JP2523909Y2 - Vehicle dynamic damper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a dynamic damper of a vehicle such as a wheel loader.

(Prior Art) As a dynamic damper of a wheel loader, for example, there is a dynamic damper as disclosed in JP-A-63-265023.

In this device, an accumulator is connected to the load holding side oil chamber of the boom cylinder in the working device, and an oil tank is connected to the load side oil chamber of the boom cylinder.

When the wheel loader travels, a dynamic damper is formed by a working device serving as a mass member, an accumulator acting as a spring, and the like, thereby suppressing pitching and bouncing of the vehicle body during traveling. .

By the way, in the above, when the wheel loader is working, the operating oil is supplied to the load holding side oil chamber of the boom cylinder, the boom cylinder is extended, and the boom and the bucket are raised. Since the hydraulic oil pressure in the room is higher than the maximum allowable pressure of the accumulator, it is necessary to shut off the oil passage between the load holding side oil chamber and the accumulator to protect the accumulator from high-pressure hydraulic oil.

For this reason, in the above, an on-off valve is interposed between the load-holding-side oil chamber of the boom cylinder and the accumulator, so that the on-off valve is in a closed position when the wheel loader is working.

(Problems to be Solved by the Invention) In the above-described conventional technology, when the wheel loader shifts from the running posture to the working posture or vice versa, the driver must operate the on-off valve. There was a problem that it was troublesome.

Further, in the above-described conventional art, when the operation of the open / close valve is forgotten when the wheel loader shifts from the running posture to the working posture,
Since high-pressure hydraulic oil acts on the accumulator and the accumulator may be damaged, there is also a problem that it is necessary to provide a safety device for forgetting to operate the on-off valve.

An object of the present invention is to provide a dynamic damper for a vehicle that can solve the above problem.

(Means for Solving the Problems) In order to solve the above problems, a means adopted by the present invention is a vehicle in which a working unit is provided on a vehicle main body so as to be able to move up and down via a lifting cylinder. An oil tank is connected to the side oil chamber, and an accumulator is connected to the load holding side oil chamber of the lifting cylinder via an on-off valve. A pressure detector that constantly communicates with the load holding side oil chamber and detects that the hydraulic oil pressure in the oil chamber has become equal to or lower than the lower limit set pressure and equal to or higher than the upper limit set pressure, and closes the on-off valve; . A switch is provided to keep the open / close valve always open, wherein the lower limit set pressure is equal to or higher than the minimum allowable pressure of the accumulator, and the upper limit set pressure is equal to or lower than the maximum allowable pressure of the accumulator.

In a vehicle in which a working unit is provided on a vehicle body so as to be able to move up and down via an elevating cylinder, an oil tank is connected to a load-side oil chamber of the elevating cylinder via an on-off valve, and a load holding-side oil chamber of the elevating cylinder is provided. , An accumulator is connected via an on-off valve. A pressure detector that constantly communicates with the load holding side oil chamber, detects that the hydraulic oil pressure in the oil chamber has become equal to or lower than the lower limit set pressure and equal to or higher than the upper limit set pressure, and sets both open / close valves to a closed position; B. A height detector that detects that the height of the working unit has become equal to or less than the set height and sets both open / close valves to a closed position;
C. A switch may be provided to make both open / close valves always open.

In addition, a relief valve for preventing an overload of the accumulator may be connected to an oil passage between the load holding side oil chamber of the lifting cylinder and the accumulator.

(Operation) When the vehicle is running, the hydraulic oil pressure in the load holding side oil chamber of the lifting cylinder is equal to or higher than the lower limit set pressure of the pressure detector and equal to or lower than the upper limit set pressure.

Thus, the load-side oil chamber of the lifting cylinder is connected to the oil tank via the on-off valve, and the load-holding oil chamber of the lifting cylinder is connected to the accumulator via the on-off valve.

When the vehicle travels, 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 portion vibrates up and down due to the spring action of the accumulator, thereby suppressing pitching and bouncing of the vehicle body.

Next, when performing work from the above state, the hydraulic oil pressure in the load holding side oil chamber of the lifting cylinder becomes higher than the maximum allowable pressure of the accumulator.

Therefore, if the upper limit setting pressure of the pressure detector is set to be equal to or less than the maximum allowable pressure of the accumulator,
The on-off valve is in the closed position.

Thus, communication between the load side oil chamber of the lift cylinder and the oil tank is cut off, and communication between the load holding side oil chamber of the lift cylinder and the accumulator is also cut off.

Therefore, as in the conventional case, the working unit can be raised by extending the elevating cylinder, the high-pressure hydraulic oil does not act on the accumulator, and the accumulator is not likely to be damaged or damaged.

(Embodiment) An embodiment in which the present invention is applied to a wheel loader will be described below with reference to the drawings. FIG. 2 shows a wheel loader, and the wheel loader is provided in a vehicle body 1 and a front part of the vehicle body 1. And the working device 2 provided.

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

The working device 2 includes a pair of left and right booms 11 pivotally supported on the front frame 4 by a pivot shaft 10 and a pair of left and right booms illustrated as a lifting cylinder interposed between the front frame 4 and each boom 11. Boom cylinder 12 and a bucket exemplified as a working unit rotatably supported at the front end of the boom 11
13 and a bucket cylinder 14 interposed between the front frame 4 and the bucket 13.

FIG. 1 shows a hydraulic circuit of the boom cylinder 12, in which hydraulic oil is supplied to the boom cylinder 12 from a hydraulic pump 16 via a control valve 17.

The control valve 17 is a 6-port 4-position switching type,
A rod-side oil chamber 19, which is a load-side oil chamber of the boom cylinder 12, is connected via a load-side oil passage 20, and a head-side oil chamber 21, which is a load-holding oil chamber of the boom cylinder 12, and a load-holding oil. It is connected via a road 22.

The control valve 17 includes a middle position for stopping the boom cylinder 12, a rising position for extending the boom cylinder 12, a descending position for contracting the boom cylinder 12, and a
It is possible to freely switch to a float posture that allows free expansion and contraction of the float.

From the middle of the load side oil passage 20 and the load holding side oil passage 22,
Each of the load side branch oil passage 24 and the load holding side branch oil passage 25 is branched.

Reference numeral 27 denotes an on-off valve which is a 4-port 2-position switching type spring offset solenoid valve. The load-side branch oil passage 24 is connected to an oil tank, and the load-holding branch oil passage 25 is connected to a bladder-type accumulator 28. Connect to

Reference numeral 30 denotes a relief valve for preventing overload of the accumulator 28,
It is connected to an oil passage between the accumulator 28 and the on-off valve 27, and its set pressure is set to the maximum allowable pressure of the accumulator 28.

A pressure detector 32, a height detector 33, and a battery 34 are connected in series to the solenoid of the on-off valve 27.

The pressure detector 32 is connected to the head-side oil chamber 21 of the boom cylinder 12.
The on-off valve 27 is set to a closed position by detecting that the hydraulic oil pressure in the inside becomes equal to or lower than the lower limit set pressure or equal to or higher than the upper limit set pressure.

As the pressure detector 32, for example, a normally closed type pressure switch is used, and is connected to an intermediate portion of the load holding side oil passage 22. The lower limit pressure of the pressure detector 32 is the accumulator
The minimum allowable pressure of the accumulator 28 is set to be equal to or lower than the minimum allowable pressure of the accumulator 28, and the upper limit set pressure of the pressure detector 32 is set to be equal to or lower than the maximum allowable pressure of the accumulator 28. , And is turned off.

The height detector 33, when the on-off valve 27 is in the open position, when the height of the bucket 13 has become less than the set height,
The on-off valve 27 is in a closed position.

As the height detector 33, for example, a normally-closed proximity switch is used, and is provided at an appropriate position of the boom 11 or the bucket 13, for example, at a connection portion between the two, so that the height of the working portion is equal to or less than the set height. When it becomes, it is turned off.

 36 is a relief valve.

According to the embodiment configured as described above, when the wheel loader travels, first, the bucket 13 is set to an appropriate height equal to or higher than the set height of the height detector 33. 33 is turned on.

In addition, the control valve 17 is set to a medium three-dimensional force, whereby the hydraulic oil pressure in the head side oil chamber 21 of the boom cylinder 12 is equal to or higher than the lower limit set pressure of the pressure detector 32 and equal to or lower than the upper limit set pressure, The pressure detector 32 is turned on.

As a result, the control circuit of the on-off valve 27 becomes a closed circuit, the solenoid of the on-off valve 27 is operated, and the on-off valve 27 is in an open position.

As a result, the rod-side oil chamber 19 of the boom cylinder 12 is
Are connected to an oil tank via a load-side oil passage 20, a load-side branch oil passage 24, and an on-off valve 27. The head-side oil chamber 21 of the boom cylinder 12 is provided with a load holding side oil passage 22 and a load holding side branch oil passage.
25, connected to an accumulator 28 via an on-off valve 27.

When the wheel loader is run in this state, the vehicle body 1 of the wheel loader pitches or bounces in accordance with the ups and downs of the road surface, or when accelerating or decelerating. As a result, the hydraulic oil in the head side oil chamber 21 of the boom cylinder 12 supporting the boom 11 fluctuates in pressure.

Since the head-side oil chamber 21 is in communication with the accumulator 28, the hydraulic oil in the head-side oil chamber 21 flows into the accumulator 28 against the pressure of the charged gas, and from the accumulator 28, The hydraulic oil flows into the head-side oil chamber 21 due to the pressure, and the accumulator 28 performs a spring action.

Also, since the rod side oil chamber 19 communicates with the oil tank,
Hydraulic oil flows between the rod-side oil chamber 19 and the oil tank, allowing the boom cylinder 12 to expand and contract.

Further, the vibration of the boom 11 is attenuated by the pressure loss of the hydraulic circuit.

That is, the boom 11 has a spring action of the accumulator 28,
Since the boom 11 vibrates up and down against the damping effect of the oil passage resistance of the hydraulic circuit, and the boom 11 moves in the direction opposite to the direction in which the front part of the vehicle body 1 tends to move, pitching and bouncing of the vehicle body 1 etc. Is suppressed, and the vibration of the boom 11 is also attenuated at an early stage by the damping effect of the oil passage resistance of the hydraulic circuit.

That is, in this wheel loader, the vehicle main body 1 is considered to be the main vibration system, and the working device 2 having a smaller weight than the vehicle main body 1 is considered to be the auxiliary vibration system, that is, the dynamic damper.

By the way, the natural frequency of the main vibration system depends on the vehicle body 1
And the spring constants of the front and rear wheels 7, 8 and the like.

The natural frequency of the dynamic damper is determined by the moment of inertia of the boom 11, the bucket 13, the bucket silling 14, etc. of the working device 2, the spring constant of the accumulator 28, and the like.

If the mass ratio and the natural frequency ratio of both the main vibration system and the dynamic damper and the damping coefficient due to the pressure loss of the hydraulic circuit are set so that the peak of the resonance curve of the main vibration system becomes as low as possible, the vehicle Regardless of the value of the frequency of the external force acting on the main body 1, pitching and bouncing of the vehicle main body 1 can be favorably suppressed.

By the way, at the time of the above-mentioned traveling, the vehicle main body 1 greatly pitches or bounces, and the boom 11 and the bucket
When 13 is greatly lowered and its height becomes lower than the set height of the height detector 33, the height detector 33 detects this and sets the on-off valve 27 to the closed posture.

Thereby, the vibration of the boom 11 is prevented, and therefore, the possibility that the bucket 13 collides with the ground and the working device 2 is damaged or damaged can be prevented.

Then, as described above, at the next moment when the bucket 13 is lowered and the on-off valve 27 is in the closed position, the boom 11 and the bucket 13 are raised by the recoil, and the height of the bucket 13 is increased to the height. It is higher than the set height of the detector 33.

As a result, the height detector 33 is turned on, the on-off valve 27 is again opened, and the working device 2 functions as a mass member of the dynamic damper.

Next, a description will be given of a case where the boom 11 and the bucket 13 are lifted when the work is performed by the wheel loader from the above state.

At this time, the control valve 17 is operated to operate the boom cylinder 12
Supply hydraulic oil into the head side oil chamber 21 of the boom cylinder.
The boom 11 and the bucket 13 are raised by extending 12.

In this case, the operating oil pressure in the head-side oil chamber 21 of the boom cylinder 12 becomes higher than the maximum allowable pressure of the accumulator 28.

However, since the upper limit set pressure of the pressure detector 32 is equal to or less than the maximum allowable pressure of the accumulator 28, in the above case, the energization of the solenoid of the on-off valve 27 is stopped,
The on-off valve 27 is in a closed position.

Thereby, communication of the load side branch oil passage 24 to the oil tank is cut off. In addition, the communication between the load holding side branch oil passage 25 and the accumulator 28 is also cut off, and the boom cylinder
By extending the boom 11, the boom 11 can be raised, the high-pressure hydraulic oil does not act on the accumulator 28, and the accumulator 28 is not likely to be damaged or damaged.

In the above case, high-pressure hydraulic oil may flow from the on-off valve 27 to the accumulator 28 due to a response delay of the on-off valve 27.

However, since an overload prevention relief valve 30 is connected to the oil passage between the on-off valve 27 and the accumulator 28,
In the above case, the relief valve 30 for overload prevention operates,
This prevents high-pressure hydraulic oil from acting on the accumulator 28, so that the accumulator 28 is not likely to be damaged or damaged.

Also, from the above state, when again shifting to the running posture, the opening and closing valve 27 is changed from the closed posture to the open posture,
At the time of the change, the hydraulic oil pressure in the head-side oil chamber 21 of the boom cylinder 12 is changed after it becomes substantially the same as the hydraulic oil pressure in the accumulator 28. There is no possibility that the bucket 11 and the bucket 13 will move up and down unexpectedly significantly.

When the control valve 17 is lowered, the hydraulic oil pressure in the head-side oil chamber 21 of the boom cylinder 12 is equal to or lower than the upper limit set pressure of the pressure detector 32, and the pressure detector 32 is in the ON state.
Until the height of the bucket 13 becomes equal to or less than the set height of the height detector 33, the height detector 33 is also in the ON state, so the on-off valve 27 is in the open position, and the rod-side oil of the boom cylinder 12 is Although the chamber 19 communicates with the oil tank, the boom 11 and the bucket 13 descend by their own weight, so there is no problem.

When the height of the bucket 13 falls below the set height of the height detector 33, the height detector 33 is turned off and the on-off valve
27 is closed.

As a result, the communication between the rod-side oil chamber 19 of the boom cylinder 12 and the oil tank is cut off, the hydraulic oil pressure in the rod-side oil chamber 19 increases, and the bucket 13 not only has its own weight of the working device 2 but also has Similarly, the pressure can be lowered by the hydraulic oil pressure supplied into the rod-side oil chamber 19.

When the control valve 17 is in the floating position, the bucket 13 is in contact with the ground, so that the height detector 33 is in the off state, and the on-off valve 27 is in the closed position.

If the pressure loss of the hydraulic circuit is too small, the first
As indicated by the imaginary line in the figure, immediately before the accumulator 28,
An aperture 40 may be provided.

Further, a battery may be connected to the solenoid of the on-off valve separately via an on-off switch, and by turning on the on-off switch, regardless of the state of the pressure detector and the height detector, Alternatively, the on-off valve may be set to be always open.

Further, in the embodiment, the on-off valve is single, but two on-off valves are used, and the rod-side oil chamber and the head-side oil chamber of the boom cylinder are respectively connected to the accumulator or the oil tank via separate on-off valves. May be connected.

Further, the present invention is applicable to vehicles such as forklift trucks.

(Effects of the Invention) As described in detail above, according to the present invention, it is necessary for the driver to perform the troublesome operation of operating the on-off valve when shifting from the running posture to the working posture or vice versa. Damage to the accumulator due to forgetting to operate the open / close valve,
There is no risk of damage, and there is no need to provide a safety device for forgetting to operate the on-off valve.

Also, when changing the on-off valve from the closed position to the open position,
Since the operating oil pressure in the load holding side oil chamber of the lifting cylinder is substantially the same as the operating oil pressure in the accumulator, there is no danger of the working device being inadvertently raised and lowered when the opening / closing valve is changed.

Further, for example, when the vehicle travels over a large step during traveling, the operating oil pressure in the load holding side oil chamber may exceed the maximum allowable pressure of the accumulator. The pressure detector detects the hydraulic oil pressure in the load holding side oil chamber not only at the time of operation but also at the time of traveling. Closed position. Therefore, there is no possibility that the accumulator is damaged or damaged.

In addition, the lower limit set pressure of the pressure detector was set to be equal to or higher than the minimum allowable pressure of the accumulator, and the upper limit set pressure of the pressure detector was set to be equal to or lower than the maximum allowable pressure of the accumulator. If the accumulator pressure is higher than the maximum allowable pressure, and of course the hydraulic oil pressure is lower than the accumulator minimum allowable pressure, the open / close valve is in the closed position, and in any case, the accumulator is damaged. There is no risk of being damaged.

Furthermore, since the switch for opening and closing the open / close valve is always provided, regardless of the operating oil pressure in the load holding side oil chamber,
The accumulator can be activated.

Furthermore, if a height detector or the like is provided as in claim 2,
When the accumulator is activated, when the height of the working unit becomes lower than the set height of the height detector, the height detector detects this and sets the open / close valve to the closed position, so the accumulator Operation stops, the work equipment stops vibrating, which causes the working part to collide with the ground and damage the work equipment,
The possibility of damage can be prevented.

Also, when the working unit is lowered during the lowering operation of the working unit, if the height of the working unit is lower than the set height of the height detector, the on-off valve is in a closed position. The pressure can also be lowered by the hydraulic oil pressure supplied to the load side oil chamber of the lifting cylinder.

Further, when the open / close valve is changed from the open position to the closed position, high-pressure hydraulic oil may flow from the open / close valve to the accumulator side due to a response delay of the open / close valve.
If the relief valve for preventing the overload of the accumulator is connected to the oil passage between the load holding side oil chamber of the lifting cylinder and the accumulator, the relief valve for preventing the overload operates in the above case. Thus, the high-pressure hydraulic oil is prevented from acting on the accumulator, and therefore, there is no possibility that the accumulator is damaged or damaged.

[Brief description of the drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a hydraulic circuit diagram of a boom cylinder, and FIG. 2 is a side view of a wheel loader. 1 ... vehicle body, 2 ... working device, 11 ... boom, 12 ...
... boom cylinder (elevating cylinder), 13 ... bucket (working part), 17 ... control valve, 19 ... rod side oil chamber (load side oil chamber), 21 ... head side oil chamber (load holding side oil chamber) ), 27
... On-off valve, 28 ... Accumulator, 30 ... Relief valve for overload prevention, 32 ... Pressure detector, 33 ... Height detector.

Claims (3)

(57) [Scope of request for utility model registration] An oil tank is connected to a load side oil chamber of a lifting cylinder, and an accumulator is connected to a load holding side oil chamber of the lifting cylinder. Are connected via an on-off valve; A pressure detector that constantly communicates with the load holding side oil chamber and detects that the hydraulic oil pressure in the oil chamber has become equal to or lower than the lower limit set pressure and equal to or higher than the upper limit set pressure, and closes the on-off valve; . A switch for constantly opening the on-off valve, wherein the lower limit set pressure is equal to or higher than the minimum allowable pressure of the accumulator, and the upper limit set pressure is equal to or lower than the maximum allowable pressure of the accumulator. Dynamic damper. 2. A vehicle in which a working unit is provided on a vehicle body so as to be able to move up and down via an elevating cylinder, wherein an oil tank is connected to a load-side oil chamber of the elevating cylinder via an on-off valve, and the load of the elevating cylinder is held. An accumulator is connected to the side oil chamber via an on-off valve. A pressure detector that constantly communicates with the load holding side oil chamber, detects that the hydraulic oil pressure in the oil chamber has become equal to or lower than the lower limit set pressure and equal to or higher than the upper limit set pressure, and sets both open / close valves to a closed position; B. A height detector that detects that the height of the working unit has become equal to or less than the set height and sets both open / close valves to a closed position; A dynamic damper for a vehicle, comprising a switch for opening both open / close valves at all times. 3. A dynamic damper for a vehicle according to claim 1, wherein a relief valve for preventing an overload of the accumulator is connected to an oil passage between the load holding side oil chamber of the lifting cylinder and the accumulator.