JPS6029375A - Tilt device of truck cab - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a truck cab tilting device that improves the operability of tilting up and down the truck cab.

Conventionally, automobiles in which the engine is located below the driver's cab, such as a trunk, are equipped with a mechanism that allows the driver's cab to be moved forward for inspection or repair of the engine. Many are of the so-called cab-over type. In order to move this driver's cabin forward relative to the vehicle body frame.

Usually equipped with a cab tilt cylinder etc.

An electric pump that supplies pressure oil is connected to this cylinder. Between this electric motor-integrated hydraulic pump and the cab tilt cylinder, there is a hydraulic circuit that extends the cab tilt cylinder and tilts the cab forward, and a hydraulic circuit that retracts the cab tilt cylinder and returns the tilted cab to its original state. Two systems of hydraulic circuits are interposed, and the hydraulic pump is equipped with a directional control valve for switching between the two systems of hydraulic circuits. FIG. 1 shows such a conventional power tilt hydraulic pump. As shown in the figure, a hydraulic pump 1 is equipped with a directional control valve 2 for switching a hydraulic circuit, and the two are connected to a hydraulic circuit car (not shown). The directional control valve 2 has a control lever 6.
is provided. The lever 6 is designed to be rotated approximately 90 degrees.

When the control lever 3 is turned to the left in the figure, the hydraulic circuit is switched to a hydraulic circuit that tilts the cab forward (hereinafter referred to as the tilt 7 subcircuit), and when the control lever 3 is turned to the right in the figure, the cab is returned to its original position. The hydraulic circuit is switched to a hydraulic circuit (hereinafter abbreviated as a tilt-down circuit) that returns to the position.

On the other hand, a tilt switch 4 for starting or stopping the hydraulic pump 1 is installed at a side position with respect to the control lever B, and when the tilt switch 4 is pushed in, the electric pump 1 is started. There is.

In such a conventional power tilt hydraulic pump, after rotating the lever 3 and switching the circuit connected to the hydraulic pump 1 to the tilt amplifier circuit or tilt down circuit, the tilt switch 4 is pressed. By continuing, pressure oil is sent and discharged from the hydraulic pump 1 to a cab tilt cylinder or the like (not shown), so that the cab tilts forward or returns to its original position. Therefore, in order to tilt the cab forward or backward, two operations are required: rotating the control foot 60 and pressing the tilt switch 4, making the operation work complicated.

The present invention has been devised in view of the above drawbacks.

A cab tilt cylinder installed between the truck cab and the chassis frame, a hydraulic circuit formed to communicate between the cylinder and a hydraulic pump driven by an electric motor, and a hydraulic circuit installed in the hydraulic circuit that allows the circuit to be moved to the tilt-down position. a directional control valve formed to control switching between the tilt-up position and the tilt-up position;
A mount roll lever provided on the same direction control valve and configured to switch and control the directional control valve by rotating the control valve over a tilt-down rotation range corresponding to the tilt-down position and a tilt-up rotation range corresponding to the tilt-up position. , which is provided on the chassis frame side, and engages and closes the control lever only when the control lever is rotated over the tilt-down and tilt-up rotation ranges, but it is closed when the control lever is rotated in both the tilt-down and tilt-up rotation ranges. a tilt command switch formed to open when the transshipment is in a stationary fixed position; a cylinder waste detection switch provided on the cab tilt cylinder and opened when detecting only the cylinder's round stage configuration; a cylinder waste detection switch provided on the cab a tilt completion switch that opens upon detecting only the tilt-up completion state of the vehicle; and a tilt completion switch that is provided on the chassis frame and switches to a down circuit that makes the cab ready for tilt-down operation when the tilt-down rotation lever is in the tilt-down rotation range. an electric circuit changeover switch formed to switch to a seven-knob circuit that engages the lever when the rotation is in the tilt amplifier rotation range and makes the tilt up operation possible; and the tilt command switch and the cylinder to drive the electric morph. The truck cab is equipped with an electric motor drive electric circuit including a forging detection switch, the tilt completion switch, and the electric circuit changeover switch, and when the control lever is rotated from a tilt-down rotation range to a tilt-up rotation range, the truck cab tilts the cab. The truck cab is characterized in that the trunk cab is tilted down by the cylinder and rotated from the above-mentioned tilt amplifier rotation range to the tilt down rotation range after completing the tilt 7 novation. The gist of the present invention is a tilt device, and the present invention operates the tilt amplifier of the trunk cab when the control lever is rotated from the tilt-down rotation range to the tilt-up rotation range, and controls the trunk cab when the cab is maintained in the tilt-up completed state. The hydraulic circuit and electric motor drive electric circuit are configured to tilt down the cab when it rotates from the lever tilt amplifier rotation range to the tilt down rotation range, so the cab can be automatically tilted 77° just by rotating the control lever with one hand. It has the advantage of being able to perform up and down operations and tilting operations extremely easily.

The present invention will be specifically explained below based on the embodiments shown in FIGS. 2 to 6. First, the cab tilt cylinder device 2 and the hydraulic pump device 4 shown in FIG. 2 have been removed from the trunk cab (hereinafter referred to as the cab) and the chassis frame. The lower end of the cylinder part 8 is connected to the chassis frame 10 and the upper end of the rod part 12 is connected to the cab 16 via the intermediate link 14.
The cab tilt cylinders 20 are pivotally connected to the side upper brackets 18, and the tilt fixing stays are pivotally attached to the pins 22 that connect the intermediate links 14 to the seven-sided upper brackets 18. The stay 20 is urged to rotate clockwise. "24
A lock lever is connected to a bracket 26 fixed to the cylinder part 8 by a pin 28, and a plurality of engagements are formed on the tilt fixing stay 20 by the spring force of a spring tensioned between the lever and the bracket 26. Lock lever 24 in hole 32
The claws 25 of the two come to engage with each other.

Reference numeral 34 is a cylinder dashed line detection switch provided on the bracket 26 for detecting the condition of the dashed line, and a suppressing piece 66 provided on the rond part engages with the switch 34 only when the rond part 12 is in the dashed line position. Down circuit 4 of the electric motor drive electric circuit 38 (hereinafter referred to as electric circuit) shown in FIG. 4, which will be described later.
It is formed to open 0. Reference numeral 42 denotes a tilt completion switch provided on the bracket 26 to detect the completion of tilt up, and is formed so as to be able to be engaged with a pressing piece 44 at the lower end of the tilt fixing stay 20, and opens the switch 46 when the cab is tilted. Note that 48 is a rod end provided at the upper end of the rod portion 12, and 48 is a rod end provided at the upper end of the rod portion 12, and 7 is used to restrict the forward tilting displacement of the cab toward the front of the vehicle when the cab is tilted up.
The lower Rond part 12 of the rod end 48 fits into a slit part 19 formed in the Tsupa bracket 18 itself, and the lower surface of the collar part 49 of the rod end 48 engages with the slit part 19, thereby making it possible to carry out the above regulation. .

Reference numerals 50 and 51 indicate mounting plates provided on the upper bracket 18 for fixing the bracket to the lower surface of the cab floor.

Next, the hydraulic pump device 4 will be explained. 52 is a hydraulic pump driven by an electric motor 54, 56 is a direction control valve integrated with the pump, and a hydraulic circuit 58 shown in FIG. , a neutral position 62 , and a tilt amplifier position 64 . In FIG. 68 is a pin 69 that drives the direction control valve 56 and swings in the direction of the arrow with respect to the shaft 57.
A Hundp lever (hereinafter referred to as lever) provided through the lever can rotate over a range of 90°, and the lever is in the first rotation range A, which is a rotation angle of 0° to 60°. When the direction control valve 56 is in the chill i/down position 1 shown in FIG.
At 660, the hydraulic pump 52 moves to the neutral position 62 when in the second rotation range B of 30° to 60°, and to the tilt-up position #64 when in the sixth rotation range C of 60° to 90°. A hydraulic circuit 58 is formed which communicates the cab tilt cylinder 6 with the cab tilt cylinder 6. Reference numeral 70 denotes an operation plate fixed to the end of the lever 68, and a cam portion 72 is provided on the lower edge of the operation plate 70, and only when the lever 68 is in the sixth rotation range C, an electric circuit changeover switch 74 (hereinafter referred to as a changeover switch) is activated. ) is formed to engage.

Reference numeral 76 denotes a cover plate attached to the hydraulic pump 52 side or the chassis frame 10 side by appropriate known attachment means, and the cover plate has the above-mentioned changeover switch 74, tilt command switch 8, and a quarter semicircular arc shape. A first holder 82 for statically fixing the guide plate 80 and the lever 68 at the O'' position and a second holder 84 for statically fixing the lever 68 at the 90° position are provided. A first step portion 86 and a second step portion 8B are formed, and a guide portion 90 is formed between the two step portions, so that when the lever 68 is in the first step portion 8B, the lever is moved to the first holder 82. In addition, when the lever 6B is in the second step part 88, it can be positioned and fixed to the second holder 84, and when the lever 6B rotates along the guide part 90, the cover plate 76 can be fixed.
The lever 68 and the operating plate 70, which are integrally fixed with each other with a certain gap from the lever 68, engage with the tilt command switch 78 provided at a position opposite to the lever 68, thereby closing an electric circuit 3B to be described later.

When the lever 6B is fixed to the first and second holders 82, 84, the operating plate 70 is separated from the engaged state of the switch 78 to open the electric circuit 3B.

92 is screwed to the operation plate 70 and has one end attached to the lock lever 24.
U connecting the other end of the control wire 94 connected to
A wire holder 96 in the shape of a letter 96 is a stopper member that is fastened together with the holder and protrudes from the back surface of the operation plate 70. This stopper member 96 comes into contact with the cover plate 76 when the lever 68 is raised in the direction of the arrow with the pin 69 as the center.
This restricts the amount by which the operation plate 70 is pressed into the tilt command switch 78 and prevents the operation plate 70 and the cam portion 72 from interfering with the cover plate 76.

Next, reference numeral 98 is a hydraulic launch mechanism provided on a floating bar (not shown) for positioning and fixing the cab 16 to the chassis frame 10 side.

100 is a hydraulic latch cylinder connected to the directional control valve 56 via a pipe 66; 102 is a bell flannel pivotally connected to the fluting bar via pin/1o4; its left end is connected to the rond part of the hydraulic latch cylinder 100; 10
1 via a pin 106. Also 1 (18
is a hook lever pivotally connected to the floating bar via a pin 110;

112 is a cab lock detection switch provided on the p-ting bar. The hook lever 102 (not shown) is always rotated clockwise by the force of a spring, and the hook lever 10B is always biased clockwise by the force of a spring (not shown), so that the cab 16 is positioned above the floating bar. The cab is positioned and fixed to the chassis frame side by the hook lever 114 fixedly attached to the cab 16 engaging with the seven levers 108 as shown in the figure.At this time, the hook lever 108 is engaged with the cab lock detection switch 112. In addition, the switch is opened in an electric circuit 38 shown in FIG. 4 and described later.

Here, to explain the tilt mechanism in this embodiment device with reference to FIGS. 5 and 6, the cab 16 and the chassis frame 1
0 through an intermediate link arm 116, a spring 118 is interposed between the link and the cab 16, and a regulating link 120 for fixing the tilt angle is interposed between the link and the chassis frame 10. ing. In the normal driving condition, the restriction link 120 is bent in a dogleg shape, and when the cab is tilted up by the cab tilt cylinder O, the intermediate rick 7-m 116 is extended until the restriction link 120 is extended as shown in FIG. It rotates around the tilt bin 122, and the tilt angle of the same rec arm 116 is adjusted by the regulation link 12.
After it is fixed at 0, the cab 1 is compressed while compressing the spring 11B.
6 is formed to rotate around the bin 124.

Note that 126 is a cushioning rubber provided on the intermediate link arm 116.

Reference numeral 128 denotes a return spring stretched between the regulation link 120 and the chassis frame 10 for returning the regulation link +20 to the state shown in FIG. 5 when the cab is tilted down.

Next, the hydraulic circuit 58 applied to the device of this embodiment will be explained. The illustrated piston 7 of the cab tilt cylinder 6 is in a state when the cab is tilted down. 130,
132 is the first. Second check valve, 134. 13'6 is a pilot circuit that opens both check valves, 158
, 140 is an oil filter, 142 is a relief valve, 14
Reference numeral 4 indicates a manual pump that can generate pressure oil by one manual operation in the event that the electric motor 54, the hydraulic pump 52, or the electric circuit system described below breaks down, and 146 indicates a tank. When the directional control valve 56 is in the tilt-up position 64, the pressure oil flows through the oil filter 138. The piston 7 is supplied to the cab tilt cylinder 6 through the first check valve 130, and the piston 7 is displaced to the right, so that the cab 16 is tilted up. At this time, since the second check valve 152 is opened by the signal pressure from the pilot circuit 136, the hydraulic pressure in the right chamber of the cylinder section 8 is maintained at the second check valve 132. Oil filter 14
0, it passes through the relief valve 142 and is returned to the tank 146. In addition, when the cab is tilted, 1.2
The tilt-up state is maintained by both check valves 1!10 and 132. Conversely, when the cab is tilted down, the directional control valve 56 is controlled to be switched to the tilt down position 60 by a lever 68.

At this time, the pressure oil from the hydraulic pop 52 is filtered through the filter 1401.
The cylinder part 8 button is fed through the second check valve 132, and the piston 7 is displaced to the left and returns to the state shown in FIG. At this time, the hydraulic pressure discharged from the left ventricle is transferred to the first check valve 13 which is opened by the signal pressure of the pilot circuit 134.
0. It is returned to tank 146 via filter 168 and relief valve 142.

Next, the electric circuit 68 of this embodiment shown in FIG.
4 form a motor circuit 15B. 16 again
2 is an anti-seizure switch 16 that prevents the motor 54 from seizing.
0, the solenoid 152, the tilt command switch 7B, the tilt completion switch 42 of the tilt amplifier circuit 46, the cylinder line inspection switch 64 of the tilt down circuit 40, the cab lock detection switch 112 of the cab lock circuit 116, the changeover switch 74, and the battery 56. This is a solenoid excitation circuit formed by And tilt up circuit 4
6. Tilt down circuit 40 and cab lock circuit 11
6 is connected in parallel between the changeover switch 74 and the tilt command switch 78. The tilt command switch 78 is closed only when the lever 68 is rotated, the tilt completion switch 42 is opened only in the negative direction when the keys and keys complete the tilt up, and the cylinder dashed line horizontal switch 34 is closed when the rod part 12 is in the cab. The cab lock detection switch 112 is opened only when the hook pin 1 of the cab is pressed and forged.
14 is formed to open only when hook lever 08 is engaged. There is also a changeover switch 74, which is set to the down-strike terminal 74' when the lever 6B is rotating to the first and second rotation ranges A and B, and to the up side when the lever 6B is rotated to the third rotation range C. It is connected to the terminal 74''.

To explain this, first, when the cab 16 is in the normal running state shown in FIG. 5, the hook pin 114 is inserted into the hook lever 1osK as shown in FIG. In this state, in which the cab is positioned and fixed on the chassis frame 10 side by engaging the bell crank lever 102 which is biased by the spring force of the spring that does not move, the lever 68 is engaged.
is fixed to the first holder 82, so the directional control valve 5
6 is in the tilt down position 60, and in the electric circuit 38 shown in FIG. 4, the switch 78 is open, the switch 42 is closed, the switch 4 is open, the switch 112 is open, and the switch 74 is in the down position Connect to terminal 741.

When tilting the cab from this state, when the lever 68 is pulled out from the first holder 82 in the direction of the arrow,
When the tilt command switch A B is pressed and closed by the operation plate 70, the lever 68 is rotated along the guide portion 90 to the sixth rotation range C as shown by the two-dot chain line.
is engaged with the selector switch 74, and the switch is switched to the amplifier side terminal 74''. - In conjunction with the rotation of the ten thousand lever 68, the control wire 94 is loosened, and the lock lever 24 is
The spring 30 rotates about the pin 28 in the open direction so as to constantly engage the engagement hole 32. In this way, the solenoid excitation circuit 162 conducts to the hunting battery 156 via the tilt/pull circuit 46, energizing the solenoid 152, and the movable switch 154 connects the motor circuit 158 to the battery 156. Then, the electric motor 54 operates and the hydraulic pump 52 is driven. At the same time, the direction control valve 56 is switched to the tilt-up position 64, so the pressure oil generated by the hydraulic pump 52 is transferred to the 1,000th pump. Valve 13
0 to the cab tilt norinda 6. Therefore, the rond portion 12 begins to expand, and the left end of the intermediate link 14 shown in FIG. 2 pushes up the lower surface of the amplifier bracket 1B.

In this state, the tilt 42 of the cab 16 is opened by engaging the pressing piece 44 at the lower end of the stay 20, as shown in FIG. 6, and as a result, the solenoid 152 is demagnetized and the power tilt relay
4 is opened, the electric motor 54 is automatically stopped, and the tilting of the cab is completed. Of course, in such a completed state, the cylinder thick/dashed line reading switch 4 also engages with the suppression piece 36 and is closed, and the cab lock switch 112 does not engage with the hook lever 108, so it is in the closed state.

In addition, when the camera 7 is at the tilt amplifier completion position.

The claw portion 25 of the stay is set to be loosely fitted into the intermediate position of the engagement hole 32 as appropriate, making it easy to disengage from the engagement hole 62 during tilt down/operation, but it may cause a slight drop in hydraulic pressure. If this occurs, the claw portion 25 will engage with the engagement hole 32 to prevent the cab from descending in the tilt-down direction, but it will also cause an abnormality in the hydraulic circuit 58 shown in FIG. If the drop occurs, the claw portion 25
By completely engaging the engagement hole 2 of the holder, it is possible to prevent the cab from unexpectedly descending.

Next, when operating the cab by tilting it down.

First, when the lever 68 is removed from the second boulder 84 to the position shown by the two-dot chain line, the tilt command switch 78 is closed and the tilt completion switch 42 is opened. At this time, move the lever 68 to 90
When reversely rotated in the fifth rotation range C in the direction from 60° to 60°, the wire 94 is pulled in conjunction with the 700 rotations of the operation plate, and the claw 25 of the lever 24 is disengaged from the engagement hole 32. Allows for relative displacement with the stay 20. Even if the oil pressure of the cab tilt cylinder O drops for some reason.

-1- Since the tilt completion switch 42 is closed and the hydraulic pump 52 is driven again, the cab is tilted by a slight amount.
Even if the engagement force becomes large, when the claw portion rotates through the second rotation range B, the direction control valve 56 is switched to the neutral position 62 as shown in FIG. 3, and the cam portion 72 of the operation plate 70 is Moving away from the selector switch 74, the switch 74 is switched to the down side terminal 74'. Then, since the tilt-down circuit 40 and the cab lock circuit 116 are in the closed state, the solenoid excitation circuit 162 is conducted and the solenoid 152 is turned on.
is excited. Therefore, the movable switch 154 is closed, the power tilt relay 150 is opened, and the electric motor 54
Although the hydraulic pump 52 is driven by the operation, pressure oil is not yet supplied to the cab tilt cylinder 6. From this state, the lever 68 is rotated from 50°, which is the first rotation range A, to 0°.
When the directional control valve 56 is rotated to the tilt-down position 60, the pressure oil from the hydraulic motor 52 is supplied to the cab tilt cylinder O via the filter 14o and the second check valve 162, and the piston 7 is displaced to the left as shown in FIG. 6, and the hydraulic pressure discharged from the cylinder 6 is applied to the first check valve 150. filter 158
．． It is returned to the tank 146 via the directional control valve 56 and the relief valve 142. At the same time, the oil pressure in the hydraulic latch cylinder 100 is also returned to the tank 146 via the directional control valve and the relief valve 142, and the bell crank clef 102 almost returns to the solid line state shown in FIG. 2.

In this way, the rond part 12 of the cab tilt cylinder O contracts and the cab 16 is tilted down, and the hook pin 114 fixed to the cab is moved into the engagement recess 109 of the hook lever 108.
It is displaced downward while still being fitted in.

As a result, the hook lever 108 rotates counterclockwise around the pin 1100 against the spring force of a spring (not shown), and due to the cam shape effect of the claw portion 1081 of the lever 108 and the claw portion 106 of the bell crank lever 102, the hook lever 108 rotates counterclockwise around the pin 1100. 108' is the claw part 1
06, the cab 16 is seated on a floating bar (not shown), and is positioned and fixed to the chassis frame 10. At the same time, the right end 108'' of the seventh lever 108 comes into contact with the gear tilt lock detection switch 112, and the switch 112 is opened.However, the cab has not yet been completely tilted down.

The suppressing piece 56 of the lost cylinder waste detection switch 34 does not touch the switch 64, and the switch 34 is in the closed state. Therefore, the hydraulic pump 52 continues to be driven, but when the rond part 12 of the cab tilt cylinder B is displaced, the switch 34 is opened, the solenoid excitation circuit 162 is opened, and the power tilt relay 154 is opened.
is operated to open, and the operation of the electric motor 54 is automatically stopped.
The cab tilts down completely. and lever 6
8 to the first holder 82, the tilt-down operation can be completed. Incidentally, at this time, the tilt command switch 78 is opened, and the electric circuit 38 is opened as a whole.

According to the device of this embodiment, when operating the cab with a tilt amplifier, the cab can be automatically tilted up and down by simply removing the lever 68 from the first holder 82 with one hand and rotating it from 0° to 90°. When operating, simply remove the lever 68 fixed to the second holder 84 from the holder with one hand and rotate it in the opposite direction from 90 degrees to 0 degrees. have

In the above embodiment, the directional control valve 56 is of 6 positions, and correspondingly the rotation range of the lever 68 is set from 1st to 60th position.
Although the directional control valve 56 is set to be able to rotate in three rotation ranges A, B, and C, it is not necessary to limit the direction control valve 56 to the above.
It is also possible to use a two-position type, that is, a structure in which the neutral position is omitted, so that the rotation range of the lever 68 can be appropriately configured to correspond to a two-rotation range without neutral position control.

Further, in the above embodiment, a configuration in which the hydraulic launch cylinder 100 of the hydraulic launch mechanism 98 of the hydraulic latch mechanism 98 is operated in conjunction with the rotational operation of the lever 68 has been described, but it can also be applied to a configuration in which the configuration of the latch mechanism 98 is not added. It goes without saying that it can be done.

Further, although the lever 68 in the above embodiment is configured to be able to rotate from 0° to 90°, the angle of rotation is not limited to this.

[Brief explanation of the drawing]

Fig. 1 is an external view of a conventional device, Fig. 2 is an exploded external perspective view of an embodiment of the present invention, Fig. 3 is a hydraulic circuit diagram of the same embodiment, and Fig. 4 is an electrical circuit diagram applied to the same embodiment. circuit diagram,
FIG. 5 is an explanatory view showing the state when the cab is tilted down, and FIG. 6 is an explanatory view showing the state when the cab is tilted up. 6; Cab tilt cylinder; 10; Undercarriage frame. 12; prad part, 16; cab. 34; Cylinder dose line detection switch. 38; Electric circuit, 42; Tilt completion switch. 52; Hydraulic pump; 54; Electric motor. 56; Directional control valve; 58; Hydraulic circuit. 60: Tilt down position, 62: Neutral position. 64; tilt amplifier position, 66; pipe. 68; Lever, 70; Operation plate, 72; Cam portion. 80; Guide plate, 74; Changeover switch. 78; Tilt command switch; 100; Hydraulic latch cylinder. 112; Cab lock detection switch. 158; motor circuit; 162; solenoid excitation path. A: first rotation range, B: second rotation range. C; 6th rotational area agent Himakayoshi-style formation Figure 1 Yuki 17 x 14 Figure

Claims (1)

[Claims] A cab tilt cylinder installed between the truck cab and the chassis frame, a hydraulic circuit formed to communicate between the cylinder and a hydraulic pump driven by an electric motor, and a hydraulic circuit installed in the hydraulic circuit that allows the circuit to be moved to the tilt-down position. a directional control valve formed to switch and control the tilt amplifier position;
The control valve is provided in the same direction control valve and controls the direction control valve by switching between a tilt-down rotation range corresponding to the above-mentioned tilt-down position and a tilt-up rotation range corresponding to the above-mentioned tilt 17 position. The control lever provided on the chassis frame side engages and closes the lever only when the tilt-down and tilt amplifier rotation ranges are operated, but the lever is closed both during tilt-down and tilt-up. A tilt command switch is formed to open when the transfer is in a stationary fixed position, a cylinder stage detection switch is provided on the cab tilt cylinder and opens when detecting only the round stage state of the cylinder, and a cylinder stage detection switch is provided on the above cylinder and opens the cab. a tilt completion switch that opens upon detecting only the tilt-up completion state of the vehicle; and a tilt completion switch that is provided on the chassis frame and switches to a down circuit that makes the cab ready for tilt-down operation when the tilt-down rotation lever is in the tilt-down rotation range. an electric circuit changeover switch formed to engage the lever when the rotation is in the tilt amplifier rotation range to switch to an amplifier circuit that enables tilt-up operation; and the tilt command switch and the cylinder stage for driving the electric motor. The truck cab is equipped with an electric motor drive electric circuit including a combination detection switch, the tilt completion switch, and the electric circuit changeover switch, and the truck cab The tilt of the truck cab is characterized in that the trunk cab is tilted down by the cab tilt cylinder and the trunk cab is tilted down when the control lever is rotated from the tilt up rotation range to the tilt down rotation range after the tilt 7 novation is completed. Device