Drive system of a utility vehicle

• US 20030173133A1
• Filed: 03/14/2003
• Published: 09/18/2003
• Est. Priority Date: 03/16/2002
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Kempt, Bernd, Bohrer, Stefan, Hofer, Jurgen
• Granted Patent: US 7,044,257 B2
• Time in Patent Office: Days
• US Class Current: 180/305
• CPC Class Codes: B60W 2300/158 Harvesters
• CPC Class Codes: F16H 2059/683 Sensing pressure in control systems or in fluid controlled devices, e.g. by pressure sensors for hydrostatic transmissions F16H2059/6861
• CPC Class Codes: F16H 59/44 dependent on machine speed of the machine, e.g. the vehicle
• CPC Class Codes: F16H 61/42 involving adjustment of a pump or motor with adjustable output or capacity F16H61/46 takes precedence
• CPC Class Codes: F16H 61/427 Motor capacity control by mechanical control means, e.g. by levers or pedals
• CPC Class Codes: F16H 61/47 for achieving a target output speed
• CPC Class Codes: F16H 61/472 for achieving a target output torque

Abstract

Disclosed are various embodiments of a drive system for use in utility vehicles, such as agricultural forage harvesters and combines. The drive system includes a hydrostatic transmission having a pump driven by a main engine of the vehicle and having first and second motors respectively coupled to front and rear axles of the vehicle by way of first and second differential gear sets. The pump and one or both of the motors have a variable displacement determined by positioning respective swash plates through the agency of a lever, in the case of the pump, and by electronic devices, in the case of the motors, the electronic devices acting in response to control signals sent by a control arrangement, which in turn, operates in response to signals produced by pressure sensors associated with the motors and by signals produced by speed sensors associated with output shafts of the hydraulic motors. The control arrangement has a memory for storage of data, such as maximum legal ground speed and the ratio of the speeds of the axles as results from a given wheel size, and uses this information for controlling the hydrostatic transmission such that the vehicle does not exceed the speed, and the front and rear axles are driven so as to produce the same ground speed.

Claims

1. In a utility vehicle having a drive system including a main drive engine connected so as to drive a hydraulic pump in turn connected with an outlet and inlet respectively coupled to an inlet and an outlet of a hydraulic motor so as to conduct hydraulic fluid to and from said hydraulic motor, with said hydraulic motor being connected so as to drive at least one wheel that is in engagement with the ground and whose fluid displacement can be varied by an actuator connected with a control arrangement, where said control arrangement is connected with a rotational speed sensor arranged to detect the rotational speed of the wheel and can be operated so as to control the actuator as a function of the signals of the rotational speed sensor, the improvement comprising:

a pressure sensor coupled to said hydraulic motor for generating a pressure signal that contains information about the difference between pressures respectively existing at said inlet and the outlet of said hydraulic motor;

said pressure sensor being connected to said control arrangement, with said pressure signal acting to effect operation of said control arrangement such that the latter causes said actuator to be controlled as a function of the pressure signal received from said pressure sensor.

2. The utility vehicle, as defined in claim 1, wherein said drive system further includes an axle having a limited slip differential gearbox between opposite ends thereof;

said at least one wheel being mounted on one end of said axle and a second wheel being mounted on another end of said axle; and

said hydraulic motor being coupled for driving said axle by way of said differential gearbox.

3. The utility vehicle, as defined in claim 2, wherein said drive system further includes a second axle having third and fourth wheels respectively mounted on opposite ends thereof;

and a second hydraulic motor being connected for being driven by said hydraulic pump and connected for driving said second axle.

4. The utility vehicle, as defined in claim 3, wherein said second hydraulic motor has a fixed displacement.

5. The utility vehicle, as defined in claim 3, wherein said second hydraulic motor has a variable displacement;

and said drive system including a second actuator coupled to said second hydraulic actuator and to said control arrangement, whereby the fluid displacement of said second motor can be varied by operation of said control arrangement.

6. The utility vehicle, as defined in claim 5, wherein said drive system further includes a second pressure sensor associated with said second hydraulic motor for sensing the pressure existing in said second hydraulic motor and generating a second pressure signal;

said second pressure sensor being connected to said control arrangement, whereby said control arrangement acts in response to said second pressure signal to effect operation of said second actuator which effects changes in the displacement of said second hydraulic motor in accordance with said second pressure signal.

7. The utility vehicle, as defined in claim 5, wherein said drive system further includes a second rotational sensor coupled for sensing the speed of rotation of said second axle and generating a second speed signal;

said second rotational sensor being connected to said control arrangement; and

said control arrangement being operative to control either or both of said first and second actuators in response to said second speed signal.

8. The utility vehicle, as defined in claim 1, wherein said actuator is an electronic actuator;

an operating arrangement for selectively sending a target velocity signal to said control arrangement; and

said control arrangement acting in response to said target velocity signal to control said electronic actuator so that said vehicle does not operate at a velocity in excess of the target velocity.

9. The utility vehicle, as defined in claim 8, wherein said drive system includes a load sensor connected for detecting a load imposed on the main engine and generating a representative load signal that is conveyed to said control arrangement;

said control arrangement acting in response to said load signal for effecting a repositioning of said electronic actuator as a function of said load signal.

10. The utility vehicle, as defined in claim 9, wherein said vehicle is a crop harvester and said load sensor detects the load on said main engine by sensing one of a rotational speed of an output shaft of said engine, or a rate at which the utility vehicle is supplied with harvested crop.