JP2009255731A - Suspension structure of work vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suspension structure of a work vehicle capable of ensuring the excellent ride quality and consistent traveling property by maintaining the damping ratio of a suspension mechanism in an adequate range irrespective of the change of the load to a vehicle body. <P>SOLUTION: A control means has a reference control mode of changing the working characteristic of a suspension mechanism based on the detection value of a pressure sensor while a front loader is mounted at the position close to a front wheel. The control means also has a correction mode of changing the working characteristic of the suspension mechanism to the insensitive side by correcting the reference control mode, based on the result of detection of a state in which a plow is mounted in the position close to a rear wheel. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention supports at least one of the front and rear wheels on a traveling machine body via a hydraulic suspension mechanism,
The present invention relates to a suspension structure for a work vehicle that includes a pressure sensor that detects an internal pressure of the suspension mechanism, and a control unit that changes and controls the operating characteristics of the suspension mechanism based on a detection value of the pressure sensor.

One of the operating characteristics of the suspension mechanism is a damping force that determines whether it is sensitive or insensitive. The damping force is expressed by a viscous force acting in a direction that prevents the displacement.
In the control of the damping force, in a reference control mode described later, a work device such as a loader is attached near the front part of the traveling machine body where the front wheel provided with the suspension mechanism is located, thereby detecting the value detected by the pressure sensor. When the pressure becomes high, the damping force is increased. On the contrary, when the work device is removed and the detected value becomes low pressure, a control form is adopted in which the damping force is reduced (Non-Patent Document 1).
Japanese Patent Application No. 2007-189612 (paragraphs [0041] [0042])

  In the case of adopting a control mode in which the damping force is reduced when the detected value of the pressure sensor is low pressure in accordance with the reference control mode described above, there are the following disadvantages. In other words, when the suspension mechanism is attached to one of the front and rear wheels and the work device is attached to a position close to the other wheel, the load acting on the suspension mechanism in a state where the work device is lifted with respect to the traveling machine body May become too light. In that case, if the damping force is small as in the prior art, there is a possibility that the suspension mechanism repeats the expansion and contraction operation with a large inertial force and a large stroke.

    If it does so, the attitude | position of a traveling body might become unstable and there existed a possibility that maneuverability and workability | operativity might fall.

  It is an object of the present invention to grasp a case where a work device is mounted on a side different from a side equipped with a suspension mechanism, and to control the damping force of the suspension mechanism so that the posture of the work vehicle can be satisfactorily controlled. It is in providing a suspension structure.

〔Constitution〕
The characteristic configuration of the invention according to claim 1 is that the traveling body supports at least one of the front and rear wheels via a hydraulic suspension mechanism,
A pressure sensor that detects an internal pressure of the suspension mechanism, and a control unit that changes and controls the operating characteristics of the suspension mechanism based on a detection value of the pressure sensor;
The control means includes a reference control mode for changing an operation characteristic of the suspension mechanism based on a detection value of the pressure sensor in a state in which a work device is attached at a position close to the one wheel, A different working device is attached at a position close to the other wheel, and based on the detection result of detecting the attached state, the reference control mode is corrected to make the operating characteristics of the suspension mechanism insensitive. There is a correction mode to be changed, and its operation and effect are as follows.

[Action]
When it is detected that the different working device is mounted near the wheel opposite to the front and rear sides of the one wheel provided with the suspension mechanism, the correction mode is executed by the control means, and the reference control mode is executed. The operating characteristics of the suspension mechanism can be switched to the insensitive side.
As a result, the load acting on the wheel is light, but the suspension mechanism itself is insensitive, so that the traveling machine body is prevented from greatly moving up and down.

〔effect〕
By making improvements only by detecting the mounting position of the work device and reflecting it in the control, it is possible to sufficiently ensure the posture stability of the traveling machine body, and to improve the stability and workability of work travel.

〔Constitution〕
According to a second aspect of the present invention, in the invention according to the first aspect, the operating characteristics of the suspension mechanism are transferred to the hydraulic cylinder spanned between the body frame and the one wheel and the hydraulic cylinder. Set with an accumulator linked to the oil flow, provided a flow control valve in the oil passage between the hydraulic cylinder and the accumulator, compared to the throttle amount of the flow control valve in the reference control mode, In the correction control mode, the throttle amount of the flow control valve is increased, and the operation and effect thereof are as follows.

[Function and effect]
A damping force is one that defines the operating characteristics of the suspension mechanism. There are an accumulator linked to a hydraulic cylinder and a flow rate control valve for restricting the hydraulic oil supplied to the accumulator as a means for producing the damping force.
As the throttle of the flow control valve is increased, the damping force increases, and the operating characteristics of the suspension mechanism move to the insensitive side.
Therefore, the suspension mechanism can be controlled to the insensitive side only by increasing the aperture amount in the correction mode compared to the aperture amount in the reference control mode, and the control configuration and control operation are easy.

〔Constitution〕
The characteristic configuration of the invention according to claim 3 is the invention according to claim 2, wherein the flow control valve is configured in a stepped manner including a plurality of orifices having different flow path cross-sectional areas,
Set a threshold for the internal pressure of the suspension mechanism,
In the reference control mode, the control means determines whether the internal pressure of the suspension mechanism is less than the threshold based on the detection value of the pressure sensor, and when the internal pressure is less than the threshold, The hydraulic cylinder and the accumulator communicate with each other through an orifice having a large channel cross-sectional area corresponding to the internal pressure less than the threshold, and when the internal pressure is equal to or higher than the threshold, the threshold Controlling the operation of the flow control valve so that the hydraulic cylinder and the accumulator communicate with each other through an orifice having a small flow path cross-sectional area corresponding to the internal pressure.
In the correction control mode, the flow control is performed by selecting an orifice having a smaller channel cross-sectional area than an orifice having a channel cross-sectional area corresponding to the internal pressure. Is as follows.

[Function and effect]
The flow rate control valve is composed of an orifice provided in a flow path connecting the hydraulic cylinder and the accumulator, and a plurality of orifices having different flow path cross-sectional areas are prepared. The orifice group is controlled by selecting an appropriate one according to the internal pressure of the hydraulic cylinder.
In this way, by adopting a plurality of orifices with different throttle amounts determined by the channel cross-sectional area, the mechanism is not complicated and control is easy compared to a mechanism that can continuously change the throttle amount. Become.
Therefore, in the correction mode, control is performed by selecting a flow passage having a smaller cross-sectional area than the orifice selected in the reference control mode.

〔Constitution〕
According to a fourth aspect of the present invention, there is provided a characteristic configuration according to the third aspect of the present invention, wherein the threshold value for switching from an orifice having a small channel cross-sectional area to an orifice having a large channel cross-sectional area is changed from an orifice having a large channel cross-sectional area. It is characterized in that it is set to a value smaller than a threshold value when switching to an orifice having a small road cross-sectional area, and its operation and effect are as follows.

[Function and effect]
For example, set the same threshold value when switching from an orifice with a small channel cross-sectional area to an orifice with a large channel cross-sectional area and a threshold value when switching from an orifice with a large channel cross-sectional area to an orifice with a small channel cross-sectional area. If the detected value of the pressure sensor is less than the threshold value, the hydraulic cylinder and the accumulator are communicated via an orifice having a large flow path cross-sectional area, and if the detected value of the pressure sensor is greater than or equal to the threshold value, When the hydraulic cylinder and the accumulator are communicated via an orifice with a small area, if the detected value of the pressure sensor changes frequently with the threshold as a boundary, an orifice with a different flow path cross-sectional area is associated with it. Are frequently changed, and the damping ratio of the suspension mechanism frequently fluctuates greatly. That is, since the suspension is frequently switched between a hard state and a soft state, the ride quality is lowered.

  On the other hand, in the invention according to claim 4 of the present invention, the threshold for switching from an orifice having a small channel cross-sectional area to an orifice having a large channel cross-sectional area is set from an orifice having a large channel cross-sectional area to a channel. Since it is set to a value smaller than the threshold value when switching to an orifice with a small cross-sectional area, even if the detected value of the pressure sensor changes frequently with either threshold value as a boundary, the pressure sensor detection As long as the value reaches the other threshold or does not exceed the other threshold, switching of orifices having different channel cross-sectional areas is not performed.

  Therefore, even when the detection value of the pressure sensor frequently changes with the threshold as a boundary, the ride comfort is reduced due to frequent switching of orifices having different flow path cross-sectional areas. Can be avoided.

〔Constitution〕
According to a fifth aspect of the invention, there is provided a characteristic configuration according to the first aspect, wherein the control unit calculates an average value of the detected value for each set time based on the detected value of the pressure sensor. It is determined whether or not the calculated internal pressure of the suspension mechanism is less than the threshold value, and if the internal pressure is less than the threshold value, the flow path cutoff corresponding to the internal pressure less than the threshold value is determined. The operation of the flow rate control valve is controlled so that the hydraulic cylinder and the accumulator communicate with each other through an orifice having a large area.

[Function and effect]
In order to identify the internal pressure of the hydraulic cylinder that serves as a reference for switching the orifices having a plurality of different flow path cross-sectional areas, the average value for each set time of the detected value is specified as the internal pressure based on the detected value of the pressure sensor. The influence of the prominent detection value in the time change can be suppressed.
Therefore, since it is possible to avoid taking a control form corresponding to the protruding detection value, the control is stabilized.

〔Constitution〕
A characteristic configuration of the invention according to claim 6 is the invention according to any one of claims 3 to 5, comprising a manual setting device that enables hardness setting of the suspension mechanism,
As the hardness of the suspension mechanism set by the setting device is harder, the threshold value is configured to be changed to a lower value with respect to the internal pressure of the suspension mechanism. It is as follows.

[Function and effect]
According to this characteristic configuration, as the hardness of the suspension mechanism is changed to a harder side by the setting device, the threshold value is changed to a lower value with respect to the internal pressure of the suspension mechanism, so that the hydraulic cylinder and the accumulator The orifice of the flow control valve that communicates with the flow passage is easily switched from a large flow passage cross-sectional area to a small flow passage cross-sectional area, and difficult to switch from a small flow passage cross-sectional area to a large flow passage cross-sectional area. Conversely, the threshold value is set to a higher value with respect to the internal pressure of the suspension mechanism as the setting mechanism changes the setting of the suspension mechanism to a softer side, thereby connecting the hydraulic cylinder and the accumulator. It becomes difficult for the orifice of the flow control valve to switch from one having a large channel cross-sectional area to one having a small channel cross-sectional area, and to switch from one having a small channel cross-sectional area to one having a large channel cross-sectional area.

  In other words, the harder the suspension mechanism set by the setting device, the easier it is to use a smaller flow passage cross-sectional orifice as the orifice of the flow control valve that communicates the hydraulic cylinder and accumulator. On the contrary, the softer the suspension mechanism set by the setting device, the easier it is to use an orifice with a larger flow cross-sectional area as the orifice of the flow control valve that connects the hydraulic cylinder and accumulator. Therefore, it is possible to give a soft feeling as a ride comfort.

  Therefore, the ride quality can be set according to the driver's preference, and the ride quality can be improved.

  Hereinafter, as an example of the best mode for carrying out the present invention, an embodiment in which the suspension structure of a work vehicle according to the present invention is applied to a tractor as an example of the work vehicle will be described with reference to the drawings.

  FIG. 1 is an overall side view of the tractor. As shown in this figure, the tractor is configured as a four-wheel drive type in which a pair of left and right front wheels 2 and rear wheels 3 provided in the body frame 1 are driven by power from an engine 4. On the rear side of the fuselage frame 1, a riding driving unit 7 is formed by arranging a steering wheel 5 for driving a front wheel, a driving seat 6, and the like.

  The fuselage frame 1 has a lower part of the engine 4 connected to the rear part of the front frame 8 positioned between the left and right front wheels 2, a clutch housing 9 connected to the rear lower part of the engine 4, and an intermediate frame to the rear part of the clutch housing 9. A transmission case (hereinafter abbreviated as “T / M case”) 11 is connected via 10.

  The machine body frame 1 is connected to an auxiliary frame 13 that can be equipped with a front loader 12 that is an example of a front mount type working device. At the rear of the T / M case 11, a pair of left and right lift arms 14 and a link mechanism 15 that enable connection of a rear mount type work device such as a rotary tiller (not shown) or a plow (not shown), etc. Has been deployed. Although not shown, the machine body frame 1 may be equipped with a link mechanism that enables connection of a mid-mount type work device such as a mower. It is also possible to equip the rear part of the T / M case with a link mechanism that enables connection of a trailer or the like.

  As shown in FIG. 2, the front frame 8 has a rear upper portion of a holder 16 formed in a U shape in a side view, with a support shaft 17 serving as a fulcrum through a support shaft 17 facing left and right. It is connected so that vertical swinging is allowed. The holder 16 is configured to support the front axle case 18 so that it can roll in the recess 16A. The front end portion of the holder 16 is connected to the front frame 8 via a pair of left and right hydraulic cylinders 19.

  In other words, in this tractor, the left and right front wheels 2 mounted on the left and right ends of the front axle case 18 are suspended from the front frame 8 of the body frame 1 via the holder 16 and the left and right hydraulic cylinders 19.

  As shown in FIGS. 2 and 3, the left and right hydraulic cylinders 19 are double-acting, and a bladder type first accumulator 21 is connected to the oil chamber 19 </ b> A on the head side via a first connection oil passage 20. It is. A bladder type second accumulator 23 is connected to the oil chamber 19 </ b> B on the rod side of each hydraulic cylinder 19 via a second connection oil passage 22. Nitrogen gas that functions as a suspension spring is sealed in the bladder of each accumulator 21, 23.

  The first connection oil passage 20 is equipped with a pilot operated first check valve 24A and a second check valve 24B that are opened and closed by pilot pressure. The second connection oil passage 22 is equipped with a pilot operated third check valve 25A and a fourth check valve 25B that are opened and closed by a pilot pressure. The second check valve 24B and the third check valve 25A prevent the backflow of hydraulic oil from the left and right hydraulic cylinders 19 to the corresponding accumulators 21 and 23 in the closed state, and allow the backflow in the open state. The first check valve 24A and the fourth check valve 25B block the flow of hydraulic oil from the accumulators 21 and 23 to the left and right hydraulic cylinders 19 in the closed state, and allow the flow in the open state.

  As described above, the first check valve 24A and the second check valve 24B are disposed in opposite directions. Similarly, the third check valve 25A and the fourth check valve 25B are arranged in opposite directions. Therefore, when both the check valves 24A and 24B and the check valves 25A and 25B are set in the closed state, the flow state of the hydraulic oil between the left and right hydraulic cylinders 19 and the both accumulators 21 and 23 is prevented, and the suspension The mechanism 50 can be locked in a non-actuated state.

  An electromagnetic switching valve 27 is connected to the first check valve 24A, the second check valve 24B, the third check valve 25A, and the fourth check valve 25B through a pilot oil passage 26. The electromagnetic switching valve 27 switches between a pressure increasing state for increasing the pilot pressure for each check valve 24A, 24B, 25A, 25B and a pressure decreasing state for decreasing the pilot pressure for each check valve 24A, 24B, 25A, 25B. It is configured to be possible. Each check valve 24A, 24B, 25A, 25B switches from the closed state to the open state when the pilot pressure for them increases, and switches from the open state to the closed state when the pilot pressure for them decreases. That is, each check valve 24A, 24B, 25A, 25B functions as a check valve when the pilot pressure decreases, and stops functioning as a check valve when the pilot pressure increases.

  A first discharge oil passage 29 including a first safety valve 28 is connected to an oil passage portion connected to the first accumulator 21 in the first connection oil passage 20. A second drain oil passage 31 including a second safety valve 30 is connected to an oil passage portion connected to the second accumulator 23 in the second connection oil passage 22.

  A first supply / discharge oil passage 32 is connected to an oil passage portion located between the left and right hydraulic cylinders 19 and the second check valve 24B in the first connection oil passage 20. A second supply / discharge oil passage 33 is connected to an oil passage portion located between the left and right hydraulic cylinders 19 and the third check valve 25 </ b> A in the second connection oil passage 22. A supply oil path 35 and a discharge oil path 36 are connected to the first supply / discharge oil path 32 and the second supply / discharge oil path 33 via a pilot-operated switching valve 34 that is switched by a pilot pressure. is there.

  The switching valve 34 includes a first supply / discharge state in which the first supply / discharge oil passage 32 is connected to the supply oil passage 35, and the second supply / discharge oil passage 33 is connected to the discharge oil passage 36. A second supply / discharge state in which the passage 32 is connected to the discharge oil passage 36 and the second supply / discharge oil passage 33 is connected to the supply oil passage 35; the first supply / discharge oil passage 32 and the second supply / discharge oil passage 33; Can be switched to a supply / discharge stop state connected to the discharge oil passage 36. The switching operation of the switching valve 34 includes a first solenoid valve 38 connected to the switching valve 34 via the first pilot oil passage 37 and a second solenoid valve connected to the switching valve 34 via the second pilot oil passage 39. This can be done by controlling the operation of 40.

  The first oil supply / drain passage 32 is equipped with a pilot operated fifth check valve 41 that is opened and closed by a pilot pressure. The second oil supply / discharge passage 33 is equipped with a pilot operated sixth check valve 42 that is opened and closed by a pilot pressure. The fifth check valve 41 and the sixth check valve 42 prevent backflow of hydraulic oil from the corresponding connecting oil passages 20 and 22 toward the switching valve 34 in the closed state, and allow backflow in the open state. .

  The fifth check valve 41 is connected to an oil passage portion on the switching valve side in the second supply / discharge oil passage 33 through a third pilot oil passage 43. The sixth check valve 42 is connected to an oil passage portion on the switching valve side in the first supply / discharge oil passage 32 via a fourth pilot oil passage 44.

  As a result, when the switching valve 34 is switched from the supply / discharge stop state to the first supply / discharge state, hydraulic oil is supplied toward the sixth check valve 42 and the pilot pressure for the sixth check valve 42 increases. When the switching valve 34 is switched from the first supply / discharge state to the supply / discharge stop state, the hydraulic oil is discharged from the sixth check valve 42 and the pilot pressure with respect to the sixth check valve 42 decreases. When the switching valve 34 is switched from the supply / discharge stop state to the second supply / discharge state, the hydraulic oil is supplied toward the fifth check valve 41 and the pilot pressure with respect to the fifth check valve 41 increases. When the switching valve 34 is switched from the second supply / discharge state to the supply / discharge stop state, the hydraulic oil is discharged from the fifth check valve 41 and the pilot pressure with respect to the fifth check valve 41 decreases.

  The fifth check valve 41 and the sixth check valve 42 switch from the closed state to the open state when the pilot pressure increases, and switch from the open state to the closed state when the pilot pressure to them decreases. That is, the fifth check valve 41 and the sixth check valve 42 function as check valves when the pilot pressure decreases, and stop functioning as check valves when the pilot pressure increases.

  A first throttle valve 45 for speed adjustment is provided on the oil passage portion of the first supply / discharge oil passage 32 closer to the first connection oil passage than the fifth check valve 41. A seventh check valve 46 is provided in the oil passage portion of the second supply / discharge oil passage 33 closer to the switching valve than the sixth check valve 42, and the sixth check valve 42, the seventh check valve 46, Between the sixth check valve 42 and the second throttle valve 47, the pressure on the rod side of the left and right hydraulic cylinders 19 is kept constant between the second throttle valve 47 for speed adjustment. A drain oil passage 49 provided with a relief valve 48 is connected.

  From the above configuration, when the switching valve 34 is maintained in the supply / discharge stop state, the pilot pressure for the fifth check valve 41 and the sixth check valve 42 is maintained low. Thereby, the 5th check valve 41 and the 6th check valve 42 are maintained in a closed state, and function as a check valve. In this state, when the electromagnetic switching valve 27 is switched from the step-down state to the step-up state to increase the pilot pressure for the first, second check valves 24A, 24B and the third, fourth check valves 25A, 25B, The two check valves 24A and 24B and the third and fourth check valves 25A and 25B are switched from the closed state to the open state, and the function as the check valve is stopped.

  Then, the flow of the hydraulic oil in both directions between the left and right hydraulic cylinders 19 and the first accumulator 21 and between the left and right hydraulic cylinders 19 and the second accumulator 23 is allowed, whereby each accumulator 21 is allowed to flow. , 23 functions as a suspension spring, and hydraulic oil filled between the left and right hydraulic cylinders 19, the first accumulator 21, and the second accumulator 23 functions as a damper.

  That is, the left and right hydraulic cylinders 19, the first connection oil passage 20, the first accumulator 21, the second connection oil passage 22, the second accumulator 23, the first safety valve 28, the second safety valve 30, the fifth check valve 41, and The hydraulic circuit portion configured to include the sixth check valve 42 functions as the hydraulic suspension mechanism 50.

  On the other hand, when the first and second check valves 24A and 24B and the third and fourth check valves 25A and 25B are maintained in the closed state, the switching valve 34 is switched from the supply / discharge stop state to the first supply / discharge state. The hydraulic oil is supplied toward the oil chamber 19A on the head side of the left and right hydraulic cylinders 19. Also, the pilot pressure on the sixth check valve 42 is increased and the sixth check valve 42 is switched from the closed state to the open state, whereby the oil discharge path from the rod side oil chamber 19B in the left and right hydraulic cylinders 19 is achieved. The hydraulic oil is allowed to drain through 49. As a result, the left and right hydraulic cylinders 19 are extended to increase the vehicle height on the front side of the tractor.

  Thereafter, when the switching valve 34 is switched from the first supply / discharge state to the supply / discharge stop state, the supply of hydraulic oil toward the oil chamber 19A on the head side of the left and right hydraulic cylinders 19 is stopped. Also, the pilot pressure on the sixth check valve 42 decreases and the sixth check valve 42 switches from the open state to the closed state, so that the oil discharge path from the rod-side oil chamber 19B in the left and right hydraulic cylinders 19 is achieved. The hydraulic oil is prevented from being discharged through 49. As a result, the left and right hydraulic cylinders 19 stop extending, and the vehicle height on the front side of the tractor is maintained.

  Conversely, when the switching valve 34 is switched from the supply / discharge stop state to the second supply / discharge state, hydraulic oil is supplied toward the oil chamber 19B on the rod side of the left and right hydraulic cylinders 19. Further, the pilot pressure for the fifth check valve 41 is increased and the fifth check valve 41 is switched from the closed state to the open state, whereby the oil discharge path from the head side oil chamber 19A in the left and right hydraulic cylinders 19 is achieved. The discharge of hydraulic oil through 36 is allowed. As a result, the left and right hydraulic cylinders 19 are contracted to reduce the vehicle height on the front side of the tractor.

  Thereafter, when the switching valve 34 is switched from the second supply / discharge state to the supply / discharge stop state, the supply of hydraulic oil toward the rod-side oil chamber 19B of the left and right hydraulic cylinders 19 is stopped. Further, the pilot pressure on the fifth check valve 41 is reduced and the fifth check valve 41 is switched from the open state to the closed state, whereby the oil discharge path from the head-side oil chamber 19A in the left and right hydraulic cylinders 19 is achieved. The discharge of hydraulic oil through 36 is prevented. As a result, the left and right hydraulic cylinders 19 stop the contraction operation, and the vehicle height on the front side of the tractor is maintained.

  That is, in the state where the first and second check valves 24A and 24B and the third and fourth check valves 25A and 25B are maintained in the closed state, the operation of the switching valve 34 is controlled so that the vehicle on the front side of the tractor The height can be adjusted.

  As a result, for example, when the front loader 12 is connected to the front part of the tractor and the weight of the front part of the tractor increases and the vehicle height on the front part of the tractor decreases, the switching valve 34 is supplied. By switching from the exhaust stop state to the first supply / exhaust state and operating the left and right hydraulic cylinders 19 to extend, the front loader 12 is connected to the front loader 12 against the weight of the front loader 12. It can be raised to the previous original height position. On the contrary, when the front loader 12 is removed from the front part of the tractor and the weight of the front part side of the tractor is lightened and the vehicle height on the front part side of the tractor is raised, the switching valve 34 is in a supply / discharge stop state. By switching from the second to the second supply / discharge state and operating the left and right hydraulic cylinders 19 to contract, the vehicle height on the front side of the tractor can be lowered to the original height position before the front loader 12 is removed.

  Further, when the front loader 12 scoops up the earth and sand and the weight on the front side of the tractor increases and the vehicle height on the front side of the tractor decreases, the switching valve 34 is moved from the supply / discharge stop state to the first state. By switching to the supply / discharge state and operating the left and right hydraulic cylinders 19 to extend, the vehicle height on the front side of the tractor against the weight of the earth and sand, the original height before the front loader 12 scoops up the earth and sand. Can be raised to position. On the other hand, when the earth and sand are discharged from the front loader 12 to reduce the weight on the front side of the tractor and raise the vehicle height on the front side of the tractor, the switching valve 34 is moved from the supply / discharge stop state to the first state. The vehicle height on the front side of the tractor can be lowered to the original height position before discharging the earth and sand from the front loader 12 by switching to the two supply / discharge state and contracting the left and right hydraulic cylinders 19. .

  In other words, the vehicle height on the front side of the tractor can be set to a predetermined height regardless of changes in the weight of the vehicle body due to attachment / detachment of a work device such as the front loader 12 or a change in load during work.

The vehicle height adjustment is performed by a control operation of a vehicle height adjustment control means (not shown) based on detection of a vehicle height sensor (not shown) that detects the vehicle height on the front side of the tractor. You may comprise, and you may comprise so that it may carry out by the control action | operation of the control means for the vehicle height adjustment based on operation of the manual operation tool (not shown).
Here, when performing an operation of scooping up the earth and sand with the front loader 12, fine position adjustment of the bucket 12 </ b> A may be necessary. In such a case, when the suspension mechanism 50 is operated, the bucket 12A position moves up and down, and there is a surface that is difficult to adjust. Therefore, in such a case, the first to fourth check valves 24A, 24B, 25A, 25B are switched to the closed state by the electromagnetic switching valve 27, so that the hydraulic cylinder 19 and the accumulators 21, 23 are switched. The suspension mechanism 50 is locked in the non-operating state. Thereby, the attitude | position of the traveling body 1 is stabilized and loader work etc. become easy.

  As shown in FIGS. 3 to 6, the oil passage portion located between the first accumulator 21 and the first check valve 24 </ b> A in the first connection oil passage 20 includes the left and right hydraulic cylinders 19 and the first accumulator 21. A flow rate control valve 51 for controlling the flow rate of the working oil flowing over is provided. The flow control valve 51 is a stepped type that includes three orifices 51a to 51c having different flow path cross-sectional areas in the spool 51A, and is configured to be a pilot operated type in which the orifices 51a to 51c to be used are switched by a pilot pressure. It is. The switching operation of the orifices 51 a to 51 c in the flow control valve 51 is controlled by the first electromagnetic valve 53 connected to the flow control valve 51 through the first pilot oil passage 52 and the flow control through the second pilot oil passage 54. This can be done by controlling the operation of the second electromagnetic valve 55 connected to the valve 51.

  An oil passage portion located between the left and right hydraulic cylinders 19 and the first check valve 24 in the first connection oil passage 20 has an internal pressure (first connection oil passage 20 on the head side of the hydraulic cylinder 19 in the suspension mechanism 50. Is provided as a pressure sensor 56 for detecting the spring load (front load of the tractor) of the suspension mechanism 50. The detection value of the pressure sensor 56 is input to an attenuation ratio adjusting control means 57 constituted by a microcomputer mounted on the tractor.

  As shown in FIG. 5, the control means 57 uses the first electromagnetic valve 53 and the first threshold value based on the detection value of the pressure sensor 56 and the first threshold value M1 and the second threshold value M2 preset for the detection value. 2 By controlling the operation of the electromagnetic valve 55, the operation of the flow control valve 51 is controlled so that the damping ratio of the suspension mechanism 50 is maintained within an appropriate range (for example, within a range of 0.5 to 1.0). To do.

  Specifically, when the internal pressure M on the head side of the hydraulic cylinder 19 in the suspension mechanism 50, which is the detection value of the pressure sensor 56, is less than the first threshold value M1, the control means 57 makes the internal pressure M correspond to the internal pressure M. The operation of the flow control valve 51 is controlled so that the left and right hydraulic cylinders 19 and the first accumulator 21 communicate with each other through the first orifice 51a having a large flow path cross-sectional area. When the internal pressure M on the head side of the hydraulic cylinder 19 in the suspension mechanism 50 is greater than or equal to the first threshold value M1 and less than the second threshold value M2, the second orifice 51b having an intermediate channel cross-sectional area corresponding to the internal pressure M is provided. The operation of the flow control valve 51 is controlled so that the left and right hydraulic cylinders 19 and the first accumulator 21 communicate with each other. When the internal pressure M on the head side of the hydraulic cylinder 19 in the suspension mechanism 50 is equal to or greater than the second threshold value M2, the left and right hydraulic cylinders 19 are connected via the third orifice 51c having a small channel cross-sectional area corresponding to the internal pressure M. And the first accumulator 21 are controlled so that the operation of the flow control valve 51 is controlled.

  That is, by connecting a working device such as the front loader 12 to the tractor, or by lifting up the earth and sand with the front loader 12 during loader work with the front loader 12 connected, the front load of the tractor (the sprung load of the suspension mechanism 50). ) Increases, the internal pressure M on the head side of the hydraulic cylinder 19 in the suspension mechanism 50 increases, and accordingly, the spring constant of the suspension mechanism 50 increases, and the damping ratio of the suspension mechanism 50 becomes relatively small and the appropriate range. When the control means 57 deviates from the above, the control means 57 switches the orifices 51a to 51c of the flow control valve 51 communicating with the left and right hydraulic cylinders 19 and the first accumulator 21 from one having a larger flow passage cross-sectional area to one having a smaller passage cross-sectional area. By increasing the Damping ratio of the mechanism 50 is adjusted to be maintained within a proper range.

  Conversely, by removing a work device such as the front loader 12 from the tractor, or by releasing earth and sand from the front loader 12 during loader work with the front loader 12 connected, the front load of the tractor (the sprung load of the suspension mechanism 50). ) Becomes smaller, the internal pressure M on the head side of the hydraulic cylinder 19 in the suspension mechanism 50 becomes smaller, and accordingly, the spring constant of the suspension mechanism 50 becomes smaller, the damping ratio of the suspension mechanism 50 becomes relatively larger, and the appropriate range. When the control means 57 deviates from the above, the control means 57 switches the orifices 51a to 51c of the flow rate control valve 51 communicating with the left and right hydraulic cylinders 19 and the first accumulator 21 from one having a small flow path cross-sectional area to one having a large flow path cross-sectional area. By lowering the suspension Damping ratio of the mechanism 50 is adjusted to be maintained within a proper range.

  Thereby, the damping coefficient of the suspension mechanism 50 is small with respect to the front load of the tractor, so that the force for converging the vibration is reduced and the vehicle body continues to shake, or the damping coefficient of the suspension mechanism 50 with respect to the front load of the tractor. Because of the large, it is possible to avoid the occurrence of inconveniences such as the fact that the force to converge the vibration is too strong and it is easy to receive an impact. As a result, it is good regardless of whether the work device is attached to or detached from the tractor and the work load fluctuates Ride comfort and stable running performance.

  When the detected value of the pressure sensor 56 is switched from less than the first threshold value M1 to more than the first threshold value M1, the control means 57 establishes communication between the left and right hydraulic cylinders 19 and the first accumulator 21 with the first flow control valve 51. The state performed at the orifice 51a is switched to the state performed at the second orifice 51b. When the detected value of the pressure sensor 56 is switched from less than the second threshold M2 to the second threshold M2 or more, the left and right hydraulic cylinders 19 and the first accumulator 21 are communicated with each other by the second orifice 51b of the flow control valve 51. To the state performed by the third orifice 51c. When the average value of the detection values of the pressure sensor 56 for each set time is switched from the second threshold value M2 or more to less than the second threshold value M2, the communication between the left and right hydraulic cylinders 19 and the first accumulator 21 is communicated to the flow control valve 51. The state performed by the third orifice 51c is switched to the state performed by the second orifice 51b. When the average value of the detection values of the pressure sensor 56 for each set time is switched from the first threshold value M1 or more to less than the first threshold value M1, the communication between the left and right hydraulic cylinders 19 and the first accumulator 21 is connected to the flow control valve 51. The state performed at the second orifice 51b is switched to the state performed at the first orifice 51a.

  That is, by connecting a working device such as the front loader 12 to the tractor, or scooping up the earth and sand with the front loader 12 during the loader operation with the front loader 12 connected, the damping ratio of the suspension mechanism 50 is relatively increased as described above. If the control means 57 is out of the proper range, the orifices 51a to 51c of the flow control valve 51 that immediately communicates with the left and right hydraulic cylinders 19 and the first accumulator 21 have a large cross-sectional area. Switch to a smaller one to increase the attenuation coefficient.

The control mode as described above is referred to as a reference control mode for changing the characteristics of the suspension mechanism 50.
In the reference control mode described above, the operation of the suspension mechanism 50 in the front loader operation has been described. However, the following control mode may be adopted. In other words, when the front loader 12 performs an operation of scooping up the earth and sand, a fine position adjustment of the bucket 12A may be necessary. In such a case, when the suspension mechanism 50 is operated, the bucket 12A position moves up and down, and there is a surface that is difficult to adjust. Therefore, in such a case, as described above, the first to fourth check valves 24A, 24B, 25A, and 25B are switched to the closed state by the electromagnetic switching valve 27, and the hydraulic cylinder 19 and each accumulator are switched. The suspension of the hydraulic mechanism 21 and 23 and the suspension mechanism 50 is locked in the non-operating state. Thereby, the attitude | position of the traveling body 1 is stabilized and loader work etc. become easy.

  As shown in FIGS. 5 and 6, the tractor is provided with a manual setting device 59 that allows the hardness of the suspension mechanism 50 to be set. The setter 59 is composed of a rotary potentiometer, and outputs the set value to the control means 57.

  As the hardness of the suspension mechanism 50 set by the setting device 59 increases, the control means 57 sets the first threshold value M1 and the second threshold value M2 to a lower value relative to the internal pressure on the head side of the hydraulic cylinder 19 in the suspension mechanism 50. Change the setting to a value.

  As a result, as the hardness of the suspension mechanism 50 is changed to a harder side by the setting device 59, the values of the first threshold value M1 and the second threshold value M2 are lower than the internal pressure M on the head side of the hydraulic cylinder 19 in the suspension mechanism 50. By changing the setting to the value on the side, the orifices 51a to 51c of the flow control valve 51 that communicates the left and right hydraulic cylinders 19 and the first accumulator 21 can be easily switched from one having a large channel cross-sectional area to one having a small channel cross-sectional area. Thus, it becomes difficult to switch from a small channel cross-sectional area to a large one. On the contrary, as the hardness of the suspension mechanism 50 is changed to a softer side by the setting device 59, the values of the first threshold value M1 and the second threshold value M2 are higher than the internal pressure M on the head side of the hydraulic cylinder 19 in the suspension mechanism 50. By changing the setting to the value on the side, the orifices 51a to 51c of the flow control valve 51 that communicates the left and right hydraulic cylinders 19 and the first accumulator 21 are difficult to switch from the one with the larger cross-sectional area of the flow path to the smaller one. Therefore, it becomes easy to switch from a small channel cross-sectional area to a large one.

  As a result, as the hardness of the suspension mechanism 50 set by the setting device 59 is increased, the damping coefficient is increased as the orifices 51a to 51c of the flow control valve 51 communicating the left and right hydraulic cylinders 19 and the first accumulator 21. Since it becomes easy to use a thing with a small channel cross-sectional area, a hard feeling can be given as riding comfort, and conversely, as the hardness of the suspension mechanism 50 set by the setting device 59 is softened, the left and right hydraulic cylinders As the orifices 51a to 51c of the flow rate control valve 51 that communicates with the first accumulator 21, it is easy to use one having a large channel cross-sectional area that reduces the damping coefficient, so that it gives a soft feeling as riding comfort. it can.

  The point of controlling the operation of the suspension mechanism 50 in the correction mode will be described. The correction mode here refers to a control mode in which the operation characteristic of the suspension mechanism is changed to the insensitive side by correcting the reference control mode. As shown in FIG. 4, a work mode changeover switch 58 is provided in the boarding operation unit 7 so that a front loader (loader) work, a road running, and a plow work form can be selected.

  In the reference control mode (# 1), the suspension mechanism 50 is controlled by the first orifice 51a when the internal pressure M of the hydraulic cylinder 19 switches to the first threshold value M1 or less as described above. In this case, as shown in FIGS. 5 and 7, if the work mode switch 58 selects a work form with a plow as a different work device (# 2), the inertial force is large and the traveling machine body 1 Taking into consideration that the posture is likely to be unstable, the following correction mode control is performed (# 3). That is, the control unit 57 selects the second orifice 51b having a smaller channel cross-sectional area than the first orifice 51a, and controls the suspension mechanism 50.

As shown by the broken line in FIG. 5, the control at the second orifice 51b has a larger attenuation rate of 1.5 to 1 than in the reference control mode in which the attenuation rate is set between 1.0 and 0.4. .0 between. As a result, the control is performed in a state in which the damping rate is increased, so that the suspension mechanism 50 switches to the insensitive side.
If the work mode is a front loader work or traveling on the road, it is performed in the reference control mode.

[Another embodiment]
[1] As a work vehicle, a passenger management machine, a riding rice transplanter, a riding mower, a tractor loader backhoe (TLB), a tractor loader mower (TLM), or a tractor loader backhoe mower (TLBM) It may be.

[2] The work equipment to be equipped on the work vehicle may be a rear-mount rotary tiller or plow, a mid-mount mower, or a front-mount fork device. It may be.

[3] The suspension mechanism 50 may include a single hydraulic cylinder 19 or may include three or more hydraulic cylinders 19.

[4] The suspension mechanism 50 may be configured by connecting the accumulators 21 and 23 to the hydraulic cylinder 19 that suspends the left and right rear wheels 3 from the body frame 1.

[5] In the oil passage portion located between the second accumulator 23 and the third check valve 25A in the second connection oil passage 22, the rod-side oil chamber 19B and the second accumulator 23 in the left and right hydraulic cylinders 19 A flow rate control valve 51 that controls the flow rate of the hydraulic oil flowing through the control unit 57 may be interposed, and the control unit 57 may be configured to control the operation of the flow rate control valve 51 based on the detection value of the pressure sensor.

[6] The flow rate control valve 51 may be an electromagnetic type.

[7] As the flow control valve 51, a stepped type having two or four or more orifices may be adopted.

[8] As the flow control valve 51, a continuously variable valve that continuously controls the flow rate of hydraulic oil may be adopted.

[9] As shown in FIG. 6, the threshold values M1a and M2a for switching from the orifices 51b and 51c having a small channel cross-sectional area to the orifices 51a and 51b having a large channel cross-sectional area are set to the orifices 51a and It may be set to a value smaller than the threshold values M1b and M2b when switching from 51b to orifices 51b and 51c having a small channel cross-sectional area.

[10] The hardness setting of the suspension mechanism 50 by the setting device 59 may be configured in a stepped manner that is performed by switching between three stages of “soft”, “normal”, and “hard”.

[11] As the accumulators 21 and 23, diaphragm type or piston type may be adopted.

[12] Based on the detection value of the pressure sensor 56, the average value of the detection value for each set time may be calculated as the internal pressure M of the suspension mechanism 50.

Overall side view of a tractor equipped with a front loader Side view of main part showing support structure of front axle case Hydraulic circuit diagram showing the structure of the suspension mechanism Block diagram showing control configuration for damping ratio adjustment Diagram showing the relationship between front load and damping ratio The figure which shows the relationship between the front load and damping ratio in another embodiment. Control flow diagram between reference control mode and correction mode

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airframe 2 Front wheel 3 Rear wheel 19 Hydraulic cylinder 21 Accumulator 50 Suspension mechanism 51 Flow control valve 51a Orifice 51b Orifice 51c Orifice 56 Pressure sensor 57 Control means 59 Setter M Internal pressure (suspension mechanism)
M1 threshold M2 threshold

Claims (6)

Support at least one of the front and rear wheels on the traveling machine body via a hydraulic suspension mechanism,
A pressure sensor that detects an internal pressure of the suspension mechanism, and a control unit that changes and controls the operating characteristics of the suspension mechanism based on a detection value of the pressure sensor;
The control means includes a reference control mode for changing an operation characteristic of the suspension mechanism based on a detection value of the pressure sensor in a state in which a work device is attached at a position close to the one wheel, A work device different from the work device is attached at a position close to the other wheel, and based on the detection result of detecting the attached state, the reference control mode is corrected to make the operation characteristics of the suspension mechanism insensitive. A suspension structure for a work vehicle that has a correction mode to be changed.   The operating characteristics of the suspension mechanism are set by a hydraulic cylinder spanned across the body frame and the one wheel, and an accumulator linked to the hydraulic cylinder, and the hydraulic cylinder and the accumulator are connected. A flow control valve is provided in an oil passage with the cumulator, and a throttle amount of the flow control valve in the correction control mode is increased as compared with a throttle amount of the flow control valve in the reference control mode. Item 1. A suspension structure for a work vehicle according to Item 1. The flow rate control valve is configured in a stepped manner including a plurality of orifices having different flow path cross-sectional areas,
Set a threshold for the internal pressure of the suspension mechanism,
In the reference control mode, the control means determines whether the internal pressure of the suspension mechanism is less than the threshold based on the detection value of the pressure sensor, and when the internal pressure is less than the threshold, The hydraulic cylinder and the accumulator communicate with each other through an orifice having a large channel cross-sectional area corresponding to the internal pressure less than the threshold, and when the internal pressure is equal to or higher than the threshold, the threshold Controlling the operation of the flow control valve so that the hydraulic cylinder and the accumulator communicate with each other through an orifice having a small flow path cross-sectional area corresponding to the internal pressure.
3. The work vehicle according to claim 2, wherein in the correction control mode, the flow control is performed by selecting an orifice having a smaller channel cross-sectional area than an orifice having a channel cross-sectional area corresponding to the internal pressure. Suspension structure.   Set the threshold for switching from an orifice with a small channel cross-sectional area to an orifice with a large channel cross-sectional area to a value smaller than the threshold for switching from an orifice with a large channel cross-sectional area to an orifice with a small channel cross-sectional area. The work vehicle suspension structure according to claim 3.   Based on the detected value of the pressure sensor, the control means calculates the average value of the detected value for each set time as the internal pressure of the suspension mechanism, and whether the calculated internal pressure of the suspension mechanism is less than the threshold value. If the internal pressure is less than the threshold value, the hydraulic cylinder and the accumulator are communicated with each other through an orifice having a large channel cross-sectional area corresponding to the internal pressure less than the threshold value. The work vehicle suspension structure according to claim 3, wherein the operation of the flow control valve is controlled. It has a manual setting device that enables the hardness setting of the suspension mechanism,
The threshold value is configured to be changed to a lower value with respect to the internal pressure of the suspension mechanism as the hardness of the suspension mechanism set by the setting device is higher. The suspension structure of the working vehicle described in 1.

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