JP2002079841A - Front wheel rotating speed correcting system of whole wheel drive vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and accurately control the rotating speeds of front wheels at vehicle turning time, and to surely prevent a tight corner braking phenomenon. SOLUTION: This front wheel rotating speed correcting system 60 works out a turning radius from the rotating speeds of the front wheels 2 and 3, and automatically rotates the front wheels 2 and 3 at a higher speed than a rear wheel 4 on the basis of this turning radius, the rotating speeds of the rear wheels 4 and 5, engine speed of an engine 6 and a speed stage of hydraulic motors 14 and 15 to thereby eliminate conventional troublesomeness for operating a correcting lever when turning a motor grader 1 and skilled work for adjusting the rotating speed of the front wheels 2 and 3 to meet the rotating speed of the rear wheel 4, and the tight corner braking phenomenon can be surely prevented by easily and accurately controlling the rotating speed of the front wheels 2 and 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an all-wheel
l) Front-Wheel rotation speed correction system for driving vehicles, including front wheel rotation correction for construction machines with all-wheel drive devices, such as motor graders and wheel loaders, and work vehicles such as dump trucks About the system.

[0002]

2. Description of the Related Art In recent years, motor graders and the like sometimes have an all-wheel drive device that drives all of the front and rear wheels. This all-wheel drive device drives a rear wheel with the output of the engine transmitted via a transmission, transmits the output of the engine to a hydraulic pump, and rotates a pair of hydraulic motors which are rotated by oil discharged from the hydraulic pump. Drives the left and right front wheels respectively.

When the vehicle turns, the turning radius of the front wheels becomes larger than the turning radius of the rear wheels due to the difference in the inner wheels, so that it is necessary to rotate the front wheels faster than the rear wheels. For example, in a rear-wheel drive type vehicle in which only the rear wheels are driven, there is no problem because the front wheels rotate freely according to the turning radius, but all-wheel drive devices in which the rotation of the front wheels is synchronized with the rotation of the rear wheels. In the vehicle provided with the above, the difference in rotation between the front and rear wheels due to the difference between the inner wheels at the time of turning cannot be completely absorbed, and the vehicle turns with the front wheels braked. Therefore, unless the front wheels are rotated at a higher speed than the rear wheels, a so-called tight corner braking phenomenon occurs during turning, and the vehicle does not turn smoothly.

A technique for rotating a front wheel driven by a hydraulic motor at a higher speed than a rear wheel driven by an engine is disclosed in JP-B-63-28.
No. 10 discloses that the front wheels are rotated at a fixed rate (several%) higher than the rear wheels by switching the control mode of the hydraulic pump. In addition, Table 6
Japanese Patent Application Publication No. 503280 discloses a technique of monitoring and controlling the hydraulic pressure applied to a hydraulic motor, thereby changing the rotation speed of the hydraulic motor according to the slip amount of the rear wheel, and rotating the front wheel at a higher speed than the rear wheel. It has been disclosed.

[0005]

[Problems to be solved by the invention]
In the technique described in Japanese Patent No. 2810, the front wheels always rotate faster by the same ratio than the rear wheels, so that there is a problem when the vehicle turns at the same speed (the same rotation speed of the rear wheels) and different turning radii. . In other words, the smaller the turning radius, the faster it is necessary to rotate the front wheels,
According to the technique in which the rotation speed of the front wheel is determined irrespective of the turning radius, the front wheel does not rotate at a rotation speed commensurate with the turning radius, and the tight corner braking phenomenon cannot be reliably prevented. In addition, if the front wheel rotates only a few percent faster than the rear wheel,
There is a problem that the front wheels cannot be rotated at a sufficiently high speed.

Further, in the technology described in Japanese Patent Application Laid-Open No. 6-503280, since the rear wheels are required to slip, the front wheels do not rotate at high speed when the vehicle turns without the rear wheels necessarily slipping. However, the tight corner braking phenomenon cannot be surely prevented. And
With this technology that monitors only the hydraulic pressure to the hydraulic motor, the slippage of the front wheels cannot be detected, so if the ground pressure of the front wheels is reduced and slippage is likely to occur, such as when working with a blade attached to the ground, the hydraulic motors There is a possibility that the front wheels will continue to slip as they rotate at high speed with insufficient hydraulic pressure. In such a state, energy is wasted.

On the other hand, in order to solve these problems, a correction lever for manually controlling the rotation of the hydraulic motor is provided, and by operating this correction lever during turning of the vehicle, the front wheels rotate faster than the rear wheels. In some cases. In such a case, the front wheels that are turning can be rotated at a higher speed than the rear wheels at an arbitrary rate, and the vehicle can be turned smoothly. However, it is troublesome to operate the correction lever throughout the turning of the vehicle and to operate the correction lever in addition to the steering operation at the time of turning. In addition, it is difficult and difficult to properly adjust the rotation speed of the front wheels according to the speed and the turning radius of the vehicle.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a front wheel rotational speed correction system for an all-wheel drive vehicle that can easily and accurately control the rotational speed of the front wheels when the vehicle turns and can surely prevent the tight corner braking phenomenon. is there.

[0009]

According to a first aspect of the present invention, there is provided a front wheel rotational speed correction system for an all-wheel drive vehicle that drives rear wheels with an output of an engine transmitted through a transmission and controls the output of the engine to a hydraulic pressure. A front wheel rotational speed correction system for an all-wheel drive vehicle, which is used in an all-wheel drive vehicle having an all-wheel drive device that transmits to a pump and drives a front wheel with a hydraulic motor that rotates with oil discharged from the hydraulic pump, A front wheel rotational speed detecting means for detecting the rotational speeds of the left and right front wheels, a turning radius calculating means for calculating a turning radius on the front wheel side based on the rotational speeds of the left and right front wheels, and after detecting the rotational speed of the rear wheel. Wheel rotation speed detection means, engine rotation speed detection means for detecting the rotation speed of the engine, and rotating the front wheel at a higher speed than the rear wheel based on the turning radius, the rotation speed of the rear wheel, and the rotation speed of the engine. front wheel Characterized in that it comprises a rolling speed control unit.

In the present invention as described above, the front wheel rotational speed detecting means detects the rotational speeds of the left and right front wheels, and then the turning radius calculating means calculates the turning radius on the front wheel side based on these rotational speeds. The front wheel speed control means first determines how many times the front wheel should be rotated at a higher speed than the rear wheel based on the turning radius, and then determines the magnification and the rear speed by the rear wheel speed detector. The required rotational speed of the front wheels, that is, the required rotational speed of the hydraulic motor is determined from the rotational speeds of the wheels. further,
In the front wheel speed control means, an optimum discharge oil flow rate from the hydraulic pump is determined according to the engine speed detected by the engine speed detection means, and this discharge oil is supplied to the hydraulic motor to provide the required rotation speed. Rotate the hydraulic motor,
Automatically rotates the front wheels faster than the rear wheels. According to the above, the inconvenience of operating the correction lever and the like during turning and the uncertainty that occurs when adjusting the number of rotations are eliminated, and the above object is achieved.

According to the second aspect of the present invention, a torque converter is provided between the engine and the transmission, and the rear wheel rotational speed detecting means detects a rotational speed of an output side of the torque converter. Side rotation speed detection means,
It is preferable that the transmission includes a speed gear detecting means connected to the output side of the torque converter for detecting a speed gear of the transmission. Some all-wheel drive vehicles have a configuration in which the output of an engine is transmitted to a transmission via a torque converter. In such a configuration, the rotation speed of the engine does not directly become the rotation speed on the input side of the transmission due to torque transmission loss in the torque converter. Therefore, in the present invention, the output speed of the torque converter, that is, the speed input to the transmission, is detected by the converter output speed detection means. As a result, even in an all-wheel drive vehicle equipped with a torque converter, the rotation speed of the rear wheels can be accurately detected by detecting the rotation speed input to the transmission and detecting the speed stage in the transmission. Become.

According to a third aspect of the present invention, the front-wheel rotational speed control means includes a discharge oil from the hydraulic pump that is supplied to the hydraulic motor based on the turning radius, the rotational speed of the rear wheel, and the rotational speed of the engine. The flow rate may be controlled. In such a configuration, the hydraulic pump side is made variable and the discharge oil flow rate is controlled, so that the structure on the hydraulic motor side can be simplified and its size can be reduced, and the hydraulic motor can be well accommodated in a narrow arrangement space on the front wheel side. Will be done.

In this case, according to the invention of claim 4, a plurality of speed stages are set in the hydraulic motor, and the front wheel speed control means controls the turning radius, the speed of the rear wheel, and the speed of the engine. In addition, it is desirable to control the flow rate of the discharged oil from the hydraulic pump based on the speed stage of the hydraulic motor. In such a configuration, the flow rate of the oil discharged from the hydraulic pump is controlled based on the speed step of the hydraulic motor. Therefore, this speed step is correctly detected, and the flow rate of the discharged oil from the hydraulic pump is optimally secured. Is performed smoothly.

[0014] On the other hand, in the invention of claim 5, the hydraulic motor is provided with a variable number of revolutions at a constant oil supply amount, and the front wheel revolution number control means controls the turning radius, the revolution number of the rear wheel,
Alternatively, the rotation speed of the hydraulic motor may be controlled based on the rotation speed of the engine. In such a configuration, since the hydraulic motors are variable, it is possible to make the rotational speeds of the left and right front wheels different by providing such hydraulic motors on each of the left and right front wheels. That is, when the vehicle makes a turn, it is advantageous to turn the outer wheel side of the left and right front wheels faster and the inner wheel side slower. Also, particularly in a configuration in which the output of the engine is transmitted to the transmission via the torque converter, if the engine speed is rapidly dropped from the high-speed side, the rear wheels may be slightly removed due to the characteristics of the torque converter. Still spinning at high speed.
At this time, the rotation difference between the engine speed (hydraulic pump) and the rear wheel increases, and even if the flow rate of the discharged oil from the hydraulic pump is maximized, the front wheel cannot be rotated at a higher speed than the rear wheel. The tight corner braking phenomenon may occur at the same time. However, according to the present invention, since the rotational speed of the hydraulic motor that drives the front wheels is directly controlled, even when the discharge oil flow rate of the hydraulic pump is small, light torque high-speed driving is reliably realized with a small discharge oil flow rate, The rotation speed of the hydraulic motor is maintained at a high speed, and the tight corner braking phenomenon is less likely to occur. The present invention controls the number of revolutions of the hydraulic motor based on the turning radius, the number of revolutions of the rear wheel, and the number of revolutions of the engine. This is different from the invention of claim 4 in which the speed stage of the hydraulic motor is used as the control.

In the invention according to claim 6, the vehicle includes a front frame provided with the front wheels, and a rear frame provided with the rear wheels, and these frames are connected so as to be adjustable in angle. Articulated angle detecting means for detecting a connection angle between the front frame and the rear frame is provided, and the turning radius calculating means determines the turning radius based on the rotation speeds of the left and right front wheels and the connection angle of each frame. May be. Such a configuration is suitably used for a refraction type motor grader having a front frame and a rear frame, and a turning radius can be more accurately obtained.

[0016]

FIG. 1 is an overall view schematically showing a motor grader 1 as an all-wheel drive vehicle to which a front wheel rotation speed correcting system according to an embodiment of the present invention is applied, and FIG. 2 is a motor grader. 1 is a plan view showing a main part of the motor grader 1, FIG. 3 is a configuration diagram showing a schematic configuration of a main mechanism of the motor grader 1, and FIG.
It is sectional drawing of the one component. First,
The main configuration of the motor grader 1 will be described with reference to FIGS.

1 and 2, the motor grader 1
Are a left front wheel 2, a right front wheel 3 which is a pair of left and right front wheels, and a left rear front wheel (not shown)
And a rear right front wheel 4 and a rear right rear wheel 5. The vehicle is a six-wheeled vehicle. Blades 50 provided between the front wheels 2, 3 and the rear wheels 4, 5 finish the ground on the ground, remove snow, and perform light Cutting, material mixing, etc. can be performed.

The front wheels 2 and 3 are provided on the front frame 51 together with the blade 50, and the rear wheels 4 and 5 are provided on the rear frame 52 side. The front frame 51 is
As shown in FIG. 2, a vertical center pin 53 is rotatably connected to the rear frame 52 at a position substantially below the cockpit. The rotation of the front frame 51 is performed by extending and contracting an articulated cylinder 54 connected between the frames 51 and 52 by operating a lever from the cockpit.

Further, as shown in FIG. 3, the front wheels 2 and 3
Hydraulic system 7 connected to one output side of engine 6
, The rear wheels 4, 5 are driven via a torque converter 8, a transmission 9, a final reduction gear 10, and a tandem gear 11 connected to the other output side of the engine 6. That is, the motor grader 1 is an all-wheel drive vehicle in which the front and rear wheels 2 to 5 are driven together by the power transmission devices 6 to 11,
The devices 6 to 11 constitute the all-wheel drive device 12.
Most of such all-wheel drive devices 12 (engine 6,
A part of the hydraulic system 7, a torque converter 8, a transmission 9, and a final reduction gear 10) are supported by a rear frame 52.

The hydraulic system 7 of the all-wheel drive 12
Is a hydraulic pump 13 driven directly by the output of the engine 6.
And a left hydraulic motor 14 and a right hydraulic motor 15 that are rotated by hydraulic oil discharged from the hydraulic pump 13 to drive the front wheels 2 and 3.

In this embodiment, the hydraulic pump 13 is a swash plate type axial plunger pump. Hydraulic pump 1
In 3, the angle of the swash plate is changed to control the discharge flow rate of hydraulic oil by a control signal CS output from the controller 100 functioning as a kind of computer (variable displacement type). In the hydraulic pump 13, the controller 100
The hydraulic oil discharge direction can be switched to each of the flow paths A and B by the direction switching signal DS output from the motor grader 1. By changing the discharge direction and changing the rotation direction of each of the hydraulic motors 14 and 15, To move forward or backward. However, the hydraulic pump used is not limited to the swash plate type, and may be a swash plate type or the like.

The hydraulic motors 14 and 15 are of a radial piston type in the present embodiment, and as shown in an enlarged cross section in FIGS.
6, a fixed core 17 into which the rotary valve 16 is inserted, and a rotatable cam ring 18 disposed on the outer peripheral side of the fixed core 17. The cam ring 18 is connected to the front wheels 2 and 3.

A plurality of cylinders 19 are formed radially on the fixed core 17, and each cylinder 19 has a roller 20 at its tip.
Is accommodated so as to be able to advance and retreat. As shown in FIG. 4A, each piston 21 is connected to a supply port 22 of a rotating rotary valve 16 through a cylinder 19.
The hydraulic oil is sequentially advanced in the circumferential direction with the hydraulic oil supplied therein, and is retracted in the order in which the hydraulic oil is advanced due to the hydraulic oil being discharged through the discharge port 23 and the urging force of the urging member (not shown). During this time, the roller 20 of the piston 21 that has advanced comes into contact with the cam surface 24 inside the cam ring 18 and rotates the cam ring 18.

On the other hand, FIG.
1 shows a state in which 1 is retracted. Such a state is realized by cutting off the supply of hydraulic oil to the hydraulic motors 14 and 15. Then, the supply of the hydraulic oil is cut off by operating the freewheel valve 25 with the drive system switching signal KS from the controller 100. In this state, the motor grader 1 is released from all-wheel drive and becomes rear-wheel drive.

By the way, the hydraulic motors 14 and 15 are set to, for example, a second speed (a fixed type, not a variable type). As the first stage, FIG.
In this case, the hydraulic oil is supplied from the supply port 22 of the rotary valve 16 to all the pistons 21 as shown in FIG. 2
As the stage, of the ten pistons 21, for example,
× Hydraulic oil is supplied only to the four pistons 21 arranged at the upper position and not adjacent to each other in the circumferential direction, and hydraulic oil is not supplied to the other six pistons 21. At this time, the other six pistons 21 are completely retracted as shown in FIG. 4B and do not come into contact with the cam ring 18. At this speed stage,
If the flow rate of the discharge oil from the hydraulic pump 13 is set to be the same as that of the first stage, the number of the pistons 21 to which the hydraulic oil is supplied is reduced to four, and the hydraulic pressure acting on the pistons 21 is increased.
Moves at a high speed, and the cam ring 18 rotates at a higher speed than the first stage. Conversely, even when the discharge oil flow rate is set to half or less of the first stage, the same rotational speed as that of the first stage can be obtained. These first and second speed stages are automatically switched according to the speed stage of the transmission 9 and the like by the solenoid valve 26 operated by the speed stage switching signal MS from the controller 100.

Returning to the hydraulic system 7 of FIG. 3, the hydraulic sensors 27,
28 is provided, and it is determined whether or not the hydraulic pressure in the hydraulic circuit is appropriate based on a hydraulic pressure detection signal OS output from the hydraulic pressure sensors 27 and 28 to the controller 100.

Further, on the hydraulic pump 13 side of the freewheel valve 25, there is provided a communication passage C for communicating the passages A and B.
9 are provided. The inching valve 29 is operated by a power transmission switching signal BS from the controller 100.
When the communication flow path C is disconnected by the inching valve 29 (the state shown in FIG. 3), the hydraulic oil discharged from the hydraulic pump 13 is supplied to the hydraulic motors 14 and 15; The oil circulates in the flow paths A to C, is not supplied to the hydraulic motors 14 and 15, and power is not transmitted. Such an inching valve 29 is used for temporarily stopping the driving of the front wheels 2 and 3 by the hydraulic motors 14 and 15 for a short period of time.

Here, the hydraulic motors 14 and 15 are connected in parallel to the flow paths A and B. Specifically, the flow path A includes a first left branch flow path D from one of the left hydraulic motors 14 and a first right branch flow path E from one of the right hydraulic motors 15.
And a second left branch flow path F from the other of the left hydraulic motor 14 and a second right branch flow path G from the other of the right hydraulic motor 15 are connected to the flow path B.

The flow path A, the first left branch flow path D, and the first right branch flow path E are connected by a flow collecting valve 30. Separation flow valve 30
Is provided with throttles 31 and 32 on the side of each branch flow path D and E, respectively. In the diversion / collection valve 30, for example, at the time of forward operation in which the hydraulic oil is discharged from the hydraulic pump 13 to the flow path A side, the hydraulic oil is divided into the hydraulic motors 14 and 15 at an equal flow rate.
For example, at the time of reverse operation in which hydraulic oil is discharged to the flow path B side,
Hydraulic oil passing through each of the branch flow paths D and E is collected at a uniform flow rate, and as a result, the flow rates diverted from the flow path B to the second left branch flow path F and the second right branch flow path G are equalized. .

First left branch flow path D and first right branch flow path E
Are connected by a bypass flow path H. A throttle 33 is provided in the bypass passage H. These bypass passages H
The throttle 33 has a function of supplying a little more hydraulic oil to one hydraulic motor 14 (15) on the outer wheel side during turning than the other hydraulic motor 15 (14) on the inner wheel side. . As a result, the one front wheel 2 (3), which is the outer wheel, is rotated somewhat faster than the other front wheel 3 (2), which is the inner wheel, so that turning can be performed more smoothly.

In FIG. 3, the controller 100 includes:
Drive system changeover switches 3 provided in the cockpit
4, a front wheel rotation control lever 35, a speed gear detection sensor 36 as speed gear detection means, a limit switch 37, and an angle sensor 38 as articulated angle detection means also shown in FIG. ing.

The drive system changeover switch 34 switches the drive system of the motor grader 1 between all-wheel drive and rear-wheel drive, and outputs a switching signal SS to the controller 100 by turning on / off the switch 34, The controller 100 that has received the signal outputs the drive mode switching signal KS to the above-described freewheel valve 25, and switches the drive mode.

The front wheel rotation control lever 35 adjusts the swash plate angle of the hydraulic pump 13 by manual operation, and outputs a swash plate angle adjustment signal FS to the controller 100 every time the tiltable control lever 35 is tilted. Then, the controller 100 receiving this outputs a control signal CS to the hydraulic pump 13 to change the angle of the swash plate. Such a front wheel rotation control lever 35 is used to reduce the torque of the front wheels 2 and 3 at which the ground pressure becomes low during work using the blade 50 and the like, and prevents the front wheels 2 and 3 from slipping. It is effective for In addition, the front wheel rotation control lever 35 is also used to adjust the target rotation speed of the front wheels 2 and 3 in the front wheel rotation speed correction system. This will be described later.

The speed position detection sensor 36 detects the position of the speed position of the transmission change lever 39, that is, when the lever 39
The speed stage detection signal TS is output to the controller 100 by detecting at which speed stage the vehicle is located among the first through sixth stages, the first through sixth reverse stages, and the neutral position. This speed stage detection signal TS
When the controller 100 determines that the front wheels 2 and 3 need to be driven at a light torque and a high speed, the controller 100 sends a speed gear switching signal M to the solenoid valve 26.
S is output to switch the speed stage of the hydraulic motors 14 and 15 to the second stage on the high-speed side. When the speed position is determined to be neutral based on the speed position detection signal TS, the controller 100 outputs a power transmission switching signal BS to the inching valve 29 to stop the power transmission to the hydraulic motors 14 and 15, and , 3 are released. In addition, the speed gear detection signal TS from the speed gear detection sensor 36 is also used in the front wheel speed correction system, which will be described later.

The limit switch 37 is turned on when the inching pedal 40 is depressed, and outputs a depression detection signal PS to the controller 100 during this state. In this state, since power is not transmitted to the rear wheels 4 and 5 by a speed switching clutch mechanism (not shown) or a forward / reverse direction switching clutch mechanism in the transmission 9, the controller 100 outputs the power transmission switching signal BS to the inching valve 29. Then, the transmission of power to the hydraulic motors 14 and 15 is stopped, and the driving of the front wheels 2 and 3 is also released.

The angle sensor 38 detects an articulated angle (connection angle) of the front frame 51 with respect to the rear frame 52 as shown in FIG. 2, and outputs an angle detection signal AS to the controller 100. The controller 100 having received the angle detection signal AS outputs a display signal to an indicator (not shown) in the cockpit, and displays the turning state of the front frame 51 on the indicator.

Hereinafter, the front wheel speed correction system 60 according to this embodiment will be described. In FIG. 3, a front wheel rotation speed correction system 60 includes a left pickup sensor 6 as a front wheel rotation speed detecting unit that detects the rotation speed of the left front wheel 2.
1, a right pickup sensor 62 as another front wheel rotation speed detecting means for detecting the rotation speed of the right front wheel 3, and a turning for determining the turning radius of the front wheels 2, 3 based on the rotation speed of the front wheels 2, 3. A radius calculating means 63; a rear wheel speed detecting means 64 for detecting the number of revolutions of the rear wheels 4 and 5; an engine speed sensor 65 as an engine speed detecting means for detecting the engine speed; A front wheel speed control means 66 for controlling the speed of the front wheels 2 and 3 based on the speed of the wheels 4 and 5 and the speed of the engine 6 is provided.

Each of the pickup sensors 61 and 62 outputs a front wheel rotation speed detection signal NS _L , N corresponding to the rotation speed of the front wheels 2 and 3.
And outputs the S _R to the controller 100. The rear wheel speed detecting means 64 includes a converter output side rotation sensor 67 as a converter output side speed detecting means for detecting the output side speed of the torque converter 8, and the transmission change lever 3.
And 9 speed speed detection sensors 36 for detecting the speed speed positions. Converter output side rotation sensor 67
Transmits the converter speed detection signal QS to the controller 10.
Output to 0. The engine speed sensor 65 outputs an engine speed detection signal ES to the controller 100.

The turning radius calculating means 63 and the front wheel speed control means 66 are software and are stored in appropriate storage means 101 such as a ROM and a RAM constituting the controller 100. Then, as shown in FIG. 3, it is called from the storage means 101 and executed by the CPU 102. Here, controller 1
The storage means 101 stores a lookup table (not shown) in which the graphs shown in FIGS. 5 to 7 are tabulated in addition to the software.

FIG. 5 shows the rotational speeds N of the front left wheel 2 and the front right wheel 3.
_L, and a graph showing the turning radius R and the turning direction of the front wheels 2 and 3 side in accordance with the N _R. FIG. 6 is a graph showing a ratio n ₁ between the front wheel rotation speed and the rear wheel rotation speed according to the turning radius R,
When turning with a predetermined turning radius R, it is possible to read how many times the front wheels 2 and 3 need to be rotated with respect to the rear wheels 4 and 5. FIG. 7 is a graph showing the optimum swash plate angle θ of the hydraulic pump 13 according to the ratio n2 between the required rotation speed of the front wheels 2 and 3 (the required rotation speed of the hydraulic motors 14 and 15) and the rotation speed of the engine 6. It is possible to read the optimum swash plate angle θ for each speed stage of the hydraulic motors 14 and 15.

Next, the control of the rotation speed of the front wheels 2 and 3 by the front wheel rotation speed correction system 60 will be specifically described.
First, in the traveling motor grader 1, the turning radius calculation means 63 monitors the front wheel rotation speed detection signals NS _L and NS _R output from the pickup sensors 61 and 62. When the motor grader 1 starts turning right, for example, the left front wheel 2
Is an outer wheel, and the right front wheel 3 is an inner wheel. Therefore, the left front wheel 2 rotates faster than the right front wheel 3 with a slight braking applied. The turning radius calculating means 63 monitoring this state,
From the information of the front wheel rotation speed detection signals NS _L and NS _R , the left front wheel 2
The rotation speed N _L of the right front wheel 3 is larger than the rotation speed N _R of the right front wheel 3, and it is determined that the vehicle is turning right. Referring to a lookup table in the storage unit 101 based on the graph of FIG. For example, it is derived that the distance is 20 m.

Next, the front wheel rotational speed control means 66
With reference to a look-up table based on the graph, a rotation speed ratio n ₁ when the turning radius R = 20 m is derived. FIG.
According to the graph, it is determined that n ₁ = 1.2, and it is necessary to rotate the front wheels 2 and 3 1.2 times faster than the rear wheels 4 and 5. In addition, the front wheel speed control means 66 controls the rear wheels 4,
5 has a function of calculating the number of rotations Mrpm. The rotational speeds Mrpm of the rear wheels 4 and 5 are calculated based on a converter rotational speed detection signal QS from the converter output side rotation sensor 67 and a speed gear detection signal TS from the speed gear detection sensor 36. The rotational speed Mrpm of the rear wheels 4 and 5 is set to 1.2
The multiplied rotation speed (1.2 Mrpm) is the required rotation speed required for the front wheels 2 and 3. Further, the front wheel speed control means 6
6 monitors the engine speed detection signal ES from the engine speed sensor 65, and outputs the speed stage switching signal MS to the solenoid valve 26, that is, the hydraulic motor 1
4 and 15 speed stages are monitored.

In the following, for example, it is assumed that the rotational speed of the engine 6 is determined to be 1000 rpm from the engine rotational speed detection signal ES, and that the speed stages of the hydraulic motors 14 and 15 are determined to be the first stage. According to this condition, the required rotation speed of the front wheels 2 and 3 is 1.2 Mrpm, and the rotation speed of the engine 6 is 1000 rpm. Therefore, the rotation speed ratio n ₂ is 1.2 × 10 ⁻³ M. Therefore, the front wheel speed control means 66 obtains the optimum swash plate angle θ ₁ when the speed stage of the hydraulic motors 14 and 15 is the first speed by referring to the lookup table based on the graph of FIG. 13 is adjusted to the swash plate angle θ ₁ to secure the optimal discharge oil flow rate of the hydraulic oil, and the front wheels 2, 3 driven by the hydraulic motors 14, 15 are driven at 1.2 times the speed of the rear wheels 4, 5. Then rotate it. When the speed stages of the hydraulic motors 14 and 15 are the second speed stage, the front wheel rotation speed control means 66 obtains the optimum swash plate angle θ ₂ as is clear from FIG. And this swash plate angle θ
_The swash plate angle θ ₁ is smaller than the swash plate angle θ ₁ .
3 will be rotated. The above is the motor grader 1
3 is a flow of the rotation correction control of the front wheels 2 and 3 at the time of turning.

The number of rotations of the rear wheels 4 and 5 is the same.
pm, the rotational speed of the engine 6 may be different. In the above example, the rotation speed of the rear wheels 4 and 5 is Mr.
At the time of, the rotation speed of the engine 6 was 1000 rpm, but the position where the speed stage of the transmission 9 is higher (small gear ratio side)
, The same rotation speed Mrpm of the rear wheels 4 and 5 can be obtained at a low engine rotation speed of, for example, about 800 rpm. Further, even when the vehicle is going down a slope, since much less torque is required, the same rotational speed Mrrpm of the rear wheels 4 and 5 can be obtained at a low engine rotational speed even though the transmission 9 has the same speed stage. . Under such conditions, in the graph of FIG.
0 rpm, the rotation speed ratio n ₂ is 1.5 × 10 ^−3.
M and becomes large. However, during such operation, n ₂
Becomes too large, and if the speed stages of the hydraulic motors 14 and 15 are set to the first speed stage, the optimum swash plate angle may become θ ₃ and exceed the maximum swash plate angle θ _MAX (the swash plate angle Even if θ is maximized, the rotational speeds of the front wheels 2 and 3 cannot keep up with the rotational speeds of the rear wheels 4 and 5), and the controller 100 automatically switches the speed stage of the motors 14 and 15 to the second stage automatically in advance. . Therefore, the front wheel speed control means 66 determines the optimum swash plate angle θ.
Instead of ₃ , an optimum swash plate angle θ ₄ is obtained.

When the motor grader 1 goes straight, there is no difference between the rotation speeds N _L and N _R of the front wheels 2 and 3, so that the turning radius is detected as R = ∞ as shown in FIG. It is determined that the rotational speed ratio in the graph is n ₁ = 1. That is, the required rotation speed of the front wheels 2 and 3 in the graph of FIG. The method for obtaining the optimum swash plate angle θ from the required rotation speed is the same as that at the time of turning.

Further, the blade 50 is turned on the ground.
Or when the ground is slippery, and
When the diameter R is 20 m as described above, as described above, the front wheels 2, 3
Was rotated 1.2 times faster than the rear wheels 4,5,
The front wheels 2 and 3 may slip. In this case
Has a rotational speed ratio n₁(Fig. 6)
I will. Therefore, the front wheel rotation speed correction system of the present embodiment
At 60, the operator who has determined the condition of the ground
By operating the front wheel rotation control lever 35 shown in FIG.
The relationship curve 68 in FIG. 6 is shifted to the left in FIG.
Rotational speed ratio n at diameter R ₁(Fig. 6) uniformly reduced
(See dash-dot line). By doing this
The torque at the front wheels 2 and 3 is reduced, causing slip
It becomes difficult.

According to this embodiment, the following effects can be obtained. (1) In front rotational speed correction system 60, the rotation speed N _L of the front wheels 2 and 3, to determine the turning radius R from the N _R, the rotation speed M of the turning radius R, the rear wheels 4 and 5, the rotation of the engine 6 On the basis of the number and the speed stage of the hydraulic motors 14 and 15,
3 is automatically rotated at a higher speed than the rear wheels 4 and 5, so that the troublesome operation of the correction lever and the like during the turning of the motor grader 1 and the rotation speed of the front wheels 2 and 3 can be reduced by the rotation of the rear wheels 4 and 5. Skilled work such as adjusting to the number can be eliminated, and the number of rotations of the front wheels 2 and 3 can be easily and accurately controlled, thereby securely preventing the tight corner braking phenomenon.

(2) The target rotation speed of the front wheels 2 and 3 is a turning radius R
Therefore, the front wheels 2 and 3 can be rotated at a high speed corresponding to the turning radius R. For example, the smaller the turning radius R, the higher the target rotation speed of the front wheels 2 and 3 can be. The braking phenomenon can be more reliably prevented. Further, in the present system 60, the rotation speeds of the front wheels 2, 3 can be sufficiently increased irrespective of the slip of the rear wheels 4, 5, and the front wheels 2, 4 can be surely secured even when the vehicle turns without the rear wheels 4, 5 slipping. High speed rotation.

(3) Since the rotation speed ratio n ₁ when the front wheels 2 and 3 are operated at high speed can be changed by the front wheel rotation control lever 35, the rotation speed ratio n ₁ when the front wheels 2 and 3 are likely to slip. By setting ₁ small, the torque at the front wheels 2 and 3 can be reduced, and the front wheels 2 and 3 can be reliably gripped on the ground to prevent slipping. Therefore, even when the ground pressure of the front wheels 2 and 3 is reduced by attaching the blade 50 to the ground, or even on the snow-covered ground, turning can be performed safely and smoothly.

(4) The front wheel rotation control lever 3
By operating 5, the flow rate of the discharged oil from the hydraulic pump 13 can be controlled, and the number of revolutions of the front wheels 2 and 3 can be arbitrarily adjusted according to the slip condition. It is possible to prevent the front wheels 2 and 3 with reduced contact pressure from continuing to slip as they are, and to suppress wasteful consumption of energy.

(5) The rear wheel rotational speed detecting means 64 includes a converter output side rotational sensor 67 for detecting the rotational speed on the output side of the torque converter 8 and the speed of the transmission 9 connected to the output side of the torque converter 8. In this embodiment, the engine speed is input to the transmission 9 even in the present embodiment in which the engine speed is not directly used as the input-side speed of the transmission 9 by the torque converter 8 because of the speed stage detection sensor 36 that detects the speed. By detecting the rotational speed and the speed stage of the transmission 9, the rotational speed Mrpm of the rear wheels 4 and 5 can be accurately calculated.

(6) In the front wheel rotational speed correction system 60, the hydraulic motors 14 and 15 and thus the front wheels 2 and 3 are rotated at high speed by controlling the flow rate of the oil discharged from the hydraulic pump 13; The structure can be simplified and its size can be reduced, for example, it is not necessary to make it variable.
For this reason, the hydraulic motors 14 and 15 can be satisfactorily accommodated in the narrow arrangement space on the front wheel 2 and 3 side.

(7) The hydraulic motors 14 and 15 have two speed stages. In the front wheel rotation speed correcting system 60, the speed stages of the hydraulic motors 14 and 15 are
3 is handled as one parameter when controlling the flow rate of the discharged oil from the hydraulic pump 1 regardless of which of the first and second speed stages is set.
The swash plate angle θ of No. 3 can be accurately adjusted, and the vehicle can smoothly turn while securing an optimal discharge oil flow rate.

(8) In order to suppress the fuel consumption of the engine 6, the speed stage of the transmission 9 is set to the small gear ratio side while the engine speed is maintained at a low speed, and the rear wheels 4, 5 are operated at a high speed. May rotate. In such a case, the hydraulic pump 13
Are also driven at a low rotational speed, even if the discharge oil flow rate of the hydraulic pump 13 is maximized, the rotation of the hydraulic motors 14 and 15 is limited, and the front wheels 2 and 3 are driven at a higher speed than the rear wheels 4 and 5. There is a possibility that rotation cannot be performed. On the other hand, if the hydraulic motors 14 and 15 in this embodiment are used,
By switching the speed stage to the second stage even when the discharge oil flow rate from the hydraulic pump 13 becomes the maximum when the first stage is the first stage and the hydraulic motors 14 and 15 cannot rotate at a high speed any more. Thus, the hydraulic motors 14 and 15 can be rotated at a higher speed. Further, by performing such a light torque high-speed drive, it is possible to realize low fuel consumption.

It should be noted that the present invention is not limited to the above-described embodiment, but includes other configurations that can achieve the object of the present invention, and the following modifications are also included in the present invention.
For example, as shown in FIG. 8, in addition to controlling the discharge oil flow rate by making the hydraulic pump 13 variable, the hydraulic motor 114,
115 is a variable displacement type of a swash plate type or an oblique axis type to make the number of revolutions at a constant supply oil flow rate variable.
115 control signal CS _L of the swash plate angle or oblique angle from the controller 100 of, by individually controlled in CS _R, 3
Without using the solenoid valve 26 shown in FIG.
3 may be rotated at a higher speed than the rear wheels 4 and 5. Such an invention is included in claim 5.

The variable hydraulic motors 114, 11
5, the hydraulic motors 114, 11
5 separately control the motor grader 1
When turning, positively use the outer wheel side of the left and right front wheels 2 and 3.
High speed, and the inner ring side can be positively rotated slowly.
Turning can be made smoother. Also, the hydraulic motor 1
14, 115 are control signals C from the controller 100.
S _L, CS_RIs directly controlled by the motor to change the rotation speed
Therefore, this is not the case when the discharge oil flow rate from the hydraulic pump 13 is small.
Thus, high-speed driving with light torque can be reliably realized. For this reason,
Due to the characteristics of the torque converter 8, the rotational speed of the engine 6
Is suddenly dropped from the high-speed side.
8 is maintained at a high speed, so that the rear wheels 4, 5
Pull the front wheels 2 and 3 even if
Continued to rotate at high speed,
It is possible to suppress the occurrence of the toner braking phenomenon.

Note that the hydraulic pump 13 is fixed,
The front wheels 2, 3 are rear wheels only by controlling the motors 114, 115.
It may be rotated at a higher speed than 4,5,
However, it is included in the invention of claim 5. In addition, hydraulic mode
The swash plate angle and the oblique axis angle of the
CS _L, CS_RRather than controlling with a single control signal
It may be controlled. In the above embodiment and the modification shown in FIG.
The left and right front wheels 2 and 3 each have an individual hydraulic motor 1
4, 15, 114, 115, but both
Even when the front wheels 2 and 3 are driven by one hydraulic motor
Included in the Ming.

In the above embodiment, the angle detection signal AS from the angle sensor 38 for detecting the articulated angle is:
The angle detection signal AS is used to display the rotation state of the front frame 51 on the indicator in the cockpit. However, the angle detection signal AS may be used as one parameter when controlling the amount of oil discharged from the hydraulic pump 13. Such an invention,
It is included in claim 6. When the front frame 51 is rotating with respect to the rear frame 52, the difference between the turning radii on the front wheels 2 and 3 and the turning radii on the rear wheels 4 and 5 is large. Compared to a state in which the front wheels 2 and 3 have the same turning radius, there is a possibility that a difference in ease of turning may occur. Therefore, when the front frame 51 is rotating, the rotational speed ratio n1 in FIG. 6 determined when the front frame 51 is not rotating may be appropriately corrected according to the articulated angle. By doing so, the rotation speeds of the front wheels 2 and 3 can be made appropriate according to the articulated angle, and a front wheel rotation speed correction system more suitable for the motor grader 1 can be provided.

The front wheel rotation speed correction system 6 of the above embodiment.
Although 0 is applied to the motor grader 1, the front wheel rotational speed correction system of the present invention is not limited to this, and is applied to, for example, other construction machines such as a wheel loader and a work vehicle such as a dump truck. In short, while driving the rear wheels with the output of the engine transmitted through the transmission, transmitting the output of the engine to the hydraulic pump,
In addition, the present invention can be applied to an all-wheel drive vehicle including an all-wheel drive device that drives front wheels by a hydraulic motor that rotates with oil discharged from the hydraulic pump.

[0060]

As described above, according to the present invention,
The number of revolutions of the front wheels during vehicle turning can be controlled easily and accurately,
This has the effect that the tight corner braking phenomenon can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is an overall view schematically showing a motor grader to which a front wheel rotation speed correction system according to an embodiment of the present invention is applied.

FIG. 2 is a plan view showing a main part of the motor grader.

FIG. 3 is a configuration diagram showing a schematic configuration of the motor grader.

FIG. 4 is a sectional view showing one component of the motor grader.

FIG. 5 is a graph showing the contents of a lookup table used in the embodiment.

FIG. 6 is a graph showing the contents of another lookup table used in the embodiment.

FIG. 7 is a graph showing the contents of still another lookup table used in the embodiment.

FIG. 8 is a configuration diagram showing a modification of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Motor grader which is an all-wheel drive vehicle 2 Left front wheel 3 Right front wheel 4 Left rear front wheel 5 Left rear wheel 6 Engine 8 Torque converter 9 Transmission 12 All-wheel drive 13 Hydraulic pump 14 Left hydraulic motor 15 Right hydraulic motor 36 Speed Speed detection sensor as step detection means 38 Angle sensor as articulated angle detection means 51 Front frame 52 Rear frame 60 Front wheel rotation speed correction system 61 Left pickup sensor as front wheel rotation detection means 62 Front wheel rotation detection means Right pickup sensor 63 Turning radius calculating means 64 Rear wheel speed detecting means 65 Engine speed sensor as engine speed detecting means 66 Front wheel speed controlling means 67 Converter output side speed sensor as converter output side speed detecting means _NL left Front wheel rotation speed N _R Right front wheel rotation speed M Rear wheel speed R Turning radius

Claims (6)

[Claims] 1. A hydraulic motor that drives the rear wheels with the output of the engine transmitted through a transmission, transmits the output of the engine to a hydraulic pump, and rotates the front wheels with hydraulic oil that is discharged from the hydraulic pump. A front-wheel rotational speed correction system for an all-wheel drive vehicle used in an all-wheel drive vehicle having an all-wheel drive device for driving a front wheel rotational speed detecting means for detecting the rotational speeds of the left and right front wheels, respectively, Turning radius calculation means for calculating a turning radius on the front wheel side based on the rotation speed of the front wheel, rear wheel rotation speed detecting means for detecting the rotation speed of the rear wheel, and engine rotation speed detecting means for detecting the rotation speed of the engine. A front wheel rotation speed control means for rotating the front wheel at a higher speed than the rear wheel based on the turning radius, the rotation speed of the rear wheel, and the rotation speed of the engine. Front wheel turn Number correction system. 2. The front wheel rotational speed correction system for an all-wheel drive vehicle according to claim 1, wherein a torque converter is provided between the engine and the transmission, and the rear wheel rotational speed detecting means includes: A converter output-side rotational speed detecting means for detecting a rotational speed on the output side of the torque converter, and a speed gear detecting means for detecting a speed gear of the transmission connected to the output side of the torque converter. A front wheel rotational speed correction system for an all-wheel drive vehicle, characterized in that: 3. The front wheel rotation speed correction system according to claim 1, wherein the front wheel rotation speed control means includes a turning radius, a rotation speed of a rear wheel, and a rotation speed of an engine. A front wheel rotational speed correction system for an all-wheel drive vehicle, wherein a flow rate of a discharge oil from the hydraulic pump supplied to the hydraulic motor is controlled based on the rotational speed. 4. The front wheel rotational speed correction system for an all-wheel drive vehicle according to claim 3, wherein a plurality of speed stages are set in said hydraulic motor, and said front wheel rotational speed control means includes: said turning radius; A front wheel rotational speed correction system for an all-wheel drive vehicle, which controls a discharge oil flow rate from the hydraulic pump based on a speed stage of the hydraulic motor in addition to the rotational speed of the engine and the rotational speed of the engine. 5. The front wheel rotational speed correction system for an all-wheel drive vehicle according to claim 1, wherein the hydraulic motor is provided with a variable rotational speed at a constant supply oil flow rate. The front wheel rotational speed control means includes the turning radius,
A front wheel rotation speed correction system for an all-wheel drive vehicle, wherein the rotation speed of the hydraulic motor is controlled based on the rotation speed of a rear wheel and the rotation speed of an engine. 6. The front wheel rotation speed correction system for an all-wheel drive vehicle according to claim 1, wherein a front frame provided with the front wheels, and a rear frame provided with the rear wheels. And these frames are connected so as to be adjustable in angle, and articulated angle detecting means for detecting a connection angle between the front frame and the rear frame is provided. The turning radius is determined based on the rotation speed of the front wheels and the connection angle of each of the frames.