JP2001200804A - Dynamic damper of working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamic damper capable of effectively suppressing the vibration of a vehicle main body even if the mass of a working device varies and reducing the cost thereof. SOLUTION: In a dynamic damper of working vehicle, a working device 2 is installed on a vehicle main body 1, the working device 2 comprises a working part 13 and a lift cylinder 12 provided between the working part 13 and the vehicle main body 1 and moving the working part 13 up and down, and an accumulator 62 is connected to the load holding side oil chamber 28 of the lift cylinder 12. The dynamic damper comprises A. a variable choke device 61 installed between the load holding side oil chamber 28 of the lift cylinder 12 and the accumulator 62, B. a detection means 49 detecting a hydraulic pressure in the load holding side oil chamber 28 of the lift cylinder 12, and C. a control means 53 increasing the choke opening of the variable choke device 61 when a hydraulic pressure detected by a detection means 49 is smaller than a set pressure and decreasing the choke opening of the variable choke device 61 when the hydraulic pressure is equal to or larger than the set pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dynamic damper for a working vehicle.

[0002]

2. Description of the Related Art In a wheel loader, a working device is provided on a vehicle body. The working device includes, for example, a boom provided on the vehicle body so as to be able to move up and down, a boom cylinder for raising and lowering the boom, and a rotating device mounted on a tip of the boom. It has a work unit (also referred to as a mounting attachment) such as a bucket movably provided, and a work unit cylinder for rotating the work unit.

In such a wheel loader, a vibration suppressing accumulator is connected via a throttle to a load holding side oil chamber of a boom cylinder in order to suppress vibration such as pitching and bouncing of the vehicle body during traveling. There has already been proposed an apparatus in which a dynamic damper is constituted by a working device serving as a mass member, an accumulator acting as a spring, and a throttle acting as a damper. In this one,
At the time of vibration of the vehicle body, the working device moves in the direction opposite to the direction in which the vehicle body tries to move, thereby suppressing vibrations such as pitching and bouncing of the vehicle body,
The vibration of the working device is also attenuated by the damping effect of the oil passage resistance of the throttle or the like. That is, the vibration system according to the wheel loader is represented by a two-degree-of-freedom system in which the vehicle body is a main vibration system and the working device having a smaller mass than the vehicle body is a sub-vibration system, that is, a dynamic damper.

In the above-mentioned wheel loader, a change in the mass of a load such as earth and sand, gravel, etc. loaded on a work unit such as a bucket, and a change in the work unit (change of the work unit (attachment attachment) using a one-touch carrier or the like) For example, a change from a bucket to a snow removal blade or the like) changes the mass of the entire working device, thereby changing the vibration characteristics. In order for the dynamic damper to fully exhibit the vibration suppression effect in response to this change, when the mass of the working device is small, the spring constant of the accumulator should be small, and the aperture of the diaphragm should be large, When the mass of the device is large, it is preferable to increase the spring constant of the accumulator and reduce the aperture of the aperture.

[0005] However, adjusting both the spring constant of the accumulator and the opening degree of the throttle in accordance with the change in the mass of the working device considerably complicates the structure of the dynamic damper and increases the cost. There is a problem with. Therefore, conventionally, a plurality of accumulators having different spring constants are provided, and one of the accumulators is selected and used according to a change in mass of the working device.

[0006]

However, even in the case described above, there is still a problem that the cost of the dynamic damper is high because a plurality of expensive accumulators must be provided.

An object of the present invention is to provide a dynamic damper for a working vehicle that solves the above problems.

[0008]

In order to achieve the above object, a feature of the present invention is that a working device is provided in a vehicle body, and the working device is provided between a working unit and the working unit and the vehicle body. A lift cylinder that is interposed and raises and lowers the working unit, wherein an accumulator is connected to a load holding side oil chamber of the lift cylinder; B. a variable throttle device interposed between the load holding side oil chamber of the lifting cylinder and the accumulator; B. detecting means for detecting the oil pressure in the load holding side oil chamber of the lifting cylinder; When the oil pressure detected by the detecting means is smaller than the set pressure, the throttle opening of the variable throttle device is increased, and when the oil pressure is equal to or higher than the set pressure, the throttle opening of the variable throttle device is reduced. It has a means. Note that the variable aperture device is a. A plurality of apertures with different apertures,
B. Under control by the control means, there may be a selection means for selecting one of the throttles and interposing between the load holding side oil chamber of the lifting cylinder and the accumulator. Further, the selection means may be a switching valve. Further, a working device is provided in the vehicle body, and the working device has a working unit, an elevating cylinder interposed between the working unit and the vehicle body and elevating the working unit, and a load holding side oil chamber of the elevating cylinder. In the case where the accumulator is connected, B. a variable throttle device interposed between the load holding side oil chamber of the lifting cylinder and the accumulator; B. detecting means for detecting the oil pressure in the load holding side oil chamber of the lifting cylinder; There may be a control unit that reduces the aperture of the variable throttle device as the hydraulic pressure detected by the detection unit is large.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention applied to a wheel loader will be described below with reference to FIGS. 1 and 2. FIG. 1 shows a wheel loader, and the wheel loader is a vehicle. The vehicle 1 includes a main body 1 and a working device 2 provided at a front portion of the vehicle main body 1.

The vehicle body 1 has a vehicle body 6 comprising front and rear frames 4, 5 and the like, a pair of left and right front and rear wheels 7, 8 and a cabin 9 and the like.

The working device 2 includes a pivot shaft 10 on the front frame 4.
A pair of left and right booms 11 pivotally supported by the
A pair of left and right boom cylinders 12 exemplifying a lifting cylinder interposed between the front frame 4 and each boom 11, and a bucket exemplifying a working unit (attachment attachment) rotatably supported by the front end of the boom 11. 13 and a bucket cylinder 14 or the like exemplified as a working unit cylinder interposed between the front frame 4 and the bucket 13.

FIG. 2 shows a hydraulic circuit and the like of the working device 2. In FIG. 2, 16 is an oil tank, 17 is a main hydraulic pump, 18 is a first control valve for a bucket cylinder, and 19 is a second control valve for a boom cylinder. Control valves, both control valves 18 and 19
Are provided in the main valve device 20.

The first control valve 18 is connected to the bucket cylinder 14
Head-side oil chamber 21 and load-side oil passage 22
And is connected via a load holding side oil passage 24 to a bottom side oil chamber 23 which is a load holding side oil chamber of the bucket cylinder 14. The first control valve 18 is a 6 port 3 position switching manual valve,
, A switching position between a neutral position (medium three-dimensional position) in which the bucket cylinder 14 is extended, a descending position (downward position) in which the bucket cylinder 14 is contracted.

The second control valve 19 is connected to a head-side oil chamber 26, which is a load-side oil chamber of the boom cylinder 12, via a load-side oil passage 27, and is a load-holding oil chamber of the boom cylinder 12. Bottom side oil chamber 28 and load holding side oil passage 29
Connected through. The second control valve 19 is a 6-port 4-position switching manual valve, and includes a neutral position for stopping the boom cylinder 12 (medium cubic position), an ascending position for extending the boom cylinder 12 (ascending posture), and a boom cylinder 1.
2 can be switched between a lowering position (downward position) for reducing the size and a float position (float position) allowing free extension and contraction of the boom cylinder 12. A load-side branch oil passage 30 and a load-hold side branch oil passage 31 are branched from a middle portion of the load-side oil passage 27 and the load-holding oil passage 29, respectively.

Reference numeral 33 denotes a switching valve, which is a 4-port 2-position switching type spring offset solenoid valve, which connects the load-side branch oil passage 30 to the oil tank 16 in an intermittent manner.
The load holding side branch oil passage 31 is intermittently connected to a vibration suppressing accumulator 62 via a variable throttle device 61. Note that the switching valve 33 is set to a disconnected position (disconnected position) by the bias of a spring when not energized, and when switched on,
The connection position (connection position) is set.

The variable aperture device 61 is an aperture device capable of adjusting the aperture of the diaphragm in a plurality of stages. In this embodiment, the aperture is adjustable in two stages. Specifically, the variable throttle device 61 includes a first throttle 64 having a larger throttle opening, a second throttle 65 having a smaller throttle opening than the first throttle 64, and a switching valve 66. Each of the apertures 64 and 65 is connected to the accumulator 62. The switching valve 66 is exemplified as a selecting means, selects one of the throttles 64 and 65, is connected to the switching valve 33, and is interposed between the bottom oil chamber 28 of the boom cylinder 12 and the accumulator 62. . Specifically, the switching valve 6
Reference numeral 6 denotes a 3-port 2-position switching type spring offset solenoid valve, which includes a switching valve 33 and first and second throttles 64,
65. The switching valve 66 is set to a first position (first posture) for selecting the first throttle 64 by the bias of the spring when the power is not supplied, and a second position (second position) for selecting the second throttle 65 when the power is supplied. 2 positions).

The accumulator 62 is, for example, a piston type filled with nitrogen gas. A space between the accumulator 62 and the first and second throttles 64 and 65 of the variable throttle device 61 is provided via a relief valve 37 for preventing overload. , And an oil tank 16. The accumulator 62 may be a bladder type, a metal bellows type, a direct pressure type, a spring type, a weight type, or the like. The set pressure of the relief valve 37 for overload prevention is set to the maximum allowable pressure of the accumulator 62 to prevent the accumulator 62 from being damaged or damaged by high-pressure oil.

Reference numeral 49 denotes a pressure sensor exemplified as a detecting means, which detects the oil pressure in the bottom oil chamber 28 of the boom cylinder 12.

Reference numeral 53 denotes a controller, which is an example of a control means. The controller 53 controls the switching valves 33 and 66. A pilot lamp 56 is connected. The controller 53 controls the solenoid of the switching valve 33 only when the oil pressure in the bottom oil chamber 28 of the boom cylinder 12 detected by the pressure sensor 49 is equal to or higher than the minimum allowable pressure of the accumulator 62 and equal to or lower than the maximum allowable pressure of the accumulator 62. To switch the switching valve 33 to the connection position. The controller 53 also energizes the solenoid of the switching valve 66 only when the hydraulic pressure is equal to or higher than the set pressure, and sets the switching valve 66 to the second position. The set pressure is, for example,
It is set as follows. That is, the working device 2 to be mounted
Assuming an appropriate set mass between the minimum mass of the work device 2 and the maximum mass of the work device 2 including the load, when the mass of the work device 2 is the above set mass and the second control valve 19 is in the neutral position, , The oil pressure of the bottom oil chamber 28 of the boom cylinder 12 is set as the set pressure. The set mass is, for example,
It is set as １ ／ of the sum of the minimum mass of the working device 2 to be mounted and the maximum mass of the working device 2 including the load.

According to the above configuration example, the boom 11 and the bucket 13 can be operated regardless of the switching position of the switching valve 33. In particular, the operation of the boom 11 will be described. When the boom 11 is lifted, the second control valve 19 is operated to supply hydraulic oil into the bottom oil chamber 28 of the boom cylinder 12 to extend the boom cylinder 12. Then, the boom 11 is raised. In this case, the boom cylinder 1
2 is provided with the second control valve 19 or the switching valve 3.
The hydraulic oil in the head-side oil chamber 26 flows to the oil tank 16 because it is in communication with the oil tank 16 via the third or the like.

When lowering the boom 11, the second
With the control valve 19 in the lowered position, hydraulic oil is supplied to the head-side oil chamber 26 of the boom cylinder 12 and the bottom-side oil chamber 28 is communicated with the oil tank 16. At this time, the switching valve 3
When 3 is in the open position, the head side oil chamber 26 of the boom cylinder 12 also communicates with the oil tank 16 via the switching valve 33 and the like, but there is no problem because the boom 11 is lowered by its own weight.

Further, as in a dozing operation by a wheel loader or the like, the oil chamber 28 on the bottom side of the boom cylinder 12 is provided.
When the work is performed by increasing the oil pressure in the inside, the work can be performed without any problem by setting the changeover switch 55 to the off state and setting the changeover valve 33 to the closed position.

To prevent vibration such as pitching and bouncing of the vehicle body 1 during running of the wheel loader, the changeover switch 55 is turned on to turn on the pilot lamp 56 and the second control valve 19 Is the neutral position. In this case, the bottom oil chamber 2 of the boom cylinder 12
8 is detected by the pressure sensor 49,
Since the hydraulic pressure is usually equal to or higher than the minimum allowable pressure of the accumulator 62 and equal to or lower than the maximum allowable pressure of the accumulator 62, the solenoid of the switching valve 33 is energized by the controller 53, and the switching valve 33 is set to the open position. .

The mass of the work unit 2 is smaller than the set mass because the mass of the load in the bucket 13 is small, and the hydraulic pressure in the bottom oil chamber 28 of the boom cylinder 12 is set at the set pressure. If smaller, the solenoid of the switching valve 66 is not energized, and is urged by a spring.
The switching valve 66 is in the first position. Also, because the mass of the load in the bucket is large or the like, the mass of the working device 2 is equal to or larger than the set mass, and the bottom oil chamber 2 of the boom cylinder 12 is
If the oil pressure in the tank 8 is higher than the set pressure, the controller 53
As a result, the solenoid of the switching valve 66 is energized, and the switching valve 66 becomes the second position.

Therefore, in the former case, the bottom oil chamber 28 of the boom cylinder 12 is connected to the load holding oil passage 29,
It communicates with the accumulator 62 via the load holding side branch oil passage 31, the switching valves 33 and 66, and the first throttle 64. In the latter case, the bottom side oil chamber 28 of the boom cylinder 12 is provided with the load holding side oil passage 29 and the load holding side branch oil passage 3.
1. It communicates with the accumulator 62 via the switching valves 33, 66 and the second throttle 65. The head-side oil chamber 26 of the boom cylinder 12 includes a load-side oil passage 27 and a load-side branch oil passage 3.
0, communicates with the oil tank 16 via the switching valve 33.

When the wheel loader is driven in this state, the vehicle body 1 of the wheel loader tends to pitch or bounc in accordance with the ups and downs of the road surface, or during acceleration or deceleration. As a result, the working device 2 vibrates, and the boom 11 attempts to swing vertically, and the bottom-side oil chamber 2 of the boom cylinder 12 that supports the boom 11
Fluctuations occur in the oil pressure in 8.

In this case, since the bottom oil chamber 28 of the boom cylinder 12 is in communication with the accumulator 62, the operating oil in the bottom oil chamber 28
2, the hydraulic oil flows into the bottom oil chamber 28 by the charged gas pressure from the accumulator 62, and the accumulator 62 performs a spring action. Further, since the head-side oil chamber 26 communicates with the oil tank 16, hydraulic oil flows between the head-side oil chamber 26 and the oil tank 16, and allows the boom cylinder 12 to freely expand and contract.

Further, the bottom oil chamber 28 is connected to the accumulator 62 via the first throttle 64 or the second throttle 65.
Because of the communication, the inflow and outflow of the hydraulic oil to and from the accumulator 62 causes a pressure loss due to the first throttle 64 or the second throttle 65, and an oil passage resistance when the hydraulic oil passes through another oil passage. Pressure loss also occurs. Due to these pressure losses, vibration of the boom 11 is attenuated. That is, the boom 11, that is, the working device 2
Are the spring action of the accumulator 62, the first throttle 64,
Alternatively, since the front portion of the vehicle body 1 vibrates up and down against the damping effect of the oil path resistance of the second throttle 65 and the like and moves in a direction opposite to the direction in which the front portion of the vehicle body 1 is going to move (vibrates), the vehicle body 1
Vibrations such as pitching and bouncing are suppressed, and the vibration of the working device 2 is also reduced by the first throttle 64 or the second
It is attenuated early due to the damping effect of the oil passage resistance of the throttle 65 and the like.

Since the load 13 such as earth and sand and gravel is loaded on the bucket 13 of the working device 2, the mass of the entire working device 2 including the load is not constant. Also, when another work unit (for example, a snow removal blade or the like) is mounted on the boom 11 instead of the bucket 13, the mass of the work device 2 changes. Due to the mass change of the working device 2 as described above, the vibration characteristics change. In the present invention, the above-described change in the vibration characteristic due to the change in the mass of the working device 2 is dealt with by switching and using the first and second throttles 64 and 65 as described above.

That is, according to the present invention, when the mass of the working device 2 is smaller than the set mass and the oil pressure in the bottom oil chamber 28 of the boom cylinder 12 is smaller than the set pressure, the throttle opening becomes large. When the mass of the working device 2 is equal to or more than the set mass and the oil pressure in the bottom oil chamber 28 of the boom cylinder 12 is equal to or more than the set pressure, the opening degree of the throttle is smaller than that of the first throttle 64. Is used. Thus, in the present invention, even when the mass of the working device 2 changes and the vibration characteristics change, vibrations such as pitching and bouncing of the vehicle body 1 can be effectively suppressed.

Next, from the above state, in order to perform work by the wheel loader, the second control valve 19 is operated to supply hydraulic oil to the bottom side oil chamber 28 of the boom cylinder 12 and to operate the boom cylinder 12. When the boom 11 is raised by being extended, the oil pressure in the bottom oil chamber 28 of the boom cylinder 12 becomes higher than the maximum allowable pressure of the accumulator 62.
Is stopped, and the switching valve 33 is brought to the closed position. As a result, the bottom oil chamber 28 of the boom cylinder 12 is shut off from the accumulator 62, the high-pressure oil is not supplied to the accumulator 62, and the accumulator 62 is not likely to be damaged or damaged. The accumulator 62 is also protected by the overload prevention relief valve 37.

FIG. 3 shows a second embodiment of the present invention, in which the variable aperture device 61 can be adjusted in three stages. Specifically, the variable aperture device 61 includes a first aperture 64 having a large aperture, a second aperture 65 having a smaller aperture than the first aperture 64, and a second aperture 65 having a smaller aperture than the first aperture 64. Each of the throttles 64, 65, 68 is connected to the accumulator 62. The switching valve 66 selects one of the throttles 64, 65, and 68 and connects to the switching valve 33. Specifically, the switching valve 66 is a four-port three-position switching type spring center type solenoid valve. Have been. Note that when the power is not supplied to the switching valve 66, the second throttle 65
Is selected in the second position (second position), and when the left solenoid of the switching valve 66 is energized, the first position (first position) of selecting the first throttle 64 is set. Is set to the third position (third position) for selecting the third aperture 68.

When the oil pressure in the bottom oil chamber 28 of the boom cylinder 12 detected by the pressure sensor 49 is smaller than the first set pressure, the controller 53 switches the switching valve 66.
When the hydraulic pressure is higher than the second set pressure, the controller 53 supplies power to the right solenoid of the switching valve 66. The first and second set pressures are set, for example, as follows. That is, assuming appropriate first and second set masses between the minimum mass of the working device 2 to be mounted and the maximum mass of the working device 2 including a load, the mass of the working device 2 is first or The hydraulic pressure of the bottom oil chamber 28 of the boom cylinder 12 at the second set mass and when the second control valve 19 is at the neutral position is set as the first or second set pressure. The first and second set masses are set, for example, as 1/3 and 2/3 of the sum of the minimum mass of the working device 2 to be mounted and the maximum mass of the working device 2 including a load. .

FIG. 4 shows a third embodiment of the present invention, in which a variable aperture device 61 is provided with a variable aperture 70 capable of continuously and continuously adjusting the aperture, and a stepping device for driving the variable aperture 70. It comprises a driving device 71 such as a motor. Then, the controller 53 controls the bottom oil chamber 28 of the boom cylinder 12 detected by the pressure sensor 49.
The throttle opening of the variable throttle 70 is continuously adjusted by the driving device 71 so that the larger the oil pressure of the throttle is, the smaller the opening of the variable throttle 70 is.

In the above embodiment, the present invention is applied to a wheel loader. However, the present invention can be applied to a work vehicle other than the wheel loader.

[0036]

As described in detail above, according to the present invention,
Even if the mass of the working device changes and the vibration characteristics change, vibration such as pitching and bouncing of the vehicle body can be effectively suppressed. In addition, since a plurality of expensive accumulators are not used and an inexpensive diaphragm is used, the cost of the dynamic damper can be reduced.

[Brief description of the drawings]

FIG. 1 is a side view of a wheel loader showing a first example of an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a first example of an embodiment of the present invention.

FIG. 3 is a circuit diagram of a main part showing a second example of the embodiment of the present invention.

FIG. 4 is a circuit diagram of a main part showing a third example of the embodiment of the present invention.

[Description of Signs] 1 Vehicle main body 2 Working device 11 Boom 12 Boom cylinder (elevating cylinder) 13 Bucket (working part) 26 Head side oil chamber (Load side oil chamber) 28 Bottom side oil chamber (Load holding side oil chamber) 49 Pressure sensor (detection means) 53 Controller (control means) 61 Variable throttle device 62 Accumulator 64, 65, 68 First, second, and third throttle 66 Switching valve (selection means) 70 Variable throttle 71 drive device

Claims (4)

[Claims] An operating device is provided in a vehicle body, the operating device includes a working unit, an elevating cylinder interposed between the operating unit and the vehicle body and elevating the operating unit, and a load holding side of the elevating cylinder. In the case where the accumulator is connected to the oil chamber, B. a variable throttle device interposed between the load holding side oil chamber of the lifting cylinder and the accumulator; B. detecting means for detecting the oil pressure in the load holding side oil chamber of the lifting cylinder; When the oil pressure detected by the detecting means is smaller than the set pressure, the throttle opening of the variable throttle device is increased, and when the oil pressure is equal to or higher than the set pressure, the throttle opening of the variable throttle device is reduced. A dynamic damper for a working vehicle having means. 2. A variable aperture device, comprising: B. A plurality of apertures with different apertures; 2. A dynamic damper for a work vehicle according to claim 1, further comprising a selection means for selecting one of the throttles and interposing between the load holding side oil chamber of the lifting cylinder and the accumulator by control by a control means. 3. The dynamic damper for a work vehicle according to claim 2, wherein the selection means is a switching valve. 4. A working device is provided in a vehicle body, the working device includes a working unit, an elevating cylinder interposed between the working unit and the vehicle body and elevating the working unit, and a load holding side of the elevating cylinder. In the case where the accumulator is connected to the oil chamber, B. a variable throttle device interposed between the load holding side oil chamber of the lifting cylinder and the accumulator; B. detecting means for detecting the oil pressure in the load holding side oil chamber of the lifting cylinder; A dynamic damper for a working vehicle, comprising a control means for reducing the aperture of the variable throttle device as the hydraulic pressure detected by the detection means is large.