JP2021046686A - Construction machine - Google Patents

Abstract

To provide a construction machine capable of preventing vibration generated in a body during operation from being transmitted to an angle sensor through transmission members and preventing the angle sensor from being damaged due to the vibration.SOLUTION: A wheel loader 1 is provided with: an arm 6 and a bell-crank 4 rotatably connected relative to each other around a center of a connecting shaft 13; and an angle sensor 12, of which a sensor body 14 is secured on the arm 6, a sensor axis 15 is projected from the sensor body 14 along a shaft line C of the connecting shaft 13 to secure one end of the arm part 16, and the other end of the arm part 16 is connected to the bell-crank 4, wherein an engaging pin 18 erected on the bell-crank 4 being inserted into an engaging hole 17 formed in the other end of the arm part 16 to form looseness between the engaging hole 17 and the engaging pin 18 allows relative displacement of the engaging hole 17 and the engaging pin 18 in a plane including a radial direction and a circumferential direction of which a center is the shaft line C of the connection shaft 13.SELECTED DRAWING: Figure 2

Description

The present invention relates to an angle sensor mounting structure in a construction machine.

The wheel loader repeats the work of scooping up minerals and earth and sand piled up on the ground and loading them on the dump truck bed. The operation of the wheel loader to scoop up the earth and sand is as follows: First, the bucket attached to the tip of the wheel loader is tilted forward at a height slightly raised from the ground, and then the wheel loader is advanced to hit the earth and sand near the ground. Use inertia to bite the bucket into the earth and sand. Next, the length of the bucket cylinder that adjusts the angle of the bucket and the length of the arm cylinder that adjusts the height of the bucket are operated, and the height of the bucket is raised while raising the angle of the bucket toward you to scoop up the earth and sand. Then, the scooped up earth and sand are discharged to the loading platform of the dump truck.

In order to perform such a series of loading operations of the wheel loader, the wheel loader is configured so that the arm is rotatably attached to the vehicle body and the bucket is rotatably attached to the arm. In order to control the position and angle of the bucket in the loading operation, the angle sensor detects the rotation angle of the movable members that make up the wheel loader, such as the bucket and arm, and the controller performs the required processing based on the detection result. are doing.

The sensor shaft of the angle sensor is connected to a movable member to be detected via an arm portion that functions as a transmission member, and rotates together with the movable member to be detected to output a voltage corresponding to the rotation angle. As a prior art, there is known a technique of acquiring the angle of a movable member by attaching an angle sensor on the axis of a connecting shaft that supports the rotation of the movable member to be detected in order to accurately detect the rotation angle. (See, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2004-279047

However, in the mounting structure of the angle sensor described in Patent Document 1, since the sensor shaft of the angle sensor is rigidly connected to the movable member to be detected via the arm portion, there is a problem that a failure occurs due to vibration. .. For example, when applied to a wheel loader, each member vibrates due to an action of biting a bucket into earth and sand by utilizing the inertia of the vehicle body. When the arm portion of the angle sensor vibrates, the space between the resistor and the electrode vibrates and wears inside the angle sensor, resulting in an error in the detected voltage.

If the acquired angle contains an error, the controller of the wheel loader cannot execute the required control, for example, when controlling the angle of the bucket of the wheel loader, it tilts forward from the desired angle and spills earth and sand. It causes problems. The state in which the angle sensor cannot accurately obtain the angle to be detected and causes a problem as described above is referred to as a failure of the angle sensor.

The present invention has been made to solve such a problem, and an object of the present invention is to avoid a situation in which vibration generated in a vehicle body during operation is transmitted to an angle sensor via a transmission member. It is an object of the present invention to provide a construction machine capable of preventing a failure of an angle sensor due to vibration.

In order to achieve the above object, the construction machine of the present invention connects the first member and the second member so as to be relatively rotatable around a connecting shaft, and fixes the sensor body to the first member. , Construction provided with an angle sensor in which the sensor shaft of the sensor body is arranged on the axis of the connecting shaft, one end of the transmission member is fixed, and the other end of the transmission member is connected to the second member. In the machine, play is formed between the first engaging portion formed on the other end of the transmission member and the second engaging portion formed on the second member, and the axis of the connecting shaft is displaced. It is characterized in that the first engaging portion and the second engaging portion are relatively displaceable in a plane including a radial direction and a circumferential direction about the center.

According to the construction machine of the present invention, it is possible to avoid a situation in which vibration generated in the vehicle body during operation is transmitted to the angle sensor via a transmission member, thereby preventing failure of the angle sensor due to vibration. Can be done.

It is a side view which shows the wheel loader of an embodiment. It is a detailed view of part A of FIG. 1 which shows the angle sensor of 1st Embodiment. It is a B arrow view of FIG. 2 which shows the angle sensor. It is a figure which showed the posture change of the wheel loader 1 when the bucket was changed from the lowest point to the highest point, and the angle change of the arm part of the angle sensor corresponding to it. It is a characteristic figure which compared the setting example of the initial angle A1 = 10 ° and the setting example of the initial angle A1 = 50 °. It is a detailed view corresponding to FIG. 2 which shows the angle sensor of 2nd Embodiment.

Hereinafter, an embodiment in which the present invention is embodied in a wheel loader will be described.
FIG. 1 is a side view showing a wheel loader of this embodiment.
The wheel loader 1 includes a front vehicle body 1a having a bucket 3, a bell crank 4 (second member), a bucket cylinder 5, an arm 6 (first member), an arm cylinder 7, a front wheel tire 8, an angle sensor 12, and the like. It is composed of a rear vehicle body 1b having a driver's cab 2, an engine chamber 10, rear wheel tires 9, and the like. The arm 6 is rotatably attached to the front vehicle body 1a in the vertical direction, and is rotationally driven by expansion and contraction of the arm cylinder 7. The bucket 3 is rotatably attached to the arm 6 at the tip of the arm 6 in the vertical direction, and is rotationally driven via the bell crank 4 by the expansion and contraction of the bucket cylinder 5.

[First Embodiment]
FIG. 2 is a detailed view of part A of FIG. 1 showing the angle sensor of the first embodiment, and FIG. 3 is a view taken along the arrow B of FIG. 2 showing the angle sensor.
The bell crank 4 is rotatably connected to the bracket 6a provided on the arm 6 by a connecting shaft 13, and the sensor body 14 of the angle sensor 12 is fixed on the bracket 6a. From the sensor body 14, the sensor shaft 15 projects laterally along the axis C of the connecting shaft 13, and one end of the arm portion 16 (transmission member) formed in a crank shape is fixed to the sensor shaft 15. There is. The other end of the arm portion 16 is overlapped on the bell crank 4 and a circular engaging hole 17 (first engaging portion) is penetrated, and the other end of the arm portion 16 is erected on the bell crank 4 in the engaging hole 17. An engaging pin 18 (second engaging portion) having a circular cross section is inserted. The outer diameter of the engaging pin 18 is set to be smaller than the inner diameter of the engaging hole 17, whereby a predetermined amount of play is formed around the engaging pin 18 in the engaging hole 17. Due to this backlash, the engaging hole 17 and the engaging pin 18 can be relatively displaced in a plane including the radial direction and the circumferential direction about the axis C of the connecting shaft 13.

The amount of backlash is set to a value larger than the relative displacement amount due to the vibration between the bell crank 4 and the arm 6 generated by the loading operation of the wheel loader 1, for example, 10 mm. When the bell crank 4 rotates about the axis C of the connecting shaft 13 with respect to the arm 6, the rotation is transmitted from the engaging pin 18 to the arm portion 16, and the sensor shaft 15 is the same via the arm portion 16. It rotates in a direction and an angle, and a voltage corresponding to the rotation angle is output from the sensor body 14.

Since a predetermined amount of backlash is provided between the engagement hole 17 and the engagement pin 18 of the arm portion 16 in this way, the size of the backlash is less than or equal to the predetermined amount between the bell crank 4 and the arm 6. Even if the relative vibration of the amplitude occurs, the vibration is absorbed within the range of play of the arm portion 16. The vibration occurs in various directions, but since the engaging hole 17 and the engaging pin 18 are separated from each other, the vibration in any direction is absorbed by the backlash. Therefore, it is possible to avoid a situation in which vibration is transmitted to the arm portion 16, and it is possible to prevent a failure of the angle sensor 12 due to vibration.

FIG. 4 shows a state in which the arm cylinder 7 is extended to the maximum from a state in which the bucket 3 is tilted toward the front (hereinafter referred to as the lowest point) and the bucket 3 is tilted to the back (hereinafter referred to as the highest point). It is a figure which showed the posture change of the wheel loader 1 and the angle change of the arm part 16 of the angle sensor 12 corresponding to this. In FIG. 2, the arm portion 16 at the lowest point is shown by a solid line, and the arm portion 16 when moving from the lowest point to the highest point is shown by a broken line.

As shown by the solid line in FIG. 4, the bucket 3 is tilted toward the front near the ground surface at the lowest point, and as shown in FIG. 2, the angle line of the engaging pin 18 with respect to the axis C of the sensor shaft 15 at this time. The angle A (hereinafter referred to as the initial angle A1) formed by L1 (hereinafter abbreviated as the pin angle line L1) and the vertical line L2 (hereinafter abbreviated as the vertical line L2) passing through the axis C of the sensor shaft 15 is, for example, 10. °. From this posture, the angle A formed by the pin angle line L1 and the vertical line L2 tends to increase regardless of whether the bucket cylinder 5 or the arm cylinder 7 is operated. When the arm cylinder 7 is operated to the maximum extension side, the positions of the arm 6, the bucket 3 and the bell crank 4 change by the amount of the arrow indicated by the lift operation in the figure, and the sensor shaft 15 also rotates. Further, when the bucket cylinder 5 is operated to the maximum to the side where it falls forward, the position changes by the amount of the arrow indicated by the bucket operation, and the posture of the wheel loader 1 changes to the highest point. At this time, the angle A formed by the pin angle line L1 and the vertical straight line L2 (hereinafter referred to as the final angle A2) is, for example, 160 °.

As a result, the rotation range of the engagement pin 18 from the lowest point to the highest point (in other words, the rotation angle of the bell crank 4 with respect to the arm) is 150 °, and the engagement pin 18 is vertical within this rotation range. It is kept in a position that does not exceed the line L2. As will be described later, in order for the backlash not affecting the detected value of the rotation angle, it is necessary that the engaging pin 18 is always in contact with the same portion of the engaging hole 17 during rotation. That is, it is necessary to design the link mechanism of the bell crank 4 so that the rotation range does not exceed the vertical line L2, or invalidate the detected value after the vertical line L2 is exceeded.

As shown in FIG. 2, the direction of rotation of the arm portion 16 due to gravity is always counterclockwise when it is on the left side of the vertical line L2 in the drawing. Therefore, in the range in which the posture changes from the lowest point to the highest point of the wheel loader 1 shown in FIG. 4, the arm portion 16 of the angle sensor 12 is always counterclockwise as shown by the solid line and the broken line in FIG. It continues to be in contact with the engagement pin 18 under the action of gravity in the direction.

FIG. 5 is a characteristic diagram comparing the above setting example of the initial angle A1 = 10 ° and the setting example of the initial angle A1 = 50 °, and the horizontal axis is the angle A formed by the pin angle line L1 and the vertical line L2. Yes, the vertical axis is the detection angle θ by the angle sensor 12.
When the initial angle A1 = 10 ° shown by the solid line, the arm portion 16 of the angle sensor 12 is always in contact with the engaging pin 18 under the action of gravity in the counterclockwise direction, whereby the engaging pin 18 rotates. Within the range (10 to 160 °), the engaging pin 18 and the arm portion 16 are maintained in the same positional relationship. Therefore, an accurate detection angle θ corresponding to the angle A formed by the pin angle line L1 and the vertical line L2 is obtained.

On the other hand, when the initial angle A1 = 50 ° shown by the broken line, the direction of gravity acting on the arm portion 16 when the engaging pin 18 exceeds the vertical line L2 (A = 180 °) is clockwise. Invert. Therefore, as shown by a virtual line in FIG. 2, the positional relationship between the engaging pin 18 and the arm portion 16 changes, and the engaging pin 18 and the engaging pin 18 are increased by the amount of play between the engaging pin 18 and the engaging hole 17. The arm portion 16 rotates separately. In FIG. 5, since the rotation of the arm portion 16 corresponding to the backlash is illustrated as 2 °, + 2 ° in the region from the time when the engaging pin 18 exceeds the vertical line L2 to the time when the final angle A2 is reached. For example, when the final angle A2 = 200 °, the detection angle θ = 202 ° is detected. Originally, the link mechanism of the bell crank 4 should be designed so that the rotation range does not exceed the vertical line L2, but since the bucket is replaced with one of various shapes and dimensions, the link mechanism corresponding to all is supported. Design can be difficult. Therefore, in the present embodiment, the output of the sensor detection angle after the time when the engaging pin 18 exceeds the vertical line L2 is invalidated.

In the present embodiment, a discontinuous change in the sensor detection angle that occurs when the engagement pin 18 exceeds the vertical line L2 (A = 180 °) in FIG. 5 is detected, and the sensor detection angle signal after that is detected. Disable. Specifically, the angle sensor uses, for example, a photoelectric element, and the detection signal of the sensor element is processed by a signal processor built in the sensor and output, so that a discontinuous change in the detected value is detected. It is possible to do. If the output signal after detecting this discontinuous change is invalidated by the signal processor, as a result, an accurate detection angle θ corresponding to the angle A formed by the pin angle line L1 and the vertical line L2 can be obtained, which is good. It is possible to realize the detection accuracy of the rotation angle. Further, an external signal processing means may be connected separately from the signal processor to detect and invalidate the discontinuous change of the detection angle signal. The discontinuous change of the detection angle signal may occur repeatedly every time the bucket rotates, but in the next discontinuous change in which the discontinuous change is detected once, the engaging pin 18 crosses the vertical line L2 again. It indicates that it has returned to the measurement target area, and it is also possible to switch the valid / invalid of the detection angle signal output each time a discontinuous change is detected.
On the other hand, since the backlash is formed around the engaging pin 18 in the engaging hole 17, another effect that the angle sensor 12 can be easily attached can be obtained.

[Second Embodiment]
FIG. 6 is a detailed view corresponding to FIG. 2 showing the angle sensor 12 of the second embodiment.
In contrast to the first embodiment using gravity, in this embodiment, the engaging pin 18 and the arm portion 16 are kept in the same positional relationship by utilizing the urging force of the compression spring 21. As shown by a solid line in FIG. 6, the engaging hole 22 (first engaging portion) of the present embodiment has a square shape, and a predetermined amount of backlash is formed around the engaging pin 18 in the engaging hole 22. Has been done. Then, the engagement pin 18 is arranged on the clockwise side (left side in the drawing) in the engagement hole 22 with the axis C of the sensor shaft 15 as the center, and the counterclockwise side in the engagement hole 22 (in the figure). A compression spring 21 is arranged on the right side). As a result, the arm portion 16 of the angle sensor 12 is always affected by the urging force of the compression spring 21 in the counterclockwise direction.
The urging direction of the arm portion 16 by the compression spring 21 is not limited to the counterclockwise direction, and may be urged in the circumferential direction centered on the axis C of the sensor shaft 15. Therefore, the urging force of the compression spring 21 may be applied clockwise.

The urging force of the compression spring 21 is strong enough to bend when it receives the vibration generated between the bell crank 4 and the arm 6 and to regulate the movement of the engaging pin 18 in the engaging hole 22. It is set. Therefore, the vibration generated between the bell crank 4 and the arm 6 is absorbed inside the backlash of the arm portion 16 while bending the compression spring 21. As a result, it is possible to avoid a situation in which vibration is transmitted to the arm portion 16, and it is possible to prevent a failure of the angle sensor 12 due to vibration.

On the other hand, in the present embodiment, the initial angle A1 is 10 °, which is the same as that in the first embodiment, but the final angle A2 is set to 200 °. Therefore, as described with reference to FIG. 5, when the engaging pin 18 exceeds the vertical line L2, the direction of gravity acting on the arm portion 16 is reversed clockwise. However, since the compression spring 21 continues to receive the urging force counterclockwise, the engaging pin 18 and the arm portion 16 have the same positional relationship within the entire rotation range of the engaging pin 18 up to the final angle A2. Be kept. As a result, in the present embodiment, by utilizing the urging force of the compression spring 21, the pin angle line L1 and the vertical line L1 are not affected by the backlash between the engaging pin 18 and the engaging hole 22 of the arm portion 16. An accurate detection angle θ corresponding to the angle A formed by the line L2 can be obtained, and a good rotation angle detection accuracy can be realized.

Although the description of the embodiment is completed above, the aspect of the present invention is not limited to this embodiment. For example, in the above embodiment, the angle sensor for detecting the rotation angle of the bell crank 4 with respect to the arm 6 of the wheel loader 1 is used, but for example, it is embodied as an angle sensor for detecting the rotation angle of the arm 6 with respect to the front vehicle body 1a. It may be applied to other construction machines.

Further, in the above embodiment, the engaging hole 17 is formed at the other end of the arm portion 16 as the first engaging portion, and the engaging pin 18 is erected on the bell crank 4 as the second engaging portion. Both may be reversed, or may be used as an engaging portion having another shape that forms backlash between the two. Alternatively, for example, the engaging pin 18 may be integrally formed with the bell crank 4.

1 Wheel loader (construction machinery)
4 Bell crank (second member)
6 arm (first member)
12 Angle sensor 13 Connecting shaft 15 Sensor shaft 16 Arm (transmission member)
17,22 Engagement holes (first engagement part)
18 Engagement pin (second engagement part)
21 compression spring

Claims (5)

The first member and the second member are connected so as to be relatively rotatable around a connecting shaft, the sensor body is fixed to the first member, and the sensor shaft of the sensor body is placed on the axis of the connecting shaft. In a construction machine provided with an angle sensor, which is arranged to fix one end of a transmission member and connect the other end of the transmission member to the second member.
A backlash is formed between the first engaging portion formed on the other end of the transmission member and the second engaging portion formed on the second member, and is centered on the axis of the connecting shaft. A construction machine characterized in that the first engaging portion and the second engaging portion are relatively displaceable in a plane including a radial direction and a circumferential direction. The first engaging portion is an engaging hole formed at the other end of the transmission member.
The second engaging portion is an engaging pin that is erected on the second member and inserted into the engaging hole.
The construction machine according to claim 1, wherein play is formed around the engaging pin in the engaging hole. The rotation range of the first member and the second member about the connecting shaft is set to less than 180 °.
The second aspect of the present invention is characterized in that the engaging pin is maintained at a position within the rotation region of the first member and the second member so as not to exceed a vertical line passing through the axis of the sensor shaft. Described construction machinery. A compression spring is disposed together with the engaging pin in the engaging hole.
The construction machine according to claim 2, wherein the transmission member is urged by the compression spring in the circumferential direction about the axis of the sensor shaft. The construction machine according to claim 2, wherein the angle sensor includes a signal processing means for detecting a discontinuous change in the detection angle and invalidating an output signal after the detection of the discontinuous change.

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