JP4436241B2 - Construction vehicle - Google Patents

Description

  The present invention relates to a construction vehicle.

  As shown in FIG. 9, a construction vehicle such as a wheel loader includes a vehicle body 51 and a work machine 52 protruding from the vehicle body 51. The work implement 52 includes a boom 21 projecting forward from the vehicle body 51 and a bucket 54 attached to the tip of the boom 21, and the vehicle body 51 and the boom 21 are connected via the boom cylinder 12. Has been. Further, the boom 21 and the bucket 54 are connected by a bucket cylinder 57 via a link 56. For this reason, the boom 21 swings around the pivot 58 on the vehicle body 51 side when the boom cylinder 12 expands and contracts, and the bucket 54 centers around the pivot 59 when the bucket cylinder 57 expands and contracts. Swing.

  By the way, in construction vehicles such as the wheel loader described above, the work implement 52 projects forward from the front axle, the weight ratio is large, the axle is unbuffered, and the whole is supported by rubber tires. For this reason, the vehicle body tends to generate vibrations when traveling on a raised road surface. In order to absorb the vibration energy and attenuate the vibration, there is a conventional one that can exhibit a traveling damper function (for example, see Patent Document 1).

  As shown in FIG. 10, the traveling vibration suppression circuit described in Patent Document 1 includes a boom cylinder 12 and a bucket cylinder 57, and is connected to a discharge circuit 63 of a work machine hydraulic pump 62 via a work machine operation valve 64. The boom cylinder 12 and the bucket cylinder 57 are connected. The circuit 66 that connects the accumulator 65 and the bottom side of the boom cylinder 12 is provided with a first on-off valve 67, and the circuit 69 that connects the head side of the boom cylinder 12 and the oil tank 68 has a solenoid valve 70. Is installed. A check valve 70 a is provided in the lower position of the solenoid valve 70. Further, a second on-off valve 73 is interposed in a circuit 72 branched from the discharge circuit 63 of the hydraulic pump 62 and connected to the accumulator 65, and a pressure switch 74 is provided between the accumulator 65 and the second on-off valve 73. It has been. A check valve 73 a is provided at the position of the second on-off valve 73. Further, a travel damper operation changeover switch 75 is provided, and this changeover switch 75 is connected to the controller 76. Reference numeral 77 is a shift control switch, and 78 is a vehicle speed sensor.

In this case, when the traveling speed reaches a predetermined speed, the bottom side of the boom cylinder 12 and the accumulator 65 communicate with each other and the traveling damper is activated. That is, the travel damper operation changeover switch 75 is operated to turn on the travel damper, and when the travel speed exceeds a predetermined speed, the controller 76 that receives a signal from the vehicle speed sensor 78 transmits a command signal to transmit the first on-off valve. 67 is opened (a position), the second on-off valve 73 is closed (b), and the solenoid valve 70 is opened (b). Accordingly, the bottom side of the boom cylinder 12 and the accumulator 65 communicate with each other, the head side of the boom cylinder 12 communicates with the oil tank 68, and the accumulator 65 exhibits a vibration suppressing function.
JP-A-9-78633

  By the way, with this kind of tractor excavator, the leveling work (grading work) as shown in FIG. 11 may be performed. That is, the boom 21 is placed on the ground with the head side and the bottom side of the boom cylinder 12 in the tank open state (the boom 21 can move freely with external force and is in a so-called floating state), and the arrow Retreat like A. Thereby, the boom 21 can slide on the ground to form the leveling surface B. Further, when the grading operation is performed in the traveling damper operating state, the head side of the boom cylinder 12 and the accumulator 65 are both in communication with the oil tank 68. When moving forward after grading work, it is necessary to raise the boom 21 and make it float from the ground. However, when the boom 21 is raised only slightly, the supply of pressure oil to the accumulator 65 is insufficient. there's a possibility that. In this case, the boom 21 may drop at the moment when the traveling speed is reached and the bottom side of the boom cylinder 12 communicates with the accumulator 65 and the navigation damper is activated.

  The present invention has been made to solve the above-described conventional drawbacks, and an object of the present invention is to provide a construction vehicle capable of avoiding a boom lowering even when a traveling damper function is activated during traveling. is there.

Therefore, the construction vehicle of claim 1 includes a boom cylinder,
A hydraulic source;
A hydraulic oil tank;
The head side port of the boom cylinder, the bottom side port of the boom cylinder, the hydraulic source, and the hydraulic oil tank are switched, and the head side and the bottom side of the boom cylinder are both operated with hydraulic oil. A boom control valve having a floating position for communicating with the tank;
An accumulator,
A travel damper switching valve having a damper operating position in which the accumulator and the bottom side of the boom cylinder are in communication with each other;
In a construction vehicle having a controller that controls the operation of the travel damper switching valve based on a predetermined condition,
Detecting means for detecting that the boom control valve is in a floating position;
When the detection means detects that the boom control valve is in the floating position, it is provided with prohibiting means for prohibiting the traveling damper switching valve from being in the damper operating position.

In the construction vehicle according to claim 2, the boom control valve is a pilot operated valve whose position is changed by receiving a pilot pressure,
The detecting means detects a pilot pressure input to the boom control valve when the bottom of the boom cylinder is in communication with the hydraulic oil tank.

The construction vehicle according to claim 3 has an operation lever that is operated by an operator to move the boom cylinder, and the detection means detects the floating position based on the operation position of the operation lever. It is a feature.

  According to the construction vehicle of the present invention, when the prohibiting means detects that the boom control valve is in the floating position, the traveling damper switching valve is prohibited from being in the damper operating position. Therefore, it is possible to prevent the boom from being lowered without being in the damper operating position.

  Next, specific embodiments of the construction vehicle of the present invention will be described in detail with reference to the drawings, taking a wheel loader as an example. FIG. 1 is a schematic view showing a main part of the first embodiment. As shown in FIG. 9, the construction vehicle includes a vehicle body 51 and a work machine 52 protruding from the vehicle body 51. The work implement 52 includes a boom 21 projecting forward from the vehicle body 51 and a bucket 54 attached to the tip of the boom 21, and the vehicle body 51 and the boom 21 are connected via the boom cylinder 12. Has been. Further, the boom 21 and the bucket 54 are connected by a bucket cylinder 57 via a link 56. For this reason, the boom 21 swings around the pivot 58 on the vehicle body 51 side when the boom cylinder 12 expands and contracts, and the bucket 54 centers around the pivot 59 when the bucket cylinder 57 expands and contracts. Swing.

  Further, as shown in FIG. 1, the construction vehicle includes the traveling damper circuit 1 and the work machine drive circuit 2. The travel damper circuit 1 includes a travel damper switch 3, a controller 4, a travel damper solenoid relay 5, and a travel damper solenoid valve 6 as a travel damper switching valve 32. A pressure switch 7 is interposed between the travel damper switch 3 and the controller 4. Furthermore, an accumulator 8 is connected to the travel damper solenoid valve 6 via a flow path 9.

  The work machine drive circuit 2 includes a hydraulic pump 10 that constitutes a hydraulic power source 30, a switching valve 11 as a boom control valve 31, a boom cylinder 12, a boom lever (operation lever) 13, and the like. In this case, the hydraulic pump 10 and the switching valve 11 are connected by the flow path 14, the switching valve 11 and the head 12 a side of the boom cylinder 12 are connected by the flow path 15, and the switching valve 11 and the travel damper solenoid valve 6 are connected. Are connected by a flow path 16, and the bottom 12 b side of the boom cylinder 12 and the flow path 16 are connected by a flow path 17. Further, the switching valve 11 and the hydraulic oil tank 18 are connected by a flow path 19. The switching valve 11 is of a pilot operation type, and is switched to four states, i.

  That is, when the switching valve 11 is in the state of (i) (the floating position), the oil discharged from the hydraulic pump 10 is blocked by the switching valve 11 and is not supplied to the boom cylinder 12 and the like, and the flow paths 15 and 17 are activated. It is connected to a flow path 19 connected to the oil tank 18. For this reason, in the state of (a), the boom cylinder 12 is in a state where the tank 12 is opened on the head 12a side and the bottom 12b side, and the boom 21 is lowered to the ground surface and can be freely moved by external force. When the switching valve 11 is in the low state (boom lowering position), the flow path 14 and the flow path 15 are connected, and the flow path 17 and the flow path 19 are connected. Therefore, the oil discharged from the hydraulic pump 10 is supplied to the head 12a side of the boom cylinder 12 via the flow path 17, and the tank cylinder is opened on the bottom 12b side of the boom cylinder 12, and the piston rod 20 of the boom cylinder 12 is The boom 21 is retracted and the boom 21 is lowered.

  Further, when the switching valve 11 is in the state of C (boom stop position), the flow paths 14, 15, 17, and 19 are blocked. Further, in the state where the switching valve 11 is in the d (boom raising position), the flow path 14 and the flow path 17 are connected, and the flow path 19 and the flow path 15 are connected. For this reason, the oil discharged from the hydraulic pump 10 is supplied to the bottom 12b side of the boom cylinder 12 via the flow path 17, and the head 12a side of the boom cylinder 12 is in the tank open state, so that the piston rod 20 of the boom cylinder 12 is It will extend and the boom 21 will rise.

  A circuit 25 is connected to the flow path 14 and the travel damper solenoid valve 6. The circuit 25 is provided with a pressure reducing valve 26 and a check valve 27, and the hydraulic pressure from the hydraulic pump 10 is supplied to the accumulator 8 with the traveling damper solenoid valve 6 in the low state. The circuit 25 is connected to a relief valve 28, a tank 29, and the like.

  The travel damper switch 3 is provided for the operator to switch the travel damper on (actuated) and off (non-actuated), and is configured to be grounded at the ON position, and the controller 4 is switched via the pressure switch 7. It is connected to the signal input unit 4a. The pressure switch 7 is a normally closed switch that detects the hydraulic pressure of the pilot oil passage 11a connected to the switching valve 11, and when a predetermined pressure is generated in the oil passage 11a for setting the switching valve 11 to the position a. The pressure switch 7 is opened. When the travel damper switch 3 is in the ON position and the pressure switch 7 is in the closed state, the potential of the switching signal input portion 4a of the controller 4 is low, otherwise it is high. Therefore, the pressure switch 7 used in the present embodiment corresponds to the detection unit and the prohibition unit in the present invention. The controller 4 sends a damper ON command to the travel damper solenoid relay 5 based on the potential of the switching signal input unit 4a and a vehicle speed signal detected by a vehicle speed detection means (not shown).

  FIG. 2 is a diagram showing a control flow by the controller 4 in the first embodiment. As shown in FIG. 2, the controller 4 sends a damper ON command when the voltage of the switching signal input unit 4a is low and the vehicle speed is, for example, 5 km / h or more. When the voltage of the switching signal input unit 4a is a high voltage or when the vehicle speed is less than 5 km / h even at a low potential, the controller 4 does not send a damper ON command.

  Returning to FIG. 1, when the damper ON command from the controller 4 is input, the traveling damper solenoid relay 5 switches the traveling damper solenoid valve 6 to the A position. At this time, the bottom 12b of the boom cylinder 12 communicates with the accumulator 8. The travel damper is activated. The traveling damper solenoid relay 5 switches the traveling damper solenoid valve 6 to the low position when no damper ON command is input from the controller 4, and at this time, the bottom 12b of the boom cylinder 12 is disconnected from the accumulator 8 and the traveling damper is in an inoperative state. It becomes.

  Next, the operation in this embodiment will be described. First, the case where the traveling damper switch 3 is OFF will be described. In this case, the voltage of the switching signal input portion 4a of the controller 4 becomes a high potential, and the controller 4 does not send a damper ON command from the traveling damper solenoid relay 5, whereby the traveling damper solenoid valve 6 is in the low position, and the boom cylinder 12 bottom 12b is cut off from the accumulator 8, and the traveling damper is inactivated.

  A case where the travel damper switch 3 is ON and the boom lever 13 is in the floating position will be described. In this case, the pressure switch 7 is opened, the voltage of the switching signal input unit 4a of the controller 4 becomes high potential, and the damper ON command is not sent from the controller 4 to the travel damper solenoid relay 5. As a result, the travel damper solenoid valve 6 is set to the low position, and the bottom 12b of the boom cylinder 12 is disconnected from the accumulator 8, and the travel damper is inactivated.

  A case where the travel damper switch 3 is ON and the boom lever 13 is in a position other than the floating position will be described. In this case, the pressure switch 7 is closed and the voltage of the switching signal input unit 4a of the controller 4 becomes a low potential. When the vehicle speed is less than 5 km / h, no damper ON command is sent from the controller 4 to the travel damper solenoid relay 5, the travel damper solenoid valve 6 is in the low position, and the bottom 12b of the boom cylinder 12 is disconnected from the accumulator 8. The traveling damper is inactive. When the vehicle speed is 5 km / h or higher, the controller 4 sends a damper ON command to the travel damper solenoid relay 5, the travel damper solenoid valve 6 is set to the A position, and the bottom 12 b of the boom cylinder 12 communicates with the accumulator 8. The travel damper is activated.

  Therefore, even after the floating work (after the leveling work), the boom 21 is raised to travel (forward), and the traveling damper circuit 1 maintains the pressure before the floating work even if the traveling damper is activated during the traveling. Therefore, the boom 21 can be avoided from descending.

  Next, FIGS. 3 and 4 show a modification of the first embodiment. FIG. 3 shows a first modification of the first embodiment. In the first modification shown in FIG. 3, the pressure switch 7 is a normally open switch, and the relay 22 is used to perform the same operation as the normally closed switch. That is, when the hydraulic pressure in the pilot oil passage 11a is increased and the pressure switch 7 is closed, the voltage of the switching signal input portion 4a of the controller 4 remains high regardless of whether the travel damper switch 3 is turned on or off by the operation of the relay 22. It becomes. Therefore, this modification also performs the same operation as in the first embodiment. In the first modification, the pressure switch 7 corresponds to both the detecting means and the prohibiting means in the present invention, and the relay 22 also constitutes a part of the prohibiting means.

  FIG. 4A is a second modification of the first embodiment, and FIG. 4B is a third modification of the first embodiment. In the second modification shown in FIG. 4 (a), a normally closed switch is used as the pressure switch 7, and a damper ON command sent from the controller 7 is sent when the hydraulic pressure in the pilot oil passage 11a increases and the pressure switch 7 is opened. It is configured to block. Therefore, this modification also performs the same operation as in the first embodiment. In the second modification, the pressure switch 7 corresponds to both the detection means and the prohibition means in the present invention.

  In the third modification shown in FIG. 4B, a normally open switch is used as the pressure switch 7 and the relay 22 is used to perform the same operation as in the second modification. That is, when the oil pressure of the pilot oil passage 11a increases and the pressure switch 7 is closed, the damper ON command sent from the controller 4 is cut off by the operation of the relay 22. Therefore, this modification also performs the same operation as in the first embodiment. In the third modification, the pressure switch 7 corresponds to both the detecting means and the prohibiting means in the present invention, and the relay 22 also constitutes a part of the prohibiting means.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a simplified view of the main part showing the second embodiment, and FIG. 6 is a diagram showing a control flow by the controller in the second embodiment.

  As shown in FIG. 5, in the second embodiment, the proximity switch 13a is provided on the boom lever (operation lever) 13, and the proximity switch ON signal is sent to the controller 4 when the operation lever 13 is tilted to the floating position. The proximity switch OFF signal is sent out except at the sending and floating positions. In the present embodiment, since the proximity switch 13a is provided instead of the pressure switch 7 and the control flow by the controller 4 is not different from that of the first embodiment, the first embodiment shown in FIG. The same components as those of the embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the second embodiment, as shown in FIG. 6, the controller 4 receives the OFF signal from the proximity switch 13a and the vehicle speed is 5 km / h when the voltage of the switching signal input unit 4a is low. When this is the case, a damper ON command is sent. When the voltage of the switching signal input unit 4a is high, or when an ON signal is input from the proximity switch 13a or when the vehicle speed is less than 5 km / h, the controller 4 does not send a damper ON command.

  Next, the operation in the second embodiment will be described. First, the case where the traveling damper switch 3 is OFF will be described. In this case, the voltage of the switching signal input unit 4 a of the controller 4 becomes a high potential, and the controller 4 does not send a damper ON command to the travel damper solenoid relay 5. As a result, the travel damper solenoid valve 6 is set to the low position, and the bottom 12b of the boom cylinder 12 is disconnected from the accumulator 8, and the travel damper is inactivated.

  A case where the travel damper switch 3 is ON and the boom lever 13 is in the floating position will be described. In this case, the voltage of the switching signal input unit 4 a of the controller 4 becomes low, but the controller 4 does not send a damper ON command to the travel damper solenoid relay 5 because the proximity switch ON signal is input. As a result, the travel damper solenoid valve 6 is set to the low position, and the bottom 12b of the boom cylinder 12 is disconnected from the accumulator 8, and the travel damper is inactivated.

  A case where the travel damper switch 3 is ON and the boom lever 13 is in a position other than the floating position will be described. In this case, the voltage of the switching signal input unit 4a of the controller 4 becomes a low voltage, and the proximity switch OFF signal is input. Therefore, when the vehicle speed is less than 5 km / h, the controller 4 does not send a damper ON command to the travel damper solenoid relay 5, the travel damper solenoid valve 6 is in the low position, and the bottom 12b of the boom cylinder 12 is disconnected from the accumulator 8. As a result, the traveling damper is inactivated. When the vehicle speed is 5 km / h or higher, the controller 4 sends a damper ON command to the travel damper solenoid relay 5, the travel damper solenoid valve 6 is set to the A position, and the bottom 12 b of the boom cylinder 12 communicates with the accumulator 8. The travel damper is activated.

  As described above, in the second embodiment, the proximity switch 13a corresponds to the detection unit in the present invention, and the control logic by the controller 4 corresponds to the prohibition unit. For this reason, also in 2nd Embodiment, the effect similar to 1st Embodiment can be acquired.

  In the second embodiment, the proximity switch 13a is used as the detection means. However, the operation position of the boom lever (operation lever) 13 is detected by a potentiometer to detect that it is in the floating position. May be.

  A third embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a simplified view of the main part showing the third embodiment, and FIG. 8 is a diagram showing a control flow by the controller in the third embodiment. Note that in the third embodiment, identical symbols are assigned to configurations identical to those in the first embodiment and second embodiment and descriptions thereof are omitted.

  As shown in FIG. 7, the pilot oil passage 11 a of the switching valve 11 is provided with a pressure detector 700 that detects the magnitude of the hydraulic pressure and converts it into an electric signal. The pressure detector 700 is electrically connected to the controller 4. Connected. The controller 4 sends a damper ON signal when the voltage of the switching signal input unit 4a is low, the hydraulic pressure of the pilot oil passage 11a is lower than a predetermined value, and the vehicle speed is 5 km / h or higher. When the voltage of the switching signal input unit 4a is high potential, when the hydraulic pressure of the pilot oil passage 11a reaches a predetermined value, or when the vehicle speed is less than 5 km / h, the controller 4 does not send out a damper ON signal. The predetermined value of the oil pressure in the pilot oil passage 11a is a pilot oil pressure necessary to switch the switching valve 11 to the floating position (a position).

  In the third embodiment, the pressure detector 700 corresponds to the detecting means in the present invention, and the control logic by the controller 4 corresponds to the prohibiting means. Note that a pressure switch may be used instead of the pressure detector 700 and an ON / OFF signal of the pressure switch may be input to the controller 4. Note that the operation of the third embodiment is substantially the same as that of the second embodiment, and thus the description thereof is omitted.

  Although specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present invention. For example, as a condition for providing the damper function by connecting the bottom 12b of the boom cylinder 12 and the accumulator 8, in the above embodiment, it is assumed that the vehicle traveling speed is (5 km / h) or more. It is not limited to. The construction vehicle is not limited to a wheel loader, and various vehicles are targeted.

It is a principal part simplification figure of 1st Embodiment. It is a figure which shows the control blow by the controller in 1st Embodiment. It is a principal part simplification figure which shows the 1st modification of 1st Embodiment. The modification of 1st Embodiment is shown, (a) is the principal part simplification figure of a 2nd modification, (b) is the principal part simplification figure of a 3rd modification. It is a principal part simplification figure which shows 2nd Embodiment. It is a figure which shows the control blow by the controller in 2nd Embodiment. It is a principal part simplified diagram which shows 3rd Embodiment. It is a figure which shows the control blow by the controller in 3rd Embodiment. It is a simplified diagram of a construction vehicle. It is a simplified diagram of a hydraulic circuit of a conventional construction vehicle. It is a perspective view which shows the leveling work by a construction vehicle.

Explanation of symbols

  4 .... Controller, 7 .... Pressure switch, 8 .... Accumulator, 12 .... Boom cylinder, 12a ... Head, 12b ... Bottom, 13 .... Control lever, 18 .... Hydraulic oil tank, 30 ... Hydraulic pressure source , 31 .. Boom control valve, 32 .. Travel damper switching valve

Claims (3)

A boom cylinder;
A hydraulic source;
A hydraulic oil tank;
The head side port of the boom cylinder, the bottom side port of the boom cylinder, the hydraulic source, and the hydraulic oil tank are switched, and the head side and the bottom side of the boom cylinder are both operated with hydraulic oil. A boom control valve having a floating position for communicating with the tank;
An accumulator,
A travel damper switching valve having a damper operation position in which the accumulator and the bottom side of the boom cylinder are in communication with each other;
In a construction vehicle having a controller for controlling the operation of the travel damper switching valve based on a predetermined condition set in advance,
Detecting means for detecting that the boom control valve is in a floating position;
A construction vehicle comprising: prohibiting means for prohibiting the travel damper switching valve from being in a damper operating position when the detecting means detects that the boom control valve is in a floating position. The boom control valve is a pilot-operated valve that switches its position upon receiving pilot pressure.
The construction vehicle according to claim 1, wherein the detection means detects a pilot pressure input to the boom control valve when the bottom of the boom cylinder is in communication with a hydraulic oil tank. 2. The construction according to claim 1, further comprising an operation lever operated by an operator to move the boom cylinder, wherein the detection means detects a floating position based on an operation position of the operation lever. vehicle.