input to the control device 7.

[0055] In this embodiment, as in the first embodiment, the control device 7 is capable of changing the rotational speed of the prime mover 2. When the prime mover 2 is a servo motor, the control device 7 changes the rotational speed of the prime mover 2 via a servo amplifier.

[0056] Furthermore, in this embodiment as in the first embodiment, the hydraulic pump 3 is a variable displacement axial piston pump with a minimum capacity set to be greater than zero. The capacity of the hydraulic pump 3 is arbitrarily changed between the minimum and maximum capacity by the regulator 31, as in the first embodiment. However, the hydraulic pump 3 may also be a two-position variable displacement pump in which the capacity can be selectively switched between a first capacity and a second capacity.

[0057] Furthermore, in this embodiment, the hydraulic pump 3 is a bidirectional pump that can rotate in both directions. That is, the hydraulic pump 3 has a first port and a second port, and when it rotates in one direction, the first port becomes the suction port and the second port becomes the discharge port, and when it rotates in the opposite direction, the second port becomes the suction port and the first port becomes the discharge port.

[0058] However, the bidirectional pump may also be a swashplate pump in which the rotation direction is unidirectional and the swashplate can be tilted from the center to both sides. In this case, the prime mover 2 may be an engine.

[0059] The hydraulic pump 3, which is a bidirectional pump, is connected to the hydraulic actuator 5 by a pair of supply and discharge passages 81 and 82 to form a closed circuit. In this embodiment, the hydraulic actuator 5 is a double-acting cylinder that extends vertically downward and retracts vertically upward. In other words, the supply and discharge passage 81 is the passage on the head side, and the supply and discharge passage 82 is the passage on the rod side. When the hydraulic actuator 5 extends, the working fluid discharged from the hydraulic pump 3 flows through the supply and discharge passage 81, and when the hydraulic actuator 5 retracts, the working fluid discharged from the hydraulic pump 3 flows through the supply and discharge passage 82.

[0060] The supply and discharge passage 81 is connected to the tank by a replenishment passage 91, which is equipped with a check valve. Similarly, the supply and discharge passage 82 is connected to the tank by a replenishment passage 92, which is also equipped with a check valve. In addition, a relief passage 93, equipped with a relief valve 94, is connected to each of the supply and discharge passages 81 and 82.

[0061] A speed control valve 84 is provided in the supply and discharge passage 82 on the rod side, and a bypass passage 85 is connected to bypass the speed control valve 84. A relief valve 86 is provided in the bypass passage 85.

[0062] The speed control valve 84 is in the neutral position when the rod is rising and when it is descending slowly. In the neutral position, the speed control valve 84 functions as a check valve that allows flow from the hydraulic pump 3 to the hydraulic actuator 5 but prohibits flow in the reverse direction. That is, when the rod is descending slowly, the rod-side pressure of the hydraulic actuator 5 is maintained at the relief valve's set pressure (relief pressure) as the rod descends. When the rod is descending quickly, the speed control valve 84 is switched by the control device 7 to the open position that allows bidirectional flow. Note that in Figure 5, some signal lines are omitted for the sake of simplifying the drawing.

[0063] A switching valve 83 is provided in the supply and discharge passage 81 on the head side. The switching valve 83 can be switched between an open position that opens the supply and discharge passage 81 and a closed position that closes the supply and discharge passage 81. In this embodiment, the open position is the neutral position, but the closed position may also be the neutral position.

[0064] Furthermore, a pressure sensor 73 is provided in the supply and discharge passage 81 between the switching valve 83 and the hydraulic pump 3. In other words, when the hydraulic actuator 5 is extended, the pressure sensor 73 measures the discharge pressure of the hydraulic pump 3 upstream of the switching valve 83.

[0065] The control device 7 receives a first operation signal, which is a command to extend the hydraulic actuator 5, and a second operation signal, which is a command to shorten the hydraulic actuator. Based on the first and second operation signals, the control device 7 controls the electric motor and regulator 31, which are prime movers 2 that drive the hydraulic pump 3.

[0066] Similar to the first embodiment, the control device 7 performs a performance check on the hydraulic pump 3 when the hydraulic actuator 5 is not operating, that is, when the hydraulic pump 3 is not supplying working fluid to the hydraulic actuator 5.

[0067] More specifically, the control device 7 first controls the regulator 31 so that the capacity of the hydraulic pump 3 is minimized. Next, the control device 7 switches the switching valve 83 to the closed position. As a result, when the hydraulic pump 3 rotates in the direction of discharging the working fluid into the supply and discharge passage 81, the discharge of working fluid from the hydraulic pump 3 is shut off as long as the discharge pressure of the hydraulic pump 3 does not exceed the set pressure (relief pressure) of the relief valve 94.

[0068] Subsequently, the control device 7 sets the rotational speed of the prime mover 2 to a predetermined value Ns that is somewhat low. The predetermined value Ns may be 0 rpm or a value greater than 0 rpm (for example, a value within the range of 1 to 200 rpm). If the predetermined value Ns is greater than 0 rpm, the control device 7 rotates the prime mover 2 in a direction that causes the hydraulic pump 3 to discharge the working fluid into the supply and discharge passage 81.

[0069] When the discharge of working fluid from the hydraulic pump 3 is shut off, and the rotational speed of the prime mover 2 is relatively low, such as a predetermined value Ns, the discharge pressure of the hydraulic pump 3 will not become very high due to internal leakage of the hydraulic pump 3, etc.

[0070] In this state, the control device 7 determines whether the performance of the hydraulic pump 3 has deteriorated based on the rotational speed of the prime mover 2 measured by the tachometer 71 and the discharge pressure of the hydraulic pump 3 measured by the pressure sensor 72. This determination is made while the regulator 31 is controlled to minimize the capacity of the hydraulic pump 3, as described above.

[0071] More specifically, as shown in Figure 2, the control device 7 increases the rotational speed of the prime mover 2 from a predetermined value Ns, and stores the rotational speed when the discharge pressure of the hydraulic pump 3, measured by the pressure sensor 72, reaches a threshold Pt, or in other words, when the discharge pressure of the hydraulic pump 3 rises to the threshold Pt, as the determination rotational speed N1.

[0072] The control device 7 stores a reference rotational speed N0 in advance. The reference rotational speed N0 is the rotational speed when the discharge pressure of the hydraulic pump 3 reaches the threshold value Pt when there is no abnormality in the hydraulic pump 3 (for example, before factory shipment after a short-time operation after the hydraulic drive device including the hydraulic pump 3 is attached to the machine, or during a short period of operation immediately after factory shipment after the machine is completed). As the reference rotational speed N0, the rotational speed when the discharge pressure of the hydraulic pump 3 reaches the threshold value Pt, which can be obtained more simply by performance confirmation of the pump alone, may be used.

[0073] The control device 7 compares the stored determination rotational speed N1 with the reference rotational speed N0. When the determination rotational speed N1 is greater than or equal to the set value V more than the reference rotational speed N0 (N1 - N0 ≧ V), it is determined that the performance of the hydraulic pump 3 has deteriorated. On the other hand, when the determination rotational speed N1 is not greater than or equal to the set value V more than the reference rotational speed N0 (N1 - N0 < V), the control device 7 determines that the performance of the hydraulic pump 3 has not deteriorated.

[0074] When the rotational speed of the prime mover 2 is increased from a certain low predetermined value Ns, depending on the degree of abnormality of the hydraulic pump 3 (for example, when the hydraulic pump 3 is a swash plate pump, wear of the shoe that slides on the swash plate provided at the tip of the piston, or wear of the sliding surface between the valve plate and the cylinder block), the rotational speed when the discharge pressure of the hydraulic pump 3 reaches the threshold value Pt changes. Therefore, by using the rotational speed of the prime mover 2 and the discharge pressure of the hydraulic pump 3 as in this embodiment, it is possible to detect a decrease in the performance of the hydraulic pump 3 without using a flow meter. Moreover, it is possible to detect a decrease in the performance of the hydraulic pump 3 with higher accuracy than measuring the drain flow rate.

[0075] Also, in this embodiment, since the rotational speed of the prime mover 2 is increased from the predetermined value Ns after the capacity of the hydraulic pump 3 is minimized, the difference between the determination rotational speed N1 and the reference rotational speed N0 when the performance of the hydraulic pump 3 deteriorates becomes large. For this reason, the detection accuracy of the performance deterioration of the hydraulic pump 3 can be improved.

[0076] <Modification Example> In the above embodiment, when the rotational speed at which the discharge pressure of the hydraulic pump 3 reaches a threshold Pt is stored as the determination rotational speed N1, the control device 7 increased the rotational speed of the prime mover 2 from a predetermined value Ns that was relatively low. Conversely, the control device 7 may decrease the rotational speed of the prime mover 2 from a predetermined value that was relatively high, and store the rotational speed at which the discharge pressure of the hydraulic pump 3, measured by the pressure sensor 72, drops to the threshold Pt as the determination rotational speed N1. Even when the rotational speed of the prime mover 2 is decreased from a predetermined value that was relatively high, the rotational speed at which the discharge pressure of the hydraulic pump 3 reaches the threshold Pt changes depending on the degree of abnormality of the hydraulic pump 3. Therefore, even in this case, by using the rotational speed of the prime mover 2 and the discharge pressure of the hydraulic pump 3, it is possible to detect a decrease in the performance of the hydraulic pump 3 without using a flow meter. Furthermore, even when the rotational speed of the prime mover 2 is reduced from a predetermined value that is somewhat high, if the rotational speed of the prime mover 2 is reduced from the predetermined value after the capacity of the hydraulic pump 3 has been set to its minimum, the difference between the rotational speed N1 used for determining when the performance of the hydraulic pump 3 has deteriorated and the reference rotational speed N0 will increase, thereby improving the accuracy of detecting the deterioration in the performance of the hydraulic pump 3.

[0077] Alternatively, the switching valve 83 may be provided in the supply and discharge passage 82 on the rod side, rather than in the supply and discharge passage 81 on the head side, and the control device 7 may rotate the prime mover 2 in a direction that causes the hydraulic pump 3 to discharge working fluid into the supply and discharge passage 82 when performing performance checks on the hydraulic pump 3. Or, the switching valve 83 may be provided in both the supply and discharge passages 81 and 82.

[0078] (Other embodiments) This disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the gist of this disclosure.

[0079] For example, in some hydraulic circuits, the hydraulic pump 3 may be a fixed-displacement pump.

[0080] (summary) In a first aspect, the present disclosure provides a hydraulic pump performance degradation detection system comprising: a hydraulic pump driven by a prime mover that supplies working fluid to a hydraulic actuator when the hydraulic actuator is in operation; a switching valve provided in a passage through which the working fluid discharged from the hydraulic pump flows, which can be switched between an open position that opens the passage and a closed position that closes the passage; a control device that can change the rotational speed of the prime mover; and a pressure sensor that measures the discharge pressure of the hydraulic pump upstream of the switching valve, wherein the control device determines whether the performance of the hydraulic pump has deteriorated based on the rotational speed of the prime mover and the discharge pressure of the hydraulic pump measured by the pressure sensor when the hydraulic actuator is not in operation and the switching valve is switched to the closed position.

[0081] With the above configuration, when the switching valve is switched to the closed position, thereby shutting off the discharge of working fluid from the hydraulic pump, the discharge pressure of the hydraulic pump will not become very high due to internal leaks in the hydraulic pump when the prime mover speed is relatively low. On the other hand, when the prime mover speed is increased from a relatively low speed or decreased from a relatively high speed, the speed at which the hydraulic pump discharge pressure reaches a threshold changes depending on the degree of abnormality in the hydraulic pump. Therefore, by using the prime mover speed and the hydraulic pump discharge pressure, it is possible to detect a decrease in the performance of the hydraulic pump without using a flow meter. Moreover, it is possible to detect a decrease in the performance of the hydraulic pump with higher accuracy than by measuring the drain flow rate.

[0082] In a second aspect, the present disclosure provides a hydraulic pump performance degradation detection system comprising: a hydraulic pump driven by a prime mover that supplies working fluid to a hydraulic actuator when the hydraulic actuator is in operation; a switching valve provided in a flow path through which the working fluid discharged from the hydraulic pump flows, which can be switched between an open position that opens the flow path and a specific throttle position with an opening degree in the range of 1 to 70%; a control device that can change the rotational speed of the prime mover; and a pressure sensor that measures the discharge pressure of the hydraulic pump upstream of the switching valve, wherein the control device determines whether the performance of the hydraulic pump has deteriorated when the hydraulic actuator is not in operation and the switching valve is switched to the specific throttle position, based on the rotational speed of the prime mover and the discharge pressure of the hydraulic pump measured by the pressure sensor.

[0083] With the above configuration, when the switching valve is switched to a specific throttle position, thereby restricting the discharge of working fluid from the hydraulic pump, the discharge pressure of the hydraulic pump will not become very high due to internal leaks in the hydraulic pump when the prime mover speed is relatively low. On the other hand, when the prime mover speed is increased from a relatively low speed or decreased from a relatively high speed, the speed at which the hydraulic pump discharge pressure reaches a threshold changes depending on the degree of abnormality in the hydraulic pump. Therefore, by using the prime mover speed and the hydraulic pump discharge pressure, it is possible to detect a decrease in the performance of the hydraulic pump without using a flow meter. Moreover, it is possible to detect a decrease in the performance of the hydraulic pump with higher accuracy than by measuring the drain flow rate.

[0084] In a third embodiment, in the first embodiment, for example, the control device may change the rotational speed of the prime mover while the switching valve is switched to the closed position, store the rotational speed at which the discharge pressure of the hydraulic pump measured by the pressure sensor reaches a threshold as the determination rotational speed, compare the stored determination rotational speed with a pre-stored reference rotational speed, and determine that the performance of the hydraulic pump has deteriorated if the determination rotational speed is greater than or equal to a set value than the reference rotational speed.

[0085] In a fourth embodiment, in the second embodiment, for example, the control device may change the rotational speed of the prime mover while the switching valve is switched to the specific throttle position, store the rotational speed at which the discharge pressure of the hydraulic pump measured by the pressure sensor reaches a threshold as the determination rotational speed, compare the stored determination rotational speed with a pre-stored reference rotational speed, and determine that the performance of the hydraulic pump has deteriorated if the determination rotational speed is greater than or equal to a set value than the reference rotational speed.

[0086] In a fifth embodiment, in the third or fourth embodiment, for example, the control device may increase the rotational speed of the prime mover from a predetermined value when storing the rotational speed at which the discharge pressure of the hydraulic pump measured by the pressure sensor reaches the threshold as the rotational speed for determination.

[0087] In a sixth embodiment, in any of the third to fifth embodiments, the hydraulic pump is a variable displacement pump with a minimum capacity greater than zero, the performance degradation detection system further includes a regulator that changes the capacity of the hydraulic pump, and the control device may determine whether the performance of the hydraulic pump has deteriorated while controlling the regulator so that the capacity of the hydraulic pump is minimized. With this configuration, the difference between the rotational speed used for determination when the performance of the hydraulic pump deteriorates and the reference rotational speed becomes larger. Therefore, the accuracy of detecting the performance degradation of the hydraulic pump can be improved.

[0088] In a seventh embodiment, in any of the first, third, fifth, and sixth embodiments, the hydraulic pump supplies working fluid to the hydraulic actuator via a control valve, the flow path is an unloading flow path branching off from a supply flow path connecting the hydraulic pump and the control valve, and the switching valve may be an unloading valve whose opening degree can be arbitrarily changed between the open position and the closed position. With this configuration, a decrease in the performance of the hydraulic pump can be detected, for example, in the hydraulic circuit of construction machinery. Moreover, since hydraulic circuits for construction machinery often include an unloading flow path equipped with an unloading valve and a pressure sensor for measuring the discharge pressure of the hydraulic pump, such hydraulic circuits can detect a decrease in the performance of the hydraulic pump without adding any equipment.

[0089] In the eighth aspect, in any of the second, fourth to sixth aspects, the hydraulic pump supplies working fluid to the hydraulic actuator via a control valve, the flow path is an unloading flow path branching off from a supply flow path connecting the hydraulic pump and the control valve, and the switching valve may be an unloading valve whose opening degree can be arbitrarily changed between the open position and the closed position that blocks the unloading flow path. With this configuration, the same effects as in the sixth aspect can be obtained.

[0090] In a ninth aspect, in the eighth aspect, the unload valve is a spool valve incorporating a spool, and the open position, the closed position, and the specific aperture position may be the stroke end of the spool. This configuration ensures the reproducibility of the opening degree at the specific aperture position.

[0091] In a tenth embodiment, in any of the first, third to seventh embodiments, the hydraulic pump is a bidirectional pump connected to the hydraulic actuator by a pair of supply and discharge passages to form a closed circuit, and the passages may be at least one of the pair of supply and discharge passages. With this configuration, a decrease in the performance of the hydraulic pump can be detected, for example, in the hydraulic circuit of an industrial machine.

[0092] In the eleventh embodiment, in any of the first to tenth embodiments, for example, the hydraulic pump may be an axial piston pump. [Explanation of Symbols]

[0093] 1A~1D Hydraulic Pump Performance Degradation Detection System 2. Engine 3. Hydraulic pump 31 Regulator 4 Control valve 5. Hydraulic actuator 61 Supply channel 64 Unloading channel 65 Unload valve (switching valve) 7 Control device 71,72 Pressure Sensor 81,82 Supply / discharge channel 83 Switching valve

Claims

1. A hydraulic pump driven by a prime mover supplies working fluid to a hydraulic actuator to operate the hydraulic actuator, A switching valve is provided in the flow path through which the working fluid discharged from the hydraulic pump flows, and is switchable between an open position that opens the flow path and a closed position that closes the flow path. A control device capable of changing the rotational speed of the prime mover, The system includes a pressure sensor located upstream of the switching valve that measures the discharge pressure of the hydraulic pump, The control device, when the hydraulic actuator is not operating, with the switching valve switched to the closed position, determines whether the performance of the hydraulic pump has deteriorated based on the rotational speed of the prime mover and the discharge pressure of the hydraulic pump measured by the pressure sensor. A hydraulic pump performance degradation detection system, wherein the control device changes the rotational speed of the prime mover when the switching valve is switched to the closed position, stores the rotational speed at which the discharge pressure of the hydraulic pump measured by the pressure sensor reaches a threshold as the determination rotational speed, compares the stored determination rotational speed with a pre-stored reference rotational speed, and determines that the performance of the hydraulic pump has deteriorated if the determination rotational speed is greater than or equal to a set value than the reference rotational speed.

2. A hydraulic pump driven by a prime mover supplies working fluid to a hydraulic actuator to operate the hydraulic actuator, A switching valve is provided in the flow path through which the working fluid discharged from the hydraulic pump flows, and is switchable between an open position that opens the flow path and a specific throttled position with an opening degree in the range of 1 to 70%. A control device capable of changing the rotational speed of the prime mover, The system includes a pressure sensor located upstream of the switching valve that measures the discharge pressure of the hydraulic pump, The control device, when the hydraulic actuator is not operating, with the switching valve switched to the specific throttle position, determines whether the performance of the hydraulic pump has deteriorated based on the rotational speed of the prime mover and the discharge pressure of the hydraulic pump measured by the pressure sensor. A hydraulic pump performance degradation detection system, wherein the control device changes the rotational speed of the prime mover when the switching valve is switched to the specific throttle position, stores the rotational speed at which the discharge pressure of the hydraulic pump measured by the pressure sensor reaches a threshold as the determination rotational speed, compares the stored determination rotational speed with a pre-stored reference rotational speed, and determines that the performance of the hydraulic pump has deteriorated if the determination rotational speed is greater than or equal to a set value than the reference rotational speed.

3. The hydraulic pump performance degradation detection system according to claim 1 or 2, wherein the control device increases the rotational speed of the prime mover from a predetermined value when the discharge pressure of the hydraulic pump measured by the pressure sensor reaches the threshold value, and stores this rotational speed as the determination rotational speed.

4. The aforementioned hydraulic pump is a variable displacement pump whose minimum capacity is set to be greater than zero. The system further includes a regulator for changing the capacity of the aforementioned hydraulic pump, The hydraulic pump performance degradation detection system according to claim 1 or 2, wherein the control device determines whether or not the performance of the hydraulic pump has deteriorated while controlling the regulator so that the capacity of the hydraulic pump is minimized.

5. The hydraulic pump supplies working fluid to the hydraulic actuator via a control valve. The aforementioned flow path is an unloading flow path that branches off from the supply flow path connecting the hydraulic pump and the control valve. The hydraulic pump performance degradation detection system according to claim 1, wherein the switching valve is an unload valve whose opening degree can be arbitrarily changed between the open position and the closed position.

6. The hydraulic pump supplies working fluid to the hydraulic actuator via a control valve. The aforementioned flow path is an unloading flow path that branches off from the supply flow path connecting the hydraulic pump and the control valve. The aforementioned switching valve is an unload valve whose opening degree can be arbitrarily changed between the open position and the closed position that blocks the unload passage. A hydraulic pump performance degradation detection system according to claim 2.

7. The hydraulic pump performance degradation detection system according to claim 6, wherein the unload valve is a spool valve containing a spool, and one of the open position and the closed position, as well as the specific throttle position, is the stroke end of the spool.

8. The hydraulic pump is a bidirectional pump connected to the hydraulic actuator by a pair of supply and discharge channels to form a closed circuit. The hydraulic pump performance degradation detection system according to claim 1, wherein the flow path is at least one of the pair of supply and discharge flow paths.

9. The hydraulic pump performance degradation detection system according to claim 1 or 2, wherein the hydraulic pump is an axial piston pump.

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