EA010279B1 - Tractor with hydraulic speed and steering control for steering at maximum speed - Google Patents

Abstract

A tractor has hydraulically driven wheels at a cab end and castor wheels at an engine end. It can be driven cab forward in a working mode with a header on the forward end. It is rotated to engine forward in the transport position for more stable higher speed travel. The driven wheels are driven by hydraulic motors each having their own drive pump the output of which is controlled by a cam plate. The speed control is effected by a manually operable lever through a servo-cylinder which locates a speed control arm moving both cam plates to the set position. In a maximum speed position both cam plates are engaged against a stop. The steering is effected by moving the cam plates differentially to drive the wheels at different speeds. The piston rod of the servo-cylinder includes a spring relief so that the speed control arm can back off from the maximum position by moving the servo-cylinder body when steering in the maximum speed position.

Description

The present invention relates to a tractor with a hydraulic control type, usually, but not necessarily used as a swath tractor, which is mounted on a pair of hydraulically-driven wheels and a pair of self-guided wheels and controlled using the difference in rotational speeds of the driving wheels.

The level of technology

Hydrostatic steering vehicles have been known for many years, and their use with roll reapers has been significant. There was a limitation on the speed of movement of such roll headers due to instability at high speed, when the driving wheels are in front of the self-guiding wheels (cab forward). Increased road speeds allow the user to travel long distances without using trailers and tractors.

At the same time pending application No. 11/116418, filed April 28, 2005, and Canadian patent application No. 2505458, filed April 27, 2005, assigned to the present applicant, a car is described, with the car moving in transport mode with self-orienting wheels in front of the leading wheels (engine forward), and in this position the machine is much more stable, and higher speeds are possible.

When turning a self-propelled machine that has steered wheels in front, the centrifugal force at the center of gravity is such that it tends to assist the rear drive wheels in leveling the machine. On the other hand, when turning a self-propelled machine that has drive wheels in front, the centrifugal force in the center of gravity is such that it facilitates the turn, and the front drive wheel must overcome this force to level the machine. Thus, the machine is more stable or tends to move in a more straight line when the caster wheels are at the front and the driven wheels are at the back.

Other two-way vehicles, such as the Horn TU140, although hydrostatically driven, do not have hydrostatic control. The machine TU140 is based on a pivotal action between the front and rear sections of the tractor to control it. Machine control TU140 is carried out using hydraulic valves and cylinders.

Soor 1pr18 manufactures a model 742 tractor with a roller header, which is a two-way tractor. This was done in order to be able to disconnect and install the header at the end of the tractor, where the driving wheels are located. It also creates a load on the drive wheels to make the car more manageable when driving.

Regarding a conventional machine of this type, ground speed and machine control are achieved by varying the capacity of two individual hydraulic pumps, each of which drives a hydraulic motor connected to a drive wheel. In the variant with the use of hydraulic piston pumps, this performance changes due to a change in the angle of the cam disc or the swash plate inside the pump, which changes the volumetric capacity of the pump.

To change the speed of the machine, the volumetric capacity of both pumps is changed simultaneously. For steering the machine, the volumetric capacity of both pumps is changed relative to each other in such a way that the feed to the wheels is different, which causes the car to turn.

For maximum efficiency, it is advisable to set the pumps to the highest possible volumetric flow rate at any given speed. Thus, to achieve the maximum speed of the machine, it is desirable to have the maximum volumetric capacity of both pumps when the machine moves at full speed. The problem here is that in order to steer the machine at full speed (with the full volumetric capacity of both pumps), the steering mechanism must reduce the volumetric productivity of one of the pumps with the opposition to the pressure from the speed regulator trying to keep it at maximum level.

In a speed control system without servo control, when the operator makes a turn at full speed, the steering system pushes the ground speed lever back from the full speed position, since it is held there only by a friction device.

The servo-controlled system uses a servo control valve / cylinder to control the pump volumetric capacity with less effort required by the operator. In this case, the power of the servo system can be quite large for resistance to forces from the pump cam disc in all cases. This may result in a large force requirement when steering by the operator.

Brief description of the invention

One aim of the invention is to provide an improved tractor of the type indicated above and, in particular, an improved device for controlling speed and steering gear.

According to one aspect of the invention, a tractor is provided comprising a tractor frame;

engine mounted on the tractor frame;

cab mounted on the tractor frame;

- 1010279 first and second tractor driving wheels mounted on the tractor leading end, the first drive wheel includes a first hydraulic drive motor for driving the first wheel, and the second drive wheel includes a second hydraulic drive engine for driving a second wheels;

two non-driven caster wheels mounted on the second end of the tractor;

a leading end having mounting assemblies for holding the harvesting header in a position in front of the leading end and in front of the cab when the leading end is forward;

the first and second hydraulic pumps, each of which is driven by an engine to create a source of working fluid under pressure, the first hydraulic pump is designed to actuate the first hydraulic motor of the first drive wheel, and the second hydraulic pump is designed to actuate the second hydraulic motor of the second driving wheel;

moreover, the first hydraulic pump includes a first cam disc moved to change the volumetric capacity of the pump to change the volume of fluid supplied when the pump is actuated, and the second hydraulic pump includes a second cam disc moved to change the volumetric capacity of the pump to change the volume of fluid supplied when the pump is actuated;

moreover, the first and second cam discs have a maximum position in which a maximum volume of fluid is created, with each maximum position being determined by an end stop;

a manually controlled steering means, moving between left and right positions, passing through the center position;

a manually controlled speed control device that is moved between the forward and backward positions to pass through the neutral position;

wherein the manually controlled speed control means is designed to control the flow rate of the working fluid supply from the first hydraulic pump to the first driving motor and from the second hydraulic pump to the second driving motor to control the cumulative speed of rotation of the driving wheels and, thus, the speed of the tractor;

manual steering means for controlling the steering mechanism is designed to control the difference in the flow rate of the working fluid supply from the first hydraulic pump to the first driving motor and from the second hydraulic pump to the second driving motor to control the relative speed of rotation of the driving wheels and, thus, the direction of rotation of the tractor;

a connection including a first connection for controlling the first cam disk and a second connection for controlling the second cam disk;

moreover, the connection includes a speed control element driven by a manually controlled speed control means, wherein the speed control element is designed, when actuated, to move both the first and second connections to move the first and second cam discs;

the connection includes a steering element driven by a manually controlled steering means, the steering element being positioned relative to the speed control element so that when actuated it moves the first and second connections relative to the speed control element to perform differential movement first and second cam discs;

wherein the manually operated speed control means includes a manually actuated lever setting the position command and a servo cylinder to move, in accordance with the position command, the speed control to the position specified by the position command, and to hold the speed control in this position by means of pressure in the servo-cylinder;

moreover, the manually controlled speed control device is designed so that it sets the maximum forward position of the speed control element, in which the first and second cam disks are in their maximum positions relative to the end stop and are held in the maximum position by pressure in the servo cylinder; and a pressure relief element actuated at the maximum forward position of the speed control element when the steering element is operating, actuated manually by the steering means for relieving the pressure in the servo cylinder to allow the first and second connections to move relative to the speed control element for differential movement first and second cam discs.

Preferably, the pressure relief member is designed to allow the speed control member to move from the maximum forward position, thus allowing movement of one of the cam discs from the end stop. However, the pressure relief member may be located so that it can allow the desired movement of the cam disc without moving the member.

- 2 010279 speed controls.

Preferably, the pressure relief member is designed to provide movement of the speed control member without the need for movement of the servo cylinder. Thus, a movable device is used which allows the necessary movement without moving the servo cylinder. However, the same effect can be obtained by relieving or regulating the pressure in the servo-cylinder in such a way that movement is achieved, but at the same time the large forces generated by the servo-cylinder are eliminated.

Another possible alternative is the precise regulation of the hydraulic pressure supplied to the servo cylinder, and the possibility of an independent relief of the hydraulic pressure by the servo cylinder to enable the operator to perform the steering at full speed. This requires the addition of a pressure relief valve, which can be expensive and possibly unreliable.

Preferably, the pressure relief element comprises a spring that is set so that it assumes the movement of the speed control element without the need for movement of the servo cylinder.

Preferably, the spring is mounted on the servo-cylinder, but it may also be located in other positions in the coupling system that allow movement of the cam disc without the need for movement of the servo-cylinder.

In particular, preferably, the spring is installed between the servo cylinder and the reference point or a fixed position, from which the servo cylinder is driven.

Alternatively, the spring mechanism may be attached to the end of the base of the servo cylinder. The problem with this design is that when a pump cam disc is subjected to large forces (for example, when the machine rises uphill and the drive pressures are high), the spring mechanism at the base of the servo cylinder may deviate and the speed of the machine may decrease. In the proposed system, if the spring mechanism on the servo cylinder deflects, the servo cylinder body moves, and since the servo control valve is fixed by the ground speed lever, the servo will be hydraulically adjusted and will maintain the selected speed.

Preferably, the spring contains two parts, each of which is located on opposite sides of the central position so that the body of the servo cylinder can move in one direction in a maximum position forward and in the opposite direction in a maximum position back, each of the two parts of the spring can abut in the central plate connected to the reference point.

Preferably, there is a support element that engages with each of the two parts of the spring and keeps it away from the central plate when the other of the spring parts is compressed and abuts against the central plate.

Thus, a finger is used that passes through the stem of a servo cylinder having a diameter that is slightly less than the thickness of the fixed mounting plate. This finger enters the slot in the fixed mounting plate when the system is in the neutral position. When one of the springs is deflected, the finger goes out of the groove and holds the compression of the other spring. Thus, the compression force of the spring increases rapidly. If this finger were not used, then when the springs are deflected, one spring weakens, and the other increases the force, and the resulting force changes much more slowly. With such a device, there is a possibility that the system can sometimes enter a pulsating mode when the servo cylinder oscillates back and forth when the springs are deflected.

Preferably, the servo cylinder includes a cylinder in which a piston and servo control valve are installed, connected to a manually controlled lever so that the servo control valve controls the supply of working fluid under pressure to one or the other side of the piston depending on the movement of the manually controlled lever.

Brief Description of the Drawings

One embodiment of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a top view, partly with imaginary lines and partially removed parts, illustrating a tractor according to the present invention in a cab forward position;

FIG. 2 is a side view of the tractor of FIG. 1, in which the driver's seat and the control panel are rotated to control the tractor in the forward position of the engine;

FIG. 3 is a schematic illustration of a tractor control system;

FIG. 4 is a top view of the control panel controls shown in FIG. 1-3;

FIG. 5 is a schematic view of the connection controlling the cam disks of pumps supplying the working fluid for driving the driving wheels of the tractor of FIG. 1, showing the connection in the neutral position of the speed control means and in the middle position of the steering means;

FIG. 6 is a schematic view of the connection of FIG. 5, showing the connection in the position of the speed control means when moving forward with the maximum speed and in the middle position of the means

- 3 010279 steering;

FIG. 7 is a schematic view of the connection of FIG. 5, showing the connection in the position of the speed control means when moving forward with maximum speed and in the position of turning the steering means;

FIG. 8 is a more detailed view of the servo cylinder of FIG. five.

FIG. 9 is a cross-sectional view along line 9-9 of FIG. five.

Detailed Description of the Invention

The swath tractor, generally designated by the reference number 10, includes a frame 11, which is mounted on the first pair of driving wheels 12 and 13 that engage with the ground and on the second pair of non-driving caster wheels 14 and 15. The driving wheels 12 and 13 are mounted on the corresponding bearings 16, which retain the wheels that engage with the ground on the frame 11. Each of the leading wheels 12 and 13 that engage with the ground is driven by a hydraulic motor 17 mounted on the support 16, which receives the working fluid od pressure from the supply line and drives the meshed ground wheel at a speed of rotation depending on working fluid flow.

The wheels 14 and 15 are mounted on conventional pivot brackets 18, which rotate around the pivot pins 19. The wheels 14 and 15 are non-driven and simply mounted to the carrier brackets 20, which can pivot around the pivot finger 19 in such a way that the caster wheels follow the movement of the vehicle, reported by the driving wheels 12 and 13. Thus, the vehicle speed relative to the ground is governed by the speed of rotation of the wheels 12 and 13, and the steering is controlled by the speed difference These wheels rotate 12 and 13.

The frame is shown only schematically, since it can have various designs in accordance with the needs well known to those skilled in the art. At the leading end 11A of the frame, the respective supports 21 and 22 are installed for mounting the header 23. Again, these elements are well known to those skilled in the art, and they can use many different designs. Thus, the supporting elements 21, 22 on the header are shown only schematically. Many different types of headers can be used, including headers with a disk-type cutter or a sickle-cutter headers. The header width can vary significantly depending on the type of crop and mowing system used.

Preferably, the header is mounted on the tractor and not on separate supports, and the tractor includes a lifting mechanism, schematically indicated by the reference numeral 23, driven to raise and lower the header on the tractor between different working positions and between working positions and the raised position with distance from the ground to move the header above the ground when not in use.

The tractor includes an engine 24 mounted on the frame 11 near the second end 11B of the frame. The engine is designed to drive several pumps 25, 26 and 27 to produce a pressurized working fluid for driving the various tractor components described below. You can use separate pumps as shown, or you can use a single pump and divert the working fluid created by it under pressure into separate adjustable fluid channels to actuate the various components.

At the leading end 11A of the frame is located the cab 30, which is located above the leading end between the driving wheels 12 and 13 in such a way that the operator can see the header when working on the field. In the cockpit 30, there is an operator’s workplace, generally designated 31, and includes seat 32, steering means 33 in the form of a conventional steering wheel, speed control means 34, and auxiliary equipment control means 35. The steering wheel 33 is a conventional steering wheel mounted on a panel in front of the seat with suitable fasteners that allow the operator to take a seat in the seat and sit comfortably in the seat behind the steering wheel. To the right of the operator is located the speed control means 34, mainly in the form of a lever that can move forward and backward between the reverse position in the reverse position, the neutral position in the center and the position of the forward movement in the forward position. Thus, the operator can intuitively pull back the lever for reversing and push the lever forward to move forward at a speed of movement regulated by the relative position of the lever along the line of its movement. In addition, there is a switch 34A that can be activated to select a speed range for the vehicle speed.

To the right of the operator, on the same speed control lever, for convenience of reaching the operator’s hand, is located the auxiliary control means 35, which includes a number of switches and levers for adjusting the position and operating parameters of the header mounted on the tractor. The switches contain controls for the height and angle of the header using the four-axis (two-axis) switch 35A, controls the height and advance of the winch drum using the four-axis (two-axis) switch 35V, and controls the speed of rotation of the winch using a two-way single-axis

- 4 010279 35C switches, thanks to which a qualified operator can adjust the header parameters during operation. The header is controlled by the main control lever 35Ό and in many cases can also be started in the opposite direction in case of blockage and, thus, the switch 35E will be used to ensure such a switch to work in the opposite direction.

Many of the above components are well known, are common and can be found in many different designs of such tractors manufactured by a number of manufacturers, including the present applicant. Additional details of the means of controlling the speed of rotation of the winch and the means of locating the winch are described in the aforementioned simultaneously considered application, to which reference can be made and which is filed simultaneously with the application for the invention.

In the construction of this application, the operator’s workplace 31 includes the operator’s seat 32, the steering wheel 33, the speed control means 34 and the auxiliary equipment control means 35, all of which are mounted on the platform or the cab support plate 40 on the upper surface of the frame 11 The support plate 40 may rotate on the support shaft 41 around a vertical axis 42 between the first position shown in FIG. 1, in which the seat faces the leading end 11A, and the second position shown in FIG. 2, in which the seat faces the end 11B where the engine is located. These positions are referred to here as a cab forward, when cab 30 is located at the front end of the tractor as it moves end 11A forward, and with the engine forward when end 11B is in front and moves forward.

The positioning of the platform in two positions is determined by a pair of switches 43 and 44, which interact with the element 45 mounted on the platform. Thus, only when the platform and operator’s workplace are properly positioned and fixed in the selected positions, this position is determined by the corresponding switch 43, 44, which is used in the control system described below. The speed control means 34 and the auxiliary equipment control means 35 and the 32 A display panel are fixed relative to the seat and platform in such a way that they rotate together with the platform. Thus, the operator in both positions has controls that are precisely in position to control in a symmetrical manner. Thus, the speed control works in such a way that it drives the vehicle backward relative to the direction of the operator’s gaze at the moment, and moving the lever forward sets the lever forward relative to the orientation of the operator at the moment. Mechanical and electrical connections pass from control systems, including steering, speed control and ancillary equipment on the platform, through the support shaft 41 under the frame, where these mechanical and electrical connections interact with the respective structures under the vehicle to control the movement of the vehicle . It will be understood that when the operator is in the cab in the cab-forward position shown in FIG. 1, moving the speed control lever toward the end 11A causes the vehicle to move toward the end 11A. When the seat is rotated in the opposite direction, moving the same lever in the direction from the operator causes the lever to move towards the end 11B and should cause the tractor to move towards the end 11B. This requires the reverse action of the joint, since the action of the lever must be reversed when the seat is rotated from one position to another. This can be achieved with a mechanical connection or can be achieved with an electric and / or hydraulic connection, as will be understood by a person skilled in the art.

The mechanical section shown in FIG. 1 and the control system shown schematically in FIG. 3. The speed control system 34 controls the pumps 25 and 26 using pump control means 46 and 47. The pump 25 supplies fluid to the drive motor 17 of the wheel 12. The pump 26 supplies fluid to the engine 17 of the wheel 13. The pumps are controlled in the usual manner to control the volumetric capacity of the pumps and, thus, the amount of fluid dispensed. The flow of fluid regulates the speed of rotation of the corresponding engine so that the wheels rotate at a given speed determined by the control of the pumps 25 and 26.

In addition, the pumps 25 and 26 are controlled by the steering 33 to generate different flow rates for creating the difference in rotational speeds of the engines 17. In a schematic illustration of the system shown in FIG. 3, this operation is shown as being performed by control unit 45, which responds to a signal from the steering and from the speed control means and, thus, selects the pump positions, respectively. However, in the system described below, this is done mechanically by sending two separate input commands to the pump control device to ensure a given speed and, in addition, the difference in actions between the two pump control means.

As shown in FIG. 3, the control unit 45 also responds to the input from the sensors 43 and 44 of the seat switches in such a way that the operation of many systems shown in FIG. 3, is only possible when the seat sensor is activated and indicates that the platform is in one of two selected positions. In addition, the corresponding seat sensor reading corresponding to the selected seat position is fed to the control unit to control the tractor in accordance with

- 5 010279 orientation of the cab forward or engine forward.

In addition to the main mode of vehicle motion control, the control unit also issues commands to control other elements of the tractor. As a first element, the control panel includes a conventional flashing light lever, indicated by the reference numeral 50, with which the operator can give turn signals or turn on four flashing lights, shown as flashing lights 51. The control unit is designed so that it can turn on four flashing lights , indicated by the reference position 51, at the same time using the means 52 for controlling the flashing lamps in both positions forwards and the engine ahead, as described above. However, since it is stipulated that the main driving mode of the tractor at high speed is the driving mode in the forward position of the engine, the turn signals are turned on by the flashing lamps control means 52 in such a way that the turn signals will turn on only when the operator panel and the tractor are oriented in the forward position which is indicated by the corresponding seat switch.

The header drive system, which includes height adjustment cylinders 23 driven by control system 55, is driven by fluid from pump 27, also driven by motor 24. The pump also supplies fluid to engine 56, which drives the header. This drive may contain a single motor that drives all the components of the header, including the cutting knife, the winch drum and the storage system, which includes blinds and / or augers. However, separate engines and separate controls may be used.

The control unit 45 is designed in such a way that, in response to the action of the seat sensor, indicating that the operator’s workplace is in a forward position, it allows actuation of the engine 56 through the drive control means 58. When the seat is out of this position and, in particular, turned to the position of the engine forward, actuation of the header is prevented.

The tool 55 for adjusting the height of the header is designed to regulate the cutting height, as well as to obtain a raised position with distance from the cutting level. The control unit 45 is designed to control the header height adjusting means 55 in such a way that the header is held in a raised non-working position and cannot be automatically controlled to bring the cutting position to a position that does not correspond to the cab forward position.

The drive motors 17 also include control means by servo control 59, which selects various ranges for the engines. This is achieved by adjusting the cam disk of the engine with setting it to positions for different volumetric capacities, as is well known to those skilled in the art.

In one embodiment of the invention, drive motors 17 are designed so that they have two different ranges, i.e. low speed range and high speed range. Of course, it is clear that the range of low speed provides higher torque.

The control unit is designed in such a way that the high speed range can only be accessed when the operator’s workplace is in the forward position of the engine and thus cannot be accessed when the operator’s workplace is in the forward position of the cab. In this configuration, when the operator controls only one of the switches 35 to select one or the other of the ranges, in a situation where the operator’s workplace is in the cab forward position, the system indicates to the operator that the high speed range cannot be accessed. Thus, the idea is that the tractor can move at significantly higher speeds in the forward position of the engine and is limited to reduced speeds when it moves in the forward position of the cab, given that the tractor is unstable at elevated speeds when it is in the cab position forward.

In an alternative embodiment of the invention, a three-band engine with available low, medium and high ranges may be used. In this embodiment, the low and medium ranges are accessible in the forward position, and the low and high ranges are accessible in the forward position. In the forward position, low ranges are available for high torque and high ranges for high speed. In the forward position, the middle range is available for field work at a higher speed.

FIG. 5 schematically shows a connection for driving the cam disks of two pumps to obtain a selected flow rate from each pump for the respective drive wheels. Thus, the first pump 25 and the second pump 26 are shown in FIG. 5 schematically, and each of them includes a corresponding control rod 60, 61 for the pump cam disc. Pumps of this type are, of course, well known, and their design is well known to a person skilled in the art, and such pumps are widely available from many manufacturers.

Each of the rods 60, 61 is adjusted in position by the respective driving lever 62, 63. In FIG. 5, the levers are shown in the neutral position, in which the cam disc has a zero offset so that when the pump rotates, no fluid flow is created. As shown in FIG. 6, the levers are moved to the maximum forward position towards the end stop 64, thus

- 6 010279 that each lever moves from the vertical position of the minimum shown in FIG. 5 to the inclined maximum position shown in FIG. 6. The end stop is shown schematically as a mechanical element, separate from the lever and located on the pump, although the end position of movement can be determined by any appropriate element located either on the pump or in another position that limits the movement of the cam disc. Of course, the physical movement of the cam disc itself can act as an end stop without any need for an additional element that comes into contact with the lever. The movement of the levers is caused by a pair of connections 65 and 66, which are of a fixed length and extend from the respective ends 65A, 66A of the connection control to the ends 65B, 66B of the respective levers. Since the length of each joint is fixed, the movement of the ends 65A, 66A is transmitted to the levers in direct proportion.

The movement of connections 65 and 66 is controlled by the two connection elements shown in FIG. 5. Thus, a manually controlled speed control device is obtained, generally designated by the reference numeral 67, which includes a manually controlled lever 68 moving in a guide groove 69. The lever 68 is connected by a rod 70 to the servo cylinder 71. The servo cylinder 71 is connected with a finger 72 to the lever 73, wherein the lever 73 forms a speed control element that is connected to both ends 65A and 66A in such a way that the pivoting movement of the lever 73 around the set pin 74 in the same plane with the connection 65 and 66 pushes the connections simultaneously. but mainly along their length so that the movement of the lever 73 communicates the movement to the levers 62 and 63 of the pumps. Thus, the amount of movement of the lever is transmitted to both levers 62 and 63 simultaneously and jointly in proportion to the angle of movement, which depends on the geometry of the system. Of course, the geometry can be modified in accordance with the decision of a person skilled in the art and is shown only schematically.

Thus, as shown, the movement of the servo 71 to the left pushes the lever 73, which pushes the connections 65 and 66, turning the levers 62 and 63 to increase the angle of the cam disc from the neutral position to the maximum position.

The control connection also includes a steering element 75, which is mounted on the lever 73 and which is connected to the ends 65A and 66A of the connections. Thus, the movement of the lever 73 is transmitted to the connections 65 and 66 through the structure of the steering element 75. The steering element 75 is mounted for rotary movement around the finger 76 at the end of the lever 73, remote from the finger 74. When the steering element 75 remains fixed in the center position, as shown in FIG. 5, relative to the finger 76, the movement of the lever 73 is transmitted to the connections 65 and 66, as a joint movement without any difference. However, the differential movement between connections 65 and 66 can be provided by turning the steering element 75 around the finger 76. Thus, when the lever 73 remains stationary, the ends 65A and 66A can move relative to each other due to the turning movement of the steering element 75 around the finger 76. The steering element 75 is actuated during this movement by the connection 77 from the manually controlled steering means 78, in general, in the form of a steering wheel. The connection is shown only schematically from the steering wheel to the steering element 75, since it can be constructed in various other ways well known to the person skilled in the art. However, it will be understood that turning the steering wheel from right to left through the middle position will activate the steering movement of the steering element 75 from right to left, as shown relative to the finger 76. Steering movement can be carried out at a stationary position of the lever 73 or when moving the lever, since these movements, in general , do not depend on each other. FIG. 5 and 6, the steering element is shown in a central position or in a straight forward position, while in FIG. 7, the steering element 75 is rotated to one end, indicated by the reference position B, so that the steering element 75 is rotated around the finger 76 of the lever 73.

The design of the servo cylinder is shown in FIG. 8. The servo cylinder 71 includes a spool 80 and a cylinder 81. A piston 82 is installed inside the cylinder 81, which moves the piston rod 83 protruding from one end 84 of the cylinder 81. Servo cylinders of this type are well known and are commonly used in systems of this type. Without going into details regarding specific fluid channels, since they are well known to those skilled in the art, we note that the overall operation of the device is that the manually operated speed control 68 moves the rod 70 attached to the slide valve 80 inside the valve body 85 . Thus, the valve is moved in the axial direction along the body 85 of the valve. The spool is located relative to the channels for supplying fluid in such a way that the movement of the spool causes the flow of working fluid under pressure to one side or to the other side of the piston 82 inside the cylinder 81. Thus, if the rod 70 moves to the right by manually acting on the control means 68, the spool also moves to the right and this ensures the supply of fluid to the right end of the cylinder in such a way that the body of the servo cylinder formed by the cylinder and the body of the slide valve moves to the right tion of the piston 82 which is held substantially immovably. Thus, the core

- 7 010279 servo-cylinder start 71 moves to the right until the spool body returns to its original or central position relative to the spool when the fluid flow to the right end of the cylinder is interrupted and servo 71 stops at this predetermined position. Symmetrically, the same operation occurs if the rod 70 moves to the left. Thus, the rod 70 acts as a means of setting the desired position of the servo-cylinder body, and the servo-cylinder body is moved to occupy this position by creating the necessary fluid flow in the cylinder to move the cylinder and the servo-cylinder body to the position thus specified.

In the device according to the present invention, the piston rod 83, which extends from the left side of the housing 71 of the servo cylinder under the rod 70 and the spool driven by this rod 70, extends from the servo cylinder to the left and is attached to the reference point 86. The reference point is essentially a fixed point in the design of the tractor and, thus, contributes to holding the piston rod 83 relative to a fixed point to obtain a reference point for the piston rod and for the piston and, thus, to control the movement of the housing 71 servocyst Indra. However, in this device, the support point 86 includes a connecting plate 87, through which the rod 83 passes. On both sides of the plate 87 are springs 88, 89, which create an elastic load between the plate 87 and the corresponding washers 90, 91, mounted on the rod 83 Thus, in the central position shown in FIG. 5, both springs are slightly compressed or unstressed in such a way that the springs hold the piston rods 83 in a position in which the washers 90 and 91 are at the same distance from the central plate 87. A pin 92 passes through the rod 83, which also passes through the plate 87 and can pass into the groove 93 (see Fig. 9) in the plate 87. Thus, the end of the spring 88 and the end of the spring 89 abut against the plate 87 and the finger 92.

As described above, the lever 73 controls the overall position of the levers 62 and 63 to the maximum position at the end stops. The steering element 75 acts independently to regulate the difference between the levers 62 and 63 by turning around the finger 76 on the lever 73. The lever 73 is adjusted by the servo 71, the piston rod 83 which in normal operation is in a fixed position due to the action of the springs 88 and 89 relative to the plate 87 .

The lever 68 is held in a predetermined position in the groove 69 by friction means denoted by 69A, so that during normal operation, the operator sets the position of the lever 68, and it sets the position of the servo cylinder and thus the lever 73, which remains fixed during operation its position will not be changed by the operator.

However, in some modes of tractor operation, the tractor operates at maximum speed when moving forward or backward when the operator moves lever 68 to the maximum front or maximum rear position. In this position, shown in FIG. 6, both levers 62 and 63 abut against the end stops 64, and the lever 73 is moved to the maximum position by moving the servo cylinder 71. This position is maintained as a straight forward position at maximum speed. However, if it is necessary to turn the vehicle in one direction, this must be achieved by moving the steering wheel control element 75 in such a way that it turns relative to the finger 76. When this turning movement occurs, one of the levers, indicated by the position 63, moves away from its end stop. In order for this to happen, the lever 73 must turn to the right to ensure this movement.

When the lever 73 is drawn to the right, the position of the piston rod 83 in the servo cylinder remains unchanged, and the cylinder rod also moves to the right. This movement is provided by the action of the plate 87, compressing the spring 88. Thus, the movement of the servo cylinder and the piston rod can occur simply due to the compression of the spring 88, and the force that the operator needs to apply to turn the steering wheel and, thus, to turn the steering element 75 , depends on the force of the spring 88 and, thus, can be adjusted to obtain a given force that is acceptable to the operator and is not excessive.

It should be noted that the spring 89 rests against the finger 92, with the result that the finger 92 pushes the spring 89 away from the plate 87 and does not apply force to the plate 87. Thus, the compression of the spring 88 resists all movement without any force applied by the spring 89. Thus, the compression force of the spring increases more rapidly to create resistance to the steering control and also to return the piston rod and servo cylinder back to the center position when the steering control returns to the middle position of the steering wheel element 75 th control.

It should be noted that the lever 68 moves with the lever 70 as the servo cylinder body 71 moves to the right, overcoming the resistance of the friction element 69A in the groove 69. Thus, only with a strong turn does the lever move away from the maximum forward position showing the movement of the lever 73. However, when steering returns in the central position, and the lever 73 moves back to its maximum position by the spring 88, the lever 68 moves back to the maximum position in the slot 69.

In the system shown above, the control lever 68 (ground speed lever) is not centered by the spring, but is held in position by the friction means 69 A. The hydraulic pressure for the servo cylinder is supplied from the hydraulic circuit that supplies oil to the pumping system. Mini

- 8 010279 minimum pressure in this circuit is determined by the needs of the hydraulic system and may change with temperature and other variables, which makes it difficult to predict the actual available pressure.

Thus, the device has a spring mechanism 88, 89 connected to the rod 83 of the servo cylinder, which allows the machine to be steered, even when the speed control is in the maximum position.

FIG. 5, the system is shown in the neutral position when the ground speed is zero and the steering is in the central position. The springs 88, 89 of the stem 83 of the servo cylinder are in a balanced state, and each of them is held between a fixed holder 87 and a washer attached to the rod of the servo cylinder. Both cam discs are at an angle of zero degrees, with the result that the pump performance is zero.

FIG. 6, the system is shown in a state at full traveling speed when moving forward. The ground speed lever 68 is in the fully forward position and both cam discs are at maximum angle, resulting in maximum pump performance. The springs 88, 89 in front of the servo-cylinder are again in a balanced state, or perhaps the front spring 88 may be slightly compressed to ensure that both pumps operate at full speed. The servo cylinder is designed in such a way that it has some additional working volume to ensure this.

FIG. 7, the system is shown in a turning state at full speed. With a very slight turn, the ground speed lever remains in a fixed position, while the front spring 88 in front of the servo cylinder deviates, allowing a reduction in the stroke of one pump when the steering plate 75 is turned. With a sharper turn, the ground speed lever 68 is pulled back, as shown, while the spring 88 in front of the servo cylinder is compressed.

Alternatively, the spring mechanism may be attached to the end 72 of the base of the servo cylinder. The problem with this design is that when a pump cam disc is subjected to large forces (for example, when the machine rises uphill and the drive pressures are high), the spring mechanism 88 at the base of the servo cylinder may deviate and the speed of the machine may decrease. In the proposed system, if the spring mechanism on the servo cylinder deflects, the servo cylinder body moves, and since the servo control valve is fixed by the ground speed lever, the servo will be hydraulically regulated and will maintain the selected speed.

Another possible alternative is the precise regulation of the hydraulic pressure supplied to the servo-cylinder, and the possibility of an independent relief of the hydraulic pressure by the servo-cylinder for the operator to perform the steering at full speed. This requires the addition of a pressure relief valve, which can be expensive and possibly unreliable.

Another feature of the described device is the manner in which the springs 88, 89 are mounted on the servo cylinder stem. The finger 92, passing through the rod of the servo cylinder, has a diameter that is slightly less than the thickness of the fixed mounting plate. This finger enters the groove 93 in the fixed mounting plate 87 when the system is in the neutral position. When one of the springs is deflected, the finger goes out of the groove and holds the compression of the other spring. Thus, the compression force of the spring increases rapidly. If this finger were not used, then when the springs are deflected, one spring weakens, and the other increases the force, and the resultant force changes much more slowly. With such a device, there is a possibility that the system can sometimes enter a pulsating mode when the servo cylinder oscillates back and forth when the springs are deflected.

Claims (10)

CLAIM 1. A tractor containing a tractor frame; engine mounted on the tractor frame; cab mounted on the tractor frame; first and second tractor driving wheels mounted on the tractor leading end, the first driving wheel including a first hydraulic drive motor for driving the first wheel, and the second driving wheel including a second hydraulic drive engine for driving the second wheel; two non-driven caster wheels mounted on the second end of the tractor; a leading end having mounting assemblies for holding the harvesting header in a position in front of the leading end and in front of the cab when the leading end is forward; the first and second hydraulic pumps, each of which is driven by an engine to create a source of working fluid under pressure, the first hydraulic pump being designed to drive the first hydraulic motor of the first drive wheel, and the second - 9 010279 hydraulic pump is designed to actuate the second hydraulic motor of the second drive wheel; moreover, the first hydraulic pump includes a first cam disc moved to change the volumetric capacity of the pump to change the volume of fluid supplied when the pump is actuated, and the second hydraulic pump includes a second cam disc moved to change the volumetric capacity of the pump to change the volume of fluid supplied when the pump is actuated; moreover, the first and second cam discs have a maximum position in which a maximum volume of fluid is created, with each maximum position being determined by an end stop; a manually controlled steering means, moving between left and right positions, passing through the center position; a manually controlled speed control device that is moved between the forward and backward positions to pass through the neutral position; wherein the manually controlled speed control means is designed to control the flow rate of the working fluid supply from the first hydraulic pump to the first driving motor and from the second hydraulic pump to the second driving motor to control the cumulative speed of rotation of the driving wheels and, thus, the speed of the tractor; manual steering means for controlling the steering mechanism is designed to control the difference in the flow rate of the working fluid supply from the first hydraulic pump to the first driving motor and from the second hydraulic pump to the second driving motor to control the relative speed of rotation of the driving wheels and, thus, the direction of rotation of the tractor; a connection including a first connection for controlling the first cam disk and a second connection for controlling the second cam disk; moreover, the connection includes a speed control element driven by a manually controlled speed control means, wherein the speed control element is designed, when actuated, to move both the first and second connections to move the first and second cam discs; the connection includes a steering element driven by a manually controlled steering means, the steering element being positioned relative to the speed control element so that when actuated it moves the first and second connections relative to the speed control element to perform differential movement first and second cam discs; moreover, the manually operated speed control means includes a manually actuated lever setting the position command and a servo cylinder to move in accordance with the position command of the speed control to the position specified by the position command and to hold the speed control in this position with relief pressure in the servo cylinder; moreover, the manually controlled speed control device is designed so that it sets the maximum forward position of the speed control element, in which the first and second cam disks are in their maximum positions relative to the end stop and are held in the maximum position by pressure in the servo cylinder; and a pressure relief element actuated at the maximum forward position of the speed control element when the steering element is operating, actuated manually by the steering means for relieving the pressure in the servo cylinder to allow the first and second connections to move relative to the speed control element for differential movement first and second cam discs. 2. The tractor according to claim 1, in which the pressure relief element is designed to ensure the movement of the speed control element from the maximum front position. 3. The tractor according to claim 1, in which the pressure relief element is designed to ensure the movement of the speed control. 4. A tractor according to any one of the preceding claims, in which the pressure relief member comprises a spring mounted so that it assumes the movement of the speed control member. 5. The tractor according to claim 4, in which the spring is installed on the servo cylinder. 6. A tractor according to any one of the preceding claims, in which a spring is installed between the servo cylinder and the supporting point. 7. The tractor according to claim 6, in which the spring contains two parts, each of which is located on opposite sides of the central position so that the body of the servo cylinder can move in one direction in the maximum forward position and in the opposite direction in the maximum rearward position. - 10 010279 8. The tractor according to claim 7, in which each of the two parts of the spring abuts against the central plate connected to the reference point. 9. The tractor of claim 8, in which there is a supporting element that engages with each of the two parts of the spring and keeps it away from the central plate when the other of the parts of the spring is compressed and abuts against the central plate. 10. A tractor according to any one of the preceding claims, in which the servo cylinder includes a cylinder in which a piston and a servo control valve are installed, connected to a manually controlled lever so that the servo control valve controls the supply of working fluid under pressure to one or the other side of the piston depending from moving the spool manually controlled lever.