JP2000159076A - Parking brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To safely regulate the car height while operating a parking brake by controlling the operation of a parking brake forced releasing means so as to release the braking force of a wheel having a smaller axial load on the basis of the axial load information from an axial load detecting means. SOLUTION: A pressure sensor 20 has the function as axial load detecting means for detecting or estimating the axial loads of front wheels and rear wheels. When it is judged that a car height regulation is performed on the basis of the information from a car height regulating switch 16 under the state where braking force is imparted to all the wheels by the operation of a parking brake, a control means 15 judges the magnitude relation of axial load between front wheels and rear wheels by use of the detection information from the pressure sensor 20, and releases the braking force of the wheels having the smaller axial load. The braking force of either of the front wheels and the rear wheels is released, whereby the height regulation can be quickly performed while permitting the change of wheelbase in the height regulation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parking brake device applied to a vehicle whose vehicle height can be adjusted, and more particularly to a parking brake device suitable for use in a vehicle such as a tractor connected to a trailer.

[0002]

2. Description of the Related Art Conventionally, an air suspension having an air spring has been widely put into practical use as one of suspension systems for vehicles such as trucks and buses. A suspension using such an air spring has an advantage that a comfortable ride can be realized, and also has an advantage that a vehicle height can be adjusted by adjusting an air pressure supplied to the air spring. It is particularly suitable for vehicles such as trucks and buses having large load fluctuations.

[0003]

By the way, it is conceivable that the above-described vehicle height adjusting function is also used for connecting and disconnecting a tractor and a trailer. In other words, in general, when connecting or disconnecting the tractor and trailer, the height of the trailer side is adjusted, and then the connection or disconnection operation is performed. By performing the adjustment, the connection or disconnection operation can be performed.

Here, a general connection operation between a tractor and a trailer will be described with reference to FIG. 2. Normally, a landing jack 102 provided on a trailer 101 is used.
The front end of the trailer 101 is held at a predetermined height by using the
4 is engaged with the pin 103. Then, the landing jack 102 is stored in the trailer 101, and the connection between the trailer 101 and the tractor 100 ends.
The above-mentioned predetermined height is a height at which the pin 103 of the connecting portion provided on the trailer 101 is slightly higher than the coupler 104.

On the other hand, if the tractor 100 is provided with an air suspension having an air spring 105, by adjusting the vehicle height on the tractor 100, the connection and disconnection of the trailer 101 can be easily performed. Will be able to do it. Specifically, the height of the front end of the trailer 101 is set sufficiently higher than the height of the coupler 104 in advance, and the tractor 100 is retracted so that the coupler 104 is positioned below the pin 103 before the tractor 100 is moved. Raise the height of the trailer 10
One is connected. Thereafter, the landing jack 102 is stored in the trailer 101 and the height of the tractor 100 is returned to the original height, thereby completing the operation. By performing such an operation, fine adjustment of the height of the trailer 101 using the landing jack 102 becomes unnecessary, and the operation becomes easy.

Incidentally, it is preferable that such a vehicle height adjustment is performed after the parking brake device is operated in consideration of safety. On the other hand, paying attention to the parking brake device, it is desirable to apply a braking force to all the wheels when the parking brake device is operated so that the vehicle can be reliably maintained in a stopped state. Therefore, in order to respond to such a request,
For example, the parking brake device may be configured as shown in FIG.

Hereinafter, the parking brake device shown in FIG. 3 will be briefly described. In the drawing, reference numeral 1 denotes a pipe of the parking brake device, 2 denotes a relay valve (R / V), and 3 denotes a hand control valve (HCV). ), 3a is a parking brake lever, 4 is a rear chamber (R chamber), and 5 is a front chamber (F chamber). The rear chamber 4 and the front chamber 5 are means capable of acting on the rear wheel 107 and the front wheel 106 shown in FIG.
When a and 5a extend, a braking force is applied, and the piston 4
The braking force is released when a and 5a are retracted.

Here, when the working fluid (pressurized air) is supplied to each of the chambers 4 and 5, the pistons 4a and 5a are retracted against the urging force of the springs provided in the chambers 4 and 5. Conversely, when the supply of the working fluid is cut off and the pressure in each of the chambers 4 and 5 decreases, the pistons 4a and 5a are extended by the biasing force of the spring, and the braking force is applied. It is configured to:

On the other hand, a working fluid supply source (air tank) is provided upstream of the passage 1a of the pipe 1, and a working fluid (high-pressure air or pressurized air) pressurized from the air tank to a predetermined pressure is provided in the passage. 1a and the passage 1 through the check valve 1h
b, 1d. The hand control valve 3 is connected to a parking brake lever 3a, and the open / close state of the hand control valve 3 is switched according to the operation state of the parking brake lever 3a.

When the hand control valve 3 is opened by operating the parking brake lever 3a and the passage 1b and the passage 1c are communicated with each other, pressurized air is supplied to the relay valve 2 via the passage 1c. Has become.
Further, when air is supplied from the passage 1c to the relay valve 2, the air acts as a pilot pressure, so that the passage 1d, the passage 1e, and the passage 1f are all in communication. Thus, pressurized air (operating pressure) is supplied from the passage 1d to the rear and front chambers 4 and 5 via the passages 1e and 1f, respectively, and the braking force is released.

On the other hand, when the hand control valve 3 is closed, the passage 1b and the passage 1c are shut off, and the air in the passage 1c is opened to the atmosphere via the hand control valve 3. As a result, the relay valve 2 is closed, the passages 1d and 1e are shut off, and the passages 1d and 1f are also shut off. Further, at this time, the pressurized air remaining in the passages 1e and 1f is opened to the atmosphere via the relay valve 2.

Therefore, the hand control valve 3
Is closed, the supply of pressurized air to each of the chambers 4 and 5 is cut off, whereby the pistons 4a and 5a are extended and a braking force is applied to each wheel. In the figure, reference numeral 6 denotes a control valve (TCV) on the trailer side, and a passage 1g according to the operation of the parking brake lever 3a.
The supply state of the pressurized air to the control valve 6 from above is switched. Accordingly, the braking force is applied and released on the trailer side in the same manner as on the tractor side wheels.

However, in the above-described parking brake device, the front wheel 106 and the rear wheel 107 are always in operation.
Since the braking force of the parking brake acts on both of them, there is a problem that the vehicle height cannot be adjusted while the parking brake is operated. That is, when the suspension operates (when the vehicle height is adjusted), the center position of the axle shaft (axle) moves and the wheelbase of the vehicle changes. on the other hand,
If both the front wheel 106 and the rear wheel 107 are locked, the change in the wheelbase cannot be absorbed, and as a result, the vehicle height cannot be adjusted.

The trajectory of the center position of the axle as described above is determined geometrically by the arrangement (geometry) of the link mechanism of the suspension. For example, a trailing leaf type as shown in FIG. In the suspension, the entire rear suspension tends to swing around the trailing leaf mounting portion A, so that the change in the wheel base is particularly large.

If the parking brake device is not operated at the time of adjusting the vehicle height, the change in the wheel base can be absorbed by the rotation of the wheels. Height adjustment is not preferable in consideration of safety. SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and an object of the present invention is to provide a parking brake device capable of safely adjusting a vehicle height while operating a parking brake.

[0016]

In the parking brake device of the present invention, when the parking brake operating means is operated, the parking braking means is operated in conjunction with the operating state, and a braking force is applied to all the wheels. On the other hand, when the vehicle height is adjusted in a state in which the braking force is applied to all the wheels by the parking braking means, the shaft loads of the front wheels and the rear wheels are detected or estimated by the shaft load detecting means. Based on the shaft load information from the shaft load detecting unit, the operation of the parking brake compulsory canceling unit is controlled so as to release the braking force of the wheel with the smaller shaft load. Accordingly, the vehicle height adjustment is performed in a state where the braking force of the front wheel or the rear wheel is selectively released regardless of the operation state of the parking brake operation means. That is, the braking force of the wheel at rest is the product of the shaft load acting on the wheel and the coefficient of static friction acting on the wheel, and therefore, if the static friction coefficient on each wheel is the same, the shaft load is large. The other wheel has a larger braking force. Then, by releasing the braking force with the smaller shaft load, the vehicle height can be adjusted without impairing the safety of the vehicle.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a parking brake device as one embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic circuit diagram showing the configuration of the main part. The parking brake device of the present invention is provided in a vehicle whose height can be adjusted by an air suspension or the like. In the present embodiment, a case in which the parking brake device is applied to a tractor that can travel by connecting a trailer will be described.

In the figure, 1 is a piping of a parking brake device, 2 is a rear side relay valve (RR / V), and 3 is a hand control valve (H.C.
V. ), 4 is a rear chamber as parking braking means, 5 is a front chamber as parking braking means, and 13 is a front side relay valve (FR / V). Reference numeral 10 denotes a parking brake forcible release means, which is provided to selectively release either the front wheel side or the rear wheel side braking force (parking brake force) even when the parking brake is activated. It is.

The parking brake device according to the present embodiment is different from the parking brake device described with reference to FIG.
The above-described parking brake forced release means 10 is added, and the relay valves are independently provided on the front side and the rear side, respectively. The rest is configured in substantially the same manner as that shown in FIG. I have. First, a basic configuration of the parking brake device will be described. As shown in FIG. 1, a working fluid supply source (air tank) (not shown) is provided upstream of the passage 1a of the pipe 1. Further, a check valve 1h is interposed on the passage 1a, and the passage 1a is provided with two passages 1 downstream of the check valve 1h.
b and 1d. Accordingly, the working fluid (high-pressure air or pressurized air) in the air tank is discharged from the check valve 1h.
Through the passages 1b and 1d.

Further, the passage 1b is branched into its further passage 1b ₁ on the downstream side and the bypass passage 1b _2, these passages 1b ₁ is a hand control valve as a parking brake operating means (H. C. V.) 3 via passage 1
c. A double check valve 12f is connected downstream of the passage 1c. Further, from the passage 1c and passage 1c ₁ is branched, the passage 1c
_A double check valve 12r is also interposed on the downstream side of ₁ .

Therefore, the hand control valve 3
Pressurized air flowing through the passage 1c and the passage 1c₁
Through the double check valves 12f and 12r
It flows in. On the other hand, the bypass 1b_Two
Is connected to the two bypass paths 1b via the solenoid valve 14._Three, 1b
_FourIt is connected to the. Here, this solenoid valve 14 is
Path 1b_TwoAnd bypass 1b_ThreeThe first to communicate with
Mode and bypass 1b_TwoAnd bypass 1b _FourAnd ream
The second mode to be passed and the bypass 1b_TwoAny of
Bypass 1b _Three, 1b_FourEach bypass without communicating with
Road 1b_Two, 1b_Three, 1b_FourAnd a third mode to shut off
It is configured as a three-mode solenoid valve.

[0022] Then, the a passage 1c ₁ described above with the bypass passage 1b ₃ is connected to a double check valve 12r, and the passage 1c described above with the bypass passage 1b ₄ is connected to a double check valve 12f. Further, passages 1c ₂ and 1c ₃ are connected to the double check valves 12f and 12r, respectively, as shown in the figure.

Here, the double check valve 12r will be briefly described.
Serves to close the passage of the passage 1b ₃ and the passage 1c ₁ Tonouchi low-pressure side opens the passage of the high pressure side and a passage 1c ₃ passages and the downstream side of the high-pressure side valve as to connect communication is there. The double check valve 12f has the same configuration.

Therefore, these double check valves
The passage 1c is formed by the valves 12f and 12r. _ThreeIs the bypass 1
b_ThreeAnd passage 1c₁One of the higher pressures
Is selectively connected to the passage 1c._TwoIs
Ipass Road 1b_FourAnd the passage 1c with the higher pressure
It is designed to be selectively connected to one of the passages
It is.

[0025] The rear-side relay valve 2 is provided on the downstream side of the passage 1c _3, also the front relay valve 13 is provided on the downstream side of the passage 1c _2. on the other hand,
As shown in FIG. 1, the passage 1d is branched on the downstream side into two passages 1d ₁ and 1d _2.
d ₁ is connected to the rear side relay valve 2 and the other passage 1
d ₂ is connected to the relay valve 13 on the front side.

[0026] Here, the relay valve 2, the pressurized air (pilot pressure) is supplied from the passage 1c _3, passage 1d
A ₁ and a passage 1e and the communicating state, and when the supply of the pilot pressure from the passage 1c ₃ is interrupted, and the passage 1e while blocking the passage 1d ₁ is configured to atmosphere. Further, the front side relay valve 13 is configured similarly to the above-mentioned rear side relay valve 2. That is, when the pressurized air from the passage 1c ₂ (pilot pressure) is supplied, and a passage 1d ₂ and the passage 1f and the communicating state, and when the supply of the pilot pressure from the passage 1c ₂ is interrupted, the passage 1d ₂ And the passage 1f is opened to the atmosphere.

As shown in the figure, the passage 1d ₁ is connected to the rear chamber 4 via a rear relay valve 2 and a passage 1e, and the passage 1d ₂ is connected via a front relay valve 13 and a passage 1f. It is connected to the chamber 5. Therefore, when the supply of the pilot pressure from both passages 1c ₃ and 1c ₂ is cut off and the passages 1e and 1f are opened to the atmosphere, for example, the pistons 4a and 5a operate by the urging force of springs (not shown) in the chambers 4 and 5. Then, the parking brake is activated.

On the other hand, when pilot pressure is supplied from the two passages 1c ₃ and 1c ₂ to operate the respective relay valves 2 and 13, the passages 1d ₁ and 1e are connected and the passages 1d ₂ and 1f are connected. Then, pressurized air is supplied to each of the chambers 4 and 5. As a result, the springs in the respective chambers 4 and 5 are compressed, and the operation of the parking brake is released.

Next, the hand control valve (H.
C. V. ) 3 will be described. The hand control valve 3, air and functions as a off valve for the cut-off state or communicating state path 1b ₁ and the passage 1c, and 1c _1, passage 1c, the air remaining in 1c ₁ It has a function as a relief valve that opens. Also,
Parking brake lever 3 on hand control valve 3
a is connected, and the on / off of the hand control valve 3 is switched according to the operation of the lever 3a.

[0030] For example, when the driver operates the parking brake lever 3a to actuate the parking brake, hand control valve 3 is switched off (closed) in conjunction with the movement of the lever 3a, a passage 1b ₁ and the passage 1c There together is cut off, the passages 1c, have residual pressurized air to 1c ₁ is adapted to be opened to the atmosphere through the hand control valve 3.

[0031] Therefore, in such a case (i.e., the passage 1b ₁ by the operation of the parking brake lever 3a and the passage 1
c, in a case where 1c ₁ and is cut off), if the passage 1b _3, 1b ₄ by the electromagnetic valve 14 if opened to the atmosphere, no longer acts also pilot pressure either for the relay valve 2, 13, The working pressure is not supplied to the passages 1e and 1f.

On the other hand, when the order to release the parking brake driver operates the parking brake lever 3a is a hand control valve 3 in conjunction with the movement of the lever 3a is switched on (opened), a passage 1b ₁ Passage 1
c, 1c ₁ and is communicating state. Thus, a double check valve 12r, and the pilot pressure acts on the relay valve 2, 13 through the 12f and passage 1c _3, 1c _2, passage 1d _1, 1d ₂ and the passage 1e, and is communicated with each other respectively 1f, An operating pressure acts on each of the chambers 4 and 5,
The parking brake is released.

It should be noted, in which the bypass passage 1b ₃ and the bypass passage 1b ₄ by the electromagnetic valve 14 of this case also the parking brake force releasing means 10 has been described which is open to the atmosphere. Next, the parking brake forced release means 10 will be described. The parking brake forced release means 10 applies the braking force (parking brake force) to one of the front wheels or the rear wheels regardless of the operation state of the parking brake lever 3a. ) Can be selectively released, mainly
Bypass channel (bypass channel) 1b ₂ , 1b ₃ , 1b
₄ , the solenoid valve 14, and the double check valve (D.C.
V. ) 12f and 12r.

The solenoid valve (M / V) 14 is a three-mode solenoid valve as described above, and is a bypass passage 1b ₂ in normal times when an operation control signal is not input.
It is configured as a normally closed solenoid valve that shuts off the air. The solenoid valve 14 is connected to the control means (ECU) 1
The operation is controlled based on the operation control signal from the control unit 5. Here, the ECU 15 includes:
As shown in FIG. 1, a vehicle height adjustment switch 16, a parking brake switch 17, and a pressure sensor 20 are connected,
The ECU 15 sets an operation control signal to the solenoid valve 14 based on information from the switches 16 and 17 and the sensor 20.

Here, the vehicle height adjustment switch 16 is an on / off switch provided in the vehicle compartment, and is a switch operated by a driver when performing vehicle height adjustment. The parking brake switch 17 is a switch (sensor) that issues an on / off signal in accordance with the operation state of the parking brake lever 3a. Here, when the parking brake lever 3a is operated to operate the parking brake, an on signal is output. Is configured to emit.

The pressure sensor 20 is a sensor for detecting the air pressure of the air suspension on the rear wheel side (not shown) of the vehicle. By detecting such air pressure on the rear wheel side, the pressure sensor 20 detects the air pressure on the rear wheel of the tractor. The shaft load can be detected. In general, the tractor greatly differs in axle load on the rear wheel side between the connected state and the single vehicle state. That is, the tractor has a heavy load such as an engine and a cab mounted on the front side, and therefore, in a single vehicle state, the front wheel has a large axial load. On the other hand, since the connecting portion (coupler) with the trailer is provided relatively near the rear wheel of the tractor (see FIG. 2), when the trailer is connected, the weight of the trailer is closer to the rear wheels than to the front wheels. Is added to increase the axial load of the rear wheel. Therefore, by detecting the axial load of the rear wheel from the air pressure on the rear wheel side, it is possible to determine the magnitude relationship between the axial loads of the front and rear wheels of the tractor. As described above, the pressure sensor 20 has a function as shaft load detecting means for detecting or estimating the shaft load of the front wheel and the rear wheel.

In this device, it is determined that the vehicle height adjustment is performed based on the information from the vehicle height adjustment switch 16 in a state where the braking force is applied to all the wheels by the operation of the parking brake. In this case, the ECU 15
Using the detection information from the pressure sensor 20, the magnitude relationship between the shaft loads of the front wheel and the rear wheel is determined, and the braking force (braking force by the parking brake) of the wheel with the smaller shaft load is released. It is.

By releasing the braking force of either the front wheel or the rear wheel in this manner, the change of the wheel base at the time of adjusting the vehicle height is allowed, and the vehicle height can be quickly adjusted. -ing Also, at the time of such vehicle height adjustment, the safety of the vehicle at the time of vehicle height adjustment can be greatly improved by releasing the braking force of the wheel on the side with the smaller shaft load. That is, generally, the braking force (parking brake force) F of the wheel at rest can be expressed by the following equation.

F = μW Here, W is the axial load acting on the wheel, and μ is the coefficient of static friction between the wheel and the road surface. Therefore, if the static friction coefficient μ of each wheel is the same, the braking force F of the wheel with the larger shaft load W is larger.

Therefore, at the time of such vehicle height adjustment, the braking force is maintained for the wheel with the larger shaft load while the braking force on the wheel with the smaller shaft load is released. It is. If the braking force of the parking brake provided between the wheel side and the vehicle body side is B, the condition for holding the vehicle in the stopped state is as follows.

B ≧ F (= μW) By the way, the release of the braking force of the front wheel or the rear wheel is as follows.
The operation is performed by controlling the operation of the parking brake forcible release means 10. In particular, in the present embodiment, the operation of the solenoid valve 14 is controlled based on the control signal of the ECU 15 so that the front wheel or the rear wheel is controlled. The braking force of the wheel can be released.

For example, when the braking force on the front wheels is released, the solenoid valve 14 is switched from the third mode (closed state) to the second mode, and the bypass path 1b ₂ and the bypass path 1b ₄ are switched. Is to be communicated. in this case,
The pilot pressure becomes to act on the double check valve 12f through the bypass passage 1b _2, 1b _4, during the parking brake operation, a passage 1b ₁ and the passage 1c is blocked by the hand control valve 3 , the double check valve 12f, and only the pressurized air from the bypass passage 1b ₄ flows.

Therefore, the double check valve 12f
By the action, the bypass passage 1b ₄ and the passage 1c ₂ are the communicating state, is supplied pilot pressure to the relay valve 13 is the parking brake force of the front wheel side is adapted to be released. Further, when releasing the parking brake force of the rear wheel side, switches the operation mode of the solenoid valve 14 to the first mode, a bypass passage 1b ₂ and the bypass passage 1b ₃ adapted to the communicating state I have. In this case, similarly to the above, the pilot pressure is supplied to the relay valve 2, and the parking brake force on the rear wheel side is released.

Since the parking brake device as one embodiment of the present invention is configured as described above, the parking brake forced release means 10 operates as follows. First,
The ECU 15 determines based on information from the parking brake switch 17 whether or not the parking brake is operating. And the parking brake is activated,
That is, when it is determined that the braking force is acting on all the wheels and that the ECU 15 has started the vehicle height adjustment based on the information from the vehicle height adjustment switch 16, E
The CU 15 estimates or determines which of the axial loads of the front wheel and the rear wheel is larger based on information from the pressure sensor 20.

In such estimation or determination, first, based on the detection information from the pressure sensor 20, the shaft load of the rear wheel is set to E.
The CU 15 calculates the front wheel load based on the calculated shaft load, and compares the front shaft load with the rear shaft load. This is because, in the case of a tractor, the trailer load acts only at one point on the tractor connection (coupler), so the magnitude relationship between the front axle and the rear axle can be defined based on vehicle specifications. The shaft load of the front shaft can be estimated from the shaft load of the rear shaft.

When the ECU 15 makes such an estimation or determination, the ECU 15 controls the operation of the parking brake forcible release means 10 so as to release the braking force of the wheel having the smaller shaft load. . For example, when it is determined that the rear wheel axle load is small, the parking brake force on the rear wheel is released by switching the solenoid valve 14 of the parking brake forcible release means 10 from the third mode to the first mode. Is done.

When the parking brake is operating,
Is the passage 1c by the hand control valve 3.₁Is the atmosphere
Pressure, the bypass path 1b_TwoAnd bypass 1
b_ThreeWhen the communication is established with the double check valve 12r
Of the bypass 1b _ThreeAnd passage 1c_ThreeAnd communication
State, pilot only on rear side relay valve 2
Pressure acts. Thereby, the passage 1d₁And passage 1e
The pressurized air is supplied only to the rear chamber 4
When the parking brake is activated, the braking force is released only on the rear wheel side.
It is done.

When the parking brake forcible release means 10 releases the braking force of either the front wheel or the rear wheel at the time of adjusting the vehicle height, the change in the wheel base is absorbed, and thus the parking brake is operated. The vehicle height adjustment is allowed. As described above, the parking brake device of the present invention has an advantage that the vehicle height can be adjusted by operating the parking brake forcible release means 10 even when the parking brake is operated. . In particular, when this device is applied to a tractor, the height of the tractor can be adjusted while the parking brake is activated, so that the connection and disconnection of the tractor and trailer can be performed while ensuring safety. It can be easier.

Further, since the braking force of the wheel having the smaller shaft load is released based on the information from the pressure sensor 20 as the shaft load detecting means, the safety of the vehicle is further improved. There are advantages that can be. In other words, for the front wheel and the rear wheel, whichever has the larger shaft load (that is, the side where the braking force is larger), the parking brake is reliably operated even when the vehicle height is adjusted. This further enhances the safety of the vehicle.

When the parking brake device is operated and the vehicle height is not adjusted, the braking force acts on all the wheels in the same manner as a general parking brake device. There is no loss of safety. by the way,
In the above, the case where the parking brake force with the smaller axle load is simply released has been described.However, in practice, the distribution of the axle load of the front and rear wheels of the tractor greatly changes during the connection work and the separation work between the tractor and the trailer. It is possible to do.

For example, in the connection work between the tractor and the trailer, the shaft load of the front wheel is generally larger before connection. Therefore, in this case, the braking force of the rear wheel is released. On the other hand, after the trailer is connected, the rear wheel axle load may increase by an amount corresponding to the weight of the trailer, and the rear wheel axle load may increase.

In such a case, when it is determined based on the information from the pressure sensor 20 that the rear wheel shaft load is larger, the operation mode of the solenoid valve 14 is switched (in this case, May be switched from the third mode to the second mode), and control may be performed so that the braking force on the front wheel side is released and at the same time the parking brake force acts on the rear wheel side.
Also, at the time of the release operation, similarly to the above, when it is determined that the axial load of the front wheel is larger, the operation mode of the electromagnetic valve 14 is switched to control the parking brake force to act on the front wheel side. Is also good.

By performing such control, a parking brake device with higher safety can be provided. Note that the parking brake device of the present invention is not limited to the above-described embodiments, and various changes can be made to the detailed configuration. For example, in the above-described embodiment, the pressure sensor 20 is provided as the shaft load detecting means. However, other than the pressure sensor 20, any other method can be used as long as the shaft load of the rear wheel can be detected or estimated. You may. Further, a sensor capable of detecting or estimating the shaft load may be provided on the front wheel side, and the detection information from the sensors of the front and rear wheels may be directly compared to determine which of the front and rear wheels has the larger shaft load. .

In the above-described embodiment, two independent passages 1f are provided for the left and right wheels. However, this passage 1f has two passages like the rear passage 1e. It may be configured to branch to a book. Also, on the contrary,
The rear passage 1e may be provided independently for each of the left and right. Further, the working fluid of the parking brake is not limited to air, and a liquid such as working oil may be used.

[0055]

As described above in detail, according to the parking brake device of the present invention, the vehicle height can be adjusted while the parking brake is operated, and the vehicle height can be adjusted without impairing the safety of the vehicle. There is the advantage that adjustments can be made. Further, at this time, since the braking force of the wheel on the side with the smaller shaft load is released and the braking force on the wheel with the larger shaft load is retained, the safety of the vehicle is further improved. It has the advantage that.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram showing a main part configuration of a parking brake device as one embodiment of the present invention.

FIG. 2 is a diagram for explaining a connection operation between a tractor having a vehicle height adjusting function and a trailer.

FIG. 3 is a schematic circuit diagram showing a main configuration of a parking brake device devised in the process of inventing the present invention.

[Explanation of symbols]

3 Parking brake operating means or hand control valve (HCV) 4 Parking brake means (rear chamber) 5 Parking brake means (front chamber) 10 Parking brake forced release means 14 Solenoid valve (or solenoid on-off valve) 15) Control means (ECU) 16 Vehicle height adjustment switch 17 Parking brake switch 20 Shaft load detecting means (pressure sensor)

Claims (1)

[Claims] 1. A parking brake device provided in a vehicle capable of adjusting a vehicle height, a parking brake means for applying a braking force to all wheels in conjunction with an operation state of a parking brake operation means, and the parking brake operation means. Parking brake forced release means capable of selectively releasing the braking force of the front wheel or the rear wheel irrespective of the operation state of the vehicle, shaft load detection means for detecting or estimating the shaft load of the front wheel and the rear wheel, and the parking brake Means for canceling the braking force of the wheel having the smaller shaft load according to the detection result from the shaft load detecting means during the vehicle height adjustment in a state where the braking force is applied to all the wheels by the means. A parking brake device comprising control means for operating a parking brake forced release means.