JP3500769B2 - Tractor brake valve - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tractor brake valve. In the tractor steering control, the lift arm is automatically raised by the turning steering angle of the steering handle, the working device is raised to a non-working height, and the turning steering brake is braked. Although there is control of the lift brake, the present invention can be effectively used in such an auto lift brake mode. 2. Description of the Related Art Since the steering brake of a tractor is provided to brake the left and right rear wheels separately, an actuator and a brake which hydraulically operate the steering brake are provided. It is also preferable to mount the solenoid valves and the like on the left and right sides of the transmission case and the axle housing, but the cost for preparing these actuators and solenoid valves separately for the right and left is high. [0003] The present invention relates to a solenoid valve 2 for a steering brake 1, a brake cylinder 3 operated by switching the solenoid valve 2, and
The left and right sides of a valve case 5 having a brake pressure release valve 4 for releasing the brake pressure by changing the hydraulic pressure to the brake cylinder 3 between them are set as symmetric mounting surfaces 6 and 7 for transmission. The brake valve is characterized in that it is commonly mounted on the mounting seats 10 and 11 on the left and right sides of the case 8 to the axle housing 9. When the valve case 5 having the solenoid valve 2 and the brake cylinder 3 for operating the steering brake 1 is mounted on the left and right sides of the transmission case 8 or the axle housing 9, Since the valve case 5 has the symmetric mounting surfaces 6 and 7,
Each mounting seat 10, 11 corresponding to the left and right steering brakes 1
, The configuration is simple, and the same valve case 5 may be prepared, so that the configuration can be made economically. Since these valve cases 5 have a brake pressure release valve 4 for releasing brake pressure together with the solenoid valve 2 and the brake cylinder 3 therein, valves of the same form provided separately for the left and right steering brakes 1 are provided. Even in the case 5, the steering brake control based on the output of the solenoid valve 2 may be stopped, and the steering may be switched to the steering only by the petal operation of the operator. A tractor body 12 integrally connects a clutch housing 15, a front transmission case 16, a middle transmission case 17, and the like from a front engine body 13 to a rear rear transmission case 14. The front wheel 19 steered by the steering wheel 18 and the rear wheel 20 are mounted on the outer side of the rear axle housing 9 integrated on the left and right sides of the rear transmission case 14, and can be driven by the engine E to drive and rotate. . 21
Is a front wheel axle, 22 is a rear wheel axle, and 23 is a hydraulic case provided above the rear transmission case 14, and the rear transmission case 14 to the hydraulic case 23 constitute the transmission case 8 of the present invention. Reference numeral 24 denotes a lift arm, which raises and lowers a working machine such as a rotary tilling device connected to a rear portion of the vehicle body 12 by a three-point link mechanism or the like. The hydraulic cylinder, the hydraulic valve and the like are provided in a hydraulic case 23. . 25 is a fender, 26 is a cockpit. A pair of left and right brake petals 46 on the floor are linked to the respective brake arms 45 so that the opposing steering brakes 1 are linked. By depressing the steering petal 46 on the turning side, the brake arm 45 is interlocked and the steering brake 1 on the interlocking side can be braked for steering. A rear axle 22 in the left and right rear axle housings 9 is provided by a differential device in the rear transmission case 14.
The steering brake 1 is provided in the middle of transmission to the mounting seats 10 and 11 on the left and right sides of the rear transmission case 14.
The brake arm 45 is pressed and rotated by the projection of the piston 27 by the brake cylinder 3 of the valve case 5 attached by a mounting bolt inserted into the bolt hole 47, and the steering brake 1 is braked. When a steering sensor 28 for detecting the steering angle of the steering handle 18 detects a steering rotation angle that is equal to or greater than a predetermined value, the elevation control valve 30 of the hydraulic circuit 29 is output from a controller CPU having a microcomputer. , Lift cylinder 31 in hydraulic case 23
By the operation of the piston 32, the lift arm 24 is raised, and the working machine is raised to the non-working position. At the same time, the output of the controller CPU activates the brake control valve composed of the electromagnetic proportional solenoid valve 2 on the steering turning side, and the steering brake 1 is braked. P is a hydraulic pump of the hydraulic circuit 29, T is a tank port, and 33 is a mode switch for performing automatic lift brake control. Reference numerals 38 and 39 denote rotation sensors for detecting the number of rotations of the front wheels 19 and the rear wheels 20. The controller CPU calculates the slip ratio of the front and rear wheels 19 and 20. The slip ratio of the front and rear wheels 19 and 20 is calculated. The steering brake 1 can be applied to make a turn so that the slip ratio of the front and rear wheels 19 and 20 does not become constant. The valve case 5 has a brake cylinder 3 disposed at an upper portion, an electromagnetic proportional solenoid valve 2 disposed at a lower portion, and a brake pressure adjusting valve 4 provided therebetween. 7 is formed. A bolt hole 47 is formed between the left and right mounting surfaces 6 and 7. The brake cylinder 3 allows the piston 27 to freely move back and forth. The solenoid valve 2 is an electromagnetic proportional solenoid 34
The operation amount (position) is controlled by the balance between the spring 35 and the pilot pressure of the pilot circuit 36 and the like, and the hydraulic pressure to the brake cylinder 3 in the hydraulic circuit 29 is controlled. be able to. The brake pressure release valve 4 is manually or electrically rotated from the outside of the valve case 5 to adjust the amount of oil or the amount of oil discharged from the cylinder port C to the tank port T. This is for stopping or adjusting the amount of oil supply from the brake cylinder 3 to the brake cylinder 3. Due to the drainage of oil from the orifice 37 to the T port of the brake pressure release valve 4, the P port is not completely shut off, and also has a pressure adjusting function for forcible semi-braking pressure. When the braking force is switched between strong and weak by controlling the output of the electromagnetic proportional solenoid valve 2 based on the calculation of the slip ratio in the controller CPU,
If the calculation of the slip ratio is not performed properly due to working conditions, soil conditions, and the like, it is necessary to forcibly switch the braking force between high and low. In such a case, the solenoid-operated proportional solenoid valve 2 operates as the maximum pressure control.
With the brake pressure release valve 4, the pressure can be adjusted so as to be a weak braking pressure. The solenoid proportional solenoid valve 2 has a spacer rod 43 having a short diameter and a predetermined diameter interposed between a rod 40 pushed by a solenoid 34 and an end face of a spool 42 in a valve sleeve 41. The spacer rod 43 is slidably provided in a spacer receiving seat 44 fitted and fixed in the valve sleeve 41. The electromagnetic proportional solenoid valve 2 having a different pilot pressure 36 can be manufactured by preparing the spacer rods 43 in the spacer receiving seats 44 having different diameters and fitting them into the valve sleeve 41. Thereby, between the models having different performances of the steering brake 1, only the spacer seats 44 and the spacer rods 43 are different, and the other valve cases 5,
The economical solenoid proportional solenoid valve 2 which shares the valve sleeve 41, the spool 42 and the like is obtained. The pilot pressure 36 of the spool 42
The springs 35 at the front and rear ends along the center of the spool 42
It communicates between the room A and the pilot room B. In the graph of the control characteristics, a curve C indicates a case where the spacer rod 43 has a standard diameter, a curve D indicates a case where the spacer rod 43 has a small diameter, and a curve F indicates a case where the spacer rod 43 has a large diameter. 6 and 7, the difference from the above example is that the brake pressure release valve 4 is in a rotary form, and the P port, T port, C port, and V
(Valve) It is configured to close or open and close four directions of the port. Various forms of the spool configuration of the brake pressure release valve 4 are shown in (1), (2) and (3) of FIG.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view and a front view of a valve case. FIG. 2 is an enlarged sectional side view thereof. FIG. 3 is a hydraulic circuit diagram and a control block diagram. FIG. 4 is a side view of the tractor. FIG. 5 is a partially enlarged view of a solenoid valve portion, a circuit diagram thereof, and a characteristic graph. FIG. 6 is a side view of a valve case showing a partially different embodiment. FIG. 7 is a sectional view of the switching operation showing various different forms of the partial brake pressure release valve portion. [Description of Signs] 1 Steering brake 2 Solenoid valve 3 Brake cylinder 4 Brake pressure release valve 5 Valve case 6 Mounting surface 7 Mounting surface 8 Transmission case 9 Axle housing 10 Mounting seat 11 Mounting seat

Claims (1)

(57) [Claims 1] Solenoid valve 2 for steering brake 1
Left and right sides of a valve case 5 having a brake cylinder 3 operated by switching of the solenoid valve 2 and a brake pressure release valve 4 interposed therebetween for changing the hydraulic pressure to the brake cylinder 3 to release the brake pressure. The both sides are symmetrical mounting surfaces 6 and 7, and the mounting seats 1 on the left and right sides of the transmission case 8 to the axle housing 9 are formed.
A brake valve characterized in that it is commonly used for 0 and 11.