JPH0542628B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a sensor for detecting the amount of displacement of a driving part of various machines and devices, and a sensor that detects when a failure occurs in the sensor. The present invention relates to a failure detection device.

[Background of the invention]

2. Description of the Related Art Appropriate sensors are attached to drive units of various machines and devices depending on the drive mode of the drive unit, and the displacement amount and position of the drive unit are detected by this sensor. The detected value is taken into the control section of the machine or device, and the desired control of the machine or device is performed based on this value.

By the way, in control based on the detection value of such a sensor, if a failure occurs in the sensor and accurate detection is no longer possible, the desired control becomes impossible and the machine or device being controlled will not be able to follow the command. It can operate in different and unexpected ways and is extremely dangerous.
However, conventionally, there has been no appropriate means to detect such sensor failures, and it is common for a sensor failure to be noticed only when the above-mentioned unexpected operation occurs in a machine or device, and there is always a risk of danger occurring. was.

[Purpose of the invention]

The present invention has been made in view of these circumstances, and its purpose is to solve the above-mentioned conventional problems, to be able to reliably detect sensor failure,
Another object of the present invention is to provide a sensor failure detection device that can improve the safety of machines and equipment.

[Summary of the invention]

To achieve the above object, the present invention provides a hydraulic pump, a hydraulic cylinder driven by discharge oil of the hydraulic pump, a link mechanism driven by the hydraulic cylinder, and a relative angle between the links of the link mechanism. and a sensor for detecting the displacement speed of the hydraulic cylinder by dividing the amount of oil discharged from the hydraulic pump, which is calculated based on at least the rotational speed of the hydraulic pump, by the inner diameter of the hydraulic cylinder. a first calculating means for calculating a value; and a second calculating means for calculating a theoretical value of a displacement speed of the hydraulic cylinder based on a detected value of the sensor and a change in a connection position between the hydraulic cylinder and the link.
a third calculating means for calculating the difference between the value obtained by the first calculating means and the value obtained by the second calculating means; The present invention is characterized in that it is provided with an output means for outputting an abnormal signal when the value exceeds a predetermined value.

The first calculation means multiplies the rotational speed of the hydraulic pump by the displacement volume of the hydraulic pump.
Alternatively, the amount of oil discharged from the hydraulic pump is calculated based on the number of revolutions of the hydraulic pump and the amount of displacement of the variable displacement mechanism of the hydraulic pump, and the calculated amount of oil discharged is divided by the inner diameter of the hydraulic cylinder to calculate the amount of oil discharged from the hydraulic cylinder. Calculate the displacement speed of On the other hand, the second calculation means is
The displacement speed of the hydraulic cylinder is calculated based on a physical quantity different from the physical quantity used in the first calculation means, that is, the relative angle between the links detected by the sensor and the change in the connection position between the hydraulic cylinder and the link. . Then, the difference between the displacement speeds of the hydraulic cylinder obtained by the first calculation means and the second calculation means is calculated as a third calculation means.
When the difference between the two exceeds a predetermined value, it is determined that the sensor is abnormal.

[Embodiments of the invention]

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

FIG. 1 is a block diagram of a failure detection device for an angle detector of a hydraulic excavator according to a first embodiment of the present invention. In the figure, 1 is a prime mover such as an engine mounted on a hydraulic excavator, 2 is a hydraulic pump driven by the prime mover 1, 3 is a boom rotatably attached to the hydraulic excavator body, and 4 is a fulcrum A of the boom 3. An arm 5 rotatably attached to the boom 3 is a hydraulic cylinder rotatably mounted between a fulcrum B of the boom 3 and a fulcrum C of the arm 4. Reference numeral 6 denotes a switching valve interposed in the hydraulic circuit between the hydraulic pump 2 and the hydraulic cylinder 5, and controls the drive of the hydraulic cylinder 5. Reference numeral 7 denotes a relief valve that defines the maximum pressure of the hydraulic circuit, and relieves oil to the tank T when the circuit pressure is equal to or higher than the set pressure.

An angle detector 8 detects the relative angle between the boom 3 and the arm 4, and outputs a signal θ according to the detected angle. A rotation speed detector 9 detects the rotation speed of the hydraulic pump 2, and outputs a signal n corresponding to the detected rotation speed. Reference numeral 10 denotes a limit switch provided for the switching valve 6, which detects when the switching valve 6 is operated at a full stroke and outputs a signal e. Reference numeral 11 denotes an arithmetic control section which inputs the angle signal .theta., the rotational speed signal n, and the stroke signal e and executes predetermined arithmetic operations and control, and is constituted by a microcomputer or the like. Reference numeral 12 denotes a display unit that displays the calculation results of the calculation control unit 11.

When the switching valve 6 is switched, for example, to the right position, pressure oil from the hydraulic pump 2 driven by the prime mover 1 is supplied to the head side of the hydraulic cylinder 5.
Further, the rod side of the hydraulic cylinder 5 is connected to the tank T via a switching valve 6. Therefore, the rod of the hydraulic cylinder 5 is extended, and the arm 4 is rotated clockwise about the fulcrum A. This rotation causes boom 3
The relative angle of the arm 4 changes, and this changed angle is detected by the angle detector 8 and output as a signal θ corresponding to this. When the switching valve 6 is returned to the neutral position, the operation of the hydraulic cylinder 5 is stopped.

In this embodiment, the arithmetic control unit 11 determines whether or not the angle detector 5 is malfunctioning. The operation of this arithmetic control section 11 will be explained with reference to the flowchart shown in FIG. First, the signal e from the limit switch 10 is read (step S ₁ ), and it is determined whether or not the switching valve 6 is operated to a full stroke (step S ₂ ). If the switching valve 6 is not operated to a full stroke, it is determined whether there is a failure. do not have. That is, in this embodiment, the determination is made while the entire amount of pressure oil in the hydraulic pump 2 is being supplied to the hydraulic cylinder 5 without being squeezed out. The reason for this will become clear from the explanation of the operation below. When it is determined that the switching valve 6 is operated at full stroke, the rotation speed n of the hydraulic pump 2 is read (step S ₃ ), and the discharge amount Q of the hydraulic pump 2 is calculated based on this (step S 3 ). Step _S4 ). The discharge amount Q is calculated by Q=Dp·n, where Dp is the displacement volume of the hydraulic pump 2. The displacement volume Dp of the hydraulic pump 2 is calculated using a well-known formula based on the design value of the hydraulic pump 2 (if the hydraulic pump 2 is a variable displacement pump, its tilt angle is also the basis for calculation). has been done. Next, the cylinder speed Vp of the hydraulic cylinder 5 is calculated based on the discharge amount Q (step S ₅ ). This cylinder speed Vp means that the discharge amount Q is the full amount hydraulic cylinder 5.
This is the theoretical speed when supplied to speed
Vp is defined as the inner diameter of the hydraulic cylinder 5 as Dc.
It is calculated using the formula Vp=Q/Dc.

Next, the angle signal θ is read from the angle detector 8 (step S ₆ ), and the cylinder length lc of the hydraulic cylinder 5 is calculated based on this angle signal θ. The calculation of this cylinder length lc will be explained with reference to the diagram shown in FIG. In Fig. 3, A, B, and C are the positions of the fulcrums A, B, and C shown in Fig. 1, and C' is the new fulcrum position due to the extension of the rod of the hydraulic cylinder 5.
θ is the angle of the hydraulic cylinder 5 before the rod is extended, and θ' is the angle after the rod is extended. Here, line segment =
a, line segment ='=b, line segment = lc, line segment
If BC′=lc+Δlc, then lc=√ ² + ² −2・……(1) lc+Δlc=√ ² + ² −2・′ Therefore, the extension Δlc of the hydraulic cylinder 5 is Δlc=√ ² + ² − It can be obtained as 2・−√ ² + ² −2・′ ……(2). Note that the lengths a and b are known, and the angles θ and θ' are obtained by the angle detector 8.

Now, in step _S7 , the length lc is determined by equation (1) above.
After calculating, after a certain minute time Δt has elapsed, the angle signal θ' is read again, and the hydraulic cylinder 5 is
Calculate the extension Δlc. Then, the cylinder speed Vc of the hydraulic cylinder 5 is calculated based on the minute time Δt and the calculated extension Δlc (procedure
_S8 ). The velocity Vc is calculated by Vc≈Δlc/Δt. This cylinder speed Vc is a speed based on the detected value of the angle detector 8, and is the actual speed of the hydraulic cylinder 5 if the angle detector 8 is not malfunctioning. Next, calculate the difference ΔV between the absolute value of the theoretical cylinder speed Vp obtained in step S ₅ and the cylinder speed Vc measured by the angle detector 8 obtained in step S ₈ (step
_S9 ). Next, the difference ΔV is compared with a certain set value ΔVs (step S ₁₀ ), and when the difference ΔV is less than the set value ΔVs, a message that the angle detector 8 is normal is displayed on the display unit 12 (step S ₁₁ ). . Further, in step _S10 , when the difference ΔV is greater than or equal to the set value ΔVs, that is, when the theoretical speed of the hydraulic cylinder 5 and the speed determined by the angle detector 8 differ by a considerable amount, the variable in the speed Vc Since there is only an angle signal, it is determined that there is a failure in the angle detector 8, and the display unit 1
2 indicates that the angle detector 8 is abnormal.

In addition, in the above operation, it is assumed that the hydraulic pump 2 is operating normally. or,
The minute time Δt is measured by a timer or the like built into the arithmetic control unit 11.

In this way, in this embodiment, the difference between the theoretical hydraulic cylinder speed calculated based on the discharge amount of the hydraulic pump and the hydraulic cylinder speed calculated based on the detection signal of the angle detector is calculated, When the difference is greater than a certain set value, it is determined that an abnormality has occurred in the angle detector. This makes it possible to reliably detect failures in the angle detector and improve safety. can.

FIG. 4 is a block diagram of a failure detection device for a hydraulic excavator angle detector according to a second embodiment of the present invention. In the figure, the same parts as those shown in FIG. 1 are given the same reference numerals. 11' is an arithmetic control section of this embodiment corresponding to the arithmetic control section shown in FIG.
14 is a bucket, 15 is a boom cylinder, 16 is a bucket cylinder, 17 is a boom angle detector, 1
8 is a bucket angle detector. As is clear from FIGS. 1 and 4, the hydraulic cylinder 5 is an arm cylinder, and the angle detector 8 is an arm angle detector.

20 is a variable capacity hydraulic pump (hereinafter simply referred to as hydraulic pump) that drives the boom cylinder 15, arm cylinder 5, and bucket cylinder 16;
21 is a tilt angle detector that detects the tilt angle of the swash plate 20a. The tilt angle detector 21 outputs a signal α corresponding to the detected tilt angle.
is output. 22a is a boom lever displacement detector, 22b is an arm lever displacement detector, and 22c is a bucket lever displacement detector, each of which has a signal.
Output l ₁ , l ₂ , l ₃ . Each signal l ₁ , l ₂ , l ₃ becomes "0" when the lever is in the neutral position, and becomes "1" when the lever is operated. 23 is a relief detector that detects whether a relief valve (not shown) is in a relief state, and its output signal γ
is "1" when the relief valve is in the relief state,
It becomes "0" when it is not in the relief state. Note that the relief detector is obtained by connecting a flow rate detector or a pressure detector and a throttle to the tank side circuit of the relief valve. The arithmetic control unit 11' receives a tilting angle signal α and a rotational speed signal n of the hydraulic pump 20,
Relief detection signal γ, lever displacement detection signal l ₁ , l ₂ ,
l ₃ and the angle signal θ from the angle detector 8 are input, and it is thereby determined whether or not the angle detector 8 of the arm 4 is malfunctioning.

The operation of the arithmetic control section 11' will be explained below with reference to the flowchart shown in FIG. first,
The lever displacement detection signals l ₁ , l ₂ , l ₃ are read in sequence (step S ₂₁ ), and the signal l ₁ =0, the signal l ₂ =1, and the signal l ₃ =0.
It is determined whether the following conditions are met (step S ₂₂ ). That is, when determining the failure of the arm angle angle detector 8, the first condition is a state in which only the arm lever is operated and pressure oil from the hydraulic pump 20 is supplied only to the hydraulic cylinder 5. . If this condition is met, then the relief detector 2
Read the relief detection signal γ of No. 3 (step S ₂₃ ),
It is determined whether the signal γ is 0 (step S ₂₄ ). That is, the second condition is that all the pressure oil of the hydraulic pump 20 is supplied to the hydraulic cylinder 5 and is not thrown away from the relief valve. By satisfying these two conditions, it is possible to determine the theoretical cylinder speed of the hydraulic cylinder 5 as determined in the previous example. The following steps S ₂₅ , S ₂₆ , and S ₂₇ are means for determining the theoretical cylinder speed Vp, and correspond to steps S ₃ , S ₄ , and S ₅ in the previous embodiment. That is, the tilt angle signal α
and the rotational speed signal n are read (step S ₂₅ ), and the discharge amount Q of the hydraulic pump 20 is calculated based on this (step S 25 ).
S ₂₆ ), the cylinder speed Vp is calculated based on the discharge amount Q and the inner diameter of the hydraulic cylinder 5 (step S ₂₇ ).

Next, steps S ₆ , S ₇ , S ₈ in the previous example
Similarly, the cylinder speed Vc of the hydraulic cylinder 5 is determined based on the detected value of the angle detector 8. That is,
The angle signal θ is read (step _S28 ), and this signal θ
Based on equation (1), the cylinder length lc is calculated (step _S29 ), and a built-in timer calculates the minute time Δt.
The elapsed time is measured (step S ₃₀ ), and then the elongation Δlc of the cylinder length is calculated using equation (2) (step S ₃₁ ), and the cylinder speed Vc is calculated from the minute time Δt and the elongation Δlc.
is calculated (step _S32 ).

Cylinder speed Vp obtained in step S ₂₇ and step S ₃₂
As in the case of the previous example, the difference ΔV between the two cylinder speeds Vc obtained in step _S33 is calculated, and this difference ΔV is compared with the set value ΔVs (step S33).
S ₃₄ ), when the difference ΔV is less than the set value ΔVs, the display section 12
is displayed as normal (step _S35 ), and abnormal is displayed when the difference ΔV is greater than or equal to the set value ΔVs (step _S36 ).

Note that it is natural that the lever displacement detector is provided on all the operating levers of the actuator whose driving source is a hydraulic pump. Further, failure detection for other angle detectors can also be performed by sequentially executing the same procedure for each angle detector.

In this way, in this embodiment, it is determined based on the lever displacement detection signal and the relief detection signal that pressure oil is being supplied only to the target hydraulic cylinder in a non-relieved state, and in this state, the discharge of the hydraulic pump is Find the difference between the theoretical hydraulic cylinder speed calculated based on the amount and the hydraulic cylinder speed calculated based on the detection signal of the angle detector, and if the difference is greater than the set value, the angle detector Since it is determined that an abnormality has occurred, the same effect as the previous embodiment is achieved.

Although the above embodiments have been described using a hydraulic shovel as an example, the present invention is not limited to a hydraulic shovel and can of course be applied to failure detection of sensors in other machines and devices. Furthermore, if the machine or device is equipped with an arithmetic control device used for other purposes, the arithmetic control section can utilize this. Furthermore, an alarm device or a system stop device can be used in place of or in conjunction with the display section. Also, if the difference in speed is greater than or equal to the set speed, an abnormal signal is not output immediately, but only when this condition continues for a predetermined period of time. It is possible to prevent incorrect failure determination.

〔Effect of the invention〕

As described above, in the present invention, the displacement speed of the same hydraulic cylinder is calculated separately based on different physical quantities, that is, the first calculating means calculates the displacement speed of the hydraulic cylinder from the discharge oil amount of the hydraulic pump and the inner diameter of the hydraulic cylinder. The theoretical value of the displacement speed is calculated, and the second calculation means calculates the theoretical value of the displacement speed of the hydraulic cylinder from the detected value of the sensor and the change in the connection position between the hydraulic cylinder and the link. Since the calculated theoretical values are compared, sensor failure can be reliably detected and the safety of machines and equipment can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a failure detection device for an angle detector of a hydraulic excavator according to a first embodiment of the present invention;
FIG. 2 is a flowchart explaining the operation of the device shown in FIG. 1, FIG. 3 is a line diagram explaining the calculations of the device shown in FIG. 1, and FIG. 4 is a diagram according to a second embodiment of the present invention. FIG. 5 is a block diagram of a failure detection device for an angle detector of a hydraulic excavator, and is a flowchart for explaining the operation of the device shown in FIG. 4. 2,20...Hydraulic pump, 3...Boom, 4...
...Arm, 5...Hydraulic cylinder, 6...Switching valve,
7... Relief valve, 8... Angle detector, 9... Rotation speed detector, 10... Limit switch, 11,
11'...Arithmetic control section, 12...Display section, 21...
...Tilt angle detector, 22a, 22b, 22c... Lever displacement detector.

Claims (1)

[Claims] 1. A hydraulic pump, a hydraulic cylinder driven by oil discharged from the hydraulic pump, a link mechanism driven by the hydraulic cylinder, and a sensor that detects the relative angle between the links of the link mechanism, a first calculating means that calculates a theoretical value of the displacement speed of the hydraulic cylinder by dividing the amount of oil discharged from the hydraulic pump, which is calculated based on at least the rotational speed of the hydraulic pump, by the inner diameter of the hydraulic cylinder; a second calculation means for calculating a theoretical value of the displacement speed of the hydraulic cylinder based on a detection value of a sensor and a change in a connection position between the hydraulic cylinder and the link; and a value obtained by the first calculation means. and a third calculation means for calculating the difference between the value obtained by the second calculation means and the value obtained by the third calculation means, and an output for outputting an abnormal signal when the value obtained by the third calculation means exceeds a predetermined value. 1. A sensor failure detection device characterized by comprising: means.