JP2936976B2 - Variable dynamic damper for work vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable 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 main body. The working device includes 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 tip end of the boom. And a bucket cylinder for rotating the bucket.

Meanwhile, recently, in order to suppress vibration such as pitching and bouncing of the vehicle body, a working device serving as a mass member is provided by connecting a vibration suppressing accumulator to a load holding side oil chamber of a boom cylinder. A structure in which a dynamic damper is formed by an accumulator acting as a spring has been proposed. In this case, in order to effectively suppress the vibration of the vehicle body, it is necessary to make the natural frequencies of the vehicle body and the working device substantially the same.

[0004] The natural frequency of the working device is determined by the mass of the entire working device and the spring constant of the accumulator. In the wheel loader, since a load such as earth and sand and gravel is loaded on the bucket, the mass of the entire working device including the load is not constant. However, the spring constant of the accumulator was fixed.

[0005]

For this reason, depending on the presence or absence of a load and the mass of the load, the natural frequencies of the vehicle body and the working device do not become substantially the same, and pitching and bouncing of the vehicle body are effected. In some cases, it could not be suppressed.

An object of the present invention is to provide a variable dynamic damper for a working vehicle which solves the above-mentioned problems.

[0007]

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. It has an elevating cylinder that is interposed and raises and lowers the working part. A vibration suppression accumulator is connected to the load holding side oil chamber of the lifting cylinder, and the vibration suppression accumulator is connected to the load holding side oil chamber of the lifting cylinder. An apparatus having an oil chamber, a gas chamber in which gas is stored, and a piston that separates the oil chamber and the gas chamber. B. detecting means for detecting a change in mass of the working device; A gas cylinder for supplying gas to a gas chamber of the vibration suppression accumulator; A control valve interposed between the gas chamber and the gas cylinder of the vibration suppression accumulator to supply and discharge gas to and from the gas chamber; In order to make the natural frequency of the vehicle body and the working device substantially the same, control means for controlling the control valve in accordance with the detected mass change of the working device and changing the spring constant of the vibration suppressing accumulator is provided. It has a point.

[0008]

When the work vehicle is driven, the vehicle body tends to pitch or bounc in response to the undulation of the road surface, or during acceleration or deceleration. However, the working device vibrates up and down due to the spring action of the accumulator, thereby suppressing vibration such as pitching and bouncing of the vehicle body. Also, the vibration of the working device is attenuated by the pressure loss due to the oil passage resistance of the working oil.

When the mass of the work equipment changes, the change in the mass is detected by the detection means, and the change is detected by the control means in order to make the natural frequencies of the vehicle body and the work equipment substantially the same. The spring constant of the accumulator is changed according to the change in the mass of the working device. Thereby, the vibration of the vehicle body is effectively suppressed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a wheel loader will be described below with reference to the drawings. FIG. 1 shows a wheel loader, and the wheel loader is provided on a vehicle body 1 and a front portion of the vehicle body 1. Working device 2.

The vehicle body 1 has a vehicle body 6 composed of front and rear frames 4, 5, etc., a pair of left and right front and rear wheels 7, 8, 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 exemplarily as lifting cylinders interposed between the front frame 4 and each boom 11, a bucket 13 exemplarily as a working unit rotatably supported by the front end of the boom 11, Frame 4 and bucket 13
It has a bucket cylinder 14 and the like interposed therebetween.

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 the bucket cylinder 14, 19
Is a second control valve for the boom cylinder 12;
8 and 19 are provided in the main valve device 20.

The first control valve 18 is connected to the bucket cylinder 14
Rod-side oil chamber 21 and load-side oil passage 22
And a head side oil chamber 23 which is a load holding side oil chamber of the bucket cylinder 14 and is connected via a load holding side oil passage 24. The first control valve 18 is a 6 port 3 position switching manual valve,
, A rising position for extending the bucket cylinder 14, and a descending position for reducing the bucket cylinder 14.

The second control valve 19 is connected to a rod-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. Head 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 at which the boom cylinder 12 is stopped, an up position at which the boom cylinder 12 is extended, a down position at which the boom cylinder 12 is contracted, and a boom cylinder. Twelve float positions allow free expansion and contraction. 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. The load-side branch oil passage 30 is connected to the oil tank 16, the load holding-side branch oil passage 31 is connected to an accumulator 34, and Connect intermittently.

The accumulator 34 is of a piston type which is a gas compression type. The cylinder 35 has an oil chamber 37 in which hydraulic oil is stored by a piston 36 and an air in which air exemplified as gas is stored. And a chamber 38.

A throttle valve 40 is interposed between the switching valve 33 and the accumulator 34, and between the accumulator 34 and the throttle valve 40 via a relief valve 41 for preventing overload.
It is connected to an oil tank 16. The set pressure of the relief valve 41 for overload prevention is set to the maximum allowable pressure of the accumulator 34 to prevent the accumulator 34 from being damaged or damaged by high-pressure oil.

A control valve 43 is interposed between the air chamber 38 of the accumulator 34 and the air cylinder 44. The control valve 43 is a three-port, three-position switching type solenoid valve. The control valve 43 is in a neutral position for shutting off the space between the air cylinder 44 and the air chamber 38 of the accumulator 34, and the air cylinder 44 and the accumulator 3
4 and a discharge position where the air chamber 38 of the accumulator 34 communicates with the outside.

Reference numerals 46 and 47 denote position sensors.
It detects that each control valve is in the neutral position.

Reference numeral 49 denotes a pressure sensor, which is a boom cylinder 1
2 by detecting the hydraulic oil pressure in the head side oil chamber 28,
It detects a change in mass of the working device 2 and is connected to the load holding side branch oil passage 31.

A traveling information device 51 outputs stop information of the wheel loader.

Reference numeral 53 denotes a controller which controls the switching valve 33 and, in order to make the natural frequencies of the vehicle body 1 and the working device 2 substantially the same (including the same), according to a change in the mass of the working device 2. It changes the spring constant of the accumulator 34, and includes the solenoids of the battery 54, the switching valve 33 and the control valve 43, the position sensors 46 and 47,
9, a travel information device 51, a changeover switch 55 for turning on the solenoid of the changeover valve 33, and a pilot lamp 56 which is turned on at the time of turning on the solenoid.

According to the embodiment configured as described above, the operation of the boom 11 and the bucket 13 is possible regardless of the switching position of the switching valve 33. In particular, the operation of the boom 11 will be described. During the ascent operation, the second
By operating the control valve 19 to supply hydraulic oil into the head-side oil chamber 28 of the boom cylinder 12, the boom cylinder 12 is extended, and the boom 11 is raised. The rod-side oil chamber 26 is
The hydraulic oil in the rod-side oil chamber 26 flows to the oil tank 16 because it is in communication with the oil tank 16 via the control valve 19 or the switching valve 33.

When the boom 11 is lowered normally, the hydraulic oil is supplied to the rod-side oil chamber 26 of the boom cylinder 12 while the second control valve 19 is set to the lowered position, and the head-side oil chamber 28 is moved to the oil position. It communicates with the tank 16. On this occasion,
When the switching valve 33 is in the open position, the rod-side oil chamber 26 of the boom cylinder 12 is also connected to the oil tank 16 via the switching valve 33 and the like.
However, since the boom 11 descends by its own weight, there is no problem.

Further, the head side oil chamber 28 of the boom cylinder 12 is used as in a dozing operation by a wheel loader or the like.
When the operation is performed by increasing the operating oil pressure in the inside, the operation can be performed without any problem by setting the switching valve 33 to the closed position.

To prevent vibration such as pitching and bouncing of the vehicle body 1 of the wheel loader, the changeover switch 55 is turned on to turn on the pilot lamp 56 and to energize the solenoid of the changeover valve 33 to switch. The valve 33 is set to the open position. Thereby, the head side oil chamber 28 of the boom cylinder 12 is connected to the accumulator 34 via the load holding side oil passage 29, the load holding side branch oil passage 31, and the switching valve 33, and the rod side of the boom cylinder 12 The oil chamber 26 includes the load-side oil passage 27 and the load-side branch oil passage 3
0, connected to the oil tank 16 via the switching valve 33.

In this state, when the wheel loader is run, the vehicle body 1 of the wheel loader pitches or bounces according to the ups and downs of the road surface, or when accelerating or decelerating. Vibrates, and the boom 11 attempts to rotate in the vertical direction, thereby causing a pressure fluctuation in the hydraulic oil in the head-side oil chamber 28 of the boom cylinder 12 supporting the boom 11.

In this case, since the head side oil chamber 28 communicates with the accumulator 34, the head side oil chamber 2
Hydraulic oil in the tank 8 flows into the accumulator 34 against the pressure of the charged gas, and the hydraulic oil flows from the accumulator 34 into the head-side oil chamber 28 due to the pressure of the charged gas. Eggplant

Since the rod-side oil chamber 26 is in communication with the oil tank 16, hydraulic oil flows between the rod-side oil chamber 26 and the oil tank 16, allowing the boom cylinder 12 to freely expand and contract.

Further, since the head-side oil chamber 28 communicates with the accumulator 34 via the throttle valve 40, the flow of hydraulic oil into and out of the accumulator 34 causes the throttle valve 40
And a pressure loss due to oil passage resistance when the hydraulic oil passes through other oil passages. Due to these pressure losses, vibration of the boom 11 is attenuated.

That is, the boom 11, that is, the working device 2
The direction in which the working device 2 vibrates up and down against the spring action of the accumulator 34 and the damping action due to the oil path resistance of the hydraulic circuit such as the throttle valve 40 so that the front part of the vehicle body 1 tends to move. Moves in the opposite direction, so that vibrations such as pitching and bouncing of the vehicle body 1 are suppressed, and vibrations of the working device 2 are also attenuated early by the damping action of the hydraulic circuit such as the throttle valve 40 due to the oil passage resistance. .

That is, in the wheel loader, the vehicle body 1 is considered to be the main vibration system, and the working device 2 having a smaller mass than the vehicle body 1 is considered to be the auxiliary vibration system, that is, the dynamic damper. In this case, if the natural frequencies of the vehicle body 1 as the main vibration system and the working device 2 as the dynamic damper are substantially the same, vibration such as pitching and bouncing of the vehicle body 1 can be effectively suppressed.

The natural frequency of the main vibration system is
Although determined by the mass of the vehicle body 1 and the spring constants of the front and rear wheels 7, 8, the mass of the vehicle body 1 is substantially constant, and the natural frequency of the vehicle body 1 is substantially constant.

On the other hand, the natural frequency of the dynamic damper depends on the entire working device 2 (the working device 2 and the bucket 1).
3) the mass m of the load such as earth and sand, gravel, etc.
It is determined as follows by the spring constant k of the accumulator 34.

[0036]

F = (1 / 2π) (k / m) ^1/2

Accordingly, if the spring constant of the accumulator 34 is changed in accordance with the change in the mass of the entire working device 2 due to the presence or absence of the load loaded on the bucket and the change in the mass, the natural frequency of the working device 2 can be reduced. It can be constant, and can be almost the same as the natural frequency of the vehicle body 1.

By the way, in the accumulator 34, the air in the air chamber 38 rises in temperature when rapidly compressed, and falls in temperature when suddenly expanded, so-called polytropic change. Spring constant k
Is determined as follows.

[0039]

K = (nA ² P ₁ / V ₀ ) (P ₁ / P ₀ ) ^{1 / n}

In the above equation, P ₀ is the cylinder 35
Absolute pressure, P ₁ of the air when the air is spread to the inner overall absolute pressure of current air, V ₀ is the volume of the cylinder 35, A pressure receiving area of the piston 36, n is the polytropic exponent.

Therefore, in response to the change in the mass of the entire working device 2, air is supplied to and exhausted from the air chamber 38 of the accumulator 34 to change P ₀ and change the spring constant k of the accumulator 34. In addition, the natural frequency of the working device 2 can be made constant, and can be substantially the same as the natural frequency of the vehicle body 1.

The change of the spring constant k of the accumulator 34 is performed by the control of the controller 53. The control by the controller 53 will be specifically described with reference to the flowchart shown in FIG.

First, in step S1, the position sensor 4
6 and 47, the first and second control valves 1
It is determined whether 8, 19 are in the neutral position. If NO, the process returns to step S1, and if YES, step S1
Move to 2.

In step S2, whether or not the wheel loader is stopped is determined based on information from the traveling information device 51. If NO, the process returns to step S1, and if YES, the process proceeds to step S3.

In step S3, the mass of the entire working device 2 is calculated from the detected pressure P detected by the pressure sensor 49, and the natural frequency of the entire working device 2 and the vehicle body 1 are made substantially the same from this mass. Then, the target pressure P (m) is calculated, and the routine goes to Step S4. still,
The first and second control valves 18 and 19 are in the neutral position,
Because the wheel loader is stopped, the working device 2 is not vibrating, and the head-side oil chamber 28 of the boom cylinder 12 is in communication with the accumulator 34,
The detected pressure P can be substantially regarded as the current air pressure of the accumulator 34, and the target pressure P (m) is
It can be almost regarded as the target air pressure of the accumulator 34.

In step S4, the detected pressure P is compared with the target pressure P (m). If P = P (m), the process returns to step S1. If P> P (m), the process moves to step S5, the control valve 43 is switched to the exhaust position, and the process returns to step S4. If P <P (m), the process proceeds to step S6, in which the control valve 43 is switched to the air supply position, and step S6 is performed.
Return to 4.

In the embodiment, as the accumulator,
The piston type was used, but bladder type, metal bellows type,
A direct pressure type, a spring type, a weight type, or the like may be used.

The present invention is also applicable to work vehicles other than wheel loaders.

[0049]

As described in detail above, according to the present invention,
Depending on the presence or absence of the load to be loaded on the work equipment and its mass, etc.
Even if the mass of the working equipment changes, pitching of the vehicle body,
Bouncing and the like can be automatically and effectively suppressed.

[Brief description of the drawings]

FIG. 1 is a side view of a wheel loader showing one embodiment of the present invention.

FIG. 2 is a circuit diagram showing one embodiment of the present invention.

FIG. 3 is a flowchart showing an 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 Rod side oil chamber (Load side oil chamber) 28 Head side oil chamber (Load holding side oil chamber) 33 Switching valve 34 Accumulator 43 Control valve 44 Air cylinder 49 Pressure sensor (detection means) 53 Controller (control means)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-8629 (JP, A) JP-A-6-286446 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) E02F 9/22 F15B 11/00

Claims (1)

(57) [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. A vibration suppression accumulator is connected to the oil chamber, and the vibration suppression accumulator divides an oil chamber connected to the load holding side oil chamber of the lifting cylinder, a gas chamber storing gas, and an oil chamber and a gas chamber. In those having a piston, B. detecting means for detecting a change in mass of the working device; B. a gas cylinder for supplying gas to the gas chamber of the vibration suppression accumulator; A control valve interposed between the gas chamber and the gas cylinder of the vibration suppression accumulator to supply and discharge gas to and from the gas chamber; Control means for controlling the control valve in accordance with the detected change in the mass of the working device to change the spring constant of the vibration suppressing accumulator in order to make the natural frequency of the vehicle body and the working device substantially the same. A variable dynamic damper for a work vehicle, comprising: