JPH085400B2 - Easy to turn skid steer vehicle - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a skid steer vehicle such as a skid steer loader capable of stable turning.

[Prior art]

As shown in FIGS. 5 and 6, the skid steer excavator loader, which is one type of skid steer vehicle, has a machine base 90 in which wheels 11 to 14 as drive wheels and a bucket are first provided.
91, an arm 911 for operating the bucket 91, and a safety guard 92. The wheels 11 to 14 are provided on both sides of the machine base 90 of the shovel loader 9, two wheels each on the front and rear sides, for a total of four wheels. Further, on the machine base 90, hydraulic pumps 88, 89 as wheel drive devices and hydraulic motors 30, 30 driven by both hydraulic pumps are provided. The drive shafts 50, 50 of the hydraulic motors 30, 30 are connected to the wheels 11-14 via chains 52, 57.

Then, the wheels 11, 12 on the left side of the shovel loader 9
By rotating the motor 30 with the pressurized hydraulic oil generated in the hydraulic pump 88, the drive shaft 50, the chain 52,
Drive through 57. The left wheels 13 and 14 are similarly driven by the pressurized hydraulic oil of the hydraulic pump 89. The hydraulic pumps 88 and 89 are operated by the engine 21.

Further, FIG. 4 shows the relationship between the left wheels 11 and 12 and the hydraulic pump 8 in more detail. This hydraulic pump 8
For this, a hydrostatic drive (HST) is used. Then, the hydraulic pump 8 and the hydraulic motor 30 are connected by the hydraulic pipe 22. The drive shaft 50 of the hydraulic motor 30 has
Fix the sprockets 51 and 55 so that they can rotate together. Also,
Left front wheel (hereinafter, front wheel) 11, left rear wheel (hereinafter,
Each axle shaft 54 of the rear wheel) 12 has a sprocket 5
Fix 3,56. The chain 52 is attached to the sprocket 51 of the drive shaft 50 and the sprocket 53 on the left front wheel 11 side.
To connect. Drive shaft 50 sprocket as well
A chain 57 is connected to 55 and the sprocket 56 on the left rear wheel 12 side. The same applies to the right front wheel 13 and the right rear wheel 14.

As is known from the above, in the conventional skid steer vehicle, the left front wheel 11 and the left rear wheel 12 which are the left drive wheels are both rotated by the hydraulic pump 8 at a constant speed, and the right front wheel 13 and the right rear wheel which are the right drive wheels. The wheel 14 and the wheel 14 are both driven at a constant rotation by the hydraulic pump 9. The operation of the skid steer vehicle in the turning direction is performed by tilting a steering lever (see FIG. 1) connected to the hydraulic pumps 88 and 89 to give a rotational speed difference between the left drive wheel and the right drive wheel. .

[Problems to be solved]

However, in the conventional skid steer vehicle, since the front wheels and the rear wheels rotate at the same rotational speed, the turning is unstable when the skid steer vehicle is turned. This is because the turning center position moves forward due to the load,
Therefore, the rotation of the rear wheels cannot follow the turning motion and is dragged.

This point will be described with reference to FIG. In the figure, reference numerals 11, 12, 13 and 14 denote a left front wheel, a left rear wheel, a right front wheel and a right rear wheel. O is the center of the four drive wheels, O ₁ is the center of gravity of the vehicle,
O ₂ is the turning center of the vehicle, ω is the turning angular velocity of the vehicle, R is the distance from the turning center O ₂ to the center of the wheel, V is the speed of the wheel center point, and θ is the angular difference between the wheel rotation direction and the turning direction. , FR is in front of the vehicle. Others are shown below.

As shown in the figure, the center of gravity O ₁ that changes depending on the load does not coincide with the vehicle center O, but is displaced forward. The deviation of the center of gravity causes a difference in frictional force between the front wheels and the rear wheels, and as a result, the turning center O
₂ moves forward relative to the vehicle center O. The turning center O ₂ also moves in the left-right direction due to the difference in rotational speed between the left and right wheels.

When the vehicle is turning at the turning angular velocity ω around the turning center O ₂ , the front wheel center is the front wheel platform turning speed V _FL (= R _F ω) and the rear wheel center is the rear wheel platform in the circumferential direction. Turning speed V
_It has a velocity of _RL (= R _R ω) (V _FL <V _RL ). However, the speed of the wheel center obtained from the rotation of the wheels is as follows: front wheel control turning speed V _F1 (= V _F * Cosθ _F ), rear wheel rear wheel control turning speed V _R1 (= V _R * Cos θ _R ), Further, since front wheel traveling speed V _F = rear wheel traveling speed V _R , θ _F <θ _R , V _F1 > V _R1 .

Since the driving force of the front wheels is stronger than that of the rear wheels, if V _FL ≈ V _{F1 then} V _RL >> V _R1 . That is,
The rotation of the rear wheels cannot keep up with the turning motion and is dragged, making the turning unstable. In addition, unstable turning also occurs due to changes in turning time, which change depending on the amount of load loaded on the bucket. For example, the time required for turning 180 degrees is not stable.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a skid steer vehicle that can make a stable turn and is easy to turn.

[Means for solving problems]

The present invention provides a skid including a machine base, drive wheels provided with two wheels on both sides of the machine base, a total of four wheels, a hydraulic motor for rotating the drive wheels, and a hydraulic pump for driving the hydraulic motor. In a steered vehicle, a load sensor for detecting the amount of load is mounted on the machine base,
A center-of-gravity position detection device that detects the center-of-gravity position of the vehicle based on a signal from the load sensor, a required rotation speed detection device for the vehicle, and front and rear wheels based on signals from the center-of-gravity position detection device and the required rotation speed detection device. A control device for calculating the number of revolutions of the vehicle is provided, and the control device obtains the turning center position of the vehicle from the center of gravity position and the required rotational speed difference between the left and right wheels, and determines the turning center position from the turning center position. The control is performed such that the rotation speed ratio between the front wheels and the rear wheels is calculated so that the turning speed becomes equal to that of the front and rear wheels. It is a skid steer vehicle that is easy to turn, characterized by being performed.

In the present invention, the load sensor is a sensor that detects the amount of load of luggage loaded in a bucket or the like. The load sensor uses, for example, a load weight of the bucket or a lift cylinder pressure, and is provided at a position where the load amount can be detected.

In addition, the center-of-gravity position detection device determines the center-of-gravity position of the vehicle during loading from the load-corresponding signal value from the load sensor and the previously determined center-of-gravity position of the vehicle itself.
It is a device that detects by using the U data table or the like. The required wheel rotation speed detection device is a device that detects the speed of the vehicle operated by the driver, and is provided for each of the two steering levers that adjust the rotation speeds of the left and right drive wheels. Then, the sliding amount of both steering levers is detected as the required rotation speed of the left and right wheels. Further, the turning angle and the turning speed are determined from the difference between the required rotation speeds.

Further, the control device obtains the turning center O ₂ from the above-mentioned center-of-gravity position and the required rotational speed difference between the left and right wheels, and based on this, calculates an appropriate rotational speed ratio between the front wheels and the rear wheels, and at the time of turning, the rotational speed ratio is calculated. The control is performed so as to match with.

That is, when a certain weight of luggage is loaded in the bucket of the shovel loader, the center of gravity O ₁ of the vehicle is located in front of the vehicle center O, which is the center of the four driving wheels, in FIG. At this time, the turning center O ₂ is determined by the difference in tire friction force between the front and rear wheels based on the deviation between the position of the vehicle center of gravity O _{1 and} the position of the vehicle center O, and is located on the straight line ll. Then, the turning center moves above ll due to the difference in rotational speed between the left and right wheels.

In order to simplify the explanation, it is assumed that the left wheel rotates forward only. At this time, with respect to the front wheel platform turning speed V _FL , which is the circumferential component of the speed of the center of the left front wheel, from the description of the problem to be solved above, if V _FL ≈V _F1 , then the speed of the center of the left rear wheel For components on the circumference V _RL >> V _R1
Becomes Here, in order to eliminate slippage (sliding) of the rear wheels, the rear wheel rotation speed V _RL due to the machine base turning and the rear wheel control turning speed V _R1 due to the rear wheel rotation are matched so that V _{R, that} is, the rear wheel rotation. Pull up.

 That is, this can be expressed by the following equation.

V _RL ＝ R _R ω ＝ V _R1 ＝ V _R Cosθ _R …… (1) V _FL ＝ R _F ω ＝ V _F1 ＝ V _F Cosθ _F …… (2) Also, rear wheel rotation speed V _R and front wheel The rotation speed V _F is expressed by the following equation, respectively.

V _R = R _A・ W _R・ ・ ・ (3) V _F ＝ R _A・ W _F・ ・ ・ (4) In the formulas (3) and (4), R _A is the wheel radius, W
_R and W _F are wheel speeds of the rear wheels and the front wheels.

Then, (1), (2) each V _R, V _F (3) where, (4) after having substituted the expression for the ratio W _R / W _F of the rear wheels and the front wheel speed calculating in formula Then, the following equation is obtained.

_{(W R / W F) =} (R R / R F) × (Cosθ F / Cosθ R) ...... (5) On the other hand, as is also known from the figure, the position of the rotation center O _2, R _R, R _F , θ _F and θ _R are unitarily determined. Therefore,
By controlling so that the ratio of the wheel rotation speeds of the rear wheels and the front wheels according to equation (5) becomes W _R / W _F , the rear wheels due to the machine base turning V _RL becomes the rear wheel control speed due to the rear wheel rotation. V _R1 can be matched. As a result, a stable turn without slippage can be performed.

As described above, by determining the position of the turning center O ₂ , the optimum value of the ratio of the rotational speeds of the front and rear wheels is centrally determined. This applies even if the turning center O ₂ is not on the left and right centerlines of the machine base.

In addition, as the rotation speed control of the front wheels and the rear wheels, there are stepless control as shown in the first embodiment or stepwise control as shown in the second embodiment. Select a number ratio.

[Action and effect]

In the present invention, as described above, the center of gravity O ₁ is detected by the center of gravity position detection device, and the required rotation speeds of the left and right wheels are detected by the required rotation speed detection device to detect the turning center O ₂
The control device determines the rotation speed ratio W _R / W _F of the front and rear wheels so that slip does not occur, and the control is performed so as to match this rotation speed ratio.

Therefore, according to the present invention, when the vehicle turns, the rotation of the rear wheels does not follow the turning motion and is not dragged, and the rear wheels rotate smoothly. Therefore, it is possible to provide a skid steer vehicle that can make a stable turn and is easy to turn.

〔Example〕

First Embodiment A skid steer shovel loader of this embodiment will be described with reference to FIG. The skid steer vehicle of this example continuously controls the rotation of the front wheels and the rear wheels.

The device of this example has a front left wheel 11, a rear left wheel 12, a front right wheel 13, and a rear right wheel 14 as driving wheels on both sides of the machine base 90. The left front wheel 11 is connected to the hydraulic motor 30 via a drive shaft 31. The hydraulic motor 30 is connected to the hydraulic pump 81 by the hydraulic pipe 22. Similarly for the other drive wheels, the left rear wheel 12 is the hydraulic pump 83 and the right front wheel 13 is the hydraulic pump.
82, the right rear wheel 14 is connected to a hydraulic pump 84. The hydraulic pumps 81 to 84 use the HST.

A load sensor 41 is arranged below the arm 911 of the bucket 91. Further, the steering levers 93, 94 for performing turning operation of the vehicle have slide sensors 43, 43 as required rotation speed detecting devices at the tip ends of the connecting rods 931, 941. Then, to the controller 4, the signal cables 42 and 44 from the load sensor 41 and the slide sensors 43 and 43 are connected. In the controller 4, a signal cable 45 is connected to the hydraulic pumps 81-84. Further, reference numeral 21 is an engine for rotating the four hydraulic pumps 8.

Since the device of this example is configured as described above, the following operational effects are exhibited.

That is, when the baggage 99 is loaded on the bucket 91, the load amount is detected by the load sensor 41, and the signal is input to the controller 4. Also, when turning is instructed by operating the steering levers 93, 94 during traveling, a signal corresponding to the required rotation speed of the machine base is input to the controller 4 from the slide sensors 43, 43.

In the controller 4, the position of the vehicle center of gravity O ₁ is detected by the signal from the load sensor 41. That is, the position of the vehicle center of gravity O ₁ at the time of loading is detected by the data table provided in the CPU in the controller 4 from the output signal value of the load sensor 41 and the preset center of gravity position of the vehicle itself. Further, the controller 4 detects the required rotation speed from the signal from the slide sensor 43. Subsequently, the controller 4 obtains the turning center O ₂ from the position of the vehicle center of gravity O ₁ and the required rotational speed difference between left and right. Then, the controller 4 determines the rotation speed W _{F of} the front wheels and the rotation speed ratio W _R / W _{F of the} rear wheels and the front wheels based on the required rotation speed and the turning center O ₂ as described below.
Is calculated and the rotation speed of both wheels is controlled.

That is, the turning radius of the front wheels is R _F , the turning radius of the rear wheels is R _R , and the angle between the front wheel chassis turning speed V _FL and the forward direction FR of the vehicle is θ.
_F (Fig. 3), the rear wheel platform turning speed V _RL is in the forward direction of the vehicle F
Assuming that the angle formed by _R is θ _R (Fig. 3), as described above, W _R / W _F = (R _R / R _F ) × (Cos θ _F / Cos θ _R ) (5) And the above R _R , R _F , θ _F , θ _R are uniquely determined from the position of the turning center O ₂ , as shown in FIG. 3, and therefore the ratio (W _R / W _F ) is determined. Also, the rotational speed W _{F of the} front wheels is determined from the required rotational speed. Therefore, the rotational speed W _{R of the} rear wheel from both
Is required.

That is, the controller 4 has the functions of the center-of-gravity position detection device and the control device.

As described above, the controller 4, the vehicle center of gravity O ₁ by a signal from the load sensor 41, further signal by calculating the required rotational speed difference between the left and right wheels from the slide sensor 43, the swirl based on both the center O ₂ Calculated and the rotation speed ratio of the front and rear wheels W _R / W _F
To decide. Next, the rotation speed of the right front wheel is determined based on the signal from the slide sensor 43 on the right steering lever 93 side. Further, the rotation speed of the left front wheel is determined based on the above signal from the slide sensor 43 of the left steering lever 94.

Then, the left / right rear wheel rotation speed is determined from the front / rear wheel rotation speed ratio W _R / W _F and the left / right front wheel rotation speed.

Next, based on the calculation result in the controller 4, the hydraulic oil delivery amount from the hydraulic pumps 81 to 84 to the hydraulic motors 30 for driving the drive wheels 11 to 14 is controlled. That is, the rotation of the hydraulic motor of each drive wheel is controlled. Each drive wheel rotates according to the rotation speed of this hydraulic motor. Therefore, each drive wheel rotates at an appropriate rotation speed according to the load amount of the bucket and the turning speed of the machine base, and the skid steer vehicle can smoothly turn. The control of the rotation speed is stepless.

Second Embodiment In this embodiment, when it is necessary to change the rotation ratios of the front and rear wheels due to the movement of the center of gravity, the rotation ratios of both wheels are changed to the stepwise illumination. This will be described with reference to FIG. This figure shows the relationship between the front and rear wheels on the left side.

First, the front wheel 11 is connected to the sprocket 53 via the axle shaft 54. Further, the acrylic shaft 54 of the rear wheel 12 is provided with sprockets 68 and 56 at two positions. The sprocket 68 is connected to the first clutch plate 65 via the chain 67.
Is connected to the sprocket 66. Further, one sprocket 56 is connected to the sprocket 59 of the second clutch plate 58 via the chain 57. The first and second clutch plates 65,5
A clutch 62 is interposed between the eight. The clutch shaft 621 of the clutch 62 is fitted to the drive shaft 61. Both have a slidable spline structure.
The clutch 62 is pressed against and connected to the first clutch plate 65 or the second clutch plate 58 by rotating a link 64 of the solenoid valve 63.

Further, the drive shaft 61 is connected to the hydraulic motor 30, and the hydraulic motor is the same as in the first embodiment.
To hydraulic pipe 22. The drive shaft 61 is connected to the front wheel side sprocket 53 via a sprocket 51 and a chain 52.

Since this example equipment value is configured as described above, the following operational effects are exhibited.

That is, the clutch 62 is connected to the first clutch plate 65 when going straight. Therefore, the front wheel 11 is the drive shaft first.
61 sprocket 51, chain 52, axle shaft 54 rotates, and rear wheel 12 has drive shaft 61, clutch 62,
It rotates via the first clutch plate 65 and the chain 67, and both have the same rotational speed.

Next, when the vehicle turns, when it becomes necessary to set the rotation speed ratio of the front wheels 11 and the rear wheels 12 to a certain value or more (for example, 1.1) in the control device as shown in the first embodiment, the solenoid valve 6
The clutch 62 is connected to the second clutch plate 58 by 3. The number of teeth of the sprocket 59 of the second clutch plate 58 is larger than that of the sprocket 66 of the first clutch plate 65. for that reason,
The number of rotations of the rear wheel 12 rotated through the sprocket 59, the chain 57, and the sprocket 56 is higher than that during straight traveling.
At this time, the front wheels 11 are only driven by the drive shaft 61 via the chain 52. Therefore,
The rotation speed of the rear wheel 12 becomes higher than that of the front wheel 11.

As described above, according to this example, when it is necessary to set the front-rear wheel rotation speed ratio to a certain value or more during the turning, the clutch can change the rotation speed ratio in two stages. In addition, the same effects as those of the first embodiment can be obtained.

In this example, the front / rear wheel rotation speed ratio can be changed in 3 to 5 steps by changing the clutch structure.

[Brief description of drawings]

FIG. 1 is an explanatory view of a skid steer vehicle according to the first embodiment, FIG. 2 is a similar explanatory view according to the second embodiment, FIG. 3 is a view for explaining a turning state of drive wheels, and FIG. Is an explanatory view of a drive wheel mechanism in a conventional skid steer vehicle, FIG. 5 is a side view of a shovel loader, and FIG. 6 is a control explanatory view of a conventional skid steer vehicle. 11〜14 …… Wheels, 21 …… Engine, 22 …… Hydraulic piping, 30 …… Hydraulic motor, 4 …… Controller, 62 …… Clutch, 8,81 ～ 84,88,89 …… Hydraulic pump, 93, 94 …… Steering lever,

Claims (1)

[Claims] 1. A machine base, a drive wheel provided with two wheels on both sides of the machine base, a total of four wheels, a hydraulic motor for rotating the drive wheel, and a hydraulic pump for driving the hydraulic motor. In a skid steer vehicle, a load sensor for detecting a load amount on the machine base, a center-of-gravity position detection device for detecting a center-of-gravity position of the vehicle by a signal from the load sensor, a required rotation speed detection device for the vehicle,
A control device for calculating the rotational speeds of the front wheels and the rear wheels based on signals from the center-of-gravity position detection device and the required rotation speed detection device is provided. The turning center position of the vehicle is calculated from the rotation speed difference, and the rotation speed ratio between the front wheels and the outer wheels is calculated from the turning center position so that the control turning speeds of the front and rear wheels are equal to the machine base turning speeds of the front and rear wheels. A skid steer vehicle that is easy to turn, characterized in that control is performed so that the rotational speeds of the front wheels and the rear wheels match the rotational speed ratio when turning.