JPH0487864A - Cooling device for hydrodynamic retarder - Google Patents

Abstract

PURPOSE:To prevent the temperature difference of an engine cylinder from increasing without deteriorating the cooling performance of working fluid by beginning to supply a cooling water to a heat exchanger simultaneously with the beginning of the operation of a hydrodynamic retarder, and stopping the supply of the cooling water with a time lag taken after the end of the operation of the retarder. CONSTITUTION:When a switch 15 is turned on as a car is braked to actuate a retarder 5, the temperature of working fluid rises with the execution of braking action. At this time, a controller 17 immediately issues a valve opening signal to an electromagnetic valve 18 to supply air to an air cylinder 14 for changing over a cut-off poppet valve 13 into a working state. Since cooling water flowing out of an engine 1 is just then returned to a radiator 7 through a heat exchanger 8 and a thermostat 10, the working fluid whose temperature has rised is cooled, and the braking ability of the retarder 5 can be therefore prevented from lowering. On the other hand, when the switch is turned off, a controller 18 issues a valve closing signal with time lag taken according to the temperature detected by a temperature sensor 16 of the cooling water (working fluid).

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a cooling device for a fluid retarder provided as auxiliary braking means for a vehicle.

<Prior art> Retarders used as auxiliary braking means for vehicles are disclosed in Japanese Utility Model Publication No. 42-3930 and Japanese Utility Model Publication No. 44-16887.
There are some such as those seen in the issue of the publication. Among these retarders, for example, a fluid type retarder has the advantage of being able to obtain a large braking force despite its small size.

In addition, since such fluid-type retarders obtain braking force by absorbing kinetic energy (torque) through the frictional resistance of the working fluid, the temperature of the working fluid increases as the retarder is used. Then, the viscosity of this working fluid decreases and the braking force decreases. Therefore, in the past, a heat exchanger was provided to cool the working fluid by exchanging heat between the working fluid and the cooling water returned from the engine to the radiator.

However, in the past, the cooling water discharged from the engine was always returned to the radiator via the heat exchanger, which increased the passage resistance in the engine cooling system and deteriorated the flow of the cooling water. There was a problem that the difference in air and water temperature increased.

<Problem to be solved by the invention> The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a fluid retarder cooling device that can avoid an increase in the air-water temperature difference in an engine without interfering with the cooling of the retarder.

<Means for Solving the Problems> In order to solve the above problems, the present invention provides a fluid retarder that obtains braking force by converting kinetic energy into heat of a working fluid. A heat exchanger is provided for exchanging heat between the cooling water and the working fluid, and a cooling water inlet and a cooling water outlet of the heat exchanger are short-circuited via a bypass passage. Then, in synchronization with the start of use of the retarder, the flow of cooling water from the engine to the heat exchanger is allowed, and the flow of cooling water in the bypass passage is blocked, while after the end of use of the retarder. The present invention is characterized in that a switching valve is provided that blocks the flow of cooling water to the heat exchanger with a time delay and allows the flow of cooling water through the bypass passage.

<Operation> In the retarder cooling device configured as above,
When the vehicle is being driven normally, that is, when the engine is running and the retarder is not in use, the switching valve is inactive and the cooling water flows to the heat exchanger installed in the retarder. This allows flow through the bypass passage. Therefore, the cooling water flowing out of the engine is returned to the radiator without passing through the heat exchanger, and the passage resistance of the engine cooling system becomes substantially equal to that without a retarder, reducing the air-water temperature difference. Increase is prevented.

Note that the retarder does not generate heat when it is not in use. Therefore, even if cooling water is not supplied to the heat exchanger, the temperature of the working fluid will not rise abnormally.

On the other hand, when the retarder is started to be used, the switching valve is operated to block the flow through the bypass passage and allow flow to the heat exchanger. In this state, the cooling water flowing out of the engine is supplied to the heat exchanger, where it exchanges heat with the working fluid of the retarder, and then returned to the radiator. For this purpose, the working fluid whose temperature has increased due to the use of the retarder is cooled by heat exchange with cooling water by the heat exchanger. Note that when the retarder is used in this way, the amount of heat generated by the engine is small, so the heat dissipation capacity of the radiator will not be insufficient.

When the use of the retarder ends and a predetermined period of time has elapsed, the switching valve operates to return to its original state, blocking the flow of cooling water to the heat exchanger and allowing the flow of water through the bypass passage. That is, after the working fluid whose temperature has increased due to use of the retarder has been sufficiently cooled, the supply of cooling water to the heat exchanger is interrupted to improve the flow of cooling water. Therefore,
Even if the heat generated by the engine increases due to the end of the use of the retarder, the cooling water flowing out of the engine is returned directly to the radiator after the temperature of the working fluid has decreased, so that it can flow smoothly. An increase in the difference is prevented.

<Example> Examples of the present invention will be described in detail below based on the drawings.

FIG. 1 is a schematic configuration diagram of an automobile engine equipped with a fluid retarder cooling device according to the present invention, in which a transmission 3 is connected to the rear part of an engine 1 mounted on a frame (not shown) via a clutch 2. A propeller shaft 6 is connected to the output shaft 4 of the hydraulic retarder 5, which is configured to convert kinetic energy into heat of a working fluid to obtain braking force, and a heat exchanger 8 is connected to the fluid retarder 5. has been established.

The heat exchanger 8 exchanges heat between the working fluid whose temperature has increased due to the braking action of the retarder 5 and the cooling water returned from the engine 1 to the radiator tough. A first cooling water passage 9 leading to a cooling water inlet of the heat exchanger 8 and a second cooling water passage 11 leading from a cooling water outlet of the heat exchanger 8 to a radiator tough via a thermostat 10 are connected via a bypass passage 12. or,
By providing the switching valve 13 at which branch point of the first cooling water passage 9 and the bypass passage 12, the cooling water flowing out from the engine 1 can be returned to the radiator 7 via the heat exchanger 8 or via the heat exchanger 8. It is possible to choose whether to return to radiator tough without letting it happen.

The switching valve 13 is configured as shown in FIGS. 2 and 3, and has a valve 13b rotatably fitted and held in a casing 13a and a forked passage 13c.
The casing 13a is provided with an engine port 13d connected and held to the cooling water outlet of the heat exchanger 8, a heat exchanger port 13e leading to the cooling water inlet of the heat exchanger 8, and a bypass port 13f leading to the bypass passage 12. When air is supplied to the air cylinder 14 connected to the valve 13b, as shown in FIG.
is connected and held to the heat exchange port 13e, but when the air supply to the air cylinder 14 is stopped, the bypass port 13f is connected to the heat exchange port 13e instead of the heat exchange port 13e as shown in FIG.
is connected to the engine boat 13e.

The fluid retarder 5 is controlled to be switched between an operating state and a non-operating state by turning on and off a manual switch 15 provided at the driver's seat.

Further, the output signal of this switch 15 and the output signal of the temperature sensor 16 provided in the second cooling water passage 11 are supplied to the controller 17 as control information. The air tank 19 and the air cylinder 14 are connected to each other via a solenoid valve 18 that opens and closes based on the output signal of the controller 17.
is connected to.

When the switch 15 is turned on, the controller 17 immediately supplies a valve opening signal to the solenoid valve 18, and when the switch 15 is turned off, the controller 17 supplies a valve closing signal to the solenoid valve 18 with a delay of the time corresponding to the output signal of the temperature sensor 16. supply That is, the cooling water (retarder 5
The structure is such that as the temperature of the working fluid increases, the delay time from when the switch 15 is turned off until the valve closing signal is output to the electromagnetic valve 18 becomes longer. 20 is a coolant pump provided in the engine 1, and 21 is a cooling fan. Cooling air generated by the cooling fan 21 promotes heat dissipation from the radiator tough.

In the fluid type retarder cooling system configured as described above, when the vehicle is being driven normally, the switch 15 is turned off to put the retarder 5 in an unused state. Then, in this state, the amount of heat generated by the engine 1 is large, but the valve opening signal is not supplied from the controller 17 to the solenoid valve 18. For this reason, the solenoid valve 14 is in a closed state and no air is supplied to the air cylinder 14, so the switching valve 13 is in an inoperative state as shown in FIG. communication is maintained. Therefore, the cooling water flowing out from the engine 1 does not pass through the heat exchanger 8 and is heated to the thermostat 10.
After that, it is returned to the radiator tough. Therefore, an increase in passage resistance due to the provision of the heat exchanger 8 can be prevented, and an increase in the circulation resistance of cooling water can be prevented, so that an increase in the air-water temperature difference in the engine 1 can be prevented.

On the other hand, when the switch 15 is turned on to start using the retarder 5 as the vehicle is braked, the temperature of the working fluid increases as the retarder 5 performs the braking action. However, when the switch 15 is turned on in this manner, a valve opening signal is immediately supplied from the controller 17 to the solenoid valve 18, and air is supplied to the air cylinder 14.
The switching valve 13 is switched to the operating state as shown in FIG. 2 to switch and connect the engine boat 13d to the heat exchanger boat 13e. Then, since the cooling water flowing out of the engine 1 is returned to the radiator tough via the heat exchanger 8 and the thermostat 10, the working fluid whose temperature has increased due to the use of the retarder 5 is cooled. A decrease in braking ability is prevented. Incidentally, when the retarder 5 is operated in this manner, the heat dissipation capacity of the radiator tough will not be insufficient because the amount of heat generated by the engine 1 is low.

Then, in order to return the retarder 5 to the unused state, switch 1 is pressed.
5 is turned off, the controller 18 stops outputting the valve open signal (after waiting for the temperature of the working fluid to decrease) by a time corresponding to the temperature of the cooling water (working fluid) detected by the temperature sensor 16 (the valve closing signal is turned off). valve signal). Then, the switching valve 13 is returned to the inactive state as shown in FIG. 3, and the supply of cooling water to the heat exchanger 8 is interrupted, thereby preventing an increase in the air-water temperature difference in the engine 1. . In the embodiment, by providing a temperature sensor 16 in the second cooling water passage 11, the delay time for returning the switching valve 13 is variably controlled in accordance with the temperature of the cooling water flowing out from the heat exchanger 8. However, it is also possible to fix the delay time regardless of temperature.

<Effects of the Invention> As is clear from the above description, according to the present invention, the supply of cooling water to the heat exchanger is started at the same time as the operation of the fluid retarder starts, and the supply of cooling water to the heat exchanger is started with a time delay after the end of use. Cooling water is supplied only when cooling of the working fluid is required, such as stopping the supply of cooling water to the heat exchanger to reduce passage resistance in the cooling system in areas where the engine generates a large amount of heat. Therefore, it is possible to prevent an increase in the air-water temperature difference in the engine without causing a decrease in the cooling performance of the working fluid by the heat exchanger.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing an embodiment of an engine equipped with a fluid type retarder cooling device according to the present invention, Fig. 2 is a sectional view showing a specific example of a switching valve in an operating state, and Fig. 3 is a similar diagram. FIG. 3 is a cross-sectional view in an inoperative state. 1... Engine 5... Fluid type retarder 7.
...Radiator 8...Heat exchanger lO...Thermostat 12...Bypass passage 13...Switching valve 14...Air cylinder 15...Switch 16...Temperature-sensor 17...Controller 18...Solenoid valve 19...Air tank patent applicant Hino Motors Co., Ltd.

Claims (1)

[Claims] (1) In a fluid-type retarder that obtains braking force by converting kinetic energy into heat of a working fluid, there is a heat exchanger that exchanges heat between the cooling water returned from the engine to the radiator and the working fluid; a bypass passage that short-circuits the cooling water inlet and the cooling water outlet of the exchanger; and a bypass passage that allows the cooling water to flow to the heat exchanger in synchronization with the start of use of the retarder, and the cooling water in the bypass passage. and a switching valve that blocks the flow of cooling water to the heat exchanger with a time delay after the end of use of the retarder and allows the flow of cooling water through the bypass passage. A cooling device for a fluid retarder, characterized in that it is provided with: