JP6457913B2 - Rigid dump truck suspension system - Google Patents

Description

  The present invention relates to a suspension device for a rigid dump truck.

  An axle with left and right wheels is supported on the vehicle body so that it can swing up and down and to the left and right. The left and right suspension cylinders are connected to the left and right sides of the axle and the vehicle body, and the oil chambers of the left and right suspension cylinders are connected via valves. A suspension device for a traveling vehicle connected to the vehicle is known (see Patent Document 1).

  In Patent Document 1, when the vehicle body is horizontal, the oil chambers of the left and right suspension cylinders communicate with the accumulator to reduce the spring constant of the suspension cylinder. When the vehicle body rolls left and right, the oil chambers of the left and right suspension cylinders are shut off. The spring constant of the suspension cylinder is increased.

  As a result, the ride comfort can be improved when the vehicle body is horizontal, and the stability of the vehicle body can be improved when rolling.

Japanese Patent Laid-Open No. 2-99417

  However, in the technique of Patent Document 1, it cannot be determined whether the differential pressure between the left and right suspension cylinders is due to a roll during turning or due to one of the left and right wheels overcoming a step. In other words, in the suspension device described in Patent Document 1, when the vehicle travels on the uneven road surface and one of the left and right wheels gets over the step, the spring constant becomes large. There was a problem of force acting.

  A suspension device for a rigid dump truck according to claim 1 is provided between a wheel support member for supporting a wheel and a vehicle body frame, and includes a plurality of suspension cylinders in which gas and compressive oil are sealed. A suspension device, a suspension cylinder located on the left wheel side (hereinafter also referred to as a left suspension cylinder), a suspension cylinder located on the right wheel side (hereinafter also referred to as a right suspension cylinder), and the left suspension cylinder An accumulator connected to the left suspension cylinder (hereinafter also referred to as a left accumulator), an accumulator connected to the right suspension cylinder (hereinafter also referred to as a right accumulator), and a differential pressure between the left suspension cylinder and the right suspension cylinder. The left suspension cylinder and the right suspension cylinder communicate with a high-pressure suspension cylinder and an accumulator connected to the suspension cylinder, and the left suspension cylinder and the right suspension cylinder have a pressure. A low-pressure suspension cylinder, an accumulator that cuts off an accumulator connected to the suspension cylinder, and a pressure difference between the left suspension cylinder and the right suspension cylinder, and the left suspension cylinder and the right suspension cylinder, A suspension cylinder having a low pressure communicates with an accumulator connected to the suspension cylinder, and the left suspension cylinder and the right suspension Of Nshirinda, characterized in that it comprises a high suspension cylinder-pressure, and a relief valve for blocking an accumulator connected to the suspension cylinder.

  According to the present invention, it is possible to reduce the torsional force acting on the vehicle body frame when one of the left and right wheels rides on the step.

The side view of the dump truck which concerns on 1st Embodiment. The top view which looked at the dump truck concerning a 1st embodiment from the upper part. The rear view which looked at the dump truck concerning a 1st embodiment from back. The rear view of the dump truck concerning a comparative example. The figure which shows the structure of the suspension apparatus by the side of the rear wheel which concerns on 1st Embodiment. The schematic diagram which shows the internal structure of a rear suspension cylinder. VII-VII line sectional circuit diagram of FIG. The figure which shows typically the cross section of an accumulator valve and a pilot pressure cutoff valve. The figure explaining the determination method of pressure accumulation start threshold-value (DELTA) P1. The figure which shows the cross section of a pressure release valve typically. (A) is a flowchart which shows the processing content of switching control of the pilot pressure cutoff valve by a controller, (b) is a flowchart which shows the processing content of switching control of the right and left forced pressure release valve by a controller. The rear view of the dump truck which shows the state which the right rear wheel got on the level | step difference. The figure explaining operation | movement of a pressure accumulation valve and a pilot pressure cutoff valve when a right rear wheel gets on the level | step difference. The figure explaining operation | movement of the pressure release valve when a right rear wheel gets on the level | step difference. The figure explaining the neutral return operation | movement of an accumulator valve. The functional block diagram of the controller which concerns on 2nd Embodiment. The flowchart which shows the processing content of switching control of the pilot pressure cutoff valve by the controller which concerns on 2nd Embodiment.

Hereinafter, an embodiment of a suspension device for a rigid dump truck according to the present invention will be described with reference to the drawings.
-First embodiment-
FIG. 1 is a side view of the dump truck according to the first embodiment. For convenience of explanation, as shown in the figure, the front, rear, left, and right directions of the dump truck are defined. The dump truck is a rigid frame type super large rigid dump truck that transports crushed stones mined in a mine or the like. The dump truck has a body frame (hereinafter simply referred to as a frame 2) as a main body, a cab (operator's cab) 10 provided at the front of the frame 2, and a loading platform (vessel) 1 on which a load 7 such as a crushed stone is placed. And a hoist cylinder 3 that is a hydraulic cylinder for driving the loading platform for rotating the loading platform 1 in the vertical direction (raising and lowering).

  The frame 2 and the loading platform 1 are connected by a hoist cylinder 3 and a hinge pin 4. By causing the hoist cylinder 3 to expand and contract, the loading platform 1 can be pivoted up and down with respect to the frame 2 with the hinge pin 4 as a fulcrum, and the load 7 can be released. The cab 10 is provided with a driver's seat on which the driver is seated, an ignition switch for starting the engine, an accelerator pedal, a brake pedal, a steering wheel (not shown), and the like.

  FIG. 2 is a plan view of the dump truck according to the first embodiment viewed from above, and FIG. 3 is a rear view of the dump truck according to the first embodiment viewed from the rear. In FIG. 2, only the parts of the frame 2 and the suspension (device for supporting the wheels) are shown for the sake of clarity.

  As shown in FIG. 2, the dump truck includes two front wheels 5a and 5b and four rear wheels 6a, 6b, 6c, and 6d, and the rear wheels 6a, 6b, 6c, and 6d are driving wheels, the front wheels 5a, 5b is configured as a driven wheel. The front wheels 5a and 5b constitute steering wheels that are steered (steered) by the driver. The outer diameter dimensions of the front wheels 5a, 5b and the rear wheels 6a, 6b, 6c, 6d range from 2 to 4 m, for example.

  The left front wheel 5a is provided with a wheel speed sensor 39a for detecting the wheel speed of the front wheel 5a. The right front wheel 5b is provided with a wheel speed sensor 39b for detecting the wheel speed of the front wheel 5b. The wheel speed sensors 39a and 39b are connected to a controller 32 described later, and output signals corresponding to the wheel speeds of the front wheels 5a and 5b to the controller 32.

  As shown in FIG. 1, the dump truck is provided with a pair of suspension cylinders (hereinafter referred to as front suspension cylinders 8) on the front side of the frame 2, and a pair of suspension cylinders (hereinafter referred to as rear suspension cylinders) on the rear side of the frame 2. 9a, 9b) are provided.

  The front suspension cylinder 8 is an independent suspension type suspension cylinder capable of moving the left and right front wheels 5a and 5b independently. The pair of left and right front suspension cylinders 8 are connected to the left lower arm 12a and the right lower arm 12b (see FIG. 2) that support the left and right front wheels 5a and 5b, respectively, and suspend the front side of the vehicle body on the left and right front wheels. , Shocks the vertical vibration of the car body.

  The rear suspension cylinders 9a and 9b are axle suspension type suspension cylinders. As shown in FIG. 3, the pair of left and right rear suspension cylinders 9a and 9b are connected to a rigid axle 13 that supports the rear wheels 6a to 6d. Between the left and right rear suspension cylinders 9a, 9b, a left / right interlocking variable rigidity device 17 is disposed. Detailed description of the left-right interlocking variable rigidity device 17 will be described later.

  The rigid axle 13 is a cylindrical body that forms an axle on the rear wheel side, and a wheel mounting cylinder (wheel hub) that rotates integrally with the rear wheels 6a to 6d is disposed therein. As shown in FIG. 2, the rigid axle 13 swings with respect to the frame 2 around a spherical joint 38 provided at the front end. The rear wheels 6 a to 6 d are driven by an electric motor (not shown) provided in the rigid axle 13, and transmit driving force and braking force to the frame 2 through the spherical joint 38.

  As shown in FIG. 3, the frame 2 and the rigid axle 13 are connected by a lateral link 16, and the lateral movement of the rigid axle 13 is restricted by the lateral link 16. The rear suspension cylinders 9a and 9b not only regulate the vertical movement of the rigid axle 13, but also regulate the roll rotational movement of the rigid axle 13, and also serve as a stabilizer.

  In many cases, the dump truck has a specification that the load capacity that can be carried is heavier than the weight of the vehicle body. The dump truck differs by about 2 to 2.5 times between the weight of the body when empty and the weight of the body when loaded. For example, the dump truck has a weight of about 200 tons when the load 7 is not loaded, and about 500 tons when the object to be transported is loaded to the maximum (upper limit).

  As described above, in the dump truck, the weight of the vehicle body is greatly different between the empty load and the loaded state. For this reason, the suspension cylinders 8, 9a, 9b have both a tire load cushioning function when overcoming road surface irregularities, a vibration damping function for improving the ride comfort of the driver, It is necessary to satisfy operability standards such as suppressing rolls during turning. Therefore, in the present embodiment, a hydropneumatic suspension cylinder in which gas and compressive oil are sealed in the cylinder and has a non-linear spring characteristic is employed as the front suspension cylinder 8 and the rear suspension cylinders 9a and 9b. doing.

  FIG. 4 is a rear view of the dump truck according to the comparative example. Gas and compressive oil are enclosed in the rear suspension cylinders 9a and 9b of the dump truck according to the comparative example, and the gas and compressive oil do not enter and exit the cylinder. That is, the dump truck according to the comparative example is different from the present embodiment in that the left-right interlocking variable rigidity device 17 (see FIG. 3) of the present embodiment described later is not provided.

  In the comparative example, the spring characteristics of the rear suspension cylinders 9a and 9b are determined only by setting the gas pressure and the injection amount of the compressible oil. For example, a case will be described in which a hard spring characteristic is imparted to the rear suspension cylinders 9a and 9b in order to improve the stability of the vehicle body during a turning operation in a loaded state (during rolling).

  Work sites where mining dump trucks travel are usually uneven off-road. For this reason, the dump truck often gets over a step of about 1 m (about 1/4 of the outer diameter of the wheel), for example. As shown in FIG. 4, when the right rear wheels 6c and 6d of the dump truck according to the comparative example ride on the step, the rear suspension cylinders 9a and 9b having hard spring characteristics are passed around the roll axis with respect to the frame 2. A large twisting force (twisting force) is applied, which may cause damage to members constituting the vehicle body. For this reason, in order to prevent damage due to a large torsional force, in the comparative example, it is necessary to impart high rigidity to the members constituting the vehicle body, which may lead to an increase in weight and cost.

  In the present embodiment, when one of the left and right wheels of the dump truck gets over the step, the spring characteristics of the rear suspension cylinders 9a and 9b are changed by the left and right interlocking variable rigidity device 17, and the frame 2 is greatly twisted. Prevent force from acting. Details will be described below.

  FIG. 5 is a diagram showing the configuration of the rear wheel side suspension device according to the first embodiment, and FIG. 6 is a schematic diagram showing the internal structure of the rear suspension cylinder. In the suspension device according to the present embodiment, the spring constants of the pair of left and right rear suspension cylinders 9a and 9b are adjusted by the left and right interlocking variable rigidity device 17 provided between the pair of left and right rear suspension cylinders 9a and 9b. It is configured.

  As shown in FIG. 6, the rear suspension cylinders 9 a and 9 b include a cylindrical tube 99, a piston 98 disposed in the tube 99, one end side fixed to the piston 98, and the other end side protruding outside the tube 99. It is comprised with the rod 97. FIG. The rod 97 and the piston 98 move in the tube 99 along the central axis direction of the tube 99. The space in the tube 99 is partitioned into a bottom chamber (main chamber) 91 and a rod chamber (subchamber) 90 by the piston 98.

  The piston 98 and the rod 97 each have a cylindrical shape, form an internal space extending in the central axis direction, and communicate with the bottom chamber 91. The rod 97 is formed with a throttle hole 35 that keeps the internal space of the rod 97 and the rod chamber 90 in communication with each other at all times. That is, the rod chamber 90 and the bottom chamber 91 communicate with each other through the throttle hole 35.

  As shown in FIG. 3, the suspension cylinders 9 a and 9 b have the upper end of the tube 99 attached to the mount 2 m of the frame 2 so that the tube 99 is located on the upper side and the rod 97 is located on the lower side. Is attached to the bracket 13 b of the rigid axle 13.

  Gas and compressive oil (hereinafter simply referred to as oil) are enclosed in the suspension cylinders 9a and 9b shown in FIG. 6 without partitioning. The suspension cylinders 9a and 9b have a double spring structure in which gas and oil are compressed when an external force is applied. During loading, the pressure in the suspension cylinders 9a and 9b is higher than when empty, and most of the gas is dissolved in the oil.

  When the dump truck (vehicle) is traveling on an uneven traveling surface, the volumes of the bottom chamber 91 and the rod chamber 90 change when the rod 97 expands and contracts in the vertical direction with respect to the tube 99 as the vehicle vibrates. To do. When oil passes through the throttle hole 35 according to the expansion / contraction operation of the rod 97, a pressure loss occurs, a throttle action according to the opening area of the throttle hole 35 occurs, and a damping force for vibration buffering is generated.

  As shown in FIG. 5, the suspension device includes a pair of left and right suspension cylinders 9 a and 9 b, a left and right interlocking variable rigidity device 17, a pair of left and right accumulators 60 a and 60 b, and a controller 32. The left-right interlocking variable rigidity device 17 includes a pressure accumulation valve 61, a pressure release valve 62, a pilot pressure cutoff valve 25, left and right forced pressure release valves 63a, 63b, and check valves 64a, 64b, 65a, 65b, 66a, 66b, 67a, 67b. including.

  In the following description, the rear suspension cylinder 9a positioned on the left rear wheel 6a, 6b side is also referred to as “left suspension cylinder 9a”, and the rear suspension cylinder 9b positioned on the right rear wheel 6c, 6d side is referred to as “right suspension cylinder”. 9b ". The accumulator 60a dedicated to the left suspension cylinder connected to the left suspension cylinder 9a is also referred to as “left accumulator 60a”, and the accumulator 60b dedicated to the right suspension cylinder connected to the right suspension cylinder 9b is also referred to as “right accumulator 60b”.

  As shown in FIG. 5, an injection port 92 and an oil discharge port 93 are provided at the upper end portion of the tube 99 constituting the bottom chamber 91. The oil discharge port 93 of the left suspension cylinder 9a is connected to the pressure accumulating valve 61 via a discharge side check valve 66a. The discharge-side check valve 66a allows oil to flow from the left suspension cylinder 9a to the pressure accumulation valve 61, and blocks oil flow from the pressure accumulation valve 61 to the left suspension cylinder 9a. The oil passage between the discharge side check valve 66 a and the pressure accumulating valve 61 is connected to the pilot pipe line 61 a connected to the left pilot oil chamber 81 a of the pressure accumulating valve 61 and the left pilot oil chamber 86 a of the pressure release valve 62. The pilot lines 62a are connected to each other.

  The oil discharge port 93 of the right suspension cylinder 9b is connected to the pressure accumulating valve 61 via the discharge side check valve 66b. The discharge-side check valve 66b allows oil to flow from the right suspension cylinder 9b to the pressure accumulation valve 61, and blocks oil flow from the pressure accumulation valve 61 to the right suspension cylinder 9b. The oil passage between the discharge side check valve 66 b and the pressure accumulating valve 61 is connected to the pilot pipe line 61 b connected to the right pilot oil chamber 81 b of the pressure accumulating valve 61 and the right pilot oil chamber 86 b of the pressure release valve 62. The pilot lines 62b are connected to each other.

  A pilot pressure cutoff valve 25 is provided in the pilot pipelines 61a and 61b. The pilot pressure cutoff valve 25 is an electromagnetic switching valve that is switched between a closed position (C) and an open position (D) according to a control signal (excitation current to the solenoid) output from the controller 32. When the ON signal is output from the controller 32, the pilot pressure shut-off valve 25 is energized and switched to the open position (D). When the OFF signal is output from the controller 32, the solenoid is demagnetized and the spring force is applied. To switch to the closed position (C).

  When the pilot pressure shut-off valve 25 is switched to the open position (D), the left suspension cylinder 9a and the left pilot oil chamber 81a of the pressure accumulation valve 61 are communicated, and the right suspension cylinder 9b and the right pilot oil chamber of the pressure accumulation valve 61 are communicated. 81b is communicated. As a result, the pressure in the bottom chamber 91 of the left and right suspension cylinders 9a and 9b (hereinafter also referred to as main chamber pressure) is guided to the left and right pilot oil chambers 81a and 81b of the pressure accumulating valve 61 as pilot pressure. For this reason, in the pressure accumulation valve 61, the spool 24a moves according to the differential pressure between the main chamber pressures of the left suspension cylinder 9a and the right suspension cylinder 9b.

  When the pilot pressure shut-off valve 25 is switched to the closed position (C), the left suspension cylinder 9a and the left pilot oil chamber 81a of the pressure accumulating valve 61 are shut off, and the right suspension cylinder 9b and the right pilot oil chamber 81b of the pressure accumulating valve 61 are Is cut off. Although details will be described later, in the present embodiment, when the pilot pressure shut-off valve 25 is switched to the closed position (C), the left pilot oil chamber 81a and the right pilot oil chamber 81b of the accumulator valve 61 are connected to each other. The pressure accumulation valve 61 is configured to return to the neutral position (N1) through the passages 91a and 93b and the second communication passages 91b and 93a (see FIG. 15).

  The accumulator valve 61 is a hydraulic pilot type three position that is switched among a neutral position (N1), a switching position (X1), and a switching position (Y1) by a differential pressure between the left suspension cylinder 9a and the right suspension cylinder 9b. It is a switching valve. When the spool 24a is in the neutral position (N1), the left suspension cylinder 9a and the left accumulator 60a are blocked, and the right suspension cylinder 9b and the right accumulator 60b are blocked. When the pressure of the left suspension cylinder 9a becomes higher than the pressure of the right suspension cylinder 9b and the differential pressure becomes larger than a predetermined value, the spool 24a is switched to the switching position (X1). When the spool 24a is in the switching position (X1), the left suspension cylinder 9a and the left accumulator 60a are communicated, and the right suspension cylinder 9b and the right accumulator 60b are blocked. When the pressure of the right suspension cylinder 9b becomes higher than the pressure of the left suspension cylinder 9a and the differential pressure becomes larger than a predetermined value, the spool 24a is switched to the switching position (Y1). When the spool 24a is in the switching position (Y1), the right suspension cylinder 9b and the right accumulator 60b are communicated, and the left suspension cylinder 9a and the left accumulator 60a are blocked.

  The pressure accumulation valve 61 is connected to the left accumulator 60a via a pressure accumulation side check valve 64a. The pressure accumulation side check valve 64a allows the flow of oil from the pressure accumulation valve 61 to the left accumulator 60a, and blocks the flow of oil from the left accumulator 60a to the pressure accumulation valve 61. The pressure accumulation valve 61 is connected to the right accumulator 60b through a pressure accumulation side check valve 64b. The pressure accumulation side check valve 64b allows the flow of oil from the pressure accumulation valve 61 to the right accumulator 60b and blocks the flow of oil from the right accumulator 60b to the pressure accumulation valve 61.

  The left accumulator 60a is connected in parallel to the pressure release valve 62 and the left forced pressure release valve 63a via a pressure release side check valve 65a. The pressure release oil passage 70a in which the pressure release valve 62 is provided and the pressure release oil passage 70b in which the left forced pressure release valve 63a are provided merge on the downstream side of the pressure release valve 62 and the left force release pressure valve 63a, and the combined oil passage is reverse to the injection side. It is connected to the injection port 92 of the left suspension cylinder 9a via a stop valve 67a.

  The right accumulator 60b is connected in parallel to the pressure release valve 62 and the right forced pressure release valve 63b via the pressure release side check valve 65b. The pressure release oil passage 71a in which the pressure release valve 62 is provided and the pressure release oil passage 71b in which the right forced pressure release valve 63b is provided merge on the downstream side of the pressure release valve 62 and the right force release valve 63b. It is connected to the injection port 92 of the right suspension cylinder 9b via a stop valve 67b.

  The pressure release side check valve 65a and the injection side check valve 67a allow the oil flow from the left accumulator 60a to the left suspension cylinder 9a, and block the oil flow from the left suspension cylinder 9a to the left accumulator 60a. The pressure release side check valve 65b and the injection side check valve 67b allow the flow of oil from the right accumulator 60b to the right suspension cylinder 9b, and block the flow of oil from the right suspension cylinder 9b to the right accumulator 60b.

  The pressure release valve 62 is a hydraulic pilot type three position that is switched among a neutral position (N2), a switching position (X2), and a switching position (Y2) by the differential pressure between the left suspension cylinder 9a and the right suspension cylinder 9b. It is a switching valve. When the spool 24b is in the neutral position (N2), the left suspension cylinder 9a and the left accumulator 60a are blocked, and the right suspension cylinder 9b and the right accumulator 60b are blocked. When the pressure of the left suspension cylinder 9a becomes higher than the pressure of the right suspension cylinder 9b and the differential pressure becomes larger than a predetermined value, the spool 24b is switched to the switching position (X2). When the spool 24b is in the switching position (X2), the right suspension cylinder 9b and the right accumulator 60b are communicated, and the left suspension cylinder 9a and the left accumulator 60a are blocked. When the pressure of the right suspension cylinder 9b becomes higher than the pressure of the left suspension cylinder 9a and the differential pressure becomes larger than a predetermined value, the spool 24b is switched to the switching position (Y2). When the spool 24b is in the switching position (Y2), the left suspension cylinder 9a and the left accumulator 60a are communicated, and the right suspension cylinder 9b and the right accumulator 60b are blocked.

  The left and right forced pressure release valves 63a and 63b are electromagnetic switching valves that are switched between an open position (E) and a closed position (F) in accordance with a control signal (excitation current to the solenoid) output from the controller 32. . When the controller 32 outputs an ON signal, the left and right forced pressure release valves 63a and 63b are energized and switched to the closed position (F). When the controller 32 outputs an OFF signal, the solenoid is demagnetized. It is switched to the open position (E) by the spring force.

  7 is a cross-sectional circuit diagram taken along line VII-VII in FIG. The pressure accumulation valve 61 is provided in the pressure accumulation valve block 61K, the pressure release valve 62 is provided in the pressure release valve block 62K, and the left and right forced pressure release valves 63a and 63b are provided in the forced pressure release valve block 63K. The pressure accumulation valve block 61K, the pressure relief valve block 62K, and the forced pressure relief valve block 63K constituting the left-right interlocking variable rigidity device 17 are arranged in the front-rear direction of the dump truck so as to overlap each other, and an upper check valve block 69U, a lower reverse valve The stop valve block 69L, the upper elbow 68U, and the lower elbow 68L are connected to and integrated with each other.

  The upper check valve block 69U includes discharge-side check valves 66a and 66b and injection-side check valves 67a and 67b. The lower check valve block 69L includes pressure accumulation side check valves 64a and 64b and pressure release side check valves 65a and 65b. Thus, in this Embodiment, since the various valves which comprise the right-and-left interlocking variable rigidity apparatus 17 are put together compactly, the attachment workability | operativity to the flame | frame 2 is good.

  FIG. 8 is a diagram schematically showing a cross section of the pressure accumulating valve 61 and the pilot pressure cutoff valve 25. FIG. 8 shows a state where the main chamber pressure of the left suspension cylinder 9a and the main chamber pressure of the right suspension cylinder 9b are in equilibrium, that is, a state where the spool 24a is in the neutral position (N1) (see FIG. 5). Yes. As shown in FIG. 8, the pressure accumulating valve 61 and the pilot pressure cutoff valve 25 shown in the hydraulic circuit diagram of FIG. 5 are integrally provided in the pressure accumulating valve block 61K. Hereinafter, the structure of the pressure accumulation valve 61 and the pilot pressure cutoff valve 25 will be described in detail. For convenience of explanation, the left-right direction is defined as shown.

  As shown in FIG. 8, the pressure accumulation valve 61 includes a spool 24a that moves in the left-right direction with respect to the casing 80 of the pressure accumulation valve block 61K, a left pilot oil chamber 81a provided on the left side of the spool 24a, and a right side of the spool 24a. And a right pilot oil chamber 81b provided. Each of the left pilot oil chamber 81a and the right pilot oil chamber 81b is provided with a spring (compression coil spring) 26 that urges the spool 24a toward the neutral position in the axial center.

  The casing 80 is provided with a main pipe 40a that is an oil passage that connects the left suspension cylinder 9a and the left accumulator 60a, and a main pipe 40b that is an oil passage that connects the right suspension cylinder 9b and the right accumulator 60b. Yes. The spool 24a is provided so as to cross the main pipes 40a and 40b, and the opening areas of the main pipes 40a and 40b change according to the amount of movement of the spool 24a in the left-right direction.

  The spool 24 a includes a central land portion 240, a pair of small diameter portions 241 provided on both right and left sides of the land portion 240, and pressure receiving portions 242 a and 242 b provided at respective end portions of the pair of small diameter portions 241. . The land part 240 is a part that closes the main pipes 40a and 40b, and the axial length of the land part 240 is such that both the main pipe 40a and the main pipe 40b can be closed. The outer diameter dimension of the small diameter part 241 is smaller than the outer diameter dimension of the land part 240. When the small diameter portion 241 is positioned in the main pipes 40a and 40b, the upstream side and the downstream side of the spool 24a in the main pipes 40a and 40b are communicated with each other.

  The pressure receiving part 242a has a pressure receiving surface on which the pressure of the left pilot oil chamber 81a acts, and an opening / closing side surface for switching opening and closing of an inlet of a check valve 51aa described later. The pressure receiving part 242b has a pressure receiving surface on which the pressure of the right pilot oil chamber 81b acts and an opening / closing side surface for switching opening and closing of an inlet of a check valve 51ba described later. A fitting recess into which the spring 26 is fitted is formed on the pressure receiving surfaces of the pressure receiving portions 242a and 242b.

  The pilot pressure cutoff valve 25 includes a left cutoff spool 25a and a right cutoff spool 25b. Each of the left blocking spool 25a and the right blocking spool 25b includes a spring 50 for driving the spool and a solenoid 29.

  A pilot line 61a branches off from the main pipe 40a, and the pilot line 61a is connected to the left pilot oil chamber 81a. A left shut-off spool 25a is disposed in the pilot line 61a, and the main pipe 40a and the left pilot oil chamber 81a are communicated or shut off according to the switching operation of the left shut-off spool 25a. A pilot pipe line 61b branches off from the main pipe 40b, and the pilot pipe line 61b is connected to the right pilot oil chamber 81b. A right shut-off spool 25b is arranged in the pilot line 61b, and the main pipe 40b and the right pilot oil chamber 81b are communicated or shut off according to the switching operation of the right shut-off spool 25b.

  The left pilot oil chamber 81a and the right pilot oil chamber 81b are connected by the first communication passages 91a and 93b and the second communication passages 91b and 93a, respectively.

  The first communication passage 91a connects the outlet port 90a of the left pilot oil chamber 81a and the inlet port 92b of the right pilot oil chamber 81b. Between the left pilot oil chamber 81a and the outlet port 90a, the oil flow from the left pilot oil chamber 81a to the right pilot oil chamber 81b is allowed, and the oil from the right pilot oil chamber 81b to the left pilot oil chamber 81a is allowed to flow. A check valve 51aa for blocking the flow is provided. The first communication passage 93b connects the inlet port 92b of the right pilot oil chamber 81b and the right pilot oil chamber 81b. The first communication passage 93b is provided with a check valve 51bb that allows oil flow from the inlet port 92b to the right pilot oil chamber 81b and blocks oil flow from the right pilot oil chamber 81b to the inlet port 92b. ing. A right shut-off spool 25b is disposed in the first communication passage 93b, and the inlet port 92b and the right pilot oil chamber 81b are communicated or shut off according to the switching operation of the right shut-off spool 25b.

  The second communication passage 91b connects the outlet port 90b of the right pilot oil chamber 81b and the inlet port 92a of the left pilot oil chamber 81a. Between the right pilot oil chamber 81b and the outlet port 90b, the oil flow from the right pilot oil chamber 81b to the left pilot oil chamber 81a is allowed, and the oil from the left pilot oil chamber 81a to the right pilot oil chamber 81b is allowed to flow. A check valve 51ba is provided to block the flow. The second communication passage 93a connects the inlet port 92a of the left pilot oil chamber 81a and the left pilot oil chamber 81a. The second communication passage 93a is provided with a check valve 51ab that allows oil flow from the inlet port 92a to the left pilot oil chamber 81a and blocks oil flow from the left pilot oil chamber 81a to the inlet port 92a. ing. The left shut-off spool 25a is disposed in the second communication passage 93a, and the inlet port 92a and the left pilot oil chamber 81a are communicated or shut off according to the switching operation of the left shut-off spool 25a.

  As shown in FIG. 8, when the main chamber pressure (the pressure in the bottom chamber 91) of the left and right suspension cylinders 9a and 9b is in an equilibrium state, the spool 24a is disposed at the neutral position, so that the left and right suspension cylinders 9a and 9b The oil flow to the accumulators 60a and 60b is blocked.

  When a difference occurs in the main chamber pressure between the left and right suspension cylinders 9a and 9b, the spool 24a slides in the direction in which the main pipe 40a or the main pipe 40b opens.

FIG. 9 is a diagram illustrating a method for determining the pressure accumulation start threshold value ΔP1. A pressure difference at which the spool 24a is switched to the open position, that is, a pressure accumulation start threshold value ΔP1, which is a pressure difference at which the accumulator pressure starts, is expressed by the following equation (1). The pressure accumulation start threshold value ΔP1 is also an upper limit value of the differential pressure.
ΔP1 = F1 / S1 = 2 · k1 · z1 / S1 (1)
Here, F1 is a force applied to the spool 24a, S1 is a pressure receiving area of the spool 24a (that is, an area of the pressure receiving surface of the pressure receiving portions 242a and 242b), k1 is a spring constant of the spring 26, and z1 is a necessary spool movement until the valve is opened. Amount.

  FIG. 10 is a view schematically showing a cross section of the pressure release valve 62. FIG. 10 shows a state where the main chamber pressure of the left suspension cylinder 9a and the main chamber pressure of the right suspension cylinder 9b are in equilibrium, that is, a neutral position (N2) (see FIG. 5). Hereinafter, the configuration of the pressure release valve 62 will be described in detail. For convenience of explanation, the left-right direction is defined as shown.

  As shown in FIG. 10, the pressure release valve 62 includes a spool 24b that moves in the left-right direction with respect to the casing 85 of the pressure release valve block 62K, a left pilot oil chamber 86a provided on the left side of the spool 24b, and a right side of the spool 24b. And a right pilot oil chamber 86b provided. Each of the left pilot oil chamber 86a and the right pilot oil chamber 86b is provided with a spring (compression coil spring) 27 that urges the spool 24b toward the neutral position in the axial center.

  The casing 85 is provided with a main pipe 41a that is an oil path connecting the left accumulator 60a and the left suspension cylinder 9a, and a main pipe 41b that is an oil path connecting the right accumulator 60b and the right suspension cylinder 9b. Yes. The spool 24b is provided so as to cross the main pipes 41a and 41b, and the opening areas of the main pipes 41a and 41b change according to the amount of movement of the spool 24b in the left-right direction.

  The spool 24 b includes a small-diameter portion 246 at the center and a pair of land portions 245 a and 245 b provided on both the left and right sides of the small-diameter portion 246. The land portions 245a and 245b are portions that block the main pipes 41a and 41b. The outer diameter size of the small diameter portion 246 is smaller than the outer diameter size of the land portions 245a and 245b. When the small diameter portion 245 is positioned in the main pipes 41a and 41b, the upstream side and the downstream side of the spool 24b in the main pipes 41a and 41b are communicated with each other.

  The land portion 245a has a pressure receiving surface on which the pressure of the left pilot oil chamber 86a acts. The land portion 245b has a pressure receiving surface on which the pressure of the right pilot oil chamber 86b acts. On the pressure receiving surfaces of the land portions 245a and 245b, fitting recesses into which the springs 27 are fitted are formed.

  As shown in FIG. 10, when the main chamber pressure (the pressure in the bottom chamber 91) of the left and right suspension cylinders 9a and 9b is in an equilibrium state, the spool 24b is disposed at the neutral position, so that the left and right suspensions are moved from the left and right accumulators 60a and 60b. The oil flow to the cylinders 9a and 9b is blocked.

  When a difference occurs in the main chamber pressure between the left and right suspension cylinders 9a and 9b, the spool 24b slides in the direction in which the main pipe 41a or the main pipe 41b opens.

A differential pressure at which the spool 24b is switched to the open position, that is, a differential pressure at which the accumulator pressure starts, is expressed by the following equation (2).
ΔP2 = F2 / S2 = 2 · k2 / z2 / S2 (2)
Here, F2 is the force applied to the spool 24b, S2 is the pressure receiving area of the spool 24b (that is, the area of the pressure receiving surface of the land portions 245a and 245b), k2 is the spring constant of the spring 27, and z2 is the necessary spool movement until the valve is opened. Amount.

  The left and right accumulators 60a and 60b reduce the residual pressure and prepare for accumulating pressure, thereby reducing the shock caused by a sudden step that occurs suddenly while the dump truck is running. The smaller the pressure release start threshold value ΔP2, the more opportunities to release pressure. Therefore, in this embodiment, the pressure release start threshold value is set so that the pressure release start threshold value ΔP2 is sufficiently smaller than the pressure accumulation start threshold value ΔP1. ΔP2 was set. That is, the magnitude relationship between the pressure release start threshold value ΔP2 and the pressure accumulation start threshold value ΔP1 is a pressure release start threshold value ΔP2 << pressure accumulation start threshold value ΔP1. For this reason, the pressure release valve 62 repeats opening and closing more frequently than the pressure accumulation valve 61.

  As shown in FIG. 5, the controller 32 outputs an angle sensor 33 for detecting the steering angle (operation amount and operation direction) of the steering wheel 34 and a pressure release command for releasing the left and right accumulators 60a and 60b. A forced pressure release switch 36 is connected, and a detection signal from the angle sensor 33 and a pressure release command from the forced pressure release switch 36 are input. When the forced release switch 36 is turned ON by the driver, a release pressure command signal is output from the forced release switch 36 to the controller 32, and when the forced release switch 36 is turned OFF by the driver. The pressure release command signal is not output from the forced pressure release switch 36 to the controller 32.

  The controller 32 includes an arithmetic processing unit having a storage device such as a CPU, ROM, RAM, and other peripheral circuits. The controller 32 functionally includes a turning motion determination unit 32a, a forced pressure release condition determination unit 32b, and a valve control unit 32c. Based on the steering angle detected by the angle sensor 33, the turning operation determination unit 32a determines whether or not the dump truck is performing a turning operation. When the absolute value | θ | of the steering angle is less than the threshold value θ0 (| θ | <θ0), the turning motion determination unit 32a determines that the dump truck is not in a turning motion, and the absolute value of the steering angle | θ When | is equal to or greater than the threshold θ0 (| θ | ≧ θ0), it is determined that the dump truck is turning. The threshold value θ0 is used to determine whether or not the dump truck is turning, and is stored in the storage device of the controller 32 in advance.

  The valve control unit 32c outputs an OFF signal to the solenoid of the pilot pressure cutoff valve 25 when the turning operation determining unit 32a determines that the dump truck is performing the turning operation. The valve control unit 32c outputs an ON signal to the solenoid of the pilot pressure cutoff valve 25 when the turning operation determination unit 32a determines that the dump truck is not turning.

  The forced pressure release condition determination unit 32b determines whether the forced pressure release condition is satisfied based on the pressure release command signal of the forced pressure release switch 36. The forced pressure release condition determination unit 32b determines that the forced pressure release condition is established when the forced pressure release switch 36 is turned on, and the forced pressure release condition when the forced pressure release switch 36 is turned off. Is determined not to hold.

  When the forced pressure release condition determining unit 32b determines that the forced pressure release condition is satisfied, the valve control unit 32c outputs an OFF signal to the solenoids of the left and right forced pressure release valves 63a and 63b. When the forced pressure release condition determining unit 32b determines that the forced pressure release condition is not satisfied, the valve control unit 32c outputs an ON signal to the solenoids of the left and right forced pressure release valves 63a and 63b.

  FIG. 11A is a flowchart showing the processing contents of the switching control of the pilot pressure cutoff valve 25 by the controller 32, and FIG. 11B shows the processing contents of the switching control of the left and right forced pressure release valves 63a, 63b by the controller 32. It is a flowchart. The processing shown in the flowcharts of FIGS. 11A and 11B is started by turning on an ignition switch (not shown), and is repeatedly executed at a predetermined control cycle after initial setting (not shown) is performed. When the ignition switch is turned on, an engine (not shown) is started by an engine controller (not shown).

  A switching control process for the pilot pressure cutoff valve 25 will be described with reference to FIG. In step S100, the controller 32 acquires information on the steering angle of the steering wheel 34 detected by the angle sensor 33, and proceeds to step S110.

  In step S110, the controller 32 determines whether or not the dump truck is in a turning motion based on the absolute value | θ | of the steering angle of the steering wheel 34 acquired in step S100. If an affirmative determination is made in step S110, the process proceeds to step S120, and if a negative determination is made in step S110, the process proceeds to step S130.

  In step S120, the controller 32 outputs an OFF signal to the pilot pressure cutoff valve 25, switches the pilot pressure cutoff valve 25 to the closed position (C), and ends the process shown in the flowchart of FIG.

  In step S130, the controller 32 outputs an ON signal to the pilot pressure cutoff valve 25, switches the pilot pressure cutoff valve 25 to the open position (D), and ends the process shown in the flowchart of FIG.

  The switching control process of the left and right forced pressure release valves 63a and 63b will be described with reference to FIG. In step S200, the controller 32 acquires operation information (pressure release command signal) of the forced pressure release switch 36, and proceeds to step S210.

  In step S210, the controller 32 determines whether the forced pressure release condition is satisfied based on the operation information (pressure release command signal) acquired in step S200. If a positive determination is made in step S210, the process proceeds to step S220, and if a negative determination is made in step S210, the process proceeds to step S240.

  In step S220, the controller 32 outputs an OFF signal to the pilot pressure cutoff valve 25, switches the pilot pressure cutoff valve 25 to the closed position (C), and proceeds to step S230. In step S230, the controller 32 outputs an OFF signal to the left and right forced pressure relief valves 63a and 63b, switches the left and right forced pressure relief valves 63a and 63b to the open position (E), and performs the processing shown in the flowchart of FIG. finish.

  In step S240, the controller 32 outputs an ON signal to the left and right forced pressure relief valves 63a and 63b, switches the left and right forced pressure relief valves 63a and 63b to the closed position (F), and performs the processing shown in the flowchart of FIG. finish.

  When the ignition switch is turned off, the engine is stopped and the solenoids of the left and right forced release valves 63a and 63b and the pilot pressure cutoff valve 25 are not energized, so that the left and right forced release valves 63a and 63b are in the open position (F ) And the pilot pressure cutoff valve 25 is switched to the closed position (C).

  The operation of the present embodiment is summarized as follows. When the driver turns on the ignition switch, the engine starts. The driver turns off the forced pressure release switch 36 in advance. Thereby, the left and right forced pressure release valves 63a and 63b are switched to the closed position (F), and the pilot pressure cutoff valve 25 is switched to the open position (D) (No in step S200 → S210 → S240).

  The dump truck travels when the driver operates operating members such as a steering wheel 34, an accelerator pedal (not shown), and a brake pedal (not shown). When a turning operation is performed by the steering wheel 34 during traveling, the front wheels 5a and 5b are steered according to the operation direction and the steering angle of the steering wheel 34, and the dump truck performs turning traveling. When the turning operation by the dump truck is performed, the pilot pressure cutoff valve 25 is switched to the closed position (C) (Yes in step S100 → S110 → S120).

  In other words, during the turning operation, oil is not discharged from the left and right suspension cylinders 9a and 9b to the left and right accumulators 60a and 60b, and the left and right accumulators 60a and 60b are not accumulated, and according to the pressure difference between the left and right suspension cylinders 9a and 9b. Only release pressure is allowed. Thus, during the turning operation, since the pilot pressure cutoff valve 25 is in the closed position (C), the springs of the left and right suspension cylinders 9a and 9b are compared to when the pilot pressure cutoff valve 25 is in the open position (D). The constant is large, that is, it has a hard characteristic. Thereby, it is possible to prevent the roll angle from increasing and to ensure the stability of the vehicle body in the turning operation.

  When the driver finishes the turning operation and travels straight on the dump truck, the pilot pressure shut-off valve 25 is switched to the open position (D) and enters a standby state in which pressure accumulation is possible (No in Step S100 → S110 → S130). ).

  FIG. 12 is a rear view of the dump truck showing a state in which the right rear wheels 6c and 6d have climbed up the step. FIG. 13 is a diagram for explaining the operation of the pressure accumulating valve 61 and the pilot pressure shut-off valve 25 when the right rear wheels 6c and 6d ride on the step, and FIG. 14 shows the state when the right rear wheels 6c and 6d ride on the step. It is a figure explaining operation | movement of the pressure release valve.

  As shown in FIG. 12, when the right rear wheel 6c, 6d rides on a step during traveling, a large compressive force is instantaneously applied to the right suspension cylinder 9b. When an axial compressive force acts on the right suspension cylinder 9b and the main chamber pressure (pressure in the bottom chamber 91) of the right suspension cylinder 9b rises, the right suspension cylinder 9b is in a higher pressure state than the left suspension cylinder 9a. . Note that an axial tensile force acts on the left suspension cylinder 9a, and the left suspension cylinder 9a extends.

  As shown in FIG. 5, when a difference occurs in the main chamber pressure between the left suspension cylinder 9a and the right suspension cylinder 9b, and the differential pressure ΔP exceeds the pressure accumulation start threshold value ΔP1 and the pressure release start threshold value ΔP2, the pressure accumulation valve 61 is switched to the switching position ( The pressure release valve 62 is switched to the switching position (Y2).

  As shown in FIG. 13, the main chamber pressure of the right suspension cylinder 9b acts on the pressure receiving surface of the pressure receiving portion 242b located in the right pilot oil chamber 81b via the pilot conduit 61b. As a result, the spool 24a moves to the left, the closed main pipe 40b opens (see the switching position (Y1) in FIG. 5), and the oil in the right suspension cylinder 9b becomes the check valve 66b and the pressure accumulating valve 61. , And the check valve 64b is supplied to the right accumulator 60b shown in FIG. Since the right accumulator 60b is accumulated and the main chamber pressure of the right suspension cylinder 9b is reduced, the spring constant of the right suspension cylinder 9b is reduced. That is, the rigidity of the right suspension cylinder 9b is reduced (becomes soft characteristics).

  As shown in FIG. 14, the main chamber pressure of the right suspension cylinder 9b acts on the pressure receiving surface of the land portion 245b located in the pilot oil chamber 86b via the pilot conduit 62b. As a result, the spool 24b moves to the left, the closed main pipe 41a opens (see the switching position (Y2) in FIG. 5), and the oil in the left accumulator 60a flows into the check valve 65a and the pressure release valve 62. , And the check valve 67a is supplied to the left suspension cylinder 9a. Since the left accumulator 60a is released and the main chamber pressure of the left suspension cylinder 9a increases, the spring constant of the left suspension cylinder 9a increases. That is, the rigidity of the left suspension cylinder 9a increases (becomes hard characteristics).

  Therefore, in the present embodiment, when the right rear wheel 6c, 6d rides on the step during traveling, the right suspension cylinder 9b changes to a soft characteristic and the left suspension cylinder 9a changes to a hard characteristic. As a result, as shown in FIG. 12, the right suspension cylinder 9b sufficiently contracts when riding on the step, so that the impact is effectively absorbed, and the left suspension cylinder 9a is held in an extended state. Thereby, since the frame 2 can be maintained in a substantially horizontal state, the load of the loading platform 1 is transmitted to the frame 2 evenly on the left and right, and a good balance state can be maintained.

  As shown in FIG. 5, the pressure difference ΔP between the left suspension cylinder 9a and the right suspension cylinder 9b is reduced by the pressure accumulation to the right accumulator 60b and the pressure release from the left accumulator 60a, and the pressure difference ΔP becomes the pressure accumulation start threshold value. When ΔP1 or less, the spool 24a of the pressure accumulating valve 61 returns to the neutral position (N1). As a result, as shown in FIG. 8, the main pipes 41a and 41b are closed and the pressure accumulation is completed. The pressure accumulation is also terminated when the pressure in the right accumulator 60b and the pressure in the right suspension cylinder 9b become equal.

  As shown in FIG. 5, when the pressure difference from the left suspension cylinder 9a and the right suspension cylinder 9b is further reduced by the pressure release from the left accumulator 60a, and the pressure difference ΔP becomes equal to or less than the pressure release start threshold value ΔP2, the pressure release valve. 62 spools 24b return to the neutral position (N2). As a result, as shown in FIG. 10, the main pipes 41a and 41b are closed, and the pressure release ends. Note that the release of pressure also ends when the pressure in the left accumulator 60a and the pressure in the left suspension cylinder 9a become equal.

  When the differential pressure ΔP between the left and right suspension cylinders 9a and 9b is reduced, a substantially equivalent force is applied to the frame 2 from the left and right suspension cylinders 9a and 9b, so that the generation of a force that greatly twists the frame 2 around the roll axis is suppressed. It is possible to prevent damage to members constituting the vehicle body.

  As shown in FIG. 12, the behavior of the pressure accumulating valve 61 when the driver performs a turning operation immediately after the right rear wheel 6c, 6d has climbed the step will be described. The right rear wheel 6c, 6d rides on the step, the right suspension cylinder 9b becomes higher pressure than the left suspension cylinder 9a, and the pressure difference ΔP between the left suspension cylinder 9a and the right suspension cylinder 9b becomes the pressure accumulation start threshold value ΔP1. When exceeding, pressure accumulation by the right accumulator 60b is started.

  Here, when the driver performs a turning operation before the pressure difference ΔP between the left suspension cylinder 9a and the right suspension cylinder 9b becomes equal to or less than the pressure accumulation start threshold value ΔP1, the controller 32 determines that the turning operation is being performed. 5 is switched to the closed position (C). FIG. 15 is a diagram for explaining the neutral return operation of the pressure accumulation valve 61. In the present embodiment, when the pilot pressure cutoff valve 25 is switched to the closed position (C), as shown in FIG. 15, the pilot line 61a is closed and the second communication path 93a is closed by the left cutoff spool 25a. be opened. Further, the right shut-off spool 25b closes the pilot pipe line 61b and opens the first communication path 93b.

  The left pilot oil chamber 81a and the right pilot oil chamber 81b communicate with each other by opening the first communication passage 93b and the second communication passage 93a. As a result, of the left pilot oil chamber 81a and the right pilot oil chamber 81b, the pressure oil in the right pilot oil chamber 81b having a high pressure passes through the check valve 51ba, the second communication passage 91b, and the check valve 51ab. It flows into the lower left pilot oil chamber 81a, and the spool 24a moves toward the neutral position. When the spool 24a moves to the neutral position, the open / close side surface of the pressure receiving portion 242b closes the inlet of the check valve 51ba (see FIG. 8). As a result, the movement of the pressure oil between the left and right pilot oil chambers stops, so the spool 24a stops at the neutral position, and the neutral return is completed.

  In the present embodiment, basically, the pressure oil of the left suspension cylinder 9a and the right suspension cylinder 9b is not mixed so that the spring constant (rigidity setting value) of the left and right suspension cylinders 9a, 9b does not change. However, the pressure oil is mixed only slightly during the above-described neutral return. However, since the amount of movement of the pressure oil is a small amount for the spool 24a to return to the neutral position, the change in the spring constant (rigidity setting value) of the left and right suspension cylinders 9a and 9b is small and does not cause a problem. .

  The initial setting of the hardness of the suspension device is performed by injecting oil with the ignition switch turned off and the engine, motor, etc. stopped. After the initial setting is completed, turn on the ignition switch and perform a test run. In the trial operation, when the pressure of the left and right accumulators 60a and 60b is equal to the pressure of the left and right suspension cylinders 9a and 9b, if the suspension device has insufficient hardness, oil is put into the suspension cylinders 9a and 9b. Inject additional, increase the hardness, and adjust to the desired hardness.

According to the embodiment described above, the following operational effects can be obtained.
(1) The suspension device includes a pressure accumulation valve 61 and a pressure release valve 62 that are switched by a pressure difference ΔP between the left suspension cylinder 9a and the right suspension cylinder 9b. The pressure accumulating valve 61 communicates a high-pressure suspension cylinder of the left suspension cylinder 9a and the right suspension cylinder 9b with an accumulator connected to the suspension cylinder. And a switching position (X1, Y1) that shuts off the suspension cylinder and the accumulator connected to the suspension cylinder. The pressure release valve 62 communicates a low pressure suspension cylinder of the left suspension cylinder 9a and the right suspension cylinder 9b with an accumulator connected to the suspension cylinder. Switching positions (X2, Y2) for shutting off a suspension cylinder having a high height and an accumulator connected to the suspension cylinder.

  As a result, when one of the left and right wheels rides on the step, the spring constant of the suspension cylinder located on the side of the wheel on the step can be temporarily reduced (it can be changed to a softer characteristic) Can be effectively absorbed. Furthermore, since the spring constant of the suspension cylinder located on the side of the wheel not riding on the step can be temporarily increased (it can be changed to a hard characteristic), the extended suspension cylinder can be made difficult to contract. . That is, the following performance of the left and right suspension cylinders 9a and 9b with respect to the road surface can be improved, and the riding comfort can be improved.

When one of the left and right wheels climbs the step, the accumulator corresponding to the suspension cylinder with high pressure is accumulated, the accumulator corresponding to the suspension cylinder with low pressure is released, and the differential pressure ΔP between the left and right suspension cylinders is reduced. As a result, the torsional force input to the frame 2 from the left and right suspension cylinders 9a and 9b due to the pressure difference between the left and right suspension cylinders 9a and 9b can be reduced. For this reason, in the comparative example described above, there is a possibility that a member constituting the vehicle body needs to have high rigidity in order to prevent damage due to a large torsional force. However, in this embodiment, high rigidity is required. There is no need to have. As a result, in this embodiment, it is possible to reduce the weight and cost of the vehicle.
Furthermore, since the frame 2 is maintained in a substantially horizontal state, the load from the loading platform 1 is also transmitted to the frame 2 equally on the left and right, and a good balance state can be maintained.

(2) As described above, in the suspension device according to the present embodiment, when one of the left and right wheels rides on a step, a differential pressure ΔP is generated in the left and right suspension cylinders 9a and 9b, and the high-pressure side suspension cylinder is softened. be able to. However, if you turn the dump truck with this function enabled, the suspension cylinder on the outside of the turn will be at a higher pressure than the suspension cylinder on the inside of the turn even on flat ground, and the amount of shrinkage will increase. As a result, the vehicle body roll angle becomes large.

  Therefore, in the present embodiment, as described above, when it is determined that the dump truck is not turning, the controller 32 controls the pilot pressure cutoff valve 25 to control the left suspension cylinder 9a and the left pilot oil chamber 81a. And the right suspension cylinder 9b and the right pilot oil chamber 81b are communicated (switching control to the open position (D)). When it is determined that the dump truck is turning, the controller 32 controls the pilot pressure shut-off valve 25 to shut off the left suspension cylinder 9a and the left pilot oil chamber 81a, and the right suspension cylinder 9b The right pilot oil chamber 81b is shut off (switching control to the closed position (C)). Thereby, an increase in the roll angle in the turning operation can be prevented, and the stability of the vehicle body can be ensured.

(3) When the steering angle detected by the angle sensor 33 is larger than a predetermined threshold, the controller 32 determines that the dump truck is performing a turning operation. Since the angle sensor 33 for detecting the steering angle is usually provided in the dump truck, it is not necessary to provide a dedicated sensor for determining the turning operation.

(4) The suspension device includes a first communication passage 91a that supplies oil in the left pilot oil chamber 81a to the right pilot oil chamber 81b when the pressure in the left pilot oil chamber 81a is higher than the pressure in the right pilot oil chamber 81b. 93b. The suspension device includes second communication passages 91b and 93a that supply oil from the right pilot oil chamber 81b to the left pilot oil chamber 81a when the pressure in the right pilot oil chamber 81b is higher than the pressure in the left pilot oil chamber 81a. ing.

  The first communication path 93b is provided with a right blocking spool 25b that opens and closes the first communication path 93b, and the second communication path 93a is provided with a left blocking spool 25a that opens and closes the second communication path 93a. When it is determined that the dump truck is not turning, the controller 32 controls the left and right blocking spools 25a and 25b to close the first communication path 93b and the second communication path 93a, and the dump truck is turning. If it is determined, the left and right blocking spools 25a and 25b are controlled to open the first communication path 93b and the second communication path 93a. When the spool 24a is in the neutral position (N1), each of the first communication path 91a and the second communication path 91b is closed by the pressure receiving portions 242a and 242b of the spool 24a.

  With such a configuration, the spool 24a of the pressure accumulating valve 61 can be moved when the dump truck turns while the differential pressure ΔP larger than the pressure accumulating start threshold value ΔP1 is generated in the left and right suspension cylinders 9a, 9b. It is possible to return to the neutral position (N1). As a result, the spring characteristics of the suspension cylinder during the turning operation can be maintained, so that the stability of the vehicle body during the turning operation can be ensured.

(5) The left forced pressure relief valve 63a is provided in the pressure relief oil passage 70b for supplying oil from the left accumulator 60a to the left suspension cylinder 9a when the pressure in the left accumulator 60a is higher than the pressure in the left suspension cylinder 9a. The pressure relief oil passage 70b is opened and closed. The right forced pressure release valve 63b is provided in a pressure release oil passage 71b for supplying oil from the right accumulator 60b to the right suspension cylinder 9b when the pressure in the right accumulator 60b is higher than the pressure in the right suspension cylinder 9b. The path 71b is opened and closed. When a pressure release command is output from the forced pressure release switch 36, the controller 32 shuts off the left suspension cylinder 9a and the left pilot oil chamber 81a, and shuts off the right suspension cylinder 9b and the right pilot oil chamber 81b. In this manner, the left forced pressure release valve 63a and the right forced pressure release valve 63b are controlled so as to control the pilot pressure cutoff valve 25 and open the pressure release oil passage 71a and the pressure release oil passage 71b.

  Thereby, the left and right accumulators 60a and 60b can be forcibly released to return the left and right suspension cylinders 9a and 9b to the initial state. The accumulator valve 61 can also be returned to the neutral position (N1).

(6) The left and right forced pressure release valves 63a and 63b are electromagnetic switching valves that are switched to the open position (E) when the solenoid is demagnetized. The pilot pressure cutoff valve 25 is an electromagnetic switching valve that is switched to the closed position (C) when the solenoid is demagnetized. For this reason, when the driver turns off the ignition switch and stops the engine, the right and left suspension cylinders are forcibly released by prohibiting the pressure accumulation and forcibly releasing the left and right accumulators 60a and 60b as in the above (5). 9a and 9b can be returned to the initial state. The accumulator valve 61 can also be returned to the neutral position (N1). In the unmanned state after the engine is stopped, the suspension device can be brought into a normal state, so that safety in the unmanned state can be ensured.

-Second Embodiment-
A rigid dump truck suspension apparatus according to a second embodiment will be described with reference to FIGS. 16 and 17. FIG. 16 is a functional block diagram of the controller 232 according to the second embodiment. In the figure, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and differences will be mainly described.

  In the first embodiment, the dump truck turns when the turning motion determination unit 32a of the controller 32 determines that the absolute value | θ | of the steering angle detected by the angle sensor 33 is larger than a predetermined threshold value θ0. An example in which it is determined to be operating has been described. On the other hand, in the second embodiment, the turning motion determination unit 232a of the controller 232 has a difference ΔV between the left and right wheel speeds detected by the wheel speed sensors 39a and 39b that is greater than a predetermined threshold value ΔV0. In this case, it is determined that the dump truck is turning.

  The dump truck according to the second embodiment has a configuration similar to that of the dump truck according to the first embodiment. The second embodiment is different from the first embodiment in that the controller 232 according to the second embodiment replaces the turning operation determination unit 32a of the first embodiment with a turning operation determination unit. 232a is functionally provided.

  The turning motion determination unit 232a calculates a difference (absolute value) ΔV between the wheel speed VL of the left front wheel 5a detected by the wheel speed sensor 39a and the wheel speed VR of the right front wheel 5b detected by the wheel speed sensor 39b. Calculate (ΔV = | VR−VL |). The turning operation determination unit 232a determines whether or not the dump truck is performing a turning operation based on the difference ΔV between the left and right wheel speeds.

  When the difference ΔV between the left and right wheel speeds is less than the threshold value ΔV0 (ΔV <V0), the turning operation determination unit 232a determines that the dump truck is not performing a turning operation, and the difference ΔV between the left and right wheel speeds is the threshold value Δ0. When the above is true (ΔV ≧ V0), it is determined that the dump truck is turning. The threshold value Δ0 is used for determining whether or not the dump truck is turning, and is stored in advance in the storage device of the controller 232.

  Similar to the first embodiment, the valve control unit 32c outputs an OFF signal to the solenoid of the pilot pressure cutoff valve 25 when the turning operation determination unit 232a determines that the dump truck is performing a turning operation. The valve control unit 32c outputs an ON signal to the solenoid of the pilot pressure cutoff valve 25 when the turning operation determination unit 232a determines that the dump truck is not turning.

  FIG. 17 is a flowchart showing the processing contents of the switching control of the pilot pressure cutoff valve 25 by the controller 232 according to the second embodiment. FIG. 17 corresponds to FIG. 11A described in the first embodiment. FIG. 17 is a flowchart in which steps S300, S305, and S310 are added instead of steps S100 and S110 in the flowchart of FIG. The process shown in the flowchart of FIG. 17 is started when an ignition switch (not shown) is turned on, and after an initial setting (not shown) is performed, it is repeatedly executed at a predetermined control cycle.

  In the second embodiment, when the ignition switch is turned on and the initial setting is performed, in step S300, the controller 232 acquires information on the left and right wheel speeds detected by the wheel speed sensors 39a and 39b, and Proceed to step S305.

  In step S305, the controller 232 calculates the difference ΔV between the left and right wheel speeds acquired in step S300, and proceeds to step S310. In step S310, the controller 232 determines whether or not the vehicle is turning based on the difference ΔV between the left and right wheel speeds calculated in step S305. If an affirmative determination is made in step S310, the process proceeds to step S120, and if a negative determination is made in step S310, the process proceeds to step S130.

  According to such 2nd Embodiment, there exists an effect similar to 1st Embodiment.

The following modifications are also within the scope of the present invention, and one or a plurality of modifications can be combined with the above-described embodiment.
(Modification 1)
In the first embodiment, an angle sensor 33 that detects the steering angle of the steering wheel 34 is provided, and based on the steering angle detected by the angle sensor 33, it is determined whether or not the dump truck is turning. Although an example has been described, the present invention is not limited to this. For example, the wheel steering angle of the axle of the front wheel constituting the steering device may be detected, and it may be determined whether or not a turning operation is being performed based on the wheel steering angle.

(Modification 2)
In the above-described embodiment, an example in which the present invention is applied to a rear suspension device (a suspension device including a rear suspension cylinder) in a dump truck has been described, but the present invention is not limited to this. The present invention may be applied to a front suspension device (a suspension device including a front suspension cylinder) in a dump truck, or the present invention may be applied to both a front suspension device and a rear suspension device.

  Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

2 frame (body frame), 5a, 5b front wheel (wheel), 6a-6d rear wheel (wheel), 8, 9a, 9b suspension cylinder, 12a left lower arm (wheel support member), 12b right lower arm (wheel support member), 13 Rigid axle (wheel support member), 17 Left / right interlocking variable rigidity device, 24a spool, 24b spool, 25 Pilot pressure cutoff valve (pilot pressure cutoff device), 25a Left cutoff spool (second opening / closing mechanism), 25b Right cutoff spool ( (First opening / closing mechanism), 32 controller (control unit), 32a turning operation determination unit, 33 angle sensor, 36 forced pressure release switch (pressure release command member), 39a, 39b wheel speed sensor, 60a, 60b accumulator, 61 pressure accumulation valve 61a Pilot pipeline (first pilot pipeline), 61b Lot line (second pilot line), 62 pressure release valve, 63a Left forced pressure release valve (third open / close mechanism), 63b Right forced pressure release valve (fourth open / close mechanism), 70b Pressure release oil path (first pressure release oil) Road), 71b Release pressure oil passage (second release oil passage), 81a Left pilot oil chamber (first pilot oil chamber), 81b Right pilot oil chamber (second pilot oil chamber), 91a, 93b First communication passage 91b, 93a Second communication path, 232 Controller (control unit), 232a Turning motion determination unit

Claims (6)

A rigid dump truck suspension device comprising a plurality of suspension cylinders provided between a wheel support member for supporting wheels and a vehicle body frame and filled with gas and compressible oil,
A suspension cylinder located on the left wheel side (hereinafter also referred to as the left suspension cylinder),
A suspension cylinder located on the right wheel side (hereinafter also referred to as the right suspension cylinder),
An accumulator connected to the left suspension cylinder (hereinafter also referred to as a left accumulator);
An accumulator connected to the right suspension cylinder (hereinafter also referred to as a right accumulator);
The left suspension cylinder and the right suspension cylinder are switched by the pressure difference between the left suspension cylinder and the right suspension cylinder, and the suspension cylinder having a high pressure is communicated with the accumulator connected to the suspension cylinder. Among the suspension cylinder and the right suspension cylinder, a suspension cylinder having a low pressure, and an accumulator valve that shuts off an accumulator connected to the suspension cylinder;
The left suspension cylinder and the right suspension cylinder are switched by a pressure difference between the left suspension cylinder and the right suspension cylinder, and a suspension cylinder having a low pressure and an accumulator connected to the suspension cylinder are communicated with each other. A suspension device for a rigid dump truck, comprising: a suspension cylinder having a high pressure among the suspension cylinder and the right suspension cylinder; and a pressure release valve for shutting off an accumulator connected to the suspension cylinder. In the suspension device of the rigid dump truck according to claim 1,
A turning operation determination unit for determining whether or not the rigid dump truck is turning operation;
A first pilot pipe line connecting the left suspension cylinder and the first pilot oil chamber of the pressure accumulating valve; and a second pilot pipe line connecting the right suspension cylinder and the second pilot oil chamber of the pressure accumulating valve. A pilot pressure shut-off device provided;
When the turning operation determination unit determines that the rigid dump truck is not turning, the left suspension cylinder and the first pilot oil chamber communicate with each other, and the right suspension cylinder and the second pilot oil chamber Communicate with
When the turning operation determination unit determines that the rigid dump truck is turning, the left suspension cylinder and the first pilot oil chamber are shut off, and the right suspension cylinder and the second pilot oil are shut off. A rigid dump truck suspension device, comprising: a control unit that controls the pilot pressure shut-off device so as to shut off the chamber. In the suspension device of the rigid dump truck according to claim 2,
An angle sensor for detecting a steering angle of the rigid dump truck;
The turning motion determination unit determines that the rigid dump truck is turning when the steering angle detected by the angle sensor is larger than a predetermined threshold value. Suspension device. In the suspension device of the rigid dump truck according to claim 2,
A wheel speed sensor for detecting wheel speeds of the left and right wheels of the rigid dump truck;
The turning operation determination unit determines that the rigid dump truck is performing a turning operation when a difference between the left and right wheel speeds detected by the wheel speed sensor is larger than a predetermined threshold value. Rigid dump truck suspension device. In the suspension device of the rigid dump truck according to any one of claims 2 to 4,
The pressure accumulating valve includes a spool that moves due to a differential pressure between the first pilot oil chamber and the second pilot oil chamber,
When the spool is in a neutral position, shut off the left suspension cylinder and the left accumulator, and shut off the right suspension cylinder and the right accumulator,
When the spool is in the first switching position, the left suspension cylinder and the left accumulator are communicated, and the right suspension cylinder and the right accumulator are shut off,
When the spool is in the second switching position, the right suspension cylinder communicates with the right accumulator, the left suspension cylinder and the left accumulator are shut off,
A first communication passage that supplies oil in the first pilot oil chamber to the second pilot oil chamber when the pressure in the first pilot oil chamber is higher than the pressure in the second pilot oil chamber;
A second communication passage that supplies oil in the second pilot oil chamber to the first pilot oil chamber when the pressure in the second pilot oil chamber is higher than the pressure in the first pilot oil chamber;
A first opening / closing mechanism provided in the first communication path, for opening and closing the first communication path;
A second opening / closing mechanism provided in the second communication path for opening and closing the second communication path;
The control unit controls the first opening and closing mechanism and the second opening and closing mechanism to be closed when the turning operation determining unit determines that the rigid dump truck is not turning, and the turning operation determining unit When it is determined that the rigid dump truck is turning, the first opening mechanism and the second opening mechanism are controlled to open,
The rigid dump truck suspension device, wherein when the spool is in a neutral position, each of the first communication path and the second communication path is closed by the spool. In the suspension device of the rigid dump truck according to any one of claims 2 to 5,
A pressure release command member that outputs a pressure release command;
When the pressure of the left accumulator is higher than the pressure of the left suspension cylinder, the first accumulator is provided in a first pressure release oil passage that supplies oil to the left suspension cylinder, and opens and closes the first pressure release oil passage. A third opening / closing mechanism that
When the pressure of the right accumulator is higher than the pressure of the right suspension cylinder, the second accumulator is provided in a second pressure release oil passage that supplies oil to the right suspension cylinder, and opens and closes the second pressure release oil passage. And a fourth opening / closing mechanism that
When the pressure release command is output from the pressure release command member, the control unit shuts off the left suspension cylinder and the first pilot oil chamber, and also controls the right suspension cylinder and the second pilot oil chamber. A suspension system for a rigid dump truck, wherein the pilot pressure shut-off device is controlled so as to shut off, and the third open / close mechanism and the fourth open / close mechanism are opened.

Images