JP6712578B2 - Hydraulic drive - Google Patents

Description

The present invention relates to a hydraulic drive system mounted on a work machine such as a hydraulic excavator or a crane.

For example, Patent Document 1 discloses a conventional hydraulic pump failure diagnosis device.

In Patent Document 1, in a hydraulic pump including a ladle volume variable mechanism that supplies pressure oil to a hydraulic actuator via a hydraulic line to drive the hydraulic actuator, a pressure detection device for detecting a discharge pressure of the hydraulic pump is disclosed. , A displacement amount detecting device for detecting the displacement amount of the variable capacity of the buttocks, a switching valve for opening and closing the hydraulic pipe, and a command means for instructing the necessity of failure diagnosis are provided, and the failure diagnosis is performed by this command means. A switching valve closing means for closing the switching valve when a necessary command is issued, and a displacement for increasing the displacement of the agate volume changing mechanism in a predetermined direction by a predetermined amount while the switching valve is closed by the switching valve closing means. Increasing means, first comparing means for comparing the detected value of the pressure detecting device with a predetermined set pressure during the displacement increasing by the displacement increasing means, and the detected value of the pressure detecting device becomes the set pressure by the pressure comparing means. Second comparing means for comparing the detected value of the displacement amount detecting device when it is judged to have reached with the set displacement amount range, and the detected value of the displacement amount detecting device by the second comparing means. A failure diagnosis device for a hydraulic pump is described, which is provided with failure signal generation means for generating a failure signal when the displacement is outside the displacement range.

In the failure diagnosis device for a hydraulic pump described in Patent Document 1, the pump tilt amount is increased with the hydraulic circuit of the hydraulic pump closed, and the pump tilt when the discharge pressure of the hydraulic pump reaches a set pressure. The amount is compared with the failure judgment value, and if the pump displacement amount is equal to or larger than the failure judgment value, a failure signal is output.Therefore, it is not necessary to disconnect the hydraulic piping to install the hydraulic tester, and therefore, the foreign matter in the hydraulic circuit. It is possible to carry out fault diagnosis automatically and promptly, without the risk of being mixed, and it is also possible to diagnose many hydraulic pumps at the same time.

Japanese Patent Publication No. 6-94868

Generally, as a variable displacement hydraulic pump for a working machine, an axial piston type pump is used, and there are a swash plate type and a swash plate type as a variable displacement mechanism. In each of them, the pump displacement is made variable by changing the stroke length of the piston to increase or decrease the displacement (pump displacement amount). In the variable displacement hydraulic pump, the sliding surfaces of the parts change according to the attitude of the variable tilting mechanism.Therefore, depending on the damage state due to wear of the sliding part, leakage may occur depending on the pump tilting amount. The condition may change.

However, in the failure diagnosis device for the hydraulic pump described in Patent Document 1, if the pump displacement amount when the discharge pressure of the hydraulic pump reaches the set pressure is less than the failure determination value, the other pump displacement amounts are used. Even if the degree of leakage is severe, the failure of the hydraulic pump may not be overlooked because it is not determined that the hydraulic pump has a failure.

The present invention has been made in view of the above problems, and an object thereof is to provide a hydraulic drive system capable of measuring the degree of damage of a variable displacement hydraulic pump over the entire variable range of the pump displacement.

In order to achieve the above object, the present invention controls a prime mover, a variable displacement hydraulic pump driven by the prime mover, a hydraulic actuator, and a flow of pressure oil supplied from the hydraulic pump to the hydraulic actuator. A control valve for controlling the rotation speed of the prime mover and a pump displacement amount of the hydraulic pump; and a pump discharge pipe line connecting the hydraulic pump and the control valve. In a hydraulic drive device including a switching valve that opens and closes a passage, and a pressure detection device that is provided on the upstream side of the switching valve in the pump discharge pipe line and that detects the discharge pressure of the hydraulic pump, the control device includes: While the switching valve is closed, the product of the rotational speed of the prime mover and the tilt amount of the hydraulic pump is kept constant while the tilt amount of the hydraulic pump is changed over the entire variable range. The discharge pressure is measured, and the damage degree of the hydraulic pump is measured based on the measurement result.

According to the present invention configured as described above, the degree of damage of the variable displacement hydraulic pump can be measured over the entire variable range of the pump displacement amount.

According to the present invention, it is possible to reduce the possibility that a failure of the variable displacement hydraulic pump is overlooked by measuring the degree of damage of the variable displacement hydraulic pump over the entire variable range of the pump displacement.

1 is a side view of a hydraulic excavator equipped with a hydraulic drive system according to a first embodiment of the present invention. It is a schematic structure figure of a hydraulic drive concerning a 1st example of the present invention. It is a figure which shows the relief characteristic of the relief valve shown in FIG. FIG. 3 is a sectional view of the oblique shaft type variable displacement hydraulic pump shown in FIG. 2. FIG. 3 is an equivalent circuit diagram showing a cause of leakage of the hydraulic pump shown in FIG. 2. FIG. 3 is a block diagram showing a relationship between each flow rate in the hydraulic drive system shown in FIG. 2 and pump discharge pressure. FIG. 3 is a control block diagram of the controller shown in FIG. 2. It is a figure which shows the measurement flow of the leak characteristic performed by the controller shown in FIG. It is a figure which shows the measurement operation with respect to the hydraulic pump with a large damage of a small tilt region. It is a figure which shows the measurement operation with respect to the hydraulic pump with large damage of a large tilt region. It is a schematic block diagram of the hydraulic drive device which concerns on the 2nd Example of this invention. FIG. 11 is a control block diagram of the controller shown in FIG. 10. It is a figure which shows the measurement flow of the leak characteristic performed by the controller shown in FIG. It is a figure which shows the relationship between oil temperature and a leak characteristic.

Hereinafter, a hydraulic excavator will be described as an example of a working machine equipped with a hydraulic drive system according to an embodiment of the present invention, and will be described with reference to the drawings. In the drawings, the same members are designated by the same reference numerals, and the duplicate description will be omitted as appropriate.

FIG. 1 is a side view of a hydraulic excavator equipped with a hydraulic drive system according to a first embodiment of the present invention.

In FIG. 1, a hydraulic excavator 100 includes a traveling body 101, a revolving body 102 rotatably mounted on the traveling body 101, and a work device 103 mounted on the front side of the revolving body 102 so as to be vertically rotatable. It has and.

The work device 103 includes a boom 104 attached to the front side of the revolving structure 102 so as to be vertically rotatable, an arm 105 attached to a tip end portion of the boom 104 so as to be vertically rotatable, and the arm 105, and the arm 105. A bucket 106 is attached to the tip of 105 so as to be rotatable in the up-down direction and the front-rear direction. The boom 104 is driven by a boom cylinder 107 which is a hydraulic actuator, the arm 105 is driven by an arm cylinder 108 which is a hydraulic actuator, and the bucket 106 is driven by a bucket cylinder 109 which is a hydraulic actuator. A cab 110 is provided on the front side of the swing body 102.

FIG. 2 is a schematic configuration diagram of a hydraulic drive device mounted on the hydraulic excavator 100.

In FIG. 2, a hydraulic drive system 200 includes an engine 20 as a prime mover, a variable displacement hydraulic pump (hereinafter simply referred to as “hydraulic pump”) 21 driven by the engine 20, and a pump displacement (hereinafter, referred to as “hydraulic pump”) of the hydraulic pump 21. "Pump displacement amount") A hydraulic pilot type displacement control device 16 for controlling qp, and a displacement control device 16 for generating pilot pressure generated by reducing the primary pressure from a pilot hydraulic pressure source (not shown). To the electromagnetic proportional valve 22, the hydraulic actuators 107 to 109, the control valve 23, the switching valve 24, the relief valve 25, the pressure sensor 26 as a pressure detecting device, the engine 20, the electromagnetic proportional valve 22, and the switching. The controller 40 is provided as a control device for controlling the valve 24 and the like.

The control valve 23 is connected to a discharge pipe line (hereinafter referred to as “pump discharge pipe line”) 27 connected to a discharge port of the hydraulic pump 21, and the hydraulic pump 21 is operated according to an operation of an operating device (not shown). To control the flow of pressure oil supplied to the hydraulic actuators 107 to 109.

The switching valve 24 is provided in the pump discharge pipeline 27, opens and closes in response to a control signal from the controller 40, and connects or disconnects the pump discharge pipeline 27.

The relief valve 25 is a safety valve that limits the pressure of the pump discharge pipeline 27, is provided on the upstream side of the switching valve 24 of the pump discharge pipeline 27, and has a pressure in the pump discharge pipeline 27 (=pump discharge pressure Pp). Exceeds a predetermined pressure (hereinafter referred to as "relief set pressure") Pr, the valve is opened and the pressure oil in the pump discharge conduit 27 is discharged to the hydraulic oil tank 28. The relief characteristic of the relief valve 25 is shown in FIG. As shown in FIG. 3, when the pump discharge pressure is equal to or lower than the relief set pressure Pr (for example, 35 MPa), the flow rate of pressure oil discharged to the hydraulic oil tank 28 (hereinafter referred to as “relief flow rate”) Qrelief becomes zero, When the pump discharge pressure Pp exceeds the relief set pressure Pr, the relief flow rate Qrelief rapidly increases according to the pump discharge pressure Pp. Due to this characteristic, the pressure in the pump discharge pipe line 27 is limited to about the relief setting pressure Pr or less.

The pressure sensor 26 is provided on the upstream side of the switching valve 24 of the pump discharge pipeline 27, converts the pressure of the pump discharge pipeline 27 (=the pump discharge pressure Pp of the hydraulic pump 21) into a pressure signal, and causes the controller 40 to do so. Output.

In response to the measurement command, the controller 40 controls the switching valve 24, the rotation speed of the engine 20 (hereinafter referred to as “engine rotation speed”) Neng, and the pump displacement amount qp, and the pump discharge pressure Pp detected by the pressure sensor 26. Based on the above, the leak characteristic (described later) of the hydraulic pump 21 is measured.

FIG. 4 is a sectional view of the hydraulic pump 21 shown in FIG.

In FIG. 4, the hydraulic pump 21 is composed of an oblique shaft type variable displacement hydraulic pump, and includes a casing 1, a rotary shaft 2, a cylinder block 3, a valve plate 8, a center shaft 10, and a tilting shaft. And a mechanism 11.

The casing 1 is composed of a substantially cylindrical casing body 1A having one end serving as a bearing portion, and a head casing 1B closing the other end of the casing body 1A. The rotating shaft 2 is rotatably provided in the casing body 1A.

The cylinder block 3 is located inside the casing body 1A and rotates together with the rotary shaft 2. A plurality of cylinders 4 are bored in the cylinder block 3 in its axial direction. A piston 5 is slidably provided in each cylinder 4, and a connecting rod 6 is attached to each piston 5.

A spherical portion 6A is formed at the tip of each connecting rod 6, and each spherical portion 6A is swingably supported by a drive disk 7 formed at the tip of the rotary shaft 2. Here, the cylinder block 3 is arranged with a valve plate 8 described later with a tilt angle θ as a tilt amount with respect to the rotating shaft 2, and the pump displacement is determined by this tilt angle θ.

The cylinder block 3 is slidably in contact with one end surface of the valve plate 8, and the other end surface of the valve plate 8 is slidably in slidable contact with a tilted slidable sliding surface 9 formed in the head casing 1B. ing. Further, a through hole 8A is bored in the center of the valve plate 8, and tip ends of a center shaft 10 and a swing pin 15 described later are inserted into the through hole 8A from both sides. The valve plate 8 is provided with a pair of supply/discharge ports (not shown) intermittently communicating with the cylinders 4 when the cylinder block 3 rotates, and is opened in the tilt sliding surface 9 of the head casing 1B. A pair of supply/discharge passages (not shown) communicate with these supply/discharge ports regardless of the tilted position (tilt angle θ) of the valve plate 8.

The center shaft 10 supports the cylinder block 3 between the drive disk 7 and the valve plate 8. A spherical portion 10A is formed on one end side of the center shaft 10, and the spherical portion 10A is swingably supported at the axial center position of the drive disk 7. On the other hand, the other end of the center shaft 10 protruding through the center of the cylinder block 3 is slidably inserted into the through hole 8A of the valve plate 8 to center the cylinder block 3 with respect to the valve plate 8. It has become.

The tilting mechanism 11 tilts the valve plate 8 along the tilt sliding surface 9. The tilting mechanism 11 is formed in the head casing 1B, has a cylinder chamber 12 having oil passage holes 12A, 12B at both axial ends, and is slidably inserted into the cylinder chamber 12 so that the tilt mechanism 11 is placed in the cylinder chamber 12. The servo piston 14 that defines the hydraulic chambers 13A and 13B, and the base end side is fixed to the servo piston 14, and the tip end side becomes the spherical tip end portion 15A and is swingably inserted into the through hole 8A of the valve plate 8. And a rocking pin 15.

The tilt control device 16 controls the tilt of the valve plate 8 via the tilt mechanism 11. The tilt control device 16 is provided outside the head casing 1B and includes a throttle switching valve (neither is shown) that feedback-controls the amount of pressure oil (pilot pressure) supplied and discharged from the pilot pump. A sleeve (not shown) is provided in the throttle switching valve, and the sleeve and the servo piston 14 are integrally connected by a feedback pin 17 inserted into the elongated hole 1C of the head casing 1B.

When the throttle switching valve of the tilt control device 16 is switched by an operating lever or the like, pressure oil (pilot pressure) corresponding to the switching operation amount at this time is tilted from the pilot pump through the oil passage holes 12A and 12B. The servo piston 14 is supplied to and discharged from the hydraulic chambers 13A and 13B of the rolling mechanism 11, and the servo piston 14 is slidably displaced by the pressure difference between the hydraulic chambers 13A and 13B. The plate 8 and the cylinder block 3 are tilted in the direction of arrow A at a tilt angle θ. The sleeve of the throttle switching valve is displaced following the displacement of the servo piston 14 to feedback control the amount of pressure oil from the pilot pump, and the displacement amount of the servo piston 14 is controlled by the switching operation amount of the throttle switching valve. Hold the state corresponding to.

In the variable displacement hydraulic pump 21 of the oblique shaft type having such a configuration, the amount of displacement of the piston per rotation (pump displacement amount) is changed by changing the amount of inclination of the oblique shaft. The discharge flow rate can be controlled. In the present embodiment, the hydraulic pump 21 is composed of an oblique shaft type variable displacement hydraulic pump, but the present invention is not limited to this, and the pump can be obtained by changing the inclination amount of the swash plate. It may be configured by a swash plate type variable displacement hydraulic pump that controls the discharge flow rate.

When wear of the tilt sliding surface 9 between the valve plate 8 and the head casing 1B progresses due to long-term operation of the hydraulic pump 21 or the like, part of the pressure oil from the cylinder 4 is discharged to the hydraulic oil tank 28 through the gap. As a result, the discharge flow rate of the hydraulic pump 21 is reduced by the leak flow rate. At this time, the valve plate 8 and the tilt sliding surface 9 of the head casing 1B change according to the pump tilt amount, and therefore the size of the gap between the tilt sliding surface 9 and the leakage flow rate also depend on the pump tilt amount. Change.

FIG. 5 is an equivalent circuit diagram showing leakage factors of the hydraulic pump 21. The leak flow rate Qleak of the hydraulic pump 21 changes according to the pump discharge pressure Pp and the pump displacement amount qp. Therefore, as shown in FIG. 5, the leakage factor of the hydraulic pump 21 is that an opening is formed in accordance with the pump tilt amount qp provided in the drain oil passage connecting the discharge port of the hydraulic pump 21 and the hydraulic oil tank 28. It can be represented by a variable diaphragm 29 that changes. Here, the pump leakage flow rate Qleak can be estimated by the following formula.

Here, f(qp) represents the leak sensitivity (hereinafter referred to as “leak characteristic”) with respect to the pump discharge pressure Pp. The relationship between the pump discharge pressure Pp and the leakage flow rate Qleak will be described below.

The relationship between each flow rate in the hydraulic drive device 200 and the pump discharge pressure Pp is expressed by the following equation.

Qpref: Theoretical pump discharge flow rate Qleak: Pump leak flow rate Qrelief: Relief flow rate Qsuppley: Circuit supply flowrate B: Volume elastic coefficient V: Pipe line volume Here, the circuit supply flowrate Qsuppley is controlled from the hydraulic pump 21 via the switching valve 24. This is the flow rate supplied to the valve 23. The theoretical pump discharge flow rate Qpref is a pump discharge flow rate when the leak flow rate Qleak is assumed to be zero, and is represented by the following equation.

qp: Pump displacement (pump displacement)
Neng: Engine speed (pump speed)
FIG. 6 is a block diagram showing the equation (1).

In FIG. 6, the pump discharge pressure Pp has a first-order lag characteristic with respect to the theoretical pump discharge flow rate Qpref minus the relief flow rate Qrelief, the leak flow rate Qleak, and the circuit supply flow rate Qsupply. The leak characteristic f can be measured by using the relationship shown in FIG. 6 and the equation (1).

In FIG. 6, when the pump discharge pressure Pp exceeds the relief set pressure, the leaf flow rate Qrelief greatly changes according to the pump discharge pressure Pp, as shown in FIG. That is, during relief, the feedback gain due to the relief characteristic becomes large.

Further, during the normal operation of driving the hydraulic actuators 107 to 109, the flow rate (circuit supply flow rate) Qsupply supplied to the control valve 23 greatly changes according to the pump discharge pressure Pp. That is, during normal operation, the feedback gain increases depending on the circuit state (stroke of each spool of the control valve 23, each load pressure of the hydraulic actuators 107 to 109, etc.).

On the other hand, it is desirable that the leak characteristic f be measured in a state where the hydraulic circuit of the hydraulic drive device 200 is static. Therefore, the leak characteristic f is measured without feedback of the relief flow rate Qrelief and the circuit supply flow rate Qsupply.

Specifically, the measurement is performed in a pressure region where the relief flow rate Qrelief becomes zero, that is, in a range in which the pump discharge pressure Pp does not exceed the relief set pressure Pr (for example, 35 MPa). As a result, the relief flow rate Qrelief is always zero, and the feedback loop of the relief flow rate Qrelief can be eliminated. Then, the measurement is performed with the switching valve 24 closed. As a result, the circuit supply flow rate Qsupply is always zero, so that the feedback loop of the circuit supply flow rate Qsupply can be eliminated. In this way, the transfer function from the theoretical pump discharge flow rate Qpref to the pump pressure Pp is expressed by the following simple equation by always setting the relief flow rate Qrelief and the circuit supply flow rate Qsupply to zero.

According to the equation (4), the time constant Tc indicating the response of the pump discharge pressure Pp to the change in the theoretical pump discharge flow rate Qpref is

And the gain k in the static state is

Becomes That is, the following relational expressions hold in the static state.

Therefore, the leak characteristic f is expressed by the following equation from the equations (7) and (3).

In this way, the leak characteristic f can be calculated based on the pump discharge pressure Pp, the pump displacement amount qp, and the engine speed Neng. In the present embodiment, the value measured by the pressure sensor 26 is used as the pump discharge pressure Pp, and each control command value of the controller 40 is used as the pump displacement amount qp and the engine speed Neng, but the pump displacement amount qp and the engine rotation speed are used. A value measured by various sensors (not shown) may be used as the number Neng.

FIG. 7 is a control block diagram of the controller 40. In FIG. 7, only the configuration relating to the measurement of the leak characteristic f of the hydraulic pump 21 is shown, and the configuration relating to the driving of the actuators 107 to 109 is omitted.

7, the controller 40 includes a measurement control unit 41, a switching valve control unit 42, an engine speed control unit 43, a pump displacement control unit 44, a theoretical pump discharge flow rate calculation unit 45, and a pump discharge pressure measurement unit. It includes a unit 46 and a leak characteristic calculation unit 47.

The measurement control unit 41 receives the measurement trigger for starting the measurement of the leak characteristic f, and controls the switching valve control unit 42, the engine speed control unit 43, and the pump displacement control unit 44. The measurement trigger may be generated through the operation of an input device (not shown) such as a switch arranged in the cab 110, or the engine 20 of the hydraulic excavator 100 is started and the controller 40 is turned on. It may be automatically generated immediately after.

The switching valve control unit 42 controls opening/closing of the switching valve 24 based on a command from the measurement control unit 41.

The engine speed control unit 43 controls the engine 20 based on a command from the measurement control unit 41 so that the engine speed Neng has a desired value.

The pump tilting control unit 44 adjusts the opening degree of the solenoid proportional valve 22 based on the command from the measurement control unit 41 so that the pump tilting amount qp of the hydraulic pump 21 becomes a desired value, and tilting is performed. The controller 16 is driven.

The theoretical pump discharge flow rate calculation unit 45 calculates the theoretical pump discharge flow rate Qpref based on the engine speed Neng from the engine speed control unit 43 and the pump displacement amount qp from the pump displacement control unit 44, and leaks. It is output to the characteristic calculator 47.

The pump discharge pressure measuring unit 46 converts the pressure signal from the pressure sensor 26 into the pump discharge pressure Pp of the hydraulic pump 21 and outputs it to the leak characteristic calculating unit 47.

The leak characteristic calculation unit 47 calculates the leak characteristic f based on the theoretical pump discharge flow rate Qpref from the theoretical pump discharge flow rate calculation unit 45 and the pump discharge pressure Pp from the pump discharge pressure measurement unit 46, and arranges it in the cab 110. Output to the monitored monitor. The leak characteristic may be notified not only to the operator in the cab 110 but also to a vehicle manager, a service department, or the like.

FIG. 8 is a diagram showing a flow of measuring the leak characteristic f executed by the controller 40. Hereinafter, each step which comprises the said measurement flow is demonstrated in order.

In step S1, the switching valve 24 is closed. As a result, the pump discharge conduit 27 is shut off, and the supply of pressure oil from the hydraulic pump 21 to the control valve 23 is stopped.

In step S2, the pump displacement amount qp is set to the minimum displacement amount qpmin, and the engine speed Neng is set to the minimum rotation speed Nmin.

In step S3, control for gently increasing the engine speed Neng is started. The term "gradual" means that the measurement error of the pump discharge pressure Pp due to the control response delay of the engine speed Neng is within a desired error range in consideration of the time constant Tc shown in the equation (4). This means suppressing the time change rate of the engine speed Neng.

In step S4, the pump discharge pressure Pp is measured.

In step S5, it is determined whether the pump discharge pressure Pp is equal to or higher than a predetermined threshold Ps. Here, it is desirable that the threshold value Ps be set to a value (eg, 30 MPa) that is smaller and relatively larger than the relief setting pressure Pr (eg, 35 MPa) of the relief valve 25. By setting the threshold value Ps to a relatively high value in this way, the circuit pressure during measurement becomes stable, and the leak flow rate Qleak becomes large even when the gap between the tilt sliding surfaces 9 is small, so the leak characteristic f The measurement accuracy of can be improved.

When it is determined in step S5 that the pump discharge pressure Pp is less than the predetermined threshold Ps (No), the process returns to step S4.

On the other hand, when it is determined in step S5 that the pump discharge pressure Pp is equal to or higher than the predetermined threshold value Ps (Yes), in step S6, control for gently increasing the pump displacement amount qp is started. The term "gradual" as used herein means that the measurement error of the pump discharge pressure Pp due to the control response delay of the pump displacement amount qp is within a desired error range in consideration of the time constant Tc shown in the equation (4). It also means that the rate of change of the pump displacement amount qp with time is suppressed.

In step S7, control for gently reducing the engine speed Neng is started so that the theoretical pump flow rate Qpref (=pump displacement amount qp×engine speed Neng) is kept constant. The term "gradual" means that the measurement error of the pump discharge pressure Pp due to the control response delay of the engine speed Neng is within a desired error range in consideration of the time constant Tc shown in the equation (4). This means suppressing the time change rate of the engine speed Neng.

In step S8, the pump discharge pressure Pp is measured and stored together with the value of the pump displacement amount qp at that time.

In step S9, the leak characteristic f is calculated as the degree of damage of the hydraulic pump 21 based on the pump discharge pressure Pp measured in step S8, and is stored together with the value of the pump displacement amount qp at that time.

In step S10, it is determined whether the pump displacement amount qp is greater than or equal to the maximum displacement amount qpmax.

When it is determined in step S10 that the pump displacement amount qp is less than the maximum displacement amount qpmax (No), the process returns to step S8.

When it is determined in step S10 that the pump displacement amount qp is greater than or equal to the maximum displacement amount qpmax (Yes), the leak characteristic f calculated in step S9 is output in step S11.

In step S12, the switching valve 24 is closed. As a result, the pump discharge pipe line 27 communicates with each other, and the pressure oil can be supplied from the hydraulic pump 21 to the control valve 23. When step S12 ends, the controller 40 ends the measurement flow and shifts to a normal control flow (not shown).

Next, the operation of the hydraulic drive device 200 when measuring the leak characteristic f of the hydraulic pump 21 will be described.

FIG. 9A is a diagram showing a measurement operation (hereinafter, referred to as “Case 1”) for the hydraulic pump 21 in which the small tilt region is damaged (sliding part gap) is large, and FIG. 9B is the large tilt region damage. It is a figure which shows the measurement operation (henceforth "Case 2") with respect to the hydraulic pump 21 with large (gap of a sliding part).

In FIG. 9A, the pump displacement amount qp gradually increases from the minimum displacement amount qpmin to the maximum displacement amount qpmax. On the other hand, the engine speed Neng decreases in inverse proportion to the pump displacement amount qp. As a result, the theoretical pump discharge flow rate Qpref (=pump displacement amount qp×engine speed Neng) is kept constant.

In the hydraulic pump 21 of the case 1, since the damage in the small tilt region is large and the damage in the large tilt region is small, the pump discharge pressure Pp is low in the small tilt amount region and is high in the large tilt region. Therefore, the leak characteristic f (=Qpref/Pp), which is inversely proportional to the pump discharge pressure Pp, becomes high at small tilts and becomes low at large tilts. In FIG. 9A, the pump displacement amount qpx1 represents the pump displacement amount qp when the pump discharge pressure Pp has the minimum value Ppmin1 (the leak characteristic f has the maximum value fmax1).

On the other hand, in the hydraulic pump 21 of the case 2, the damage in the small tilt region is small and the damage in the large tilt region is large. Therefore, as shown in FIG. 9B, the pump discharge pressure Pp is high in the small tilt region and large. It becomes lower in the tilt range. Therefore, the leak characteristic f (=Qpref/Pp), which is inversely proportional to the pump discharge pressure Pp, becomes low in the small tilt and becomes high in the large tilt. In FIG. 9B, the pump displacement amount qpx2 represents the pump displacement amount qp when the pump discharge pressure Pp has the minimum value Ppmin2 (the leak characteristic f has the maximum value fmax2).

As described above, the degree of damage to the hydraulic pump 21 can be evaluated by the magnitude of the leak characteristic f.

According to the hydraulic drive device 200 configured as described above, the leak characteristic f representing the degree of damage of the variable displacement hydraulic pump 21 is set in the entire variable range of the pump displacement amount qp (from the minimum displacement amount qpmin to the maximum displacement amount qpmin). over qpmax). This makes it possible to check the degree of damage to the hydraulic pump 21 over the entire variable range of the pump displacement amount qp (minimum displacement amount qpmin to maximum displacement amount qpmax), so that the variable displacement hydraulic pump 21 fails. Can reduce the likelihood of being overlooked.

In the present embodiment, the leak characteristic f is measured while changing the pump displacement amount qp from the minimum displacement amount qpmin to the maximum displacement amount qpmax. However, the present invention is not limited to this, and the maximum displacement amount qpmax The leak characteristic f may be measured while changing the minimum tilt amount qpmin.

The hydraulic drive system according to the second embodiment of the present invention will be described with a focus on the differences from the first embodiment.

Generally, when the temperature of the hydraulic oil (hereinafter referred to as “oil temperature”) increases, the viscosity of the hydraulic oil decreases, and the leak flow rate Qleak of the hydraulic pump 21 increases. On the other hand, when the oil temperature decreases, the viscosity of the hydraulic oil increases, and the leak flow rate Qleak decreases. Therefore, the hydraulic drive device 200 according to the first embodiment has a problem that the value of the leak characteristic f varies depending on the oil temperature even if the hydraulic pump 21 is in the same damaged state. The present embodiment eliminates the influence of the oil temperature on the leak characteristic f.

FIG. 10 is a schematic configuration diagram of a hydraulic drive system according to a second embodiment of the present invention. The differences from the first embodiment (shown in FIG. 2) will be described below.

In FIG. 10, the hydraulic drive device 200A further includes a temperature sensor 30 as an oil temperature detection device that detects the temperature of hydraulic oil drawn into the hydraulic pump 21 (hereinafter referred to as “oil temperature”). The oil temperature signal output from the temperature sensor 30 is input to the controller 40A.

FIG. 11 is a control block diagram of the controller 40A shown in FIG. Hereinafter, differences from the control block diagram (shown in FIG. 7) in the first embodiment will be described.

In FIG. 11, the controller 40A further includes an oil temperature measuring unit 48.

The oil temperature measuring unit 48 converts the temperature signal from the temperature sensor 30 into oil temperature and outputs it to the leak characteristic calculating unit 47A.

The leak characteristic calculation unit 47A calculates the leak characteristic f calculated based on the theoretical pump discharge flow rate Qpref from the theoretical pump discharge flow rate calculation unit 45 and the pump discharge pressure Pp from the pump discharge pressure measurement unit 46, and the oil temperature measurement unit 48. It is corrected based on the oil temperature from and output to a monitor.

FIG. 12 is a diagram showing a flow of measuring the leak characteristic f executed by the controller 40A. Hereinafter, differences from the measurement flow (shown in FIG. 8) in the first embodiment will be described.

In FIG. 12, the measurement flow in the present embodiment is configured to further execute steps S9a and S9b after execution of step S9 and before execution of step S10. The added steps S9a and S9b will be described below.

In step S9a, the controller 40A measures the oil temperature based on the temperature signal from the temperature sensor 30.

In step S9b, the controller 40A corrects the leak characteristic (damage level) f calculated in step S9 based on the oil temperature measured in step S9a. The correction method will be described below.

FIG. 13 is a diagram showing the relationship between the oil temperature and the leak characteristic.

In FIG. 13, the leak characteristics fN, fL, and fH are values measured by the same hydraulic pump 21, the leak characteristics fN are values measured when the oil temperature is the standard temperature, and the leak characteristics fL are higher than the standard temperature. The value measured at a low oil temperature and the leak characteristic fH are values measured at an oil temperature higher than the standard temperature. As described above, even with the hydraulic pump 21 having the same degree of damage, the leak characteristic f becomes smaller as the oil temperature becomes lower, and the leak characteristic becomes larger as the oil temperature becomes higher. Therefore, by multiplying the leak characteristic f calculated on the basis of the theoretical pump discharge flow rate Qpref and the pump discharge pressure Pp by a correction coefficient according to the difference between the standard temperature and the oil temperature, regardless of the oil temperature, The leak characteristic f when measured at the standard temperature can be obtained.

Also in the present embodiment configured as described above, the same effect as in the first embodiment can be obtained.

Moreover, since the influence of the oil temperature on the leak characteristic f is eliminated by correcting the leak characteristic f based on the oil temperature, the reliability of the measurement result of the leak characteristic f can be improved.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments and includes various modifications.

For example, in the above-described embodiment, the case where the present invention is applied to the hydraulic drive device mounted on the hydraulic excavator has been described, but the present invention can also be applied to the hydraulic drive device mounted on other working machines such as a crane. Further, in the above-described embodiment, the case where the present invention is applied to the one-pump hydraulic drive device has been described, but the present invention can also be applied to a hydraulic drive device having a plurality of hydraulic pumps. Further, in the above-described embodiment, the example in which the present invention is applied to the hydraulic drive device including the swash plate type variable displacement hydraulic pump has been described, but the hydraulic drive device including the swash plate type variable displacement hydraulic pump is described. Can also be applied.

Further, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to add a part of the structure of another embodiment to the structure of a certain embodiment, and it is also possible to replace a part of the structure of a certain embodiment with a part of the structure of another embodiment. ..

1... Casing, 1A... Casing body, 1B... Head casing, 2... Rotating shaft, 3... Cylinder block, 4... Cylinder, 5... Piston, 6... Connecting rod, 6A... Spherical part, 7... Drive disk, 8... Valve Plate, 8A... Through hole, 9... Tilt sliding surface, 10... Center shaft, 11... Tilt mechanism, 12... Cylinder chamber, 12A, 12B... Oil passage hole, 13A, 13B... Hydraulic chamber, 14... Servo Piston, 15... Oscillating pin, 15A... Spherical tip part, 16... Tilt control device, 17... Feedback pin, 20... Engine (motor), 21... Hydraulic pump, 22... Electromagnetic proportional valve, 23... Control valve, 24... Switching valve, 25... Relief valve, 26... Pressure sensor (pressure detection device), 27... Pump discharge pipe line, 28... Hydraulic oil tank, 29... Variable throttle, 30... Temperature sensor (oil temperature detection device), 40 , 40A... Controller (control device), 41... Measurement control section, 42... Switching valve control section, 43... Engine speed control section, 44... Pump tilt control section, 45... Theoretical pump discharge flow rate calculation section, 46... Pump Discharge pressure measuring unit, 47, 47A... Leakage characteristic calculating unit, 48... Oil temperature measuring unit, 100... Hydraulic excavator, 101... Traveling body, 102... Revolving structure, 103... Working device, 104... Boom, 105... Arm, 106 ... bucket, 107 ... boom cylinder (hydraulic actuator), 108 ... arm cylinder (hydraulic actuator), 109 ... bucket cylinder (hydraulic actuator), 110 ... cab, 200, 200A ... hydraulic drive device.

Claims (2)

Prime mover,
A variable displacement hydraulic pump driven by the prime mover,
Hydraulic actuator,
A control valve for controlling the flow of pressure oil supplied from the hydraulic pump to the hydraulic actuator;
A control device for controlling the rotation speed of the prime mover and the pump displacement amount of the hydraulic pump;
A switching valve that is provided in a pump discharge pipe line that connects the hydraulic pump and the control valve, and that opens and closes the pump discharge pipe line;
In a hydraulic drive device that is provided on the upstream side of the switching valve in the pump discharge pipe line and includes a pressure detection device that detects the discharge pressure of the hydraulic pump,
The controller changes the tilt amount of the hydraulic pump over the entire variable range while keeping the product of the rotation speed of the prime mover and the tilt amount of the hydraulic pump constant with the switching valve closed. A hydraulic drive device, wherein the discharge pressure of the hydraulic pump is measured, and the degree of damage to the hydraulic pump is measured based on the measurement result. The hydraulic drive system according to claim 1,
Further comprising a temperature sensor for detecting the temperature of the hydraulic oil drawn into the hydraulic pump,
A hydraulic drive device, wherein the degree of damage is corrected based on the temperature detected by the temperature sensor.

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