JPS6231555A - Brake circuit for working vehicle - Google Patents

Abstract

PURPOSE:To simplify construction of a brake circuit and secure and facilitate the selection and operation of braking conditions by connecting the normal position of a control valve to the neutral position of a selector valve by means of lines which pass through these positions in order and carry out discharge. CONSTITUTION:The input port of a selector valve 2 is connected to a pressure air source 1 through a line 2d and one of its output ports is connected to one of the input ports of a control valve 3 through a line 13 while the other output port is connected to the air cylinder 11a of a parking brake device 11 through a line 15, and each of these positions can be shifted by operating a lever 12a. On the other hand, one of the input ports of the control valve 3 is connected to the pressure air source 1 through a line 2a while the other input port is connected to said output port of the selector valve 12 through the line 13, and its output port is connected to the air chamber 8a of a main brake device 8 through a line 14. And, when the pedal 3a of the valve 3 is depressed, pressure air in the pressure air source 1 is fed to the main brake device 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a brake circuit for a work vehicle that uses pressurized air as a power source for operating a brake device, and particularly to a brake circuit for improving the reliability and workability of the brake device. This brake circuit is suitable for

[Background of the invention]

A brake device is an important safety component for not only work vehicles but also moving vehicles, and must operate reliably under any circumstances. In particular, work vehicles used for civil engineering and construction are heavy and have a large inertial energy, so poor braking can directly lead to a serious accident, so a particularly reliable braking system is required. . By the way, a work vehicle repeatedly performs work at a work site and then moves to the next work site and performs the work, during which time it travels on public roads like a general vehicle. For this reason, the brake system of a work vehicle is used for braking to decelerate or stop while driving (hereinafter referred to as driving braking) required for general vehicles, and braking to prevent movement of the vehicle body while parked (hereinafter referred to as braking during work). In addition to braking (hereinafter referred to as braking), an additional function is required to perform braking to prevent the vehicle body from moving against external forces applied to the vehicle body during work such as excavation work (hereinafter referred to as work braking). Of these, braking while driving and braking while working are both braking while the engine is running, but braking while driving is a deceleration while driving that includes deceleration that leads to a stop, as shown in @, and braking while working is braking when the engine is running. Since this is braking during work,
Naturally, the control times are different and require separate valves, such as the pedal type and manual lever type, for example. However, since both brakes are applied while the engine is running, a positive brake type is used, and the brake system is shared and used separately for driving and work.

On the other hand, parking braking is braking when the engine is stopped as mentioned above, but the brake system cannot receive pressurized air because the engine is stopped, and if there is an air leak in the brake circuit. Since the pressure decreases and it becomes difficult to maintain the pressure necessary for braking, a negative type brake system is installed that releases the pressure inside the brake system to perform braking, and a valve is installed to control the brake force. However, when parking the brake is released (the engine is driven and the vehicle is ready to travel), pressure is used to release the brake since the vehicle can be supplied with pressurized air.

A brake circuit shown in FIG. 5 is known as a general brake circuit for a conventional work vehicle equipped with each of the brake devices described above. In the figure, 1 is a pressure source, 1a is an engine, 1
b is a compressor driven by engine 1m, 1c is an air tank connected to compressor 1b via check valve 1d, 1
e is a relief valve that maintains the pressure inside the air tank Ie at a set value. Reference numeral 3 designates a 3/- to 2-position switching control valve for braking during running; the input port is connected to a pressure air source 1 via a conduit 2a and is operated by a pedal 3a; and 3b is a ventilation port. Reference numeral 4 denotes a three-point/two-position switching valve for braking during work, and its input port is connected to a pressure air source 1 through a pipe 2blC, and is operated by a lever 4a. 4b is a ventilation port. Reference numeral 5 designates a three-point/two-position switching valve for braking during parking, the input port of which is connected to the pressure air source 1 through a pipe 2c, and is operated by a lever 5a. 5b is a ventilation hoard. Reference numeral 6 designates a shuttle valve, one of which is connected to the output port of the control valve 3 and a pipe line 7a, and the other is connected to the output port of the switching valve 4 through a pipe line 7b. Reference numeral 8 denotes a positive type main brake device for both driving and working braking, which includes a pressure-hydraulic conversion booster 8m, a brake device 8b built into each of a plurality of wheels, and a pressure-hydraulic conversion booster 8a. and a conduit 8c connecting the brake device 8b and the brake device 8b. The pressure-hydraulic conversion booster 8a has a piston 8111 fitted into a cylinder consisting of a large-diameter air chamber 8ag and a small-diameter oil chamber 8a3. The oil chamber 8a3 is connected to the pipe line 8c. Moreover, the brake device 8b is a wheel cylinder 8b1. Brake shoe 8b operated by expansion and contraction of wheel cylinder 8b1
2. Wheel cylinder 8bt and brake shoe 8
It consists of a brake drum 8b3 that accommodates bz, etc. Here, if a pneumatic type wheel cylinder 8bl is used instead of a hydraulic type, the pressure pressure/hydraulic pressure conversion booster 8a becomes unnecessary. Reference numeral 11 denotes a half tip-shaped parking brake device for braking during parking, which includes an air cylinder 11a and a brake device ti b.
In other words, the air cylinder 11a is composed of a piston 11a1 that moves within an air chamber 11a2, and a spring 11a3 that pushes the piston 1iar and brakes the brake device 11b when the pressure inside the air chamber 11a2 is released. Also, the brake device 11b is the brake shoe 11b! , a brake drum 11b2, a spring 11ha, etc., and an air chamber fla2 is connected to an output port of the parking brake valve 5 through a conduit 10.

The states of each valve shown in the figure are control valve 3. Both the switching valve 4 and the switching valve 5 are switched to the OFF position, and the main brake device 8 is blocked from receiving pressure from the pressure air source 1, and the pressure in the air chamber 8 is released from the ventilation port 3b, so that the braking state is released. In this state, the parking brake device 11 is in a state in which pressure air from the pressure air source 1 is supplied to the air chamber 11a2 through the switching valve 5, and the brake device 11b is released. In other words, the work vehicle is running or is ready to run. In this state 4 Dal 3a
When the operator steps on and switches the control valve 3 to the ON position, the pressure air from the pressure air source 1 is supplied to the main brake device 8 via the shuttle valve 6, and the brake device 8b is braked. When the vehicle brakes and stops traveling, the pedal 3a is released and the control valve 3 returns to the OFF position, returning to the brake released state as shown in the figure. When the lever 4a is operated to switch the switching valve 4 to the ON position, the pressure from the pressure air source 1 is supplied to the main brake device 8 via the shuttle valve 6, and the brake device 8b is braked. At this time, when the lever 5a is subsequently operated to switch the switching valve 5 to the ON position, the pressure in the air chamber 11a2 is released from the ventilation port 5b, and the brake device 11b is braked, and the braking force is reduced during work. Becomes in a braking state. When the work is completed and the vehicle starts traveling, the levers 4a and 5a are operated to the OFF position to release both brake devices 8 and 11. When the vehicle travels to a predetermined location, stops the engine 1 m, and parks the vehicle, the lever 5a is switched to the ON position and the brake device 11b is applied in the same manner as during the above-mentioned work.

In the conventional work vehicle brake circuit having the above configuration,
It has the following problems. That is, (1) the shuttle valve 6 is used in the above-mentioned brake circuit, but due to the structure of the shuttle valve 6, dust in the operating pressure air gets caught in the shuttle piston, or moisture in the operating pressure air gets caught in the shuttle piston. If it freezes inside the valve 6, it is likely to stick. The fact is that the stick of the shuttle valve 6 cannot be sufficiently prevented even if considerable countermeasures are taken, since the working environment of the working vehicle is outside the mold, where there is a lot of dust, and the work is often done in cold regions. Once a stick occurs, depending on the degree of stick, the pressure supplied from the valve switched to the ON position is released from the ventilation port of the other valve via the shuttle valve 6, and the pressure in the brake circuit is reduced accordingly. Therefore, a brake circuit using the shuttle valve 6 is not suitable for the brake system of a work vehicle, which requires high reliability like a general vehicle, since there is a risk that the brake system 8b will be unable to brake due to a drop in air pressure. be.

(2) Even if pressure leaks from the shuttle valve 6 or other causes such as stickiness of the shuttle valve 6, the pressure inside the brake circuit decreases, and the brake device 8b becomes unable to brake, the brake circuit remains in the negative type. Although the parking brake device 11 is configured to automatically brake and act on the safe side, the braking device 11 when driving is
In order to perform braking during work and braking during parking, the control valve 3
゜The switching valve 4 and the switching valve 5 are required, and in order to perform braking during work, both the switching valve 4 and the switching valve 5 must be operated, resulting in erroneous operation, which poses problems in workability and economy. [Object of the Invention] The present invention solves the problems of the prior art described above, and it simplifies the configuration of the brake circuit in a working vehicle to facilitate control, thereby improving the reliability of the operation of the brake device and the workability. The purpose is to provide a brake circuit for high-performance vehicles.

[Summary of the invention]

The present invention provides a positive type main brake device and a negative type parking brake device that operate by supplying and discharging pressurized air.
In a brake circuit for a work vehicle that includes a pressure air source that supplies pressurized air to each of the brake devices and a plurality of valves that control the supply and discharge of the pressure air, the plurality of valves are placed at work positions for braking each of the brake devices. , a switching valve having a parking position for braking the parking brake device and a neutral position for releasing the braking state of each brake device, and a control valve for fully controlling the operation of the main brake device, the control valve and The switching valve is connected by a pipe line that sequentially passes through a normal position of the control valve and a neutral position of the switching valve to discharge the pressurized air supplied to the main brake device,
The brake circuit configuration is simplified to facilitate control operations.
This improves the reliability and workability of the brake system.

[Embodiments of the invention]

The details of the present invention will be explained with reference to FIGS. 1 to 4. In the figure, the same symbols as in FIG. 5 indicate the same parts.

FIG. 1 shows a first embodiment of the present invention, in which one switching valve, for example, a 5-point and 3-position switching valve, is used as a control valve instead of the conventional switching valves 4 and 5. It is designed to be provided together with 3. Reference numeral 12 denotes a switching valve, which releases pressurized air supplied to the main brake device 8 to the atmosphere through a ventilation port 12bl, and supplies pressurized air to the parking brake device 11 to control the braking state during driving. At the neutral position (hereinafter referred to as N position), pressurized air is supplied to the main brake device 8 and also to the parking brake device 11. a working position (hereinafter referred to as the W position), and a parking position (hereinafter referred to as the P position) where the pressurized air supplied to both brake devices 8 and 11 is released to the atmosphere through the ventilation ports 12bl and 12b2 to perform parking braking. are provided, the input port of which is connected to the pressure source 1 by a pipe 2d, one output port is connected to one input port of the control valve 3 by a pipe 13, and the other output port is connected to the parking brake system by a pipe 15. 11 air cylinder 11
m, and the respective positions can be switched by operating the lever 12m. On the other hand, one input port of the control valve 3 is connected to the pressure air source 1 through a pipe line 2a, and the other input port is connected to one output port of the switching valve 12 through a pipe line 13 as described above. It is connected to the air chamber 81L2 of the main brake device 8 by a passage 14.

The operation in this embodiment will be explained. When the switching valve 12 is in the N position shown in FIG. By being connected, conduit 14. OFF position of control valve 3, pipe line 13. Passing through the N position of the switching valve 12 in order, the ventilation de
At the same time, the parking brake device 11 is supplied with pressurized air through the conduit 15 and is brought out of the braking state. In this state, when the pedal 3a of the control valve 3 is pressed and switched to the ON position, the pressure of the pressure air source 1 is transferred to the pipe 2&, the control valve 3. It is supplied to the main brake device 8 through the conduit 14, and the brake device 8b is braked. When you release the pedal 31L and return the control valve 3 to the OFF position,
The pressure in the air chamber 8a2 is transferred to the pipe 14. Control valve 3. Conduit 13.
The switching valve 120 is opened to the atmosphere through the ventilation port 12bl, the braking state of the brake device 8b is released, and the state shown in the figure is returned. Next, when the lever 12m is operated to switch to the P position, the pressure in the air cylinder 11m of the parking brake device 11 is released to the atmosphere from the ventilation port 12b2 through the pipe 15, and the brake device 11b is braked. In the example, at the same time, the pressurized air in the air chamber 8az of the main brake device 8 is also released to the atmosphere through the ventilation J-) 12bt, and the braking state of the brake device 8b is released. Next tZ -12
When switching to the W position by operating the main brake device 8, the pressure from the pressure air source 1 is applied to the main brake device 8 through the pipe 2d, the switching valve 12, and the pipe 13. Control valve 3. It is supplied through the conduit 14' and brakes the brake device 8b. At the same time, the pressure in the air cylinder 11m of the parking brake device 11 is released from the ventilation port 12b2, and the brake device 11b is braked.

As described above, in the first embodiment, braking during traveling is performed by setting the switching valve 12 to the N position and operating the control valve 3, and braking during work is performed by simply switching the switching valve 12 to the W position. Furthermore, since braking during parking is performed simply by switching the switching valve 12 to the P position, the selection of each of these braking operations can be performed reliably and easily, and there is no problem with brake shoes caused by malfunctioning switching of the shuttle valve as in the conventional case. No wear occurs. Further, the valves are only the control valve 3 and the switching valve 12, and the valves are operated only by the pedal 3a and the lever 12m, which makes the operation easy and eliminates the risk of erroneous operation, improving economic efficiency and workability. Furthermore, in this embodiment, in the case of braking during running, pressure air from the pressure air source 1 is supplied to the main brake device 8 without passing through the switching valve 12.

This eliminates the need for pressure loss when pressure air passes through the switching valve 12, improves the responsiveness of the main brake device t8, and prevents the pressure from passing through the switching valve 12 and the pipe 13.
Even if the air pressure is cut off between the two, the main brake device 8 can be activated by the control valve 3, so braking can be performed more safely during driving.

A second embodiment will be explained with reference to FIG. In this embodiment, compared to the first embodiment shown in FIG. 1 in which the control valve 3 and the switching valve 12 are connected by locating the control valve 3 on the downstream side of the conduit 13, The control valve 3' is connected to the upstream side of the conduit 13', and the other configurations are the same.

However, due to this difference in structure, the ventilation port 12bt provided in the switching valve 12 for releasing the pressure in the air chamber 8az is eliminated, and a ventilation port 3'b is provided in the control valve 3' instead. In addition, the ventilation hole 12b2ij provided in the switching valve 12 that releases the pressure of the air cylinder 11a2
, changes to the ventilation port 12'b of the switching valve 12'.

The operation of this embodiment is different from that in the first embodiment in which pressurized air is supplied to the main brake device 8 during running braking (N position) without via the switching valve 12. Other than that, the operation of the switching valve 12' at each position is the same.

In this way, in the second embodiment, since the arrangement of the valves is different from that in the first embodiment, the pressure when the pressure air from the pressure air source l supplied to the main brake device 8 passes through the switching valve 12' is Although there will be a loss, a commercially available valve with a configuration widely used in general vehicles can be used as the control valve 3', making it easily available, improving compatibility and economic efficiency. There is. Other effects are the same as in the first embodiment.

A third embodiment will be explained with reference to FIG. The present first embodiment differs from the configuration of the second embodiment in that it is possible to supply pressurized air to the main brake device 8 through the control valve 3' without using the switching valve 12' during braking during running. A pipe 9 circuit 16 for connecting the pipes 13' and 14' is added to the above, and the other configurations are the same. A check valve 17 is provided in the pi-9 gas circuit 16 to prevent backflow of the pressurized air supplied to the air chamber 8a2.

In the third embodiment with such a configuration, when braking is performed during running, the pressure air from the pressure air source 1 does not pass through the switching valve 12' due to the difference in circuit resistance, but passes through the pi/spa circuit 16 to the main brake device 8. Since the control valve 3' is supplied to the first and second embodiments, it does not suffer from the pressure loss as in the second embodiment, and on the other hand, a commercially available control valve 3' having the same configuration as the second embodiment can be used. This has an effect that combines the effects of the second embodiment.

FIG. 4 shows a fourth embodiment, in which a sequence valve is added to the configuration of the third embodiment shown in FIG. 1f is added, and the other configurations are the same as in FIG. 3. The sequence valve 1f is usually provided upstream of the pipe line 2d in the pressure air source 1 for reasons such as piping and maintenance, and prevents pressure from decreasing for whatever reason on the downstream side of the pipe line 2d during travel. - Ensures that the pressure does not drop below a set constant pressure (pressure that allows braking while driving) when
It is a valve that does. By adding the sequence valve lf, the minimum operating pressure of the line for braking the main brake device 8 is ensured, resulting in a circuit with even higher safety. Other effects are the same as in the third embodiment. It goes without saying that the sequence valve 1f described in this embodiment can be similarly installed in each of the embodiments described above, and in that case, its effects will be added to the effects of each of the embodiments described above.

〔Effect of the invention〕

As explained above, the brake circuit of the working vehicle according to the invention uses a plurality of valves disposed between the pressurized air source and both the main and parking brake devices to brake the respective brake devices. a control valve that controls the operation of the main brake device, and a control valve that controls the operation of the main brake device; The configuration of the brake circuit is simplified because the switching valve is connected with a pipe that sequentially passes through the normal position of the control valve and the neutral position of the switching valve to discharge the pressurized air supplied to the main brake device. , the selection and operation of each braking state can be reliably and easily performed, erroneous valve operations and switching failures can be eliminated, and the reliability and workability of the operation of the brake device can be improved, which is a remarkable effect in practical use.

[Brief explanation of the drawing]

1 to 4 are explanatory diagrams of embodiments according to the present invention, in which FIG. 1 is the first embodiment, FIG. 2 is the second embodiment, and the third embodiment.
The figure is a third embodiment, and FIG. 4 is an explanatory diagram of the fourth embodiment. FIG. 5 is an explanatory diagram of a general brake circuit in a conventional work vehicle.

Claims (1)

[Scope of Claims] 1. A positive type main brake device and a negative type parking brake device that operate by supplying and discharging pressurized air, a pressurized air source that supplies pressurized air to each brake device, and controlling the supply and discharge of the pressurized air. In the brake circuit for a work vehicle, the plurality of valves are arranged at a working position where each of the brake devices is braked, a parking position where the parking brake device is braked, and a braking state of each of the brake devices is released. and a control valve that controls the operation of the main brake device, and the control valve and the switching valve control the pressure air supplied to the main brake device to A brake circuit for a work vehicle, characterized in that the brake circuit is connected to a neutral position of the switching valve by a conduit that sequentially passes through the neutral position of the switching valve. 2. The brake circuit for a work vehicle according to claim 1, wherein a switching valve is connected to the upstream side of the conduit. 3. The brake circuit for a working vehicle as set forth in claim 1, wherein a switching valve is connected to the downstream side of the conduit. 4. A positive type main brake device and a negative type parking brake device that are operated by supplying and discharging pressurized air, a pressurized air source that supplies pressurized air to each brake device, and a plurality of valves that control the supply and discharge of the pressurized air. In the brake circuit for a work vehicle, the plurality of valves have a working position where each of the brake devices is braked, a parking position where the parking brake device is braked, and a neutral position where the brake state of each of the brake devices is released. It is composed of a switching valve and a control valve that controls the operation of the main brake device, and the control valve and the switching valve transfer the pressurized air supplied to the main brake device to the normal position of the control valve and the control valve that controls the operation of the switching valve. A pipe line that sequentially passes through a neutral position and discharges water, is connected to a switching valve located downstream of the pipe line, and is characterized by being provided with a bypass circuit that connects the upstream side and the downstream side of the switching valve. brake circuit for work vehicles.