JPS6032986A - Failure diagnostic device for oil hydraulic pump - Google Patents

Abstract

PURPOSE:To provide automatic and quick diagnosis of failure in an oil hydraulic pump by determining the difference between the deformation amount sensed by a sensing means and a command value given by a command generating means. CONSTITUTION:When a control lever 9 is operated, a swash plate 6a is moved according to the deviation of a displacement signal Y from control signal X in following-up to the motion of control lever 9. On the other hand, the control signal X is put into an adding circuit 12a of a failure judgement circuit 11, where an addition to the tolerable value is conducted. The sum obtained is compared with the signal Y by a comparator 13a, and if the signal Y exceeds this sum, the comparator 13a emits an output 1. Signal Y exceeding the sum signifies that any failure has occurred in this oil hydraulic pump 6 in question, which otherwise involves only mechanical plays, and therefore the magnitude of the failure in this pump is represented by said output of the comparator 13a.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a failure diagnosis device for a hydraulic pump used in a floor desk as a power source for hydraulic excavators, cranes, and various other hydraulic machines and hydraulic devices.

Hydraulic pumps are the most important machines that generate hydraulic energy in hydraulic excavators, cranes, other hydraulic machines, and hydraulic equipment, and if the performance of the hydraulic pump deteriorates due to failure or aging, it may be necessary to replace it as a power source. This will cause serious damage to the operation of machinery and equipment. Therefore, it is required to check the hydraulic pumps used. A conventional apparatus for checking a hydraulic pump in this way and determining its failure or performance deterioration (hereinafter referred to as failure) will be described.

FIG. 1 is a hydraulic circuit diagram of a conventional failure diagnosis device. 1 is a variable displacement hydraulic pump to be diagnosed, 1α is a displacement variable mechanism of the variable displacement hydraulic pump (hereinafter, this is represented by a swash plate), and 2 is a variable displacement hydraulic pump that tilts according to the discharge pressure of the variable displacement hydraulic pump. A regulator operates the plate IC, and 4 is a hydraulic pressure tester for diagnosis. The oil pressure tester 4 is composed of a pressure gauge 4α for measuring oil pressure, a flow plate gauge 4b for measuring oil flow rate, and a manual variable throttle 4C for increasing the discharge pressure of the variable displacement hydraulic pump 1. . Reference numeral 5 denotes a tachometer connected to the variable displacement hydraulic pump 1 to measure its rotation speed. Note that 3α indicates piping such as a hydraulic hose that connects the variable displacement hydraulic pump 1 and the hydraulic tester 4, and 3b indicates piping such as a hydraulic hose that connects the hydraulic tester 4 and a pipeline to the hydraulic oil tank.

To diagnose a failure in the variable displacement hydraulic pump 1, first, disconnect the piping connected to the discharge side of the variable displacement hydraulic pump 1 at the part α and the part shown in the figure, and then connect the piping between the parts α and b. Connect piping 3a, 3b and hydraulic tester 4. Next. , the hydraulic pump 1 is connected to a prime mover such as an engine (not shown).
The rotation speed N of the variable displacement hydraulic ring 1 at that time is
It is measured by a tachometer 5. In this state, operate the variable restrictor 4'c to restrict the pipe until the pressure on the pressure gauge 4a (discharge pressure of the variable displacement hydraulic pump 1) reaches the set value Pr6f, and at this time the discharge of the variable displacement hydraulic pump 1 increases. The quantity Q is measured by the flow 1it4b. In this case, the discharge amount is determined by the position of the swash plate 1α, which is controlled by the regulator 2 according to the discharge pressure. Next, the theoretical discharge 11Qref of the variable displacement hydraulic pump 1 is calculated based on the rotation speed N and the set pressure Pref. Finally, this discharge f
Compare itQref and the previously measured discharge ffQ,
When the difference exceeds the allowable value, it is determined that the variable displacement hydraulic pump 1 is in a failure state.

In such a conventional fault diagnosis device, the late 1141
Although it is possible to diagnose, when performing diagnosis, it is necessary to cut a part of the installed hydraulic piping and install piping 3α.

3b, the hydraulic tester 4 must be attached, which requires a lot of time, and there is a risk that foreign matter such as dust may get mixed into the piping when cutting the hydraulic piping. In general, the diagnosis itself requires operating the variable throttle 4c and reading the indicated values of the pressure gauge 4 and cL% flowmeter 4b, which also requires a lot of time and makes the diagnosis troublesome. Additionally, if a machine or device is equipped with a large number of hydraulic pumps, such as a large hydraulic excavator, and it is known that a failure has occurred in one of the hydraulic pumps, the above-mentioned conventional failure diagnosis method may be used. In the equipment, it took a lot of time to find out which hydraulic pump was malfunctioning.

The purpose of the present invention is to solve the above-mentioned problems of the conventional technology, and to do so without disconnecting hydraulic piping or installing a hydraulic tester.
It is an object of the present invention to provide a failure diagnosis device for a hydraulic pump that can automatically and quickly perform failure diagnosis and can simultaneously perform failure diagnosis for a large number of hydraulic pumps.

In order to achieve this object, the present invention aims at the difference between a command value for causing a required flat displacement of the variable displacement mechanism of a hydraulic pump and a displacement of the variable displacement mechanism according to this command value.
Compare the absolute value with a predetermined allowable value, output a signal when the absolute value exceeds the allowable value, and output a failure signal for the hydraulic pump only when the output of this signal continues for a predetermined period or more. It is characterized by being made to do.

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 2 is a block diagram of a hydraulic pump failure diagnosis device according to the first embodiment of the present invention. In the figure, 6 is a double tilting type variable volume J? which is the target of failure diagnosis. Th hydraulic pump (hereinafter referred to as
It is simply called a hydraulic pump. ), 6α is a variable displacement mechanism such as a swash plate and a slant shaft of the hydraulic pump 6 (hereinafter, this will be represented by the swash plate); 7 is a swash plate drive device that drives the swash plate 6a according to an input signal; 8 is a displacement meter 9 for detecting the amount of displacement of the swash plate 6cL, and 9 is an operating lever for operating the hydraulic pump 6.

The displacement meter 8 outputs a displacement signal Y corresponding to the detected displacement amount of the swash plate, and the operating lever 9 outputs an operation signal X corresponding to the operated amount. 10 is a control device that drives and controls the swash plate 6α according to the operation of the operating lever 9;
and the signal X from the operating lever 9, calculate the difference (X-Y) between both signals Swash plate 6
Drive cL. In this way, the swash plate 6α moves following the operating lever 9, and when the output signal @YfJ″ of the displacement meter that detects the displacement of the swash plate 6α becomes equal to the output signal X of the operating lever 9, the control device 10 The output to the plate driving device 7 is stopped.

Reference numeral 11 denotes a failure judgment/determination circuit for detecting a failure of the hydraulic pump 6, which is constructed of two adder circuits 12α, 1 and 2b, two comparators 13 (Z, 13b, and one OR circuit 14). 12a adds the signal
li12b subtracts the Fl' g value Δ from the signal X (-
Δ). Further, the comparator 13α compares the added value of the adder 12G with the signal Y, and produces an output when the 1 signal Y exceeds the added value.

Comparator 13b compares the subtraction value output from adder 12b with signal Y, and produces an output when signal Y is less than the subtraction value. Furthermore, the OR circuit 14 includes comparators 13α and 13b.
, and outputs the signal when an output is generated in either of the comparators 13α and 13b.

Here, we will explain the above-mentioned allowable value Δ. Normally, in structures such as the swash plate of a hydraulic pump, the operation signal do not match and a difference occurs. However, if such tlA horizontal play is within a certain range, there is no problem with the operation of the hydraulic pump, and there is no need to treat it as a failure. In order to exclude the difference between the signal Y and the signal Y caused by this from a failure, this difference is treated as an allowable value Δ.

The value of the allowable value Δ is determined by each hydraulic pump.

Reference numeral 15 denotes a delay circuit which receives the signal from the failure determination circuit 11 and generates a failure signal only when this signal is output for a predetermined period or more. The delay 1gl path 15 is a pulse generating circuit 16,
NOT circuit 1 that inverts the signal from the failure determination circuit 11
7. It is composed of an AND circuit which inputs the pulse of the pulse generation circuit 16 and the output of the NOT circuit 17, and a retriggerable monostable multipipe circuit 19 which uses the output signal of the AND circuit 18 as a trigger signal. When a trigger signal is input to the retriggerable monostable multi-pipe rake 19, its output becomes, for example, a low level signal rOJ, and after a predetermined period of time, the output becomes a high level signal "1", and the output becomes a high level signal "1" again within the predetermined period. When a trigger signal is input,
It has a characteristic of continuing to output the low level signal rOJ for the predetermined period from the time when this trigger signal is input. 2o is a light emitting diode that emits light in response to the high level signal rlJ of the retrigger pull monostable multivibrator 19.

Next, the operation of this embodiment will be explained with reference to the output characteristics of the comparison circuits 13α, 13b and the OR circuit 14 shown in FIGS. 3(α) to (C) and the time chart shown in FIG. 4. When the operating lever 9 is operated, the swash plate 6α is driven according to the deviation between the operating signal X and the displacement signal Y, and follows the movement of the operating lever 9.

On the other hand, the operation signal
It is input to L and is added to the allowable value Δ. This added value (X+Δ) is compared with the signal Y by the comparator 13α, and when the signal Y exceeds the added value (X+Δ), an output “1” is generated from the comparator 13α.

This state is shown in FIG. 3(α). That is, when the signal Y is less than the addition value (X+Δ), the comparator 13α outputs "0".
However, when the addition value (X+Δ) is exceeded and Y>(X+Δ), the comparator 13α outputs “1”. The fact that the signal Y exceeds the added value (X+Δ) means that a failure greater than the allowable mechanical play described above has occurred in the hydraulic pump 6. Therefore, the output of the comparator 13a is "1".
indicates a hydraulic pump failure.

Similarly, the signal
is compared with the signal Y, and as shown in Figure 3(b), Y≧
(X-Δ), the comparator 13b outputs “OJ, Y<
CX-Δ)0), the comparator 13b outputs "1". Then, by comparing the signal Y, the addition value 1 signal Y, and the subtraction value using the 1 comparators 13α and 13b as described above, in other words, the absolute value of the difference between the signal Y and the signal X and the tolerance value Δ
By comparing these, it is possible to detect all failures that appear in the movement of the swash plate 6α. Since the outputs of comparator 1:1.13b(7) are simultaneously input to the OR circuit 14, the OR circuit 14 determines whether the output of either the comparators 13cL or 13b is "1" as shown in FIG. 3(C). When it becomes ``1'', it outputs ``1''.

That is, in a normal case where the swash plate 6a is controlled in accordance with the operation signal of the operation lever 9, the signal Y satisfies X-Δ≦Y≦
It is within the range of X0Δ, and no signal is output from the OR circuit 14. Further, when the swash plate 6a is no longer controlled due to a failure of the hydraulic pump, the signal Y falls outside the range of X-Δ≦Y≦X+j, and a signal is output from the S, OR circuit 14.

From the above explanation, it is possible to directly connect the OR circuit 14 to the light emitting diode 20 and, when there is an output from the OR circuit 14, use this output as a failure signal to cause the light emitting diode 20 to emit light to indicate a failure of the hydraulic pump. is also possible.

However, if the OR circuit 14 and the light emitting diode 20 are directly connected in this way, the following situation may occur, which is not desirable. That is, the operating lever 9 is operated by an operator, and the operating speed varies. When the operation speed is slow, the rise of the operation signal becomes steep (the speed of change of signal X is large), and the swash plate 6α cannot follow this operation, resulting in a slight delay. When a delay occurs in the movement of the swash plate 6α, this delay naturally appears in the displacement signal Y. Therefore, the discrimination circuit 12, which compares the operation signal X and the displacement signal Y, Even if there is a slight delay, a failure signal will be output during the delay, and the light emitting diode 20 will light up to indicate a failure even though the hydraulic pump is normal, so it is not recognized. The delay circuit 15 is provided to avoid such a situation.

The output of the OR circuit 14 is the output of the delay circuit 15 (OT circuit I7).
The signal is human-powered and becomes an inverted signal. The output signal of the OR circuit 14 is shown in FIG. 4(b), and the inverted signal is NOT
The output signal of circuit 18 is shown in FIG. 4(C). On the other hand, as shown in FIG. 4 (8), the I-cruse generating circuit 16 outputs a constant period /cruse, and this pulse and NO
7 for TM path 17 is input to AND circuit 18 . AN
The output of the D circuit 18 is shown in FIG. 4(d). Now, at time t0, it is assumed that the operation signal X and the displacement signal Y1 tolerance value Δ have a relationship of Y≦X+l. In this case, O
The output of the R circuit 14 is r OJ , N, OT I[11m
Since the output is "1", the AND circuit 18 outputs the pulse of the pulse generating circuit 16 as is.

Due to the rise of the pulse from the AND circuit 18 at time t0, the retrigger pull monostable multivibrator 19
becomes an output "0", and this state is maintained for a period tw. If the above relationship Y≦X+Δ still continues at time t1, the ANDljlW618 outputs a pulse again. Incidentally, since the period ty is set to be longer than the interval between pulses output from the pulse generating circuit 16, the period ty is set to be longer than the interval between pulses output from the pulse generating circuit 16, so that the period ty is set to be longer than the interval between pulses output from the pulse generating circuit 16. Now, the retrigger pull monostable multivibrator 19 is still in the state of output "0". Then, since the pulse is manually applied again at time t, the retrigger pull monostable multi-bi-break 19 maintains its output at 10'' for a period ty starting from time t1. Assume that from this state, the operating lever 9 is rapidly operated at time t, and a situation arises in which the swash plate 6α cannot follow this as described above. In this case, the relationship of Y≦X+Δ is lost, and the relationship of Y>X+Δ is established. This relationship shows that if the swash plate 6α is able to follow up to time t, then time t, to t4
It lasts only for a while. Therefore, during this time, the OR circuit 14
is the output [xJ, the NOT circuit 17 becomes the output "O", and A
The ND circuit 18 does not output the pulse from the pulse generating circuit I6, and the F regrable monostable multipipe rake 19 is not retriggered. However, the period tw is at time t,
to time t, the output of the retrigger pull monostable multivibrator 19 is maintained at "0" even if no pulse is input during this period. When the diagonal 1&i6a follows up at time t, the relationship between the operation signal x1 and the displacement signal Y1 tolerance value Δ returns to Y≦X0Δ again, and the output of the 1NOT circuit 17 becomes “1”. Therefore, the retriggerable monostable multipipe rake 19 is retriggered by the pulse output from the AND circuit 18 immediately after time t4, and from that point on, period 1vlt is started again. In the end, by setting the period ttv appropriately, the swash plate 6
Even if there is a delay in tracking α, a failure signal will not be output and the light emitting diode 2° will not emit light.

Time t? If you are busy and the hydraulic pump malfunctions, the relationship between the operation signal X, displacement signal Y, and allowable value Δ is Y>X+Δ
and is continued. Therefore, the OR circuit 14 outputs [IJ], the NOT circuit 17 outputs "0", and there is no pulse input to the retrigger pull monostable multivibrator 19 @Therefore, the output of the retrigger pull monostable multivibrator 19 is at time t, During the period tw from the input of the pulse at time t6 immediately before, that is, one time 1
．． Until then, the output is held at "0", but after time t8, the output becomes "1", and thereafter, the output remains at "1" as long as the failure continues. Therefore, during this time, the light emitting diode 20 continues to emit light, indicating a failure.

In addition, other indicators or shapes can be used instead of the light emitting diode 2o.
A container or a combination of these can be used,
Further, the black part of the delay circuit 15 can be used as an indicator or an alarm, or can be used alone to drive an emergency stop mechanism of a hydraulic pump, or can be used to monitor a failure. and,
When the output of the delay circuit 15 is used to drive the emergency stop mechanism of the hydraulic pump, the installation of the delay circuit 15 is particularly effective in avoiding unnecessary stops of the hydraulic pump.

In this way, in this embodiment, two adder circuits, 12 comparison circuits 1'F, and an OR circuit are used to compare the addition and subtraction values of the operation signal and the tolerance value with the displacement signal, so that the displacement signal is within a predetermined range. A signal is output when it is outside, and a failure signal is output to indicate a failure only when this output signal continues, so there is no need to disconnect the hydraulic piping or install a tester. Failure diagnosis of a hydraulic pump can be performed automatically and quickly at all times without fear of foreign matter entering the hydraulic circuit. Further, since the failure determination circuit and the delay circuit can be constructed in a small size and at low cost, they can be installed in each hydraulic pump. Furthermore, since the delay circuit is provided, it is possible to prevent generation of temporary failure signals due to delays in tracking of the swash plate, and to generate failure signals only in response to one steady failure.

5F21&'1 is a block diagram of a failure diagnosis device for a commercial pump, which is an example of a hanger decoration of the tank 2 of the present invention. In the figures, the same parts as those shown in FIG. 2 are given the same reference numerals. 21 is a control device configured using a microcomputer, which inputs the operation signal XS and the displacement signal Y, and controls the swash plate drive device 7.
A swash plate control signal is output to the light emitting diode 20, and a failure signal is output to the light emitting diode 20. This control device 21 has the functions of the control device 10, failure determination circuit 11, and delay circuit 15 in the previous example. 22 is signal X
23 is an A/D converter that converts signal X and signal Y into one digital unit; 24 is a predetermined calculation based on signal X and signal Y;
CPU (central processing unit) that performs control, 25 is CPU
ROM (read/write) that stores 24 calculation and control procedures.
26 is a RAM (random access memory) for temporarily storing input data and calculated values, etc.; 27 is a RAM (random access memory) for temporarily storing input data and calculated values; 27 is a RAM (random access memory) for temporarily storing input data and calculated values; This is an output section that outputs to.

The operation of this embodiment will be explained with reference to the 74-chart shown in FIGS. 6 to 9. First, the operation signal X and the displacement signal Y are stored in the RAM 26 via the multiplexer 22 and the A/D converter 23 (block a in FIG. 6). Next, control is performed to drive the swash plate 6a (block b in Fig. 6).
. The detailed procedure of this control is shown in FIG. In block b, first, the deviation ΔX(Δ
X-X-Y') is calculated (block b1), and it is determined whether the deviation ΔX is positive, negative, or O (block b2''l).

If the deviation ΔX is negative, the swash plate 6
Block b3) outputs a signal to reduce the displacement of α from the output unit 22; if deviation ΔX is 0, outputs a signal to stop the swash plate 6α; block b4); if deviation ΔX is positive, block b4) Outputs a signal that increases the displacement of 6G (
Block b5).

In this way, normal swash plate control is performed by blocks a and b.

Next, a failure determination of the hydraulic pump 6 is performed (block C in FIG. 6). Details of the procedure of block C are shown in FIG. In block C, first, the allowable value Δ explained in the previous embodiment is subtracted from the operation signal
(Xs-X, -Δ) is calculated and stored in the RAM 26 (block cl). This determination value x1 corresponds to the subtraction value that is the output of the adder circuit 12b in the rabbit embodiment.

Next, add the operation signal X and the allowable value Δ to determine the upper limit judgment value
x (Xz −X + j) and store it in RAM26
(block c2). This judgment value X corresponds to the addition value that is the output of the addition circuit 12α in the embodiment shown in FIG. Next, take out the displacement signal Y stored in the RAM 26 and the lower limit judgment value X1, and judge whether the signal Y is greater than or equal to the judgment value X1 (block C3).The signal Y is greater than or equal to the judgment value X1. Then, the process moves to block C4, and this time, the signal Y and the upper limit judgment value X are taken out from the RAM 26, and it is judged whether the signal Y is less than or equal to the judgment value X. If the signal Y is less than or equal to the determination value Xt, the process moves to block C5. In block c5, error flag data stored in advance at a predetermined address in the RAM 26 is set to "0". In this case, error 7 lag data is "0"
This means that there is no failure in the hydraulic pump 6 because it is determined in blocks ca' and c4 that the displacement signal Y is within the predetermined range. On the other hand, if it is determined in block C3 that the signal Y is less than the determination value X1, or if it is determined in block C4 that the signal Y exceeds the determination value x2, the process moves to block C6. In block C6, the error flag data is set to "1", which means that the displacement signal @Y is outside a predetermined range and there is a failure.

Next, the process moves to failure indication delay processing shown in block ClIC in FIG. This process is carried out by the delay circuit 15 shown in the previous embodiment.
The details are shown in FIG. 9. In block d1 of FIG. 9, error 7 lag data is retrieved from the RAM 26, and it is determined whether the value is "0" or not. Error 7 If the lag data is “0”, R
Set the value of the error counter set at the predetermined address of AM26 to 0 (block d2) o Here, the 1 error counter counts the set delay time, and the processing of fixes α to d is 1 1 each time it is repeated
are added up step by step. Since the processing of block d3 is performed in the case of no failure, there is no need for delay, and the error counter is set to 0.

If it is determined that the error 7 lag data is not "0" in the fix d1, then the value of the error counter in the RAM 26 is taken out and it is determined whether this value is the preset value. (block d3). If the set value has not been reached, that is, if the predetermined delay time has not been reached, 1 is added to the value of the error counter in the RAM 26, and the process from block α is repeated again in block d4).

In block d3, when it is determined that the value of the error counter has reached the set value iC, that is, the predetermined delay time has been reached, a signal is output from the output section 27 to cause the light emitting diode 20 to emit light.

In the above process, the operating lever 9 is rapidly operated,
If the swash plate 6α cannot follow this, block C6
processing is performed, the error 7 lag data becomes "1", and the processing of blocks d 1 , (1'3, d 4 is performed). Since the setting is made so that the time is longer than the time required to catch up with rapid operation, the swash plate 6α follows the operating lever 9 within the set value, and at the time it follows, the processing of blocks C3edl and d2 is performed. Therefore, a failure signal is not output to the light emitting diode 20. On the other hand, in the case of a continuous failure, the process passing through blocks c6.al and d3.d4 is repeated, so that no error signal is output to the light emitting diode 20. The value of the counter increases by 1 each time it is repeated, and finally reaches the set value, processing by block d5 is performed, and a failure signal is output.

Note that the failure signal output from the output unit 27 is displayed on a display,
The points that can be used to operate alarms, emergency stop mechanisms, failure monitors, etc. are the same as in the first embodiment, and the installation of a delay circuit is particularly effective when an emergency stop mechanism is adopted. This is the same as in the embodiment.

In this way, in this embodiment, the swash plate is controlled using a microcomputer, and the substitute signal and displacement signal are taken in, and the lower limit judgment value and the upper limit judgment value are determined using the sweeping signal and the tolerance value. Therefore, these judgment values are compared with the displacement signal, and a signal is output when the displacement signal is less than the lower limit judgment value or exceeds the upper limit judgment value, and a failure signal is output only when this output signal continues. As a result, hydraulic pump failures can be diagnosed automatically and quickly at all times without disconnecting hydraulic piping or installing a tester, and without the risk of objects getting into the hydraulic circuit. can be done. Furthermore, since a microcomputer is used, similar processing can be sequentially performed on each of a large number of hydraulic pumps, and failure diagnosis of these hydraulic pumps can be performed simultaneously. In addition, since the delay means is provided, it is possible to prevent generation of a temporary failure signal due to a delay in follow-up of the swash plate, and to generate a failure signal only in response to a steady failure.

In each of the above embodiments, the operation signal was explained as a signal taken out from the operation lever, but it is not limited to this, and even if it is a command signal for the final swash plate position to the swash plate drive device. good.

As described above, in the present invention, the absolute value of the difference between the operation signal and the displacement signal is compared with a predetermined tolerance value, and when the absolute value of the difference exceeds the tolerance value, a signal is output. Since the system outputs a signal indicating a failure only when the above conditions continue, there is no need to disconnect the hydraulic piping or install a tester, and there is no fear of foreign matter getting into the hydraulic circuit, automatically and quickly. Failure diagnosis of a hydraulic pump can be performed simultaneously, and failure diagnosis of a large number of hydraulic bonders can also be performed simultaneously. In general, a fault signal can only be generated for steady faults.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a hydraulic circuit diagram of a conventional hydraulic pump failure diagnosis device, FIG. 2 is a block diagram of a hydraulic pump failure diagnosis device according to the first embodiment of the present invention, and FIG. A time chart explaining the operation of the illustrated device; FIG. 5 is a block diagram of a hydraulic ring failure diagnosis device according to a second embodiment of the present invention; FIG. 6;
7, 8, and 9 are flowcharts showing the operation of the failure diagnosis device shown in FIG. 5. 6... Hydraulic bonder, 6a... Swash plate, 7
... Swash plate drive device, 8 ... Displacement meter, 9
......Operating lever, 11...Failure determination circuit, 12α, 12b...Addition circuit, 13α, 1
3b...Comparator, 14...OR@road,
15...Delay circuit, 16...Pulse circuit, 17...NOT circuit, 18...A
ND circuit, 19... retrigger pull monostable multivibrator, 21... control device, 22...
...Multiplexer, 23...A/D converter, 24...CPU, 25...ROM
. 26...RAM, 27...Output section. 1311 (0) (C) R

Claims (1)

[Scope of Claims] 1. A hydraulic pump equipped with a variable displacement mechanism, comprising: a displacement command generation means for generating a command value for displacing the variable displacement mechanism by a required amount; a detection means for detecting, and a comparison means for comparing the absolute value of the difference between the command value of the displacement amount command generation means and the displacement amount detected by the detection means with a predetermined tolerance value;
The comparison means includes output means for outputting a signal when it is determined that the absolute value exceeds the allowable value, and a delay means for outputting a failure signal only when the signal from the output means continues for a predetermined period or more. A hydraulic pump failure diagnosis device characterized by: 2. In claim 1, the comparison means:
an addition means for adding the tolerance value to the command value; a subtraction means for subtracting the tolerance value from the command value; and when the amount of displacement detected by the detection means exceeds the value added by the addition means. The first comparison means outputs a signal, and the second comparison means outputs a signal when the amount of displacement detected by the detection means is less than the value subtracted by the subtraction means. Features: Hydraulic pump failure diagnosis device. & In claim 1, the delay means:
an inverting circuit that inverts the signal output from the output means; a pulse generating circuit that generates pulses of a predetermined period; an AND circuit that receives the output of the pulse generating circuit and the output of the inverting circuit; A failure diagnosis device for a hydraulic pump, characterized in that it is equipped with a retriggerable monostable multivibrator triggered by the output of an AND circuit.