WO2018032496A1

WO2018032496A1 - Surface compactor

Info

Publication number: WO2018032496A1
Application number: PCT/CN2016/095980
Authority: WO
Inventors: Alan Liu; Yeager WANG; Jeff DIAO
Original assignee: Volvo Construction Equipment AB
Current assignee: Volvo Construction Equipment AB
Priority date: 2016-08-19
Filing date: 2016-08-19
Publication date: 2018-02-22
Anticipated expiration: 2019-02-19

Abstract

A surface compactor (1) including at least one drum (2) for pressing a surface by rolling on the ground comprises: a first variable displacement hydraulic pump (11), a fixed displacement hydraulic pump (15) and a propelling motor (12) hydraulically connected to the first variable displacement hydraulic pump in a closed loop hydraulic circuit, the first variable displacement hydraulic pump and the fixed displacement hydraulic pump being connected to an engine (10); a drum motor (30) hydraulically connected to a second variable displacement hydraulic pump (31) and configured to drive the drum; and a towing control valve (40) disposed in the axle brake fluid line (26), and including a reciprocating pump (41) configured to provide a pressurized fluid from a hydraulic tank (T) to both the axle brake cylinder (25) and drum brake cylinder (34) in case where the engine stops, so that the compactor is movably operated for towing.

Description

Surface Compactor

TECHNICAL FIELD

The present disclosure relates to a surface compactor, more particularly, to a surface compactor that is to be moved for towing by simply releasing an axle brake and a drum brake even if an engine is abnormally in a stop state.

BACKGROUND OF THE INVENTION

In general, a surface compactor is well known as a mobile vehicle that propels itself with hydraulic pressure generated by an engine to level the ground.

The surface compactor includes at least one drum disposed at the front of the vehicle body to roll on the ground, and a pair of wheels disposed at the rear of the car body. The surface compactor is equipped with a brake system for decelerating and stopping the drum and the wheels. During compaction work, the vehicle body is propelled to compact the soil, while the drum presses the surface of the soil on the ground, thereby increasing the density of the soil.

For example, there is Japanese Patent Application Publication No. JP 2005-344288 A. The compactor disclosed in this Patent Document is a compaction machine used suitably for pavement of a road surface, such as a tire roller, which includes braking units for a drum brake and an axle brake.

In such a surface compactor, the brake units are designed to maintain a braking state, when the engine is shut down. If an engine stops due to breakdown or malfunction of an engine during compaction work, the compactor remains in braking state at the work site. An operator has to take a step to enable the vehicle to tow in order to repair the surface compactor.

The axle brake and the drum brake should be able to be forcibly unlocked for towing and the compactor should be allowed to move.

Accordingly, it is urgently needed such that a compactor is to be towed by an operator by simply releasing or unlocking brakes even if brakes remain locked in a braking state due to breakdown or malfunction of an engine.

SUMMARY OF THE INVENTION

According to one aspect of the present disclosure, there is provided a surface compactor, the compactor comprising a first variable displacement hydraulic pump, a fixed displacement hydraulic pump and a propelling motor hydraulically connected to the first variable displacement hydraulic pump in a closed loop hydraulic circuit, the first variable displacement hydraulic pump and the fixed displacement hydraulic pump being connected to an engine； a drum motor hydraulically connected to a second variable displacement hydraulic pump and configured to drive the drum； an axle brake including an axle brake cylinder, the axle brake cylinder being connected to the fixed displacement hydraulic pump via an axle brake fluid line and configured to release a braking state of an axle； a drum brake including a drum brake cylinder and a gear module connected to the second variable hydraulic pump, the drum brake cylinder being connected to the fixed displacement hydraulic pump via a drum brake fluid line branched off from the axle brake fluid line and configured to release a braking state of the drum； and a towing control valve disposed in the axle brake fluid line, and including a reciprocating pump configured to provide a pressurized fluid from a hydraulic tank to both the axle brake cylinder and drum brake cylinder in case where the engine stops, so that the compactor is movably operated for towing.

According to the present disclosure, the towing control valve further comprises a first flow path connected to the axle brake fluid line via an inlet port and an outlet port； an orifice formed in the first flow path between the inlet port and the outlet port； a second flow path branched off from the first flow path, and configured to communicate the first flow path with a hydraulic tank； and a plurality of check valves disposed in the second flow path.

According to the present disclosure, the towing control valve is detachably connected to the axle brake fluid line by a joint connection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the configuration of an entire surface compactor according to an embodiment of the present disclosure.

FIG. 2 is a hydraulic circuit diagram related to a propelling system of the surface compactor shown in FIG. 1.

FIG. 3 is a hydraulic circuit diagram related to a drum and a drum brake of the surface compactor shown in FIG. 1.

FIG. 4 is a perspective view showing a towing control valve of the present disclosure.

FIG. 5 is a hydraulic circuit diagram of the towing control valve shown in 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 which may be included within the sprit 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. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present disclosure.

FIG. 1 illustrates the schematic configuration of an entire surface compactor. As shown in FIG. 1, a compactor 1 is composed of a front drum 2, a pair of rear wheels 3, a front body 4, and a rear body 5. A driver's seat 6 is mounted either on the front body 4 or on the rear body 5. A brake manipulation member 9, such as an axle brake button or an axle parking brake button, may be installed adjacent to the driver’s seat 6. Preferably, the compactor 1 is a soil compactor.

The bodies 4, 5 are connected with each other by means of a pivot joint 7 so that the compactor 1 can be steered. The rear wheels 3 can be replaced by a rear drum in certain applications.

FIG. 2 is a hydraulic circuit diagram related to a propelling system of the compactor shown in FIG. 1. As shown in FIG. 2, a closed loop hydraulic circuit is provided for driving the compactor 1. More particularly, the closed loop hydraulic circuit has a variable displacement &reversible first variable displacement hydraulic pump 11 driven by a diesel engine 10, and a propelling motor 12, such as a fixed displacement hydraulic motor, connected to a drive train (not shown) .

The first variable displacement hydraulic pump 11 and the propelling motor 12 are fluidly connected by a first conduit 13 and a second conduit 14. The first variable displacement hydraulic pump 11 may be an axial reciprocating pump of which the fluid displacement can be determined by a tilted angle of swash plate 11a. A pump regulator 8 is provided for changing the angle of the swash plate 11a, which may be adjusted with a control valve (not shown) .

By changing the angle of the swash plate 11a, the flow rate discharged from of the pump 11 can be varied continuously. Namely, if the swash plate 11a is perpendicular to the axis of rotation, i.e., a zero angle, no fluid will flow and the speed of the propelling motor 10 is zero. If it is at a sharp angle, a large volume of fluid will be pumped and the speed of the propelling motor 12 is increased.

The first variable displacement hydraulic pump 11 allows the swash plate 11a to be moved in both directions from the zero position, pumping fluid in either direction without reversing the rotation of the first variable displacement hydraulic pump 11. In other words, the swash plate angle can vary from a zero angle, i.e., a neutral position, to a positive angle and to a negative angle. Consequently, propelling motors 12a, 12b are caused to rotate in a forward direction and a reverse direction, which correspond to the intended forward or backward travel movement of the vehicle.

Depending upon the direction of the movement of the swash plate 11a, the first conduit (or the second conduit 14) of the circuit 10 can be a high-pressure supply line or a low-pressure return line. In this embodiment, it is assumed that the first conduit 13 becomes a supply line and the second conduit 14 becomes a return line when the propelling motor 12 rotates in the forward direction, i.e., when the compactor 1 travels forward.

A fixed displacement hydraulic pump 15, also driven via the engine 10, is installed a flow path 17 which is connected between the first conduit 13 and the second conduit 14, and is configured to compensate for any possible loss of hydraulic pressure associated with the hydraulic circuit when the engine 10 is in a normal operation without malfunction or breakdown and the propel motor 12 is actuated by the first variable hydraulic pump 11.

According to the present disclosure, when the engine 10 is in a normal operation, a fluid from the fixed displacement hydraulic pump 15 can be provided for brake release. More detailed explanation will be described later.

Meanwhile, first and second

main relief valves

18, 19 are provided between the first conduit 13 and the second conduit 14 and protect each conduit from pressure overload during operation. For example, the overload pressure generated from either of the first conduit 13 or the second conduit 14 may be introduced through a branch line 20 during compaction or propulsion of the vehicle. Then, the first main relief valve 18 provides a relief function for the first conduit 13 and the second main relief valve 19 provides a relief function for the second conduit 14.

According to the present disclosure, an axle brake 23 includes an axle brake cylinder 25 and the axle brake cylinder 25 is connected to the fixed displacement hydraulic pump 15 via an axle brake fluid line 26 and configured to release a braking state of an axle.

Preferably, the axle brake cylinder 25 includes a pair of cylinders 51a, 51b, and the axle brake 23 is configured to release an axle by manipulation of the brake manipulation member 9, such an axle parking brake button.

A brake control valve 24 is disposed between an axle brake cylinder 25 and a branch line 21 which is fluidly in communication with the fixed displacement hydraulic pump 15, and a fluid for releasing the axle brake 23 is selectively applied to the axle brake cylinder 25 through an axle brake fluid line 26 in response to an operation of the brake manipulation member 9. The brake control valve 24 may include an electric control valve, which can be controlled by a solenoid signal or an electromagnetic pilot signal in response to an operation of the brake manipulation member 9.

For example, if the swash plate 11a of the first variable hydraulic pump 11 is in a neutral positon during the engine 10 is in a normal state without malfunction, the brake control valve 24 can be switched to an open position by an operation of the brake manipulation member 9. Then, the fluid from the fixed displacement hydraulic pump 15 is supplied to the chamber of the axle brake cylinder 25 through the axle brake fluid line 26, so that the axle brake 23 is in brake release state and the rear wheel 3 is capable of moving or propelling on the ground.

On the other hand, when the axle brake 23 is deactivated, the fluid from the chamber of the axle brake cylinder 25 is returned to a hydraulic tank T by switching to the closed position of the brake control valve 24.

Meanwhile, according to an embodiment of the present disclosure, the compactor 1 comprises a towing control valve 40. The towing control valve 40 is disposed in the axle brake fluid line 26, and includes a reciprocating pump 41.

The towing control valve 40 includes at least one pressure sensor 45 that is disposed close to the first outlet port 49 and the pressure sensor 45 detects and indicates a pressure generated in the axle brake fluid line 26 by operating the reciprocating pump 41. Preferably, the pressure sensor 45 is installed at the axle brake fluid line 26. The pressure sensor 45 may be installed at the drum brake fluid line 35. The pressure sensor 45 may be a pressure gauge.

Although not shown in the drawings, in consideration of notification or identification of a pressurized fluid, an additional sensor can be installed at the upstream point of the drum brake fluid line 35 branched off from the axle brake fluid line 26. The pressure sensor 45 may be a pressure gauge.

More detailed explanation about the towing control valve 40 will be described, referring to FIG. 4 and FIG. 5.

FIG. 3 is a hydraulic circuit diagram related to a drum and a drum brake of the surface compactor shown in FIG. 1. In order to configure a drum motor 30 for driving a drum 2, a second variable displacement hydraulic pump 31 having a swash plate 31a is driven by the engine 10 and is connected with a drum brake 50 via a shaft 38. The second variable displacement hydraulic pump 31 is configured such that the tilted angle of the swash plate 31a is controlled by a pump regulator 32.

A control valve 36 is connected to a chamber of a pump regulator 33 by

flow paths

33a, 33b and controls a hydraulic fluid in response to a valve control signal applied from the outside, so that the pump regulator 33 adjusts volumetrically the tilt angle of the swash plate 31a of the second variable displacement hydraulic pump 31.

For example, in order to roll the drum 2 on the ground, the second variable displacement hydraulic pump 31 allows the swash plate 30a to be moved in both directions from the zero position. In other words, the swash plate angle of the second variable displacement hydraulic pump 31 can vary from a zero angle, i.e., a neutral position, to a positive angle and to a negative angle via the pump regulator 32. Consequently, the second variable displacement hydraulic pump 31 is caused to rotate the drum 2 in a forward direction and a reverse direction, which correspond to the intended forward or backward travel movement of the compactor 1. The rotational speed of the drum 2 may be increased or decreased, depending on the tilted angle of the swash plate 30a.

Preferably, a drum brake 50 includes a drum brake cylinder 34 and a gear module 37 which is connected to the second variable hydraulic pump 31 and the drum brake cylinder 34 is connected to the fixed displacement hydraulic pump 15 via a drum brake fluid line 35 branched off from the axle brake fluid line 26 and be configured to release a braking state of the drum 2.

More particularly, in order to release the drum brake 50, the drum brake cylinder 34 having a chamber is installed a gear module 37 and is configured to communicate with the axle brake fluid line 26 through the drum brake fluid line 35. Preferably, the drum brake fluid line 35 is connected to the axle brake fluid line 26 at an upstream point of the axle brake cylinder 25.

In case where the engine 10 is normally operated without malfunction and the second variable hydraulic pump 31 is in a neutral positon, the brake control valve 24 can be switched to an open position by an operation of the brake manipulation member 9. Then, the fluid from the fixed displacement hydraulic pump 15 is supplied to the chamber of the drum brake cylinder 34 through the axle brake fluid line 26 and the drum brake fluid line 35, so that the drum brake 50 is in brake release state and the drum 2 is capable of moving on the ground.

In an embodiment of the present disclosure, although not shown in the drawings, the axle brake 23 or the drum brake 50 may include a conventional wet disk brake.

FIG. 4 is a perspective view showing a control valve according to the present disclosure and FIG. 5 is a hydraulic circuit diagram of the control valve shown in FIG. 4.

According to an embodiment of the present disclosure, the compactor 1 comprises a towing control valve 40 disposed in the axle brake fluid line 26, and is configured to adjust a pressurized fluid delivered from a hydraulic tank T to both the axle brake cylinder 25 and the drum brake cylinder 34 in case where the engine is abnormally in a stop state. Preferably, the towing control valve 40 includes a reciprocating pump 41 configured to provide a pressurized fluid from a hydraulic tank T to both the axle brake cylinder 25 and drum brake cylinder 34 in case where the engine 10 stops, so that the compactor is movably operated for towing.

Further, the towing control valve 40 includes a first flow path 46 which is connected to the axle brake fluid line 26 via an inlet port 48a and an outlet port 49. Also, the towing control valve 40 includes an orifice 44 formed in the first flow path 46 between the inlet port 48a and the outlet port 49, a second flow path 47 branched off from the first flow path 46. The second flow path 47 is configured to communicate the first flow path 46 with a hydraulic tank T via a second inlet port 48b. The hydraulic tank T may be composed of an auxiliary hydraulic tank.

The towing control valve 40 comprises a plurality of check valves 49 that are disposed in the second flow path 47.

According to the present disclosure, the reciprocating pump 41 is installed at the second flow path 47 between the check valves 49, and may control a flow mount or a flow rate of the pressurized fluid from a hydraulic tank T to both the axle brake cylinder 25 and drum brake cylinder 34.

For example, the fluid sucked from the hydraulic tank T by the reciprocating pump 41 is pressurized or pumped out, and be delivered to the axle brake cylinder 25 and the drum brake cylinder 34 via the outlet port 49, the axle brake fluid line 26 and the drum brake fluid line 35 with a predetermined brake release pressure. The predetermined brake release pressure may be adaptive for various ranges in response to the requirements for achieving brake release.

The reciprocating pump 41 includes a lever 42 and a plunger 43 which is connected to the lever 42, and the plunger 43 is reciprocated in the cylinder of the reciprocating pump 41 by external force applied to the lever 42.

The check valves 49 include a first check valve 49a for preventing backflow of the brake release fluid flow from the first fluid path 46. Preferably, the first check valve 49a is configured to prevent backflow of the pressurized fluid from the axle brake fluid line 26 in case where the engine 10 stops. Also, the check valves 49 include a second check valve 49b for preventing backflow of the pressurized fluid from the cylinder of the reciprocating pump 41

Meanwhile, referring to the FIG. 5, the towing control valve 40 includes a rotational switch 51 thread-fastened to a valve housing 52 to adjust an opening degree of the orifice 44. The rotational switch 51 alternatively includes a needle valve for adjusting an open state or a closed state of the first flow path 46 in case where the engine 10 stops.

The towing control valve 40 may be detachably connected to the axle brake fluid line by a joint connection. The joint connection may be configured by brake line connecting hoses which are connected to the inlet port 48a and the outlet port 49, respectively.

According to the present disclosure, in case where the engine 10 is normally operated without malfunction of breakdown, the first flow path 46 or the orifice 44 of the towing control valve 40 is maintained by an open position at the axle brake fluid line 26.

However, in case where the engine 10 is abnormally in a stop state due to malfunction of breakdown at a work site, the first flow path 46 or the orifice 44 of the towing control valve 40 can be changed in a closed position at the axle brake fluid line 26. For example, when an operator manipulates the needle valve to be closed, the axle brake cylinder 25 and the drum brake cylinder 34 are fluidly in communication to the hydraulic tank T via the reciprocating pump 41 of the towing control valve 40.

Then, the reciprocating pump 41 provides a pressurized fluid delivered from a hydraulic tank T to both the axle brake cylinder 25 and the drum brake cylinder 34. The reciprocating pump 41 may be operated manually by the operator.

Preferably, the pressurized fluid in the cylinder of the reciprocating pump 41 is provided through the first check valve 49a of the towing control valve 40 and the axle brake fluid line 26, and it can be delivered until a pressure in the chamber of the axle brake cylinder 25 reaches 20 to 24 bar. The axle brake 25 is released by the pressurized fluid, and thus the wheel 3 can be moved.

Further, the pressurized fluid in the cylinder of the reciprocating pump 41 flows into a drum brake releasing channel 35 via the axle brake fluid line 26 and the drum brake fluid line 35. The drum brake 50 is released by the pressurized fluid, and thus the drum 2 can be moved.

The pressurized fluid required for brake release and generated in the axle brake fluid line 26 and the drum brake fluid line 35 may be variously set as a predetermined brake release pressure, depending on the specifications of the compactor or brake units applicable for the compactor. For example, a pressure larger than 24bars may be provided by a predetermined brake release pressure.

As described above, according to the present disclosure, the surface compactor having a towing control valve according to the present disclosure is advantageous in that, even if a brake is maintained in a braking state due to stopping of an engine when the engine breaks down or a malfunction occurs in the engine, an operator can easily release the axle brake and the drum brake, thus capable of towing the compactor for maintenance.

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 surface compactor including at least one drum for pressing a surface by rolling on the ground, the surface compactor comprising:

a first variable displacement hydraulic pump, a fixed displacement hydraulic pump and a propelling motor hydraulically connected to the first variable displacement hydraulic pump in a closed loop hydraulic circuit, the first variable displacement hydraulic pump and the fixed displacement hydraulic pump being connected to an engine；

a drum motor hydraulically connected to a second variable displacement hydraulic pump and configured to drive the drum；

an axle brake including an axle brake cylinder, the axle brake cylinder being connected to the fixed displacement hydraulic pump via an axle brake fluid line and configured to release a braking state of an axle；

a drum brake including a drum brake cylinder and a gear module that is connected to the second variable hydraulic pump, the drum brake cylinder being connected to the fixed displacement hydraulic pump via a drum brake fluid line branched off from the axle brake fluid line and configured to release a braking state of the drum； and

a towing control valve disposed in the axle brake fluid line, and including a reciprocating pump configured to provide a pressurized fluid from a hydraulic tank to both the axle brake cylinder and drum brake cylinder in case where the engine stops, so that the compactor is movably operated for towing.
The surface compactor of claim 1, wherein the towing control valve further comprises: a first flow path connected to the axle brake fluid line via an inlet port and an outlet port； an orifice formed in the first flow path between the inlet port and the outlet port； a second flow path branched off from the first flow path, and configured to communicate the first flow path with a hydraulic tank； and a plurality of check valves disposed in the second flow path.
The surface compactor of claim 1, wherein the reciprocating pump includes a lever and a plunger connected to the lever, and the plunger be reciprocated in the cylinder of the reciprocating pump by external force applied to the lever.
The compactor as claimed in claim 2, wherein the check valves include a first check valve for preventing backflow of the pressurized fluid from the axle brake fluid line in case where the engine stops.
The compactor as claimed in claims 2 or 4, wherein the check valves include a second check valve for preventing backflow of the pressurized fluid from the cylinder of the reciprocating pump.
The compactor as claimed in claims 1 or 2, wherein the towing control valve includes a rotational switch thread-fastened to a valve housing to adjust an opening degree of the orifice.
The compactor as claimed in claim 6, wherein the towing control valve includes a needle valve for adjusting a closed state of the first flow path in case where the engine stops.
The compactor as claimed in claim 6, wherein the towing control valve includes a pressure sensor disposed close to the first outlet port and the pressure sensor indicates a pressure generated in the axle brake fluid line by operating the reciprocating pump.
The compactor as claimed in claim 1, wherein the pressurized fluid is generated in the range of 20 to 24 bars in the axle brake fluid line.
The compactor as claimed in claim 8, the towing control valve is detachably connected to the axle brake fluid line by a joint connection.
The compactor as claimed in claim 8, wherein the pressure sensor is installed at the axle brake fluid line.
The compactor as claimed in claim 8, wherein the pressure sensor is installed at the drum brake fluid line.
The compactor as claimed in claim 1, the compactor is a soil compactor.