JPS6215388B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a braking device for a trailer (towed vehicle) connected to a tractor (towed vehicle).

The braking operation of the trailer described above will be explained based on a general trailer braking device shown in FIG. When a trailer and a tractor are connected, a service line 1 and an emergency line 2 on the trailer side are connected to a service line and an emergency line on the tractor side via couplings 3 and 4, respectively. When the brake valve of the tractor is operated, air pressure corresponding to the operating force is input as a signal pressure to the relay emergency valve (hereinafter referred to as REV) 5 through the service line 1, and air pressure proportional to the signal pressure is input to the air reservoir 6. From REV
5 to the air chamber 7 (or air booster in the air-over-hydraulic brake shown by the chain line, hereinafter referred to as air chamber 7) of the end braking unit, and is connected to the air chamber 7 (not shown). operates to brake each wheel of the trailer.

In addition, the REV5 normally functions to fill air pressure from the tractor side air reservoir to the trailer air reservoir 6 through the emergency line 2 and the air reservoir 6 through the emergency valve built inside the REV5, but the piping system If the pressure in the emergency line 2 drops below a predetermined value due to failure or separation of the trailer and tractor, the emergency line 2 and the air reservoir 6
It also has the function of shutting off the air reservoir 6 and the air chamber 7 and supplying air pressure to the air chamber 7 for braking.

In this case, in the above conventional configuration, when the pressure in the emergency line 2 (hereinafter referred to as pressure PE) drops to atmospheric pressure, air pressure is supplied to the air chamber 7 until it becomes equal to the air pressure in the air reservoir 6.

This reduction in the pressure PE to atmospheric pressure frequently occurs when other tractors are disconnected in an emergency, and especially when disconnected from the tractor, the terminal brake of the trailer is connected to the normal service line 1. During braking operations, an unnecessarily large braking force is applied for a long period of time, which occurs rarely and only for a short period of time, which is a major factor in reducing the durability and strength of the brake body.

Therefore, the present invention provides a trailer braking device configured to reduce the braking air pressure supplied from the pressure supply source to the end braking unit to the level necessary for braking when the pressure PE decreases. It is something.

Embodiments of the present invention will be described below based on the drawings. However, in the embodiments shown in FIGS. 2 and 5, only essential parts are shown, and the same reference numerals are given to the same components as in FIG. 1.

In the first embodiment shown in FIG. 2, a limiting and quick release valve (hereinafter referred to as LQRV) 8 is installed in the piping connecting the discharge port of the REV 5 and the air chamber 7 in the conventional configuration shown in FIG.
The pressure PE led from the pipe 9 where the LQRV 8 is branched from the emergency line 2
It is configured to operate as a pilot signal. LQRV8 has an internal structure as shown in FIG. Now, when the trailer is connected to the tractor and the pressure PE is maintained above a predetermined value, the pressure PE led to the input port of LQRV8 is added to the stepped annular surface _A1 of the plunger 11. and the pressure is applied to the plunger 1
1, the plunger 11 is pushed down by overcoming the resistance of the spring 12 biased against the lower surface of the spring 12, and the stopper 1 is pushed down.
It is pressed against 3. In this state, plunger 11
The lower end spherical part of the valve stem 14 passing through the center hole of the valve closes the exhaust port 15, and the inlet port 16 formed between the center hole and the valve stem 14 is opened and connects to the discharge port of the REV5. The port 17 and the outlet port 18 connected to the air chamber 7 are electrically connected.

Therefore, the signal pressure from service line 1 (hereinafter referred to as pressure PS) accompanying the braking operation on the tractor side
The braking pressure corresponding to REV is applied from air reservoir 6.
When sent to LQRV8 through 5, LQRV
8 transfers the braking pressure to the air chamber 7 with the same pressure through the conducted inlet port 16.
Braking is performed in the same way as before.

Next, the pressure PE drops below a predetermined value and REV
When the emergency valve 5 is opened,
The pressure PE causes the plunger 11 to move to the stopper 13.
Inlet port 1 while being pressed against
6 through LQRV8 upstream and downstream pressure i.e. REV
The discharge pressure of REV 5 and the pressure of air chamber 7 are equal, but when the discharge pressure of REV 5 increases to a predetermined value exceeding pressure PE, the plunger 11 is lifted upward due to the difference in area between the upper and lower surfaces of the plunger 11 and the valve system 14 The inner wall of the plunger 11 comes into pressure contact with the upper spherical portion of the inlet port 16, thereby closing the inlet port 16. In such a state, the pressure balance is maintained by the following relational expression. That is, PD・S ₁ +PE・S ₂ =PF・S ₃ +F (1) However, PD; REV discharge pressure PE; emergency line pressure PF; air chamber pressure S ₁ ; pressure receiving area S ₂ of pressure PD; Pressure receiving area of pressure PE S ₃ ; Pressure receiving area of pressure PF = S ₁ + S ₂ F ; Resistance of spring 12 Transforming equation (1), PF=S ₁ /S ₃・PD+C …(2) However, C=(PE・If PE is constant at S ₂ −F)/S ₃ , it becomes a constant.

Therefore, the relationship between the REV discharge pressure and the air chamber pressure in this case is shown by broken line A in FIG. 4, and the air supplied to the air chamber 7 is reduced in pressure at a constant rate.

In particular, when the pressure PE is released to atmospheric pressure, if the drag force F of the spring 12 is ignored, the above (2)
In the formula, C=O and PF=S ₁ /S ₃・PD holds, so the PEV discharge pressure-air chamber pressure characteristic is the fourth
It will look like straight line B in the figure. (The broken line in the figure is the pressure PS
(showing the characteristics during regular braking) Therefore, the ratio of the pressure receiving areas S ₁ and S ₃ of the plunger 11 is
By setting S ₁ /S ₃ appropriately, the supply pressure to the air chamber is reduced to a necessary and sufficient level when the pressure PE decreases, especially when the tractor is disconnected and released to the atmosphere, thereby improving the durability of the brake body. Strength is improved.

As explained above, the present invention has a limit system that operates the trailer's emergency braking line, which functions when the piping fails or is disconnected from the tractor, by inputting the air pressure from the pressure supply source and the emergency line pressure as a pilot signal. Since the piping is configured so that the pressure is reduced by the brake release valve and then supplied to the end braking section, the durability and strength of the brake body is significantly increased as only the minimum required braking force is applied to the brake body of the end braking section. It has the effect of increasing Furthermore, it can be implemented with the simplest possible configuration of just adding one valve, which is advantageous in terms of cost.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the piping configuration of a conventional trailer braking device, FIG. 2 is a diagram showing the main piping configuration of a first embodiment of the present invention, and FIG. 3 is a diagram showing the piping configuration of the main part of the first embodiment according to the present invention. Vertical sectional view showing the internal structure of the limiting and quick release valve used in
The figure is a graph showing the characteristics of air chamber pressure versus REV discharge pressure in the same example. 2...Emergency Line, 6...Air Riverza, 7...Air Chamber, 8...Limiting and Quiet Release Valve.

Claims (1)

[Claims] 1 Equipped with a relay emergency valve that inputs the pressure from the service line and the emergency line that connects and separates from the tractor side as a pilot signal, and the relay emergency valve allows the braking operation to be performed according to the pressure from the service line. the air pressure is supplied from the air pressure source to the end brake part via the air line, and when the pressure from the emergent engine line is below a predetermined value, the air pressure source is supplied to the end brake part via the airline line. In a trailer braking device which performs braking by supplying air pressure, a limiting device that inputs the pressure of an emergency line as a pilot signal to the air line connecting the relay emergency valve and the end braking section. A limiting and quick release valve is installed, and when the emergency line pressure is below a predetermined value, the limiting and quick release valve operates to control the discharge output from the relay emergency valve at a substantially constant ratio. A brake device for a trailer, characterized in that it is configured to reduce pressure and supply it to a terminal brake section.