WO2017124371A1

WO2017124371A1 - Differential locking system in inboard wet brake axle

Info

Publication number: WO2017124371A1
Application number: PCT/CN2016/071565
Authority: WO
Inventors: Eric Wang
Original assignee: Volvo Construction Equipment Ab
Priority date: 2016-01-21
Filing date: 2016-01-21
Publication date: 2017-07-27

Abstract

A differential locking system (600) in inboard wet brake axles (112, 113) is provided. The differential locking system (600) includes: a first locking member (610) fixedly installed at a differential casing (310); a second locking member (620) spline-connected to a drive shaft; a cylinder housing (630) fixed to an axle housing (200) and having a hydraulic port (631) formed at one side of an inner wall thereof; a piston (640) installed in an inner space of the cylinder housing (630) to be elastically supported by a return spring (650); and a connecting bar (660) connecting the piston (640) and the second locking member (620) so that the second locking member (620) is moved by being linked with movement of the piston (640). The differential locking system (600) can be installed in inboard wet brake axles (112, 113) with very small inner spaces and can also enable construction vehicles to smoothly and efficiently operate in areas that are very slippery.

Description

DIFFERENTIAL LOCKING SYSTEM IN INBOARD WET BRAKE AXLE

DESCRIPTION

TITLE OF THE INVENTION

Differential Locking System in Inboard Wet Brake Axle

TECHNICAL FIELD

The present disclosure relates to differential locking system for construction vehicles and, more particularly, toa differential locking system in inboard brake axles of construction vehicles.

BACKGROUND OF THE INVENTION

In the area of construction vehicles such as wheel loaders, there usually exist two kinds of brake axles, namely inboard axles and outboard axles. Inboard brake axlesrefers toaxles thathave brakes inside the axles, such as inboard wet brake axles,which are popular,but construction vehicles havenot been equipped with a differential locking systemininboardbrake axles until now.

One of the reasonsis that it is difficult to design a differential locking system thatcan be installed in inboard wet brake axles because of a limited space inthe inboard wet brake axles.

However, it is desirable to provide a differential locking system in inboard wet brake axles so that smooth and efficient operation of construction vehicles in working areas that are very slippery, for example, muddy areas, can be performed.

SUMMARY OF THE INVENTION

According to one aspect of the present disclosure, provided is a differential locking system in an inboard wet brake axle. The differential locking system is installed in and applied to a central part of an inboard wet brake axle in which a differential assembly is installed in an axle housing. The differential locking system includes: a first locking member fixedly installed at a differential casing of a differential assembly； a second locking member spline-connected to a drive shaft so as to glide between a position causing a rotation relative to the first locking member and a position not causing a rotation relative to the first locking member； a cylinder housing fixed to the axle housing so as to have an inner space elongated in a direction that is approximately consistent with an axle direction, the cylinder housing having a hydraulic port, for supplying external oil pressure, formed at one side of an inner wall thereof； a piston installed in an inner space of the cylinder housing to be elastically supported by a return spring, the piston receiving a force in a first direction by oil pressure supplied to the hydraulic port and receiving a force in a second direction by an elastic force of the return spring； and a connecting bar connecting the piston and the second locking member so that the second locking member is moved by being linked with movement of the piston.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows side view of a wheel loader；

FIG. 2 schematically shows a central part of an inboard wet brake axle including a differential locking system of an embodiment of the present disclosure in which the differential locking system is in its locking state；

FIG. 3shows an enlargement ofpart A of FIG. 2；

FIG. 4 schematically shows the same central part of the inboard wet brake axle as that of FIG. 1 including the differential locking system in which the differential locking system is inits unlocking state； and

FIG. 5 shows an enlargement of part B of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. While the present disclosure will be described in conjunction with the following embodiments, it will be understood that they are not intended to limit the present disclosure to these embodiments alone. On the contrary, the present disclosure is intended to cover alternatives, modifications, and equivalents that may be included within the spirit and scope of the present disclosure as defined by the appended claims. Furthermore, in the following detailed description of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, embodiments of the present disclosure may be practiced without these specific details.

FIG. 1 shows a construction vehicle constituting a wheel loader 101. The body of the wheel loader 101 comprises a front body section 102 and a rear body section 103, each section of which has axles, namely, afront axle 112 and a rear axle 113for driving a pair of wheels. The rear body section 103 comprises a cab 114. The body sections 102, 103 are connected to each other in such a way that they can pivot in relation to each other around a vertical axis by means of two first actuators in the form of hydraulic cylinders 104, 105 arranged between the two sections. The hydraulic cylinders 104, 105 are thus arranged one on each side of a horizontal centerline of the vehicle in a vehicle traveling direction in order to turn the wheel loader 101.

The wheel loader 101 comprisesequipment 111 for handling objects or material. The equipment 111 comprises a load-arm unit 106 and an implement 107 in the form of a bucket fitted on the load-arm unit. A first end of the load-arm unit 106 is pivotally connected to the front vehicle section102. The implement 107 is pivotally connected to a second end of the load-arm unit 106. The load-arm unit 106 can be raised and lowered relative to the front section 102 of the vehicle by means of two second actuators in the form of two hydraulic cylinders 108, 109, each of which is connected at one end to the front vehicle section 102 and at the other end to the load-arm unit 106. The bucket 107 can be tilted relative to the load-arm unit 106 by means of a third actuator in the form of a hydraulic cylinder 110, which is connected at one end to the front vehicle section 102 and at the other end to the bucket 107 via a link-arm system 115.

FIG. 2 schematically shows a central part of an inboard wet brake axle including a differential locking systemaccording to an embodiment of the present disclosure in which differential locking is in its locking state. The inboard wet brake axle of FIG. 2 may be a front axle 112 or a rear axle 113.

As illustrated, in the central part of the inboard wet brake axle according to the embodiment of the present disclosure, a differential assembly 300 is installed in an axle housing 200, and

brake assemblies

410, 420 are installed at opposite sides of the differential assembly300, respectively.

The differential assembly 300 includes: a differential casing310；

side gears

320, 330；

andpinion gears

340, 350.

The differential casing310 is formed to have left and right

drive shaftinsertion holes

301, 302 to which two drive shafts (not shown) connected to left and right wheels (notshown) are rotatably inserted, and an inner part of the differential casing 310 is formed to have an internal cavity S. The two drive shafts are not shown throughout the present disclosure in order to show interior of differential assembly 300 more clearly. A flange 311 is provided at an outer wall of the differential casing310 such that a ring gear 313 is fixedly installed at the flange 311 via a fastening bolt 312. The ring gear313 is gear-connected to adrive pinion 500 which is connected to and rotated by an output shaft (not shown) of a transmission (not shown) . As such, the differential casing310 rotates on an axis connecting the

drive shaftinsertion holes

301, 302 when thedrive pinion500 rotates.

The side gears 320, 330are rotatably installed at an inner wall of the differential casing310 and are spline-connected to the two drive shaftsinserted via the drive

shaft insertion holes

310, 302, respectively. Thepinion

gears

340, 350 are rotatably installed at an upper part and a lower part of a stationary shaft 345 and are gear-connected to the

side gears

320, 330, respectively, wherein the stationary shaft345 traverses the differential casing 310 up and down.

The

brake assemblies

410, 420 installed at the opposite sides of the differential assembly 300 includes:

first brake discs

411, 421 fixedly installed at the axle housing200； and

second brake discs

412, 422, taking turns with the

first brake discs

411, 421, spline-connected to the drive shafts. The

brake assemblies

410, 420 are known in the field of inboard wet brake axles, and are not directly related to the present disclosure. Thus, the detailed description on the configuration and operation thereof are omitted.

In the drawing, it is illustrated that a first axle housing component 210 and a second axle housing component 220 are connected to each other to form the axle housing 200. However, the present disclosure is not limited thereto, and those having ordinary skill in the art can easily understand that an integrated axle housing may be also formed, and an axle housing may be formed by a combination of more than two axle housing components.

In the present disclosure, in addition to the configuration above, a differential locking system 600 is provided in the axle housing200. The differential locking system 600 includes: a first locking member 610 fixedly installed at the differential casing310； and a second locking member620spline-connected to a drive shaft so as to glide between a position causing a rotation relative to the first locking member 610, and a position not causing a rotation relative to the first locking member.

In the first locking member610 and thesecond locking member620, it is possible that surfaces facing each other are formed in frictionalsurfaces so that the first locking member 610 and the second locking member 620 cannot relatively rotate due to a frictional force between the frictionalsurfaces. It is also possible that the first locking member610 and thesecond locking member620is configured not to relatively rotate upon coupling thereof by forming the first locking member 610 asa dog gear and forming the second locking member 620 asa dog sleeve to form a dog clutch to gether.

The configuration for enabling the second locking member620to glide to the position not causing a rotation relative to the first locking member610 as needed will be described with reference to FIGS. 2 and 3 as follows. Acylinder housing 630 is formed at one side of the axle housing 200, the cylinder housing having an inner space elongated in a direction that is approximately consistent with an axle direction. The axle direction means the direction of an axis connecting the

insertion holes

301, 302, namely, an axle axis. The cylinder housing630 may be integrally formed with the axle housing200, or the cylinder housing630 may be individually fabricated and may be then fixed to a position corresponding to a predetermined part of the axle housing 200. A hydraulic port 631 is formed in an inner wall of the cylinder housing630 so that external oil pressure can be selectively supplied to an inner part of the cylinder housing630. A piston640 is installed in an inner space of the cylinder housing630 to be moved in a first direction D1 by oil pressure supplied to the hydraulic port 631. The piston640 is also installed to be elastically supported by a return spring650, so when there is no supply of oil pressure via the hydraulic port631, the piston640 returns to a second directionD2 opposite to the first direction D1 (see FIGS. 4 and 5) .

The piston640 and the second locking member620 are connected to each other using a connecting bar 660 so that the second locking member620 is moved by being linked with movement of the piston 640. An insertion hole 661 is formed at one end of the connecting bar660 so that the piston 640 is inserted into the insertion hole 661. One end of the insertion hole 661 contacts the return spring 650 and the other end of the insertion hole 661 contacts a first flange 641 of the piston 640 that has a larger outer diameter than an inner diameter ofthe insertion hole 661. Thanks to this configuration, the connecting bar660 is moved by being linked withthe movement of the piston 640. The other end of the connecting bar660 is connected to a coupling groove 621 formed at the second locking member620. Thanks to this configuration, the second locking member620is moved by being linked with movement of the connecting bar660. As described above, since the connecting bar660 is moved by being linked with the movement of the piston640, thesecond locking member620 is moved by being linked with the movement of the piston640.

A secondflange642 is formed at a position adjacent to the hydraulic port631 of the piston 640 so that the piston 640 can be moved by oil pressure supplied to the hydraulic port631. A sealing ring 644 may be installed on an outer circumference of the second flange 642 so that a side wall of the second flange 642 can receive oil pressure without any leak. In addition, if oil pressure leaks in a direction opposite to the second flange 642 with the hydraulic port 631 at the centerin the inner space of the cylinder housing 630, with the oil pressure supplied to the hydraulic port631, sufficient pressure may not be applied to the side wall of the second flange 642. Furthermore, although a part from which the leak is generated is sealed by a cover, if the cover is movable, a movementrange of the piston 640 will be undesirably reduced. Accordingly, an end of the cylinder housing 630 facing the second flange 642 with the hydraulic port 631 atthe center may be sealed by a cover 670 connected to be unmovable. This cover670 may have a receiving hole 671 thatreceives one end of the piston 640 and is formed in a lengthwise direction. Thus, thanks to the receiving hole 671, movement of the piston 640 may be guided, and a length of the cylinder housing630 may be reduced so that an installation space can be reduced. In such a case, asealing ring672may be inserted into a part that contacts the piston640. The cover 670 may be connected to the end of the cylinder housing 630in a tight-fit way, or may be connected by screw-coup lingway to the end of the cylinder housing 630, for example, by forming a male thread in at least one part of an outer circumference of the cover 670 and forming a female thread in a corresponding part of an inner circumference of the cylinder housing 630.

An operation of the inboard wet brake axles having the differential locking system 600 with the structure described above will be described as follows.

When the drive pinion 500 installed at the output shaft rotates, the differential casing310 rotates ontheaxis connecting

theinsertion holes

301, 302, namely, theaxle axis according to rotation of the ring gear 313 which is gear-connected to the drive pinion 500. When a wheel loader 101 drives on a straight and level road, since left and right wheels have the same resistance, the left and right side gears 320, 330 have the same rotational speed, and the pinion gears 340, 350 do not turn around on the stationary shaft 345. Meanwhile, when the rotational resistances of the left and right wheels are changed due to cornering, or a difference betweenleft and right surface resistances, a difference in the rotational speeds between the left and rightside gears 320, 330 is generated, and a driving torque transmitted to the wheels is determined by the wheel having a small rotational resistance.

This functionis called a differential function. In general, this function is of help to safe driving when there is no special problem. However, when one wheel drives on a normal road, and an opposite one wheel drives on a slippery road, if the wheel driving on the slippery road spins with no traction by losing a contact force, a problem may be generated. That is, since the driving torque transmitted to the wheels is determined by the wheel having a small rotational resistance, in such a case, the wheel driving on the normal road may not receive a rotational force. Due to this, a wheel loader is not driven.

However, in the case of a wheel loader to which the inboard wet brake axle having the differential locking system 600 according to the present disclosure is applied, even in such a situation, the wheel loader 101 can be driven by operating the differential locking system. In order to operate the differential locking system 600, when an operator performs a manipulation so that oil pressure is supplied to the hydraulic port331, pressure is applied to a side wall of the second flange 642 of the piston 640, and a force by the pressure is beyond an elastic force of the return spring 650, so the piston 640 is moved in the first direction D1. Accordingly, the second locking member 620 connected to the piston 640 via the connecting bar 660 is moved in the first direction D1 so that the first locking member610 and thesecond locking member620 are fixed not to rotate relative to each other. That is, a relative rotation cannot be caused between the drive shaftspline-connected to the second locking member620 and the differential casing310 at which the first locking member610 is fixedly installed. Thus, since the differential function is released, the wheel loader can be driven.

Meanwhile, after theabnormal situation written above has passed, in order to normally operate the differential function, the operator performs a manipulation so that oil pressure is not supplied to the hydraulic port331. Thus, while pressure applied to the side wall of the second flange 642 of the piston 640 is reduced, the piston 640 is moved in the second direction D2 by the elastic force of the return spring650. Accordingly, the second locking member620 connected to the piston 640 via the connecting bar660 is moved in the second direction D2 so that the first locking member610 and thesecond locking member620 can rotate relative to each other. That is, the drive shaft spline-connected to the second locking member620 and the differential casing310 at which the first locking member610 is fixedly fixed can rotate relative to each other, thereby facilitating the normal differential function.

The differential locking system 600 according to the presentdisclosure can be installed in inboard wet brake axles that were thought impossible to have a differential locking system installed thereindue to very small inner spaces, and can also enable construction vehicles to smoothly and efficiently operate in areas thatare very slippery, such asmuddy areas.

Although the invention has been described with reference to the preferred embodiments in the attached figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims.

Claims

A differential locking system in inboard wet brake axles, which is applied to a central part of an inboard wet brake axle in which a differential assembly is installed in an axle housing, the system comprising:

afirst locking memberfixedly installed at a differential casing of the differential assembly；

a second locking member spline-connected to a drive shaft coupled to the differential assembly so as to glide between a position causing a rotation relative to the first locking member and a position not causing a rotation relative to the first locking member；

a cylinder housing fixed to the axle housing so as to have an inner space elongated in a direction that is approximately consistent with an axle direction, the cylinder housing having a hydraulic port, for supplying external oil pressure, formed at one side of an inner wall thereof；

a piston installed in an inner space of the cylinder housing to be elastically supported by a return spring, the piston receiving a force in a first direction by oil pressure supplied to the hydraulic port and receiving a force in a second direction by an elastic force of the return spring； and

a connecting bar connecting the piston and the second locking member so that the second locking member is moved by being linked with movement of the piston.
The differential locking system of claim 1, wherein the first locking member is composed of a dog gear, and the second locking member is composed of a dog sleeve corresponding to the dog gear, thereby forming a dog clutch.
The differential locking system of claim 1, wherein the cylinder housing is integrally formed with the axle housing.
The differential locking system of claim 1, wherein an insertion hole is formed at one end of the connecting bar so that the piston is inserted thereto, and one end of the insertion hole contacts the return spring, and the other end of the insertion hole contacts a first flange of the piston having a larger outer diameter than an inner diameter of the insertion hole.
The differential locking system of claim 4, wherein a coupling groove is formed at the second locking member and is connected to the other end of the connecting bar.
The differential locking system of claim 4, wherein a second flange is formed at a position adjacent to the hydraulic port of the piston so that the piston can be moved by oil pressure supplied to the hydraulic port.
The differential locking system of claim 1, whereinan end of the cylinder housing adjacent to the hydraulic port is sealed by a cover connected to be unmovable.
The differential locking system of claim 7, wherein the cover comprises a receiving holereceiving one end of the piston, the receiving hole being formed in a lengthwise direction.
The differential locking system of claim 7, whereina male thread is formed in at least one part of an outer circumference of the cover and a female thread is formed in acorresponding part of an inner circumference of the cylinder housing so that the cover and the end of the cylinder housing are screw-coupled to each other.
An inboard wet brake axle comprising a differential locking system according to any one of claims 1 to 9.
A construction vehicle comprisingan inboard wet brake axle according to claim 10.