192 clutches and power-stop control – Clutch and brake – Vehicle type
Reexamination Certificate
1999-11-19
2001-09-04
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Clutch and brake
Vehicle type
C192S01200R, C180S006700
Reexamination Certificate
active
06283263
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a clutch and brake control system for tracklaying construction vehicles, such as bulldozers.
BACKGROUND ART
FIG. 5
shows the structure of one known clutch and brake control system for bulldozers. The clutch and brake control system of this conventional structure is designed such that a steering lever
50
, which also serves as a forward/reverse drive lever, is coupled to a steering control valve
53
integral with a brake valve through many rods
51
,
52
and others, in order to operate right and left clutches and brakes. When slightly pushing the steering lever
50
down to the left (or to the right), the left (or right) steering clutch is brought into its half-disengaged state so that the vehicle gradually turns leftward (or rightward). When fully pushing the steering lever
50
down to the left (or to the right), the left (or right) steering clutch is brought into a completely disengaged state while the steering brake becomes actuated so that the vehicle turns quickly to the left (or to the right). A brake pedal
54
is coupled to the steering control valve
53
through rods
55
,
56
and others. By depressing the brake pedal
54
, only the right and left steering brakes are put in operation thereby stopping the vehicle.
The clutch and brake control system having the above conventional structure however reveals the following problem. Since the brake valve and the steering valve are integrally formed with the steering control valve
53
, the system inevitably involves a complicated control linkage for coupling these integral valves to the steering lever and to the brake pedal, so that the looseness and deflection of the control linkage, and the like, hinder the vehicle from maintaining good operability.
The present invention is directed to overcoming the foregoing problem and therefore a prime object of the invention is to provide a clutch and brake control system for a tracklaying construction vehicle, the system enabling an improvement in the operability of the tracklaying construction vehicle by simplifying the control linkage extending from the operation section to the valves to reduce looseness and deflection.
DISCLOSURE OF THE INVENTION
The above object can be achieved by a clutch and brake control system for a tracklaying construction vehicle according to a first aspect of the invention. This control system comprises a turning operation system and a driving brake operation system,
the turning operation system being operative to deliver a fluid pressure from an oil pressure source to either of clutches or to remove a fluid pressure therefrom, the clutches being provided for right and left crawler belts for the purpose of transmitting driving force to the crawler belts, so that engagement or disengagement of said either one of the clutches is carried out to slowly turn the vehicle,
the turning operation system being also operative to reduce a fluid pressure delivered from the oil pressure source to either of brakes which are provided for right and left crawler belts for the purpose of stopping the rotation of the crawler belts, so that said either one of the brakes is actuated to quickly turn the vehicle,
the driving brake operation system being operative to reduce a fluid pressure delivered from the oil pressure source to only both of the brakes so that both brakes are actuated to stop the vehicle,
the clutch and brake control system comprising, in a brake hydraulic circuit extending from the oil pressure source to the brakes, (1) steering brake valves for delivering a fluid pressure into the brake hydraulic circuit to release the brakes or reducing a fluid pressure within the brake hydraulic circuit to actuate the brakes, in accordance with the operation of the turning operation system and (2) driving brake valves for reducing a fluid pressure within the brake hydraulic circuit to actuate the brakes in accordance with the operation of the driving brake operation system.
According to the invention, the brakes each comprise, in combination, the steering brake valve operated based on the operation of the turning operation system and the driving brake valve operated based on the operation of the driving brake operation system. Therefore, the degree of freedom for the arrangement of the steering brake valves and driving brake valves increases so that each control valve can be positioned in the vicinity of the operation lever, and the like. This allows considerable simplification of the control linkage extending from the operating section to each control valve and, in consequence, reduces looseness and deflection, thereby attaining improved operability.
A preferred arrangement of the invention is such that each of the steering brake valves is interlocked and paired with a steering clutch valve for controlling clutch disengagement and two sets of the steering brake valve and the steering clutch valve are laterally disposed, so that each of the steering clutch valves and its associated steering brake valve are subsequently operated by one steering operation lever. This simplifies the structure and therefore enables improved operability.
Preferably, the driving brake valves are operated by one foot pedal.
In the invention, it is preferable that the steering brake valves be positioned on the upstream side of the brake hydraulic circuit while the driving brake valves being on the downstream side of the brake hydraulic circuit. With this arrangement, when driving the vehicle in a braked condition by operating the driving brake valves with the foot pedal, pressure reducing control is performed by operating either of the steering brake valves so as to make the fluid pressure at the inlet side be less than or equal to a reduced relief control pressure by the associated driving brake valve thereby switching the fluid pressure downstream of the driving brake valve to a reduced control pressure by the associated upstream steering brake valve so that the drive braking force of the brake which has been steering-operated can be changed to vary the rotational speeds of the right and left crawler belts in order to adjust the direction of steering.
Preferably, the steering clutch valves are connected to the clutches respectively within a steering clutch hydraulic circuit and are variable pressure reducing valves which are operated by the steering operation lever to variably reduce the pressure of a fluid input to the steering clutch hydraulic circuit. Preferably, the steering brake valves are connected to the brakes respectively within the steering brake hydraulic circuit and are variable pressure reducing valves which are operated by the steering operation lever to reduce the pressure of a brake releasing pressure fluid input to the steering brake hydraulic circuit. Alternatively, the steering brake valves are connected to the brakes respectively within the steering brake hydraulic circuit and the driving brake valves are variable pressure reducing valves which are operated by the foot pedal to reduce the pressure of a brake releasing pressure fluid input to the steering brake hydraulic circuit downstream of the driving brake valves.
Preferably, in the invention, the steering brake hydraulic circuit has bypasses, each of which bypasses the upstream and downstream sides of its associated driving brake valve, and check valves which open its associated bypass when the inlet fluid pressures upstream of the driving brake valve become lower than the outlet fluid pressure downstream of the driving brake valve. With this arrangement, during the operation of the steering operation lever in combination with the foot pedal, each check valve opens when the inlet pressure of the driving brake valve, that is, the control pressure of the steering valve becomes lower than the outlet pressure of the driving brake valve, so that the control pressure of the steering clutch valve on the upstream side can be ensured, resulting in better operability.
According to a second aspect of the invention, there is provided a clutch and brake control system for a trackl
Armstrong Westerman Hattori McLeland & Naughton LLP
Komatsu Ltd.
Lorence Richard M.
LandOfFree
Clutch and brake control system for tracklaying construction... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Clutch and brake control system for tracklaying construction..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Clutch and brake control system for tracklaying construction... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2534555