JPH0440009Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a descending speed control device for a front loader.

(Prior art) A front loader, which is attached to a tractor body and performs work, has a boom pivotably attached to the tractor body so that it can be raised and lowered, and a bucket rotatably attached to the tip of the boom. is operated by a boom cylinder and bucket cylinder.

(Problem to be solved by the invention) Conventionally, in this type of front loader, a manual or electromagnetic control valve is provided in the hydraulic circuit of each cylinder, and by switching the control valve, the boom can be raised and lowered, However, when the boom is lowered, the lowering speed of the boom becomes faster in proportion to the weight of the object being lifted by the bucket.

That is, since the lifting load always acts on the boom cylinder in the downward direction, when the control valve is switched to the downward direction, if the lifting load is large, the boom rapidly descends. Therefore, the larger the tractor, the higher the center of gravity, and if the operating lever is operated too quickly, the boom will lower rapidly, creating the risk of the tractor overturning.

In view of these conventional problems, the present invention controls the descending speed of the boom during its descending operation so that the greater the load to be lifted, the slower the descending speed of the boom becomes, allowing work to be carried out safely. The purpose is to do so.

(Means for solving the problem) The present invention has a boom 6 having a bucket 8 at its tip.
In this front loader, the boom 6 is pivotably mounted on the vehicle body 1 side so as to be freely raised and lowered, and the boom 6 is raised and lowered by a boom cylinder 7. A sensor 16 is provided to detect the weight of the object to be transported by the bucket 8, and the boom 6 is lowered. A control circuit 17 is provided for controlling the flow rate of the boom cylinder 7 in proportion to the lifting load based on a signal from the sensor 16 so that the lowering speed of the boom 6 becomes slower as the lifting speed increases during operation. It is something.

(Function) When the boom 6 is raised, the sensor 16 detects the weight of the object being lifted by the bucket 8. and,
When the boom 6 starts to move down, the control circuit 17 drives the regulating valve 12 or the control valve 10, and if the lifting load is large, the downward flow rate of the boom cylinder 7 is limited. The descending speed of the boom 6 is controlled so as to be slow.

(Embodiment) Hereinafter, the present invention will be described in detail with reference to the illustrated embodiment. In FIG. 2, 1 is a tractor body, 2 is a front wheel, and 3 is a rear wheel. 4 is a front loader, and masts 5 are attached to both the left and right sides of the tractor body 1.
, a pair of left and right booms 6 pivotally mounted to the upper end of the mast 5 so as to be freely raised and lowered, a boom cylinder 7 for raising and lowering the boom 6, and a bucket 8 rotatably pivotally mounted to the tip of the boom 6. , a bucket cylinder 9 for dumping and scooping the bucket 8
It is composed of etc.

FIG. 1 shows the hydraulic circuits of the boom cylinder 7 and bucket cylinder 9. 10 is boom cylinder 7
The boom control valve can be manually switched to a neutral position a, a raised position b, a lowered position c, and a floating position d. 11 is a bucket cylinder 9
It is possible to manually switch between neutral position a, dump position b, and scoop position c using a bucket control valve that controls the position. Reference numeral 12 denotes an electromagnetic proportional flow rate adjustment valve, which is installed in an oil passage 13 connecting the boom control valve 10 and the ascending cylinder chamber of the boom cylinder 7, and a check valve 14 connected in parallel to this adjustment valve 12. tied together. 15 is a hydraulic system for lifting and lowering the working machine on the tractor body 1 side. Reference numeral 16 denotes a pressure sensor as a sensor for detecting the lifting load, and the pressure sensor 16 detects the lifting load of the object to be transported in the bucket 8 based on the pressure in the rising cylinder chamber of the boom cylinder 7. 17 is a control circuit that controls the regulating valve 12 based on a signal from the pressure sensor 16, and as shown in FIG. 4, when the boom 6 is lowered, the larger the lifting load, the lower the boom cylinder 7 The regulating valve 12 is configured to operate so that the flow rate becomes small.

In FIG. 3, 18 is a hold circuit which holds the pressure signal detected by the pressure sensor 16 when the boom 6 is raised. 19 is regulating valve 1
2 is a power amplifier that drives the proportional solenoid 20, and 21 is a PWM converter, which converts the signal from the previous stage comparator 22 into PWM using the triangular wave signal from the oscillator 23.
It's starting to convert. Reference numeral 24 denotes an output current detector, which detects changes in the output current of the power amplifier 19. The comparator 22 compares the signal sent from the hold circuit 18 via the amplifier 25 with the signal from the output current detector 24 to determine whether the resistance value changes due to a temperature rise in the proportional solenoid 20. This is to compensate so that the current flowing through the proportional solenoid 20 does not fluctuate.

In the above configuration, when raising the boom 6 after scooping earth and sand into the bucket 8, the boom control valve 10 is switched to the raised position b. Then, oil from the hydraulic pump is sent to the cylinder chamber on the rising side of boom cylinder 7, so this boom cylinder 7
extends, and the boom 6 rises. At this time, the pressure sensor 16 senses the pressure in the ascending cylinder chamber of the boom cylinder 7, and the hold circuit 18 holds the pressure signal.

When the pressure sensor 16 measures the load lifted by the bucket 8, such as earth and sand, the pressure in the ascending cylinder chamber of the boom cylinder 7 during the upward movement of the boom 6 almost accurately reflects the lifted load. Measure in advance and then boom 6
It is held by the hold circuit 18 in preparation for the lowering operation.

When lowering the boom 6 to load earth and sand onto a truck, the boom control valve 10 is switched to the lowered position c. Then, the oil from the hydraulic pump flows into the oil passage 26.
The oil in the boom cylinder 7 is sent to the boom cylinder 7 via the oil passage 13 and the regulating valve 12. At this time, hold circuit 18
PWM converts the pressure signal held in
The signal is applied to the proportional solenoid 20 via the power amplifier 19, causing a current proportional to the pressure signal to flow through the proportional solenoid 20. Therefore, when the lifting load is large, the pressure signal from the pressure sensor 16 is large, and a current proportional to this is applied to the proportional solenoid 2.
0, the descending flow rate is reduced by the regulating valve 12, and the descending speed of the boom 6 can be maintained at an optimal speed. The pressure of the pressure sensor 16 at this time and the descending flow rate when the boom descends have a relationship as shown in FIG. 4. Therefore, as the load to be lifted increases, the lowering speed of the boom 6 becomes slower, and the work can be carried out safely without the risk of the tractor falling over.

In FIG. 5, an electromagnetic proportional solenoid having a rising proportional solenoid 27 and a descending proportional solenoid 28 is used as the boom control valve 10. This system determines the direction and controls the elevation. The proportional solenoids 27 and 28 are connected to a power amplifier 33 and a PWM converter 34 via analog switches 31 and 32, and
Connected between the PWM converter 34 and the amplifier 35 are a series circuit of a variable gain amplifier 36 and an analog switch 37, and an analog switch 38 parallel to this. The variable gain amplifier 36 is designed to greatly attenuate the command signal from the command unit 29 when the pressure signal from the pressure sensor 16 is large, and to reduce the attenuation when the pressure signal is small. The analog switches 31 and 38 are turned on by the rising signal from the direction discriminator 30, and the analog switches 32 and 37 are turned on.
is turned on by a falling signal.

In this case, if there is a command signal from the command device 29, the direction discriminator 30 determines whether the direction is ascending or descending. If it is a rise, the analog switches 31 and 38 are turned on, and the command signal is PWM-converted by the PWM converter 34, and is then applied to the rise-side proportional solenoid 27 via the power amplifier 33.
to rise. At this time, the pressure sensor 16 detects the lifting load.

If there is a descending command, the analog switch 32,
37 turns on. Therefore, the command signal is attenuated by the variable gain amplifier 36 according to the signal from the pressure sensor 16, and after PWM conversion with that signal, the descending proportional solenoid 28 is driven via the power amplifier 33. Therefore, the lowering speed of the boom 6 is optimally controlled depending on the magnitude of the lifted load.

Next to the command device 29 and the left and right sensors 16, a sixth
As shown in the figure, A/D converters 37 and 38 are provided,
Digitally processed by a microcomputer 39 and sent to each solenoid 4 via a power amplifier 33.
0 and 41 may be driven. In this case, if the lifting load is large, when the boom 6 is lowered, the duty ratio is made smaller (shorter on time) than when the lifting load is small, thereby reducing the current and lowering the boom cylinder 7. The flow rate is restricted and the descending speed of the boom 6 is slowed down.

(Effects of the invention) According to the invention, in a front loader in which a boom 6 having a bucket 8 at its tip is pivotally attached to the vehicle body 1 side so as to be able to rise and fall freely, and this boom 6 is raised and lowered by a boom cylinder 7, the bucket 8 is A sensor 16 is provided to detect the weight of the object being lifted by the boom 6, and when the boom 6 is lowered, a signal from the sensor 16 is sent so that the lowering speed of the boom 6 becomes slower as the lifting load increases. A control circuit 17 is provided to control the flow rate of the boom cylinder 7 in proportion to the load, so when the lifting load is large and there is a risk of falling, the boom 6 can be safely lowered at a slow speed, and the lifting load can be lowered safely. When the boom 6 is small and there is no risk of it falling over, the boom 6 will descend at a high speed. Therefore, work can be carried out safely and efficiently depending on the magnitude of the lifting load of the transported object.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention;
Figure 2 is a side view of the front loader, Figure 3 is a block diagram of the control circuit, Figure 4 is a pressure-flow characteristic diagram, and Figures 5 and 6 are block diagrams showing other embodiments. be. 1...Tractor body, 4...Front loader,
6...Boom, 7...Boom cylinder, 8...Bucket, 9...Bucket cylinder, 10...Boom control valve, 12...Solenoid proportional flow rate adjustment valve, 16...
...Pressure switch, 17...Control circuit, 36...Variable gain amplifier.

Claims (1)

[Scope of utility model registration request] In a front loader in which a boom 6 having a bucket 8 at its tip is pivotally mounted on the side of a vehicle body 1 so as to be able to rise and fall freely, and this boom 6 is raised and lowered by a boom cylinder 7, a sensor detects the weight of an object to be transported by the bucket 8. 16 is provided, and the sensor 16 is configured such that the lowering speed of the boom 6 becomes slower as the lifting load increases during the lowering operation of the boom 6.
A lowering speed control device for a front loader, characterized in that a control circuit 17 is provided for controlling the flow rate of the boom cylinder 7 in proportion to the lifting load based on a signal from the lifting load.