JP5075107B2 - Work vehicle suspension structure - Google Patents

Description

  The present invention relates to a suspension structure in a work vehicle such as a tractor or a construction vehicle.

  In a tractor that is an example of a work vehicle, for example, as disclosed in Patent Document 1, a traveling wheel (Patent Document 1) via a hydraulic cylinder (FIGS. 1, 2 and 16, 17 of Patent Document 1). Fig. 1 of No. 14) and a hydraulic cylinder and an accumulator (Fig. 1, No. 36, 38 of Patent Document 1) are connected. Thereby, when the hydraulic cylinder tries to expand and contract due to the unevenness of the ground, the hydraulic oil reciprocates between the hydraulic cylinder and the accumulator, and the hydraulic cylinder operates as a suspension mechanism for the traveling wheels.

In Patent Document 1, the hydraulic passage connecting the hydraulic cylinder and the accumulator (FIGS. 1, 2, 30 of Patent Document 1, 30 and 31) is opened, and the hydraulic cylinder and the accumulator are disconnected, and the hydraulic cylinder and the accumulator are shut off. It is considered to provide an on-off valve that can be operated in a closed state.
In this case, when the on-off valve is operated to open, the hydraulic oil reciprocates between the hydraulic cylinder and the accumulator as described above, and the hydraulic cylinder operates as a suspension mechanism for the traveling wheels.

  When the on-off valve is operated to the closed state, the oil passage connecting the hydraulic cylinder and the accumulator is blocked, so that the hydraulic cylinder cannot be expanded and contracted. For example, when a forklift is installed at the front of the aircraft and the forklift is inserted into the opening of the pallet, the height of the aircraft changes when the hydraulic cylinder operates as a suspension mechanism for the traveling wheels. It becomes difficult to perform an operation such as inserting into the opening of the pallet. Therefore, in such a state, the on-off valve is operated to the closed state, and the hydraulic cylinder is set in a state where it cannot be expanded and contracted so that the height of the airframe does not change.

USP 6145859

  When a hydraulic cylinder and an accumulator as in Patent Document 1 are provided so that the hydraulic cylinder operates as a suspension mechanism for a traveling wheel and the above-described on-off valve is provided, the following inconvenience occurs. Sometimes.

  For example, when a front loader is provided at the front of the aircraft in Patent Document 1, the front loader bucket is empty (the weight applied to the front of the aircraft is light and the hydraulic cylinder (FIG. 16 and 17) and the accumulator (FIG. 1, Patent Nos. 36 and 38 of FIG. 1, Patent Document 1) is under low pressure, the on-off valve is operated to be closed, and the hydraulic cylinder and accumulator Is shut off (FIG. 1, Patent Nos. 30 and 31 of Patent Document 1) (the hydraulic cylinder cannot be expanded and contracted).

Next, when earth and sand are picked up (loaded) by the bucket of the front loader, the weight applied to the front part of the machine body increases due to the weight of the earth and sand. In this case, since the on-off valve is operated to be closed and the oil passage connecting the hydraulic cylinder and the accumulator is shut off, the pressure of the hydraulic cylinder becomes high, but the pressure of the accumulator is maintained at low pressure.
In the above-described state, when the on-off valve is operated to open and the oil passage connecting the hydraulic cylinder and the accumulator communicates, the hydraulic pressure is increased due to the difference between the pressure of the hydraulic cylinder (high pressure) and the pressure of the accumulator (low pressure). The hydraulic oil in the cylinder flows into the accumulator, and the hydraulic cylinder expands and contracts. Accordingly, the hydraulic cylinder expands and contracts at the moment when the on-off valve is operated to open, the height of the fuselage changes, and the driver may feel uncomfortable.

  The present invention relates to a suspension structure for a work vehicle that includes a hydraulic cylinder and an accumulator, and that is configured so that the hydraulic cylinder operates as a suspension mechanism for a traveling wheel. The hydraulic cylinder is connected to an oil passage that connects the hydraulic cylinder and the accumulator. Suppresses the expansion and contraction of the hydraulic cylinder when the open / close valve is operated in the open state when the open / close valve is operated in the open state in which the open / close valve communicates with the accumulator and the closed state in which the hydraulic cylinder and the accumulator are shut off. It is an object.

[I]
(Constitution)
A first feature of the present invention is that a traveling wheel is supported via a hydraulic cylinder, the hydraulic cylinder and an accumulator are connected, and hydraulic oil is reciprocated between the hydraulic cylinder and the accumulator. The suspension structure of a work vehicle configured to operate a cylinder as a suspension mechanism for a traveling wheel is configured as follows.
An oil passage connecting the hydraulic cylinder and the accumulator is provided with an open / close valve that can be operated in an open state in which the hydraulic cylinder and the accumulator communicate with each other and a closed state in which the hydraulic cylinder and the accumulator are shut off.
When the on-off valve is operated from the closed state to the open state, the hydraulic oil is supplied to the hydraulic cylinder or discharged from the hydraulic cylinder to operate the hydraulic cylinder to the preset reference position side. Is provided.

(Function)
For example, as shown in FIG. 3, when the weight applied to the airframe is light, the pressure of the hydraulic cylinder 7 is low, and the pressure of the accumulator 11 is low, the on-off valve 13 is operated to close, and the hydraulic cylinder 7 and the accumulator are operated. Suppose that the oil passage 9 that connects to the hydraulic cylinder 11 is blocked (the hydraulic cylinder 7 cannot expand and contract).
Next, in a state where the on-off valve 13 is operated to be closed and the oil passage 9 connecting the hydraulic cylinder 7 and the accumulator 11 is shut off, if the weight applied to the airframe increases, the pressure of the hydraulic cylinder 7 becomes high. However, the pressure of the accumulator 11 is maintained at a low pressure.

In the above-described state, when the on-off valve 13 is operated to open and the oil passage 9 connecting the hydraulic cylinder 7 and the accumulator 11 communicates, the pressure of the hydraulic cylinder 7 (high pressure) and the pressure of the accumulator 11 (low pressure) Therefore, the hydraulic oil in the hydraulic cylinder 7 flows into the accumulator 11.
In this case, according to the first feature of the present invention, the hydraulic oil is supplied to the hydraulic cylinder by the hydraulic oil operating means, and the hydraulic oil flows into the accumulator from the hydraulic cylinder, whereas the hydraulic oil is supplied by the hydraulic oil operating means. Since the hydraulic oil is supplemented to the cylinder, it is difficult for the hydraulic cylinder to expand and contract at the moment when the on-off valve is operated to open.

  On the other hand, when the pressure of the hydraulic cylinder becomes lower than the pressure of the accumulator when the on-off valve is operated to be closed and the oil passage connecting the hydraulic cylinder and the accumulator is shut off, Is opened and the oil passage connecting the hydraulic cylinder and the accumulator communicates, the hydraulic fluid of the accumulator flows into the hydraulic cylinder due to the difference between the pressure of the hydraulic cylinder (low pressure) and the pressure of the accumulator (high pressure) To do.

  In this case, according to the first feature of the present invention, the hydraulic oil is discharged from the hydraulic cylinder by the hydraulic oil operating means, whereas the hydraulic oil flows into the hydraulic cylinder from the accumulator, but by the hydraulic oil operating means. Since the hydraulic oil is drained from the hydraulic cylinder, it is difficult for the hydraulic cylinder to expand and contract at the moment when the on-off valve is operated to open.

(Effect of the invention)
According to a first aspect of the present invention, in a suspension structure for a work vehicle that includes a hydraulic cylinder and an accumulator, and the hydraulic cylinder operates as a suspension mechanism for a traveling wheel, the hydraulic cylinder and the accumulator are connected. When the oil passage is provided with an open / close valve that can be operated in an open state in which the hydraulic cylinder and the accumulator communicate with each other and in a closed state in which the hydraulic cylinder and the accumulator are shut off, the hydraulic cylinder when the open / close valve is operated in the open state As a result, it was possible to suppress the expansion and contraction of the aircraft, to suppress the change in the height of the aircraft, and to reduce the state where the driver felt uncomfortable, and to improve the ride comfort.

[II]
(Constitution)
The second feature of the present invention is that the work vehicle suspension structure of the first feature of the present invention is configured as follows.
First detection means for detecting the pressure of the hydraulic cylinder when the on-off valve is operated from the open state to the closed state, and second for detecting the pressure of the hydraulic cylinder when the on-off valve is operated from the closed state to the open state A detecting means,
When the on-off valve is operated from the closed state to the open state, if the difference between the detection values of the first and second detection means is larger than a preset value, the hydraulic oil operation means is operated, and the first And when the difference of the detection value of a 2nd detection means is smaller than the preset value set beforehand, the operation check means which stops a hydraulic-oil operation means is provided.

(Function)
As described in [I] above, when the on-off valve is operated to open and the oil passage connecting the hydraulic cylinder and the accumulator communicates, there is a large difference between the pressure of the hydraulic cylinder and the pressure of the accumulator. Then, due to this pressure difference, the hydraulic oil in the hydraulic cylinder flows into the accumulator (the hydraulic oil in the accumulator flows into the hydraulic cylinder).

According to the second feature of the present invention, when the on-off valve is operated from the open state to the closed state and then operated from the closed state to the open state, the hydraulic cylinder when the on-off valve is operated from the open state to the closed state The pressure of the hydraulic cylinder when the on-off valve is operated from the closed state to the open state is detected, and the difference between the detected pressures is detected.
If the detected pressure difference is large, it can be determined that there is a large difference between the pressure of the hydraulic cylinder and the pressure of the accumulator.In this case, when the on-off valve is operated to open, The hydraulic oil is supplied to the hydraulic cylinder by the hydraulic oil operating means (the hydraulic oil in the hydraulic cylinder is discharged by the hydraulic oil operating means), and the expansion / contraction operation of the hydraulic cylinder is suppressed.

If the detected pressure difference is small, it can be determined that there is no significant difference between the hydraulic cylinder pressure and the accumulator pressure, and the hydraulic oil from the hydraulic cylinder to the accumulator can be operated even if the open / close valve is opened. Inflow (inflow of hydraulic oil from the accumulator to the hydraulic cylinder) is unlikely to occur. In this state, when hydraulic oil is supplied to the hydraulic cylinder by the hydraulic oil operating means (the hydraulic oil from the hydraulic cylinder is discharged by the hydraulic oil operating means). The hydraulic cylinder expands and contracts.
According to the second feature of the present invention, if the detected pressure difference is small, hydraulic oil is not supplied to the hydraulic cylinder (hydraulic cylinder hydraulic oil is not discharged), so the hydraulic cylinder does not expand and contract.

(Effect of the invention)
According to the second feature of the present invention, when there is no significant difference between the pressure of the hydraulic cylinder and the pressure of the accumulator when the on-off valve is operated in the open state, the hydraulic oil operating means actuates the hydraulic cylinder. By preventing the supply of oil (discharge of hydraulic oil from the hydraulic cylinder by the hydraulic oil operating means), unnecessary expansion and contraction of the hydraulic cylinder can be suppressed, improving riding comfort. I was able to.

[1]
As shown in FIG. 1, a tractor, which is an example of a work vehicle, includes right and left front wheels 1 (corresponding to traveling wheels) and right and left rear wheels 2. The right and left rear wheels 2 are not supported by the transmission case 3 at the rear of the airframe via a suspension mechanism, but are supported in a fixed position.

  As shown in FIGS. 1, 2, and 4, a support frame 5 is connected to a lower portion of the engine 4 disposed at the front of the airframe and extends forward, and a support bracket 6 having a U-shape in side view is formed. Two hydraulic cylinders 7 are connected across the front part of the support frame 5 and the front part of the support bracket 6 so as to be swingable up and down around the horizontal axis P1 at the rear part of the support frame 5. Yes. A front axle case 8 is supported in a freely rolling manner around the front and rear axis P2 of the support bracket 6, and the right and left front wheels 1 are supported on the right and left sides of the front axle case 8.

[2]
Next, the hydraulic circuit structure of the hydraulic cylinder 7 will be described.
As shown in FIG. 3, the hydraulic cylinder 7 is configured as a double-acting type having an oil chamber 7a on the bottom side and an oil chamber 7b on the piston side. An oil passage 9 (corresponding to an oil passage connecting the hydraulic cylinder and the accumulator) connected to the oil chamber 7a of the hydraulic cylinder 7 is provided with a gas-filled accumulator 11 and a pair of pilot operated check valves 13 (open / close valves). And a relief valve 15 for protecting the hydraulic circuit is connected. A pilot-operated switching valve 17 having three kinds of orifices of “large”, “medium”, and “small” is provided in front of the accumulator 11, and a pilot valve 20 for operating the switching valve 17 is provided. ing. In the oil passage 9, a pressure sensor 36 is connected between the hydraulic cylinder 7 and the check valve 13, and the pressure of the oil chamber 7 a of the hydraulic cylinder 7 can be detected by the pressure sensor 36.

  As shown in FIG. 3, an oil passage 10 (corresponding to an oil passage connecting the hydraulic cylinder and the accumulator) connected to the oil chamber 7b of the hydraulic cylinder 7 is connected to a gas-filled accumulator 12 and a pair of pilot operation types. A check valve 14 (corresponding to an on-off valve) and a relief valve 16 for protecting the hydraulic circuit are connected.

  As shown in FIG. 3, the check valves 13 and 14 are provided with a pilot valve 19 for supplying and discharging pilot hydraulic oil, and the check valves 13 and 14 are closed by the pilot valve 19 (the hydraulic cylinder 7 is closed). (Corresponding to a state where the oil chambers 7a, 7b and the accumulators 11, 12 are shut off) and an open state (corresponding to a state where the oil chambers 7a, 7b of the hydraulic cylinder 7 and the accumulators 11, 12 are communicated) (accumulators 11, 12 From the oil chambers 7a, 7b of the hydraulic cylinder 7 and the oil chambers 7a, 7b of the hydraulic cylinder 7 to the accumulators 11, 12).

  As shown in FIG. 3, the hydraulic oil of the pump 30 is supplied to the control valve 18 via the filter 31, the diversion valve 32 and the check valve 33, and the relief valve is provided between the diversion valve 32 and the check valve 33. 34 is connected. An oil passage 21 is connected across the portion between the oil chamber 7a of the hydraulic cylinder 7 and the check valve 13 in the oil passage 9 and the control valve 18, and is opposite to the oil chamber 7b of the hydraulic cylinder 7 in the oil passage 10. An oil passage 22 is connected across the portion between the stop valve 14 and the control valve 18.

  As shown in FIG. 3, the control valve 18 supplies the operating oil to the oil passage 21 (the oil chamber 7 b of the hydraulic cylinder 7) and the oil passage 22 (the oil chamber 7 b of the hydraulic cylinder 7). A three-position switching type, that is, a lowered position 18D to be supplied and a neutral position 18N, is configured as a pilot operated type, and is provided with a pilot valve 29 for operating the control valve 18.

As shown in FIG. 3, a pilot operated check valve 23 and a throttle portion 25 are provided in the oil passage 21. The oil passage 22 is provided with a pilot operated check valve 24, a check valve 26 (the check valve 24 is on the oil passage 10 side and the check valve 26 is on the control valve 18 side), and a throttle portion 27. A relief valve 28 is connected between the stop valve 24 and the check valve 26 (throttle portion 27).
The pilot valves 19, 20, and 29 are electromagnetically operated, and the pilot valve 19 and the pilot valves 20, 29 are operated by the control device 35 as described in [3] to [9] described later and FIG. The check valves 13 and 14, the control valve 18 and the switching valve 17 are operated.

[3]
Next, the operation of the hydraulic cylinder 7 as a suspension mechanism will be described.
With the structure described in [2] above, as shown in FIG. 3, the control valve 18 is operated to the neutral position 18N and the check valves 13 and 14 are operated to the open state, depending on the unevenness of the ground. When the front axle case 8 and the support bracket 6 try to swing up and down around the horizontal axis P1, the hydraulic cylinder 7 expands and contracts and operates between the oil chambers 7a, 7b of the hydraulic cylinder 7 and the accumulators 11, 12. The oil reciprocates, and the hydraulic cylinder 7 operates as a suspension mechanism having a spring constant K1.

In this case, the pressure in the oil chamber 7b and the oil passage 10 of the hydraulic cylinder 7 is maintained at the set pressure MP1 by the relief valve 28. The pressure of the oil chamber 7a of the hydraulic cylinder 7 is PH, the pressure receiving area of the piston of the oil chamber 7a of the hydraulic cylinder 7 is AH, and the pressure receiving area of the piston of the oil chamber 7b of the hydraulic cylinder 7 is AR (for the piston rod, AR is AH If the weight applied to the front part of the airframe (the weight applied to the hydraulic cylinder 7) is M and the gravitational acceleration is g, the following equation (1) is established.
Formula (1) M * g = PH * AH-MP1 * AR

  Accordingly, the pressure MP1 of the oil chamber 7b of the hydraulic cylinder 7, the pressure receiving area AH of the piston of the oil chamber 7a of the hydraulic cylinder 7, and the pressure receiving area AR of the piston of the oil chamber 7b of the hydraulic cylinder 7 are constant. The pressure PH of the oil chamber 7a is higher than the pressure MP1 of the oil chamber 7b of the hydraulic cylinder 7, and varies depending on the weight (weight applied to the hydraulic cylinder 7) M applied to the front of the machine body.

  The spring constant K1 of the hydraulic cylinder 7 is determined by the pressures PH and MP1 of the oil chambers 7a and 7b of the hydraulic cylinder 7, and increases as the pressure PH of the oil chamber 7a of the hydraulic cylinder 7 increases. The pressure PH of the oil chamber 7a of the hydraulic cylinder 7 decreases as the pressure PH decreases. Therefore, the spring constant K1 of the hydraulic cylinder 7 is determined by the weight (weight applied to the hydraulic cylinder 7) M applied to the front portion of the airframe, and the weight applied to the front portion of the airframe (weight applied to the hydraulic cylinder 7) M is large. As it becomes larger, the weight applied to the front part of the airframe (weight applied to the hydraulic cylinder 7) M becomes smaller.

  As shown in FIG. 3, when the check valves 13 and 14 are operated in the closed state and the control valve 18 is operated to the raised position 18 U, hydraulic oil is supplied from the control valve 18 to the oil chamber 7 a of the hydraulic cylinder 7. Then, the hydraulic oil is discharged from the oil chamber 7 b of the hydraulic cylinder 7 through the check valve 24 (operated to be opened by the pilot hydraulic oil of the control valve 18) and the relief valve 28. In this case, the pressure in the oil chamber 7b and the oil passage 10 of the hydraulic cylinder 7 is maintained at the set pressure MP1 by the relief valve 28.

  As a result, the hydraulic cylinder 7 is extended and the front part of the airframe is raised (corresponding to a state in which the operation of the hydraulic cylinder 7 is changed to the airframe rising side). Thereafter, when the control valve 18 is operated to the neutral position 18N and the check valves 13 and 14 are operated to open, the hydraulic cylinder 7 operates as a suspension mechanism as described above with the hydraulic cylinder 7 extended. To do.

  As shown in FIG. 3, when the check valves 13 and 14 are operated to be closed and the control valve 18 is operated to the lowered position 18 </ b> D, hydraulic oil is supplied from the control valve 18 to the oil chamber 7 b of the hydraulic cylinder 7. Then, the hydraulic oil is discharged from the oil chamber 7 a of the hydraulic cylinder 7 through the check valve 23 (operated to be opened by the pilot pressure of the control valve 18), the throttle portion 25, and the control valve 18. In this case, the pressure in the oil chamber 7b and the oil passage 10 of the hydraulic cylinder 7 is maintained at the set pressure MP1 by the relief valve 28.

  As a result, the hydraulic cylinder 7 is contracted and the front part of the airframe is lowered (corresponding to a state where the operation of the hydraulic cylinder 7 is changed to the airframe lowering side). Thereafter, when the control valve 18 is operated to the neutral position 18N and the check valves 13 and 14 are operated to open, the hydraulic cylinder 7 operates as a suspension mechanism with the hydraulic cylinder 7 contracted as described above. To do.

As shown in FIGS. 3 and 6, the detection value of the pressure sensor 36 is input to the control device 35, and based on the detection value of the pressure sensor 36, the weight applied to the front portion of the machine body (the weight applied to the hydraulic cylinder 7). ) M is calculated.
As a result, when the weight applied to the front part of the machine body (weight applied to the hydraulic cylinder 7) M is increased by the working device attached to the front part of the machine body (for example, the soil is scooped up (loaded) by the bucket of the front loader) In addition, since the spring constant K1 of the hydraulic cylinder 7 is increased, the switching valve 17 is operated to the throttle side (the orifice portion side having a small diameter) and the hydraulic cylinder 7 is loaded. The damping force increases.

  When the weight applied to the front part of the machine body (weight applied to the hydraulic cylinder 7) M is reduced by the work device mounted on the front part of the machine body (for example, the state where the sand and sand have been discharged by the front loader, or the load was unloaded) State), the spring constant K1 of the hydraulic cylinder 7 decreases, and accordingly, the switching valve 17 is operated to the throttle side (orifice portion side having a large diameter), and the damping force of the hydraulic cylinder 7 decreases.

[4]
Next, the first half of the operation of the first attitude control means 41 of the hydraulic cylinder 7 will be described with reference to FIG.
As described in [3] above, in the state where the hydraulic cylinder 7 operates as a suspension mechanism, as shown in FIG. 6, the hydraulic cylinder 7 is operated to supply and discharge hydraulic oil to maintain the machine body substantially horizontally. One attitude control means 41 is provided in the control device 35. Hereinafter, the first half of the first attitude control means 41 will be described.

  As shown in FIG. 6, an operation position sensor 37 that detects an operation position (extension / contraction position) of the hydraulic cylinder 7 is provided, and a detection value of the operation position sensor 37 is input to the control device 35. The operating position (extension / contraction position) of the hydraulic cylinder 7 is stored. In this case, the telescopic operation position sensor 37 is directly attached to the hydraulic cylinder 7 to detect the operation position (extension position) of the hydraulic cylinder 7, or the rotary operation position sensor 37 is shown in FIG. The operating position (extension / contraction position) of the hydraulic cylinder 7 is detected by attaching the support bracket 6 to the support frame 5 and detecting the angle of the support bracket 6.

  As shown in FIG. 5, when the central position of the operation of the hydraulic cylinder 7 is set in the control device 35 and the operation position (extension position) of the hydraulic cylinder 7 is the central position, the airframe is substantially parallel to the ground (substantially horizontal). ) State. A target range H1 (corresponding to a reference position) having a certain range on the airframe ascending side and the airframe descending side with respect to the central position is set in the control device 35.

  The number of times of integration N is set in the control device 35. First, the number of times of integration N is set to “0” (step S1). In a state where the control valve 18 is operated to the neutral position 18N and the check valves 13 and 14 are opened (the hydraulic cylinder 7 operates as a suspension mechanism) (step S2), the control cycle T12 starts to be counted. (Step S3), the operating position (expanded position) of the hydraulic cylinder 7 is detected and stored (Step S4).

  When the control cycle T12 elapses (step S5) (see time point T2 in FIG. 5), the operating positions (extension positions) of all the hydraulic cylinders 7 past the set time T11 from time point T2 (see time point T2 to time point T1 in FIG. 5). ), The maximum position A1 and the minimum position A2 of the operation of the hydraulic cylinder 7 are detected (step S6), and the intermediate position B1 between the maximum and minimum positions A1, A2 (the center between the maximum and minimum positions A1, A2). Is detected (step S7).

  As shown in FIG. 5, the maximum position A1 is a position where the operating position of the hydraulic cylinder 7 is displaced to the body ascending side and then displaced to the body descending side (a position where the hydraulic cylinder 7 is switched from the extending operation to the contracting operation). . The minimum position A2 is a position (position where the hydraulic cylinder 7 switches from the contraction operation to the extension operation) after the operation position of the hydraulic cylinder 7 is displaced to the body lowering side and then displaced to the body raising side.

  In this case, the operation position (extension / contraction position) of the hydraulic cylinder 7 from the time when the previous control cycle T12 has elapsed to the time when the current control cycle T12 has elapsed (see time T2 in FIG. 5) The operation position (extension / contraction position) is stored as the operation position (extension / contraction position), and the previous operation position (extension / contraction position) of the hydraulic cylinder 7 from the time T1 past the set time T11 from the time T2 is erased. A part of the operation position (extension / contraction position) of the hydraulic cylinder 7 stored in the control device is updated.

In steps S5 and S6, if the set time T11 is set to be slightly longer than one period of the resonance frequency of the hydraulic cylinder 7, one maximum position A1 and one minimum position A2 are detected during the set time T11. In this case, the intermediate position B1 is detected from one maximum and minimum position A1, A2 (step S7).
In steps S5 and S6, when the set time T11 is set to be somewhat long, a plurality of maximum positions A1 and a plurality of minimum positions A2 are detected during the set time T11. In this case, the maximum maximum position A1 of the plurality of maximum positions A1 is detected, the minimum minimum position A2 of the plurality of minimum positions A2 is detected, and the maximum maximum position A1 and the minimum maximum position A2 are detected. An intermediate position B1 is detected from the minimum position A2 (step S7).

  When the intermediate position B1 is detected, the intermediate position B1 is compared with the target range H1 (step S8), and if the intermediate position B1 deviates from the target range H1 to the aircraft lowering side, the accumulated number N is “1”. Is subtracted (step S9), and if the intermediate position B1 deviates from the target range H1 to the aircraft ascending side, “1” is added to the cumulative number N (step S10). When the intermediate position B1 is within the target range H1, addition and subtraction to the integration number N are not performed. Next, the process proceeds to step S3, where steps S3 to S10 are performed, and the detection of the intermediate position B1, the comparison between the intermediate position B1 and the target range H1, the addition and subtraction of the number N of integrations are performed, and step S3 is again performed. Steps S3 to S10 are repeated.

[5]
Next, the second half of the operation of the first attitude control means 41 of the hydraulic cylinder 7 will be described with reference to FIG.
The controller 35 is set with the descending set number of times ND1 and the ascending side set number of times NU1, and each time it passes through steps S8, S9, S10, the integration number N, the descending side set number of times ND1, and the ascending side set number of times NU1 They are compared (steps S11 and S14).

  When the cumulative number N reaches the lower set number of times ND1 (below) (step S11), it is determined that the front part of the machine body is lowered and the machine body is in a front lowered state with respect to the ground. 14 is operated to the closed state (step S12), and the control valve 18 is operated to the raised position 18U (step S13).

  As a result, as described in [3] above, the hydraulic cylinder 7 expands and the fuselage is in a state where the pressure in the oil chamber 7b and the oil passage 10 of the hydraulic cylinder 7 is maintained at the set pressure MP1 by the relief valve 28. The front of the rises. When the hydraulic cylinder 7 is extended by an amount corresponding to the difference between the intermediate position B1 and the target range H1 (when the intermediate position B1 detected in the past for a set time from the present time enters the target range H1), the process proceeds to step S1. Thus, the cumulative number N is set to “0”, the control valve 18 is operated to the neutral position 18N, and the check valves 13 and 14 are opened (the hydraulic cylinder 7 operates as a suspension mechanism). Return to.

  When the cumulative number N reaches the rising side set number NU1 (exceeds) (step S14), the front part of the aircraft rises, and it is determined that the aircraft is in a front-up state with respect to the ground. 14 is operated to the closed state (step S15), and the control valve 18 is operated to the lowered position 18D (step S16).

  As a result, as described in [3] above, the hydraulic cylinder 7 contracts and the fuselage is operated while the pressure in the oil chamber 7b and the oil passage 10 of the hydraulic cylinder 7 is maintained at the set pressure MP1 by the relief valve 28. The front part of the descent. When the hydraulic cylinder 7 is contracted by an amount corresponding to the difference between the intermediate position B1 and the target range H1 (when the intermediate position B1 detected in the past for the set time from the present time enters the target range H1), the process proceeds to step S1. Thus, the cumulative number N is set to “0”, the control valve 18 is operated to the neutral position 18N, and the check valves 13 and 14 are opened (the hydraulic cylinder 7 operates as a suspension mechanism). Return to.

  As described above, even if steps S3 to S10 are repeated, the integration number N does not reach the lower set number ND1 (does not fall below) (step S11), and the up side integration number NU is set to the up side. If the number of times NU1 is not reached (does not exceed) (step S14), the control valve 18 is operated to the neutral position 18N and the check valves 13 and 14 are opened (the hydraulic cylinder 7 operates as a suspension mechanism). State) is maintained.

  As described above, in the first attitude control means 41, the control valve is controlled based on the cumulative number N reaching the lower side set number ND1 (below) and reaching the upper side set number NU1 (exceeded). 18 is operated to the raised position 18U and the lowered position 18D, the control valve 18 is operated less frequently to the raised position 18U and the lowered position 18D (the state in which the operation of the first attitude control means 41 is relatively insensitive). ).

[6]
Next, the flow of operation of the first and second attitude control means 41 and 42 and the first detection means 45 in a state where the traveling speed V of the aircraft is changed from high speed to low speed will be described with reference to FIG.
As shown in FIG. 6, the second attitude control means 42 and the first detection means 45 are provided in the control device 35. A traveling speed sensor 38 for detecting the traveling speed V of the aircraft is provided, and a detection value of the traveling speed sensor 38 is input to the control device 35 (step S21), and the traveling speed V of the aircraft is set in advance. If the speed is higher than the speed V1, the check valves 13 and 14 are operated to open, and the first attitude control means 41 (see the preceding paragraphs [4] and [5]) is operating.

  When the traveling speed V of the airframe is lower than the set speed V1 (step S22), the check valves 13 and 14 are operated to be closed (step S25), and the first attitude control means 41 is stopped (step S26). . When the check valves 13 and 14 are operated to be closed (step S25), the oil passages 9 and 10 connecting the oil chambers 7a and 7b of the hydraulic cylinder 7 and the accumulators 11 and 12 are shut off. 7 will be unable to expand and contract.

  At this time, immediately before the check valves 13, 14 are operated from the open state to the closed state, the oil chamber 7a of the hydraulic cylinder 7 and the pressure A1 of the accumulator 11 (when the on-off valve is operated from the open state to the closed state). (Corresponding to the pressure of the hydraulic cylinder) is detected and stored by the pressure sensor 36 and the first detecting means 45 (step S24).

  For example, when a driver brakes a brake (not shown) in order to stop the airframe while traveling at high speed, the airframe is in a state where the front part of the airframe is lowered due to inertia (the hydraulic cylinder 7 is contracted). The traveling speed V of the vehicle may be reduced and exceed the set speed V1. When the check valves 13 and 14 are operated to be closed in such a state, the hydraulic cylinder 7 cannot be expanded and contracted with the front portion of the fuselage lowered.

In this case, when the traveling speed V of the airframe becomes lower than the set speed V1 and the check valves 13 and 14 are operated in the closed state, the second posture control means 42 starts operating (step S27). The operating position (expanded position) of the hydraulic cylinder 7 is detected by the operating position sensor 37 by the second attitude control means 42 (step S28), and the operating position (expanded position) of the hydraulic cylinder 7 falls within the target range H1. The control valve 18 is operated to the ascending and descending positions 18U and 18D (step S29).
The second posture control means 42 operates sufficiently sensitively compared to the first posture control means 41 because the operation position (extension / contraction position) of the hydraulic cylinder 7 and the target range H1 are directly compared. The aircraft immediately returns to a state substantially parallel (substantially horizontal) to the ground.

[7]
Next, in the first and second attitude control means 41, 42, the hydraulic oil operation means 43, the operation check means 44, and the second detection means 46, the state in which the traveling speed V of the airframe increases from low to high is shown in FIGS. 10 will be described.

  As shown in FIG. 6, the hydraulic oil operation means 43, the operation check means 44, and the second detection means 46 are provided in the control device 35. In the state where the aircraft traveling speed V is low (see [6] in the previous section), when the aircraft traveling speed V becomes higher than the set speed V1 (step S22), the check valves 13 and 14 are operated to open. (Steps S44, S52, S59) (time T10 in FIG. 10).

At this time, the pressure A2 in the oil chamber 7a of the hydraulic cylinder 7 immediately before the check valves 13 and 14 are operated from the closed state to the open state (the hydraulic cylinder when the on-off valve is operated from the closed state to the open state). (Corresponding to pressure) is detected and stored by the pressure sensor 36 and the second detection means 46 (step S41).
The pressure A1 of the hydraulic cylinder 7 and the accumulator 11 immediately before the check valves 13 and 14 are operated from the open state to the closed state (see [6] in the previous section), and the check valves 13 and 14 from the closed state. The pressure A2 in the oil chamber 7a of the hydraulic cylinder 7 immediately before being operated to the open state is compared, and a difference A3 (A2-A1) is detected (step S42).

  If the difference A3 is between the preset value (−A4) and the preset value (A4), it is determined that the difference between the pressure in the oil chamber 7a of the hydraulic cylinder 7 and the pressure in the accumulator 11 is small ( Step S43), the second attitude control means 42 (refer to the previous item [6]) stops (Step S60), and the first attitude control means 41 (refer to the previous items [4] and [5]) starts operating (Step S61). (Equivalent to the state in which the hydraulic oil operating means is stopped by the operating check means).

If the difference A3 is larger than a preset value (A4), it is determined that the pressure in the oil chamber 7a of the hydraulic cylinder 7 is high and the pressure in the accumulator 11 is low (step S43).
In such a state, for example, when a front loader (not shown) is provided at the front part of the aircraft, the check valve 13, 14 is set as described in [6] above when the front loader bucket is empty. It is operated in the closed state (step S25), and after that, the sand load is picked up (loaded) by the bucket of the front loader, and the weight applied to the front part of the machine body is increased by the weight of the soil, and the oil chamber 7a of the hydraulic cylinder 7 is increased. However, it is assumed that the accumulator 11 is maintained at a low pressure.

If the difference A3 is smaller than the preset value (−A4), it is determined that the pressure in the oil chamber 7a of the hydraulic cylinder 7 is low and the pressure in the accumulator 11 is high (step S43).
For example, when a front loader (not shown) is provided at the front part of the aircraft, this state is a state in which earth and sand are scooped up (loaded) on the bucket of the front loader, as described in [6] above. The valves 13 and 14 are operated to the closed state (step S25), and thereafter the sand and sand in the bucket of the front loader is discharged, the weight applied to the front part of the machine body is reduced, and the pressure in the oil chamber 7a of the hydraulic cylinder 7 is low. However, it is assumed that the accumulator 11 is maintained at a high pressure.

[8]
Next, following the previous item [7], in the first and second attitude control means 41, 42, the hydraulic oil operation means 43, the operation check means 44, and the second detection means 46, the traveling speed V of the airframe increases from low to high. With regard to the flow of operation in a state where the pressure of the oil chamber 7a of the hydraulic cylinder 7 is high and the pressure of the accumulator 11 is low (the difference A3 is larger than the set value (A4)) in FIG. And it demonstrates based on FIG.

  When the check valves 13 and 14 are operated to open (step S44), the timer counts the first and second set times T1 and T2 (the second set time T2 is longer than the first set time T1). The operation is started (step S45), the operation signal (upward position 18U) of the control valve 18 is output by the hydraulic oil operating means 43 (step S46), and the control valve 18 is operated to the up position 18U (time T10 in FIG. 10). (When the on-off valve is operated from the closed state to the open state, when the difference between the detection values of the first and second detection means is larger than the preset value, the hydraulic oil is operated by the operation check means. Equivalent to the state in which the means is activated).

  As described above, when the check valve 13 or 14 is opened while the pressure of the oil chamber 7a of the hydraulic cylinder 7 is high and the pressure of the accumulator 11 is low, the hydraulic pressure is increased as shown in FIG. Due to the difference between the pressure (high pressure) in the oil chamber 7a of the cylinder 7 and the pressure (low pressure) in the accumulator 11, the hydraulic oil in the oil chamber 7a of the hydraulic cylinder 7 flows into the accumulator 11 via the oil passage 9, and the hydraulic cylinder 7 tries to contract. In this case, when the control valve 18 is operated to the raised position 18U, the hydraulic oil of the hydraulic pump 30 is supplied to the oil chamber 7a of the hydraulic cylinder 7 through the control valve 18 (lifted position 18U) and the oil passage 21. Therefore, it is difficult for the hydraulic cylinder 7 to expand and contract at the moment when the check valves 13 and 14 are operated to the open state.

  Even if the check valves 13 and 14 are operated in the open state (step S44), the second posture control means 42 maintains the operation until the first set time T1 elapses (step S47). Since the first set time T1 is relatively short, even if it can be said that the second posture control means 42 maintains the operation between the time points T10 and T11 in FIG. Only by performing a direct comparison between the expansion / contraction position and the target range H1 (see [6] in the previous section), the operation signal for the control valve 18 (the raised position 18U) is output by the second attitude control means 42. Absent.

  When the first set time T1 has elapsed (step S47), the second attitude control means 42 outputs an operation signal (upward position 18U) for the control valve 18 (step S48). The operation signal (upward position 18U) of the control valve 18 of the hydraulic oil operating means 43 and the operation signal (upward position 18U) of the control valve 18 of the second attitude control means 42 overlap, but the control valve 18 It is only maintained at the raised position 18U, and there is no problem (time points T11 and T12 in FIG. 10).

  When the first set time T1 elapses (step S47), the first attitude control means 41 (see the preceding paragraphs [4] and [5]) starts operating (step S49). Since the operation of the first attitude control means 41 is relatively insensitive as described in the preceding items [4] and [5], even if the first attitude control means 41 starts to operate, the first attitude control means still remains. 41 does not output the operation signal of the control valve 18 (time T11 in FIG. 10).

  When the second set time T2 elapses (step S50), the operation signal (upward position 18U) of the control valve 18 of the hydraulic oil operation means 43 stops (step S51) (time T12 in FIG. 10). In the second attitude control means 42, the control valve 18 is maintained at the raised position 18U until the operation position (extension / contraction position) of the hydraulic cylinder 7 enters the target range H1 (see [6] in the previous section). Even after T2 has elapsed (step S50), the operation signal (upward position 18U) of the control valve 18 is often output by the second attitude control means 42, and the operating position (expanded position) of the hydraulic cylinder 7 is the target. When entering the range H1, the operation signal (the raised position 18U) of the control valve 18 of the second attitude control means 42 stops (the second attitude control means 42 stops) (time T13 in FIG. 10).

  When the operation signal (upward position 18U) of the control valve 18 of the second attitude control means 42 stops, the operation signal of the control valve 18 is output by the first attitude control means 41. From the stop of the posture control means 42 to the operation of the first posture control means 41, a state is established in which there is no break.

[9]
Next, following the previous item [7], in the first and second attitude control means 41, 42, the hydraulic oil operation means 43, the operation check means 44, and the second detection means 46, the traveling speed V of the airframe increases from low to high. In the state where the pressure of the oil chamber 7a of the hydraulic cylinder 7 is low and the pressure of the accumulator 11 is high (the difference A3 is smaller than the set value (−A4)), 9 and FIG.

  When the check valves 13 and 14 are operated to open (step S52), the timer counts the first and second set times T1 and T2 (the second set time T2 is longer than the first set time T1). The operation is started (step S53), the operation signal (lowering position 18D) of the control valve 18 is output by the hydraulic oil operating means 43 (step S54), and the control valve 18 is operated to the lowering position 18D (time T10 in FIG. 10). (When the on-off valve is operated from the closed state to the open state, if the difference between the detection values of the first and second detection means is smaller than a preset value, the hydraulic oil is operated by the operation check means. Equivalent to the state in which the means is activated).

  As described above, when the pressure in the oil chamber 7a of the hydraulic cylinder 7 is low, the pressure of the accumulator 11 is high, and the check valves 13 and 14 are operated to open, as shown in FIG. Due to the difference between the pressure (low pressure) in the oil chamber 7 a of the cylinder 7 and the pressure (high pressure) in the accumulator 11, the hydraulic oil in the accumulator 11 flows into the oil chamber 7 a of the hydraulic cylinder 7 through the oil passage 9. 7 tries to extend. In this case, when the control valve 18 is operated to the lowered position 18D, the hydraulic oil is discharged from the oil chamber 7a of the hydraulic cylinder 7 through the oil passage 22 and the control valve 18 (the lowered position 18D). It is difficult for the hydraulic cylinder 7 to be extended at the moment when the stop valves 13 and 14 are operated to the open state.

  Even if the check valves 13 and 14 are operated in the open state (step S52), the second posture control means 42 maintains the operation until the first set time T1 elapses (step S55). Since the first set time T1 is relatively short, even if it can be said that the second posture control means 42 maintains the operation between the time points T10 and T11 in FIG. Only by performing a direct comparison between the expansion / contraction position and the target range H1 (see [6] in the previous section), the operation signal of the control valve 18 (the lowered position 18D) is output by the second posture control means 42. Absent.

  When the first set time T1 has elapsed (step S55), the second attitude control means 42 outputs an operation signal (lowering position 18D) for the control valve 18 (step S56). The operation signal (lowering position 18D) of the control valve 18 of the hydraulic oil operating means 43 and the operation signal (lowering position 18D) of the control valve 18 of the second attitude control means 42 overlap, but the control valve 18 It is only maintained at the lowered position 18D, and there is no problem (time points T11 and T12 in FIG. 10).

  When the first set time T1 elapses (step S55), the first attitude control means 41 (see the preceding paragraphs [4] and [5]) starts operating (step S57). Since the operation of the first attitude control means 41 is relatively insensitive as described in the preceding items [4] and [5], even if the first attitude control means 41 starts to operate, the first attitude control means still remains. 41 does not output the operation signal of the control valve 18 (time T11 in FIG. 10).

  When the second set time T2 elapses (step S58), the operation signal (lowering position 18D) of the control valve 18 of the hydraulic oil operation means 43 stops (step S51) (time T12 in FIG. 10). In the second attitude control means 42, the control valve 18 is maintained at the lowered position 18D until the operating position (extension / contraction position) of the hydraulic cylinder 7 enters the target range H1 (see [6] in the previous section). Even after T2 has elapsed (step S58), the operation signal (lowering position 18D) of the control valve 18 is often output by the second attitude control means 42, and the operating position (expanded position) of the hydraulic cylinder 7 is the target. When entering the range H1, the operation signal (lowering position 18D) of the control valve 18 of the second attitude control means 42 stops (the second attitude control means 42 stops) (time T13 in FIG. 10).

  When the operation signal of the control valve 18 (the lowered position 18D) of the second attitude control means 42 stops, the operation signal of the control valve 18 is output by the first attitude control means 41, and the second From the stop of the posture control means 42 to the operation of the first posture control means 41, a state is established in which there is no break.

[First Alternative Embodiment of the Invention]
In steps S4 to S8 in FIG. 7 of the above-mentioned [Best Mode for Carrying Out the Invention], the set time T11 is set slightly longer to detect a plurality of maximum positions A1 and a plurality of minimum positions A2. In this case, the intermediate position B1 in step S8 in FIG. 7 may be detected as follows.

(1) In a plurality of maximum positions A1 and a plurality of minimum positions A2, one maximum position A1 and one minimum position A2 are set as one set, and a plurality of sets of maximum and minimum positions A1 and A2 are obtained. Separately, by detecting the intermediate position B1 in each group, a plurality of intermediate positions B1 are detected, and the average value of the plurality of intermediate positions B1 is set as the intermediate position B1 in step S8 of FIG.

(2) The average value of the maximum position A1 is detected at the plurality of maximum positions A1, the average value of the minimum position A2 is detected at the plurality of minimum positions A2, and the intermediate position is determined from the average value of the maximum and minimum positions A1 and A2. B1 is detected and set as an intermediate position B1 in step S8 of FIG.

[Second Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention] [First Alternative Embodiment], the intermediate position B1 is not set at the center position between the maximum and minimum positions A1 and A2, but the airframe. The intermediate position B1 is slightly raised from the central position between the maximum and minimum positions A1 and A2 (hydraulic cylinder) based on the presence or absence of the work device (for example, front loader) attached to the front part of the 7), or the intermediate position B1 is set to a position slightly lower from the center between the maximum and minimum positions A1 and A2 (on the contraction side of the hydraulic cylinder 7). Also good.
For example, when a work device (for example, a front loader) is mounted on the front of the machine body, the intermediate position B1 is slightly raised from the center position between the maximum and minimum positions A1 and A2 (the extension side of the hydraulic cylinder 7). By setting to, the aircraft should be raised slightly forward relative to the ground.

[Third Another Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention] [First Alternative Embodiment] [Second Alternative Embodiment], the maximum position at the set time T11 is used instead of the maximum position A1. Alternatively, the minimum position at the set time T11 may be used instead of the minimum position A2. Instead of the check valves 13 and 14, an open / close valve (not shown) for sliding or rotating the spool may be used. [Best Mode for Carrying Out the Invention] to [Third Alternative Embodiment of the Invention] may be applied to the rear wheel 2.

Overall side view of tractor Side view of the front axle case, support bracket, and hydraulic cylinder Diagram showing hydraulic circuit structure of hydraulic cylinder Perspective view of support bracket The figure which shows the state of the operation position (extension position) of a hydraulic cylinder Diagram showing the relationship between the control device and the pilot valve The figure which shows the flow of an action | operation of a 1st attitude | position control means. The figure which shows the flow of an action | operation in the state (the 1st attitude | position control means stops and the 2nd attitude | position control means act | operates) in which the traveling speed of the body is low. The figure which shows the flow of an action | operation in the state (The 1st attitude | position control means act | operates and the 2nd attitude | position control means stops) where the traveling speed of the body is high. The figure which shows the action | operation of a non-return valve, a 1st and 2nd attitude | position control means, and a hydraulic oil operation means in the state from which the running speed of a body changes from low speed to high speed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wheel for driving | running | working 7 Hydraulic cylinder 9,10 Oil path 11,12 Accumulator 13,14 On-off valve 43 Hydraulic oil operation means 44 Operation | movement check means 45 1st detection means 46 2nd detection means A4 Set value H1 Reference position

Claims (2)

A traveling wheel is supported via a hydraulic cylinder, the hydraulic cylinder and an accumulator are connected, and hydraulic oil is configured to reciprocate between the hydraulic cylinder and the accumulator. A suspension structure for a work vehicle configured to operate as a suspension mechanism for a wheel,
An oil passage connecting the hydraulic cylinder and the accumulator is provided with an open / close valve that can be operated in an open state in which the hydraulic cylinder and the accumulator communicate with each other and a closed state in which the hydraulic cylinder and the accumulator are shut off,
When the on-off valve is operated from the closed state to the open state, the hydraulic oil is supplied to or discharged from the hydraulic cylinder, and the hydraulic cylinder is operated to a preset reference position side. A suspension structure for a work vehicle provided with oil operating means. First detecting means for detecting the pressure of the hydraulic cylinder when the on-off valve is operated from the open state to the closed state, and detecting the pressure of the hydraulic cylinder when the on-off valve is operated from the closed state to the open state A second detection means,
When the on-off valve is operated from the closed state to the open state, if the difference between the detection values of the first and second detection means is larger than a preset value, the hydraulic oil operation means is operated. 2. The work vehicle according to claim 1, further comprising an operation check unit that stops the hydraulic oil operation unit when a difference between detection values of the first and second detection units is smaller than a preset set value. Suspension structure.

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