JP6503874B2 - Steering device for work vehicle - Google Patents

Description

  The present invention relates to a steering device of a working vehicle provided with a steering cylinder for respectively steering wheels on both front and rear sides of a traveling body.

  As a steering device of a conventional working vehicle, a front wheel steering cylinder for steering the front wheels of the traveling body, a rear wheel steering cylinder for steering the rear wheels of the traveling body, a front wheel steering cylinder and a rear wheel steering cylinder There is known a hydraulic fluid circuit connected in series and having a hydraulic fluid circuit through which hydraulic fluid for driving a front wheel steering cylinder and a rear wheel steering cylinder flows (see, for example, Patent Document 1).

  In the steering device, the front wheel steering that steers only the front wheel, the rear wheel steering that steers only the rear wheel, and the front wheel in the width direction of the traveling body are switched by switching the flow path of the hydraulic fluid circuit. It is possible to switch between the clamp steering which steers the rear wheel at the same time in the width direction of the traveling body and the club steering which steers the front wheel and the rear wheel simultaneously in the same direction.

  In addition, as a working vehicle provided with the steering device, for example, a traveling vehicle such as a three-axle vehicle in which two axles are disposed in the front and rear direction on the front side of the traveling body and one axle is disposed on the rear side of the traveling body. Some have a traveling body in which the number of axes on the front side is larger than the number of axes on the rear side.

Unexamined-Japanese-Patent No. 2010-179797

  In a work vehicle having a traveling body having a larger number of axes on the front side than the number of axes on the rear side of the traveling body, in clamp steering and club steering, in order to synchronize the operation amounts of the front wheel steering cylinder and the rear wheel steering cylinder. A rear wheel steering cylinder is used which has an inner diameter which is larger than the inner diameter of the front wheel steering cylinder. The rear wheel steering cylinder exerts an output larger than that required to steer the rear wheel, so a large load acts on the member on the traveling body side to which the rear wheel steering cylinder is connected in clamp steering and club steering. .

  An object of the present invention is to provide a steering apparatus for a working vehicle capable of protecting a member on a traveling body side to which a rear wheel steering cylinder is connected from being damaged.

  In order to achieve the above object, the present invention exerts an output larger than that of the front wheel steering cylinder for steering the front wheels of the traveling body and an output of the front wheel steering cylinder, and steers the rear wheels of the traveling body A wheel steering cylinder, a front wheel steering cylinder and a rear wheel steering cylinder are connected in series to one another, and a hydraulic fluid circuit through which hydraulic fluid for driving the front wheel steering cylinder and the rear wheel steering cylinder flows Flow path switching mechanism for switching between the front wheel steering flow path for driving the rear wheel steering cylinder and the rear wheel steering cylinder alone or the special steering flow path for simultaneously driving the front wheel steering cylinder and the rear wheel steering cylinder; By discharging the fluid outside the hydraulic oil circuit A first pressure holding mechanism that holds the pressure in the oil circuit below a predetermined first pressure, and discharging the hydraulic oil in the hydraulic oil circuit out of the hydraulic oil circuit, the first pressure in the hydraulic oil circuit When the front wheel steering channel is set by the second pressure holding mechanism that holds the second pressure lower than the second pressure and the flow channel switching mechanism, the pressure in the hydraulic fluid circuit is held by the first pressure holding mechanism, And a holding pressure switching unit configured to hold the pressure in the hydraulic fluid circuit by the second pressure holding mechanism when the special steering flow passage is set by the flow passage switching mechanism.

  As a result, since the output of the rear wheel steering cylinder at the time of steering the rear wheel is reduced, it is possible to reduce the load acting on the traveling body side member to which the rear wheel steering cylinder is connected.

  According to the present invention, it is possible to reduce the load acting on the traveling body side member to which the rear wheel steering cylinder is connected, so that the traveling body side member to which the rear wheel steering cylinder is connected is protected from damage. Is possible.

It is a side view of a mobile crane which shows one embodiment of the present invention. It is a schematic block diagram of a steering device. It is a block diagram showing a control system. 5 is a flowchart of holding pressure switching processing.

  1 to 4 show an embodiment of the present invention.

  The mobile crane 1 as a working vehicle provided with the steering apparatus according to the present invention performs crane work with a vehicle body 10 as a traveling body for traveling in a general road or work area, as shown in FIG. And a cab 30 for operating the traveling of the vehicle body 10 and the crane operation by the crane device 20. The crane apparatus 20 and the cab 30 are supported by a swivel table 40 which can be horizontally swiveled with respect to the vehicle body 10. The crane apparatus 20 is disposed at one widthwise direction of the swivel platform 40 and the cab 30 is disposed at the other widthwise direction. ing.

  The vehicle body 10 is a three-axle car in which two axles are provided on the front side of a carrier frame 11 extending in the front and rear direction and one axle is provided on the rear side of the carrier frame 11. It is provided. The vehicle body 10 travels by driving the wheels 12 by the power of the engine 13 provided on the rear side of the carrier frame 11. In addition, outriggers 14 are provided on both the front and rear sides of the front wheel 12 and the rear wheel 12 of the carrier frame 11.

  The crane apparatus 20 is provided with a telescopic boom 21 which is provided to be able to move up and down with respect to the vehicle body 10 and which is telescopic. The telescopic boom 21 performs a hoisting operation by means of a hydraulic hoisting cylinder 22. The telescopic boom 21 is telescopic by a telescopic mechanism constituted by a plurality of cylindrical boom members, and performs telescopic operation by a hydraulic cylinder (not shown).

  Inside the cab 30, a seat on which a passenger is seated, a steering handle for traveling of the vehicle body 10 and a crane operation, an operation lever, a foot pedal, and the like are provided. The mobile crane 1 travels with the front of the cab 30 directed to the front of the vehicle body 10.

  The mobile crane 1 includes one of four wheels 12 (hereinafter referred to as front wheels 12) located on the front side of the vehicle body 10 and two wheels 12 (hereinafter referred to as rear wheels 12) located on the rear side. A steering device 100 is provided to steer both or both. The steering apparatus 100 has a front wheel steering mode in which only the front wheel 12 is steered, a rear wheel steering mode in which only the rear wheel 12 is steered, and a clamp steering mode in which the front wheel 12 is steered in one width direction and the rear wheel 12 is steered in the other width direction. Four types of steering modes can be set: a club steering mode in which the front wheel 12 and the rear wheel 12 are steered simultaneously in the same direction. Here, the rear wheel steering mode other than the front wheel steering mode, the clamp steering mode and the club steering mode are defined as the special steering mode.

  As shown in FIG. 2, the steering device 100 includes a first left front wheel steering cylinder 101 for steering the wheel 12 provided on the left side of an axle located on the front side among the front wheels 12 and a wheel provided on the right side. 12. A first right front wheel steering cylinder 102 for steering 12, a second left front wheel steering cylinder 103 for steering a wheel 12 provided on the left side of an axle located on the rear side of the front wheels 12, and A second right front wheel steering cylinder 104 for steering the wheels 12 provided, a left rear wheel steering cylinder 105 for steering the wheels 12 provided on the left side of the rear wheels 12, and a right rear wheel Supply the hydraulic fluid for driving the right rear wheel steering cylinder 106 for steering the wheel 12 and the steering cylinders 101 to 106 And a steering valve unit for adjusting the flow direction and flow rate of hydraulic oil discharged from the hydraulic pump 110 to the steering cylinders 101 to 106 according to the operation direction and operation amount of the steering wheel in the cab 30 120 and a mode switching valve unit 130 as a flow channel switching mechanism for switching the steering mode.

  The steering cylinders 101 to 106 are double-acting single rod cylinders, and one of a cylinder tube and a piston rod is connected to a member on the vehicle body 10 side, and the other is a steering provided so as to freely slide relative to the member on the vehicle body 10 side. It is connected to knuckles. Here, the steering cylinders 101 and 102 are provided in front of the axle of the front wheel 12 located on the front side. The steering cylinders 103 and 104 are provided in front of the axle of the front wheel 12 located on the rear side. Furthermore, steering cylinders 105 and 106 are provided behind the axles of the rear wheel 12.

  The front wheels 12 are steered to the right by reducing the steering cylinders 101 and 103 located on the left side of the vehicle body 10 and extending the steering cylinders 102 and 104 located on the right side. The front wheel 12 is steered leftward by extending the steering cylinders 101 and 103 located on the left side of the vehicle body 10 and reducing the steering cylinders 102 and 104 located on the right side.

  The rear wheel 12 is steered to the right by extending the steering cylinder 105 located on the left side of the vehicle body 10 and reducing the steering cylinder 106 located on the right side. The rear wheel 12 is steered in the left direction by reducing the steering cylinder 105 located on the left side of the vehicle body 10 and extending the steering cylinder 106 located on the right side.

  The front wheel steering cylinders 101 to 104 have the same inner diameter. Rear wheel steering cylinders 105 and 106 have the same inner diameter. Further, the inner diameter of each of the rear wheel steering cylinders 105 and 106 is formed larger than the inner diameter of each of the front wheel steering cylinders 101 to 104. The cross-sectional area inside the rear wheel steering cylinders 105 and 106 is approximately twice the cross-sectional area inside the front wheel steering cylinders 101-104. Therefore, when the rear wheel steering cylinders 105 and 106 are connected in series to the front wheel steering cylinders 101 to 104 and hydraulic fluid is supplied, extension and contraction operations of the front wheel steering cylinders 101 to 104 and the rear wheel steering cylinders 105 and 106 Can be synchronized. When the rear wheel steering cylinders 105 and 106 are connected in series to the front wheel steering cylinders 101 to 104 to supply hydraulic fluid, the outputs of the rear wheel steering cylinders 105 and 106 are the same as those of the front wheel steering cylinders 101 to 104. It becomes large compared with the output.

  The hydraulic pump 110 is driven by the power of the engine 13 and supplies hydraulic oil to a swing motor (not shown) for swinging the swing table 40, for example, in addition to the drive of the steering device 100.

  The steering valve unit 120 includes a P port, a T port, an R port for discharging hydraulic fluid when the steering wheel is rotated clockwise, and an L port for discharging hydraulic fluid when the steering wheel is rotated counterclockwise. ,have.

  The mode switching valve unit 130 has a P port, a T port, an A1 port, a B1 port, an A2 port and a B2 port. The mode switching valve unit 130 has a front wheel steering switching valve 131 for switching a setting related to steering of the front wheel 12 and a rear wheel steering switching valve 132 for switching a setting related to steering of the rear wheel 12. The front wheel steering switching valve 131 is a four-port two-position electromagnetic pilot switching valve, and switches between setting for steering the front wheel 12 according to the operation of the steering wheel and setting for fixing the direction of the front wheel 12. Further, the rear wheel steering switching valve 132 is a 5-port 3-position electromagnetic pilot switching valve, and is configured to steer the rear wheel 12 in the same direction as the steering handle operation direction, and reverse to the steering wheel operation direction. The setting for steering in the direction and the setting for fixing the direction of the rear wheel 12 are switched. The mode switching valve unit 130 includes a hydraulic oil circuit described later by the front wheel steering switching valve 131 and the rear wheel steering switching valve 132 as any of a front wheel steering channel, a rear wheel steering channel, a clamp steering channel or a club steering channel. Switch to Here, the rear wheel steering flow path other than the front wheel steering flow path, the clamp steering flow path, and the club steering flow path are defined as the special steering flow path.

  Further, in the steering device 100, a hydraulic fluid circuit 140 is configured by connecting the steering cylinders 101 to 106, the hydraulic pump 110, the steering valve unit 120, and the mode switching valve unit 130 with a pipe or hose for hydraulic fluid circulation. ing.

  Here, the circuit configuration of the hydraulic fluid circuit 140 will be described in detail.

  A hydraulic oil tank is connected to the suction side of the hydraulic pump 110. The P port of the steering valve unit 120 is connected to the discharge side of the hydraulic pump 110. The R port of the steering valve unit 120 is connected to the P port of the mode switching valve unit 130. Further, the L port of the steering valve unit 120 is connected to the T port of the mode switching valve unit 130. The reduction side port of the second left front wheel steering cylinder 103 and the extension side port of the second right front wheel steering cylinder 104 are connected in parallel with each other at the A1 port of the mode switching valve unit 130. Further, the extension side port of the first left front wheel steering cylinder 101 and the reduction side port of the first right front wheel steering cylinder 102 are connected in parallel to each other at the B1 port of the mode switching valve unit 130. Further, in the first left front wheel steering cylinder 101 and the second left front wheel steering cylinder 103, the reduction side oil chambers and the extension side oil chambers are connected to each other. Further, in the first right front wheel steering cylinder 101 and the second right front wheel steering cylinder 103, reduction side oil chambers are connected to each other and extension side oil chambers are connected to each other. The extension side port of the left rear wheel steering cylinder 105 and the reduction side port of the right rear wheel steering cylinder 106 are connected in parallel with each other at the A2 port of the mode switching valve unit 130. In addition, the reduction-side port of the left rear wheel steering cylinder 105 and the extension-side port of the right rear wheel steering cylinder 106 are connected in parallel to each other at the B2 port of the mode switching valve unit 130.

  Further, the hydraulic oil circuit 140 includes a first relief valve 141 as a first pressure holding mechanism that holds the pressure in the hydraulic oil circuit 140 at a predetermined first pressure or less, and the hydraulic oil circuit 140 when setting the special steering mode. A second relief valve 142 as a second pressure holding mechanism is provided which holds the internal pressure at or below a second pressure which is smaller than the first pressure.

  The first relief valve 141 discharges the hydraulic fluid in the hydraulic fluid circuit 140 out of the hydraulic fluid circuit 140 at a predetermined first pressure (for example, 16 MPa).

  The second relief valve 142 discharges the hydraulic fluid in the hydraulic fluid circuit 140 out of the hydraulic fluid circuit 140 at a predetermined second pressure (e.g., 10 MPa) smaller than the first pressure. The second relief valve 142 is connected to the hydraulic fluid circuit 140 via a flow path opening / closing valve 143 as a holding pressure switching unit consisting of a three-port two-position electromagnetic pilot switching valve. The second relief valve 142 discharges the hydraulic oil in the hydraulic oil circuit 140 only when the flow path on / off valve 143 opens the flow path.

  The mobile crane 1 also includes a controller 150 for controlling the operation of the steering device 100.

  The controller 150 has a CPU, a ROM, a RAM, and the like. When the controller 150 receives an input signal from a device connected to the input side, the CPU reads a program stored in the ROM based on the input signal, and stores the state detected by the input signal in the RAM, It sends an output signal to a device connected to the output side.

  On the input side of the controller 150, as shown in FIG. 3, a parking brake 151 for switching between a state in which the vehicle body 10 can not travel and a state in which traveling can be performed, and a select lever 152 for inputting transmission settings. A mode setting button 153 for setting the steering mode is connected.

  As shown in FIG. 3, the mode switching valve unit 130 and the flow path opening / closing valve 143 are connected to the output side of the controller 150.

  In the mobile crane 1 configured as described above, when traveling by the vehicle body 10, the rider operates the mode setting button 153 to operate the front wheel steering mode, rear wheel steering mode, clamp steering mode and club steering mode. Choose one.

  In the hydraulic fluid circuit 140 in the clamp steering mode and the club steering mode, the steering cylinders 101 to 104 for steering the front wheels 12 and the steering cylinders 105 and 106 for steering the rear wheels 12 are connected in series with each other. As an example showing that the steering cylinders 101 to 104 and the steering cylinders 105 and 106 are connected in series with each other, FIG. 2 shows the flow path of hydraulic oil when steering the front wheel 12 in the right direction in the clamp steering mode. It shows by.

  Further, the controller 150 changes the pressure in the hydraulic fluid circuit 140 to the holding by the first relief valve 141 or the holding by the second relief valve 142 in accordance with the steering mode and the setting state of the parking brake 151 and the select lever 152. Perform switching processing. The operation of the CPU of the controller 150 at this time will be described with reference to the flowchart of FIG.

(Step S1)
In step S1, the CPU determines whether the parking brake 151 is released. If it is determined that the parking brake 151 is released, the process proceeds to step S2. If it is not determined that the parking brake 151 is released, the process proceeds to step S5.

(Step S2)
If it is determined in step S1 that the parking brake 151 is released, the CPU determines whether or not the select lever 152 is set to neutral in step S2. If it is determined that the select lever 152 is set to neutral, the process proceeds to step S5. If it is not determined that the select lever 152 is set to neutral, the process proceeds to step S3.

(Step S3)
If it is not determined in step S2 that the select lever 152 is set to neutral, the CPU determines whether the special steering mode is set by the mode setting button 153 in step S3. If it is determined that the special steering mode is set by the mode setting button 153, the process proceeds to step S4, and if it is not determined that the special steering mode is set by the mode setting button 153, the process proceeds to step S5. Transfer the process.

(Step S4)
If it is determined in step S3 that the special steering mode is set by the mode setting button 153, the CPU sets the flow path of the flow path opening / closing valve 143 to open in step S4, and ends the holding pressure switching process.

(Step S5)
If it is determined in step S1 that the parking brake 151 is not released, or if it is determined in step S2 that the select lever 152 is set to neutral, or the special steering mode is set by the mode setting button 153. If it is not determined, the CPU sets the flow path of the flow path opening / closing valve 143 to be closed in step S5, and ends the holding pressure switching process.

  As described above, according to the steering device of the working vehicle of the present embodiment, when the front wheel steering flow path is set by the mode switching valve unit 130, the pressure in the hydraulic fluid circuit 140 is held by the first relief valve 141 When the special steering flow path is set by the mode switching valve unit 130, the pressure in the hydraulic fluid circuit 140 is held by the second relief valve 142 which is lower in pressure than the first relief valve 141.

  This makes it possible to reduce the load acting on the members on the side of the vehicle body 10 connected to the rear wheel steering cylinders 105 and 106, so the members on the side of the vehicle body 10 connected to the rear wheel steering cylinders 105 and 106 are It is possible to protect from damage.

  Further, when the parking brake 151 can not travel the vehicle body 10 while the special steering flow path is set by the mode switching valve unit 130, the first relief valve 141 holds the pressure in the hydraulic fluid circuit 140. ing.

  When the transmission of the vehicle body 10 is set to neutral in a state where the special steering flow path is set by the mode switching valve unit 130, the first relief valve 141 holds the pressure in the hydraulic fluid circuit 140. ing.

  Thereby, in a state where traveling by the vehicle body 10 is not actually made, the first relief valve 141 which has a pressure higher than that of the second relief valve 142 in the hydraulic fluid circuit 140 regardless of the setting state of the mode switching valve unit 130. Since the pressure can be held, it is possible to prevent the reduction in the output of the steering device 100 and the other devices (e.g., the swing motor) when the common hydraulic pump 110 drives the other devices.

  In the above embodiment, although the mobile crane 1 is applied as a working vehicle, it is also applicable to a working machine such as an excavating machine if it is a working vehicle equipped with a steering device but steering wheels by cylinders. It is possible.

  Moreover, in the said embodiment, although the vehicle body 10 which has two axles in the front side of the vehicle body 10 and has one axle shaft in the rear side was shown, it is not restricted to this. For example, it may be a vehicle body having three axles on the front side of the vehicle body and two axles on the rear side, and three or more axles on the front side of the vehicle body, with a smaller number of axles than the number of front axles. What is necessary is just to be provided on the rear side.

  Reference Signs List 1 mobile crane 10 vehicle body 12 wheels 100 steering device 101 first left front wheel steering cylinder 102 first right front wheel steering cylinder 103 second left front wheel steering cylinder 104 second Right front wheel steering cylinder, 105: left rear wheel steering cylinder, 106: right rear wheel steering cylinder, 130: mode switching valve unit, 140: hydraulic fluid circuit, 141: first relief valve, 142: second relief valve, 143: Flow path open / close valve, 150: controller, 151: parking brake, 152: select lever, 153: mode setting button.

Claims (3)

A front wheel steering cylinder for steering the front wheels of the traveling body;
A rear wheel steering cylinder that produces an output larger than that of the front wheel steering cylinder and steers the rear wheels of the traveling body;
A hydraulic fluid circuit in which a front wheel steering cylinder and a rear wheel steering cylinder are connected in series with each other and hydraulic fluid for driving the front wheel steering cylinder and the rear wheel steering cylinder flows;
Flow path switching mechanism that switches the hydraulic fluid circuit to the front wheel steering flow path that drives only the front wheel steering cylinder, and the special steering flow path that simultaneously drives the rear wheel steering cylinder only, or the front wheel steering cylinder and the rear wheel steering cylinder simultaneously When,
A first pressure holding mechanism that holds the pressure in the hydraulic oil circuit below a predetermined first pressure by discharging the hydraulic oil in the hydraulic oil circuit out of the hydraulic oil circuit;
A second pressure holding mechanism that holds the pressure in the hydraulic oil circuit at or below a second pressure smaller than the first pressure by discharging the hydraulic oil in the hydraulic oil circuit out of the hydraulic oil circuit;
When the front wheel steering passage is set by the passage switching mechanism, the pressure in the hydraulic fluid circuit is held by the first pressure holding mechanism, and the special steering passage is set by the passage switching mechanism. A steering apparatus for a working vehicle, comprising: a holding pressure switching unit that holds the pressure in the hydraulic fluid circuit by the second pressure holding mechanism. In the state where the special steering is set by the flow path switching mechanism, the holding pressure switching unit sets the first pressure when the parking brake makes the traveling body unable to travel or the transmission of the traveling body is set to neutral. The steering apparatus according to claim 1, wherein the pressure in the hydraulic fluid circuit is held by the holding mechanism. In the state where the special steering is set by the flow path switching mechanism, the holding pressure switching unit is in the state where the parking brake can not travel the traveling body and in the state where the transmission of the traveling body is set to neutral. The steering apparatus according to claim 1, wherein the pressure in the hydraulic fluid circuit is held by the holding mechanism.

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