JP2538712Y2 - Hydraulic circuit of small excavator - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for a swing parking brake of a small shovel.

[0002]

2. Description of the Related Art FIG. 2 is a side view of a small shovel.
In the drawing, 1 is a lower traveling body of a small shovel, 2L and 2R are left and right traveling motors, 3 is an upper revolving body, 5 is a revolving motor, 6 is a work attachment mounted on a front portion of the upper revolving body 3, and 7 is Boom of work attachment 6,
8 is an arm, 9 is a bucket, 10 is a boom cylinder, 1
1 is an arm cylinder, 12 is a bucket cylinder, 13 is a dozer device, and 14 is a dozer cylinder of the dozer device 13.

FIG. 3 is a circuit diagram of a conventional small shovel. In the figure, 15 is a mechanical brake device for turning parking of the turning motor 5, 16 is a brake cylinder which is a cylinder of the mechanical brake device 15, 17 and 18 are overload relief valves, 19 is a turning speed reducer, and 20 is a multi-unit. Control valve of valve type configuration, 21
Is a direct push-pull operation type switching valve disposed in the control valve 20, and 22,..., 26 are switchings for controlling other actuators (other actuators are not shown in FIG. 3 for convenience of explanation). Valves, 27 and 28 are first and second hydraulic pumps, 29 is an oil tank, 30
Is a pressure reducing valve, 31 is a pressure reducing valve for a brake circuit in the pressure reducing valve 30, 32 is a pressure reducing valve for a main circuit, 33 is an electromagnetic switching valve for brake, 34 is a solenoid of the electromagnetic switching valve 33, 35 is an electric circuit, and 36 is an electric circuit. A switch 37 in the circuit 35 is a power supply.

Next, a prior art circuit will be described with reference to FIGS. 2 and 3. FIG. In the prior art circuit of a small excavator, various hydraulic actuators are divided into two groups A and B, each of which is driven by a first hydraulic pump 27 and a second hydraulic pump 28, and one of the groups A and B is used. The discharge side of a hydraulic pump (first hydraulic pump 27) that arranges the turning switching valve 21 in one of the groups and drives a group (for example, group A as shown in FIG. 3) in which the turning switching valve 21 is arranged. Is provided with a brake pressure reducing valve 31 so that when the small shovel turns, the hydraulic oil derived from the brake pressure reducing valve 31 is applied to the mechanical brake device 15 for turning parking to release the turning parking brake. ing.

When the small excavator stops the engine, the first hydraulic pump 27 and the second hydraulic pump also stop rotating. Therefore, no hydraulic pressure acts on the brake cylinder 16, and the mechanical brake device 15 performs the turning parking brake by the spring force of the built-in spring A provided in the brake cylinder 16. Next, when the switch 36 is turned off with the engine started, the solenoid 34 is de-energized. Since the brake electromagnetic switching valve 33 is located at the tank communication oil path position B, the pressure oil does not act on the brake cylinder 16. Therefore, also in this state, the mechanical brake device 15 performs the turning parking brake. However, when the small shovel turns, the switch 36 is first turned on. Since the solenoid 34 is energized, the electromagnetic switching valve 33 switches from the tank communication oil passage position B to the open oil passage position C. The pressure oil from the first hydraulic pump 27 passes through the pipe 38, the pressure reducing valve 31 for the brake circuit in the pressure reducing valve 30, the pipe 39, the C position of the electromagnetic switching valve 33, and the pipe 40, and passes through the rod of the brake cylinder 16. Oil is sent to the side oil chamber. Since the brake cylinder 16 operates to contract against the spring force of the built-in spring b, the turning parking brake of the mechanical brake device 15 is released. Thus, the small excavator can turn without any trouble.

[0006]

When the small shovel turns, the turning parking brake must be released by operating a switch, and the switch must be operated when the brake is operated. The trouble was troublesome, and sometimes the switch operation was inadvertently forgotten. In addition, a switch in the electric circuit for the turning parking brake may rust and cause a failure, which is a problem in maintenance. The problem to be solved by the present invention is to provide a hydraulic circuit which can automatically operate and release the turning parking brake without the need for an electric circuit for the turning parking brake.

[0007]

According to the present invention, a turning valve is provided with a sub-valve which is operated in conjunction with the turning valve, and when the turning valve is in a neutral position, the sub-valve is in a shutoff oil passage position. In addition, when the turning switching valve is in the switching position, the sub-valve is set so as to switch to the open oil passage position, and a line communicating the cylinder of the turning parking mechanical brake device and the brake circuit pressure reducing valve is provided. A pipe having a brake pilot switching valve interposed therebetween, which communicates the pilot pressure receiving portion of the brake pilot switching valve with the sub-valve via a pipe line, and from the brake circuit pressure reducing valve to the brake pilot switching valve. A part of the pressure oil led out to the road is passed through the sub-valve.

[0008]

1 is a hydraulic circuit diagram of the present invention. In the figure, the same reference numerals are given to components using the same components as the conventional technology. Reference numeral 41 denotes a switching for turning, reference numeral 42 denotes a sub-valve of the switching valve for turning 41, reference numeral 43 denotes a pilot switching valve for brake, and reference numeral 44 denotes a pilot pressure receiving portion of a pilot switching valve 43 for brake (hereinafter referred to as a brake valve 43).

Next, the configuration of the hydraulic circuit of the present invention will be described with reference to FIG. The turning switching valve 41 is provided with the turning switching valve 41.
A sub-valve 42 is provided for switching operation in conjunction with 1. The sub-valve 42 is in the shutoff oil passage position when the turning switching valve 41 is in the neutral position, and the sub-valve 42 is in the open oil passage position when the turning switching valve 41 is in the switching position. And a brake valve 43 is provided in a conduit communicating the brake cylinder 16 of the mechanical brake device 15 for turning parking and the pressure reducing valve 31 for the brake circuit, and the pilot pressure of the brake valve 43 is provided. Pressure receiving section 44 and sub valve 42
And a part of the pressure oil led from the brake circuit pressure reducing valve 31 to a pipe 46 communicating with the brake valve 43 is passed through the sub-valve.

When the small excavator stops the engine, the first hydraulic pump 27 and the second hydraulic pump also stop rotating. Therefore, no hydraulic pressure acts on the brake cylinder 16, and in this case, the mechanical brake device 15 performs the turning parking brake as in the prior art. Next, when turning is not performed with the engine started, that is, when the turning switching valve 41 is in the neutral position, the sub-valve 42 is in the shutoff oil path position.
Pressure oil does not act on the pilot pressure receiving portion 44 of the brake valve 43. Since the brake valve 43 is located at the tank communication oil path position d, no pressure oil acts on the brake cylinder 16. Therefore, also in this state, the mechanical brake device 15
Is turning the parking brake. However, when turning the small excavator, the turning switching valve 41 is operated to switch from the neutral position. In conjunction with the switching operation of the turning switching valve 41, the sub-valve 42 switches to the open oil passage position. Part of the pressure oil from the first hydraulic pump 27 branches off from the line 46, and the line 47, the position of the open oil passage of the sub-valve 42,
5 and acts on the pilot pressure receiving portion 44. The brake valve 43 switches from the tank communication oil passage position d to the open oil passage position E. The pressure oil from the first hydraulic pump 27 branches in the pressure reducing valve 30, one of which passes through the switching positions of the main circuit pressure reducing valve 32 and the turning switching valve 41, and is supplied to the turning motor 5, and the other is braked. The oil is supplied to the rod-side oil chamber of the brake cylinder 16 through the circuit pressure reducing valve 31, the pipe line 46, the E position of the brake valve 43, and the pipe line 40 '. Since the brake cylinder 16 operates to contract against the spring force of the built-in spring b, the turning parking brake of the mechanical brake device 15 is released. As described above, the turning parking brake of the small shovel can be automatically activated and released.

[0011]

As described above, according to the present invention, the turning switching valve in the hydraulic circuit mounted on the small shovel is provided with a sub-valve that performs a switching operation in conjunction with the turning switching valve.
When the turning switching valve is in the neutral position, the sub-valve is set to the shutoff oil passage position, and when the turning switching valve is in the switching position, the sub-valve is switched to the open oil passage position. A pilot switching valve for brake is provided in a pipeline communicating with the pressure reducing valve for a brake circuit, and a pilot pressure receiving portion of the pilot switching valve for brake communicates with the sub-valve through a pipeline. A part of the pressure oil led from the pressure reducing valve for the brake circuit to the pipe leading to the pilot switching valve for the brake is passed through the sub-valve. Thereby,
This eliminates the need for an electric circuit (including a switch) for the turning parking brake, which is provided in the conventional small shovel, and enables the turning parking brake to be automatically activated and released.
Therefore, in the small shovel having the hydraulic circuit of the present invention, the turning operability and the maintainability are improved.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of the small shovel of the present invention.

FIG. 2 is a side view of the small shovel.

FIG. 3 is a hydraulic circuit diagram of a conventional art.

[Explanation of symbols]

 Reference Signs List 5 swing motor 15 mechanical brake device 16 brake cylinder 21, 41 swing switching valve 27, 28 first and second hydraulic pumps 31 pressure reducing valve for brake circuit 42 sub-valve 43 pilot switching valve for brake

Claims (1)

(57) [Scope of request for utility model registration] 1. A hydraulic excavator mounted on a small excavator is divided into two groups A and B, each of which is driven by first and second hydraulic pumps, and one of the groups A and B. And a pressure reducing valve is provided on the discharge side of a hydraulic pump that drives a group in which the switching valve is disposed, so that when the small shovel turns, pressure oil derived from the pressure reducing valve is turned. In a hydraulic circuit that acts on a mechanical brake device for parking to release a turning parking brake, a turning switching valve is provided with a sub-valve that switches in conjunction with the turning switching valve, and the turning switching valve is When the neutral position is at the neutral position, the sub-valve is set to the shutoff oil passage position, and when the turning switching valve is at the switching position, the sub-valve is set to the open oil passage position. A brake pilot switching valve is interposed in a pipe connecting the cylinder of the mechanical parking brake device for braking and the pressure reducing valve, and a pilot pressure receiving portion of the brake pilot switching valve and the sub valve are connected via a pipe. A hydraulic circuit for a small shovel, characterized in that a part of the pressure oil which is communicated and is led to a pipe from the pressure reducing valve to a pilot switching valve for brake is passed through the sub-valve.