JP3473327B2 - Auxiliary braking device for vehicles - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary braking device for a vehicle, which assists a braking force when decelerating the vehicle to reduce the vehicle speed.

[0002]

2. Description of the Related Art In addition to a vehicle braking device such as a disc brake or a drum brake, a vehicle may be equipped with an auxiliary braking device for assisting a braking force to improve safety. This auxiliary braking device absorbs the kinetic energy of the vehicle to assist the braking, and exhaust brakes, retarders and the like are known. There are various types of retarders such as a fluid type, an electromagnetic type, and a permanent magnet type. Among them, the structure of the fluid type retarder is similar to that of a torque converter of an automatic transmission.

Therefore, Japanese Utility Model Laid-Open No. 5-1058 proposes a technique of using the torque converter as a retarder. That is, the torque converter is caused to perform two operations, that is, an operation as a torque converter used in a normal automatic transmission and an operation as a retarder. In the torque converter described in this publication, the lockup clutch connects the pump impeller to the turbine liner and the stator clutch fixes the stator to the stationary transmission housing when the vehicle is decelerated. Therefore, during deceleration, the pump impeller and the turbine liner rotate in the same direction, but the rotation is blocked by the stator, and the kinetic energy of the vehicle is absorbed.

[0004]

In the technique described in the above publication, a stator fixed to the transmission housing is used to suppress the rotation of the pump impeller and the turbine liner. However, a stator used in a normal torque converter has a smaller size (capacity) than a pump impeller or a turbine liner. Therefore, even if the stator is used for absorbing kinetic energy, the absorption amount of the kinetic energy is reduced. Is small. Therefore, there is a problem that it is difficult to increase the absorption amount of kinetic energy, and it is desired to increase the absorption amount of kinetic energy.

Therefore, an object of the present invention is to provide an auxiliary braking device for a vehicle which can improve the absorption amount of kinetic energy of the vehicle during deceleration when the torque converter is used as the auxiliary braking device.

[0006]

According to a first aspect of the present invention, in an auxiliary braking device for a vehicle, which assists a braking force by using a torque converter during deceleration of the vehicle, an input shaft for inputting a driving force of an engine to the torque converter. And a pump impeller of the torque converter, and a connecting / disconnecting means for connecting / disconnecting the input shaft and the pump impeller to each other, and between the pump impeller and the torque converter housing, the pump impeller is temporarily installed in the torque converter housing. Switching means that can switch between a fixed state in which the pump impeller is rotated with respect to the torque converter housing and a rotating state in which the pump impeller is rotatable with respect to the torque converter housing. When the vehicle is decelerated by switching to each state, the connecting / disconnecting means is set to the disconnecting state and the switching means is set to the fixed state. It is a structure and a control means for switching. With this configuration, when decelerating, the pump impeller is fixed to the torque converter housing by the connecting / disconnecting means, and the pump impeller is separated from the input shaft by the switching means. Occurs, the kinetic energy of the vehicle is absorbed, and the vehicle speed is reduced.

According to a second aspect of the invention, in the auxiliary braking device for a vehicle according to the first aspect, there is provided an auxiliary braking switch for permitting the operation of the auxiliary braking device, and accelerator pedal operation detecting means for detecting depression of the accelerator pedal. It is a composition.
With this configuration, when the input of the auxiliary braking switch is detected and it is detected by the accelerator pedal operation detecting means that the accelerator pedal is not depressed,
Since the control means determines that the vehicle is decelerating, the auxiliary braking device is activated when the driver turns off the auxiliary braking switch when the auxiliary braking device is activated or when the driver depresses the accelerator pedal. Is released.

According to a third aspect of the present invention, in the auxiliary braking device for a vehicle according to the first or second aspect, when the vehicle is decelerated,
The control means controls the fuel supply means so as to drive the engine at a predetermined idle speed,
Fuel is supplied to the engine by the fuel supply means so that the engine is driven at a predetermined idle speed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 indicates a torque converter of an automatic transmission (automatic transmission). In the figure, an engine (not shown) is arranged in front of the torque converter 1 (left side in the figure), and a transmission 2 is arranged in the rear side (right side in the figure) of the torque converter 1. The alternate long and short dash line A indicates the rotation axis of the torque converter 1.

The torque converter 1 transmits the driving force from the crankshaft 3 of the engine to the driveshaft 10 that communicates with the inside of the transmission 2. As is well known, the torque converter 1 is rotated by the driving force from the crankshaft 3. A pump impeller 11 and a turbine liner 12 fixed to the end of the drive shaft 10,
The stator 15 is supported by the torque converter housing 14 via the one-way clutch 13. The pump impeller 11 and the turbine liner 12 are
They have substantially the same size (capacity). The crankshaft 3 is an input shaft for inputting the driving force of the engine to the torque converter 1, and the flywheel 4 and the drive plate 5 are fixed to this end portion.

Between the torque converter 1 and the engine, three units (an inner unit 20, a center unit 21 and an outer unit 22) for connecting and disconnecting the pump impeller 11 to the crankshaft 3 or the torque converter housing 14 are provided. Two hydraulic multi-plate clutches 30 and 40, which will be described later, for connecting and disconnecting each other are respectively disposed.

The retarder 6 is mainly composed of a torque converter 1, an inner unit 20, a center unit 21, an outer unit 22, a hydraulic multi-plate clutch 30 as a connecting / disconnecting means, and a hydraulic multi-plate clutch 40 as a switching means. .

The inner unit 20 is formed in a disk shape with the rotation axis A as an axis, and is fixed to the flywheel 4 via a drive plate 5 with bolts.
The torque converter 1 is provided at the center of the inner unit 20.
A shaft 20a projecting to the side is provided. The center unit 21 is formed in an annular shape with the rotation axis A as an axis, and is rotatably supported by the shaft 21a via a bearing 21a. The hub 11a of the pump impeller 11 is engaged with the end surface of the center unit 21 on the torque converter 1 side, and the center unit 21 and the pump impeller 11 are integrally formed with each other. Outer unit 22
Is formed in an annular shape with the rotation axis A as an axis, and the outer peripheral portion thereof is fixed to the torque converter housing 14 with bolts. Each unit 20, 21, 22
The units 20, 21 and 22 are rotatable relative to each other about the rotation axis A, and the units 20, 21, 22 are sealed by a seal member (not shown).

In FIG. 2, between the inner unit 20 and the center unit 21, a hydraulic multi-plate clutch 30 serving as a connecting / disconnecting means for connecting the two units 20, 21 to each other or for separating the two units 20, 21 from each other. Is provided. The hydraulic multi-plate clutch 30 generates a plurality of clutch plates 31 around the rotation axis A, an annular piston 32 that presses the clutch plates 31, and an urging force that separates the annular piston 32 from the clutch plates 31. And a clutch spring 33 that operates.

A hydraulic chamber 34 for driving the annular piston 32 is formed on the back surface of the annular piston 32, and an oil passage 35 for supplying pressure oil to the hydraulic chamber 34 is connected to the hydraulic chamber 34. . The oil passage 35 includes the center unit 21, the outer unit 22, and the torque converter housing 14.
Of the control solenoid valve 54a (see FIG. 3) in the valve body (not shown) disposed in the lower portion of the transmission 2 respectively.

Outer unit 22 of center unit 21
Oil grooves 21b and 22b having substantially the same shape are formed on the outer peripheral surface in contact with the outer peripheral surface and the outer peripheral surface in contact with the center unit 21 of the outer unit 22, respectively. The grooves 21b and 22b are formed over the entire circumference of the center unit 21 and the outer unit 22.
A hydraulic chamber 36 is formed by the space formed by b and 22b. Sealing members (not shown) are provided on both sides of the grooves 21b and 22b, respectively, and the hydraulic chamber 36 formed by the sealing members is sealed.

Although the oil grooves 21b and 22b are formed on the outer peripheral surfaces of the center unit 21 and the outer unit 22, respectively, the oil grooves are formed on one of the outer peripheral surfaces of the center unit 21 and the outer unit 22. May be.

Center unit 21 and outer unit 22
Between the two units 21, 22 are connected to each other,
Alternatively, a hydraulic multi-plate clutch 40 is provided as a switching unit that separates the two units 21 and 22 from each other. That is, the hydraulic multi-plate clutch 40 switches between a fixed state in which the pump impeller 11 is temporarily fixed to the torque converter housing 14 and a rotating state in which the pump impeller 11 is rotatable with respect to the torque converter housing 14.

The hydraulic multi-plate clutch 40, like the hydraulic multi-plate clutch 30, is composed of a plurality of clutch plates 41, an annular piston 42 and a clutch spring 43. On the back surface of the annular piston 42, the annular piston 42
A hydraulic chamber 44 for driving the hydraulic chamber 4 is formed.
An oil passage 45 for supplying pressure oil to the hydraulic chamber 44 is connected to the hydraulic pressure chamber 4. The oil passages 45 are respectively formed inside the outer unit 22 and the torque converter housing 14, and like the oil passages 35, the control solenoid valve 5 in the valve body.
4b (see FIG. 3). The valve body is
It is used to perform various hydraulic controls and has multiple control solenoid valves built-in. Of these, control solenoid valves 54a, 54b
As a result, pressure oil is supplied to the hydraulic chambers 34 and 44, and the annular pistons 32 and 42 are driven.

In FIG. 3, the control solenoid valves 54a and 54b for driving the annular pistons 32 and 42 are connected to the control means 50, and their operations are controlled by the control means 50. The control means 50 includes a retarder switch 51 as an auxiliary braking switch that allows the retarder 6 to operate or deactivates the retarder 6, and an accelerator pedal operation detection means that detects that the accelerator pedal is not depressed. The accelerator pedal switch 52 is connected to each. Further, the control means 50 is connected to a fuel supply means 53 for controlling fuel supply to the engine.

The retarder switch 51 is arranged on the instrument panel in the cab and is operated by the driver. The retarder switch 51 permits the operation of the retarder 6 when turned on, and deactivates the retarder 6 when turned off. Therefore, the operation of the retarder 6 can be selected according to the driver's intention. The accelerator pedal switch 52 outputs a signal to the control means 50 when the accelerator pedal is not depressed. As the accelerator pedal actuation detecting means, instead of the accelerator pedal switch 52,
It is also possible to use accelerator pedal opening detection means for detecting the opening of the accelerator pedal.

Next, the operation of the retarder 6 having the above structure will be described. At normal times, the control means 50 operates the control solenoid valve 54a in the valve body to supply the pressure oil into the hydraulic chamber 34. When the hydraulic pressure in the hydraulic chamber 34 rises above the urging force of the clutch spring 33, the annular piston 32
Presses the clutch plate 31, and the clutch plate 3
1 are crimped together. The inner unit 20 and the center unit 21 are connected to each other by crimping the clutch plate 31. When the inner unit 20 and the center unit 21 are connected to each other, the driving force from the crankshaft 3 is transmitted to the inner unit 20 and the center unit 21 via the flywheel 4 and the drive plate 4. Therefore, the pump impeller 11 rotates, the working fluid (ATF) flows from the pump impeller 11 to the turbine liner 12, and the drive shaft 10 is driven.

When the driver wants to reduce the vehicle speed,
First, the retarder switch 51 is turned on to stop pressing the accelerator pedal. By stopping the depression of the accelerator pedal, a signal is output from the accelerator pedal switch 52 to the control means 50. The control means 50 operates the retarder 6 on the basis of the above two conditions, judging that the vehicle speed is to be reduced.

The control means 50 operates the control solenoid valve 54a in the valve body to discharge the pressure oil in the hydraulic chamber 34. The pressure oil in the hydraulic chamber 34 is discharged, and the pressing force of the annular piston 32 on the clutch plate 31 is reduced by the urging force of the clutch spring 33. The pressure contact of the clutch plate 31 is also released, and the connection between the inner unit 20 and the center unit 21 is released. That is, the inner unit 20 and the center unit 21 are disconnected from each other, and the center unit 21 is rotatable with respect to the shaft 20a.

On the other hand, at the same time as the pressure oil in the hydraulic chamber 34 is discharged, the control means 50 causes the control solenoid valve 54 in the valve body to move.
When b is operated and pressure oil is supplied into the hydraulic chamber 44, the annular piston 42 presses the clutch plate 41. By pressing the clutch plates 41 against each other, the center unit 21 and the outer unit 22 are connected to each other, and the center unit 21 is temporarily fixed to the torque converter housing 14.

Kinetic energy from the wheels rotationally drives the turbine liner 12 via the drive shaft 10.
Due to the rotation of the turbine liner 12, the working fluid flows from the turbine liner 12 to the pump impeller 11, and the pump impeller 11 is rotated. However, the center unit 2
Since No. 1 is fixed to the torque converter housing 14, absorption torque is generated due to stirring resistance (pumping loss) of the working fluid, and kinetic energy is absorbed. Therefore, the vehicle speed is reduced by absorbing the kinetic energy. Also, the torque converter 1
Since the absorption torque is generated by, the strength of the absorption torque acting on the drive shaft 10 can be adjusted by switching the shift speed in the transmission 2, and a stronger absorption torque (deceleration force) can be obtained as the speed is lower. You can

When the retarder 6 is in operation, the control means 50
Instructs the fuel supply means 53 to supply fuel to the engine. At this time, the fuel supply amount is the amount by which the engine is idling. In the retarder 6 of the present embodiment, the inner unit 20 and the center unit 21 are in a disconnected state when the retarder 6 operates, so that the engine is not activated when the auxiliary braking device is activated, as in a vehicle having a conventional auxiliary braking device. If the fuel supply is temporarily stopped, the engine may be stalled. Therefore, in this embodiment, in order to prevent the engine stall, fuel is supplied to the engine when the retarder 6 is operated.

When the driver turns off the retarder switch 51 during operation of the retarder 6 or when the driver depresses the accelerator pedal, the operation of the retarder 6 is released. That is, the hydraulic multi-plate clutch 40 is disengaged to bring the center unit 21 into a rotatable state, and the hydraulic multi-plate clutch 30 is put into the contact state to allow the inner unit 20 to rotate.
And the center unit 21 are connected to each other.
When the operation of the retarder 6 is released in this way, the driving force of the crankshaft 3 is transmitted to the torque converter 1 by switching the connection and disconnection of the hydraulic multi-plate clutches 30 and 40. Further, when the retarder 6 is not desired to be operated, the operation of the retarder 6 can be disabled by turning off the retarder switch 51 in advance, and the operation of the retarder 6 can be selected by the driver's intention.

Therefore, the vehicle speed can be reduced by using the turbine liner 12 and the pump impeller 11 as a fluid retarder. In other words, by fixing the pump impeller 11 to the torque converter housing 14 during deceleration, an absorption torque is generated between the turbine liner 12 and the pump impeller 11 to absorb the kinetic energy of the vehicle and reduce the vehicle speed. Be slowed down. At this time, since the kinetic energy is absorbed by the pump impeller 11 having substantially the same size (capacity) as the turbine liner 12, the kinetic energy absorption amount can be increased more than that of the retarder using the conventional torque converter 1. A large deceleration force can be obtained.

FIG. 4 shows the results of measuring the respective amounts of absorbed torque by the retarder 6 of the present invention, the conventional electromagnetic retarder and the exhaust brake. The transmission 2 described above has a configuration capable of shifting forward five speeds. Figure 4
In the figure, the horizontal axis shows the number of revolutions (rpm) of the propeller shaft (A / T output), and the vertical axis shows the amount of absorption torque (kgfm) with respect to the propeller shaft (A / T output). Further, in the figure, the solid line E is the characteristic line of the absorption torque amount by the exhaust brake when the transmission is in the 5th gear, and the solid line R is the absorption torque amount by the electromagnetic retarder of the type attached to the front part of the propeller shaft. In the characteristic lines, solid lines S1 to S5 show characteristic lines of the amount of torque absorbed by the retarder 6, respectively. Characteristic lines S1 to S
Reference numeral 5 shows the characteristic of the absorption torque amount according to the shift stage of the transmission 3, the characteristic line S1 shows the case where the transmission gear stage is one stage, and the characteristic line S2 shows the case where the transmission gear stage is two stages. , The characteristic line S3 is the characteristic line S when there are three transmission gears.
Reference numeral 4 shows the case where the transmission gear stage is four, and characteristic line S5 shows the case where the transmission gear stage is five.

Comparing the amounts of torque absorbed by the retarder 6 and the exhaust brake when the transmission has five gears, the amount of torque absorbed by the retarder 6 is larger than that of the exhaust brake in the entire rotation range. This has the same relationship in all gears of the transmission. Therefore, since the retarder 6 has a larger absorption torque than the exhaust brake, it is possible to assist the braking force more effectively than the exhaust brake when decelerating the vehicle.

Comparing the absorption torque amounts of the retarder 6 and the electromagnetic retarder, the absorption torque of the retarder 6 is larger than that of the electromagnetic retarder in most regions including the normal rotation range. Therefore, when the vehicle is decelerated, The braking force can be assisted more effectively than the expression type retarder. Further, since the retarder 6 uses the torque converter 1, the amount of absorption torque can be increased or decreased according to the gear stage of the transmission 2, and the gear stage can be selected in a timely manner.
The amount of absorption torque can also be adjusted.

For example, when the retarder 6 is operated and the transmission 2 has five gears, the absorption torque amount according to the characteristic line S5 acts on the propeller shaft. When it is necessary to further assist the braking force than by the braking force assistance, the amount of absorption torque acting on the propeller shaft is changed from the characteristic line S5 to the characteristic line S4 by performing downshifting (5th to 4th steps). Therefore, the amount of absorption torque can be increased. That is, the braking force assistance can be increased, and the deceleration force can be improved.

Next, a second embodiment is shown in FIG. 5, and this embodiment will be described. In the figure, the same members as those shown in FIG. 1 are designated by the same reference numerals as those used in FIG. 1, and the description thereof will be omitted. Differences will be described. In the second embodiment, the band brake 7 is used as the switching means.
The difference is that 0 is adopted.

As shown in FIG. 5, the retarder 7 includes a torque converter 1, a hydraulic multi-plate clutch unit 60 as a connecting / disconnecting means for connecting / disconnecting the crankshaft 3 and the pump impeller 11, and the pump impeller 11 to the torque converter. A fixed state in which it is temporarily fixed to the housing 14,
Pump impeller 11 to torque converter housing 14
And a band brake unit 70 as a switching unit capable of switching to a rotation state that allows rotation.

A hydraulic multi-plate clutch unit 60 is arranged between the torque converter 1 and the engine.
The hydraulic multi-plate clutch unit 60 includes the drive plate 5
An inner unit 61 fixed to the flywheel 4 by a bolt via a center unit 62 fixed to the pump impeller 11 by being engaged with a hub 11a projecting from the pump impeller 11; 62
Are connected to each other, or both units 61 and 62 are separated from each other by a hydraulic multi-plate clutch 63.

The inner unit 61 is formed in a disk shape with the axis of rotation A as an axis, and the center unit 62 is provided.
At the central portion opposite to, there is provided a relief for preventing interference with a tip portion 10a described later. Center unit 62
Is formed in an annular shape with the rotation axis A as an axis, and the tip portion 10a of the drive shaft 10 is interposed via the bearing 62a.
It is rotatably supported by. Each unit 61, 62
Can rotate relative to each other about the rotation axis A, and the units 61 and 62 are sealed by a seal member (not shown).

As shown in FIG. 6, the hydraulic multi-plate clutch 63
Is composed of a plurality of clutch plates 64, an annular piston 65 and a clutch spring 66, like the hydraulic multi-plate clutches 30 and 40 described above. Annular piston 6
A hydraulic chamber 67 for driving the annular piston 65
Are formed. On the other hand, inside the drive shaft 10, a hydraulic passage 10b for supplying pressure oil from the valve body.
Is provided. The hydraulic chamber 67 and the hydraulic path 10b are
The oil passages 68 communicate with each other. The hydraulic pressure supply control to the hydraulic chamber 67 is performed by a control solenoid valve in the valve body.

A band brake unit 70 is arranged on the outer peripheral portion of the pump impeller 11. The band brake unit 70 includes a brake band 71 that tightens or loosens the outer peripheral surface of the pump impeller 11, and a hydraulic servo 72 that performs a tightening / loosening operation of the brake band 71.

As shown in FIG. 7, the brake band 71
Is formed of an annular belt that covers the outer circumference of the pump impeller 11, and is partially cut away. A friction material is attached to the inner surface of the brake band 71 that contacts the pump impeller 11. One end 71 a of the brake band 71 is fixed to the torque converter housing 14 via a fixing member 73.

A hydraulic servo 72 is fixed to the torque converter housing 14. The operating piston 74 of the hydraulic servo 72 is connected to the other end 71b of the brake band 71.
The other end 71b is moved forward and backward in the direction of arrow B in the figure. A hydraulic chamber 75 that drives the operating piston 74 is formed behind the operating piston 74, and pressure oil is supplied to the hydraulic chamber 75 by a hydraulic control valve (not shown). This hydraulic control valve is connected to the control means 50, and its operation is controlled by the control means 50.

In the retarder 7 of the second embodiment, a band brake unit 70 is applied instead of the hydraulic multi-plate clutch 40 of the first embodiment, and its operation is the retarder 6 of the first embodiment. The description is omitted here.

The above-mentioned retarders 6 and 7 are ATF (Automatic Transmission Fluid) as a working fluid.
When the retarder is operated, the ATF may be agitated and the ATF temperature may rise. Therefore, AT
By increasing the size of the F cooler, an increase in ATF temperature can be suppressed. Also, when the retarder is activated,
When the ATF temperature rises above a predetermined temperature, the control means 50 has a fail-safe function of stopping the operation of the retarder.
You can improve safety by preparing for.

[0044]

As described above, according to the first aspect of the present invention.
According to the invention, when the deceleration is performed, the pump impeller is fixed to the torque converter housing by the connecting / disconnecting means, and the pump impeller is separated from the input shaft by the switching means, so that the turbine impeller is separated from the turbine liner. Absorption torque is generated, the kinetic energy of the vehicle is absorbed, and the vehicle speed is reduced. At this time, the kinetic energy is absorbed by the pump impeller having substantially the same size (capacity) as the turbine liner, so that the kinetic energy absorption amount of the vehicle can be efficiently absorbed, and the kinetic energy absorption amount is obtained by using the conventional torque converter. It can be increased more than the retarder, and a large deceleration force can be obtained.

According to the second aspect of the present invention, when the input of the auxiliary braking switch is detected and the accelerator pedal actuation detecting means detects that the accelerator pedal is not depressed, the control means decelerates the vehicle. Since it is determined that the auxiliary braking device is operated, the auxiliary braking device is deactivated if the driver turns off the auxiliary braking switch or the driver depresses the accelerator pedal when the auxiliary braking device is operating. . Also, when it is not desired to operate the auxiliary braking device, the auxiliary braking switch can be turned off in advance to disable the operation of the auxiliary braking device.
The operation of the auxiliary braking device can be selected according to the intention of the driver.

According to the third aspect of the present invention, when the vehicle is decelerated, the fuel is supplied to the engine by the fuel supply means so that the engine is driven at a predetermined idle speed. Engine stall can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a torque converter according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view on one side of the torque converter shown in FIG.

FIG. 3 is a block diagram of control means.

FIG. 4 is a characteristic diagram showing the results of measuring the absorption torque amounts of the retarder of the present invention, a conventional electromagnetic retarder, and an exhaust brake.

FIG. 5 is a schematic vertical sectional view of a torque converter according to a second embodiment of the present invention.

6 is an enlarged cross-sectional view on one side of the torque converter shown in FIG.

7 is a sectional view taken along line VII-VII of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 torque converter 3 crankshaft (input shaft) 6 retarder (auxiliary braking device) 10 drive shaft 11 pump impeller 12 turbine liner 14 torque converter housing 30 hydraulic multi-plate clutch (disconnecting / connecting means) 40 hydraulic multi-plate clutch (switching means) 50 Control means 51 Retarder switch (auxiliary braking switch) 52 Accelerator switch (accelerator pedal operation detection means) 53 Fuel supply means

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F16H 47/00 B60T 1/087 F16H 41/24

Claims (3)

(57) [Claims] 1. An auxiliary braking device for a vehicle, which assists a braking force by using a torque converter during deceleration of the vehicle, between an input shaft for inputting a driving force of an engine to the torque converter and a pump impeller of the torque converter. A connection / disconnection means for connecting / disconnecting the input shaft and the pump impeller to each other; and a fixing member provided between the pump impeller and the torque converter housing for temporarily fixing the pump impeller to the torque converter housing. A switching means capable of switching between a state and a rotation state in which the pump impeller is rotatable with respect to the torque converter housing; and, in a running state of the vehicle, the switching means is rotated with the connecting / disconnecting means in a contact state. When the vehicle is decelerated by switching to the respective states, the connecting / disconnecting means is in the disconnected state, Auxiliary braking device for a vehicle, characterized in that it comprises a control means for switching each switch means in a fixed state, the. 2. The auxiliary braking device for a vehicle according to claim 1, further comprising: an auxiliary braking switch that permits the operation of the auxiliary braking device, and accelerator pedal operation detecting means for detecting depression of an accelerator pedal. When the input of the braking switch is detected and the accelerator pedal operation detecting means detects that the accelerator pedal is not depressed, it is determined that the control means is in a state of decelerating the vehicle. An auxiliary braking device for a vehicle. 3. An auxiliary braking device for a vehicle according to claim 1 or 2, wherein the control means controls the fuel supply means so as to drive the engine at a predetermined idle speed when the vehicle is in a decelerating state. An auxiliary braking device for a vehicle characterized by: